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Vol. 47 n°11 - Juin 2008 [texte imprimé] . - 2008 . - p. 3795-4028 : ill. ; 28 cm. Chemical engineering Langues : Anglais (eng)
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Ajouter le résultat dans votre panierRhodium metal complex and hydrotalcite based environmentally friendly catalyst system for the selective synthesis of C8-aldehydes from propylene / Vivek K. Srivastava in Industrial & engineering chemistry research, Vol. 47 n°11 (Juin 2008)
Titre : Rhodium metal complex and hydrotalcite based environmentally friendly catalyst system for the selective synthesis of C8-aldehydes from propylene Type de document : texte imprimé Auteurs : Vivek K. Srivastava, Auteur ; Sumeet K. Sharma, Auteur ; Ram S. Shukla, Auteur ; Raksh V. Jasra, Auteur Année de publication : 2008 Article en page(s) : p. 3795–3803 Note générale : Bibliogr. p. 3802-3803 Langues : Anglais (eng) Mots-clés : Rhodium complex Catalytic activity Kinetic profiles Reaction rates Résumé : Catalytic activity of a novel catalyst [HFN + HT] containing a rhodium complex, HRh(CO)(PPh3)3 [HFN], and a solid base, hydrotalcite Mg1-xAlx(OH2)x+(CO32−)x/n·mH2O [HT], was evaluated for carrying out hydroformylation, aldol condensation, and hydrogenation in a single pot for the synthesis of C8-aldehydes, 2-ethylhexenal and 2-ethylhexanal, from propylene. In typical catalytic experiments conducted in a high-pressure reactor of 100 mL capacity, the selectivity for the formation of 2-ethylhexanal (54%) was found to be four times more than that of 2-ethylhexenal (13%) at 150 °C with employed partial pressures of propylene, carbon monoxide, and hydrogen at 10, 5, and 15 bar, respectively. Detailed investigations were performed on the effects of various reaction parameters, Mg/Al molar ratio (X) of [HT], amount of [HFN] complex, amount of [HT], and reaction temperature, on the formation of C8-aldehydes from propylene in a single pot. Under the employed reaction conditions, the maximum selectivity for 2-ethylhexanal was observed using hydrotalcite of Mg/Al molar ratio 3.5. Increasing the amounts of both [HFN] complex and [HT] favored the selectivities for the formation of 2-ethylhexanal up to certain amounts, and after that, on further increasing the amounts, the selectivities for the same were decreased. The kinetic profiles for the formation of various products with time and reaction rates were determined. For comparative studies, the kinetic profiles and reaction rates with the commercially employed catalyst, [HFN + KOH], were also determined under identical reaction conditions of [HFN + HT(3.5)], and the selectivity of 2-ethylhexanal was found to be almost identical at 7 h for the both systems. On the basis of experiments and kinetic profiles, reaction pathways are suggested for the formation of C8-aldehydes from propylene in a single pot. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071108r
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3795–3803[article] Rhodium metal complex and hydrotalcite based environmentally friendly catalyst system for the selective synthesis of C8-aldehydes from propylene [texte imprimé] / Vivek K. Srivastava, Auteur ; Sumeet K. Sharma, Auteur ; Ram S. Shukla, Auteur ; Raksh V. Jasra, Auteur . - 2008 . - p. 3795–3803.
Bibliogr. p. 3802-3803
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3795–3803
Mots-clés : Rhodium complex Catalytic activity Kinetic profiles Reaction rates Résumé : Catalytic activity of a novel catalyst [HFN + HT] containing a rhodium complex, HRh(CO)(PPh3)3 [HFN], and a solid base, hydrotalcite Mg1-xAlx(OH2)x+(CO32−)x/n·mH2O [HT], was evaluated for carrying out hydroformylation, aldol condensation, and hydrogenation in a single pot for the synthesis of C8-aldehydes, 2-ethylhexenal and 2-ethylhexanal, from propylene. In typical catalytic experiments conducted in a high-pressure reactor of 100 mL capacity, the selectivity for the formation of 2-ethylhexanal (54%) was found to be four times more than that of 2-ethylhexenal (13%) at 150 °C with employed partial pressures of propylene, carbon monoxide, and hydrogen at 10, 5, and 15 bar, respectively. Detailed investigations were performed on the effects of various reaction parameters, Mg/Al molar ratio (X) of [HT], amount of [HFN] complex, amount of [HT], and reaction temperature, on the formation of C8-aldehydes from propylene in a single pot. Under the employed reaction conditions, the maximum selectivity for 2-ethylhexanal was observed using hydrotalcite of Mg/Al molar ratio 3.5. Increasing the amounts of both [HFN] complex and [HT] favored the selectivities for the formation of 2-ethylhexanal up to certain amounts, and after that, on further increasing the amounts, the selectivities for the same were decreased. The kinetic profiles for the formation of various products with time and reaction rates were determined. For comparative studies, the kinetic profiles and reaction rates with the commercially employed catalyst, [HFN + KOH], were also determined under identical reaction conditions of [HFN + HT(3.5)], and the selectivity of 2-ethylhexanal was found to be almost identical at 7 h for the both systems. On the basis of experiments and kinetic profiles, reaction pathways are suggested for the formation of C8-aldehydes from propylene in a single pot. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071108r Exemplaires
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Titre : Facile method for fabricating boron-doped TiO2 nanotube array with enhanced photoelectrocatalytic properties Type de document : texte imprimé Auteurs : Jingyuan Li, Auteur ; Na Lu, Auteur ; Xie Quan, Auteur ; Shuo Chen, Auteur Année de publication : 2008 Article en page(s) : p. 3804–3808 Note générale : Bibliogr. p. 3807-3808 Langues : Anglais (eng) Mots-clés : TiO2 nanotube arrays Electrodeposition method X-ray diffraction Résumé : Highly ordered boron-doped TiO2 nanotube arrays were fabricated via a facile electrodeposition method. X-ray photoelectron spectroscopy (XPS) analysis revealed incorporated B atoms in the lattice of a TiO2 nanotube array. The X-ray diffraction (XRD) spectrum indicated improved crystallinity of boron-doped TiO2 nanotube arrays, relative to undoped TiO2 nanotube arrays. A shift of the absorption edge toward the visible region and a new absorption shoulder (380–510 nm) of boron-doped TiO2 nanotube arrays were observed via diffuse reflectance spectroscopy (DRS). In photoelectrochemical measurements, under either ultraviolet (UV) or visible-light irradiation, the photocurrent conversion efficiency was enhanced because of boron doping. The photoelectrocatalysis of phenol under simulated solar irradiation was performed using boron-doped or undoped TiO2 nanotube arrays, and the kinetic constant of a boron-doped TiO2 nanotube array photoelectrode was increased by ca. 28%, compared to that of an undoped TiO2 nanotube array photoelectrode. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0712028
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3804–3808[article] Facile method for fabricating boron-doped TiO2 nanotube array with enhanced photoelectrocatalytic properties [texte imprimé] / Jingyuan Li, Auteur ; Na Lu, Auteur ; Xie Quan, Auteur ; Shuo Chen, Auteur . - 2008 . - p. 3804–3808.
Bibliogr. p. 3807-3808
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3804–3808
Mots-clés : TiO2 nanotube arrays Electrodeposition method X-ray diffraction Résumé : Highly ordered boron-doped TiO2 nanotube arrays were fabricated via a facile electrodeposition method. X-ray photoelectron spectroscopy (XPS) analysis revealed incorporated B atoms in the lattice of a TiO2 nanotube array. The X-ray diffraction (XRD) spectrum indicated improved crystallinity of boron-doped TiO2 nanotube arrays, relative to undoped TiO2 nanotube arrays. A shift of the absorption edge toward the visible region and a new absorption shoulder (380–510 nm) of boron-doped TiO2 nanotube arrays were observed via diffuse reflectance spectroscopy (DRS). In photoelectrochemical measurements, under either ultraviolet (UV) or visible-light irradiation, the photocurrent conversion efficiency was enhanced because of boron doping. The photoelectrocatalysis of phenol under simulated solar irradiation was performed using boron-doped or undoped TiO2 nanotube arrays, and the kinetic constant of a boron-doped TiO2 nanotube array photoelectrode was increased by ca. 28%, compared to that of an undoped TiO2 nanotube array photoelectrode. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0712028 Exemplaires
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Titre : Effects of carboxyl content on the characteristics of TMP long fibers Type de document : texte imprimé Auteurs : Lianshan Mao, Auteur ; Kweinam Law, Auteur ; Daneault Claude, Auteur ; Brouillette Francois, Auteur Année de publication : 2008 Article en page(s) : p. 3809–3812 Note générale : Bibliogr. p. 3812 Langues : Anglais (eng) Mots-clés : TMP long fibers Carboxyl groups Oxidation Résumé : This work examined the effects of carboxyl content on the characteristics of TMP long fibers. The carboxyl groups on TMP long fibers were generated by a TEMPO-mediated oxidation using different amounts of sodium hypochlorite. In general, the increases in carboxyl content improved the tensile and burst indices but reduced the tear index and fines retention. It was also found that low carboxyl content on oxidized long fibers could adsorb part of the dissoluble substance (DS) and other substances, reducing the DS and total organic carbon (TOC) in whitewater; the adsorption capacity decreased with increasing carboxyl content. Addition of cationic polymer increased the retention of fines and decreased the DS and other substances in whitewater. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071274z
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3809–3812[article] Effects of carboxyl content on the characteristics of TMP long fibers [texte imprimé] / Lianshan Mao, Auteur ; Kweinam Law, Auteur ; Daneault Claude, Auteur ; Brouillette Francois, Auteur . - 2008 . - p. 3809–3812.
Bibliogr. p. 3812
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3809–3812
Mots-clés : TMP long fibers Carboxyl groups Oxidation Résumé : This work examined the effects of carboxyl content on the characteristics of TMP long fibers. The carboxyl groups on TMP long fibers were generated by a TEMPO-mediated oxidation using different amounts of sodium hypochlorite. In general, the increases in carboxyl content improved the tensile and burst indices but reduced the tear index and fines retention. It was also found that low carboxyl content on oxidized long fibers could adsorb part of the dissoluble substance (DS) and other substances, reducing the DS and total organic carbon (TOC) in whitewater; the adsorption capacity decreased with increasing carboxyl content. Addition of cationic polymer increased the retention of fines and decreased the DS and other substances in whitewater. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071274z Exemplaires
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Titre : Removal of 2-chlorophenol from aqueous solution by Mg/Al layered double hydroxide (LDH) and modified LDH Type de document : texte imprimé Auteurs : Ya Hui Chuang, Auteur ; Yu Min Tzou, Auteur ; Ming Kuang Wang, Auteur ; Cheng Hua Liu, Auteur Année de publication : 2008 Article en page(s) : p. 3813–3819 Note générale : Bibliogr. p. 3818-3819 Langues : Anglais (eng) Mots-clés : 2-chlorophenol Layered double hydroxide Organic pollutant Sodium dodecyl sulfate intercalated LDH Sorption Résumé : Sorption is a common treatment for removing pollutants from natural environments. Layered double hydroxides (LDHs), which consist of brucite-like positive layers and sodium dodecyl sulfate intercalated with LDH (SDS−LDH), are considered to be potential organic pollutant sorbents. The objectives of this study were (1) to evaluate the impact of removing 2-chlorophenol (2-CP) using Mg3-Al-(NO3) LDH and SDS−LDH and (2) to investigate the removal efficiencies of these two compounds. All fitted sorption data reveal that the second-order model and the Langmuir model best describe the sorption kinetics and isotherms, respectively. By visual MinteqA2 (2000) calculation, the dissociation pKa of 2-CP is 8.56. The experimental results indicate that a high concentration of 2-CP is sorbed by the hydrophilic-hydrophilic physical interaction of LDH when the pH is >8.56; however, the hydrophobic−hydrophobic partition interaction of SDS−LDH is more vital when the pH is En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071508e
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3813–3819[article] Removal of 2-chlorophenol from aqueous solution by Mg/Al layered double hydroxide (LDH) and modified LDH [texte imprimé] / Ya Hui Chuang, Auteur ; Yu Min Tzou, Auteur ; Ming Kuang Wang, Auteur ; Cheng Hua Liu, Auteur . - 2008 . - p. 3813–3819.
Bibliogr. p. 3818-3819
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3813–3819
Mots-clés : 2-chlorophenol Layered double hydroxide Organic pollutant Sodium dodecyl sulfate intercalated LDH Sorption Résumé : Sorption is a common treatment for removing pollutants from natural environments. Layered double hydroxides (LDHs), which consist of brucite-like positive layers and sodium dodecyl sulfate intercalated with LDH (SDS−LDH), are considered to be potential organic pollutant sorbents. The objectives of this study were (1) to evaluate the impact of removing 2-chlorophenol (2-CP) using Mg3-Al-(NO3) LDH and SDS−LDH and (2) to investigate the removal efficiencies of these two compounds. All fitted sorption data reveal that the second-order model and the Langmuir model best describe the sorption kinetics and isotherms, respectively. By visual MinteqA2 (2000) calculation, the dissociation pKa of 2-CP is 8.56. The experimental results indicate that a high concentration of 2-CP is sorbed by the hydrophilic-hydrophilic physical interaction of LDH when the pH is >8.56; however, the hydrophobic−hydrophobic partition interaction of SDS−LDH is more vital when the pH is En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071508e Exemplaires
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Titre : Decontamination reactions of chemical warfare agent simulants with alcohols in the basic ionic liquid tetramethylammonium hydroxide/1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)amide Type de document : texte imprimé Auteurs : John S. Wilkes, Auteur ; Patrick J. Castle, Auteur ; Joseph A. Levisky, Auteur ; Cynthia A. Corley, Auteur Année de publication : 2008 Article en page(s) : p. 3820–3826 Note générale : Bibliogr. p. 3826 Langues : Anglais (eng) Mots-clés : Chemical warfare simulants Ionic liquid Tetramethylammonium hydroxide pentahydrate Résumé : Increased acts of international terrorism called for the development of rapid and reliable chemical agent decontamination reactions to minimize human exposure and material loss. Even though many chemical reaction processes have been reported, most remain unattractive for various reasons. In order to eliminate many of the adversities, these processes were studied in an ionic liquid solvent. In this report, we describe the reaction between chemical warfare simulants with alcohols in the ionic liquid 1,2-dimethyl-3-propylimmidazolium bis(trifluoromethylsulfonyl)amide made basic with tetramethylammonium hydroxide pentahydrate. The chemical agent simulants used in this study were diisopropylfluorophosphate, bis(2-ethylhexyl) phosphite, and chloroethylphenyl sulfide, which simulate agents GD, VX, and HD, respectively. The reactions were rapid, and products were identified by LC/MS-TOF and GC/MS. All of the reaction products of the VX and HD simulants remained in the ionic liquid, whereas the products from GD simulant partitioned between the ionic liquid and water extract. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800237z
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3820–3826[article] Decontamination reactions of chemical warfare agent simulants with alcohols in the basic ionic liquid tetramethylammonium hydroxide/1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)amide [texte imprimé] / John S. Wilkes, Auteur ; Patrick J. Castle, Auteur ; Joseph A. Levisky, Auteur ; Cynthia A. Corley, Auteur . - 2008 . - p. 3820–3826.
Bibliogr. p. 3826
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3820–3826
Mots-clés : Chemical warfare simulants Ionic liquid Tetramethylammonium hydroxide pentahydrate Résumé : Increased acts of international terrorism called for the development of rapid and reliable chemical agent decontamination reactions to minimize human exposure and material loss. Even though many chemical reaction processes have been reported, most remain unattractive for various reasons. In order to eliminate many of the adversities, these processes were studied in an ionic liquid solvent. In this report, we describe the reaction between chemical warfare simulants with alcohols in the ionic liquid 1,2-dimethyl-3-propylimmidazolium bis(trifluoromethylsulfonyl)amide made basic with tetramethylammonium hydroxide pentahydrate. The chemical agent simulants used in this study were diisopropylfluorophosphate, bis(2-ethylhexyl) phosphite, and chloroethylphenyl sulfide, which simulate agents GD, VX, and HD, respectively. The reactions were rapid, and products were identified by LC/MS-TOF and GC/MS. All of the reaction products of the VX and HD simulants remained in the ionic liquid, whereas the products from GD simulant partitioned between the ionic liquid and water extract. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800237z Exemplaires
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Titre : Nitrogen oxides absorption on calcium hydroxide at low temperature Type de document : texte imprimé Auteurs : Xiaowen Zhang, Auteur ; Huiling Tong, Auteur ; Hu Zhang, Auteur ; Changhe Chen, Auteur Année de publication : 2008 Article en page(s) : p. 3827–3833 Note générale : Bibliogr. p. 3833 Langues : Anglais (eng) Mots-clés : Calcium hydroxide Nitrogen oxides Water vapor Absorption process Résumé : Solid Ca(OH)2 was used to absorb NO and NO2 with water vapor present in the flue gas. Nitrogen oxides were captured as nitrite and nitrate, and part of NO could be released into the gas as the HNO2 decomposed, which was produced in the absorption process. A mathematical model was founded to predict the process of NOx absorption and nitrite and nitrate production. With the overall kinetic parameters (OKPs) evaluated by the typical experimental result at 70 °C and 60% relative humidity, the model can simulate the experimental results at various conditions quantitatively. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070660d
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3827–3833[article] Nitrogen oxides absorption on calcium hydroxide at low temperature [texte imprimé] / Xiaowen Zhang, Auteur ; Huiling Tong, Auteur ; Hu Zhang, Auteur ; Changhe Chen, Auteur . - 2008 . - p. 3827–3833.
Bibliogr. p. 3833
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3827–3833
Mots-clés : Calcium hydroxide Nitrogen oxides Water vapor Absorption process Résumé : Solid Ca(OH)2 was used to absorb NO and NO2 with water vapor present in the flue gas. Nitrogen oxides were captured as nitrite and nitrate, and part of NO could be released into the gas as the HNO2 decomposed, which was produced in the absorption process. A mathematical model was founded to predict the process of NOx absorption and nitrite and nitrate production. With the overall kinetic parameters (OKPs) evaluated by the typical experimental result at 70 °C and 60% relative humidity, the model can simulate the experimental results at various conditions quantitatively. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070660d Exemplaires
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Titre : Zirconia-supported Cu-KNO3 catalyst : characterization and catalytic behavior in the catalytic combustion of soot with a NO/O2 mixture Type de document : texte imprimé Auteurs : Ileana D. Lick, Auteur ; Alfredo L. Carrascull, Auteur ; Marta I. Ponzi, Auteur ; Esther N. Ponzi, Auteur Année de publication : 2008 Article en page(s) : p. 3834–3839 Note générale : Bibliogr. p. 3838-3839 Langues : Anglais (eng) Mots-clés : Diesel soot Catalytic combustion NO/O2 mixture Résumé : The catalytic combustion of diesel soot was studied in the presence of catalysts: CuZrO2, KNO3ZrO2, and CuKNO3ZrO2. The catalysts were prepared by impregnation of ZrO2·nH2O into an aqueous solution of Cu(NO3)2, KNO3, or both salts simultaneously. The catalysts were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and temperature-programmed reduction (TPR). Cu(n)KNO3ZrO2 catalysts present high activity, and the value of the combustion temperature decreases 200 °C with respect to the temperature of the process without catalyzing, with Tmax values between 370 and 380 °C. The activity is associated with KNO3 presence, and the role of KNO3 can be attributed to (i) an increase of contact between soot and the surface of the catalyst and (ii) a redox reaction in which the nitrate is reduced to nitrite by reaction with carbon and again reoxidized to nitrate. The copper contribution is associated with the reaction selectivity toward CO2 formation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071194v
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3834–3839[article] Zirconia-supported Cu-KNO3 catalyst : characterization and catalytic behavior in the catalytic combustion of soot with a NO/O2 mixture [texte imprimé] / Ileana D. Lick, Auteur ; Alfredo L. Carrascull, Auteur ; Marta I. Ponzi, Auteur ; Esther N. Ponzi, Auteur . - 2008 . - p. 3834–3839.
Bibliogr. p. 3838-3839
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3834–3839
Mots-clés : Diesel soot Catalytic combustion NO/O2 mixture Résumé : The catalytic combustion of diesel soot was studied in the presence of catalysts: CuZrO2, KNO3ZrO2, and CuKNO3ZrO2. The catalysts were prepared by impregnation of ZrO2·nH2O into an aqueous solution of Cu(NO3)2, KNO3, or both salts simultaneously. The catalysts were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and temperature-programmed reduction (TPR). Cu(n)KNO3ZrO2 catalysts present high activity, and the value of the combustion temperature decreases 200 °C with respect to the temperature of the process without catalyzing, with Tmax values between 370 and 380 °C. The activity is associated with KNO3 presence, and the role of KNO3 can be attributed to (i) an increase of contact between soot and the surface of the catalyst and (ii) a redox reaction in which the nitrate is reduced to nitrite by reaction with carbon and again reoxidized to nitrate. The copper contribution is associated with the reaction selectivity toward CO2 formation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071194v Exemplaires
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Titre : Kinetics of the hydrodechlorination of 4-chlorophenol in water using Pd, Pt, and Rh/Al2O3 catalysts Type de document : texte imprimé Auteurs : Elena Díaz, Auteur ; José A. Casas, Auteur ; Ángel F. Mohedano, Auteur ; Luisa Calvo, Auteur Année de publication : 2008 Article en page(s) : p. 3840–3846 Note générale : Bibliogr. p. 3845-3846 Langues : Anglais (eng) Mots-clés : 4-chlorophenol Hydrodechlorination Tank reactor Catalytic activity Résumé : The hydrodechlorination of 4-chlorophenol in an aqueous phase was studied in a semicontinuous basket stirred tank reactor using Pd, Pt, and Rh on γ-alumina commercial catalysts (0.5% w/w) under mild reaction conditions. The catalytic activity was studied in the temperature range of 20−40 °C. Pd and Rh showed a higher catalytic activity than Pt. From consumption of 4-chlorophenol and evolution of the reaction products, phenol, cyclohexanone, and cyclohexanol, a reaction scheme based on a parallel-series pathway and a kinetic model based on pseudo-first-order dependence on 4-chlorophenol have been proposed. Hydrodechlorination of 4-chlorophenol to phenol exhibits the largest apparent kinetic constant for Pd (k1 = 0.42–0.73 h−1) and Pt (k1 = 0.20–0.42 h−1) catalysts, while in the case of Rh, the three reactions, hydrodechlorination of 4-chlorophenol to phenol (k1 = 0.43–0.64 h−1) and hydrogenation of phenol to cyclohexanone (k3 = 0.42–0.78 h−1) and to cyclohexanol (k4 = 0.38–0.65 h−1), have comparable values of the kinetic constant. The apparent activation energy for 4-chlorophenol disappearance was determined, and values of 21.0, 26.2, and 15.3 kJ/mol were obtained for Pd, Pt, and Rh, respectively. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071517n
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3840–3846[article] Kinetics of the hydrodechlorination of 4-chlorophenol in water using Pd, Pt, and Rh/Al2O3 catalysts [texte imprimé] / Elena Díaz, Auteur ; José A. Casas, Auteur ; Ángel F. Mohedano, Auteur ; Luisa Calvo, Auteur . - 2008 . - p. 3840–3846.
Bibliogr. p. 3845-3846
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3840–3846
Mots-clés : 4-chlorophenol Hydrodechlorination Tank reactor Catalytic activity Résumé : The hydrodechlorination of 4-chlorophenol in an aqueous phase was studied in a semicontinuous basket stirred tank reactor using Pd, Pt, and Rh on γ-alumina commercial catalysts (0.5% w/w) under mild reaction conditions. The catalytic activity was studied in the temperature range of 20−40 °C. Pd and Rh showed a higher catalytic activity than Pt. From consumption of 4-chlorophenol and evolution of the reaction products, phenol, cyclohexanone, and cyclohexanol, a reaction scheme based on a parallel-series pathway and a kinetic model based on pseudo-first-order dependence on 4-chlorophenol have been proposed. Hydrodechlorination of 4-chlorophenol to phenol exhibits the largest apparent kinetic constant for Pd (k1 = 0.42–0.73 h−1) and Pt (k1 = 0.20–0.42 h−1) catalysts, while in the case of Rh, the three reactions, hydrodechlorination of 4-chlorophenol to phenol (k1 = 0.43–0.64 h−1) and hydrogenation of phenol to cyclohexanone (k3 = 0.42–0.78 h−1) and to cyclohexanol (k4 = 0.38–0.65 h−1), have comparable values of the kinetic constant. The apparent activation energy for 4-chlorophenol disappearance was determined, and values of 21.0, 26.2, and 15.3 kJ/mol were obtained for Pd, Pt, and Rh, respectively. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071517n Exemplaires
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Titre : Calculation of the optimal macropore size in nanoporous catalysts and its application to DeNOx catalysis Type de document : texte imprimé Auteurs : Gang Wang, Auteur ; Marc-Olivier Coppens, Auteur Année de publication : 2008 Article en page(s) : p. 3847–3855 Note générale : Bibliogr. p. 3855 Langues : Anglais (eng) Mots-clés : Macropores Nanoporous catalyst Molecular diffusion DeNOx catalysis Résumé : Macropores act as broad highways for molecules to move in and out of a nanoporous catalyst. The macropore “distributor” network in such a hierarchically structured porous catalyst, containing both nanopores and macropores, is optimized with the aim to find the optimal effectiveness factor, ηopt, of a single reaction with general kinetics in the catalyst. Molecular diffusion is assumed to dominate transport in macropores. It is found that the ηopt−Φ0 relation qualitatively recovers the universal η−Φ relation when the generalized distributor Thiele modulus, Φ0, is defined in a way analogous to the generalized Thiele modulus, Φ, but using the molecular diffusivity in the macropores rather than the effective diffusivity in the nanopores. This is because the concentration gradient inside the optimal hierarchically structured, porous catalyst exists only in one principle direction (e.g., the radial direction in a spherical catalyst particle), and molecular diffusion in the macropores dominates the transport process in this principle direction. The universal ηopt−Φ0 relation is used to design a catalyst for power plant NOx emission control. Overall catalytic activity in a mesoporous catalyst with a median pore size of 32.5 nm could be increased by a factor of 1.8−2.8 simply by introducing macropores (occupying 20−40% of the total volume of the catalyst) with a width of 2−22 µm into the mesoporous catalytic material, so that the remaining mesoporous macropore walls are 5−33 µm thick. In practice, this would correspond to a deNOx catalyst consisting of mesoporous particles with a diameter of 5−33 µm and macropores in between them with a size of around 2−22 µm. Information like this is readily applicable to practical catalyst synthesis. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071550%2B
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3847–3855[article] Calculation of the optimal macropore size in nanoporous catalysts and its application to DeNOx catalysis [texte imprimé] / Gang Wang, Auteur ; Marc-Olivier Coppens, Auteur . - 2008 . - p. 3847–3855.
Bibliogr. p. 3855
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3847–3855
Mots-clés : Macropores Nanoporous catalyst Molecular diffusion DeNOx catalysis Résumé : Macropores act as broad highways for molecules to move in and out of a nanoporous catalyst. The macropore “distributor” network in such a hierarchically structured porous catalyst, containing both nanopores and macropores, is optimized with the aim to find the optimal effectiveness factor, ηopt, of a single reaction with general kinetics in the catalyst. Molecular diffusion is assumed to dominate transport in macropores. It is found that the ηopt−Φ0 relation qualitatively recovers the universal η−Φ relation when the generalized distributor Thiele modulus, Φ0, is defined in a way analogous to the generalized Thiele modulus, Φ, but using the molecular diffusivity in the macropores rather than the effective diffusivity in the nanopores. This is because the concentration gradient inside the optimal hierarchically structured, porous catalyst exists only in one principle direction (e.g., the radial direction in a spherical catalyst particle), and molecular diffusion in the macropores dominates the transport process in this principle direction. The universal ηopt−Φ0 relation is used to design a catalyst for power plant NOx emission control. Overall catalytic activity in a mesoporous catalyst with a median pore size of 32.5 nm could be increased by a factor of 1.8−2.8 simply by introducing macropores (occupying 20−40% of the total volume of the catalyst) with a width of 2−22 µm into the mesoporous catalytic material, so that the remaining mesoporous macropore walls are 5−33 µm thick. In practice, this would correspond to a deNOx catalyst consisting of mesoporous particles with a diameter of 5−33 µm and macropores in between them with a size of around 2−22 µm. Information like this is readily applicable to practical catalyst synthesis. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071550%2B Exemplaires
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Titre : An empirical mathematical model for the predictive analysis of the chemical absorption of hydroxide in eucalyptus wood Type de document : texte imprimé Auteurs : M. M. Costa, Auteur ; J. L. Gomide, Auteur ; J. L. Colodette, Auteur Année de publication : 2008 Article en page(s) : p. 3856–3860 Note générale : Bibliogr. p. 3859-3860 Langues : Anglais (eng) Mots-clés : Basic density Chip impregnation Empirical mathematical modeling Eucalyptus Kraft pulping pulping operational conditions Résumé : Chip steaming, heating, impregnation, and sugar acid neutralization of wood chips by an alkaline kraft liquor during the pretreatment and initial phase of pulping are critical physical−chemical phenomena for executing successful industrial kraft pulping operations. Specifically, these physical and chemical phenomena significantly affect the kraft pulping process performance in terms of chemical mass transfer that influences both delignification rate and the homogeneity of the pulp produced. Detailed fundamental knowledge about the aforementioned phenomena during the initial phase is necessary to obtain selective wood delignification and as a consequence better pulp homogeneities and yield. The present work evaluates the effect of selected critical variables on impregnation and neutralization of Eucalyptus spp wood chips. The independent variables used for this study were as follows: wood basic density (BD), 430, 490, and 550 kg/m3; effective alkali charge (EA), 5%, 9%, and 13% at 25% sulfidity; time (t), 30, 60, and 90 min; and temperature (T), 90, 110, and 130 °C. The wood chips were impregnated with the kraft liquor of specific EA and sliced into five layers, each having a thickness of 1 mm. The sodium and hydroxide ion contents in the layers were measured first by emission photometry and then by volumetric titration. These combined methods demonstrated a hydroxide ion consumption of 67%−69% from wood neutralization reactions. A nonlinear model that has a high correlation coefficient (R2 = 96.2%) was developed that described the effects of the operational variables on the sodium hydroxide content (Y) in the chip core (Y = −1.83 + 1.04 × t0.11 × 0.96 × T0.42 × 0.59 × EA0.69 × 0.82 × BD−0.33 + ε, where ε is the random error). A correlation matrix demonstrated that the sodium hydroxide content in the chip core is strongly influenced by the initial EA value. On the other hand, the wood density had a smaller influence. Reaction temperature and time were determined to have an intermediate influence. Neutralization reactions conducted with 40 mesh sawdust (i.e., material that has low physical limitations to impregnation, under the test conditions (60 min at 100 °C and 2% consistency) at different initial alkali concentrations) showed a consumption of 3.8% ± 0.4% of sodium hydroxide by wood weight at the point the alkali concentration tended toward zero. Therefore, it is anticipated that the amount of sodium hydroxide in the wood chip core should be ~3.8% by wood weight to obtain neutralization. From an operational control point of view, this proposed empirical mathematical model may be used to predict different Eucalyptus wood chip impregnation conditions to achieve uniform and selective kraft pulping operations. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071119k
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3856–3860[article] An empirical mathematical model for the predictive analysis of the chemical absorption of hydroxide in eucalyptus wood [texte imprimé] / M. M. Costa, Auteur ; J. L. Gomide, Auteur ; J. L. Colodette, Auteur . - 2008 . - p. 3856–3860.
Bibliogr. p. 3859-3860
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3856–3860
Mots-clés : Basic density Chip impregnation Empirical mathematical modeling Eucalyptus Kraft pulping pulping operational conditions Résumé : Chip steaming, heating, impregnation, and sugar acid neutralization of wood chips by an alkaline kraft liquor during the pretreatment and initial phase of pulping are critical physical−chemical phenomena for executing successful industrial kraft pulping operations. Specifically, these physical and chemical phenomena significantly affect the kraft pulping process performance in terms of chemical mass transfer that influences both delignification rate and the homogeneity of the pulp produced. Detailed fundamental knowledge about the aforementioned phenomena during the initial phase is necessary to obtain selective wood delignification and as a consequence better pulp homogeneities and yield. The present work evaluates the effect of selected critical variables on impregnation and neutralization of Eucalyptus spp wood chips. The independent variables used for this study were as follows: wood basic density (BD), 430, 490, and 550 kg/m3; effective alkali charge (EA), 5%, 9%, and 13% at 25% sulfidity; time (t), 30, 60, and 90 min; and temperature (T), 90, 110, and 130 °C. The wood chips were impregnated with the kraft liquor of specific EA and sliced into five layers, each having a thickness of 1 mm. The sodium and hydroxide ion contents in the layers were measured first by emission photometry and then by volumetric titration. These combined methods demonstrated a hydroxide ion consumption of 67%−69% from wood neutralization reactions. A nonlinear model that has a high correlation coefficient (R2 = 96.2%) was developed that described the effects of the operational variables on the sodium hydroxide content (Y) in the chip core (Y = −1.83 + 1.04 × t0.11 × 0.96 × T0.42 × 0.59 × EA0.69 × 0.82 × BD−0.33 + ε, where ε is the random error). A correlation matrix demonstrated that the sodium hydroxide content in the chip core is strongly influenced by the initial EA value. On the other hand, the wood density had a smaller influence. Reaction temperature and time were determined to have an intermediate influence. Neutralization reactions conducted with 40 mesh sawdust (i.e., material that has low physical limitations to impregnation, under the test conditions (60 min at 100 °C and 2% consistency) at different initial alkali concentrations) showed a consumption of 3.8% ± 0.4% of sodium hydroxide by wood weight at the point the alkali concentration tended toward zero. Therefore, it is anticipated that the amount of sodium hydroxide in the wood chip core should be ~3.8% by wood weight to obtain neutralization. From an operational control point of view, this proposed empirical mathematical model may be used to predict different Eucalyptus wood chip impregnation conditions to achieve uniform and selective kraft pulping operations. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071119k Exemplaires
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Titre : Comparative simulations of cobalt- and iron-based Fischer-Tropsch synthesis slurry bubble column reactors Type de document : texte imprimé Auteurs : I. Iliuta, Auteur ; F. Larachi, Auteur ; J. Anfray, Auteur ; N. Dromard, Auteur Année de publication : 2008 Article en page(s) : p. 3861–3869 Note générale : Bibliogr. p. 3869 Langues : Anglais (eng) Mots-clés : Iron Cobalt Fischer-Tropsch synthesis Résumé : The influence of the catalyst type (Fe and Co) on CO and H2 conversions, CO2 selectivity, and the composition in Fischer-Tropsch synthesis slurry bubble column reactors was simulated for representative commercial-scale units (7 m i.d. and 30 m height). A nonisothermal, core-annulus multicompartment multicomponent two-bubble class model was used to account for a relatively detailed hydrodynamics. It was coupled to comprehensive Fischer-Tropsch synthesis and water−gas-shift reactions, in addition to descriptions of thermodynamics and thermal effects, variable gas flow rate due to chemical/physical contraction, and gas and slurry backmixing and (re)circulation. Two mechanistic kinetic models with consideration of olefin readsorption were employed to describe the paraffin and olefin formation with cobalt- and iron-based catalysts, in addition to relatively large activities for CO2 and oxygenate formation, mainly alcohols, for the latter catalyst. The influence of the temperature and superficial gas velocity on CO and H2 conversions was more evident for a cobalt-based catalyst. For both catalysts, the space-dependent superficial gas velocity directly affected the gas-phase mean residence time, influencing in the return reactor temperature and conversions. Reliable estimation of the gas velocity due to chemical contraction was critical for conversions exceeding 50%. For both catalysts, the nonisothermal simulations reveal that, because heat removal is well managed from the heat-exchange area, the reactor operation can be considered as nearly isothermal. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701764y
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3861–3869[article] Comparative simulations of cobalt- and iron-based Fischer-Tropsch synthesis slurry bubble column reactors [texte imprimé] / I. Iliuta, Auteur ; F. Larachi, Auteur ; J. Anfray, Auteur ; N. Dromard, Auteur . - 2008 . - p. 3861–3869.
Bibliogr. p. 3869
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3861–3869
Mots-clés : Iron Cobalt Fischer-Tropsch synthesis Résumé : The influence of the catalyst type (Fe and Co) on CO and H2 conversions, CO2 selectivity, and the composition in Fischer-Tropsch synthesis slurry bubble column reactors was simulated for representative commercial-scale units (7 m i.d. and 30 m height). A nonisothermal, core-annulus multicompartment multicomponent two-bubble class model was used to account for a relatively detailed hydrodynamics. It was coupled to comprehensive Fischer-Tropsch synthesis and water−gas-shift reactions, in addition to descriptions of thermodynamics and thermal effects, variable gas flow rate due to chemical/physical contraction, and gas and slurry backmixing and (re)circulation. Two mechanistic kinetic models with consideration of olefin readsorption were employed to describe the paraffin and olefin formation with cobalt- and iron-based catalysts, in addition to relatively large activities for CO2 and oxygenate formation, mainly alcohols, for the latter catalyst. The influence of the temperature and superficial gas velocity on CO and H2 conversions was more evident for a cobalt-based catalyst. For both catalysts, the space-dependent superficial gas velocity directly affected the gas-phase mean residence time, influencing in the return reactor temperature and conversions. Reliable estimation of the gas velocity due to chemical contraction was critical for conversions exceeding 50%. For both catalysts, the nonisothermal simulations reveal that, because heat removal is well managed from the heat-exchange area, the reactor operation can be considered as nearly isothermal. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701764y Exemplaires
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Titre : Intensification of catalytic oxidation with a T-junction microchannel reactor for deep desulfurization Type de document : texte imprimé Auteurs : D. Huang, Auteur ; Y. C. Lu, Auteur ; Y. J. Wang, Auteur ; L. Yang, Auteur Année de publication : 2008 Article en page(s) : p. 3870–3875 Note générale : Bibliogr. p. 3874-3875 Langues : Anglais (eng) Mots-clés : Microreactor system Dibenzothiophene Deep desulfurization Résumé : In this paper, a microreactor system is developed to enhance the oxidation of dibenzothiophene (DBT) and 4,6-DMDBT for deep desulfurization with the oxidant of hydrogen peroxide. A T-junction microchannel was applied to form the aqueous slug flow and a long PTFE (polytetrafluoroethylene) capillary with an inner diameter of 1 mm was connected directly downstream to maintain the two-phase dispersion condition. Surfactant of octadecyltrimethyl ammonium bromide (STAB) and phosphotungstic acid (TPA) were mixed in the microchannel to form the combined amphiphilic catalyst directly. The parameters affecting slug formation and DBT oxidation were investigated, including two-phase flow rates, temperature, surfactant type, and catalyst concentrations. DBT conversion of 97% was achieved with a residence time of 1.3 min at 60 °C. Furthermore, 4,6-DMDBT could also be effectively oxidized, and increasing the reaction temperature from 25 to 70 °C led to a substantial increase in 4,6-DMDBT conversions, from 57% at 25 °C to 97% at 70 °C. This T-junction microchannel reactor is far superior to the conventional equipment in terms of providing more interfacial area with much less power input. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701781r
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3870–3875[article] Intensification of catalytic oxidation with a T-junction microchannel reactor for deep desulfurization [texte imprimé] / D. Huang, Auteur ; Y. C. Lu, Auteur ; Y. J. Wang, Auteur ; L. Yang, Auteur . - 2008 . - p. 3870–3875.
Bibliogr. p. 3874-3875
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3870–3875
Mots-clés : Microreactor system Dibenzothiophene Deep desulfurization Résumé : In this paper, a microreactor system is developed to enhance the oxidation of dibenzothiophene (DBT) and 4,6-DMDBT for deep desulfurization with the oxidant of hydrogen peroxide. A T-junction microchannel was applied to form the aqueous slug flow and a long PTFE (polytetrafluoroethylene) capillary with an inner diameter of 1 mm was connected directly downstream to maintain the two-phase dispersion condition. Surfactant of octadecyltrimethyl ammonium bromide (STAB) and phosphotungstic acid (TPA) were mixed in the microchannel to form the combined amphiphilic catalyst directly. The parameters affecting slug formation and DBT oxidation were investigated, including two-phase flow rates, temperature, surfactant type, and catalyst concentrations. DBT conversion of 97% was achieved with a residence time of 1.3 min at 60 °C. Furthermore, 4,6-DMDBT could also be effectively oxidized, and increasing the reaction temperature from 25 to 70 °C led to a substantial increase in 4,6-DMDBT conversions, from 57% at 25 °C to 97% at 70 °C. This T-junction microchannel reactor is far superior to the conventional equipment in terms of providing more interfacial area with much less power input. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701781r Exemplaires
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Titre : Improvement of electrochemical performance of Li[Ni0.8Co0.15Al0.05]O2 cathode materials by AlF3 coating at various temperatures Type de document : texte imprimé Auteurs : Byung-Chun Park, Auteur ; Hyung-Bae Kim, Auteur ; Hyun Joo Bang, Auteur ; Jai Prakash, Auteur Année de publication : 2008 Article en page(s) : p. 3876–3882 Note générale : Bibliogr. p. 3881-3882 Langues : Anglais (eng) Mots-clés : AlF3 coating Electrochemical impedance spectroscopy Résumé : A thin AlF3 layer of ∼10 nm was uniformly coated on the particle surface of Li[Ni0.8Co0.15Al0.05]O2. The AlF3 coating improved cycle performance at 55, 30, and –10 °C and improved storage characteristics at 60 °C. In studies of differential capacity (dQ/dV) versus voltage, the AlF3-coated Li[Ni0.8Co0.15Al0.05]O2 showed little variation in redox peaks with cycling. Electrochemical impedance spectroscopy suggested that the AlF3 coating played an important role in stabilizing the interface between the cathode and the electrolyte. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0715308
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3876–3882[article] Improvement of electrochemical performance of Li[Ni0.8Co0.15Al0.05]O2 cathode materials by AlF3 coating at various temperatures [texte imprimé] / Byung-Chun Park, Auteur ; Hyung-Bae Kim, Auteur ; Hyun Joo Bang, Auteur ; Jai Prakash, Auteur . - 2008 . - p. 3876–3882.
Bibliogr. p. 3881-3882
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3876–3882
Mots-clés : AlF3 coating Electrochemical impedance spectroscopy Résumé : A thin AlF3 layer of ∼10 nm was uniformly coated on the particle surface of Li[Ni0.8Co0.15Al0.05]O2. The AlF3 coating improved cycle performance at 55, 30, and –10 °C and improved storage characteristics at 60 °C. In studies of differential capacity (dQ/dV) versus voltage, the AlF3-coated Li[Ni0.8Co0.15Al0.05]O2 showed little variation in redox peaks with cycling. Electrochemical impedance spectroscopy suggested that the AlF3 coating played an important role in stabilizing the interface between the cathode and the electrolyte. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0715308 Exemplaires
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Titre : Effect of metal salt on the pore structure evolution of pitch-based activated carbon microfibers Type de document : texte imprimé Auteurs : Samir H. Mushrif, Auteur ; Alejandro D. Rey, Auteur Année de publication : 2008 Article en page(s) : p. 3883–3890 Note générale : Bibliogr. p. 3889-3890 Langues : Anglais (eng) Mots-clés : Metal salt Activated carbon fibers Pore structure Barrett− Joyner− Halenda methodology Résumé : The effect of palladium acetylacetonate on the pore structure evolution of isotropic petroleum pitch-based activated carbon fibers (ACFs) is characterized by comparing the pore structure evolution of ACFs that have been prepared from pure pitch and from palladium acetylacetonate-containing pitch. The pore structure was interpreted by applying chi-theory, Brunauer−Emmett−Teller (BET) surface area analysis, Barrett−Joyner−Halenda (BJH) methodology, t-plots, adsorption potential distribution (APD), and nonlocal density functional theory (NL-DFT) to experimental N2 adsorption isotherms. Pore size and pore volume calculations from chi-theory are in agreement with those from APD and NL-DFT, respectively, whereas, those from the BET, BJH, and t-plot methods are not. However, chi-theory underestimates the total surface area. The validated porosity and surface area results, pore size distribution, and APD were then studied as a function of burnoff value. The pore structure evolution analysis of both types of ACFs showed that the addition of palladium acetylacetonate to the pitch, prior to fiber formation, causes (i) the formation of macropores, (ii) a small increase in microporosity during the early stages of activation, and (iii) increased mesoporosity at burnoff values of >60%. The presented data and analysis provide a new understanding of the porous structure of novel pitch-based activated carbon adsorbents and potential hydrogen storage materials. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0712784
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3883–3890[article] Effect of metal salt on the pore structure evolution of pitch-based activated carbon microfibers [texte imprimé] / Samir H. Mushrif, Auteur ; Alejandro D. Rey, Auteur . - 2008 . - p. 3883–3890.
Bibliogr. p. 3889-3890
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3883–3890
Mots-clés : Metal salt Activated carbon fibers Pore structure Barrett− Joyner− Halenda methodology Résumé : The effect of palladium acetylacetonate on the pore structure evolution of isotropic petroleum pitch-based activated carbon fibers (ACFs) is characterized by comparing the pore structure evolution of ACFs that have been prepared from pure pitch and from palladium acetylacetonate-containing pitch. The pore structure was interpreted by applying chi-theory, Brunauer−Emmett−Teller (BET) surface area analysis, Barrett−Joyner−Halenda (BJH) methodology, t-plots, adsorption potential distribution (APD), and nonlocal density functional theory (NL-DFT) to experimental N2 adsorption isotherms. Pore size and pore volume calculations from chi-theory are in agreement with those from APD and NL-DFT, respectively, whereas, those from the BET, BJH, and t-plot methods are not. However, chi-theory underestimates the total surface area. The validated porosity and surface area results, pore size distribution, and APD were then studied as a function of burnoff value. The pore structure evolution analysis of both types of ACFs showed that the addition of palladium acetylacetonate to the pitch, prior to fiber formation, causes (i) the formation of macropores, (ii) a small increase in microporosity during the early stages of activation, and (iii) increased mesoporosity at burnoff values of >60%. The presented data and analysis provide a new understanding of the porous structure of novel pitch-based activated carbon adsorbents and potential hydrogen storage materials. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0712784 Exemplaires
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Titre : Composites of polypropylene with layered Mg-silsesquioxanes show an unusual combination of properties Type de document : texte imprimé Auteurs : Guruswamy Kumaraswamy, Auteur ; Yogesh S. Deshmukh, Auteur ; Vishal V. Agrawal, Auteur ; Anuya A. Nisal, Auteur Année de publication : 2008 Article en page(s) : p. 3891–3899 Note générale : Bibliogr. p. 3898-3899 Langues : Anglais (eng) Mots-clés : Magnesium silsesqiuoxanes Isotactic polypropylene Melt compounding Résumé : We report the synthesis of vinyl modified magnesium silsesqiuoxanes (“vinyl clay”), and the formation of their composites with isotactic polypropylene (iPP) by melt compounding. Vinyl clay is a layered compound with a layer thickness of approximately 1 nm. Vinyl clay does not exfoliate in iPP; rather, it disperses to form a network that exhibits a characteristic low frequency solid-like plateau in the elastic modulus in dynamic melt rheological measurements. Strangely, vinyl clay also plasticizes iPP—there is a decrease in the high frequency complex viscosity. The decrease in the complex viscosity is higher at higher frequencies, suggesting the influence of slip at the iPP−vinyl clay interface. The combination of the low frequency elastic plateau and plasticization makes the vinyl clay composite significantly more shear thinning than the matrix iPP. In the solid state, vinyl clay−iPP composites exhibit increased tensile modulus (showing ≈50% increase for a 5% loading), but surprisingly, no corresponding decrease in the elongation at break. Thus, while microstructural characterization indicates that only a small fraction, if any, of the vinyl clay is exfoliated, the enhancement in mechanical properties is similar to that observed for iPP-exfoliated montmorillonite nanocomposites. Our compounding protocol is unable to effectively disperse the clay in the iPP at clay loadings greater than about 7.5%. Therefore, the low frequency plateau in the melt elastic modulus and the solid tensile modulus increase with clay loading until 7.5% but exhibit a nonmonotonic decrease at higher clay loadings. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071658p
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3891–3899[article] Composites of polypropylene with layered Mg-silsesquioxanes show an unusual combination of properties [texte imprimé] / Guruswamy Kumaraswamy, Auteur ; Yogesh S. Deshmukh, Auteur ; Vishal V. Agrawal, Auteur ; Anuya A. Nisal, Auteur . - 2008 . - p. 3891–3899.
Bibliogr. p. 3898-3899
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3891–3899
Mots-clés : Magnesium silsesqiuoxanes Isotactic polypropylene Melt compounding Résumé : We report the synthesis of vinyl modified magnesium silsesqiuoxanes (“vinyl clay”), and the formation of their composites with isotactic polypropylene (iPP) by melt compounding. Vinyl clay is a layered compound with a layer thickness of approximately 1 nm. Vinyl clay does not exfoliate in iPP; rather, it disperses to form a network that exhibits a characteristic low frequency solid-like plateau in the elastic modulus in dynamic melt rheological measurements. Strangely, vinyl clay also plasticizes iPP—there is a decrease in the high frequency complex viscosity. The decrease in the complex viscosity is higher at higher frequencies, suggesting the influence of slip at the iPP−vinyl clay interface. The combination of the low frequency elastic plateau and plasticization makes the vinyl clay composite significantly more shear thinning than the matrix iPP. In the solid state, vinyl clay−iPP composites exhibit increased tensile modulus (showing ≈50% increase for a 5% loading), but surprisingly, no corresponding decrease in the elongation at break. Thus, while microstructural characterization indicates that only a small fraction, if any, of the vinyl clay is exfoliated, the enhancement in mechanical properties is similar to that observed for iPP-exfoliated montmorillonite nanocomposites. Our compounding protocol is unable to effectively disperse the clay in the iPP at clay loadings greater than about 7.5%. Therefore, the low frequency plateau in the melt elastic modulus and the solid tensile modulus increase with clay loading until 7.5% but exhibit a nonmonotonic decrease at higher clay loadings. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071658p Exemplaires
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Titre : Co-precipitation of β-carotene and polyethylene glycol with compressed CO2 as an antisolvent : effect of temperature and concentration Type de document : texte imprimé Auteurs : Facundo Mattea, Auteur ; Angel Martin, Auteur ; Maria J. Cocero, Auteur Année de publication : 2008 Article en page(s) : p. 3900–3906 Note générale : Bibliogr. p. 3906 Langues : Anglais (eng) Mots-clés : β -carotene Polyethylene glycol X-ray diffraction Differential scanning calorimetry Scanning electron microscopy Résumé : In this work, the coprecipitation of β-carotene and polyethylene glycol (PEG) is studied. First, the effect of pressure and temperature was studied (pressures of 8−12 MPa, temperatures of 288−313 K), Afterward, the effect of the initial concentration of the different substances on the morphologies of the particles was studied. X-ray diffraction (XRD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) analysis were used to observe the nature of the particles that were obtained. The results indicated the sensitivity of the precipitation to temperature, making impossible to obtain particles at temperatures above 288 K. With regard to the concentration effect on the morphology of the particles, it was possible to obtain different morphologies just by changing the concentration ratio between the substances. Also, the analysis of the coprecipitates indicated that the β-carotene inside the polymer matrix must be in an amorphous form. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071326k
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3900–3906[article] Co-precipitation of β-carotene and polyethylene glycol with compressed CO2 as an antisolvent : effect of temperature and concentration [texte imprimé] / Facundo Mattea, Auteur ; Angel Martin, Auteur ; Maria J. Cocero, Auteur . - 2008 . - p. 3900–3906.
Bibliogr. p. 3906
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3900–3906
Mots-clés : β -carotene Polyethylene glycol X-ray diffraction Differential scanning calorimetry Scanning electron microscopy Résumé : In this work, the coprecipitation of β-carotene and polyethylene glycol (PEG) is studied. First, the effect of pressure and temperature was studied (pressures of 8−12 MPa, temperatures of 288−313 K), Afterward, the effect of the initial concentration of the different substances on the morphologies of the particles was studied. X-ray diffraction (XRD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) analysis were used to observe the nature of the particles that were obtained. The results indicated the sensitivity of the precipitation to temperature, making impossible to obtain particles at temperatures above 288 K. With regard to the concentration effect on the morphology of the particles, it was possible to obtain different morphologies just by changing the concentration ratio between the substances. Also, the analysis of the coprecipitates indicated that the β-carotene inside the polymer matrix must be in an amorphous form. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071326k Exemplaires
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Titre : Real-time end-point detection using modified principal component analysis for small open area SiO2 plasma etching Type de document : texte imprimé Auteurs : Kyounghoon Han, Auteur ; En Sup Yoon, Auteur Année de publication : 2008 Article en page(s) : p. 3907–3911 Note générale : Bibliogr. p. 3911 Langues : Anglais (eng) Mots-clés : PCA algorithm End-point detection SiO2 etching Résumé : Principal component analysis (PCA) was modified for real-time applications and applied to the end-point detection of small open area SiO2 plasma etching. Typically, the end point of plasma etching is determined from a few manually selected wavelengths. Determining the end point of the plasma etching using this approach is quite a challenge when the exposed open area is less than several percent. To increase the sensitivity, information was extracted from the entire spectra of 2755 signals in the range of 200−1100 nm, using a PCA algorithm. In this study, the PCA algorithm was modified to allow real-time applications of end-point detection. The loading vector was determined from the model wafer, and the score vector was determined using the real-time data of the target wafer to reduce the processing time. This algorithm was tested for the small open area of SiO2 etching of a 200 ms sampling period, using the entire optical emission spectra, through a comparison with a defined signal-to-noise ratio. The results were compared with the conventional single wavelength signals of SiF (440.2 nm), CO (482.5 nm), and Si (505.6 nm). The end-point detection of 0.4%−0.8% SiO2 open area was achieved using the suggested algorithm, while the single wavelength showed limitations in the open areas above a few percent. The sensitivity was also increased by a factor of 2.15, compared to the signal-to-noise ratio of the single wavelength method. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070930s
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3907–3911[article] Real-time end-point detection using modified principal component analysis for small open area SiO2 plasma etching [texte imprimé] / Kyounghoon Han, Auteur ; En Sup Yoon, Auteur . - 2008 . - p. 3907–3911.
Bibliogr. p. 3911
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3907–3911
Mots-clés : PCA algorithm End-point detection SiO2 etching Résumé : Principal component analysis (PCA) was modified for real-time applications and applied to the end-point detection of small open area SiO2 plasma etching. Typically, the end point of plasma etching is determined from a few manually selected wavelengths. Determining the end point of the plasma etching using this approach is quite a challenge when the exposed open area is less than several percent. To increase the sensitivity, information was extracted from the entire spectra of 2755 signals in the range of 200−1100 nm, using a PCA algorithm. In this study, the PCA algorithm was modified to allow real-time applications of end-point detection. The loading vector was determined from the model wafer, and the score vector was determined using the real-time data of the target wafer to reduce the processing time. This algorithm was tested for the small open area of SiO2 etching of a 200 ms sampling period, using the entire optical emission spectra, through a comparison with a defined signal-to-noise ratio. The results were compared with the conventional single wavelength signals of SiF (440.2 nm), CO (482.5 nm), and Si (505.6 nm). The end-point detection of 0.4%−0.8% SiO2 open area was achieved using the suggested algorithm, while the single wavelength showed limitations in the open areas above a few percent. The sensitivity was also increased by a factor of 2.15, compared to the signal-to-noise ratio of the single wavelength method. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070930s Exemplaires
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Titre : Robust optimization for petrochemical network design under uncertainty Type de document : texte imprimé Auteurs : K. Al-Qahtani, Auteur ; A. Elkamel, Auteur ; K. Ponnambalam, Auteur Année de publication : 2008 Article en page(s) : p. 3912–3919 Note générale : Bibliogr. p. 3918-3919 Langues : Anglais (eng) Mots-clés : Petrochemical network Two-stage stochastic MINLP Résumé : This paper addresses the strategic planning, design, and optimization of a network of petrochemical processes under uncertainty and risk considerations. In this work, we extend the deterministic model proposed by Al-Sharrah et al. [Ind. Eng. Chem. Res. 2001, 40, 2103; Chem. Eng. Res. Des. 2006, 84, 1019] to account for parameter uncertainty in process yield, raw material cost, product prices, and lower product market demand. The problem was formulated as a two-stage stochastic mixed-integer nonlinear programming model (MINLP). Risk was accounted for in terms of deviation in both projected benefits in the first stage variables and process yield and forecasted demand in terms of the recourse variables. For each term, a different scaling factor was used to analyze the sensitivity of the petrochemical network due to variations of each component. The study showed that the final petrochemical network bears more sensitivity to variations in product demand and process yields for scaling parameters values that maintain the final petrochemical structure obtained form the stochastic model. The concept of expected value of perfect information (EVPI) and value of the stochastic solution (VSS) are also investigated to numerically illustrate the value of including the randomness of the different model parameters. Modeling uncertainty in the process parameters provided a more robust analysis and practical perspective of this type of problem in the chemical industry. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0713184
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3912–3919[article] Robust optimization for petrochemical network design under uncertainty [texte imprimé] / K. Al-Qahtani, Auteur ; A. Elkamel, Auteur ; K. Ponnambalam, Auteur . - 2008 . - p. 3912–3919.
Bibliogr. p. 3918-3919
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3912–3919
Mots-clés : Petrochemical network Two-stage stochastic MINLP Résumé : This paper addresses the strategic planning, design, and optimization of a network of petrochemical processes under uncertainty and risk considerations. In this work, we extend the deterministic model proposed by Al-Sharrah et al. [Ind. Eng. Chem. Res. 2001, 40, 2103; Chem. Eng. Res. Des. 2006, 84, 1019] to account for parameter uncertainty in process yield, raw material cost, product prices, and lower product market demand. The problem was formulated as a two-stage stochastic mixed-integer nonlinear programming model (MINLP). Risk was accounted for in terms of deviation in both projected benefits in the first stage variables and process yield and forecasted demand in terms of the recourse variables. For each term, a different scaling factor was used to analyze the sensitivity of the petrochemical network due to variations of each component. The study showed that the final petrochemical network bears more sensitivity to variations in product demand and process yields for scaling parameters values that maintain the final petrochemical structure obtained form the stochastic model. The concept of expected value of perfect information (EVPI) and value of the stochastic solution (VSS) are also investigated to numerically illustrate the value of including the randomness of the different model parameters. Modeling uncertainty in the process parameters provided a more robust analysis and practical perspective of this type of problem in the chemical industry. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0713184 Exemplaires
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Titre : Numerical bifurcation analysis of delay in a coupled reactor separator system Type de document : texte imprimé Auteurs : P. Balasubramanian, Auteur Année de publication : 2008 Article en page(s) : p. 3920–3929 Note générale : Bibliogr. p. 3928-3929 Langues : Anglais (eng) Mots-clés : Coupled reactor separator system DDE-BIFTOOL software package Delay arising Résumé : The effect of delay on the stability of a coupled reactor separator system is investigated in this work, using the DDE-BIFTOOL software package. The reactor considered is a continuously stirred tank reactor (CSTR), and the separator is modeled as a flash unit operating isothermally and isobarically. A first-order isothermal irreversible reaction A → B is considered to investigate the effect of delay arising as a result of transportation lag from the CSTR to the flash. The dynamic behavior of the coupled CSTR−flash system is governed by the delay differential equations. In this work, the dynamic instability induced by delay that is crucially dependent on the flow control strategy of the system is investigated using DDE-BIFTOOL. It is shown that delay can destabilize the steady state of the coupled system when the reactor effluent flow rate F is flow-controlled, and the molar holdup MR in the reactor is allowed to vary. When the fresh feed flow rate F0 is flow-controlled, the system exhibits delay-independent stability. The critical delay and frequency of oscillation obtained using DDE-BIFTOOL show good agreement with the same obtained using the analytical expressions proposed in the literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071010c
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3920–3929[article] Numerical bifurcation analysis of delay in a coupled reactor separator system [texte imprimé] / P. Balasubramanian, Auteur . - 2008 . - p. 3920–3929.
Bibliogr. p. 3928-3929
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3920–3929
Mots-clés : Coupled reactor separator system DDE-BIFTOOL software package Delay arising Résumé : The effect of delay on the stability of a coupled reactor separator system is investigated in this work, using the DDE-BIFTOOL software package. The reactor considered is a continuously stirred tank reactor (CSTR), and the separator is modeled as a flash unit operating isothermally and isobarically. A first-order isothermal irreversible reaction A → B is considered to investigate the effect of delay arising as a result of transportation lag from the CSTR to the flash. The dynamic behavior of the coupled CSTR−flash system is governed by the delay differential equations. In this work, the dynamic instability induced by delay that is crucially dependent on the flow control strategy of the system is investigated using DDE-BIFTOOL. It is shown that delay can destabilize the steady state of the coupled system when the reactor effluent flow rate F is flow-controlled, and the molar holdup MR in the reactor is allowed to vary. When the fresh feed flow rate F0 is flow-controlled, the system exhibits delay-independent stability. The critical delay and frequency of oscillation obtained using DDE-BIFTOOL show good agreement with the same obtained using the analytical expressions proposed in the literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071010c Exemplaires
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Titre : Estimation of still trajectory for batch reactive distillation systems Type de document : texte imprimé Auteurs : James Chin, Auteur ; Jae W. Lee, Auteur Année de publication : 2008 Article en page(s) : p. 3930–3936 Note générale : Bibliogr. p. 3936 Langues : Anglais (eng) Mots-clés : Liquid still trajectory Batch reactive distillation Résumé : This work addresses a new method for estimating the liquid still composition trajectory of batch reactive distillation systems based on material balance and reaction equilibrium data. The still trajectory information is essential to determining whether pure products are reachable from this still pot trajectory when several distillation boundaries are present, initial feed compositions can vary, and the number of components exceeds our visualization capability. For a given feed to product flow ratio with constant feed charge and product compositions, the still pot composition trajectory is mathematically confined to the intersection between the reaction equilibrium manifold and a “material balance plane” that is the union of stoichiometric lines and material balance rays connecting still and product compositions. Starting from this estimated still pot trajectory, we can easily extend feasibility studies of various batch reactive distillation configurations even for multireaction systems. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0713947
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3930–3936[article] Estimation of still trajectory for batch reactive distillation systems [texte imprimé] / James Chin, Auteur ; Jae W. Lee, Auteur . - 2008 . - p. 3930–3936.
Bibliogr. p. 3936
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3930–3936
Mots-clés : Liquid still trajectory Batch reactive distillation Résumé : This work addresses a new method for estimating the liquid still composition trajectory of batch reactive distillation systems based on material balance and reaction equilibrium data. The still trajectory information is essential to determining whether pure products are reachable from this still pot trajectory when several distillation boundaries are present, initial feed compositions can vary, and the number of components exceeds our visualization capability. For a given feed to product flow ratio with constant feed charge and product compositions, the still pot composition trajectory is mathematically confined to the intersection between the reaction equilibrium manifold and a “material balance plane” that is the union of stoichiometric lines and material balance rays connecting still and product compositions. Starting from this estimated still pot trajectory, we can easily extend feasibility studies of various batch reactive distillation configurations even for multireaction systems. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0713947 Exemplaires
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Titre : Transfer units approach to the fricdiff separation process Type de document : texte imprimé Auteurs : E. A. J. F. Peters, Auteur ; B. Breure, Auteur ; P. van den Heuvel, Auteur ; P. J. A. M. Kerkhof, Auteur Année de publication : 2008 Article en page(s) : p. 3937–3942 Note générale : Bibliogr. p. 3942 Langues : Anglais (eng) Mots-clés : FricDiff separation Feed-side Sweep-side Gas mixture Résumé : FricDiff (friction difference) is a recently introduced separation technology. The separation occurs because of differences in interspecies friction in a multicomponent mixture. We present a description of a FricDiff unit. Such a unit consists of two compartments, the feed-side and the sweep-side, with a porous screen in between. The gas mixtures at the feed-side and the sweep gas interdiffuse through the screen. The basic modeling assumption is that the binary interaction of each feed-component with a counterflowing sweep gas is dominant. The interaction between the components diffusing in the same direction is neglected. This assumption leads us to introduce the number of “binary transfer units”. We show that more detailed models introduced earlier are approximated well by this approach. Also, experiments seem to exhibit the same scaling, although the constants needed to fit the experimental results deviate quite a lot from the theoretical predictions. The equations derived can be used straightforwardly for incorporating a FricDiff unit in a process design. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071395z
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3937–3942[article] Transfer units approach to the fricdiff separation process [texte imprimé] / E. A. J. F. Peters, Auteur ; B. Breure, Auteur ; P. van den Heuvel, Auteur ; P. J. A. M. Kerkhof, Auteur . - 2008 . - p. 3937–3942.
Bibliogr. p. 3942
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3937–3942
Mots-clés : FricDiff separation Feed-side Sweep-side Gas mixture Résumé : FricDiff (friction difference) is a recently introduced separation technology. The separation occurs because of differences in interspecies friction in a multicomponent mixture. We present a description of a FricDiff unit. Such a unit consists of two compartments, the feed-side and the sweep-side, with a porous screen in between. The gas mixtures at the feed-side and the sweep gas interdiffuse through the screen. The basic modeling assumption is that the binary interaction of each feed-component with a counterflowing sweep gas is dominant. The interaction between the components diffusing in the same direction is neglected. This assumption leads us to introduce the number of “binary transfer units”. We show that more detailed models introduced earlier are approximated well by this approach. Also, experiments seem to exhibit the same scaling, although the constants needed to fit the experimental results deviate quite a lot from the theoretical predictions. The equations derived can be used straightforwardly for incorporating a FricDiff unit in a process design. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071395z Exemplaires
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Titre : Characterizing nonzeolitic pores in MFI membranes Type de document : texte imprimé Auteurs : Yu Miao, Auteur ; Falconer, John L., Auteur ; Richard D. Noble, Auteur Année de publication : 2008 Article en page(s) : p. 3943–3948 Note générale : Bibliogr. p. 3947-3948 Langues : Anglais (eng) Mots-clés : n-hexane MFI zeolite membranes Résumé : Methods that use n-hexane (n-hexane permporosimetry and n-hexane/2,2-dimethylybutane (DMB) separation) are shown to not be effective for characterizing MFI zeolite membranes because n-hexane adsorption swells MFI crystals and shrinks the size of nonzeolitic pores. Measurements on a membrane in which 30% of its helium flux at 300 K was through nonzeolitic pores demonstrate that benzene permporosimetry and isooctane vapor permeation as a function of feed activity provide better characterizations. Isooctane condensed in nonzeolitic pores at high activities, and this was used to estimate the sizes of those pores. The average nonzeolitic pore size in this membrane decreased from approximately 3.0 to 1.5 nm as the temperature increased from 300 to 348 K, apparently due to thermal expansion of MFI crystals. Benzene permporosimetry yielded dramatically different results from n-hexane permporosimetry because benzene does not swell the MFI crystals significantly. Single-component pervaporation fluxes as a function of molecular kinetic diameter verified the results from benzene permporosimetry. Larger molecules had higher fluxes than n-hexane because they diffused through nonzeolitic pores that were shrunk by n-hexane adsorption. Nonzeolitic pores were estimated to account for only 0.5% of the membrane permeation area, but 30% of the helium flux, because these pores were significantly larger than MFI pores. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071577t
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3943–3948[article] Characterizing nonzeolitic pores in MFI membranes [texte imprimé] / Yu Miao, Auteur ; Falconer, John L., Auteur ; Richard D. Noble, Auteur . - 2008 . - p. 3943–3948.
Bibliogr. p. 3947-3948
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3943–3948
Mots-clés : n-hexane MFI zeolite membranes Résumé : Methods that use n-hexane (n-hexane permporosimetry and n-hexane/2,2-dimethylybutane (DMB) separation) are shown to not be effective for characterizing MFI zeolite membranes because n-hexane adsorption swells MFI crystals and shrinks the size of nonzeolitic pores. Measurements on a membrane in which 30% of its helium flux at 300 K was through nonzeolitic pores demonstrate that benzene permporosimetry and isooctane vapor permeation as a function of feed activity provide better characterizations. Isooctane condensed in nonzeolitic pores at high activities, and this was used to estimate the sizes of those pores. The average nonzeolitic pore size in this membrane decreased from approximately 3.0 to 1.5 nm as the temperature increased from 300 to 348 K, apparently due to thermal expansion of MFI crystals. Benzene permporosimetry yielded dramatically different results from n-hexane permporosimetry because benzene does not swell the MFI crystals significantly. Single-component pervaporation fluxes as a function of molecular kinetic diameter verified the results from benzene permporosimetry. Larger molecules had higher fluxes than n-hexane because they diffused through nonzeolitic pores that were shrunk by n-hexane adsorption. Nonzeolitic pores were estimated to account for only 0.5% of the membrane permeation area, but 30% of the helium flux, because these pores were significantly larger than MFI pores. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071577t Exemplaires
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Titre : Stirring-assisted cloud-point extraction of polycyclic aromatic hydrocarbons Type de document : texte imprimé Auteurs : BingJia Yao, Auteur ; Li Yang, Auteur Année de publication : 2008 Article en page(s) : p. 3949–3956 Note générale : Bibliogr. p. 3955-3956 Langues : Anglais (eng) Mots-clés : CPE process Stirring rate Polycyclic aromatic hydrocarbons Résumé : A novel cloud-point extraction (CPE) process, namely, stirring-assisted cloud-point extraction (S-CPE), was developed with a stirring rate over 380 rpm in a PEG/PPG-18-18 dimethicone aqueous solution at a temperature over its cloud point. Compared with a general CPE process with centrifugation (C-CPE), the stirring process successfully accelerated the phase separation, where the whole process was able to be finished in 15 min and a lower water content in the surfactant-rich phase was also obtained, e.g., the water content was as low as 52 wt % at a 2 wt % surfactant solution, indicating a higher resulting distribution coefficient. The phase separation of the process was studied with dynamic lighting scattering. Because of the increasing contact chances between micelles and extractable species, the stirring operation is also in favor to increase the extractability of the CPE process, where higher recoveries of polycyclic aromatic hydrocarbons (PAHs) were obtained even with a lower surfactant concentration, e.g., a 98.9% recovery of anthracene was obtained in a 1 wt % surfactant solution. What is more important is that the stirring operation is suitable for a scaling-up process, and the surfactant-rich phase floating upon the solution is more easily collected and removed. In addition, the extractant used in the S-CPE, PEG/PPG-18-18 dimethicone, has little UV absorbance, avoiding the disturbance to the signal of PAHs in UV or fluorescence detector, so it is convenient to determine PAHs concentration in every phase during S-CPE process by high-performance liquid chromatography (HPLC) directly. The stirring operation successfully avoids the low phase-separation efficiency like in the CPE process with heating and has no treatment capacity limitation like in C-CPE. Therefore, S-CPE offers an efficient possibility for scaling up a typical CPE process to be applied in the separation of PAHs in the water treatment.
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3949–3956[article] Stirring-assisted cloud-point extraction of polycyclic aromatic hydrocarbons [texte imprimé] / BingJia Yao, Auteur ; Li Yang, Auteur . - 2008 . - p. 3949–3956.
Bibliogr. p. 3955-3956
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3949–3956
Mots-clés : CPE process Stirring rate Polycyclic aromatic hydrocarbons Résumé : A novel cloud-point extraction (CPE) process, namely, stirring-assisted cloud-point extraction (S-CPE), was developed with a stirring rate over 380 rpm in a PEG/PPG-18-18 dimethicone aqueous solution at a temperature over its cloud point. Compared with a general CPE process with centrifugation (C-CPE), the stirring process successfully accelerated the phase separation, where the whole process was able to be finished in 15 min and a lower water content in the surfactant-rich phase was also obtained, e.g., the water content was as low as 52 wt % at a 2 wt % surfactant solution, indicating a higher resulting distribution coefficient. The phase separation of the process was studied with dynamic lighting scattering. Because of the increasing contact chances between micelles and extractable species, the stirring operation is also in favor to increase the extractability of the CPE process, where higher recoveries of polycyclic aromatic hydrocarbons (PAHs) were obtained even with a lower surfactant concentration, e.g., a 98.9% recovery of anthracene was obtained in a 1 wt % surfactant solution. What is more important is that the stirring operation is suitable for a scaling-up process, and the surfactant-rich phase floating upon the solution is more easily collected and removed. In addition, the extractant used in the S-CPE, PEG/PPG-18-18 dimethicone, has little UV absorbance, avoiding the disturbance to the signal of PAHs in UV or fluorescence detector, so it is convenient to determine PAHs concentration in every phase during S-CPE process by high-performance liquid chromatography (HPLC) directly. The stirring operation successfully avoids the low phase-separation efficiency like in the CPE process with heating and has no treatment capacity limitation like in C-CPE. Therefore, S-CPE offers an efficient possibility for scaling up a typical CPE process to be applied in the separation of PAHs in the water treatment. Exemplaires
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Titre : Arsenate removal from aqueous media by nanosized hydrated ferric oxide (HFO)-loaded polymeric sorbents : effect of HFO loadings Type de document : texte imprimé Auteurs : Qingjian Zhang, Auteur ; Bingcai Pan, Auteur ; Weiming Zhang, Auteur ; Bingjun Pan, Auteur Année de publication : 2008 Article en page(s) : p. 3957–3962 Note générale : Bibliogr. p. 3961-3962 Langues : Anglais (eng) Mots-clés : HFO Arsenate sorption Aqueous solution Résumé : Hydrated ferric oxide-loaded hybrid sorbents are of considerable concern for arsenic removal from waters. In the current study, several nanosized hydrated ferric oxide (HFO)-loaded polymer sorbents were prepared and assayed to examine the effect of HFO loadings on arsenate sorption from aqueous solution. Batch and column sorption studies showed that the sorption capacity of arsenate increased with the increase of HFO loadings from 3 to 15% (in Fe mass); however, a further increase in the HFO loadings resulted in a dramatic decrease of the sorption capacity. At relatively low arsenate levels (e.g., En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800275k
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3957–3962[article] Arsenate removal from aqueous media by nanosized hydrated ferric oxide (HFO)-loaded polymeric sorbents : effect of HFO loadings [texte imprimé] / Qingjian Zhang, Auteur ; Bingcai Pan, Auteur ; Weiming Zhang, Auteur ; Bingjun Pan, Auteur . - 2008 . - p. 3957–3962.
Bibliogr. p. 3961-3962
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3957–3962
Mots-clés : HFO Arsenate sorption Aqueous solution Résumé : Hydrated ferric oxide-loaded hybrid sorbents are of considerable concern for arsenic removal from waters. In the current study, several nanosized hydrated ferric oxide (HFO)-loaded polymer sorbents were prepared and assayed to examine the effect of HFO loadings on arsenate sorption from aqueous solution. Batch and column sorption studies showed that the sorption capacity of arsenate increased with the increase of HFO loadings from 3 to 15% (in Fe mass); however, a further increase in the HFO loadings resulted in a dramatic decrease of the sorption capacity. At relatively low arsenate levels (e.g., En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800275k Exemplaires
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Titre : Validation of activity coefficient models using resonances in light scattering from evaporating multicomponent droplets Type de document : texte imprimé Auteurs : HaoHua Tu, Auteur ; Asit K. Ray, Auteur Année de publication : 2008 Article en page(s) : p. 3963–3973 Note générale : Bibliogr. p. 6372-6374 Langues : Anglais (eng) Mots-clés : Light scattering spectra Multicomponent droplet Résumé : We present a technique for determining parameters of any activity coefficient model from the times at which resonances appear in light scattering spectra from an evaporating multicomponent droplet of known initial composition. Using individual component droplet evaporation data along with assumed values for the parameters of a chosen activity coefficient model, the size and the composition of the droplet as functions of time are theoretically predicted, and the times at which resonances appear are calculated from Mie theory. By minimizing the errors between the calculated and observed resonance appearance times, the optimum parameter values of the activity coefficient model are established. The technique has been applied to examine binary and ternary systems consisting of diethyl phthalate, dipropyl phthalate, and dimethyl phthalate. In addition, the technique has been validated by comparing the prediction from the optimum parameter values with independently determined activity coefficient data for binary mixtures of dioctyl phthalate and dimethyl phthalate. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070851g
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3963–3973[article] Validation of activity coefficient models using resonances in light scattering from evaporating multicomponent droplets [texte imprimé] / HaoHua Tu, Auteur ; Asit K. Ray, Auteur . - 2008 . - p. 3963–3973.
Bibliogr. p. 6372-6374
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3963–3973
Mots-clés : Light scattering spectra Multicomponent droplet Résumé : We present a technique for determining parameters of any activity coefficient model from the times at which resonances appear in light scattering spectra from an evaporating multicomponent droplet of known initial composition. Using individual component droplet evaporation data along with assumed values for the parameters of a chosen activity coefficient model, the size and the composition of the droplet as functions of time are theoretically predicted, and the times at which resonances appear are calculated from Mie theory. By minimizing the errors between the calculated and observed resonance appearance times, the optimum parameter values of the activity coefficient model are established. The technique has been applied to examine binary and ternary systems consisting of diethyl phthalate, dipropyl phthalate, and dimethyl phthalate. In addition, the technique has been validated by comparing the prediction from the optimum parameter values with independently determined activity coefficient data for binary mixtures of dioctyl phthalate and dimethyl phthalate. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070851g Exemplaires
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Titre : Liquid backmixing and particle distribution in a novel multistage internal-loop airlift slurry reactor Type de document : texte imprimé Auteurs : Wei Yu, Auteur ; Tiefeng Wang, Auteur ; Malin Liu, Auteur ; Zhanwen Wang, Auteur Année de publication : 2008 Article en page(s) : p. 3974–3982 Note générale : Bibliogr. p. 3982 Langues : Anglais (eng) Mots-clés : Liquid backmixing Interstage internals Axial distribution Résumé : The control of liquid backmixing is an important issue in reactor design for processes with high conversions. In this work, interstage internals were used in a novel multistage internal-loop airlift slurry reactor to decrease backmixing in the liquid phase. Two types of interstage internals, namely, Internal I (perforated plate) and Internal II (perforated plate with tubes) were investigated. The axial distributions of the solid particles inside each stage and between different stages were measured with a sampling method. Interstage liquid backmixing was measured with two electrical conductivity probes using the tracing method. The effects of the structure of the interstage internal, superficial gas and liquid velocities, and particle size on interstage liquid backmixing and the distribution of solid particles were investigated. The superficial liquid velocity had more effect on interstage liquid backmixing than the superficial gas velocity. Backmixing in the liquid phase became negligible when the superficial liquid velocity exceeded a small critical value. Internal II, which was specially designed for this work, was better than the perforated plate for the uniform distribution of solid particles in the different stages. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071100h
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3974–3982[article] Liquid backmixing and particle distribution in a novel multistage internal-loop airlift slurry reactor [texte imprimé] / Wei Yu, Auteur ; Tiefeng Wang, Auteur ; Malin Liu, Auteur ; Zhanwen Wang, Auteur . - 2008 . - p. 3974–3982.
Bibliogr. p. 3982
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3974–3982
Mots-clés : Liquid backmixing Interstage internals Axial distribution Résumé : The control of liquid backmixing is an important issue in reactor design for processes with high conversions. In this work, interstage internals were used in a novel multistage internal-loop airlift slurry reactor to decrease backmixing in the liquid phase. Two types of interstage internals, namely, Internal I (perforated plate) and Internal II (perforated plate with tubes) were investigated. The axial distributions of the solid particles inside each stage and between different stages were measured with a sampling method. Interstage liquid backmixing was measured with two electrical conductivity probes using the tracing method. The effects of the structure of the interstage internal, superficial gas and liquid velocities, and particle size on interstage liquid backmixing and the distribution of solid particles were investigated. The superficial liquid velocity had more effect on interstage liquid backmixing than the superficial gas velocity. Backmixing in the liquid phase became negligible when the superficial liquid velocity exceeded a small critical value. Internal II, which was specially designed for this work, was better than the perforated plate for the uniform distribution of solid particles in the different stages. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071100h Exemplaires
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Titre : Freezing point depression of electrolyte solutions : experimental measurements and modeling using the cubic-plus-association equation of state Type de document : texte imprimé Auteurs : Hooman Haghighi, Auteur ; Antonin Chapoy, Auteur ; Bahman Tohidi, Auteur Année de publication : 2008 Article en page(s) : p. 3983–3989 Note générale : Bibliogr. p. 3988-3989 Langues : Anglais (eng) Mots-clés : Electrolyte solutions Freezing point depressions Résumé : New experimental freezing point depressions of six binary solutions (H2O−NaCl, H2O−CaCl2, H2O−MgCl2, H2O−KOH, H2O−ZnCl2, and H2O−ZnBr2) and four ternary solutions (H2O−NaC1−KCl, H2O−NaC1−CaCl2, H2O−KC1−CaCl2, and H2O−NaC1−MgCl2) have been measured by a reliable differential temperature technique. The available experimental literature data on the freezing point depression in addition to the vapor pressure data of aqueous electrolyte solutions for NaCl, KCl, KOH, CaCl2, MgCl2, CaBr2, ZnCl2, and ZnBr2 have been used to optimize binary interaction parameters between salts and water. The fugacity of water in salt-free aqueous phase has been modeled by the cubic-plus-association (CPA) equation of state. The Debye–Hückel electrostatic term has been used for taking into account the effect of salt on the fugacity of water when electrolytes are present. Model predictions are validated against independent experimental data generated in this work for both single and mixed electrolyte solutions and a good agreement between predictions and experimental data is observed, supporting the reliability of the developed model. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800017e
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3983–3989[article] Freezing point depression of electrolyte solutions : experimental measurements and modeling using the cubic-plus-association equation of state [texte imprimé] / Hooman Haghighi, Auteur ; Antonin Chapoy, Auteur ; Bahman Tohidi, Auteur . - 2008 . - p. 3983–3989.
Bibliogr. p. 3988-3989
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3983–3989
Mots-clés : Electrolyte solutions Freezing point depressions Résumé : New experimental freezing point depressions of six binary solutions (H2O−NaCl, H2O−CaCl2, H2O−MgCl2, H2O−KOH, H2O−ZnCl2, and H2O−ZnBr2) and four ternary solutions (H2O−NaC1−KCl, H2O−NaC1−CaCl2, H2O−KC1−CaCl2, and H2O−NaC1−MgCl2) have been measured by a reliable differential temperature technique. The available experimental literature data on the freezing point depression in addition to the vapor pressure data of aqueous electrolyte solutions for NaCl, KCl, KOH, CaCl2, MgCl2, CaBr2, ZnCl2, and ZnBr2 have been used to optimize binary interaction parameters between salts and water. The fugacity of water in salt-free aqueous phase has been modeled by the cubic-plus-association (CPA) equation of state. The Debye–Hückel electrostatic term has been used for taking into account the effect of salt on the fugacity of water when electrolytes are present. Model predictions are validated against independent experimental data generated in this work for both single and mixed electrolyte solutions and a good agreement between predictions and experimental data is observed, supporting the reliability of the developed model. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800017e Exemplaires
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Titre : Correlation and prediction of partition coefficients from the gas phase and from water to alkan-1-ols Type de document : texte imprimé Auteurs : Michael H. Abraham, Auteur ; Asadollah Nasezadeh, Auteur ; William E. Acree Jr., Auteur Année de publication : 2008 Article en page(s) : p. 3990–3995 Note générale : Bibliogr. p. 3994-3995 Langues : Anglais (eng) Mots-clés : Partition coefficients -- correlation Water Gas Résumé : Partition coefficients, PS, have been obtained from the literature for partitions from water and from the gas phase to wet butan-1-ol, pentan-1-ol, hexan-1-ol, heptan-1-ol, nonan-1-ol, and decane-1-ol. Equations based on the Abraham descriptors have been constructed for the correlation of the 12 sets of coefficients to yield equations for the prediction of further coefficients. The number of compounds used in the regressions ranges from 54 (the decan-1-ol system) to 106 (the pentan-1-ol system), and the standard deviation (SD) in the regression equations is from 0.13 to 0.18 in log PS, except for the water-to-butan-1-ol system, where it is 0.23 log units. For the gas-to-wet alcohol partitions, the SD values are about 0.02 log units larger than for the corresponding water-to-wet alcohol partitions. The coefficients in the regression equations alter quite regularly with increase in size of the alcohol and can be used to deduce the chemical properties of the wet alcohols that influence partition. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800020s
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3990–3995[article] Correlation and prediction of partition coefficients from the gas phase and from water to alkan-1-ols [texte imprimé] / Michael H. Abraham, Auteur ; Asadollah Nasezadeh, Auteur ; William E. Acree Jr., Auteur . - 2008 . - p. 3990–3995.
Bibliogr. p. 3994-3995
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3990–3995
Mots-clés : Partition coefficients -- correlation Water Gas Résumé : Partition coefficients, PS, have been obtained from the literature for partitions from water and from the gas phase to wet butan-1-ol, pentan-1-ol, hexan-1-ol, heptan-1-ol, nonan-1-ol, and decane-1-ol. Equations based on the Abraham descriptors have been constructed for the correlation of the 12 sets of coefficients to yield equations for the prediction of further coefficients. The number of compounds used in the regressions ranges from 54 (the decan-1-ol system) to 106 (the pentan-1-ol system), and the standard deviation (SD) in the regression equations is from 0.13 to 0.18 in log PS, except for the water-to-butan-1-ol system, where it is 0.23 log units. For the gas-to-wet alcohol partitions, the SD values are about 0.02 log units larger than for the corresponding water-to-wet alcohol partitions. The coefficients in the regression equations alter quite regularly with increase in size of the alcohol and can be used to deduce the chemical properties of the wet alcohols that influence partition. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800020s Exemplaires
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Titre : Mass transfer performance in karr reciprocating plate extraction columns Type de document : texte imprimé Auteurs : Angela Stella, Auteur ; Kathryn H. Mensforth, Auteur ; Tim Bowser, Auteur ; Geoffrey W. Steven, Auteur Année de publication : 2008 Article en page(s) : p. 3996–4007 Note générale : Bibliogr.p . 4006-4007 Langues : Anglais (eng) Mots-clés : Karr reciprocating plate Hydrodynamic performance Mass transfer Résumé : A study of the hydrodynamic and mass transfer performance for Karr reciprocating plate extraction columns has been presented for a range of operating conditions and column diameters of 50, 100, and 450 mm. Although the use of Karr columns has been widespread for many years for a range of important applications, the need for more reliable methods for predicting the performance and scale-up of such columns continues to be a matter of significant importance. The present study has examined the hydrodynamic performance in terms of the dispersed phase hold up and droplet size distribution and mass transfer performance which has incorporated the effects of backmixing in the continuous phase. Work was initially carried out in a 50 mm diameter laboratory scale Karr column using the system 10 v/v% tributyl phosphate/kerosene (continuous)−phenol−water (dispersed) where hydrodynamic and mass transfer performance was analyzed for both directions of mass transfer. Using these data, models were investigated and developed to predict performance over a range of operating conditions. An alternative system consisting of an organic solvent (continuous)−phenolic alkaloid−aqueous caustic (dispersed) was also studied, using both 100 and 450 mm diameter Karr columns. These data were used to validate the hydrodynamic and mass transfer performance models developed for the phenol system in the 50 mm diameter column. Dispersed phase holdup data were found to fit the correlation presented by Kumar and Hartland [Ind. Eng. Chem. Res. 1995, 34, 3925−3940], and the drop size distribution also agreed with the relationship presented by Kumar and Hartland [Ind. Eng. Chem. Res. 1996, 35, 2682−2695] within reasonable accuracy. The mass transfer performance results indicated that the continuous phase controlled the mass transfer rate, and thus, column design was simplified by assuming that the overall mass transfer coefficient can be obtained using a standard mass transfer correlation for the continuous phase. The current mass transfer results were found to be best predicted by a refitted form of the overall mass transfer coefficient correlation developed by Harikrishnan et al. [Chem. Eng. J. 1994, 54, 7−16]. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071623p
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3996–4007[article] Mass transfer performance in karr reciprocating plate extraction columns [texte imprimé] / Angela Stella, Auteur ; Kathryn H. Mensforth, Auteur ; Tim Bowser, Auteur ; Geoffrey W. Steven, Auteur . - 2008 . - p. 3996–4007.
Bibliogr.p . 4006-4007
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3996–4007
Mots-clés : Karr reciprocating plate Hydrodynamic performance Mass transfer Résumé : A study of the hydrodynamic and mass transfer performance for Karr reciprocating plate extraction columns has been presented for a range of operating conditions and column diameters of 50, 100, and 450 mm. Although the use of Karr columns has been widespread for many years for a range of important applications, the need for more reliable methods for predicting the performance and scale-up of such columns continues to be a matter of significant importance. The present study has examined the hydrodynamic performance in terms of the dispersed phase hold up and droplet size distribution and mass transfer performance which has incorporated the effects of backmixing in the continuous phase. Work was initially carried out in a 50 mm diameter laboratory scale Karr column using the system 10 v/v% tributyl phosphate/kerosene (continuous)−phenol−water (dispersed) where hydrodynamic and mass transfer performance was analyzed for both directions of mass transfer. Using these data, models were investigated and developed to predict performance over a range of operating conditions. An alternative system consisting of an organic solvent (continuous)−phenolic alkaloid−aqueous caustic (dispersed) was also studied, using both 100 and 450 mm diameter Karr columns. These data were used to validate the hydrodynamic and mass transfer performance models developed for the phenol system in the 50 mm diameter column. Dispersed phase holdup data were found to fit the correlation presented by Kumar and Hartland [Ind. Eng. Chem. Res. 1995, 34, 3925−3940], and the drop size distribution also agreed with the relationship presented by Kumar and Hartland [Ind. Eng. Chem. Res. 1996, 35, 2682−2695] within reasonable accuracy. The mass transfer performance results indicated that the continuous phase controlled the mass transfer rate, and thus, column design was simplified by assuming that the overall mass transfer coefficient can be obtained using a standard mass transfer correlation for the continuous phase. The current mass transfer results were found to be best predicted by a refitted form of the overall mass transfer coefficient correlation developed by Harikrishnan et al. [Chem. Eng. J. 1994, 54, 7−16]. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071623p Exemplaires
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Titre : Hydrodynamics and axial dispersion in a gas−liquid−(solid) EL-ALR with different sparger designs Type de document : texte imprimé Auteurs : Changqing Cao, Auteur ; Shuqin Dong, Auteur ; Qijin Geng, Auteur ; Qingjie Guo, Auteur Année de publication : 2008 Article en page(s) : p. 4008–4017 Note générale : Bibliogr. p. 4017 Langues : Anglais (eng) Mots-clés : Gs− liquid− (solid) External-loop airlift reactor Résumé : The gas−liquid−(solid) three-phase hydrodynamics in an external-loop airlift reactor (EL-ALR) with an upward pipe 0.47 m in diameter and 2.5 m in height, two external loop downward pipes 0.08 m in diameter and 2.5 m in height, were investigated using four different gas sparger designs. The microconductivity probe and the three-dimensional (3-D) laser Doppler anemometry (LDA) techniques were, respectively, implemented to measure the local gas holdup in the riser (αGr) and liquid phase velocity in the downcomer (ULd) using air as the gas phase, water as the liquid phase, and alginate gel beads as the solid phase, over a wide range of operation conditions. The tracer age distribution was measured using the pulse-pursuit response technology. Axial dispersion model (ADM) was used to estimate the model parameter Peclet number (Pe) values as a fitted parameter with the measured data, using the gold partition method for nonlinear programming strategy inequation restrict conditions. The ADM gave better fits to the experimental data at high axial locations and lower superficial gas velocity (UG) for an EL-ALR used with a large L/DR ratio. A synergistic effect of ULd, αGr, Pe, solids loading (SL), and sparger designs on the performance of an EL-ALR was observed in our experiments. The sparger designs were determined to have a noticeable effect on the αGr and Pe in the lower gas velocity and lower solid loading ranges (UG 0.030 m/s and SL > 3%). However, the effect of sparger designs on the ULd is greater in the gas velocity from 0.025 m/s to 0.045 m/s. For the lower solids loading, the increase of orifice diameter leads to a decrease in αGr. This is in accordance with what was presented in the gas−liquid two-phase system. Moreover, the influence of orifice diameters of the spargers is negligible for solids loading of >3%. Although the Pe values decreased with the operating gas velocity, the gas velocity change from 0.03 m/s to 0.04 m/s yielded lower Pe values, as a result of the reduced bubble size. As the gas velocity further increased to 0.06 m/s, the αGr and the ULd values increased, while the Pe values negligibly increased. For a gas−liquid two-phase system, Pe decreases with the orifice diameter and, for 1% of solids, Pe is also lower for sparger P-2 (ϕ 0.6 mm) than for sparger P-1 (ϕ 0.3 mm). For higher amounts of solids (3%), Pe does not have a defined trend. In addition to the gas velocity and sparger design effects, the solids loading had the effect of decreasing the ULd values, while such effect became small and flattened at high solid loadings. The ULd values, especially with VO = 100%, are ~20% lower in three-phase flow than that in two-phase flow. In addition, the ULd profiles in three-phase flow are flatter than that in two-phase flow with VO = 50%−100%, actually showing a parabolic shape rather than the almost linear one encountered in two-phase flow. This is very important for design and optimum operation that are used to systemically investigate the synergistic effect of ULd, αGr, Pe, solid loading (SL), and sparger designs on hydrodynamic performance of an EL-ALR. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0715254
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 4008–4017[article] Hydrodynamics and axial dispersion in a gas−liquid−(solid) EL-ALR with different sparger designs [texte imprimé] / Changqing Cao, Auteur ; Shuqin Dong, Auteur ; Qijin Geng, Auteur ; Qingjie Guo, Auteur . - 2008 . - p. 4008–4017.
Bibliogr. p. 4017
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 4008–4017
Mots-clés : Gs− liquid− (solid) External-loop airlift reactor Résumé : The gas−liquid−(solid) three-phase hydrodynamics in an external-loop airlift reactor (EL-ALR) with an upward pipe 0.47 m in diameter and 2.5 m in height, two external loop downward pipes 0.08 m in diameter and 2.5 m in height, were investigated using four different gas sparger designs. The microconductivity probe and the three-dimensional (3-D) laser Doppler anemometry (LDA) techniques were, respectively, implemented to measure the local gas holdup in the riser (αGr) and liquid phase velocity in the downcomer (ULd) using air as the gas phase, water as the liquid phase, and alginate gel beads as the solid phase, over a wide range of operation conditions. The tracer age distribution was measured using the pulse-pursuit response technology. Axial dispersion model (ADM) was used to estimate the model parameter Peclet number (Pe) values as a fitted parameter with the measured data, using the gold partition method for nonlinear programming strategy inequation restrict conditions. The ADM gave better fits to the experimental data at high axial locations and lower superficial gas velocity (UG) for an EL-ALR used with a large L/DR ratio. A synergistic effect of ULd, αGr, Pe, solids loading (SL), and sparger designs on the performance of an EL-ALR was observed in our experiments. The sparger designs were determined to have a noticeable effect on the αGr and Pe in the lower gas velocity and lower solid loading ranges (UG 0.030 m/s and SL > 3%). However, the effect of sparger designs on the ULd is greater in the gas velocity from 0.025 m/s to 0.045 m/s. For the lower solids loading, the increase of orifice diameter leads to a decrease in αGr. This is in accordance with what was presented in the gas−liquid two-phase system. Moreover, the influence of orifice diameters of the spargers is negligible for solids loading of >3%. Although the Pe values decreased with the operating gas velocity, the gas velocity change from 0.03 m/s to 0.04 m/s yielded lower Pe values, as a result of the reduced bubble size. As the gas velocity further increased to 0.06 m/s, the αGr and the ULd values increased, while the Pe values negligibly increased. For a gas−liquid two-phase system, Pe decreases with the orifice diameter and, for 1% of solids, Pe is also lower for sparger P-2 (ϕ 0.6 mm) than for sparger P-1 (ϕ 0.3 mm). For higher amounts of solids (3%), Pe does not have a defined trend. In addition to the gas velocity and sparger design effects, the solids loading had the effect of decreasing the ULd values, while such effect became small and flattened at high solid loadings. The ULd values, especially with VO = 100%, are ~20% lower in three-phase flow than that in two-phase flow. In addition, the ULd profiles in three-phase flow are flatter than that in two-phase flow with VO = 50%−100%, actually showing a parabolic shape rather than the almost linear one encountered in two-phase flow. This is very important for design and optimum operation that are used to systemically investigate the synergistic effect of ULd, αGr, Pe, solid loading (SL), and sparger designs on hydrodynamic performance of an EL-ALR. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0715254 Exemplaires
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Titre : Voidage and pressure profile characteristics of sand-iron ore−coal−FCC single-particle systems in the riser of a pilot plant circulating fluidized bed Type de document : texte imprimé Auteurs : M. Das, Auteur ; B. C. Meikap, Auteur ; R. K. Saha, Auteur Année de publication : 2008 Article en page(s) : p. 4018–4024 Note générale : Bibliogr. p. 4024 Langues : Anglais (eng) Mots-clés : Single-particle systems Circulating fluidized bed Iron ore Coal Résumé : Hydrodynamic behaviors of single system of particles were investigated in a circulating fluidized bed (CFB) unit. Particles belonging to Geldart groups A and B like sand of various sizes (80, 300, 417, 522, 599, and 622 μm), FCC catalyst (120 μm), iron ore (166 and 140 μm), and coal (335 and 168 μm) were used to study the hydrodynamic characteristics. Superficial air velocity used in the present study ranged between 2.01 and 4.681 m/s and corresponding mass fluxes were 12.5−50 kg/(m2 s). A CFB needs the creation of some special hydrodynamic conditions, namely a certain combination of superficial gas velocity, solids circulation rate, particle diameter, density of particle, etc. which can give rise to a state wherein the solid particles are subjected to an upward velocity greater than the terminal or free fall velocity of the majority of the individual particles. The hydrodynamics of the bed was investigated in depth and theoretical analysis is presented to support the findings. Based on gas−solid momentum balance in the riser, a distinction between apparent and real voidage has been made. The effects of acceleration and friction on the real voidage have been estimated. Results indicated a 0.995 voidage for higher superficial gas velocity of 4.681 m/s. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800282f
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 4018–4024[article] Voidage and pressure profile characteristics of sand-iron ore−coal−FCC single-particle systems in the riser of a pilot plant circulating fluidized bed [texte imprimé] / M. Das, Auteur ; B. C. Meikap, Auteur ; R. K. Saha, Auteur . - 2008 . - p. 4018–4024.
Bibliogr. p. 4024
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 4018–4024
Mots-clés : Single-particle systems Circulating fluidized bed Iron ore Coal Résumé : Hydrodynamic behaviors of single system of particles were investigated in a circulating fluidized bed (CFB) unit. Particles belonging to Geldart groups A and B like sand of various sizes (80, 300, 417, 522, 599, and 622 μm), FCC catalyst (120 μm), iron ore (166 and 140 μm), and coal (335 and 168 μm) were used to study the hydrodynamic characteristics. Superficial air velocity used in the present study ranged between 2.01 and 4.681 m/s and corresponding mass fluxes were 12.5−50 kg/(m2 s). A CFB needs the creation of some special hydrodynamic conditions, namely a certain combination of superficial gas velocity, solids circulation rate, particle diameter, density of particle, etc. which can give rise to a state wherein the solid particles are subjected to an upward velocity greater than the terminal or free fall velocity of the majority of the individual particles. The hydrodynamics of the bed was investigated in depth and theoretical analysis is presented to support the findings. Based on gas−solid momentum balance in the riser, a distinction between apparent and real voidage has been made. The effects of acceleration and friction on the real voidage have been estimated. Results indicated a 0.995 voidage for higher superficial gas velocity of 4.681 m/s. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800282f Exemplaires
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Titre : Principal component analysis/UV Spectroscopy for the determination of 1-ethyl-3-methylimidazolium ethylsulfate ionic liquid and toluene concentrations in aqueous solutions Type de document : texte imprimé Auteurs : José S. Torrecilla, Auteur ; Ester Rojo, Auteur ; Julián García, Auteur ; Francisco Rodríguez, Auteur Année de publication : 2008 Article en page(s) : p. 4025–4028 Note générale : Bibliogr. p. 4028 Langues : Anglais (eng) Mots-clés : Principal component analysis UV spectroscopy Aqueous solutions Résumé : In this paper, a new approach based on the principal component analysis technique (PCA) and UV spectroscopy was applied to the determination of low concentrations of 1-ethyl-3-methylimidazolium ethylsulfate ionic liquid ([Emim][EtSO4]) and toluene in aqueous solutions. By optimizing 10 parameters, the integrated PCA/UV spectroscopy system is able to predict [Emim][EtSO4] and toluene concentrations with a mean predictive error of 2.6% without any previous phenomenological knowledge. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701677m
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 4025–4028[article] Principal component analysis/UV Spectroscopy for the determination of 1-ethyl-3-methylimidazolium ethylsulfate ionic liquid and toluene concentrations in aqueous solutions [texte imprimé] / José S. Torrecilla, Auteur ; Ester Rojo, Auteur ; Julián García, Auteur ; Francisco Rodríguez, Auteur . - 2008 . - p. 4025–4028.
Bibliogr. p. 4028
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 4025–4028
Mots-clés : Principal component analysis UV spectroscopy Aqueous solutions Résumé : In this paper, a new approach based on the principal component analysis technique (PCA) and UV spectroscopy was applied to the determination of low concentrations of 1-ethyl-3-methylimidazolium ethylsulfate ionic liquid ([Emim][EtSO4]) and toluene in aqueous solutions. By optimizing 10 parameters, the integrated PCA/UV spectroscopy system is able to predict [Emim][EtSO4] and toluene concentrations with a mean predictive error of 2.6% without any previous phenomenological knowledge. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701677m Exemplaires
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