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Kinetics of epoxidation of hydroxyl-terminated polybutadiene with hydrogen peroxide under phase transfer catalysis / Qingfa Wang in Industrial & engineering chemistry research, Vol. 48 N°3 (Février 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°3 (Février 2009) . - p. 1364–1371 Titre : Kinetics of epoxidation of hydroxyl-terminated polybutadiene with hydrogen peroxide under phase transfer catalysis Type de document : texte imprimé Auteurs : Qingfa Wang, Auteur ; Xiangwen Zhang, Auteur ; Wang, Li, Auteur Année de publication : 2009 Article en page(s) : p. 1364–1371 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Hydroxyl-terminated  polybutadiene  --  epoxidation  Hydrogen  peroxide  Phosphoric  acid  Ammonium Résumé : The epoxidation of hydroxyl-terminated polybutadiene (HTPB) via phase transfer catalysis (PTC) using H2O2 as the oxidant and ammonium tungstate hydrate and phosphoric acid as the cocatalysts was successfully carried out in an acidic solution/organic solvent two-phase medium. The microstructures of original and epoxidized HTPB products were confirmed by 1H NMR and 13C NMR. The influence of some process variables such as stirring speed, ammonium tungstate hydrate amount, Aliquat 336 amount, phosphoric acid amount, hydrogen peroxide amount, and reaction temperature on the epoxidation of HTPB were studied in detail. The reactions in organic phase were the rate-controlling steps. Based on the experimental results, a rational PTC mechanism was proposed and a pseudo-steady-state kinetic model was applied to describe the epoxidation of HTPB. The apparent kinetic constants for the three configurations in HTPB under the temperatures of 20−60 °C were determined (kapp,c = (2.7−6.43) × 10−2 min−1, kapp,t = (0.95−4.49) × 10−2 min−1, kapp,v = (0.08−0.65) × 10−2 min−1). The activation energies of cis, trans, and vinyl configurations in the epoxidation of HTPB were 19.72, 31.35, and 90.75 kJ mol−1, respectively. This method (Aliquat 336 as PTC/H2O2/ammonium tungstate hydrate and phosphoric acid as the cocatalysts) was very effective for the epoxidation of HTPB. The chemoselectivity of epoxidation of three configurations in HTPB (cis, trans, and vinyl) was evaluated. The reactivity of double bonds toward epoxidation, depending on the chain microstructure, decreased in the following order: 1,4-cis > 1,4-trans > 1,2-vinyl. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800875h [article] Kinetics of epoxidation of hydroxyl-terminated polybutadiene with hydrogen peroxide under phase transfer catalysis [texte imprimé] / Qingfa Wang, Auteur ; Xiangwen Zhang, Auteur ; Wang, Li, Auteur . - 2009 . - p. 1364–1371. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°3 (Février 2009) . - p. 1364–1371 Mots-clés : Hydroxyl-terminated  polybutadiene  --  epoxidation  Hydrogen  peroxide  Phosphoric  acid  Ammonium Résumé : The epoxidation of hydroxyl-terminated polybutadiene (HTPB) via phase transfer catalysis (PTC) using H2O2 as the oxidant and ammonium tungstate hydrate and phosphoric acid as the cocatalysts was successfully carried out in an acidic solution/organic solvent two-phase medium. The microstructures of original and epoxidized HTPB products were confirmed by 1H NMR and 13C NMR. The influence of some process variables such as stirring speed, ammonium tungstate hydrate amount, Aliquat 336 amount, phosphoric acid amount, hydrogen peroxide amount, and reaction temperature on the epoxidation of HTPB were studied in detail. The reactions in organic phase were the rate-controlling steps. Based on the experimental results, a rational PTC mechanism was proposed and a pseudo-steady-state kinetic model was applied to describe the epoxidation of HTPB. The apparent kinetic constants for the three configurations in HTPB under the temperatures of 20−60 °C were determined (kapp,c = (2.7−6.43) × 10−2 min−1, kapp,t = (0.95−4.49) × 10−2 min−1, kapp,v = (0.08−0.65) × 10−2 min−1). The activation energies of cis, trans, and vinyl configurations in the epoxidation of HTPB were 19.72, 31.35, and 90.75 kJ mol−1, respectively. This method (Aliquat 336 as PTC/H2O2/ammonium tungstate hydrate and phosphoric acid as the cocatalysts) was very effective for the epoxidation of HTPB. The chemoselectivity of epoxidation of three configurations in HTPB (cis, trans, and vinyl) was evaluated. The reactivity of double bonds toward epoxidation, depending on the chain microstructure, decreased in the following order: 1,4-cis > 1,4-trans > 1,2-vinyl. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800875h

New method of catalytic cracking of hydrocarbon fuels using a highly dispersed nano-HZSM-5 catalyst / Shiguo Bao in Industrial & engineering chemistry research, Vol. 49 N° 8 (Avril 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 8 (Avril 2010) . - pp. 3972–3975 Titre : New method of catalytic cracking of hydrocarbon fuels using a highly dispersed nano-HZSM-5 catalyst Type de document : texte imprimé Auteurs : Shiguo Bao, Auteur ; Guozhu Liu, Auteur ; Xiangwen Zhang, Auteur Année de publication : 2010 Article en page(s) : pp. 3972–3975 Note générale : Industrial Chemistry Langues : Anglais (eng) Mots-clés : Catalytic  Cracking  Hydrocarbon  Fuels  Highly  Dispersed  Nano Résumé : A pseudohomogeneous method of catalytic cracking of hydrocarbon fuels using a highly dispersed nano-HZSM-5 catalyst is developed. Hydrophilic nano-HZSM-5 is transformed into a hydrophobic form via organic silanization of the zeolite surface, which makes it dispersible in a model endothermic fuel such as n-dodecane. Compared with thermal cracking, catalytic cracking of n-dodecane with highly dispersed nano-HZSM-5 catalyst exhibits remarkably enhanced conversion. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901801q [article] New method of catalytic cracking of hydrocarbon fuels using a highly dispersed nano-HZSM-5 catalyst [texte imprimé] / Shiguo Bao, Auteur ; Guozhu Liu, Auteur ; Xiangwen Zhang, Auteur . - 2010 . - pp. 3972–3975. Industrial Chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 8 (Avril 2010) . - pp. 3972–3975 Mots-clés : Catalytic  Cracking  Hydrocarbon  Fuels  Highly  Dispersed  Nano Résumé : A pseudohomogeneous method of catalytic cracking of hydrocarbon fuels using a highly dispersed nano-HZSM-5 catalyst is developed. Hydrophilic nano-HZSM-5 is transformed into a hydrophobic form via organic silanization of the zeolite surface, which makes it dispersible in a model endothermic fuel such as n-dodecane. Compared with thermal cracking, catalytic cracking of n-dodecane with highly dispersed nano-HZSM-5 catalyst exhibits remarkably enhanced conversion. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901801q

Photoisomerization of norbornadiene to quadricyclane using transition metal doped TiO2 / Lun Pan in Industrial & engineering chemistry research, Vol. 49 N° 18 (Septembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 18 (Septembre 2010) . - pp. 8526–8531 Titre : Photoisomerization of norbornadiene to quadricyclane using transition metal doped TiO2 Type de document : texte imprimé Auteurs : Lun Pan, Auteur ; Ji-Jun Zou, Auteur ; Xiangwen Zhang, Auteur Année de publication : 2010 Article en page(s) : pp. 8526–8531 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Photoisomerization  Norbornadiene Résumé : Metal(V, Fe, Ce, Cu, Cr)-doped TiO2 were synthesized for the photoisomerization of norbornadiene. Characterizations indicate that V and Fe are located in the substitutional sites of TiO2, Ce ions dispersed in the interstitial sites, while Cr and Cu aggregated on the surface. The order of activity is Fe−TiO2 > V−TiO2 > Cr−TiO2 > Ce−TiO2 > TiO2 > Cu−TiO2, suggesting the local structure and type of dopant are crucial. Materials with various V and Fe content were further studied. Fe ions are well dispersed in TiO2 lattice even at high metal content, whereas many separated V2O5 phases are formed. The activity of V−TiO2 changes with V content and the optimal Ti/V ratio is 15, but the activity of Fe−TiO2 is independent of the metal content. Attributed to the high dispersion, Fe−TiO2 is much more active than V−TiO2. The photoreactivity is correlated with the surface lattice oxygen, and a mechanism is proposed to explain the photoisomerization and role of Fe dopant. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100841w [article] Photoisomerization of norbornadiene to quadricyclane using transition metal doped TiO2 [texte imprimé] / Lun Pan, Auteur ; Ji-Jun Zou, Auteur ; Xiangwen Zhang, Auteur . - 2010 . - pp. 8526–8531. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 18 (Septembre 2010) . - pp. 8526–8531 Mots-clés : Photoisomerization  Norbornadiene Résumé : Metal(V, Fe, Ce, Cu, Cr)-doped TiO2 were synthesized for the photoisomerization of norbornadiene. Characterizations indicate that V and Fe are located in the substitutional sites of TiO2, Ce ions dispersed in the interstitial sites, while Cr and Cu aggregated on the surface. The order of activity is Fe−TiO2 > V−TiO2 > Cr−TiO2 > Ce−TiO2 > TiO2 > Cu−TiO2, suggesting the local structure and type of dopant are crucial. Materials with various V and Fe content were further studied. Fe ions are well dispersed in TiO2 lattice even at high metal content, whereas many separated V2O5 phases are formed. The activity of V−TiO2 changes with V content and the optimal Ti/V ratio is 15, but the activity of Fe−TiO2 is independent of the metal content. Attributed to the high dispersion, Fe−TiO2 is much more active than V−TiO2. The photoreactivity is correlated with the surface lattice oxygen, and a mechanism is proposed to explain the photoisomerization and role of Fe dopant. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100841w

Roles of hydrogen donors and organic selenides in inhibiting solid deposits from thermal stressing of n-dodecane and chinese RP-3 jet fuel / Wei Guo in Industrial & engineering chemistry research, Vol. 48 N° 18 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8320–8327 Titre : Roles of hydrogen donors and organic selenides in inhibiting solid deposits from thermal stressing of n-dodecane and chinese RP-3 jet fuel Type de document : texte imprimé Auteurs : Wei Guo, Auteur ; Xiangwen Zhang, Auteur ; Guozhu Liu, Auteur Année de publication : 2010 Article en page(s) : pp. 8320–8327 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Hydrocarbon  fuels  Hydrogen  donors  Organic  selenides Résumé : Use of hydrocarbon fuels as coolants for future high-Mach aircraft is challenged by the formation of carbonaceous deposits during thermal stressing at high temperatures (>500 °C). Three hydrogen donors, tetralin (THN), α-tetralone (THNone), and benzyl alcohol (BzOH), and two organic selenides, diphenyl selenide (Ph2Se) and diphenyl diselenide (Ph2Se2), as well as their mixtures, are selected as thermally stable additives to inhibit the deposition from the thermal stressing of n-dodecane and Chinese RP-3 (No. 3 jet fuel). It is found that the amount of solid deposits from thermal stressing of RP-3 is reduced by 77.0% with the additive of Ph2Se2/THN/THNone. The carbonaceous solid is further characterized using temperature-programmed oxidation (TPO), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). It is revealed that hydrogen donor THN/THNone and organic selenides possibly reduce the carbon deposits through retarding the thermal cracking rate, blocking surface catalysis, and depressing reactivity of sulfur with the surface metals, as well as their synergistic effect. The morphologies of deposits also dramatically change after adding organic selenides or hydrogen donors. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900735c [article] Roles of hydrogen donors and organic selenides in inhibiting solid deposits from thermal stressing of n-dodecane and chinese RP-3 jet fuel [texte imprimé] / Wei Guo, Auteur ; Xiangwen Zhang, Auteur ; Guozhu Liu, Auteur . - 2010 . - pp. 8320–8327. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8320–8327 Mots-clés : Hydrocarbon  fuels  Hydrogen  donors  Organic  selenides Résumé : Use of hydrocarbon fuels as coolants for future high-Mach aircraft is challenged by the formation of carbonaceous deposits during thermal stressing at high temperatures (>500 °C). Three hydrogen donors, tetralin (THN), α-tetralone (THNone), and benzyl alcohol (BzOH), and two organic selenides, diphenyl selenide (Ph2Se) and diphenyl diselenide (Ph2Se2), as well as their mixtures, are selected as thermally stable additives to inhibit the deposition from the thermal stressing of n-dodecane and Chinese RP-3 (No. 3 jet fuel). It is found that the amount of solid deposits from thermal stressing of RP-3 is reduced by 77.0% with the additive of Ph2Se2/THN/THNone. The carbonaceous solid is further characterized using temperature-programmed oxidation (TPO), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). It is revealed that hydrogen donor THN/THNone and organic selenides possibly reduce the carbon deposits through retarding the thermal cracking rate, blocking surface catalysis, and depressing reactivity of sulfur with the surface metals, as well as their synergistic effect. The morphologies of deposits also dramatically change after adding organic selenides or hydrogen donors. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900735c