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Adding microsized silica particles to the catalysis/ultrafiltration system / Zhaoxiang Zhong in Industrial & engineering chemistry research, Vol. 48 N° 10 (Mai 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 10 (Mai 2009) . - pp. 4933–4938 Titre : Adding microsized silica particles to the catalysis/ultrafiltration system : catalyst dissolution inhibition and flux enhancement Type de document : texte imprimé Auteurs : Zhaoxiang Zhong, Auteur ; Xin Liu, Auteur ; Rizhi Chen, Auteur Année de publication : 2009 Article en page(s) : pp. 4933–4938 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Catalytic  reactionCrossflow  ultrafiltration  Microsized  silica  particles Résumé : A system combining catalytic reaction with crossflow ultrafiltration (UF) was used to catalytic ammoximation of cyclohexanone to the oxime over titanium silicalite-1 (TS-1) catalysts. The effect of microsized silica particles on the performance of the catalysis/UF system was investigated in terms of catalytic activity and membrane filterability through dissolution and ultrafiltration experiments. Adding silica particles in the system inhibits the dissolution of TS-1 catalysts and increases both the reaction conversion and the selectivity significantly. Further characterizations (XRF, XRD, FTIR, etc.) indicated that the presence of silica particles remarkably limits the ammonia damage to the microstructure frame of TS-1 catalyst. In addition, silica particles play an important role in substantially removing the deposited TS-1 cake from the membrane surface, benefiting from the scouring effect. According to the results of visual observation to the tested membranes and the estimation of hydrodynamic forces acting on particles, microsized particles are hard to deposit on the membrane surface at the studied conditions and therefore a flux improvement has been achieved. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801774a [article] Adding microsized silica particles to the catalysis/ultrafiltration system : catalyst dissolution inhibition and flux enhancement [texte imprimé] / Zhaoxiang Zhong, Auteur ; Xin Liu, Auteur ; Rizhi Chen, Auteur . - 2009 . - pp. 4933–4938. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 10 (Mai 2009) . - pp. 4933–4938 Mots-clés : Catalytic  reactionCrossflow  ultrafiltration  Microsized  silica  particles Résumé : A system combining catalytic reaction with crossflow ultrafiltration (UF) was used to catalytic ammoximation of cyclohexanone to the oxime over titanium silicalite-1 (TS-1) catalysts. The effect of microsized silica particles on the performance of the catalysis/UF system was investigated in terms of catalytic activity and membrane filterability through dissolution and ultrafiltration experiments. Adding silica particles in the system inhibits the dissolution of TS-1 catalysts and increases both the reaction conversion and the selectivity significantly. Further characterizations (XRF, XRD, FTIR, etc.) indicated that the presence of silica particles remarkably limits the ammonia damage to the microstructure frame of TS-1 catalyst. In addition, silica particles play an important role in substantially removing the deposited TS-1 cake from the membrane surface, benefiting from the scouring effect. According to the results of visual observation to the tested membranes and the estimation of hydrodynamic forces acting on particles, microsized particles are hard to deposit on the membrane surface at the studied conditions and therefore a flux improvement has been achieved. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801774a

Adsorption of lignocelluloses dissolved in prehydrolysis liquor of kraft - based dissolving pulp process on oxidized activated carbons / Xin Liu in Industrial & engineering chemistry research, Vol. 50 N° 20 (Octobre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 20 (Octobre 2011) . - pp. 11706–11711 Titre : Adsorption of lignocelluloses dissolved in prehydrolysis liquor of kraft - based dissolving pulp process on oxidized activated carbons Type de document : texte imprimé Auteurs : Xin Liu, Auteur ; Pedram Fatehi, Auteur ; Yonghao Ni, Auteur Année de publication : 2011 Article en page(s) : pp. 11706–11711 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Adsorption  Lignocelluloses Résumé : The prehydrolysis stage is essential in producing high-purity cellulose from the kraft-based process and is effective in removing hemicelluloses from wood chips. To convert hemicelluloses and other dissolved materials of the prehydrolysis liquor (PHL) into value-added products, they must first be recovered from the PHL. In this work, we investigated the use of activated carbon (AC) to adsorb such materials from the PHL. The adsorption of hemicelluloses on unmodified AC was significantly higher in neutral than acidic environment. To improve the adsorption performance of AC, the AC was oxidized with H2O2 or H2SO4. The H2O2- and H2SO4-modified ACs prepared under milder conditions had higher capacities than those prepared under stronger conditions for adsorbing hemicelluloses, lignin, and furfural. Additionally, the modifications increased the adsorption rate of dissolved materials on the AC, especially that of hemicelluloses. Oxidized activated carbon is a promising adsorbent for lignocellulosic materials of the PHL that can be employed in biorefinery processes conducted during the kraft-based dissolved pulp production process DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201036q [article] Adsorption of lignocelluloses dissolved in prehydrolysis liquor of kraft - based dissolving pulp process on oxidized activated carbons [texte imprimé] / Xin Liu, Auteur ; Pedram Fatehi, Auteur ; Yonghao Ni, Auteur . - 2011 . - pp. 11706–11711. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 20 (Octobre 2011) . - pp. 11706–11711 Mots-clés : Adsorption  Lignocelluloses Résumé : The prehydrolysis stage is essential in producing high-purity cellulose from the kraft-based process and is effective in removing hemicelluloses from wood chips. To convert hemicelluloses and other dissolved materials of the prehydrolysis liquor (PHL) into value-added products, they must first be recovered from the PHL. In this work, we investigated the use of activated carbon (AC) to adsorb such materials from the PHL. The adsorption of hemicelluloses on unmodified AC was significantly higher in neutral than acidic environment. To improve the adsorption performance of AC, the AC was oxidized with H2O2 or H2SO4. The H2O2- and H2SO4-modified ACs prepared under milder conditions had higher capacities than those prepared under stronger conditions for adsorbing hemicelluloses, lignin, and furfural. Additionally, the modifications increased the adsorption rate of dissolved materials on the AC, especially that of hemicelluloses. Oxidized activated carbon is a promising adsorbent for lignocellulosic materials of the PHL that can be employed in biorefinery processes conducted during the kraft-based dissolved pulp production process DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201036q

Effect of microwave treatment on structural changes and gasification reactivity of petroleum coke / Xin Liu in Industrial & engineering chemistry research, Vol. 50 N° 15 (Août 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 15 (Août 2011) . - pp. 9063-9068 Titre : Effect of microwave treatment on structural changes and gasification reactivity of petroleum coke Type de document : texte imprimé Auteurs : Xin Liu, Auteur ; Zhi-jie Zhou, Auteur ; Bao-shen Zhang, Auteur Année de publication : 2011 Article en page(s) : pp. 9063-9068 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Petroleum  Chemical  reactivity  Gasification  Microwave Résumé : The gasification reactivity of petroleum coke, which was treated by microwave at different times, powers, and temperatures, was investigated by using thermogravimetric analysis (TGA) at 1473 K at atmospheric pressure. The results showed that the gasification rate of petroleum coke increased with the increase of conversion and then decreased after reaching its maximum; the conversion corresponding to the maximal gasification rate is about x=0.1. The gasification rate of petroleum coke increased with the increase of microwave irradiation time and irradiation power, but as the irradiation temperature increased, the gasification rate of petroleum coke first increased and then decreased. Petroleum coke before and after microwave treatment was analyzed by X-ray diffraction (XRD), infrared absorption spectroscopy (IR), and the accelerated surface area and porosimetry system (ASAP). The results showed that the crystalline structure of petroleum coke becomes amorphous and the BET surface area and pore volume become larger with increase of microwave irradiation time and irradiation power. As the irradiation temperature increased, the crystalline ordering degree of petroleum coke became weakened and then strengthened and the BET surface area and pore volume increased and then decreased, which agrees with the change in the petroleum coke gasification reaction rate. Results show that microwave treatment is an effective way to change the structure of petroleum coke and promote its gasification reactivity. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24395853 [article] Effect of microwave treatment on structural changes and gasification reactivity of petroleum coke [texte imprimé] / Xin Liu, Auteur ; Zhi-jie Zhou, Auteur ; Bao-shen Zhang, Auteur . - 2011 . - pp. 9063-9068. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 15 (Août 2011) . - pp. 9063-9068 Mots-clés : Petroleum  Chemical  reactivity  Gasification  Microwave Résumé : The gasification reactivity of petroleum coke, which was treated by microwave at different times, powers, and temperatures, was investigated by using thermogravimetric analysis (TGA) at 1473 K at atmospheric pressure. The results showed that the gasification rate of petroleum coke increased with the increase of conversion and then decreased after reaching its maximum; the conversion corresponding to the maximal gasification rate is about x=0.1. The gasification rate of petroleum coke increased with the increase of microwave irradiation time and irradiation power, but as the irradiation temperature increased, the gasification rate of petroleum coke first increased and then decreased. Petroleum coke before and after microwave treatment was analyzed by X-ray diffraction (XRD), infrared absorption spectroscopy (IR), and the accelerated surface area and porosimetry system (ASAP). The results showed that the crystalline structure of petroleum coke becomes amorphous and the BET surface area and pore volume become larger with increase of microwave irradiation time and irradiation power. As the irradiation temperature increased, the crystalline ordering degree of petroleum coke became weakened and then strengthened and the BET surface area and pore volume increased and then decreased, which agrees with the change in the petroleum coke gasification reaction rate. Results show that microwave treatment is an effective way to change the structure of petroleum coke and promote its gasification reactivity. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24395853

Fick diffusion coefficients in ternary liquid systems from equilibrium molecular dynamics simulations / Xin Liu in Industrial & engineering chemistry research, Vol. 51 N° 30 (Août 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 30 (Août 2012) . - pp. 10247-10258 Titre : Fick diffusion coefficients in ternary liquid systems from equilibrium molecular dynamics simulations Type de document : texte imprimé Auteurs : Xin Liu, Auteur ; Ana Martín-Calvo, Auteur ; Erin McGarrity, Auteur Année de publication : 2012 Article en page(s) : pp. 10247-10258 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Modeling  Dynamic  model  Molecular  dynamics  method  Diffusion  coefficient Résumé : An approach for computing Fick diffusivities directly from equilibrium molecular dynamics (MD) simulations is presented and demonstrated for a ternary chloroform―acetone―methanol liquid mixture. In our approach, Fick diffusivities are calculated from the Maawell―Stefan (MS) diffusivities and the so-called matrix of thermodynamic factors. MS diffusivities describe the friction between different molecular species and can be directly computed from MD simulations. The thermodynamic factor describes the deviation from ideal mixing behavior and is difficult to extract from both experiments and simulations. Here, we show that the thermodynamic factor in ternary systems can be obtained from density fluctuations in small subsystems embedded in a larger simulation box. Since the computation uses the Kirkwood―Buff coefficients, the present approach provides a general route toward the thermodynamics of the mixture. In experiments, Fick diffusion coefficients are measured, while previously equilibrium molecular dynamics simulation only provided MS transport diffusivities. Our approach provides an efficient and accurate route to predict multicomponent diffusion coefficients in liquids based on a consistent molecular picture and therefore bridges the gap between theory and experiment. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26201442 [article] Fick diffusion coefficients in ternary liquid systems from equilibrium molecular dynamics simulations [texte imprimé] / Xin Liu, Auteur ; Ana Martín-Calvo, Auteur ; Erin McGarrity, Auteur . - 2012 . - pp. 10247-10258. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 30 (Août 2012) . - pp. 10247-10258 Mots-clés : Modeling  Dynamic  model  Molecular  dynamics  method  Diffusion  coefficient Résumé : An approach for computing Fick diffusivities directly from equilibrium molecular dynamics (MD) simulations is presented and demonstrated for a ternary chloroform―acetone―methanol liquid mixture. In our approach, Fick diffusivities are calculated from the Maawell―Stefan (MS) diffusivities and the so-called matrix of thermodynamic factors. MS diffusivities describe the friction between different molecular species and can be directly computed from MD simulations. The thermodynamic factor describes the deviation from ideal mixing behavior and is difficult to extract from both experiments and simulations. Here, we show that the thermodynamic factor in ternary systems can be obtained from density fluctuations in small subsystems embedded in a larger simulation box. Since the computation uses the Kirkwood―Buff coefficients, the present approach provides a general route toward the thermodynamics of the mixture. In experiments, Fick diffusion coefficients are measured, while previously equilibrium molecular dynamics simulation only provided MS transport diffusivities. Our approach provides an efficient and accurate route to predict multicomponent diffusion coefficients in liquids based on a consistent molecular picture and therefore bridges the gap between theory and experiment. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26201442

Multicomponent maxwell−stefan diffusivities at infinite dilution / Xin Liu in Industrial & engineering chemistry research, Vol. 50 N° 8 (Avril 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 8 (Avril 2011) . - pp. 4776–4782 Titre : Multicomponent maxwell−stefan diffusivities at infinite dilution Type de document : texte imprimé Auteurs : Xin Liu, Auteur ; Andre Bardow, Auteur ; Thijs J.H. Vlugt, Auteur Année de publication : 2011 Article en page(s) : pp. 4776–4782 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Chemical  processes Résumé : Diffusion plays an important role in (bio)chemical processes. It is usually difficult to obtain Maxwell−Stefan diffusivities from experiments as well as molecular simulation. Therefore, predictive models based on easily measurable quantities are highly desired. The Vignes equation is commonly used to describe the concentration dependence of Maxwell−Stefan diffusivities. In mixtures containing at least three components, the generalized Vignes equation requires the value of the quantity Đijxk→1, which describes the friction between components i and j when both are infinitely diluted in component k. Over the past decades, several empirical models were proposed for estimating Đijxk→1, and all of these are lacking a sound theoretical basis. In this study, we show that Đijxk→1 actually exists (i.e., its value does not depend on the molar ratio xi/xj), and we derive an analytical expression for Đijxk→1 that is based on the linear response theory and the Onsager relations. We find that Đijxk→1 can be expressed in terms of binary and pure-component self-diffusivities and integrals over velocity cross-correlation functions. By neglecting the latter terms, we obtain a convenient predictive model for Đijxk→1. Molecular dynamics simulations are used to validate the assumptions made in this model. The following test systems are considered: a ternary system consisting of particles interacting using Weeks−Chandler−Andersen (WCA) interactions and the ternary systems n-hexane−cyclohexane−toluene and ethanol−methanol−water. Our results show that (1) for the WCA system, as well as the n-hexane−cyclohexane−toluene system, neglecting the integrals over velocity cross-correlation functions results in accurate predictions for Đijxk→1; (2) for the WCA system, our model prediction is superior, compared to the existing models for Đijxk→1; (3) in the ethanol−methanol−water system, the integrals over velocity cross-correlation functions cannot be neglected, because of the presence of hydrogen bonds (models for predicting Đijxk→1 in this system will require detailed information on the collective motion of molecules); and (4) our model may provide an explanation why the Maxwell−Stefan diffusivity describing the friction between adsorbed components in a porous material is usually very large. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102515w [article] Multicomponent maxwell−stefan diffusivities at infinite dilution [texte imprimé] / Xin Liu, Auteur ; Andre Bardow, Auteur ; Thijs J.H. Vlugt, Auteur . - 2011 . - pp. 4776–4782. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 8 (Avril 2011) . - pp. 4776–4782 Mots-clés : Chemical  processes Résumé : Diffusion plays an important role in (bio)chemical processes. It is usually difficult to obtain Maxwell−Stefan diffusivities from experiments as well as molecular simulation. Therefore, predictive models based on easily measurable quantities are highly desired. The Vignes equation is commonly used to describe the concentration dependence of Maxwell−Stefan diffusivities. In mixtures containing at least three components, the generalized Vignes equation requires the value of the quantity Đijxk→1, which describes the friction between components i and j when both are infinitely diluted in component k. Over the past decades, several empirical models were proposed for estimating Đijxk→1, and all of these are lacking a sound theoretical basis. In this study, we show that Đijxk→1 actually exists (i.e., its value does not depend on the molar ratio xi/xj), and we derive an analytical expression for Đijxk→1 that is based on the linear response theory and the Onsager relations. We find that Đijxk→1 can be expressed in terms of binary and pure-component self-diffusivities and integrals over velocity cross-correlation functions. By neglecting the latter terms, we obtain a convenient predictive model for Đijxk→1. Molecular dynamics simulations are used to validate the assumptions made in this model. The following test systems are considered: a ternary system consisting of particles interacting using Weeks−Chandler−Andersen (WCA) interactions and the ternary systems n-hexane−cyclohexane−toluene and ethanol−methanol−water. Our results show that (1) for the WCA system, as well as the n-hexane−cyclohexane−toluene system, neglecting the integrals over velocity cross-correlation functions results in accurate predictions for Đijxk→1; (2) for the WCA system, our model prediction is superior, compared to the existing models for Đijxk→1; (3) in the ethanol−methanol−water system, the integrals over velocity cross-correlation functions cannot be neglected, because of the presence of hydrogen bonds (models for predicting Đijxk→1 in this system will require detailed information on the collective motion of molecules); and (4) our model may provide an explanation why the Maxwell−Stefan diffusivity describing the friction between adsorbed components in a porous material is usually very large. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102515w

Predictive darken equation for maxwell-stefan diffusivities in multicomponent mixtures / Xin Liu in Industrial & engineering chemistry research, Vol. 50 N° 17 (Septembre 2011) 

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SO3H-functionalized ionic liquid catalyzed alkylation of catechol with tert-butyl alcohol / Xiaowa Nie in Industrial & engineering chemistry research, Vol. 49 N° 17 (Septembre 1, 2010) 

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