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Anionic dye adsorption on chemically modified ordered mesoporous carbons / Chun He in Industrial & engineering chemistry research, Vol. 50 N° 24 (Décembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 24 (Décembre 2011) . - pp. 14070–14083 Titre : Anionic dye adsorption on chemically modified ordered mesoporous carbons Type de document : texte imprimé Auteurs : Chun He, Auteur ; Xijun Hu, Auteur Année de publication : 2012 Article en page(s) : pp. 14070–14083 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Adsorption  Mesoporous  Carbons Résumé : The surface chemistry of ordered mesoporous carbon CMK-3 was successfully modified by heat treatment in ammonia gas at a temperature of 1173 K, without destroying its hexagonally ordered mesoporous structure significantly. The adsorption kinetics and equilibrium of three commercial anionic dyes, i.e., orange II, reactive red 2 (RR2), and acid black 1(AB1), on the novel functionalized carbon were investigated. It was found that the ammonia-tailored CMK-3 showed a much higher uptake rate than that of a commercial activated carbon, due to its desirable ordered mesoporous structure and the electron-donating effect of the incorporated nitrogen-containing functional groups, particularly for the adsorption of the large molecule dye with a long chain, AB1. The dye initial concentration and adsorption temperature had little influence on the adsorption rate, while the size and spatial structure of dye molecules and the shaking speed played an important role during the adsorption process. The adsorption of AB1 which has a long chain required the longest time to reach equilibrium. Film mass transfer (the mass transport between the carbon surface and the flowing dye fluid) might be the rate-controlling step. This novel functionalized adsorbent could enhance the adsorption capacity of the three anionic dyes by 90–200% and 40–60% compared to the commercial activated carbon and unmodified CMK-3, respectively. This significant improvement was attributed to the enhanced dispersive forces between the carbon surface and the dye molecules induced by the nitrogen-containing functional groups. The Freundlich isotherm showed better correlation with the experimental adsorption data in all cases than the Langmuir isotherm as a result of the functional groups induced energetic heterogeneous surface. Slow desorption rate and low desorption efficiency of RR2 indicated that the adsorption of RR2 on the modified CMK-3 was extremely favorable, tending to be weakly reversible. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201469p [article] Anionic dye adsorption on chemically modified ordered mesoporous carbons [texte imprimé] / Chun He, Auteur ; Xijun Hu, Auteur . - 2012 . - pp. 14070–14083. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 24 (Décembre 2011) . - pp. 14070–14083 Mots-clés : Adsorption  Mesoporous  Carbons Résumé : The surface chemistry of ordered mesoporous carbon CMK-3 was successfully modified by heat treatment in ammonia gas at a temperature of 1173 K, without destroying its hexagonally ordered mesoporous structure significantly. The adsorption kinetics and equilibrium of three commercial anionic dyes, i.e., orange II, reactive red 2 (RR2), and acid black 1(AB1), on the novel functionalized carbon were investigated. It was found that the ammonia-tailored CMK-3 showed a much higher uptake rate than that of a commercial activated carbon, due to its desirable ordered mesoporous structure and the electron-donating effect of the incorporated nitrogen-containing functional groups, particularly for the adsorption of the large molecule dye with a long chain, AB1. The dye initial concentration and adsorption temperature had little influence on the adsorption rate, while the size and spatial structure of dye molecules and the shaking speed played an important role during the adsorption process. The adsorption of AB1 which has a long chain required the longest time to reach equilibrium. Film mass transfer (the mass transport between the carbon surface and the flowing dye fluid) might be the rate-controlling step. This novel functionalized adsorbent could enhance the adsorption capacity of the three anionic dyes by 90–200% and 40–60% compared to the commercial activated carbon and unmodified CMK-3, respectively. This significant improvement was attributed to the enhanced dispersive forces between the carbon surface and the dye molecules induced by the nitrogen-containing functional groups. The Freundlich isotherm showed better correlation with the experimental adsorption data in all cases than the Langmuir isotherm as a result of the functional groups induced energetic heterogeneous surface. Slow desorption rate and low desorption efficiency of RR2 indicated that the adsorption of RR2 on the modified CMK-3 was extremely favorable, tending to be weakly reversible. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201469p

Catalytic activity of clay-based titanium silicalite-1 composite in cyclohexanone ammoximation / Alex C. K. Yip 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. 8441–8450 Titre : Catalytic activity of clay-based titanium silicalite-1 composite in cyclohexanone ammoximation Type de document : texte imprimé Auteurs : Alex C. K. Yip, Auteur ; Xijun Hu, Auteur Année de publication : 2010 Article en page(s) : pp. 8441–8450 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Cyclohexanone  ammoximation  Catalyst  External  diffusion  Internal  diffusion Résumé : Following the recent report on the synthesis of a clay-based titanium silicalite-1 (TS-1) composite, this work provided important information on the catalytic activity of the catalyst developed for cyclohexanone ammoximation. Experimental works showed that the optimum molar ratio of cyclohexanone:H2O2:NH3 was 1:1.6:2.5. It was found that the cyclohexanone ammoximation over the clay-based catalytic composite gave the highest oxime yield when H2O2 and NH3 was continuously added and was evenly distributed in 5 doses, respectively, to the reaction mixture. The external and internal diffusions can be eliminated by using a water:t-butanol mixture as a solvent, with sufficiently fast agitation speed and having TS-1 crystal with size smaller than 500 nm. On the basis of the adsorption studies and the spectroscopic evidence, the mechanism of the cyclohexanone ammoximation over the catalyst developed are suggested to follow Langmuir−Hinshelwood and Eley−Rideal kinetics. The data acquired in this study is particularly essential for industrial reactor design. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900731s [article] Catalytic activity of clay-based titanium silicalite-1 composite in cyclohexanone ammoximation [texte imprimé] / Alex C. K. Yip, Auteur ; Xijun Hu, Auteur . - 2010 . - pp. 8441–8450. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8441–8450 Mots-clés : Cyclohexanone  ammoximation  Catalyst  External  diffusion  Internal  diffusion Résumé : Following the recent report on the synthesis of a clay-based titanium silicalite-1 (TS-1) composite, this work provided important information on the catalytic activity of the catalyst developed for cyclohexanone ammoximation. Experimental works showed that the optimum molar ratio of cyclohexanone:H2O2:NH3 was 1:1.6:2.5. It was found that the cyclohexanone ammoximation over the clay-based catalytic composite gave the highest oxime yield when H2O2 and NH3 was continuously added and was evenly distributed in 5 doses, respectively, to the reaction mixture. The external and internal diffusions can be eliminated by using a water:t-butanol mixture as a solvent, with sufficiently fast agitation speed and having TS-1 crystal with size smaller than 500 nm. On the basis of the adsorption studies and the spectroscopic evidence, the mechanism of the cyclohexanone ammoximation over the catalyst developed are suggested to follow Langmuir−Hinshelwood and Eley−Rideal kinetics. The data acquired in this study is particularly essential for industrial reactor design. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900731s

Formulation of Reaction Kinetics for Cyclohexanone Ammoximation Catalyzed by a Clay-Based Titanium Silicalite-1 Composite in a Semibatch Process / Alex C. K. Yip in Industrial & engineering chemistry research, Vol. 50 N° 24 (Décembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 24 (Décembre 2011) . - pp. 13703–13710 Titre : Formulation of Reaction Kinetics for Cyclohexanone Ammoximation Catalyzed by a Clay-Based Titanium Silicalite-1 Composite in a Semibatch Process Type de document : texte imprimé Auteurs : Alex C. K. Yip, Auteur ; Xijun Hu, Auteur Année de publication : 2012 Article en page(s) : pp. 13703–13710 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Kinetics Résumé : This article focuses on the kinetic modeling of cyclohexanone ammoximation catalyzed by the clay-based titanium silicalite-1 (TS-1) composite. With the use of computational tools, modeling was carried out systematically, and a rational interpretation of the reaction mechanism was successfully achieved. By fitting the experimental and calculated data, it was found that cyclohexanone ammoximation over the clay-based TS-1 composite follows the Eley–Rideal mechanism in which the reaction takes place between adsorbed H2O2 and other reactants in the free state. It is concluded that a full understanding of the mechanism and kinetics of the reaction allows one to engineer the overall cyclohexanone ammoximation process by influencing elementary steps. The pre-exponential factor and activation energy of the reaction were also determined as a reference for industrial reactor design. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201467u [article] Formulation of Reaction Kinetics for Cyclohexanone Ammoximation Catalyzed by a Clay-Based Titanium Silicalite-1 Composite in a Semibatch Process [texte imprimé] / Alex C. K. Yip, Auteur ; Xijun Hu, Auteur . - 2012 . - pp. 13703–13710. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 24 (Décembre 2011) . - pp. 13703–13710 Mots-clés : Kinetics Résumé : This article focuses on the kinetic modeling of cyclohexanone ammoximation catalyzed by the clay-based titanium silicalite-1 (TS-1) composite. With the use of computational tools, modeling was carried out systematically, and a rational interpretation of the reaction mechanism was successfully achieved. By fitting the experimental and calculated data, it was found that cyclohexanone ammoximation over the clay-based TS-1 composite follows the Eley–Rideal mechanism in which the reaction takes place between adsorbed H2O2 and other reactants in the free state. It is concluded that a full understanding of the mechanism and kinetics of the reaction allows one to engineer the overall cyclohexanone ammoximation process by influencing elementary steps. The pre-exponential factor and activation energy of the reaction were also determined as a reference for industrial reactor design. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201467u

Study on the synthesis of clay-based titanium silicalite-1 catalytic composite / Alex C. K. Yip in Industrial & engineering chemistry research, Vol. 48 N° 11 (Juin 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 11 (Juin 2009) . - pp. 5266–5275 Titre : Study on the synthesis of clay-based titanium silicalite-1 catalytic composite Type de document : texte imprimé Auteurs : Alex C. K. Yip, Auteur ; Frank L. Y. Lam, Auteur ; Xijun Hu, Auteur Année de publication : 2009 Article en page(s) : pp. 5266–5275 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Clay-based  titanium  silicalite-1  (TS-1)  catalytic  composite  Bentonite  Crystallization Résumé : A clay-based titanium silicalite-1 (TS-1) catalytic composite was synthesized using hydrothermal treatment to crystallize TS-1 (300−400 nm) on a bentonite support. The presence of bentonite is favorable to supported growth attributed to the adsorption properties of the substrate which enhanced the interaction with the dissolved crystallizing species. The rapid crystallization on the bentonite support caused formation of silicalite-1 prior to Ti incorporation. An FT-IR spectroscopic study revealed that the Si defective sites were the exact location at which Ti was bonded. The Ti has been confirmed to exist in the form of a Si−O−Ti bridge instead of a Ti═O group in the clay-based TS-1. The influence of the synthesis temperature, duration, H2O to SiO2 molar ratio, and Ti and TPAOH concentrations in the starting gel on the characteristics of the clay-based TS-1 composite were also studied. In addition to the high and stable catalytic activity, the excellent settling efficiency of the clay-based TS-1 composite allowed it to become a reusable catalyst for TS-1-catalyzed processes. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9002798 [article] Study on the synthesis of clay-based titanium silicalite-1 catalytic composite [texte imprimé] / Alex C. K. Yip, Auteur ; Frank L. Y. Lam, Auteur ; Xijun Hu, Auteur . - 2009 . - pp. 5266–5275. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 11 (Juin 2009) . - pp. 5266–5275 Mots-clés : Clay-based  titanium  silicalite-1  (TS-1)  catalytic  composite  Bentonite  Crystallization Résumé : A clay-based titanium silicalite-1 (TS-1) catalytic composite was synthesized using hydrothermal treatment to crystallize TS-1 (300−400 nm) on a bentonite support. The presence of bentonite is favorable to supported growth attributed to the adsorption properties of the substrate which enhanced the interaction with the dissolved crystallizing species. The rapid crystallization on the bentonite support caused formation of silicalite-1 prior to Ti incorporation. An FT-IR spectroscopic study revealed that the Si defective sites were the exact location at which Ti was bonded. The Ti has been confirmed to exist in the form of a Si−O−Ti bridge instead of a Ti═O group in the clay-based TS-1. The influence of the synthesis temperature, duration, H2O to SiO2 molar ratio, and Ti and TPAOH concentrations in the starting gel on the characteristics of the clay-based TS-1 composite were also studied. In addition to the high and stable catalytic activity, the excellent settling efficiency of the clay-based TS-1 composite allowed it to become a reusable catalyst for TS-1-catalyzed processes. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9002798