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Glycerol steam reforming over bimetallic Co − Ni / Al2O3 / Cheng Chin Kui in Industrial & engineering chemistry research, Vol. 49 N° 21 (Novembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10804–10817 Titre : Glycerol steam reforming over bimetallic Co − Ni / Al2O3 Type de document : texte imprimé Auteurs : Cheng Chin Kui, Auteur ; Say Yei Foo, Auteur ; Adesoji A. Adesina, Auteur Année de publication : 2011 Article en page(s) : pp. 10804–10817 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Glycerol  Bimetallic Résumé : Glycerol steam reforming has been performed in a fixed-bed microreactor containing bimetallic Co−Ni/Al2O3 catalyst using a wide range of steam-to-glycerol ratios (3 ≤ STGR ≤ 12) for reaction temperatures between 773 and 823 K at atmospheric pressure. Physicochemical characterization revealed the presence of both Lewis and Brönsted acid sites on the catalyst although the catalyst appears to have a net surface acidity (acid:basic site concentration ratio = 9.0). Co and Ni oxides as well as the metal aluminates were identified from XRD pattern with crystallite size (131.5 nm) similar to that obtained from H2 chemisorption experiments (136.0 nm). Glycerol consumption rate data analysis implicates fractional orders with respect to both glycerol (0.25) and steam (0.36) with an activation energy of 63.3 kJ mol−1. Similar treatment for H2, CO2, CO, and CH4 production rate evinced positive fractional orders for both reactants with the exception of CO which has mild inhibition by steam (−0.065). Mechanistic considerations and associated Langmuir−Hinshelwood and Eley−Rideal kinetic models were derived for both single- and dual-site adsorption modes. However, statistical discrimination as well as thermodynamic evaluation of the associated parameter estimates suggest that the most adequate representation involved molecular adsorption of glycerol and steam on two different sites with surface reaction as the rate-controlling step consistent with the presence of both Brönsted acid and basic sites on the catalyst. Carbon deposition during reaction appeared to be responsible for the loss in surface area and pore volume of the used catalysts. However, these attributes were nearly recovered after regeneration (>90%) using TPR−TPO−TPR−TPO cycles. Significantly, carbon deposition is a strong function of glycerol partial pressure but somewhat insensitive to the presence of steam, suggesting that the carbon residue was probably unreactive with steam under the reaction conditions. Indeed, temperature-programmed heat treatment (TPO−TPR−TPO−TPR and TPR−TPO−TPR−TPO) revealed at least two types of carbonaceous deposits. However, one of these carbon pools was resistant to removal with H2. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100462t [article] Glycerol steam reforming over bimetallic Co − Ni / Al2O3 [texte imprimé] / Cheng Chin Kui, Auteur ; Say Yei Foo, Auteur ; Adesoji A. Adesina, Auteur . - 2011 . - pp. 10804–10817. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10804–10817 Mots-clés : Glycerol  Bimetallic Résumé : Glycerol steam reforming has been performed in a fixed-bed microreactor containing bimetallic Co−Ni/Al2O3 catalyst using a wide range of steam-to-glycerol ratios (3 ≤ STGR ≤ 12) for reaction temperatures between 773 and 823 K at atmospheric pressure. Physicochemical characterization revealed the presence of both Lewis and Brönsted acid sites on the catalyst although the catalyst appears to have a net surface acidity (acid:basic site concentration ratio = 9.0). Co and Ni oxides as well as the metal aluminates were identified from XRD pattern with crystallite size (131.5 nm) similar to that obtained from H2 chemisorption experiments (136.0 nm). Glycerol consumption rate data analysis implicates fractional orders with respect to both glycerol (0.25) and steam (0.36) with an activation energy of 63.3 kJ mol−1. Similar treatment for H2, CO2, CO, and CH4 production rate evinced positive fractional orders for both reactants with the exception of CO which has mild inhibition by steam (−0.065). Mechanistic considerations and associated Langmuir−Hinshelwood and Eley−Rideal kinetic models were derived for both single- and dual-site adsorption modes. However, statistical discrimination as well as thermodynamic evaluation of the associated parameter estimates suggest that the most adequate representation involved molecular adsorption of glycerol and steam on two different sites with surface reaction as the rate-controlling step consistent with the presence of both Brönsted acid and basic sites on the catalyst. Carbon deposition during reaction appeared to be responsible for the loss in surface area and pore volume of the used catalysts. However, these attributes were nearly recovered after regeneration (>90%) using TPR−TPO−TPR−TPO cycles. Significantly, carbon deposition is a strong function of glycerol partial pressure but somewhat insensitive to the presence of steam, suggesting that the carbon residue was probably unreactive with steam under the reaction conditions. Indeed, temperature-programmed heat treatment (TPO−TPR−TPO−TPR and TPR−TPO−TPR−TPO) revealed at least two types of carbonaceous deposits. However, one of these carbon pools was resistant to removal with H2. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100462t

Oxidative photomineralization of dichloroacetic acid in an externally-irradiated rectangular bubble tank reactor: computational fluid dynamics modeling and experimental verification studies / Francisco J. Trujillo in Industrial & engineering chemistry research, Vol. 49 N° 15 (Août 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 15 (Août 2010) . - pp 6722–6734 Titre : Oxidative photomineralization of dichloroacetic acid in an externally-irradiated rectangular bubble tank reactor: computational fluid dynamics modeling and experimental verification studies Type de document : texte imprimé Auteurs : Francisco J. Trujillo, Auteur ; Tomasz Safinski, Auteur ; Adesoji A. Adesina, Auteur Année de publication : 2010 Article en page(s) : pp 6722–6734 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Oxidative  photomineralization  Fluid  dynamics. Résumé : The effect of antecedent factors on the performance of an aerated tank photoreactor containing externally irradiated suspended titania particles has been carried out using the oxidative photomineralisation of dichloroacetic acid (DCA) as the model reaction. The phase hold-up contours, velocity distribution profiles, and the spatial variation of the incident radiative flux as well as the local volumetric rate of photon absorption (LVPRA) inside the reactor were obtained from computational fluid dynamics (CFD) simulation based on the simultaneous solution of the Navier−Stokes equation (NSE) and radiation transport equation (RTE). The species modeling equation (SME) for the oxidative decomposition of DCA to HCl and CO2 was then coupled to the NSE and RTE to determine the influence of catalyst loading, air superficial velocity, pollutant concentration, and radiation intensity on the reactor performance. The SME utilized the intrinsic kinetic expression provided by Zalazar et al. [Chem. Eng. Sci. 2005, 60, 5240−5254] with rate parameters secured from a preliminary fit of our experimental data. The good agreement between numerical results and empirical data for practically all predictor variables suggest that CFD modeling is a reliable and valid tool for the design and evaluation of the new photoreactor system and may in fact be used as a surrogate for subsequent optimization studies. Within the range of variables examined, it is evident that although reaction rate initially increased with air flow rate, a “plateau” was attained after about 30 L min−1. The rate also exhibited a maximum at a catalyst loading of about 2.5 g L−1 while a characteristic Langmuir-type dependency on DCA concentration was observed. However, reaction rate varied only linearly with light intensity indicating the absence of deleterious hole−electron recombination at the relatively low values (20−80 W m−2) employed. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901364z [article] Oxidative photomineralization of dichloroacetic acid in an externally-irradiated rectangular bubble tank reactor: computational fluid dynamics modeling and experimental verification studies [texte imprimé] / Francisco J. Trujillo, Auteur ; Tomasz Safinski, Auteur ; Adesoji A. Adesina, Auteur . - 2010 . - pp 6722–6734. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 15 (Août 2010) . - pp 6722–6734 Mots-clés : Oxidative  photomineralization  Fluid  dynamics. Résumé : The effect of antecedent factors on the performance of an aerated tank photoreactor containing externally irradiated suspended titania particles has been carried out using the oxidative photomineralisation of dichloroacetic acid (DCA) as the model reaction. The phase hold-up contours, velocity distribution profiles, and the spatial variation of the incident radiative flux as well as the local volumetric rate of photon absorption (LVPRA) inside the reactor were obtained from computational fluid dynamics (CFD) simulation based on the simultaneous solution of the Navier−Stokes equation (NSE) and radiation transport equation (RTE). The species modeling equation (SME) for the oxidative decomposition of DCA to HCl and CO2 was then coupled to the NSE and RTE to determine the influence of catalyst loading, air superficial velocity, pollutant concentration, and radiation intensity on the reactor performance. The SME utilized the intrinsic kinetic expression provided by Zalazar et al. [Chem. Eng. Sci. 2005, 60, 5240−5254] with rate parameters secured from a preliminary fit of our experimental data. The good agreement between numerical results and empirical data for practically all predictor variables suggest that CFD modeling is a reliable and valid tool for the design and evaluation of the new photoreactor system and may in fact be used as a surrogate for subsequent optimization studies. Within the range of variables examined, it is evident that although reaction rate initially increased with air flow rate, a “plateau” was attained after about 30 L min−1. The rate also exhibited a maximum at a catalyst loading of about 2.5 g L−1 while a characteristic Langmuir-type dependency on DCA concentration was observed. However, reaction rate varied only linearly with light intensity indicating the absence of deleterious hole−electron recombination at the relatively low values (20−80 W m−2) employed. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901364z