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Effectiveness factors for partially wetted catalysts / Arie Jan Van Houwelingen in Industrial & engineering chemistry research, Vol. 49 N° 17 (Septembre 1, 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 17 (Septembre 1, 2010) . - pp 8114–8124 Titre : Effectiveness factors for partially wetted catalysts Type de document : texte imprimé Auteurs : Arie Jan Van Houwelingen, Auteur ; Schalk Kok, Auteur ; Willie Nicol, Auteur Année de publication : 2010 Article en page(s) : pp 8114–8124 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Catalysts  Partially  wetted. Résumé : The finite element method (FEM) is used to solve the diffusion-reaction equation for spherical particles that are partially wetted by the liquid reagent in a trickle-bed reactor. Boundary conditions are specified using true wetting geometries from photographs of spherical particles that were partially wetted under trickle-flow conditions. Three types of reactions were investigated: completely liquid-limited reactions, completely gas-limited reactions, and reactions that are dependent on both the gas and the liquid reagent, following elementary kinetics. The study is limited to spheres, since wetting geometries were only available for these particles. Both monodispersed and eggshell catalysts were simulated. On the basis of the results, existing models for trickle-bed pellet efficiency factors were verified and models are proposed for the prediction of reaction rates in a partially wetted eggshell and monodispersed catalysts for gas-limited reactions, liquid-limited reactions, and elementary reactions for which both gas- and liquid-reagent concentrations are of importance. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9017176 [article] Effectiveness factors for partially wetted catalysts [texte imprimé] / Arie Jan Van Houwelingen, Auteur ; Schalk Kok, Auteur ; Willie Nicol, Auteur . - 2010 . - pp 8114–8124. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 17 (Septembre 1, 2010) . - pp 8114–8124 Mots-clés : Catalysts  Partially  wetted. Résumé : The finite element method (FEM) is used to solve the diffusion-reaction equation for spherical particles that are partially wetted by the liquid reagent in a trickle-bed reactor. Boundary conditions are specified using true wetting geometries from photographs of spherical particles that were partially wetted under trickle-flow conditions. Three types of reactions were investigated: completely liquid-limited reactions, completely gas-limited reactions, and reactions that are dependent on both the gas and the liquid reagent, following elementary kinetics. The study is limited to spheres, since wetting geometries were only available for these particles. Both monodispersed and eggshell catalysts were simulated. On the basis of the results, existing models for trickle-bed pellet efficiency factors were verified and models are proposed for the prediction of reaction rates in a partially wetted eggshell and monodispersed catalysts for gas-limited reactions, liquid-limited reactions, and elementary reactions for which both gas- and liquid-reagent concentrations are of importance. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9017176

Multiplicity behavior of trickle flow liquid−solid mass transfer / Rita Joubert 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. 8387–8392 Titre : Multiplicity behavior of trickle flow liquid−solid mass transfer Type de document : texte imprimé Auteurs : Rita Joubert, Auteur ; Willie Nicol, Auteur Année de publication : 2010 Article en page(s) : pp. 8387–8392 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Multiplicity  Liquid−solid  mass  transfer Résumé : Dissolution as well as electrochemical techniques confirmed the existence of multiplicity. The commonly accepted upper multiplicity branch (achieved by Kan liquid prewetting) outperformed the lower branch (achieved by Levec prewetting) by as much as 1.6 times in Sherwood numbers. Although similar trends were observed for the two measurement techniques, the dissolution measurements were significantly lower than the electrochemical measurements. It was further shown that the multiplicity behavior of liquid−solid mass transfer is not linked solely to liquid hold-up and wetting efficiency variations, indicating major differences in flow structures between the multiplicity modes employed. In addition, a decrease in Sherwood numbers with bed depth was observed for both multiplicity modes. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9002552 [article] Multiplicity behavior of trickle flow liquid−solid mass transfer [texte imprimé] / Rita Joubert, Auteur ; Willie Nicol, Auteur . - 2010 . - pp. 8387–8392. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8387–8392 Mots-clés : Multiplicity  Liquid−solid  mass  transfer Résumé : Dissolution as well as electrochemical techniques confirmed the existence of multiplicity. The commonly accepted upper multiplicity branch (achieved by Kan liquid prewetting) outperformed the lower branch (achieved by Levec prewetting) by as much as 1.6 times in Sherwood numbers. Although similar trends were observed for the two measurement techniques, the dissolution measurements were significantly lower than the electrochemical measurements. It was further shown that the multiplicity behavior of liquid−solid mass transfer is not linked solely to liquid hold-up and wetting efficiency variations, indicating major differences in flow structures between the multiplicity modes employed. In addition, a decrease in Sherwood numbers with bed depth was observed for both multiplicity modes. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9002552