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Catalytic vapor phase epoxidation of propene with nitrous oxide as an oxidant / Thomas Thömmes in Industrial & engineering chemistry research, Vol. 49 N° 6 (Mars 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 6 (Mars 2010) . - pp. 2624–2637 Titre : Catalytic vapor phase epoxidation of propene with nitrous oxide as an oxidant : investigations on catalyst composition and reaction conditions Type de document : texte imprimé Auteurs : Thomas Thömmes, Auteur ; Ingo Gräf, Auteur ; Andreas Reitzmann, Auteur Année de publication : 2010 Article en page(s) : pp. 2624–2637 Note générale : Industrial Chemistry Langues : Anglais (eng) Mots-clés : Catalytic  Vapor  Epoxidation  Propene  Nitrous  Oxide  Oxidant  Investigations  Catalyst  Composition Résumé : The vapor phase epoxidation of propene with nitrous oxide (N2O) was experimentally investigated in a fixed bed reactor using different Csx/Fey/SiO2 catalysts. This was done with a systematic approach which comprises the derivation of kinetic parameters for directly comparing catalyst performance. Therefore, kinetic measurements were made for each catalyst by variation of the residence time. It was found that the addition of an alkali promoter to the Fey/SiO2 catalyst is essential for the formation of propylene oxide and a proper alkali/Fe molar ratio is crucial for both activity and selectivity. Maxima in both activity and selectivity were observed for alkali/Fe ratios in the region 1.2−1.7. A further increase in activity without any loss in selectivity was obtained by adjusting the calcination temperature to 783 K. The conversion of PO was used as a tool to measure the product stability and a minimum reaction rate was also found for alkali/Fe ratios in the region 1.2−1.7. The promoter is responsible for the formation of active centers and it reduces surface acidity which leads to an increased stability of PO through the inhibition of the consecutive conversion. Maximum selectivities to PO of about 40% at 5−10% conversion were achieved at moderate reaction temperatures of 648 K. Because of parallel and consecutive formation of carbonaceous deposits on the catalyst, the catalyst deactivated within 2 h of operation to a remaining activity of around 40%. Neglecting the carbonaceous deposits as a reaction product and considering only the vapor phase products, PO selectivity is more than 75% at 5−10% propene conversion. The attempt to slow down the deactivation through the addition of supplementary gases (H2, O2, NH3, H2O) was partially successful, but unfortunately this is always accompanied by lower PO selectivity. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901342t [article] Catalytic vapor phase epoxidation of propene with nitrous oxide as an oxidant : investigations on catalyst composition and reaction conditions [texte imprimé] / Thomas Thömmes, Auteur ; Ingo Gräf, Auteur ; Andreas Reitzmann, Auteur . - 2010 . - pp. 2624–2637. Industrial Chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 6 (Mars 2010) . - pp. 2624–2637 Mots-clés : Catalytic  Vapor  Epoxidation  Propene  Nitrous  Oxide  Oxidant  Investigations  Catalyst  Composition Résumé : The vapor phase epoxidation of propene with nitrous oxide (N2O) was experimentally investigated in a fixed bed reactor using different Csx/Fey/SiO2 catalysts. This was done with a systematic approach which comprises the derivation of kinetic parameters for directly comparing catalyst performance. Therefore, kinetic measurements were made for each catalyst by variation of the residence time. It was found that the addition of an alkali promoter to the Fey/SiO2 catalyst is essential for the formation of propylene oxide and a proper alkali/Fe molar ratio is crucial for both activity and selectivity. Maxima in both activity and selectivity were observed for alkali/Fe ratios in the region 1.2−1.7. A further increase in activity without any loss in selectivity was obtained by adjusting the calcination temperature to 783 K. The conversion of PO was used as a tool to measure the product stability and a minimum reaction rate was also found for alkali/Fe ratios in the region 1.2−1.7. The promoter is responsible for the formation of active centers and it reduces surface acidity which leads to an increased stability of PO through the inhibition of the consecutive conversion. Maximum selectivities to PO of about 40% at 5−10% conversion were achieved at moderate reaction temperatures of 648 K. Because of parallel and consecutive formation of carbonaceous deposits on the catalyst, the catalyst deactivated within 2 h of operation to a remaining activity of around 40%. Neglecting the carbonaceous deposits as a reaction product and considering only the vapor phase products, PO selectivity is more than 75% at 5−10% propene conversion. The attempt to slow down the deactivation through the addition of supplementary gases (H2, O2, NH3, H2O) was partially successful, but unfortunately this is always accompanied by lower PO selectivity. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901342t

Performance and Kinetics of Flame-Made Vanadia/Titania Catalyst Nanoparticles in the Partial Oxidation of o-Xylene / Philip Mulheims in Industrial & engineering chemistry research, Vol. 51 N° 43 (Octobre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 43 (Octobre 2012) . - pp. 13980-13992 Titre : Performance and Kinetics of Flame-Made Vanadia/Titania Catalyst Nanoparticles in the Partial Oxidation of o-Xylene Type de document : texte imprimé Auteurs : Philip Mulheims, Auteur ; Anika Ritter, Auteur ; Andreas Reitzmann, Auteur Année de publication : 2013 Article en page(s) : pp. 13980-13992 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Partial  oxidation  Nanoparticle  Catalyst  Flame  Kinetics Résumé : Vanadia/titania catalyst particles were made by flame-spray pyrolysis and deposited onto ceramic sponge monoliths either by direct deposition of the flame-made particles or by a dip-coating technique. In the partial oxidation of o-xylene, the influence of the coating thickness and porosity on the catalytic performance was investigated. It was found that the highly porous coatings obtained by direct deposition exhibit insufficient heat transfer properties, while dip-coated layers are prone to internal mass transfer limitations if a certain thickness of the coating is exceeded. In the absence of transport limitations, kinetic experiments were carried out to derive a reaction network and to develop a quantitative kinetic model. The resulting model describes well the influences of reactant concentrations and temperature on the product distributions in the oxidation of o-xylene to phthalic anhydride over the novel flame-made catalyst and can be used for reactor simulations. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26593325 [article] Performance and Kinetics of Flame-Made Vanadia/Titania Catalyst Nanoparticles in the Partial Oxidation of o-Xylene [texte imprimé] / Philip Mulheims, Auteur ; Anika Ritter, Auteur ; Andreas Reitzmann, Auteur . - 2013 . - pp. 13980-13992. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 43 (Octobre 2012) . - pp. 13980-13992 Mots-clés : Partial  oxidation  Nanoparticle  Catalyst  Flame  Kinetics Résumé : Vanadia/titania catalyst particles were made by flame-spray pyrolysis and deposited onto ceramic sponge monoliths either by direct deposition of the flame-made particles or by a dip-coating technique. In the partial oxidation of o-xylene, the influence of the coating thickness and porosity on the catalytic performance was investigated. It was found that the highly porous coatings obtained by direct deposition exhibit insufficient heat transfer properties, while dip-coated layers are prone to internal mass transfer limitations if a certain thickness of the coating is exceeded. In the absence of transport limitations, kinetic experiments were carried out to derive a reaction network and to develop a quantitative kinetic model. The resulting model describes well the influences of reactant concentrations and temperature on the product distributions in the oxidation of o-xylene to phthalic anhydride over the novel flame-made catalyst and can be used for reactor simulations. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26593325