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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