The vapor phase epoxidation of propene with nitrous oxide (N2O) was experimentally investigated in a fixed bed reactor using different Cs-x/Fe-y/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 Fe-y/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 (H-2, O-2, NH3, H2O) was partially Successful, but unfortunately this is always accompanied by lower PO selectivity.

Chemie Ingenieur TechnikVolume 80, Issue 9 p. 1263-1263 PosterFree Access Epoxidierung von Propen mit N2O – Reaktionsbedingungen, Katalysator- zusammensetzung und ihr Einfluss auf die Performance T. Thömmes Dipl.-Ing., T. Thömmes Dipl.-Ing. thomas.thoemmes@cvt.uni-karlsruhe.de Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76128 KarlsruheSearch for more papers by this authorA. Reitzmann Dr.-Ing., A. Reitzmann Dr.-Ing. Süd-Chemie AG, Waldheimer Straße 15, D-83052 BruckmühlSearch for more papers by this authorB. Kraushaar-Czarnetzki Prof. Dr., B. Kraushaar-Czarnetzki Prof. Dr. Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76128 KarlsruheSearch for more papers by this author T. Thömmes Dipl.-Ing., T. Thömmes Dipl.-Ing. thomas.thoemmes@cvt.uni-karlsruhe.de Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76128 KarlsruheSearch for more papers by this authorA. Reitzmann Dr.-Ing., A. Reitzmann Dr.-Ing. Süd-Chemie AG, Waldheimer Straße 15, D-83052 BruckmühlSearch for more papers by this authorB. Kraushaar-Czarnetzki Prof. Dr., B. Kraushaar-Czarnetzki Prof. Dr. Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76128 KarlsruheSearch for more papers by this author First published: 12 September 2008 https://doi.org/10.1002/cite.200750605AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume80, Issue9Special Issue: ProcessNet Jahrestagung 2008September, 2008Pages 1263-1263 ReferencesRelatedInformation

Introduction Propylene oxide (PO) is an important intermediate for the chemical industry with an annual worldwide production capacity of more than 5 megatons [1]. However, PO production technology is dominated by disadvantageous, liquid phase processes containing multiple reaction steps, namely the chlorhydrin process and several peroxidation routes [1-3]. Particularly in the last ten years, different approaches led to progress concerning a direct epoxidation of propene. However, a high amount of organic solvent reacting both with the feed and the products, catalyst deactivation and mass transfer limitations may still be problems for liquid phase processes using H2O2 as oxidant [2-5]. Due to the disadvantages, a direct, vapour phase route is still in the focus of research because of simpler reactor technology, absence of mass transfer limitations and more convenient catalyst handling. One promising route in the vapour phase could be the use of nitrous oxide (N2O) as an oxidant, which was firstly demonstrated by Duma and Hönicke using silica supported iron oxide promoted with Na [6]. An improvement of the catalyst led to a promising silica supported iron oxide system promoted with cesium ions and –oxides (CsOx/FeOy/SiO2), which provides at 375 °C a maximum selectivity to PO of ~75% among the vapour phase products at a propene conversion of ~10% [7]. Other research groups claimed to obtain even higher PO selectivities using similar catalysts with KCl or Rb2SO4 as promoters [8-11], underlining the potential of this route. However, a strong deactivation was always observed, probably due to coking. As a consequence, real product selectivities obtained from the carbon balance must be lower in the above mentioned investigations. The present study focuses on the reaction network of the catalytic epoxidation of propene using nitrous oxide and a CsOx/FeOy/SiO2-catalyst under the condition of a proper carbon-balance. The residence time was varied in a broad range, and propylene oxide and propionaldehyde were added to the reactor feed to determine the importance of different side reactions.

The vapour phase epoxidation of propene with nitrous oxide (N2O) was experimentally investigated in a fixed bed reactor using a CsOx/FeOy/SiO2 catalyst over a broad range of residence times. The influence of feed composition on the conversion and product distribution was determined for the reactants propene, propylene oxide (PO), propionaldehyde (PA), and N2O. The experimental results were used to derive a formal kinetic model to describe the reactions in a network deduced in the first part of this publication [Thömmes, T., Zürcher, S., Wix, A., Reitzmann, A., Kraushaar-Czarnetzki, B., 2007. Catalytic vapour phase epoxidation of propene with nitrous oxide as an oxidant: I. Reaction network and product distribution. Applied Catalysis A 318, 160–169]. Self-inhibition of the propene conversion was observed, and an inhibition of the PO conversion through PO isomerisation products. The N2O concentration has almost no effect on the conversion of propene and PO, but the PA conversion is accelerated significantly through N2O. Propene related and N2O related PO selectivities display opposed dependencies from reactant concentration. The modelling results indicate that coke is predominantly formed from oxygenated products. It is the key issue for future developments to prevent the fast consecutive conversion of PO.

Chemie Ingenieur TechnikVolume 77, Issue 8 p. 990-991 Poster Kinetische Untersuchungen zur Propenepoxidierung mit N2O an CsOx-promotierten FeOx/SiO2-Trägerkatalysatoren A. Wix, A. Wix Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76131 KarlsruheSearch for more papers by this authorT. Thömmes, T. Thömmes Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76131 KarlsruheSearch for more papers by this authorA. Reitzmann Dr.-Ing., A. Reitzmann Dr.-Ing. andreas.reitzmann@cvt.uni-karlsruhe.de Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76131 KarlsruheSearch for more papers by this authorB. Kraushaar-Czarnetzki Prof. Dr., B. Kraushaar-Czarnetzki Prof. Dr. Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76131 KarlsruheSearch for more papers by this author A. Wix, A. Wix Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76131 KarlsruheSearch for more papers by this authorT. Thömmes, T. Thömmes Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76131 KarlsruheSearch for more papers by this authorA. Reitzmann Dr.-Ing., A. Reitzmann Dr.-Ing. andreas.reitzmann@cvt.uni-karlsruhe.de Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76131 KarlsruheSearch for more papers by this authorB. Kraushaar-Czarnetzki Prof. Dr., B. Kraushaar-Czarnetzki Prof. Dr. Institut für Chemische Verfahrenstechnik, Universität Karlsruhe (TH), Kaiserstraße 12, D-76131 KarlsruheSearch for more papers by this author First published: 10 August 2005 https://doi.org/10.1002/cite.200580046AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume77, Issue8Special Issue: GVC/DECHEMA-JahrestagungenAugust, 2005Pages 990-991 RelatedInformation