from first principles PP-I-1

PP-III-57Mechanism of Propane Dehydrogenation in the Presence of Carbon Dioxideover Chromium and Gallium Oxides CatalystsLapidus A.L., Gaidai N.A., Nekrasov N.V., Agafonov Yu.A., Botavina M.A.N.D. Zelinsky Institute of Organic Chemistry, RAS, Moscow, Russiagaidai@server.ioc.ac.ruPropene is one of the most important substances for chemical industry. The increasingdemand of propene takes the development of new methods for its production. A perspectiveone is dehydrogenation of propane in CO 2 presence. Chromium and gallium oxides catalystsare to be promising ones for oxidative dehydrogenation of low paraffins because of their highdehydrogenation activity and selectivity. Designing new catalysts requires depth knowledgeon the reaction mechanism. Data on the mechanism of low paraffin dehydrogenation in theCO 2 presence are few. This work is devoted to the study of propane dehydrogenation in CO 2presence over chromium and gallium catalysts prepared by impregnation of silica from watersolutions of chromium and gallium nitrates and direct hydrothermal synthesis embeddingchromium and gallium species in the siliceous framework of MCM-41. Catalysts wereinvestigated by DR-UV-Vis and IR-FTIR spectroscopy, XRD, TEM, BET, TPR. It wasshown that the activity, selectivity and stability of chromium oxides catalysts were higherthan these parameters for gallium ones. Mechanism of propane dehydrogenation was studiedusing kinetics (stationary and unstationary) and spectroscopic methods. It was shown thatsurface hydroxides took participation in propene formation over Cr-catalysts and hydrides –over Ga-ones. Propane and carbon dioxide participated in the reaction from the adsorbedstates over investigated catalysts but they differed by the adsorption capacity of the reactioncomponents and their surface covering. The role of CO 2 in this process was determined: CO 2took an active participation in reverse water-gas shift reaction and in the oxidation of thecatalyst surface over chromium oxides catalysts, the main role of CO 2 in propanedehydrogenation consisted in a decrease of coke deposition over gallium oxide catalysts.Step-schemes of propene and cracking products formation were proposed.211