abstracts - Институт катализа им. Г.К. Борескова

С 2 -С 3 OLEFIN PRODUCTION PATHWAYS DURING PROPANE OXIDATIONOVER Li/MgO CATALYSTS: CONTRIBUTION OF HETEROGENEOUS ANDHOMOGENEOUS FACTORSSinev M.Yu., Korchak V.N., Seshan K. 1 , Lefferts L. 1KS-I-2N.N. Semenov Institute of Chemical Physics RAS, Moscow, Russia1 University of Twente, Faculty of Science and Technology, Enschede, The NetherlandsE-mail: k.seshan@utwente.nlThe demand for bulk chemicals including light olefins (ethylene, propylene, butenes) isconstantly increasing. However, the rate at which their production can be increased viatraditional processes from different oil fractions (steam cracking of naphtha, fluid catalyticcracking) is limited by several factors, including accessibility of additional raw materials anddramatically increasing oil prices. Catalytic dehydrogenation of alkanes, as an alternativeroute to olefins, shows some disadvantages such as thermodynamic limitations, a hightendency to coking and short catalyst lifetimes. In principal, oxidative dehydrogenation(ODH) of light alkanes can provide with a possibility to avoid these limitations. However,despite the research efforts invested, industrial scale application of ODH reaction has not beenrealized up to now due to the insufficient olefin yields, which typically do not exceed 30%,especially for C 3+ olefins. The latter is caused by a high reactivity of product olefins ascompared with that of initial alkanes. Further, in spite of the absence of thermodynamiclimitations, ODH processes still require relatively high temperatures, similar to those at whichadvanced yields of olefins can be obtained in non-oxidative mode. One more disadvantage ofthe oxidative conversion of propane and higher alkanes in a substantial contribution ofcracking route (formation of C-C bond splitting products) accompanying the desired ODHroute.In this paper, the reaction pathways of ODH and cracking product formation are analyzedin terms of a heterogeneous-homogeneous mechanism. It was demonstrated in manypublications that ODH reaction proceeds via the formation and further transformation of alkylradicals generated by the catalyst (see, for instance, [1-3]). Li/MgO catalyst is a convenientmodel for the evaluation of reaction pathways because of its well-known capability ofproducing free radicals from alkanes [3] and the existence of information required for theevaluation of rate constants of elementary gas-solid reactions [4].Catalysts containing 1-7 wt.% Li were prepared by conventional impregnation of MgOwith water solution of LiNO 3 and finally calcined at 750 o C. Catalytic measurements wereperformed in a quartz microreactor (4 mm inner diameter) at 1 atm and temperatures < 600 o C.25