from first principles PP-I-1

PP-III-98Different Catalytic Activity of Zeolites Modified by Transition Metal andAluminum Chloride on Liquid- and Gas-Phase Conversion of AlkanesShilina M.I. 1 , Nevskaya S.M. 1 , Udalova O.V. 2 , Vasilevskii G.Y. 11 Lomonosov Moscow State University, Moscow, Russia2 Semenov Institute of Chemical Physics, RAS, Moscow, Russiamish@kinet.chem.msu.ruEarlier we have established that complexes of transition metals and aluminum halides canactivate alkanes at low temperatures (170-230K) providing the products of isomerization andmetathesis reactions [1]. In this work the synergetic effect of transition metal cation andLewis acid immobilized on oxide surfaces is tested. High silica zeolites (ZSM-5, BEA)modified by the transition metal (Co, Ni, Cu) and aluminum salts catalyze of paraffin (С 7 -С 12 )conversion in soft conditions at 370-430К temperatures. The activity of the modified supportsdepends strongly on a phase state of the reagents. In a liquid the efficiency of catalystsexceeds one of initial zeolites in 5-10 times while in a gas phase the activities of two systemsare comparable. The reaction products consisted in all cases of isomers and alkanes with bothlower and higher molecules than the feed; no alkenes were seen. A similar influence of theaggregate state of the reactants on the alkane transformations on zeolites ZSM-5 and MOR atmoderate temperatures was noted in [2], where the conversion of 3-methylpentane was higherthan that of n-hexane on the order in liquid, but in the gas phase inverse relationship wasobtained.Based on DRIFT spectral studies of adsorbed probe molecules (carbon monoxide, ethane) anddata of EPR and UV/vis spectroscopy new active sites of transitional metals includingcoordination with immobilized aluminum chloride are formed by modification of oxidesupport with different additives. For example, new intensive band at 490 nm is recorded inelectronic spectra of Сu(Al)BEA and changes in the EPR spectra are registered at the sametime. The mechanism of alkane transformation appears to be different on the zeolite catalystsin the liquid- and gas-phase processes. Adsorption phenomena linked to the confinementeffects of zeolites are decisive in the gas-phase reactions, but the mutual influence of red-oxproperties of transition metals and immobilized Lewis acids is crucial in liquid.This work was supported by RFBR (12-03-00595а and 11-03-00403a).References:[1] M.I. Shilina, R.V. Bakharev,V.V. Smirnov, Dokl. Phys. Chem. 401 (2005) 63[2] D. Farcasiu, K. Lee, J. Catal. 219 (2003) 186257