Study of Molybdenum Components in (K, Mo) Y-Zeolites by EXAFS

The local structures of the oxidic and sulfided molybdenum loaded KHMoY zeolites prepared by solid-state reaction and the sulfided mixtures of KHY/MoO3have been investigated by EXAFS. The alcohol synthesis of CO hydrogenation is used to characterize catalytic performance for the sulfided (K, Mo)Y catalysts which is well explained by the EXAFS results. The results indicate that the local structures of Mo(VI) species depend on the atomic ratio of (K+2Mo)/Al. At the ratio of (K+2Mo)/Al lower than the exchange capacity, i.e., 1, the molybdenum species are completely dispersed into the supercages of the zeolites as small atomic cluster of MoS2. At the ratio of (K+2Mo)/Al lager than 1, the molybdenum species could exist in two phases, including both inside and outside of the zeolite supercages. Moreover, the size of MoS2located at the out-surface of the zeolite supercages is much larger than the one in the zeolite supercages. We present that MoS2cluster in the zeolite supercages of zeolites has a higher selectivity of alcohol synthesis for the CO hydrogenation than the MoS2particles located at the out-surface of the zeolite supercages.