Ethylene polymerization using dealuminated ZSM-2 zeolite nanocrystals as an active metallocene catalyst support

Abstract

Abstract The preparation of dealuminated (DEAL) ZSM-2 zeolite nanocrystals for use as an active metallocene polymerization catalyst support is presented. The DEAL-ZSM-2 zeolite form was prepared by using steam treatment; metallocene catalyst was directly supported on the zeolite; and evaluated in the polymerization of ethylene using either methylaluminoxane (MAO) or an alkylaluminun as cocatalysts. In order to elucidate the activator effect of the acidic zeolite support, a detailed material characterization was performed. Metallocene catalyst supported on DEAL-ZSM-2 zeolite exhibited high activity values. The metallocene activation is attributed to the action of soluble cocatalyst (MAO or alkylaluminun) into the reactor and to the activator effect of extraframework aluminum species with strong Lewis acidity existing in the DEAL-ZSM-2 zeolite structure. High external surface area of the nanosized zeolite also contributes to reduce the diffusion effects commonly observed in microsized zeolite supports. The results of this work demonstrate that DEAL-ZSM-2 zeolite support does not necessitate to be treated with MAO previous fixation of the metallocene catalyst, and that polymerization activity can be also achieved using a trialkyaluminum as cocatalyst. Thus, the use of DEAL-ZSM-2 zeolite as metallocene support could contribute to reduce the amount of MAO required for ethylene polymerization.