Mesoporous Y zeolite with homogeneous aluminum distribution obtained by sequential desilication–dealumination and its performance in the catalytic cracking of cumene and 1,3,5-triisopropylbenzene

Abstract

The aluminum–silicon distribution and mesoporosity of Y zeolites prepared by sequential NaOH desilication and ammonium hexafluorosilicate (AHFS) dealumination are compared with that of Y samples prepared via AHFS dealumination only. AHFS treatment led to severe non-uniform dealumination and substantial surface silicon deposition. Y samples obtained by sequential desilication and dealumination had substantially better dealumination uniformity and aluminum–silicon distribution. The mesopore formation in these zeolites is discussed in detail. The desilication creates defects in the framework of the parent NaY zeolite. These defects improve the intra-crystalline transport and induce mesopore formation during dealumination. The desilication- plus dealumination-treated zeolites showed higher initial activity and lower deactivation tendency in the case of 1,3,5-triisopropylbenzene cracking, and higher conversion rate of cumene than those zeolites modified by AHFS treatment only. These catalytic data indicate that the former could be a viable catalyst in the catalytic cracking of heavy hydrocarbons.