Catalytic performance of X molecular sieve modified by alkali metal ions for the side-chain alkylation of toluene with methanol

摘要

The X molecular sieve catalysts modified by several alkali metal ions for the side-chain alkylation of toluene with methanol were prepared by an ion exchange method, and characterized by low temperature N2 adsorption, DTA, XRD, SEM, FT-IR and ~(27)A1 solid NMR. The effects of the reaction conditions (the reaction temperature, space velocity and reactant composition) on the side-chain alkylation of toluene with methanol and the effects of different ions and ratio of SiO2/Al2O3 on the catalytic performance of the KCsX catalyst were investigated. The results show that the X molecular sieve catalyst modified by several alkali metal ions exhibits much higher catalytic performance than the one modified by single alkali metal ions and the catalyst with lower ratio of SiO2/Al2O3 has higher activity for the side-chain alkylation of toluene with methanol. And the acid-base property of the catalyst affects obviously the methanol utilization efficiency and selectivity to product. A low temperature is in favor of increasing the selectivity to styrene, and high space velocity helps to increase the methanol utilization efficiency. With an increase in the reaction temperature, this catalyst would be deactivated due to the coke deposition on the catalyst and the slight structure damage, which results from small part of framework Al has transformed to extra-framework Al.