Promoting effect of copper oxide on CsX zeolite catalyst for side-chain alkylation of toluene with methanol

Abstract

Cesium exchanged X zeolites (CsX) have been widely used as the catalyst for toluene side-chain alkylation with methanol to produce styrene. In this work, copper oxide was recognized as an efficient promoter to improve the performance of CsX catalyst in both the reactivity and styrene selectivity. Based on systematic characterization of CuO modified CsX samples and further analysis of their catalytic performance, the promoting effect of CuO additive was explored. On one hand, the introduced Cu species promoted the dehydrogenation of methanol to formaldehyde, which acted as real alkylating agent and enhanced toluene conversion. On the other hand, the catalyst acid-base property was sensitively modulated, and thereby the undesired transfer hydrogenation of styrene to ethylbenzene was suppressed. Furthermore, the universality of CuO promoter was proved by loading on some well-known catalysts (Cs2O/CsX, B2O3/CsX and ZnO/CsX), and the effect of reaction condition was also studied with the most efficient CuO–B2O3/CsX catalyst.