Shape selective alkylation of ethylbenzene with isobutylene over ZSM-12: Effect of acid distribution and morphology

Para-tert-butyl ethylbenzene (p-TBEB) is an important polymer monomer raw material to produce poly (tert-butylstyrene). Achieving relatively high selectivity to p-TBEB (Sp-TBEB) by shape selective alkylation of ethylbenzene with isobutylene is highly attractive, and it is crucial to clarify the major factors affecting Sp-TBEB. Herein, ZSM-12 zeolites with various morphology or acid distribution were synthesized by altering alkalinity or structure directing agent (SDA). Despite different morphology of MTW(70)-M-x series samples using MTEACl as the SDA, they show similar catalytic performance in alkylation of ethylbenzene with isobutylene due to their similar acid distribution. On the other hand, MTW(1 0 0)-M-0.06 and MTW(1 0 0)-T with various morphology, synthesized with MTEACl and TEAOH as the SDA, respectively, exhibit quite different selectivity to the target product in this reaction. MTW(1 0 0)-M-0.06 has much higher STBEB (87 % vs. 70 %) and Sp-TBEB (95 % vs. < 60 %) than MTW(1 0 0)-T, which is attributed to that MTW(1 0 0)-M-0.06 possesses much more Brønsted acid sites distributed in the micropore channel. This provides a route to improve the selectivity to main product (TBEB, especially p-TBEB) of alkylation of ethylbenzene with isobutylene over ZSM-12 zeolite even other zeolites.