Achieving long-lived MWW zeolite catalyst for alkylation of benzene with 1-dodecene: Insights into confinement effect of surface cavities and underlying mechanism

The environmentally benign and long-lived zeolite catalyst is highly desired for Friedel-Crafts (FC) alkylation of benzene with long-chain olefins. Herein, MWW zeolites with different layer arrangements and surface structures are employed as model catalysts to investigate the effects of microscale structure on the catalytic behaviors for the alkylation of benzene with 1-dodecene. It is revealed that two kinds of acid sites located on the external surface and within surface 12-membered ring (12MR) pockets of MWW zeolites are effective for this reaction. Unexpectedly, the turnover frequency (TOF) of the effective acid sites over single-layer MWW (SL-MWW) is significantly lower than that of MCM-22. Kinetic study indicates that apparent activation energy ( E a ) is decreased in the order of MCM-36 > MCM-22 > SL-MWW. Combined with DFT calculation, the lowest TOF and E a over SL-MWW can be reasonably attributed to the higher proportion of acid sites in the 12MR pockets and its higher diffusional limitation for products. Moreover, the highest E a of MCM-36 and adsorption energy verified the decreased diffusion limitation of 12MR pockets due to the structure defect resulting from the desilication. Finally, the highly efficient and stable MCM-36 catalyst was achieved in the optimal reaction conditions, which is a potential catalyst for industrial application in the field of FC alkylation reactions.