Synthesis of mesoporous MFI zeolite by dry gel conversion with ZnO particles and the catalytic activity on TMB cracking

摘要

A facile synthesis method for mesoporous MFI zeolite (MMZ) has been developed. MFI zeolite was synthesized by a dry gel conversion in the presence of ZnO nanoparticles with a size of 20 nm. The as-synthesized MFI zeolite included crystalline layered zinc silicate and already possessed 5-15 nm mesopores. After calcination, MMZ/zinc silicate composite was treated with hydrochloric acid to remove unreacted ZnO particles. The micropore (1-2 nm) volume was increased after the HCl treatment, suggesting that ZnO nanoparticles (1-2 nm) remained during crystallization as well as zinc silicate. The catalytic activity of MMZ on 1,3,5-trimethylbenzene (TMB) cracking was compared with that of conventional MFI nanocrystals with a size of 80-100 nm. The conversion of TMB on MMZ was much higher than that on the MFI nanocrystals even though crystal size of MMZ is larger than the conventional MFI zeolite. These results suggest that acid sites on the internal surface of mesopores of MMZ contribute to the high conversion of TMB.