Side-chain alkylation of toluene with methanol to styrene over cesium ion-exchanged zeolite X modified with metal borates

摘要

Cesium ion-exchanged zeolite X (Cs-X) was modified with metal borates to prepare efficient catalysts for side-chain alkylation of toluene with methanol to styrene. The catalytic behavior of Cs-X was improved by the modification with metal borates such as zirconium borate, zinc borate, copper borate and lanthanum borate. Modification was performed by mechanical mixing of Cs-X and a metal borate in dry state followed by calcination. Significant enhancement of activity was observed for modification with zirconium borate and zinc borate. The selectivity to styrene was increased by modification with all metal borates. Modification with metal component or boron alone was not so effective as that with metal borate. The highest activity was obtained with the Cs-X modified with 10 wt% zirconium borate and calcined at 773 K. The high activity of metal borate-modified Cs-X is due to the ability to selectively form formaldehyde from methanol, which is suggested by appearance of clear IR peak at 1690 cm~(-1) assigned to unidentate formate species on adsorption of methanol. The basic sites and acidic sites of Cs-X were slightly weakened by modification with metal borates. It was revealed that mechanical mixing of Cs-X and metal borates followed by calcination is a good method to prepare Cs-X modified with both metal components and boron.