Vapor-phase highly selective O-methylation of catechol with methanol over ZnCl2 modified γ-Al2O3 catalysts

Abstract It is firstly discovered that ZnCl 2 modified γ-Al 2 O 3 solid Lewis acidic catalysts (ZnCl 2 /γ-Al 2 O 3 ), which are prepared by solid-state reaction, are very active and extremely selective for the preparation of guaiacol by the vapor phase O -methylation of catechol with methanol in a fixed-bed reactor at 553 K, under the optimum reaction conditions, the conversion of catechol and the selectivity for guaiacol are up to 81.8 and 90.9%, respectively over ZnCl 2 (10%)/γ-Al 2 O 3 and by far better than the reaction results over the solid Bronsted acid catalyst (HY), proposing that the weak coordination of catechol with the Zn 2+ sites of ZnCl 2 /γ-Al 2 O 3 plays a key impact on the high selectivity for guaiacol. The recycling tests indicate that the modification of ZnCl 2 could significantly improve the catalytic stability of γ-Al 2 O 3 by it efficiently restraining the catalyst's coking. And the deactivation of ZnCl 2 /γ-Al 2 O 3 is mainly caused by its ZnCl 2 leaching and surface coking in the run procedure, therefore its catalytic activity can be only partly recovered by the calcination in air at 773 K for 4 h.