How basic properties of MgO-based mixed oxides affect the catalytic performance in gas-phase and liquid-phase methylation of m-cresol

摘要

The reactivity of MgO-based mixed oxides in the gas-phase alkylation of m-cresol with methanol was studied, with the aim of finding relationships between basic surface features and catalytic performance. Conversion and products distribution were compared with those obtained in liquid-phase methylation. Catalysts investigated included: MgO, Mg/Al/O, Mg/Fe/O, Mg/Al/Zr/O, Mg/Al/Ce/O and H-Y zeolite, the latter used as reference for Bronsted-type activity. It was found that the regio-selectivity of the reaction is greatly affected by the presence of (ⅰ) medium-strength and strong basic sites, the latter playing a relevant role only in gas-phase reaction, and (ⅱ) metal cations having acid, Lewis-type, coordination properties.