Fluorine-modified mesoporous Mg–Al mixed oxides: Mild and stable base catalysts for O-methylation of phenol with dimethyl carbonate

A series of fluorine-modified Mg–Al mixed oxides were synthesized by thermal decomposition of the fluorine-containing Mg–Al hydrotalcites and then were characterized by ICP, TGA, XRD, FTIR, CO2-TPD and N2 adsorption/desorption technique. The results revealed that the mesoporous structure was formed during calcination and that fluorine was successfully introduced into the Mg–Al mixed oxides via the phase of MgF2. Simultaneously, such fluorine-modified Mg–Al mixed oxides were effective catalysts for the O-methylation of phenol with dimethyl carbonate (DMC), and their catalytic performance was found to be closely correlated with their basicity. With the optimal catalyst composition, the highest yield of anisole reached 99.3%, with a DMC/phenol molar ratio of 2 at 473 K.

In order to further improve the base-catalytic performance of Mg–Al mixed oxides, the fluorine-modified Mg–Al mixed oxides, F/Mgx(Al)O (x = 1.54, 2.26, 2.93, 3.80), were prepared from fluorine-containing Mg–Al hydrotalcites. And their catalytic performances were investigated in the O-methylation of phenol with dimethyl carbonate. It was found that the F/Mgx(Al)O showed much higher performance than the corresponding pure Mg–Al mixed oxides due to their improved basicity.Figure optionsDownload as PowerPoint slide