Effect of the P/Al ratio of Al-P-O on the catalytic activity of o-methylation of catechol with methanol

Abstract

Al-P-O catalysts with different P/Al ratios from 0 to 2.0 were synthesized by conventional precipitation method. The effect of P/Al ratio on the textural and surface properties, and the catalytic activity in the reaction of catechol with methanol were studied by XRD, IR, BET and TPD methods. At P/Al<1.0, the samples were mixtures of aluminium phosphate and amorphous alumina. With increasing P/Al ratio, crystalline AlPO₄ and NH₄AlP₂O₇ phases were formed and the surface area of the samples decreased. The catalytic activities for the O-methylation of catechol with methanol have a correlation with the acid amounts. Guaiacol was obtained as a major product and the highest guaiacol yield of ca. 45% was obtained from the sample with P/Al=1.