Influence of Acid-Base Properties of K-Loaded Aluminophosphate Catalysts on Their Catalytic Behavior in the O-Methylation of Catechol

Abstract

Kloaded aluminophosphates prepared by impregnation were characterized by Xray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, N2 adsorption, and NH3 as well as CO2 temperatureprogramed desorption (NH3-TPD, CO2-TPD). The results show that potassium was highly dispersed on the surface of the aluminophosphates. The amount of surface acidic and basic sites decreased upon adding a small amount of potassium. With an increase in potassium, the amount of surface acid sites decreased and the amount of surface base sites did not obviously change. Vapor-phase O-methylation of catechol with methanol was carried out to investigate the catalytic performance of the Kloaded aluminophosphates. Selectivity toward guaiacol obviously increased when a small amount of potassium was added. With an increase in the potassium content, selectivity toward guaiacol increased further and the conversion of catechol decreased. Combined with the characterization results, the surface weak acidic sites play an important role in improving the conversion of catechol and the surface weak basic sites are suitable for improving selectivity toward guaiacol.