Direct and facile synthesis of LaPO4 containing SBA-15 catalyst for selective O-methylation of phenol to anisole in continuous process

Abstract

Abstract With an aim to set up acid-base functionalities in mesoporous SBA-15, herein we report one pot hydrothermal synthetic strategy to incorporate LaPO4 into SBA-15 (LaP-SBA-15). ICP-OES and EDX results confirmed successful incorporation of large amount of LaPO4 in SBA-15. The small angle XRD, N2-isotherms and TEM studies unveiled the presence of ordered mesoporous and its characteristic features in LaP-SBA-15 catalysts. The incorporated LaPO4 is existed in monoclinic phase which is authenticated by wide angle XRD and FT-IR results. In addition to this, electron microscope images of LaP-SBA-15 catalysts clearly illustrate the crystalline growth of monoclinic LaPO4 nanoparticles across the hexagonal mesopore channels of SBA-15. NH3/CO2 -TPD demonstrated existence of both surface acidic and basic sites which are imparted to SBA-15 through LaPO4 incorporation. LaP-SBA-15 catalysts have been evaluated for the selective O-alkylation of phenol with methanol in continuous process. LaP-SBA-15 catalysts offer excellent catalytic activity and selectivity towards anisole. The surface acidic and basic sites could be tuned by adjusting the LaPO4 content, which leads to the tunable selectivity in the O-methylation of phenol. Especially, 30 wt % LaP-SBA- 15 catalyst exhibited constant selectivity to anisole up to 16 h of time-on-stream. This superior catalytic performance of 30 wt% LaP-SBA-15 catalyst is attributed to dispersion of balanced amount weak acidic and moderate basic sites through mesopores and the transportation of reactant and product molecules through uniform channels of SBA-15 containing LaPO4.