Synthesis, Characterization, and Catalytic Performance of Mesoporous Al-SBA-15 for Tert-butylation of Phenol

Mesoporous Al-SBA-15 was synthesized by the post-synthesis grafting of Al atoms on a parent siliceous SBA-15. Both SBA-15 and Al-SBA-15 with different Si/Al ratios were characterized by powder X-ray diffraction, transmission electron microscopy, and N2 adsorption-desorption. The hexagonal p6mm mesostructure of the parent siliceous SBA-15 was maintained very well in Al-SBA-15. NH3 temperature-programmed desorption indicated that Al-SBA-15 has both medium and strong acid sites. During the alkylation of phenol with tert-butanol, the Al-SBA-15 catalyst showed a higher conversion of phenol and selectivity for 2,4-di-tert-butyl phenol (2,4- DTBP) than the traditional Al-MCM-41 catalyst. At a reaction temperature of 145°C, a higher phenol conversion of 75.2% and a 2,4-DTBP selectivity of 31.3% over Al-SBA-15 were observed as compared to those over Al-MCM-41, which were 61.3% and 13.4%, respectively. Due to the large pore size (about 9 nm), which allows a faster diffusion of reactants and products, catalyst deactivation of Al-SBA-15 was not observed even after reaction for 5 h.