Synthesis, characterization, and catalytic performance of mesoporous Al-SBA-15 for tert-butylation of phenol

Mesoporous Al-SBA-15 was successfully synthesized by post-synthesis grafting Al atoms on 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 N-2 adsorption-desorption methods. The analytic results show that the hexagonal p6mm mesostructure of parent siliceous SBA-15 is maintained very well in Al-SBA-15. NH3 temperature-programmed desorption result indicates that Al-SBA-15 has both medium and strong acid sites. During the alkylation of phenol with tert-butanol, the Al-SBA-15 catalyst displays higher conversion of phenol and selectivity for 2,4-di-tert-butyl phenol (2,4-DTBP) than traditional Al-MCM-41 catalyst. At the reaction temperature of 145 degrees C, a high phenol conversion of 75.2% and 2,4-DTBP selectivity of 31.3% over Al-SBA-15 are observed, but those over Al-MCM-41 are only 61.3% and 13.4%, respectively. Due to the large pore size (about 9 nm) which is beneficial to the effective diffusion of reactants and products, obvious catalyst deactivation of Al-SBA-15 is not observed even after reaction for 5 h.