Ke Song

Synthesis, characterization and catalytic activity of cubic Ia3d and hexagonal p6mm mesoporous aluminosilicates with enhanced acidity

Through a two-step crystallization procedure, an ordered mesoporous aluminosilicate with cubic Ia3d structure denoted as MB48 has been synthesized from the assembly of preformed zeolite beta precursors, utilizing cetyltrimethylammonium bromide (CTAB) as a template. By adjusting the alkalinity during the second crystallization step, an ordered mesoporous aluminosilicate with hexagonal p6mm structure named as MB41 has also been prepared. MB48 and MB41 were characterized with PXRD, FTIR, 27Al-MAS NMR, N2 adsorption–desorption and NH3-TPD techniques, etc. Experiments show that both MB48 and MB41 are pure mesoporous phases, containing the secondary structural units of zeolite beta. Compared with conventional mesoporous aluminosilicates, MB48 and MB41 have enhanced acidity and show higher catalytic activity in the cracking of cumene and the phenol alkylation with tert-butanol.

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

Abstract 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.