Highly active and selective AlSBA-15 catalysts for the vapor phase tert-butylation of phenol

Abstract

Hexagonally ordered mesoporous AlSBA-15 catalysts having nSi/nAl ratios from 7 to 215 have been synthesized hydrothermally using a cheap non-ionic block copolymer as the structure-directing agent. The obtained materials were analyzed by XRD and nitrogen adsorption to determine the structural order and the textural properties. It has been observed by 27Al MAS NMR spectroscopy that aluminum atoms are exclusively in tetrahedral coordination for all samples except AlSBA-15(7), where octahedral aluminum has been detected to some extent. Temperature-programmed desorption of pyridine showed that AlSBA-15(45) has a higher number of strong acid sites as compared to other mesoporous materials such as FeMCM-41, AlMCM-41 and FeAlMCM-41. The catalyst AlSBA-15(45) showed superior performance in the acid-catalyzed tertiary butylation of phenol employing tert-butanol as the alkylation agent. A high phenol conversion of 86.3% is observed for this catalyst at a reaction temperature of 150 8C. Over AlSBA-15(45), the 4-TBP yield amounts to 40.5% and the 2,4-DTBP yield corresponds to 37.9%.