Preparation of highly ordered mesoporous AlSBA-15 and its application to isopropylation of m-cresol

Abstract

Aluminum incorporated SBA-15 mesoporous molecular sieves with different n Si/ n Al ratios have been hydrothermally synthesized by adjusting the synthesis gel pH below the isoelectric point of silica (pH ∼ 2) using nonionic surfactant as the structure directing agent. All the samples were characterized by X-ray diffraction, N 2 adsorption to determine specific pore volume, pore size and specific surface area, FT-IR, TGA-TPD to determine the acid sites and 27Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). Vapor phase alkylation of m-cresol with isopropanol was carried out over large pore AlSBA-15 catalysts with different n Si/ n Al ratios. The influence of various reaction parameters such as reaction temperature, reactant feed ratio and space velocity affecting the activity and selectivity of AlSBA-15, were studied. 2-Isopropyl-5-methylphenol (2I-5MP) was obtained as a major product with high selectivity. AlSBA-15 (45) was found to be the most active catalyst in this study. It showed 73.5% m-cresol conversion and a selectivity of 45.68% for 2I-5MP under the optimized reaction conditions. Further, large pore AlSBA-15 (45) catalyst was not deactivated when the reaction was carried out for several hours of reaction time.