Characterization and the catalytic applications of mesoporous AlSBA-1

Abstract

Three-dimensional mesoporous cage type aluminosilicates (AlSBA-1) with different n Si/ n Al ratios have been prepared by using cetyltriethylammonium bromide as a structure directing agent under highly acidic medium at hydrothermal conditions. The materials were characterized by various analytical techniques. XRD results reveal that the AlSBA-1 samples exhibit well-ordered three dimensional cage type porous structure, which is almost similar to its parent silica SBA-1. The nitrogen adsorption results show that the textural parameters of AlSBA-1 materials are much superior to those of the pure SBA-1 silica. The Al atoms in the AlSBA-1 samples are incorporated in the silica framework and mostly occupy tetrahedral position, which was confirmed by 27Al magic angle spinning nuclear magnetic resonance. The AlSBA-1 catalysts were tested in the acylation of veratrole using acetic anhydride as the acylation agent under liquid phase conditions. The reaction conditions were optimized in order to get more conversion of acetic anhydride and the catalytic results of AlSBA-1 with different Al contents were compared with BEA, MOR, MFI, and AlMCM-41. Of the AlSBA-1 catalysts studied, AlSBA-1(39) where the number in the parenthesis indicates the n Si/ n Al ratio in the final product was found to be the best catalyst, showing a high acetic anhydride conversion with almost 100% selectivity to 3,4-dimethoxyacetophenone. On the other hand, the catalytic activity of AlSBA-1(39) is almost similar to that of BEA but higher than MOR and MFI. In addition, the kinetics of the acylation of veratrole by acetic anhydride in excess of veratrole over AlSBA-1(39) was also thoroughly investigated and the results were discussed.