Hexagonally ordered mesoporous highly acidic AlSBA-15 with different morphology: An efficient catalyst for acetylation of aromatics

Hexagonally ordered mesoporous AlSBA-15 with different n(si)/n(A1) ratios and morphology have been hydrothermally synthesized using the non-ionic copolymer Pluronic P123 surfactant as the structure directing agent and characterized by XRD. N-2 adsorption-desorption, SEM-EDX, elemental mapping, Al-27 MAS NMR, and NH3-TPD. it has been found that the shape and size of the particles can be controlled by the simple adjustment of the amount of Al content in the silica framework. Polygonal shaped particles with small (ca. 600 nm) and uniform size are observed for the AlSBA-15 materials with higher amount of Al in the framework. Acetylation of the aromatic compounds veratrole, anisole, and 2-methoxynaphthalene with acetic anhydride has been investigated over AlSBA-15 with different n(si)/n(A1), ratios under liquid phase conditions and the results are discussed. The activity of the AlSBA-15 catalysts in the acetylation of veratrole was found to increase with decreasing the n(si)/nA(1), ratio up to 45, and decreased with the further loading of Al in the framework. The effect of various reaction parameters such as reactant mole ratio, temperature, and catalyst concentration on the acetic anhydride conversion has been investigated in detail. The activity of the AlSBA-15 catalysts with different All contents in the acetylation of veratrole was compared with various zeolite catalysts such as BEA, FAU, MOR, MFI, and AIMCM-41(22) where the number in parentheses denotes the n(si)/n(A1), ratio. It has been found that AlSBA-15 with the n(si)/n(A1) ratio of 45 showed the best performance in the acetylation of veratrole, with high acetic anhydride conversion and 100% selectivity to 3,4-dimethoxyacetophenone under the optimized reaction conditions. Moreover, the kinetics of the acetylation of veratrole over AlSBA-15 catalysts is discussed in detail. (C) 2008 Elsevier Inc. All rights reserved.