Ga doped SBA-15 as an active and stable catalyst for Friedel-Crafts liquid-phase acylation

Gallium containing SBA-15 mesoporous materials with different Si/Ga ratio were synthesized using a post-treatment procedure with an aqueous solution of Ga(NO3)(3). The materials were characterised by means of elemental analysis, BET, XRD, TEM and H/D isotope exchange techniques. It appears that stable Ga-species were anchored to the siliceous matrix of SBA-15, thus generating acid properties in their host material. The catalytic activity of Ga-SBA-15 materials has been evaluated in the Friedel-Crafts acylation of anisole with benzoyl chloride. The results were compared with nanoporous zeolite BEA to study the influence of the framework crystallinity, pore size, and acidity on the overall conversion and stability. A conversion of 98% of benzoyl chloride over Ga-SBA-15 materials has been reached after 24 h of reaction with a 98% selectivity toward the desired para-methoxybenzophenone. Nanoporous zeolite HBEA exhibited a higher activity, but a drastic decrease in the catalyst activity was observed after successive runs. In contrast, Ga-SBA-15 samples present a higher stability during repeated runs. The observed results indicate that Ga-SBA-15 mesoporous materials can be used as versatile and stable acid catalysts for Friedel-Crafts reactions. (c) 2005 Elsevier B.V. All rights reserved.