Mesoporous silica-aluminas as catalysts for the alkylation of aromatic hydrocarbons with olefins

Two amorphous mesoporous silica-aluminas (MSA and MCM-41) are compared with the amorphous microporous silica-alumina (ERS-8) and the zeolite beta in t he liquid-phase alkylation of toluene with propylene. The catalytic activit y, the selectivity to o-, m- and p-cymenes and the formation of polyalkylat es are discussed as a function of acidity and porosity. The catalytic behav iour of MSA, MCM-41, ERS-8 and zeolite beta is also compared with data repo rted in the literature for traditional alkylation catalysts (AlCl3-HCl and supported phosphoric acid, SPA) and for other acidic zeolites. MSA and MCM- 41 show alkylation activities comparable with zeolite beta, while their iso merization and transalkylation activities are lower than those of zeolite b eta and AlCl3-HCl, but similar to SPA. Such behaviour is in agreement with the Bronsted acidity of the materials studied. (C) 1999 Elsevier Science B. V. All rights reserved.