Highly active three-dimensional cage type mesoporous ferrosilicate catalysts for the Friedel–Crafts alkylation

Three-dimensional cage type ferrosilicate catalysts with different n_Si/n_Fe ratios (FeSBA-1(x) where x denotes the n_Si/n_Fe molar ratio) have been prepared at a molar hydrochloric acid to silicon ratio of 10 using cetyltriethylammonium bromide as the template. The obtained materials have been unambiguously characterized by XRD, N₂ adsorption, and ESR spectroscopy, and their catalytic activity in the benzylation of benzene and the substituted benzene has also been investigated. The catalytic results of the FeSBA-1 catalysts with different n_Si/n_Fe ratios have been compared with the uni-dimensional FeSBA-15, AlSBA-15 and FeHMS catalysts. It has been found that the activity of the FeSBA-1 catalysts is much higher as compared to that of the FeSBA-15, FeHMS and AlSBA-15 catalysts. The activity of the catalysts declines in the following order: FeSBA-1(36) > FeSBA-1(90) > FeSBA-1(120) > FeSBA-1(344) > FeSBA-15(152) > FeHMS(50) > AlSBA-15(45). The effect of various reaction parameters such as reaction time, reaction temperature, reactant feed ratio and the various electron donating groups on the benzene ring affecting the activity and selectivity of FeSBA-1(344) have also been studied. The catalysts are highly active and show a complete conversion of benzyl chloride and a clean selectivity to diphenylmethane (DPM) within a short period of time under the optimized reaction conditions. The reaction kinetics of the catalysts has been extensively investigated and the results are presented. The apparent rate constant of the FeSBA-1(344) and the BC conversion sharply increase with increasing the reaction temperature. The activity of the FeSBA-1(344) catalyst for the benzylation of different aromatic compounds is in the following order: benzene > anisole > mesitylene > p-xylene > toluene.