Alkylation of benzene by long-chain alkenes on immobilized phosphotungstic acid

Linear alkylbenzenes (LAB) are semi-products in the manufacture of linear alkylbenzene sulfonate surfactants that are active ingredients of various detergents. The use of traditional soluble acids (e.g. hydrofluoric acid or aluminum chloride) as catalysts for production of LAB results in the formation of large amounts of acidic toxic wastes. In this work, an efficient heterogeneous catalyst containing immobilized phosphotungstic acid (PTA) was synthesized and tested in the alkylation of benzene by higher alkenes. Sol–gel synthesis of silica gel from tetraethyl orthosilicate and PTA, as precursors, produced a mesoporous material containing covalently embedded PTA clusters. Obtained superacidic catalyst demonstrated high catalytic activity in liquid-phase alkylation of benzene by higher alkenes. Conversion of alkenes to corresponding phenylalkanes on this catalyst was significantly higher than on pure PTA. Covalent embedding of catalytically active HPA clusters prevented their leaching from the catalyst surface, which enabled its excellent catalytic properties.