Alkylation of Toluene with 2-Propanol over Titania-Silica-Alumina Catalysts

Article abstract of DOI:10.1246/bcsj.62.2657

The alkylating activity of titania supported on silica-alumina has been reported earlier (V.G.Kumar, T.S.Shoba, and K.V.C.Rao, Tetrahedron Lett., 26, 3281 (1985)).Further investigations to synthesize such a catalyst with optimum alkylation activity resulted in the coprecipitation of the catalyst from a solution of pH 4-the test reaction selected being the alkylation of toluene with 2-propanol in a fixed bed tubular reactor.The product mixtures at different reaction times are analyzed to have a view on the variation of yields of different alkylated products with reaction time.The alkylated products are o-cymene, p-cymene, and diisopropyltoluenes (DIT).The presence of titania exerts a synergistic effect upon the alkylating activity of silica-alumina.Also the catalytic activity is governed by the physical caracteristics of the catalyst like surface area and porosity.The trend of para-rich isomer distribution observed in the product mixture is attributed to the steric factors.It has been observed that o-cymene is formed at a constant rate whereas p-cymene formation decreased with reaction time.Increased formation of diisopropyltoluenes are observed with the passing of reaction time.Alkylation studies in the temperature range 165-240 degC have been done to find the effect of reaction temperature on the product distribution.Thus a decrease in the ortho to para molar ratio with increase in reaction temperature and increased formation of diisopropyltoluenes at lower temperatures are observed.No considerable reduction in the alkylation activity has been noticed up to five regeneration cycles.