Aluminium exchanged heteropoly tungstate supported on titania catalysts: The generation of Lewis acidity and its role for benzylation reaction

Aluminium exchanged heteropoly tungstate (AlTPA) supported on titania catalysts were prepared and characterized by FT-Infra red, X-ray diffraction, Laser Raman, temperature programmed desorption of ammonia and X-ray photo electron spectroscopy. The catalytic properties of the catalysts were evaluated for benzylation of anisole with benzyl alcohol. The catalysts showed high activity for anisole benzylation and the catalyst with 20 wt% of AlTPA exhibited highest activity. The presence of Al resulted in generation of Lewis acidic sites. Acidic property and chemical structure of AlTPA on different supports also evaluated by supporting AlTPA on Nb2O5, ZrO2 and SnO2. The catalytic activity of these catalysts is in the order of AlTPA/TiO2 > AlTPA/SnO2 > AlTPA/ZrO2 > AlTPA/Nb2O5. The benzylation activity and selectivity towards benzylated product also depends on the reaction temperature, catalyst weight and anisole to benzyl alcohol ratio.

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► AlTPA/TiO2 as an efficient Lewis acid catalyst for the benzylation of arenes.
► Lewis acidity generated by exchange of Al with protons of heteropoly tungstate.
► Acidity relate to AlTPA content and nature of support.
► The benzylation activity also depends on reaction parameters.