Catalytic activity of niobium phosphate in the Friedel-Crafts reaction of anisole with alcohols

The catalytic activity of niobium phosphate was evaluated in the benzylation reaction of the anisole with benzyl alcohol, 2-phenyl-ethanol and 1-phenyl-ethanol in liquid phase. The influence of concentration of the catalysts was evaluated. The niobium phosphate was characterized by DRX, thermogravimetry analysis, BET surface area and IV-pyridine. We found high activities (100%) and selectivity (> 90%) in the benzylation with benzyl alcohol and 1-phenyl-ethanol. No result was obtained with 2-phenyl-ethanol. In the reaction with benzyl alcohol a side reaction occurs to form dibenzylether. It has been concluded that Lewis acid sites are responsible for the ether formation and Bronsted acid sites (POH and NbOH) are responsible for the benzylation of anisole with alcohols. The isomer composition in benzylation products from anisole alkylation gave predominantly ortho-para substitution in accordance with a typical eletrophilic aromatic substitution pathway. (c) 2006 Elsevier B.V. All rights reserved.