Alkylation of toluene and anisole with 1-octen-3-ol over niobium catalysts

Abstract

Niobic acid and niobium phosphate were characterized by BET surface area, X-ray powder diffraction (XRD), infrared (IR), thermogravimetry analysis (TGA), and n-propylamine temperature-programmed desorption (TPD). Their catalytic activity was evaluated in the alkylation of anisole and toluene with 1-octen-3-ol. The reaction was processed in the liquid phase at 120 °C for anisole and 110 °C for toluene with an aromatic/alcohol molar ratio of 10. The influence of the pretreatment temperature (110, 200, 300, 400, 500, and 600 °C) on the catalytic activity of commercial niobium phosphate for alkylation of anisole with allylic alcohol was studied. The best results were achieved when niobium phosphate was calcined at 400 °C. The alcohol conversion was 100% for the reaction with anisole and 57% for toluene. The catalytic activity of niobium phosphate was greater than niobic acid for the reaction with anisole and the selectivity for monoalkylation products was > 80%. The activity and selectivity of the toluene reaction were lower. Two alkylation products (linear and branched) arising from an attack on the 1 or 3 position of the 1-octen-3-ol are observed for both reactions. Formation of the corresponding diene by dehydration of 1-octen-3-ol, especially in the toluene reaction, is a competing side reaction.