Vapour phase alkylation of phenol with methanol over vanadium oxide supported on zirconia

A series of vanadium oxide supported on zirconia catalysts with varying vanadium oxide content (2.5-12.5 wt.%) were prepared by wet impregnation method. The catalysts were characterised by X-ray diffraction (XRD), temperature-programmed reduction (TPR) of hydrogen, temperature-programmed desorption (TPD) of NH3 and specific surface area measurements. X-ray diffraction patterns indicate the presence of crystalline V2O5 phase from 7.5 wt.% Of V2O5 on zirconia. TPR patterns reveal the presence of V3+ species on zirconia. Ammonia TPD results suggest that acidity of the catalysts increased with increase in V2O5 loading up to 7.5 wt.% and decreased with further increase in V2O5 loading. The catalytic properties were evaluated for the vapour-phase alkylation of phenol with methanol. During alkylation of phenol with methanol exclusively C-alkylated (alkylation proceeds through ring) products were formed. The selectivity towards 2,6-xylenol was high when compared to o-cresol. The activity of the catalysts was found to increase With V2O5 loading up to 7.5 wt.% Of V2O5 and decreased with increase in further vanadia content. (C) 2002 Published by Elsevier Science B.V.