Zirconia-supported phosphotungstic acid as catalyst for alkylation of phenol with benzyl alcohol

Abstract

The liquid-phase alkylation of phenol with benzyl alcohol was carried out using zirconia-supported phosphotungstic acid (PTA) as catalyst. The catalysts with different PTA loadings (5–20 wt.% calcined at 750 ◦C) and calcination temperature (15 wt.% calcined from 650 to 850 ◦C) were prepared and characterized by 31P MAS NMR and FT-IR pyridine adsorption spectroscopy. The catalyst with optimum PTA loading (15%) and calcination temperature (750 ◦C) was prepared in different solvents. 31P MAS NMR spectra of the catalysts showed two types of phosphorous species, one is the Keggin unit and the other is the decomposition product of PTA and the relative amount of each depends on PTA loading, calcination temperature and the solvent used for the catalyst preparation. The catalysts with 15% PTA on zirconia calcined at 750 ◦C showed the highest Br¨onsted acidity. At 130 ◦C and phenol/benzyl alcohol molar ratio of 2 (time, 1 h), the most active catalyst, 15% PTA calcined at 750 ◦C gave 98% benzyl alcohol conversion with 83% benzyl phenol selectivity.