12-Phosphotungstic acid immobilized on activated-bentonite as an efficient heterogeneous catalyst for the hydroxyalkylation of phenol

12-Phosphotungstic acid (PTA) supported on commercially activated-bentonite (BNT) was demonstrated to be efficient in the synthesis of bisphenol F (BPF) by hydroxyalkylation of phenol. In the series of PTA (10–40 wt.%) impregnated-BNT catalysts prepared, 20% PTA/BNT showed the highest product yield (93%) and selectivity (97%), which was higher than that of parent PTA and BNT individually, due to the excellent dispersion of PTA on BNT leading to the redistribution of Brönsted and Lewis acid sites on BNT. NH3-TPD studies of various catalysts revealed that an appropriate combination of both strong and weak acid sites could contribute to a higher yield of BPF compared to the catalyst Al-MCM-41, and the Brönsted acid sites were more crucial in achieving a higher selectivity to 4,4′-isomer than Lewis acid sites.