Selective hydroxyalkylation of phenol to bisphenol F over dodecatungstophosphoric acid (DTP) impregnated on fumed silica

The catalyst activity of various solid acids, such as fumed silica (SiO2), dodecatungstophosphoric acid (DTP), DTP impregnated on SiO2, amberlyst-15 and montmorillonite KSF/0, was studied for the hydroxyalkylation of phenol to bisphenol F. A well-dispersed DTP on SiO2 catalyst was prepared by the wet impregnation method. The effect of DTP loading on SiO2 was also compared with bulk DTP and other solid acid catalysts. 20% DTP/SiO2 catalyst gave the highest products yield of 34.2% and selectivity of 90.1% to bisphenol F, at 353 K and with a phenol-to-formaldehyde mole ratio of 5:1. Ammonia TPD studies of various catalysts showed that an appropriate combination of both strong and weak acid sites of DTP/SiO2 was mainly responsible, rather than only the stronger acidity of bulk DTP, for its highest catalytic activity and selectivity. The effect of various reaction parameters like mole ratio, catalyst concentration, temperature and reaction time on product yield and bisphenol F selectivity was also investigated. The catalyst recycle was established by catalyst activity testing.

A well-dispersed 20% DTP/SiO2 catalyst gave the highest product yield (34.2%) and bisphenol F selectivity (90.1%) in hydroxyalkylation of phenol due to an appropriate combination of both strong and weak acid sites. For 40% DTP/SiO2 catalyst, an increase in strong acid sites caused further reaction of bisphenol F to give a trimer with a decrease in selectivity (75%) to bisphenol F.Figure optionsDownload as PowerPoint slide