Studies on heteropoly acid supported zirconia: III: Oxidative bromination of phenol using phosphotungstic acid supported on zirconia

A series of ecofriendly solid acid catalyst were synthesized by supporting phosphotungstic acid onto hydrous zirconia by an incipient wetness impregnation method in order to contribute towards clean technology. The support and resulting catalysts were characterized by various spectral and physicochemical techniques. Their catalytic activities were evaluated for oxybromination reaction of phenol by varying different reaction parameters. The electrophilic substitution of bromine generated in situ from KBr as a bromine source and hydrogen peroxide as an oxidant. The 15 wt.% of phosphotungstic acid supported on hydrous zirconia shows highest surface area, acid sites and gives about 93% conversion with 81% para-selectivity.

The electrophilic substitution of bromine generated in situ from KBr as a bromine source and hydrogen peroxide as an oxidant. In presence of H2O2, the acetic acid gives peracetic acid, which is stronger oxidant than H2O2 and efficiently oxidizes the Br− to Br+, which reacts in presence of BrØnsted acidic centres of ZPTA with the organic substrate phenol to give, brominated compounds. Figure optionsDownload as PowerPoint slide