Studies on heteropoly acid supported zirconia II. Liquid phase bromination of phenol and various organic substrates

Heteropoly acid promoted zirconia sample were prepared by an incipient wetness impregnation method using different types of heteropoly acid. The liquid phase bromination of phenol was carried out using heteropoly acid supported zirconia as catalyst, KBr as brominating agent and hydrogen peroxide as an oxidant in acetic acid medium at room temperature. The reaction proceeds through the formation of Br+ (bromonium ion), which attacks the phenol ring forming different brominated products. Among all the HPAs loaded samples, phosphotungstic acid supported zirconia shows highest catalytic activity with 93% conversion and 81% para selectivity.