Preparation, characterisation of molybdophosphoric and tungstophosphoric acid intercalated zinc aluminium hydrotalcite-like compounds and their catalytic evaluation towards the oxidative bromination of phenol

Abstract

Oxybromination of phenol was carried out using an efficient and highly regioselective catalyst that is molybdophosphoric acid (MPA) and tungstophosphoric acid (TPA) intercalated zinc aluminium hydrotalcite-like-compounds (ZAH). The ZAH was prepared by co-precipitation method. The intercalation of MPA and TPA was done following indirect method by taking terephthalic acid intercalated ZAH as the precursor. All the materials were characterized by XRD, FT-IR, BET-surface area and surface acidity. The catalytic activity of these materials towards oxybromination of phenol was studied using KBr as a bromine source and H2O2 as an oxidant. The percentage of conversion was found to be maximum in case of 15 wt% molybdophosphoric acid loaded sample; 82% of phenol conversion with 58% para, 38% ortho and 4% dibromo selectivity. (c) 2006 Elsevier B.V. All rights reserved.