Synthesis and structure of copper hydroxyphosphate and its high catalytic activity in hydroxylation of phenol by H2O2

A complex oxide of Cu-2(OH)PO4 has been successfully synthesized by the hydrothermal method, and its structure was investigated by X-ray analysis. It crystallizes in the orthorhombic space group of Pnnm with a = 8.058(2), b = 8.393(2), and c = 5.889(2) A. Furthermore, the sample was characterized by thermal analysis (DTA and TG), and these results indicated that the sample was stable below 650 degreesC. After calcination at 850 degreesC, Cu-2(OH)PO4 was dehydrated to form Cu4O(PO4)(2). The sample isotherm for N-2 showed that there wre no micropores or mesopores, and the surface area was only at 1.4 m(2)/g when the particle size of the sample was 150 mum. Moreover, when this sample was used as a catalyst for phenol hydroxylation by H2O2, the catalytic data showed high activity, which was comparable to that of TS-1. Various factors that influence this catalytic reaction, such as the solvent, reaction temperature, reaction time, catalyst size, catalyst amount, molar ratio of phenol to H2O2, and mode of H2O2 addition, were investigated intensively Additionally, this catalytic reaction was characterized by electron spin resonance (ESR), and it was found that on the Cu-2(OH)PO4 catalyst hydroxyl radicals possibly resulting from Cu2+ and H2O2 were important intermediates for formation of catechol and hydroquinone from hydroxylation phenol. (C) 2001 Academic Press.