Novel catalyst of copper hydroxyphosphate with high activity in wet oxidation of aromatics

A novel catalyst of copper hydroxyphosphate (Cu₂(OH)PO₄) that has neither microporous nor mesoporous pores was successfully synthesized by a hydrothermal method. Catalytic data in the hydroxylation of phenol, benzene and naphthol by hydrogen peroxide showed that copper hydroxyphosphate is a very active catalyst. Comparison of various catalysts on phenol hydroxylation suggests that the unusual catalytic activity on the Cu₂(OH)PO₄ catalyst may be dependent on the unique structure of as-synthesized Cu₂(OH)PO₄. Characterization of catalytic phenol hydroxylation over Cu₂(OH)PO₄ catalyst by electron spin resonance (ESR) gives very strong signals assigned to hydroxyl radical (•OH) species, the intensities of which are linearly related to the catalytic conversion, suggesting that hydroxyl radicals are important intermediates in the catalysis.