Aqueous phenol oxidation catalysed by molybdenum and tungsten carbonyl complexes Original Research Article

The catalytic activities of the complexes, Cp′M(CO)3X (Cp′ = Cp (η5-C5H5), Cp* (η5-C5Me5); M = Mo, W; X = Cl, CH3) and Mo(CO)6 have been examined for the oxidation of phenol (37.6 g/L) using H2O2 as oxidant in aqueous solution. Among them, CpMo(CO)3Cl and CpMo(CO)3(CH3) showed the highest catalytic activity. Conversion of phenol at 55 °C is more than 80% after 24 h when water is used as solvent and the ratio of catalyst:phenol:H2O2 is 1:50:200. The main oxidation products observed in solution are oxalic acid and catechol, together with trace amount of p-benzoquinone and maleic acid. Under similar conditions, binary Mo(CO)6 catalyses phenol oxidation giving hydroquinone and p-benzoquinone as main products.