Selective hydrogenation of maleic anhydride to γ-butyrolactone using homogeneous Ru/PPh3 catalyst system

The hydrogenation of maleic anhydride (MA) using various homogeneous transition metal complex catalysts has been studied. It is revealed that RuCl3·3H2O is the most active catalyst and triphenylphosphine is the optimum ligand for the preparation of γ-butyrolactone. The effects of catalyst concentration, mole ratio of triphenylphosphine to Ru, temperature and hydrogen pressure on the hydrogenation have been investigated. By changing reaction conditions, γ-butyrolactone could be produced selectively. A possible reaction mechanism is proposed.