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.