A novel production of γ-butyrolactone catalyzed by homogeneous ruthenium complexes

Abstract

γ-Butyrolactone (GBL) is produced by a two-stage hydrogenation of maleic anhydride (MAH) in the liquid phase: a hydrogenation of MAH to succinic anhydride (SAH) in the first stage and a subsequent hydrogenation of SAH to GBL in the second stage. A novel ruthenium catalyst system consisting of Ru salts, trialkylphosphine and p-toluenesulfonic acid (p-TsOH) was found very effective for the hydrogenation of SAH affording GBL in selectivities not less than 95%. Acid promoters like p-TsOH induce structural change in the Ru complexes, leading to the cationic complexes, which show higher catalytic activity and selectivity than the neutral ones. A new process to produce GBL was also developed, in which the features are external preparation of Ru complexes, the reaction protocol which combine over-flow reaction with stripping and the catalyst recovery system by the extraction.