Influence of Re-M interactions in Re-M/C bimetallic catalysts prepared by a microwave-assisted thermolytic method on aqueous-phase hydrogenation of succinic acid

Carbon-supported Re-M (M = Pt and Rh) bimetallic catalysts with controlled size and composition were synthesized by using a microwave-assisted thermolytic method and evaluated in the aqueous phase hydrogenation of succinic acid. The Re-M interaction contributes to the inhibition of aggregation of particles and to the improvement in the catalytic activity for succinic acid hydrogenation through decreasing the activation energy. The Re-M interaction favors the ring opening of.-butyrolactone, an intermediate product, to 1,4-butanediol instead of the hydrogenation and dehydration to tetrahydrofuran observed over a Re/C catalyst. The kinetic study proves that the Re-M interaction can increase the relative formation rate of 1,4-butanediol more than that of tetrahydrofuran, while the strength of the Re-M interaction has a limited influence on the product selectivity. It was shown that the Re-Rh interaction can reduce the direct hydrogenolysis of succinic acid, but it cannot avoid the hydrogenolysis of 1,4-butanediol, thus limiting the selectivity to this product. According to the kinetic mechanism, ring opening of.-butyrolactone is favored at low temperature while direct hydrogenation to tetrahydrofuran is favored at high temperature.