Role of Re and Ru in Re-Ru/C Bimetallic Catalysts for the Aqueous Hydrogenation of Succinic Acid

To obtain an effective supported metallic catalyst for aqueous hydrogenation of succinic acid (SA), C-supported Re-Ru catalysts with different Re/Ru ratios were sought by using a convenient and environmentally friendly microwave-assisted thermolytic method. The results indicate that the as-prepared Re-Ru/C catalysts exhibit high dispersion with fairly small average particle size (0.7-1.6 nm) and well structural properties. During the transformation of SA, the Ru composition is responsible for the hydrogenolysis of SA, while the Re composition favors the hydrogenation of SA. The bimetallic Re Ru interaction promotes the formation of 1,4-butanediol (selectivity is 70.1% with complete conversion), which could rarely be detected when using Re/C or Ru/C monometallic catalysts. The kinetic study further reveals that the introduction of Ru significantly reduces the apparent activation energy from 62 to 40 kJ mol(-1) and increases the saturation ability of hydrogenation intermediates on the surface of catalysts compared with Re/C. A Re Ru/C bimetallic catalyst accelerates the formation rate of 1,4-butanediol relative to that of tetrahydrofuran. According to a kinetic mechanism, ring opening of gamma-butyrolactone is favored at low temperature, while direct hydrogenation is favored at high temperature: