Aqueous-Phase Hydrogenation of Succinic Acid Using Bimetallic Ir–Re/C Catalysts Prepared by Strong Electrostatic Adsorption

Aqueous phase hydrogenation of succinic acid was investigated using a series of Ir–Re/C bimetallic catalysts prepared by strong electrostatic adsorption. Activity measurements show remarkable synergistic effects, forming a volcano-shaped plot over a range of bulk Re mole fractions with a peak at a fraction of 0.4–0.5, which corresponds to a 20-fold enhancement of activity over either monometallic catalyst. This intermediate catalyst composition exhibiting optimum activity strongly suggests a bifunctional effect. Through a consecutive reaction pathway with γ-butyrolactone as an intermediate, the main product is tetrahydrofuran with 60–75% selectivity. Butanol formation is minimized with decreasing Re mole fraction.