Vapor-phase hydrogenolysis of biomass-derived lactate to 1,2-propanediol over supported metal catalysts

Vapor-phase hydrogenolysis of ethyl lactate to 1,2-propanediol was performed over a series of SiO2 supported metal (Fe, Co, Ni, Ru, and Pd) catalysts in a fixed-bed reactor. Among them, the Co/SiO2 and Cu/SiO2 catalysts exhibit promising performance, and the Co/SiO2 were more active than the traditional copper Catalysts Under mild conditions. Effects Of Support, metal loading and preparation method were investigated to optimize the performance of the Co-based catalysts. Over the optimal catalyst (a 10 wt.% Co/SiO2 catalyst prepared via rotary evaporation drying method), the 1,2-propanediol selectivity was in excess of 98% at 90.2% lactate conversion, 2.5 MPa and 160 degrees C. The cobalt catalysts were characterized by X-ray diffraction (XRD) and temperature programmed reduction by H-2 (H-2-TPR) and temperature programmed desorption of H-2 (H-2-TPD). Interestingly, a quasi-linear correlation is observed between the average reaction rate and the percentage of bulk-like Co3O4 phase precursors, suggesting that the metallic cobalt from the bulk-like Co3O4 phase precursor is more active than that from the cobalt surface support species. The emerging technologies for production of low-cost lactate ester, make this high-yield route a sustainable benign process for 1,2-propanediol. (c) 2008 Elsevier B.V. All rights reserved.