Hydrogenation of Lactic Acid to 1,2-Propanediol over Ru-Based Catalysts.

The catalytic hydrogenation of lactic acid to 1,2-propanediol with supported Ru catalysts in water was investigated. The influence of catalyst support (activated carbon, γ-Al2 O3 , SiO2 , TiO2 , and CeO2 ) and promoters (Pd, Au, Mo, Re, Sn) on the catalytic performance was evaluated. Catalytic tests revealed that TiO2 yields the best Ru catalysts. With a monometallic Ru/TiO2 catalyst, a 1,2-propanediol yield of 70 % at 79 % lactic acid conversion was achieved at 130 °C after 20 h reaction. Minor byproducts of the hydrogenation reaction were propionic acid, ethanol, 1-propanol, and 2-propanol. For the bimetallic catalysts, the addition of Pd and Au slightly enhanced the performance of Ru/TiO2 , whereas the addition of common hydrogenation promoters such as Re, Mo, and Sn impaired the activity.