Selective Hydrogenation of Lactic Acid to 1,2‐Propanediol over Highly Active Ruthenium–Molybdenum Oxide Catalysts

Modification of Ru/C with a small amount of MoO x (RuMoO x /C) enhanced the catalytic activity in the hydrogenation of L ‐lactic acid to form 1,2‐propanediol and maintained high selectivity. The turnover frequency based on the amount of Ru over the optimized RuMoO x /C catalyst (Mo/Ru molar ratio=1:16) was 114 h −1 at 393 K, which was about 4 times higher than that over Ru/C. The same effect of MoO x was obtained over RuMoO x /SiO 2 , although RuMoO x /SiO 2 showed slightly lower activity than that of RuMoO x /C. RuMoO x /C achieved a high yield of 95 % in 18 h at 393 K and was applicable to various carboxylic acids to provide the corresponding alcohols in high yields. Modification with MoO x also brought about suppression of racemization and ( S )‐1,2‐propanediol was obtained in high enantiomeric excess at 353 K. Based on kinetic analysis and characterization data, such as XRD, TEM, CO adsorption by a volumetric method, FTIR spectroscopy, and X‐ray absorption spectroscopy, for RuMoO x /C and RuMoO x /SiO 2 , the catalyst structure and reaction mechanism are proposed.