Enantio-differentiating hydrogenation of methyl acetoacetate over tartaric acid-modified nickel catalysts: effects of preparation method of supported nickel on activity and selectivity of catalysts

Abstract

Enantio-differentiating hydrogenation of methyl acetoacetate was carried out over supported nickel catalysts modified by (R,R)-tartaric acid and NaBr. The types of support and the preparation methods affected the enantiomeric excess of the obtained product, methyl (R)-3-hydroxybutyrate. Nickel supported on aluminum oxide gave the best enantio-selectivity. Silica-supported catalysts showed lower selectivities. In particular, precipitation deposition of nickel on silica forms nickel silicate, which was difficult to be reduced and constituted a lattice defect of nickel surface. Even reduced nickel surface could be contaminated by silicon in nickel silicate. This defect and the surface contamination may disrupt the arranged adsorption of tartaric acid and reduce the enantio-selectivity of the catalysts.