The effect of metal particle size on the enantioselective hydrogenation of methylacetoacetate (MAA) to methyl 3-hydroxybutyrate (MHB) in the gas and the liquid phases was studied over Ni/SiO2 modified with R,R tartaric acid. The Ni particle size of the catalyst at controlled Ni load was increased from 3.3 nm up to about 11 nm by Ostwald ripening, due to the formation and decomposition of gaseous Ni(CO)4. The experimental data showed no significant particle size effect on enantioselectivity within this size range. Atomic absorption analysis of the solution after modification showed that up to 50% of the Ni in the catalyst can be leached out during modification under severe conditions.
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