Role of the modifier in the enantioselective hydrogenation of ethyl pyruvate over Pt/Al2O3 catalyst
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The time dependence of the conversion and enantioselectivity during the hydrogenation of ethyl pyruvate has been studied over an industrial Pt/Al2O3 catalyst. Various cinchona alkaloids were used as modifier and two different modes were applied for their introduction into the reaction system. The dependence of the enantioselectivity on conversion is strongly influenced by the mode of introduction and the structure of the modifier used. The conversion dependence of the enantioselectivity is attributed to the chemical transformations of the parent alkaloid observed under hydrogenation conditions. Experimental evidence is shown for the dynamic nature of the interaction between the modifier and the catalyst.
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