CONICET | Buscador de Institutos y Recursos Humanos

The effect of noble metal catalysts supported on an ionic exchange resin for the enantioselectivehydrogenation of ethyl pyruvate to ethyl lactate was studied. High activity and moderateenantioselectivity levels were obtained. Pt was the best enantioselective metallic phase, followedby Pd and Au; Rh was the less enantioselective metallic phase. The effect of the active site wasevaluated for the most enantioselective catalyst: 2Pt-WA30 (prefix indicates the metal loading). Anovel method for sintering the Pt metal particles by nitriles reduction was used, and a controlledmigration of the metal particles to the surface layers was observed. There existed an optimalparticle size with maximization of the enantiomeric excess, corresponding to 24 h sintering.The hydrogenation of ethyl pyruvate to ethyl lactate was found to be structure-sensitive and theimportance of the metal particle size for the adsorption of the chiral modifier was proved. Twodifferent chirality induction methods were tried for the 2Pt-WA30 catalyst: (i) the addition of thechiral modifier (CM) to the reaction media, or (ii) the modification of the catalyst in a swellingmedium prior to the reaction in order to encapsulate CM. Lower activity but higher enantioselectivitylevels were obtained with method (ii). Finally, the reuse of the catalysts was also assessed bymeans of consecutive reaction tests.