Structural properties of alumina- and silica-supported Iridium catalysts and their behavior in the enantioselective hydrogenation of ethyl pyruvate

Iridium catalysts were prepared using alumina or silica as supports and two preparation methods, incipient wetness impregnation and flame spray pyrolysis. These catalysts were characterized, after reduction in hydrogen, by transmission electron microscopy, infrared spectroscopy of adsorbed CO and microcalorimetry of CO chemisorption. Aliquots of these catalysts were tested in the ethyl pyruvate hydrogenation using cinchonidine as a chiral modifier. Different enantioselectivities to (R)-ethyl lactate were obtained depending on the support material and the preparation method. Based on the structural characterization it is proposed that the different enantioselectivities are mainly due to different surface structure of the iridium nanoparticles caused by the support interaction.

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► Iridium catalysts were studied in the asymmetric hydrogenation of ethyl pyruvate.
► Iridium nanoparticles were prepared by impregnation or flame spray pyrolysis.
► Catalytic performance is influenced by particle size and morphology, and support.
► A correlation between enantioselectivity and the heat of CO adsorption was suggested.