Iridium-supported catalyst for enantioselective hydrogenation of 1-phenyl-1,2-propanedione: The effects of the addition of promoter and the modifier concentration

Abstract

The enantioselective hydrogenation of 1-phenyl-1,2-propanedione at 298 K and 40 bar over modified iridium-supported catalysts has been studied, using cinchonidine as modifier. The catalysts were prepared by impregnation of Ir(acac) 3 on two different supports: SiO 2 and TiO 2, followed by calcination in air and reduction under hydrogen flow at 773 K. The effects produced by the reduction temperature (473 and 773 K) and the effect of the addition of promoters (CeO 2 and MoO 3) on catalyst surface properties were studied in Ir/TiO 2 catalysts. All the samples were characterized by nitrogen adsorption–desorption isotherms at 77 K, H 2 chemisorption, XRD, TEM, XRD and XPS. In some cases, there was an enhancement in the reaction rate when Ir δ+ species were in the catalysts. The effect of the chiral modifier concentration was also studied and the results revealed a bell-type curve dependence of the enantiomeric excess with the modifier concentration.