Crucial parameters in the selective biphasic hydrogenation of cinnamaldehyde by biphasic Ru-TPPTS and RhCl(TPPTS)3 catalysts

A number of important features in the selective hydrogenation of CALD by biphasic Ru-TPPTS catalysts (TPPTS = tris(m-sulfonatophenyl) phosphine trisodium salt) are discussed. These include the methods of synthesis of water-soluble Ru-TPPTS catalysts, the influence of pH during the synthesis and the hydrogenation reaction conditions (the concentration of catalysts, excess amounts of TPPTS, mass transfer characteristics). The Ru-TPPTS catalyst is not only selective at Cdouble bond; length as m-dashO bonds (which is generally known) but also at Cdouble bond; length as m-dashC bonds if certain parameters are controlled carefully. Ninety-six percentage selectivity to unsaturated alcohol and 97% selectivity to saturated aldehyde were achieved under optimum conditions. Some characteristics of the biphasic hydrogenation by RhCl(TPPTS)3 catalyst are also mentioned and compared, particularly those promoting the high selectivity to saturated aldehyde.