Supported transition metal complexes: V. Liquid phase catalytic hydrogenation of hexene-1, cyclohexene and isoprene under continuous flow conditions

Abstract

Listen

Translate article

Three complexes of rhodium and one of iridium of the type MX(phosphine) n , where X = halide and n = 2 or 3, have been chemically bonded to silica. The resulting materials have been shown to catalyze the hydrogenation of hexene-1, cyclohexene, and isoprene in the liquid phase under a variety of continuous flow conditions (15–50 atm H 2 , 20–160 °C). n -Butyl mercaptan in the feedstock reduces the activity, but increases the thermal stability of the catalysts. Continuous flow operation for 70 hr without loss of activity in the hydrogenation of hexene-1 and cyclohexene has been demonstrated for the heterogeneous complex RhBr(SIL CH 2 CH 2 PPh 2 ) 2 . (SIL CH 2 CH 2 PPh 2 represents the phosphine ligand linked to the surface of silica.) Rhodium elution from the catalysts was extremely small, generally below the limit of detection (0.2 ppm).