Catalysis by the Rh/B system Part 1. Vapour-phase hydroformylation of ethylene at atmospheric pressure on Rh/B on silica

A Rh/B system with rhodium crytallites of small dimensions was formed by reducing rhodium trichloride supported on silica with NaBH4 atlow temperature. Thermal treatments in Ar and/or in CO/H2 strongly modify the surface composition but induce only a small modification in the crystallite diameter. After treatment in Ar at 543 K and in CO/H2 the Rh/B system catalyzes the vapor-phase hydroformylation of ethylene at atmospheric pressure in a flow reactor. The reaction proceeds with very good chemoselectivity toward the hydroformylation products (at 398 K, R is ≥0.7). The formation of the catalytic species and the surface modifications were studied by X-Ray diffraction, FT-IR and XP spectroscopy. The presence of boron seems to play an important role both in preventing sintering of rhodium particles and in favouring good chemoselectivity toward the hydroformylation reaction. © 1993.