Rhodium complexes supported on zinc aluminate spinel as catalysts for hydroformylation and hydrogenation:: Preparation and activity

The heterogenization of active homogeneous rhodium catalysts on zinc aluminate spinel has been studied. The ZnAl2O4 support was prepared by a hydrothermal process and characterized by transmission electron microscope (TEM), RTG, and textural investigations. The rhodium(I) complexes, Rh(acac)(CO)(2), Rh(acac)(CO)(PPh3), and RhCl(CO)(PPh3)(2), Supported on the spinel, gave Rh(CO)(2)(+), Rh(CO)(PPh3)(+), and Rh(CO)(PPh3)(2)(+) species. respectively, as confirmed by IR spectra. Rh(CO)(2)(+) on the spinel with an excess of PPh3 effectively catalysed the hydroformylation of 1-hexene under 1 MPa of H-2/CO at 356 K. Aldehydes yield of 40-95% were obtained with an n/iso ratio of ca. 3. The coordination of 1-hexene to supported Rh(CO)(2)(+) species was evidenced by the appearance of a v(CO) band at 2053 cm(-1). Rh(CO)(2)(+)-supported on the spinel catalysed the hydrogenation of nitrobenzene and chloronitrobenzene at 1 MPa of H-2 and 356 K with a TON of 400-500 h(-1). (C) 2002 Elsevier Science B.V All rights reserved.