The oxidation state of dispersed Rh on Al2O3

Abstract

An extensive infrared investigation of the CO/Rh/Al2O3 system has revealed the presence of eight different CO/Rh species including two which have not been observed previously. It has been shown that Rh loading on an alumina support is more critical than reduction temperature in effecting infrared spectral changes in the 1800–2200 cm−1 region. The oxidation state of Rh for the various CO/Rh species has been discussed; it has been postulated that for several of the species the oxidation state of Rh is greater than O. Furthermore, this work indicates that there is significant atomic dispersion on Rh/Al2O3 catalysts prepared from RhCl3⋅3H2O/Al2O3 by a procedure described originally by Yang and Garland. These catalysts retain appreciable amounts of chlorine even following hydrogenation at 673 K.