Preparation and characterisation of Rh/Al2O3 catalysts and their application in the adiponitrile partial hydrogenation and styrene hydroformylation

Rh/Al2O3 catalysts with a low metal loading were prepared using different preparation methods (ion exchange and homogeneous precipitation through urea decomposition). Catalysts with very high rhodium dispersion were obtained by properly choosing the preparation parameters. Moreover the kinetic parameters for the adsorption of the precursor on the support were determined. The catalysts were tested in two industrially important reactions: the adiponitrile hydrogenation and hydroformylation reaction of styrene. The hydrogenation of adiponitrile was carried out in mild conditions in a slurry reactor, at temperatures between 70 and 100 °C and under a hydrogen pressure of 3 MPa. The catalyst prepared with the ion exchange technique gave aminocapronitrile with a conversion of 60% and a selectivity of 99%. The catalyst was very active in the hydroformylation of styrene, but it suffered leaching problems such as many supported catalysts.