Preparation and evaluation of novel hydrous metal oxide (HMO)-supported noble metal catalysts

Hydrous Metal Oxides (HMOs) are chemically synthesized materials that, because of their high cation exchange capacity, possess a unique ability to allow the preparation of highly dispersed supported-metal catalyst precursors with high metal loadings. This study evaluates high weight loading Rh/HMO catalysts with a wide range of HMO support compositions, including hydrous titanium oxide (HTO), silica-doped hydrous titanium oxide (HTO:Si), hydrous zirconium oxide (HZO), and silica-doped hydrous zirconium oxide (HZO:Si), against conventional oxide-supported Rh catalysts with similar weight loadings and support chemistries. Catalyst activity measurements for a structure-sensitive model reaction (n-butane hydrogenolysis) as a function of catalyst activation conditions show superior activity and stability for the ZrO{sub 2}, HZO, and HZO:Si supports, although all of the Rh/HMO catalysts have high ethane selectivity indicative of high Rh dispersion. For the TiO{sub 2}-, HTO-, and HTO:Si supported Rh catalysts, a significant loss of both catalyst activity and Rh dispersion is observed at more aggressive activation conditions, consistent with TiO{sub x} migration associated with SMSI phenomena. Of all the Rh/HMO catalysts, the Rh/HZO:Si catalysts appear to offer the best tradeoff in terms of high Rh dispersion, high activity, and high selectivity