Abstract
The adsorptive and reactive properties of a series of Rh/Al2O3 catalysts promoted with various levels of Cs were investigated by IR spectroscopy of CO adsorption, temperature-programmed desorption of H2, and CO hydrogenation reactions. The results indicate that a significant fraction of the added Cs interacts directly with the support rather than with the Rh crystallites. The degree of interaction between the alkali species and both metal and support sites on the catalyst depends strongly on the method of preparation of the catalyst, which may affect the chemical state of the alkali species. Trends for CO hydrogenation reaction activity and product selectivity were consistent with those reported for promoted Rh on other supports except that the level of promotion required to achieve similar results is much higher for Rh supported on Al2O3. These investigations demonstrate how a combination of experimental techniques may provide significantly more information about the effects of alkali promotion than would any of the methods used alone.