The Effect of Supports on the Activity of Methane Dissociation over Rh Catalysts

Abstract

The Rh-CeO2, interaction and the activity of CH4 dissociation were investigated on Al2O3- and SiO2-supported Rh catalysts by using the pulse reaction technique, infrared spectroscopy of CO adsorbed, and infrared spectroscopy of pyridine adsorbed. The Rh-CeO2 interaction was strongly influenced by the acidity of support. Addition of CeO2, to Rh/Al2O3 increased the number of Lewis acid sites on Al2O3, which in turn enhanced the ability of Al2O3 to accept electrons. This decreased the electron density of Rh and consequently facilitated the activation and dissociation of CH4 on Rh. On the contrary, the addition of CeO2 to Rh/SiO2 decreased both the number and the strength of Lewis acid sites on SiO2, which weakened the electron- accepting ability of SiO2. As a result, it brought out an increase in the electron density of Rh and inhibited CH4 dissociation on Rh.