Temperature-programmed desorption (TPD), reaction (TPR) and oxidation (TPO) of species formed on Rh/MgO after interaction with H2 and CO

Abstract

Chemisorption and reaction of CO on a 2.5 wt. % Rh/MgO catalyst appears to be sensitive to the adsorption temperature and the extent of CO/He treatment. CO, CO2 and H2 are produced during temperature-programmed desorption following CO chemisorption. Results from 13CO experiments suggest that most CO2 arises from interaction of CO residing on Rh with -OH groups on the magnesia support, and also from direct interaction of CO with the support. Inactive carbon accumulates on the Rh surface during CO/He treatment at 573 K. This can only partly be removed by H2 or O2 treatments at 723 K, and is considered to be partly responsible for deactivation of the catalyst and suppression of H2 and CO chemisorption after prolonged treatment of the catalyst with CO/He. Hydrogen chemisorption on the present Rh/MgO catalyst is found to be an activated process. The results suggest that this activated chemisorbed H2 is present on the Rh and not on the support. © 1991.