Kinetics of selective CO oxidation in hydrogen-rich mixtures on Pt/alumina catalysts

Abstract

Selective CO oxidation on Pt/alumina catalysts in hydrogen-rich mixtures was studied in a temperature range of 150–350°C and a concentration range of 0.5–2% for oxygen and carbon monoxide. The intrinsic kinetics of the CO oxidation was well described by a simple power-law expression with an activation energy of 78kJ/mol and the reaction orders of −0.51 and 0.76 for the CO and the oxygen partial pressure, respectively. The selectivity showed a maximum with increasing temperature and was dependent mainly on the feed composition and the reaction temperature. But the selectivity did not show any appreciable change with respect to flow rate, indicating a constant selectivity along the catalyst bed, and Pt loading of the catalyst in the range of 0.04–1wt.%, even though the 1wt.% catalyst exhibited severe internal diffusional limitation. For this, the selectivity once measured for a Pt/alumina catalyst as a function of feed composition and temperature could be used for other Pt/alumina catalysts of different activities and for different conversion levels. A reactor model with an approximation of the internal effectiveness factor was developed to simulate the integral reactor performance with the 1wt.% catalyst.