Effect of temperature and pressure on the surface kinetic parameters of Pt/γ-Al2O3 during selective CO oxidation

The results of this investigation showed that under this reaction condition, increasing reaction temperature and total pressure had similar effects on the overall activity and surface kinetic parameters of the Pt catalyst for the selective oxidation of CO. The effects of temperature and total pressure can be summarized as follows: - Increasing temperature from 80 to 110 °C or total pressure from 1.2 to 3 atm increased the rate of reaction significantly, but had only a slight effect on the selectivity. - As shown by ITKA, reaction temperature or total pressure affects the surface concentration of CO2 intermediates, but not average site activity (average pseudo-first-order rate constant). - Since Ni-CO2 seemed to be limited by the amount of adsorbed oxygen at lowtemperatures (80-110 °C), the increase in Ni-CO2 while total concentration of surface CO remained essentially constant suggests that increasing temperature or total pressure plays a significant role in activating nonactive or less active sites by increasing the probability of oxygen adsorption. We conclude that, for the selective oxidation of CO on Pt/γ-Al2O3 at relatively low temperatures, one can increase the rate of CO oxidation without significantly affecting selectivity by changing the operating conditions (total pressure, temperature) and thus the surface concentration of intermediates. Since the reaction appears to be limited by the amount of adsorbed oxygen, increasing oxygen adsorption by either increasing temperature or total pressure increases the overall rate of reaction. Loss of hydrogen (nonselective oxidation) and the amount of oxygen consumed can be minimized by using higher operating pressures instead of an increased O2/CO ratio to get higher CO conversion. © 2004 Elsevier Inc. All rights reserved.