Oxidation of carbon monoxide by oxygen, nitric oxide and mixtures of O2 and NO over palladium(100)

The rate of CO[sub 2] formation in each of the three reactant mixtures, CO + O[sub 2], CO + NO, and CO + O[sub 2] + NO, was measured over Pd(100) at partial pressures of 1 Torr and temperatures in the range 430-580 K. The rate in both CO + O[sub 2] and CO + NO followed the Arrhenius behavior; in CO + NO, the rate was about 2 orders of magnitude lower than in CO + O[sub 2], whereas the apparent activation energy was about 30% lower. The rate in CO + O[sub 2] + NO, however, was the same as in CO + O[sub 2] at temperatures above 480 K and was even greater at temperatures below 480 K. This behavior may be contrasted with that in the case of Rh, where the addition of No to CO + O[sub 2] drastically reduces the rate of CO[sub 2] formation. 8 refs., 1 fig.