Rates for NO chemisorption were measured on different samples of SnO2 in the temperature range 25-150 °C. Kinetic measurements revealed that the extent and the rate of NO adsorption on different surfaces increase in the order SnO2(oxidized) ≪ SnO2(activated) < SnO2(reduced). It was found that preadsorbed NO promotes the adsorption of CO, which was attributed to the formation of a surface isocyanate complex. Electrical conductivity measurements during NO adsorption revealed that both negatively and positively adsorbed species are present on activated surfaces. The catalytic reduction of NO with CO on SnO2 proceeded with reproducible rates only above 360 °C. The reaction was of zero order with respect to CO and first order with respect to NO. The value of the activation energy is 36.6 kcal/mole. It was found that the catalytic reaction takes place on a weakly reduced surface. It is postulated that the reduced centers play an important role in the activation of NO, and NO dissociates upon adsorption. A possible mechanism of the catalytic reduction of NO is discussed.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry