Catalytic oxidation of NO with O2 over Pt/γ-Al2O3 and La0.8Sr0.2MnO3

Catalytic oxidations of NO with O2 over a number of catalysts were scanned with a tubular reactor at various times and temperatures. La0.8Sr0.2MnO3 and Pt/γ-Al2O3 gave the promising reactivity to catalyze this reaction. Under the conditions of 0.720 s space time, 0.05 vol% NO concentration, 5 vol% O2 concentration and 473 K, the steady-state conversion of NO oxidation over Pt/γ-Al2O3 and La0.8Sr0.2MnO3 reached 22.4% and 90.5%, respectively. A kinetic model consisting of 12 elementary reactions was developed to fit the experimental data. The results showed that the rate-limiting step of NO oxidation over Pt/γ-Al2O3 was the reaction between gaseous NO and dissociative O on the catalyst surface with activation energy of 80.01 kJ mol−1 in the temperature range 423–573 K, and that the rate-limiting step of NO oxidation over the most promising catalyst La0.8Sr0.2MnO3 was the desorption of NO2 from catalyst surface with activation energy of 101.0 kJ mol−1 in the range of 373–473 K.

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► A kinetic model was developed to interpret the catalytic oxidation of NO.
► NO oxidation on Pt/γ-Al2O3 was controlled by reaction of gas NO and O on the surface.
► NO oxidation on La0.8Sr0.2MnO3 was controlled by desorption of NO2 from the surface.