Nitric oxide reduction with carbon monoxide over copper chromite catalyst

Abstract

Main pollutants in automobile exhaust gases can be controlled by the following reaction in a catalytic reactor. $$NO\,+\,CO\;-\;\frac{1}{2}N_2\,+\,CO_2$$ The reaction was studied in view of the effects of the operating conditions and thermal treating of the catalysts on reaction rates by using copper chromite catalysts in a integral reactor. Two types of copper chromite, normal and spinel type, were used in this experiment. The normal type catalyst contained CuO and $CuCr_2O_4$, and spinel type catalyst was almost pure $CuCr_2O_4$. After thermal treating at 800$^\circ$C for 24 hours, the activity of the spinel type slightly decreased, but that of normal type decreased markedly to 50\% of the thermally untreated one. At low CO concentration $(3<CO/NO<8)$, the kinetics of this reaction exhibited an effective reaction order of unity with respect to NO. However at relatively high CO concentration $(CO/NO>8)$ CO caused reaction inhibition. By analyzing the experiental data, the following rate equation based on the adsorption control model was obtained. $$r_m = \frac{4.04 \exp(-2600/RT) C_{NO}}{1+1.29 \times 10^5 \exp(-11270/RT)C_{CO}}$$ The system performances were taken at temperature range of 150 - 270$^\circ$C, 1000 to 6000 ppm of No and 1 to 5\% CO, and contact times in the order of tenths of a second.