Catalytic reduction of NO by hydrocarbons over a mechanical mixture of spinel Ni–Ga oxide and manganese oxide

Abstract

NO reduction with propylene over Mn2O3, spinel Ni–Ga oxide and their mechanical mixtures has been investigated. Mn2O3 has no activity to NO reduction, but has a high activity for NO oxidation to NO2. Spinel Ni–Ga oxide showed an apparent activity to NO reduction only at temperatures above 400°C. Mixing of Mn2O3 to the Ni–Ga oxide resulted in a significant enhancement of NO reduction in the temperature range of 250–450°C. The optimal Mn2O3 content in the mixture catalyst was about 10–20 wt%. It is suggested that the synergetic effect of Mn2O3 and Ni–Ga oxide plays an important role in the catalysis of NO reduction. The Ni–Ga oxide and Mn2O3 mixture catalyst is superior to Pt/Al2O3 and Cu-ZSM-5 by showing a higher NO reduction conversion, resistance to water and negligible harmful by-product formation. Other lower hydrocarbons C2H4, C2H6 and C3H8 also give a maximum NO reduction conversion as high as 50%. The difference from using C3H6 is that the temperature at the maximum NO reduction is higher than it is with C3H6.