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

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 degrees C. Mixing of Mn2O3 to the Ni-Ga oxide resulted in a significant enhancement of NO reduction in the temperature range of 250-450 degrees 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.