INVESTIGATION ON CATALYTIC REDUCTION OF NO WITH METHANE OVER METAL-CATALYSTS

Catalytic reduction of NO with methane over Pd/MgO, Pd/Al2O3, Co/MgO a nd Pt/Al2O3 catalysts has been studied using a closed circulation appa ratus. The reaction activities of catalysts are: Pd/MgO > Pd/Al2O3) > Pt/Al2O3 > Co/MgO. The mol. ratio of CO2 and N-2 in the products is ne ar 1/2, which indicates that the reaction can be described as 4NO+CH4 --> 2N(2), + CO2 + 2H(2)O. With N2O as an intermediate, the reaction m echanism can be described as (NO-->N2O-->N2)-N-k1-N-k2. The values of k(1) and k(2) for the catalysts used are related as follows: Co/MgO ca talyst, k(1) much less than k(2) at 600 degrees C; Pd/MgO catalyst, k( 1) approximate to k(2) at 420 degrees C; and Pd/Al2O3 catalyst, k(1) > k(2) at 420 degrees C. Methane can be used as reductant to remove the emission under mild reaction condition. CO is detected when NO+CH4 re acts on Pd/Al2O3. It is assumed that the excess CH4 would react furthe r with the reaction product CO2 to produce CO.