Catalytic Reduction of Nitrogen Oxide with Ammonia over Copper: and Iron Sulfate Catalysts

Abstract

The catalytic reduction of nitrogen oxide with ammonia in the presence of NO-02-H₂0-N2 and NO-S02-0g-H₂0-N, mixtures (N0 (2/3) NH, -+ (5/6)N2+ HP) was studied using a flow reactor (inside diameter: 12.0 mm) at atmospheric pressure and temperatures of 300 to 500° C (mainly 400° C).
The catalysts used were coprecipii'ated metal oxides (CuO-Al203, Fe2O^3-A1, 03 etc.), metal oxides treated ith S02-02-N2 mixtures, - and supported sulfates on alumina [CuSO₄-Al203, Fe2(SO₄), -Al203, FeSO₄-Al208]. The average diameter of the granular catalysts was 1.0 min. Inlet gas, concentrations ware 500 ppm NO-0--3000 ppm (mainly 1000 ppm) SO^2-334-1000 ppm (Plainly 667 ppm) NI-1370-45%, (mainl3n5670) 0, -0-20% (mainly 10%) H₂0-N2, and the total gas flow rate was 1000 Ncm3/min for 0.25 3.00 g of the catalyst.
Copper and iron sulfas were found to be excellent with respect to activity and selectivity at lower temperatures -below ca.400° C. It was also confirmed that t4e reaction between NO and NH₃ proceeded equimolally, and that higher as the concentration of 0, increased the -red-action' rate became. For copper sulfate catalyst the presence of SO s made the reduction rate higher.
From these results, the reduction mechanisms were described as follows.