FIELD: inorganic compounds technology. SUBSTANCE: invention relates to reduction of nitrogen monoxide formed in catalytic combustion of ammonia by oxygen into nitrogen oxides involving catalyst system consisting of at least one first catalyst grid and at least one second catalyst grid, the former being platinum-rhodium grid and the latter as well as a grid disposed below being palladium-rhodium ones with at least 92 wt % palladium and 2-4 wt % rhodium (the rest platinum). EFFECT: enhanced efficiency of nitrogen monoxide reduction and increased degree of ammonia-into-nitrogen oxide conversion. 1 cl, 10 ex
