Nitric Oxide Reduction with Hydrogen on Mixed Metal Oxide Catalysts

Abstract

Catalytic reduction of nitric oxide with hydrogen was investigated on a number of mixed oxide and oxide mixtures in a laboratory integral reactor using a feed gas containing 520 ppm of NO and 3000 ppm of H/sub 2/ in a nitrogen carrier gas to determine catalytic activity and ammonia formation. Then some of the more promising catalysts were tested in actual automobile exhaust to determine their feasibility in catalytic reactors for NO reduction. Highest yields of NH/sub 3/ at 90 percent conversion of NO or higher in the first test were observed with rare earth nickel iron oxide and copper-vanadium oxide, copper-nickel oxides, monel, platinum, palladium, and rhodium. Each of these catalysts showed stoichiometric conversion to NH/sub 3/ at a specific temperature. Platinum and palladium maintained this stoichiometric conversion up to 500 C; monel showed a sharp drop in NH/sub 3/ yield above the temperature of stoichiometric conversion (450 C). Lowest NH/sub 3/ maxima for NO conversion levels above 90 percent were observed with ruthenium, mixed ruthenium oxides, and a series of nickel- containing catalysts. When tested in auto exhaust, ruthenium and mixed ruthenium oxides were particularly active and appeared to exhibit true selectivity for reduction of NO to N/submore » 2/. (Air Pollut. Abstr.)« less