METHOD FOR CATALYTICALLY REDUCING NITROGEN OXIDE

PROBLEM TO BE SOLVED: To catalytically reduce nitrogen oxides by bringing a gaseous stream contg. one kind or more nitrogen oxides and hydrogen into contact with a monolithic supported noble metal catalyst. SOLUTION: A gaseous stream contg. nitrogen oxides consisting of nitrogen monoxide and/or dinitrogen oxide and hydrogen is brought into contact with a monolithic supported noble metal catalyst at a temp. of from about 100 deg.F (38 deg.C) to about 600 deg.F (316 deg.C) to reduce it and to convert the nitrogen oxides into nitrogen, ammonia and water at about a 95-99.9% conversion rate. The gaseous stream preferably has a compsn. contg. about 0.5-5.0 vol.% nitrogen monoxide, about 0.5-5.0 vol.% dinitrogen oxide, about 3.0-40.0 vol.% hydrogen and about 50-96 vol.% other gases such as nitrogen, methane and ammonia. The monolithic carrier is preferably obtd. by coating a single honeycomb structure made of an inert, porous refractory ceramic with alumina. The catalyst is obtd. by supporting a catalytic noble metal, preferably platinum, rhodium or a mixture of them on the carrier.