A ZEOLITE CATALYST FOR THE DECOMPOSITION OF NITROGEN OXIDES IN A NET-OXIDIZING FLUE GAS

AMONG THE MOST IMPORTANT OF THE POLLUTANTS ARISING FROM THE COMBUSTION OF COAL ARE THE NITROGEN OXIDES (NO AND NO2, OR NOX). CURRENTLY, THE ONLY CATALYTIC PROCESSES CAPABLE OF CONTROLLING NOX IN THE AIR-RICH FLUE GASES OF A COAL-FIRED POWERPLANT REQUIRE THE ADDITION OF A REDUCING GAS, SUCH AS AMMONIA OR UREA, TO THE FLUE GAS. THIS NOT ONLY LEADS TO INCREASED COSTS, BUT EMISSIONS OF THE REDUCING GAS MAY ADD TO THE POLLUTION PROBLEM. EVEN THOUGH THE DECOMPOSITION OF NITROGEN OXIDES TO NITROGEN AND OXYGEN IS THERMODYNAMICALLY FAVORED, THERE ARE NO COMMERCIAL CATALYSTS CURRENTLY CAPABLEOF CARRYING OUT THIS REACTION. A DIRECT CATALYTIC DECOMPOSITION PROCESS THAT DOES NOT REQUIRE THE USE OF A REDUCING GAS WOULD BE A MAJOR ADVANCE. THIS PROJECT WILL TEST ZEOLITE CATALYSTS EXPECTED TO BE CAPABLE OF CARRYING OUT THIS REACTION. THESE MATERIALS HAVE A LOWER AFFINITY FOR OXYGEN THAN DO OTHER CATALYSTS AND ARE THEREFORE NOT POISONED BY THE REACTION PRODUCTS. IN PHASE I, SUBSTITUTED ZEOLITES ARE BEING PRODUCED AND THEIR PERFORMANCE EVALUATED UNDER CONDITIONS REPRESENTATIVE OF THE FLUE GASES FROM A COAL-FIRED POWERPLANT. IMPROVED CATALYSTS ARE BEING DEVELOPED, MODIFYING THE STRUCTURE AND COMPOSITION OF THE MATERIAL. IN PHASE II, THE CATALYTIC ACTIVITY WILL BE IMPROVED FURTHER, THE EFFECT OF KNOWN POISONS WILL BE EVALUATED, AND THE CATALYST CAPABILITIES WILL BE DEMONSTRATED IN A FLUE GAS SLIPSTREAM.