Nitrous Oxide Abatement by Catalytic Treatment: Preliminary Study

摘要

Decomposition of N_2O on Fe-exchanged zeolites supported over ceramic monoliths has been studied in a fixed bed reactor. Simulated gas mixtures were used under operating conditions reproducing those typical for fluidized bed combustion. A series of screening tests has been carried out. A strong enhancement of the N_2O decomposition by increasing reaction temperature was observed. Different monolith blocks showed similar behaviour. An increment of gas hourly space velocity led to a considerable decrease of N_2O conversion. The entering N_2O concentration had no significant effect on the N_2O decomposition. N_2O decomposition appears to be first order with respect to partial N_2O pressure, in the presence of oxygen, with an activation energy of about 22 KJ/mol. A strong improvement of the N_2O decomposition by addition of a reducing agent, like propane, was found even under deactivating environment. Finally, a long-term stability test has been carried out with propane addition in the presence of the most deactivating gas constituents. The catalyst maintained high catalytic activity after five hundred hours of continuous operation. The combination of Fe-ZSM-5 supported on ceramic monoliths with propane addition appears to be a promsing development for N_2O decomposition under fludidized bed combustion conditions, but further researches are still necessary.