FTIR and kinetic studies of the mechanism of Fe{sup 3+}-exchanged TiO{sub 2}-pillared clay catalyst for selective catalytic reduction of NO with ammonia
A series of FTIR spectroscopic and kinetic studies of the selective catalytic reduction (SCR) of nitric oxide by ammonia were conducted on Fe{sup 3+}-exchanged TiO{sub 2}-pillared clay (Fe-TiO{sub 2}-PILC) catalyst. It was found that No molecules were absorbed on the fresh Fe-TiO{sub 2}-PILC catalyst and then oxidized by O{sub 2} to adsorbed NO{sub 2} and nitrate species. These NO{sub x} adspecies could be reduced by NH{sub 3} at high temperatures. NH{sub 3} molecules could also be adsorbed on the Broensted acid and Lewis acid sites on the Fe-TiO{sub 2}-PILC catalyst to generate, respectively, NH{sup +}{sub 4} ions and coordinated NH{sub 3} species. These NH{sub 3} adspecies were active in reacting with NO, NO + O{sub 2} and NO{sub 2}, but the reaction rates of NH{sub 3} + NO + O{sub 2} and NH{sub 3} + NO{sub 2} were much higher than that of NNO + NH{sub 3}. However, under reaction conditions, the surface of Fe-TiO{sub 2}-PILC was mainly covered by NH{sup +}{sub 4} ions and coordinated NH{sub 3}, and no NO{sub x} adspecies were detected. This is in agreement with the zero-order for the SCR reaction with respect to NH{sub 3}. A possible reaction scheme for the SCR reaction on Fe-TiO{sub 2}-PILC was proposed. NO reduction initially involved the reaction between NO{sub 2} and pairs of NH{sub 3} adspecies to form an active intermediate, which finally reacted with gaseous or weakly adsorbed NO to produce N{sub 2} and H{sub 2}O.
- Research Organization:
- Univ. of Michigan, Ann Arbor, MI (US)
- Sponsoring Organization:
- Electric Power Research Institute
- OSTI ID:
- 20017451
- Journal Information:
- Journal of Catalysis, Vol. 190, Issue 1; Other Information: PBD: 15 Feb 2000; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
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