Reduction of NO with CH{sub 4} effected by copper oxide clusters in the channels of ZSM-5
Nitrogen oxides (NO{sub x}) are the main air pollutants that cause photochemical smog formation, acid rain, and general atmospheric visibility degradation. Worldwide, over 3 x 10{sup 7} tons of nitrogen oxides are vented to the atmosphere each year. Reduction of NO{sub x} emission has become one of the major problems to be solved for environmental protection. Many methods for reduction of NO{sub x} emissions such as reduction absorption, chelation absorption, catalytic decomposition, and catalytic reduction have been widely studied. Selective catalytic reduction with ammonia (NH{sub 3}-SCR) has been put to practical uses; however, the system is expensive in terms of handling the toxic ammonia. It has been recognized that the selective catalytic reduction of NO with hydrocarbons (HC-SCR) using copper-exchanged ZSM-5 (Cu-ZSM-5) catalysts is very effective. Fine structures of the copper oxide clusters involved in catalytic reduction of NO were studied by X-ray absorption spectroscopy. The Extended X-ray absorption fine structural (EXAFS) spectra indicate that about 2.89 nearest oxygen atoms bond to the Cu central atoms with a Cu-O bond distance of 1.96 {angstrom} for the oxidized Cu-ZSM-5 catalyst. Reduction of the catalyst in hydrogen at 573 K led to the formation of mainly Cu-Cu (2.54 {angstrom}) species with the coordination number (CN) of 2.91. The Cu{sub 4}O{sub 2} clusters in the channels of ZSM-5 observed by EXAFS were formed in the NO reduction process via incorporation of oxygen into the metallic copper matrix with desorption of N{sub 2}. Due to the restricted channel structure of ZSM-5, the Cu{sub 4}O{sub 2} clusters were reduced promptly by CH{sub 4}.
- Research Organization:
- National Cheng Kung Univ., Tainan (TW)
- OSTI ID:
- 20003182
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Vol. 103, Issue 33; Other Information: PBD: 19 Aug 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Preparation, characterization, and performance of Fe-ZSM-5 catalysts
On the mechanism of NO selective catalytic reduction by hydrocarbons over Cu-ZSM-5 via X-ray absorption spectroscopic study