Sulfur-resistant NO.sub.x traps containing tungstophosphoric aci

Details Sulfur-resistant NO.sub.x traps containing tungstophosphoric aci Sulfur-resistant NO.sub.x traps containing tungstophosphoric aci

1997-03-10

1999-07-13

Tran, Hien

Chemistry of inorganic compounds

Modifying or removing component of normally gaseous mixture

Mixture is exhaust from internal-combustion engine

4232132, 4232135, 4232391, 423235, 422177, 422171, 60274, 60297, 502208, 502210, 502213, 502305, 502313, B01J 802, B01D 5334

Patent

active

059222956

ABSTRACT:
The invention is a nitrogen oxide trap comprising a porous support of alumina; and loaded thereon materials consisting essentially of particular amounts of: (I) tungstophosphoric acid and (II) precious metal selected from platinum, palladium, rhodium and mixtures thereof. The trap is useful for trapping nitrogen oxides produced in the exhaust gas generated by an internal combustion gasoline engine during lean-burn operation of the engine. The trap releases the nitrogen oxides during decreased oxygen concentration in the exhaust gas. The desorbed NOx may be converted over the precious metal to N.sub.2 and O.sub.2 by reductants like hydrocarbons present in the exhaust gas.

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Raymond Belanger and John B. Moffat, "A Comparative Study of the Adsorption and Reaction of Nitrogen Oxides on 12-Tungstophosphoric, 12-Tungstosilicic, and 12-Molybdophosphoric Acids," 1995, pp. 179-188, Journal of Catlysis 152.

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