摘要：

This invention discloses a durable catalyst for internal combustion engine or power plant exhaust gas purification which is comprised of a zeolite as the support and Fe (II) base-exchanged cation as the active component for the NO.sub.x selective catalytic reduction (SCR). It has stable activity with up to 20% H.sub.2 O and up to 250 ppm SO.sub.2 and combinations thereof over many hours in the exhaust stream. It is resistant to temperature excursions up to about 1,000° C. The method of producing this catalyst preferably comprises ion- exchanging the zeolite with Fe (II) in an aqueous solution of iron (II) oxalate, iron (II) citrate or iron (II) formate, or a mixture of oxalic acid, citric acid/salts, formic acid/salts, 2,3,4,5,6-pentahydroxyl caproic acid/salts and iron (II) salts, for example, sulfate, nitrate, chloride, carboxylate, chloride acetate, phosphate and carbonate, in the pH range from 3 to 13 under anaerobic conditions. The catalyst produced in this way shows no noticeable deactivation in its activity for reducing NO.sub. x to N.sub.2 under accelerated aging conditions (up to about 20% H.sub.2 O and up to about 250 ppm SO.sub.2 present in the mixture of NO, HC (iso- butane), and O.sub.2) for at least 2,500 hours which meets the Government standard. A method of using this catalyst is also disclosed. Methane can be used satisfactorily as the reducing agent but in the temperature range of greater than 600° C. but less than 750° C.

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