Patent ID: 6139813
Filing Date: 2000-10-31
Classification: B01D,B01J,Y02T

Abstract:
A method for treating exhaust gas containing carbon monoxide, hydrocarbons, and nitrogen oxides generated by a lean-burn internal combustion engine, the method comprising the step of:bringing said exhaust gas from said lean-burn engine in contact with a metal-zirconium oxide material made by sol-gel techniques which includes at least 0.1 wt. % precious metal selected from the group consisting of platinum, palladium, rhodium, and a mixture of any of them, said metal-zirconium oxide material made by sol-gel techniques, the material comprising: at least one heterometallic alkoxide selected from the group consisting of:(a) alkali metal-zirconium alkoxides having the general chemical formulas: M[Zr(OR).sub.5 ], M[Zr.sub.2 (OR).sub.9, M.sub.2 [Zr.sub.3 (OR).sub.14 ], where M is an alkali metal; and(b) alkaline earth metal-zirconium alkoxides having the general chemical formulas: M'[Zr.sub.2 (OR).sub.9 ].sub.2 or M'[Zr.sub.3 (OR).sub.14 ], where M' is an alkaline earth metal, wherein under lean-burn conditions, where said exhaust gas contains more oxygen than is required for oxidizing components to be oxidized in the exhaust gas, nitrogen oxides are absorbed on said oxide material and when the oxygen concentration in said gas is lowered the absorbed nitrogen oxides are desorbed and reduced over said precious metal.