Ford Global Technolgoies, LLC

Amy Berris

Mohinder S Chattha

William Lewis Henderson Watkins

Jun (John) Li

Jun Li

An automobile exhaust system includes a catalytic converter and a modified NOx trap wit improved sulfur tolerance. Sulfur oxide has a deleterious effect on the performance of nitrogen oxide traps. In the modified NOx trap, a sulfur oxide trap is integrated with a nitrogen oxide trap by coating the catalyst contained within a nitrogen oxide trap with a mixed oxide layer of calcium oxide and magnesium oxide. The NOx trap is regenerated by heating at elevated temperature for a short time period.

Vehicle sulfur oxide trap and related method

An automobile exhaust system includes a catalytic converter, a NOx trap, and a sulfur oxide trap. The sulfur oxide trap improves the efficiency of the NOx trap. Sulfur oxide has a deleterious effect on the performance of nitrogen oxide traps. The sulfur oxide trap comprises a monolithic substrate which is over-coated with an aluminum oxide layer and a mixed oxide layer of calcium oxide and magnesium oxide. In a variation, a sulfur oxide trap is integrated with a nitrogen oxide trap by coating the catalyst contained within a nitrogen oxide trap with a mixed oxide layer of calcium oxide and magnesium oxide. In each embodiment, the sulfur oxide trap can be regenerated by heating at elevated temperature for a short time period.

The invention is a method of treating exhaust gases generated by an internal combustion engine using a NO trap in the exhaust flow system. The method comprises locating a nitrogen oxide trap in the exhaust gas passage and cycling the air/fuel ratio of the exhaust gases entering the trap between lean and rich, such that the trap absorbs nitrogen oxides during the lean cycle and desorbs the nitrogen oxides when the concentration of the oxygen in the exhaust flow is lowered as during a rich cycle. The trap comprises: (a) a porous support material comprising mostly &ggr;-alumina; (b) a sulfur-suppressing metal selected from the group consisting of cesium, zinc and a combination of cesium and zinc; (c) a precious metal; and (d) a NO sorption metal such as barium, the metals being deposited in the support material, the amount of the metals being individually dependent on the weight of the support material. The desorbed nitrogen oxides may be converted over the precious metal to N by reductants like hydrogen, hydrocarbon and carbon monoxide present in the exhaust gas.

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Royal Oak, MI, United States of America

Amy Berris