US 7,094,722 B2 · NOx catalyst and method of suppressing sulfate formation in an exhaust purification system

Abstract

The activity and durability of a zeolite lean-bum NOx catalyst can be increased by loading metal cations on the outer surface of the zeolite. However, the metal loadings can also oxidize sulfur dioxide to cause sulfate formation in the exhaust. The present invention is a method of suppressing sulfate formation in an exhaust purification system including a NOx catalyst. The NOx catalyst includes a zeolite loaded with at least one metal. The metal is selected from among an alkali metal, an alkaline earth metal, a lanthanide metal, a noble metal, and a transition metal. In order to suppress sulfate formation, at least a portion of the loaded metal is complexed with at least one of sulfate, phosphate, and carbonate.

Claims8

Dependent claims

A NOx reducing catalyst with sulfate formation suppression, comprising:

a zeolite loaded with at least one metal;
the metal is selected from a group consisting of an alkali metal, an alkaline earth metal, a noble metal, a lanthanide metal and a transition metal;
a second portion of the loaded metal being loaded on an outer surface and chemically bonded to an SO2 oxidation suppressant that is selected from a group consisting of sulfate, phosphate, and carbonate, and a first portion of the loaded metal being metal cations at exchange sites of the zeolite;
and
the first portion being to promote NOx reduction, but the second portion being to suppress oxidation of SO2 when an outer surface of the zeolite contacts internal combustion engine exhaust mixed with a reductant.

2 more elements

Dependencies are inferred from the claim text.

NOx catalyst and method of suppressing sulfate formation in an exhaust purification system

Life of this patent

NOx catalyst and method of suppressing sulfate formation in an exhaust purification system

Life of this patent

Abstract

Claims8