US 5,352,337 A · Method for reducing nitrogen oxides

Abstract

A direct current voltage is applied between an anodic portion containing an oxidizing catalyst provided on one surface of a proton conductive solid electrolyte which separates the flow path of the gas to be treated into two parts, and a cathodic portion containing a reducing catalyst provided on the other surface of the solid electrolyte, the reducing catalyst comprising at least one selected from oxides of elements of Group 5A, Group 6A, and Group 7A of the periodic table, palladium, palladium alloys, transition elements carried on alumina, cerium oxide, and La.sub.1-x Sr.sub.x Co.sub.1-y Fe.sub.y O.sub.3 (where, 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1), while bringing a gas containing water vapor into contact with the anodic portion and bringing a gas containing nitrogen oxides into contact with the cathodic portion. As a result, the water vapor is electrolytically oxidized into protons and oxygen on the anodic portion, so that the protons having been transported to the cathodic portion can be utilized to reduce nitrogen oxides by the reducing power of hydrogen. The method efficiently reduces nitrogen oxides in a gas even under an oxidizing atmosphere.

Claims27

Dependent claims

A method for reducing nitrogen oxides in a gas to be treated which comprises:

applying a direct current (DC) voltage between
an anodic portion comprising an oxidizing catalyst provided on one surface of a proton conductive solid electrolyte which separates the flow path of the gas to be treated into two parts, to face one flow path, and
a cathodic portion comprising a reducing catalyst provided on the other surface of said proton conductive solid electrolyte to face the other flow path, said reducing catalyst comprising at least one member selected from the group consisting of oxides of elements of Group 5A, Group 6A, and Group 7A of the periodic table, palladium, palladium alloys, transition elements carried on alumina, cerium oxide, and La.sub.1-x Sr.sub.x Co.sub.1-y Fe.sub.y O.sub.3 where, 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1),
to electrolytically oxidize water vapor in said gas on said anodic portion in said one flow path;
and
transporting protons obtained as a result of said oxidation to said cathodic portion through said solid electrolyte based on the potential gradient, thereby reducing nitrogen oxides within the other flow path by using the reducing power of hydrogen brought to said cathodic portion.

3 more elements

Dependencies are inferred from the claim text.

Method for reducing nitrogen oxides

Life of this patent

Method for reducing nitrogen oxides

Life of this patent

Abstract

Claims27