Catalyst and method for reducing nitrogen oxides in exhaust streams with hydrocarbons or alcohols

Abstract

A catalyst system and a method for reducing nitrogen oxides in an exhaust gas by reduction with a hydrocarbon or oxygen-containing organic compound reducing agent are provided. The catalyst system contains a silver catalyst and a modifier catalyst, where the modifier catalyst contains a modifier oxide, where the modifier oxide is selected from the group consisting of iron oxide, cerium oxide, copper oxide, manganese oxide, chromium oxide, a lanthanide oxide, an actinide oxide, molybdenum oxide, tin oxide, indium oxide, rhenium oxide, tantalum oxide, osmium oxide, barium oxide, calcium oxide, strontium oxide, potassium oxide, vanadium oxide, nickel oxide, tungsten oxide, and mixtures thereof. The modifier oxide is supported on an inorganic oxide support or supports, where at least one of the inorganic oxide supports is an acidic support. The catalyst system of the silver catalyst and the modifier catalyst provides higher NOx conversion than either the silver catalyst or the modifier catalyst alone.

Description

[0001] priority claim [0002] This application claims the benefit of US Provisional Application No. 60 / 657,500, filed February 28, 2005, under 35 U.S.C. 119(e). technical field [0003] This invention relates to catalysts and methods for the selective reduction of nitrogen oxides in exhaust gases containing excess oxygen by hydrocarbons or oxygen-containing organic compounds. Background technique [0004] Exhaust gases from internal combustion engines, power plants, industrial furnaces, heaters, diesel engines, and other devices contain nitrogen oxides, carbon monoxide, and unburned hydrocarbons. Exhaust gases from these sources also contain excess oxygen, water vapor and sulfur dioxide. [0005] Emissions of nitrogen oxides, carbon monoxide and hydrocarbons are limited due to environmental regulations. [0006] Nitrogen oxides from static and dynamic sources are one of the causes of acid rain. Various methods have been proposed to reduce nitrogen oxide emissions from ex...

AI Technical Summary

Problems solved by technology

Three-way catalysts are not effective in removing NO from exhaust gases with high concentrations of oxygen, such as those from steam turbines, diesel engines, and gasoline engines operating in lean burn mode x , this is because there is not enough reducing agent in the exhaust gas to reduce NO x

It is also necessary to selectively reduce NO with hydrocarbons or alcohols x Catalysts and methods wherein the catalyst system does not rely on the spacing between the two catalysts, as this spacing can lead to non-reproducible or bulky systems unsuitable for space-constrained applications

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