초록 ▼

A method for reducing gaseous nitrogen oxides present in a gas stream by reaction with a reductant species is practiced by flowing the gas stream under lean NO.sub.X -reducing conditions in contact with a catalytic material containing a catalytically effective amount of a catalytic species, e.g., a

A method for reducing gaseous nitrogen oxides present in a gas stream by reaction with a reductant species is practiced by flowing the gas stream under lean NO.sub.X -reducing conditions in contact with a catalytic material containing a catalytically effective amount of a catalytic species, e.g., a platinum group metal, and a reductant storage material, e.g., a zeolite, effective for storing reductant species for reaction with NO.sub.X, and providing an intermittent supply of the reductant to the gas stream. The catalytic material may be prepared in any manner, but one method is to incorporate a catalytically effective amount of the platinum into a template-bearing molecular sieve material, preferably ZSM-5 zeolite, to hinder the platinum from being incorporated into the pores of the molecular sieve material, and then calcining the molecular sieve material, whereby the template is removed from the molecular sieve material after the platinum is incorporated therein. Another method is to add a blocking agent to the molecular sieve material, then incorporate the platinum therein, and then calcine the material to remove the blocking agent. The catalytic material may contain less than about two percent by weight of zeolite plus platinum, e.g., less than about 0.5%, or from about 0.025% to 0.1% or 0.2% platinum.

대표청구항 ▼

[ What is claimed is:] [1.] A method for reducing gaseous nitrogen oxides present in a gas stream by reaction with reductant species, comprising flowing the gas stream under lean NO.sub.X reducing conditions in contact with a catalytic material comprising a catalytically effective amount of a cataly

[ What is claimed is:] [1.] A method for reducing gaseous nitrogen oxides present in a gas stream by reaction with reductant species, comprising flowing the gas stream under lean NO.sub.X reducing conditions in contact with a catalytic material comprising a catalytically effective amount of a catalytic species incorporated into a molecular sieve material, and providing an intermittent supply of reductant to the gas stream, wherein the catalytic material is the product of a process comprising incorporating a catalytically effective amount of a catalytic species into a template-bearing molecular sieve material and then calcining the molecular sieve material whereby the template is removed from the molecular sieve material after the catalytic species is incorporated therein.