US 5,520,895 A · Method for the reduction of nitrogen oxides using iron impregnated zeolites

Abstract

There is provided a process for the treatment of exhaust gas, which process uses a specially prepared catalyst composition, for the selective catalytic reduction of NO.sub.x contained in the exhaust gas. An embodiment of the process of this invention comprises a catalytic stage to selectively catalytically reduce NO.sub.x over a catalyst composition comprising an intermediate pore size zeolite catalyst that has been treated with a water soluble iron salt or salt precursor in a way effective to maximize iron dispersion. The intermediate pore size zeolite of this invention preferably has a silica:alumina molar ratio of between about 20 and about 1000. The catalyst of this invention typically comprises a silica, titania, or zirconia binder, preferably a binder including a high molecular weight, hydroxyl functional silicone resin. The catalyst of this invention is preferably formed, e.g., extruded, and then simultaneously calcined and hydrothermally treated.

Claims20

Dependent claims

A method for treating a gas mixture comprising NO.sub.x and ammonia, said method comprising directing the gas mixture along with a source of oxygen over a catalyst under treating conditions effective for the selective catalytic reduction of NO.sub.x ;

said catalyst comprising an intermediate pore size zeolite powder which has been contacted with a water soluble iron salt or salt precursor under contacting conditions effective to produce an iron loading on the zeolite component of the catalyst of at least about 0.4 wt. %;
said catalyst having been composited and integrally formed with a binder comprising at least one selected from the group consisting of titania, zirconia, and silica;
said method further comprising simultaneously calcining and hydrothermally treating said catalyst at a temperature of from about 400.degree. C. to about 850.degree. C. under conditions effective to produce a catalyst that is capable of conversion of greater than about 80 percent of the NO.sub.x and ammonia to innocuous compounds when the catalyst has been aged using 100 percent steam at 700.degree. C. for 7 hours, prior to directing said gas mixture over said catalyst.

Dependencies are inferred from the claim text.

Method for the reduction of nitrogen oxides using iron impregnated zeolites

Life of this patent

Method for the reduction of nitrogen oxides using iron impregnated zeolites

Life of this patent

Abstract

Claims20