KR920021199A - Catalyst system minimizes NH_3 production - Google Patents

Abstract

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Description

Catalyst system to minimize NH3 production

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FIG. 1 is a graph showing the relationship between the conversion rate of NO _x , CO, and hydrocarbons, the amount of ammonia produced, and the redox rate in a commercial vehicle catalyst Pt / Rh / Al ₂ O ₃ / CeO ₂ .

2 is a graph showing the relationship between the conversion rate of NO _x , CO, and hydrocarbons, the amount of ammonia produced, and the acid reduction rate in Pt / Al ₂ O ₃ / CeO ₂ / Rh / zeolite catalysts.

₃ shows the relationship between the conversion rate of NO _x , CO, and hydrocarbon, the amount of ammonia produced and the redox rate in the RH / zeolite catalyst (first step) and Pt / Al ₂ O ₃ / CeO ₂ catalyst (second step) It is a graph.

Claims (12)

NO _x . In a multistage catalyst system suitable for catalyzing the conversion of CO and hydrocarbons into harmless substances, the system comprises a) a fluid mixture comprising the NO _x , the CO and the hydrocarbons, with the majority of NO _x and CO and hydrocarbons. A first stage consisting of contacting the first stage reaction to convert the toxic substance into a harmless substance, and b) converting the effluent mixture from the first stage to CO and hydrocarbons into a harmless substance so that the second stage reaction is carried out. And a second step consisting of connecting, wherein in the first step, the flowable mixture has a molar ratio of reducing agent to oxidant of about 0.8 about 1.5, and the first step is a first catalyst catalyzed with a first stage catalyst It consists of a stage substrate, the first stage catalyst comprises a noble metal component and a support component, the precious metal component is rhodium, a binding material of platinum and rhodium, palladium and rhodium A binding material, and a precious metal selected from the group consisting of a binding material of platinum, palladium and rhodium, wherein the support component is selected from the group consisting of molecular sieves, oxides, ceramics, and binding materials thereof, and the first stage catalyst Does not include a water gas shift component, the second stage is composed of a second stage substrate catalyzed by a second stage catalyst, the second stage catalyst may catalytically activate the water gas shift reaction, The second stage catalyst comprises a support noble metal component, the noble metal component is selected from the group consisting of platinum, palladium and combinations thereof, and the second stage catalyst does not comprise rhodium and the platinum and / or in the system Or the weight ratio of filadium to rhodium is at least about 15 to 1, and the treatment of the system does not produce a significant amount of ammonia. Air catalyst system characterized in that the NO _x, at least about 80% by volume of CO and hydrocarbon conversion to harmless substances were. The catalyst system of claim 1 wherein the molar ratio of reducing agent to oxidant is from about 1.0 to about 1.25. The catalyst system of claim 1, wherein the molecular sieve is zeolite. The catalyst system of claim 1, wherein the first stage catalyst comprises noble metal components selected from the group consisting of rhodium, and a binding material of rhodium and piladium, and support components selected from the group consisting of zeolite, alumina, and combinations thereof. . 5. The catalyst system of claim 4, wherein at least about 95% by volume of NO _x is converted into a harmless material as a result of said system treatment. The catalyst system according to claim 4, wherein the first stage catalyst is composed mainly of zeolites having rhodium and pentasil structure. The catalyst system according to claim 4, wherein the first stage catalyst is composed mainly of zeolites having rhodium, palladium and pentasil structures. 5. The catalyst system of claim 4, wherein the first stage catalyst is mainly composed of rhodium and gamma alumina. 5. The catalyst system of claim 4, wherein the first stage catalyst is based on rhodium, palladium and gamma alumina. The catalyst system of claim 1, wherein the second stage catalyst is composed of alumina, ceria, and precious metals selected from the group consisting of platinum, palladium, and a combination of platinum and palladium. The catalyst system of claim 1, wherein the substrate is made of a material selected from the group consisting of ceramics, glass ceramics, metals, metal oxides, molecular sieves, and combinations thereof. A process for catalyzing the conversion of harmless substances of NO _x , CO and hydrocarbons comprising contacting a fluid mixture comprising NO _x , CO and hydrocarbons with a catalyst using the catalyst system of claim 1. ※ Note: The disclosure is based on the initial application.