Engine NH3 by-product purification catalyst based on equivalent combustion technology

Abstract

The present invention relates to a gas engine NH3 by-product purification catalyst using equivalent combustion technology, the catalyst comprises two different types of coatings, the first coating is mainly responsible for the oxygen supply function of the catalyst under the oxygen-free working condition, and at the same time, the oxidation of partial NH3 and NO is promoted; the second coating is mainly responsible for efficient SCR reaction, and NH3 is selectively reduced into N2. The catalyst has excellent hydrothermal stability, and has excellent NH3 purification capacity after being aged for 100 hours under the conditions that the temperature is 800 DEG C, the water content is 20% and the air content is 80%. And the catalyst also has the advantages of simple preparation process and low cost.

Description

Technical Field

[0001] This invention relates to a catalyst for purifying NH3 byproducts of gas engines using stoichiometric combustion technology, belonging to the field of exhaust gas purification technology for natural gas-fueled engines. Background Technology

[0002] The after-treatment system of the China VI equivalent combustion technology engine uses a three-way catalyst to achieve synergistic purification of CO, HC, and NOx. To better control NOx emissions, the air-fuel ratio of the China VI equivalent combustion technology engine is λ≤1. When engine exhaust passes through the three-way catalyst, under the condition of λ<0.995, a large amount of byproduct NH3 is generated. NH3 mainly comes from the byproducts of the NOx reduction reaction process, primarily through the reactions 2CO + 2NO + 3H2→ 2NH3+ 2CO2 and 2NO + 5H2→2NH3+ 2H2O. As can be seen from the above reaction equations, the generation of NH3 depends on the concentrations of NO and H2 in the exhaust gas. As long as the stoichiometric requirement is met, i.e., H2 / NO≥2.5, NH3 can be formed through the reaction of NO and H2 on a precious metal. When H2 / NO<2.5, if CO is present, it can be generated through the reaction 2CO + 2NO + 3H2→ 2NH3+ 2CO2.

[0003] Both reactions involve the dissociation and adsorption of NO and H2 at the active sites of noble metals. When the H2 content in the exhaust gas is low, the dissociated H first reacts with O to generate H2O. Only after all the O is consumed can H react with NO to generate NH3. However, when CO is present in the exhaust gas, CO inhibits the oxidation of H2 and increases NH3 emissions. Therefore, NH3 is mainly generated under reducing conditions (oxygen-deficient conditions), while under oxidizing conditions (oxygen-rich conditions), O2 preferentially consumes H2. The H2O content in the exhaust gas of the gas turbine is as high as 21%. When the catalyst operates under oxygen-deficient conditions, when H2O in the exhaust gas passes through the catalyst at high temperatures (>300℃), it generates a large amount of H2 through two reactions: CO + H2O → CO2 + H2 and CH4 + H2O → CO + 3H2, further promoting the formation of NH3 byproducts.

[0004] Currently, to address the issue of NH3 byproducts in stoichiometric combustion engines, engineers generally employ two methods to achieve efficient NH3 control. One method involves precisely calibrating the three-way catalytic converter to achieve synergistic purification of CO, HC, NOx, and NH3. This method places high demands on engine hardware, software control, and the performance of the three-way catalytic converter. The other method involves coupling an ASC catalyst at the downstream end of the three-way catalytic converter to selectively oxidize the NH3 produced by the three-way catalytic converter.

[0005] The NH3 in diesel vehicle exhaust comes from urea over-injection, which is fundamentally different from the source of NH3 in the exhaust of engines using stoichiometric combustion technology. Gas engine exhaust reaches a maximum temperature of 800℃, with a water content of 25%, while diesel engine exhaust reaches a maximum temperature of 500℃, with a water content of 10%, nearly 300℃ lower than gas engine exhaust and more than 10% lower water content. This results in a sharp decline in the selective oxidation capacity of ASC catalysts adapted for diesel engines after high-temperature hydrothermal aging at 800℃ with a water content of 20%. The NH3 emissions from the aged ASC catalyst exceed 10 ppm, failing to meet the China VI emission standards. Therefore, a dedicated ASC catalyst suitable for this working environment needs to be developed for gas engines.

[0006] Chinese patent CN118403670A discloses a low N2O selectivity ammonia oxidation catalyst and its preparation method. The ammonia oxidation catalyst of this invention has high NH3 conversion rate and low N2O selectivity in both low temperature and high temperature regions, and can be widely used in the denitrification system for treating NOx in diesel vehicles. However, the stability of the catalyst described in this patent was only tested at 650°C for 100 hours under water conditions.

[0007] Chinese patent CN119604362A discloses a catalytic product containing an ammonia oxidation catalyst, used for treating exhaust gas. In its first coating structure, it comprises a substrate, a coating containing a first catalyst containing a noble metal component and a second catalyst containing a molecular sieve component; or in its second coating structure, it comprises a substrate, a first coating containing a first catalyst containing a noble metal component, and a second coating covering at least a portion of the first coating and containing a second catalyst containing a molecular sieve component. The coating in the first coating structure or the second coating in the second coating structure each has interparticle pores with a porosity of 5.7% or greater. The catalyst described in this patent was only tested for stability at 650°C for 50 hours under aqueous conditions, primarily for treating ammonia oxidation at low temperatures. Summary of the Invention

[0008] The purpose of this invention is to solve the problem that the selective oxidation capacity of traditional ASC catalysts for NH3 decreases sharply after high temperature and high hydrothermal aging, improve the hydrothermal resistance of ammonia oxidation catalysts, and provide a catalyst for purifying NH3 byproducts in gas engines using stoichiometric combustion technology.

[0009] The present invention adopts the following technical route: a catalyst for purifying NH3 byproducts of gas engines using equivalence combustion technology. The catalyst consists of two different types of coatings. The first coating is composed of a high hydrothermal stability oxygen storage material loaded with Pt metal, which is coated at the inlet end of the carrier, and the coating height is 70% to 80% of the total height of the carrier. The second coating is composed of FER molecular sieve with an Fe content of 5% to 6%, which is coated at the outlet end of the carrier, and the coating height is 70% to 80% of the total height of the carrier.

[0010] Furthermore, the high hydrothermal stability oxygen storage material supported on Pt metal is composed of 0.12 wt% ~ 1.17 wt% platinum and 98.83 wt% ~ 99.88 wt% Ce / Y / Al composite material.

[0011] Furthermore, in the Ce / Y / Al composite material, the Ce content is 50% to 70%, the Y content is 20%, and the Al content is 10% to 30%.

[0012] Furthermore, the Ce / Y / Al composite material, after aging for 100 hours at 800°C with a water content of 20% and an air content of 80%, has a specific surface area of ​​55-65 m². 2 / g.

[0013] Furthermore, the Fe-based FER molecular sieve, after aging for 100 hours at 800°C with a water content of 20% and an air content of 80%, has a specific surface area of ​​120-150 m². 2 / g.

[0014] Furthermore, the first coating loading is 120 g / L ~ 180 g / L.

[0015] Furthermore, the second coating loading is 100 g / L ~ 160 g / L.

[0016] This application describes a method for preparing a catalyst for purifying NH3 byproducts in a gas-fired engine using stoichiometric combustion technology, comprising the following steps: (1) A certain amount of platinum nitrate was loaded onto Ce / Y / Al composite material by impregnation, and a certain amount of deionized water and cellulose were added. The mixture was stirred to obtain a suspension, wherein the solid mass percentage concentration in the suspension was 35% and the viscosity was between 3500 and 4500 cP. (2) The slurry prepared in step (1) is coated into the air inlet channel of the 400 mesh wall flow honeycomb carrier. The amount of slurry is 120 g / L ~ 180 g / L and the coating height is 80% of the total height of the carrier.

[0017] (3) The honeycomb carrier with the first coating obtained in step (2) is dried at 150°C for 30 minutes and then set aside for use.

[0018] (4) A certain amount of FER molecular sieve with a Fe content of 5% to 6% is added to deionized water containing cellulose and stirred to obtain a suspension. The solid mass percentage concentration of the suspension is 38% and the viscosity is between 2500 and 3500 cP.

[0019] (5) The slurry obtained in step (4) is applied to the air outlet position of the honeycomb carrier with the first coating obtained in step (3). The amount of slurry applied is 100 g / L ~ 160 g / L, and the coating height is 80% of the total height of the carrier.

[0020] (6) The honeycomb carrier with the first and second coatings obtained in step (5) is dried at 150°C for 30 min and then calcined at 550°C for 2 hours.

[0021] This invention relates to a catalyst for purifying NH3 byproducts in gas engines using stoichiometric combustion technology. The catalyst consists of two different types of coatings. The first coating is mainly responsible for supplying nutrients to the catalyst under anaerobic conditions, while also promoting the oxidation of some NH3 and NO. The second coating is mainly responsible for the efficient SCR reaction, selectively reducing NH3 to N2.

[0022] This catalyst exhibits excellent hydrothermal stability and demonstrates superior NH3 purification capabilities after aging for 100 hours at 800℃ with 20% water and 80% air content. Furthermore, the catalyst boasts advantages such as simple preparation process and low cost. Detailed Implementation

[0023] The present invention will be further described below with reference to specific implementation examples, all in weight percentage.

[0024] Comparative Example 1: A selective oxidation catalyst for NH3 was prepared by impregnating 2000g of alumina material with 13.668g of 17.58% platinum nitrate and mixing it with 3714g of water to form a slurry. This slurry was then coated onto a honeycomb ceramic support with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 80g / L, with the coating height being 100% of the total support height. The catalyst was then dried at 130℃ and set aside for later use. Next, a slurry was prepared by mixing 2000g of SSZ-13 molecular sieve with a Cu content of 3.0% and 3250g of water. This slurry was then coated onto the prepared catalyst at a coating loading of 120g / L, with the coating height being 100% of the total support height. The catalyst was dried at 130℃ and calcined at 500℃ for 2 hours to prepare an NH3 selective oxidation catalyst. The prepared catalyst was then aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0025] Comparative Example 2: A selective oxidation catalyst for NH3 was prepared by impregnating 2000g of alumina material with 134.682g of 17.58% platinum nitrate and mixing it with 3714g of water to form a slurry. This slurry was then coated onto a honeycomb ceramic support with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 80g / L, with the coating height being 100% of the total support height. The catalyst was then dried at 130℃ and set aside for later use. Next, a slurry was prepared by mixing 2000g of SSZ-13 molecular sieve with a Cu content of 3.0% and 3250g of water. This slurry was then coated onto the prepared catalyst at a coating loading of 120g / L, with the coating height being 100% of the total support height. The catalyst was dried at 130℃ and calcined at 500℃ for 2 hours to prepare an NH3 selective oxidation catalyst. The prepared catalyst was then aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0026] Example 1: A catalyst for purifying NH3 byproducts from a gas-fired engine using stoichiometric combustion technology was prepared by impregnating 13.668g of 17.58% platinum nitrate onto 2000g of Ce / Y / Al composite material and mixing it with 3714g of water to form a slurry. The slurry was then coated onto a honeycomb ceramic support with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 120g / L, with the coating height being 80% of the total height of the support. The catalyst was dried at 130℃ to obtain a catalyst with a first coating.

[0027] A slurry was prepared by mixing 2000g of FER molecular sieve with 5.0% Fe content and 3250g of water. The slurry was coated onto the gas outlet end of the catalyst with the first coating at a coating loading of 100g / L. The coating height was 80% of the total height of the support. The catalyst was dried at 130℃ and calcined at 500℃ for 2 hours to prepare a catalyst for purifying NH3 byproducts of gas engines using equivalent combustion technology. The prepared catalyst was aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0028] The aforementioned Ce / Y / Al composite material, by weight percentage, contains 50% Ce, 20% Y, and 30% Al. After aging at 800°C for 100 hours under conditions of 20% water vapor and 80% air, its specific surface area is 65 m². 2 / g. The Fe content is 5.0%. After aging at 800℃ under conditions of 20% water vapor and 80% air for 100 hours, the specific surface area of ​​the FER molecular sieve is 150 m² / g. 2 / g.

[0029] Example 2: A catalyst for purifying NH3 byproducts from a gas-fired engine using stoichiometric combustion technology was prepared by impregnating 2000g of Ce / Y / Al composite material with 67.341g of 17.58% platinum nitrate and mixing it with 3714g of water to form a slurry. The slurry was then coated onto a honeycomb ceramic support with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 120g / L. The coating height was 80% of the total height of the support. The catalyst was dried at 130℃ to obtain a catalyst with a first coating. A slurry was prepared by mixing 2000g of FER molecular sieve with 5.0% Fe content and 3250g of water. The slurry was coated onto the gas outlet end of the catalyst with the first coating at a coating loading of 100g / L. The coating height was 80% of the total height of the support. After drying at 130℃ and calcining at 500℃ for 2 hours, a catalyst for purifying NH3 byproducts of gas engines using equivalent combustion technology was prepared. The prepared catalyst was aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0030] The aforementioned Ce / Y / Al composite materials, all by weight percentage, contain 50% Ce, 20% Y, and 30% Al. After aging for 100 hours at 800°C with 20% moisture and 80% air, the specific surface area is 65 m². 2 / g. FER molecular sieves with an Fe content of 5.0% were aged at 800℃ for 100 hours under conditions of 20% water vapor and 80% air, resulting in a specific surface area of ​​150 m² / g. 2 / g.

[0031] Example 3: A catalyst for purifying NH3 byproducts from a gas-fired engine using stoichiometric combustion technology was prepared by impregnating 134.682g of 17.58% platinum nitrate onto 2000g of Ce / Y / Al composite material and mixing it with 3714g of water to form a slurry. The slurry was then coated onto a honeycomb ceramic support with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 120g / L, with the coating height being 80% of the total height of the support. The catalyst was then dried at 130℃ to obtain a catalyst with a first coating. A slurry was prepared by mixing 2000g of FER molecular sieve with a Fe content of 5.0% and 3250g of water. The slurry was coated onto the gas outlet end of the catalyst with the first coating at a coating loading of 100g / L. The coating height was 80% of the total height of the support. The catalyst was dried at 130℃ and calcined at 500℃ for 2 hours to prepare a catalyst for purifying NH3 byproducts of gas engines using equivalent combustion technology. The prepared catalyst was aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0032] The aforementioned Ce / Y / Al composite materials, all by weight percentage, contain 50% Ce, 20% Y, and 30% Al. After aging for 100 hours at 800°C with 20% moisture and 80% air, the specific surface area is 65 m². 2 / g. FER molecular sieves with an Fe content of 5.0% were aged at 800℃ for 100 hours under conditions of 20% water vapor and 80% air, resulting in a specific surface area of ​​150 m² / g. 2 / g.

[0033] Example 4: A catalyst for purifying NH3 byproducts from a gas-fired engine using stoichiometric combustion technology was prepared by impregnating 134.682g of 17.58% platinum nitrate onto 2000g of Ce / Y / Al composite material and mixing it with 3714g of water to form a slurry. The slurry was then coated onto a honeycomb ceramic carrier with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 120g / L, with the coating height being 80% of the total height of the carrier. The catalyst was then dried at 130℃ to obtain a catalyst with a first coating. A slurry was prepared by mixing 2000g of FER molecular sieve with 5.0% Fe content and 3250g of water. The slurry was coated onto the gas outlet end of the catalyst with the first coating at a coating loading of 100g / L. The coating height was 80% of the total height of the support. After drying at 130℃ and calcining at 500℃ for 2 hours, a catalyst for purifying NH3 byproducts of gas engines using equivalent combustion technology was prepared. The prepared catalyst was aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0034] The aforementioned Ce / Y / Al composite materials, all by weight percentage, contain 60% Ce, 20% Y, and 20% Al. After aging for 100 hours at 800°C with 20% moisture and 80% air, the specific surface area is 58 m². 2 / g. FER molecular sieves with an Fe content of 5.0% were aged at 800℃ for 100 hours under conditions of 20% water vapor and 80% air, resulting in a specific surface area of ​​150 m² / g. 2 / g.

[0035] Example 5: A catalyst for purifying NH3 byproducts from a gas-fired engine using stoichiometric combustion technology was prepared by impregnating 134.682g of 17.58% platinum nitrate onto 2000g of Ce / Y / Al composite material and mixing it with 3714g of water to form a slurry. The slurry was then coated onto a honeycomb ceramic carrier with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 120g / L, with the coating height being 80% of the total height of the carrier. The catalyst was then dried at 130℃ to obtain a catalyst with a first coating. A slurry was prepared by mixing 2000g of FER molecular sieve with an Fe content of 5.0% and 3250g of water. The slurry was coated onto the gas outlet end of the catalyst with the first coating at a coating loading of 80g / L. The coating height was 80% of the total height of the support. After drying at 130℃ and calcining at 500℃ for 2 hours, a catalyst for purifying NH3 byproducts of gas engines using equivalent combustion technology was prepared. The prepared catalyst was aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0036] The aforementioned Ce / Y / Al composite materials, all by weight percentage, contain 70% Ce, 20% Y, and 10% Al. After aging for 100 hours at 800°C with 20% moisture and 80% air, the specific surface area is 55 m². 2 / g. FER molecular sieves with an Fe content of 5.0% were aged at 800℃ for 100 hours under conditions of 20% water vapor and 80% air, resulting in a specific surface area of ​​150 m² / g. 2 / g.

[0037] Example 6: A catalyst for purifying NH3 byproducts from a gas-fired engine using stoichiometric combustion technology was prepared by impregnating 134.682g of 17.58% platinum nitrate onto 2000g of Ce / Y / Al composite material and mixing it with 3714g of water to form a slurry. The slurry was then coated onto a honeycomb ceramic carrier with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 120g / L, with the coating height being 80% of the total height of the carrier. The catalyst was then dried at 130℃ to obtain a catalyst with a first coating. A slurry was prepared by mixing 2000g of FER molecular sieve with an Fe content of 6.0% and 3250g of water. The slurry was coated onto the gas outlet end of the catalyst with the first coating at a coating loading of 100g / L. The coating height was 80% of the total height of the carrier. After drying at 130℃ and calcining at 500℃ for 2 hours, a catalyst for purifying NH3 byproducts of gas engines using equivalent combustion technology was prepared. The prepared catalyst was then aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0038] The aforementioned Ce / Y / Al composite material, with a Ce content of 50%, a Y content of 20%, and an Al content of 30%, has a specific surface area of ​​65 m² after aging at 800°C for 100 hours under conditions of 20% water vapor and 80% air. 2 / g. FER molecular sieves with an Fe content of 6.0% had a specific surface area of ​​150 m² after aging at 800℃ for 100 hours under conditions of 20% water vapor and 80% air. 2 / g.

[0039] Example 7: A catalyst for purifying NH3 byproducts from a gas-fired engine using stoichiometric combustion technology was prepared by impregnating 134.682g of 17.58% platinum nitrate onto 2000g of Ce / Y / Al composite material and mixing it with 3714g of water to form a slurry. The slurry was then coated onto a honeycomb ceramic support with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 180g / L, with the coating height being 80% of the total height of the support. The catalyst was then dried at 130℃ to obtain a catalyst with a first coating. A slurry was prepared by mixing 2000g of FER molecular sieve with an Fe content of 5.0% and 3250g of water. The slurry was coated onto the gas outlet end of the catalyst with the first coating at a coating loading of 100g / L. The coating height was 80% of the total height of the support. After drying at 130℃ and calcining at 500℃ for 2 hours, a catalyst for purifying NH3 byproducts of gas engines using equivalent combustion technology was prepared. The prepared catalyst was then aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0040] The aforementioned Ce / Y / Al composite materials, all by weight percentage, contain 50% Ce, 20% Y, and 30% Al. After aging for 100 hours at 800°C with 20% moisture and 80% air, the specific surface area is 65 m². 2 / g. FER molecular sieves with an Fe content of 6.0% had a specific surface area of ​​145 m² after aging at 800℃ for 100 hours under conditions of 20% water vapor and 80% air. 2 / g.

[0041] Example 8: A catalyst for purifying NH3 byproducts from a gas-fired engine using stoichiometric combustion technology was prepared by impregnating 134.682g of 17.58% platinum nitrate onto 2000g of Ce / Y / Al composite material and mixing it with 3714g of water to form a slurry. The slurry was then coated onto a honeycomb ceramic support with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 150g / L, with the coating height being 80% of the total height of the support. The catalyst was then dried at 130℃ to obtain a catalyst with a first coating. A slurry was prepared by mixing 2000g of FER molecular sieve with a Fe content of 5.0% and 3250g of water. The slurry was coated onto the gas outlet end of the catalyst with the first coating at a coating loading of 180g / L. The coating height was 80% of the total height of the support. After drying at 130℃ and calcining at 500℃ for 2 hours, a catalyst for purifying NH3 byproducts of gas engines using equivalent combustion technology was prepared. The prepared catalyst was then aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0042] The aforementioned Ce / Y / Al composite material, with a Ce content of 50%, a Y content of 20%, and an Al content of 30%, has a specific surface area of ​​65 m² after aging at 800°C for 100 hours under conditions of 20% water vapor and 80% air. 2 / g. FER molecular sieves with an Fe content of 6.0% had a specific surface area of ​​120 m² after aging at 800℃ for 100 hours under conditions of 20% water vapor and 80% air. 2 / g.

[0043] Example 9: A catalyst for purifying NH3 byproducts from a gas-fired engine using stoichiometric combustion technology was prepared by impregnating 134.682g of 17.58% platinum nitrate onto 2000g of Ce / Y / Al composite material and mixing it with 3714g of water to form a slurry. The slurry was then coated onto a honeycomb ceramic carrier with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 150g / L, with the coating height being 80% of the total height of the carrier. The catalyst was then dried at 130℃ to obtain a catalyst with a first coating. A slurry was prepared by mixing 2000g of FER molecular sieve with a Fe content of 5.0% and 3250g of water. The slurry was coated onto the gas outlet end of the catalyst with the first coating at a coating loading of 180g / L. The coating height was 80% of the total height of the support. After drying at 130℃ and calcining at 500℃ for 2 hours, a catalyst for purifying NH3 byproducts of gas engines using equivalent combustion technology was prepared. The prepared catalyst was then aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0044] The aforementioned Ce / Y / Al composite materials, all by weight percentage, contain 20% Ce, 20% Y, and 60% Al. After aging at 800°C for 100 hours under conditions of 20% moisture and 80% air, the specific surface area is 69 m². 2 / g. FER molecular sieves with an Fe content of 6.0% had a specific surface area of ​​120 m² after aging at 800℃ under conditions of 20% water vapor and 80% air for 100 hours. 2 / g.

[0045] Example 10: A catalyst for purifying NH3 byproducts from a gas-fired engine using stoichiometric combustion technology was prepared by impregnating 134.682g of 17.58% platinum nitrate onto 2000g of Ce / Y / Al composite material and mixing it with 3714g of water to form a slurry. The slurry was then coated onto a honeycomb ceramic carrier with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 150g / L, with the coating height being 80% of the total height of the carrier. The catalyst was then dried at 130℃ to obtain a catalyst with a first coating.

[0046] A slurry was prepared by mixing 2000g of FER molecular sieve with an Fe content of 5.0% and 3250g of water. The slurry was coated onto the gas outlet end of the catalyst with the first coating at a coating loading of 180g / L. The coating height was 80% of the total height of the support. The catalyst was dried at 130℃ and calcined at 500℃ for 2 hours to prepare a catalyst for purifying NH3 byproducts of gas engines using equivalent combustion technology. The prepared catalyst was aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0047] The aforementioned Ce / Y / Al composite materials, all by weight percentage, contain 74.5% Ce, 20% Y, and 5.5% Al. After aging for 100 hours at 800°C with 20% moisture and 80% air, the specific surface area is 47 m². 2 / g.

[0048] FER molecular sieves with an Fe content of 6.0% were aged at 800℃ for 100 hours under conditions of 20% water vapor and 80% air, and the specific surface area was 145 m² / g. 2 / g.

[0049] Example 11: A catalyst for purifying NH3 byproducts in a gas-fired engine using stoichiometric combustion technology was prepared by impregnating 134.682g of 17.58% platinum nitrate onto 2000g of Ce / Y / Al composite material and mixing it with 3714g of water to form a slurry. The slurry was then coated onto a honeycomb ceramic carrier with a diameter of 304.8mm and a length of 101.6mm at a coating loading of 150g / L, with the coating height being 70% of the total height of the carrier. The catalyst was then dried at 130℃ to obtain a catalyst with a first coating.

[0050] A slurry was prepared by mixing 2000g of FER molecular sieve with a Fe content of 5.0% and 3250g of water. The slurry was coated onto the gas outlet end of the catalyst with the first coating at a coating loading of 180g / L. The coating height was 70% of the total height of the support. After drying at 130℃ and calcining at 500℃ for 2 hours, a catalyst for purifying NH3 byproducts of gas engines using equivalent combustion technology was prepared. The prepared catalyst was aged at 800℃ under conditions of 20% water vapor and 80% air for 100 hours before use.

[0051] The aforementioned Ce / Y / Al composite materials, all by weight percentage, contain 74.5% Ce, 20% Y, and 5.5% Al. After aging for 100 hours at 800°C with 20% moisture and 80% air, the specific surface area is 47 m². 2 / g.

[0052] FER molecular sieves with an Fe content of 6.0% were aged at 800℃ for 100 hours under conditions of 20% water vapor and 80% air, and the specific surface area was 145 m² / g. 2 / g.

[0053] The hydrothermal aging catalyst samples prepared in Comparative Examples 1 and 2, and Examples 1 to 10, were respectively installed at the rear end of the three-way catalytic converter of a China VI emission engine after hydrothermal aging. The aging conditions for the three-way catalytic converter were 800℃, 20% water vapor, and 80% air for 100 hours. The vehicle emission test was conducted according to the WHTC cycle, and the engine displacement was 15L. The NH3 test results are shown in Table 1 below. The catalyst preparation methods for Examples 2 to 10 were completely consistent with those for Example 1. Table 1: Main differences between catalysts in Examples 1 to 10 Ce content (%) Y content (%) Al content (%) <![CDATA[Specific surface area of Ce / Y / Al composite material after aging (m 2 / g)]]> Fe content (%) <![CDATA[Specific surface area of FER molecular sieve after aging (m 2 / g)]]> First coating loading (g / L) Second coating loading (g / L) Pt content (%) First and second coating height as a percentage of carrier height (%) Example 1 50 20 30 65 5 150 120 100 0.12 80 Example 2 50 20 30 65 5 150 120 100 0.36 80 Example 3 50 20 30 65 5 150 120 100 1.17 80 Example 4 60 20 20 58 5 150 120 100 1.17 80 Example 5 70 20 10 55 5 150 120 80 1.17 80 Example 6 50 20 30 65 6 150 120 100 1.17 80 Example 7 50 20 30 65 6 145 180 100 1.17 80 Example 8 50 20 30 65 6 120 150 180 1.17 80 Example 9 20 20 60 69 6 120 150 180 1.17 80 Example 10 74.5 20 5.5 47 6 145 150 180 1.17 80 Example 11 74.5 20 5.5 47 6 145 150 180 1.17 70 The hydrothermal aging catalyst samples prepared by Comparative Example 1, Comparative Example 2, and Examples 1 to 10 were respectively installed at the rear end of the three-way catalyst of a China VI emission engine after hydrothermal aging. The aging conditions of the three-way catalyst were 800℃, 20% water vapor and 80% air for 100 hours. The vehicle emission test was carried out according to the WHTC cycle. The engine displacement was 15L. The NH3 test results are shown in Table 2 below.

[0054] Table 2: NH3 Test Results <![CDATA[NH3(ppm)]]> <![CDATA[NH3 conversion efficiency (%)]]> Three-way catalyst 68.74 0.00 Comparative Example 1 21.35 68.94 Comparative Example 2 20.6 70.03 Example 1 11.21 83.69 Example 2 10.58 84.61 Example 3 8.3 87.93 Example 4 7.89 88.52 Example 5 7.2 89.53 Example 6 6.52 90.51 Example 7 5.81 91.55 Example 8 6.3 90.84 Example 9 12.05 82.47 Example 10 10.82 84.26 Example 11 11.13 83.81 As shown in Table 1, the present invention utilizes an equivalence combustion technology catalyst for purifying NH3 byproducts from gas-fired engines. This catalyst exhibits excellent hydrothermal stability, maintaining excellent NH3 purification capabilities even after aging for 100 hours at 800°C with 20% water and 80% air content. Furthermore, this catalyst boasts advantages such as simple preparation process and low cost.

Claims

1. A catalyst for purifying NH3 byproducts in a gas-fired engine using stoichiometric combustion technology, characterized in that: The catalyst has two different types of coatings. The first coating is composed of a Ce / Y / Al composite material with high hydrothermal stability supported on Pt metal. The first coating is applied to the inlet end of the support, and the coating height is 70% to 80% of the total height of the support. The second coating is composed of FER molecular sieve with an Fe content of 5% to 6%. The second coating is applied to the outlet end of the support, and the coating height is 70% to 80% of the total height of the support.

2. The catalyst for purifying NH3 byproducts of a gas-fired engine using stoichiometric combustion technology as described in claim 1, characterized in that... The high hydrothermal stability Ce / Y / Al composite material loaded with Pt metal consists of 0.12 wt% ~ 1.17 wt% platinum and 98.83 wt% ~ 99.88 wt% Ce / Y / Al composite material, which has an oxygen storage function.

3. The catalyst for purifying NH3 byproducts of a gas-fired engine using stoichiometric combustion technology as described in claim 1 or 2, characterized in that... By weight percentage, the Ce / Y / Al composite material contains 50% to 70% Ce, 20% Y, and 10% to 30% Al.

4. The catalyst for purifying NH3 byproducts of a gas-fired engine using stoichiometric combustion technology as described in claim 1 or 2, characterized in that... The Ce / Y / Al composite material, after aging for 100 hours at 800℃ with a water content of 20% and an air content of 80%, has a specific surface area of ​​55-65 m². 2 / g.

5. The catalyst for purifying NH3 byproducts of a gas-fired engine using stoichiometric combustion technology as described in claim 1, characterized in that: The molecular sieve, after aging for 100 hours at 800℃ with a water content of 20% and an air content of 80%, has a specific surface area of ​​120-150 m². 2 / g.

6. The catalyst for purifying NH3 byproducts of a gas-fired engine using stoichiometric combustion technology as described in claim 1, characterized in that: The first coating has a loading of 120 g / L ~ 180 g / L.

7. The catalyst for purifying NH3 byproducts of a gas-fired engine using stoichiometric combustion technology as described in claim 1, characterized in that: The second coating has a loading of 100 g / L to 160 g / L.

8. A method for preparing a catalyst for purifying NH3 byproducts in a gas-fired engine using stoichiometric combustion technology, characterized in that: The preparation method includes the following steps: S1. A certain amount of platinum nitrate is loaded onto Ce / Y / Al composite material by impregnation, a certain amount of deionized water and cellulose are added, and the mixture is stirred to obtain a suspension, wherein the solid mass percentage concentration of the suspension is 35% and the viscosity is between 3500 and 4500 cP. S2. The slurry prepared in step S1 is coated into the air inlet channel of a 400 mesh wall-flow honeycomb carrier. The amount of slurry coated is 120 g / L ~ 180 g / L, and the coating height is 80% of the total height of the carrier. S3. The honeycomb carrier with the first coating obtained in step S2 is dried at 150°C for 30 minutes and then set aside for later use. S4. Add FER molecular sieve with an Fe content of 5% to 6% to deionized water containing cellulose and stir to obtain a suspension, wherein the solid mass percentage concentration of the suspension is 32% and the viscosity is between 2500 and 3500 cP. S5. Apply the slurry obtained in step S4 to the air outlet position of the honeycomb carrier with the first coating obtained in step S3. The amount of slurry applied is 100 g / L ~ 160 g / L, and the coating height is 80% of the total height of the carrier. S6. The honeycomb carrier with the first and second coatings obtained in step S5 is dried at 150°C for 30 min and then calcined at 550°C for 2 hours.

9. The preparation method of the catalyst for purifying NH3 byproducts of a gas-fired engine using stoichiometric combustion technology as described in claim 8, characterized in that: The specified amount of platinum nitrate is 17.58% platinum nitrate used in the impregnation method; the specified amount of deionized water and cellulose is mixed at a ratio of 1L:1.2g.