CN113274879A - Tail gas aftertreatment system for gas engine and preparation method and application thereof - Google Patents

Tail gas aftertreatment system for gas engine and preparation method and application thereof Download PDF

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CN113274879A
CN113274879A CN202110827711.6A CN202110827711A CN113274879A CN 113274879 A CN113274879 A CN 113274879A CN 202110827711 A CN202110827711 A CN 202110827711A CN 113274879 A CN113274879 A CN 113274879A
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scr catalyst
gas
molecular sieve
scr
honeycomb ceramic
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张昭良
孟庆华
张娜娜
辛颖
董翠梅
高培海
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Shandong Atk Environmental Protection Technology Co ltd
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Abstract

The invention discloses a tail gas aftertreatment system for a gas engine and a preparation method and application thereof. The invention combines the preposed TWC device with low temperature, oxidation capability and high temperature and TWC function with SCR device as the tail gas post-treatment device of the gas engine to realize CH4Complete combustion, conversion and low NOx polluting emissions. The invention can reduce gas on the basis of greatly reducing the use amount of noble metalThe post-treatment system has high production cost, realizes the standard requirement of the emission control of pollutants in the tail gas of the gas machine, and has wide application prospect in the aspect of tail gas purification of the gas machine.

Description

Tail gas aftertreatment system for gas engine and preparation method and application thereof
Technical Field
The invention relates to the technical field of tail gas treatment of gas machines, in particular to a tail gas post-treatment system for a gas machine and a preparation method and application thereof.
Background
With natural gas (CH)4) Engines that are fuel are commonly referred to collectively as gas engines. Compared with other fossil fuels, due to CH4The advantages of low greenhouse effect, less generated particles and the like become important substitutes of diesel vehicle/gasoline vehicle fuel. However, CH4The global warming effect caused by incomplete combustion of (A) is CO2More than 20 times. In addition, NO in gas engine exhaustxAnd is also one of the important contaminants that needs to be controlled. The gas engine mainly adopts a lean burn technology in the national V stage, and mainly utilizes an oxidation catalyst aiming at a pollutant post-treatment system in tail gas. With the implementation of national VI, the gas engine is changed from a lean combustion technology to equivalent combustion (theoretical air-fuel ratio), and a catalyst in an aftertreatment system is changed into a TWC (namely a three-way catalytic converter) which takes Pt-Pd-Rh/Pd-Rh (Pd is used as a main component) noble metal as an active component, wherein the TWC can simultaneously purify CO, HC and NO in automobile exhaustxThree pollutant catalytic converters) three-way catalysts. The TWC catalyst can simultaneously treat CO, HC and NOxThe three harmful substances play a role in catalytic purification, and research shows that only the content of the noble metal in the post-treatment system of the national VI gas engine reaches 60-120 g/ft3Can meet the requirement of simultaneously removing CO, HC and NOxThe requirements of the three harmful substances meet the emission regulation of the pollutants in the tail gas. However, in recent years, the prices of the noble metals Pd and Rh have continued to increase, which has greatly increased the cost of gas engine tail gas aftertreatment products. Therefore, how to reduce the production cost of the gas engine after-treatment system and simultaneously meet the requirements of emission regulations is a problem to be solved urgently.
Disclosure of Invention
Aiming at the existing gas engine tail gas after-treatment systemThe invention provides a tail gas post-treatment system for a gas engine, which adopts a TWC technology and an SCR technology (namely a selective catalytic reduction technology) aiming at NO in tail gas emission of diesel vehiclesxThe treatment process of (1) is to spray reducing agent ammonia or urea under the action of catalyst to treat NO in tail gasxReduction to N2And H2O, therefore, the SCR device is generally provided with a urea injection device), the SCR device is connected with the rear end of the TWC device, and the two devices treat the tail gas of the gas engine together, thereby not only reducing the content of the noble metal catalyst in the TWC device and the cost, but also simultaneously treating CO, HC and NOxThe three harmful tail gas pollutants play a good role in eliminating and meet the requirements of national emission regulations.
In order to achieve the purpose, the technical scheme of the invention is as follows: the utility model provides a tail gas aftertreatment system for gas engine, this system is including consecutive TWC device and SCR device, and the TWC device is the honeycomb ceramic carrier that has the coating noble metal, and the SCR device is including honeycomb ceramic carrier and the urea injection apparatus that have the SCR catalyst, and the urea injection apparatus includes urea solution storage tank and urea pump, sprays urea in to the SCR device through the urea pump, and urea solution storage tank sprays urea to the front end that has the honeycomb ceramic carrier of SCR catalyst through the urea pump.
Furthermore, the tail gas inlet end is used as the front end, the tail gas outlet end is used as the rear end, the TWC device is located at the front end of the tail gas after-treatment system, and the SCR device is located at the rear end of the tail gas after-treatment system.
Further, the content of the noble metal on the honeycomb ceramic carrier is 28-30 g/ft3. The invention greatly reduces the content of noble metal and the cost.
Preferably, the noble metal is Pt, Pd, Rh, wherein Pt: pd: the weight ratio of Rh is 6-7: 21-22: 1. the invention changes the proportion of noble metal elements, reduces the content of Pd and Rh with higher cost, and takes the three-way catalyst as CH4Catalyst of combustion, lowering CH4The combustion temperature of (1). Meanwhile, Pd and Ph in the catalyst can play a role of three-way catalysis at high temperature,the three-way catalyst fully exerts the low-temperature oxidation effect. However, the reduction performance of Pd and Rh is reduced to some extent due to the reduction of the used amount of Pd and Rh, and NO x The removal effect is reduced, therefore, the invention adds an SCR device at the rear end of the TWC device to eliminate pollutant NO x . The optimization of the structural combination form and the catalyst components reduces the production cost and realizes CH4The pollutants can be completely combusted and converted, and the pollutants meet the requirements of national emission regulations.
Further, the SCR catalyst is a catalyst having SCR catalytic effect, and components that can be used for SCR catalysis reported in the prior art may be used in the present invention, for example, V-based SCR catalyst, Ce-based SCR catalyst, Fe-based small pore molecular sieve SCR catalyst, Cu-based small pore molecular sieve SCR catalyst. These catalysts can be purchased directly from the market or prepared themselves according to the reports of the prior art.
In one embodiment of the invention, the V-based SCR catalyst is V2O5-WO3/TiO2Catalyst, V2O5-WO3/TiO2The catalyst is in powder form, WO3At V2O5-WO3/TiO2The content in the powdered catalyst is 5-10 wt.%, preferably 5 wt.%, V2O5At V2O5-WO3/TiO2The content in the powdered catalyst is 1-3 wt.%, preferably 3 wt.%.
In one embodiment of the present invention, V is provided2O5-WO3/TiO2The preparation method of the powder catalyst comprises the following steps: commercially available containing WO3The titanium tungsten powder is put into a precursor ammonium metabisulfite aqueous solution containing V, in order to ensure better dissolution of the ammonium metabisulfite, a certain amount of oxalic acid is added into the aqueous solution, and the preferable molar ratio of the ammonium metabisulfite to the oxalic acid is 1: 1.1, drying in a forced air drying oven after full impregnation, wherein the drying is generally divided into two processes, namely drying at 60-80 ℃ for 10-12 h, and then drying at 100-110 ℃ for 10-12 h. Drying, roasting in air atmosphere at 450-500 deg.CThe time is generally 4 to 6 hours to obtain V2O5-WO3/TiO2A powder catalyst.
In one embodiment of the invention, the Cu-based small pore molecular sieve SCR catalyst is in the form of a powder comprising a Cu-SSZ-13 molecular sieve, a Cu-SSZ-39 molecular sieve or a Cu-LTA molecular sieve, preferably a Cu-SSZ-13 molecular sieve. The Cu content in the Cu-based small pore molecular sieve SCR catalyst is 1.5-4.0 wt.%, preferably 3.0 wt.%.
In one embodiment of the invention, the Fe-based small pore molecular sieve SCR catalyst comprises a Fe-SSZ-13 molecular sieve, a Fe-SSZ-39 molecular sieve or a Fe-LTA molecular sieve. The content of Fe in the Fe-based small pore molecular sieve SCR catalyst is 0.5-3.0 wt.%, preferably 1.5 wt.%.
Further, the coating amount of the SCR catalyst in the SCR device is controlled to completely realize NO x The dosage can refer to the coating amount of the SCR catalyst of the gasoline vehicle and the diesel vehicle.
Further, in the SCR device, the honeycomb ceramic carrier has a binder in addition to the SCR catalyst, and preferably, the total amount of the SCR catalyst and the binder is coated on the honeycomb ceramic carrier in an amount of 5 to 10 g/ft3。
Further, the SCR device also comprises a urea solution storage tank used for spraying urea into the SCR device, and a liquid outlet of the urea solution storage tank is positioned at the front end of the honeycomb ceramic carrier coated with the SCR catalyst.
Further, in the TWC device and the SCR device, the material of the honeycomb ceramic carrier used may be a component reported in the prior art as being capable of serving as a carrier for gasoline vehicles and diesel vehicles, such as cordierite.
The invention also provides a preparation method of the tail gas after-treatment system for the gas engine, which comprises the following steps:
(1) preparing a noble metal precursor, a carrier, a binder and water into slurry, uniformly coating the slurry on a honeycomb ceramic carrier, drying and roasting to obtain a TWC device;
(2) preparing an SCR catalyst, a binder and water into slurry, uniformly coating the slurry on a honeycomb ceramic carrier, drying and roasting to obtain an SCR device;
(3) and connecting the TWC device and the SCR device together to obtain the tail gas after-treatment system for the gas engine.
Further, the noble metal precursor may be a water-soluble salt of each noble metal, for example, the platinum precursor may be platinum nitrate or the like, the palladium precursor may be palladium nitrate, palladium acetate or the like, and the rhodium precursor may be rhodium nitrate, rhodium acetate or the like.
Further, in the step (1), the carrier may be selected from reports in the prior art, and may be, for example, modified alumina or cerium-zirconium-based composite oxide. The modified alumina is one or more of Y, Zr, La, Ce, Sr and Ba elements, wherein the molar ratio of the Al element is not less than 65%, preferably 80%, so as to ensure better sintering resistance. In the cerium-zirconium-based composite oxide, one or more of Mn, La, Y, Pr and Nd elements are doped, and the cerium-zirconium-based composite oxide is a quaternary or quinary composite oxide generally, wherein the molar ratio of the Ce element is not less than 50%, preferably 60%, so that the cerium-zirconium-based composite oxide has better oxygen storage performance. These supports can be purchased directly from the market or prepared by themselves according to the reports of the prior art, and modified alumina or cerium-zirconium-based composite oxide which can be used as a catalyst support for exhaust gas treatment, reported in the prior art, can be used in the present invention.
Further, in the step (1), the noble metal precursor, the carrier, the binder and water are prepared into slurry, and the concentrations of the noble metal precursor, the carrier and the binder can be selected and adjusted according to the reports of the prior art, so that the aim of uniformly, conveniently and quickly coating the catalyst on the honeycomb ceramic carrier can be fulfilled.
Further, in the steps (1) and (2), the binder may be selected from reports in the prior art, such as silica gel, pseudoboehmite, and the like.
Further, in the step (2), the SCR catalyst, the binder and water are prepared into slurry, and the concentration of the SCR catalyst and the concentration of the binder can be selected and adjusted according to the report of the prior art, so that the purpose of uniformly, conveniently and quickly coating the catalyst on the honeycomb ceramic carrier can be realized.
Further, in the steps (1) and (2), the coating mode of the slurry belongs to the conventional technology in the field, and is generally divided into layered coating or segmented coating, and the layered coating or the segmented coating can be adopted as long as uniform and firm adhesion of the catalyst is realized.
Further, in the steps (1) and (2), the coating amount of the slurry can meet the content requirement of the catalyst on the TWC device and the SCR device.
Further, in the step (1), the drying temperature is 50-80 ℃, and the drying time is generally 10-12 h. The roasting temperature is 800-1000 ℃, and the roasting time is generally 5-8 h.
Further, in the step (2), the drying temperature is 70-110 ℃, and the drying time is generally 10-12 h. The roasting temperature is 500-550 ℃, and the roasting time is generally 2-3 h.
The invention also provides the application of the tail gas after-treatment system in the elimination of pollutants of the tail gas of the gas engine, wherein the pollutants are CO, HC and NO x . After the tail gas passes through the tail gas after-treatment system, CO, HC and NO x Can be well eliminated, and can meet the requirements of national emission regulations.
The invention provides a method for compositely using a preposed TWC device with low temperature, oxidation capability, high temperature and TWC function and a postpositioned SCR device for aftertreatment of tail gas of a gas engine, and the use amount of noble metal is reduced on the preposed TWC device to reach CH4Complete oxidation, combustion and partial NO x Reduced function, and the SCR device arranged behind the SCR device can be used for remaining NO which is not reduced x All selective catalytic reduction. The invention can greatly reduce the production cost of the gas engine tail gas post-treatment system and simultaneously can meet the standard requirement of the emission control of the gas engine tail gas pollutants. Compared with the prior art, the invention has the following beneficial effects:
1. the content of noble metal in the tail gas post-treatment system is low, so that the production cost is greatly reduced; in addition, the TWC device contains Pt, Pd and Rh, and the presence of Pt and Pd can make CH4The combustion of (2) is carried out at a low temperature to exert an oxidizing action; at high temperature, Pd and Rh can generate three-effect catalysis effect on the catalyst, and CO and NO are realized x Low emission.
2. The present invention places the SCR device downstream of the TWC device. Since the amount of Rh used in the TWC is greatly reduced, the reduction effect is greatly reduced, so that only part of NO is present x Is reduced in the TWC device while remaining NO x Can realize NO reduction through a post SCR catalyst x Elimination of (2).
3. The invention can realize methane (CH)4) Complete combustion, conversion and low NO x The pollution emission can realize the standard requirement of the emission control of pollutants in the tail gas of the gas machine, and the method has wide application prospect in the aspect of tail gas purification of the gas machine.
Drawings
The present invention will now be further described with reference to the accompanying drawings.
FIG. 1 is a schematic view of a part of the structure of an exhaust gas post-treatment system for a gas engine according to the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the examples which follow, Y-ZrO was used2-Al2O3The carrier was obtained from SASOL corporation and used as CeZrLaNdYO2The carriers were purchased from the Solvay group.
Example 1
The utility model provides a tail gas aftertreatment system for gas engine, is including TWC device 1 and SCR device 2 that communicate each other in proper order, and TWC device 1 is the honeycomb ceramic carrier that has the coating noble metal, and SCR device 2 is including the honeycomb ceramic carrier and the urea injection apparatus that have the SCR catalyst of coating, and urea injection apparatus includes urea solution storage tank 3 and urea pump 4, sprays urea in to SCR device 2 through urea pump 4, and urea solution storage tank 3 sprays urea to the front end of the honeycomb ceramic carrier that has the SCR catalyst through urea pump 4.
1. Pt, Pd and Rh noble metal are loaded on cordierite honeycomb ceramic carrier
Coating Pt and Pd noble metal on cordierite carrier
First, Y-ZrO is oxidized2-Al2O3The carrier, silica gel and water are mixed according to a weight ratio of 50: 5: 45, and fully stirring for 30 min to obtain uniform slurry; then adding a platinum nitrate aqueous solution until the mass fraction is 1 wt.%, adding a palladium nitrate aqueous solution until the mass fraction is 2 wt.%, fully stirring to obtain viscous slurry, inputting a certain volume of slurry to the cordierite honeycomb ceramic carrier by using a grouting machine, uniformly coating the slurry on 40% of the length of the cordierite honeycomb ceramic carrier from top to bottom, and enabling the mass sum of Pt and Pd in the catalyst on the cordierite honeycomb ceramic carrier to be 14 g/ft3And then coating the other end of the carrier in the reverse direction so that the sum of the mass of Pt and Pd on the cordierite honeycomb ceramic carrier is 5g/ft3. The coated carrier was placed in a vacuum oven and dried at 70 ℃ for 12 h.
② coating Pd and Rh noble metal on cordierite carrier
Reacting Y-ZrO2-Al2O3The carrier, silica gel and water are mixed according to a weight ratio of 50: 5: 45, and fully stirring for 30 min to obtain uniform slurry; then, a palladium nitrate aqueous solution was added to a mass fraction of 1 wt.%, and a rhodium nitrate aqueous solution was added to a mass fraction of 0.05 wt.%, and the mixture was sufficiently stirred to obtain a viscous slurry. Inputting a certain volume of slurry into the cordierite honeycomb ceramic carrier coated in the step I by using a grouting machine, uniformly coating the slurry on 40% of the length of the carrier from top to bottom, and ensuring that the mass sum of Pd and Rh in the catalyst on the cordierite honeycomb ceramic carrier is 6 g/ft3And then coating the other end of the carrier in the reverse direction so that the sum of the mass of Pd and Rh on the cordierite honeycomb ceramic carrier is 3 g/ft3. The total mass sum of Pt, Pd and Rh of the whole TWC device is 28g/ft3Specifically, Pt: pd: the weight ratio of Rh is 6: 21: 1. and (3) putting the coated carrier into a vacuum drying oven, drying at 80 ℃ for 10 h, and then roasting in a roasting furnace at 1000 ℃ for 5 h in the air atmosphere to obtain the noble metal-containing honeycomb ceramic carrier.
2、V2O5-WO3/TiO2Preparation of SCR catalyst
Firstly, measuring 10 mL of deionized water in a 25 mL glass beaker, adding 0.0383 g of oxalic acid with the mass fraction of 99.5%, and quickly stirring until the oxalic acid is dissolved; then adding 0.0195 g of ammonium metavanadate with the mass fraction of 99%, and stirring for 30 min until the ammonium metavanadate is completely dissolved to obtain a grass green transparent solution; then 1g of WO was weighed3Adding 5 wt.% titanium-tungsten powder into the solution, and rapidly stirring at 70 deg.C until the solution is completely evaporated to dryness; then putting the dried solid into a 80 ℃ blast drying oven for heat preservation for 12 h, and then moving the dried solid into a 110 ℃ drying oven for heat preservation for 12 h; finally, the fully dried sample is heated to 500 ℃ in a tubular furnace at the heating rate of 5 ℃/min in the air atmosphere, and the temperature is maintained for 5 h to obtain V2O5-WO3/TiO2An SCR catalyst.
3、V2O5-WO3/TiO2SCR catalyst is loaded on cordierite honeycomb ceramic carrier
Ready V2O5-WO3/TiO2Mixing SCR catalyst powder, silica gel and water according to the weight ratio of 40: 5: 55, and fully stirring for 30 min to obtain uniform slurry; the cordierite honeycomb ceramic carrier is immersed into the slurry in the positive and negative directions to realize V2O5-WO3/TiO2Coating of (V)2O5-WO3/TiO2The coating amount of the SCR catalyst and the silica gel on the cordierite honeycomb ceramic carrier is 10 g/ft3. Then, drying the coated cordierite carrier at 70-110 ℃ for 12 h, and roasting at 500 ℃ for 2 h to obtain a coating V2O5-WO3/TiO2A honeycomb ceramic support for an SCR catalyst.
4. Exhaust aftertreatment system assembly
Coating the noble metal-containing honeycomb ceramic carrier with coating V2O5-WO3/TiO2Connecting and assembling the honeycomb ceramic carrier of the SCR catalyst, coating the honeycomb ceramic carrier of the noble metal at the tail gas inlet end with V2O5-WO3/TiO2And the honeycomb ceramic carrier of the SCR catalyst is arranged at the exhaust end of the exhaust to obtain an exhaust aftertreatment system.
Example 2
The utility model provides a tail gas aftertreatment system for gas engine, is including TWC device 1 and SCR device 2 that communicate each other in proper order, and TWC device 1 is the honeycomb ceramic carrier that has the coating noble metal, and SCR device 2 is including the honeycomb ceramic carrier and the urea injection apparatus that have the SCR catalyst of coating, and urea injection apparatus includes urea solution storage tank 3 and urea pump 4, sprays urea in to SCR device 2 through urea pump 4, and urea solution storage tank 3 sprays urea to the front end of the honeycomb ceramic carrier that has the SCR catalyst through urea pump 4.
1. Pt, Pd and Rh noble metal are loaded on cordierite honeycomb ceramic carrier
Coating Pt and Pd noble metal on cordierite carrier
First, CeZrLaNdYO is mixed2The carrier, silica gel and water are mixed according to a weight ratio of 50: 5: 45, and fully stirring for 30 min to obtain uniform slurry; then adding a platinum nitrate aqueous solution until the mass fraction is 1 wt.%, adding a palladium nitrate aqueous solution until the mass fraction is 2 wt.%, fully stirring to obtain viscous slurry, inputting a certain volume of slurry to the cordierite honeycomb ceramic carrier by using a grouting machine, uniformly coating the slurry on 40% of the length of the cordierite honeycomb ceramic carrier from top to bottom, and enabling the mass sum of Pt and Pd in the catalyst on the cordierite honeycomb ceramic carrier to be 14 g/ft3And then coating the other end of the carrier in the reverse direction so that the sum of the mass of Pt and Pd on the cordierite honeycomb ceramic carrier is 5g/ft3. The coated carrier was placed in a vacuum oven and dried at 70 ℃ for 12 h.
② coating Pd and Rh noble metal on cordierite carrier
CeZrLaNdYO2The carrier, silica gel and water are mixed according to a weight ratio of 50: 5: 45, and fully stirring for 30 min to obtain uniform slurry; then, a palladium nitrate aqueous solution was added to a mass fraction of 1 wt.%, and a rhodium nitrate aqueous solution was added to a mass fraction of 0.05 wt.%, and the mixture was sufficiently stirred to obtain a viscous slurry. The same step is that a grouter is used for inputting a certain volume of slurry to the cordierite honeycomb ceramic carrier coated in the stepUniformly coating the slurry on the position 40% of the length of the carrier from top to bottom to make the mass sum of Pd and Rh in the catalyst on the cordierite honeycomb ceramic carrier be 6 g/ft3And then coating the other end of the carrier in the reverse direction so that the sum of the mass of Pd and Rh on the cordierite honeycomb ceramic carrier is 5g/ft3. The total mass of the whole Pt, Pd and Rh is 30g/ft3Specifically, Pt: pd: the weight ratio of Rh is 7: 22: 1. and (3) putting the coated carrier into a vacuum drying oven, drying at 80 ℃ for 10 h, and then roasting in a roasting furnace at 1000 ℃ for 5 h in the air atmosphere to obtain the noble metal-containing honeycomb ceramic carrier.
2. Preparation of Cu-SSZ-13 SCR catalyst
1g of molecular sieve SSZ-13 in Na form with Si/Al molar ratio =6 was weighed into a three-neck flask, and 46 mL of 0.1M NH was added4NO3Solution with 5 wt.% NH3·H2Adjusting the pH value to 3-4 by O, and keeping for 10 min; then, transferring the three-neck flask into a water bath kettle at 80 ℃, and keeping for 2 hours for ion exchange; after the exchange is finished, centrifuging, washing and drying the suspension; this process is repeated again for sufficient ion exchange to obtain NH4-SSZ-13。
Subsequently, 1g of NH4-SSZ-13 molecular sieve powder was placed in 40 mL of 0.1M CuSO4And (3) keeping the solution at 80 ℃ for 1 h, and finally centrifugally washing, drying and roasting the product at 575 ℃ for 8 h to obtain the Cu-SSZ-13 SCR catalyst.
3. Cu-SSZ-13 SCR catalyst is loaded on cordierite honeycomb ceramic carrier
Mixing the prepared Cu-SSZ-13 SCR catalyst powder with silica gel and water according to the weight ratio of 15: 5: 80, and fully stirring for 30 min to obtain uniform slurry; dipping the cordierite honeycomb ceramic carrier into the slurry in the positive and negative directions to realize the coating of Cu-SSZ-13, wherein the coating amount of the Cu-SSZ-13 SCR catalyst and silica gel on the cordierite honeycomb ceramic carrier is 5g/ft3. And then, drying the coated cordierite carrier at 70-110 ℃ for 12 h, and roasting at 500 ℃ for 2 h to obtain the Cu-SSZ-13 SCR catalyst coated honeycomb ceramic carrier.
4. Exhaust aftertreatment system assembly
Connecting and assembling a honeycomb ceramic carrier containing noble metal and a honeycomb ceramic carrier coated with a Cu-SSZ-13 SCR catalyst, wherein the honeycomb ceramic carrier containing noble metal is arranged at the tail gas inlet end, and the honeycomb ceramic carrier coated with the Cu-SSZ-13 SCR catalyst is arranged at the tail gas outlet end to obtain the tail gas after-treatment system.
The cordierite honeycomb ceramic carrier, the urea solution tank 3 and the urea pump 4 used in the above-described examples 1 and 2 are prior art, and the structural principle and the like thereof will not be described herein again.
Application example
Coated with Pt-Pd-Rh/La-Al prepared in the above examples2O3、Pt-Pd-Rh/CeZrLaNdYO2Of a novel three-way catalytic material and V2O5-WO3/TiO2Filter catalyzed CH for Cu-SSZ-13 SCR catalyst4Combustion and NO x The performance of the reduction was evaluated. The method comprises the following steps:
1. the experimental steps are as follows:
1.1 detection of coating amounts of noble metal catalyst and SCR catalyst in examples 1 and 2
The weight of the cordierite honeycomb ceramic carrier dried before coating and after coating is obtained by a weighing method, the obtained difference value is the loading amount of the slurry, and each ft is calculated according to the loading amount and the content of the components in the slurry3Coating amount of noble metal per ft on (cubic foot) cordierite honeycomb ceramic carrier3The coating amounts of SCR catalyst and binder on the (cubic foot) cordierite honeycomb ceramic substrate are shown in tables 1 and 2, respectively.
1.2 coating of Pt-Pd-Rh/Y-ZrO in examples 1 and 22-Al2O3、Pt-Pd-Rh/CeZrLaNdYO2The cordierite honeycomb ceramic carrier catalyzes CH4Test of Combustion Performance
Coating Pt-Pd-Rh/Y-ZrO2-Al2O3、Pt-Pd-Rh/CeZrLaNdYO2The cordierite honeycomb ceramic carrier is cut into ϕ 10 x 15 mm cylinder-like bodies, then the cylinders are put into a ϕ 10 mm quartz reaction tube, and a catalytic reaction flat is connectedA stage (mixing and switching of different gases without exposure to air can be achieved). The specific experimental method is as follows: the temperature is raised to 200 ℃ for pretreatment for 30 min under Ar atmosphere at the temperature raising rate of 10 ℃/min, and the total flow of gas is 1L/min. After the incubation was complete, the reaction was cooled to room temperature and then switched into the reaction atmosphere: 1000 ppm CH4，10 vol.% O2He as balance gas, raising the temperature to 800 deg.C at a rate of 10 deg.C/min, and detecting CH with continuous gas infrared analyzer4、CO、CO 2 、NO、NO2、H2The signal O, the total flow of gas was kept constant throughout the experiment.
CH can be detected during this experiment4The results of the concentration change with temperature are shown in Table 1.
1.3 coating V of examples 1 and 22O5-WO3/TiO2Cu-SSZ-13 cordierite honeycomb ceramic carrier for SCR performance test
Will coat V2O5-WO3/TiO2The cordierite honeycomb ceramic carrier is cut into ϕ 10 mm-15 mm-like cylinders, then the cylinders are placed into a ϕ 10 mm quartz reaction tube, and the quartz reaction tube is connected to an SCR catalytic reaction platform self-made by a laboratory. Reaction atmosphere: 500 ppm NO, 500 ppm NH3，5.3 vol.% O2the/He and the He are used as balance gas, and the gas flow is 1L/min. The reaction temperature is 500 ℃ from 150 ℃ according to the actual situation, one temperature point is taken at intervals of 25 ℃ or 50 ℃, and the value is recorded after the concentration of each reactant is stable at each temperature point. During the whole test, NO x Analyzer detecting NO and NO2Concentration of (3), detection of NH by Mass Spectrometry3And N2The concentration of O.
NO can be detected during this experiment x The results of the concentration change with temperature are shown in Table 2.
2. Results of the experiment
2.1 Pair coating of Pt-Pd-Rh/Y-ZrO2-Al2O3And Pt-Pd-Rh/CeZrLaNdYO2The performance of the cordierite honeycomb ceramic carrier is evaluated, and the test results are shown in the following table 1:
TABLE 1
Sample (I) Noble metal coating weight (g/ft)3） CH4 T50 （℃） CH4 T90 （℃）
Example 1 28 292 347
Example 2 30 283 338
2.2 Pair of coatings V2O5-WO3/TiO2The performance of the cordierite honeycomb ceramic carrier of Cu-SSZ-13 is evaluated, and the test results are shown in the following table 2:
TABLE 2
Sample (I) SCR catalyst and binder coating weight (g/ft)3） NO x Temperature interval (. degree.C.) for 90% conversion
Example 1 10 250-425
Example 2 5 200-550
As can be seen from tables 1 and 2, the products obtained in the examples, even though the content of noble metals is low, have CH4Can be catalytically combusted at low temperature, and can realize NO at high temperature section by compounding SCR device x The exhaust gas pollution reduction can be realized.
The above are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention. Any equivalent changes and modifications that can be made by one skilled in the art without departing from the spirit and principles of the invention should fall within the protection scope of the invention.

Claims (8)

1. The utility model provides a tail gas aftertreatment system for gas engine which characterized in that: including TWC device and the SCR device that communicates each other in proper order, TWC device is the honeycomb ceramic carrier who coats the noble metal, and the SCR device is including the honeycomb ceramic carrier who coats the SCR catalyst and the urea injection apparatus that the front end set up, and the noble metal is Pt, Pd, Rh, wherein Pt: pd: the weight ratio of Rh is 6-7: 21-22: 1, the coating amount of the noble metal on the honeycomb ceramic carrier is 28-30 g/ft3。
2. The exhaust gas after-treatment system for gas engine as claimed in claim 1, wherein: the SCR catalyst is V-based SCR catalyst, Ce-based SCR catalyst, Fe-based SCR catalyst or Fe-based small pore molecular sieve SCR catalystThe SCR catalyst is a Cu-based small pore molecular sieve SCR catalyst, a honeycomb ceramic carrier is also coated with a binder, and the coating amount of the total amount of the SCR catalyst and the binder on the honeycomb ceramic carrier is 5-10 g/ft3。
3. The exhaust gas after-treatment system for gas engine as claimed in claim 2, wherein: the V-based SCR catalyst is V2O5-WO3/TiO2The Cu-based small-pore molecular sieve SCR catalyst is a Cu-SSZ-13 molecular sieve, a Cu-SSZ-39 molecular sieve or a Cu-LTA molecular sieve, and the Fe-based small-pore molecular sieve SCR catalyst is a Fe-SSZ-13 molecular sieve, a Fe-SSZ-39 molecular sieve or a Fe-LTA molecular sieve.
4. An exhaust gas after-treatment system for a gas engine as claimed in claim 3, wherein: v2O5-WO3/TiO2In the powder catalyst, WO3In an amount of 5-10 wt.%, V2O5In an amount of 1-3 wt.%; in the Cu-based small pore molecular sieve powder SCR catalyst, the content of Cu is 1.5-4.0 wt.%; in the Fe-based small-pore molecular sieve SCR catalyst, the content of Fe is 0.5-3.0 wt.%.
5. An exhaust gas after-treatment system for gas engines according to any one of claims 1 to 4, characterized in that: the TWC device is located at the front end for intake and the SCR device is located at the rear end for exhaust.
6. A method of making an exhaust gas after-treatment system for a gas engine as claimed in any one of claims 1 to 4, comprising the steps of:
(1) preparing a noble metal precursor, a carrier, a binder and water into slurry, uniformly coating the slurry on a honeycomb ceramic carrier, drying and roasting to obtain a TWC device;
(2) preparing an SCR catalyst, a binder and water into slurry, uniformly coating the slurry on a honeycomb ceramic carrier, drying and roasting to obtain an SCR device;
(3) and connecting the TWC device and the SCR device together to obtain the tail gas after-treatment system for the gas engine.
7. The method of claim 6 for preparing an exhaust gas after-treatment system for a gas engine, comprising: in the step (1), the binder comprises silica gel or pseudo-boehmite; in the step (1), the carrier is modified alumina doped with one or more of Y, Zr, La, Ce, Sr and Ba elements or cerium-zirconium-based composite oxide doped with one or more of Mn, La, Y, Pr and Nd elements; in the step (1), the roasting temperature is 800-1000 ℃, and in the step (2), the roasting temperature is 500-550 ℃.
8. Use of an exhaust gas after-treatment system for a gas engine according to claim 1 for the abatement of pollutants in the exhaust gas of a gas engine, the pollutants being CO, HC, NOx。
CN202110827711.6A 2021-07-22 2021-07-22 Tail gas aftertreatment system for gas engine and preparation method and application thereof Pending CN113274879A (en)

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Application publication date: 20210820