A post-processing device for a vehicle

Abstract

The application discloses a post-processing device and a vehicle, and belongs to the technical field of engine post-processing devices. The post-processing device is used for the vehicle, the vehicle comprises a methanol lean-burn engine, and the post-processing device comprises a methanol oxidation catalyst and a topological structure catalyst; the methanol oxidation catalyst and the topological structure catalyst are sequentially arranged along the exhaust gas exhaust direction of the methanol lean-burn engine; the methanol oxidation catalyst is used for performing first purification on the exhaust gas; the topological structure catalyst is used for performing second purification on the exhaust gas after the first purification; the second purification comprises the following steps: the topological structure catalyst adsorbs and stores hydrocarbons in the exhaust gas after the first purification, releases and migrates the stored hydrocarbons to the reaction active sites of the topological structure catalyst, and reduces nitrogen oxides in the exhaust gas after the first purification into nitrogen. The post-processing device does not need a urea supply device, has simple structure and low cost, and can realize efficient purification of the exhaust gas.

Description

Technical Field

[0001] This invention relates to the field of engine aftertreatment devices, and more particularly to an aftertreatment device and a vehicle. Background Technology

[0002] Currently, mass-produced methanol lean-burn engines generally control the excess air coefficient below 1.5. Under this condition, the methanol combustion process is relatively complete and stable, resulting in lower emissions of carbon monoxide (CO) and hydrocarbons (HC) in the exhaust gas, but lower emissions of nitrogen oxides (NOx). x The generation of CO and HC increases significantly. For the treatment of CO and HC, a methanol oxidation catalyst (MOC) alone can achieve efficient oxidation and purification, meeting current emission regulations. However, due to the lean-burn conditions leading to a high oxygen concentration in the exhaust gas, conventional three-way catalytic converters are less effective at reducing NO production. x Limited conversion efficiency leads to NO x Emissions remain high. To effectively reduce NO... x To meet stringent emission standards, an additional selective catalytic reduction (SCR) device must be installed. This involves injecting a reducing agent, such as urea solution, to perform a targeted catalytic reduction reaction. Therefore, current methanol lean-burn engines generally adopt a combined "MOC + active SCR" after-treatment system to address CO, HC, and NO emissions. x Synergistic control and efficient purification of multiple pollutants.

[0003] However, active SCR aftertreatment requires additional urea storage and supply devices, which has the following drawbacks: (1) complex structure and large space occupation; (2) daily use of urea injection requires precise and complex calibration to ensure optimal SCR conversion efficiency, and the development and calibration costs are high; (3) urea nozzles in the aftermarket are prone to clogging, the market failure rate is high, and the user's maintenance costs are high.

[0004] To improve the shortcomings of the above-mentioned "MOC+Active SCR" methanol lean-burn engine aftertreatment system, reduce development and usage costs, and lower the system failure rate, it is particularly important to study a new aftertreatment scheme to replace active SCR. Summary of the Invention

[0005] The main objective of this invention is to provide an aftertreatment device and vehicle that solves the technical problems of complex structure and difficult maintenance of existing "MOC+Active SCR" type methanol lean-burn engine aftertreatment systems.

[0006] To achieve the above objectives, the present invention provides an aftertreatment device for a vehicle, the vehicle including a methanol lean-burn engine, the aftertreatment device including a methanol oxidation catalyst and a topological catalyst, the methanol oxidation catalyst and the topological catalyst being arranged sequentially along the exhaust direction of the methanol lean-burn engine. The methanol oxidation catalyst is used for the initial purification of the exhaust gas. The topologically structured catalyst is used for a second purification of the exhaust gas after the first purification. The second purification includes: the topological catalyst adsorbing and storing hydrocarbons in the exhaust gas after the first purification, and releasing and migrating the stored hydrocarbons to the reactive sites of the topological catalyst to reduce nitrogen oxides in the exhaust gas after the first purification to nitrogen.

[0007] In some embodiments of the present invention, the first purification includes: the methanol oxidation catalyst oxidizing carbon monoxide and some hydrocarbons in the exhaust gas.

[0008] In some embodiments of the present invention, the topological catalyst is a hierarchical porous structure, including macropores, mesopores and micropores, wherein the pore size of the macropores is >50nm, the pore size of the mesopores is in the range of 2nm~50nm, and the pore size of the micropores is <2nm.

[0009] In some embodiments of the present invention, the reactive sites are distributed with noble metals.

[0010] In some embodiments of the present invention, the noble metal includes at least one of Pd and Pt.

[0011] In some embodiments of the present invention, the excess air coefficient of the methanol lean-burn engine is greater than 1.8.

[0012] In some embodiments of the present invention, the excess air coefficient of the methanol lean-burn engine is 1.8 to 2.5.

[0013] The present invention also provides a vehicle that includes the after-treatment device described above.

[0014] In some embodiments of the present invention, the methanol lean-burn engine includes a high-pressure oil pump; And / or, the ignition system of the methanol lean-burn engine is a high-energy ignition system; And / or, the methanol lean-burn engine is fueled by direct injection.

[0015] In some embodiments of the present invention, the methanol lean-burn engine includes a high-pressure oil pump, wherein the injection pressure of the high-pressure oil pump is 10MPa~50MPa; And / or, The ignition system of the methanol lean-burn engine is a high-energy ignition system, and the high-energy ignition system satisfies at least one of the following: Ignition energy ranges from 120 mJ to 254 mJ; The energy of the ignition coil is 220mJ~250mJ; Ignition voltage is greater than or equal to 30,000V; The discharge duration is 2.6ms to 4.3ms.

[0016] The beneficial effects that this invention can achieve are: The aftertreatment device of the present invention simplifies the existing "MOC+active SCR" structure containing a urea supply device to a "MOC+HC-SCR" structure, completely eliminating complex auxiliary systems such as urea storage, injection and electronic control calibration. Under the premise of ensuring that emissions meet standards, the structure of the aftertreatment device is significantly simplified, space is saved, and development, use and maintenance costs are reduced.

[0017] The working principle of the "MOC+HC-SCR" structure of this invention is as follows: The exhaust gas generated by the methanol lean-burn engine first flows through the methanol oxidation catalyst (MOC). Carbon monoxide and some hydrocarbons in the exhaust gas are oxidized into carbon dioxide and water in the MOC, completing the first purification. The exhaust gas treated by the MOC enters the topological structure catalyst (HC-SCR). The HC-SCR has a multi-level pore structure. With its high specific surface area and pore topology, it selectively adsorbs and stores excess hydrocarbons in the exhaust gas inside the pores. Under suitable temperature conditions, the stored hydrocarbons desorb from the pores and diffuse to the reactive sites where the catalyst is distributed. Under the catalytic action of the catalyst, the hydrocarbons act as reducing agents and undergo selective catalytic reduction reactions with nitrogen oxides in the exhaust gas. The nitrogen oxides are reduced to pollution-free nitrogen gas, while carbon dioxide and water are generated, thus completing the second purification. After the above two-stage purification treatment, the exhaust gas meets the emission standards. The aftertreatment device of the present invention uses the hydrocarbons in the exhaust gas that have not been oxidized by MOC as the endogenous reducing agent of the topological catalyst, realizing "waste treatment with waste", without the need for external supply of reducing agent, making full use of exhaust gas resources and turning waste into treasure. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0019] Figure 1This is a schematic diagram of the structure of a post-processing device according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a topological catalyst according to an embodiment of the present invention; Figure 3 This is a schematic diagram showing the changing trends of methanol combustion emissions under different excess air coefficients.

[0020] The illustrations in the instruction manual are numbered as follows: 200. Methanol lean-burn engine; 100. After-treatment device; 10. Methanol oxidation catalyst; 20. Topological structure catalyst; 21. Macropore; 22. Mesopore; 23. Micropore.

[0021] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0022] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] In this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination should be considered non-existent and not within the scope of protection claimed by this invention.

[0025] In the field of methanol lean-burn engines, mass-produced methanol lean-burn engines generally control the excess air coefficient below 1.5. Under this condition, the methanol combustion process is relatively complete and stable, resulting in lower emissions of carbon monoxide and hydrocarbons in the exhaust gas, but a significant increase in the formation of nitrogen oxides. For the treatment of carbon monoxide and hydrocarbons, a methanol oxidation catalyst (MOC) can achieve efficient oxidation and purification. However, due to the high oxygen concentration in the exhaust gas caused by lean-burn conditions, conventional three-way catalytic converters have limited efficiency in converting nitrogen oxides, resulting in persistently high nitrogen oxide emissions. To effectively reduce nitrogen oxide emissions, an additional active selective catalytic reduction (SCR) device must be installed, which uses urea solution to perform a targeted catalytic reduction reaction.

[0026] However, active SCR aftertreatment requires additional urea storage and supply devices, which have drawbacks such as complex structure, large space occupation, high development and calibration costs, and easy clogging of urea nozzles.

[0027] In view of this, the present invention provides a post-processing apparatus, with reference to Figure 1 The aftertreatment device 100 is used in a vehicle, which includes a methanol lean-burn engine 200. The aftertreatment device 100 includes a methanol oxidation catalyst 10 and a topological structure catalyst (HC-SCR) 20. The methanol oxidation catalyst 10 and the topological structure catalyst 20 are arranged sequentially along the exhaust direction of the methanol lean-burn engine 200.

[0028] The exhaust gases produced by methanol lean-burn engines typically include hydrocarbons (HC), nitrogen oxides (NOx), and carbon monoxide (CO), as well as a certain amount of oxygen (O2), carbon dioxide (CO2), and water (H2O). Among these, hydrocarbons (HC), nitrogen oxides (NOx), and carbon monoxide (CO) need to be purified and removed to meet exhaust gas requirements.

[0029] The methanol oxidation catalyst in the aftertreatment device of this invention is used for the first purification of the exhaust gas.

[0030] In some embodiments, the methanol oxidation catalyst is used to oxidize and purify carbon monoxide and some hydrocarbons in the exhaust gas, and the excess hydrocarbons will be used as a reducing agent to reduce nitrogen oxides in the topological catalyst stage.

[0031] In this invention, the topological catalyst refers to a catalyst support with a three-dimensional network configuration having interconnected channels, used to perform a second purification on the exhaust gas after the first purification. The second purification includes: the topological catalyst using its unique channel topology to adsorb and store hydrocarbons in the exhaust gas after the first purification, and releasing and migrating the stored hydrocarbons to the reactive sites of the topological catalyst, thereby reducing nitrogen oxides in the exhaust gas after the first purification to nitrogen.

[0032] The methanol lean-burn engine produces exhaust gas during operation, and the exhaust gas is purified by an after-treatment device before being discharged. The process is as follows: S10, the exhaust gas reaches the methanol oxidation catalyst and is purified for the first time; S20. The exhaust gas, after the first purification, reaches the topological catalyst and is purified a second time. S30, exhaust gas that has undergone a second purification process.

[0033] Understandably, the exhaust gas from a methanol lean-burn engine first flows through a methanol oxidation catalyst. This catalyst oxidizes carbon monoxide and some hydrocarbons in the exhaust gas into carbon dioxide and water, completing the first stage of purification. The purified exhaust gas contains nitrogen oxides and excess hydrocarbons. When this purified exhaust gas reaches a topological catalyst, the catalyst, with its well-developed porous structure, selectively adsorbs and stores the excess hydrocarbons within its pores. The topological configuration and surface chemistry of the catalyst control the timing of hydrocarbon desorption and diffusion, allowing them to migrate to the catalyst's active sites at appropriate times and concentrations. This selectively reduces the nitrogen oxides in the exhaust gas to harmless N2, while simultaneously generating CO2 and H2O.

[0034] In some embodiments, nitrogen oxides (NOx) primarily include NO2.

[0035] In some embodiments, the reaction process in which nitrogen oxides are reduced to nitrogen gas in the topological catalyst is as follows: NO2 + HC → CO2 + N2 + H2O.

[0036] The entire aftertreatment system of the present invention is simplified from the existing "MOC + active SCR" with urea supply device to a two-stage series configuration of "MOC + HC-SCR". It completely eliminates complex auxiliary systems such as urea storage, injection and electronic control calibration. Under the premise of ensuring emission compliance, it significantly simplifies the structure, saves space and reduces development, use and maintenance costs.

[0037] In some embodiments, refer to Figure 2The topological catalyst 20 has a hierarchical pore structure, comprising macropores 21, mesopores 22, and micropores 23, which are interconnected. This hierarchical pore structure offers the following advantages: macropores and mesopores provide channels for rapid transport of reactants and products, facilitating the diffusion and migration of hydrocarbons and nitrogen oxides; micropores provide sufficient reactive sites and good shape selectivity, promoting efficient catalytic reactions. This embodiment utilizes the synergistic effect of the hierarchical pore structure, enabling the topological catalyst to possess both high adsorption and storage capacity and excellent catalytic activity.

[0038] In some embodiments, the pore size of macropores is >50nm, and can be 55nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, etc.; the pore size of mesopores ranges from 2nm to 50nm, and can be 2nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, etc.; and the pore size of micropores is <2nm, and can be 1.9nm, 1.8nm, 1.5nm, 1nm, 0.8nm, 0.5nm, 0.3nm, 0.1nm, etc. This allows for the simultaneous consideration of rapid exhaust gas flow, gas diffusion transport, and efficient adsorption and storage of hydrocarbons, precisely controlling the hydrocarbon desorption rate to stably reduce nitrogen oxides, and improving denitrification efficiency and catalytic thermal stability.

[0039] In some embodiments, the reactive sites of the topological catalyst are distributed with noble metals. As catalytically active components, noble metals can lower the activation energy of the reaction and improve the rate and efficiency of hydrocarbon reduction reactions.

[0040] In some embodiments, the topological catalyst includes at least one of ZSM-5, SAPO-5, SAPO-34, and MCM-41.

[0041] In some embodiments, the adsorption operating temperature of the topological catalyst is -40℃ to 150℃; the desorption operating temperature is 300℃ to 850℃.

[0042] For example, the noble metal includes at least one of Pd and Pt. Pd and Pt have good adsorption and activation capabilities for hydrocarbons, and can efficiently catalyze the reduction reaction between hydrocarbons and nitrogen oxides at the reactive sites of the topological catalyst.

[0043] The excess air coefficient of a methanol lean-burn engine affects the emissions of hydrocarbons (HC), nitrogen oxides (NOx), and carbon monoxide (CO) in the exhaust gas. Generally, it refers to... Figure 3 , Figure 3This diagram illustrates the changing trends of methanol combustion emissions under different excess air coefficients. When the excess air coefficient is greater than 1.8, NOx emissions are very small and tend to stabilize, CO emissions are also low and tend to stabilize, while HC emissions increase.

[0044] The aftertreatment device of the methanol lean-burn engine of this invention can use hydrocarbons in the exhaust gas as a reducing agent to reduce and purify nitrogen oxides in the exhaust gas. Therefore, in some embodiments, the excess air coefficient of the methanol lean-burn engine is greater than or equal to 1.8, and can be 1.8, 2.0, 2.5, etc. An excess air coefficient greater than or equal to 1.8 has the emission characteristics of low NOx emissions, low CO emissions, and high HC emissions, which constitutes the key premise for the efficient operation of the technical solution of this invention: the engine, through lean combustion with an excess air coefficient greater than 1.8, suppresses NOx to a low level at the source and fully oxidizes CO, while retaining sufficient HC as an endogenous reducing agent to supply the downstream HC-SCR catalyst. This allows the aftertreatment system to achieve selective catalytic reduction of NOx without the need for external addition of urea, ultimately achieving comprehensive purification of hydrocarbons (HC), nitrogen oxides (NOx), and carbon monoxide (CO).

[0045] The present invention further provides a vehicle comprising the aftertreatment device and methanol lean-burn engine as described above, and possessing at least all the beneficial effects of the aftertreatment device. Continuing with reference to... Figure 1 The vehicle's aftertreatment device 100 is located downstream of the exhaust manifold of the methanol lean-burn engine 200, and sequentially includes a methanol oxidation catalyst 10 and a topological catalyst 20 along the exhaust direction. The inlet end of the methanol oxidation catalyst 10 is connected to the exhaust manifold of the methanol lean-burn engine 200 through an exhaust pipe, and the outlet end of the methanol oxidation catalyst 10 is connected to the inlet end of the topological catalyst 20 through an exhaust pipe.

[0046] When the vehicle is operating, the exhaust gas produced by the methanol lean-burn engine 200 burning methanol fuel contains CO, HC, NO. x Excess CO and some HC in the exhaust gas are discharged through the exhaust manifold. The exhaust gas first flows through the methanol oxidation catalyst 10, where CO and some HC are oxidized to CO2 and H2O, completing the first purification. The exhaust gas after treatment by the methanol oxidation catalyst 10 enters the topological catalyst 20. The multi-level porous structure of the topological catalyst 20 selectively adsorbs and stores the excess HC in the exhaust gas inside the pores. Under suitable exhaust temperature conditions, such as 300°C, the stored HC desorbs from the pores and diffuses to the reactive sites where the catalyst is distributed. Under the catalytic action of the catalyst, HC and NO are reacted. x A selective catalytic reduction reaction occurs, NO xThe gas is reduced to N2, and HC is oxidized to CO2 and H2O, completing the second stage of purification. The exhaust gas after the above two-stage purification process is finally discharged from the outlet of the topological catalyst 20.

[0047] Since the above-mentioned vehicles do not need to be equipped with urea supply devices such as urea storage tanks, metering pumps, delivery pipelines, atomizing nozzles, mixers and corresponding electronic control units, the layout structure of the vehicle is simplified, the overall vehicle layout space is freed up, and the overall vehicle weight is reduced. On the other hand, after-sales failure points such as urea nozzle blockage are eliminated, and the total life cycle cost of the vehicle is reduced.

[0048] Furthermore, the methanol lean-burn engine 200, through lean combustion with an excess air coefficient >1.8, eliminates NO from the source. x By reducing emissions to a low level and retaining sufficient HC as an endogenous reducing agent to supply the downstream topological catalyst 20, the vehicle emissions meet current emission regulations without relying on external reducing agent supply.

[0049] However, when the excess air coefficient of a methanol lean-burn engine is greater than 1.8, it will cause unstable combustion in the cylinder. To solve this problem, some adaptive improvements have been made to the methanol lean-burn engine to promote stable and complete combustion of methanol in the cylinder.

[0050] In some embodiments, the fuel pump of the methanol lean-burn engine is designed as a high-pressure fuel pump. The high injection pressure is beneficial to the atomization and mixing of methanol fuel, improving combustion efficiency, and also helps to achieve a higher excess air coefficient.

[0051] For example, the injection pressure of the high-pressure oil pump is 10MPa~50MPa, which can be 10MPa, 15MPa, 20MPa, 25MPa, 30MPa, 35MPa, 40MPa, 45MPa, 50MPa, etc.

[0052] In some embodiments, the ignition system of the methanol lean-burn engine is designed as a high-energy ignition system. The high-energy ignition system can provide sufficiently high ignition energy to ensure that the methanol mixture can be reliably ignited and stably burned under lean-burn conditions. This is an important guarantee for achieving lean combustion with a high excess air coefficient.

[0053] For example, the high-energy ignition system satisfies at least one of the following: ignition energy is 120mJ to 254mJ, which can be 120mJ, 150mJ, 180mJ, 200mJ, 220mJ, 240mJ, 250mJ, 254mJ, etc.; the ignition coil energy is 220mJ to 250mJ, which can be 220mJ, 230mJ, 240mJ, 250mJ, etc.; the ignition voltage is greater than or equal to 30000V; and the discharge duration is 2.6ms to 4.3ms, which can be 2.6ms, 2.8ms, 3.0ms, 3.5ms, 4.0ms, 4.1ms, 4.3ms, etc. This provides sufficiently high ignition energy to ensure reliable ignition and stable combustion of the methanol mixture under lean-burn conditions, which is beneficial for achieving the goal of lean combustion with a high excess air coefficient.

[0054] In some embodiments, the methanol lean-burn engine is designed with direct injection as the fuel supply method. Direct injection can inject methanol fuel directly into the cylinder, achieving more precise fuel metering and a more flexible injection strategy, which is beneficial to improving combustion efficiency and reducing emissions.

[0055] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A post-processing apparatus, characterized in that, For use in a vehicle, the vehicle includes a methanol lean-burn engine, and the aftertreatment device includes a methanol oxidation catalyst and a topological catalyst, wherein the methanol oxidation catalyst and the topological catalyst are arranged sequentially along the exhaust direction of the methanol lean-burn engine. The methanol oxidation catalyst is used for the initial purification of the exhaust gas. The topologically structured catalyst is used for a second purification of the exhaust gas after the first purification. The second purification includes: the topological catalyst adsorbing and storing hydrocarbons in the exhaust gas after the first purification, and releasing and migrating the stored hydrocarbons to the reactive sites of the topological catalyst to reduce nitrogen oxides in the exhaust gas after the first purification to nitrogen.

2. The post-processing apparatus according to claim 1, characterized in that, The first purification includes: the methanol oxidation catalyst oxidizing carbon monoxide and some hydrocarbons in the exhaust gas.

3. The post-processing apparatus according to claim 1, characterized in that, The topological catalyst has a hierarchical porous structure, including macropores, mesopores and micropores. The macropores have a diameter > 50 nm, the mesopores have a diameter range of 2 nm to 50 nm, and the micropores have a diameter < 2 nm.

4. The post-processing apparatus according to claim 1, characterized in that, The reactive sites are distributed with noble metals.

5. The post-processing apparatus according to claim 4, characterized in that, The precious metal includes at least one of Pd and Pt.

6. The post-processing apparatus according to claim 1, characterized in that, The excess air coefficient of the methanol lean-burn engine is greater than 1.

8.

7. The post-processing apparatus according to claim 6, characterized in that, The excess air coefficient of the methanol lean-burn engine is 1.8 to 2.

5.

8. A vehicle, characterized in that, The vehicle includes the after-processing device as described in any one of claims 1 to 7.

9. The vehicle according to claim 8, characterized in that, The methanol lean-burn engine includes a high-pressure oil pump; And / or, the ignition system of the methanol lean-burn engine is a high-energy ignition system; And / or, the methanol lean-burn engine is fueled by direct injection.

10. The vehicle according to claim 9, characterized in that, The methanol lean-burn engine includes a high-pressure oil pump, and the injection pressure of the high-pressure oil pump is 10MPa~50MPa; And / or, The ignition system of the methanol lean-burn engine is a high-energy ignition system, and the high-energy ignition system satisfies at least one of the following: Ignition energy ranges from 120 mJ to 254 mJ; The energy of the ignition coil is 220mJ~250mJ; Ignition voltage is greater than or equal to 30,000V; The discharge duration is 2.6ms to 4.3ms.

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