Space coupling type engine tail gas treatment method and device

Abstract

The invention provides an engine tail gas treatment method which comprises the following steps: introducing ammonia gas generated by an ammonia gas generation module into carbon dioxide tail gas generated by an engine to obtain mixed gas; under the action of an ammonia decomposition-methanation reaction coupling catalyst loaded in the coupling reaction module, the mixed gas is subjected to an ammonia decomposition and methanation coupling reaction, and methane, nitrogen and water are obtained; and the pressurizing module is used for pressurizing the methane from the coupling reaction module and introducing the methane into the engine for supplying energy to the engine. A large amount of carbon dioxide gas in engine tail gas is utilized, ammonia gas and carbon dioxide directly react to prepare methane through an ammonia decomposition-methanation reaction coupling catalyst, methane gas capable of being used for supplying energy to an engine is generated, and then a methane energy supply system is added on the basis of an original energy supply system of the engine.

Description

Technical Field

[0001] The present invention relates to the field of engine exhaust treatment, and in particular to a spatially coupled engine exhaust treatment method and device. Background Art

[0002] As the global demand for reducing carbon emissions and achieving sustainable energy solutions continues to rise, the development of clean fuel vehicles has become a key way to reduce the carbon footprint of traditional fuel vehicles. Ammonia, as a zero-emission fuel, has received widespread attention in the clean energy field due to its rich hydrogen content and easy storage and transportation.

[0003] At the same time, the use of ammonia as a fuel for automobile engines is gradually becoming a trend. However, the combustion process of ammonia is challenging and it easily produces N2O and NO. x Before the relevant technology is fully mature, it is not practical to directly use ammonia as a source of engine power.

[0004] The processing and utilization of the engine's exhaust gas can be improved directly on the basis of the engine, but the engine's exhaust gas treatment pipe is limited in length and cannot be equipped with an overly complex exhaust gas treatment device.

[0005] Therefore, a method for treating and utilizing tail gas based on an existing engine is needed. Summary of the invention

[0006] In view of this, in order to at least partially solve at least one of the above-mentioned technical problems, the present invention provides an engine exhaust treatment method and a coupling device.

[0007] According to an embodiment of one aspect of the present invention, there is provided a method for treating engine exhaust gas, comprising:

[0008] The ammonia generated by the ammonia generation module is introduced into the carbon dioxide tail gas generated by the engine to obtain a mixed gas;

[0009] The mixed gas is introduced into a coupling reaction module, and under the action of a coupling catalyst loaded in the coupling reaction module, the mixed gas undergoes a coupling reaction of ammonia decomposition and methanation to obtain methane, nitrogen and water;

[0010] The methane from the coupled reaction module is pressurized and introduced into the engine to power the engine.

[0011] According to another embodiment of the present invention, there is provided a device for treating engine exhaust gas, comprising:

[0012] An ammonia generation module, used for generating ammonia;

[0013] A coupling reaction module loaded with a coupling catalyst is arranged at the exhaust gas outlet of the engine, and is used to couple the ammonia generated by the ammonia generation module and the carbon dioxide exhaust gas generated by the engine under the action of the coupling catalyst to obtain methane, nitrogen and water;

[0014] The energy supply module is used to pass the methane obtained by the coupling reaction module into the engine to supply energy to the engine.

[0015] According to an embodiment of the present invention, a large amount of carbon dioxide gas in the engine exhaust is utilized, and ammonia and carbon dioxide are directly reacted to prepare methane using a coupling catalyst of ammonia decomposition-methanation reaction, thereby generating methane gas that can be used for engine energy supply, thereby increasing the utilization of a methane energy supply system on the basis of the original energy supply system of the engine. Through a one-step reaction, only a coupling reaction module needs to be added to the engine exhaust, and there is no excessive requirement for the length of the engine exhaust pipe, which is easy to modify and apply. At the same time, ammonia, as a carbon-free hydrogen carrier, has a high volume and mass energy density, and the storage and transportation technology is relatively mature. The gas discharged from the entire engine is converted from carbon dioxide to nitrogen, a byproduct of ammonia decomposition, and water, a byproduct of methanation, which reduces the emission of nitrogen oxides and other harmful gases, realizes the recycling of energy, improves energy utilization efficiency, and realizes the operation of the "ammonia-powered" engine while having low or even carbon-free emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0017] Figure 1 Schematic diagram of the engine exhaust treatment method and coupling device according to an embodiment of the present invention; (a) is a chemical reaction path diagram; (b) is a schematic diagram of the engine and exhaust pipe assembly; (c) is a schematic diagram of the engine exhaust treatment coupling device;

[0018] Figure 2 The performance characterization diagram of the ruthenium-based nanocluster magnesium aluminate catalyst; (a) is a spherical aberration-corrected scanning transmission electron micrograph of the Ru / MgAl2O4 catalyst prepared in Example 1; (b) is an X-ray absorption spectrum of the Ru / MgAl2O4 catalyst prepared in Example 1. ;

[0019] Figure 3 The catalytic performance test results of the ruthenium-based nanocluster magnesium aluminate catalyst of the embodiment of the present invention are shown in FIG. (a) is the result of hydrogen temperature-programmed reduction; (b) is the result of carbon dioxide temperature-programmed desorption experiment;

[0020] Figure 4The catalytic performance test results of the ruthenium-based nanocluster magnesium aluminate catalyst are shown in Figure 2; (a) is a graph showing the change of ammonia conversion rate with temperature; (b) is a graph showing the change of carbon dioxide conversion rate and methane selectivity with temperature;

[0021] Figure 5 This is a graph showing the stability test results of the ruthenium-based nanocluster magnesium aluminate catalyst of the present invention. DETAILED DESCRIPTION

[0022] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0023] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0024] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0025] In the process of realizing the concept of the present invention, it was found that reacting CO2 in tail gas with renewable hydrogen to prepare fuel for automobile power is a feasible path. However, due to the difficulties in transportation and storage, it is not economically feasible to transport H2 for on-site hydrogenation of CO2. In recent years, the direct use of zero-carbon fuels such as NH3 in engines has been the focus of achieving carbon neutrality in the transportation industry. However, due to the difficulty in burning NH3, N2O and NO xThe amount of release is high, so it is not practical to use NH3 to power engines before mature technology is mature. The direct reaction of ammonia and carbon dioxide to produce methane is a new reaction, and the equation is written as: 8NH3 +3CO2→ 3CH4 + 4N2 + 6H2O.

[0026] At present, no methane-mediated ammonia-powered engine has been designed using this reaction process. In addition, due to the existence of reaction energy barriers, when using catalysts, the optimal CO2 methanation activity temperature is usually 300~400℃, and the temperature for complete decomposition of NH3 to produce hydrogen is generally above 500℃. Therefore, designing a catalyst that can directly couple these two reaction processes is the key to effectively solving the above problems. Based on the methane-mediated ammonia-powered engine system, it is expected to achieve carbon neutrality, provide an efficient energy conversion method, and further promote the development of clean energy.

[0027] Specifically, according to an embodiment of one aspect of the present invention, a method for treating engine exhaust gas is provided, comprising the following steps S1 to S5:

[0028] Figure 1 Schematic diagram of the engine exhaust treatment method and coupling device according to an embodiment of the present invention; (a) is a chemical reaction pathway diagram; (b) is a schematic diagram of the engine and exhaust pipe assembly; (c) is a schematic diagram of the engine exhaust treatment coupling device.

[0029] Step S1: introducing ammonia generated by the ammonia generation module into carbon dioxide tail gas generated by the engine to obtain a mixed gas;

[0030] Step S2: passing the mixed gas into a coupling reaction module, and under the action of a coupling catalyst loaded in the coupling reaction module, the mixed gas undergoes a coupling reaction of ammonia decomposition and methanation to obtain methane, nitrogen and water;

[0031] Step S3: pressurizing the methane from the coupled reaction module and introducing it into the engine to supply energy to the engine.

[0032] According to the embodiment of the present invention, in step S1, ammonia is very easy to compress and liquefy, and storage and transportation are safe and convenient. The volume energy density of liquid ammonia is much greater than that of liquid hydrogen. The hydrogen storage density of the same volume of liquid ammonia is 60% higher than that of liquid hydrogen. In addition, the storage and transportation cost of liquid ammonia is lower, the explosion limit range of ammonia is narrower, the boiling point is higher, the possibility of fire and explosion is lower, and ammonia has a pungent smell, so leakage is easy to be found, which is safer and more reliable.

[0033] According to an embodiment of the present invention, in step S2, the coupled catalyst of the ammonia decomposition-methanation reaction allows ammonia and carbon dioxide to react in one step to directly prepare methane, and can simultaneously convert carbon dioxide and ammonia, so that the carbon dioxide methanation reaction with exothermic properties can increase the optimal temperature to a high temperature zone suitable for ammonia decomposition, and the synchronous conversion is not two independent reactions, but a synchronous coupled conversion at the mechanism level. At the same time, the coupled reaction module can directly use the temperature of the engine exhaust gas to power the reaction, and directly obtain methane in one step.

[0034] According to an embodiment of the present invention, in step S3, the generated methane gas usually needs to be pressurized by a pressurizing device such as a booster pump, a compressor, etc. to increase its pressure and density so as to make it suitable for the combustion requirements of the engine.

[0035] According to an embodiment of the present invention, a large amount of carbon dioxide gas in the engine exhaust is utilized, and ammonia and carbon dioxide are directly reacted to prepare methane using a coupling catalyst of ammonia decomposition-methanation reaction, thereby generating methane gas that can be used for engine energy supply, thereby increasing the utilization of a methane energy supply system on the basis of the original energy supply system of the engine. Through a one-step reaction, only a coupling reaction module needs to be added to the engine exhaust, and there is no excessive requirement for the length of the engine exhaust pipe, which is easy to modify and apply. At the same time, ammonia, as a carbon-free hydrogen carrier, has a high volume and mass energy density, and the storage and transportation technology is relatively mature. The gas discharged from the entire engine is converted from carbon dioxide to nitrogen, a byproduct of ammonia decomposition, and water, a byproduct of methanation, which reduces the emission of nitrogen oxides and other harmful gases, realizes the recycling of energy, improves energy utilization efficiency, and realizes the operation of the "ammonia-powered" engine while achieving low-carbon or even carbon-free emissions.

[0036] According to an embodiment of the present invention, the engine is an internal combustion engine powered by fuel oil and / or methane as raw materials.

[0037] According to an embodiment of the present invention, Figure 1 As shown in (b), the generated methane returns to the engine from the tailpipe through the pipeline for combustion and energy supply. For example, in a four-cylinder internal combustion engine, the other three cylinders are powered by burning fuel, and one cylinder is powered by burning methane, forming a hybrid engine. At the same time, ammonia is considered to be a potential renewable resource, so it can not only save fuel usage and resources, but also reduce pollutants and carbon emissions, making it more environmentally friendly. Methane engines can also be modified to increase resource utilization efficiency while reducing carbon emissions.

[0038] In some specific embodiments of the present invention, the modification of the engine exhaust treatment can be to add methane-powered cylinders to the original engine.

[0039] In some specific embodiments of the present invention, methane gas can be used for energy supply, and a new power system can be added to realize energy supply by a dual power system.

[0040] In some specific embodiments of the present invention, methane can be mixed with fuel and then burned to provide energy.

[0041] According to an embodiment of the present invention, the concentrations of the ammonia gas and the carbon dioxide tail gas are respectively monitored by concentration sensors;

[0042] According to the monitoring results of the concentrations of the ammonia gas and the carbon dioxide tail gas, the flow rates of the ammonia gas and the carbon dioxide tail gas are respectively controlled by flow controllers to adjust the degree of the coupling reaction.

[0043] According to an embodiment of the present invention, Figure 1 (c) It can be seen that the concentration of ammonia and carbon dioxide can be monitored by the concentration sensor. The monitored values ​​of each concentration can be further calculated. According to the chemical equilibrium and kinetics of the coupling reaction, the current concentration data can be evaluated to determine whether the flow rate of ammonia and carbon dioxide tail gas needs to be adjusted to optimize the reaction. The flow controller can accurately adjust the gas flow rate to achieve fine control of the reaction conditions to maintain the optimal degree of coupling reaction and reduce the waste of reactants and the generation of by-products.

[0044] According to an embodiment of the present invention, the coupling catalyst includes at least one of a ruthenium-based nanocluster catalyst and a nickel-based nanocluster catalyst.

[0045] According to the embodiments of the present invention, the ruthenium-based nanocluster catalyst and the nickel-based nanocluster catalyst have a single-atom nanocatalytic structure, and the atomically dispersed metal ruthenium and nickel provide a larger metal surface area for the catalytic reaction to occur. The ruthenium-based nanocluster catalyst can catalyze the ammonia decomposition reaction, provide the active sites required for the reaction, reduce the activation energy of the ammonia decomposition reaction, and enable the reaction to proceed at a lower temperature and pressure, which is conducive to narrowing the temperature difference with the carbon dioxide methanation reaction. According to the engine exhaust gas flow rate of 0.1-1.0 m 3 / s can determine that the catalyst loading of the coupling reaction module is 1-5 kg ​​and the particle size is 40-200 mesh.

[0046] According to an embodiment of the present invention, the coupling catalyst loading is 1 kg, 2 kg, 3 kg, 4 kg, and 5 kg, respectively, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. The particle size of the coupling catalyst is 40 mesh, 60 mesh, 100 mesh, 120 mesh, 150 mesh, 180 mesh, and 200 mesh, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. According to an embodiment of the present invention, the coupling catalyst is a ruthenium-based nanocluster magnesium aluminate catalyst.

[0047] According to the embodiment of the present invention, the ruthenium-based nanocluster magnesium aluminate catalyst is obtained by high-temperature calcination of a magnesium-aluminum hydrotalcite precursor, has high thermal stability, and has a strong "anchoring" effect on precious metals, especially ruthenium; in addition, the magnesium-aluminum hydrotalcite is synthesized by a simple coprecipitation method, and the specific morphology of the magnesium-aluminum hydrotalcite creates a higher specific surface area and total pore volume for the carrier to accommodate more active sites. The ruthenium-based nanocluster magnesium aluminate catalyst has a suitable alkaline site to adsorb carbon dioxide and ammonia; the atomically dispersed metal ruthenium provides a larger metal surface area to couple and convert carbon dioxide and ammonia into methane.

[0048] In some specific embodiments of the present invention, the preparation method of the ruthenium-based nanocluster magnesium aluminate catalyst includes: preparing magnesium-aluminum hydrotalcite by a coprecipitation method; drying and screening the magnesium-aluminum hydrotalcite, and then performing a first calcination at 800~1200°C to obtain a magnesium-aluminum composite oxide support, wherein the magnesium-aluminum composite oxide support includes magnesium oxide and spinel structure magnesium aluminate; using an equal volume impregnation method, the magnesium-aluminum composite oxide support is impregnated into a ruthenium salt solution, and after drying, a second calcination is performed at 300~600°C to obtain a ruthenium-based nanocluster catalyst.

[0049] According to an embodiment of the present invention, the temperature of the coupling reaction is 450-600° C.; the pressure of the methane entering the engine for energy supply after supercharging is 0.5-1.5 bar.

[0050] According to an embodiment of the present invention, the temperature of the coupling reaction may be 450° C., 500° C., 550° C., or 600° C., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0051] According to the embodiment of the present invention, the temperature of the exhaust gas discharged from the engine to the exhaust manifold is about 800-900°C, which is reduced to 600-700°C after passing through the front-stage three-way catalytic converter, and is only 450°C at idle speed. Therefore, it is necessary to select a suitable catalyst to reduce the reaction temperature to the range of 450-600°C while allowing sufficient reaction.

[0052] According to an embodiment of the present invention, the pressure of methane entering the engine for energy supply after supercharging may be 0.5 bar, 0.7 bar, 0.9 bar, 1.1 bar, 1.2 bar, or 1.5 bar, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] According to another embodiment of the present invention, there is provided an engine exhaust treatment device, comprising:

[0054] An ammonia generation module, used for generating ammonia;

[0055] A coupling reaction module loaded with a coupling catalyst for ammonia decomposition-methanation reaction is arranged at the exhaust gas outlet of the engine, and is used to couple the ammonia generated by the ammonia generation module and the carbon dioxide exhaust gas generated by the engine under the action of the coupling catalyst to obtain methane, nitrogen and water;

[0056] The energy supply module is used to pass the methane obtained by the coupling reaction module into the engine to supply energy to the engine.

[0057] According to an embodiment of the present invention, the ammonia generation module can be achieved by loading an ammonia cracker in a system where a vehicle or other engine is located, or storing and outputting ammonia through an ammonia storage tank. It can also use solid ammonia technology (SSCR) to use inorganic salt powder as an ammonia storage material and release ammonia from the ammonia storage material by heating.

[0058] According to an embodiment of the present invention, the engine exhaust treatment device can be used to modify the existing engine. By directly loading a coupled reaction module with a coupled catalyst, the recycling of the exhaust gas can be more efficient. Not only can the substance and temperature of the exhaust gas be utilized, but also carbon emissions can be reduced to protect the environment. At the same time, energy utilization efficiency can be improved. There is no need to change the structure of the engine on a large scale. It can be applied to various types of internal combustion engines in current vehicles to save the original fuel usage of the internal combustion engine.

[0059] According to an embodiment of the present invention, Figure 1 As shown in (b), the coupled reaction module can be realized by a membrane or fixed bed reactor wrapped around the engine exhaust pipe.

[0060] Specifically, the coupled reaction module can be constructed by installing a shell, a cushion layer, a carrier and a catalyst on the basis of the original tailpipe, and a temperature sensor can also be configured to monitor the reaction temperature.

[0061] In some specific implementations of the present invention, a turbocharger is provided in the energy supply module to pressurize the methane produced by the coupled reaction module and then pump it into the engine through a pipeline for combustion and energy supply.

[0062] In some specific embodiments of the present invention, a separation device is provided in the energy supply module to purify the methane gas entering the engine, for example, nitrogen and water are separated by membrane separation technology to obtain methane with higher purity for energy supply.

[0063] According to an embodiment of the present invention, the engine exhaust treatment coupling device may further include:

[0064] an ammonia sensor, disposed between the ammonia generation module and the coupling reaction module, for monitoring the concentration of the ammonia;

[0065] an ammonia flow controller, used to control the flow of the ammonia gas entering the coupling reaction module according to the monitoring result of the ammonia gas sensor;

[0066] A carbon dioxide sensor for monitoring the concentration of carbon dioxide exhaust generated by the engine;

[0067] A carbon dioxide flow controller is used to control the flow of carbon dioxide tail gas generated by the engine that is passed into the coupled reaction module according to the monitoring result of the carbon dioxide sensor.

[0068] According to an embodiment of the present invention, an ammonia sensor can monitor the ammonia concentration involved in the ammonia decomposition reaction, and a carbon dioxide sensor can monitor the concentration of carbon dioxide. The monitoring value of the ammonia concentration can be used to configure the corresponding ammonia flow rate according to the chemical reaction equilibrium, thereby making the coupling reaction more complete, improving the conversion rate, reducing the generation of by-products, and reducing the waste of ammonia.

[0069] According to an embodiment of the present invention, the engine exhaust treatment device may further include: an ammonia capture module, disposed between the coupling reaction module and the energy supply module, for capturing ammonia that has not been completely reacted in the coupling reaction module.

[0070] According to an embodiment of the present invention, the ammonia trap can be dilute sulfuric acid or other solid ammonia absorbing materials. The ammonia trap can also be connected to the ammonia generation module to release the captured ammonia for use in the ammonia decomposition reaction. Ammonia has a pungent odor, and by collecting it in the trap, it can be prevented from being discharged into the atmosphere through the tail pipe to pollute the environment.

[0071] The scheme of the present invention will be further explained below based on specific embodiments.

[0072] Example 1 Preparation of Ruthenium-based Nanocluster Magnesium Aluminate Catalyst

[0073] Preparation of 5%Ru / MgAl2O4 catalyst

[0074] Step S1: weigh 19.2305 g of Mg(NO3)2·6H2O and 11.2540 g of Al(NO3)3·9H2O, add 100 mL of deionized water to fully dissolve to obtain a salt solution, then mix with 3 mol / L of sodium hydroxide and 2 mol / L of sodium carbonate as a precipitant, and co-titrate the salt solution to a pH of 10 to obtain a precipitate solution;

[0075] Step S2: After stirring the precipitate solution at 100° C. and aging for 24 h, the aged precipitate is fully dried in a forced air drying oven at 120° C. to obtain a carrier precursor magnesium-aluminum hydrotalcite;

[0076] Step S3: crushing and screening the carrier precursor magnesium-aluminum hydrotalcite, and then placing it in a muffle furnace at 1000°C for calcination for 2 h, i.e., the first calcination, to obtain a MgAl2O4 carrier;

[0077] Step S4: The calcined MgAl2O4 carrier is taken out and loaded with 5% metal Ru by an equal volume impregnation method, and then placed in a muffle furnace for calcination at 500°C for 2 h, i.e., the second calcination, to obtain a 5% Ru / MgAl2O4 nanocluster catalyst.

[0078] Figure 2 : It is a performance characterization diagram of the ruthenium-based nanocluster magnesium aluminate catalyst; (a) is a spherical aberration-corrected scanning transmission electron micrograph of the Ru / MgAl2O4 catalyst prepared in Example 1; (b) is an X-ray absorption spectrum of the Ru / MgAl2O4 catalyst prepared in Example 1.

[0079] according to Figure 2 It can be seen that spherical aberration-corrected transmission electron microscopy shows the formation of ruthenium clusters with a size of about 1.2 nm, and X-ray absorption spectroscopy data proves that ruthenium mainly exists in metallic form.

[0080] Example 2 Catalytic Performance Test of Ruthenium-based Nanocluster Magnesium Aluminate Catalyst

[0081] Test conditions:

[0082] The gas composition entering the ammonia-carbon dioxide methanation coupling reactor is: 3 mL / min CO2+8 mL / min NH3+39 mL / min N2, and the catalyst is Ru / MgAl2O4 prepared in Example 1; the reactor temperature is 400 o C.

[0083] Catalyst preparation: 0.1 g Ru / MgAl2O4 was granulated into 40-60 mesh and reduced in situ with 50 mL / min H2 for 2 h; then the catalyst was diluted with 0.6 g quartz sand and placed in an ammonia-carbon dioxide methanation coupling reactor.

[0084] Product testing:

[0085] The gas at the end of the coupling reactor is introduced into an online gas chromatograph equipped with a thermal conductivity detector and a hydrogen flame ionization detector for detection. Before the product flows into the gas chromatograph, the generated water is removed using a trap filled with anhydrous calcium sulfate. The calculation formulas for CO2 conversion, ammonia conversion, and methane selectivity are as follows:

[0086] X(CO2)=(CO2,in-CO2,out) / CO2,in×100%

[0087] X(NH3)=(NH3,in-NH3,out) / NH3,in×100%

[0088] S(CH4)= CH4,out / (CO2,in-CO2,out),in×100%

[0089] Among them, X(CO2), X(NH3) and S(CH4) represent CO2 conversion rate, NH3 conversion rate and CH4 selectivity respectively; CO2,in, CO2,out, NH3,in, NH3,out and CH4,out are CO2 input molar amount, CO2 output molar amount, NH3 input molar amount, NH3 output molar amount and CH4 output molar amount respectively.

[0090] Test results: NH3 conversion rate is 1.7%, CO2 conversion rate is 4.1%, and CH4 selectivity is 32.3%.

[0091] Figure 3 The catalytic performance test results of the ruthenium-based nanocluster magnesium aluminate catalyst of the embodiment of the present invention are shown in FIG. (a) is the result of hydrogen temperature-programmed reduction; (b) is the result of carbon dioxide temperature-programmed desorption experiment.

[0092] according to Figure 3 It can be seen that the hydrogen temperature-programmed reduction results indicate the uniform metal-support effect of the catalyst, and the carbon dioxide temperature-programmed desorption experimental results demonstrate the concentrated basic site distribution of the catalyst.

[0093] Example 3 Catalytic Performance Test of Ruthenium-based Nanocluster Magnesium Aluminate Catalyst

[0094] The same test method and detection calculation method as in Example 2 were used, except that the temperature of the reactor was 500°C.

[0095] Test results: NH3 conversion rate is 59.8%, CO2 conversion rate is 43.5%, and CH4 selectivity is 67.9%.

[0096] Example 4 Catalytic Performance Test of Ruthenium-based Nanocluster Magnesium Aluminate Catalyst

[0097] The same test method and detection calculation method as in Example 2 were used, except that the temperature of the reactor was 550°C.

[0098] Test results: NH3 conversion rate is 80.6%, CO2 conversion rate is 50.0%, and CH4 selectivity is 79.0%.

[0099] Example 5 Catalytic Performance Test of Ruthenium-based Nanocluster Magnesium Aluminate Catalyst

[0100] The same test method and detection calculation method as in Example 2 were used, except that the temperature of the reactor was 600°C.

[0101] Test results: NH3 conversion rate is 78.7%, CO2 conversion rate is 43.4%, and CH4 selectivity is 68.4%.

[0102] Figure 4 The catalytic performance test results of ruthenium-based nanocluster magnesium aluminate catalyst are shown in Figure 2; (a) is a graph showing the variation of ammonia conversion rate with temperature; (b) is a graph showing the variation of carbon dioxide conversion rate and methane selectivity with temperature.

[0103] according to Figure 4 It can be seen that under the action of ruthenium-based nanocluster magnesium aluminate catalyst, the conversion rate of ammonia can reach a relatively high level above 450°C, and can be close to a stable ammonia conversion rate above 500°C; the conversion rate of carbon dioxide can reach a relatively high level above 450°C, and the carbon dioxide conversion rate tends to be stable above 500°C. Therefore, the coupling reaction can ensure a relatively high and stable ammonia conversion rate and carbon dioxide conversion rate in the range of 450~600°C.

[0104] Example 6 Stability test of ruthenium-based nanocluster magnesium aluminate catalyst

[0105] The same test method and detection calculation method as in Example 3 were used to continuously evaluate the stability of the catalyst in the process for 1000 hours. The results were as follows: Figure 5 shown.

[0106] Figure 5 This is a graph showing the stability test results of the ruthenium-based nanocluster magnesium aluminate catalyst of the present invention.

[0107] according to Figure 5 It can be seen that the NH3 conversion rate is 80.5%, the CO2 conversion rate is 49.9%, the CH4 selectivity is 79.0%, and the performance is stable for 1000 hours. Therefore, the ruthenium-based nanocluster magnesium aluminate catalyst has a relatively stable and efficient carbon dioxide conversion rate and selectivity, and can produce methane relatively stably for engine power supply.

[0108] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for treating engine exhaust, comprising: The ammonia generated by the ammonia generation module is introduced into the carbon dioxide tail gas generated by the engine to obtain a mixed gas; The mixed gas is passed into a coupling reaction module, and under the action of a coupling catalyst loaded in the coupling reaction module, the mixed gas undergoes a coupling reaction of ammonia decomposition and methanation to obtain methane, nitrogen and water; The methane from the coupled reaction module is pressurized and introduced into the engine to power the engine.

2. The method according to claim 1, wherein: The engine is an internal combustion engine powered by fuel oil and / or methane as raw materials.

3. The method according to claim 1, wherein: Also includes: The concentrations of the ammonia gas and the carbon dioxide tail gas are respectively monitored by concentration sensors; According to the monitoring results of the concentrations of the ammonia gas and the carbon dioxide tail gas, the flow rates of the ammonia gas and the carbon dioxide tail gas are respectively controlled by flow controllers to adjust the degree of the coupling reaction.

4. The method according to claim 1, wherein: The coupling catalyst includes at least one of a ruthenium-based nanocluster catalyst and a nickel-based nanocluster catalyst; The catalyst loading amount of the coupling reaction module is 1~5 kg, and the particle size is 40~200 mesh.

5. The method according to claim 1 or 4, wherein: The coupling catalyst is a ruthenium-based nanocluster magnesium aluminate catalyst.

6. The method according to claim 1 or 5, wherein: The temperature of the coupling reaction is 450-600°C; The pressure of the supercharged methane entering the engine to supply energy is 0.5~1.5 bar.

7. A device for treating engine exhaust, comprising: An ammonia generation module, used for generating ammonia; A coupling reaction module loaded with a coupling catalyst is arranged at the exhaust gas outlet of the engine, and is used to couple the ammonia generated by the ammonia generation module and the carbon dioxide exhaust gas generated by the engine under the action of the coupling catalyst to obtain methane, nitrogen and water; The energy supply module is used to pass the methane obtained by the coupling reaction module into the engine to supply energy to the engine.

8. The device according to claim 7, wherein: Also includes: an ammonia sensor, disposed between the ammonia generation module and the coupling reaction module, for monitoring the concentration of the ammonia; an ammonia flow controller, used to control the flow of the ammonia gas entering the coupling reaction module according to the monitoring result of the ammonia gas sensor; A carbon dioxide sensor for monitoring the concentration of carbon dioxide exhaust generated by the engine; A carbon dioxide flow controller is used to control the flow of carbon dioxide tail gas generated by the engine that is passed into the coupled reaction module according to the monitoring result of the carbon dioxide sensor.

9. The device according to claim 7, wherein: Also includes: The ammonia capture module is arranged between the coupling reaction module and the energy supply module, and is used to capture the ammonia that has not been completely reacted in the coupling reaction module.

10. The device according to claim 7, wherein: The coupling reaction module is at least one of a membrane reactor or a fixed bed reactor which is sleeved outside the engine exhaust pipe and is connected to the engine exhaust pipe.

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