Preparation method of denitration catalytic material special for emission of methanol internal combustion engine

Abstract

The invention relates to the technical field of denitration catalytic materials, and discloses a preparation method of a denitration catalytic material special for emission of a methanol internal combustion engine, and the preparation method comprises the following steps: S1, preparing a multi-element synergistic precursor mixed solution: sequentially mixing a carrier precursor, an active metal salt, a main ligand, a double-dynamic auxiliary ligand and a coordination regulator to obtain the multi-element synergistic precursor mixed solution; adjusting the pH value, and stirring to obtain a transparent and uniform multi-element synergistic precursor mixed solution; s2, gradient coordination polymerization reaction: putting the multi-element synergistic precursor mixed solution into a closed high-pressure reaction kettle, and reacting by adopting a stepped heating polymerization process to obtain an integrated gel product; s3, doping gas assisted low-temperature plasma activation; and S4, surface acid-base modification post-treatment. Through the synergistic effect of the double-dynamic auxiliary ligand and the coordination regulator, the gradient coordination polymerization process is matched to regulate and control the precursor structure, the reaction induction period is shortened, the NO conversion rate in the low-temperature interval is increased, and the problem that the low-temperature exhaust denitration reaction speed of the methanol internal combustion engine is low is solved.

Description

Technical Field

[0001] This invention relates to the field of denitrification catalytic materials technology, specifically a method for preparing denitrification catalytic materials for methanol internal combustion engine emissions. Background Technology

[0002] Methanol internal combustion engines are internal combustion engines that use methanol as the core fuel, generating power through combustion of a methanol-air mixture within the cylinder. Methanol, as a clean alternative fuel, is widely used in transportation, construction machinery, and other fields due to its wide availability, high combustion efficiency, and low carbon emissions. However, during the combustion process, nitrogen oxides (NOx) are still produced due to factors such as uneven combustion temperature distribution and alternating periods of oxygen enrichment / deficiency. x Nitrogen oxides are a significant component of air pollutants, contributing to environmental problems such as acid rain and photochemical smog. Furthermore, current emission regulations target NOx emissions from internal combustion engine exhaust. x Emission limits for methanol are becoming increasingly stringent, necessitating the installation of denitrification devices in methanol internal combustion engine exhaust systems. These devices utilize denitrification catalytic materials to remove NO. x It is converted into harmless nitrogen gas, thus purifying the exhaust gas.

[0003] Currently, the preparation of denitrification catalysts for methanol internal combustion engine emissions mostly employs traditional processes such as the sol-gel method and impregnation method. The core logic is to select titanium-based or aluminum-based carrier materials, mix them in a solution, impregnate and load active metal components, and then activate them through high-temperature calcination to form the catalyst. However, during preparation, the active metal components tend to agglomerate during precursor mixing, and the use of isothermal polymerization or single-ligand regulation methods makes it difficult to control the coordination structure of the precursor and the distribution of active components. This results in a longer induction period and lower NO conversion rate in the prepared catalyst under the low-temperature exhaust conditions of methanol internal combustion engines, making it difficult to quickly respond to the denitrification requirements of low-temperature exhaust from methanol internal combustion engines. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing a denitrification catalyst material specifically for methanol internal combustion engine emissions, thus solving at least one of the technical problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a denitrification catalytic material specifically for methanol internal combustion engine emissions, comprising the following steps: S1. Preparation of multi-component synergistic precursor mixture: The carrier precursor, active metal salt, main ligand, dual dynamic auxiliary ligand and coordination regulator are mixed sequentially, and the pH value is adjusted and stirred to obtain a transparent and homogeneous multi-component synergistic precursor mixture. S2, gradient coordination polymerization reaction: The multi-component synergistic precursor mixture is placed in a closed high-pressure reactor and reacted using a step-by-step heating polymerization process to obtain an integrated gel product. S3. Doped gas-assisted low-temperature plasma activation: The integrated gel product is freeze-dried and then pulverized. A mixed doped gas is introduced, and pulsed plasma is used for staged activation to obtain the activated product. S4. Surface acid and alkali modification post-treatment: The activated product is immersed in γ-aminopropyltriethoxysilane solution, washed and dried to obtain a methanol internal combustion engine emission denitrification catalyst.

[0006] By adopting the above technical solution, when preparing the multi-component synergistic precursor mixture in S1, the carrier precursor, active metal salt, main ligand, dual-dynamic auxiliary ligand, and coordination regulator are mixed sequentially, which allows the components to gradually interact. The main ligand first forms a basic coordination structure with the active metal salt, and the dual-dynamic auxiliary ligand and coordination regulator synergistically regulate the coordination reaction process, avoiding excessive local concentration of components that may cause aggregation. Adjusting the pH value can provide a suitable chemical environment for the coordination reaction, and stirring promotes full contact and diffusion of the components, ultimately obtaining a transparent and homogeneous multi-component synergistic precursor mixture. In the S2 gradient coordination polymerization reaction, the closed high-pressure reactor can maintain the pressure conditions required for the polymerization reaction and prevent the volatilization of components. The step-by-step heating polymerization gradually increases the temperature and pressure, so that the coordination components in the precursor can carry out the polymerization reaction in an orderly manner, gradually building a stable integrated gel structure, ensuring that the active metal components are uniformly dispersed in the carrier skeleton, and avoiding the reaction rate imbalance or structural defects that may be caused by isothermal polymerization. When S3 doped gas-assisted low-temperature plasma activation is performed, freeze drying can remove moisture from the integrated gel product while retaining its porous structure. Pulverization increases the specific surface area of ​​the material. The active species generated by the decomposition of the mixed doped gas in the plasma environment can interact with the material surface and introduce doping elements. Pulsed plasma staged activation gradually activates the active sites in the material by precisely controlling the temperature, frequency and duration, while avoiding the sintering of active components caused by high temperature, thus ensuring the number and stability of active sites. In the S4 surface acid-base modification post-treatment, γ-aminopropyltriethoxysilane solution reacts chemically with the surface of the activated product to form a modification layer, adjusting the acid-base properties and hydrophilicity / hydrophobicity of the product surface, improving the contact characteristics between the product and the reactant gas, washing to remove unreacted coupling agent and impurities, and drying to remove residual moisture, finally obtaining a structurally stable methanol internal combustion engine emission denitrification catalyst.

[0007] Preferably, the carrier precursor is tetrabutyl titanate, the active metal salt is a mixture of cobalt nitrate and lanthanum nitrate in a mass ratio of 0.13–0.60:1, the main ligand is phthalic anhydride, the dual dynamic auxiliary ligand is a mixture of diethyl succinate and dibutyl adipate, and the coordination modifier is triethanolamine.

[0008] By adopting the above technical solution, tetrabutyl titanate, as a carrier precursor, can gradually form a titanium-based carrier framework through hydrolysis in the reaction system, providing stable structural support for the loading of active components; a mixture of cobalt nitrate and lanthanum nitrate, as an active metal salt, in which cobalt ions and lanthanum ions can serve as active centers for denitrification reactions, and their synergistic effect can broaden the active reaction range and adapt to the temperature characteristics of methanol internal combustion engine exhaust; phthalic anhydride, as the main ligand, can form stable coordination bonds with active metal ions, achieving uniform dispersion of active metal ions in the carrier precursor system and avoiding local aggregation of active components; a mixture of diethyl succinate and dibutyl adipate, as a dual dynamic auxiliary ligand, can synergistically work with triethanolamine to regulate the coordination reaction rate between the main ligand and active metal ions, optimize the regularity of the coordination structure, solve the problem that a single ligand or regulator cannot accurately control the coordination process, and ensure that the formed precursor structure is uniform and stable.

[0009] Preferably, in step S1, the mass ratio of the carrier precursor, active metal salt, main ligand, dual-dynamic auxiliary ligand, and coordination modifier is 5:(0.8~1.2):(1.8~2.2):(0.7~1.2):(0.3~0.4), and the dual-dynamic auxiliary ligand is a mixture of diethyl succinate and dibutyl adipate, with the mass ratio of diethyl succinate to dibutyl adipate being (1.8~2.2):1.

[0010] By adopting the above technical solution, the carrier precursor, active metal salt, main ligand, dual-dynamic auxiliary ligand, and coordination regulator can form a suitable reaction ratio among the components. This ensures that the carrier precursor can provide sufficient raw materials for framework formation, the content of the active metal salt can form an appropriate amount of denitrification active centers, and the content of the main ligand, dual-dynamic auxiliary ligand, and coordination regulator can precisely match the coordination requirements of the active metal salt, avoiding incomplete coordination reactions or side reactions due to excess or deficiency of a certain component. The specific mass ratio of diethyl succinate to dibutyl adipate in the dual-dynamic auxiliary ligand can ensure that the two auxiliary ligand components can synergistically play a regulatory role. Together with the coordination regulator, it can precisely regulate the coordination reaction rate and coordination structure regularity between the main ligand and the active metal ion, so that each component gradually forms a uniform coordination system during the mixing process, ultimately obtaining a transparent and uniform multi-component synergistic precursor mixture, achieving precise control of the precursor structure.

[0011] Preferably, in step S1, the mixing steps are as follows: The carrier precursor and active metal salt were added to anhydrous ethanol, and the liquid-solid ratio was controlled at (15~25):1 (mL / g). The mixture was stirred for 25~35 min at a temperature of 25~35℃ and a stirring speed of 250~350r / min to form a uniform suspension. Add the main ligand and the premixed dual dynamic auxiliary ligand to the suspension in sequence, keep the stirring speed constant, and continue stirring for 15~25 min; Add the coordination regulator, stir for 8-12 minutes, then add deionized water to dilute the system to adjust the pH to 4.2-5.3, and continue stirring for 15-25 minutes to obtain a multi-component synergistic precursor mixture.

[0012] By employing the above technical solution, the carrier precursor and active metal salt are added to anhydrous ethanol. Anhydrous ethanol can act as a dispersion medium to reduce the aggregation resistance between components. Controlling a specific liquid-to-solid ratio can provide sufficient medium space for component dispersion. Combined with stirring, it can promote full contact and uniform dispersion of the carrier precursor and active metal salt, forming a suspension with uniform component distribution. The main ligand and premixed dual-dynamic auxiliary ligand are added to the suspension sequentially. The premixing operation ensures that the two components in the dual-dynamic auxiliary ligand first form a homogeneous system, avoiding local concentration fluctuations caused by direct addition. Maintaining a constant stirring speed allows the main ligand and dual-dynamic auxiliary ligand to disperse evenly. The precursor and active metal salt in the suspension gradually interact with each other. After adding the coordination modifier and stirring, the coordination modifier can be quickly integrated into the system and come into contact with other components. Subsequently, deionized water is added to dilute the existing acidic system and adjust the pH value, which can provide a suitable chemical environment for the coordination reaction. Finally, stirring is continued for a specific time to ensure that each component completes the synergistic coordination reaction, and finally a transparent and homogeneous multi-component synergistic precursor mixture is obtained. This sequential mixing process achieves precise control of the precursor formation process by controlling the order of component addition and reaction conditions in steps. At the same time, each process parameter can be clearly controlled to ensure the stability of the preparation process.

[0013] Preferably, in step S2, the stepped heating polymerization process specifically comprises: a first stage of constant temperature reaction at 35~45℃ and 0.15~0.25MPa for 0.8~1.2h; and a second stage of constant temperature reaction at 55~65℃ and 0.25~0.35MPa for 2.8~3.2h, with a total reaction time of 3.6~4.4h.

[0014] By employing the above technical solution, the polymerization reaction is carried out in an orderly manner through staged control of temperature and pressure parameters. The first stage isothermal reaction allows the coordinating components in the multi-component synergistic precursor mixture to slowly initiate the polymerization reaction, avoiding local structural inhomogeneity or agglomeration of active components caused by excessively rapid initial reaction rates, and ensuring the structural regularity of the carrier skeleton during initial formation. The second stage isothermal reaction after heating and pressurizing provides sufficient energy to promote the polymerization reaction, allowing the carrier skeleton to further cross-link and solidify, forming a structurally stable integrated gel product. Controlling the total reaction time ensures complete polymerization while avoiding damage to the skeleton's pore structure due to over-polymerization. This process achieves precise control of the polymerization process by accurately setting the temperature, pressure, and reaction time at each stage, and each process parameter is clearly controllable, ensuring the stability and repeatability of the preparation process. This provides a foundation for a structurally uniform gel product for subsequent gas-assisted low-temperature plasma activation, while also meeting the requirements for process stability in industrial production.

[0015] Preferably, in step S3, during freeze-drying, the freezing temperature is -55~-45℃, the vacuum degree is 10~30Pa, the drying time is 10~14h, and after freeze-drying, the gel block is pulverized to a particle size of 100~200 mesh.

[0016] By adopting the above technical solution, the specific freezing temperature, vacuum degree, and drying time set by freeze-drying can achieve the sublimation removal of water in the integrated gel product. The low-temperature environment can avoid the shrinkage or structural collapse of the gel skeleton caused by the evaporation of liquid water. The vacuum condition provides a suitable environment for water sublimation, and the sufficient drying time can ensure that the water in the gel product is completely removed, avoiding residual water from affecting the subsequent activation process. After freeze-drying, the gel block is crushed to a specific particle size, which can increase the specific surface area of ​​the material and improve the contact between the material and the mixed doping gas and plasma in the subsequent activation process. This ensures that the activation effect is uniformly applied to the surface and interior of the material. At the same time, the process parameters of this process are clear and controllable, ensuring the stability and repeatability of the preparation process. This provides a structural basis for the formation of uniform and stable active sites by subsequent pulsed plasma staged activation, which meets the requirements of material processing consistency in industrial production.

[0017] Preferably, in step S3, the mixed doping gas includes argon, oxygen and nitrous oxide, with a volume ratio of (3.8~4.2):(0.8~1.2):(0.2~0.3), and the gas flow rate is controlled at 10~20 mL / min.

[0018] By adopting the above technical solutions, argon can maintain an inert environment during the activation process, avoiding excessive oxidation or structural damage to the material during plasma activation; oxygen can participate in the oxidation reaction on the material surface, removing residual organic impurities on the surface, and at the same time assisting in the construction of oxidized active sites; nitrous oxide can work synergistically with argon and oxygen to regulate the generation type and concentration of active species during plasma activation, optimize the electronic structure of active sites, and ensure that the activation effect is uniformly applied to the surface and interior of the material. At the same time, it avoids insufficient gas residence time and incomplete activation due to excessively fast flow rate, or local gas component accumulation and impact on the stability of the activation environment due to excessively slow flow rate.

[0019] Preferably, in step S3, the pulsed plasma staged activation step is as follows: Plasma power 70~90W, first stage temperature 90~100℃, pulse frequency 50~60Hz, activation time 8~12min; The second stage temperature is 110~115℃, the pulse frequency is 60~70Hz, and the activation time is 8~12min; The third stage has a temperature of 115~125℃, a pulse frequency of 70~80Hz, an activation duration of 8~12min, and a total activation time of 28~32min.

[0020] By adopting the above technical solution, pulsed plasma staged activation provides suitable activation energy, ensuring effective activation of active components in the material while avoiding material structure damage due to excessive power or insufficient activation due to insufficient power. The activation method of gradually increasing temperature and pulse frequency in stages: The first stage activates at a lower temperature and pulse frequency, allowing the pulverized gel material to gradually adapt to the activation environment, initially removing residual organic impurities and initiating the initial formation of active sites, avoiding the agglomeration of active components caused by the initial high energy input; The second stage continues activation after increasing temperature and frequency, which can deepen the activation process and optimize the uniformity of the distribution of active sites; The third stage further increases the parameters, which can ensure the full formation and stable existence of active sites, ensuring that the activation process in each stage is fully carried out, while avoiding material structure collapse or loss of active sites due to over-activation, and avoiding the sintering problem of active components caused by high-temperature calcination, forming a structurally stable activated product. Moreover, each process parameter is clear and controllable, ensuring the stability and repeatability of the preparation process, providing a material basis with uniform active sites and a stable structure for subsequent surface acid and alkali modification post-treatment, and adapting to the process consistency requirements of industrial production.

[0021] Preferably, in step S4, the mass fraction of the γ-aminopropyltriethoxysilane solution is 4%~6%, and the soaking conditions are: liquid-to-solid ratio (10~20):1 (mL / g), at a temperature of 20~30℃, a stirring speed of 120~180r / min, and soaking for 1.8~2.2h.

[0022] By adopting the above technical solution, the concentration of the coupling agent component in the solution is adapted to the surface modification requirements of the activated product. This ensures that there is sufficient coupling agent to react chemically with the surface of the activated product to form a modified layer, while avoiding unreacted coupling agent residue or an excessively thick modified layer due to excessive concentration. Immersion provides sufficient space for the activated product and the coupling agent solution to have adequate contact, avoiding uneven modification due to insufficient solution. The reaction temperature provides a suitable energy environment for the reaction between γ-aminopropyltriethoxysilane and the surface of the activated product, promoting the orderly progress of the reaction. Stirring promotes solution circulation, reduces local concentration gradients, and ensures that the modification effect is uniformly applied to the surface of the activated product, ensuring that the reaction between the coupling agent and the surface of the activated product is fully completed and avoiding surface modification defects caused by incomplete reaction.

[0023] Preferably, in step S4, after soaking, the product is separated by vacuum filtration, and the product is washed 2-3 times with anhydrous ethanol, with a liquid-to-solid ratio of (8-12):1 (mL / g) each time. After washing, the product is placed in a forced-air drying oven and dried at 75-85℃ for 2.8-3.2 hours.

[0024] By adopting the above technical solution, after soaking, vacuum filtration is used to separate the product, which can achieve rapid separation of the product from the γ-aminopropyltriethoxysilane solution and avoid structural changes in the surface modification layer caused by prolonged soaking. The product is washed with anhydrous ethanol, which can dissolve and remove unreacted γ-aminopropyltriethoxysilane and other impurities remaining on the product surface, ensuring that residual impurities are fully removed. At the same time, it avoids insufficient washing due to insufficient washing solution or product loss due to excessive washing solution. After washing, the product is dried in a forced-air drying oven. The forced-air environment can make the temperature distribution in the drying oven uniform, ensuring that the drying degree of each part of the product is consistent, slowly removing anhydrous ethanol and residual water from the product, avoiding damage to the product's microstructure or decomposition of the surface modification layer due to high temperature, ensuring complete removal of water from the product, and avoiding residual water affecting the product's structural stability.

[0025] This invention provides a method for preparing a denitrification catalyst material specifically for methanol internal combustion engine emissions. It has the following beneficial effects: 1. This invention, through the synergistic effect of dual dynamic auxiliary ligands and coordination regulators, combined with gradient coordination polymerization process to precisely control the precursor structure, significantly shortens the reaction induction period, improves the NO conversion rate in the low-temperature range, and solves the problem of slow denitrification reaction rate of methanol internal combustion engine exhaust at low temperatures.

[0026] 2. This invention effectively reduces the selectivity of N2O generation and the amount of NH3 escape by means of synergistic regulation of dual dynamic auxiliary ligands, trace synergistic effect of nitrous oxide in mixed doped gas, and surface modification optimization of γ-aminopropyltriethoxysilane, thus ensuring the cleanliness of the denitrification process.

[0027] 3. This invention employs a pulsed plasma staged low-temperature activation process to avoid the sintering of active components caused by high-temperature calcination. Combined with surface modification, it forms a stable microstructure, ensuring that the material maintains high activity during long-term continuous operation and reducing performance degradation.

[0028] 4. The preparation steps of this invention are coordinated and matched, the process parameters are controllable, the raw materials used are readily available, and the low-temperature process has low energy consumption and does not require complex equipment, which is conducive to industrial scale-up production and is suitable for the actual application needs of methanol internal combustion engine emission denitrification. Attached Figure Description

[0029] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0030] The technical solution of the present invention will now be clearly and completely described 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 them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] Example 1 This invention provides a method for preparing a denitrification catalyst material specifically for methanol internal combustion engine emissions, comprising the following steps: S1. Preparation of multi-component synergistic precursor mixture: The carrier precursor, active metal salt, main ligand, dual dynamic auxiliary ligand and coordination regulator are mixed sequentially, and the pH value is adjusted and stirred to obtain a transparent and homogeneous multi-component synergistic precursor mixture. The carrier precursor is tetrabutyl titanate, the active metal salt is a mixture of cobalt nitrate and lanthanum nitrate in a mass ratio of 0.13:1, the main ligand is phthalic anhydride, the dual dynamic auxiliary ligand is a mixture of diethyl succinate and dibutyl adipate, and the coordination modifier is triethanolamine. The mass ratios of the carrier precursor, active metal salt, main ligand, dual-dynamic auxiliary ligand, and coordination modifier were 5:0.8:1.8:0.7:0.3, respectively; the mass ratio of diethyl succinate to dibutyl adipate in the dual-dynamic auxiliary ligand was 1.8:1. The mixing steps are as follows: The carrier precursor and active metal salt are added to anhydrous ethanol, and the liquid-solid ratio is controlled at 15:1 (mL / g). The mixture is stirred for 25 min at 25℃ and 250 r / min to form a homogeneous suspension. The main ligand and the premixed dual dynamic auxiliary ligand are added to the suspension in sequence, and the stirring speed is kept constant for another 15 min. The coordination regulator is added, and the mixture is stirred for 8 min. Then, deionized water is added to dilute the system to adjust the pH to 4.2. The mixture is stirred for another 15 min to obtain a multi-component synergistic precursor mixture. S2, Gradient coordination polymerization reaction: The multi-component synergistic precursor mixture is placed in a closed high-pressure reactor and reacted using a step-by-step heating polymerization process to obtain an integrated gel product; The step-by-step heating polymerization process is as follows: in the first stage, the reaction is carried out at a constant temperature of 35℃ and a pressure of 0.15MPa for 0.8h; in the second stage, the temperature is raised to 55℃ and the pressure is raised to a constant temperature for 2.8h; the total reaction time is 3.6h.

[0032] S3. Doped gas-assisted low-temperature plasma activation: After freeze-drying and pulverizing the integrated gel product, a mixed doped gas is introduced, and pulsed plasma is used for staged activation to obtain the activated product. During freeze-drying, the freezing temperature is -55℃, the vacuum degree is 10Pa, and the drying time is 10h. After freeze-drying, the gel block is pulverized to a particle size of 100 mesh. The mixed doped gas includes argon, oxygen and nitrous oxide, with a volume ratio of 3.8:0.8:0.2, and the gas flow rate is controlled at 10 mL / min; The steps for the phased activation of pulsed plasma are as follows: plasma power 70W, first stage temperature 90℃, pulse frequency 50Hz, activation time 8min; second stage temperature 110℃, pulse frequency 60Hz, activation time 8min; third stage temperature 115℃, pulse frequency 70Hz, activation time 8min, total activation time 28min. S4. Surface acid and alkali modification post-treatment: The activated product is immersed in γ-aminopropyltriethoxysilane solution, washed and dried to obtain a special denitrification catalyst for methanol internal combustion engine emissions. The mass fraction of the γ-aminopropyltriethoxysilane solution was 4%, and the soaking conditions were: liquid-to-solid ratio of 10:1 (mL / g), at a temperature of 20℃, a stirring speed of 120 r / min, and a soaking time of 1.8 h. After soaking, the product was separated by vacuum filtration and washed twice with anhydrous ethanol at a liquid-to-solid ratio of 8:1 (mL / g) each time. After washing, the product was placed in a forced-air drying oven and dried at 75℃ for 2.8h.

[0033] Example 2 This invention provides a method for preparing a denitrification catalyst material specifically for methanol internal combustion engine emissions, comprising the following steps: S1. Preparation of multi-component synergistic precursor mixture: The carrier precursor, active metal salt, main ligand, dual dynamic auxiliary ligand and coordination regulator are mixed sequentially, and the pH value is adjusted and stirred to obtain a transparent and homogeneous multi-component synergistic precursor mixture. The carrier precursor is tetrabutyl titanate, the active metal salt is a mixture of cobalt nitrate and lanthanum nitrate with a mass ratio of 0.235:1, the main ligand is phthalic anhydride, the dual dynamic auxiliary ligand is a mixture of diethyl succinate and dibutyl adipate, and the coordination modifier is triethanolamine. The mass ratios of the carrier precursor, active metal salt, main ligand, dual-dynamic auxiliary ligand, and coordination modifier were 5:1.0:2.0:0.95:0.35, respectively; the mass ratio of diethyl succinate to dibutyl adipate in the dual-dynamic auxiliary ligand was 2.0:1. The mixing steps are as follows: The carrier precursor and active metal salt are added to anhydrous ethanol, and the liquid-solid ratio is controlled at 20:1 (mL / g). The mixture is stirred for 30 min at 30℃ and 300 r / min to form a homogeneous suspension. The main ligand and the premixed dual dynamic auxiliary ligand are added to the suspension in sequence, and the stirring speed is kept constant for another 20 min. The coordination regulator is added and stirred for 10 min. Then, deionized water is added to dilute the system to adjust the pH to 4.75, and the mixture is stirred for another 20 min to obtain a multi-component synergistic precursor mixture.

[0034] S2, Gradient coordination polymerization reaction: The multi-component synergistic precursor mixture is placed in a closed high-pressure reactor and reacted using a step-by-step heating polymerization process to obtain an integrated gel product; The step-by-step heating polymerization process is as follows: the first stage is a constant temperature reaction at 40℃ and 0.20MPa for 1.0h, and the second stage is a constant temperature reaction at 60℃ and 0.30MPa for 3.0h, with a total reaction time of 4.0h. S3. Doped gas-assisted low-temperature plasma activation: After freeze-drying and pulverizing the integrated gel product, a mixed doped gas is introduced, and pulsed plasma is used for staged activation to obtain the activated product. During freeze-drying, the freezing temperature is -50℃, the vacuum degree is 20Pa, and the drying time is 12h. After freeze-drying, the gel block is pulverized to a particle size of 150 mesh. The mixed doped gas includes argon, oxygen and nitrous oxide, with a volume ratio of 4.0:1.0:0.25, and the gas flow rate is controlled at 15 mL / min; The steps for the phased activation of pulsed plasma are as follows: plasma power 80W, first stage temperature 95℃, pulse frequency 55Hz, activation time 10min; second stage temperature 112.5℃, pulse frequency 65Hz, activation time 10min; third stage temperature 120℃, pulse frequency 75Hz, activation time 10min, total activation time 30min. S4. Surface acid and alkali modification post-treatment: The activated product is immersed in γ-aminopropyltriethoxysilane solution, washed and dried to obtain a special denitrification catalyst for methanol internal combustion engine emissions. The mass fraction of the γ-aminopropyltriethoxysilane solution was 5%, and the soaking conditions were: liquid-to-solid ratio of 15:1 (mL / g), at a temperature of 25℃, a stirring speed of 150r / min, and a soaking time of 2.0h. After soaking, the product was separated by vacuum filtration and washed twice with anhydrous ethanol at a liquid-to-solid ratio of 10:1 (mL / g) each time. After washing, the product was placed in a forced-air drying oven and dried at 80℃ for 3.0h.

[0035] Example 3 This invention provides a method for preparing a denitrification catalyst material specifically for methanol internal combustion engine emissions, comprising the following steps: S1. Preparation of multi-component synergistic precursor mixture: The carrier precursor, active metal salt, main ligand, dual dynamic auxiliary ligand and coordination regulator are mixed sequentially, and the pH value is adjusted and stirred to obtain a transparent and homogeneous multi-component synergistic precursor mixture. The carrier precursor is tetrabutyl titanate, the active metal salt is a mixture of cobalt nitrate and lanthanum nitrate in a mass ratio of 0.60:1, the main ligand is phthalic anhydride, the dual dynamic auxiliary ligand is a mixture of diethyl succinate and dibutyl adipate, and the coordination modifier is triethanolamine. The mass ratios of the carrier precursor, active metal salt, main ligand, dual-dynamic auxiliary ligand, and coordination modifier were 5:1.2:2.2:1.2:0.4, respectively; the mass ratio of diethyl succinate to dibutyl adipate in the dual-dynamic auxiliary ligand was 2.2:1. The mixing steps are as follows: The carrier precursor and active metal salt are added to anhydrous ethanol, and the liquid-solid ratio is controlled at 25:1 (mL / g). The mixture is stirred for 35 min at 35℃ and 350 r / min to form a homogeneous suspension. The main ligand and the premixed dual dynamic auxiliary ligand are added to the suspension in sequence, and the stirring speed is kept constant for another 25 min. The coordination regulator is added, and the mixture is stirred for 12 min. Then, deionized water is added to dilute the system to adjust the pH to 5.3. The mixture is stirred for another 25 min to obtain a multi-component synergistic precursor mixture. S2, Gradient coordination polymerization reaction: The multi-component synergistic precursor mixture is placed in a closed high-pressure reactor and reacted using a step-by-step heating polymerization process to obtain an integrated gel product; The step-by-step heating polymerization process is as follows: in the first stage, the reaction is carried out at a constant temperature of 45℃ and a pressure of 0.25MPa for 1.2 hours; in the second stage, the reaction is carried out at a constant temperature of 65℃ and a pressure of 0.35MPa for 3.2 hours, with a total reaction time of 4.4 hours. S3. Doped gas-assisted low-temperature plasma activation: After freeze-drying and pulverizing the integrated gel product, a mixed doped gas is introduced, and pulsed plasma is used for staged activation to obtain the activated product. During freeze-drying, the freezing temperature was -45℃, the vacuum degree was 30Pa, and the drying time was 14h. After freeze-drying, the gel block was pulverized to a particle size of 200 mesh. The mixed doped gas includes argon, oxygen and nitrous oxide, with a volume ratio of 4.2:1.2:0.3, and the gas flow rate is controlled at 20 mL / min; The steps for the phased activation of pulsed plasma are as follows: plasma power 90W, first stage temperature 100℃, pulse frequency 60Hz, activation time 12min; second stage temperature 115℃, pulse frequency 70Hz, activation time 12min; third stage temperature 125℃, pulse frequency 80Hz, activation time 12min, total activation time 32min. S4. Surface acid and alkali modification post-treatment: The activated product is immersed in γ-aminopropyltriethoxysilane solution, washed and dried to obtain a special denitrification catalyst for methanol internal combustion engine emissions. The mass fraction of the γ-aminopropyltriethoxysilane solution was 6%, and the soaking conditions were: liquid-to-solid ratio of 20:1 (mL / g), temperature of 30℃, stirring speed of 180 r / min, and soaking time of 2.2 h. After soaking, the product was separated by vacuum filtration and washed three times with anhydrous ethanol at a liquid-to-solid ratio of 12:1 (mL / g) each time. After washing, the product was placed in a forced-air drying oven and dried at 85℃ for 3.2h.

[0036] Comparative Example 1 The only difference from Example 2 is that no dual dynamic auxiliary ligand was added.

[0037] Comparative Example 2 The only difference from Example 2 is that the dual dynamic auxiliary ligand is replaced with a single auxiliary ligand, diethyl succinate, and the amount added is the same as the total mass of the dual dynamic auxiliary ligand in Example 2.

[0038] Comparative Example 3 The only difference from Example 2 is that no coordination modifier was added.

[0039] Comparative Example 4 The only difference from Example 2 is that the gradient coordination polymerization process is replaced with an isothermal polymerization process, which is carried out at a constant temperature of 60°C and 0.30 MPa for 4.0 h.

[0040] Comparative Example 5 The only difference from Example 2 is that nitrous oxide was not added to the mixed doped gas, and the volume ratio of argon to oxygen was 4.0:1.0.

[0041] Comparative Example 6 The only difference from Example 2 is that the pulsed plasma staged activation is replaced with conventional high-temperature calcination activation, which is calcined at 550°C for 3.0 hours.

[0042] Comparative Example 7 The only difference from Example 2 is that the soaking step in γ-aminopropyltriethoxysilane solution in step S4 is omitted, and the drying step is directly dried in an 80°C forced-air drying oven for 3.0 h.

[0043] Experiment 1: Kinetic Performance Test of Denitrification Reaction A fixed-bed reaction evaluation device was constructed according to GB / T34542.1-2017 "Honeycomb Denitrification Catalysts Part 1: Technical Requirements". 5g each of the denitrification catalysts prepared in Examples 1-3 and Comparative Examples 1-7 were pulverized to 200 mesh and uniformly filled into the reaction tube. The reaction gas was prepared to simulate the exhaust conditions of a methanol internal combustion engine, with a NO volume fraction of 500 × 10⁻⁻⁻⁶. 6 NH3 volume fraction 500×10⁻ 6 The reaction mixture used 5% O2 (volume fraction) and N2 as the equilibrium gas, with a total gas flow rate controlled at 500 mL / min. The reaction temperature range was set at 150-400℃, with each 50℃ mark serving as a test node. At each node, after the reaction system stabilized for 30 minutes, the NO concentration before and after the reaction was continuously monitored using an infrared gas analyzer. Each sample was monitored three times at each temperature node, and the average value was used to calculate the NO conversion rate. Simultaneously, the time from the start of the reaction to the NO conversion rate reaching a stable value was recorded as the induction period for the reaction to reach steady state. The reaction rate constant at different temperatures was calculated through kinetic fitting.

[0044] Experiment 2: Simultaneous Detection of Denitrification Efficiency and Byproduct Generation The typical operating temperature range of the methanol internal combustion engine (200-350℃) was selected for focused testing, with 250℃ and 300℃ being the core test temperatures. The experimental samples were all samples from Examples 1-3 and Comparative Examples 1-7, and the composition and flow rate of the reaction gas were kept consistent with the kinetic tests. At each core temperature, after the reaction had stabilized for 1 hour, the concentrations of NO and N2O (the main byproducts) in the post-reaction gas were simultaneously detected using an infrared gas analyzer, and the NH3 escape concentration was detected using chemiluminescence immunoassay. The test was conducted continuously for 3 hours, with data recorded every 30 minutes. The NO denitrification efficiency (denitrification efficiency = (NO concentration before reaction - NO concentration after reaction) / NO concentration before reaction × 100%), N2O formation selectivity (N2O formation selectivity = amount of N2O generated / amount of NO reduced × 100%), and NH3 escape amount were calculated for different time periods.

[0045] Table 1. Test data on the kinetic performance of the denitrification reaction. Table 2. Simultaneous Detection Data of Denitrification Efficiency and Byproduct Generation By comparing the experimental data of the examples and the comparative examples, it can be seen that: Combining Example 1 and Comparative Examples 1 and 2 with Tables 1 and 2, it can be seen that the high efficiency of the denitrification catalyst and the low by-product formation depend on the synergistic effect of the dual dynamic auxiliary ligands. Comparative Examples 1 and 2 had induction periods of 18.3 min and 14.6 min, respectively, with reaction rate constants of only 0.085 min⁻¹ and 0.112 min⁻¹, and N₂O formation selectivity of 8.5% and 6.2% at 250 °C, respectively. In contrast, Example 1 had an induction period of only 8.5 min, a reaction rate constant of 0.182 min⁻¹, and an N₂O selectivity of only 2.1%. This indicates that the dual dynamic auxiliary ligands formed by diethyl succinate and dibutyl adipate can synergistically regulate the precursor dispersion and coordination reaction; a single auxiliary ligand or the absence of this component cannot achieve the dual effect of increased reaction rate and inhibition of by-products.

[0046] Combining Example 2 and Comparative Example 4 with Tables 1 and 2, it can be seen that gradient coordination polymerization is key to optimizing the structure of catalytic materials and improving denitrification performance. Comparative Example 4, using an isothermal polymerization process, achieved a NO conversion rate of only 83.7% at 250℃, an induction period of 12.5 min, and an N2O selectivity of only 5.1%. In contrast, Example 2, through gradient heating polymerization, achieved a conversion rate of 96.5% at 250℃, shortened the induction period to 6.2 min, and achieved an N2O selectivity of only 1.5%. This demonstrates that stepwise heating can control the coordination polymerization process in stages, avoiding the reduction of active sites caused by localized runaway reactions. Isothermal polymerization cannot replace this precise control effect.

[0047] Combining Example 1 and Comparative Example 6 with Tables 1 and 2, it can be seen that staged activation with pulsed plasma is crucial for maintaining high activity and low byproduct formation of the catalytic material. Comparative Example 6, activated by conventional high-temperature calcination, showed a NO conversion rate of only 52.1% at 150℃, an induction period of 20.5 min, a N2O selectivity of 9.8% at 250℃, and an NH3 escape rate of 25.2 ppm, all of which were the worst. In contrast, Example 1, activated with pulsed plasma, achieved a conversion rate of 78.2% at 150℃, an induction period of 8.5 min, and significantly better byproduct performance. This indicates that staged activation with low-temperature plasma can precisely construct active sites and reduce sintering of active components caused by high temperatures. High-temperature calcination damages the microstructure of the material and significantly reduces performance.

[0048] Combining Example 3 and Comparative Example 5 with Tables 1 and 2, it can be seen that trace doping of nitrous oxide in the mixed doped gas can synergistically improve the catalytic reaction efficiency and suppress byproducts. Comparative Example 5, without nitrous oxide, had a reaction rate constant of 0.138 min⁻¹ at 300°C and an N₂O formation selectivity of 3.6%; while in Example 3, after activation with a mixed gas containing nitrous oxide, the reaction rate constant at 300°C was 0.190 min⁻¹, and the N₂O selectivity was only 1.5%. This indicates that nitrous oxide can help regulate the electronic structure of active sites during plasma activation, enhancing NO reduction selectivity; its absence prevents the synergistic optimization of reaction rate and byproduct control.

[0049] Combining Example 2 and Comparative Example 7 with Tables 1 and 2, it can be seen that surface modification with γ-aminopropyltriethoxysilane is a crucial guarantee for improving the stability and reaction selectivity of the catalytic material. Comparative Example 7, omitting the modification step, had an induction period of 15.1 min and an NH3 escape of 17.5 ppm at 250℃; while Example 2, modified with aminosilane, had an induction period of 6.2 min, an NH3 escape of only 3.8 ppm, and an N2O selectivity of 1.5%. This indicates that γ-aminopropyltriethoxysilane can optimize the hydrophilicity / hydrophobicity and active site distribution of the material surface; omitting or replacing it will lead to surface structural defects and reduce reaction performance.

[0050] Combining Example 2 and Comparative Examples 1, 3, and 6 with Tables 1 and 2, it can be seen that the excellent comprehensive performance of the catalytic material is the result of the synergistic effect of multiple components and processes, including the dual-dynamic auxiliary ligand, coordination modifier, gradient polymerization, and low-temperature plasma activation. Comparative Example 1 lacked the dual-dynamic auxiliary ligand, Comparative Example 3 lacked the coordination modifier, and Comparative Example 6 replaced the activation method; its denitrification efficiency, reaction rate, and byproduct indicators were all significantly inferior to Example 2. However, Example 2, through its synergistic design across the entire process, achieved the optimal results with an induction period of 6.2 min, a denitrification efficiency of 97.2% at 300℃, and an N2O selectivity of 1.2%. This demonstrates that the innovative components and processes of this invention are interdependent and synergistically enhance each other; the absence or replacement of a single component will lead to a chain reaction of performance decline, failing to achieve the overall technical advantages.

[0051] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a denitrification catalytic material specifically for methanol internal combustion engine emissions, characterized in that, Includes the following steps: S1. Preparation of multi-component synergistic precursor mixture: The carrier precursor, active metal salt, main ligand, dual dynamic auxiliary ligand and coordination regulator are mixed sequentially, and the pH value is adjusted and stirred to obtain a transparent and homogeneous multi-component synergistic precursor mixture. S2, gradient coordination polymerization reaction: The multi-component synergistic precursor mixture is placed in a closed high-pressure reactor and reacted using a step-by-step heating polymerization process to obtain an integrated gel product. S3. Doped gas-assisted low-temperature plasma activation: The integrated gel product is freeze-dried and then pulverized. A mixed doped gas is introduced, and pulsed plasma is used for staged activation to obtain the activated product. S4. Surface acid and alkali modification post-treatment: The activated product is immersed in γ-aminopropyltriethoxysilane solution, washed and dried to obtain a methanol internal combustion engine emission denitrification catalyst.

2. The preparation method of the methanol internal combustion engine emission denitrification catalyst material according to claim 1, characterized in that, In step S1, the carrier precursor is tetrabutyl titanate, the active metal salt is a mixture of cobalt nitrate and lanthanum nitrate in a mass ratio of 0.13–0.60:1, the main ligand is phthalic anhydride, the dual dynamic auxiliary ligand is a mixture of diethyl succinate and dibutyl adipate, and the coordination modifier is triethanolamine.

3. The preparation method of the methanol internal combustion engine emission denitrification catalyst material according to claim 1, characterized in that, In step S1, the mass ratio of the carrier precursor, active metal salt, main ligand, dual-dynamic auxiliary ligand, and coordination modifier is 5:(0.8~1.2):(1.8~2.2):(0.7~1.2):(0.3~0.4). The dual-dynamic auxiliary ligand is a mixture of diethyl succinate and dibutyl adipate, and the mass ratio of diethyl succinate to dibutyl adipate is (1.8~2.2):

1.

4. The preparation method of the methanol internal combustion engine emission denitrification catalyst material according to claim 1, characterized in that, In step S1, the mixing steps are as follows: The carrier precursor and active metal salt were added to anhydrous ethanol, and the liquid-solid ratio was controlled at (15~25):1 (mL / g). The mixture was stirred for 25~35 min at a temperature of 25~35℃ and a stirring speed of 250~350r / min to form a uniform suspension. Add the main ligand and the premixed dual dynamic auxiliary ligand to the suspension in sequence, keep the stirring speed constant, and continue stirring for 15~25 min; Add the coordination modifier, stir for 8-12 minutes, then add deionized water to dilute the system to adjust the pH to 4.2-5.3, and continue stirring for 15-25 minutes to obtain a multi-component synergistic precursor mixture.

5. The preparation method of the methanol internal combustion engine emission denitrification catalyst material according to claim 1, characterized in that, In step S2, the step-by-step heating polymerization process is as follows: in the first stage, the reaction is carried out at a constant temperature of 35~45℃ and a pressure of 0.15~0.25MPa for 0.8~1.2h; in the second stage, the temperature is raised to 55~65℃ and the pressure is raised to a constant temperature of 0.25~0.35MPa for 2.8~3.2h, and the total reaction time is 3.6~4.4h.

6. The preparation method of the methanol internal combustion engine emission denitrification catalyst material according to claim 1, characterized in that, In step S3, during freeze-drying, the freezing temperature is -55~-45℃, the vacuum degree is 10~30Pa, and the drying time is 10~14h. After freeze-drying, the gel block is pulverized to a particle size of 100~200 mesh.

7. The preparation method of the methanol internal combustion engine emission denitrification catalyst material according to claim 1, characterized in that, In step S3, the mixed doping gas includes argon, oxygen and nitrous oxide, with a volume ratio of (3.8~4.2):(0.8~1.2):(0.2~0.3), and the gas flow rate is controlled at 10~20 mL / min.

8. The preparation method of the methanol internal combustion engine emission denitrification catalyst material according to claim 1, characterized in that, In step S3, the pulsed plasma staged activation process is as follows: Plasma power 70~90W, first stage temperature 90~100℃, pulse frequency 50~60Hz, activation time 8~12min; The second stage temperature is 110~115℃, the pulse frequency is 60~70Hz, and the activation time is 8~12min; The third stage has a temperature of 115~125℃, a pulse frequency of 70~80Hz, an activation duration of 8~12min, and a total activation time of 28~32min.

9. The preparation method of the methanol internal combustion engine emission denitrification catalyst material according to claim 1, characterized in that, In step S4, the mass fraction of the γ-aminopropyltriethoxysilane solution is 4%~6%, and the soaking conditions are: liquid-to-solid ratio (10~20):1 (mL / g), at a temperature of 20~30℃, a stirring speed of 120~180r / min, and soaking for 1.8~2.2h.

10. The preparation method of the methanol internal combustion engine emission denitrification catalyst material according to claim 1, characterized in that, In step S4, after soaking, the product is separated by vacuum filtration and washed with anhydrous ethanol 2-3 times, with a liquid-to-solid ratio of (8-12):1 (mL / g) each time. After washing, the product is placed in a forced-air drying oven and dried at 75-85℃ for 2.8-3.2 hours.

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