A hydrogen internal combustion engine after-treatment catalyst, preparation method and catalytic system

Abstract

This application relates to a preparation method, preparation method, and catalytic system for a hydrogen internal combustion engine aftertreatment catalyst, comprising the following steps: mixing a titanium dioxide precursor with a solvent to hydrolyze and form a titanium dioxide sol; adding nanocarbon and a soluble salt of a precious metal to the titanium dioxide sol and dispersing the mixture to obtain an M@C / TiO2 sol, wherein M is a precious metal; solidifying the M@C / TiO2 sol gel and heating and drying it to obtain M@C / TiO2 crystals; and grinding the M@C / TiO2 crystals into a powder, irradiating it with light, and calcining it to obtain an M@TiO2 powder catalyst. This application addresses the problem of conventional NOx aftertreatment devices in the prior art failing to achieve near-zero NOx emissions. The catalyst exhibits high catalytic activity during low-temperature cold starts, with a NOx conversion efficiency exceeding 80% and reaching 100% at 150°C, essentially achieving near-zero NOx emissions.

Description

Technical Field

[0001] The present application relates to the technical field of automobile exhaust treatment, and in particular to a hydrogen internal combustion engine after-treatment catalyst, a preparation method and a catalytic system. Background Art

[0002] As the automotive and transportation industries accelerate their efforts to reduce and decarbonize carbon, hydrogen internal combustion engines are attracting industry attention due to their environmental and sustainable advantages. Hydrogen internal combustion engines, also known as hydrogen fuel engines, are based on traditional internal combustion engines. By changing the fuel supply system, injection system, and fuel, they burn hydrogen to generate power, thereby driving the vehicle. Hydrogen internal combustion engines retain the main structures and systems of traditional internal combustion engines. Most parts of traditional internal combustion engines are universally compatible with hydrogen internal combustion engines, which can significantly reduce manufacturing costs. Hydrogen internal combustion engines are adaptable to multiple fuels, and the fuel hydrogen they use does not require high purity. Industrial by-product hydrogen can be used directly without further purification, further reducing costs. In addition, hydrogen internal combustion engines are more adaptable to high-load operating conditions than hydrogen fuel cells, and are more suitable for heavy-duty, off-road, construction, and special commercial vehicles. Major automakers are actively developing hydrogen internal combustion engine projects.

[0003] Due to the physical and chemical characteristics of hydrogen, the air-fuel ratio control and fuel injection methods of hydrogen-fueled engines differ from those of natural gas and gasoline engines. Hydrogen is more flammable, making it more prone to problems such as pre-ignition, backfire, and detonation compared to gasoline engines, as well as nitrogen oxide atmospheric pollution emissions caused by burning oil, which presents a difficult technical hurdle to overcome. Although hydrogen-fueled internal combustion engines do not emit the greenhouse gas carbon dioxide, CO, HC, or soot, their raw NOx emissions are relatively high due to the narrow operating range for achieving a uniform lean combustion mixture. Even with conventional NOx aftertreatment devices, the vehicle's NOx emissions are still 3.9% of the US ultra-low emissions, failing to achieve near-zero NOx emissions. Summary of the Invention

[0004] The embodiments of the present application provide a hydrogen internal combustion engine after-treatment catalyst, a preparation method and a catalytic system to solve the problem that conventional NOx after-treatment devices in the related art cannot achieve near-zero NOx emissions.

[0005] In a first aspect, a method for preparing a hydrogen internal combustion engine aftertreatment catalyst is provided, comprising the following steps:

[0006] mixing a titanium dioxide precursor with a solvent to hydrolyze and form a titanium dioxide sol;

[0007] Adding nanocarbon and a soluble salt of a noble metal to the titanium dioxide sol and dispersing the mixture to obtain an M@C / TiO2 sol, wherein M is a noble metal;

[0008] solidifying the M@C / TiO2 sol-gel, and heating and drying it to obtain M@C / TiO2 crystals;

[0009] The M@C / TiO2 crystals are ground into powder, and then subjected to light irradiation and calcination to obtain an M@TiO2 powder catalyst.

[0010] When M@C / TiO2 powder is irradiated under natural light for 2 to 8 hours, the electrons e- in the valence band of TiO2 are excited and jump to the conduction band. The electrons and holes migrate to different positions on the surface of the TiO2 particles. Nanocarbon can play a role similar to a bridge, which is conducive to the transfer of electrons e- from TiO2 to the precious metal M and the formation of more zero-valent single-atom M species, among which the zero-valent single-atom M is the active center of the H2SCR catalyst. In addition, the hydrogen overflow from the precious metal M to the carrier TiO2 is crucial to the H2SCR reaction. The hydrogen overflow is closely related to the dispersion of the precious metal M. When the dispersion decreases, the hydrogen overflow is restricted, thereby suppressing the NO x The reduction reaction proceeds, and the doping of nanocarbon in the synthesis process can greatly improve the dispersion of the noble metal M. The chemical state and microstructure of the noble metal M are changed by light, thereby increasing the NO x Removal efficiency: its catalytic activity is high during low-temperature cold start, and the NOx conversion efficiency reaches more than 80%, and reaches 100% at 150°C, basically achieving near-zero NOx emissions.

[0011] In summary, the preparation method of the hydrogen internal combustion engine aftertreatment catalyst provided by the present application is to synthesize a M@TiO2 catalyst with a noble metal M as the catalytic active center and TiO2 as the carrier. TiO2 is a wide bandgap n-type semiconductor, and its band structure is generally composed of a low-energy valence band (VB) and a high-energy conduction band (CB), wherein the valence band is filled with electrons, the conduction band is empty, and there is a bandgap between them. When light with energy greater than the bandgap width irradiates TiO2, the electrons (e-) in the valence band are excited and transition to the conduction band, and the photogenerated electrons and photogenerated holes are effectively separated under the action of the spatial electric field, and the electrons and holes migrate to different positions on the surface of the TiO2 particles, respectively, and they produce redox reactions with substances adsorbed on the TiO2 surface.

[0012] In some embodiments, the titanium dioxide precursor includes one or more of butyl titanate, titanium ethoxide, and titanium isopropoxide;

[0013] And / or, the nanocarbon includes one or more of carbon nanotubes, graphene and carbon fibers;

[0014] And / or, the solvent includes one or more of anhydrous ethanol, methanol, acetone, and ethyl acetate;

[0015] And / or, the noble metal soluble salt includes one or more of noble metal nitrates and noble metal sulfates;

[0016] And / or, the noble metal M includes one or more of Pt, Pd, Rh and Ir.

[0017] In some embodiments, the volume ratio of the titanium dioxide precursor to the solvent is 1:2-5.

[0018] In some embodiments, the amount of the nanocarbon added is 1% to 5% of the mass of the titanium dioxide precursor;

[0019] And / or, the amount of the noble metal soluble salt added is 1% to 4% of the mass of the titanium dioxide precursor.

[0020] In some embodiments, the dispersion is performed at a speed of 3000 r / min to 6000 r / min to obtain the M@C / TiO2 sol;

[0021] And / or, gel curing includes: freezing the M@C / TiO2 sol at a temperature of -35°C to -25°C for 3 to 6 hours, and sublimating and curing it under a vacuum degree of 0.1 to 0.001 Pa;

[0022] And / or, the heating and drying includes: heating and drying at a temperature of 60° C. to 80° C. for 8 hours.

[0023] In some embodiments, the illumination includes: irradiation under natural light for 2 hours to 8 hours.

[0024] In some embodiments, the calcination includes: calcining at a temperature of 400° C. to 600° C. for 2 to 6 hours.

[0025] In some embodiments, a titanium dioxide precursor is mixed with a solvent to be hydrolyzed to form a titanium dioxide sol, which specifically includes: mixing the titanium dioxide precursor with the solvent, stirring for 3 to 6 hours, and then ultrasonically vibrating to form the titanium dioxide sol.

[0026] In a second aspect, a hydrogen internal combustion engine after-treatment catalyst is provided, which is prepared using any of the above methods for preparing a hydrogen internal combustion engine after-treatment catalyst.

[0027] In a third aspect, a catalytic system is provided, which includes a carrier, wherein the carrier is provided with the hydrogen internal combustion engine after-treatment catalyst as described above, and a Cu-based molecular sieve or a V-based catalyst.

[0028] The beneficial effects of the technical solution provided by this application include:

[0029] The embodiment of the present application provides a hydrogen internal combustion engine after-treatment catalyst, preparation method and catalytic system. When M@C / TiO2 powder is irradiated under natural light for 2h to 8h, the electrons e- on the valence band of TiO2 are excited to jump to the conduction band, and the electrons and holes migrate to different positions on the surface of the TiO2 particles respectively. Nanocarbon can play a role similar to a bridge, which is conducive to the transfer of electrons e- from TiO2 to the precious metal M and the formation of more zero-valent single-atom M species, wherein the zero-valent single-atom M is the active center of the H2 SCR catalyst. In addition, the hydrogen overflow from the precious metal M to the carrier TiO2 is crucial to the H2 SCR reaction. The hydrogen overflow is closely related to the dispersion of the precious metal M. When the dispersion decreases, the hydrogen overflow is restricted, thereby suppressing NO x The reduction reaction proceeds, and the doping of nanocarbon in the synthesis process can greatly improve the dispersion of the noble metal M. The chemical state and microstructure of the noble metal M are changed by light, thereby increasing the NO x removal efficiency, ultimately achieving near-zero NOx emissions.

[0030] The main reason for calcining to remove nano-carbon in the catalyst is: the tail exhaust of hydrogen internal combustion engines contains O2, NO, NO2, etc., and the tail exhaust temperature is about 400 ° C. Nano-carbon will undergo oxidation reaction to generate CO2 under high temperature aerobic conditions. On the one hand, high temperature will be generated during the oxidation process, which may destroy the catalyst support structure. On the other hand, the H2 SCR reaction is: 2NO+4H2+O2→N2+4H2O. If the catalyst contains carbon, it will consume the oxygen required for the H2 SCR reaction. Moreover, the NO2 content in the tail exhaust of hydrogen internal combustion engines is lower than the NO2 content in diesel exhaust. The reductive nano-carbon can also react with the NO2 in the tail gas, further reducing the NO2 content, thereby affecting subsequent NH3 SCR reaction (fast SCR reaction is 2NH3+NO+NO2→2N2+3H2O, and the standard reaction is 4NH3+4NO+O2→4N2+6H2O). The noble metal-based catalyst in this application has good low-temperature activity and is a better choice for H2 SCR reaction.

[0031] In summary, the preparation method of the hydrogen internal combustion engine aftertreatment catalyst provided by the present application is to synthesize a M@TiO2 catalyst with a noble metal M as the catalytic active center and TiO2 as the carrier. TiO2 is a wide bandgap n-type semiconductor, and its band structure is generally composed of a low-energy valence band (VB) and a high-energy conduction band (CB), wherein the valence band is filled with electrons, the conduction band is empty, and there is a bandgap between them. When light with energy greater than the bandgap width irradiates TiO2, the electrons (e-) in the valence band are excited and transition to the conduction band, and the photogenerated electrons and photogenerated holes are effectively separated under the action of the spatial electric field, and the electrons and holes migrate to different positions on the surface of the TiO2 particles, respectively, and they produce redox reactions with substances adsorbed on the TiO2 surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0033] Figure 1 This is a flow chart of the preparation method of the hydrogen internal combustion engine after-treatment catalyst provided in the embodiment of the present application. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0035] In order to solve the problem that conventional NOx post-treatment devices in related technologies cannot achieve near-zero NOx emissions. Figure 1 As shown, the embodiment of the present application provides a method for preparing a hydrogen internal combustion engine after-treatment catalyst, which includes the following steps:

[0036] 101: A titanium dioxide precursor is mixed with a solvent to be hydrolyzed and form a titanium dioxide sol.

[0037] In this step 101 , a titanium dioxide precursor is mixed and dispersed with a solvent, and a hydrolysis reaction is performed to form a titanium dioxide sol.

[0038] There are a variety of optional substances for the titanium dioxide precursor, which can be selected according to actual preparation needs. For example, as an example, the titanium dioxide precursor includes one or more of butyl titanate, titanium ethoxide, and titanium isopropoxide.

[0039] There are many optional substances for the solvent, which can be selected according to actual preparation needs. For example, as an example, the solvent includes one or more of anhydrous ethanol and methanol, acetone, and ethyl acetate.

[0040] The volume ratio of the titanium dioxide precursor to the solvent is 1:2 to 5. Below this range, titanium alkoxide is difficult to hydrolyze to form titanium dioxide gel, while above this range, solvent waste is caused and the subsequent gel curing and drying process is also troublesome. Preferably, the volume ratio of the titanium dioxide precursor to the solvent is 1:2.

[0041] In step 101, a titanium dioxide precursor is mixed with a solvent to be hydrolyzed to form a titanium dioxide sol, which specifically includes: mixing the titanium dioxide precursor with the solvent, stirring for 3 to 6 hours under a magnetic stirrer, and then ultrasonically oscillating to form the titanium dioxide sol.

[0042] 102: Add nanocarbon and a soluble salt of a noble metal to the titanium dioxide sol, and disperse them to obtain an M@C / TiO2 sol, wherein M is a noble metal.

[0043] In step 102, after adding the nanocarbon and the soluble noble metal salt, the mixture is mixed and dispersed at a speed of 3000 r / min to 6000 r / min to obtain the M@C / TiO2 sol. Preferably, the mixture is mixed and dispersed at a speed of 4000 r / min to obtain the M@C / TiO2 sol.

[0044] There are a variety of optional materials for the nanocarbon, which can be selected according to actual preparation needs. For example, as an example, the nanocarbon includes one or more of carbon nanotubes, graphene and carbon fibers.

[0045] The noble metal soluble salt has a variety of optional substances, which can be selected according to actual preparation needs. For example, as an example, the noble metal soluble salt includes one or more of noble metal nitrates and noble metal sulfates;

[0046] There are many optional materials for the precious metal M, which can be selected according to actual preparation needs. For example, as an example, the precious metal M includes one or more of platinum Pt, palladium Pd, rhodium Rh and iridium Ir.

[0047] It can be seen that the soluble salt of the noble metal can be selected from platinum nitrate, palladium nitrate, rhodium nitrate and iridium nitrate. Platinum sulfate, palladium sulfate, rhodium sulfate and iridium sulfate can also be selected.

[0048] In step 102, the amount of the nanocarbon added is 1% to 5% of the mass of the titanium dioxide precursor; the amount of the noble metal soluble salt added is 1% to 4% of the mass of the titanium dioxide precursor.

[0049] Preferably, 2% of the mass of the titanium dioxide precursor is added, and 2% of the mass of the titanium dioxide precursor is added, and platinum nitrate is added.

[0050] 103: solidifying the M@C / TiO2 sol-gel, and heating and drying it to obtain M@C / TiO2 crystals.

[0051] The heating and drying comprises: heating and drying at a temperature of 60° C. to 80° C. for 8 hours.

[0052] The gel solidification adopts a freeze-drying process, and the specific operation is: freezing the M@C / TiO2 sol at a temperature of -35°C to -25°C for 3 to 6 hours, and sublimating and solidifying it under a vacuum degree of 0.1 to 0.001Pa.

[0053] Compared with the ordinary drying process, the gel freezing process is more conducive to the distribution of precious metal ions inside the carrier, because the ordinary drying process uses drying at 100°C for 4 hours. During the evaporation of water, the precious metal ions will migrate to the surface with the evaporation of water, causing the precious metal ions to gather on the surface of the carrier and agglomerate, and the catalytic activity will decrease.

[0054] Preferably, the specific operation of gel curing is: freezing the gel at -30°C for 4 hours, and sublimating and curing it under a vacuum degree of 0.01 Pa to obtain a cured gel.

[0055] 104: Grind the M@C / TiO2 crystal into powder, and irradiate and calcine the powder to obtain a M@TiO2 powder catalyst.

[0056] In step 104, the irradiation includes: grinding the M@C / TiO2 crystal into powder and placing it under natural light for 2 hours to 8 hours.

[0057] The purpose of grinding the M@C / TiO2 crystals into powder is to facilitate M@C / TiO2 to obtain sufficient light exposure.

[0058] The purpose of using natural light to illuminate the powdered M@C / TiO2 is: when the M@C / TiO2 powder is irradiated under natural light for 2h to 8h, the electrons e- in the valence band of TiO2 are excited and jump to the conduction band, and the electrons and holes migrate to different positions on the surface of the TiO2 particles. Nanocarbon can play a role similar to a bridge, which is conducive to the transfer of electrons e- from TiO2 to the precious metal M and the formation of more zero-valent single-atom M species, among which the zero-valent single-atom M is the active center of the H2SCR catalyst. In addition, the hydrogen overflow from the precious metal M to the carrier TiO2 is crucial to the H2SCR reaction. The hydrogen overflow is closely related to the dispersion of the precious metal M. When the dispersion decreases, the hydrogen overflow is restricted, thereby inhibiting NO x The reduction reaction proceeds, and the doping of nanocarbon in the synthesis process can greatly improve the dispersion of the noble metal M. The chemical state and microstructure of the noble metal M are changed by light, thereby increasing the NO x Removal efficiency.

[0059] After the light exposure, the present application further removes the nano-carbon by calcination, wherein the calcination includes: calcining at a temperature of 400° C. to 600° C. for 2 to 6 hours.

[0060] The main reason for calcining to remove nano-carbon in the catalyst is: the tail exhaust of hydrogen internal combustion engines contains O2, NO, NO2, etc., and the tail exhaust temperature is about 400 ° C. Nano-carbon will undergo oxidation reaction to generate CO2 under high temperature aerobic conditions. On the one hand, high temperature will be generated during the oxidation process, which may destroy the catalyst support structure. On the other hand, the H2 SCR reaction is: 2NO+4H2+O2→N2+4H2O. If the catalyst contains carbon, it will consume the oxygen required for the H2 SCR reaction. Moreover, the NO2 content in the tail exhaust of hydrogen internal combustion engines is lower than the NO2 content in diesel exhaust. The reductive nano-carbon can also react with the NO2 in the tail gas, further reducing the NO2 content, thereby affecting subsequent NH3 SCR reaction (fast SCR reaction is 2NH3+NO+NO2→2N2+3H2O, and the standard reaction is 4NH3+4NO+O2→4N2+6H2O). The noble metal-based catalyst in this application has good low-temperature activity and is a better choice for H2 SCR reaction.

[0061] In summary, the preparation method of the hydrogen internal combustion engine after-treatment catalyst provided by the present application is to synthesize an M@TiO2 catalyst with a noble metal M as the catalytic active center and TiO2 as the carrier. TiO2 is a wide bandgap n-type semiconductor, and its band structure is generally composed of a low-energy valence band (VB) and a high-energy conduction band (CB), wherein the valence band is filled with electrons, the conduction band is empty, and there is a bandgap between them. When light with energy greater than the bandgap width irradiates TiO2, the electrons (e-) in the valence band are excited and transition to the conduction band, and the photogenerated electrons and photogenerated holes are effectively separated under the action of the spatial electric field, and the electrons and holes migrate to different positions on the surface of the TiO2 particles, respectively, and they produce redox reactions with substances adsorbed on the TiO2 surface. In addition, studies have shown that with Pt nanoparticles as the center and a radius of The NOx adsorbed species within this range are all reactive species, while the species outside this range are inactive.

[0062] An embodiment of the present application further provides a hydrogen internal combustion engine after-treatment catalyst, which is prepared using the preparation method of the hydrogen internal combustion engine after-treatment catalyst mentioned in any of the above embodiments.

[0063] The M@TiO2 powder catalyst obtained in this embodiment, namely the H2 SCR catalyst, can be used alone in a hydrogen internal combustion engine. For example, when the engine adopts high-pressure direct injection technology (>100 bar), the M@TiO2 powder catalyst can be used alone.

[0064] An embodiment of the present application further provides a catalytic system, which includes a carrier, wherein the carrier is provided with the hydrogen internal combustion engine after-treatment catalyst as described above, and a Cu-based molecular sieve or a V-based catalyst.

[0065] Cu molecular sieve is an SCR catalyst, which is Cu loaded on molecular sieve, and V-based catalyst is generally vanadium oxide loaded on titanium dioxide carrier. This application combines the M@TiO2 powder catalyst with the Cu-based molecular sieve, which can broaden the activity window of the Cu-based molecular sieve, which is beneficial to control cold start NOx emissions and meet the National VI and later National VI emission requirements; combining the M@TiO2 powder catalyst with the V-based catalyst can broaden the activity window of the V-based molecular sieve, which is beneficial to control cold start NOx emissions and meet the National VI and later National VI emission requirements. It can be seen that this application can also be used in diesel engines, expanding the temperature range of existing diesel engine SCR catalysts,

[0066] The present application is described in detail below through several embodiments and comparative examples.

[0067] It should be noted that the operating conditions of a diesel engine are more complex than those of a hydrogen internal combustion engine, and the diesel engine is more mature. Therefore, the following embodiments and comparative examples are applied to diesel engines for data testing.

[0068] Example 1

[0069] 101: Butyl titanate and anhydrous ethanol were mixed in a volume ratio of 1:2, stirred under a magnetic stirrer for 4 h, and ultrasonically vibrated to form a titanium dioxide sol.

[0070] 102: Add 2% of carbon nanotubes and 2% of platinum nitrate to the titanium dioxide sol, and mix and disperse at a speed of 4000 r / min to obtain a Pt@C / TiO2 sol.

[0071] 103: solidifying the Pt@C / TiO2 sol-gel, heating and drying at 80°C for 8 hours to obtain Pt@C / TiO2 yellow crystals.

[0072] The gel solidification includes: freezing the gel at -30°C for 4 hours, and sublimating and solidifying the gel under a vacuum degree of 0.01 Pa to obtain a solidified gel.

[0073] 104: The yellow Pt@C / TiO2 crystals were then ground into powder, the Pt@C / TiO2 powder was irradiated under natural light for 2 h, and calcined at 500°C for 2 h to obtain a Pt@TiO2 powder catalyst, i.e., an H2 SCR catalyst.

[0074] Using the H2 SCR catalyst prepared by this method in conjunction with a Cu-based molecular sieve can broaden the activity window of the Cu-based molecular sieve, which is beneficial for controlling cold-start NOx emissions and meeting the National VI and post-National VI emission requirements.

[0075] Example 2

[0076] 101: Butyl titanate and anhydrous ethanol were mixed in a volume ratio of 1:3, stirred under a magnetic stirrer for 4 h, and ultrasonically vibrated to form a titanium dioxide sol.

[0077] 102: Add 2% of carbon nanotubes based on the mass of butyl titanate and 3% of platinum nitrate based on the mass of butyl titanate to the titanium dioxide sol, and mix and disperse at a high speed of 4000 r / min to obtain a Pt@C / TiO2 sol.

[0078] 103: solidifying the Pt@C / TiO2 sol-gel, heating and drying at 80°C for 6 hours to obtain Pt@C / TiO2 yellow crystals.

[0079] The gel solidification includes: freezing the gel at -30°C for 4 hours, and sublimating and solidifying the gel under a vacuum degree of 0.01 Pa to obtain a solidified gel.

[0080] 104: The yellow Pt@C / TiO2 crystals were then ground into powder, the Pt@C / TiO2 powder was irradiated under natural light for 4 h, and calcined at 600°C for 2 h to obtain a Pt@TiO2 powder catalyst, i.e., an H2 SCR catalyst.

[0081] Using the H2 SCR catalyst prepared by this method in conjunction with a V-based catalyst can broaden the activity window of the V-based molecular sieve, which is beneficial for controlling cold-start NOx emissions and meeting the National VI and post-National VI emission requirements.

[0082] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that no carbon nanotubes are added.

[0083] 101: Butyl titanate and anhydrous ethanol were mixed in a volume ratio of 1:2, stirred under a magnetic stirrer for 4 h, and ultrasonically vibrated to form a titanium dioxide sol.

[0084] 102: Add 2% of platinum nitrate by weight of butyl titanate to the titanium dioxide sol, and mix and disperse at a high speed of 4000 r / min to obtain a Pt / TiO2 sol.

[0085] 103: solidifying the Pt / TiO2 sol-gel, heating and drying at 80°C for 8 hours to obtain Pt / TiO2 yellow crystals.

[0086] The gel solidification includes: freezing the gel at -30°C for 4 hours, and sublimating and solidifying the gel under a vacuum degree of 0.01 Pa to obtain a solidified gel.

[0087] 104: The yellow Pt / TiO2 crystals are then ground into powder, the Pt / TiO2 powder is irradiated under natural light for 2 h, and calcined at 500° C. for 2 h to obtain a Pt / TiO2 powder catalyst, i.e., an H2 SCR catalyst.

[0088] The H2 SCR catalyst prepared by this method is used in conjunction with a Cu-based molecular sieve.

[0089] Comparative Example 2: The difference between this example and Example 1 is that in step 103, a common drying process is used. The details are as follows:

[0090] 101: Butyl titanate and anhydrous ethanol were mixed in a volume ratio of 1:2, stirred under a magnetic stirrer for 4 h, and ultrasonically vibrated to form a titanium dioxide sol.

[0091] 102: Add 2% of carbon nanotubes and 2% of platinum nitrate to the titanium dioxide sol, and mix and disperse at a speed of 4000 r / min to obtain a Pt@C / TiO2 sol.

[0092] 103: Dry and solidify the Pt@C / TiO2 sol, and heat and dry it at 80°C for 8 hours to obtain Pt@C / TiO2 yellow crystals.

[0093] The drying and curing process includes: drying the gel at 100° C. for 4 hours to cure the gel, thereby obtaining a cured gel.

[0094] 104: The yellow Pt@C / TiO2 crystals were then ground into powder, the Pt@C / TiO2 powder was irradiated under natural light for 2 h, and calcined at 500°C for 2 h to obtain a Pt@TiO2 powder catalyst, i.e., an H2 SCR catalyst.

[0095] The H2 SCR catalyst prepared by this method is used in conjunction with a Cu-based molecular sieve.

[0096] Comparative Example 3: The difference between this example and Example 2 is that in step 103, a common drying process is used. The details are as follows:

[0097] 101: Butyl titanate and anhydrous ethanol were mixed in a volume ratio of 1:2, stirred under a magnetic stirrer for 4 h, and ultrasonically vibrated to form a titanium dioxide sol.

[0098] 102: Add 2% of carbon nanotubes and 2% of platinum nitrate to the titanium dioxide sol, and mix and disperse at a speed of 4000 r / min to obtain a Pt@C / TiO2 sol.

[0099] 103: Dry and solidify the Pt@C / TiO2 sol, and heat and dry it at 80°C for 8 hours to obtain Pt@C / TiO2 yellow crystals.

[0100] The drying and curing process includes: drying the gel at 100° C. for 4 hours to cure the gel, thereby obtaining a cured gel.

[0101] 104: The yellow Pt@C / TiO2 crystals were then ground into powder, the Pt@C / TiO2 powder was irradiated under natural light for 2 h, and calcined at 500°C for 2 h to obtain a Pt@TiO2 powder catalyst, i.e., an H2 SCR catalyst.

[0102] The H2 SCR catalyst prepared by this method is used in conjunction with a Cu-based molecular sieve.

[0103] The test data on NOx conversion efficiency of Example 1, Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3 are shown in Table 1 below:

[0104] Table 1

[0105]

[0106] Combining the NOx conversion efficiency data of Comparative Example 1 and Example 1, the front end of Comparative Example 1 is not coated with the H2SCR catalyst of the present application. During low-temperature cold start, the conversion rate of the Cu-based molecular sieve is relatively low, and NOx conversion is difficult to achieve. Carbon nanotubes are added to Example 1, and its NOx conversion efficiency reaches more than 80% between 100°C and 175°C, and reaches 100% at 150°C, basically achieving near-zero NOx emissions. This shows that carbon nanotubes can play a role similar to a bridge, which is conducive to the transfer of electrons e- from TiO2 to precious metal Pt and the formation of more zero-valent single-atom Pt species, where zero-valent single-atom Pt is the active center of the H2SCR catalyst. In addition, hydrogen overflow from precious metal Pt to carrier TiO2 is crucial to the H2 SCR reaction. Hydrogen overflow is closely related to the dispersion of precious metal Pt. When the dispersion decreases, hydrogen overflow is restricted, thereby suppressing NO x The reduction reaction proceeds, and doping carbon nanotubes during the synthesis process can greatly improve the dispersion of precious metal Pt. The chemical state and microstructure of precious metal Pt are changed by light, thereby increasing the NO x Removal efficiency.

[0107] After Example 1 and Example 2 were coated with the H2 SCR catalyst of the present application, the low-temperature activity was significantly enhanced, and 100% NOx conversion could be achieved at about 150°C.

[0108] Since a hydrogen internal combustion engine uses H2 as fuel, its main products are H2O and a small amount of NOx. NOx mainly comes from the oxidation of N2 in the air at high temperature. Compared with a diesel engine, its NOx sources are fewer. Based on the above data, in a diesel engine with more complex conditions, the H2 SCR catalyst of the present application can directly decompose a small amount of NOx, thereby achieving near-zero NOx emissions. It is even easier to achieve near-zero NOx emissions for a hydrogen internal combustion engine.

[0109] Combining the NOx conversion efficiency data for Comparative Example 2, Examples 1, and 2, shows that Comparative Example 2 uses a conventional drying process. During water evaporation, the precious metal Pt ions migrate to the surface as the water evaporates, causing them to aggregate on the carrier surface. Consequently, catalytic activity is low during low-temperature cold starts, with a NOx conversion efficiency of only 50% to 70%. Examples 1 and 2 use a freeze-drying process, which is more conducive to the distribution of precious metal Pt ions within the carrier. Consequently, their catalytic activity is higher during low-temperature cold starts, with NOx conversion efficiencies exceeding 80% and reaching 100% at 150°C, essentially achieving near-zero NOx emissions.

[0110] Combining the NOx conversion efficiency data for Comparative Example 3, Examples 1, and 2, we can see that Comparative Example 3 uses a conventional drying process. During water evaporation, the precious metal Pt ions migrate to the surface, causing them to aggregate on the support surface. Consequently, catalytic activity is low during low-temperature cold starts, with a NOx conversion efficiency of only 50% to 70%. Examples 1 and 2 use a freeze-drying process, which is more conducive to the distribution of precious metal Pt ions within the support. Consequently, their catalytic activity is higher during low-temperature cold starts, with NOx conversion efficiencies exceeding 80% and reaching 100% at 150°C, essentially achieving near-zero NOx emissions.

[0111] In the description of this application, it should be noted that the terms "upper" and "lower" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0112] It should be noted that, in this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0113] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing a hydrogen internal combustion engine post-treatment catalyst, characterized in that: It includes the following steps: mixing a titanium dioxide precursor with a solvent to hydrolyze and form a titanium dioxide sol; Adding nanocarbon and a soluble salt of a noble metal to the titanium dioxide sol and dispersing the nanocarbon to obtain an M@C / TiO2 sol, wherein the nanocarbon comprises one or more of carbon nanotubes, graphene, and carbon fibers, and M is a noble metal; solidifying the M@C / TiO2 sol gel and heating and drying it to obtain M@C / TiO2 crystals; The M@C / TiO2 crystals are ground into powder, and then subjected to light irradiation and calcination to obtain an M@TiO2 powder catalyst.

2. The method for preparing a hydrogen internal combustion engine post-treatment catalyst according to claim 1, wherein: The titanium dioxide precursor includes one or more of butyl titanate, titanium ethoxide, and titanium isopropoxide; And / or, the solvent includes one or more of anhydrous ethanol, methanol, acetone, and ethyl acetate; And / or, the noble metal soluble salt includes one or more of noble metal nitrates and noble metal sulfates; And / or, the noble metal M includes one or more of Pt, Pd, Rh and Ir.

3. The method for preparing a hydrogen internal combustion engine post-treatment catalyst according to claim 1, wherein: The volume ratio of the titanium dioxide precursor to the solvent is 1:2-5.

4. The method for preparing a hydrogen internal combustion engine post-treatment catalyst according to claim 1, wherein: The amount of nanocarbon added is 1% to 5% of the mass of the titanium dioxide precursor; And / or, the amount of the noble metal soluble salt added is 1% to 4% of the mass of the titanium dioxide precursor.

5. The method for preparing a hydrogen internal combustion engine post-treatment catalyst according to claim 1, wherein: Dispersing at a speed of 3000 r / min to 6000 r / min to obtain M@C / TiO2 sol; And / or, gel curing includes: freezing the M@C / TiO2 sol at a temperature of -35°C to -25°C for 3 to 6 hours, and sublimating and curing it under a vacuum degree of 0.1 to 0.001 Pa; And / or, the heating and drying includes: heating and drying at a temperature of 60° C. to 80° C. for 8 hours.

6. The method for preparing a hydrogen internal combustion engine post-treatment catalyst according to claim 1, wherein: The illumination includes: irradiating under natural light for 2 hours to 8 hours.

7. The method for preparing a hydrogen internal combustion engine post-treatment catalyst according to claim 1, wherein: The calcination comprises: calcining at a temperature of 400° C. to 600° C. for 2 to 6 hours.

8. The method for preparing a hydrogen internal combustion engine post-treatment catalyst according to claim 1, wherein: The titanium dioxide precursor is mixed with a solvent to be hydrolyzed and form a titanium dioxide sol, specifically comprising: mixing the titanium dioxide precursor with the solvent, stirring for 3 to 6 hours, and ultrasonically vibrating to form the titanium dioxide sol.

9. A hydrogen internal combustion engine post-treatment catalyst, characterized in that: The catalyst is prepared by the method for preparing a hydrogen internal combustion engine post-treatment catalyst as claimed in any one of claims 1 to 8.

10. A catalytic system, characterized in that: The catalyst comprises a carrier, wherein the carrier is provided with the hydrogen internal combustion engine after-treatment catalyst as claimed in claim 9, and a Cu-based molecular sieve or a V-based catalyst.

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