A catalyst for purifying exhaust gas of an automobile and a method for preparing the same

Abstract

The application relates to a catalyst for automobile exhaust purification and a preparation method thereof, and the preparation method comprises the following steps: (1) mixing a silicon source, water and a template agent to obtain a mixed solution A, and performing first heat treatment on the mixed solution A to obtain a treated mixed solution A; (2) mixing a complex containing platinum and an auxiliary active metal with the treated mixed solution A to obtain a mixed solution B, and sequentially performing second heat treatment, first crystallization treatment and first drying treatment on the mixed solution B to obtain a catalyst precursor; (3) sequentially performing calcination treatment and reduction treatment on the catalyst precursor to obtain a pretreated catalyst; and (4) mixing the pretreated catalyst, a silicon source, water and a fluorine source to obtain a mixed solution C, and sequentially performing third heat treatment, second crystallization treatment and second drying treatment on the mixed solution C to obtain the catalyst. The catalyst prepared by the method has good high-temperature resistance and low light-off temperature.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automobile exhaust catalysts, in particular to a catalyst for automobile exhaust purification and a preparation method thereof. BACKGROUND

[0002] The automobile exhaust treatment mainly adopts the technology route of Three-Way Catalyst + Gasoline Particulate Filter (TWC+GPF). Among them, zeolite molecular sieve as a catalyst carrier will remain mainstream in the future due to its excellent performance, and its amount will be significantly improved with the increase of the number of catalysts. The active metal components in the catalyst, such as Pt, Rh or Pd, etc. noble metals, through oxidation and reduction reactions, can convert the three main pollutants in engine exhaust: carbon monoxide (CO), hydrocarbons and nitrogen oxides (NO x ), into water (H2O), carbon dioxide (CO2) and nitrogen (N2) at the same time. However, the existing catalysts also have obvious limitations: one is high cost, and the other is relatively low high-temperature resistance, which still needs to be further optimized and improved in practical application.

[0003] CN117443433A discloses a kind of S-1 molecular sieve encapsulated metal low carbon alkane dehydrogenation catalyst and its preparation method and application, its preparation method includes the following steps: (1) the preparation of S-1 molecular sieve: take deionized water, template agent, alkali metal source, silicon source and stir uniformly, obtain uniform mixed sol; then the mixed sol is crystallized at 140~180 ℃ for 24~72 hours, after cooling, obtain crystallization slurry, after drying, obtain S-1 molecular sieve carrier;(2) preparation of impregnation solution: take deionized water, metal source, chelating agent and stir uniformly in 25~35 ℃ temperature range, obtain impregnation solution;(3) the impregnation solution obtained in step (2) is impregnated with S-1 molecular sieve carrier obtained in step (1) at 30~60 ℃, the mass ratio of impregnation solution to S-1 molecular sieve carrier is (2~5):1, the impregnation time is 3~9 hours, after drying at 70~90 ℃, obtain dry gel material, and control the water mass percentage of dry gel material between 17~25%;(4) transfer the dry gel material obtained in step (3) to the crystallization kettle, and carry out dry gel crystallization reaction at 140~180 ℃ for 24~72 hours, to obtain crystallization product;(5) after drying, molding, calcining under nitrogen atmosphere, oxidation calcining under air atmosphere and hydrogen atmosphere reduction, obtain S-1 molecular sieve encapsulated metal low carbon alkane dehydrogenation catalyst. At the same time, it discloses that the dehydrogenation reaction performance of the catalyst is evaluated at 580 ℃, and whether the catalyst will be inactivated at 800~900 ℃ is not disclosed.

[0004] CN113070098A discloses a preparation method of an element modified BEA / MOR eutectic molecular sieve composite catalyst, comprising the following steps: S1: adding water, an aluminum source, a base, a silicon source, a template agent and a fluorine source into a polytetrafluoroethylene lining in a certain proportion, stirring uniformly for 30-60 min to obtain a hydrothermal synthesis system; S2: transferring the hydrothermal synthesis system obtained in S1 into a reaction kettle for crystallization treatment, and post-treating the crystallization product to obtain the BEA / MOR eutectic molecular sieve in one step; S3: ion exchanging the BEA / MOR eutectic molecular sieve obtained in step S2 with an ammonium salt solution of 1-4 mol / L at 20-100℃ for 0.5-12 h, filtering, washing, and then calcining in a muffle furnace at 300-700℃ for 1-10 h; S4: mixing the product obtained in step S3 with a solution containing 0.001-5 mol / L of active metal elements by equal volume impregnation method, uniformly mixing, drying at 30-100℃ for 10-20 h, and then calcining in a muffle furnace at 400-600℃ for 2-5 h to obtain the corresponding catalyst. Meanwhile, it discloses the use of the catalyst for selective hydrogenation of acetylene at 30-350℃, but does not disclose whether the catalyst will be deactivated at 800-900℃.

[0005] In summary, there is a need to develop a catalyst with good high-temperature resistance and low light-off temperature, which can be used for purification of automobile exhaust. SUMMARY

[0006] To solve the above technical problems, the present application provides a catalyst for purification of automobile exhaust and a preparation method thereof. The present application first synthesizes a molecular sieve loaded with platinum and active metal by one-pot method to obtain a pretreated catalyst, and further optimizes the defects of the molecular sieve in the pretreated catalyst by liquid synthesis mediation modification to obtain a catalyst for purification of automobile exhaust with good high-temperature resistance and low light-off temperature.

[0007] To achieve this purpose, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a preparation method of a catalyst for purification of automobile exhaust, comprising the following steps:

[0009] (1) first mixing a silicon source, water and a template agent to obtain a mixed solution A; and first heat treating the mixed solution A to obtain a treated mixed solution A;

[0010] (2) second mixing a complex containing platinum and an active metal with the treated mixed solution A to obtain a mixed solution B, and sequentially second heat treating, first crystallizing and first drying the mixed solution B to obtain a catalyst precursor;

[0011] (3) sequentially performing calcination treatment and reduction treatment on the catalyst precursor to obtain a pretreated catalyst;

[0012] (4) performing third mixing on the pretreated catalyst, a silicon source, water and a fluorine source to obtain a mixed solution C, and sequentially performing third heat treatment, second crystallization treatment and second drying treatment on the mixed solution C to obtain the catalyst.

[0013] The application first directly synthesizes a molecular sieve loaded with platinum and a promoter active metal by using a one-pot method to obtain a pretreated catalyst, then performs third mixing on the pretreated catalyst, a silicon source, water and a fluorine source, and sequentially performs third heat treatment, second crystallization treatment and second drying treatment on the mixed solution to further optimize the defects of the molecular sieve in the pretreated catalyst through liquid synthesis-mediated modification, so as to obtain an automobile exhaust purification catalyst with good high-temperature resistance and low light-off temperature. The preparation method of the catalyst provided by the application is simple and controllable, easy to scale up, suitable for industrial application, and has a wide application prospect in automobile exhaust treatment.

[0014] As a preferred technical solution of the application, the preparation of the platinum-containing and promoter active metal-containing complex includes: performing pre-mixing on a platinum source, a promoter active metal source, a potassium source and an amine salt to obtain the platinum-containing and promoter active metal-containing complex.

[0015] In the application, compared with other metals, the platinum-containing and promoter active metal-containing complex formed by the platinum source and the promoter active metal is more stable, and the melting point of platinum is 1768℃, so when the temperature of automobile exhaust reaches 800℃ or above, the catalyst prepared by using platinum as an active component in the application can still maintain the non-sintering of active sites.

[0016] Preferably, the platinum source includes any one or a combination of at least two of chloroplatinic acid, platinum acetylacetonate, sodium chloroplatinate or potassium chloroplatinate, wherein a typical but non-limiting combination includes: a combination of chloroplatinic acid and platinum acetylacetonate, a combination of chloroplatinic acid and sodium chloroplatinate, a combination of chloroplatinic acid and potassium chloroplatinate, a combination of platinum acetylacetonate and sodium chloroplatinate, a combination of platinum acetylacetonate and potassium chloroplatinate, a combination of sodium chloroplatinate and potassium chloroplatinate, a combination of chloroplatinic acid, platinum acetylacetonate and sodium chloroplatinate, a combination of chloroplatinic acid, platinum acetylacetonate and potassium chloroplatinate, a combination of chloroplatinic acid, sodium chloroplatinate and potassium chloroplatinate, a combination of platinum acetylacetonate, sodium chloroplatinate and potassium chloroplatinate, and a combination of chloroplatinic acid, platinum acetylacetonate, sodium chloroplatinate and potassium chloroplatinate.

[0017] Preferably, the promoter metal source comprises a metal soluble salt corresponding to the promoter metal, the metal soluble salt comprising any one or a combination of metal chloride, metal nitrate or metal sulfate, wherein typical but non-limiting combinations include: a combination of metal chloride and metal nitrate, a combination of metal chloride and metal sulfate, a combination of metal nitrate and metal sulfate, a combination of metal chloride, metal nitrate and metal sulfate.

[0018] Preferably, the promoter metal in the promoter metal source comprises any one or a combination of nickel, copper, iron or tin, wherein typical but non-limiting combinations include: a combination of nickel and copper, a combination of nickel and iron, a combination of nickel and tin, a combination of copper and iron, a combination of copper and tin, a combination of iron and tin, a combination of nickel, copper and iron, a combination of nickel, copper and tin, a combination of nickel, iron and tin, a combination of copper, iron and tin, a combination of nickel, copper, iron and tin.

[0019] Preferably, the potassium source comprises potassium chloride and / or potassium nitrate.

[0020] Preferably, the amine salt comprises ethylenediamine.

[0021] It should be noted that ethylenediamine is a bidentate ligand, the two nitrogen atoms of which can simultaneously coordinate with platinum ions to form stable chelates, because bidentate ligands are more firmly bound than monodentate ligands, which can reduce the loss of free platinum ions, improve the stability of the complex, and at the same time, the complex is not easy to dissociate in solution, which can avoid platinum precipitation. Further, the coordination of ethylenediamine can produce a synergistic effect with the potassium source, wherein potassium ions can enhance the dispersibility of platinum and induce an electron-rich chemical environment to balance the charge of platinum complexes, thereby improving their solubility in water or polar solvents. In subsequent reduction treatment, potassium ions can stabilize the intermediate state through electrostatic interaction, promoting the formation of highly dispersed platinum nanoparticles.

[0022] Preferably, the molar ratio of the platinum source, the promoter metal source, the potassium source and the amine salt in the premixing process is 1:(3~10):(5~10):(50~100), for example, it can be 1:3:5:50, 1:3:10:50, 1:6:8:80, 1:10:5:100 or 1:10:10:100, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0023] As a preferred technical solution of the present application, the silicon source comprises n-propylsilane.

[0024] Preferably, the template agent comprises tetrapropylamine.

[0025] Preferably, the mass ratio of the silicon source, water and template agent in the first mixing process is 1: (200-1000) : (2-300), for example, it can be 1:200:2, 1:200:300, 1:600:200, 1:1000:2 or 1:1000:300, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0026] As a preferred technical solution of the present application, the temperature of the first heat treatment, the second heat treatment and the third heat treatment is independently 20-80℃, for example, it can be 20℃, 40℃, 50℃, 60℃ or 80℃, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0027] Preferably, the first heat treatment, the second heat treatment and the third heat treatment are each independently carried out under stirring.

[0028] Preferably, the stirring speed is 500-1000 rpm, for example, it can be 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm or 1000 rpm, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0029] Preferably, the time of the first heat treatment is 1-3h, for example, it can be 1h, 1.5h, 2h, 2.5h or 3h, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0030] Preferably, the mass ratio of the complex containing platinum and a promoter metal to the silicon source in the treated mixed solution A in the second mixing process is 1: (200-1000), for example, it can be 1:200, 1:400, 1:600, 1:800 or 1:1000, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0031] The present application limits the mass ratio of the complex containing platinum and a promoter metal to the silicon source in the treated mixed solution A in the second mixing process to 1: (200-1000), so that the prepared catalyst has good high-temperature resistance, and at the same time, the platinum nanoparticles in the catalyst are uniformly dispersed and agglomeration is avoided; if the mass ratio is less than 1:1000, i.e. the content of platinum in the catalyst is too low and the content of silicon is too high, the active sites will be insufficient, leading to reduced CO and NO x conversion and decreased catalytic efficiency; at the same time, excessive silicon will make the acid sites adsorb NO xIf the mass ratio of the two is greater than 1:200, i.e. the content of silicon in the catalyst is too small and the content of platinum is too large, the structural stability and oxygen storage capacity of the catalyst will be weakened, and the platinum particles will also be aggregated. In addition, the increase of the content of platinum will increase the preparation cost of the catalyst.

[0032] Preferably, the time of the second heat treatment is 2-10h, for example, can be 2h, 4h, 6h, 8h or 10h, but not limited to the listed values, other values not listed in the above numerical range are also applicable.

[0033] Preferably, the time of the third heat treatment is 1-5h, for example, can be 1h, 2h, 3h, 4h or 5h, but not limited to the listed values, other values not listed in the above numerical range are also applicable.

[0034] As a preferred technical solution of the present application, the temperature of the first crystallization treatment and the second crystallization treatment is independently 150-200℃, for example, can be 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃, but not limited to the listed values, other values not listed in the above numerical range are also applicable.

[0035] Preferably, the time of the first crystallization treatment is 24-96h, for example, can be 24h, 48h, 72h or 96h, but not limited to the listed values, other values not listed in the above numerical range are also applicable.

[0036] Preferably, the time of the second crystallization treatment is 2-8h, for example, can be 2h, 4h, 6h or 8h, but not limited to the listed values, other values not listed in the above numerical range are also applicable.

[0037] Preferably, the temperature of the first drying treatment and the second drying treatment is independently 60-150℃, for example, can be 60℃, 80℃, 100℃, 120℃, 140℃ or 150℃, but not limited to the listed values, other values not listed in the above numerical range are also applicable.

[0038] Preferably, the time of the first drying treatment and the second drying treatment is independently 5-10h, for example, can be 5h, 6h, 7h, 8h, 9h or 10h, but not limited to the listed values, other values not listed in the above numerical range are also applicable.

[0039] Preferably, the temperature of the calcination treatment is 400-600℃, for example, it can be 400℃, 450℃, 500℃, 550℃ or 600℃, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0040] Preferably, the time of the calcination treatment is 5-10h, for example, it can be 5h, 6h, 7h, 8h, 9h or 10h, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0041] Preferably, the temperature of the reduction treatment is 350-650℃, for example, it can be 350℃, 450℃, 550℃ or 650℃, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0042] Preferably, the time of the reduction treatment is 1.5-3h, for example, it can be 1.5h, 2h, 2.5h or 3h, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0043] Preferably, the atmosphere of the reduction treatment comprises hydrogen.

[0044] Preferably, the fluorine source comprises any one or a combination of at least two of ammonium fluoride, tetramethylammonium fluoride or tetraethylammonium fluoride, wherein a typical but non-limiting combination comprises a combination of ammonium fluoride and tetramethylammonium fluoride, a combination of ammonium fluoride and tetraethylammonium fluoride, a combination of tetramethylammonium fluoride and tetraethylammonium fluoride, a combination of ammonium fluoride, tetramethylammonium fluoride and tetraethylammonium fluoride.

[0045] Preferably, the mass ratio of the pretreated catalyst, the silicon source, water and the fluorine source in the third mixing process is 1:(1.5-3):(10-50):(1.5-3), for example, it can be 1:1.5:10:1.5, 1:1.5:50:3, 1:2:30:2, 1:3:10:3 or 1:3:50:3, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0046] Preferably, the preparation method further comprises a first washing treatment between the first crystallization treatment and the first drying treatment.

[0047] After the first crystallization treatment, the present application cools to room temperature, and the material after the first crystallization treatment is subjected to a first washing treatment, washed to neutral, and then subjected to a first drying treatment.

[0048] Preferably, the preparation method further comprises a second washing treatment between the second crystallization treatment and the second drying treatment.

[0049] After the second crystallization treatment is completed, the second crystallization treated material is cooled to room temperature, and a second washing treatment is performed to wash the second crystallization treated material to neutral, and a second drying treatment is performed.

[0050] Preferably, the washing agent of the first washing treatment and the second washing treatment each independently comprises any one or a combination of at least two of water, methanol, ethanol or acetone, wherein typical but non-limiting combinations include: a combination of water and methanol, a combination of water and ethanol, a combination of water and acetone, a combination of water, methanol and acetone, a combination of water, ethanol and acetone.

[0051] Preferably, the preparation method comprises the following steps:

[0052] (1) Pre-mixing a platinum source, an auxiliary active metal source, a potassium source and an amine salt according to a mass ratio of 1: (3-10): (5-10): (50-100) to obtain a complex containing platinum and auxiliary active metal;

[0053] (2) First mixing a silicon source, water and a template agent according to a mass ratio of 1: (200-1000): (2-300) to obtain a mixed solution A; and performing a first heat treatment on the mixed solution A at a temperature of 20-80°C for 1-3h to obtain a treated mixed solution A;

[0054] (3) Second mixing the complex containing platinum and auxiliary active metal with the treated mixed solution A according to a mass ratio of 1: (200-1000) to obtain a mixed solution B, and performing a second heat treatment on the mixed solution B at a temperature of 20-80°C for 2-10h to obtain a treated mixed solution B; sequentially performing a first crystallization treatment at a temperature of 150-200°C for 24-96h, a first washing treatment and a first drying treatment at a temperature of 60-150°C for 5-10h on the treated mixed solution B to obtain a catalyst precursor;

[0055] (4) Sequentially performing a calcination treatment at a temperature of 400-600°C for 5-10h and a reduction treatment at a temperature of 350-650°C for 1.5-3h on the catalyst precursor to obtain a pretreated catalyst;

[0056] (5) mixing the pretreatment catalyst, the silicon source, the water and the fluorine source according to a mass ratio of 1: (1.5-3): (10-50): (1.5-3) to obtain a mixed solution C, and performing a third heat treatment on the mixed solution C at a temperature of 20-80 ℃ for 1-5 h; obtaining a treated mixed solution C, and sequentially performing a second crystallization treatment at a temperature of 150-200 ℃ for 2-8 h, a second washing treatment and a second drying treatment at a temperature of 60-150 ℃ for 5-10 h on the treated mixed solution C, to obtain the catalyst;

[0057] Step (1) and step (2) have no order.

[0058] In a second aspect, the present application provides a catalyst for automobile exhaust purification, which is prepared by the preparation method of the catalyst for automobile exhaust purification in the first aspect.

[0059] The catalyst provided by the present application has good high-temperature resistance, low light-off temperature, and wide application prospect in automobile exhaust treatment.

[0060] As a preferred technical solution of the present application, the catalyst comprises a carrier, and an active component and an auxiliary active component supported on the carrier.

[0061] Preferably, the carrier comprises a zeolite molecular sieve.

[0062] Preferably, the active component comprises platinum.

[0063] Preferably, the auxiliary active component comprises any one or a combination of at least two of nickel, copper, iron or tin, wherein a typical but non-limiting combination comprises: a combination of nickel and copper, a combination of nickel and iron, a combination of nickel and tin, a combination of copper and iron, a combination of copper and tin, a combination of iron and tin, a combination of nickel, copper and iron, a combination of nickel, copper and tin, a combination of nickel, iron and tin, a combination of copper, iron and tin, and a combination of nickel, copper, iron and tin.

[0064] As a preferred technical solution of the present application, the catalyst has a crystalline phase structure.

[0065] Preferably, the average particle size D50 of the active component in the catalyst is 1-10 nm, for example, can be 1 nm, 2 nm, 4 nm, 6 nm, 8 nm or 10 nm, but is not limited to the listed values, and other values not listed in the above value range are also applicable.

[0066] The present application can make the atomic proportion of the active component on the surface of the catalyst large, expose more active sites, and improve the conversion rate of CO and NOx by preparing a catalyst with an average particle size D50 of the active component of 1-10 nm. xThe average particle size of the active component is 1-10 nm, the active component is firmly anchored on the carrier, and the active component is not easy to agglomerate at high temperature (above 800℃); if the average particle size of the active component is less than 1 nm, the active component particles will easily aggregate through surface diffusion at high temperature, resulting in poor thermal stability of the catalyst; if the average particle size of the active component is greater than 10 nm, the proportion of active component atoms on the surface of the catalyst will decrease, and the catalytic activity will decrease.

[0067] Preferably, the catalyst comprises 99.2-99.6% of the carrier, 0.3-0.4% of the active component, and 0.1-0.5% of the active component, based on 100% of the mass of the catalyst, wherein the mass content of the carrier is 99.2-99.6%, for example, it can be 99.2%, 99.3%, 99.4%, 99.5%, or 99.6%, the mass content of the active component is 0.3-0.4%, for example, it can be 0.3%, 0.32%, 0.35%, 0.37%, 0.38%, or 0.4%, and the mass content of the active component is 0.1-0.5%, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, or 0.5%, but not limited to the listed values, other values not listed in the above value range are also applicable.

[0068] Preferably, the particle size of the catalyst is 300-460 nm, for example, it can be 300 nm, 320 nm, 340 nm, 360 nm, 380 nm, 400 nm, 420 mm, 440 mm, or 460 mm, but not limited to the listed values, other values not listed in the above value range are also applicable.

[0069] Preferably, the pore volume of the catalyst is 0.15-0.50 cm 3 / g, for example, it can be 0.15 cm 3 / g, 0.20 cm 3 / g, 0.30 cm 3 / g, 0.40 cm 3 / g, 0.45 cm 3 / g, or 0.50 cm 3 / g, but not limited to the listed values, other values not listed in the above value range are also applicable.

[0070] Preferably, the specific surface area of the catalyst is 180-340 m 2 / g, for example, it can be 180 m 2 / g, 200 m 2 / g, 250 m 2 / g, 300 m 2 / g, or 340 m 2but are not limited to the recited numerical values, other non-recited numerical values within the above numerical range are also applicable.

[0071] Compared with the prior art, the present application has at least the following beneficial effects:

[0072] (1) The automobile exhaust purification catalyst prepared by the present application has good high-temperature resistance and low light-off temperature, and the service life of the catalyst at 800℃ can reach 800h or more, and the T 50 can be controlled within 100℃;

[0073] (2) The preparation method of the catalyst provided by the present application is simple and controllable, easy to scale up, suitable for industrial application, and has wide application prospect in automobile exhaust treatment. BRIEF DESCRIPTION OF DRAWINGS

[0074] Figure 1 is the SEM diagram of the catalyst provided by Example 1 of the present application.

[0075] Figure 2 is the TEM diagram of the catalyst provided by Example 1 of the present application.

[0076] Figure 3 is the XRD spectrum of the catalyst provided by Example 1 of the present application.

[0077] Figure 4 is the reaction activity diagram of the catalyst provided by Example 1 of the present application. DETAILED DESCRIPTION

[0078] The technical solutions of the present application will be further described below by combining with the drawings and through specific embodiments. However, the following examples are only simple examples of the present application, and do not represent or limit the protection scope of the present application, and the protection scope of the present application is subject to the claims.

[0079] Example 1

[0080] The present embodiment provides a catalyst for automobile exhaust purification, which comprises a zeolite molecular sieve carrier, an active component platinum and an auxiliary active component nickel, and the catalyst comprises 99.2% of zeolite molecular sieve, 0.35% of platinum and 0.45% of nickel, based on 100% of the mass of the catalyst.

[0081] As shown in Figure 1 , the particle size of the catalyst is 350nm, and as shown in Figure 2 , the average particle size D50 of the active component platinum in the catalyst is 1.5nm.

[0082] As shown in Figure 3 , the catalyst has a crystalline structure, and the pore volume of the catalyst is 0.35cm 3 / g, and the specific surface area of the catalyst is 320 m 2 / g.

[0083] The embodiment also provides a preparation method of the catalyst for automobile exhaust purification, and the preparation method comprises the following steps:

[0084] (1) Pre-mix chloroplatinic acid, nickel nitrate, potassium chloride and ethylenediamine according to a mass ratio of 1:5:8:70 to obtain a complex containing platinum and auxiliary active metals;

[0085] (2) First mix n-propylsilane, water and tetrapropylamine according to a mass ratio of 1:600:150 to obtain a mixed solution A; and perform first heat treatment on the mixed solution A at a temperature of 50 ℃ for 2 h at a rotating speed of 500 rpm; and obtain a treated mixed solution A;

[0086] (3) Second mix the complex containing platinum and auxiliary active metals with the treated mixed solution A according to a mass ratio of 1:600 to obtain a mixed solution B; and perform second heat treatment on the mixed solution B at a temperature of 60 ℃ for 5 h at a rotating speed of 500 rpm; and obtain a treated mixed solution B; and sequentially perform first crystallization treatment at a temperature of 180 ℃ for 60 h, first washing treatment and first drying treatment at a temperature of 100 ℃ for 8 h on the treated mixed solution B, to obtain a catalyst precursor; wherein the washing agent used in the first washing treatment is water and acetone in a volume ratio of 1:1;

[0087] (4) Sequentially perform calcination treatment at a temperature of 500 ℃ for 8 h and reduction treatment at a temperature of 500 ℃ for 2 h in a hydrogen atmosphere on the catalyst precursor, to obtain a pretreated catalyst;

[0088] (5) Third mix the pretreated catalyst, n-propylsilane, water and ammonium fluoride according to a mass ratio of 1:2:30:2 to obtain a mixed solution C; and perform third heat treatment on the mixed solution C at a temperature of 40 ℃ for 3.5 h at a rotating speed of 500 rpm; and obtain a treated mixed solution C; and sequentially perform second crystallization treatment at a temperature of 200 ℃ for 2 h, second washing treatment and second drying treatment at a temperature of 150 ℃ for 5 h on the treated mixed solution C, to obtain the catalyst; wherein the washing agent used in the second washing treatment is water and ethanol in a volume ratio of 1:1;

[0089] Steps (1) and (2) have no sequence.

[0090] Embodiment 2

[0091] The embodiment provides a catalyst for automobile exhaust purification, which comprises a zeolite molecular sieve carrier, an active component platinum and an active component copper, wherein the catalyst comprises the zeolite molecular sieve 99.4%, the platinum 0.32% and the copper 0.28% based on 100% of the mass of the catalyst;

[0092] The particle size of the catalyst is 300 nm, and the average particle size D50 of the active component platinum in the catalyst is 2 nm;

[0093] The catalyst has a crystal phase structure, the pore volume of the catalyst is 0.45 cm 3 / g, and the specific surface area of the catalyst is 300 m 2 / g.

[0094] The embodiment also provides a preparation method of the catalyst for automobile exhaust purification, which comprises the following steps:

[0095] (1) acetylacetone platinum, copper sulfate, potassium chloride and ethylenediamine are premixed according to a mass ratio of 1:3:5:100 to obtain a complex containing platinum and an active metal;

[0096] (2) n-propylsilane, water and tetrapropylamine are first mixed according to a mass ratio of 1:200:300 to obtain a mixed solution A; and the mixed solution A is subjected to first heat treatment at a temperature of 80 DEG C for 1 h at a rotating speed of 800 rpm to obtain a treated mixed solution A;

[0097] (3) the complex containing platinum and an active metal is second mixed with the treated mixed solution A according to a mass ratio of 1:200 to obtain a mixed solution B, and the mixed solution B is subjected to second heat treatment at a temperature of 20 DEG C for 10 h at a rotating speed of 800 rpm to obtain a treated mixed solution B; the treated mixed solution B is sequentially subjected to first crystallization treatment at a temperature of 150 DEG C for 96 h, first washing treatment and first drying treatment at a temperature of 150 DEG C for 5 h to obtain a catalyst precursor; wherein the washing agent used in the first washing treatment is water and acetone in a volume ratio of 2:1;

[0098] (4) the catalyst precursor is sequentially subjected to calcination treatment at a temperature of 400 DEG C for 10 h and reduction treatment at a temperature of 650 DEG C for 1.5 h in a hydrogen atmosphere to obtain a pretreated catalyst;

[0099] (5) the pre-treatment catalyst, n-propylsilicon, water and tetramethylammonium fluoride are mixed in a mass ratio of 1:1.5:50:3 to obtain a mixed solution C, the mixed solution C is subjected to a third heat treatment at a temperature of 40℃ for 3.5h at a rotation speed of 800rpm; a treated mixed solution C is obtained, and the treated mixed solution C is sequentially subjected to a second crystallization treatment at a temperature of 180℃ for 5h, a second washing treatment and a second drying treatment at a temperature of 60℃ for 10h, to obtain the catalyst, wherein the washing agent used in the second washing treatment is water and methanol in a volume ratio of 2:1;

[0100] Steps (1) and (2) have no sequence.

[0101] Example 3

[0102] The catalyst for purifying automobile exhaust provided in the embodiment includes a zeolite molecular sieve carrier, an active component platinum and an auxiliary active component iron, and the catalyst includes 99.6% of the zeolite molecular sieve, 0.3% of the platinum and 0.1% of the iron, based on 100% of the mass of the catalyst.

[0103] The particle size of the catalyst is 400nm, and the average particle size D50 of the active component platinum in the catalyst is 1nm.

[0104] The catalyst has a crystal phase structure, the pore volume of the catalyst is 0.38cm 3 / g, and the specific surface area of the catalyst is 340m 2 / g.

[0105] The embodiment also provides a preparation method of the catalyst for purifying automobile exhaust, and the preparation method includes the following steps:

[0106] (1) sodium chloroplatinate, ferric chloride, potassium chloride and ethylenediamine are premixed in a mass ratio of 1:10:10:50 to obtain a complex containing platinum and an auxiliary active metal;

[0107] (2) n-propylsilicon, water and tetrapropylamine are mixed in a mass ratio of 1:1000:2 to obtain a mixed solution A; and the mixed solution A is subjected to a first heat treatment at a temperature of 20℃ for 3h at a rotation speed of 900rpm; a treated mixed solution A is obtained;

[0108] (3) the platinum and promoter metal containing complex and the treated mixture A are second mixed according to a mass ratio of 1:1000 of the platinum and promoter metal containing complex to n-propylsilane, to obtain mixture B, and the mixture B is subjected to a second heat treatment at a temperature of 80℃ for 2h and a rotation speed of 900rpm, to obtain treated mixture B; the treated mixture B is sequentially subjected to a first crystallization treatment at a temperature of 200℃ for 24h, a first washing treatment and a first drying treatment at a temperature of 60℃ for 10h, to obtain a catalyst precursor; wherein the washing agent used in the first washing treatment is water, methanol and acetone at a volume ratio of 1:1:1;

[0109] (4) the catalyst precursor is sequentially subjected to a calcination treatment at a temperature of 600℃ for 5h and a reduction treatment at a temperature of 350℃ for 3h in a hydrogen atmosphere, to obtain a pretreated catalyst;

[0110] (5) the pretreated catalyst, n-propylsilane, water and tetraethylammonium fluoride are third mixed according to a mass ratio of 1:3:10:1.5, to obtain mixture C, and the mixture C is subjected to a third heat treatment at a temperature of 80℃ for 1h and a rotation speed of 900rpm; treated mixture C is obtained, and the treated mixture C is sequentially subjected to a second crystallization treatment at a temperature of 150℃ for 8h, a second washing treatment and a second drying treatment at a temperature of 100℃ for 8h, to obtain the catalyst; wherein the washing agent used in the second washing treatment is water, ethanol and acetone at a volume ratio of 1:1:1;

[0111] Steps (1) and (2) have no order.

[0112] Example 4

[0113] The present example provides a catalyst for automobile exhaust purification, which is identical to Example 1 except that the ethylenediamine in step (1) is replaced by diethylenetriamine.

[0114] Example 5

[0115] The present example provides a catalyst for automobile exhaust purification, which is identical to Example 1 except that the ethylenediamine in step (1) is replaced by ammonia.

[0116] Example 6

[0117] The present example provides a catalyst for automobile exhaust purification, which is identical to Example 1 except that the mass ratio of the platinum and promoter metal containing complex to n-propylsilane in the second mixing process in step (3) is adjusted from 1:600 to 1:100.

[0118] Example 7

[0119] The present example provides a catalyst for automobile exhaust purification, which is identical to Example 1 except that the mass ratio of the complex containing platinum and the auxiliary active metal to n-propylsilicon in the second mixing process of step (3) is adjusted from 1:600 to 1:1500.

[0120] Example 8

[0121] The present example provides a catalyst for automobile exhaust purification, which is identical to Example 1 except that the average particle size D50 of the active component platinum in the catalyst is 20 nm, i.e. the preparation method does not include ethylenediamine in the premixing process of step (1).

[0122] Comparative Example 1

[0123] The present comparative example provides a catalyst for automobile exhaust purification, which is identical to Example 1 except that the preparation method does not include step (5), i.e. the pretreated catalyst is recorded as the catalyst.

[0124] Comparative Example 2

[0125] The present comparative example provides a catalyst for automobile exhaust purification, which is identical to Example 1 except that the preparation method does not include step (5), and step (1) is adjusted to: premixing according to the mass ratio of 1:5:8:70:3 chloroplatinic acid, nickel nitrate, potassium chloride, ethylenediamine and ammonium fluoride, i.e. maintaining the mass ratio of chloroplatinic acid and ammonium fluoride in the preparation process.

[0126] Comparative Example 3

[0127] The present comparative example provides a catalyst for automobile exhaust purification, which is identical to Example 1 except that the preparation method does not include step (5), and step (2) is adjusted to: first mixing according to the mass ratio of 1:600:150:50 n-propylsilicon, water, tetrapropylamine and ammonium fluoride, i.e. maintaining the mass ratio of chloroplatinic acid and ammonium fluoride in the preparation process.

[0128] Comparative Example 4

[0129] The present comparative example provides a catalyst for automobile exhaust purification, which is identical to Example 1 except that the chloroplatinic acid in step (1) is replaced by sodium aluminate of the same mass.

[0130] The characteristics of the catalysts for purifying automobile exhaust of Examples 4-8 and Comparative Examples 1-4 of the present application are shown in Table 1, wherein the content of platinum element of the catalysts is obtained by X-ray photoelectron spectroscopy analysis, the specific surface area of the catalysts is obtained by BET test, the pore volume of the catalysts is obtained by N2 adsorption-desorption experiment, the particle size of the catalysts and the active component platinum is obtained by SEM image, and the crystal structure of the catalysts is obtained by XRD spectrum.

[0131] Table 1

[0132]

[0133] The denitration activity experiment of the catalysts prepared by using Examples 1-8 and Comparative Examples 1-4 was carried out at 800℃ on the simulated automobile exhaust. The simulated flue gas contained CO 1500ppm and NO 1500ppm, and the balance gas was argon. 100mg of the catalyst was mixed with 300mg of quartz sand uniformly and was loaded in a quartz tube with an inner diameter of 0.6mm to test the catalytic activity, wherein the test results of Example 1 are shown in Figure 4 , and the T 50 of the catalysts was detected, wherein T 50 is the temperature when the conversion rate of CO reaches 50%.

[0134] After the experiment, the conversion rates of NO and CO were calculated, wherein the calculation formula of the conversion rate of NO is: , wherein [NO] in is the NO concentration at the inlet of the reactor, [NO] out is the NO concentration at the outlet of the reactor, and the conversion rate of CO can be calculated in the same way. The service life of the catalyst was also tested, and the service life of the catalyst was the time when the NO conversion rate was greater than 90% of the initial NO conversion rate. The detection results are shown in Table 2.

[0135] Table 2

[0136]

[0137] From the test results, it can be seen that:

[0138] (1) From Examples 1-3, it can be seen that the present application first synthesizes a molecular sieve loaded with platinum and a promoter active metal by one-pot method to obtain a pretreated catalyst, and then further optimizes the defects of the molecular sieve in the pretreated catalyst by liquid synthesis mediated modification to obtain a T 50 purification catalyst for automobile exhaust with a NO conversion rate of more than 48% and a CO conversion rate of more than 98% at 100℃, and a service life of more than 870h.

[0139] (2) By comparing Example 1 with Examples 4-5, it can be seen that the amine salt used in Example 1 is ethylenediamine, and the T 50 of the catalyst prepared by using the ethylenediamine is 80℃, the service life is 1000h, the conversion rate of NO is 57% and the conversion rate of CO is 100% in the process of treating automobile exhaust; while the amine salt used in Example 4 is diethylenetriamine, and the T 50 of the catalyst prepared by using the diethylenetriamine is 132℃, the service life is 840h, the conversion rate of NO is 13% and the conversion rate of CO is 90% in the process of treating automobile exhaust; the amine salt used in Example 5 is ammonia water, and the T 50 of the catalyst prepared by using the ammonia water is 126℃, the service life is 220h, the conversion rate of NO is 24% and the conversion rate of CO is 96% in the process of treating automobile exhaust. It can be seen that, by selecting ethylenediamine as the amine salt, the two nitrogen atoms of the ethylenediamine can be coordinated with platinum ions at the same time to form a stable chelate, and the complex is not easy to dissociate in solution, so that the precipitation of platinum can be avoided. Further, the coordination of ethylenediamine can produce a synergistic effect with potassium source, and finally a catalyst for purifying automobile exhaust with good high-temperature resistance, low light-off temperature and long service life is prepared.

[0140] (3) By comparing Example 1 with Examples 6-7, it can be seen that the mass ratio of the complex containing platinum and the promoter active metal to n-propylsilicon in the second mixing process in step (3) of Example 1 is 1:600, and the T 50 of the catalyst prepared by using the complex is 80℃, the service life is 1000h, the conversion rate of NO is 57% and the conversion rate of CO is 100% in the process of treating automobile exhaust; while the mass ratio of the complex containing platinum and the promoter active metal to n-propylsilicon in the second mixing process in step (3) of Example 6 is 1:100, and the T 50 of the catalyst prepared by using the complex is 130℃, the service life is 160h, the conversion rate of NO is 28% and the conversion rate of CO is 90% in the process of treating automobile exhaust; the mass ratio of the complex containing platinum and the promoter active metal to n-propylsilicon in the second mixing process in step (3) of Example 7 is 1:1500, and the T 50 of the catalyst prepared by using the complex is 133℃, the service life is 290h, the conversion rate of NO is 21% and the conversion rate of CO is 82% in the process of treating automobile exhaust. It can be seen that, by limiting the mass ratio of the complex containing platinum and the promoter active metal to the silicon source in the mixed solution A after treatment in the second mixing process, the catalyst prepared can have good high-temperature resistance.

[0141] (4) By comparing Example 1 with Example 8, it can be seen that the average particle size of the active component platinum in the catalyst of Example 1 is 1.5nm, and the T 50is 80℃, the service life is 1000h, the conversion rate of NO is 57% and the conversion rate of CO is 100% in the process of treating automobile exhaust; the average particle size of the active component platinum in the catalyst of Example 8 is 20nm, the T 50 is 141℃, the service life is 110h, the conversion rate of NO is 14% and the conversion rate of CO is 85% in the process of treating automobile exhaust, which shows that, by preparing the catalyst with the average particle size of the active component being 1-10nm, the atomic proportion of the active component on the surface of the catalyst can be large, more active sites can be exposed, the conversion efficiency of CO and NO can be improved, and the active component with the average particle size of 1-10nm can be firmly anchored on the carrier and is not easy to agglomerate at high temperature (above 800℃).

[0142] (5) It can be seen from Example 1 and Comparative Examples 1-3 that, by further optimizing the defects of the molecular sieve in the pretreated catalyst through liquid synthesis mediation modification, the automobile exhaust purification catalyst with good high-temperature resistance, low light-off temperature and long service life can be prepared.

[0143] (6) It can be seen from Example 1 and Comparative Example 4 that, by limiting platinum as the active metal, the automobile exhaust purification catalyst with good high-temperature resistance, low light-off temperature and long service life can be prepared.

[0144] In summary, the molecular sieve loaded with platinum is directly synthesized by one-pot method to obtain a pretreated catalyst, and the defects of the molecular sieve in the pretreated catalyst are further optimized through liquid synthesis mediation modification, so that the automobile exhaust purification catalyst with good high-temperature resistance and low light-off temperature can be obtained, the service life of the catalyst at 800℃ can be more than 800h, and the T 50 can be controlled to be less than 100℃.

[0145] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by those skilled in the art, and all of them fall within the protection scope and disclosure scope of the present application.

Claims

1. Use of a catalyst for the purification of exhaust gases from motor vehicles, characterized in that, The preparation method of the catalyst comprises the following steps: (1) a first mixing of a silicon source, water and a template agent to obtain a mixed solution A; and a first heat treatment of the mixed solution A; to obtain a treated mixed solution A; (2) a pre-mixing of a platinum source, an active metal source, a potassium source and ethylenediamine to obtain a complex containing platinum and an active metal; and a second mixing of the complex containing platinum and an active metal with the treated mixed solution A to obtain a mixed solution B, and a second heat treatment, a first crystallization treatment and a first drying treatment of the mixed solution B in sequence to obtain a catalyst precursor; (3) a calcination treatment and a reduction treatment of the catalyst precursor in sequence to obtain a pretreated catalyst; (4) a third mixing of the pretreated catalyst, a silicon source, water and a fluorine source to obtain a mixed solution C, and a third heat treatment, a second crystallization treatment and a second drying treatment of the mixed solution C in sequence to obtain the catalyst; wherein the active metal in the active metal source comprises any one or a combination of at least two of nickel, copper, iron or tin; a mass ratio of the complex containing platinum and an active metal to the silicon source in the treated mixed solution A in the second mixing process is 1:(200-1000).

2. Use according to claim 1, characterized in that, the platinum source comprises any one or a combination of at least two of chloroplatinic acid, platinum acetylacetonate, sodium chloroplatinate or potassium chloroplatinate; the active metal source comprises a metal soluble salt corresponding to the active metal, and the metal soluble salt comprises any one or a combination of at least two of a metal chloride, a metal nitrate or a metal sulfate; the potassium source comprises potassium chloride and / or potassium nitrate; a molar ratio of the platinum source, the active metal source, the potassium source and ethylenediamine in the pre-mixing process is 1:(3-10):(5-10):(50-100).

3. Use according to claim 1 or 2, characterized in that, the silicon source comprises n-propylsilicon; the template agent comprises tetrapropylamine; a mass ratio of the silicon source, water and the template agent in the first mixing process is 1:(200-1000):(2-300).

4. Use according to claim 1, characterized in that, temperatures of the first heat treatment, the second heat treatment and the third heat treatment are each independently 20-80℃; a time of the first heat treatment is 1-3h; a time of the second heat treatment is 2-10h; a time of the third heat treatment is 1-5h.

5. The use according to claim 1, characterized in that, temperatures of the first crystallization treatment and the second crystallization treatment are each independently 150-200℃; a time of the first crystallization treatment is 24-96h; a time of the second crystallization treatment is 2-8h; temperatures of the first drying treatment and the second drying treatment are each independently 60-150℃; times of the first drying treatment and the second drying treatment are each independently 5-10h.

6. The use according to claim 1, characterized in that, a temperature of the calcination treatment is 400-600℃; a time of the calcination treatment is 5-10h; a temperature of the reduction treatment is 350-650℃; a time of the reduction treatment is 1.5-3h; an atmosphere of the reduction treatment comprises hydrogen.

7. The use according to claim 1, characterized in that, the fluorine source comprises any one or a combination of at least two of ammonium fluoride, tetramethylammonium fluoride or tetraethylammonium fluoride; The mass ratio of the pretreatment catalyst, the silicon source, the water and the fluorine source in the third mixing process is 1:(1.5-3):(10-50):(1.5-3).

8. The use according to claim 1, characterized in that, The catalyst comprises a carrier and active components and auxiliary active components supported on the carrier; The carrier comprises a zeolite molecular sieve; The active components comprise platinum; The auxiliary active components comprise any one or a combination of at least two of nickel, copper, iron or tin.

9. Use according to claim 8, characterized in that, The catalyst has a crystalline structure; The average particle size D50 of the active components in the catalyst is 1-10 nm; The catalyst comprises 99.2-99.6% of the carrier, 0.3-0.4% of the active components and 0.1-0.5% of the auxiliary active components, based on 100% of the mass of the catalyst; The particle size of the catalyst is 300-460 nm.

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