Catalyst for purifying automobile exhaust and preparation method thereof

Abstract

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

Description

Technical Field

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

[0002] The main technology used for automobile exhaust treatment is the three-way catalytic converter + gasoline particulate filter (TWC+GPF). Zeolite molecular sieve, as a catalyst carrier, will continue to maintain its mainstream position in the future due to its excellent performance, and its usage will increase significantly with the increase in the number of catalysts. The active metal components in the catalyst, such as precious metals such as Pt, Rh or Pd, can reduce the three main pollutants in engine exhaust: carbon monoxide (CO), hydrocarbons and nitrogen oxides (NOx) through oxidation and reduction reactions. x ), and simultaneously convert it into water (H2O), carbon dioxide (CO2), and nitrogen (N2). However, existing catalysts also have obvious limitations: first, high cost, and second, relatively low high-temperature resistance. These shortcomings still need further optimization and improvement in practical applications.

[0003] CN117443433A discloses an S-1 molecular sieve encapsulated metal low-carbon alkane dehydrogenation catalyst and its preparation method and application. The preparation method comprises the following steps: (1) preparation of S-1 molecular sieve: weighing deionized water, template, alkali metal source, and silicon source and stirring them uniformly to obtain a uniform mixed sol; then crystallizing the mixed sol at 140-180°C for 24-72 hours, cooling to obtain a crystallized slurry, and drying the crystallized slurry to obtain an S-1 molecular sieve carrier; (2) preparation of an impregnation solution: weighing deionized water, metal source, and chelating agent and stirring them uniformly at a temperature range of 25-35°C to obtain an impregnation solution; (3) the impregnation solution obtained in step (2) is heated at 30-60°C. The S-1 molecular sieve carrier obtained in step (1) is impregnated at a temperature of 2 to 5:1 by mass, the impregnation liquid and the S-1 molecular sieve carrier are impregnated for 3 to 9 hours, and the dry glue material is obtained after drying at 70 to 90°C, and the water content of the dry glue material is controlled to be between 17 and 25% by mass; (4) the dry glue material obtained in step (3) is transferred to a crystallization kettle, and the dry glue crystallization reaction is carried out at 140 to 180°C for 24 to 72 hours to obtain a crystallized product; (5) the crystallized product obtained in step (4) is dried, formed, calcined under a nitrogen atmosphere, oxidized calcined under an air atmosphere, and reduced under a hydrogen atmosphere to obtain an 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°C, but does not disclose whether the catalyst will be deactivated at 800 to 900°C.

[0004] CN113070098A discloses a method for preparing an element-modified BEA / MOR eutectic molecular sieve composite catalyst, comprising the following steps: S1: adding water, an aluminum source, an alkali, a silicon source, a template, and a fluorine source in a certain proportion to a polytetrafluoroethylene liner, mixing and stirring for 30 to 60 minutes to obtain a hydrothermal synthesis system; S2: transferring the hydrothermal synthesis system obtained in S1 to a reactor for crystallization treatment, and performing post-treatment on the crystallized product to obtain a BEA / MOR eutectic molecular sieve in one step; S3: adding the hydrothermal synthesis system obtained in step S1 to a reactor for crystallization treatment, and performing post-treatment on the crystallized product to obtain a BEA / MOR eutectic molecular sieve in one step; The BEA / MOR eutectic molecular sieve prepared in step S2 is ion-exchanged with a 1-4 mol / L ammonium salt solution at 20-100°C for 0.5-12 hours, filtered, washed, and then calcined in a muffle furnace at 300-700°C for 1-10 hours. In step S4, the product obtained in step S3 is mixed uniformly with a solution containing 0.001-5 mol / L of an active metal element using an equal volume impregnation method, dried at 30-100°C for 10-20 hours, and then calcined in a muffle furnace at 400-600°C for 2-5 hours to obtain the corresponding catalyst. While the disclosure discloses the selective hydrogenation of acetylene using the catalyst at 30-350°C, it does not disclose whether the catalyst deactivates at 800-900°C.

[0005] In summary, it is necessary to develop a catalyst with good high temperature resistance and low ignition temperature so that it can be used to purify automobile exhaust. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a catalyst for automobile exhaust purification and a preparation method thereof. The present invention first uses a one-pot method to directly synthesize a molecular sieve loaded with platinum and an active metal to obtain a pretreatment catalyst, and further optimizes the defects of the molecular sieve in the pretreatment catalyst through liquid synthesis-mediated modification to obtain an automobile exhaust purification catalyst with good high-temperature resistance and a low ignition temperature.

[0007] To achieve this object, the present invention adopts the following technical solutions:

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

[0009] (1) a silicon source, water, and a template are first mixed to obtain a mixed solution A; and the mixed solution A is first heat-treated to obtain a treated mixed solution A;

[0010] (2) performing a second mixing of the complex containing platinum and the co-active metal with the treated mixed solution A to obtain a mixed solution B, and sequentially performing a second heat treatment, a first crystallization treatment, and a first drying treatment on the mixed solution B to obtain a catalyst precursor;

[0011] (3) performing calcination and reduction treatment on the catalyst precursor in sequence to obtain a pre-treated catalyst;

[0012] (4) The pretreatment catalyst, silicon source, water and fluorine source are mixed for the third time to obtain a mixed solution C, and the mixed solution C is sequentially subjected to a third heat treatment, a second crystallization treatment and a second drying treatment to obtain the catalyst.

[0013] The present invention first utilizes a one-pot process to directly synthesize a molecular sieve loaded with platinum and a promoter metal to obtain a pretreatment catalyst. The pretreatment catalyst, a silicon source, water, and a fluorine source are then subjected to a third mixing step. The mixture is then sequentially subjected to a third heat treatment, a second crystallization treatment, and a second drying treatment. This liquid synthesis-mediated modification further optimizes the defects of the molecular sieve in the pretreatment catalyst, resulting in an automobile exhaust purification catalyst with excellent high-temperature resistance and a low light-off temperature. The catalyst preparation method provided by the present invention is simple and controllable, easily scalable, and suitable for industrial application. It has broad application prospects in automobile exhaust treatment.

[0014] As a preferred technical solution of the present invention, the preparation of the complex containing platinum and auxiliary active metal includes: premixing a platinum source, an auxiliary active metal source, a potassium source and an amine salt to obtain the complex containing platinum and auxiliary active metal.

[0015] In the present invention, the complex containing platinum and the co-active metal formed by the platinum source and the co-active metal is more stable than other metals. At the same time, the melting point of platinum is 1768°C. When the temperature of automobile exhaust reaches above 800°C, the catalyst prepared with platinum as the active component in the present invention can still keep the active sites from sintering.

[0016] Preferably, the platinum source comprises any one of chloroplatinic acid, acetylacetonate platinum, sodium chloroplatinate or potassium chloroplatinate, or a combination of at least two thereof, wherein typical but non-limiting combinations include: a combination of chloroplatinic acid and acetylacetonate platinum, a combination of chloroplatinic acid and sodium chloroplatinate, a combination of chloroplatinic acid and potassium chloroplatinate, a combination of acetylacetonate platinum and sodium chloroplatinate, a combination of acetylacetonate platinum and potassium chloroplatinate, a combination of sodium chloroplatinate and potassium chloroplatinate, a combination of chloroplatinic acid, acetylacetonate and sodium chloroplatinate, a combination of chloroplatinic acid, acetylacetonate and potassium chloroplatinate, a combination of chloroplatinic acid, sodium chloroplatinate and potassium chloroplatinate, a combination of acetylacetonate platinum, sodium chloroplatinate and potassium chloroplatinate, a combination of chloroplatinic acid, 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 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. Other values ​​not listed within the above numerical range are also applicable.

[0026] As a preferred technical solution of the present invention, the temperatures of the first heat treatment, the second heat treatment and the third heat treatment are each independently 20~80°C, for example, 20°C, 40°C, 50°C, 60°C or 80°C, but are not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

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

[0028] Preferably, the stirring speed is 500-1000 rpm, for example, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm or 1000 rpm, but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0029] Preferably, the time of the first heat treatment is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0030] Preferably, the mass ratio of the complex containing platinum and the auxiliary active metal to the silicon source in the treated mixed solution A during 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. Other values ​​not listed within the above numerical range are also applicable.

[0031] The present invention limits the mass ratio of the complex containing platinum and the auxiliary active 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 evenly dispersed to avoid agglomeration; if the mass ratio of the two is less than 1:1000, that is, the platinum content in the catalyst is too low and the silicon content is too high, it will lead to insufficient active sites, resulting in CO and NO x The conversion rate decreases and the catalytic efficiency decreases; at the same time, the excess silicon will cause its acidic sites to adsorb NO x, competing with the platinum active sites to inhibit the reduction reaction. If the mass ratio of the two is greater than 1:200, that is, the silicon content in the catalyst is too little and the platinum content is too much, the structural stability and oxygen storage capacity of the catalyst will be weakened, and the platinum particles will also agglomerate. At the same time, due to the increase in platinum content, the preparation cost of the catalyst will increase.

[0032] Preferably, the second heat treatment time is 2 to 10 hours, for example, 2 hours, 4 hours, 6 hours, 8 hours or 10 hours, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0033] Preferably, the time of the third heat treatment is 1 to 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

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

[0035] Preferably, the time of the first crystallization treatment is 24 to 96 hours, for example, 24 hours, 48 ​​hours, 72 hours or 96 hours, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0036] Preferably, the second crystallization treatment time is 2 to 8 hours, for example, 2 hours, 4 hours, 6 hours or 8 hours, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0037] Preferably, the temperature of the first drying treatment and the second drying treatment are independently 60~150℃, for example, 60℃, 80℃, 100℃, 120℃, 140℃ or 150℃, but are not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

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

[0039] As a preferred technical solution of the present invention, 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. Other values ​​not listed within the above numerical range are also applicable.

[0040] Preferably, the calcination treatment time is 5 to 10 hours, for example, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0041] Preferably, the temperature of the reduction treatment is 350-650°C, for example, 350°C, 450°C, 550°C or 650°C, but is not limited to the listed values, and other values ​​not listed within the above range are also applicable.

[0042] Preferably, the reduction treatment time is 1.5 to 3 hours, for example, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

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

[0044] As a preferred technical solution of the present invention, the fluorine source includes any one of ammonium fluoride, tetramethylammonium fluoride or tetraethylammonium fluoride, or a combination of at least two of them, wherein typical but non-limiting combinations include: a combination of ammonium fluoride and tetramethylammonium fluoride, a combination of ammonium fluoride and tetraethylammonium fluoride, a combination of tetramethylammonium fluoride and tetraethylammonium fluoride, and a combination of ammonium fluoride, tetramethylammonium fluoride and tetraethylammonium fluoride.

[0045] Preferably, the mass ratio of the pretreatment catalyst, silicon source, water and 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 within the above numerical range are also applicable.

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

[0047] After the first crystallization treatment is completed, the material is cooled to room temperature, and a first washing treatment is performed on the material after the first crystallization treatment until it becomes neutral, and then a first drying treatment is performed.

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

[0049] After the second crystallization treatment is completed, the material is cooled to room temperature, and a second washing treatment is performed on the material after the second crystallization treatment until it is neutral, and then a second drying treatment is performed.

[0050] Preferably, the detergents for the first washing treatment and the second washing treatment each independently include any one of water, methanol, ethanol or acetone, or a combination of at least two of them, 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, and a combination of water, ethanol and acetone.

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

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

[0053] (2) a silicon source, water, and a template are first mixed in a mass ratio of 1:(200-1000):(2-300) to obtain a mixed solution A; and the mixed solution A is first heat-treated at a temperature of 20-80° C. for 1-3 hours to obtain a treated mixed solution A;

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

[0055] (4) The catalyst precursor is subjected to a calcination treatment at a temperature of 400-600° C. for 5-10 hours and a reduction treatment at a temperature of 350-650° C. for 1.5-3 hours to obtain a pre-treated catalyst;

[0056] (5) The pre-treatment catalyst, silicon source, water and fluorine source are mixed for a third time in a mass ratio of 1:(1.5-3):(10-50):(1.5-3) to obtain a mixed solution C, and the mixed solution C is subjected to a third heat treatment at a temperature of 20-80°C for 1-5 hours; 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 150-200°C for 2-8 hours, a second washing treatment and a second drying treatment at a temperature of 60-150°C for 5-10 hours to obtain the catalyst;

[0057] There is no particular order in which steps (1) and (2) are performed.

[0058] In a second aspect, the present invention provides a catalyst for automobile exhaust purification, wherein the catalyst is prepared using the method for preparing the catalyst for automobile exhaust purification described in the first aspect.

[0059] The catalyst provided by the present invention has good high temperature resistance and low ignition temperature, and has broad application prospects in automobile exhaust treatment.

[0060] As a preferred technical solution of the present invention, the catalyst includes a carrier and an active component and a co-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 co-active component comprises any one or a combination of at least two 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, and a combination of nickel, copper, iron and tin.

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

[0065] Preferably, the average particle size D50 of the active component in the catalyst is 1 to 10 nm, for example, 1 nm, 2 nm, 4 nm, 6 nm, 8 nm or 10 nm, but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0066] The present invention prepares a catalyst with an average particle size D50 of 1-10 nm of the active component, which can make the active component atoms on the catalyst surface account for a large proportion, expose more active sites, and increase the CO and NO xThe conversion efficiency is high. At the same time, the active components with an average particle size of 1~10nm are firmly anchored on the carrier and are not easy to agglomerate at high temperatures (above 800℃); if the average particle size of the active components is less than 1nm, the active component particles will easily diffuse and aggregate through the surface at high temperatures to form large particles, resulting in poor thermal stability of the catalyst. If the average particle size of the active components is greater than 10nm, the atomic proportion of the active components on the catalyst surface will decrease, and the catalytic activity will decrease.

[0067] Preferably, based on the mass of the catalyst as 100%, the catalyst includes 99.2~99.6% of the carrier, 0.3~0.4% of the active component and 0.1~0.5% of the co-active component, 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 co-active component is 0.1~0.5%, for example, it can be 0.1%, 0.2%, 0.3%, 0.4% or 0.5%, but it is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

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

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

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

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

[0072] (1) The present invention prepares an automobile exhaust purification catalyst with good high temperature resistance and low ignition temperature. The service life of the catalyst at 800°C can reach more than 800 hours, and the T 50 Can be controlled within 100℃;

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

[0074] Figure 1 This is a SEM image of the catalyst provided in Example 1 of the present invention.

[0075] Figure 2 This is a TEM image of the catalyst provided in Example 1 of the present invention.

[0076] Figure 3 This is the XRD spectrum of the catalyst provided in Example 1 of the present invention.

[0077] Figure 4 This is a reaction activity diagram of the catalyst provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0078] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0079] Example 1

[0080] This embodiment provides a catalyst for automobile exhaust purification, the catalyst comprising a zeolite molecular sieve carrier, an active component of platinum, and a co-active component of nickel. Based on 100% by mass of the catalyst, the catalyst comprises 99.2% zeolite molecular sieve, 0.35% platinum, and 0.45% nickel.

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

[0082] like Figure 3 As shown, the catalyst has a crystalline structure and a pore volume of 0.35 cm 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] This embodiment provides a catalyst for automobile exhaust purification, the catalyst comprising a zeolite molecular sieve carrier, an active component of platinum, and a co-active component of copper. Based on 100% by mass of the catalyst, the catalyst comprises 99.4% zeolite molecular sieve, 0.32% platinum, and 0.28% copper.

[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 crystalline structure and a pore volume of 0.45 cm 3 / g, the specific surface area of ​​the catalyst is 300m 2 / g.

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

[0095] (1) premixing platinum acetylacetonate, copper sulfate, potassium chloride, and ethylenediamine in a mass ratio of 1:3:5:100 to obtain a complex containing platinum and a co-active metal;

[0096] (2) n-propyl silicon, water, and tetrapropylamine are first mixed in a mass ratio of 1:200:300 to obtain a mixed solution A; and the mixed solution A is first heat-treated at a temperature of 80° C., a time of 1 hour, and a rotation speed of 800 rpm to obtain a treated mixed solution A;

[0097] (3) The platinum-containing and co-active metal complex is mixed with the treated mixed solution A for a second time according to a mass ratio of the platinum-containing and co-active metal complex to n-propyl silicon of 1:200 to obtain a mixed solution B, and the mixed solution B is subjected to a second heat treatment at a temperature of 20°C, a time of 10 hours, and a rotation speed of 800 rpm to obtain a treated mixed solution B; the treated mixed solution B is sequentially subjected to a first crystallization treatment at a temperature of 150°C, a time of 96 hours, a first washing treatment, and a first drying treatment at a temperature of 150°C, a time of 5 hours to obtain a catalyst precursor; wherein the detergent used in the first washing treatment is water and acetone in a volume ratio of 2:1;

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

[0099] (5) The pre-treatment catalyst, n-propyl silicon, water and tetramethylammonium fluoride are mixed for a third time in a mass ratio of 1:1.5:50:3 to obtain a mixed solution C, and the mixed solution C is subjected to a third heat treatment at a temperature of 40°C, a time of 3.5 hours and a rotation speed of 800 rpm; 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°C and a time of 5 hours, a second washing treatment and a second drying treatment at a temperature of 60°C and a time of 10 hours to obtain the catalyst, wherein the detergent used in the second washing treatment is water and methanol in a volume ratio of 2:1;

[0100] There is no particular order in which steps (1) and (2) are performed.

[0101] Example 3

[0102] This embodiment provides a catalyst for automobile exhaust purification, the catalyst comprising a zeolite molecular sieve carrier, an active component of platinum, and an auxiliary active component of iron. Based on the mass of the catalyst as 100%, the catalyst comprises 99.6% zeolite molecular sieve, 0.3% platinum, and 0.1% iron.

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

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

[0105] This embodiment also provides a method for preparing the catalyst for automobile exhaust purification, which comprises the following steps:

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

[0107] (2) n-propyl silicon, water and tetrapropylamine are first mixed in a mass ratio of 1:1000:2 to obtain a mixed solution A; and the mixed solution A is first heat-treated at a temperature of 20° C., a time of 3 hours and a rotation speed of 900 rpm to obtain a treated mixed solution A;

[0108] (3) The platinum-containing and co-active metal complex and the treated mixed solution A are mixed for a second time in a mass ratio of the platinum-containing and co-active metal complex to n-propyl silicon of 1:1000 to obtain a mixed solution B, and the mixed solution B is subjected to a second heat treatment at a temperature of 80°C, a time of 2 hours, and a rotation speed of 900 rpm to obtain a treated mixed solution B; the treated mixed solution B is sequentially subjected to a first crystallization treatment at a temperature of 200°C, a time of 24 hours, a first washing treatment, and a first drying treatment at a temperature of 60°C, a time of 10 hours to obtain a catalyst precursor; wherein the washing agent used in the first washing treatment is water, methanol, and acetone in a volume ratio of 1:1:1;

[0109] (4) The catalyst precursor is subjected to a calcination treatment at a temperature of 600° C. for 5 h and a reduction treatment at a temperature of 350° C. for 3 h in a hydrogen atmosphere to obtain a pretreated catalyst;

[0110] (5) The pre-treatment catalyst, n-propyl silicon, water and tetraethylammonium fluoride are mixed for a third time in a mass ratio of 1:3:10:1.5 to obtain a mixed solution C, and the mixed solution C is subjected to a third heat treatment at a temperature of 80°C, a time of 1 hour and a rotation speed of 900 rpm; 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 150°C and a time of 8 hours, a second washing treatment and a second drying treatment at a temperature of 100°C and a time of 8 hours to obtain the catalyst, wherein the detergent used in the second washing treatment is water, ethanol and acetone in a volume ratio of 1:1:1;

[0111] There is no particular order in which steps (1) and (2) are performed.

[0112] Example 4

[0113] This embodiment provides a catalyst for automobile exhaust purification. The only difference from Example 1 is that, except that ethylenediamine in step (1) is replaced by diethylenetriamine, the rest is the same as Example 1.

[0114] Example 5

[0115] This embodiment provides a catalyst for automobile exhaust purification. The only difference from Example 1 is that, except that the ethylenediamine in step (1) is replaced by ammonia water, the rest is the same as Example 1.

[0116] Example 6

[0117] This embodiment provides a catalyst for automobile exhaust purification. The only difference from Example 1 is that, in addition to adjusting the mass ratio of the complex containing platinum and the auxiliary active metal to n-propyl silicon in the second mixing process of step (3) from 1:600 ​​to 1:100, the rest is the same as Example 1.

[0118] Example 7

[0119] This embodiment provides a catalyst for automobile exhaust purification. The only difference from Example 1 is that, in addition to adjusting the mass ratio of the complex containing platinum and the auxiliary active metal to n-propyl silicon in the second mixing process of step (3) from 1:600 ​​to 1:1500, the rest is the same as Example 1.

[0120] Example 8

[0121] This embodiment provides a catalyst for automobile exhaust purification. The only difference from Example 1 is that, except that the average particle size D50 of the active component platinum in the catalyst is 20 nm, that is, ethylenediamine is not included in the premixing process of step (1) in the preparation method, the rest is the same as Example 1.

[0122] Comparative Example 1

[0123] This comparative example provides a catalyst for automobile exhaust purification, which is the same as Example 1 except that the preparation method does not include step (5), that is, the pre-treatment catalyst is recorded as the catalyst.

[0124] Comparative Example 2

[0125] This comparative example provides a catalyst for automobile exhaust purification, which differs from Example 1 only in that the preparation method does not include step (5), and step (1) is adjusted to: premixing chloroplatinic acid, nickel nitrate, potassium chloride, ethylenediamine and ammonium fluoride in a mass ratio of 1:5:8:70:3, that is, keeping the mass ratio of chloroplatinic acid to ammonium fluoride unchanged during the preparation process, and the rest is the same as Example 1.

[0126] Comparative Example 3

[0127] This comparative example provides a catalyst for automobile exhaust purification, which differs from Example 1 only in that the preparation method does not include step (5), and step (2) is adjusted to: n-propyl silicon, water, tetrapropylamine and ammonium fluoride are first mixed in a mass ratio of 1:600:150:50, that is, the mass ratio of chloroplatinic acid and ammonium fluoride is kept unchanged during the preparation process. Otherwise, everything else is the same as Example 1.

[0128] Comparative Example 4

[0129] This comparative example provides a catalyst for automobile exhaust purification, which is the same as 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 automobile exhaust purification corresponding to Examples 4 to 8 of the present invention and Comparative Examples 1 to 4 are shown in Table 1, wherein the platinum content of the catalysts is obtained by X-ray photoelectron spectroscopy analysis, the specific surface area of ​​the catalysts is obtained by BET testing, the pore volume of the catalysts is obtained by N2 adsorption and desorption experimental testing, the particle size of the catalysts and the active component platinum is obtained by SEM images, and the crystal structure of the catalysts is obtained by XRD spectra.

[0131] Table 1

[0132]

[0133] The catalysts prepared in Examples 1 to 8 and Comparative Examples 1 to 4 were used to conduct denitration activity tests on simulated automobile exhaust at 800°C. The simulated exhaust contained 1500ppm CO and 1500ppm NO, with argon as the balance gas. 100mg of the catalyst was mixed evenly with 300mg of quartz sand and placed in a quartz tube with an inner diameter of 0.6mm to test the catalytic activity. The test results of Example 1 are as follows: Figure 4 As shown, and the T of the catalyst 50 Detection, where T 50 is the temperature at which the CO conversion rate reaches 50%.

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

[0135] Table 2

[0136]

[0137] The test results show that:

[0138] (1) It can be seen from Examples 1 to 3 that the present invention first uses a one-pot method to directly synthesize a molecular sieve loaded with platinum and a co-active metal to obtain a pre-treatment catalyst, and then further optimizes the defects of the molecular sieve in the pre-treatment catalyst through liquid synthesis-mediated modification to obtain T 50 Within 100°C, the NO conversion rate is over 48%, the CO conversion rate is over 98%, and the service life of the automobile exhaust purification catalyst can reach over 870 hours.

[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 50The temperature is 80℃ and the service life is 1000h. In the process of treating automobile exhaust, the conversion rate of NO is 57% and the conversion rate of CO is 100%. The average particle size of the active component platinum in the catalyst of Example 8 is 20nm. The T 50 The temperature is 141°C and the service life is 110 hours. During the automobile exhaust treatment process, the NO conversion rate is 14% and the CO conversion rate is 85%. This shows that the present invention can prepare a catalyst with an average particle size of active components of 1-10 nm, so that the active component atoms account for a large proportion on the catalyst surface, expose more active sites, and improve the CO and NO conversion efficiency. At the same time, the active components with an average particle size of 1-10 nm are firmly anchored on the carrier and are not easy to agglomerate at high temperatures (above 800°C).

[0142] (5) It can be seen from Example 1 and Comparative Examples 1-3 that the present invention further optimizes the defects of the molecular sieve in the pretreatment catalyst through liquid synthesis-mediated modification, and can prepare an automobile exhaust purification catalyst with good high temperature resistance, low ignition temperature and long service life.

[0143] (6) It can be seen from Example 1 and Comparative Example 4 that the present invention can prepare an automobile exhaust purification catalyst with good high temperature resistance, low ignition temperature and long service life by limiting the use of platinum as the active metal.

[0144] In summary, the present invention firstly utilizes a one-pot method to directly synthesize a platinum-loaded molecular sieve to obtain a pretreatment catalyst, and further optimizes the defects of the molecular sieve in the pretreatment catalyst through liquid synthesis-mediated modification, thereby obtaining an automobile exhaust purification catalyst with good high temperature resistance and low ignition temperature. The service life of the catalyst at 800°C can reach more than 800 hours, and the T 50 Can be controlled within 100℃.

[0145] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a catalyst for automobile exhaust purification, characterized in that: The preparation method comprises the following steps: (1) a silicon source, water, and a template are first mixed to obtain a mixed solution A; and the mixed solution A is first heat-treated to obtain a treated mixed solution A; (2) performing a second mixing of the complex containing platinum and the co-active metal with the treated mixed solution A to obtain a mixed solution B, and sequentially performing a second heat treatment, a first crystallization treatment, and a first drying treatment on the mixed solution B to obtain a catalyst precursor; (3) performing calcination and reduction treatment on the catalyst precursor in sequence to obtain a pre-treated catalyst; (4) The pretreatment catalyst, silicon source, water and fluorine source are mixed for the third time to obtain a mixed solution C, and the mixed solution C is sequentially subjected to a third heat treatment, a second crystallization treatment and a second drying treatment to obtain the catalyst.

2. The preparation method according to claim 1, characterized in that The preparation of the complex containing platinum and the auxiliary active metal comprises: premixing a platinum source, an auxiliary active metal source, a potassium source and an amine salt to obtain the complex containing platinum and the auxiliary active metal; The platinum source includes any one of chloroplatinic acid, platinum acetylacetonate, sodium chloroplatinate or potassium chloroplatinate, or a combination of at least two thereof; The auxiliary active metal source includes a metal soluble salt corresponding to the auxiliary active metal, and the metal soluble salt includes any one of metal chloride, metal nitrate or metal sulfate, or a combination of at least two thereof; The auxiliary active metal in the auxiliary active metal source includes any one of nickel, copper, iron or tin, or a combination of at least two thereof; The potassium source includes potassium chloride and / or potassium nitrate; The amine salt includes ethylenediamine; During the premixing process, the molar ratio of the platinum source, the auxiliary active metal source, the potassium source and the amine salt is 1:(3-10):(5-10):(50-100).

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

4. The preparation method according to claim 1, characterized in that The temperatures of the first heat treatment, the second heat treatment, and the third heat treatment are each independently 20-80° C.; The time of the first heat treatment is 1 to 3 hours; In the second mixing process, the mass ratio of the complex containing platinum and the auxiliary active metal to the silicon source in the treated mixed solution A is 1:(200-1000); The second heat treatment time is 2 to 10 hours; The third heat treatment time is 1 to 5 hours.

5. The preparation method according to claim 1, characterized in that The temperature of the first crystallization treatment and the second crystallization treatment are each independently 150-200° C.; The first crystallization treatment time is 24 to 96 hours; The second crystallization treatment time is 2 to 8 hours; The temperature of the first drying process and the second drying process are independently 60-150° C.; The time for the first drying treatment and the second drying treatment is independently 5 to 10 hours.

6. The preparation method according to claim 1, characterized in that The temperature of the calcination treatment is 400-600°C; The calcination time is 5 to 10 hours; The temperature of the reduction treatment is 350-650°C; The reduction treatment time is 1.5 to 3 hours; The atmosphere of the reduction treatment includes hydrogen.

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

8. A catalyst for automobile exhaust purification, characterized in that: The catalyst is prepared by the method for preparing a catalyst for automobile exhaust purification according to any one of claims 1 to 7.

9. The catalyst according to claim 8, characterized in that The catalyst comprises a carrier and an active component and a co-active component supported on the carrier; The carrier includes zeolite molecular sieve; The active component includes platinum; The co-active component includes any one of nickel, copper, iron or tin, or a combination of at least two of them.

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

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