Functionalized Pd-based molecular sieve cold start adsorbent and preparation method thereof

Abstract

The invention provides a functionalized Pd-based molecular sieve cold start adsorbent and a preparation method thereof, and belongs to the technical field of internal combustion engine tail gas governance, and the preparation method comprises the following steps: mixing a silicon source and an aluminum source in proportion, adding deionized water and a Pd precursor, and carrying out a high temperature and high pressure reaction to obtain a Pd-based molecular sieve; mixing the Pd-based molecular sieve with an auxiliary metal precursor, and carrying out ultrasonic impregnation and high-temperature roasting to obtain a Pd-based molecular sieve loaded with an auxiliary metal; mixing the Pd-based molecular sieve loaded with the auxiliary metal with a functional material through a hydrothermal reaction to obtain a composite material; and soaking the composite material in a functionalized solvent, washing with deionized water, and drying to finally obtain the functionalized Pd-based molecular sieve cold start adsorbent. The problems that in an existing internal combustion engine tail gas treatment technology, the adsorbent is low in removal efficiency, prone to inactivation when high-concentration CO exists, small in specific surface area, unreasonable in pore size distribution and the like are solved, and a more effective technical means is provided for internal combustion engine tail gas treatment.

Description

Technical Field

[0001] The invention relates to the technical field of internal combustion engine tail gas treatment, and in particular to a functionalized Pd-based molecular sieve cold start adsorbent and a preparation method thereof. Background Art

[0002] Internal combustion engine exhaust emissions have become one of the major sources of air pollution. Internal combustion engine exhaust contains NO x , CO and other harmful pollutants, which not only form acid rain, photochemical smog and other environmental hazards, but also cause serious damage to the human respiratory and cardiovascular systems.

[0003] In the internal combustion engine exhaust treatment technology, traditional adsorbents and catalysts have obvious deficiencies in the cold start stage. For example, many conventional adsorbents have poor NO absorption at low temperatures (50-150°C). x The removal efficiency is low, making it difficult to meet the increasingly stringent environmental protection requirements. In addition, in the presence of high concentrations of CO, existing adsorbents are easily deactivated, resulting in a shortened service life and a significant reduction in the treatment effect. In addition, some traditional adsorbents have a small specific surface area and an unreasonable pore size distribution, which limits their adsorption capacity and reaction activity for pollutants in exhaust gas.

[0004] Therefore, there is an urgent need for a cold start adsorbent that is efficient, stable, and has good adsorption performance at low temperatures. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a functionalized Pd-based molecular sieve cold start adsorbent and a preparation method thereof, which solves the problems of low adsorbent removal efficiency, easy deactivation in the presence of high concentration of CO, small specific surface area and unreasonable pore size distribution in the existing internal combustion engine exhaust treatment technology, and provides a more effective technical means for internal combustion engine exhaust treatment.

[0006] To achieve the above object, the present invention provides the following solutions: A method for preparing a functionalized Pd-based molecular sieve cold start adsorbent comprises the following steps: S1, mixing a silicon source and an aluminum source in proportion, adding deionized water and a Pd precursor, and obtaining a Pd-based molecular sieve after a high temperature and high pressure reaction; S2, mixing the Pd-based molecular sieve with an auxiliary metal precursor, and subjecting the mixture to ultrasonic impregnation and high-temperature calcination to obtain a Pd-based molecular sieve loaded with an auxiliary metal; S3, mixing the Pd-based molecular sieve loaded with auxiliary metals with the functionalized material through a hydrothermal reaction to obtain a composite material, i.e., a functionalized Pd-based molecular sieve; S4, soaking the composite material in an organic solvent containing amino or carboxyl groups, washing with deionized water and drying, and finally obtaining a functionalized Pd-based molecular sieve cold start adsorbent.

[0007] Preferably, in S1, the synthesis process of the Pd-based molecular sieve is: mixing the silicon source and the aluminum source in proportion, then adding deionized water, stirring evenly and adding the Pd precursor to form a uniform mixed solution; transferring the mixed solution to a high-pressure reactor, reacting at 110-150°C for 24-48h, cooling to room temperature, filtering to obtain a Pd-based molecular sieve precipitate; finally, washing the precipitate with deionized water to remove unreacted precursors, and finally drying at 60°C to obtain a Pd-based molecular sieve.

[0008] Preferably, the silicon source is sodium silicate, the aluminum source is sodium aluminate, the mass ratio of the silicon source to the aluminum source is 4:1, and the Pd precursor is sodium chloroplatinate.

[0009] Preferably, in S2, the synthesis process of the Pd-based molecular sieve loaded with auxiliary metals is: the synthesized Pd-based molecular sieve and the auxiliary metal precursor are evenly mixed in proportion, and then dissolved in deionized water to obtain an impregnation solution; the impregnation solution is treated by ultrasonic-assisted impregnation method for 30 minutes to promote uniform loading of the auxiliary metal; finally, the precipitate is filtered and washed, and calcined at 500°C for 2 hours to form a stable metal oxide on the Pd-based molecular sieve to obtain a Pd-based molecular sieve loaded with auxiliary metals.

[0010] Preferably, the mass ratio of the Pd-based molecular sieve to the auxiliary metal precursor is 1:2 to 50:1.

[0011] Preferably, the auxiliary metal precursor is one or more of cobalt nitrate, nickel nitrate, cerium nitrate, copper nitrate or europium nitrate.

[0012] Preferably, in S3, the synthesis process of the composite material is: mixing the Pd-based molecular sieve loaded with auxiliary metal and the functional material in proportion, then adding deionized water and stirring evenly; reacting at 120° C. for 12 hours by a hydrothermal method to obtain the composite material.

[0013] Preferably, the functional material is a pyrolyzed MOFs derivative or activated carbon, and the mass ratio of the Pd-based molecular sieve loaded with auxiliary metals to the functional material is 1:1; the preparation process of the pyrolyzed MOFs derivative is: pyrolysis treatment is performed in an anaerobic environment, and the metal organic framework material MOFs is heated to 500~600℃ for 2~3h to remove organic ligands to obtain a pyrolyzed MOFs derivative, and the pyrolyzed MOFs derivative includes metal oxides or carbon-based materials.

[0014] The present invention also provides a functionalized Pd-based molecular sieve cold start adsorbent prepared by the above preparation method, wherein the functionalized Pd-based molecular sieve cold start adsorbent is composed of the following components: Pd-based molecular sieve, wherein the Pd-based molecular sieve is Pd / Beta, Pd / ZSM-5 or Pd / CHA; Auxiliary metal, wherein the auxiliary metal is one or more of cobalt, nickel, cerium or europium, and the loading amount of the auxiliary metal is 2% to 200% of the mass of the Pd-based molecular sieve; Functionalized material, wherein the functionalized material is a pyrolyzed MOFs derivative or activated carbon.

[0015] Preferably, the functionalized Pd-based molecular sieve cold start adsorbent is effective for NO x The removal efficiency is greater than 90%, and the deactivation rate is less than 5% in the presence of high concentration of CO. The specific surface area of ​​the functionalized Pd-based molecular sieve cold start adsorbent is greater than 300m 2 / g, pore size is 2~10nm.

[0016] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: (1) In the preparation process of the functionalized Pd-based molecular sieve cold start adsorbent of the present invention, the Pd-based molecular sieve is compounded with the auxiliary metal and the functionalized material through the steps provided. Since the Pd-based molecular sieve itself has certain adsorption performance, the loading of the auxiliary metal changes its electronic structure and enhances the adsorption of NO. x The functionalized material further optimizes the adsorption environment, making the adsorbent absorb NO in the low temperature range of 50-150℃. x The removal efficiency is greater than 90%, which effectively solves the problem of traditional adsorbents for NO at low temperatures. x Eliminate inefficiencies.

[0017] (2) The present invention loads auxiliary metals during the synthesis process and compounds with functional materials to form a stable structure. In the presence of high concentrations of CO, the auxiliary metals and functional materials work synergistically to inhibit CO from occupying and destroying the active sites of the adsorbent, making the adsorbent deactivation rate less than 5%, greatly improving the stability and service life of the adsorbent in complex exhaust gas environments.

[0018] (3) The present invention undergoes a multi-step preparation process, and the functionalized Pd-based molecular sieve cold start adsorbent obtained ultimately has a specific surface area greater than 300 m 2 / g, pore size is 2~10nm. The larger specific surface area provides more adsorption space, and the reasonable pore size distribution is conducive to the diffusion and adsorption of gas molecules, which enhances the adsorption capacity and reaction activity of the adsorbent to pollutants in the exhaust gas, overcomes the defects of small specific surface area and unreasonable pore size distribution of traditional adsorbents, and thus provides a more effective technical means for the treatment of exhaust gas from internal combustion engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0020] Figure 1 The present invention is a flow chart of a method for preparing a functionalized Pd-based molecular sieve cold start adsorbent. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1 As shown, the present invention provides a method for preparing a functionalized Pd-based molecular sieve cold start adsorbent, comprising the following steps: S1, mixing a silicon source and an aluminum source in proportion, adding deionized water and a Pd precursor, and obtaining a Pd-based molecular sieve after a high temperature and high pressure reaction; S2, mixing the Pd-based molecular sieve with an auxiliary metal precursor, and subjecting the mixture to ultrasonic impregnation and high-temperature calcination to obtain a Pd-based molecular sieve loaded with an auxiliary metal; S3, mixing the Pd-based molecular sieve loaded with auxiliary metals with the functionalized material through a hydrothermal reaction to obtain a composite material, i.e., a functionalized Pd-based molecular sieve; S4, soaking the composite material in an organic solvent containing amino or carboxyl groups, washing with deionized water and drying, and finally obtaining a functionalized Pd-based molecular sieve cold start adsorbent.

[0024] In S1, the synthesis process of the Pd-based molecular sieve is as follows: the silicon source and the aluminum source are mixed in a ratio of 4:1, and then deionized water is added. After stirring evenly, a Pd precursor is added to form a uniform mixed solution; the mixed solution is transferred to a high-pressure reactor, and the reaction is carried out at 110-150°C for 24-48 hours, preferably at 150°C for 24 hours; after cooling to room temperature, the Pd-based molecular sieve precipitate is obtained by filtration; finally, the precipitate is washed with deionized water to remove the unreacted precursor, and finally dried at 60°C to obtain the Pd-based molecular sieve. Among them, the silicon source is sodium silicate, the aluminum source is sodium aluminate, and the Pd precursor is sodium chloroplatinate. While providing a silicon source, the alkaline environment generated by the hydrolysis of sodium silicate is conducive to the crystallization process of the molecular sieve, and can regulate the crystal structure and pore size distribution of the molecular sieve. Sodium aluminate provides an aluminum source, and aluminum atoms in the molecular sieve framework can affect the distribution and number of its acidic sites, thereby affecting the NO x Sodium chloroplatinate has good solubility and stability in aqueous solution, which is easy to disperse evenly during the synthesis process, ensuring high dispersion of Pd in ​​the molecular sieve and improving its catalytic activity. At the same time, under high temperature and high pressure reaction conditions, sodium chloroplatinate can smoothly participate in the reaction, introduce Pd into the molecular sieve framework, and form a stable structure.

[0025] In S2, the synthesis process of the Pd-based molecular sieve loaded with auxiliary metals is as follows: the synthesized Pd-based molecular sieve and the auxiliary metal precursor are mixed uniformly in a ratio of 1:2 to 50:1, and then dissolved in deionized water to obtain an impregnation solution; the impregnation solution is treated by ultrasonic assisted impregnation for 30 minutes to promote the uniform loading of the auxiliary metal; finally, the precipitate is filtered and washed, and calcined at 500°C for 2 hours to form a stable metal oxide on the Pd-based molecular sieve to obtain a Pd-based molecular sieve loaded with auxiliary metals. The auxiliary metal precursor is one or more of cobalt nitrate, nickel nitrate, cerium nitrate, copper nitrate or europium nitrate.

[0026] In S3, the synthesis process of the composite material is: mixing the Pd-based molecular sieve loaded with auxiliary metal and the functional material in a ratio of 1:1, then adding deionized water and stirring evenly; reacting at 120°C for 12 hours by a hydrothermal method to obtain a composite material. The functional material is a pyrolyzed MOFs derivative or activated carbon. The preparation process of the pyrolyzed MOFs derivative is: performing pyrolysis treatment in an oxygen-free environment, heating the metal organic framework material MOFs to 500~600°C, and the heating time is 2~3 hours to remove the organic ligand to obtain a pyrolyzed MOFs derivative, and the pyrolyzed MOFs derivative includes metal oxides or carbon-based materials.

[0027] In addition, the functionalized Pd-based molecular sieve cold start adsorbent prepared by the above preparation method is composed of the following components: Pd-based molecular sieve, wherein the Pd-based molecular sieve is Pd / Beta, Pd / ZSM-5 or Pd / CHA; Auxiliary metal, wherein the auxiliary metal is one or more of cobalt, nickel, cerium or europium, and the loading amount of the auxiliary metal is 2% to 200% of the mass of the Pd-based molecular sieve; Functionalized material, wherein the functionalized material is a pyrolyzed MOFs derivative or activated carbon.

[0028] The functionalized Pd-based molecular sieve cold start adsorbent prepared above has a high adsorption capacity for NO at 50-150 °C. x The removal efficiency is greater than 90%, and the deactivation rate is less than 5% in the presence of high concentration of CO. The specific surface area of ​​the functionalized Pd-based molecular sieve cold start adsorbent is greater than 300m 2 / g, pore size is 2~10nm.

[0029] Example 1 In this embodiment, the Pd-based molecular sieve type is Pd / Beta; the auxiliary metal precursor is cobalt nitrate; the functionalized material is: a pyrolyzed MOFs derivative; and the preparation process is as follows: (1) Sodium silicate and sodium aluminate are mixed in a ratio of 4:1, and then deionized water is added. After stirring evenly, sodium chloroplatinate is added to form a uniform mixed solution; the mixed solution is transferred to a high-pressure reactor, reacted at 150°C for 24 hours, cooled to room temperature, and filtered to obtain a Pd / Beta molecular sieve precipitate; finally, the precipitate is washed with deionized water to remove unreacted sodium chloroplatinate, and finally dried at 60°C to obtain a Pd / Beta molecular sieve.

[0030] (2) The synthesized Pd / Beta molecular sieve and the cobalt nitrate precursor are mixed uniformly in a ratio of 1:1, and then dissolved in deionized water to obtain an impregnation solution; the impregnation solution is treated by an ultrasonic-assisted impregnation method for 30 minutes to promote the uniform loading of the cobalt nitrate; finally, the precipitate is filtered and washed, and calcined at 500°C for 2 hours to form a stable cobalt nitrate oxide on the Pd / Beta molecular sieve, thereby obtaining a Pd / Beta molecular sieve loaded with cobalt nitrate.

[0031] (3) Pd / Beta molecular sieve loaded with cobalt nitrate was mixed with the pyrolyzed MOFs derivative in a ratio of 1:1, and then deionized water was added and stirred evenly; the mixture was reacted at 120°C for 12 hours by a hydrothermal method to obtain a composite material.

[0032] (4) The composite material is immersed in an organic solvent containing amino groups, washed with deionized water and dried to finally obtain a functionalized Pd / Beta molecular sieve cold start adsorbent. According to the test, the specific surface area of ​​the functionalized Pd / Beta molecular sieve cold start adsorbent obtained in this embodiment is 350m2 / g, pore size is 5nm.

[0033] Example 2 In this embodiment, the Pd-based molecular sieve type is Pd / ZSM-5; the auxiliary metal precursor is nickel nitrate; the functional material is activated carbon; and the preparation process is as follows: (1) Sodium silicate and sodium aluminate are mixed in a ratio of 4:1, and then deionized water is added. After stirring evenly, sodium chloroplatinate is added to form a uniform mixed solution; the mixed solution is transferred to a high-pressure reactor, reacted at 150°C for 24 hours, cooled to room temperature, and filtered to obtain a Pd / ZSM-5 molecular sieve precipitate; finally, the precipitate is washed with deionized water to remove unreacted sodium chloroplatinate, and finally dried at 60°C to obtain a Pd / ZSM-5 molecular sieve.

[0034] (2) The synthesized Pd / ZSM-5 molecular sieve and the nickel nitrate precursor are mixed uniformly in a ratio of 1:2, and then dissolved in deionized water to obtain an impregnation solution; the impregnation solution is treated by an ultrasonic-assisted impregnation method for 30 minutes to promote the uniform loading of nickel nitrate; finally, the precipitate is filtered and washed, and calcined at 500°C for 2 hours to form a stable nickel nitrate oxide on the Pd / ZSM-5 molecular sieve, thereby obtaining a Pd-based molecular sieve loaded with nickel nitrate.

[0035] (3) Pd / ZSM-5 molecular sieve loaded with nickel nitrate was mixed with activated carbon in a ratio of 1:1, and then deionized water was added and stirred evenly; the mixture was reacted at 120°C for 12 hours by a hydrothermal method to obtain a composite material.

[0036] (4) The composite material is immersed in an organic solvent containing a carboxyl group, washed with deionized water and dried to finally obtain a functionalized Pd / ZSM-5 molecular sieve cold start adsorbent. According to the test, the specific surface area of ​​the functionalized Pd / ZSM-5 molecular sieve cold start adsorbent obtained in this embodiment is 320 m 2 / g, pore size is 6nm.

[0037] Example 3 In this embodiment, the Pd-based molecular sieve type is Pd / Beta; the auxiliary metal precursor is cerium nitrate; the functionalized material is: a pyrolyzed MOFs derivative; and the preparation process is as follows: (1) Sodium silicate and sodium aluminate are mixed in a ratio of 4:1, and then deionized water is added. After stirring evenly, sodium chloroplatinate is added to form a uniform mixed solution; the mixed solution is transferred to a high-pressure reactor, reacted at 150°C for 24 hours, cooled to room temperature, and filtered to obtain a Pd / Beta molecular sieve precipitate; finally, the precipitate is washed with deionized water to remove unreacted sodium chloroplatinate, and finally dried at 60°C to obtain a Pd / Beta molecular sieve.

[0038] (2) The synthesized Pd / Beta molecular sieve and the cerium nitrate precursor are mixed uniformly in a ratio of 1:0.5, and then dissolved in deionized water to obtain an impregnation solution; the impregnation solution is treated by ultrasonic-assisted impregnation for 30 minutes to promote uniform loading of cerium nitrate; finally, the precipitate is filtered and washed, and calcined at 500°C for 2 hours to form a stable cerium nitrate oxide on the Pd / Beta molecular sieve, thereby obtaining a Pd / Beta molecular sieve loaded with cerium nitrate.

[0039] (3) Pd / Beta molecular sieve loaded with cerium nitrate was mixed with the pyrolyzed MOFs derivative in a ratio of 1:1, and then deionized water was added and stirred evenly; the mixture was reacted at 120°C for 12 hours by a hydrothermal method to obtain a composite material.

[0040] (4) The composite material is immersed in an organic solvent containing amino groups, washed with deionized water and dried to finally obtain a functionalized Pd / Beta molecular sieve cold start adsorbent. According to the test, the specific surface area of ​​the functionalized Pd / Beta molecular sieve cold start adsorbent obtained in this embodiment is 340 m 2 / g, pore size is 5nm.

[0041] Example 4 In this embodiment, the Pd-based molecular sieve type is Pd / ZSM-5; the auxiliary metal precursor is europium nitrate; the functional material is activated carbon; and the preparation process is as follows: (1) Sodium silicate and sodium aluminate are mixed in a ratio of 4:1, and then deionized water is added. After stirring evenly, sodium chloroplatinate is added to form a uniform mixed solution; the mixed solution is transferred to a high-pressure reactor, reacted at 150°C for 24 hours, cooled to room temperature, and filtered to obtain a Pd / ZSM-5 molecular sieve precipitate; finally, the precipitate is washed with deionized water to remove unreacted sodium chloroplatinate, and finally dried at 60°C to obtain a Pd / ZSM-5 molecular sieve.

[0042] (2) The synthesized Pd / ZSM-5 molecular sieve and the europium nitrate precursor are mixed uniformly in a ratio of 1:1.5, and then dissolved in deionized water to obtain an impregnation solution; the impregnation solution is treated by an ultrasonic-assisted impregnation method for 30 minutes to promote the uniform loading of europium nitrate; finally, the precipitate is filtered and washed, and calcined at 500°C for 2 hours to form a stable europium nitrate oxide on the Pd / ZSM-5 molecular sieve, thereby obtaining a Pd-based molecular sieve loaded with europium nitrate.

[0043] (3) Pd / ZSM-5 molecular sieve loaded with europium nitrate was mixed with activated carbon in a ratio of 1:1, and then deionized water was added and stirred evenly; the mixture was reacted at 120°C for 12 hours by a hydrothermal method to obtain a composite material.

[0044] (4) The composite material is immersed in an organic solvent containing a carboxyl group, washed with deionized water and dried to finally obtain a functionalized Pd / ZSM-5 molecular sieve cold start adsorbent. According to the test, the specific surface area of ​​the functionalized Pd / ZSM-5 molecular sieve cold start adsorbent obtained in this embodiment is 310 m 2 / g, pore size is 6nm.

[0045] Comparative Example 1 The difference from Example 1 is that no auxiliary metal precursor is added, and the selection and preparation process of other raw materials are the same.

[0046] Comparative Example 2 The difference from Example 2 is that no auxiliary metal precursor is added, and the selection and preparation process of other raw materials are the same.

[0047] Comparative Example 3 The difference from Example 1 is that no auxiliary metal precursor and pyrolyzed MOFs derivative are added, and the preparation process is: sodium silicate and sodium aluminate are mixed, deionized water and sodium chloroplatinate are added, and Pd / Beta molecular sieve is obtained through high temperature and high pressure reaction; Pd / Beta molecular sieve is used directly without any functional treatment.

[0048] Comparative Example 4 The difference from Example 2 is that no auxiliary metal precursor and pyrolyzed MOFs derivative are added, and the preparation process is: sodium silicate and sodium aluminate are mixed, deionized water and sodium chloroplatinate are added, and Pd / ZSM-5 molecular sieve is obtained through high temperature and high pressure reaction; Pd / ZSM-5 molecular sieve is directly used without any functional treatment.

[0049] The auxiliary metal loading, NO x The removal efficiency and deactivation rate under high concentration of CO were tested, and the results are shown in Table 1: Table 1 Performance test results ;

[0050] According to the results shown in Table 1, the NO x The removal efficiency reached 95%, 92% in Example 2, 94% in Example 3, and 91% in Example 4. xThe removal efficiencies are 75%, 70%, 60% and 58%, respectively. This shows that the use of auxiliary metal precursors and functionalized materials in Examples 1 to 4 significantly improves the removal efficiency of the catalyst and enhances its adsorption capacity for pollutants in the exhaust gas. The deactivation rates of Examples 1 and 3 under high concentrations of CO are 3% and 3.5%, respectively, and the deactivation rates of Examples 2 and 4 are 4% and 4.5%. The deactivation rates of Comparative Examples 1 to 4 are higher, at 10%, 12%, 15% and 16%, respectively. This shows that the functionalized Pd-based molecular sieves in Examples 1 to 4 have better stability and resistance to deactivation in a high concentration of CO environment, and can effectively maintain their catalytic performance.

[0051] Therefore, the above-mentioned functionalized Pd-based molecular sieve cold start adsorbent and its preparation method are used to solve the problems of low adsorbent removal efficiency, easy deactivation in the presence of high concentration of CO, small specific surface area and unreasonable pore size distribution in the existing internal combustion engine exhaust treatment technology, providing a more effective technical means for internal combustion engine exhaust treatment.

[0052] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0053] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a functionalized Pd-based molecular sieve cold start adsorbent, characterized in that: The following steps are involved: S1, mixing a silicon source and an aluminum source in proportion, adding deionized water and a Pd precursor, and obtaining a Pd-based molecular sieve after a high temperature and high pressure reaction; S2, mixing the Pd-based molecular sieve with an auxiliary metal precursor, and subjecting the mixture to ultrasonic impregnation and high-temperature calcination to obtain a Pd-based molecular sieve loaded with an auxiliary metal; S3, mixing the Pd-based molecular sieve loaded with auxiliary metals with the functionalized material through a hydrothermal reaction to obtain a composite material, i.e., a functionalized Pd-based molecular sieve; S4, soaking the composite material in an organic solvent containing amino or carboxyl groups, washing with deionized water and drying, and finally obtaining a functionalized Pd-based molecular sieve cold start adsorbent.

2. The method for preparing a functionalized Pd-based molecular sieve cold start adsorbent according to claim 1, characterized in that: In S1, the synthesis process of the Pd-based molecular sieve is as follows: a silicon source and an aluminum source are mixed in proportion, deionized water is then added, and after stirring evenly, a Pd precursor is added to form a uniform mixed solution; the mixed solution is transferred to a high-pressure reactor, reacted at 110-150°C for 24-48h, cooled to room temperature, and filtered to obtain a Pd-based molecular sieve precipitate; finally, the precipitate is washed with deionized water to remove unreacted precursors, and finally dried at 60°C to obtain a Pd-based molecular sieve.

3. The method for preparing a functionalized Pd-based molecular sieve cold start adsorbent according to claim 2, characterized in that: The silicon source is sodium silicate, the aluminum source is sodium aluminate, the mass ratio of the silicon source to the aluminum source is 4:1, and the Pd precursor is sodium chloroplatinate.

4. The method for preparing a functionalized Pd-based molecular sieve cold start adsorbent according to claim 1, characterized in that: In S2, the synthesis process of the Pd-based molecular sieve loaded with the auxiliary metal is as follows: the synthesized Pd-based molecular sieve and the auxiliary metal precursor are uniformly mixed in proportion, and then dissolved in deionized water to obtain an impregnation solution; The impregnation solution is treated by ultrasonic-assisted impregnation for 30 minutes to promote uniform loading of the auxiliary metal; finally, the precipitate is filtered and washed, and calcined at 500° C. for 2 hours to form a stable metal oxide on the Pd-based molecular sieve, thereby obtaining a Pd-based molecular sieve loaded with the auxiliary metal.

5. The method for preparing a functionalized Pd-based molecular sieve cold start adsorbent according to claim 4, characterized in that: The mass ratio of the Pd-based molecular sieve to the auxiliary metal precursor is 1:2-50:

1.

6. The method for preparing a functionalized Pd-based molecular sieve cold start adsorbent according to claim 5, characterized in that: The auxiliary metal precursor is one or more of cobalt nitrate, nickel nitrate, cerium nitrate, copper nitrate or europium nitrate.

7. The method for preparing a functionalized Pd-based molecular sieve cold start adsorbent according to claim 1, characterized in that: In S3, the synthesis process of the composite material is: mixing the Pd-based molecular sieve loaded with auxiliary metal and the functional material in proportion, then adding deionized water and stirring evenly; reacting at 120° C. for 12 hours by a hydrothermal method to obtain the composite material.

8. The method for preparing a functionalized Pd-based molecular sieve cold start adsorbent according to claim 7, characterized in that: The functional material is a pyrolyzed MOFs derivative or activated carbon, and the mass ratio of the Pd-based molecular sieve loaded with auxiliary metals to the functional material is 1:1; the preparation process of the pyrolyzed MOFs derivative is: pyrolysis treatment is performed in an oxygen-free environment, and the metal organic framework material MOFs is heated to 500-600°C for 2-3 hours to remove organic ligands to obtain a pyrolyzed MOFs derivative, and the pyrolyzed MOFs derivative includes metal oxides or carbon-based materials.

9. A functionalized Pd-based molecular sieve cold-start adsorbent prepared by the method for preparing a functionalized Pd-based molecular sieve cold-start adsorbent according to any one of claims 1 to 8, characterized in that: The functionalized Pd-based molecular sieve cold start adsorbent is composed of the following components: Pd-based molecular sieve, wherein the Pd-based molecular sieve is Pd / Beta, Pd / ZSM-5 or Pd / CHA; Auxiliary metal, wherein the auxiliary metal is one or more of cobalt, nickel, cerium, copper or europium, and the loading amount of the auxiliary metal is 2% to 200% of the mass of the Pd-based molecular sieve; Functionalized material, wherein the functionalized material is a pyrolyzed MOFs derivative or activated carbon.

10. The functionalized Pd-based molecular sieve cold-start adsorbent prepared by the method for preparing a functionalized Pd-based molecular sieve cold-start adsorbent according to claim 9, characterized in that: The functionalized Pd-based molecular sieve cold start adsorbent has a high activity on NO at 50-150°C. x The removal efficiency is greater than 90%, and the deactivation rate is less than 5% in the presence of high concentration of CO. The specific surface area of ​​the functionalized Pd-based molecular sieve cold start adsorbent is greater than 300m 2 / g, pore size is 2~10nm.

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