Method for preparing molecular sieve and molecular sieve

Abstract

The method comprises the following steps: mixing a silicon-based precursor solution, a first metal complexing solution and a second metal complexing solution to obtain a mixed solution, the silicon-based precursor solution comprises a silicon source substance, a strong alkali, a structure-directing agent and water, the first metal complexing solution comprises a soluble noble metal salt and a complexing agent, and the second metal complexing solution comprises a soluble noble metal salt and a complexing agent; the second metal complexing solution comprises soluble transition metal salt and a complexing agent, and the structure-directing agent comprises a quaternary ammonium compound; and performing crystallization treatment on the mixed solution to obtain the molecular sieve. The method is simple to operate, the time for preparing the molecular sieve is short, and the prepared molecular sieve is good in particle dispersity.

Description

Technical Field

[0001] The present application relates to the field of catalysts, and in particular, to a method for preparing a molecular sieve and a molecular sieve. Background Art

[0002] Metal nanoclusters show high catalytic activity and selectivity in many catalytic reactions because they have high specific surface area, more exposed active atoms and special electronic structure. At the same time, metal nanoclusters are less stable than large-particle nanomaterials such as mesoporous silicon and graphene. The structure of metal nanoclusters will change in an environment with slightly higher temperature, such as slightly above 100 degrees Celsius. Introducing suitable porous carriers to exert the catalytic effect of metal nanoclusters is an important means to protect their cluster structure and exert catalytic effects. Among them, molecular sieves have attracted widespread attention for their regular pore structure and stability. Summary of the invention

[0003] In the first aspect of the present application, the present application proposes a method for preparing a molecular sieve, comprising: mixing a silicon-based precursor solution, a first metal complex solution, and a second metal complex solution to obtain a mixed solution, wherein the silicon-based precursor solution includes a silicon source material, a strong base, a structure directing agent, and water, the first metal complex solution includes a soluble precious metal salt and a complexing agent, the second metal complex solution includes a soluble transition metal salt and a complexing agent, and the structure directing agent includes a quaternary ammonium compound; the mixed solution is crystallized to obtain a molecular sieve. The method for preparing a molecular sieve proposed in the present application is to complete the crystallization process by mixing the silicon-based precursor solution with the first metal complex solution and the second metal complex solution, thereby encapsulating the two types of metal nanoclusters together in the pores of the molecular sieve. The method is simple to operate, the time required for preparing the molecular sieve is short, and the prepared molecular sieve particles have good dispersibility.

[0004] In some embodiments, in the silicon-based precursor solution, the molar ratio of the silicon source material, the structure directing agent, the strong base, and the water is (0.05-0.2):(0.1-0.3):(5-30):(230-690). Thus, the formed molecular sieve has a crystalline porous structure with ordered channels.

[0005] In some embodiments, the silicon source material includes at least one of silica sol and tetraethyl orthosilicate.

[0006] In some embodiments, the quaternary ammonium compound comprises a quaternary ammonium hydroxide.

[0007] In some embodiments, the strong base includes at least one of sodium hydroxide and potassium hydroxide. Thus, the silicon source material provides a molecular sieve framework Si-O structure; the quaternary ammonium compound and the strong base assist the molecular sieve framework to form a relatively regular molecular morphology.

[0008] In some embodiments, the molar ratio of the soluble noble metal salt to the complexing agent in the first metal complexing solution is 1:(2-20).

[0009] In some embodiments, the molar ratio of the soluble transition metal salt to the complexing agent in the second metal complexing solution is 1:(2-20). Thus, the metal complexing solution is relatively stable.

[0010] In some embodiments, the soluble precious metal salt includes at least one of chloroplatinic acid, platinum chloride, platinum nitrate, dichlorotetraammine platinum, tetraammine platinum nitrate, tetraammine platinum acetate, acetylacetonate platinum, palladium chloride, palladium nitrate, palladium acetate, and acetylacetonate palladium; and / or, the soluble transition metal salt includes at least one of zinc nitrate, zinc chloride, zinc sulfate, zinc acetate and its hydrate, nickel nitrate, nickel chloride, nickel sulfate, nickel acetate and its hydrate, cobalt nitrate, cobalt chloride, cobalt sulfate, cobalt acetate and its hydrate. Thus, the bimetallic nanoclusters encapsulated in the metal sieve formed by the above-mentioned soluble metal salt and soluble transition metal salt have a relatively uniform particle size and better dispersibility.

[0011] In some embodiments, the complexing agent includes at least one of ethylenediamine, tetraethylenepentamine, ethylenediaminetetraacetic acid, and triethylenediamine. Thus, the complexing agent can form a complex with the metal ion, so that it can be encapsulated in the pores of the molecular sieve.

[0012] In some embodiments, the temperature of the crystallization treatment is 150° C.-210° C., and the time of the crystallization treatment is 5 min-60 min.

[0013] In some embodiments, the reaction vessel for the crystallization process comprises a tubular reactor, thereby increasing the yield of metal clusters.

[0014] In some embodiments, before the mixing, the step further includes: subjecting the silicon-based precursor liquid to an aging treatment, wherein the aging treatment temperature is 80° C.-100° C., and the aging treatment time is 8 h-24 h.

[0015] In some embodiments, the mixed solution is subjected to an aging treatment, wherein the aging treatment temperature is 80° C.-100° C., and the aging treatment time is 1 h-3 h. Thus, the chemical properties of the silicon-based precursor solution and the mixed solution after the aging treatment are more stable, which is conducive to forming a more regular molecular sieve structure.

[0016] In some embodiments, the process further comprises: sintering the molecular sieve at a temperature of 350°C-450°C and a sintering time of 6h-8h. Thus, the pore structure of the prepared molecular sieve can be further adjusted, and the physical and chemical properties of the molecular sieve can be adjusted to meet the requirements for the use of the molecular sieve as a product.

[0017] In the second aspect of the present application, the present application proposes a molecular sieve prepared by the aforementioned method. As a result, the particle size of the bimetallic nanoclusters encapsulated in the molecular sieve is small and the uniformity is high. The ligand effect and group effect of the bimetallic nanoclusters can be used to effectively improve the catalytic efficiency of the molecular sieve as a catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0019] Figure 1 This is the XRD pattern of the molecular sieve prepared in one embodiment of the present application;

[0020] Figure 2 This is a SEM image of a molecular sieve prepared in one embodiment of the present application;

[0021] Figure 3 This is a HRTEM image of a molecular sieve prepared in one embodiment of the present application;

[0022] Figure 4 This is a HRTEM image of a molecular sieve prepared in one embodiment of the present application;

[0023] Figure 5 This is a HRTEM image of the molecular sieve prepared in one example of the present application. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the drawings, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0025] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0026] The terms "including" and "having" in the specification and claims of the present application and any modifications thereof are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0027] In the description of this application, regardless of whether the words "about" or "approximately" are used, all the numbers disclosed herein are approximate values. The value of each number may differ by less than 10% or a reasonable difference considered by those skilled in the art, such as 1%, 2%, 3%, 4% or 5%.

[0028] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0029] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0030] Metal nanoclusters have excellent catalytic properties due to their unique geometric configuration and outer electronic structure. In the past few decades, metal nanocluster catalysts have been widely studied for hydrogenation, dehydrogenation, oxidation and other reaction processes. However, single metal nanocluster catalysts have a single active site, poor anti-toxicity and competitive adsorption, and insufficient catalytic efficiency. To improve the above shortcomings, a second metal is further introduced into the single metal to form a bimetallic nanocluster. However, bimetallic nanoclusters are small in size, large in surface free energy, and thermodynamically unstable. They are very easy to sinter during thermal activation and / or catalysis, resulting in rapid deactivation. By introducing molecular sieves, bimetallic nanoclusters are encapsulated in the molecular sieve pores, and the pore structure and hydrothermal stability of the molecular sieve can be used to protect the metal nanoclusters, thereby being able to give full play to the advantages of bimetallic nanoclusters and molecular sieves. On the basis of maintaining the catalytic activity of bimetallic nanoclusters, the confinement effect of the molecular sieve pores is used to prevent the sintering and growth of metal clusters. The method for preparing molecular sieves proposed by the present invention can encapsulate bimetallic nanoclusters in molecular sieves. At the same time, the method is simple to operate, has a short production and preparation time, and a high yield.

[0031] In the first aspect of the present application, a method for preparing a molecular sieve is proposed, comprising: mixing a silicon-based precursor solution, a first metal complex solution, and a second metal complex solution to obtain a mixed solution, wherein the silicon-based precursor solution comprises a silicon source material, a strong base, a structure directing agent, and water, the first metal complex solution comprises a soluble precious metal salt and a complexing agent, the second metal complex solution comprises a soluble transition metal salt and a complexing agent, and the structure directing agent comprises a quaternary ammonium compound; and crystallizing the mixed solution to obtain a molecular sieve.

[0032] The method for preparing molecular sieves provided in the present application is a universal method for ultra-fast preparation of bimetallic encapsulated MFI molecular sieve catalysts. The silicon-based precursor solution contains a silicon source material, a strong base and a structure-directing agent, as shown in FIG. Figure 1 , generating MFI molecular sieve. Furthermore, the precipitation of two different metals and the crystallization rate of molecular sieve can be adjusted to match the three to precipitate simultaneously, refer to Figure 2 , thereby uniformly encapsulating the bimetallic nanoclusters in the molecular sieve. The method provided in the present application can quickly encapsulate the bimetallic nanoclusters in the molecular sieve, with fast synthesis speed, good metal dispersion, and easy to scale up the synthesis process.

[0033] In some embodiments, in the silicon-based precursor solution, the molar ratio of the silicon source material, the structure directing agent, the strong base, and the water is (0.05-0.2):(0.1-0.3):(5-30):(230-690).

[0034] Within the range of the components and component molar ratios of the aforementioned silicon-based precursor solution, the silicon source material can be fully dispersed in the solvent water. Under the alkaline conditions provided by the strong base, the structure directing agent can guide the silicon source material to nucleate according to a specific structure, while adjusting the growth rate of the molecular sieve crystals along different crystal axis directions, reducing its bulk nucleation rate, thereby forming a structurally regular MFI molecular sieve in the subsequent preparation process.

[0035] In some embodiments, the silicon source material includes at least one of silica sol and tetraethyl orthosilicate; and / or the quaternary ammonium compound includes quaternary ammonium hydroxide.

[0036] In some embodiments, the strong base includes at least one of sodium hydroxide and potassium hydroxide.

[0037] The silicon source material forms silicon oxide after being dispersed in the solution, which has thermal stability and weather resistance, and forms silicon-based precursor solution required for preparing molecular sieve after being mixed with quaternary ammonium compound and strong base as structure directing agent.

[0038] In some embodiments, the molar ratio of the soluble noble metal salt to the complexing agent in the first metal complexing solution is 1:(2-20).

[0039] In some embodiments, the molar ratio of the soluble transition metal salt to the complexing agent in the second metal complexing solution is 1:(2-20).

[0040] The complexing agent can form stable complexes with the noble metal ions released by the soluble noble metal salt in the solution, and the soluble transition metal ions released by the soluble transition metal salt in the solution, thereby adjusting the reduction rate of the metal ions and the growth kinetics of the nanoparticles to control the size, shape and dispersity of the formed metal nanoclusters.

[0041] In some embodiments, the soluble precious metal salt includes at least one of chloroplatinic acid, platinum chloride, platinum nitrate, tetraamineplatinum dichloride, tetraamineplatinum nitrate, tetraamineplatinum acetate, platinum acetylacetonate, palladium chloride, palladium nitrate, palladium acetate, and palladium acetylacetonate.

[0042] In some embodiments, the soluble transition metal salt includes at least one of zinc nitrate, zinc chloride, zinc sulfate, zinc acetate and hydrates thereof, nickel nitrate, nickel chloride, nickel sulfate, nickel acetate and hydrates thereof, cobalt nitrate, cobalt chloride, cobalt sulfate, cobalt acetate and hydrates thereof.

[0043] The soluble noble metal salt can provide platinum ions or palladium ions; the soluble transition metal salt can provide zinc ions, nickel ions, and cobalt ions. By adjusting the ratio and interaction of the two types of metal ions, the synergistic effect between the metal nanoclusters and the molecular sieve carrier can be regulated, so that it exhibits excellent thermal stability and catalytic performance under high temperature conditions.

[0044] In some embodiments, the complexing agent includes at least one of ethylenediamine, tetraethylenepentamine, ethylenediaminetetraacetic acid, and triethylenediamine.

[0045] The complexing agent is an organic complexing agent, which contains a ligand that can provide an electron pair and is helpful for the formation of metal nanoclusters.

[0046] In some embodiments, the temperature of the crystallization treatment is 150° C.-210° C., and the time of the crystallization treatment is 5 min-60 min.

[0047] Within the temperature range of the aforementioned crystallization treatment, the components that can form the molecular sieve provided by the silicon-based precursor liquid will self-assemble to form a precursor, and further undergo hydrothermal crystallization to form a molecular sieve. By adding ligands to complex with metal ions, the surface free energy is reduced and the sedimentation time of the metal elements is adjusted. Within the time range of the aforementioned crystallization treatment, the crystallization process of the molecular sieve is carried out synchronously with the sedimentation of the bimetallic nanoclusters, so that the bimetallic nanoclusters can be packed in the pores of the molecular sieve.

[0048] In some embodiments, the reaction vessel for the crystallization process comprises a tubular reactor.

[0049] In some embodiments, the tubular reactor is a stainless steel tubular container with both ends closed.

[0050] Since the tubular reactor has a large heat exchange surface per unit reactor volume, good thermal effect, and low thermal hysteresis, it can achieve rapid heating in different media.

[0051] In some embodiments, before the mixing, the method further comprises: subjecting the silicon-based precursor liquid to an aging treatment, wherein the aging treatment temperature is 80° C.-100° C., and the aging treatment time is 8 h-24 h.

[0052] The synthesis of molecular sieves requires a high temperature and strong alkaline environment, in which metal ions with high surface free energy will quickly form precipitation, resulting in inconsistent crystallization time of molecular sieves and metal nanoclusters. Therefore, in the silicon-based precursor solution, quaternary ammonium hydroxide, such as tetrapropylammonium hydroxide (TPAOH), is used as a structure directing agent, and aging is performed within the temperature conditions and time range of the aforementioned aging treatment, which can effectively control the nucleation and growth of the zeolite structure molecular sieve, and then control the morphology structure and crystallization rate of the molecular sieve, so that the metal nanoclusters can be precipitated and encapsulated with the molecular sieve at a relatively consistent time in the subsequent preparation process.

[0053] In some embodiments, the mixed solution is subjected to an aging treatment, wherein the aging treatment temperature is 80° C.-100° C., and the aging treatment time is 1 h-3 h.

[0054] Since the impregnation kinetics and ion exchange kinetics of different metal precursors are different, their respective sedimentation rates are also different, which will affect the composition of the final prepared bimetallic nanoclusters and the spatial distribution uniformity of the bimetallic nanoclusters in the molecular sieve. By aging the mixed solution, the interaction between the metal nanoclusters and the carrier can be enhanced. The enhanced interaction helps to improve the dispersibility and catalytic activity of the nanoclusters, and further increase the encapsulation amount of the metal nanoclusters in the molecular sieve.

[0055] In some embodiments, the method further comprises: sintering the molecular sieve, wherein the sintering temperature is 350° C.-450° C., and the sintering time is 6 h-8 h.

[0056] The molecular sieve is sintered to remove the structure directing agent in the molecular sieve using a reducing atmosphere. Figure 3-Figure 5 The bimetallic particles in the molecular sieve prepared by the method of the present invention are small and uniform in size and have excellent anti-sintering performance.

[0057] In the second aspect of the present application, the present application proposes a molecular sieve prepared by the aforementioned method.

[0058] The molecular sieve prepared by the method described in the present application has encapsulated bimetallic nanoclusters with small particle size and uniform cluster size, and the molecular sieve has excellent anti-sintering performance, which can effectively improve the catalytic efficiency of the molecular sieve when used as a catalyst.

[0059] The scheme of the present application is described below by specific examples. It should be noted that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are specified in the examples, the technology or conditions described in the literature in this area or the product instructions are used. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be obtained commercially.

[0060] Example 1

[0061] Step 1: weigh 0.4 g NaOH and 2.1 g TPAOH (40 wt%), mix and stir until completely dissolved, then add 9.22 g LudoxAs-40, age at 90° C. for 13 h to obtain a silicon-based precursor solution.

[0062] Step 2: Measure 858 μL of a solution containing 10 wt% H2PtCl6 and add it to 8.42 g of water, and then add 146 μL of ethylenediamine to obtain a first metal complex solution.

[0063] Step 3: weigh 0.14 g zinc nitrate and dissolve it in 10 g water. After it is completely dissolved, add 0.1 g ethylenediamine to obtain a second metal complex solution.

[0064] Step 4: Add the metal complex solutions in step 2 and step 3 dropwise to the silicon-based precursor solution in step 1, and continue aging at 90° C. for 1 hour to obtain a mixed solution.

[0065] Step 5, transferring the mixed solution obtained in step 4 to a tubular reactor, followed by crystallization at 210° C. for 5 min, centrifuging and washing the obtained product, and then drying at 80° C. for 8 h to obtain a dried molecular sieve.

[0066] Step six, calcining the dried molecular sieve in step five at 400° C. in a flowing hydrogen atmosphere for 6 hours to obtain a molecular sieve. Testing shows that the Pt content in the molecular sieve is about 1 wt %, and the Zn content is about 1 wt %.

[0067] Example 2

[0068] Step 1: weigh 0.4 g NaOH and 2.1 g TPAOH (40 wt%), mix and stir until completely dissolved, then add 9.22 g LudoxAs-40, age at 90° C. for 13 h to obtain a silicon-based precursor solution.

[0069] Step 2: Measure 358 μL of a solution containing 10 wt% H2PtCl6 and add it to 8.42 g of water, and then add 61 μL of ethylenediamine to obtain a first metal complex solution.

[0070] Step 3: weigh 0.14 g zinc nitrate and dissolve it in 10 g water. After it is completely dissolved, add 0.1 g ethylenediamine to obtain a second metal complex solution.

[0071] Step 4: Add the metal complex solutions in step 2 and step 3 dropwise to the silicon-based precursor solution in step 1, and continue aging at 90° C. for 1 hour to obtain a mixed solution.

[0072] Step 5, transferring the mixed solution obtained in step 4 to a tubular reactor, followed by crystallization at 210° C. for 5 min, centrifuging and washing the obtained product, and then drying at 80° C. for 8 h to obtain a dried molecular sieve.

[0073] Step six, calcining the dried molecular sieve in step five at 400° C. in a flowing hydrogen atmosphere for 6 hours to obtain a molecular sieve. Testing shows that the molecular sieve has a Pt content of 0.5 wt % and a Zn content of about 1 wt %.

[0074] Example 3

[0075] Step 1: weigh 0.4 g NaOH and 2.1 g TPAOH (40 wt%), mix and stir until completely dissolved, then add 9.22 g LudoxAs-40, age at 90° C. for 8 h to obtain a silicon-based precursor solution.

[0076] Step 2: Measure 858 μL of a solution containing 10 wt% H2PtCl6 and add it to 8.42 g of water, and then add 146 μL of ethylenediamine to obtain a first metal complex solution.

[0077] Step 3: weigh 0.27 g zinc nitrate and dissolve it in 10 g water. After it is completely dissolved, add 0.19 g ethylenediamine to obtain a second metal complex solution.

[0078] Step 4: Add the metal complex solutions in step 2 and step 3 dropwise to the silicon-based precursor solution in step 1, and continue aging at 90° C. for 1 hour to obtain a mixed solution.

[0079] Step 5, transferring the mixed solution obtained in step 4 to a tubular reactor, followed by crystallization at 150° C. for 20 min, centrifuging and washing the obtained product, and then drying at 80° C. for 8 h to obtain a dried molecular sieve.

[0080] Step six, calcining the dried molecular sieve in step five at 400° C. in a flowing hydrogen atmosphere for 6 hours to obtain a molecular sieve. Testing shows that the Pt content in the molecular sieve is 1 wt % and the Zn content is about 2 wt %.

[0081] Example 4

[0082] Step 1: weigh 0.4 g NaOH and 2.1 g TPAOH (40 wt%), mix and stir until completely dissolved, then add 9.22 g LudoxAs-40, age at 90° C. for 13 h to obtain a silicon-based precursor solution.

[0083] Step 2: Measure 858 μL of a solution containing 10 wt% H2PtCl6 and add it to 8.42 g of water, and then add 146 μL of ethylenediamine to obtain a first metal complex solution.

[0084] Step 3: weigh 0.07 g of nickel nitrate and dissolve it in 10 g of water. After it is completely dissolved, add 0.05 g of ethylenediamine to obtain a second metal complex solution.

[0085] Step 4: Add the metal complex solutions in step 2 and step 3 dropwise to the silicon-based precursor solution in step 1, and continue aging at 90° C. for 1 hour to obtain a mixed solution.

[0086] Step 5, transferring the mixed solution obtained in step 4 to a tubular reactor, followed by crystallization at 190° C. for 5 min, centrifuging and washing the obtained product, and then drying at 80° C. for 8 h to obtain a dried molecular sieve.

[0087] Step six, calcining the dried molecular sieve in step five at 400° C. in a flowing hydrogen atmosphere for 6 hours to obtain a molecular sieve. Testing shows that the molecular sieve has a Pt content of 1 wt % and a nickel content of about 0.5 wt %.

[0088] Example 5

[0089] Step 1: weigh 0.4 g NaOH and 2.1 g TPAOH (40 wt%), mix and stir until completely dissolved, then add 9.22 g LudoxAs-40, age at 90° C. for 13 h to obtain a silicon-based precursor solution.

[0090] Step 2: Measure 858 μL of a solution containing 10 wt% H2PtCl6 and add it to 8.42 g of water, and then add 146 μL of ethylenediamine to obtain a first metal complex solution.

[0091] Step 3: weigh 0.06 g of cobalt chloride and dissolve it in 10 g of water. After it is completely dissolved, add 0.05 g of ethylenediamine to obtain a second metal complex solution.

[0092] Step 4: Add the metal complex solutions in step 2 and step 3 dropwise to the silicon-based precursor solution in step 1, and continue aging at 90° C. for 1 hour to obtain a mixed solution.

[0093] Step 5, transferring the mixed solution obtained in step 4 to a tubular reactor, followed by crystallization at 210° C. for 5 min, centrifuging and washing the obtained product, and then drying at 80° C. for 8 h to obtain a dried molecular sieve.

[0094] Step six, calcining the dried molecular sieve in step five at 400° C. in a flowing hydrogen atmosphere for 6 hours to obtain a molecular sieve. Testing shows that the molecular sieve has a Pt content of 1 wt % and a Co content of about 0.5 wt %.

[0095] Example 6

[0096] Step 1: weigh 0.4 g NaOH and 2.1 g TPAOH (40 wt%), mix and stir until completely dissolved, then add 9.22 g LudoxAs-40, age at 90° C. for 19 h to obtain a silicon-based precursor solution.

[0097] Step 2: Measure 143 μL of a solution containing 10 wt% H2PtCl6 and add it to 8.42 g of water, and then add 24 μL of ethylenediamine to obtain a first metal complex solution.

[0098] Step 3: weigh 0.18 g of cobalt acetate and dissolve it in 10 g of water. After it is completely dissolved, add 0.21 g of ethylenediamine to obtain a second metal complex solution.

[0099] Step 4: Add the metal complex solutions in step 2 and step 3 dropwise to the silicon-based precursor solution in step 1, and continue aging at 90° C. for 1 hour to obtain a mixed solution.

[0100] Step 5, transferring the mixed solution obtained in step 4 to a tubular reactor, followed by crystallization at 170° C. for 10 min, centrifuging and washing the obtained product, and then drying at 80° C. for 8 h to obtain a dried molecular sieve.

[0101] Step six, calcining the dried molecular sieve in step five at 400° C. in a flowing hydrogen atmosphere for 6 hours to obtain a molecular sieve. Testing shows that the Pt content in the molecular sieve is 0.2 wt % and the Co content is about 2 wt %.

[0102] Example 7

[0103] Step 1: weigh 0.4 g NaOH and 2.1 g TPAOH (40 wt%), mix and stir until completely dissolved, then add 9.22 g LudoxAs-40, age at 90° C. for 8 h to obtain a silicon-based precursor solution.

[0104] Step 2: Measure 858 μL of a solution containing 10 wt% H2PtCl6 and add it to 8.42 g of water, and then add 146 μL of ethylenediamine to obtain a first metal complex solution.

[0105] Step 3: weigh 0.25 g of nickel acetate and dissolve it in 10 g of water. After it is completely dissolved, add 0.21 g of ethylenediamine to obtain a second metal complex solution.

[0106] Step 4: Add the metal complex solutions in step 2 and step 3 dropwise to the silicon-based precursor solution in step 1, and continue aging at 90° C. for 1 hour to obtain a mixed solution.

[0107] Step 5, transferring the mixed solution obtained in step 4 to a tubular reactor, followed by crystallization at 210° C. for 5 min, centrifuging and washing the obtained product, and then drying at 80° C. for 8 h to obtain a dried molecular sieve.

[0108] Step six, calcining the dried molecular sieve in step five at 400° C. in a flowing hydrogen atmosphere for 6 hours to obtain a molecular sieve. Testing shows that the Pt content in the molecular sieve is 1 wt % and the Ni content is about 2 wt %.

[0109] Example 8

[0110] Step 1: weigh 0.4 g NaOH and 2.1 g TPAOH (40 wt%), mix and stir until completely dissolved, then add 9.22 g LudoxAs-40, age at 90° C. for 16 h to obtain a silicon-based precursor solution.

[0111] Step 2: Measure 858 μL of a solution containing 10 wt% H2PtCl6 and add it to 8.42 g of water, and then add 146 μL of ethylenediamine to obtain a first metal complex solution.

[0112] Step 3: weigh 0.13 g of nickel sulfate and dissolve it in 10 g of water. After it is completely dissolved, add 0.11 g of ethylenediamine to obtain a second metal complex solution.

[0113] Step 4: Add the metal complex solutions in step 2 and step 3 dropwise to the silicon-based precursor solution in step 1, and continue aging at 90° C. for 1 hour to obtain a mixed solution.

[0114] Step 5, transferring the mixed solution obtained in step 4 to a tubular reactor, followed by crystallization at 170° C. for 10 min, centrifuging and washing the obtained product, and then drying at 80° C. for 8 h to obtain a dried molecular sieve.

[0115] Step six, calcining the dried molecular sieve in step five at 400° C. in a flowing hydrogen atmosphere for 6 hours to obtain a molecular sieve. Testing shows that the molecular sieve has a Pt content of 1 wt % and a Ni content of about 1 wt %.

[0116] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. "First feature" and "second feature" may include one or more of the features.

[0117] In the description of the present application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for examples and may be any technical feature connected by "and / or" in the present application.

[0118] In the description of this application, "same chemical composition" should be understood in a broad sense, that is, the main components of the two have the same chemical composition, or the chemical composition of the two is basically the same, and may have errors within the allowable range in the field that are understandable to those skilled in the art or contain impurities within the allowable range.

[0119] In the present application, the writing order of each step does not mean a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) can be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0120] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a molecular sieve, characterized in that: include: Mixing a silicon-based precursor solution, a first metal complex solution, and a second metal complex solution to obtain a mixed solution, wherein the silicon-based precursor solution includes a silicon source material, a strong base, a structure directing agent, and water, the first metal complex solution includes a soluble noble metal salt and a complexing agent, the second metal complex solution includes a soluble transition metal salt and a complexing agent, and the structure directing agent includes a quaternary ammonium compound; The mixed solution is subjected to a crystallization treatment to obtain a molecular sieve.

2. The method according to claim 1, characterized in that In the silicon-based precursor solution, the molar ratio of the silicon source material, the structure directing agent, the strong base, and the water is (0.05-0.2):(0.1-0.3):(5-30):(230-690).

3. The method according to claim 1 or 2, characterized in that: The silicon source material includes at least one of silica sol and tetraethyl orthosilicate; and / or, The quaternary ammonium compound comprises a quaternary ammonium hydroxide; and / or, The strong base includes at least one of sodium hydroxide and potassium hydroxide.

4. The method according to claim 1, characterized in that: The molar ratio of the soluble noble metal salt to the complexing agent in the first metal complexing solution is 1:(2-20); and / or, The molar ratio of the soluble transition metal salt to the complexing agent in the second metal complexing solution is 1:(2-20).

5. The method according to claim 4, characterized in that The soluble precious metal salt includes at least one of chloroplatinic acid, platinum chloride, platinum nitrate, tetraammineplatinum dichloride, tetraammineplatinum nitrate, tetraammineplatinum acetate, platinum acetylacetonate, palladium chloride, palladium nitrate, palladium acetate, and palladium acetylacetonate; and / or, The soluble transition metal salt includes at least one of zinc nitrate, zinc chloride, zinc sulfate, zinc acetate and hydrates thereof, nickel nitrate, nickel chloride, nickel sulfate, nickel acetate and hydrates thereof, cobalt nitrate, cobalt chloride, cobalt sulfate, cobalt acetate and hydrates thereof.

6. The method according to claim 4, characterized in that The complexing agent includes at least one of ethylenediamine, tetraethylenepentamine, ethylenediaminetetraacetic acid, and triethylenediamine.

7. The method according to claim 1 or 2, characterized in that: The temperature of the crystallization treatment is 150° C.-210° C., and the time of the crystallization treatment is 5 min-60 min; and / or, The reaction vessel for the crystallization treatment includes a tubular reactor.

8. The method according to claim 1 or 2, characterized in that: Before the mixing, the method further comprises: subjecting the silicon-based precursor liquid to an aging treatment, wherein the aging treatment temperature is 80° C.-100° C., and the aging treatment time is 8 h-24 h; and / or, The mixed solution is subjected to an aging treatment, wherein the aging treatment temperature is 80° C.-100° C., and the aging treatment time is 1 h-3 h.

9. The method according to claim 1 or 2, characterized in that: Further including: The molecular sieve is sintered at a temperature of 350° C. to 450° C. and for a time of 6 h to 8 h.

10. A molecular sieve, characterized in that: The method is prepared by any one of claims 1 to 9.

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