Metal modified hydrogen type ZSM-5 molecular sieve, synthetic method thereof and 1-hexene hydroformylation reaction catalyst

Abstract

The invention provides a metal modified hydrogen type ZSM-5 molecular sieve, a synthesis method thereof and a 1-hexene hydroformylation reaction catalyst. The synthesis method comprises the following steps: dissolving an organic amine ligand and metal salt in deionized water, and stirring to obtain a solution A; dissolving a sodium-free silicon source and an aluminum source in deionized water, and stirring to obtain a solution B; mixing the solution B with the solution A, adding a template agent and ammonia water to obtain a reaction solution, and performing hydrothermal crystallization, cooling, centrifuging, drying and roasting to obtain the metal modified hydrogen type ZSM-5 molecular sieve. According to the method, ammonia water is adopted as a mineralizer, and metal is directly introduced into the hydrogen type HZSM-5 molecular sieve in situ by a one-step method, so that the steps of multiple ion exchange and roasting in the traditional method are omitted, and wastewater discharge and pollution are reduced. According to the present invention, the metal in the metal modified hydrogen type ZSM-5 molecular sieve is uniformly dispersed, and the metal modified hydrogen type ZSM-5 molecular sieve can be used as the 1-hexene hydroformylation reaction catalyst, and has characteristics of high 1-hexene conversion rate and high n-heptanal selectivity.

Description

Technical Field

[0001] The invention relates to the field of catalytic materials, and in particular to a synthesis method of a metal-modified hydrogen-type ZSM-5 molecular sieve and a 1-hexene hydroformylation reaction catalyst. Background Art

[0002] ZSM-5 molecular sieve has adjustable acidity, good thermal stability and hydrothermal stability. The special pore structure determines its shape selectivity advantage in catalysis. It has been widely used in many chemical fields such as catalytic cracking, alkylation to produce toluene and xylene, isomerization, methanol to olefins, etc. In order to improve the catalytic activity, selectivity and stability of ZSM-5 molecular sieve in different reaction processes, it is necessary to modify it with appropriate metals. For example, the addition of Fe improves the selectivity of light olefins and propylene in the catalytic cracking reaction of naphtha and the stability of ZSM-5. The introduction of Zn improves the aromatics yield of methanol reaction to aromatics. Studies have shown that Zn-ZSM-5 is the most effective catalyst for improving the selectivity of monocyclic aromatics including BTX (benzene, toluene, xylene). The introduction of a small amount of Cu can maintain the balance between metal dehydrogenation activity and ZSM-5 shape selectivity, which is beneficial to improve the yield of light olefins in the FCC process.

[0003] Wang (J Mater Sci 56, 18050-18060 (2021)) reported a one-pot green synthesis method for Fe-ZSM-5 molecular sieves. This method does not add seed templates. Ferric nitrate and sodium aluminate, sodium hydroxide, and alkaline silica sol are mixed evenly, dried at 100°C to form a dry gel, and crystallized at 170°C by steam-assisted crystallization (SAC). Finally, it is cooled, filtered, washed and dried to prepare Na-type Fe-ZSM-5 zeolite.

[0004] CN104525246B discloses a method for preparing a template-free small-grain Zn-ZSM-5 catalyst and its application. The method is to directly add zinc salt during the preparation of the molecular sieve, and obtain a sodium-type Zn-ZSM-5 molecular sieve catalyst through hydrothermal crystallization, filtration, drying, and roasting. Then, the Zn-ZSM-5 molecular sieve catalyst is ion exchanged in an ammonium salt solution to obtain a hydrogen-type small-grain Zn-ZSM-5 catalyst required for the methanol to gasoline reaction. No template is added during the catalyst preparation process, and the obtained Zn-ZSM-5 has a uniform particle size and a regular morphology, but the process requires multiple ion exchanges.

[0005] CN114950351A discloses a method for modifying ZSM-5 molecular sieves by adding metal cations (Cu 2+ ,La 2+ 、Ce 3+The specific experimental steps are as follows: take the ZSM-5 molecular sieve, add the prepared metal salt solution, move it to a hydrothermal reactor, heat it to 80-150°C, and react for 4-10 hours. Naturally cool to room temperature, filter, dry, and calcine to obtain a metal cation-doped molecular sieve. The synthesis conditions are mild and easy to control. The molecular sieves synthesized by the above method are all sodium-type, and multiple ion exchanges and calcinations are required to obtain hydrogen-type molecular sieves, and the process is relatively cumbersome.

[0006] CN114426290A discloses a method for synthesizing a sodium-free Fe-ZSM-5 molecular sieve. First, Silicate-1 seed crystals are hydrothermally treated under alkaline conditions, then added into a molecular sieve synthesis raw material solution, and then hydrothermally treated to obtain a sodium-free Fe-ZSM-5 molecular sieve. The synthesis process does not require ion exchange. The b-axis size of the synthesized molecular sieve is 5-50nm. The small size is conducive to the mass transfer of the reaction molecules, and effectively improves the reduction of ammonia to remove atmospheric pollution NO. x However, the synthesis process requires the addition of seed crystals and size inhibitors (NH2-C6H4-CH2-C6H4-NH2), and requires two hydrothermal processes.

[0007] At present, the conventional method of preparing metal-modified hydrogen-type ZSM-5 molecular sieve catalysts mostly adopts the post-impregnation method, which is a cumbersome process; and when the metal source is directly added to the alkaline system of ZSM-5 molecular sieve synthesis, the metal precipitation rate is much faster than the molecular sieve crystallization rate, so it is difficult to achieve effective dispersion of the metal in the molecular sieve crystal. In addition, in the traditional molecular sieve synthesis, sodium hydroxide is often used as the alkaline source, and the obtained molecular sieve is a sodium-type molecular sieve. A large amount of alkali metal ions (Na + ) needs to go through multiple ion exchange steps to convert it into an ammonium molecular sieve (NH4 + ), and then calcined to obtain hydrogen-type HZSM-5 with acidic catalytic active centers. Among them, the ion exchange process will produce a large amount of wastewater, which increases the cost of wastewater treatment. However, if alkali metal ions are not added, multiple hydrothermal crystallization processes are required, which is cumbersome and energy-intensive.

[0008] Therefore, there is a need to provide a method for directly synthesizing metal-modified hydrogen-type ZSM-5 molecular sieves without adding alkali metal ions, so as to solve the current problems of complicated steps, difficulty in introducing metals, generation of a large amount of sodium-containing wastewater, high energy consumption, and long process. Summary of the invention

[0009] In order to solve the above technical problems, the purpose of the present invention is to provide a metal-modified hydrogen-type ZSM-5 molecular sieve and a synthesis method thereof. The method can directly synthesize the metal-modified hydrogen-type ZSM-5 molecular sieve.

[0010] The present invention also aims to provide a 1-hexene hydroformylation catalyst.

[0011] To achieve the above object, the present invention provides a method for synthesizing a metal-modified hydrogen-type ZSM-5 molecular sieve, wherein the synthesis method comprises:

[0012] S1, dissolving an organic amine ligand and a metal salt in deionized water to obtain a solution A;

[0013] S2, dissolving a sodium-free silicon source and a sodium-free aluminum source in deionized water to obtain a solution B;

[0014] S3, mixing solution B with solution A, adding a template and aqueous ammonia to obtain a reaction solution, and subjecting the mixture to hydrothermal crystallization, cooling, centrifugation, drying, and calcination to obtain a metal-modified hydrogen-type ZSM-5 molecular sieve;

[0015] Wherein, in step S3, the chemical composition of the reaction solution satisfies the following molar ratio range: SiO2 / Al2O3=50-200, ammonia / SiO2=2-10, TPA + / SiO2=0.05-0.35,H2O / SiO2=40-80,M / SiO2=0.001-0.05,organic amine ligand / M=5-20,wherein, TPA + is the molar number of cations in the template, M is the molar number of metal ions in the metal salt, and ammonia water is calculated as ammonium ions.

[0016] According to a specific embodiment of the present invention, preferably, in step S3, the ammonia water is added under stirring, and the stirring time is 12-24 hours, more preferably 12-18 hours. If the stirring time after adding the ammonia water is too short, the alkaline dissolution effect on the silicon source and the aluminum source at room temperature will be reduced, making the obtained molecular sieve particle size uneven; if the stirring time is too long, the alkalinity of the synthesis system will decrease as the ammonia water continues to volatilize; within the time range provided by the present invention, the above problems can be well avoided.

[0017] According to a specific embodiment of the present invention, preferably, in step S3, the solution B and the solution A are mixed by stirring, and the stirring time is 5-20 minutes, more preferably 10-15 minutes.

[0018] According to a specific embodiment of the present invention, preferably, in step S3, the template is added under stirring, and the stirring time is 0.5-3h, more preferably 1-2h.

[0019] According to a specific embodiment of the present invention, preferably, in step S3, the solution B, the template and the ammonia water should be slowly added dropwise and vigorously stirred.

[0020] According to a specific embodiment of the present invention, preferably, the stirring speed when adding the ammonia water is 500-2000 rpm.

[0021] According to a specific embodiment of the present invention, preferably, the stirring speed when the solution B is mixed with the solution A is 800-1500 rpm.

[0022] According to a specific embodiment of the present invention, preferably, the stirring speed when adding the template is 950-1100 rpm.

[0023] According to a specific embodiment of the present invention, preferably, in step S1, the metal in the metal salt is a transition metal, preferably one or a combination of two or more of Fe, Co, Cu, Zn, Rh, Pd and Pt.

[0024] According to a specific embodiment of the present invention, preferably, in step S1, the organic amine ligand is ethylenediamine and / or 3-aminopropyltriethoxysilane.

[0025] According to a specific embodiment of the present invention, preferably, in step S2, the sodium-free silicon source includes tetraethyl orthosilicate and / or silica sol, preferably silica sol with a particle size of 5-50nm. The selection of the sodium-free silicon source will affect the distribution of the metal in the molecular sieve. For example, the solid particle size of the coarse-pore silica gel is large, the alkali dissolution rate in the ammonia system is slow, and it tends to solid phase transition during the synthesis process, which leads to uneven particle size of the synthesized molecular sieve and the inability of the metal to effectively enter the molecular sieve crystal. In contrast, the particle size of the silica sol oxide silica particles is 5-50nm, which is conducive to the doping of metals and aluminum sources into the "-Si-O-Si-" network structure, thereby facilitating the embedding of transition metals and the formation of molecular sieves.

[0026] According to a specific embodiment of the present invention, preferably, in step S2, the sodium-free aluminum source includes one or a combination of two or more of pseudo-boehmite, aluminum nitrate, aluminum chloride and aluminum sulfate, preferably pseudo-boehmite. Among them, in the ammonia system, the depolymerization and conversion rate of pseudo-boehmite and silica sol are well matched, and if ammonia or weak base is added to other aluminum salt solutions not within the above range, a white colloidal precipitate will be obtained, and the transition metal will be complexed and adsorbed, which is not conducive to the metal entering the molecular sieve crystal.

[0027] According to a specific embodiment of the present invention, preferably, in step S3, the template agent is tetrapropylammonium hydroxide and / or tetrapropylammonium bromide.

[0028] According to a specific embodiment of the present invention, preferably, in step S3, the drying temperature is 60-150°C, more preferably 60-80°C.

[0029] According to a specific embodiment of the present invention, preferably, the drying time is 8-24 hours, more preferably 12 hours.

[0030] According to a specific embodiment of the present invention, preferably, in step S3, the temperature of the hydrothermal crystallization is 140-180° C., more preferably 170° C. When the crystallization temperature is lower than 140° C. or higher than 180° C., the molecular sieve will have too low or too high a crystallization rate, which does not match the precipitation rate of the doped metal, resulting in the metal being unable to effectively enter the molecular sieve crystals.

[0031] According to a specific embodiment of the present invention, preferably, the hydrothermal crystallization time is 12-96 hours, more preferably 48 hours.

[0032] According to a specific embodiment of the present invention, preferably, in step S3, the calcination temperature is 350-500° C., more preferably 450° C. If the calcination temperature is too high, metal migration and aggregation will occur, and the particle size distribution will be uneven; if the calcination temperature is too low, the template cannot be effectively removed.

[0033] The present invention requires a lower temperature during hydrothermal crystallization and calcination, and reduces energy consumption while obtaining a hydrogen-type ZSM-5 molecular sieve with uniformly dispersed metals.

[0034] According to a specific embodiment of the present invention, preferably, the calcination time is 3-8 hours, more preferably 5 hours.

[0035] According to a specific embodiment of the present invention, preferably, in step S3, after the crystallization is completed, the reaction kettle containing the reaction solution should be cooled rapidly.

[0036] According to a specific embodiment of the present invention, preferably, the above-mentioned synthesis method specifically comprises the following steps:

[0037] S1. Dissolve the organic amine ligand and the metal salt in deionized water in sequence, and stir to obtain solution A;

[0038] S2, dissolving a sodium-free silicon source and a sodium-free aluminum source in deionized water, and stirring to obtain a solution B;

[0039] S3. Add solution B to solution A and stir for 5-20 min (speed 500-2000 rpm), then add template and stir for 0.5-3 h (speed 8000-1500 rpm), finally add ammonia water and stir for 12-24 h (speed 950-1100 rpm) to mix evenly to obtain a reaction solution, and perform hydrothermal crystallization at 140-180 ° C in a reactor for 12-96 h; after the crystallization is completed, take out the reactor, cool it, and centrifuge it. The product is dried at 60-150 ° C for 8-24 h and calcined at 350-500 ° C for 3-8 h to obtain a metal-modified hydrogen-type ZSM-5 molecular sieve.

[0040] The present invention also provides a metal-modified hydrogen-type ZSM-5 molecular sieve, which is obtained by the above preparation method.

[0041] According to a specific embodiment of the present invention, preferably, the metal particle size of the metal-modified hydrogen-type ZSM-5 molecular sieve is 1-4 nm, more preferably 2-3 nm.

[0042] The present invention also provides a 1-hexene hydroformylation reaction catalyst, which comprises the above-mentioned metal-modified hydrogen-type ZSM-5 molecular sieve.

[0043] The present invention also provides a 1-hexene hydroformylation method, which is achieved by using the metal-modified hydrogen-type ZSM-5 molecular sieve or the 1-hexene hydroformylation reaction catalyst.

[0044] According to a specific embodiment of the present invention, preferably, the reaction temperature of the 1-hexene hydroformylation method is 50° C.-100° C. (preferably 70° C.), and the reaction time is 2 h-8 h (preferably 4 h).

[0045] The beneficial effects of the present invention are:

[0046] 1. The present invention uses ammonia water as a mineralizer to directly synthesize ammonium-type ZSM-5 molecular sieves. The process does not require the addition of alkali metal ions. Metal-modified hydrogen-type ZSM-5 molecular sieves can be obtained through a simple one-time roasting, eliminating the cumbersome steps of multiple ion exchange and roasting in the traditional method, reducing wastewater discharge and pollution, and saving energy and protecting the environment.

[0047] 2. The present invention directly introduces metal into the hydrogen-type HZSM-5 molecular sieve in situ in one step, and the metal is evenly dispersed in the molecular sieve with uniform particle size, which has great potential value for industrial production.

[0048] 3. The metal-modified hydrogen-type ZSM-5 molecular sieve synthesized in the present invention can be used as a catalyst in the hydroformylation reaction of 1-hexene, and has a high 1-hexene conversion rate and n-heptanal selectivity. At the same time, its catalytic effect has a certain cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The XRD spectra of the samples prepared in Examples 1-3 and Comparative Examples 1-3 are shown.

[0050] Figure 2 The scanning electron microscope (top) and transmission electron microscope (bottom) comparison diagrams of sample C of Example 3 and sample E of comparative example 2 are shown respectively.

[0051] Figure 3 This is a performance comparison chart of sample C of Example 3 and sample E of Comparative Example 2 for 1-hexene hydroformylation reaction. DETAILED DESCRIPTION

[0052] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0053] Example 1

[0054] This embodiment provides a metal-modified hydrogen-type ZSM-5 molecular sieve, and the synthesis method thereof comprises:

[0055] 0.40g of ethylenediamine was dissolved in 20ml of deionized water, and then 0.54g of ferric nitrate (98.5wt.%) was added to dissolve and stirred for 5min to obtain solution A. 13.4g of silica sol (30wt.% solution) and 0.189g of pseudo-boehmite (alumina dry mass fraction of about 71.6wt.%) were added to 25ml of deionized water in sequence and stirred for 15min to obtain solution B. Solution B was slowly added dropwise to solution A and stirred vigorously for 15min (speed 1000rpm), and then 9g of tetrapropylammonium hydroxide (25wt.% aqueous solution) was slowly added dropwise and stirred vigorously for 1h (speed 1000rpm), and finally 20ml of ammonia water (25-28wt.% solution) was slowly added and stirred vigorously for 12h (speed 1000rpm). The mixed reaction liquid was transferred to a reactor for hydrothermal crystallization at 170°C for 48 hours. After the crystallization was completed, the reactor was taken out for cooling and centrifugation. The product was dried in an oven at 80°C for 12 hours and then calcined at 450°C for 5 hours to obtain Fe-ZSM-5 molecular sieve, which was recorded as sample A (Fe / SiO2=0.02). The particle size of the nano-iron particles in the obtained sample A was 2-3nm by electron microscopy analysis.

[0056] Example 2

[0057] This embodiment provides a metal-modified hydrogen-type ZSM-5 molecular sieve, and the synthesis method thereof comprises:

[0058] 0.40g of ethylenediamine was dissolved in 20ml of deionized water, and then 0.19g of cobalt nitrate hexahydrate was added and dissolved, and stirred for 5min to obtain solution A. 13.4g of silica sol (30wt.% solution) and 0.189g of pseudo-boehmite (alumina dry mass fraction of about 71.6wt.%) were added to 25ml of deionized water and stirred for 15min to obtain solution B. Solution B was slowly added dropwise to solution A and stirred vigorously for 15min (speed 1000rpm), and then 9g of tetrapropylammonium hydroxide (25wt.% aqueous solution) was slowly added dropwise and stirred vigorously for 1h (speed 1000rpm), and finally 20ml of ammonia water (25-28wt.% solution) was slowly added and stirred vigorously for 12h (speed 1000rpm). The mixed reaction liquid was transferred to a reactor for hydrothermal crystallization at 170°C for 48 hours. After the crystallization was completed, the reactor was taken out for cooling and centrifugation. The product was dried in an oven at 80°C for 12 hours and then calcined at 450°C for 5 hours to obtain Co-ZSM-5 molecular sieve, which was recorded as sample B (Co / SiO2=0.01). The particle size of the nano-iron particles in the obtained sample B was 2-3nm by electron microscopy analysis.

[0059] Example 3

[0060] This embodiment provides a metal-modified hydrogen-type ZSM-5 molecular sieve, and the synthesis method thereof comprises:

[0061] 0.40g of ethylenediamine was dissolved in 20ml of deionized water, and then 0.18g of rhodium chloride trihydrate was added and dissolved, and stirred for 5min to obtain solution A. 13.4g of silica sol (30wt.% solution) and 0.189g of pseudo-boehmite (alumina dry mass fraction of about 71.6wt.%) were added to 25ml of deionized water and stirred for 15min to obtain solution B. Solution B was slowly added dropwise to solution A and stirred vigorously for 15min (speed 1000rpm), and then 9g of tetrapropylammonium hydroxide (25wt.% aqueous solution) was slowly added dropwise and stirred vigorously for 1h (speed 1000rpm), and finally 20ml of ammonia water (25-28wt.% solution) was slowly added and stirred vigorously for 12h (speed 1000rpm). The mixed reaction liquid was transferred to a reactor for hydrothermal crystallization at 170°C for 48 hours. After the crystallization was completed, the reactor was taken out for cooling and centrifugation. The product was dried in an oven at 80°C for 12 hours and then calcined at 450°C for 5 hours to obtain Rh-ZSM-5 molecular sieve, which was recorded as sample C (Rh / SiO2=0.01). The particle size of the nano-iron particles in the obtained sample C was 2-3nm by electron microscopy analysis.

[0062] Comparative Example 1

[0063] This comparative example provides a metal-modified hydrogen-type ZSM-5 molecular sieve, and its synthesis method comprises:

[0064] 0.54g of ferric nitrate (98.5wt.%) was dissolved in 20ml of deionized water and stirred for 5min to obtain solution A. 13.4g of silica sol (30wt.% solution) and 0.189g of pseudo-boehmite (alumina dry mass fraction of about 71.6wt.%) were added to 25ml of deionized water and stirred for 15min to obtain solution B. Solution B was slowly added dropwise to solution A and stirred vigorously for 15min (speed 1000rpm), and then 9g of tetrapropylammonium hydroxide (25wt.% aqueous solution) was slowly added dropwise and stirred vigorously for 1h (speed 1000rpm), and finally 20ml of ammonia water (25-28wt.% solution) was slowly added and stirred for 12h (speed 1000rpm). The mixed reaction liquid was transferred to a reactor for hydrothermal crystallization at 170°C for 48 hours. After the crystallization was completed, the reactor was taken out for cooling and centrifugation. The product was dried in an oven at 80°C for 12 hours and then calcined at 450°C for 5 hours to obtain Fe-ZSM-5 molecular sieve, which was recorded as sample D (Fe / SiO2=0.02). The particle size of the nano-iron particles in the obtained sample D was 5-40nm by electron microscopy analysis.

[0065] Comparative Example 2

[0066] This comparative example provides a metal-modified hydrogen-type ZSM-5 molecular sieve, and its synthesis method comprises:

[0067] 0.18g of rhodium chloride trihydrate was dissolved in 20ml of deionized water and stirred for 5min to obtain solution A. 13.4g of silica sol (30wt.% solution) and 0.189g of pseudo-boehmite (alumina dry mass fraction of about 71.6wt.%) were added to 25ml of deionized water and stirred for 15min to obtain solution B. Solution B was slowly added dropwise to solution A and stirred for 15min (speed 300rpm), and then 9g of tetrapropylammonium hydroxide (25wt.% aqueous solution) was slowly added dropwise and stirred for 1h (speed 300rpm), and finally 20ml of ammonia water (25-28wt.% solution) was slowly added and stirred for 12h (speed 300rpm). The mixed reaction liquid was transferred to a reactor for hydrothermal crystallization at 170°C for 48 hours. After the crystallization was completed, the reactor was taken out for cooling and centrifugation. The product was dried in an oven at 80°C for 12 hours and then calcined at 550°C for 4 hours to obtain Rh-ZSM-5 molecular sieve, which was recorded as sample E (Rh / SiO2=0.01). The particle size of the nano-iron particles in the obtained sample E was 5-40nm by electron microscopy analysis.

[0068] Comparative Example 3

[0069] This comparative example provides a metal-modified hydrogen-type ZSM-5 molecular sieve, and its synthesis method comprises:

[0070] 13.4g silica sol (30wt.% solution) and 0.189g pseudo-boehmite (alumina dry mass fraction of about 71.6wt.%) were added to 45ml deionized water in turn and stirred for 15min, then 9g tetrapropylammonium hydroxide (25wt.% aqueous solution) was slowly added dropwise and stirred vigorously for 1h, and finally 0.25g sodium hydroxide was added and stirred for 12h. The mixed reaction liquid was transferred to a reactor for hydrothermal crystallization at 170℃ for 48h. After the crystallization was completed, the reactor was taken out for cooling and centrifugation. The product was dried in an oven at 80℃ for 12h, and then calcined at 550℃ for 4h to obtain sodium-type NaZSM-5 molecular sieve. The obtained molecular sieve was mixed with 1mol / L ammonium nitrate solution at a ratio of 30ml / g, and ion exchanged for 4h in a water bath at 80℃ with stirring. After drying, the above ion exchange process was repeated once, and the HZSM-5 molecular sieve was obtained after drying and calcination at 550℃ for 4h. Finally, a solution containing 0.54 g of ferric nitrate was used for wet impregnation to load the metal onto the obtained HZSM-5 molecular sieve, and the final sample Fe-ZSM-5 molecular sieve was obtained by calcination at 550° C. for 4 h, which was recorded as sample F (Fe / SiO2=0.02). The particle size of the nano-iron particles in the obtained sample F was 5-40 nm by electron microscopy analysis.

[0071] Test Example 1

[0072] The reaction performance of sample C and sample E was compared and analyzed by taking the hydroformylation reaction of 1-hexene as an example. The specific reaction conditions are: 50 mg of sample was placed in a 50 mL high pressure reactor, 3 mmol of 1-hexene was added as the reaction substrate, 10 mL of toluene was added as the solvent, and n-octane was added as the internal standard. The reactor was filled with 4.0 MPa of synthesis gas (CO / H2 molar ratio 1:1) at room temperature, and then heated to 70 ° C under 800 rpm magnetic stirring conditions for reaction. After 4 hours of reaction, the heating was stopped and the reactor was cooled. After depressurization, the catalyst and liquid components were separated by centrifugation. The liquid phase composition was analyzed by chromatography. After the catalyst was dried at 100 ° C overnight, it was reloaded into the reactor to test its cyclic stability.

[0073] Depend on Figure 1 It can be seen that regardless of whether an organic amine ligand is added or not, a hydrogen-type molecular sieve with high crystallinity can be directly synthesized under the condition of ammonia water, indicating that the synthesis of molecular sieves using ammonia water as a mineralizer can save ion exchange and multiple calcination steps. Figure 2 It can be seen that when ethylenediamine or 3-aminopropyltriethoxysilane is used as a ligand, the metal rhodium particles in the obtained sample C are relatively small and are more evenly distributed in the molecular sieve; when no ethylenediamine ligand is added, the metal rhodium in the obtained sample E appears in aggregate and is deposited on the outside of the molecular sieve crystals, indicating that the ligand used in the present invention can effectively inhibit the rapid precipitation of the modified metal during the molecular sieve synthesis process, thereby allowing it to enter the molecular sieve crystals.

[0074] The results of the 1-hexene hydroformylation reaction of samples C and E are shown in Figure 3 As shown, it can be seen that since the particle size and dispersion of the rhodium metal particles in the sample C molecular sieve are better than those in the sample E, the 1-hexene conversion rate corresponding to the sample C is higher than that of the sample E with the same number of cycles; and since the rhodium particles have entered the interior of the ZSM-5 molecular sieve crystals, the pore confinement effect of the molecular sieve also improves the regional selectivity of the reaction, making the selectivity of n-heptanal in the sample C significantly higher than the selectivity of 2-methylhexanal and 2-ethylpentanal.

Claims

1. A method for synthesizing a metal-modified hydrogen-type ZSM-5 molecular sieve, wherein: The synthesis method comprises: S1, dissolving an organic amine ligand and a metal salt in deionized water to obtain a solution A; S2, dissolving a sodium-free silicon source and a sodium-free aluminum source in deionized water to obtain a solution B; S3, mixing solution B with solution A, adding a template and aqueous ammonia to obtain a reaction solution, and subjecting the mixture to hydrothermal crystallization, cooling, centrifugation, drying, and calcination to obtain a metal-modified hydrogen-type ZSM-5 molecular sieve; Wherein, in step S3, the chemical composition of the reaction solution satisfies the following molar ratio range: SiO2 / Al2O3=50-200, ammonia / SiO2=2-10, TPA + / SiO2=0.05-0.35,H2O / SiO2=40-80,M / SiO2=0.001-0.05,organic amine ligand / M=5-20,wherein, TPA + is the molar number of cations in the template, M is the molar number of metal ions in the metal salt, and ammonia water is calculated as ammonium ions.

2. The synthesis method according to claim 1, wherein In step S3, the ammonia water is added under stirring, and the stirring time is 12-24 hours, preferably 12-18 hours; More preferably, the solution B and solution A are mixed by stirring for 5-20 min, preferably 10-15 min; Further preferably, the template is added under stirring, and the stirring time is 0.5-3h, preferably 1-2h.

3. The synthesis method according to claim 2, wherein In step S3, the stirring speed when adding the ammonia water is 500-2000 rpm; Preferably, the stirring speed when the solution B is mixed with the solution A is 800-1500 rpm; More preferably, the stirring speed when adding the template is 950-1100 rpm.

4. The synthesis method according to claim 1, wherein In step S1, the metal in the metal salt is one or a combination of two or more of Fe, Co, Cu, Zn, Rh, Pd and Pt.

5. The synthesis method according to claim 1, wherein In step S1, the organic amine ligand is ethylenediamine and / or 3-aminopropyltriethoxysilane.

6. The synthesis method according to claim 1, wherein In step S2, the sodium-free silicon source includes tetraethyl orthosilicate and / or silica sol, preferably silica sol with a particle size of 5-50 nm.

7. The synthesis method according to claim 1, wherein In step S2, the sodium-free aluminum source includes one or a combination of two or more of pseudo-boehmite, aluminum nitrate, aluminum chloride and aluminum sulfate.

8. The synthesis method according to claim 1, wherein In step S3, the template is tetrapropylammonium hydroxide and / or tetrapropylammonium bromide.

9. The synthesis method according to claim 1, wherein In step S3, the drying temperature is 60-150°C, preferably 60-80°C; Preferably, the drying time is 8-24h; Preferably, the temperature of the hydrothermal crystallization is 140-180°C; Preferably, the hydrothermal crystallization time is 12-96h; Preferably, the calcination temperature is 350-500°C; Preferably, the calcination time is 3-8 hours.

10. A metal-modified hydrogen-type ZSM-5 molecular sieve obtained by the synthesis method according to any one of claims 1 to 9; Preferably, the particle size of the metal particles of the metal-modified hydrogen-type ZSM-5 molecular sieve is 1-4 nm, more preferably 2-3 nm.

11. A 1-hexene hydroformylation catalyst, wherein: The 1-hexene hydroformylation reaction catalyst comprises the metal-modified hydrogen-type ZSM-5 molecular sieve according to claim 10.

12. A method for hydroformylating 1-hexene, wherein: The method is achieved by using the metal-modified hydrogen-type ZSM-5 molecular sieve described in claim 10 or the 1-hexene hydroformylation reaction catalyst described in claim 11; Preferably, the reaction temperature of the 1-hexene hydroformylation method is 50° C.-100° C., and the reaction time is 2 h-8 h.

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