Metal-modified hydrogen-type zsm-5 molecular sieve, its synthesis method and 1-hexene hydroformylation reaction catalyst

Abstract

This invention provides a metal-modified hydrogen-form ZSM-5 molecular sieve, its synthesis method, and a catalyst for the hydroformylation of 1-hexene. The synthesis method includes dissolving an organic amine ligand and a metal salt in deionized water and stirring to obtain solution A; dissolving a sodium-free silicon source and an aluminum source in deionized water and stirring to obtain solution B; mixing solution B with solution A, adding a template agent and ammonia to obtain a reaction solution; and then subjecting the reaction solution to hydrothermal crystallization, cooling, centrifugation, drying, and calcination to obtain the metal-modified hydrogen-form ZSM-5 molecular sieve. This invention uses ammonia as a mineralizing agent and directly introduces the metal in situ into the hydrogen-form ZSM-5 molecular sieve in a one-step process, eliminating the multiple ion exchange and calcination steps required in traditional methods, thus reducing wastewater discharge and pollution. The metal in the metal-modified hydrogen-form ZSM-5 molecular sieve of this invention is uniformly dispersed and can be used as a catalyst for the hydroformylation of 1-hexene, exhibiting high 1-hexene conversion and n-heptaldehyde selectivity.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials, and more particularly to a method for synthesizing metal-modified hydrogen-type ZSM-5 molecular sieves and a catalyst for the hydroformylation reaction of 1-hexene. Background Technology

[0002] ZSM-5 molecular sieves possess tunable acidity, good thermal and hydrothermal stability, and their unique pore structure determines their shape selectivity in catalysis. They have been widely used in numerous chemical fields, including catalytic cracking, alkylation to produce toluene and xylene, isomerization, and methanol-to-olefins. To improve the catalytic activity, selectivity, and stability of ZSM-5 molecular sieves in different reaction processes, appropriate metal modification is necessary. For example, the addition of Fe improves the selectivity of light olefins and propylene in naphtha catalytic cracking, as well as the stability of ZSM-5. The introduction of Zn increases the aromatic yield in methanol-to-aromatics reactions. Studies have shown that Zn-ZSM-5 is the most effective catalyst for improving the selectivity of monocyclic aromatic hydrocarbons, including BTX (benzene, toluene, and xylene). The introduction of a small amount of Cu can maintain a balance between metal dehydrogenation activity and ZSM-5 shape selectivity, which is beneficial for improving the yield of light olefins in FCC processes.

[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 template agents. Ferric nitrate, sodium aluminate, sodium hydroxide, and alkaline silica sol are mixed evenly and dried at 100°C to form a dry gel. The gel is then crystallized at 170°C by steam-assisted crystallization (SAC). Finally, the Na-type Fe-ZSM-5 zeolite is prepared by cooling, filtering, washing, and drying.

[0004] CN104525246B discloses a method for preparing a template-free small-crystal Zn-ZSM-5 catalyst and its application. The method involves directly adding zinc salt during the molecular sieve preparation process, followed by hydrothermal crystallization, filtration, drying, and calcination to obtain a sodium-type Zn-ZSM-5 molecular sieve catalyst. Then, the Zn-ZSM-5 molecular sieve catalyst undergoes ion exchange in an ammonium salt solution to obtain the hydrogen-type small-crystal Zn-ZSM-5 catalyst required for the methanol-to-gasoline reaction. No template agent is needed during catalyst preparation, and the obtained Zn-ZSM-5 particles are uniform in size and have regular morphology; however, this process requires multiple ion exchanges.

[0005] CN114950351A discloses a method for modifying ZSM-5 molecular sieves, using metal cations (Cu) 2+ La 2+ Ce 3+(e.g.,) doping is incorporated into the framework structure of ZSM-5 molecular sieves to improve their VOCs adsorption performance. The specific experimental steps are as follows: Take ZSM-5 molecular sieves, add a prepared metal salt solution, and transfer it to a hydrothermal reactor. Heat to 80-150℃ and react for 4-10 hours. After natural cooling to room temperature, filter, dry, and calcinate to obtain the metal cation-doped molecular sieve. The synthesis conditions are mild and easy to control. The molecular sieves synthesized by the above methods are all in the sodium form, requiring multiple ion exchanges and calcinations to obtain the hydrogen form, which is a relatively cumbersome process.

[0006] CN114426290A discloses a method for synthesizing sodium-free Fe-ZSM-5 molecular sieves. First, Silicate-1 seed crystals are hydrothermally treated under alkaline conditions, then added to the molecular sieve synthesis raw material solution. After further hydrothermal treatment, sodium-free Fe-ZSM-5 molecular sieves are obtained. The synthesis process does not require ion exchange. The synthesized molecular sieve has a b-axis dimension of 5-50 nm, which is small and facilitates mass transfer of reacting molecules, effectively improving the reduction of NO2 by ammonia. x The reactivity is good. However, the synthesis process requires the addition of seed crystals and size inhibitors (NH2-C6H4-CH2-C6H4-NH2), and requires two hydrothermal processes.

[0007] Currently, conventional methods for preparing metal-modified hydrogen-type ZSM-5 molecular sieve catalysts mostly employ post-impregnation, a relatively cumbersome process. Furthermore, when a metal source is directly added to the alkaline system during ZSM-5 molecular sieve synthesis, the metal precipitation rate far exceeds the molecular sieve crystallization rate, making effective metal dispersion within the molecular sieve crystals difficult. Additionally, traditional molecular sieve synthesis often uses sodium hydroxide as the alkaline source, resulting in sodium-type molecular sieves with a large amount of alkali metal ions (Na₂O₃). + It needs to undergo multiple ion exchange steps to transform it into an ammonium-type molecular sieve (NH4). + Only after calcination can the hydrogen form HZSM-5 with acidic catalytic active centers be obtained. However, the ion exchange process generates a large amount of wastewater, increasing wastewater treatment costs. Furthermore, without the addition of alkali metal ions, multiple hydrothermal crystallization processes are required, which are cumbersome and energy-intensive.

[0008] Therefore, there is a need for a method that can directly synthesize metal-modified hydrogen-type ZSM-5 molecular sieves without adding alkali metal ions, in order to solve the problems of cumbersome steps, difficulty in introducing metals, large amounts of sodium-containing wastewater, high energy consumption, and long process. Summary of the Invention

[0009] To address the aforementioned technical problems, the present invention aims to provide a metal-modified hydrogen-form ZSM-5 molecular sieve and its synthesis method. This method can directly synthesize metal-modified hydrogen-form ZSM-5 molecular sieves.

[0010] Another objective of this invention is to provide a catalyst for the hydroformylation of 1-hexene.

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

[0012] S1. Dissolve the organic amine ligand and metal salt in deionized water to obtain solution A;

[0013] S2. Dissolve the sodium-free silicon source and the sodium-free aluminum source in deionized water to obtain solution B;

[0014] S3. Mix solution B with solution A, add template agent and ammonia water to obtain reaction solution, and obtain metal-modified hydrogen-type ZSM-5 molecular sieve through hydrothermal crystallization, cooling, centrifugation, drying and calcination.

[0015] In step S3, the chemical composition of the reaction solution satisfies the following molar ratio ranges: 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, where TPA + denoted as the number of moles of cations in the template agent, M as the number of moles of metal ions in the metal salt, and ammonia is expressed as ammonium ions.

[0016] According to a specific embodiment of the present invention, preferably, in step S3, the ammonia water is added under stirring for 12-24 hours, more preferably 12-18 hours. Too short a stirring time after adding ammonia water will reduce the alkali solubility effect on the silicon and aluminum sources at room temperature, resulting in uneven particle size of the obtained molecular sieves; if the stirring time is too long, the alkalinity of the synthesis system will decrease as the ammonia water continuously evaporates. 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, solution B and solution A are mixed by stirring for 5-20 minutes, more preferably 10-15 minutes.

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

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

[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 mixing solution B and solution A is 800-1500 rpm.

[0022] According to a specific embodiment of the present invention, preferably, the stirring speed when adding the template agent 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 5-50 nm. The selection of the sodium-free silicon source affects the distribution of metals within the molecular sieve. For example, coarse-porous silica gel has a large solid particle size, a slow alkali dissolution rate in an ammonia system, and tends to undergo a solid-phase transformation during synthesis, resulting in uneven particle size of the synthesized molecular sieve and the inability of metals to effectively enter the molecular sieve crystals. In contrast, the silica sol with silica oxide particles having a particle size of 5-50 nm is conducive to the entry of doped metals and aluminum sources into the "-Si-O-Si-" network structure, thereby facilitating the intercalation of transition metals and the formation of the molecular sieve.

[0026] According to a specific embodiment of the present invention, preferably, in step S2, the sodium-free aluminum source includes one or more combinations of boehmite, aluminum nitrate, aluminum chloride, and aluminum sulfate, preferably boehmite. In the ammonia system, the depolymerization and conversion rates of boehmite and silica sol are well matched. However, if ammonia or a weak alkali is added to other aluminum salt solutions outside the aforementioned range, a white colloidal precipitate will be obtained, which will complex and adsorb transition metals, thus hindering the entry of metals into the molecular sieve crystals.

[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 hydrothermal crystallization temperature is 140-180°C, more preferably 170°C. When the crystallization temperature is below 140°C or above 180°C, the molecular sieve will have an excessively low or high crystallization rate, which is mismatched with the precipitation rate of the doped metal, resulting in the metal being unable to effectively enter the molecular sieve crystal.

[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, it will cause metal migration and aggregation, resulting in uneven particle size distribution; if the calcination temperature is too low, the template agent cannot be effectively removed.

[0033] The present invention requires lower temperatures for hydrothermal crystallization and calcination, and also reduces energy consumption while obtaining hydrogen-type ZSM-5 molecular sieves with uniform metal dispersion.

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

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

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

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

[0038] S2. Dissolve sodium-free silicon source and sodium-free aluminum source in deionized water and stir to obtain solution B;

[0039] S3. Add solution B to solution A and stir for 5-20 min (500-2000 rpm). Then add template agent and stir for 0.5-3 h (8000-1500 rpm). Finally, add ammonia water and stir for 12-24 h (950-1100 rpm) until the mixture is homogeneous. The reaction solution is then subjected to hydrothermal crystallization at 140-180℃ for 12-96 h in a reaction vessel. After crystallization, remove the reaction vessel, cool it, and centrifuge it. The resulting product is dried at 60-150℃ for 8-24 h and calcined at 350-500℃ for 3-8 h to obtain metal-modified hydrogen-form 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 particles of the metal-modified hydrogen-type ZSM-5 molecular sieve have a particle size of 1-4 nm, more preferably 2-3 nm.

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

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

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

[0045] The beneficial effects of this invention are as follows:

[0046] 1. This invention uses ammonia water as a mineralizing agent to directly synthesize ammonium-type ZSM-5 molecular sieves. This process does not require the addition of alkali metal ions. Metal-modified hydrogen-type ZSM-5 molecular sieves can be obtained through a simple single calcination, eliminating the cumbersome steps of multiple ion exchanges and calcinations in traditional methods, reducing wastewater discharge and pollution, and saving energy and protecting the environment.

[0047] 2. The present invention directly introduces metals in situ into hydrogen-type HZSM-5 molecular sieves in one step. The metals are uniformly dispersed in the molecular sieves 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 this invention can be used as a catalyst in the hydroformylation reaction of 1-hexene, exhibiting high 1-hexene conversion and n-heptaldehyde selectivity, while its catalytic effect also has certain cycle stability. Attached Figure Description

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

[0050] Figure 2 The images show a comparison of scanning electron microscope (SEM) images (top) and transmission electron microscope (TEM) images (bottom) of sample C from Example 3 and sample E from Comparative Example 2, respectively.

[0051] Figure 3 This is a comparison chart showing the performance of sample C from Example 3 and sample E from Comparative Example 2 in the 1-hexene hydroformylation reaction. Detailed Implementation

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

[0053] Example 1

[0054] This embodiment provides a metal-modified hydrogen-type ZSM-5 molecular sieve, the synthesis method of which includes:

[0055] Dissolve 0.40 g of ethylenediamine in 20 ml of deionized water, then add 0.54 g of ferric nitrate (98.5 wt.%) and stir for 5 min to obtain solution A. Add 13.4 g of silica sol (30 wt.%) and 0.189 g of boehmite (approximately 71.6 wt.% alumina on a dry basis) sequentially to 25 ml of deionized water and stir for 15 min to obtain solution B. Slowly add solution B dropwise to solution A and stir vigorously for 15 min (1000 rpm). Then slowly add 9 g of tetrapropylammonium hydroxide (25 wt.% aqueous solution) and stir vigorously for 1 h (1000 rpm). Finally, slowly add 20 ml of ammonia water (25-28 wt.% solution) and stir vigorously for 12 h (1000 rpm). The mixed reaction solution was transferred to a reaction vessel and hydrothermally crystallized at 170℃ for 48 hours. After crystallization, the reaction vessel was removed, cooled, and centrifuged. The product was dried in an oven at 80℃ for 12 hours, and then calcined at 450℃ for 5 hours to obtain Fe-ZSM-5 molecular sieve, denoted as sample A (Fe / SiO2=0.02). Electron microscopy analysis showed that the nano-iron particles in sample A had a particle size of 2-3 nm.

[0056] Example 2

[0057] This embodiment provides a metal-modified hydrogen-type ZSM-5 molecular sieve, the synthesis method of which includes:

[0058] Dissolve 0.40 g of ethylenediamine in 20 ml of deionized water, then add 0.19 g of cobalt nitrate hexahydrate and stir for 5 min to obtain solution A. Add 13.4 g of silica sol (30 wt.% solution) and 0.189 g of boehmite (approximately 71.6 wt.% alumina on a dry basis) sequentially to 25 ml of deionized water and stir for 15 min to obtain solution B. Slowly add solution B dropwise to solution A and stir vigorously for 15 min (1000 rpm). Then slowly add 9 g of tetrapropylammonium hydroxide (25 wt.% aqueous solution) and stir vigorously for 1 h (1000 rpm). Finally, slowly add 20 ml of ammonia water (25-28 wt.% solution) and stir vigorously for 12 h (1000 rpm). The mixed reaction solution was transferred to a reactor and hydrothermally crystallized at 170℃ for 48 hours. After crystallization, the reactor was removed, cooled, and centrifuged. The product was dried in an oven at 80℃ for 12 hours, and then calcined at 450℃ for 5 hours to obtain Co-ZSM-5 molecular sieve, denoted as sample B (Co / SiO2=0.01). Electron microscopy analysis showed that the nano-iron particles in sample B had a particle size of 2-3 nm.

[0059] Example 3

[0060] This embodiment provides a metal-modified hydrogen-type ZSM-5 molecular sieve, the synthesis method of which includes:

[0061] Dissolve 0.40 g of ethylenediamine in 20 ml of deionized water, then add 0.18 g of rhodium chloride trihydrate and stir for 5 min to obtain solution A. Add 13.4 g of silica sol (30 wt.% solution) and 0.189 g of boehmite (approximately 71.6 wt.% alumina on a dry basis) sequentially to 25 ml of deionized water and stir for 15 min to obtain solution B. Slowly add solution B dropwise to solution A and stir vigorously for 15 min (1000 rpm). Then slowly add 9 g of tetrapropylammonium hydroxide (25 wt.% aqueous solution) and stir vigorously for 1 h (1000 rpm). Finally, slowly add 20 ml of ammonia water (25-28 wt.% solution) and stir vigorously for 12 h (1000 rpm). The mixed reaction solution was transferred to a reactor and hydrothermally crystallized at 170℃ for 48 hours. After crystallization, the reactor was removed, cooled, and centrifuged. The product was dried in an oven at 80℃ for 12 hours, and then calcined at 450℃ for 5 hours to obtain Rh-ZSM-5 molecular sieve, denoted as sample C (Rh / SiO2=0.01). Electron microscopy analysis showed that the nano-iron particles in sample C had a particle size of 2-3 nm.

[0062] Comparative Example 1

[0063] This comparative example provides a metal-modified hydrogen-type ZSM-5 molecular sieve, the synthesis method of which includes:

[0064] Dissolve 0.54 g of ferric nitrate (98.5 wt.%) in 20 ml of deionized water and stir for 5 min to obtain solution A. Add 13.4 g of silica sol (30 wt.%) and 0.189 g of boehmite (approximately 71.6 wt.% alumina on a dry basis) sequentially to 25 ml of deionized water and stir for 15 min to obtain solution B. Slowly add solution B dropwise to solution A and stir vigorously for 15 min (1000 rpm). Then slowly add 9 g of tetrapropylammonium hydroxide (25 wt.% aqueous solution) and stir vigorously for 1 h (1000 rpm). Finally, slowly add 20 ml of ammonia water (25-28 wt.% solution) and stir for 12 h (1000 rpm). The mixed reaction solution was transferred to a reactor and hydrothermally crystallized at 170℃ for 48 hours. After crystallization, the reactor was removed, cooled, and centrifuged. The product was dried in an oven at 80℃ for 12 hours, and then calcined at 450℃ for 5 hours to obtain Fe-ZSM-5 molecular sieve, denoted as sample D (Fe / SiO2=0.02). Electron microscopy analysis showed that the nano-iron particles in sample D had a particle size of 5-40 nm.

[0065] Comparative Example 2

[0066] This comparative example provides a metal-modified hydrogen-type ZSM-5 molecular sieve, the synthesis method of which includes:

[0067] Dissolve 0.18 g of rhodium chloride trihydrate in 20 ml of deionized water and stir for 5 min to obtain solution A. Add 13.4 g of silica sol (30 wt.% solution) and 0.189 g of boehmite (approximately 71.6 wt.% alumina on a dry basis) sequentially to 25 ml of deionized water and stir for 15 min to obtain solution B. Slowly add solution B dropwise to solution A and stir for 15 min (300 rpm). Then slowly add 9 g of tetrapropylammonium hydroxide (25 wt.% aqueous solution) and stir for 1 h (300 rpm). Finally, slowly add 20 ml of ammonia water (25-28 wt.% solution) and stir for 12 h (300 rpm). The mixed reaction solution was transferred to a reactor and hydrothermally crystallized at 170℃ for 48 hours. After crystallization, the reactor was removed, cooled, and centrifuged. The product was dried in an oven at 80℃ for 12 hours, and then calcined at 550℃ for 4 hours to obtain Rh-ZSM-5 molecular sieve, denoted as sample E (Rh / SiO2=0.01). Electron microscopy analysis showed that the nano-iron particles in sample E ranged in size from 5 to 40 nm.

[0068] Comparative Example 3

[0069] This comparative example provides a metal-modified hydrogen-type ZSM-5 molecular sieve, the synthesis method of which includes:

[0070] 13.4 g of silica sol (30 wt.% solution) and 0.189 g of pseudoboehmite (approximately 71.6 wt.% alumina on a dry basis) were sequentially added to 45 ml of deionized water and stirred for 15 min. Then, 9 g of tetrapropylammonium hydroxide (25 wt.% aqueous solution) was slowly added dropwise while stirring vigorously for 1 h. Finally, 0.25 g of sodium hydroxide was added and stirred for 12 h. The mixed reaction solution was transferred to a reaction vessel and hydrothermally crystallized at 170 °C for 48 h. After crystallization, the reaction vessel was removed, cooled, and centrifuged. The product was dried in an oven at 80 °C for 12 h and then calcined at 550 °C for 4 h to obtain sodium-type NaZSM-5 molecular sieve. The obtained molecular sieve was mixed with 1 mol / L ammonium nitrate solution at a ratio of 30 ml / g and ion-exchanged in a water bath at 80 °C with stirring for 4 h. After drying, the above ion-exchange process was repeated once. After drying and calcination at 550 °C for 4 h, HZSM-5 molecular sieve was obtained. Finally, the metal was loaded onto the obtained HZSM-5 molecular sieve by wet impregnation with a solution containing 0.54 g of ferric nitrate, and then calcined at 550 °C for 4 h to obtain the final sample Fe-ZSM-5 molecular sieve, denoted as sample F (Fe / SiO2 = 0.02). Electron microscopy analysis showed that the particle size of the iron nanoparticles in sample F was 5-40 nm.

[0071] Test Example 1

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

[0073] Depend on Figure 1 It can be seen that, regardless of the addition of organic amine ligands, highly crystalline hydrogen-form molecular sieves can be directly synthesized under ammonia conditions, indicating that using ammonia as a mineralizing agent in molecular sieve synthesis 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 rhodium particles in the obtained sample C are relatively small and are more uniformly distributed in the molecular sieve; while when no ethylenediamine ligand is added, the rhodium in the obtained sample E aggregates and deposits on the outside of the molecular sieve crystal, indicating that the ligand used in this invention can effectively inhibit the rapid precipitation of modified metals during the molecular sieve synthesis process, thereby allowing them to enter the molecular sieve crystal.

[0074] The results of the 1-hexene hydroformylation reaction of samples C and E are as follows: Figure 3 As shown, since the rhodium metal particles in sample C have better particle size and dispersion than those in sample E, the 1-hexene conversion rate of sample C is higher than that of sample E with the same number of cycles. Furthermore, since the rhodium particles enter the interior of the ZSM-5 molecular sieve crystal, the pore confinement effect of the molecular sieve also improves the regioselectivity of the reaction, making the selectivity of n-heptaldehyde in sample C significantly higher than that of 2-methylhexanal and 2-ethylpentanal.

Claims

1. A method for synthesizing metal-modified hydrogen-type ZSM-5 molecular sieve, wherein, The synthesis method includes: S1. Dissolve the organic amine ligand and metal salt in deionized water to obtain solution A; S2. Dissolve the sodium-free silicon source and the sodium-free aluminum source in deionized water to obtain solution B; S3. Add solution B to solution A and stir for 5-20 min, then add template agent and stir for 0.5-3 h, and finally add ammonia water and stir for 12-24 h to mix evenly to obtain a reaction solution. After hydrothermal crystallization, cooling, centrifugation, drying and calcination, metal-modified hydrogen-type ZSM-5 molecular sieve is obtained. In step S3, the chemical composition of the reaction solution satisfies the following molar ratio ranges: 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, where TPA + The molar number of cations in the template agent, M is the molar number of metal ions in the metal salt, and ammonia is expressed as ammonium ions; The sodium-free silicon source is silica sol.

2. The synthesis method according to claim 1, wherein, In step S3, the ammonia water is added under stirring for 12-18 hours.

3. The synthesis method according to claim 1, wherein, Solution B and solution A are mixed by stirring for 10-15 minutes.

4. The synthesis method according to claim 1, wherein, The template agent is added under stirring for 1-2 hours.

5. The synthesis method according to claim 2, wherein, In step S3, the stirring speed when adding the ammonia water is 500-2000 rpm.

6. The synthesis method according to claim 3, wherein, The stirring speed when mixing solution B and solution A is 800-1500 rpm.

7. The synthesis method according to claim 4, wherein, The stirring speed when adding the template agent is 950-1100 rpm.

8. 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.

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

10. The synthesis method according to claim 1, wherein, In step S2, the sodium-free silicon source is a silica sol with a particle size of 5-50 nm.

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

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

13. The synthesis method according to claim 1, wherein, In step S3, the drying temperature is 60-150°C.

14. The synthesis method according to claim 13, wherein, In step S3, the drying temperature is 60-80 ℃.

15. The synthesis method according to claim 1, wherein, In step S3, the drying time is 8-24 hours.

16. The synthesis method according to claim 1, wherein, In step S3, the temperature of the hydrothermal crystallization is 140-180℃.

17. The synthesis method according to claim 1, wherein, In step S3, the hydrothermal crystallization time is 12-96 hours.

18. The synthesis method according to claim 1, wherein, In step S3, the calcination temperature is 350-500℃.

19. The synthesis method according to claim 1, wherein, In step S3, the calcination time is 3-8 hours.

20. A metal-modified hydrogen-type ZSM-5 molecular sieve, which is obtained by the synthesis method according to any one of claims 1-19.

21. The metal-modified hydrogen-type ZSM-5 molecular sieve according to claim 20, wherein, The metal particles of the metal-modified hydrogen-type ZSM-5 molecular sieve have a particle size of 1-4 nm.

22. The metal-modified hydrogen-type ZSM-5 molecular sieve according to claim 21, wherein, The metal particles of the metal-modified hydrogen-type ZSM-5 molecular sieve have a particle size of 2-3 nm.

23. A catalyst for the hydroformylation of 1-hexene, wherein, The 1-hexene hydroformylation catalyst comprises the metal-modified hydrogen-type ZSM-5 molecular sieve according to any one of claims 20-22.

24. A method for hydroformylation of 1-hexene, wherein, This method is achieved using the metal-modified hydrogen-type ZSM-5 molecular sieve according to any one of claims 20-22 or the 1-hexene hydroformylation catalyst according to claim 23.

25. The method for hydroformylation of 1-hexene according to claim 24, wherein, The reaction temperature for the 1-hexene hydroformylation method is 50℃-100℃, and the reaction time is 2 h-8 h.

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