Method for synthesizing 4-hexene-3-one using zinc chloride as catalyst

Abstract

The invention discloses a method for synthesizing 4-hexene-3-one using zinc chloride as a catalyst, and belongs to the technical field of catalyst materials. The method optimizes reaction conditions, such as temperature and stirring speed, by reacting under a nitrogen environment to improve reaction efficiency and product yield. A specially designed loaded zinc chloride catalyst significantly improves catalytic performance through a combination of sepiolite, metal organic framework materials and molecular sieves. The preparation method of the catalyst includes phosphoric acid pretreatment, hydrothermal crystallization and calcination steps, ensuring its high specific surface area and thermal stability. Compared with the prior art, the present invention not only improves the yield and purity of 4-hexene-3-one, but also reduces production costs while reducing environmental impact.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst materials, in particular to a method for synthesizing 4-hexene-3-one by using zinc chloride as a catalyst. Background Art

[0002] Currently, in the field of chemical synthesis, 4-hexen-3-one is an important organic compound widely used in the production of spices, medicines, pesticides and chemical raw materials. The traditional method of synthesizing 4-hexen-3-one has some limitations, including but not limited to low yield, many by-products, low catalyst efficiency and potential negative impact on the environment.

[0003] One of the common methods for synthesizing 4-hexen-3-one is the dehydration reaction of propionic anhydride and propylene using zinc chloride as a catalyst. However, the conventional catalysts have problems such as low activity, poor selectivity, insufficient stability, and difficulty in recycling and reuse. These problems lead to increased production costs, reduced product purity, and challenges in safety and environmental protection.

[0004] Chinese invention patent application CN111096339A discloses that the present invention provides a catalyst for preparing oxabicyclohexadecene and its preparation method and application, which belongs to the field of catalyst material technology. The catalyst includes a modified carrier and a composite active component loaded on the modified carrier; the composite active component includes a first active component and a second active component; the first active component includes a first metal salt and / or a hydrate of a first metal salt; the second active component includes a second noble metal salt and / or a hydrate of a second noble metal salt. The invention utilizes the above-mentioned catalyst to catalyze the free radical addition-dehydration cyclization reaction of cyclododecanone and allyl alcohol in a step under mild reaction conditions, and specifically generates oxabicyclohexadecene, which not only improves the selectivity and yield of the product, eliminates or reduces the occurrence of side reactions, and realizes continuous production, but also simplifies the process flow of the reaction and reduces the production cost and energy consumption of the product. However, the catalytic efficiency and specific surface area of ​​the catalyst prepared by the invention need to be improved. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide an improved method for synthesizing 4-hexen-3-one using zinc chloride as a catalyst, and realizes a high-yield, high-stability and environmentally friendly 4-hexen-3-one synthesis process through innovative catalyst preparation technology and optimized reaction conditions.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0007] A method for synthesizing 4-hexen-3-one using zinc chloride as a catalyst is as follows, in parts by weight:

[0008] First, the reactor is purified under a nitrogen environment to avoid oxidation, and then 250-350 parts of dichloromethane are added and the temperature is maintained at 2-8°C; then, 15-25 parts of a supported zinc chloride catalyst are added to the reaction mixture and stirred to ensure its uniform distribution; then, 40-60 parts of propionic anhydride are gradually added dropwise and stirred for 1-3 hours, and then 20-30 parts of propylene gas are introduced to continue the reaction for 1-3 hours; after the reaction is completed, the mixture is transferred to a quenching kettle containing 80-120 parts of water at 3-8°C for hydrolysis, and the hydrolysis temperature is controlled and stirred; the mixture is transferred to a layering kettle, and the layering kettle is allowed to stand and layer; the water layer is decompressed to recover the by-product propionic acid; the material layer is washed with 25-35 parts of a saturated sodium carbonate solution, stirred for 1-3 hours, and layered; the product layer is distilled in a distillation tower, and dichloromethane is recovered by atmospheric distillation in the distillation tower; and 4-hexene-3-one is obtained by decompression distillation.

[0009] The dropping speed of the propionic anhydride is 0.4-0.6 parts / minute.

[0010] The temperature of the atmospheric distillation is 40-60°C.

[0011] The pressure of the reduced pressure distillation is -0.02~-0.04Mpa, and the temperature is 80~110°C.

[0012] The hydrolysis temperature is controlled to be 2-15° C. and the stirring is performed for 1-3 hours.

[0013] The preparation method of the supported zinc chloride catalyst is as follows, in parts by weight:

[0014] S1. Mix sepiolite with 70-85wt% phosphoric acid solution at a solid-liquid ratio of 0.5-2g:15-25mL, stir and react at room temperature for 1-5 hours, wash with water until pH is neutral after the reaction is completed, and dry the washed material at 70-90°C for 5-10 hours to obtain a pretreated material; dissolve 0.1-0.3 parts of aluminum nitrate in 100-140 parts of water and stir evenly; gradually add 5-15 parts of triethylamine, 5-10 parts of pretreated material and 0.1-0.3 parts of sodium hydroxide and mix evenly; stir and reflux the mixed solution at 70-80°C for 15-25 hours, then transfer it to a high-pressure reactor for hydrothermal crystallization; after completion, wash with water 1-3 times, then dry at 80-120°C for 5-15 hours, and calcine to obtain a molecular sieve;

[0015] S2, dissolving 1-1.5 parts of titanium tetrachloride, 0.5-1.2 parts of pyromellitic acid and 0.3-0.5 parts of 4-aminomethylbenzoic acid in 500-700 parts of dimethyl sulfoxide; adding 50-70 parts of cysteine ​​and 30-40 parts of water in sequence, and after the mixed solution is clarified, transferring it to an autoclave for hydrothermal crystallization; after completion, naturally cooling to room temperature, centrifuging, and washing with dimethyl sulfoxide and anhydrous ethanol 1-3 times each, and drying at 80-100°C for 3-10 hours to obtain a metal organic framework material;

[0016] S3. Evenly mix zinc chloride, metal organic framework material and molecular sieve to obtain a loaded zinc chloride catalyst.

[0017] The calcination is carried out at 400-500° C. for 3-5 hours.

[0018] The hydrothermal crystallization in step S1 is performed at 150-170° C. for 25-60 hours.

[0019] The hydrothermal crystallization in step S2 is performed at 80-120° C. for 15-25 hours.

[0020] The zinc chloride, metal organic framework material and molecular sieve are uniformly mixed in a mass ratio of 0.5-2:1-3:2-4.

[0021] In the present invention, the functions of each substance are as follows:

[0022] As an active component of the catalyst, zinc chloride plays a key role in the synthesis of 4-hexen-3-one. It can promote the dehydration reaction of propionic anhydride and propylene to generate the target product.

[0023] Dichloromethane is used as the reaction medium. Dichloromethane is added into the reactor at low temperature (5°C), which provides a suitable solvent environment for the mixing of zinc chloride catalyst and propionic anhydride, and is conducive to the uniform distribution of reactants and the progress of the reaction.

[0024] As one of the reactants, propionic anhydride reacts with propylene during the gradual dropwise addition to generate 4-hexen-3-one. The dropwise addition speed and reaction time of propionic anhydride have a direct impact on the formation and yield of the product.

[0025] Propylene is another reactant. After the dropwise addition of propionic anhydride, propylene gas is introduced into the reaction system to react with propionic anhydride.

[0026] Nitrogen is used to purify the reactor before the reaction. The use of nitrogen can eliminate oxygen, avoid the occurrence of oxidation reactions, and ensure the smooth progress of the reaction and the purity of the product.

[0027] After the reaction is complete, water is used to quench the reaction and terminate the reaction process. At the same time, the hydrolysis step helps to separate the reactants and catalyst from the products.

[0028] Sodium carbonate is used as a detergent, and a saturated sodium carbonate solution is used to wash the material layer to remove by-products and impurities and improve the purity of the product.

[0029] As a carrier of zinc chloride catalyst, sepiolite provides good pore structure and specific surface area after being pretreated with phosphoric acid, which is helpful for uniform dispersion of zinc chloride and improvement of catalytic activity.

[0030] Phosphoric acid is used to pretreat sepiolite. The phosphoric acid solution reacts with the sepiolite to enhance its porosity and surface activity, providing a basis for the subsequent loading of zinc chloride.

[0031] Compounds such as aluminum nitrate, triethylamine and sodium hydroxide are used in the step of preparing molecular sieves. Aluminum nitrate provides an aluminum source, and triethylamine and sodium hydroxide adjust the pH of the solution and the reaction conditions to promote the formation of molecular sieves.

[0032] Compounds such as titanium tetrachloride, pyromellitic acid, 4-aminomethylbenzoic acid, and cysteine ​​are used to synthesize metal-organic framework materials. Materials with specific pore structures and chemical properties are formed through hydrothermal crystallization and used as part of the supported zinc chloride catalyst to improve catalytic performance.

[0033] Dimethyl sulfoxide is used as a solvent to dissolve the above compounds and provide a uniform reaction environment for the synthesis of metal organic framework materials.

[0034] Through the synergistic effect of these substances, the present invention successfully prepares a highly efficient supported zinc chloride catalyst and achieves a high-yield synthesis of 4-hexene-3-one.

[0035] Compared with the prior art, it has the following beneficial effects:

[0036] 1) The supported zinc chloride catalyst used in the present invention achieves high efficiency and high yield in catalytic synthesis of 4-hexen-3-one through carefully designed preparation steps and component matching. The optimized catalyst structure and reaction conditions significantly increase the output of the target product and reduce the occurrence of side reactions, thereby improving the selectivity and economy of the product.

[0037] 2) The catalyst of the present invention exhibits good thermal stability and structural stability by using a specific porous material as a carrier and the synergistic effect of the metal organic framework material and the molecular sieve. This not only helps to maintain the catalytic activity during the continuous reaction process, but also improves the regeneration ability and service life of the catalyst, reducing the cost in industrial applications.

[0038] 3) The present invention carries out the reaction under a nitrogen environment, effectively avoiding the occurrence of oxidation side reactions and reducing the potential impact on the environment. At the same time, by precisely controlling the reaction conditions and post-processing steps, the purity and quality of the product are improved, the separation and purification process is simplified, the operational complexity and safety risks are reduced, and the requirements of green chemistry and industrial safety production are met. DETAILED DESCRIPTION

[0039] Main sources of substances:

[0040] The Chinese herbal medicines used in the following examples and comparative examples are all commercially available products.

[0041] Metal organic framework MIL-53: CAS: 1370461-06-5, unit molecular formula: C8H4O5Al, unit molecular weight: 230.107, coordination metal: Al, ligand: fumaric acid, particle forming process: drop ball method, particle strength: 24N, particle diameter: 0.5-3mm.

[0042] Metal organic framework ZIF-8, particle size (nm): 150-300, specific surface area (m 2 / g): 888, pore size (nm): 0.9-1.8, preparation method: solution method.

[0043] Zeolite: average surface area is 200m 2 / g.

[0044] Diatomaceous earth: average specific surface area is 60m 2 / g.

[0045] Sepiolite: Specific surface area is 300m 2 / g.

[0046] The design idea of ​​the present invention is to optimize the pore structure and chemical composition of the loaded zinc chloride catalyst by carefully selecting and preparing it, so as to improve the efficiency and selectivity of the catalytic synthesis of 4-hexene-3-one. By using porous materials such as sepiolite as carriers, combining metal organic framework materials and molecular sieves, and undergoing a series of steps such as phosphoric acid pretreatment, hydrothermal crystallization, and calcination, a catalyst with high specific surface area and good thermal stability is successfully prepared. This catalyst not only exhibits excellent catalytic performance in the synthesis reaction, but also further improves the yield and quality of 4-hexene-3-one by precisely controlling reaction conditions such as temperature, stirring speed, and reaction time, reflecting a deep understanding and application of catalyst design and optimization in fine chemical synthesis.

[0047] Example 1 A method for synthesizing 4-hexen-3-one using zinc chloride as a catalyst is as follows:

[0048] First, the reactor was purified under a nitrogen environment to avoid oxidation, and then 300 kg of dichloromethane was added and the temperature was maintained at 5°C; then, 20 kg of zinc chloride was added to the reaction mixture and stirred to ensure uniform distribution; then, 50 kg of propionic anhydride was gradually added dropwise and stirred for 2 hours at a dropping speed of 0.5 kg / min, and 25 kg of propylene gas was introduced to continue the reaction for 2 hours; after the reaction was completed, the mixture was transferred to a quenching kettle containing 100 kg of 5°C water for hydrolysis, the hydrolysis temperature was controlled to 5°C and stirred for 1.5 hours; the mixture was transferred to a layering kettle, and the layering kettle was allowed to stand and layered; the water layer was decompressed to recover the by-product propionic acid; the material layer was washed with 30 kg of saturated sodium carbonate solution, stirred for 2 hours, and layered; the product layer was distilled in a distillation tower, and dichloromethane was recovered by atmospheric distillation at 45°C in the distillation tower; 4-hexene-3-one was obtained by distillation at 100°C under reduced pressure of -0.03Mpa.

[0049] Example 2 A method for synthesizing 4-hexene-3-one using zinc chloride as a catalyst is as follows:

[0050] First, the reactor was purified under a nitrogen environment to avoid oxidation, and then 300 kg of dichloromethane was added and the temperature was maintained at 5°C; then, 20 kg of loaded zinc chloride catalyst was added to the reaction mixture and stirred to ensure uniform distribution; then, 50 kg of propionic anhydride was gradually added dropwise and stirred for 2 hours at a dropping speed of 0.5 kg / min, and 25 kg of propylene gas was introduced to continue the reaction for 2 hours; after the reaction was completed, the mixture was transferred to a quenching kettle containing 100 kg of 5°C water for hydrolysis, the hydrolysis temperature was controlled to 5°C and stirred for 1.5 hours; the mixture was transferred to a layering kettle, and the layering kettle was allowed to stand and layered; the water layer was decompressed to recover the by-product propionic acid; the material layer was washed with 30 kg of saturated sodium carbonate solution, stirred for 2 hours, and layered; the product layer was distilled in a distillation tower, and dichloromethane was recovered by atmospheric distillation at 45°C in the distillation tower; 4-hexene-3-one was obtained by distillation at -0.03Mpa and reduced pressure at 100°C.

[0051] The preparation method of the supported zinc chloride catalyst is as follows:

[0052] S1. Mix sepiolite with 80wt% phosphoric acid solution at a solid-liquid ratio of 1g:20mL, stir and react at room temperature for 3 hours. After the reaction is completed, wash with water until the pH is neutral, and dry the washed material at 80°C for 7 hours to obtain a pretreated material; take 0.2g of aluminum nitrate and dissolve it in 120g of water, and stir it evenly; gradually add 10g of triethylamine, 8g of pretreated material and 0.2g of sodium hydroxide, and mix them evenly; stir and reflux the mixed solution at 75°C for 20 hours, then transfer it to a high-pressure reactor, and hydrothermally crystallize it at 160°C for 50 hours; after the end, wash it with water twice, then dry it at 100°C for 10 hours, and calcine it at 450°C for 4 hours to obtain a molecular sieve;

[0053] S2, dissolving 1.2g of titanium tetrachloride, 0.9g of pyromellitic acid and 0.4g of 4-aminomethylbenzoic acid in 600g of dimethyl sulfoxide; adding 60g of cysteine ​​and 36g of water in sequence, and after the mixed solution is clarified, transferring it to an autoclave, and performing hydrothermal crystallization at 100°C for 20 hours; after completion, naturally cooling to room temperature, centrifuging, and washing with dimethyl sulfoxide and anhydrous ethanol twice each, and drying at 90°C for 6 hours to obtain a metal organic framework material;

[0054] S3. Evenly mix zinc chloride, metal organic framework material and molecular sieve in a mass ratio of 1:2:3 to obtain a loaded zinc chloride catalyst.

[0055] Example 3 A method for synthesizing 4-hexen-3-one using zinc chloride as a catalyst is basically the same as Example 1, the only difference being that the preparation method of the supported zinc chloride catalyst is different.

[0056] The preparation method of the supported zinc chloride catalyst is as follows:

[0057] S1. Mix diatomaceous earth with 80wt% phosphoric acid solution at a solid-liquid ratio of 1g:20mL, stir and react at room temperature for 3 hours. After the reaction is completed, wash with water until the pH is neutral, and dry the washed material at 80°C for 7 hours to obtain a pretreated material; take 0.2g of aluminum nitrate and dissolve it in 120g of water, and stir it evenly; gradually add 10g of triethylamine, 8g of pretreated material and 0.2g of sodium hydroxide, and mix them evenly; stir and reflux the mixed solution at 75°C for 20 hours, then transfer it to a high-pressure reactor, and hydrothermally crystallize it at 160°C for 50 hours; after completion, wash it with water twice, then dry it at 100°C for 10 hours, and calcine it at 450°C for 4 hours to obtain a molecular sieve;

[0058] S2, dissolving 1.2g of titanium tetrachloride, 0.9g of pyromellitic acid and 0.4g of 4-aminomethylbenzoic acid in 600g of dimethyl sulfoxide; adding 60g of cysteine ​​and 36g of water in sequence, and after the mixed solution is clarified, transferring it to an autoclave, and performing hydrothermal crystallization at 100°C for 20 hours; after completion, naturally cooling to room temperature, centrifuging, and washing with dimethyl sulfoxide and anhydrous ethanol twice each, and drying at 90°C for 6 hours to obtain a metal organic framework material;

[0059] S3. Evenly mix zinc chloride, metal organic framework material and molecular sieve in a mass ratio of 1:2:3 to obtain a loaded zinc chloride catalyst.

[0060] Example 4 A method for synthesizing 4-hexen-3-one using zinc chloride as a catalyst is basically the same as Example 1, the only difference being that the preparation method of the supported zinc chloride catalyst is different.

[0061] The preparation method of the supported zinc chloride catalyst is as follows:

[0062] S1. Mix zeolite with 80wt% phosphoric acid solution at a solid-liquid ratio of 1g:20mL, stir and react at room temperature for 3 hours. After the reaction is completed, wash with water until the pH is neutral, and dry the washed material at 80°C for 7 hours to obtain a pretreated material; take 0.2g of aluminum nitrate and dissolve it in 120g of water, and stir it evenly; gradually add 10g of triethylamine, 8g of pretreated material and 0.2g of sodium hydroxide, and mix them evenly; stir and reflux the mixed solution at 75°C for 20 hours, then transfer it to a high-pressure reactor, and hydrothermally crystallize it at 160°C for 50 hours; after the end, wash it with water twice, then dry it at 100°C for 10 hours, and calcine it at 450°C for 4 hours to obtain a molecular sieve;

[0063] S2, dissolving 1.2g of titanium tetrachloride, 0.9g of pyromellitic acid and 0.4g of 4-aminomethylbenzoic acid in 600g of dimethyl sulfoxide; adding 60g of cysteine ​​and 36g of water in sequence, and after the mixed solution is clarified, transferring it to an autoclave, and performing hydrothermal crystallization at 100°C for 20 hours; after completion, naturally cooling to room temperature, centrifuging, and washing with dimethyl sulfoxide and anhydrous ethanol twice each, and drying at 90°C for 6 hours to obtain a metal organic framework material;

[0064] S3. Evenly mix zinc chloride, metal organic framework material and molecular sieve in a mass ratio of 1:2:3 to obtain a loaded zinc chloride catalyst.

[0065] Example 5 A method for synthesizing 4-hexen-3-one using zinc chloride as a catalyst is basically the same as Example 1, the only difference being that the preparation method of the supported zinc chloride catalyst is different.

[0066] The preparation method of the supported zinc chloride catalyst is as follows:

[0067] S1. Mix sepiolite with 80wt% phosphoric acid solution at a solid-liquid ratio of 1g:20mL, stir and react at room temperature for 3 hours. After the reaction is completed, wash with water until the pH is neutral, and dry the washed material at 80°C for 7 hours to obtain a pretreated material; take 0.2g of aluminum nitrate and dissolve it in 120g of water, and stir it evenly; gradually add 10g of triethylamine, 8g of pretreated material and 0.2g of sodium hydroxide, and mix them evenly; stir and reflux the mixed solution at 75°C for 20 hours, then transfer it to a high-pressure reactor, and hydrothermally crystallize it at 160°C for 50 hours; after the end, wash it with water twice, then dry it at 100°C for 10 hours, and calcine it at 450°C for 4 hours to obtain a molecular sieve;

[0068] S2. Evenly mix zinc chloride, metal organic framework ZIF-8 and molecular sieve in a mass ratio of 1:2:3 to obtain a loaded zinc chloride catalyst.

[0069] Example 6 A method for synthesizing 4-hexen-3-one using zinc chloride as a catalyst is basically the same as Example 1, the only difference being that the preparation method of the supported zinc chloride catalyst is different.

[0070] The preparation method of the supported zinc chloride catalyst is as follows:

[0071] S1. Mix sepiolite with 80wt% phosphoric acid solution at a solid-liquid ratio of 1g:20mL, stir and react at room temperature for 3 hours. After the reaction is completed, wash with water until the pH is neutral, and dry the washed material at 80°C for 7 hours to obtain a pretreated material; take 0.2g of aluminum nitrate and dissolve it in 120g of water, and stir it evenly; gradually add 10g of triethylamine, 8g of pretreated material and 0.2g of sodium hydroxide, and mix them evenly; stir and reflux the mixed solution at 75°C for 20 hours, then transfer it to a high-pressure reactor, and hydrothermally crystallize it at 160°C for 50 hours; after the end, wash it with water twice, then dry it at 100°C for 10 hours, and calcine it at 450°C for 4 hours to obtain a molecular sieve;

[0072] S2. Evenly mix zinc chloride, metal organic framework MIL-53 and molecular sieve in a mass ratio of 1:2:3 to obtain a loaded zinc chloride catalyst.

[0073] Comparative Example 1

[0074] A method for synthesizing 4-hexen-3-one using zinc chloride as a catalyst is substantially the same as that of Example 1, the only difference being that the preparation method of the supported zinc chloride catalyst is different.

[0075] The preparation method of the supported zinc chloride catalyst is as follows:

[0076] S1. Mix sepiolite with 80wt% phosphoric acid solution at a solid-liquid ratio of 1g:20mL, stir and react at room temperature for 3 hours. After the reaction is completed, wash with water until the pH is neutral, and dry the washed material at 80°C for 7 hours to obtain a pretreated material; take 0.2g of aluminum nitrate and dissolve it in 120g of water, and stir it evenly; gradually add 10g of triethylamine, 8g of pretreated material and 0.2g of sodium hydroxide, and mix them evenly; stir and reflux the mixed solution at 75°C for 20 hours, then transfer it to a high-pressure reactor, and hydrothermally crystallize it at 160°C for 50 hours; after the end, wash it with water twice, then dry it at 100°C for 10 hours, and calcine it at 450°C for 4 hours to obtain a molecular sieve;

[0077] S2. Evenly mix zinc chloride and molecular sieve in a mass ratio of 1:3 to obtain a supported zinc chloride catalyst.

[0078] Comparative Example 2

[0079] A method for synthesizing 4-hexen-3-one using zinc chloride as a catalyst is substantially the same as that of Example 1, the only difference being that the preparation method of the supported zinc chloride catalyst is different.

[0080] The preparation method of the supported zinc chloride catalyst is as follows:

[0081] S1. Dissolve 1.2 g of titanium tetrachloride, 0.9 g of pyromellitic acid and 0.4 g of 4-aminomethylbenzoic acid in 600 g of dimethyl sulfoxide; add 60 g of cysteine ​​and 36 g of water in sequence, and after the mixed solution is clarified, transfer it to an autoclave and perform hydrothermal crystallization at 100° C. for 20 hours; after completion, naturally cool to room temperature, centrifuge, wash with dimethyl sulfoxide and anhydrous ethanol twice each, and dry at 90° C. for 6 hours to obtain a metal organic framework material;

[0082] S2. Evenly mix zinc chloride and metal organic framework material in a mass ratio of 1:2 to obtain a loaded zinc chloride catalyst.

[0083] Test Example 1

[0084] 4-Hexene-3-one yield test

[0085] The 4-hexen-3-one prepared in the comparative examples and the examples was statistically analyzed, and the theoretical yield was calculated based on the molar mass of the reactants and the chemical equation of the reaction.

[0086] The test results are shown in Table 1.

[0087] Table 1

[0088] Experimental protocol Yield (%) Example 1 95.5 Example 2 98.4 Example 3 97.7 Example 4 97.3 Example 5 97.6 Example 6 97.4 Comparative Example 1 97.0 Comparative Example 2 96.8

[0089] Test Example 2

[0090] Determination of specific surface area

[0091] The test was carried out by using the BELSORP-Ⅱ model adsorption instrument produced by BEL Company of Japan. Before the test, the loaded zinc chloride catalyst used in Examples 2 to 6 of the present invention and Comparative Examples 1 to 2 needs to be vacuum dehydrated at a high temperature of 200°C for about 3 hours to ensure the dry state of the sample. Subsequently, the specific surface area of ​​the catalyst is calculated according to the BET theoretical formula using the nitrogen adsorption-desorption isotherm. In addition, the BJH model is also used to analyze the pore volume characteristics of the catalyst pore structure, so as to comprehensively evaluate the pore properties of the catalyst. Through this series of standardized test procedures, the surface characteristics and pore structure of the catalyst can be accurately quantified, providing important data for the performance evaluation of the catalyst. The test results are shown in Table 2.

[0092] Table 2

[0093] Experimental protocol <![CDATA[Specific surface area (m 2 / g)]]> Example 2 698.3 Example 3 672.4 Example 4 612.8 Example 5 652.6 Example 6 671.3 Comparative Example 1 583.6 Comparative Example 2 626.4

[0094] It can be seen from the data in Table 1 and Table 2 that the supported zinc chloride catalyst used in Example 2 performs well in terms of specific surface area and yield of 4-hexen-3-one.

[0095] Sepiolite is a natural porous material with high porosity and specific surface area. This structure enables sepiolite to provide more active sites and larger reaction contact area when used as a catalyst carrier. This helps to improve the dispersibility of the catalyst and the contact efficiency of the reactants, thereby improving the reaction rate and product yield. In Example 2, sepiolite is first mixed with a phosphoric acid solution for pretreatment. Phosphoric acid is a strong acid that can effectively remove impurities on the surface of sepiolite and increase the acidity and hydrophilicity of its surface. This pretreatment not only improves the pore structure of sepiolite, but also may enhance its interaction with zinc chloride and metal organic framework materials, thereby improving the overall performance of the catalyst.

[0096] The metal organic framework material is mixed with zinc chloride and molecular sieves. The metal organic framework material has a highly ordered pore structure and adjustable pore size, which helps to improve the selectivity and stability of the catalyst. At the same time, the introduction of the metal organic framework material may enhance the thermal stability and mechanical strength of the catalyst, which is beneficial to maintain the structural integrity of the catalyst during the reaction.

[0097] In the preparation process of the catalyst, the hydrothermal crystallization and calcination steps have an important influence on the pore structure and surface properties of the catalyst. High-temperature hydrothermal crystallization helps to form a stable crystal structure and increase porosity, while the subsequent calcination process can further remove the organic template and improve the thermal and chemical stability of the catalyst.

[0098] The metal organic framework material used in Example 2 was prepared by a specific chemical synthesis method, while ZIF-8 and MIL-53 were used in Examples 5 and 6, respectively. The pore structure, chemical stability and thermal stability of the metal organic framework material have a significant impact on the performance of the catalyst. The metal organic framework material used in Example 2 may have a more optimized pore size and higher chemical stability, thereby providing more active sites and better reactant contact efficiency in the catalytic reaction.

[0099] Example 2 Compared with Comparative Examples 1 and 2, the mixing ratio of zinc chloride to metal organic framework material and molecular sieve is 1:2:3, and this ratio may be carefully designed to achieve the best chemical composition and physical structure. Zinc chloride is used as an active component, the metal organic framework material provides structural support, and the molecular sieve may play a role in regulating pores and enhancing thermal stability. This synergistic effect may improve the overall performance of the catalyst.

Claims

1. A method for synthesizing 4-hexen-3-one using zinc chloride as a catalyst, characterized in that: By weight: First, the reactor was purged under nitrogen to avoid oxidation, and then 250-350 parts of dichloromethane were added and the temperature was maintained at 2-8°C; then, 15-25 parts of the supported zinc chloride catalyst were added to the reaction mixture and stirred to ensure uniform distribution; Subsequently, 40-60 parts of propionic anhydride are gradually added dropwise and stirred continuously for 1-3 hours, and then 20-30 parts of propylene gas are introduced to continue the reaction for 1-3 hours; after the reaction is completed, the mixture is transferred to a quenching kettle containing 80-120 parts of water at 3-8°C for hydrolysis, and the hydrolysis temperature is controlled and stirred; the mixture is transferred to a layering kettle, and the layering kettle is allowed to stand and layer; the water layer is decompressed to recover the by-product propionic acid; the material layer is washed with 25-35 parts of a saturated sodium carbonate solution, stirred for 1-3 hours, and layered; The product layer is distilled in a distillation tower, and distilled under normal pressure in the distillation tower to recover dichloromethane; and distilled under reduced pressure to obtain 4-hexen-3-one; The preparation method of the supported zinc chloride catalyst is as follows, in parts by weight: S1. Mix sepiolite with 70-85wt% phosphoric acid solution at a solid-liquid ratio of 0.5-2g:15-25mL, stir and react at room temperature for 1-5 hours, and after the reaction is completed, wash with water until the pH is neutral, and dry the washed material at 70-90°C for 5-10 hours to obtain a pretreated material; Take 0.1-0.3 parts of aluminum nitrate and dissolve it in 100-140 parts of water, and stir it evenly; gradually add 5-15 parts of triethylamine, 5-10 parts of pretreatment materials and 0.1-0.3 parts of sodium hydroxide, and mix them evenly; stir and reflux the mixed solution at 70-80°C for 15-25 hours, and then transfer it to a high-pressure reactor for hydrothermal crystallization; after completion, wash it with water 1-3 times, and then dry it at 80-120°C for 5-15 hours, and calcine it to obtain a molecular sieve; S2, dissolving 1-1.5 parts of titanium tetrachloride, 0.5-1.2 parts of pyromellitic acid and 0.3-0.5 parts of 4-aminomethylbenzoic acid in 500-700 parts of dimethyl sulfoxide; adding 50-70 parts of cysteine ​​and 30-40 parts of water in sequence, and after the mixed solution is clarified, transferring it to an autoclave for hydrothermal crystallization; after completion, naturally cooling to room temperature, centrifuging, and washing with dimethyl sulfoxide and anhydrous ethanol 1-3 times each, and drying at 80-100°C for 3-10 hours to obtain a metal organic framework material; S3, mixing zinc chloride, metal organic framework material and molecular sieve uniformly to obtain a supported zinc chloride catalyst; The zinc chloride, metal organic framework material and molecular sieve are uniformly mixed in a mass ratio of 0.5-2:1-3:2-4.

2. The method for synthesizing 4-hexene-3-one using zinc chloride as a catalyst as claimed in claim 1, characterized in that: The dropping speed of the propionic anhydride is 0.4-0.6 parts / minute.

3. The method for synthesizing 4-hexene-3-one using zinc chloride as a catalyst as claimed in claim 1, characterized in that: The temperature of the atmospheric distillation is 40-60°C.

4. The method for synthesizing 4-hexene-3-one using zinc chloride as a catalyst as claimed in claim 1, characterized in that: The pressure of the reduced pressure distillation is -0.02~-0.04Mpa, and the temperature is 80~110°C.

5. The method for synthesizing 4-hexene-3-one using zinc chloride as a catalyst as claimed in claim 1, characterized in that: The hydrolysis temperature is controlled to be 2-15° C. and the stirring is performed for 1-3 hours.

6. The method for synthesizing 4-hexene-3-one using zinc chloride as a catalyst as claimed in claim 1, characterized in that: The calcination is carried out at 400-500° C. for 3-5 hours.

7. The method for synthesizing 4-hexene-3-one using zinc chloride as a catalyst as claimed in claim 1, characterized in that: The hydrothermal crystallization in step S1 is performed at 150-170° C. for 25-60 hours.

8. The method for synthesizing 4-hexene-3-one using zinc chloride as a catalyst as claimed in claim 1, characterized in that: The hydrothermal crystallization in step S2 is performed at 80-120° C. for 15-25 hours.