Application of ruthenium-based catalysts modified with pyridine ligands in acetylene hydrochlorination

Abstract

The present invention relates to the use of a ruthenium-based catalyst modified with a pyridine ligand in the hydrochlorination reaction of acetylene. The catalyst comprises a ruthenium salt, a pyridine ligand and a carbon support, wherein the pyridine ligand is one or more of pyridine, 2-picoline, 3-picoline, 4-picoline, 3-ethylpyridine, 3-isobutylpyridine, 4-ethylpyridine, 4-tert-butylpyridine and 3,5-dimethylpyridine; the ruthenium salt and one or more pyridine ligands are loaded on the surface of the carbon support, wherein the ruthenium salt cation mainly exists in the form of Ru 3+ Introducing specific pyridine ligands into the ruthenium-based catalyst used in the acetylene hydrochlorination reaction can help stabilize the valence state of high-valent ruthenium species, while reducing the amount of metallic ruthenium incorporated, effectively improving the activity and stability of the ruthenium-based catalyst.

Description

Technical Field

[0001] The invention belongs to the field of chemical catalysis, and particularly relates to the application of a ruthenium-based catalyst modified with a pyridine ligand in acetylene hydrochlorination reaction and the catalyst. Background Art

[0002] Polyvinyl chloride (PVC) is an important thermoplastic and one of the five major general-purpose resins. Its advantages include high mechanical strength, easy processing, and low price, making it one of the most widely used plastics. As of the end of 2020, my country's existing PVC production capacity reached 26.64 million tons, and 4.74 million tons of new PVC projects are expected to be commissioned over the next two years. PVC is produced by the polymerization of vinyl chloride monomer (VCM), a toxic, colorless, and flammable gas. Currently, over 96% of VCM is used in the production of PVC products worldwide. Due to my country's coal-rich, oil-poor energy structure, 80% of industrial vinyl chloride production is produced via the acetylene process using mercury dichloride as a catalyst. Mercury is highly toxic and easily sublimates and escapes during the reaction, posing significant risks to both the environment and humans. Therefore, the development of green, efficient, and mercury-free catalysts is urgent.

[0003] Currently, the most mature precious metal system in the field of acetylene hydrochlorination catalysis is the gold-based precious metal system. Gold-based catalysts have excellent catalytic performance, but due to their high price, many factories and enterprises are reluctant to use them, and they cannot be popularized. Among various precious metal catalysts, ruthenium has good catalytic performance and stability, and its price is only one-fifth of gold, which has the potential to become a metal substitute for gold-based catalysts. In 2012, Dai Bin's research group used the DFT method to calculate and compare the reaction energy barriers of HgCl2, AuCl3, and RuCl3, and found that the reaction energy barrier corresponding to the ruthenium catalyst was the lowest (9.1kcal / mol), which indicates that the ruthenium catalyst may be the most suitable system for acetylene hydrochlorination. Subsequently, ruthenium-based catalysts were widely studied and reported.

[0004] Currently available ruthenium-based catalysts for acetylene hydrochlorination reactions include those modified with coordination agents such as thiourea and nitrogen-containing five-membered heterocyclic ligands, those modified by adding additives such as oxalic acid and potassium chloride, and those modified using ionic liquids as dispersants. Like other metals, ruthenium has inherent problems, such as the susceptibility of high-valent ruthenium ions to reduction and the agglomeration of ruthenium particles during the reaction. This application provides a novel ruthenium-based catalyst for acetylene hydrochlorination, characterized by low catalyst dosage, high conversion rate, good stability, and high economic efficiency, promising industrial application prospects and broadening the range of catalysts for acetylene hydrochlorination. Summary of the Invention

[0005] The present invention aims to provide a ruthenium-based catalyst modified with a pyridine ligand for use in the hydrochlorination of acetylene. The catalyst exhibits both activity and stability, has potential for industrial application, and is economical and suitable for industrial deployment.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A ruthenium-based catalyst modified with a pyridine ligand is used in the hydrochlorination reaction of acetylene. The catalyst comprises a ruthenium salt, a pyridine ligand and a carbon support. The pyridine ligand is one or more of pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 3-ethylpyridine, 3-isobutylpyridine, 4-ethylpyridine, 4-tert-butylpyridine and 3,5-dimethylpyridine. The ruthenium salt and one or more pyridine ligands are loaded on the surface of the carbon support. The ruthenium salt cation mainly exists in the form of Ru 3+ .

[0008] The preparation method of the catalyst is:

[0009] Step 1: dissolving the ruthenium salt and the pyridine ligand in a specific solvent at a certain temperature and in a certain proportion to obtain a mixed solution, wherein the specific solvent is capable of completely dissolving the ruthenium salt and the pyridine ligand to obtain a uniform and stable mixed solution;

[0010] Step 2: At the same temperature, the mixed solution is uniformly loaded onto the activated carbon support by impregnation, spraying, precipitation, ion exchange or spray evaporation;

[0011] Step 3: Drying for a certain time under a certain temperature and pressure environment to obtain the catalyst.

[0012] The molar ratio of ruthenium salt to pyridine ligand in the mixed solution is 1:0.5 to 10; more preferably, the molar ratio of ruthenium salt to pyridine ligand in the mixed solution is 1:1 to 8; the solvent is selected from at least one of deionized water, anhydrous ethanol, acetone, dichloromethane, ethylene glycol dimethyl ether (DME), and N,N-dimethylformamide (DMF); more preferably, the solvent is a mixed solvent of water / ethylene glycol dimethyl ether (DME), and the mass ratio of organic solvent to water in the mixed solvent is 1:0.5 to 10.

[0013] The mass fraction of Ru element in the mixed solution accounts for 0.05% to 0.1% of the mass fraction of the finished catalyst, such as 0.05 to 0.06wt.%, 0.06 to 0.07wt.%, 0.07 to 0.09wt.%, and 0.07 to 0.1wt.%.

[0014] The stirring and dissolving temperature of the mixed solution is 30-110°C, such as 30-45°C, 45-60°C, or 65-80°C.

[0015] The carbon carrier is one or more of coal-based activated carbon, wood-based activated carbon, and asphalt-based activated carbon; the wood-based activated carbon is coconut shell activated carbon; the water capacity of the carbon carrier is 60-130%, the bulk density is 0.3-0.8 g / mL; and the loading temperature is 30-110°C.

[0016] The process of catalyst drying treatment is: drying at 5 to 20° C. higher than the boiling point of the solvent and 0.1 MPa for 6 to 20 hours.

[0017] More preferably, in step 3, the drying is carried out at a temperature 15° C. higher than the boiling point of the solvent for 20 h.

[0018] The reaction conditions for the application of ruthenium-based catalyst modified with pyridine ligand in acetylene hydrochlorination are as follows: temperature of 90-250°C, acetylene volume space velocity of 5-200h -1 , the pressure is 0.01~0.2Mpa.

[0019] The products were analyzed by gas chromatography and the reaction activity was expressed by acetylene conversion.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention introduces a specific pyridine ligand into the ruthenium-based catalyst used in the acetylene hydrochlorination reaction, which can help stabilize the valence state of high-valent ruthenium species, while reducing the amount of metallic ruthenium incorporated, effectively improving the activity and stability of the ruthenium-based catalyst.

[0022] The catalyst of the present invention has high catalytic activity, good stability, low loading, and good industrial application potential. 3,5-dimethylpyridine has a loading of 0.1 wt.% Ru, a reaction temperature of 180°C, and an acetylene space velocity of 80 h -1 The volume ratio of hydrogen chloride to acetylene is 1.2:1, and the acetylene conversion rate of the catalyst is stable at above 98%, which has good industrial application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The graph shows the life performance test results of ruthenium-based catalysts (evaluation conditions: T = 180 ° C, GHSV = 80h). -1 , HCl / C2H2=1.2). DETAILED DESCRIPTION

[0024] The following examples illustrate the technical solutions of the present invention. The following examples are provided to help those skilled in the art understand the present invention in more detail and are not intended to limit the scope of protection of the present invention. The scope of protection of the present invention is set forth in the appended claims.

[0025] Example 1

[0026] (1) At 50°C, 0.0135 g of ruthenium trichloride trihydrate and 15.6 μL of pyridine were dissolved in 3.5 g of a water / DME mixed solvent (2 g of water) and stirred to obtain an impregnation solution;

[0027] (2) Use the equal volume impregnation method to impregnate 5g of activated carbon with the impregnation solution and let it stand at room temperature for 1 hour;

[0028] (3) The activated carbon was dried at 110°C for 6 hours to obtain catalyst A1.

[0029] Example 2

[0030] (1) Dissolve 0.0135 g of ruthenium trichloride trihydrate and 22.2 μL of 3-ethylpyridine in 3.5 g of a water / DME mixed solvent at 50° C. and stir to obtain an impregnation solution;

[0031] (2) Use the equal volume impregnation method to impregnate 5g of activated carbon with the impregnation solution and let it stand at room temperature for 1 hour;

[0032] (3) The activated carbon was dried at 110°C for 6 hours to obtain catalyst A2.

[0033] Example 3

[0034] (1) Dissolve 0.0135 g of ruthenium trichloride trihydrate and 18.4 μL of 3-methylpyridine in 3.5 g of a water / DME mixed solvent at 50° C. and stir to obtain an impregnation solution;

[0035] (2) Use the equal volume impregnation method to impregnate 5g of activated carbon with the impregnation solution and let it stand at room temperature for 1 hour;

[0036] (3) The activated carbon was dried at 110°C for 6 hours to obtain catalyst A3.

[0037] Example 4

[0038] (1) At 50°C, 0.0135 g of ruthenium trichloride trihydrate and 21.2 μL of 3,5-lutidine were dissolved in 3.5 g of a water / DME mixed solvent and stirred to obtain a mixed solution, which was the impregnation solution;

[0039] (2) Use the equal volume impregnation method to impregnate 5g of activated carbon with the impregnation solution and let it stand at room temperature for 1 hour;

[0040] (3) The activated carbon was dried at 110°C for 6 hours to obtain catalyst A4.

[0041] Example 5-Example 6

[0042] The steps of this embodiment are the same as those of embodiment 4, except that the mass fraction of Ru element in the mixed solution in this embodiment accounts for 0.08% and 0.05% of the mass fraction of the finished catalyst.

[0043] Comparative Example 1

[0044] The purpose of Comparative Example 1 is to compare with all the examples listed above to illustrate that the catalytic effect of the ruthenium-based catalyst modified with pyridine ligands is better than the reported ruthenium-based catalyst modified with thiourea.

[0045] (1) At 50°C, 0.0135 g of ruthenium trichloride trihydrate and 0.0151 g of thiourea were dissolved in 3.5 g of a water / DME mixed solvent and stirred to obtain an impregnation solution;

[0046] (2) Use the equal volume impregnation method to impregnate 5g of activated carbon with the impregnation solution and let it stand at room temperature for 1 hour;

[0047] (3) The activated carbon was dried at 110°C for 6 hours to obtain catalyst D1.

[0048] Comparative Example 2

[0049] The purpose of Comparative Example 2 is to compare with Example 4 and to illustrate that the acetylene conversion rate of the catalyst modified with the pyridine ligand - 3,5-dimethylpyridine is further increased.

[0050] (1) At 50°C, 0.0135 g of ruthenium trichloride trihydrate and 42 μL of 4,5-dimethylthiazole were dissolved in 3.5 g of a water / DME mixed solvent and stirred to obtain an impregnation solution;

[0051] (2) Use the equal volume impregnation method to impregnate 5g of activated carbon with the impregnation solution and let it stand at room temperature for 1 hour;

[0052] (3) The activated carbon was dried at 110°C for 6 hours to obtain catalyst D2.

[0053] Examples 1, 2, 3, 4 and Comparative Examples 1 and 2 were all heated at 180°C and an acetylene space velocity of 160 h -1 The evaluation was carried out under the reaction conditions of a hydrogen chloride to acetylene volume ratio of 1.2:1, wherein the catalyst ruthenium loading (5g activated carbon) was 0.1wt%.

[0054] The catalysts obtained in Example 4 and Comparative Example 2 were simultaneously heated at 180°C and an acetylene space velocity of 80 h -1 The life evaluation was carried out under the reaction conditions of a hydrogen chloride to acetylene volume ratio of 1.2:1, wherein the catalyst ruthenium loading (5g activated carbon) was 0.1wt%.

[0055] The exhaust gas composition was analyzed using gas chromatography, with samples taken every 0.5 hours. The 4-hour reaction point was used as a representative data point to compare the acetylene conversion rates of ruthenium-based catalysts with different pyridine ligands. The results are shown in Table 1. In addition, a 50-hour life test was conducted on Example 4 and Comparative Example 2. The experimental results are shown in Table 2:

[0056] Table 1 (160 airspeed)

[0057] Sample number ligand solvent Acetylene conversion rate Example 1 A1 Pyridine Water / DME 89％ Example 2 A2 3-Ethylpyridine Water / DME 82％ Example 3 A3 3-Methylpyridine Water / DME 91％ Example 4 A4 3,5-Dimethylpyridine Water / DME 93％ Example 5 A5 3,5-Dimethylpyridine Water / DME 90％ Example 6 A6 3,5-Dimethylpyridine Water / DME 85％ Comparative Example 1 D1 Thiourea Water / DME 68％ Comparative Example 2 D2 4,5-Dimethylthiazole Water / DME 90％

[0058] Table 2 50h life test

[0059]

[0060] From the experimental results of Comparative Example 1 and Examples 1, 2 and 3, it can be seen that the introduction of pyridine ligands in the present invention can improve the activity of ruthenium-based catalysts under the same conditions, and is superior to the ruthenium-based catalyst modified with thiourea in the published patent. -1 In comparison, the present invention achieves a high conversion rate of acetylene and a high stability of the catalyst under acetylene space velocity evaluation conditions far higher than industrial requirements.

[0061] From the 50h life test results of Example 4 and Comparative Example 3, it can be seen that the catalyst with excellent performance after modification of the specially selected pyridine ligand, namely the ruthenium-based catalyst modified with 3,5-dimethylpyridine ligand, has a 0.1wt.% Ru loading and acetylene 80h -1 Under these conditions, after 50 hours of reaction, the acetylene conversion rate remained stable at over 98%, with no significant downward trend. Compared to the ruthenium-based catalyst modified with a 4,5-dimethylthiazole ligand, the ruthenium-based catalyst modified with a 3,5-dimethylpyridine ligand exhibited an even higher conversion rate, suggesting that this catalyst has potential for industrial application.

[0062] The present invention modifies the ruthenium-based catalyst by adding a pyridine ligand, thereby significantly improving the catalytic activity and stability of the catalyst. This allows the Ru-based catalyst to achieve the same catalytic effect as other Ru-based catalysts with higher ruthenium loadings at an extremely low metal loading (Ru ion loading is 0.05-0.1wt%). When the Ru loading is increased under the same conditions, the catalytic performance is better than that of existing catalysts, effectively reducing industrial costs.

[0063] Any matters not described in the present invention are applicable to the prior art.

Claims

1. Application of a ruthenium-based catalyst modified with a pyridine ligand in the hydrochlorination of acetylene, the catalyst comprising a ruthenium salt, a pyridine ligand and a carbon support, characterized in that: The pyridine ligand is one or more of 3-methylpyridine and 3,5-dimethylpyridine; the ruthenium salt and one or more pyridine ligands are loaded on the surface of the carbon support, wherein the ruthenium salt cation exists mainly in the form of Ru 3+ ; The preparation method of the catalyst is: Step 1: dissolving the ruthenium salt and the pyridine ligand in a specific solvent at a certain temperature and in a certain proportion to obtain a mixed solution, wherein the specific solvent is capable of completely dissolving the ruthenium salt and the pyridine ligand to obtain a uniform and stable mixed solution; Step 2: At the same temperature, the mixed solution is uniformly loaded onto the activated carbon support by impregnation, spraying, precipitation, ion exchange or spray evaporation; Step 3: Drying for a certain period of time under a certain temperature and pressure environment to obtain the catalyst; The specific solvent is a mixed solvent of water / ethylene glycol dimethyl ether (DME), wherein the mass ratio of organic solvent to water in the mixed solvent is 1.5:2; The mass fraction of Ru element in the mixed solution accounts for 0.05-0.1% of the mass fraction of the finished catalyst.

2. The use of the ruthenium-based catalyst modified with a pyridine ligand according to claim 1 in the hydrochlorination of acetylene, characterized in that: The ruthenium salt is selected from one or more of ruthenium trichloride, hydrated ruthenium trichloride, ruthenium acetate, ruthenium iodide, and ammonium chlororuthenate.

3. The use of the ruthenium-based catalyst modified with a pyridine ligand according to claim 1 in the hydrochlorination of acetylene, characterized in that: The stirring and dissolving temperature of the mixed solution is 30-110°C.

4. The use of the ruthenium-based catalyst modified with a pyridine ligand according to claim 1 in the hydrochlorination of acetylene, characterized in that: The carbon carrier is one or more of coal-based activated carbon, wood-based activated carbon, and asphalt-based activated carbon; the wood-based activated carbon is coconut shell activated carbon; the water capacity of the carbon carrier is 60-130%, the bulk density is 0.3-0.8 g / mL; and the loading temperature is 30-110°C.

5. Use of the ruthenium-based catalyst modified with a pyridine ligand according to claim 1 in acetylene hydrochlorination, characterized in that: The process of catalyst drying treatment is: drying at 5 to 20° C. above the boiling point of the solvent and 0.1 MPa for 6 to 20 hours.

6. Use of the ruthenium-based catalyst modified with a pyridine ligand according to claim 1 in acetylene hydrochlorination, characterized in that: The reaction conditions for the application of ruthenium-based catalyst modified with pyridine ligand in acetylene hydrochlorination are as follows: temperature of 90-250°C, acetylene volume space velocity of 5-200h -1 , the pressure is 0.01~0.2MPa.

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