Preparation method and application of a CPS-supported heteropolyacid ionic liquid catalyst
By chemically bonding imidazole cations to heteropolyacid anion and solidly loading them on CPS, a synergistically catalyzed heteropolyacid ion liquid catalyst was prepared, which solved the problems of high viscosity, difficulty in separation and recovery and poor stability of traditional catalysts in the synthesis of cyclic carbonate in CO2, and achieved efficient catalytic performance and good industrial application prospects.
Patent Information
- Application Number
- CN202111213844.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-10-19
- Publication Date
- 2025-06-17
- Estimated Expiration
- 2041-10-19
AI Technical Summary
In the prior art, in the use of ionic liquids to catalyze the esterification reaction of CO2 synthesis into cyclic carbonate, there are problems such as high viscosity and difficulty in separation and recovery, and traditional solid-loaded catalysts have problems such as easy de-loading, loss of active components, and poor stability.
By connecting the imidazole cations and heteropolyacid anions together through chemical bonding, a CPS-supported heteropolyacid ion liquid catalyst is prepared to achieve the synergistic catalytic action between metal and acid active sites.
The catalytic performance is improved, and the problems of easy de-loading, loss of active components and poor stability of traditional solid-loaded catalysts are solved. The catalyst has high industrial application prospects.
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Figure CN113976178B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical fields of material preparation and catalytic reaction, and particularly relates to a preparation method of a CPS-supported heteropolyacid ionic liquid and its application in the catalytic synthesis of cyclic carbonates from CO2. Background Art
[0002] With the proposal of the concept of "carbon neutrality", it has become extremely urgent to deal with CO2 in a green and efficient manner. Currently, it has been found that CO2 can be converted into high-value-added chemicals such as polycyclic carbonates, carbonates, polyurethanes, etc. through new technologies. Cyclic carbonates have characteristics such as strong chemical stability and high ionic conductivity, and are good organic solvents. Using CO2 as a raw material for producing cyclic carbonates not only reduces the emissions of carbon dioxide in the atmosphere and mitigates the greenhouse effect, meeting the standards of modern green chemistry, but also can obtain high-value-added chemicals, realizing carbon recycling. It is one of the most promising methods for fixing CO2 recognized in the world at present.
[0003] Ionic liquids refer to salts composed of anions and cations that are in a molten state at room temperature. They have characteristics such as pollution-free, stable properties, and low volatility, and are commonly used as catalysts. Modifying ionic liquids for the esterification reaction of catalytic synthesis of cyclic carbonates from CO2 has high catalytic efficiency. However, ionic liquids also have defects such as high viscosity during preparation and difficult separation and recovery, which limit their large-scale application. Therefore, ionic liquids must be immobilized on a suitable carrier to solve these problems. Currently reported carriers such as molecular sieves, activated carbon, SiO2, etc. have problems such as complex synthesis steps and amorphous carriers. Therefore, there is an urgent need to develop a method for preparing immobilized ionic liquid catalysts with simple synthesis steps and easy control of reaction conditions.
[0004] So far, there has been no report on using chloromethylated polystyrene resin (CPS) to support heteropolyacid ionic liquid catalysts. This catalyst is a solid catalyst with stable structural properties, high catalytic efficiency, good recycling performance, and has high industrial application prospects. Summary of the Invention
[0005] Object of the Invention
[0006] The present invention provides a preparation method and application of a CPS-supported heteropolyacid ionic liquid catalyst, aiming to bond imidazole cations and heteropolyacid anions together through chemical bonding to prepare an organic-inorganic hybrid catalyst, realizing the synergistic catalytic effect of metals and acidic active sites, effectively solving the problems of easy deloading, loss of active components, and poor stability existing in the traditional immobilized catalyst for catalytic synthesis of propylene carbonate from CO2, and further improving the catalytic performance.
[0007] Technical Solution
[0008] A preparation method of a CPS-supported heteropolyacid ionic liquid catalyst, comprising the following steps:
[0009] (1) Preparation of heteropolyacid
[0010] Sodium tungstate, central atom salt and coordination atom salt are dissolved in distilled water according to a molar ratio of 1:1 - 3:1 - 3, and heated. After dissolution is completed, the pH is adjusted to 4 - 5 with a pH regulator, and the reaction is carried out at 60 - 85 °C for 2.0 - 6.0 h. After washing, concentration and drying, the heteropolyacid is obtained;
[0011] (2) Preparation of intermediate CPS-supported imidazole ionic liquid
[0012] CPS, N-methylimidazole, n-butyl bromide and acetonitrile are added to a reactor according to a molar ratio of 1:2 - 6:0.8 - 1.2:10 - 25, and the reaction is carried out at 60 - 80 °C for 24 - 48 h. After suction filtration, washing and drying, CPS-MIM-Br is obtained;
[0013] (3) Preparation of polystyrene resin-supported heteropolyacid ionic liquid catalyst by chemical bonding method
[0014] The heteropolyacid is dissolved in a solvent, cation exchange resin and CPS-MIM-Br are added, and the reaction is carried out with slow stirring at 25 - 30 °C for 8 - 12 h. After the reaction is stopped, suction filtration, washing and drying are carried out to obtain the CPS-supported heteropolyacid ionic liquid CPS-MIM-WM.
[0015] In step (1), the molar ratio of sodium tungstate to distilled water is 1:80 - 100.
[0016] In step (1), the pH regulator is one of acetic acid and HCl.
[0017] In step (1), the central atom salt is one of manganese acetate and zirconium oxychloride; the coordination atom salt is one of cobalt acetate and zinc chloride, and the heteropolyacid is CoW 11 Mn, ZnW 11 Mn, CoW 11 Zr, ZnW 11 One of Zr.
[0018] In step (3), the molar ratio of heteropolyacid, cation exchange resin, CPS-MIM-Br and solvent is n = 1:0.005 - 0.04:0.02 - 0.05:10 - 25; the solvent is one or a mixture of any two of ethanol, methanol and dichloromethane in any proportion.
[0019] The heteropolyacid is of the Keggin type, and the central heteroatom and the vacant atom can play a synergistic catalytic role with the imidazole structure.
[0020] Application of a CPS-supported heteropolyacid ionic liquid catalyst in the synthesis of cyclic carbonates from CO2
[0021] The present invention has the following advantages and good effects:
[0022] The catalyst of the present invention has a high catalytic effect, solving the problems of high viscosity during the preparation of ionic liquids and difficult separation and recovery in the esterification reaction of using ionic liquids to catalyze the synthesis of cyclic carbonates from CO2
[0023] The catalyst of the present invention has a good service life. After being recycled 6 times, the yield of propylene carbonate can reach 80.08%, and the selectivity can reach 93.81%, still maintaining a good catalytic effect. Description of the drawings
[0024] Figure 1 It is a schematic diagram of catalyst synthesis;
[0025] Figure 2 It is an infrared spectrum analysis chart of the prepared supported catalyst;
[0026] Figure 3 It is an X-ray spectrum chart of the prepared supported catalyst. Detailed implementation manners
[0027] The present invention will be described in more detail below with reference to the accompanying drawings of the specification.
[0028] As Figure 1 shown, the present invention relates to a supported heteropolyacid ionic liquid catalyst, its preparation method and its application in catalyzing the synthesis of propylene carbonate from CO2. Using CPS spheres as carriers, heteropolyacid ionic liquids are immobilized by chemical bonding to prepare heteropolyacid ionic liquid catalysts. The catalysts are in a solid phase state, having the characteristics of stable carrier structure and large specific surface area. Moreover, the heteropolyacid metal ions and imidazole structure have a synergistic catalytic effect, which can further improve the catalytic activity. The chemical bond between the heteropolyacid ionic liquid and the CPS carrier can make the immobilized structure more firm, improve the stability and strength of the catalyst, further improve the loss and detachment of the active components of the immobilized ionic liquid catalyst, and the spherical solid catalyst is more conducive to recovery and recycling.
[0029] The structure and appearance morphology of the supported catalyst were characterized by an infrared spectrometer (FT-IR), a scanning electron microscope (SEM), etc. Using propylene oxide and CO2 as raw materials, the above-mentioned CPS sphere-supported heteropolyacid ionic liquid was used as a catalyst to investigate its catalytic performance. After the products were detected by a gas chromatograph, the percentage content of each component in the product was determined by the area normalization method, and the conversion rate, selectivity and yield of the reactants and target products were calculated to evaluate the catalytic performance.
[0030] Example 1
[0031] (1) Preparation of heteropolyacid
[0032] Sodium tungstate, 1 mol of cobalt acetate and 1 mol of manganese acetate were dissolved in 80 mol of distilled water according to a molar ratio of 1 mol and heated. After dissolution was completed, acetic acid was used to adjust the pH to 4, and the reaction was carried out at 60 °C for 2 h. After washing, concentration and drying, the heteropolyacid (CoW 11 Mn) was obtained.
[0033] (2) Preparation of intermediate CPS-supported imidazolium ionic liquid (CPS-MIM-Br)
[0034] 1 mol of CPS, 2 mol of N-methylimidazole, 0.8 mol of n-butyl bromide and 10 mol of acetonitrile were added to the reactor according to a molar ratio, and the reaction was carried out at 60 °C for 24 h. After suction filtration, washing and drying, CPS-MIM-Br was obtained.
[0035] (3) Preparation of polystyrene resin-supported heteropolyacid ionic liquid catalyst by impregnation method
[0036] 1 mol of CoW 11 Mn was dissolved in 10 mol of methanol, 0.005 mol of cation exchange resin and 0.02 mol of CPS-MIM-Br were added, and the reaction was carried out with slow stirring at 25 °C for 8 h. After the reaction was stopped, suction filtration, washing and drying were carried out to obtain CPS-supported heteropolyacid ionic liquid CPS-MIM-CoW 11 Mn.
[0037] In the present invention, the CPS-supported heteropolyacid ionic liquid catalyst is preferably CPS-MIM-CoW 11 Mn.
[0038] Example 2
[0039] (1) Preparation of heteropolyacid
[0040] Sodium tungstate, 1.5 mol of zinc chloride and 2 mol of manganese acetate were dissolved in 90 mol of distilled water according to a molar ratio of 1 mol and heated. After dissolution was completed, HCl was used to adjust the pH to 4.3, and the reaction was carried out at 70 °C for 4.0 h. After washing, concentration and drying, the heteropolyacid (ZnW 11 Mn) was obtained.
[0041] (2) Preparation of intermediate CPS-supported imidazolium ionic liquid (CPS-MIM-Br)
[0042] 1 mol of CPS, 6 mol of N-methylimidazole, 0.9 mol of n-butyl bromide and 20 mol of acetonitrile were added to the reactor according to a molar ratio, and the reaction was carried out at 80 °C for 35 h. After suction filtration, washing and drying, CPS-MIM-Br was obtained.
[0043] (3) Preparation of Polystyrene Resin-Supported Heteropolyacid Ionic Liquid Catalyst by Impregnation Method
[0044] Dissolve 1 mol of ZnW 11 Mn in 15 mol of ethanol and 10 mol of dichloromethane, add 0.03 mol of cation exchange resin and 0.04 mol of CPS-MIM-Br, stir slowly, react at 26 °C for 9 h, stop the reaction, and obtain CPS-supported heteropolyacid ionic liquid CPS-MIM-ZnW 11 Mn through suction filtration, washing and drying.
[0045] Example 3
[0046] (1) Preparation of Heteropolyacid
[0047] Dissolve sodium tungstate, 3 mol of cobalt acetate and 2.5 mol of zirconium oxychloride in 100 mol of distilled water according to the molar ratio of 1 mol, and heat. After dissolution is complete, adjust the pH to 4.8 with acetic acid and react at 65 °C for 6.0 h. Obtain heteropolyacid (CoW 11 Zr) through washing, concentration and drying.
[0048] (2) Preparation of Intermediate CPS-Supported Imidazole Ionic Liquid (CPS-MIM-Br)
[0049] Add 1 mol of CPS, 5 mol of N-methylimidazole, 1.2 mol of n-butyl bromide and 25 mol of acetonitrile to the reactor according to the molar ratio, react at 75 °C for 48 h, and obtain CPS-MIM-Br through suction filtration, washing and drying.
[0050] (3) Preparation of Polystyrene Resin-Supported Heteropolyacid Ionic Liquid Catalyst by Impregnation Method
[0051] Dissolve 1 mol of CoW 11 Zr in 20 mol of dichloromethane, add 0.01 mol of cation exchange resin and 0.03 mol of CPS-MIM-Br, stir slowly, react at 30 °C for 10 h, stop the reaction, and obtain CPS-supported heteropolyacid ionic liquid CPS-MIM-CoW 11 Zr through suction filtration, washing and drying.
[0052] Example 4
[0053] (1) Preparation of Heteropolyacid
[0054] Dissolve sodium tungstate, 2 mol of zinc chloride and 3 mol of zirconium oxychloride in 85 mol of distilled water according to the molar ratio of 1 mol, and heat. After dissolution is complete, adjust the pH to 5 with HCl and react at 80 °C for 5.0 h. Obtain heteropolyacid (ZnW 11 Zr) through washing, concentration and drying.
[0055] (2) Preparation of intermediate CPS-supported imidazolium ionic liquid (CPS-MIM-Br)
[0056] Add 1 mol of CPS, 4 mol of N-methylimidazole, 1.0 mol of n-butyl bromide and 15 mol of acetonitrile into the reactor according to the molar ratio, react at 70 °C for 28 h, and obtain CPS-MIM-Br after filtration, washing and drying.
[0057] (3) Preparation of polystyrene resin-supported heteropolyacid ionic liquid catalyst by impregnation method
[0058] Dissolve 1 mol of ZnW 11 Zr in 15 mol of ethanol, add 0.04 mol of cation exchange resin and 0.05 mol of CPS-MIM-Br, stir slowly and react at 28 °C for 12 h, then stop the reaction, and obtain CPS-supported heteropolyacid ionic liquid CPS-MIM-ZnW 11 Zr after filtration, washing and drying.
[0059] Apply the catalysts prepared in Examples 1-4 to the catalytic carbonylation of CO2 and propylene oxide to synthesize propylene carbonate in a batch reactor respectively. The reaction is stopped after 5 h at a catalyst dosage of 3.0 g, 150 ml of propylene oxide, a reaction kettle temperature of 130 °C and a pressure of 2.5 Mpa, and the catalytic evaluation results are shown in Table 1.
[0060] Table 1 Catalytic effect evaluation of Examples 1-4
[0061]
[0062] Table 1 is the catalytic effect evaluation of the catalysts prepared in Examples 1-4 for the carbonylation reaction to synthesize propylene carbonate. The experimental results show that the catalyst CPS-MIM-CoW 11 Mn prepared in Example 1 has the best catalytic effect, with a yield of 91.11% and a selectivity of 98.76%.
[0063] Example 5
[0064] Conduct a study on the recycling performance of the supported catalyst CPS-MIM-CoW 11 Mn prepared in Example 1. The catalytic reaction conditions are the same as above, and the cyclic catalytic evaluation results are shown in Table 2.
[0065] Table 2 Recycling performance of CPS-MIM-CoW 11 Mn
[0066]
[0067] Table 2 is for the supported catalyst CPS-MIM-CoW11 The cyclic use performance of Mn. The experimental results show that this catalyst has a good service life. After being recycled 6 times, the yield of propylene carbonate is 80.08% and the selectivity is 93.81%, still maintaining a good catalytic effect.
[0068] According to the catalytic evaluation experiment, it can be known that the catalyst CPS-MIM-CoW prepared in the example 11 has the best catalytic effect of Mn. The infrared spectrum test was carried out on this catalyst, and the infrared spectrum is as Figure 2 shown. From Figure 2 it can be seen the characteristic peaks of the Keggin structure of the heteropolyacid ionic liquid and polystyrene. The Keggin structure contains metal ions, which are more likely to form a complexation with the oxygen atom of the epoxide, promoting ring opening and increasing the conversion rate. At the same time, this structure is acidic and has a synergistic catalytic effect. Therefore, the infrared spectrum shows that the heteropolyacid ionic liquid has been successfully loaded onto the polystyrene chloride beads. (a) CoW 11 Mn; (b) CPS-MIM-CoW 11 Mn.
[0069] For the above catalyst CPS-MIM-CoW 11 Mn, an X-ray test was carried out, and the spectrum is as Figure 3 shown. The characteristic diffraction peaks of the W, Mn, and Co metal elements of the Keggin structure heteropolyacid are respectively distributed in the ranges of 7°-10°, 16°-22°, and 25°-34°. From Figure 3 it can be obtained that the loaded catalyst CPS-MIM-CoW 11 Mn shows diffraction peaks containing W, Mn, and Co at 9.17, 19.79, and 28.38 respectively. Combining the results of the infrared spectrum further shows that the heteropolyacid ionic liquid catalyst CPS-MIM-CoW 11 Mn is successfully prepared.
Claims
1. A preparation method of a CPS-supported heteropolyacid ionic liquid catalyst for synthesizing cyclic carbonates from CO2, characterized in that: It includes the following steps: (1) Preparation of heteropolyacid Sodium tungstate, central atom salt and coordination atom salt are dissolved in distilled water according to a molar ratio of 1:1 - 3:1 - 3, and heated. After dissolution is completed, the pH is adjusted to 4 - 5 with a pH regulator, and the reaction is carried out at 60 - 85 °C for 2.0 - 6.0 h. After washing, concentration and drying, the heteropolyacid is obtained; the central atom salt is one of manganese acetate and zirconium oxychloride; the coordination atom salt is one of cobalt acetate and zinc chloride; the heteropolyacid is of the Keggin type; (2) Preparation of intermediate CPS-supported imidazolium ionic liquid CPS, N-methylimidazole, n-butyl bromide and acetonitrile are added to a reactor according to a molar ratio of 1:2 - 6:0.8 - 1.2:10 - 25, and the reaction is carried out at 60 - 80 °C for 24 - 48 h. After suction filtration, washing and drying, CPS-MIM-Br is obtained; (3) Preparation of polystyrene resin-supported heteropolyacid ionic liquid catalyst by chemical bonding method The heteropolyacid is dissolved in a solvent, cation exchange resin and CPS-MIM-Br are added, and after slowly stirring and reacting at 25 - 30 °C for 8 - 12 h, the reaction is stopped. After suction filtration, washing and drying, the CPS-supported heteropolyacid ionic liquid CPS-MIM-WM is obtained; In step (1), the heteropolyacid is CoW 11 Mn, ZnW 11 Mn, CoW 11 Zr, ZnW 11 Zr; In step (3), the molar ratio n of heteropolyacid, cation exchange resin, CPS-MIM-Br and solvent is 1:0.005 - 0.04:0.02 - 0.05:10 - 25.
2. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of sodium tungstate to distilled water is 1:80 - 100.
3. The preparation method according to claim 1, characterized in that: In step (1), the pH regulator is one of acetic acid and HCl.
4. The preparation method according to claim 1, characterized in that: In step (3), the solvent is one or a mixture of any two of ethanol, methanol and dichloromethane in any proportion.
5. Application of a CPS-supported heteropolyacid ionic liquid catalyst prepared by the preparation method according to claim 1 in synthesizing cyclic carbonates from CO2.