A highly efficient and stable lewis acid-containing heterogeneous catalyst, its preparation method and application
By designing a heterogeneous catalyst containing Lewis acid, and introducing Lewis acid active sites through the reaction of chloromethyl polystyrene resin with nitrogen-containing heterocycles, the problems of difficult catalyst separation and low activity in the prior art were solved, and the stability and activity of the highly efficient catalytic reaction of CO2 with epoxide cycloaddition were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENYANG INSTITUTE OF CHEMICAL TECHNOLOGY
- Filing Date
- 2024-08-19
- Publication Date
- 2026-05-15
AI Technical Summary
In the prior art, homogeneous ionic liquid catalysts containing metal salts have problems such as difficult separation, low activity, easy loss of active components and complicated preparation process in the cycloaddition reaction of CO2 and epoxides, while heterogeneous catalysts have insufficient activity.
By employing a highly efficient and stable heterogeneous catalyst containing Lewis acid, and through the design of strong nucleophilic and electrophilic groups, Lewis acid active sites are introduced by reacting chloromethyl polystyrene resin with nitrogen-containing heterocycles, thus preparing a catalyst with ultra-strong stability and excellent activity.
This method achieves simple preparation and high-efficiency catalytic performance of the catalyst, solves the problem of low activity of heterogeneous catalysts, exhibits good substrate adaptability and catalytic activity, and the catalyst is easy to separate and recover.
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Figure CN119241743B_ABST
Abstract
Description
Technical Field
[0001] This application relates to a highly efficient and stable heterogeneous catalyst containing Lewis acid, its preparation method, and its application, belonging to the field of cycloaddition reaction catalyst technology. Background Technology
[0002] Carbon dioxide (CO2) is one of the greenhouse gases contributing to global warming and extreme climate change. However, it is considered a non-toxic and economical C1 resource. Therefore, the efficient conversion of CO2 into high-value chemicals (such as low-carbon alcohols, low-carbon hydrocarbons, cyclic carbonates, amides, carboxylic acids, or nitrogen-containing heterocyclic compounds) has attracted widespread attention in terms of resource conversion and the environment. The cycloaddition reaction of carbon dioxide with epoxides is one of the most successful reactions due to its advantages of high atom utilization and low cost. Furthermore, cyclic carbonates are an important industrial raw material with wide applications in lithium-ion battery electrolytes, polar aprotic solvents, additives, pharmaceutical intermediates, and polycarbonates.
[0003] Due to the high thermodynamic stability and kinetic inertness of CO2, most chemical conversion reactions based on it require highly efficient catalysts. To date, catalysts such as metal halides, quaternary ammonium salts, quaternary phosphate salts, ionic liquids, poly(ionic liquids), organic bases, metal complexes, metal-organic frameworks, conjugated organic frameworks, and supported catalysts have been used in the cycloaddition reaction of epoxides and CO2. However, many catalysts suffer from drawbacks such as low stability or catalytic activity, and the need for co-catalysts. Ionic liquids, as catalysts, have solved these problems to some extent. Ionic liquids possess tunable structures and good thermal stability. They are commonly used in the cycloaddition reaction of PO and CO2, yielding valuable results. Subsequently, research revealed that metal ions can participate in the reaction of CO2 and PO as Lewis acid active sites. Therefore, metal salts (ZnBr2) have been widely used as co-catalysts in the cycloaddition reaction of PO and CO2. Compared with traditional ionic liquids, their catalytic performance has been significantly improved. However, homogeneous catalysts suffer from drawbacks such as high energy consumption and epoxide polymerization in high-temperature distillation separation methods. To address these issues, numerous metal-containing heterogeneous catalysts have been developed for the cycloaddition reaction of PO and CO2. However, although several heterogeneous catalysts have shown good performance in catalyst separation and product purification, their low catalytic activity makes them less than ideal for practical applications. As mentioned above, metal salt-containing ionic liquids exhibit better activity than traditional ionic liquids. Therefore, metal salt-containing heterogeneous ionic liquids are considered an effective strategy for developing highly efficient heterogeneous ionic liquid catalysts. Summary of the Invention
[0004] To address the problems in existing technologies for synthesizing PC via the cycloaddition reaction of EO / PO with CO2, such as the difficulty in separating homogeneous ionic liquid catalysts containing metal salts, the low activity of heterogeneous catalysts, the easy loss of active components, and the complexity of catalyst preparation processes, this application provides a highly efficient and stable heterogeneous catalyst containing Lewis acid, its preparation method, and its application. Utilizing the strong nucleophilic and electrophilic groups in the catalyst structure and solving the aforementioned technical problems, it exhibits superior stability and excellent activity in the cycloaddition reaction of PO / EO with CO2.
[0005] The technical solution adopted in this application is as follows:
[0006] A highly efficient and stable heterogeneous catalyst containing Lewis acid, wherein the highly efficient and stable heterogeneous catalyst containing Lewis acid has the structure shown in Formula I:
[0007]
[0008] Among them, R 1 R 2 Independently selected from C1 to C6 alkylene groups, n 1 n 2 Independently, the range is 1000–3000;
[0009] M is selected from at least one of Zn, Co, Cu, Fe, Mg, Ni, Ca, Mn, Pb, and Sn.
[0010] The active centers are electrophilic cations and nucleophilic halide ions.
[0011] According to another aspect of this application, a method for preparing the above-mentioned highly efficient and stable Lewis acid-containing heterogeneous catalyst is provided, comprising the following steps:
[0012] S1. Chloromethyl polystyrene resin is swollen in solvent I, then a nitrogen-containing heterocycle is added, reaction I is carried out, and precursor I is obtained;
[0013] S2. Add the organic raw material to a mixture containing precursor I and solvent II, and heat to react II to obtain precursor II;
[0014] S3. Add the Lewis acid-containing raw material to a mixture containing precursor II and solvent III, and heat to react in reaction III to obtain the highly efficient and stable Lewis acid-containing heterogeneous catalyst.
[0015] Optionally, in step S1, the chloromethyl polystyrene resin has the structure of formula II:
[0016] Wherein, R is selected from C1 to C6 alkylene groups, and n = 1000 to 3000;
[0017] Optionally, in step S1, the degree of crosslinking of the chloromethyl polystyrene resin is 4-10%, and the chlorine content is 15-25%.
[0018] Optionally, in step S1, the solvent I is selected from at least one of acetonitrile, methanol, ethanol, diethyl ether, ethyl acetone, and petroleum ether.
[0019] Optionally, in step S1, the molar ratio of chlorine to the nitrogen-containing heterocycle in the chloromethyl polystyrene tree is 1:1 to 10.
[0020] Optionally, in step S1, the nitrogen-containing heterocycle is selected from the structure shown in Formula III-1:
[0021]
[0022] Optionally, in step S1, the conditions for reaction I include: a reaction temperature of 60–80°C and a reaction time of 1–24 h.
[0023] Optionally, in step S1, the swelling conditions include stirring at 60–80°C for 0.5–2 hours.
[0024] Optionally, in step S2, the organic raw material is selected from bromoacetic acid.
[0025] Optionally, in step S2, solvent II is selected from at least one of methanol, ethanol, ethylene glycol, acetonitrile, ethyl acetate, and petroleum ether.
[0026] Optionally, in step S2, the molar ratio of organic raw material to solvent II is 1:1 to 15.
[0027] Optionally, in step S2, the molar ratio of organic raw material to precursor I is 1:0.8 to 1.
[0028] Optionally, in step S2, the conditions for heating reaction II include: a reaction temperature of 70–110°C and a reaction time of 1–24 h.
[0029] Optionally, in step S3, the Lewis acid raw material is selected from at least one of zinc acetate, cobalt acetate, copper acetate, ferrous acetate, magnesium acetate, nickel acetate, calcium acetate, manganese acetate, and lead acetate.
[0030] Optionally, in step S3, solvent III is selected from at least one of methanol, ethanol, and ethylene glycol;
[0031] Optionally, in step S3, the molar ratio of the Lewis acid-containing raw material to solvent III is 1:1 to 15;
[0032] Optionally, in step S3, the molar ratio of the Lewis acid-containing raw material to precursor II is 1:0.8 to 1.
[0033] Optionally, in step S3, the conditions for heating reaction III include: a temperature of 50–90°C and a reaction time of 1–24 h.
[0034] Optionally, in step S3, the temperature in the heating reaction III is selected from any value of 50°C, 60°C, 70°C, 80°C, or 90°C, or any range between two.
[0035] Optionally, in step S3, the reaction time in the heating reaction III is selected from any value among 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, and 24h, or any range between the two.
[0036] Optionally, reactions I, II, and III may be carried out independently under stirring conditions.
[0037] Optionally, the reaction I, reaction II, and reaction III may also include a washing and drying step independently.
[0038] Optionally, the washing conditions include: adding 2 to 5 times the weight of the product as a washing solvent to the product after the reaction, stirring and washing, and filtering.
[0039] The washing solvent is selected from at least one of methanol, ethanol, acetonitrile, ethyl acetate, acetone, benzene, toluene, and xylene.
[0040] Optionally, the drying conditions include: vacuum drying at 60–80°C for 6–24 hours.
[0041] According to another aspect of this application, the application of the above-mentioned highly efficient and stable heterogeneous catalyst containing Lewis acid or the highly efficient and stable heterogeneous catalyst containing Lewis acid prepared according to the above preparation method in the catalytic cycloaddition reaction of epoxides with CO2 to prepare propylene carbonate is also provided.
[0042] Optionally, the epoxide is selected from ethylene oxide and / or propylene oxide;
[0043] Optionally, the reaction temperature window of the homogeneous catalyst is 80–160 °C.
[0044] Optionally, the reaction temperature window of the homogeneous catalyst is selected from any value or a range between 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, and 160°C.
[0045] In this application, "PS-[EIMBr-COO]2Co" refers to 1-methyl-3-cobalt ethyl imidazolate bromide.
[0046] In this application, "PS-[EIMBr-COO]2Zn" refers to 1-methyl-3-zinc ethyl imidazole bromide.
[0047] In this application, "PS-[EIMBr-COO]2Cu" refers to 1-methyl-3-copper ethylimidazolium bromide.
[0048] In this application, "PS-[EIMBr-COO]2Fe" refers to 1-methyl-3-iron ethyl imidazolium bromide.
[0049] In this application, "PS-[EIMBr-COO]2Mg" refers to 1-methyl-3-magnesium ethyl imidazole bromide.
[0050] In this application, "PS-[EIMBr-COO]2Ni" refers to 1-methyl-3-nickel ethyl imidazolate bromide.
[0051] In this application, "PS-[EIMBr-COO]2Mn" refers to 1-methyl-3-manganese ethyl imidazobromide.
[0052] In this application, "EO" refers to ethylene oxide.
[0053] In this application, "PO" refers to propylene oxide.
[0054] In this application, "CO2" refers to carbon dioxide.
[0055] In this application, "EC" refers to ethylene carbonate.
[0056] In this application, "PC" refers to propylene carbonate.
[0057] The beneficial effects that this application can produce include:
[0058] This application provides a highly efficient and stable heterogeneous catalyst containing Lewis acid, its preparation method, and its applications. The catalyst possesses strong nucleophilic and electrophilic groups, exhibiting superior stability and excellent catalytic activity in cycloaddition reactions. The prepared Lewis acid-containing heterogeneous catalyst demonstrates good substrate adaptability in the cycloaddition reactions of various epoxides with CO2. It addresses the problems of harsh reaction conditions, low catalyst activity, and poor stability inherent in existing heterogeneous catalysts. The preparation method of this highly efficient and stable Lewis acid-containing heterogeneous catalyst involves synthesizing a precursor using a simple method and introducing Lewis acid active sites (metals) using a common solvent method. The preparation process is simple and user-friendly, overcoming the problem of low activity in existing heterogeneous catalysts. Attached Figure Description
[0059] Figure 1 This is a schematic diagram of the synthesis process of the precursor and the heterogeneous catalyst containing Lewis acid in this application.
[0060] Figure 2 This is a schematic diagram of the structure of the Lewis acid heterogeneous catalysts in this application series.
[0061] Figure 3 The infrared spectrum is shown for the catalyst sample prepared in this application.
[0062] Figure 4 Thermogravimetric analysis (TGA) of the catalyst sample prepared in this application.
[0063] Figure 5 This study illustrates the effect of reaction temperature on the catalytic performance (EO / CO2) of the heterogeneous catalyst PS-[EIMBr-COO]2Co in this application.
[0064] Figure 6 This study investigates the effect of reaction temperature on the catalytic performance (PO / CO2) of the heterogeneous catalyst PS-[EIMBr-COO]2Co.
[0065] Figure 7 This study evaluates the effect of reaction time on the catalytic performance of the heterogeneous catalyst PS-[EIMBr-COO]2Co in this application.
[0066] Figure 8 This study investigates the effect of reaction pressure on the catalytic performance of the heterogeneous catalyst PS-[EIMBr-COO]2Co in this application.
[0067] Figure 9 This study evaluates the catalytic stability of the heterogeneous catalyst PS-[EIMBr-COO]2Co used in this application.
[0068] Figure 10 The image shows an infrared spectrum of a sample of the catalyst prepared in this application after use.
[0069] Figure 11 Evaluation of the heterogeneous catalyst PS-[EIMBr-COO]2Co catalyzing the reaction of different substrates with CO2. Detailed Implementation
[0070] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0071] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0072] Unless otherwise specified, all test methods are conventional and all instrument settings are those recommended by the manufacturer.
[0073] In the embodiments of this application, the acid content calculation, NMR H-scopy analysis, NMR C-scopy analysis (Ascend III 500MHz liquid-solid dual-purpose NMR instrument, Bruker, Switzerland), and infrared spectroscopy analysis (IRTracer-100 Fourier transform infrared spectrometer, Shimadzu, Japan), thermogravimetric and differential thermal analysis (TG-DTA8122) and characterization analysis are all routine operations, which can be performed by those skilled in the art according to the instrument instructions.
[0074] In the embodiments of this application, the PO conversion rate, PC selectivity, PC yield, and TOF value are calculated as follows:
[0075] X PO / % = (n PC) × 100 / (n PC + n PO (1)
[0076] S PC / % = n PC × 100 / (n PC + n byproducts) (2)
[0077] Y PC / % = X PO × S PC (3)
[0078] TOF = (n PO ×PC yield) / (n Cat. ×t)(4)
[0079] In the formula, X PO S represents the conversion rate of PO. PC For the selectivity of PC, Y PC For the yield of PC, n PO Let n be the molar mass of PO. PC n is the molar mass of PC. Cat t represents the molar mass of the active site in the catalyst, and t represents the reaction time.
[0080] In the test cases of this application, the EO conversion rate, EC selectivity, EC yield, and TOF value were calculated as follows:
[0081] X EO / % = (n EC) × 100 / (n EC + n EO (1)
[0082] S EC / % = n EC × 100 / (n EC + n byproducts) (2)
[0083] YEC / % = X EO × S EC (3)
[0084] TOF = (n EO ×EC yield) / (n Cat. ×t)(4)
[0085] In the formula, X EO S represents the conversion rate of EO. EC For the selectivity of EC, Y EC n is the yield of EC. EO n is the molar mass of EO. EC n is the molar mass of EC. Cat t represents the molar mass of the active site in the catalyst, and t represents the reaction time.
[0086] Example 1: Heterogeneous catalyst containing Lewis acid
[0087] Synthesis mechanism such as Figure 1 As shown, the steps include:
[0088] S1. Add 10g PS-Cl to acetonitrile and stir for 1h. Then dissolve 4g imidazole in the above solution and stir for 24h. Wash the product with acetonitrile and dry it at -0.1MPa and 70℃ for 12h. The precursor I obtained is named PS-IM.
[0089] S2. Add the precursor synthesized in step S1 and 30 ml of acetonitrile to a 250 ml three-necked round-bottom flask. Dissolve bromoacetic acid (0.05 mol) in the above solution and stir. After refluxing at 70 °C for 24 h, wash the product three times with ethyl acetate and dry it under vacuum at 70 °C for 24 h to obtain a heterogeneous catalyst, and obtain precursor II, named PS-[ECOOHIM]Br.
[0090] S3. Add the PS-[ECOOHIM]Br synthesized in step S2 and 60 ml of methanol (MeOH) to a 250 ml three-necked round-bottom flask. Dissolve cobalt acetate (0.05 mol) in the above solution and stir. Reflux at 70 °C for 24 h. After the complexation reaction is complete, wash three times with MeOH, and then dry in a vacuum oven at 70 °C for 24 h. Finally, a highly efficient and stable heterogeneous catalyst containing Lewis acid is obtained, named PS-[EIMBr-COO]2Co.
[0091] Examples 2-7 Different Heterogeneous Catalysts Containing Lewis Acids (Metal Ions)
[0092] The preparation method is the same as in Example 1, except that the cation structure is different. In Examples 2-7, cobalt acetate is replaced with zinc acetate, copper acetate, iron acetate, magnesium acetate, nickel acetate, and manganese acetate, respectively, resulting in a series of catalysts containing different metal ions, named PS-[EIMBr-COO]2Y, where Y represents Zn, Cu, Fe, Mg, Ni, and Mn. The structure of the prepared PS-[EIMBr-COO]2Y is as follows. Figure 2 As shown.
[0093] Test Example 1: Fourier Transform Infrared Spectroscopy (FT-IR) Characterization
[0094] Taking the Lewis acid-containing heterogeneous catalyst PS-[EIMBr-COO]2Co sample prepared in Example 1 as an example, in the sample Figure 3 The characteristic peaks of the imidazole ring group were clearly observed in the image. (3131–2925 cm⁻¹) -1 The absorption peak is caused by the CH stretching vibration of the imidazole ring-substituted alkyl group. It is located between 1516 and 1377 cm⁻¹. -1 and 1149cm -1 The absorption peak at 1168 cm⁻¹ is caused by the stretching vibrations of the C=N and C=C bonds in the imidazole ring. The C=N bond in the imidazole ring has a peak at 1168 cm⁻¹. -1 There is an in-plane bending vibration peak at 825–750 cm⁻¹. -1 The absorption peak at this point belongs to the in-plane and out-of-plane bending vibrations of the CH bond in the imidazole ring. The results indicate that subsequent introduction of Co... 2+ During the functionalization process, the imidazole groups in the samples remained stable. Meanwhile, 1632 cm⁻¹ -1 The absorption peak at [location] is attributed to the C=O stretching vibration of the -COOH group in PS-[EIMBr-COO]2Co. These experimental results demonstrate the successful synthesis of PS-[EIMBr-COO]2Co.
[0095] Test Example 2: Thermogravimetric-Differential Thermal Analysis (TG-DTA) Characterization
[0096] The Lewis acid-containing heterogeneous catalyst PS-[EIMBr-COO]2Co sample prepared in Example 1 is used as a typical example. Figure 4TG and DTA data for PS-[EIMBr-COO]2Co are presented. The initial decomposition temperature of PS-[EIMBr-COO]2Co is above 223℃. This suggests that the synthesized catalyst possesses good thermal stability. The thermogravimetric analysis (TGA) curve of PS-[EIMBr-COO]2Co can be divided into three weight loss stages. The first stage (25-223℃) involves a weight loss of 3.77%, mainly due to the departure of small amounts of bound water and solvent molecules. In the second stage (223-438℃), the CH bond cleavage of the methyl and methylene groups leads to partial decomposition of the imidazole cation, resulting in a weight loss of 23.84%. The third stage (438-574℃) represents the complete decomposition of the polystyrene resin, with a weight loss of 32.65%. Notably, the initial decomposition temperature of PS-[EIMBr-COO]2Co (223℃) is significantly higher than the cycloaddition reaction temperature of PO with CO2 (110℃), indicating that the synthesized PS-[EIMBr-COO]2Co maintains structural integrity throughout the reaction process.
[0097] Test Example 3: Effect of Reaction Temperature on the Catalytic Performance of the Heterogeneous Catalyst PS-[EIMBr-COO]2Co (EO / CO2)
[0098] As attached Figure 5 As shown, using PS-[EIMBr-COO]2Co prepared in Example 1 as a catalyst, the effect of different reaction temperatures on the synthesis of EC via the cycloaddition reaction of EO and CO2 is illustrated. The reaction conditions were 0.14 mol EO, 2.6 MPa CO2, and 3.81 × 10⁻⁶ mol / L CO2. - 4 The cycloaddition of EO to CO2 catalyzed by PS-[EIMBr-COO]2Co was carried out at 90, 100, 110, and 120 °C. As the reaction temperature increased from 70 °C to 120 °C, the EC yield gradually increased, showing the following order: 90 °C (82.46%) > 100 °C (90.82%) > 110 °C (99.02%) > 120 °C (99.57%), while the corresponding TOF values showed the following order: 90 °C (92.33%) > 120 °C (92.33%). -1 <100℃ (113.54h) -1 <110℃ (121.75h) -1 <120℃ (122.88h) -1 Clearly, the catalytic activity gradually increases with increasing temperature. This is because the increased temperature promotes the movement frequency of CO2 molecules, thus facilitating rapid contact between CO2 and EO in the liquid phase. Experimental results show that PS-[EIMBr-COO]2Co exhibits excellent catalytic activity for the cycloaddition reaction of EO and CO2.
[0099] Test Example 4: Effect of Reaction Temperature on the Catalytic Performance of the Heterogeneous Catalyst PS-[EIMBr-COO]2Co (PO / CO2)
[0100] As attached Figure 6 As shown, using PS-[EIMBr-COO]2Co prepared in Example 1 as a catalyst, the effect of different reaction temperatures on the synthesis of PC via the cycloaddition reaction of PO and CO2 was investigated. The reaction conditions were 0.14 mol PO, 2.6 MPa CO2, and 3.81 × 10⁻⁶ mol / L. -4 The cycloaddition reaction of PO with CO2 catalyzed by PS-[EIMBr-COO]2Co was carried out at 70, 80, 90, 100, 110, and 120 °C. As the reaction temperature increased from 70 °C to 120 °C, the yield of PC gradually increased, showing the following order: 90 °C (72.36%) > 100 °C (84.82%) > 110 °C (98.92%) > 120 °C (99.03%), while the corresponding TOF values showed the following order: 90 °C (88.33%) > 12 ... -1 <100℃ (103.54h) -1 <110℃ (120.75h) -1 <120℃ (120.88h) -1 Clearly, the catalytic activity gradually increases with increasing temperature. This is because the increase in temperature promotes the movement frequency of CO2 molecules, which in turn promotes the rapid contact between CO2 and PO in the liquid phase.
[0101] Evaluation of the effect of reaction time on the catalytic performance of the heterogeneous catalyst PS-[EIMBr-COO]2Co in Test Example 5
[0102] As attached Figure 7 As shown, using PS-[EIMBr-COO]2Co prepared in Example 1 as a catalyst, the effect of different reaction times on the synthesis of PC via the cycloaddition reaction of PO and CO2 is illustrated. The reaction conditions were 0.14 mol PO, 110 °C, and 3.81 × 10⁻⁶ ppm. -4 molPS-[EIMBr-COO]2Co. Extending the reaction time from 1 h to 2 h increased the PC yield from 79.32% to 86.53%, with TOF values of 290.47 and 158.44 h, respectively. -1 Extending the reaction time to 3 hours increased the PC yield to 98.92% and the TOF value to 120.75 h. -1 Notably, when the reaction time was extended to 4 hours, the PC yield and TOF value were 99.01% and 90.64 h, respectively. -1The results were essentially the same as those obtained at 3 hours. Experimental results show that the PC yield in the reaction system increases with increasing reaction time. However, the reaction rate in the later stages is very slow, indicating that the decrease in effective PO molecule concentration is the key factor for the low reaction rate. Furthermore, it is believed that further extending the reaction time will lead to the polymerization of PC and the generation of side reactions such as PO isomerization and hydration. The results indicate that a cycloaddition reaction time of 3 hours is optimal for PO and CO2.
[0103] Test Example 6: Effect of Reaction Pressure on the Catalytic Performance of Heterogeneous Catalyst PS-[EIMBr-COO]2Co
[0104] As attached Figure 8 As shown, using PS-[EIMBr-COO]2Co prepared in Example 1 as a catalyst, the effect of different CO2 pressures on the synthesis of PC via the cycloaddition reaction of PO and CO2 is illustrated. The reaction conditions were 0.14 mol PO, 110 °C, and 3.81 × 10⁻⁶ ppm. -4 mol PS-[EIMBr-COO]2Co. When the initial CO2 pressure was 2.2 MPa (CO2 / PO molar ratio of 1.2 / 1), the PC yield reached 87.35%, and the TOF value was 106.62 h⁻¹. -1 Under an initial CO2 pressure of 2.4 MPa (CO2 / PO molar ratio of 1.4 / 1), the PC yield was 91.38%, and the TOF value was 111.55 h⁻¹. -1 When the initial CO2 pressure was 2.6 MPa (CO / PO molar ratio of 1.6 / 1), the PC yield decreased to 98.92%, and the TOF value increased to 120.75 h⁻¹. -1 However, when the initial CO2 pressure was continuously increased to 2.8 MPa (CO2 / PO molar ratio of 2.0 / 1) and 3.0 MPa (CO2 / PO molar ratio of 2.0 / 1), the PC yield decreased to 92.26% and 92.98%, respectively, and the TOF values decreased to 112.62 and 113.49 h, respectively. -1 As CO2 pressure increases (2.2–2.6 MPa), the continuous dissolution of CO2 in the PO phase also increases, promoting the cycloaddition reaction. Conversely, excess CO2 (2.6–3.0 MPa) not only hinders the interaction between PS-[EIMBr-COO]2Co and PO, but also dilutes the PO concentration in the bottom phase, leading to a decrease in PC yield.
[0105] Test Example 7: Evaluation of the catalytic stability of the heterogeneous catalyst PS-[EIMBr-COO]2Co
[0106] As attached Figure 9As shown, using PS-[EIMBr-COO]2Co prepared in Example 1 as a catalyst, under optimal reaction conditions (110℃, 2.6MPa, 3.81×10⁻⁶), the reaction was carried out successfully. -4 Seven cycloaddition reactions of PO with CO2 were conducted at mol / L (3 h) to evaluate the recyclability and reusability of the catalyst. PS-[EIMBr-COO]2Co was easily separated from the reaction mixture by filtration. The catalyst was washed with methanol and dried at 70 °C for 24 h. The PC yield varied slightly among the different cycles (from 98.92% to 98.87%), while maintaining consistent PC selectivity. FT-IR characterization confirmed the structural integrity of the recovered catalyst. The FT-IR characteristic peaks of fresh and recovered PS-[EIMBr-COO]2Co catalysts were compared, as shown in the figure. Figure 10 As shown, their peak positions are almost identical, indicating that the catalyst structure has not changed significantly.
[0107] Test Example 8: Evaluation of the heterogeneous catalyst PS-[EIMBr-COO]2Co catalyzing the reaction of different substrates with CO2.
[0108] Using the PS-[EIMBr-COO]2Co prepared in Example 1 as a catalyst, under optimal reaction conditions (110℃, 2.6MPa, 3.81×10⁻⁶), -4 At mol, 3h), cycloaddition reactions were performed with epoxides of different substituents and CO2 to synthesize the corresponding cyclic carbonates. For example... Figure 11As shown, after 3 hours of reaction, the experimental results indicate that PS-[EIMBr-COO]2Co can effectively catalyze the formation of corresponding cyclic carbonates from various epoxides with high selectivity (>99%). Notably, PS-[EIMBr-COO]2Co exhibits greater catalytic activity for EO (a) and PO (b) than 1,2-epoxybutane (c), which has a larger alkyl side chain, with conversions of 99.52%, 98.92%, and 82.04%, respectively. This may be due to the limited diffusion of the longer alkyl chain (i.e., substrate with a larger R group) into the active site within the catalyst, thus reducing the conversion rate. Surprisingly, the conversion rates of epichlorohydrin (d) and glycidyl (e) are significantly improved, reaching 96.91% and 95.64%, respectively. The electron-withdrawing properties of the halogen atoms in epichlorohydrin play a crucial stabilizing role in the intermediates formed during the ring-opening process of epoxides, thereby promoting the cycloaddition reaction. The conversion of glycerol is satisfactory, likely due to the formation of intermolecular hydrogen bonds between glycerol molecules. Furthermore, in cycloaddition reactions, glycol can act as both a substrate and a catalyst (hydrogen bond donor). Styrene oxide, phenyl glycidyl ether, and allyl glycidyl ether (f, j, and h) are widely considered difficult-to-convert substrates, with few successful conversions. However, PS-[EIMBr-COO]2Co catalyzed the cycloaddition reactions of styrene, phenyl glycidyl ether, and allyl glycidyl ether (f, j, and h) with CO2, successfully producing the corresponding cyclic carbonates. The corresponding substrate conversions were 80.85%, 84.22%, and 84.91%, respectively. The relatively unsatisfactory catalytic activity can be explained by relatively strong steric hindrance (strong conjugation effect), which hinders molecular diffusion and contact between the active site and the epoxide. In summary, the extended epoxide catalysis of the PS-[EIMBr-COO]2Co catalyst reflects its excellent efficiency.
[0109] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. The application of a highly efficient and stable heterogeneous catalyst containing Lewis acid in the catalytic cycloaddition reaction of epoxides with CO2 to prepare propylene carbonate, characterized in that, The epoxide is selected from ethylene oxide, propylene oxide, 1,2-epoxybutane, epichlorohydrin, glycidyl ether, styrene oxide, phenyl glycidyl ether and allyl glycidyl ether. The reaction temperature window of the homogeneous catalyst is 80~160 ℃; The preparation method of the highly efficient and stable heterogeneous catalyst containing Lewis acid includes the following steps: S1. Chloromethyl polystyrene resin is swollen in solvent I, then a nitrogen-containing heterocycle is added, reaction I is carried out, and precursor I is obtained; S2. Add the organic raw material to a mixture containing precursor I and solvent II, and heat to react II to obtain precursor II; S3. Add the Lewis acid-containing raw material to a mixture containing precursor II and solvent III, and heat to react in reaction III to obtain the highly efficient and stable Lewis acid-containing heterogeneous catalyst; the molar ratio of the Lewis acid-containing raw material to the precursor II is 1:0.8-1. Solvent I is selected from at least one of acetonitrile, methanol, ethanol, diethyl ether, ethyl acetone, and petroleum ether; The nitrogen-containing heterocycle is selected from the structure shown in Formula III-1: Formula III-1; The organic raw material is selected from bromoacetic acid; Solvent II is selected from at least one of methanol, ethanol, ethylene glycol, acetonitrile, ethyl acetate, and petroleum ether; Lewis acid raw materials are selected from at least one of zinc acetate, cobalt acetate, copper acetate, ferrous acetate, magnesium acetate, nickel acetate, calcium acetate, manganese acetate, lead acetate, and tin acetate. Solvent III is selected from at least one of methanol, ethanol, and ethylene glycol; The highly efficient and stable Lewis acid-containing heterogeneous catalyst has the structure shown in Formula I: Equation I; Among them, R 1 R 2 Independently selected from C1-C6 alkylene groups, n 1 n 2 Independently, the range is 1000~3000; M is selected from at least one of Zn, Co, Cu, Fe, Mg, Ni, Ca, Mn, Pb, and Sn; The active centers are electrophilic cations and nucleophilic halide ions.
2. The application according to claim 1, characterized in that, In step S1, the chloromethyl polystyrene resin has the structure of formula II: Formula II; wherein R is selected from C1 to C6 alkylene groups, and n = 1000 to 3000.
3. The application according to claim 1, characterized in that, In step S1, the degree of crosslinking of the chloromethyl polystyrene resin is 4-10%, and the chlorine content is 15-25%.
4. The application according to claim 1, characterized in that, In step S1, the molar ratio of chlorine to the nitrogen-containing heterocycle in the chloromethyl polystyrene tree is 1:1 to 10.
5. The application according to claim 1, characterized in that, In step S1, the conditions for reaction I include: a reaction temperature of 60~80 ℃ and a reaction time of 1~24 h.
6. The application according to claim 1, characterized in that, In step S1, the swelling conditions include stirring at 60~80℃ for 0.5~2h.
7. The application according to claim 1, characterized in that, In step S2, the molar ratio of organic raw material to solvent II is 1:1~15.
8. The application according to claim 1, characterized in that, In step S2, the molar ratio of organic raw material to precursor I is 1:0.8~1.
9. The application according to claim 1, characterized in that, In step S2, the conditions for heating reaction II include: a reaction temperature of 70~110 ℃ and a reaction time of 1~24 h.
10. The application according to claim 2, characterized in that, In step S3, the molar ratio of Lewis acid-containing raw material to solvent III is 1:1~15.
11. The application according to claim 1, characterized in that, In step S3, the conditions for heating reaction III include: a temperature of 50~90 ℃ and a reaction time of 1~24 h.