Process for the continuous production of cyclic carbonates

Abstract

This invention relates to the field of cyclic carbonate synthesis technology, specifically to a method for the continuous preparation of cyclic carbonates. The method includes the following steps: (1) mixing an epoxide compound and a solvent to obtain a homogeneous mixture; (2) in the presence of a quaternary ammonium salt coordination bimetallic catalyst, reacting the homogeneous mixture with CO. 2 A synthetic reaction is carried out to obtain cyclic carbonate products. This invention utilizes a specific quaternary ammonium salt-coordinated bimetallic catalyst, which can continuously, efficiently, controllably, and precisely catalyze the preparation of cyclic carbonates from raw materials. The catalyst's catalytic activity shows almost no decrease after 24 hours of continuous use. The catalyst in the reactor is insoluble in the reaction solution, thus simplifying the subsequent separation process and reducing the use of expensive catalysts. Using the method of this invention, the reaction time is reduced from hours to minutes, greatly improving the reaction efficiency.

Description

Method for continuous preparation of cyclic carbonates Technical Field

[0001] This invention relates to the field of cyclic carbonate synthesis technology, and more specifically to a method for the continuous preparation of cyclic carbonates. Background Technology

[0002] With the escalating global greenhouse effect and energy crisis, CO2 has attracted widespread attention from researchers in recent years as an abundant, non-toxic, and inexpensive C1 starting material. Synthesizing cyclic carbonates using carbon dioxide and epoxides as raw materials is a low-pollution, environmentally friendly, and highly efficient atom-utilization technology. Cyclic carbonates are widely used in pesticides, pharmaceuticals, resins, dyes, coatings, electronic chemicals, food additives, and solvents, serving as important fine chemical intermediates and high-performance organic solvents.

[0003] The cycloaddition reaction of epoxides with CO2 is a typical gas-liquid multiphase catalytic reaction. The adequacy of the gas-liquid two-phase contact and mixing, as well as the mass transfer effect, directly affects the reaction efficiency. Currently, the cycloaddition reaction of epoxides with CO2 is mainly achieved through high-pressure batch mixers. However, traditional batch mixer processes suffer from relatively low production efficiency due to imperfect mass transfer and gas-liquid contact, and also have disadvantages such as long reaction time and poor mixing performance.

[0004] To address the aforementioned issues, CN110878077A discloses a method using a microchannel mixer. This mixer breaks down CO2 into small bubbles and disperses them in a continuous phase, achieving rapid mixing of the gas and liquid phases and improving the mass and heat transfer efficiency of the reaction substrate. This enables the efficient, controllable, and continuous preparation of cyclic carbonates. However, the homogeneous catalyst in this method cannot be recycled, increasing the complexity of the post-processing. Summary of the Invention

[0005] The purpose of this invention is to overcome numerous problems in existing technologies, such as poor mass transfer, low production efficiency, uneven mixing of multiphase reactants, and the inability to recover and reuse catalysts in continuous production, and to provide a method for the continuous preparation of cyclic carbonates. This invention improves the heat and mass transfer efficiency of the reactants by selecting a specific quaternary ammonium salt-coordinated bimetallic catalyst and using a microchannel reactor, enabling the continuous and efficient conversion of raw materials into cyclic carbonates. The catalyst in the reactor is insoluble in the reaction solution, thus simplifying the subsequent separation process and reducing the use of expensive catalysts.

[0006] To achieve the above objectives, the present invention provides a method for the continuous preparation of cyclic carbonates, characterized in that the method comprises the following steps:

[0007] (1) Mix the epoxy compound and the solvent to obtain a homogeneous mixture;

[0008] (2) In the presence of a quaternary ammonium salt coordinated bimetallic catalyst, the mixture was reacted with CO2 to obtain a cyclic carbonate product.

[0009] Through the above technical solution, the method for continuous preparation of cyclic carbonates provided by the present invention achieves the following beneficial effects:

[0010] By selecting specific quaternary ammonium salt coordination bimetallic catalysts, using microchannel reactors to enhance the mass and heat transfer of materials, and selecting specific reaction conditions, this method can continuously, efficiently, and controllably convert raw materials into cyclic carbonates, reduce side reactions, and reduce reaction time from hours to minutes, greatly improving reaction efficiency.

[0011] The catalyst exhibits excellent catalytic stability, with almost no decrease in catalytic activity after 24 hours of continuous use; furthermore, the catalyst is insoluble in the reaction solution, thus simplifying the subsequent separation process. Attached Figure Description

[0012] Figure 1 is a schematic diagram of the process flow for the continuous preparation of cyclic carbonates according to the present invention;

[0013] Figure 2 is the 1H NMR spectrum of the product obtained in Example 1;

[0014] Figure 3 shows the 1H NMR spectrum of the product obtained in Example 8;

[0015] Figure 4 shows the infrared spectrum of the catalyst obtained in Preparation Example 1.

[0016] Explanation of reference numerals in the attached figures

[0017] 1-Inlet of the mixture; 2-Inlet of CO2; 3-Mixer; 4-Microchannel reactor; 5-Back pressure valve; 6-Outlet of cyclic carbonate product. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] To achieve the above objectives, a first aspect of the present invention provides a method for the continuous preparation of cyclic carbonates, characterized in that the method comprises the following steps:

[0020] (1) Mix the epoxy compound and the solvent to obtain a homogeneous mixture;

[0021] (2) In the presence of a quaternary ammonium salt coordinated bimetallic catalyst, the mixture was reacted with CO2 to obtain a cyclic carbonate product.

[0022] In this invention, steps (1) and (2) are only used to describe the method, and there is no particular limitation on the order of the methods. For example, depending on the needs of the preparation environment, the epoxide, solvent and CO2 can be fed into the mixer together for reaction in the presence of a quaternary ammonium salt coordination bimetallic catalyst.

[0023] This catalyst is a heterogeneous catalyst, which simplifies the subsequent separation process and also reduces the use of expensive catalysts. Using the method of this invention, through the combination of catalyst and reaction conditions, the reaction time is reduced from hours to minutes, greatly improving the reaction efficiency.

[0024] According to the present invention, the volume ratio of the epoxy compound to the solvent is 1:(0.1-10), preferably 1:(0.1-3).

[0025] In this invention, when the volume ratio of the epoxy compound to the solvent is within the above-mentioned range, it can ensure that the epoxy compound is fully dissolved and the gas-liquid mixing reaction achieves better results.

[0026] According to the present invention, the solvent is selected from at least one of tetrahydrofuran, dimethylformamide, dialkylacetamide, dimethyl sulfoxide, and acetonitrile.

[0027] In this invention, the use of the above-mentioned solvents can improve the solubility of CO2 and effectively control the reaction rate.

[0028] According to the present invention, the epoxy compound is selected from at least one of ethylene oxide, propylene oxide, epichlorohydrin, allyl glycidyl ether, cyclohexene oxide, 4-vinylcyclohexene oxide, styrene oxide, and alkyl-substituted styrene oxide.

[0029] In this invention, the reaction rate can be adjusted by controlling the molar ratio of CO2 to the epoxide compound. Preferably, the molar ratio of CO2 flow rate to the epoxide compound is (1-30):1.

[0030] In this invention, the feed rate can be adjusted according to the selected reactor. Taking a microchannel reactor as an example, the CO2 flow rate is 0.001-0.1 mol / min. When a larger reactor is selected, the CO2 flow rate can be appropriately increased.

[0031] According to the present invention, the synthesis reaction is carried out in a microchannel reactor.

[0032] In this invention, the reactor provides the production site for the synthesis reaction, and the mixer provides a place for the reaction raw materials to be fully mixed. After the reaction raw materials are mixed in the mixer, continuous production is carried out in the reactor. Preferably, the mixer is selected from T-type mixers or Y-type mixers. The above-mentioned mixers can achieve better mixing effect, so that gaseous CO2 and liquid epoxide are mixed quickly and uniformly. Combined with a microchannel reactor, the reaction time is reduced from hours to minutes, improving production efficiency.

[0033] According to the present invention, the synthesis reaction time is 0.1-30 min, preferably 0.1-10 min.

[0034] According to the present invention, the temperature of the synthesis reaction is 50-150°C.

[0035] According to the present invention, the pressure of the synthesis reaction is 0.1-5 MPa.

[0036] In this invention, although increasing the temperature and pressure improves the conversion rate, it also gradually increases the side reactions in the reaction system and reduces the yield of the target product. In this invention, when the reaction temperature is 80-120℃ and the pressure is 0.5-3MPa, the conversion rate and yield can be maintained at a high level, and the purity of the product is high.

[0037] According to the present invention, the quaternary ammonium salt coordination bimetallic catalyst is prepared by the following method:

[0038] The solution containing a potassium polycyanometallic acid salt and a terminal hydroxyl quaternary ammonium salt ligand is reacted with a metal salt solution to obtain the quaternary ammonium salt coordination bimetallic catalyst.

[0039] This invention uses a quaternary ammonium salt with terminal hydroxyl groups as a ligand, coordinating the quaternary ammonium salt within a metal catalyst. The terminal hydroxyl groups can replace water-soluble polymers as ligands and also promote the reaction between CO2 and epoxides. Furthermore, the quaternary ammonium salt does not dissolve in the reaction solution during the catalytic process, allowing the catalyst to be used continuously. After five days of continuous use, the catalyst shows almost no loss of catalytic activity. This results in reagent savings and accelerated reaction.

[0040] This invention coordinates quaternary ammonium salts in a metal catalyst to further enhance its catalytic effect; the metal catalyst is preferably a bimetallic catalyst, which can efficiently catalyze the cycloaddition reaction between CO2 and epoxide.

[0041] The preparation process of this invention is simple. Using terminal hydroxyl quaternary ammonium salts as ligands, quaternary ammonium salt coordination bimetallic catalysts are directly prepared simultaneously with the synthesis of bimetallic catalysts. The synthesis of terminal hydroxyl quaternary ammonium salts is simple, the synthesized catalysts have high activity, and they can be recycled and reused repeatedly without changing their activity.

[0042] According to the present invention, the general formula of the terminal hydroxyl quaternary ammonium salt ligand is:

[0043]

[0044] In formula (I), X is selected from halogens, and n is 1-10;

[0045] Preferably, X is selected from chlorine, bromine or iodine, and n = 1-8.

[0046] According to the present invention, the terminal hydroxyl quaternary ammonium salt ligand is selected from the terminal hydroxyl quaternary ammonium salt represented by Formula 1, Formula 2, or Formula 3:

[0047]

[0048] In the preparation examples, comparative preparation examples, and embodiments of the present invention, the terminal hydroxyl quaternary ammonium salts represented by Formula 1, Formula 2, and Formula 3 were prepared by the following methods:

[0049] The preparation method of the terminal hydroxyl quaternary ammonium salt represented by Formula 1 includes the following steps: weigh 0.1 mol of triethylamine into a flask, slowly add 10 mL of 2 mol / L hydrochloric acid; after the addition is completed, slowly add 0.2 mol of ethylene oxide, then heat to 80℃ and react for 20 min; after the reaction is completed, dry at 100℃ for 24 h to obtain the terminal hydroxyl quaternary ammonium salt represented by Formula 1.

[0050] The preparation method of the terminal hydroxyl quaternary ammonium salt represented by Formula 2 includes the following steps: weigh 0.1 mol of tributylamine into a flask, slowly add 10 mL of 2 mol / L hydrobromic acid; after the addition is completed, slowly add 0.2 mol of ethylene oxide, then heat to 80℃ and react for 20 min; after the reaction is completed, dry at 100℃ for 24 h to obtain the terminal hydroxyl quaternary ammonium salt represented by Formula 2.

[0051] The preparation method of the terminal hydroxyl quaternary ammonium salt represented by Formula 3 includes the following steps: weigh 0.1 mol of trioctylamine into a flask, slowly add 10 mL of 2 mol / L hydroiodic acid; after the addition is completed, slowly add 0.2 mol of ethylene oxide, then heat to 80℃ and react for 20 min; after the reaction is completed, dry at 100℃ for 24 h to obtain the terminal hydroxyl quaternary ammonium salt represented by Formula 2.

[0052] According to the present invention, the molar ratio of the potassium polycyanate and the terminal hydroxyl quaternary ammonium salt ligand is 1:1-10.

[0053] According to the present invention, the molar ratio of the potassium polycyanate and the metal salt solution is 1:3-20.

[0054] According to the present invention, in the solution containing potassium polycyanate and terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of potassium polycyanate is 1-50%.

[0055] According to the present invention, in the solution containing potassium polycyanate and terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the terminal hydroxyl quaternary ammonium salt ligand is 1-50%.

[0056] According to the present invention, the polycyanometallic potassium salt is selected from at least one of potassium hexacyanocobaltate, potassium hexacyanoferrate, potassium tetracyanonitrile, potassium tetracyancadmium, potassium monobromopentanocobaltate, potassium mononitropentanocobalt complex, and potassium monoazidopentanocobaltate.

[0057] Preferably, the metal salt is selected from at least one of metal halides, nitrates, phosphates, and sulfates.

[0058] More preferably, the metal is selected from at least one of zinc, cobalt, and cadmium.

[0059] According to the present invention, the mass concentration of the metal salt solution is 1-60%, and water is selected as the solvent for preparing the metal salt solution in the present invention.

[0060] It should be noted that the catalyst of the present invention is a bimetallic catalyst. Therefore, the metal in the potassium polycyanometalate salt is different from the metal in the metal salt. For example, when the potassium polycyanometalate salt is selected from potassium hexacyanocobaltate, the metal in the metal salt is selected from zinc or cadmium, but cannot be selected from cobalt; when the potassium polycyanometalate salt is selected from potassium hexacyanoferrate, the metal in the metal salt can be selected from zinc, cobalt or cadmium.

[0061] According to the present invention, the reaction temperature is 0-100°C and the time is 0.5-72h.

[0062] Preferably, the reaction temperature is 25-50℃ and the time is 3-12h.

[0063] In this invention, the obtained cyclic carbonate product may contain a certain amount of impurities. To purify the cyclic carbonate product, it can be subjected to distillation and vacuum drying to obtain a purified cyclic carbonate product. The distillation and vacuum drying processes used in this invention are conventional operations in the art and are not specifically limited herein. For example, the distillation conditions are: temperature 50-150℃, pressure 1.3-2.0 kPa; the vacuum drying conditions are: temperature 50℃, pressure 1.3 Pa, for 5 hours.

[0064] A brief description of a preferred embodiment of the present invention is provided with reference to Figure 1. The epoxy compound and solvent are mixed to obtain a homogenate. This homogenate is then mixed with CO2 introduced through inlet 1 in a mixer 3, and subsequently enters a microchannel reactor 4 containing a catalyst for reaction. The cyclic carbonate product is discharged from the system through outlet 6. During the reaction, the pressure in the microchannel reactor 4 can be adjusted using a back pressure valve 5.

[0065] In the following embodiments, unless otherwise specified, all raw materials used are commercially available.

[0066] Microchannel reactor: Purchased from Vaportec, UK, model Vapourtec R series flow synthesizer, using a standard column reactor, with a maximum ambient temperature of 150℃.

[0067] The following are the testing methods for performance parameters in embodiments of the present invention:

[0068] (1) Conversion rate: Mass of reacted epoxy compound ÷ Mass of total epoxy compound in feed × 100%.

[0069] (2) Yield: Mass of cyclic carbonate in the product ÷ Mass of theoretically generated cyclic carbonate × 100%.

[0070] Preparation Example 1

[0071] Dissolve 1.0 g potassium hexacyanocobalaminate in 50 mL of deionized water, add 2.0 g of the terminal hydroxyl quaternary ammonium salt represented by Formula 1, stir until completely dissolved, and then add dropwise to 10 mL of aqueous solution containing 5.0 g zinc chloride. Stir at 25 °C for 2 h, and then filter and vacuum dry to obtain the terminal hydroxyl quaternary ammonium salt coordinated Co and Zn catalyst.

[0072] The catalyst was subjected to elemental analysis using an Agilent 720ES inductively coupled plasma atomic emission spectrometer (ICP). The ICP elemental analysis results were: Co: 1.50 wt%, Zn: 3.45 wt%.

[0073] The obtained catalyst was analyzed using a Bruker TENSOR 27 infrared spectrometer, and the infrared spectrum shown in Figure 4 was obtained. The wavelength in the spectrum is 2200 cm⁻¹. -1 The peaks shown represent characteristic peaks of the cyano group in the bimetallic cyanide moiety of the catalyst. Furthermore, the wavelength in the figure is 2900 cm⁻¹. -1 and 1120cm -1 The two peaks at the specified position represent the characteristic peaks of the CH and CN bonds in the terminal hydroxyl quaternary ammonium salt group of the catalyst, respectively. This proves the successful synthesis of the catalyst.

[0074] Preparation Example 2

[0075] 5.0 g of potassium tetracyanide nickelate was dissolved in 50 mL of deionized water, and 10.0 g of the terminal hydroxyl quaternary ammonium salt represented by Formula 1 was added. The mixture was stirred until completely dissolved, and then added dropwise to 40 mL of aqueous solution containing 15.0 g of zinc chloride. The mixture was stirred at 50 °C for 48 h, and then filtered and dried under vacuum to obtain the terminal hydroxyl quaternary ammonium salt coordinated Ni and Zn catalyst.

[0076] The catalyst was subjected to elemental analysis using an Agilent 720ES inductively coupled plasma atomic emission spectrometer (ICP). The ICP elemental analysis results were: Ni: 2.31 wt%, Zn: 4.25 wt%.

[0077] Preparation Example 3

[0078] 7.0 g of potassium bromopentacyanocobaltate was dissolved in 40 mL of deionized water, and 15.0 g of the terminal hydroxyl quaternary ammonium salt represented by Formula 1 was added. The mixture was stirred until completely dissolved, and then added dropwise to 40 mL of an aqueous solution containing 18.0 g of zinc chloride. The mixture was stirred at 80 °C for 72 h, and then filtered and dried under vacuum to obtain the terminal hydroxyl quaternary ammonium salt-coordinated Co and Zn catalyst.

[0079] The catalyst was subjected to elemental analysis using an Agilent 720ES inductively coupled plasma atomic emission spectrometer (ICP). The ICP elemental analysis results were: Co: 2.11 wt%, Zn: 3.16 wt%.

[0080] Preparation Example 4

[0081] Dissolve 1.0 g potassium hexacyanocobalaminate in 50 mL of deionized water, add 2.0 g of the terminal hydroxyl quaternary ammonium salt represented by Formula 2, stir until completely dissolved, and then add dropwise to 10 mL of aqueous solution containing 5.0 g zinc chloride. Stir at 25 °C for 2 h, and then filter and vacuum dry to obtain the terminal hydroxyl quaternary ammonium salt coordinated Co and Zn catalyst.

[0082] The catalyst was subjected to elemental analysis using an Agilent 720ES inductively coupled plasma atomic emission spectrometer (ICP). The ICP elemental analysis results were: Co: 1.61 wt%, Zn: 3.23 wt%.

[0083] Preparation Example 5

[0084] Dissolve 1.0 g potassium hexacyanocobalaminate in 50 mL of deionized water, add 2.0 g of the terminal hydroxyl quaternary ammonium salt represented by Formula 3, stir until completely dissolved, and then add dropwise to 10 mL of aqueous solution containing 5.0 g zinc chloride. Stir at 25 °C for 2 h, and then filter and vacuum dry to obtain the terminal hydroxyl quaternary ammonium salt coordinated Co and Zn catalyst.

[0085] The catalyst was subjected to elemental analysis using an Agilent 720ES inductively coupled plasma atomic emission spectrometer (ICP). The ICP elemental analysis results were: Co: 1.87 wt%, Zn: 3.15 wt%.

[0086] Comparative Preparation Example 1

[0087] Dissolve 1.0 g potassium hexacyanocobalaminate in 50 mL of deionized water, then add 2.0 g tert-butanol and stir until completely dissolved. Then add it dropwise to 10 mL of aqueous solution containing 5.0 g zinc chloride. Stir at 25 °C for 2 h. After filtration, multiple washings, and vacuum drying, mix with the terminal hydroxyl quaternary ammonium salt represented by Formula 1 in a 1:1 ratio to obtain the catalyst.

[0088] The catalyst was subjected to elemental analysis using an Agilent 720ES inductively coupled plasma atomic emission spectrometer (ICP). The ICP elemental analysis results were: Co: 1.38 wt%, Zn: 3.39 wt%.

[0089] Examples 1-5 and Comparative Example 1

[0090] (1) 1.0 g of the catalysts prepared in Preparation Examples 1-5 and Comparative Preparation Example 1 were respectively packed into a microchannel reactor; 1.0 g of epichlorohydrin was mixed with 1.0 mL of dimethylformamide to obtain a homogeneous mixture;

[0091] (2) CO2 is introduced into the T-type mixer at a flow rate of 0.01 mol / min, and the pressure in the microchannel reactor is adjusted to 3 MPa by the back pressure valve;

[0092] (3) After the mixture is continuously fed into a T-type mixer and mixed, a synthesis reaction is carried out in a microchannel reactor. The molar ratio of CO2 to epichlorohydrin is 10:1, the reaction temperature is controlled at 120℃, and the reaction time is about 1 min, yielding a cyclic carbonate product. The cyclic carbonate product is then subjected to distillation and vacuum drying to finally obtain a purified chloromethyldioxacyclophenone product.

[0093] The conversion rate and yield of the refined product were obtained by gas chromatography analysis and material balance calculation, as shown in Table 1.

[0094] The purified chloromethyldioxacyclophenone product from Example 1 was analyzed using a Bruker Avance 400 instrument, and the 1H NMR spectrum shown in Figure 2 was obtained. The 1H NMR data are as follows: 1¹H NMR (400MHz, Chloroform-d) δ 4.97 (dtd, J = 8.2, 5.6, 3.8 Hz, 1H), 4.58 (t, J = 8.6 Hz, 1H), 4.40 (dd, J = 8.9, 5.7 Hz, 1H), 3.75 (qd, J = 12.1, 4.7 Hz, 2H); the product was confirmed to be chloromethyldioxacyclophenone.

[0095] Example 6

[0096] (1) 1.0 g of the catalyst prepared in Preparation Example 1 was packed into a microchannel reactor; 1.0 g of styrene oxide was mixed with 2.6 mL of acetonitrile to obtain a homogeneous mixture;

[0097] (2) CO2 is introduced into the T-type mixer at a flow rate of 0.1 mol / min, and the pressure in the microchannel reactor is adjusted to 3 MPa by the back pressure valve;

[0098] (3) After the mixture and CO2 gas are continuously introduced into the T-type mixer for mixing, the synthesis reaction is carried out in the microchannel reactor. The molar ratio of CO2 to styrene oxide is 30:1, the reaction temperature is controlled at 120℃, and the reaction time is about 1.0 min to obtain cyclic carbonate product. The cyclic carbonate product is then processed by distillation and vacuum drying to finally obtain refined styrene cyclic carbonate product.

[0099] The conversion rate and yield of the refined product were obtained by gas chromatography analysis and material balance calculation, as shown in Table 1.

[0100] Example 7

[0101] (1) 1.0 g of the catalyst prepared in Preparation Example 1 was packed into a microchannel reactor; 1.0 g of cyclohexene oxide was mixed with 1.0 mL of dimethylformamide to obtain a homogeneous mixture;

[0102] (2) CO2 is introduced into the T-type mixer at a flow rate of 0.1 mol / min, and the pressure in the microchannel reactor is adjusted to 0.5 MPa by the back pressure valve;

[0103] (3) The mixture and CO2 gas are continuously introduced into a T-type mixer for synthesis reaction. The molar ratio of CO2 to cyclohexene oxide is 10:1. The reaction temperature is controlled at 80℃ and the reaction time is about 1.0 min to obtain cyclic carbonate product. The cyclic carbonate product is then processed by distillation and vacuum drying to finally obtain purified hexahydro-1,3-benzodioxane-2-one product.

[0104] The conversion rate and yield of the refined product were obtained by gas chromatography analysis and material balance calculation, as shown in Table 1.

[0105] Example 8

[0106] (1) 1.0 g of the catalyst prepared in Preparation Example 1 was packed into a microchannel reactor; 1.0 g of epichlorohydrin was mixed with 1.0 mL of dimethylformamide to obtain a homogeneous mixture;

[0107] (2) CO2 is introduced into the Y-type mixer at a flow rate of 0.01 mol / min, and the pressure in the microchannel reactor is adjusted to 3 MPa by the back pressure valve;

[0108] (3) The mixture and CO2 gas are continuously introduced into a T-type mixer for synthesis reaction. The molar ratio of CO2 to epichlorohydrin is 10:1, the reaction temperature is controlled at 120℃, and the reaction time is about 10 min to obtain cyclic carbonate product. The cyclic carbonate product is then processed by distillation and vacuum drying to finally obtain purified chloromethyldioxane product.

[0109] The collected product was analyzed using a Bruker Avance 400 instrument, resulting in the 1H NMR spectrum shown in Figure 3. The 1H NMR data are as follows: 1 ¹H NMR (400MHz, Chloroform-d) δ 7.50–7.31 (m, 5H), 5.68 (t, J = 8.0 Hz, 1H), 4.80 (t, J = 8.4 Hz, 1H), 4.34 (t, J = 8.3 Hz, 1H); the product was confirmed to be styrene carbonate.

[0110] The conversion rate and yield of the refined product were obtained by gas chromatography analysis and material balance calculation, as shown in Table 1.

[0111] Example 9

[0112] (1) 1.0 g of the catalyst prepared in Preparation Example 1 was packed into a microchannel reactor; 1.0 g of epichlorohydrin was mixed with 1.0 mL of dimethylformamide to obtain a homogeneous mixture;

[0113] (2) CO2 is introduced into the T-type mixer at a flow rate of 0.1 mol / min, and the pressure in the microchannel reactor is adjusted to 5 MPa by the back pressure valve;

[0114] (3) The mixture and CO2 gas are continuously introduced into a T-type mixer for synthesis reaction. The molar ratio of CO2 to epichlorohydrin is 30:1, the reaction temperature is controlled at 150℃, and the reaction time is about 10 min to obtain cyclic carbonate product. The cyclic carbonate product is then processed by distillation and vacuum drying to finally obtain purified chloromethyldioxane product.

[0115] The conversion rate and yield of the refined product were obtained by gas chromatography analysis and material balance calculation, as shown in Table 1.

[0116] Example 10

[0117] (1) 1.0 g of the catalyst prepared in Preparation Example 1 was packed into a microchannel reactor; 1.0 g of epichlorohydrin was mixed with 8.0 mL of dimethylformamide to obtain a homogeneous mixture;

[0118] (2) CO2 is introduced into the Y-type mixer at a flow rate of 0.01 mol / min, and the pressure in the microchannel reactor is adjusted to 3 MPa by the back pressure valve;

[0119] (3) The mixture and CO2 gas are continuously introduced into a Y-type mixer for synthesis reaction. The molar ratio of CO2 to epichlorohydrin is 10:1, the reaction temperature is controlled at 60℃, and the reaction time is about 30 min to obtain cyclic carbonate product. The cyclic carbonate product is then processed by distillation and vacuum drying to finally obtain purified chloromethyldioxane product.

[0120] The conversion rate and yield of the refined product were obtained by gas chromatography analysis and material balance calculation, as shown in Table 1.

[0121] The conversion rate and yield of the purified product were obtained by gas chromatography analysis and material balance calculation, as shown in Table 1.

[0122] Table 1

[0123]

[0124]

[0125] Test Example 1

[0126] The reaction in Example 1 was continued for 5 days, and the results were tested every 24 hours. The test results are shown in Table 2.

[0127] Table 2

[0128] Duration Conversion Rate (%) Yield (%) 24h 94.29 3.14 8h 94.19 3.37 2h 94.29 39 6h 94.39 3.11 20h 94.29 3 surface

[0129] In this invention, by selecting the above-mentioned quaternary ammonium salt coordination bimetallic catalyst, the mass and heat transfer effects of the material are improved through a microchannel reactor, and the reaction time is reduced from the hour level in the prior art to the minute level. While improving the reaction efficiency, the conversion rate and yield are both above 90%.

[0130] As shown in Table 2, the catalyst can achieve continuous reaction. After 5 days, the conversion rate and yield are almost unchanged, indicating that the catalyst is stable and not easily lost.

[0131] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for the continuous preparation of cyclic carbonates, characterized in that, The method includes the following steps: (1) mixing an epoxy compound and a solvent to obtain a homogeneous mixture; (2) reacting the homogeneous mixture with CO2 in the presence of a quaternary ammonium salt coordination bimetallic catalyst to obtain a cyclic carbonate product; wherein the solvent is selected from at least one of tetrahydrofuran, dimethylformamide, dialkylacetamide, dimethyl sulfoxide, and acetonitrile; wherein the epoxy compound is selected from at least one of ethylene oxide, propylene oxide, epichlorohydrin, allyl glycidyl ether, cyclohexene oxide, 4-vinylcyclohexene oxide, styrene oxide, and alkyl-substituted styrene oxide; wherein the quaternary ammonium salt coordination bimetallic catalyst is prepared by reacting a solution containing a potassium polycyanometalate and a terminal hydroxyl quaternary ammonium salt ligand with a metal salt solution to obtain the quaternary ammonium salt coordination bimetallic catalyst; wherein the general formula of the terminal hydroxyl quaternary ammonium salt ligand is: Formula (I); in Formula (I), X is selected from halogens, and n is 1-10; wherein, the polycyanometallic potassium salt is selected from at least one of potassium hexacyanocobaltate, potassium hexacyanoferrate, potassium tetracyanonitrile, potassium tetracyancadmium ...

2. The method according to claim 1, wherein, The volume ratio of the epoxy compound to the solvent is 1:(0.1-10).

3. The method according to claim 2, wherein, The volume ratio of the epoxy compound to the solvent is 1:(0.1-3).

4. The method according to any one of claims 1-3, wherein, The molar ratio of CO2 to the epoxy compound is (1-30):

1.

5. The method according to any one of claims 1-3, wherein, The temperature of the synthesis reaction is 50-150℃; and / or the pressure of the synthesis reaction is 0.1-5MPa; and / or the time of the synthesis reaction is 0.1-30min.

6. The method according to claim 5, wherein, The temperature of the synthesis reaction is 80-120℃; and / or the pressure of the synthesis reaction is 0.5-3MPa; and / or the time of the synthesis reaction is 0.1-10min.

7. The method according to claim 4, wherein, The temperature of the synthesis reaction is 50-150℃; and / or the pressure of the synthesis reaction is 0.1-5MPa; and / or the time of the synthesis reaction is 0.1-30min.

8. The method according to claim 7, wherein, The temperature of the synthesis reaction is 80-120℃; and / or the pressure of the synthesis reaction is 0.5-3MPa; and / or the time of the synthesis reaction is 0.1-10min.

9. The method according to any one of claims 1-3 and 6-8, wherein, The synthesis reaction takes place in a microchannel reactor.

10. The method according to claim 4, wherein, The synthesis reaction takes place in a microchannel reactor.

11. The method according to claim 5, wherein, The synthesis reaction takes place in a microchannel reactor.

12. The method according to any one of claims 1-3, 6-8, and 10-11, wherein, X is selected from chlorine, bromine, or iodine, and n = 1-8.

13. The method according to claim 4, wherein, X is selected from chlorine, bromine, or iodine, and n = 1-8.

14. The method according to claim 5, wherein, X is selected from chlorine, bromine, or iodine, and n = 1-8.

15. The method according to claim 9, wherein, X is selected from chlorine, bromine, or iodine, and n = 1-8.

16. The method according to any one of claims 1-3, 6-8, 10-11, and 13-15, wherein, The terminal hydroxyl quaternary ammonium salt ligand is selected from the terminal hydroxyl quaternary ammonium salt represented by Formula 1, Formula 2, or Formula 3: 。 17. The method according to claim 4, wherein, The terminal hydroxyl quaternary ammonium salt ligand is selected from the terminal hydroxyl quaternary ammonium salt represented by Formula 1, Formula 2, or Formula 3: 。 18. The method according to claim 5, wherein, The terminal hydroxyl quaternary ammonium salt ligand is selected from the terminal hydroxyl quaternary ammonium salt represented by Formula 1, Formula 2, or Formula 3: 。 19. The method according to claim 9, wherein, The terminal hydroxyl quaternary ammonium salt ligand is selected from the terminal hydroxyl quaternary ammonium salt represented by Formula 1, Formula 2, or Formula 3: 。 20. The method according to claim 12, wherein, The terminal hydroxyl quaternary ammonium salt ligand is selected from the terminal hydroxyl quaternary ammonium salt represented by Formula 1, Formula 2, or Formula 3: 。 21. The method according to any one of claims 1-3, 6-8, 10-11, 13-15, and 17-20, wherein, The molar ratio of the potassium polycyanate metal salt to the terminal hydroxyl quaternary ammonium salt ligand is 1:1-10; and / or, the molar ratio of the potassium polycyanate metal salt to the metal salt solution is 1:3-20; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the potassium polycyanate metal salt is 1-50%; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the terminal hydroxyl quaternary ammonium salt ligand is 1-50%.

22. The method according to claim 4, wherein, The molar ratio of the potassium polycyanate metal salt to the terminal hydroxyl quaternary ammonium salt ligand is 1:1-10; and / or, the molar ratio of the potassium polycyanate metal salt to the metal salt solution is 1:3-20; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the potassium polycyanate metal salt is 1-50%; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the terminal hydroxyl quaternary ammonium salt ligand is 1-50%.

23. The method according to claim 5, wherein, The molar ratio of the potassium polycyanate metal salt to the terminal hydroxyl quaternary ammonium salt ligand is 1:1-10; and / or, the molar ratio of the potassium polycyanate metal salt to the metal salt solution is 1:3-20; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the potassium polycyanate metal salt is 1-50%; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the terminal hydroxyl quaternary ammonium salt ligand is 1-50%.

24. The method according to claim 9, wherein, The molar ratio of the potassium polycyanate metal salt to the terminal hydroxyl quaternary ammonium salt ligand is 1:1-10; and / or, the molar ratio of the potassium polycyanate metal salt to the metal salt solution is 1:3-20; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the potassium polycyanate metal salt is 1-50%; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the terminal hydroxyl quaternary ammonium salt ligand is 1-50%.

25. The method according to claim 12, wherein, The molar ratio of the potassium polycyanate metal salt to the terminal hydroxyl quaternary ammonium salt ligand is 1:1-10; and / or, the molar ratio of the potassium polycyanate metal salt to the metal salt solution is 1:3-20; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the potassium polycyanate metal salt is 1-50%; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the terminal hydroxyl quaternary ammonium salt ligand is 1-50%.

26. The method of claim 16, wherein, The molar ratio of the potassium polycyanate metal salt to the terminal hydroxyl quaternary ammonium salt ligand is 1:1-10; and / or, the molar ratio of the potassium polycyanate metal salt to the metal salt solution is 1:3-20; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the potassium polycyanate metal salt is 1-50%; and / or, in the solution containing the potassium polycyanate metal salt and the terminal hydroxyl quaternary ammonium salt ligand, the mass concentration of the terminal hydroxyl quaternary ammonium salt ligand is 1-50%.

27. The method according to any one of claims 1-3, 6-8, 10-11, 13-15, 17-20, and 22-26, wherein, The mass concentration of the metal salt solution is 1-60%.

28. The method according to claim 4, wherein, The mass concentration of the metal salt solution is 1-60%.

29. The method according to claim 5, wherein, The mass concentration of the metal salt solution is 1-60%.

30. The method according to claim 9, wherein, The mass concentration of the metal salt solution is 1-60%.

31. The method according to claim 12, wherein, The mass concentration of the metal salt solution is 1-60%.

32. The method according to claim 16, wherein, The mass concentration of the metal salt solution is 1-60%.

33. The method according to claim 21, wherein, The mass concentration of the metal salt solution is 1-60%.

34. The method according to any one of claims 1-3, 6-8, 10-11, 13-15, 17-20, 22-26, and 28-33, wherein, The reaction is carried out at a temperature of 0-100℃ for a time of 0.5-72h.

35. The method according to claim 34, wherein, The reaction is carried out at a temperature of 25-50℃ for 3-12 hours.

36. The method according to claim 4, wherein, The reaction is carried out at a temperature of 0-100℃ for a time of 0.5-72h.

37. The method of claim 36, wherein, The reaction is carried out at a temperature of 25-50℃ for 3-12 hours.

38. The method according to claim 5, wherein, The reaction is carried out at a temperature of 0-100℃ for a time of 0.5-72h.

39. The method according to claim 38, wherein, The reaction is carried out at a temperature of 25-50℃ for 3-12 hours.

40. The method according to claim 9, wherein, The reaction is carried out at a temperature of 0-100℃ for a time of 0.5-72h.

41. The method according to claim 40, wherein, The reaction is carried out at a temperature of 25-50℃ for 3-12 hours.

42. The method according to claim 12, wherein, The reaction is carried out at a temperature of 0-100℃ for a time of 0.5-72h.

43. The method according to claim 42, wherein, The reaction is carried out at a temperature of 25-50℃ for 3-12 hours.

44. The method of claim 16, wherein, The reaction is carried out at a temperature of 0-100℃ for a time of 0.5-72h.

45. The method according to claim 44, wherein, The reaction is carried out at a temperature of 25-50℃ for 3-12 hours.

46. ​​The method according to claim 21, wherein, The reaction is carried out at a temperature of 0-100℃ for a time of 0.5-72h.

47. The method according to claim 46, wherein, The reaction is carried out at a temperature of 25-50℃ for 3-12 hours.

48. The method according to claim 27, wherein, The reaction is carried out at a temperature of 0-100℃ for a time of 0.5-72h.

49. The method according to claim 48, wherein, The reaction is carried out at a temperature of 25-50℃ for 3-12 hours.

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