Method for directly synthesizing dimethyl carbonate from supercritical CO2-methanol in microchannel continuous flow reactor
By employing a supercritical CO2-methanol system in a microchannel continuous flow reactor and using alcohol oxysalts and iodomethane catalysts, the stability and continuity issues in the synthesis of dimethyl carbonate were resolved, achieving highly selective and high-yield production of dimethyl carbonate, suitable for industrial applications.
Patent Information
- Application Number
- CN202511854123.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-10
- Publication Date
- 2026-02-10
AI Technical Summary
Existing methods for synthesizing dimethyl carbonate suffer from problems such as poor stability, high cost, and difficulty in separating byproducts. Furthermore, traditional reactors have poor production continuity, making it difficult to meet industrialization needs.
A supercritical CO2-methanol system was used in a microchannel continuous flow reactor, with oxyethanol as the catalyst and iodomethane as the co-catalyst. The reaction conditions were 8-10 MPa, 100-160 °C, and 5-15 minutes. Dimethyl carbonate was obtained after post-treatment.
It achieves high selectivity and high yield of dimethyl carbonate, with water as the only byproduct. The reaction is safe and efficient, and suitable for industrial production.
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Figure CN121494722A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of chemical technology, in particular to a method for directly synthesizing dimethyl carbonate from supercritical CO2-methanol in a micro-channel continuous flow reactor. BACKGROUND
[0002] Dimethyl carbonate is a non-toxic, non-corrosive green chemical raw material. The active groups such as methyl, methoxy and carbonyl in its molecule endow it with multifunctional reaction characteristics, and it can safely replace the highly toxic dimethyl sulfate and phosgene as a methylating and carbonylating reagent. As an environmentally friendly compound, dimethyl carbonate has important application value in the fields of polycarbonate synthesis, lithium ion battery electrolyte preparation, etc. The traditional industrial preparation methods of dimethyl carbonate mainly include methanol oxidative carbonylation method, ester exchange method, urea alcoholysis method and direct synthesis method of carbon dioxide and methanol. The methanol oxidative carbonylation method has low stability and low safety; the ester exchange method has high cost and low safety; the urea alcoholysis method has the disadvantages of difficult separation of by-products, etc. The direct synthesis method of carbon dioxide and methanol has an atomic economy close to the theoretical limit, has no redundant by-products, can utilize carbon dioxide resources, reduces the dependence on petroleum-based raw materials, and has both environmental protection and raw material flexibility, so it is the most potential synthesis process of dimethyl carbonate at present.
[0003] According to the difference of the reactor, it can be divided into batch reactor and continuous reactor. The batch reactor needs to repeatedly carry out the processes of charging, reaction and unloading due to batch operation, and has poor production continuity, and the reaction conditions are easy to fluctuate with batches, resulting in poor product quality stability. The continuous reactor can realize stable operation of continuous feeding of raw materials and continuous discharge of products, not only has significantly higher unit time productivity, but also can maintain operation stability and reduce energy consumption in large-scale production, and is more suitable for industrial high-efficiency production needs. In view of the above, it is urgent to develop an environmentally friendly, low-cost and high-yield new method for directly synthesizing dimethyl carbonate from carbon dioxide and methanol, which has important significance for promoting the industrial production of dimethyl carbonate and developing the market application of dimethyl carbonate. SUMMARY
[0004] In view of the defects in the generation process of dimethyl carbonate in the prior art, the technical problem solved by the present application is to provide a method for directly synthesizing dimethyl carbonate from supercritical CO2-methanol in a micro-channel continuous flow reactor. Methanol is used as raw material, supercritical carbon dioxide is used as both reactant and solvent, alcoholate is used as catalyst, and iodomethane is used as co-catalyst, which can provide abundant methyl (CH3 * ) groups. The reaction system has the characteristics of high reaction efficiency, easy operation and reaction safety, and the selectivity of dimethyl carbonate is high, the by-product is only water, and the reaction can be completed in a very short time.
[0005] The objective of this invention is achieved through the following approach.
[0006] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor involves first introducing carbon dioxide to reach a supercritical state in a closed reactor, then introducing an alcohol-oxygen salt catalyst, a co-catalyst, and methanol. The reaction is carried out for 5-15 minutes at a pressure of 8-10 MPa and a temperature of 100-160 °C, followed by post-treatment to obtain the product dimethyl carbonate.
[0007] Furthermore, in the above-mentioned method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor, the alkoxide catalyst and co-catalyst are first dissolved in methanol to obtain a reaction substrate solution, which is then introduced into a closed reactor via a pump.
[0008] Furthermore, in the above-described method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor, the flow rate of the reaction substrate solution is 1-10 mL / min.
[0009] Furthermore, in the above-described method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor, the flow rate of carbon dioxide is 20-100 mL / min.
[0010] Furthermore, in the above-described method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor, the alcohol-oxygen salt catalyst is one or any combination of magnesium methoxide, potassium methoxide, and sodium methoxide.
[0011] Furthermore, in the above-described method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor, the co-catalyst is iodomethane.
[0012] Furthermore, in the above-described method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor, the mass ratio of methanol to catalyst is 1:(0.0009−0.0046).
[0013] Furthermore, in the above-described method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor, the molar ratio of the alcohol-oxygen salt catalyst to the co-catalyst is 1:0.5-1.5.
[0014] Furthermore, in the above-described method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor, the reactor is a microchannel continuous flow reactor with a tube diameter of 3 mm.
[0015] Furthermore, in the above-described method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor, the post-treatment involves transferring the reaction solution to a low-temperature condenser via pipeline after the reaction is completed. When the reaction solution is cooled to -15-25°C and the pressure of the reaction system drops to 0.5-1.5 MPa, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed, liquefied, and reused. The low-boiling-point dimethyl carbonate and unreacted methanol are liquefied into a liquid phase and discharged from the delivery pipeline for collection.
[0016] The analytical method for the reaction results in this application is as follows: After the reaction is complete, a certain amount of the reaction solution is taken for gas chromatography analysis. Using n-butanol as an internal standard, the selectivity and yield of dimethyl carbonate are calculated using the gas chromatography data.
[0017] Compared with the prior art, the present invention has the following beneficial effects:
[0018] 1. The technical solution provided by this invention uses an alkoxide as a catalyst and iodomethane as a co-catalyst to catalyze the preparation of dimethyl carbonate from methanol. The alkoxide catalyst exhibits good catalytic activity, enabling a selectivity of 95.4%-98.1% for dimethyl carbonate and a yield of 6.8%-23.8%.
[0019] 2. The technical solution provided by this invention uses carbon dioxide as both a reactant and a solvent to react with methanol. This solution features simple process conditions and high reaction efficiency.
[0020] 3. The alkoxide salt catalyst used in this invention has high activity, excellent solubility in the reaction system, low catalyst dosage, and a green and environmentally friendly process, thus showing good application prospects. Attached Figure Description
[0021] Figure 1 This is the chromatogram of the product obtained by online sampling and gas chromatography analysis in Example 1. Detailed Implementation
[0022] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.
[0023] All reagents used in the examples were commercially available analytical grade reagents.
[0024] The pump used in this application is a dual-plunger constant flow pump.
[0025] Example 1
[0026] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor includes the following steps:
[0027] 1) Add 350 mg of magnesium methoxide and 0.37 mL of iodomethane to 8 g of methanol to obtain a reaction substrate solution;
[0028] 2) High-purity carbon dioxide is introduced into the microchannel continuous flow reactor at a gas flow rate of 20 mL / min. When the back pressure of the microchannel continuous flow reactor reaches 8 MPa, the reaction substrate solution prepared in step 1) is pumped into the microchannel continuous flow reactor at a flow rate of 8 mL / min, and high-purity carbon dioxide is continuously introduced into the microchannel continuous flow reactor at a gas flow rate of 8 mL / min to maintain the back pressure of the microchannel continuous flow reactor at 8 MPa. Then the temperature is raised to 140℃ and the reaction is carried out continuously for 8.5 min.
[0029] 3) After the reaction is complete, the reaction solution is transferred to a low-temperature condenser through pipeline. When the reaction solution is cooled to -20℃ and the pressure of the reaction system drops to 1 MPa, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is condensed and liquefied and then collected for reuse. The low-boiling-point vaporized organic compound dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the liquid delivery pipeline.
[0030] 4) Collect the liquid product discharged in step 3), use n-butanol as an internal standard, take samples online, analyze the product using gas chromatography, and quantify the product using the internal standard method.
[0031] See results Figure 1 ,pass Figure 1 It can be seen that the selectivity of dimethyl carbonate is 98.1%, and the yield of dimethyl carbonate is 23.8%. This indicates that the supercritical microchannel continuous flow method used in this invention can be used for the efficient catalytic direct preparation of dimethyl carbonate from carbon dioxide and methanol.
[0032] Example 2
[0033] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor includes the following steps:
[0034] 1) Add 420 mg potassium methoxide and 0.37 mL iodomethane to 8 g methanol to obtain a reaction substrate solution;
[0035] 2) High-purity carbon dioxide is introduced into the microchannel continuous flow reactor at a gas flow rate of 20 mL / min. When the back pressure of the microchannel continuous flow reactor reaches 8 MPa, the reaction substrate solution prepared in step 1) is pumped into the microchannel continuous flow reactor at a flow rate of 8 mL / min, and high-purity carbon dioxide is continuously introduced into the microchannel continuous flow reactor at a gas flow rate of 8 mL / min to maintain the back pressure of the microchannel continuous flow reactor at 8 MPa. Then the temperature is raised to 140℃ and the reaction is carried out continuously for 8.5 min.
[0036] 3) After the reaction is complete, the reaction solution is transferred to a low-temperature condenser through pipeline. When the reaction solution is cooled to -20℃ and the pressure of the reaction system drops to 1 MPa, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed, liquefied, and reused. The low-boiling-point vaporized organic compound dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the liquid delivery pipeline.
[0037] 4) Collect the liquid product discharged in step 3), use n-butanol as an internal standard, take online samples and analyze the product using gas chromatography, and quantify the product using the internal standard method.
[0038] The results showed that the selectivity for dimethyl carbonate was 97.3%, and the yield of dimethyl carbonate was 14.5%. This indicates that the supercritical microchannel continuous flow method used in this invention can be used for the efficient catalytic direct preparation of dimethyl carbonate from carbon dioxide and methanol.
[0039] Example 3
[0040] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor includes the following steps:
[0041] 1) Add 324 mg of sodium methoxide and 0.37 mL of iodomethane to 8 g of methanol to obtain a reaction substrate solution;
[0042] 2) High-purity carbon dioxide is introduced into the microchannel continuous flow reactor at a gas flow rate of 20 mL / min. When the back pressure of the microchannel continuous flow reactor reaches 8 MPa, the reaction substrate solution prepared in step 1) is pumped into the microchannel continuous flow reactor at a flow rate of 8 mL / min, and high-purity carbon dioxide is continuously introduced into the microchannel continuous flow reactor at a gas flow rate of 8 mL / min to maintain the back pressure of the microchannel continuous flow reactor at 8 MPa. Then the temperature is raised to 140℃ and the reaction is carried out continuously for 8.5 min.
[0043] 3) After the reaction is completed, the reaction liquid is transferred to the low-temperature condenser through the pipeline. When the reaction liquid is cooled to -20℃, the pressure of the reaction system drops to 1 MPa. Then, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed and liquefied, and collected for reuse. The low-boiling-point vaporized organic compound dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the liquid delivery pipeline.
[0044] 4) Collect the liquid product discharged in step 3), use n-butanol as an internal standard, take online samples and analyze the product using gas chromatography, and quantify the product using the internal standard method.
[0045] The results showed that the selectivity for dimethyl carbonate was 96.2%, and the yield of the product dimethyl carbonate was 6.8%. This indicates that the supercritical microchannel continuous flow method used in this invention can be used for the efficient catalytic direct preparation of dimethyl carbonate from carbon dioxide and methanol.
[0046] Example 4
[0047] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor includes the following steps:
[0048] 1) Add 350 mg of magnesium methoxide and 0.37 mL of iodomethane to 8 g of methanol to obtain a reaction substrate solution;
[0049] 2) High-purity carbon dioxide is introduced into the microchannel continuous flow reactor at a gas flow rate of 20 mL / min. When the back pressure of the microchannel continuous flow reactor reaches 9 MPa, the reaction substrate solution prepared in step 1) is pumped into the microchannel continuous flow reactor at a flow rate of 8 mL / min, and high-purity carbon dioxide is continuously introduced into the microchannel continuous flow reactor at a gas flow rate of 8 mL / min to maintain the back pressure of the microchannel continuous flow reactor at 9 MPa. Then the temperature is raised to 140℃ and the reaction is carried out continuously for 8.5 min.
[0050] 3) After the reaction is completed, the reaction liquid is transferred to the low-temperature condenser through the pipeline. When the reaction liquid is cooled to -20℃, the pressure of the reaction system drops to 1 MPa. Then, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed and liquefied, and collected for reuse. The low-boiling-point vaporized organic compound dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the liquid delivery pipeline.
[0051] 4) Collect the liquid product discharged in step 3), use n-butanol as an internal standard, take online samples and analyze the product using gas chromatography, and quantify the product using the internal standard method.
[0052] The results showed that the selectivity for dimethyl carbonate was 97.3%, and the yield of dimethyl carbonate was 21.6%. This indicates that the supercritical microchannel continuous flow method used in this invention can be used for the efficient catalytic direct preparation of dimethyl carbonate from carbon dioxide and methanol.
[0053] Example 5
[0054] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor includes the following steps:
[0055] 1) Add 350 mg of magnesium methoxide and 0.37 mL of iodomethane to 8 g of methanol to obtain a reaction substrate solution;
[0056] 2) High-purity carbon dioxide is introduced into the microchannel continuous flow reactor at a gas flow rate of 20 mL / min. When the back pressure of the microchannel continuous flow reactor reaches 10 MPa, the reaction substrate solution prepared in step 1) is pumped into the microchannel continuous flow reactor at a flow rate of 8 mL / min, and high-purity carbon dioxide is continuously introduced into the microchannel continuous flow reactor at a gas flow rate of 8 mL / min to maintain the back pressure of the microchannel continuous flow reactor at 10 MPa. Then the temperature is raised to 140℃ and the reaction is carried out continuously for 8.5 min.
[0057] 3) After the reaction is completed, the reaction liquid is transferred to the low-temperature condenser through the pipeline. When the reaction liquid is cooled to -20℃, the pressure of the reaction system drops to 1 MPa. Then, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed and liquefied, and collected for reuse. The low-boiling-point vaporized organic compound dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the liquid delivery pipeline.
[0058] 4) Collect the liquid product discharged in step 3), use n-butanol as an internal standard, take online samples and analyze the product using gas chromatography, and quantify the product using the internal standard method.
[0059] The results showed that the selectivity for dimethyl carbonate was 96.8%, and the yield of dimethyl carbonate was 20.2%. This indicates that the supercritical microchannel continuous flow method used in this invention can be used for the efficient catalytic direct preparation of dimethyl carbonate from carbon dioxide and methanol.
[0060] Example 6
[0061] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor includes the following steps:
[0062] 1) Add 350 mg of magnesium methoxide and 0.37 mL of iodomethane to 8 g of methanol to obtain a reaction substrate solution;
[0063] 2) High-purity carbon dioxide is introduced into the microchannel continuous flow reactor at a gas flow rate of 20 mL / min. When the back pressure of the microchannel continuous flow reactor reaches 8 MPa, the reaction substrate solution prepared in step 1) is pumped into the microchannel continuous flow reactor at a flow rate of 8 mL / min, and high-purity carbon dioxide is continuously introduced into the microchannel continuous flow reactor at a gas flow rate of 8 mL / min to maintain the back pressure of the microchannel continuous flow reactor at 8 MPa. Then the temperature is raised to 120℃ and the reaction is carried out continuously for 8.5 min.
[0064] 3) After the reaction is completed, the reaction liquid is transferred to the low-temperature condenser through the pipeline. When the reaction liquid is cooled to -20℃, the pressure of the reaction system drops to 1 MPa. Then, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed and liquefied, and collected for reuse. The low-boiling-point vaporized organic compound dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the liquid delivery pipeline.
[0065] 4) Collect the liquid product discharged in step 3), use n-butanol as an internal standard, take online samples and analyze the product using gas chromatography, and quantify the product using the internal standard method.
[0066] The results showed that the selectivity for dimethyl carbonate was 95.4%, and the yield of dimethyl carbonate was 18.3%. This indicates that the supercritical microchannel continuous flow method used in this invention can be used for the efficient catalytic direct preparation of dimethyl carbonate from carbon dioxide and methanol.
[0067] Example 7
[0068] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor includes the following steps:
[0069] 1) Add 350 mg of magnesium methoxide and 0.37 mL of iodomethane to 8 g of methanol to obtain a reaction substrate solution;
[0070] 2) High-purity carbon dioxide is introduced into the microchannel continuous flow reactor at a gas flow rate of 20 mL / min. When the back pressure of the microchannel continuous flow reactor reaches 10 MPa, the reaction substrate solution prepared in step 1) is pumped into the microchannel continuous flow reactor at a flow rate of 8 mL / min, and high-purity carbon dioxide is continuously introduced into the microchannel continuous flow reactor at a gas flow rate of 8 mL / min to maintain the back pressure of the microchannel continuous flow reactor at 10 MPa. Then the temperature is raised to 160℃ and the reaction is carried out continuously for 8.5 min.
[0071] 3) After the reaction is completed, the reaction liquid is transferred to the low-temperature condenser through the pipeline. When the reaction liquid is cooled to -20℃, the pressure of the reaction system drops to 1 MPa. Then, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed and liquefied, and collected for reuse. The low-boiling-point vaporized organic compound dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the liquid delivery pipeline.
[0072] 4) Collect the liquid product discharged in step 3), use n-butanol as an internal standard, take online samples and analyze the product using gas chromatography, and quantify the product using the internal standard method.
[0073] The results showed that the selectivity for dimethyl carbonate was 97.4%, and the yield of dimethyl carbonate was 21.8%. This indicates that the supercritical microchannel continuous flow method used in this invention can be used for the efficient catalytic direct preparation of dimethyl carbonate from carbon dioxide and methanol.
[0074] Comparative Example 1
[0075] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor includes the following steps:
[0076] 1) Add 350 mg of magnesium methoxide to 8 g of methanol to obtain a reaction substrate solution;
[0077] 2) High-purity carbon dioxide is introduced into the microchannel continuous flow reactor at a gas flow rate of 20 mL / min. When the back pressure of the microchannel continuous flow reactor reaches 8 MPa, the reaction substrate solution prepared in step 1) is pumped into the microchannel continuous flow reactor at a flow rate of 8 mL / min, and high-purity carbon dioxide is continuously introduced into the microchannel continuous flow reactor at a gas flow rate of 8 mL / min to maintain the back pressure of the microchannel continuous flow reactor at 8 MPa. Then the temperature is raised to 140℃ and the reaction is carried out continuously for 8.5 min.
[0078] 3) After the reaction is completed, the reaction liquid is transferred to the low-temperature condenser through the pipeline. When the reaction liquid is cooled to -20℃, the pressure of the reaction system drops to 1 MPa. Then, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed and liquefied, and collected for reuse. The low-boiling-point vaporized organic compound dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the liquid delivery pipeline.
[0079] 4) Collect the liquid product discharged in step 3), use n-butanol as an internal standard, take online samples and analyze the product using gas chromatography, and quantify the product using the internal standard method.
[0080] The results showed that the selectivity for dimethyl carbonate was 91.1%, and the yield of dimethyl carbonate was 6.9%. This indicates that the supercritical microchannel continuous flow method used in this invention can be used for the efficient catalytic direct preparation of dimethyl carbonate from carbon dioxide and methanol.
[0081] Comparative Example 2
[0082] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor includes the following steps:
[0083] 1) Add 420 mg of potassium methoxide to 8 g of methanol to obtain a reaction substrate solution;
[0084] 2) High-purity carbon dioxide is introduced into the microchannel continuous flow reactor at a gas flow rate of 20 mL / min. When the back pressure of the microchannel continuous flow reactor reaches 8 MPa, the reaction substrate solution prepared in step 1) is pumped into the microchannel continuous flow reactor at a flow rate of 8 mL / min, and high-purity carbon dioxide is continuously introduced into the microchannel continuous flow reactor at a gas flow rate of 8 mL / min to maintain the back pressure of the microchannel continuous flow reactor at 8 MPa. Then the temperature is raised to 140℃ and the reaction is carried out continuously for 8.5 min.
[0085] 3) After the reaction is completed, the reaction liquid is transferred to the low-temperature condenser through the pipeline. When the reaction liquid is cooled to -20℃, the pressure of the reaction system drops to 1 MPa. Then, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed and liquefied, and collected for reuse. The low-boiling-point vaporized organic compound dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the liquid delivery pipeline.
[0086] 4) Collect the liquid product discharged in step 3), use n-butanol as an internal standard, take online samples and analyze the product using gas chromatography, and quantify the product using the internal standard method.
[0087] The results showed that the selectivity for dimethyl carbonate was 88.2%, and the yield of dimethyl carbonate was 4.9%. This indicates that the supercritical microchannel continuous flow method used in this invention can be used for the efficient catalytic direct preparation of dimethyl carbonate from carbon dioxide and methanol.
[0088] Comparative Example 3
[0089] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor includes the following steps:
[0090] 1) Add 324 mg of sodium methoxide and 0.37 mL of iodomethane to 8 g of methanol to obtain a reaction substrate solution;
[0091] 2) High-purity carbon dioxide is introduced into the microchannel continuous flow reactor at a gas flow rate of 20 mL / min. When the back pressure of the microchannel continuous flow reactor reaches 8 MPa, the reaction substrate solution prepared in step 1) is pumped into the microchannel continuous flow reactor at a flow rate of 8 mL / min, and high-purity carbon dioxide is continuously introduced into the microchannel continuous flow reactor at a gas flow rate of 8 mL / min to maintain the back pressure of the microchannel continuous flow reactor at 8 MPa. Then the temperature is raised to 140℃ and the reaction is carried out continuously for 8.5 min.
[0092] 3) After the reaction is completed, the reaction liquid is transferred to the low-temperature condenser through the pipeline. When the reaction liquid is cooled to -20℃, the pressure of the reaction system drops to 1 MPa. Then, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed and liquefied, and collected for reuse. The low-boiling-point vaporized organic compound dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the liquid delivery pipeline.
[0093] 4) Collect the liquid product discharged in step 3), use n-butanol as an internal standard, take online samples and analyze the product using gas chromatography, and quantify the product using the internal standard method.
[0094] The results showed that the selectivity for dimethyl carbonate was 85.5%, and the yield of dimethyl carbonate was 2.3%. This indicates that the supercritical microchannel continuous flow method used in this invention can be used for the efficient catalytic direct preparation of dimethyl carbonate from carbon dioxide and methanol.
[0095] Comparative Example 4
[0096] A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor includes the following steps:
[0097] 1) Add 0.37 mL of iodomethane to 8 g of methanol to obtain a reaction substrate solution;
[0098] 2) High-purity carbon dioxide is introduced into the microchannel continuous flow reactor at a gas flow rate of 20 mL / min. When the back pressure of the microchannel continuous flow reactor reaches 8 MPa, the reaction substrate solution prepared in step 1) is pumped into the microchannel continuous flow reactor at a flow rate of 8 mL / min, and high-purity carbon dioxide is continuously introduced into the microchannel continuous flow reactor at a gas flow rate of 8 mL / min to maintain the back pressure of the microchannel continuous flow reactor at 8 MPa. Then the temperature is raised to 140℃ and the reaction is carried out continuously for 8.5 min.
[0099] 3) After the reaction is completed, the reaction liquid is transferred to the low-temperature condenser through the pipeline. When the reaction liquid is cooled to -20℃, the pressure of the reaction system drops to 1 MPa. Then, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed and liquefied, and collected for reuse. The low-boiling-point vaporized organic compound dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the liquid delivery pipeline.
[0100] 4) Collect the liquid product discharged in step 3), use n-butanol as an internal standard, take online samples and analyze the product using gas chromatography, and quantify the product using the internal standard method.
[0101] The results showed that the selectivity for dimethyl carbonate was 88.5%, and the yield of dimethyl carbonate was 3.6%. This indicates that the supercritical microchannel continuous flow method used in this invention can be used for the efficient catalytic direct preparation of dimethyl carbonate from carbon dioxide and methanol.
[0102] By comparing Examples 1-8 with Comparative Examples 1-4, it can be concluded that using magnesium methoxide and iodomethane as a combined catalyst can achieve the most efficient catalytic reaction of carbon dioxide and methanol to directly produce dimethyl carbonate.
[0103] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A method for the direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor, characterized in that, In a closed reactor, carbon dioxide is first introduced to reach a supercritical state, and then an alcohol oxygen salt catalyst, a co-catalyst, and methanol are introduced. The reaction is carried out for 5-15 minutes under the conditions of 8-10 MPa pressure and 100-160 ℃ temperature. The product, dimethyl carbonate, is obtained after post-treatment.
2. The method for direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor according to claim 1, characterized in that, The alkoxysalt catalyst and co-catalyst are first dissolved in methanol to obtain a reaction substrate solution, which is then fed into a closed reactor via a pump.
3. The method for direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor according to claim 2, characterized in that, The flow rate of the reaction substrate solution is 1-10 mL / min.
4. The method for direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor according to claim 1, characterized in that, The flow rate of the carbon dioxide is 20-100 mL / min.
5. The method for direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor according to claim 1 or 2, characterized in that, The alkoxide catalyst is one or any combination of magnesium methoxide, potassium methoxide, and sodium methoxide.
6. The method for direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor according to claim 1 or 2, characterized in that, The co-catalyst is iodomethane.
7. The method for direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor according to claim 1 or 2, characterized in that, The mass ratio of methanol to catalyst is 1:(0.0009−0.0046).
8. The method for direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor according to claim 1 or 2, characterized in that, The molar ratio of the alkoxyl salt catalyst to the co-catalyst is 1:0.5-1.
5.
9. The method for direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor according to claim 1, characterized in that, The reactor described is a microchannel continuous flow reactor.
10. The method for direct synthesis of dimethyl carbonate from supercritical CO2-methanol in a microchannel continuous flow reactor according to claim 1, characterized in that, The post-processing involves transferring the reaction solution to a low-temperature condenser via pipeline after the reaction is completed. When the reaction solution is cooled to -15 to -25°C and the pressure of the reaction system drops to 0.5 to 1.5 MPa, carbon dioxide is discharged from the gas pipeline. The discharged carbon dioxide is collected, condensed, liquefied, and then collected and reused. Low-boiling-point dimethyl carbonate and unreacted methanol are liquefied into liquid phase and discharged from the delivery pipeline for collection.