A method for preparing carbon dioxide-based polycarbonate polyol

Abstract

The present application relates to the technical field of the preparation of polycarbonate polyols, and discloses a method for preparing a carbon dioxide-based polycarbonate polyol, comprising the following steps: (1) adding cyclohexane oxide, an organic boron compound, a sodium benzimidazole sulfinate initiator, and a chain transfer agent to a high-pressure reactor, respectively, and introducing carbon dioxide to carry out copolymerization reaction; (2) stopping heating and cooling after the reaction is completed, adding a small amount of acid to the reaction system to terminate the reaction, and then using a solvent to precipitate and purify the product multiple times, and drying it to obtain a pure carbon dioxide-based polycarbonate polyol. The present application can use organic boron compounds and sodium benzimidazole sulfinate initiators as the catalyst system, overcome the problem of material residues caused by the use of metal catalysts, and has a faster reaction efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of preparation of polycarbonate polyols, and in particular to a method for preparing carbon dioxide-based polycarbonate polyols. Background Art

[0002] Carbon dioxide is considered to be one of the most attractive renewable C1 resources due to its abundant resources, non-toxicity and low cost. However, carbon dioxide is also an industrial waste that causes the greenhouse effect. Therefore, developing efficient green technologies to convert carbon dioxide into valuable chemicals is an environmentally friendly solution to achieve sustainable social development. Among various carbon dioxide chemical conversion strategies, the ring-opening alternating copolymerization of carbon dioxide and epoxides can produce carbon dioxide-based polycarbonates, which are particularly attractive due to their 100% atom economy and degradability. Among them, carbon dioxide-based polycarbonate polyols, as a new type of biomass synthetic material, have broad research and application prospects. They are a new type of biomass synthetic material with excellent performance and broad application prospects.

[0003] In the method for synthesizing polycarbonate polyols, the catalyst used is more often a metal-based catalyst, which has the advantages of small dosage and high reaction efficiency. For example, the existing Chinese invention patent document with application number 202310197448.6 discloses a method for producing polycarbonate polyols using carbon dioxide as a raw material, in which a catalyst is selected from one or more of an alkoxy metal compound and an organic tin compound to catalyze the reaction.

[0004] Metal catalysts are solid catalysts with metal as the main active component, which play a vital role in chemical reactions. Although metal-based catalysts are widely used in the method of synthesizing polycarbonate polyols, the application of metal-based catalysts is limited by the complex post-treatment process, especially in removing metal residues in CO2-polycarbonate products. Therefore, the study of alternative metal catalysts for the synthesis of polycarbonate polyols remains a hot topic in this field. Summary of the invention

[0005] The present application provides a method for preparing a carbon dioxide-based polycarbonate polyol.

[0006] This application adopts the following technical solutions: A method for preparing a carbon dioxide-based polycarbonate polyol comprises the following steps: 1. Add cyclohexene oxide, organic boron compounds, sodium benzimidazole sulfinate initiator, and chain transfer agent into a high-pressure reactor, and introduce carbon dioxide to carry out copolymerization reaction; 2. After the reaction is completed, stop heating and cool, add a small amount of acid to the reaction system to terminate the reaction, and then use a solvent to precipitate and purify the product multiple times and dry it to obtain pure carbon dioxide-based polycarbonate polyol.

[0007] By adopting the above technical scheme, sodium benzimidazole sulfinate initiators replace traditional initiators and are combined with Lewis acid organic boron compounds to form a catalyst system, which shortens the reaction time. In addition, the catalyst used in this application is a non-metallic catalyst, the polymerization process is more environmentally friendly, the post-processing of the product is simple, a high-purity product can be obtained, and the problem of metal catalyst residues is avoided.

[0008] Optionally, the sodium benzimidazole sulfinate initiator is prepared by the following method: adding differently substituted benzimidazole sulfonyl chloride, sodium sulfite and sodium bicarbonate to water, stirring, dissolving and reacting under heating conditions, and after the reaction is completed, recrystallizing and filtering to obtain the sodium benzimidazole sulfinate initiator.

[0009] By adopting the above technical scheme, the preparation of sodium benzimidazole sulfinate initiator is simple, the reaction regulation is mild, and it can be suitable for large-scale industrial mass production.

[0010] Optionally, the differently substituted benzimidazole sulfonyl chloride is selected from one or more of benzimidazole sulfonyl chloride, pentafluorobenzimidazole sulfonyl chloride and 4-methoxybenzimidazole sulfonyl chloride.

[0011] By adopting the above technical solution, the sodium benzimidazole sulfinate initiators prepared by reacting the above components can form a catalyst system with the organic boron compound to improve the reaction efficiency.

[0012] Optionally, the molar ratio of the differently substituted benzimidazole sulfonyl chloride, sodium sulfite, sodium bicarbonate and water is 1:2:2:20.

[0013] Optionally, in step (1), the molar ratio of the organic boron compound to the sodium benzimidazole sulfinate initiator is 1:1 to 1:8.

[0014] By adopting the above technical solution, the molar ratio of the organic boron compound to the sodium benzimidazole sulfinate initiator is 1:1 to 1:8, such as 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7 or 1:8, and the catalytic effect is better in this range.

[0015] Optionally, the chain transfer agent is a polyol or a polycarboxylic acid, and the functionality is not less than 2.

[0016] By adopting the above technical scheme, a good chain transfer effect is achieved, and the chain transfer agent can be selected from one of 1,4-butanediol, 1,6-hexanediol, 1,3-propylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, 1,4-benzenedimethanol, neopentyl glycol, 1,4-succinic acid, terephthalic acid and phthalic acid.

[0017] Optionally, the organic boron compound is selected from one or more of triphenylboron, triethylboron, boron trichloride or boron trifluoride.

[0018] Optionally, in step (1), the molar ratio of the cyclohexene oxide to the sodium benzimidazole sulfinate initiator is 2000:1 to 2000:20.

[0019] Optionally, in step (1), the copolymerization reaction pressure is 0.5-2.0 MPa, and the reaction temperature is 40-80°C.

[0020] By adopting the above technical solution, the reaction can be better promoted under this environment.

[0021] In summary, the present application includes at least one of the following beneficial effects: 1. The sodium benzimidazole sulfinate initiator synthesized by different substituted benzimidazole sulfonyl chloride and sodium sulfite replaces the traditional initiator and forms a catalyst system with Lewis acid organic boron compound, which shortens the reaction time and significantly shortens the reaction time to 4-8 hours, improves the polymerization reaction efficiency, reduces the production cost, and can obtain the target product in a shorter time; 2. The present invention combines an organic boron compound with a sodium benzimidazole sulfinate initiator to form a catalytic system. The catalyst system is a non-metallic catalyst, the polymerization process is green and environmentally friendly, the product post-treatment is simple, and the problem of metal catalyst residue can be effectively reduced; the reaction conditions are mild and the polymerization temperature is low. DETAILED DESCRIPTION

[0022] Preparation Example 1 Under a nitrogen atmosphere, benzimidazole sulfonyl chloride, sodium sulfite, sodium bicarbonate and water are added to a reaction bottle, and stirred and dissolved under heating conditions to allow the benzimidazole sulfonyl chloride to react chemically with the sodium sulfite; after reacting at 60°C for 4 hours, the temperature is lowered to room temperature and the water is removed in vacuo; wherein the molar ratio of benzimidazole sulfonyl chloride, sodium sulfite, sodium bicarbonate and water is 1:2:2:20.

[0023] The obtained crude sodium benzimidazole sulfinate was recrystallized with ethanol, and finally the sodium benzimidazole sulfinate was placed in a vacuum drying oven at 40° C. and dried for 24 hours to obtain a solid powdery sodium benzimidazole sulfinate initiator.

[0024] Preparation Example 2 Pentafluorobenzimidazole sulfonyl chloride, sodium sulfite, sodium bicarbonate and water are added to a reaction bottle under a nitrogen atmosphere, and stirred and dissolved under heating conditions to allow the benzimidazole sulfonyl chloride to react chemically with the sodium sulfite; react at 60°C for 4 hours, then cool to room temperature and remove water in vacuo; wherein the molar ratio of pentafluorobenzimidazole sulfonyl chloride, sodium sulfite, sodium bicarbonate and water is 1:2:2:20.

[0025] The obtained crude sodium pentafluorobenzimidazole sulfinate was recrystallized with ethanol, and finally the sodium pentafluorobenzimidazole sulfinate was placed in a vacuum drying oven at 40° C. and dried for 24 hours to obtain a solid powdery sodium pentafluorobenzimidazole sulfinate initiator.

[0026] Preparation Example 3 Under a nitrogen atmosphere, 4-methoxybenzimidazole sulfonyl chloride, sodium sulfite, sodium bicarbonate and water are added to a reaction bottle, and stirred and dissolved under heating conditions to allow the benzimidazole sulfonyl chloride to react chemically with the sodium sulfite; after reacting at 60°C for 4 hours, the temperature is lowered to room temperature and the water is removed in vacuo; wherein the molar ratio of 4-methoxybenzimidazole sulfonyl chloride, sodium sulfite, sodium bicarbonate and water is 1:2:2:20.

[0027] The obtained crude 4-methoxybenzimidazole sodium sulfinate was recrystallized with ethanol, and finally the 4-methoxybenzimidazole sodium sulfinate was placed in a vacuum drying oven at 40° C. and dried for 24 hours to obtain a solid powdery 4-methoxybenzimidazole sodium sulfinate initiator.

[0028] Example 1 200 mmol of cyclohexene oxide, 0.1 mmol of triethyl boron, 0.1 mmol of 1,4-butanediol and 0.2 mmol of sodium benzimidazole sulfinate initiator prepared in Preparation Example 1 were added to a high-pressure reactor, carbon dioxide was introduced into the reactor to replace the air in the reactor for 10 minutes, and then the pressure was increased to 1.5 MPa of carbon dioxide reaction pressure, the reaction temperature was set to 80°C, and the polymerization reaction lasted for 8 hours. After the polymerization reaction was completed, a few drops of glacial acetic acid were added to the reaction system after the reactor was cooled to room temperature, and then methanol was added to it at room temperature to repeatedly precipitate the purified product, and the purified product was placed in a vacuum oven at 40°C and dried for 12 hours.

[0029] Example 2 200 mmol of cyclohexene oxide, 0.1 mmol of triethyl boron, 0.1 mmol of 1,4-butanediol and 0.2 mmol of sodium benzimidazole sulfinate initiator prepared in Preparation Example 2 were added to a high-pressure reactor, carbon dioxide was introduced into the reactor to replace the air in the reactor for 10 minutes, and then the pressure was increased to 1.5 MPa of carbon dioxide reaction pressure, the reaction temperature was set to 80°C, and the polymerization reaction lasted for 8 hours. After the polymerization reaction was completed, a few drops of glacial acetic acid were added to the reaction system after the reactor was cooled to room temperature, and then methanol was added to it at room temperature to repeatedly precipitate the purified product, and the purified product was placed in a vacuum oven at 40°C and dried for 12 hours.

[0030] Example 3 200 mmol of cyclohexene oxide, 0.1 mmol of triethyl boron, 0.1 mmol of 1,4-butanediol and 0.2 mmol of sodium benzimidazole sulfinate initiator prepared in Preparation Example 3 were added to a high-pressure reactor, carbon dioxide was introduced into the reactor to replace the air in the reactor for 10 minutes, and then the pressure was increased to 1.5 MPa of carbon dioxide reaction pressure, the reaction temperature was set to 80°C, and the polymerization reaction lasted for 8 hours. After the polymerization reaction was completed, a few drops of glacial acetic acid were added to the reaction system after the reactor was cooled to room temperature, and then methanol was added to it at room temperature to repeatedly precipitate and purify the product, and the purified product was placed in a vacuum oven at 40°C and dried for 12 hours.

[0031] Example 4 300 mmol of cyclohexene oxide, 0.0125 mmol of triethyl boron, 0.1 mmol of 1,4-butanediol and 0.1 mmol of sodium benzimidazole sulfinate initiator prepared in Preparation Example 1 were added to a high-pressure reactor, carbon dioxide was introduced into the reactor to replace the air in the reactor for 10 minutes, and then the pressure was increased to 1 MPa of carbon dioxide reaction pressure, the reaction temperature was set to 40°C, and the polymerization reaction lasted for 8 hours. After the polymerization reaction was completed, a few drops of glacial acetic acid were added to the reaction system after the reactor was cooled to room temperature, and then methanol was added to it at room temperature to repeatedly precipitate and purify the product, and the purified product was placed in a vacuum oven at 40°C and dried for 12 hours.

[0032] Comparative Example 1 200mmol of cyclohexene oxide, 0.1mmol of triethyl boron, 0.1mmol of 1,4-butanediol and 0.2mmol of sodium benzenesulfinate initiator were added to a high-pressure reactor, carbon dioxide was introduced into the reactor to replace the air in the reactor for 10 minutes, and then the pressure was increased to 1.5MPa. The reaction temperature was set to 80°C, and the polymerization reaction lasted for 8 hours. After the polymerization reaction was completed, a few drops of glacial acetic acid were added to the reaction system after the reactor was cooled to room temperature, and then methanol was added to it at room temperature to repeatedly precipitate and purify the product, and the purified product was placed in a vacuum oven at 40°C and dried for 12 hours.

[0033] Comparative Example 2 200mmol of cyclohexene oxide, 0.1mmol of triethyl boron, 0.1mmol of 1,4-butanediol and 0.2mmol of sodium methanesulfinate initiator were added to a high-pressure reactor, carbon dioxide was introduced into the reactor to replace the air in the reactor for 10 minutes, and then the pressure was increased to 1.5MPa. The reaction temperature was set to 80°C, and the polymerization reaction lasted for 8 hours. After the polymerization reaction was completed, a few drops of glacial acetic acid were added to the reaction system after the reactor was cooled to room temperature, and then methanol was added to it at room temperature to repeatedly precipitate the purified product, and the purified product was placed in a vacuum oven at 40°C and dried for 12 hours.

[0034] Comparative Example 3 200mmol of cyclohexene oxide, 0.1mmol of triethyl boron, 0.1mmol of 1,4-butanediol and 0.2mmol of bis(triphenylphosphorane)ammonium chloride initiator were added to a high-pressure reactor, carbon dioxide was introduced into the reactor to replace the air in the reactor for 10 minutes, and then the pressure was increased to 1.5MPa. The reaction temperature was set to 80°C, and the polymerization reaction lasted for 8 hours. After the polymerization reaction was completed, a few drops of glacial acetic acid were added to the reaction system after the reactor was cooled to room temperature, and then methanol was added to it at room temperature to repeatedly precipitate the purified product, and the purified product was placed in a vacuum oven at 40°C and dried for 12 hours.

[0035] Performance Testing The hydroxyl value of the product was determined by hydroxyl value titration method, and the number average molecular weight and dispersity index of the polymer were determined. The test results of Examples 1-4 and Comparative Examples 1-3 are shown in Table 1 below.

[0036] Table 1 Test results of Examples 1-4 and Comparative Examples 1-3 Number average molecular weight Proportional Dispersion Index (PDI) Hydroxyl value Example 1 2220 1.1 247 Example 2 2450 1.1 239 Example 3 2640 1.2 268 Example 4 2140 1.2 228 Comparative Example 1 1630 1.4 161 Comparative Example 2 1440 1.3 153 Comparative Example 3 1480 1.6 136 By comparing Examples 1-3 and Comparative Examples 1 and 2, it can be seen that, when other polymerization conditions remain unchanged, the sodium benzimidazole sulfinate initiator prepared in the present application can obtain a polycarbonate polyol product with a higher molecular weight and a narrower molecular weight distribution in a shorter time compared to commercially available sodium sulfinate initiators.

[0037] By comparing Examples 1-3 and Comparative Example 3, it can be seen that, when other polymerization conditions remain unchanged, the sodium benzimidazole sulfinate initiator synthesized by the present invention can significantly increase the molecular weight of the polycarbonate polyol product in a shorter time, and the molecular weight distribution is narrower than that of the traditional organic ammonium salt initiator.

[0038] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a carbon dioxide-based polycarbonate polyol, characterized in that: The following steps are involved: (1) adding cyclohexene oxide, an organic boron compound, a sodium benzimidazole sulfinate initiator, and a chain transfer agent into a high-pressure reactor, and introducing carbon dioxide to carry out copolymerization reaction; (2) After the reaction is completed, the heating is stopped and the reaction system is cooled. A small amount of acid is added to the reaction system to terminate the reaction. The product is then purified by multiple precipitations and dried using a solvent to obtain pure carbon dioxide-based polycarbonate polyol.

2. The method for preparing a carbon dioxide-based polycarbonate polyol according to claim 1, characterized in that: The sodium benzimidazole sulfinate initiator is prepared by the following method: adding different substituted benzimidazole sulfonyl chlorides, sodium sulfite and sodium bicarbonate into water, stirring, dissolving and reacting under heating conditions, and after the reaction is completed, recrystallizing and filtering to obtain the sodium benzimidazole sulfinate initiator.

3. The method for preparing a carbon dioxide-based polycarbonate polyol according to claim 2, characterized in that: The differently substituted benzimidazole sulfonyl chloride is selected from one or more of benzimidazole sulfonyl chloride, pentafluorobenzimidazole sulfonyl chloride and 4-methoxybenzimidazole sulfonyl chloride.

4. The method for preparing a carbon dioxide-based polycarbonate polyol according to claim 2, characterized in that: The molar ratio of the differently substituted benzimidazole sulfonyl chloride, sodium sulfite, sodium bicarbonate and water is 1:2:2:

20.

5. The method for preparing a carbon dioxide-based polycarbonate polyol according to claim 1, characterized in that: In the step (1), the molar ratio of the organic boron compound to the sodium benzimidazole sulfinate initiator is 1:1 to 1:

8.

6. The method for preparing a carbon dioxide-based polycarbonate polyol according to claim 5, characterized in that: The chain transfer agent is a polyol or a polycarboxylic acid, and the functionality is not less than 2.

7. The method for preparing a carbon dioxide-based polycarbonate polyol according to claim 6, characterized in that: The organic boron compound is selected from one or more of triphenylboron, triethylboron, boron trichloride or boron trifluoride.

8. The method for preparing a carbon dioxide-based polycarbonate polyol according to claim 7, characterized in that: In the step (1), the molar ratio of the cyclohexene oxide to the sodium benzimidazole sulfinate initiator is 1000:1 to 3000:

1.

9. The method for preparing a carbon dioxide-based polycarbonate polyol according to claim 1, characterized in that: In the step (1), the copolymerization reaction pressure is 0.5-2.0 MPa, and the reaction temperature is 40-80°C.