An ionic liquid containing boron-containing oxygen ring and benzene ring, a preparation method and application thereof

Abstract

The application discloses an ionic liquid containing a boron-containing oxygen ring and a benzene ring, a preparation method and application, and the ionic liquid is obtained by the reaction of tris(trimethylsilyl) borate, dichloroethylene, 4-p-chlorophenyl imidazoline and diisopropylamine; the ionic liquid can be used for alcoholysis of PET to obtain DMT, improve the conversion rate of DMT, and has a significant prospect in the application of PET degradation and recycling of DMT.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and in particular to an ionic liquid containing boron-oxygen rings and benzene rings, its preparation method, and its applications. Background Technology

[0002] In recent years, due to rapid industrial development and improved living standards, people have used plastic packaging products and plastic bags everywhere for convenience. While this has made life easier, it has also placed a heavy burden on the Earth and caused environmental pollution; white pollution has swept the globe. If buried underground, plastic bags take about 200 years to decompose, which will adversely affect the soil's pH level, deteriorate the soil environment, and seriously affect crop growth.

[0003] Because plastic bags are mostly made from non-renewable and non-degradable materials, their stable structure makes them difficult for natural microorganisms to break down, causing them to remain in the natural environment for extended periods. This poses a significant threat to the land, altering soil pH, severely polluting the soil, hindering crop nutrient and water absorption, leading to reduced agricultural yields, and impacting the sustainable use of land. Furthermore, the harmful smoke and toxic gases produced by incineration also pollute the atmosphere. With continuous population growth and increasing demand for plastics, the trend of plastic waste accumulation will only accelerate, as these materials do not easily degrade and cannot be eliminated from the environment.

[0004] Therefore, reducing the pollution of plastic waste to the environment and improving the recycling rate of plastics to reduce the burden on the earth and human beings has become a major issue. Finding a new material that can enable plastics to degrade and be recycled quickly has become crucial.

[0005] Ionic liquids are typically composed of cations and anions and exist in a liquid state at room temperature or operating temperature. Compared to traditional organic solvents, ionic liquids possess superior properties. In recent years, ionic liquids have been a research focus as a novel green reaction solvent and catalyst. In existing technologies, the catalytic alcoholysis of PET (polyethylene terephthalate) using methanol as a solvent involves high temperatures and high energy consumption in batch processing, but there is still room for improvement in the conversion rate of DMT (dimethyl terephthalate). Therefore, it is necessary to develop an ionic liquid with stronger catalytic activity. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide ionic liquids containing boron-oxygen rings and benzene rings, preparation methods and applications, so as to improve the catalytic activity of ionic liquids and further improve the conversion rate of DMT obtained by catalytic alcoholysis.

[0007] Therefore, the solution of the present invention is as follows:

[0008] An ionic liquid containing a boron-oxygen ring and a benzene ring has the following structural formula:

[0009]

[0010] This invention proposes a method for preparing ionic liquids with the above-mentioned structural formula, comprising the following steps:

[0011] S1. Add dichloroethylene to a solution of tris(trimethylsilane)borate and react at 50-70°C for 2-5 hours to obtain intermediate I;

[0012] S2. Add 4-p-chlorophenylimidazoline to intermediate I and react at 60-90℃ for 8-10 h to obtain intermediate II;

[0013] S3. Add diisopropylamine to intermediate II and react at 120-150℃ for 10-20 h to obtain an ionic liquid.

[0014] Further, in step S1, the tris(trimethylsilane)borate solution is cooled to 0-5°C, and dichloroethylene is added dropwise over a period of 0.5-2 hours.

[0015] Further, in step S1, the molar ratio of dichloroethylene to tris(trimethylsilane)borate is 1:(1.5-4).

[0016] Further, in step S1, the solvent in the tri(trimethylsilane)borate solution is one of N,N-dimethylformamide, tetrahydrofuran, and carbonates; the dichloroethylene is diluted with one of cyclohexane, n-hexane, ethyl acetate, and carbonates.

[0017] Further, in step S2, the molar ratio of 4-p-chlorophenylimidazoline to intermediate I is 1:(1.5-3).

[0018] Further, in step S2, the 4-p-chlorophenylimidazoline is diluted with one of dioxane, cyclohexane, and carbonate.

[0019] Further, in step S3, the molar ratio of intermediate II to diisopropylamine is 1:(2-5).

[0020] Another object of the present invention is to propose the application of the above-described ionic liquid in the alcoholysis of PET.

[0021] Furthermore, the amount of ionic liquid added is 0.3-1 wt% of PET, and alcoholysis is carried out at 120-150°C for 2-3 hours.

[0022] Compared with the prior art, the advantages of this invention are:

[0023] 1. This invention provides an ionic liquid containing boron-oxygen rings and benzene rings, which contains organic anions and organic cations. It exhibits excellent degradation effects in the alcoholysis of PET, thus broadening the application scope of ionic liquids in the alcoholysis of PET.

[0024] 2. The method for preparing ionic liquids of boron-oxygen rings and benzene rings provided by the present invention can obtain ionic liquids with a purity of more than 99% and a yield of more than 80% through a three-step reaction, which can be fully used for industrial-scale production.

[0025] 3. The ionic liquids of boron-oxygen ring and benzene ring proposed in this invention have low addition amount, low energy consumption, high alcoholysis efficiency and further improved DMT conversion rate when applied to PET alcoholysis. They have significant economic value for industrial PET alcoholysis and DMT recovery, and are green, with considerable social and economic benefits. Detailed Implementation

[0026] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described in this specification are merely for explaining the invention and are not intended to limit the invention.

[0027] In one specific embodiment of the present invention, an ionic liquid containing a boron-oxygen ring and a benzene ring is proposed, having the following structural formula:

[0028]

[0029] In another embodiment, a method for preparing the above-structured ionic liquid is proposed, comprising the following steps:

[0030] S1. Add dichloroethylene to a solution of tris(trimethylsilane)borate and react at 50-70°C for 2-5 hours to obtain intermediate I;

[0031] S2. Add 4-p-chlorophenylimidazoline to intermediate I and react at 60-90℃ for 8-10 h to obtain intermediate II;

[0032] S3. Add diisopropylamine to intermediate II and react at 120-150℃ for 10-20 h to obtain an ionic liquid.

[0033] Specifically, the synthetic route is as follows:

[0034]

[0035] In a preferred embodiment, to control the temperature, in step S1, the tris(trimethylsilane)borate solution is cooled to 0-5°C, and dichloroethylene is added dropwise over a period of 0.5-2 hours. The solvent in the tris(trimethylsilane)borate solution is one of N,N-dimethylformamide, tetrahydrofuran, and carbonates; the dichloroethylene is diluted using one of cyclohexane, n-hexane, ethyl acetate, and carbonates. To avoid introducing impurities, the tris(trimethylsilane)borate dilution process is carried out under an inert gas atmosphere.

[0036] In a preferred embodiment, in step S1, the molar ratio of dichloroethylene to tris(trimethylsilane)borate is 1:(1.5-4), preferably 1:(2-3); in step S2, the molar ratio of 4-p-chlorophenylimidazoline to intermediate I is 1:(1.5-3), preferably 1:(1.5-2); in step S3, the molar ratio of intermediate II to diisopropylamine is 1:(2-5), preferably 1:(3-4). This preparation method yields an ionic liquid with a purity greater than 99% and a yield greater than 80%.

[0037] In a preferred embodiment, in step S2, the 4-p-chlorophenylimidazoline is diluted with one of dioxane, cyclohexane, and carbonate, and then added dropwise to intermediate I to control the reaction temperature.

[0038] In another embodiment, the application of the ionic liquid with the above structure in the alcoholysis of PET is proposed. The amount of ionic liquid added is 0.3-1 wt% of PET, and alcoholysis is carried out at 120-150°C for 2-3 hours. This can efficiently decompose PET to generate DMT, improving the DMT recovery rate to 100%.

[0039] In this plan, all raw materials are commercially available. Without a description of the preparation of the raw materials, they are considered as commercially available standards or common concentrations or purities.

[0040] Example 1

[0041] Under argon protection, 1 mol of tris(trimethylsilane)borate was dissolved and diluted in 100 ml of dimethyl carbonate and added to a three-necked flask. The mixture was then cooled to 5°C. Next, 0.25 mol of dichloroethylene dissolved in 100 ml of n-hexane was added slowly dropwise to a constant-pressure dropping funnel with mechanical stirring. After 1 hour of addition, the temperature was raised to 66°C and maintained at this temperature with stirring for 3 hours. After the reaction was complete, intermediate product I was obtained. After extraction and rotary evaporation to obtain purified intermediate I, the next reaction was carried out using 200... 0.33 mol of 4-p-chlorophenylimidazoline diluted with dioxane was added to a constant-pressure dropping funnel. After the addition was complete, the temperature was raised to 80°C, and the reaction was carried out for 9 hours to obtain imidazoline intermediate II containing boron-oxygen rings and benzene rings. The product was then transferred to a continuous pipeline reactor, and 2 mol of diisopropylamine was added. The reactor was heated to 140°C and reacted continuously for 15 hours to obtain the ionic liquid capable of degrading plastic waste. The final product was an ionic liquid with a purity of 99.5% and a yield of 82.7% (based on the amount of dichloroethylene added, the same below). The structure of the product was confirmed by 1H NMR spectroscopy, confirming it as the ionic liquid containing boron-oxygen rings and benzene rings of this invention.

[0042] Example 2

[0043] Under nitrogen protection, 1 mol of tris(trimethylsilane)borate was dissolved and diluted in 90 mL of tetrahydrofuran and added to a three-necked flask. The temperature was then lowered to 8 °C. 0.67 mol of dichloroethylene dissolved in 40 mL of ethyl acetate was then added slowly dropwise to a constant-pressure dropping funnel with mechanical stirring. After the addition was complete in 0.5 h, the temperature was raised to 55 °C and maintained at this temperature with stirring for 4 h. After the reaction was complete, intermediate I was obtained. The purified intermediate was obtained by extraction and rotary evaporation before proceeding to the next step of the reaction. 0.4 mol of 4-p-chlorophenylimidazoline, diluted with 120 ml of dimethyl carbonate, was added to a constant-pressure dropping funnel. After the addition was complete, the temperature was raised to 90 °C, and the reaction was carried out for 8 hours to obtain imidazoline intermediate II containing a boron-oxygen ring and a benzene ring. The product was then transferred to a continuous pipeline reactor, and 5 mol of diisopropylamine was added. The reactor was heated to 150 °C and reacted continuously for 10 hours to obtain the ionic liquid capable of degrading plastic waste. The final ionic liquid had a purity of 98.9% and a yield of 83.6%. The structure of the product was confirmed by 1H NMR spectroscopy, confirming it as the ionic liquid containing a boron-oxygen ring and a benzene ring of this invention.

[0044] Example 3

[0045] Under argon protection, 1 mol of tris(trimethylsilane)borate was dissolved and diluted in 110 ml of tetrahydrofuran and added to a three-necked flask. The mixture was then cooled to 5°C. Next, 0.5 mol of dichloroethylene dissolved in 70 ml of n-hexane was added slowly dropwise to a constant-pressure dropping funnel with mechanical stirring. After the addition was completed in 1.5 h, the temperature was raised to 70°C and maintained at this temperature with stirring for 2 h. After the reaction was complete, an intermediate product was obtained. This intermediate was extracted and rotary evaporated to obtain purified intermediate I, which was then used for the next reaction. 0.67 mol of 4-p-chlorophenylimidazoline, diluted with 200 ml of dioxane, was added to a constant-pressure dropping funnel. After the addition was complete, the temperature was raised to 70 °C, and the reaction was allowed to proceed for 10 h to obtain imidazoline intermediate II containing a boron-oxygen ring and a benzene ring. The product was then transferred to a continuous pipeline reactor, and 3 mol of diisopropylamine was added. The reactor was heated to 135 °C and reacted continuously for 17 h to obtain the ionic liquid capable of degrading plastic waste. The final product had a purity of 99.8% and a yield of 86.7%. The structure of the product was confirmed by 1H NMR spectroscopy, confirming it as the ionic liquid containing a boron-oxygen ring and a benzene ring of this invention.

[0046] Example 4

[0047] Under argon protection, 1 mol of tris(trimethylsilane)borate was dissolved and diluted in 140 ml of N,N-dimethylformamide and added to a three-necked flask. The mixture was then cooled to 8°C. Next, 0.33 mol of dichloroethylene dissolved in 130 ml of cyclohexane was added slowly dropwise to a constant-pressure dropping funnel with mechanical stirring. After the addition was completed over 2 hours, the temperature was raised to 50°C and maintained at this temperature with stirring for 5 hours. After the reaction was complete, an intermediate product was obtained. This intermediate was extracted and rotary evaporated to obtain purified intermediate I, which was then further processed. In a one-step reaction, 0.5 mol of 4-p-chlorophenylimidazoline diluted with 160 ml of cyclohexane was added to a constant-pressure dropping funnel. After the addition was complete, the temperature was raised to 85°C, and the reaction was carried out for 14 h to obtain imidazoline intermediate II containing a boron-oxygen ring and a benzene ring. The product was then transferred to a continuous tubular reactor, and 4 mol of diisopropylamine was added. The reactor was heated to 120°C and reacted continuously for 20 h to obtain the ionic liquid capable of degrading plastic waste. The final ionic liquid had a purity of 99.7% and a yield of 86.5%. The structure of the product was confirmed by 1H NMR spectroscopy, confirming it as the ionic liquid containing a boron-oxygen ring and a benzene ring of this invention.

[0048] Experimental Example

[0049] Waste PET bottle flakes and methanol (4:1 by mass) were added to a degradation reactor, followed by the addition of an ionic liquid, and the reaction was initiated at elevated temperature. After the reaction was complete, the mass of the product DMT and the remaining PET were analyzed, and the yield of DMT and the conversion rate of PET were calculated. The reaction conditions and results of the methanol alcoholysis of PET catalyzed by different ionic liquids are detailed in Table 1.

[0050] Table 1:

[0051]

[0052]

[0053] As can be seen from Table 1, using the boron-oxygen ring and benzene ring-containing ionic liquid in this scheme, at a dosage of 0.3-1 wt%, alcoholysis is basically completed in 2-3 hours within the range of 120-150℃, and a high DMT recovery rate can be achieved. In contrast, using commercially available ionic liquids requires a temperature above 150℃ and an alcoholysis time exceeding 3 hours to achieve a PET degradation conversion rate of only 92%, and the DMT recovery rate is below 70%. Relatively speaking, the boron-oxygen ring and benzene ring-containing ionic liquid exhibits significantly stronger catalytic activity, requires less dosage, consumes less energy, has higher alcoholysis efficiency, and further improves DMT conversion rate when applied to PET alcoholysis. Therefore, it has significant economic value for DMT recovery from industrial PET alcoholysis.

[0054] This invention is not limited to the schemes and principles described in the specification and embodiments. Therefore, other effects and alternatives can be easily achieved by those skilled in the art. Thus, without departing from the spirit and scope of the general concept defined by the claims and their equivalents, this invention is not limited to the specific details, representative data and examples shown and described herein.

Claims

1. An ionic liquid containing a boron-oxygen ring and a benzene ring, characterized in that, It has the following structural formula: 。 2. The method for preparing the ionic liquid according to claim 1, characterized in that, Includes the following steps: S1. Add cis-1,2-dichloroethylene to a solution of tris(trimethylsilane)borate and react at 50-70°C for 2-5 h to obtain intermediate I; S2. Add 4-p-chlorophenylimidazoline to intermediate I and react at 60-90℃ for 8-10 h to obtain intermediate II; S3. Add diisopropylamine to intermediate II and react at 120-150℃ for 10-20 h to obtain an ionic liquid.

3. The preparation method according to claim 2, characterized in that, In step S1, the tris(trimethylsilane)borate solution is cooled to 0-5°C, and the cis-1,2-dichloroethylene is added dropwise over a period of 0.5-2 hours.

4. The preparation method according to claim 2, characterized in that, In step S1, the molar ratio of cis-1,2-dichloroethylene to tris(trimethylsilane)borate is 1:(1.5-4).

5. The preparation method according to claim 2, characterized in that, In step S1, the solvent in the tri(trimethylsilane)borate solution is one of N,N-dimethylformamide, tetrahydrofuran, and carbonates; the cis-1,2-dichloroethylene is diluted with one of cyclohexane, n-hexane, ethyl acetate, and carbonates.

6. The preparation method according to claim 2, characterized in that, In step S2, the molar ratio of the amount of 4-p-chlorophenylimidazoline added to intermediate I is 1:(1.5-3).

7. The preparation method according to claim 2, characterized in that, In step S2, the 4-p-chlorophenylimidazoline is diluted with one of dioxane, cyclohexane, and carbonate.

8. The preparation method according to claim 2, characterized in that, In step S3, the molar ratio of diisopropylamine to intermediate II is (2-5):

1.

9. The application of the ionic liquid according to claim 1 in the alcoholysis of PET.

10. The application according to claim 9, characterized in that, The amount of ionic liquid added is 0.3-1 wt% of PET, and alcoholysis is carried out at 120-150℃ for 2-3 hours.

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