Method for preparing 1, 4-dioxane compound by degrading polyethylene glycol

Abstract

The invention discloses a method for preparing a 1, 4-dioxane compound by degrading polyethylene glycol, and belongs to the technical field of chemical catalytic degradation. According to the invention, the ionic liquid is used as a catalyst and can form a dihydrogen bond with ether group O and hydroxyl group H of a polyethylene glycol compound, so that polyethylene glycol is degraded. According to the degradation process disclosed by the invention, high-efficiency conversion under a mild condition is realized without participation of a metal catalyst, the reaction process is simplified, and generation of byproducts is effectively avoided; by virtue of the non-volatile characteristic of the ionic liquid, the risk of environmental pollution in the reaction process is reduced; meanwhile, the designability of the ionic liquid provides a space for optimizing the catalytic performance, and the reusability of the ionic liquid further improves the economical efficiency and environmental protection benefits of the ionic liquid. The method for degrading and preparing the 1, 4-dioxane compound has the advantages of no organic solvent, no metal participation, mild conditions, high conversion efficiency, no by-product and simplicity in separation, and has very high industrial application value.

Description

Technical Field

[0001] The invention relates to the technical field of chemical catalytic degradation, and in particular to a method for preparing 1,4-dioxane compounds by degrading polyethylene glycol. Background Art

[0002] Polyethylene glycol (PEG), as a highly functional water-soluble polymer material, is used in many key fields such as medicine, cosmetics, textiles and paints, demonstrating its indispensable practical value. However, behind this wide application, millions of tons of PEG waste are generated every year, posing a significant pollution threat to natural water bodies, air and soil, highlighting the urgency and importance of PEG waste treatment.

[0003] However, traditional polyethylene glycol waste treatment strategies rely heavily on incineration or landfill or water disposal, which leads to environmental problems such as the release of large amounts of carbon dioxide, increased greenhouse gas emissions, and water pollution. Therefore, exploring the chemical degradation pathways of PEG and converting it into high-value-added chemicals is not only a positive response to environmental challenges, but also an important part of promoting the development of a circular economy.

[0004] In recent years, a series of PEG degradation strategies have been developed and reported. For example, thermal oxidation and photooxidation PEG degradation strategies. Among them, although there has been some progress in thermal oxidation and photooxidation technology, they are mainly carried out by catalyzing the random breakage of CO and CC bonds in PEG, resulting in the formation of a large number of oligomer products, which are difficult to be directly applied to the production of high-value chemicals. Although various new methods such as metal catalysts and hydrosilation catalysts have successfully achieved the conversion to chemicals such as ethane, chloroesters, and ethylene glycol diesters by catalyzing the breakage of CO bonds in PEG, they have opened up new paths for the degradation of PEG. However, the limitations of these methods cannot be ignored: complex separation processes, harsh reaction conditions, and dependence on metal-based composite catalysts and halogen reagents have hindered their large-scale application to a certain extent.

[0005] Therefore, how to provide a new degradation method to efficiently decompose polyethylene glycol into valuable compounds while minimizing the environmental burden has become a technical problem that technicians in this field urgently need to overcome. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing 1,4-dioxane compounds by degrading polyethylene glycol, so as to overcome the limitations of the traditional method for degrading polyethylene glycol.

[0007] The present invention solves the above technical problems through the following technical solutions: A method for preparing 1,4-dioxane compounds by degrading polyethylene glycol comprises the following steps: The ionic liquid is used as a catalyst to carry out a degradation reaction of polyethylene glycol to obtain a 1,4-dioxane compound; wherein the ionic liquid includes cations and anions, and during the degradation reaction, the cations and anions respectively form double hydrogen bonds with the ether group O and the hydroxyl group H of the polyethylene glycol.

[0008] Furthermore, the cation is at least one of an alkyl imidazolium cation and a quaternary ammonium salt cation modified with a functional group, and the functional group is specifically -OH; and the anion is trifluoromethanesulfonate.

[0009] Furthermore, the ionic liquid is any one of the ionic liquids of the following structures: .

[0011] Furthermore, every 1 mmol of ionic liquid corresponds to 100 mg of polyethylene glycol.

[0012] Furthermore, the degradation reaction temperature is 80°C ~ 200°C, and the time is 2 ~ 24 h.

[0013] Furthermore, the degradation reaction temperature is 120 ~ 130 °C, and the time is 8 ~ 12 h.

[0014] Furthermore, the relative molecular mass of polyethylene glycol is 200 g / mol to 1000 g / mol.

[0015] The ionic liquid is used as a catalyst in the above-mentioned method for preparing 1,4-dioxane by degrading polyethylene glycol. The ionic liquid includes cations and anions, which form double hydrogen bonds with the ether group O and the hydroxyl group H of the polyethylene glycol respectively.

[0016] A catalyst product comprises an ionic liquid, the ionic liquid comprises a cation and an anion, the cation is at least one of an alkyl imidazole cation and a quaternary ammonium salt cation modified with a functional group, the functional group is specifically -OH, and the anion is trifluoromethanesulfonate.

[0017] Furthermore, the ionic liquid is any one of the ionic liquids of the following structures: .

[0019] Compared with the prior art, the positive and progressive effects of the present invention are: The method for preparing 1,4-dioxane compounds by degrading polyethylene glycol provided by the present invention adopts ionic liquid as a catalyst, which can form double hydrogen bonds with the ether group O and the hydroxyl group H of the polyethylene glycol compound, thereby degrading polyethylene glycol. The degradation process of the present invention realizes efficient conversion under mild conditions without the participation of metal catalysts, simplifies the reaction process, and effectively avoids the generation of by-products; relying on the non-volatile characteristics of ionic liquids, the environmental pollution risk during the reaction process is reduced; at the same time, the designability of ionic liquids provides space for optimizing catalytic performance, and its reusability further improves its economic and environmental benefits. The method for degrading and preparing 1,4-dioxane compounds has the advantages of no organic solvent, no metal participation, mild conditions, high conversion efficiency, no by-products, and simple separation, and has strong industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is a schematic diagram of the reaction equation for preparing 1,4-dioxane compound by using ionic liquid to catalyze the degradation of polyethylene glycol in the present invention; Figure 2 is the GC-MS spectrogram of Example 1; Figure 3 It is a detailed schematic diagram of the first peak in the GC-MS spectrum of Example 1; Figure 4 It is a detailed schematic diagram of the second peak in the GC-MS spectrum of Example 1; Figure 5 This is a detailed schematic diagram of the third peak in the GC-MS spectrum of Example 1. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings, which are intended to explain the present invention rather than to limit it.

[0023] See also Figure 1 , the reaction equation for preparing 1,4-dioxane compounds by using ionic liquid to catalyze the degradation of polyethylene glycol.

[0024] The method for preparing 1,4-dioxane compound by degrading polyethylene glycol provided by the present invention comprises: using ionic liquid as catalyst, performing degradation reaction of polyethylene glycol to obtain 1,4-dioxane compound; wherein the ionic liquid comprises cations and anions, and during the degradation reaction, the cations and anions respectively form double hydrogen bonds with the ether group O and the hydroxyl group H of the polyethylene glycol. The reaction temperature is 80-200°C; specifically 120-130°C; the reaction time is 2-24 hours; specifically 8-12 hours.

[0025] The degree of polymerization of the above polyethylene glycol is mainly 3-4, 6-7, 9-10, 12-13, 16-17, specifically 6-7, more specifically 6.4; The relative molecular mass of the polyethylene glycol is 200 g / mol to 1000 g / mol, specifically 200 g / mol, 400 g / mol, 600 g / mol, 800 g / mol, 1000 g / mol, and more specifically 400 g / mol.

[0026] In the chemical reaction step, the feeding amounts of the ionic liquid and the polyethylene glycol compound are 0.4 mmol and 40 mg respectively. Specifically, the anion is selected from trifluoromethanesulfonate ([OTf]); Specifically, the cation is selected from an alkyl imidazolium cation modified with a functional group; the functional group is specifically selected from -OH; and the ionic liquid is any one of the ionic liquids of the following structures:

[0027] Specifically, every 1 mmol of ionic liquid corresponds to 100 mg of polyethylene glycol.

[0028] The method specifically comprises the following steps: a certain amount of ionic liquid and polyethylene glycol are placed in a thick-walled pressure-resistant glass reaction tube, sealed, placed in an oil bath, and reacted at a desired temperature for a certain time to promote the degradation reaction. When the reaction is completed, the reactor is cooled in ice water. The product phase (upper layer liquid) and the ionic liquid phase are collected separately.

[0029] Gas chromatography-mass spectrometry and gas chromatography were used to carry out qualitative and quantitative analysis of the products.

[0030] In the method for preparing 1,4-dioxane by catalyzing the degradation of polyethylene glycol using ionic liquid provided by the present invention, the ionic liquid is used as a catalyst, which is a liquid salt composed of organic cations and inorganic / organic anions, has strong solubility, no volatility, high thermal and chemical stability, strong designability, and strong repeatability. The method has the advantages of no organic solvent, no metal participation, mild conditions, high conversion efficiency, no by-products, simple separation, etc., and has strong industrial application value.

[0031] The present invention provides an application of an ionic liquid as a catalyst for use in the above-mentioned method for preparing 1,4-dioxane by degrading polyethylene glycol. The ionic liquid comprises cations and anions, which respectively form double hydrogen bonds with the ether group O and the hydroxyl group H of the polyethylene glycol.

[0032] The ionic liquid catalyst has mild catalytic performance, no pollution to the environment, and is easy to recycle. The degradation reaction of polyethylene glycol compounds with different polymerization degrees is carried out to obtain 1,4-dioxane compounds. The reaction process is simple and the catalytic activity is good.

[0033] The present invention also provides a catalyst product, including an ionic liquid, the ionic liquid including a cation and an anion, the cation is at least one of an alkyl imidazole cation modified with a functional group and a quaternary ammonium salt cation, the functional group is specifically -OH, and the anion is trifluoromethanesulfonate. Specifically, the ionic liquid is any one of the ionic liquids with the following structures: .

[0035] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention.

[0036] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0037] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0038] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the existence of other devices / apparatuses before or after the combination device / apparatus or the insertion of other devices / apparatuses between these explicitly mentioned two devices / apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0039] Example 1 Using ionic liquid [HO-EtMIm][OTf] as catalyst, polyethylene glycol with a relative molecular mass of about 400 g / mol was degraded to prepare 1,4-dioxane compounds with a degree of polymerization of 6~7.

[0040] 0.4 mmol of ionic liquid [HO-EtMIm][OTf] and 40 mg of PEG (Mn=400 g / mol) were placed in a 15 ml thick-walled pressure-resistant glass reaction tube, sealed, placed in an oil bath, and reacted at a preset temperature (130 °C) for 12 hours. After the reaction, the reactor was cooled to 0 °C with an ice-water bath. After cooling, n-dodecane was added to the reaction mixture as an internal standard and ether as a solvent, and the product phase (upper liquid) and the ionic liquid phase were collected separately. The product was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography. See Figure 2 , is the GC-MS spectrum of the product phase of preparing 1,4-dioxane by degradation of polyethylene glycol catalyzed by ionic liquid in Example 1, proving that the product is a 1,4-dioxane compound. According to the analysis results, the selectivity of 1,4-dioxane is 100% and the yield is 96%.

[0041] Example 2 The ionic liquid [HO-EtMIm][OTf] was used as a catalyst to catalyze the degradation of polyethylene glycol with a relative molecular mass of about 200 g / mol to prepare 1,4-dioxane.

[0042] 0.4 mmol of ionic liquid [HO-EtMIm][OTf] and 40 mg of PEG (Mn=200 g / mol) were placed in a 15 ml thick-walled pressure-resistant glass reaction tube, sealed, placed in an oil bath, and reacted at a preset temperature (130 ℃) for 12 hours. After the reaction, the reactor was cooled to 0 ℃ with an ice-water bath. After cooling, n-dodecane was added to the reaction mixture as an internal standard and ether as a solvent, and the product phase (upper liquid) and the ionic liquid phase were collected separately. The product was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography. According to the analysis results, the selectivity of 1,4-dioxane was 100% and the yield was 97%.

[0043] Example 3 The ionic liquid [HO-EtN 111 ][OTf] was used as a catalyst to catalyze the degradation of polyethylene glycol with a relative molecular mass of about 400 g / mol to prepare 1,4-dioxane compounds.

[0044] 0.4 mmol of ionic liquid [HO-EtN 111][OTf] and 40 mg of PEG (Mn=400 g / mol) were placed in a 15 ml thick-walled pressure-resistant glass reaction tube, sealed, placed in an oil bath, and reacted at a preset temperature (130 °C) for 12 hours. After the reaction, the reactor was cooled to 0 °C with an ice-water bath. After cooling, n-dodecane was added to the reaction mixture as an internal standard and ether as a solvent, and the product phase (upper liquid) and ionic liquid phase were collected separately. The product was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography. According to the analysis results, the selectivity of 1,4-dioxane was 100% and the yield was 20%.

[0045] Example 4 The ionic liquid [HO-EtMIm][OTf] was used as a catalyst to catalyze the degradation of polyethylene glycol with a relative molecular mass of about 600 g / mol to prepare 1,4-dioxane.

[0046] 0.4 mmol of ionic liquid [HO-EtMIm][OTf] and 40 mg of PEG (Mn=600 g / mol) were placed in a 15 ml thick-walled pressure-resistant glass reaction tube, sealed, placed in an oil bath, and reacted at a preset temperature (130 ℃) for 15 hours. After the reaction, the reactor was cooled to 0 ℃ with an ice-water bath. After cooling, n-dodecane was added to the reaction mixture as an internal standard and ether as a solvent, and the product phase (upper liquid) and the ionic liquid phase were collected separately. The product was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography. According to the analysis results, the selectivity of 1,4-dioxane was 100% and the yield was 97%.

[0047] Example 5 The ionic liquid [HO-EtMIm][OTf] was used as a catalyst to catalyze the degradation of polyethylene glycol with a relative molecular mass of about 800 g / mol to prepare 1,4-dioxane.

[0048] 0.4 mmol of ionic liquid [HO-EtMIm][OTf] and 40 mg of PEG (Mn=800 g / mol) were placed in a 15 ml thick-walled pressure-resistant glass reaction tube, sealed, placed in an oil bath, and reacted at a preset temperature (130 ℃) for 15 hours. After the reaction, the reactor was cooled to 0 ℃ with an ice-water bath. After cooling, n-dodecane was added to the reaction mixture as an internal standard and ether as a solvent, and the product phase (upper liquid) and the ionic liquid phase were collected separately. The product was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography. According to the analysis results, the selectivity of 1,4-dioxane was 100% and the yield was 97%.

[0049] Example 6 The ionic liquid [HO-EtMIm][OTf] was used as a catalyst to catalyze the degradation of polyethylene glycol with a relative molecular mass of about 1000 g / mol to prepare 1,4-dioxane.

[0050] 0.4 mmol of ionic liquid [HO-EtMIm][OTf] and 40 mg of PEG (Mn=1000 g / mol) were placed in a 15 ml thick-walled pressure-resistant glass reaction tube, sealed, placed in an oil bath, and reacted at a preset temperature (130 ℃) for 15 hours. After the reaction, the reactor was cooled to 0 ℃ with an ice-water bath. After cooling, n-dodecane was added to the reaction mixture as an internal standard and ether as a solvent, and the product phase (upper liquid) and the ionic liquid phase were collected separately. The product was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography. According to the analysis results, the selectivity of 1,4-dioxane was 100% and the yield was 96%.

[0051] In summary, the method for preparing 1,4-dioxane compounds by degrading polyethylene glycol provided by the present invention uses ionic liquid as a catalyst, which can form double hydrogen bonds with the ether group O and the hydroxyl group H of the polyethylene glycol compound, thereby degrading the polyethylene glycol.

[0052] The method is used to degrade and prepare 1,4-dioxane compounds. The entire degradation process does not require the intervention of metal catalysts, which not only simplifies the process flow, but also avoids environmental problems that may be caused by metal residues; high-efficiency conversion can be achieved under relatively mild reaction conditions, reducing energy consumption and operating difficulty; the non-volatile characteristics of ionic liquids significantly reduce the emission of volatile organic compounds and reduce the risk of environmental pollution; by precisely controlling the degradation path, the generation of by-products is effectively avoided, and the purity and yield of the target product are improved; the reaction system is simple, and the product is easy to separate and purify, further improving the production efficiency; the designability and reusability of ionic liquids not only optimize the catalytic performance, but also significantly reduce the production cost, and enhance the economy and sustainability of the technology. This method provides a new idea for solving the problem of PEG degradation and is expected to play an important role in the future chemical industry.

[0053] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing 1,4-dioxane compounds by degradation of polyethylene glycol, characterized in that: The following steps are involved: The ionic liquid is used as a catalyst to carry out a degradation reaction of polyethylene glycol to obtain a 1,4-dioxane compound; wherein the ionic liquid includes cations and anions, and during the degradation reaction, the cations and anions respectively form double hydrogen bonds with the ether group O and the hydroxyl group H of the polyethylene glycol.

2. The method for preparing 1,4-dioxane compound by degradation of polyethylene glycol according to claim 1, characterized in that: The cation is at least one of an alkyl imidazole cation and a quaternary ammonium salt cation modified with a functional group, and the functional group is specifically -OH; and the anion is trifluoromethanesulfonate.

3. The method for preparing 1,4-dioxane compound by degradation of polyethylene glycol according to claim 1, characterized in that: The ionic liquid is any one of the ionic liquids with the following structures: 。 4. The method for preparing 1,4-dioxane compound by degrading polyethylene glycol according to claim 1, characterized in that: Each 1 mmol of ionic liquid corresponds to 100 mg of polyethylene glycol.

5. The method for preparing 1,4-dioxane compound by degrading polyethylene glycol according to claim 1, characterized in that: The temperature of the degradation reaction is 80℃ ~ 200℃, and the time is 2 ~ 24 h.

6. The method for preparing 1,4-dioxane compound by degradation of polyethylene glycol according to claim 5, characterized in that: The degradation reaction temperature is 120 ~ 130 ℃ and the time is 8 ~ 12 h.

7. The method for preparing 1,4-dioxane compound by degrading polyethylene glycol according to claim 1, characterized in that: The relative molecular mass of polyethylene glycol is 200 g / mol ~ 1000 g / mol.

8. Use of ionic liquid as catalyst, characterized in that: Used in the method for preparing 1,4-dioxane by degrading polyethylene glycol as claimed in any one of claims 1 to 7, the ionic liquid comprises cations and anions, which respectively form double hydrogen bonds with the ether group O and the hydroxyl group H of the polyethylene glycol.

9. A catalyst product, characterized in that: The catalyst product comprises an ionic liquid, which comprises a cation and an anion. The cation is at least one of an alkyl imidazole cation modified with a functional group and a quaternary ammonium salt cation, wherein the functional group is specifically -OH, and the anion is trifluoromethanesulfonate.

10. A catalyst product according to claim 9, characterized in that: The ionic liquid is any one of the ionic liquids with the following structures: 。

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