Dicarboxylic acid-quaternary ammonium salt synergistic catalytic system and its application in reaction of carbon dioxide and epoxide

Abstract

The application discloses a dicarboxylic acid-quaternary ammonium salt synergistic catalytic system and application thereof in carbon dioxide and epoxide reaction. The catalytic system comprises a dicarboxylic acid compound and a quaternary ammonium salt, wherein the dicarboxylic acid serves as a hydrogen bond donor, the quaternary ammonium salt provides a nucleophilic anion, and both of them synergistically promote epoxide activation and carbon dioxide insertion reaction. The dicarboxylic acid preferably has a first dissociation constant pKa1 of 4.0-7.0, and the quaternary ammonium salt is preferably a bromide or iodide tetraalkylammonium salt. In the presence of the catalytic system, carbon dioxide can be efficiently reacted with various epoxides under relatively mild conditions to generate corresponding cyclic carbonates. The catalytic system has the advantages of simple structure, no metal, high catalytic efficiency, wide substrate application range and the like, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide resource utilization and green catalysis, specifically to a synergistic catalytic system composed of dicarboxylic acid and quaternary ammonium salt, and the application of this catalytic system in the reaction of carbon dioxide and epoxides to prepare cyclic carbonates. Background Technology

[0002] With the acceleration of global industrialization, carbon dioxide emissions have continued to grow, leading to increasingly severe environmental and climate problems. Converting carbon dioxide, a cheap, abundant, and renewable C1 resource, into high-value-added chemicals is considered a crucial pathway to achieving carbon resource recycling and sustainable development. Among these methods, the cycloaddition reaction of carbon dioxide with epoxides to form cyclic carbonates is of significant value in solvents, electrolytes, and intermediates due to its high atom economy and wide range of applications.

[0003] In existing technologies, the catalytic systems used for this reaction mainly include metal complexes, metal oxides, ionic liquids, and quaternary ammonium salts (Chem. Rev. 2012, 112, 724–781). Although metal-based catalysts exhibit high activity to some extent, they generally suffer from high preparation costs, difficulty in removing metal residues, and insufficient environmental friendliness. Metal-free or low-metal catalytic systems, especially those represented by quaternary ammonium salts, have attracted widespread attention due to their simple structure and low cost. However, single quaternary ammonium salt systems typically require high temperature or pressure conditions, resulting in limited catalytic efficiency.

[0004] In recent years, the introduction of hydrogen bond donors (HBDs) to enhance the activation ability of epoxides in the cycloaddition reaction of carbon dioxide with epoxides has become a research hotspot. Studies have shown that catalytic systems containing hydrogen bond donors such as hydroxyl groups can form hydrogen bond interactions with epoxides, thereby lowering the ring-opening energy barrier of epoxides and improving the yield and selectivity of cyclic carbonates. For example, introducing hydrogen bond donors into polyionic liquids can significantly improve the activation and catalytic efficiency of epoxides (Phys. Chem. Chem. Phys., 2021, 23: 2005–2014); co-catalytic systems of hydrogen bond donors such as boric acid and quaternary ammonium salts have shown excellent performance in promoting the activation of hydroxyl groups in epoxides through hydrogen bonding (ACS Catal. 2016, 6, 4871−4876); in addition, novel double hydrogen bond donor catalysts have also been reported to exhibit high activity in the cycloaddition of CO2 with epoxides, further illustrating the important role of hydrogen bond donors in epoxide activation (Tetrahedron, 2025, 177: 134587). However, most of the reported hydrogen bond donors are strong acidic compounds or polyhydroxy compounds, which have poor solubility in nonpolar or weakly polar reaction media. Excessively strong hydrogen bonding may inhibit reaction activity, and the reaction conditions are harsh, limiting their practical application (CN115155656B). Therefore, developing a novel synergistic catalytic system that combines moderate acidity, good system compatibility, and high catalytic efficiency remains a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a dicarboxylic acid-quaternary ammonium salt synergistic catalytic system for efficiently catalyzing the reaction of carbon dioxide with epoxides to prepare cyclic carbonates, thereby overcoming the shortcomings of existing technologies such as low catalytic efficiency, harsh reaction conditions, and poor system applicability.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a catalytic system for the reaction of carbon dioxide with epoxides to prepare cyclic carbonates, characterized in that it comprises a dicarboxylic acid compound and a quaternary ammonium salt.

[0007] Furthermore, the dicarboxylic acid is one or more of aliphatic dicarboxylic acids, unsaturated dicarboxylic acids, or dicarboxylic acids with hydroxyl substitution, and its first dissociation constant pKa1 is 4.0~7.0.

[0008] Furthermore, the dicarboxylic acid is one or more of sebacic acid, octanoic acid, azelaic acid, pimelic acid, adipic acid, and decenoic acid.

[0009] Further, the quaternary ammonium salt is a halide anionic tetraalkylammonium salt; preferably, the quaternary ammonium salt is one or more of tetramethylammonium bromide, tetramethylammonium iodide, tetraethylammonium bromide, tetraethylammonium iodide, tetrabutylammonium bromide or tetrabutylammonium iodide.

[0010] Furthermore, the molar ratio of the dicarboxylic acid to the quaternary ammonium salt is 1:0.1~5.

[0011] This invention also provides the application of the above-described catalytic system in the reaction of carbon dioxide with epoxides to prepare cyclic carbonates. This includes the following steps: A dicarboxylic acid compound and a quaternary ammonium salt were added to a reaction vessel at a molar ratio of 1:0.1~5; then an epoxide and carbon dioxide were added to the reaction vessel; the reaction was carried out at 40~120 °C and 0.5~5 MPa for 1~24 h; after the reaction was completed, the reaction mixture was cooled to room temperature to release unreacted carbon dioxide, and a mixture of cyclic carbonate products was obtained.

[0012] Furthermore, the epoxide is one or more of propylene oxide, ethylene oxide, butane oxide, and styrene oxide.

[0013] Furthermore, the molar ratio of the dicarboxylic acid to the epoxide is 1:50~100.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The dicarboxylic acid and the quaternary ammonium salt form a synergistic effect. The dicarboxylic acid acts as a hydrogen bond donor to activate the epoxide, and the quaternary ammonium salt provides a nucleophilic anion to attack the epoxide and open its ring, thereby improving the carbon dioxide conversion rate and the yield of cyclic carbonates. (2) The catalytic system does not contain transition metals, has a simple composition, and the raw materials are readily available, which meets the requirements of green chemistry and sustainable development; (3) The dicarboxylic acid exhibits good dispersibility and applicability in the reaction system, avoiding the problems of poor solubility and limited activity of traditional strong hydrogen bond donors; (4) The reaction conditions are mild and suitable for a variety of epoxide substrates, and have good prospects for industrial application. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0016] Appendix Figure 1 This is the product mixture provided in Example 1 of the present invention.1 H NMR spectrum.

[0017] Appendix Figure 2 This is a graph showing the relationship between yield and reaction time provided in Example 1 of the present invention. Detailed Implementation

[0018] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0019] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0020] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0021] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0022] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0023]

Example 1

[0024] Appendix Figure 1 The image shows the ¹H NMR spectrum of the product mixture. Three characteristic resonance peaks of the cyclic carbonate product are observed in the 4.0–5.0 ppm range, while the 2.4–3.0 ppm range corresponds to the characteristic resonance peak of propylene oxide. By comparing the integrated areas of these characteristic peaks, the yield of the cyclic carbonate is calculated to be 97%. Furthermore, no characteristic peaks of any byproducts are present in this spectrum.

[0025] Appendix Figure 2 The figure shows the relationship between yield and reaction time. After 0.25 h, the yield was close to 70%; after 1 h, the yield further increased to approximately 90%; and when the reaction time was extended to 3 h, the yield approached 100%. These results indicate that this system can efficiently catalyze the formation of cyclic carbonates within a short reaction time, exhibiting excellent catalytic activity and high reaction efficiency.

[0026]

Example 2

[0027]

Example 3

[0028]

Example 4

[0029] Comparative Example 1 Based on Example 1, only tetrabutylammonium bromide was replaced with tetrabutylammonium iodide or tetrabutylammonium chloride, while the other reaction conditions remained unchanged. The yields of the target products after the reaction were measured to be 98% and 32%, respectively. The results indicate that the reactivity using bromide or iodide quaternary ammonium salts is significantly better than that using chlorides. This is consistent with the combined synergistic effect of the nucleophilic and leaving abilities of halide anions, further verifying the influence of quaternary ammonium salt anions on the reaction efficiency.

[0030] Comparative Example 2 Based on Example 1, only azelaic acid was replaced with 2,6-dimethylphenylboronic acid, while all other reaction conditions remained unchanged. After the reaction, the yield of the target product was measured to be 58%, significantly lower than the yield obtained in Example 1. These results indicate that, compared to 2,6-dimethylphenylboronic acid, azelaic acid, with its aliphatic chain structure, exhibits superior catalytic activity due to its smaller steric hindrance, higher carbon chain flexibility, and moderate acidity.

[0031] Comparative Example 3 Based on Example 1, only azelaic acid was replaced with oxalic acid (pKa1 = 1.25) or malonic acid (pKa1 = 2.85), while all other reaction conditions remained unchanged. After the reaction, the yields of the target products were measured to be 41% and 56%, respectively, significantly lower than the yields obtained in Example 1. These results indicate that moderately acidic dicarboxylic acids with a first dissociation constant pKa1 in the range of 4.0–7.0 exhibit superior catalytic activity; when pKa1 is below or above this range, the catalytic performance decreases significantly, making it difficult to obtain high yields.

[0032] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A catalytic system for the reaction of carbon dioxide with epoxides to prepare cyclic carbonates, characterized in that, This includes dicarboxylic acid compounds and quaternary ammonium salts.

2. The catalytic system as described in claim 1, characterized in that, The dicarboxylic acid is one or more of aliphatic dicarboxylic acids, unsaturated dicarboxylic acids, or dicarboxylic acids with hydroxyl substitution, and its first dissociation constant pKa1 is 4.0~7.

0.

3. The catalytic system as described in claim 2, characterized in that, The dicarboxylic acid is one or more of sebacal, octanoic acid, azelaic acid, pimelic acid, adipic acid, and decenoic acid.

4. The catalytic system as described in claim 1, characterized in that, The quaternary ammonium salt is a halide anionic tetraalkylammonium salt; preferably, the quaternary ammonium salt is one or more of tetramethylammonium bromide, tetramethylammonium iodide, tetraethylammonium bromide, tetraethylammonium iodide, tetrabutylammonium bromide or tetrabutylammonium iodide.

5. The catalytic system as described in claim 1, characterized in that, The molar ratio of the dicarboxylic acid to the quaternary ammonium salt is 1:0.1~5.

6. The application of the system described in claim 1 in the synthesis of cyclic carbonates, characterized in that, The reaction includes the following steps: adding a dicarboxylic acid compound and a quaternary ammonium salt to a reaction vessel at a molar ratio of 1:0.1~5; then adding an epoxide and carbon dioxide to the reaction vessel; reacting at 40~120 °C and 0.5~5 MPa for 1~24 h; after the reaction is completed, cooling the reaction mixture to room temperature to release unreacted carbon dioxide, and obtaining a mixture of cyclic carbonate products.

7. The preparation method according to claim 6, characterized in that, The epoxide is one or more of propylene oxide, ethylene oxide, butane oxide, and styrene oxide.

8. The preparation method according to claim 6, characterized in that, The molar ratio of the dicarboxylic acid to the epoxide is 1:50~100.

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