Preparation method and application of a polymer-supported organic guanidine solid catalyst

Abstract

This invention provides a method for preparing and applying a polymer-supported organic guanidine solid catalyst, belonging to the field of catalyst technology. Using a polymer material as a support, this invention chemically bonds an organic guanidine to obtain a solid catalyst. The active substance, organic guanidine, and the polymer support are chemically bonded, resulting in strong stability and preventing the active substance from detaching during the reaction. In the transesterification reaction of DMC and EtOH, this catalyst not only exhibits high catalytic activity but also demonstrates the characteristic of being easily separated from a heterogeneous catalyst. After separation, it can be directly recycled, and even after multiple reuses, it maintains a high transesterification yield. This fully demonstrates the excellent recyclability of the polymer-supported organic guanidine solid catalyst, effectively reducing the cost of catalyst use and thus lowering the production cost of the transesterification process, resulting in significant economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a method for preparing a polymer-supported organic guanidine solid catalyst and its application in the transesterification reaction of dimethyl carbonate and ethanol. Background Technology

[0002] Ethyl methyl carbonate (EMC) is an environmentally friendly asymmetric carbonate. Its mixture with dimethyl carbonate (DMC) and diethyl carbonate (DEC) serves as a lithium-ion battery electrolyte, increasing the solubility of lithium salts and thus improving the battery's energy density and discharge capacity. Furthermore, the mixed solvent possesses excellent thermal conductivity, a low freezing point, a high boiling point, and good electrochemical stability, allowing for use over a wide temperature range and effectively enhancing the safety performance and extending the battery's lifespan. Therefore, it is widely used as an electrolyte in lithium-ion batteries. The unique performance advantages of lithium-ion batteries have driven the development of the electric vehicle industry, leading to a continuous increase in the demand for lithium-ion battery electrolytes.

[0003] The main methods for synthesizing EMC include the phosgene method, the oxidative carbonylation method, and the transesterification method. Among these, the transesterification method is considered the most promising process route due to its mild reaction conditions, ease of control, and low environmental pollution. Current reports on the synthesis of methyl ethyl carbonate (MEC) via transesterification mainly focus on the DMC and ethanol (EtOH) transesterification route, where the transesterification product is a mixture of EMC and DEC.

[0004] In the DMC and EtOH transesterification process for preparing EMC and DEC, the choice of catalyst is crucial. Currently, transesterification catalysts are inorganic bases and organic bases. Inorganic base catalysts mainly include sodium alkoxides (e.g., CN109096115 A) and metal composite oxides (e.g., CN106748781 B). Inorganic base catalysts are highly basic and have high reactivity, but their post-processing is complex and they can easily impact the environment. Organic base catalysts include functionalized ionic liquids and anion exchange resins.

[0005] Chinese patent CN114763322 A invented a novel organic nonionic phosphonic base catalyst to catalyze the transesterification reaction of DMC and EtOH to obtain a mixed ester of EMC and DEC, wherein the mass ratio of EMC to DEC in the mixed ester is 2.0:1.0 to 15.0:1.0. However, the yield of EMC and DEC in this catalytic reaction is not high. Chinese patent CN113813996 A invented a strong base anion exchange resin, which is prepared from the following components: styrene, divinylbenzene, porogen, benzoyl peroxide, polyvinyl alcohol solution, zinc chloride, chloromethyl ether, DMF, and a quaternary ammonium salt (prepared from trimethylamine and chloroalkanol). Using this strong base anion exchange resin to catalyze the transesterification reaction of DMC and EtOH to synthesize EMC, the reaction is carried out at 95°C for 2 hours, achieving an EMC yield of over 86.0%. However, the preparation of this strong base anion exchange resin is complex, requires many materials, is costly, and is not suitable for industrialization.

[0006] Organic guanidines, due to the conjugation of their three nitrogen atoms and the distribution of positive charges on the central carbon atom and the three nitrogen atoms, possess good thermal stability and are widely used organic base catalysts in organic synthesis reactions. Using organic guanidines as catalysts in the transesterification process of dimethyl carbonate and ethanol to prepare a mixture of EMC and DEC has yielded good catalytic results. However, organic guanidines are liquid catalysts, dissolved in the transesterification system, requiring distillation for separation and being difficult to reuse. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention proposes a polymer-supported organic guanidine solid catalyst for the transesterification reaction of dimethyl carbonate and ethanol. It not only has high catalytic activity for transesterification but is also easy to separate as a heterogeneous catalyst. Furthermore, the chemical bonding between the organic guanidine and the polymer allows the catalyst to be recycled, and it still has high catalytic activity for transesterification when recycled, effectively reducing the cost of catalyst use.

[0008] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a polymer-supported organic guanidine solid catalyst is as follows: using a polymer as a support and an organic guanidine as an active component, the polymer support and the organic guanidine are added in batches in a reaction solvent at room temperature (20-25℃) under inert gas protection. The mixture is heated under reflux and reacted. After the reaction is completed, the mixture is filtered to obtain a filter cake. The filter cake is stripped with an organic solvent and then dried under vacuum to obtain the polymer-supported organic guanidine solid catalyst.

[0010] Furthermore, the organic polymer carrier is one of polyethylene glycol and chloride-type ion exchange resin; the organic guanidine is one of tetramethylguanidine, 1-acetylguanidine, and 1-(diaminomethylene)guanidine; the reaction solvent is a benzene solvent, selected from benzene, toluene, and xylene; and the stripping organic solvent is one of chloroalkanes (e.g., dichloromethane), esters (e.g., ethyl acetate), ketones (e.g., acetone), and alcohols (e.g., ethanol).

[0011] Furthermore, the mass ratio of each component is as follows: organic guanidine: carrier = 1.0~2.0:1.0; organic guanidine: solvent = 1.0:4.0~10.0; reaction time 8~16h.

[0012] Furthermore, the mass ratio of each component is: organic guanidine: carrier = 1.0~1.5:1.0; organic guanidine: solvent = 1.0:4.0~8.0; the reaction time is 8~12h.

[0013] Furthermore, the application of the polymer-supported organic guanidine solid catalyst prepared by the above preparation method in the transesterification reaction of dimethyl carbonate and ethanol.

[0014] Further, the transesterification reaction step is as follows: DMC and EtOH are used as raw materials and added to a reactor in proportion. The reactor contains a distillation column and a distillation tower. The transesterification reaction distillation device is filled with θ-rings. A metered-prepared polymer-supported organic guanidine catalyst is added, and the temperature is raised to the reaction temperature to carry out the transesterification reaction.

[0015] Furthermore, the mass ratio of each component is: ETOH:DMC = 1.0~4.0:1.0; polymer-supported organic guanidine catalyst:DMC = 2.0%~10.0%:1.0; heating temperature: 80℃~120℃; reaction time: 8~14h.

[0016] Furthermore, after the transesterification reaction, the temperature is lowered to room temperature, and the catalyst is recovered by filtration. The catalyst can be recycled multiple times for the transesterification reaction of DMC and EtOH.

[0017] Compared with existing technologies, the advantages of this invention are:

[0018] (1) The present invention uses a one-step method to prepare polymer-supported organic guanidine solid catalysts. The process is simple, the raw materials are readily available, and it is suitable for large-scale production.

[0019] (2) Compared with single organic guanidine catalysts, polymer-supported organic guanidine solid catalysts not only maintain higher catalytic activity in the transesterification reaction of DMC and EtOH, but also have the characteristics of easy separation of heterogeneous catalysts.

[0020] (3) The catalyst of the present invention has strong chemical bonding between the active material organic guanidine and the polymer support, which makes the catalyst more stable. The active material will not fall off and can be directly recycled after separation. After repeated use, it can still maintain a high transesterification yield, which fully demonstrates that the polymer supported organic guanidine solid catalyst has excellent recycling performance, effectively reducing the cost of catalyst use and thus reducing the production cost of transesterification reaction process. Detailed Implementation

[0021] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0022]

[0023]

[0024] Example 1

[0025] 5.0 g of polyethylene glycol was added to 20.0 g of benzene. 5.0 g of 1-acetylguanidine was added at room temperature (25°C) under nitrogen protection. The mixture was heated under reflux for 8 h under nitrogen protection, filtered, and the solid was stripped with dichloromethane for 6 h. After filtration, the solid was filtered and dried under vacuum to obtain 5.7 g of polyethylene glycol-supported 1-acetylguanidine solid catalyst.

[0026] Example 2

[0027] 5.0 g of chloride-form ion exchange resin was added to 30.0 g of toluene. 7.5 g of tetramethylguanidine was added at room temperature (25 °C) under nitrogen protection. The mixture was heated under reflux for 12 h under nitrogen protection, filtered, and the solid was stripped with ethanol for 6 h. After filtration, the solid was filtered again and dried under vacuum to obtain 4.8 g of tetramethylguanidine solid catalyst supported on chloride-form ion exchange resin.

[0028] Example 3

[0029] 5.0 g of polyethylene glycol was added to 50.0 g of xylene. Under nitrogen protection, 10.0 g of 1-(diaminomethylene)guanidine was added at room temperature (25°C). The mixture was heated under reflux for 16 h under nitrogen protection, filtered, and the solid was stripped with acetone for 6 h. After filtration, the solid was filtered again and dried under vacuum to obtain 6.2 g of polyethylene glycol-supported 1-(diaminomethylene)guanidine solid catalyst.

[0030] Example 4

[0031] 5.0 g of chloride-form ion exchange resin was added to 30.0 g of toluene. Under nitrogen protection, 12.5 g of tetramethylguanidine was added at room temperature (20 °C). The mixture was heated under reflux for 12 h under nitrogen protection. After filtration, the solid was stripped with ethyl acetate for 6 h, filtered, and dried under vacuum to obtain 5.1 g of tetramethylguanidine solid catalyst supported on chloride-form ion exchange resin.

[0032] Example 5

[0033] 45.0 g of DMC and 90.0 g of EtOH were added to an ester transesterification distillation apparatus (including a distillation column and a distillation tower, with θ rings as the packing material), along with 2.25 g of the polyethylene glycol-supported 1-acetylguanidine solid catalyst prepared in Example 1 above. The temperature was raised to 100 °C, the reaction temperature was 76 °C, and the reaction was carried out for 8 h. Gas chromatography analysis showed that the DMC conversion rate was 82.2%, and the selectivity of the EMC and DEC mixed ester was 100%.

[0034] Example 6

[0035] 45.0 g of DMC and 90.0 g of EtOH were added to an ester exchange reactive distillation apparatus (including a distillation column and a distillation tower, with θ rings as the packing material), along with 2.25 g of tetramethylguanidine solid catalyst supported on chloride-type ion exchange resin prepared in Example 2 above. The temperature was raised to 100 °C, the reaction temperature was 76 °C, and the reaction was carried out for 8 h. Gas chromatography analysis showed that the DMC conversion rate was 80.5%, and the selectivity of the EMC and DEC mixed ester was 100%.

[0036] Example 7

[0037] 45.0 g of DMC and 90.0 g of EtOH were added to an ester transesterification distillation apparatus (including a distillation column and a distillation tower, with θ rings as the packing material). 2.25 g of the polyethylene glycol-supported 1-(diaminomethylene)guanidine solid catalyst prepared in Example 3 above was also added. The temperature was raised to 100 °C, the reaction temperature was 76 °C, and the reaction was carried out for 8 h. Gas chromatography analysis showed that the DMC conversion rate was 83.5%, and the selectivity of the EMC and DEC mixed ester was 100%.

[0038] Example 8

[0039] 45.0 g of DMC and 90.0 g of EtOH were added to an ester exchange reactive distillation apparatus (including a distillation column and a distillation tower, with θ rings as the packing material), along with 2.25 g of tetramethylguanidine solid catalyst supported on chloride-type ion exchange resin prepared in Example 4 above. The temperature was raised to 100 °C, the reaction temperature was 76 °C, and the reaction was carried out for 8 h. Gas chromatography analysis showed that the DMC conversion rate was 81.8%, and the selectivity of the EMC and DEC mixed ester was 100%.

[0040] Comparative Example 1

[0041] 45.0 g of DMC and 90.0 g of EtOH were added to an ester exchange reactive distillation apparatus (including a distillation column and a distillation tower, with θ rings as the packing material), along with 2.25 g of chloride-form ion exchange resin. The temperature was raised to 100 °C, the reaction temperature was 76 °C, and the reaction was carried out for 8 hours. Gas chromatography analysis showed that the DMC conversion rate was 0.6%.

[0042] Comparative Example 2

[0043] 45.0 g of DMC and 90.0 g of EtOH were added to an ester transesterification reaction distillation apparatus (including a distillation column and a distillation tower, with θ rings as the packing material), along with 2.25 g of polyethylene glycol. The temperature was raised to 100 °C, the reaction temperature was 76 °C, and the reaction was carried out for 8 hours. Gas chromatography analysis showed that the DMC conversion rate was 0.1%.

[0044] Table 1: Comparison of Results between Examples 5-8 and Comparative Examples 1-2

[0045] DMC conversion rate % EMC and DEC mixed ester selectivity % Example 5 82.2 100 Example 6 80.5 100 Example 7 83.5 100 Example 8 81.8 100 Comparative Example 1 0.6 / Comparative Example 2 0.1 /

[0046] Example 9

[0047] Ester exchange condition experiment: Taking the tetramethylguanidine solid catalyst supported on the chloride ion exchange resin prepared in Example 2 as an example, the effects of different conditions on the conversion rate of DMC and the selectivity of the mixed ester of EMC and DEC were investigated. The results are shown in Table 2.

[0048] a) 45.0 g of DMC and 45.0 g of EtOH were added to an ester exchange reactive distillation apparatus (including a distillation column and a distillation tower, with θ rings as the packing material), along with 2.25 g of tetramethylguanidine solid catalyst supported on chloride-type ion exchange resin prepared in Example 2 above. The temperature was raised to 100 °C, the reaction temperature was 76 °C, and the reaction was carried out for 8 h. Gas chromatography analysis showed that the DMC conversion rate was 73.2%, and the selectivity of the EMC and DEC mixed ester was 100%.

[0049] b) 45.0 g of DMC and 180.0 g of EtOH were added to an ester exchange reactive distillation apparatus (including a distillation column and a distillation tower, with θ rings as the packing material), along with 2.25 g of tetramethylguanidine solid catalyst supported on chloride-type ion exchange resin prepared in Example 2 above. The temperature was raised to 100 °C, the reaction temperature was 76 °C, and the reaction was carried out for 8 h. Gas chromatography analysis showed that the DMC conversion rate was 81.3%, and the selectivity of the EMC and DEC mixed ester was 100%.

[0050] c) 45.0 g of DMC and 90.0 g of EtOH were added to an ester exchange reactive distillation apparatus (including a distillation column and a distillation tower, with θ rings as the packing material), along with 0.9 g of tetramethylguanidine solid catalyst supported on chloride-type ion exchange resin prepared in Example 2 above. The temperature was raised to 100 °C, the reaction temperature was 76 °C, and the reaction was carried out for 8 h. Gas chromatography analysis showed that the DMC conversion rate was 63.1%, and the selectivity of the EMC and DEC mixed ester was 100%.

[0051] d) 45.0 g of DMC and 90.0 g of EtOH were added to an ester exchange reaction distillation apparatus (including a distillation column and a distillation tower, with θ rings as the packing material), along with 4.5 g of tetramethylguanidine solid catalyst supported on chloride-type ion exchange resin prepared in Example 2 above. The temperature was raised to 100 °C, the reaction temperature was 76 °C, and the reaction was carried out for 8 h. Gas chromatography analysis showed that the DMC conversion rate was 90.1%, and the selectivity of the EMC and DEC mixed ester was 100%.

[0052] e) 45.0 g of DMC and 90.0 g of EtOH were added to an ester exchange reactive distillation apparatus (including a distillation column and a distillation tower, with θ rings as the packing material), along with 2.25 g of tetramethylguanidine solid catalyst supported on chloride-type ion exchange resin prepared in Example 2 above. The temperature was raised to 80 °C, the reaction temperature was 76 °C, and the reaction was carried out for 8 h. Gas chromatography analysis showed that the DMC conversion rate was 75.6%, and the selectivity of the EMC and DEC mixed ester was 100%.

[0053] Table 2: Comparison of catalytic performance of catalysts obtained in Example 2 under different conditions

[0054]

[0055] Example 10

[0056] Catalyst recycling

[0057] 45.0 g of DMC and 90.0 g of EtOH were added to a transesterification reactive distillation apparatus (including a distillation column and a distillation tower, packed with θ-rings). 2.25 g of the tetramethylguanidine-supported polymeric solid catalyst prepared in Example 4 was also added. The temperature was raised to 120 °C, the reaction temperature was 76 °C, and the reaction was carried out for 14 h. Gas chromatography analysis showed that the DMC conversion rate was 92.6%, and the selectivity for the EMC and DEC mixed ester was 100%. After filtration and catalyst recovery, under the same transesterification conditions, the catalyst was reused 15 times, and the DMC conversion rate was 92.5%, with no significant decrease in conversion rate.

[0058] The results from the above examples show that, in catalyst preparation, the solid mass of the chloride-form ion exchange resin loaded with organic guanidine is less than that loaded with ethylene glycol, possibly because the chlorine in the chloride-form ion exchange resin exchanges with the amino group. In the transesterification reaction, using only the polymeric support polyethylene glycol and the chloride-form ion exchange resin, DMC and EtOH hardly react. With the same polymeric support, the more organic guanidine used, the greater the solid mass of the polymerically loaded organic guanidine. Under the same dosage conditions, the DMC conversion rate is slightly higher in the transesterification reaction. The higher the reflux temperature, the higher the DMC conversion rate. The more EtOH used, the higher the DMC conversion rate, but when the mass ratio exceeds ETOH:DMC = 2.0:1.0, the DMC conversion rate tends to stabilize. The longer the reaction time, the higher the DMC conversion rate, but when the reaction time exceeds 12 hours, the reaction tends to reach equilibrium. The DMC conversion rate tends to stabilize. This reaction uses DMC and EtOH as raw materials, avoiding the introduction of other ester side reactions by transesterification of DMC with long-chain alkane esters. The products are only EMC and DEC. The experimental results show that the chemical bonding between the active material organic guanidine and the polymer support ensures that the reaction performance is very stable after the catalyst is recycled. After the polymer-supported organic guanidine catalyst is recycled 15 times, the DMC conversion rate basically does not decrease, indicating that the active component is not lost. Unlike inorganic composite materials supported by impregnation or precipitation methods, the active component is not easily lost during the reaction, which leads to a decrease in reaction performance.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. Use of a high molecular load organic guanidine solid catalyst in the transesterification reaction of dimethyl carbonate and ethanol, characterized in that, The preparation method of the polymer-supported organic guanidine solid catalyst comprises: using a polymer as a carrier and an organic guanidine as an active component, under the protection of an inert gas at room temperature, batch adding the polymer carrier and the organic guanidine, heating and refluxing for reaction, filtering after the reaction is completed, vacuum drying after stripping with an organic solvent, and thus the polymer-supported organic guanidine solid catalyst is obtained; the polymer carrier is polyethylene glycol; the organic guanidine is selected from one of tetramethyl guanidine, 1-acetyl guanidine and 1-(diamino methylene) guanidine; the reaction solvent is selected from one of benzene, toluene and xylene; the stripping organic solvent is selected from one of dichloromethane, ethyl acetate, acetone and ethanol; the mass ratio of the components is: organic guanidine: carrier = 1.0-1.5:1.0; organic guanidine: solvent = 1.0:4.0-8.0; and the reaction time is 8-12 h.

2. Use according to claim 1, characterized in that, The ester exchange reaction step is: using DMC and EtOH as raw materials, adding them into a reactor in proportion, the reactor being a rectifying tower, the filler being an ester exchange reaction rectifying device with theta rings, adding the polymer-supported organic guanidine solid catalyst prepared in a metering manner, and heating to a reaction temperature to perform the ester exchange reaction.

3. Use according to claim 2, characterized in that, The mass ratio of the components is: ETOH: DMC = 1.0-4.0:1.0; polymer-supported organic guanidine catalyst: DMC = 2.0%-8.0%:1.0; the heating temperature is: 80-120 DEG C; and the reaction time is: 8-16 h.

4. Use according to claim 2, characterized in that, Cooling to room temperature, filtering and recovering the catalyst, and under the same ester exchange reaction conditions, the catalyst can be recycled for the ester exchange reaction of DMC and EtOH.

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