Synthesis method and application of polyethyleneimine-based green quaternary ammonium alkali ionic liquid
A novel strongly basic ionic liquid catalyst was prepared by a green quaternization reaction based on polyethyleneimine, which solves the problems of complex preparation and poor thermal stability of existing ionic liquids, and achieves highly efficient catalysis of transesterification reaction, showing good prospects for industrial application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHENYANG INSTITUTE OF CHEMICAL TECHNOLOGY
- Filing Date
- 2024-12-12
- Publication Date
- 2026-06-12
AI Technical Summary
Existing ionic liquid catalysts are complicated to prepare, have poor thermal stability, and are difficult to purify, which hinders their industrial application and lacks efficient catalytic activity.
A novel quaternary ammonium salt ionic liquid catalyst was prepared by using a strongly basic ionic liquid based on the green quaternization of polyethyleneimine. The catalyst is prepared by quaternizing dimethyl carbonate (the raw material or product of transesterification) with polyethyleneimine in a high-pressure reactor. This catalyst is used to catalyze transesterification reactions, avoids the introduction of solvent impurities, and has good substrate versatility and recyclability.
The prepared strongly basic ionic liquid exhibits high thermal stability, strong basicity, and high catalytic activity. In particular, in the catalytic transesterification reaction of ethylene carbonate and ethanol, the catalyst achieves an EC conversion rate of 74.8%, a DEC selectivity and yield of 92.8% and 69.4%, respectively, and a TOF value as high as 120.2 h⁻¹, demonstrating significant industrial application value.
Smart Images
Figure CN122188145A_ABST
Abstract
Description
Technical Field
[0001] This application relates to a method for synthesizing and applying a strongly basic ionic liquid based on the green quaternization of polyethyleneimine, belonging to the field of transesterification catalyst technology. Background Technology
[0002] Polyethyleneimine (PEI), also known as polyazidecyclopropane, is a colorless, viscous, water-soluble polymeric polyamine. As a water-soluble functional macromolecular polymer, PEI has attracted widespread attention due to its non-toxicity, low cost, and biocompatibility. Based on its structure, PEI can be divided into linear polyethyleneimine (L-PEI) and branched polyethyleneimine (B-PEI). B-PEI molecules contain a large number of primary, secondary, and tertiary amine groups, exhibiting high reactivity and adsorption properties. By quaternizing the tertiary amine groups, functionalized groups can be introduced into B-PEI, resulting in macromolecular ionic liquids with excellent catalytic performance.
[0003] Ionic liquids (ILs) are a class of compounds with unique chemical properties, composed of organic cations or organic and inorganic anions. Due to their high solubility, good stability, environmental friendliness, and low volatility, they are widely used in electrochemistry, separation and purification, drug synthesis, and catalysis. Especially in catalysis, ionic liquids exhibit outstanding catalytic activity and reusability. They demonstrate good catalytic activity in various organic reactions, including Mannich reactions, Pekin reactions, cycloaddition reactions, and transesterification reactions. Common ionic liquids include quaternary ammonium salts, imidazole salts, pyridinium salts, and quaternary phosphate salts. However, the development of these materials faces challenges such as complex preparation processes, poor thermal stability, and difficulty in purification, hindering their industrial application. As alternatives to these ionic liquids, functionalized ionic liquids can introduce catalytically active groups into their anions or cations, thereby achieving stable and efficient catalytic capabilities. Therefore, the development and design of functionalized ionic liquids that are simple to prepare, structurally stable, highly catalytically active, do not produce impurities, and are suitable for industrial production have attracted much attention. Summary of the Invention
[0004] To address the aforementioned issues, this application provides a method for synthesizing a strongly basic ionic liquid based on the green quaternization of polyethyleneimine. Dimethyl carbonate, derived from transesterification reaction feedstocks or products, is quaternized with nitrogen-rich polyethyleneimine in a high-pressure reactor to obtain a novel quaternary ammonium salt ionic liquid catalyst. This method introduces no solvents or other impurities during synthesis, exhibits good substrate versatility, and can be recycled. It demonstrates excellent catalytic ability for transesterification reactions in the synthesis of various carbonate chemicals, and thus possesses significant industrial application value.
[0005] The technical solution adopted in this application is as follows:
[0006] According to one aspect of this application, a strongly basic ionic liquid based on green quaternization of polyethyleneimine is provided, the strongly basic ionic liquid comprising cations and anions;
[0007] The cation is polyethyleneimine containing several quaternary ammonium cation structural units as shown in Formula I.
[0008]
[0009] The anion is selected from at least one of the structures shown in Formulas II to V;
[0010]
[0011] Optionally, the cation has the structure shown in Formula Ia;
[0012]
[0013] Optionally, the strong alkaline ionic liquid has an alkalinity of 9.8 to 15.0 and an alkalinity of 1.0 to 1.27 mmol / L.
[0014] Optionally, the anions in the strongly alkaline ionic liquid originate from the raw materials or products of the transesterification reaction.
[0015] According to one aspect of this application, a method for preparing the above-mentioned strongly basic ionic liquid based on the green quaternization of polyethyleneimine is provided, comprising the following steps:
[0016] The activated reaction was carried out in a sealed container containing polyethyleneimine and carbonate compounds, followed by rotary evaporation under reduced pressure to obtain the strongly basic ionic liquid based on the green quaternization of polyethyleneimine.
[0017] Optionally, the carbonate compound is selected from at least one of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and propylene carbonate.
[0018] Optionally, the activation reaction conditions include: being carried out under stirring, with an activation reaction temperature of 70–110°C and an activation reaction time of 2–10 h.
[0019] Optionally, the activation reaction temperature in the activation reaction conditions is selected from any value of 70℃, 80℃, 90℃, 100℃, and 110℃, or any range between the two.
[0020] Optionally, the activation reaction time in the activation reaction conditions is selected from any value of 2h, 4h, 6h, 8h, 10h, or any range between the two.
[0021] Optionally, the activation reaction conditions further include: slowly heating to the activation reaction temperature at a rate of 2-3 °C / min.
[0022] Optionally, the weight ratio of the polyethyleneimine to the carbonate compound is 1:1 to 5.
[0023] Optionally, the weight ratio of the polyethyleneimine and the carbonate compound is selected from any value among 1:1, 1:1.5, 1:2, 1:3, 1:4, and 1:5, or any range between the two.
[0024] In this application, the activation reaction time is preferably 6 hours; the activation reaction temperature is preferably 100°C; and the mass ratio of polyethyleneimine to carbonate compound raw materials in the activation reaction is selected as 1:2.
[0025] Optionally, the conditions for vacuum heating rotary evaporation include: heating to 50-80°C and then rotary evaporating for 3-6 hours under an ambient vacuum of -0.1 to -0.08 Pa.
[0026] Optionally, the conditions for vacuum heating rotary evaporation include: maintaining a temperature of 50–80°C for 0.5–6 hours at an ambient vacuum of -0.1 to -0.08 Pa.
[0027] Optionally, the conditions for vacuum heating rotary evaporation include: heating sequentially to 50-60°C, 60-70°C, and 70-80°C under an ambient vacuum of -0.1 to -0.08 Pa, and rotary evaporating for 0.5 to 2 hours respectively.
[0028] Optionally, the time for maintaining the vacuum heating rotary evaporation at a temperature in the range of 50–80°C is selected from any value among 0.5h, 1h, 1.5h, and 2h, or any value between two of them.
[0029] During the reaction of polyethyleneimine and dimethyl carbonate, methanol, a byproduct of the reaction, is simultaneously separated from the reaction system by rotary evaporation.
[0030] According to one aspect of this application, the above-mentioned strongly basic ionic liquid based on green quaternization of polyethyleneimine or the strongly basic ionic liquid based on green quaternization of polyethyleneimine obtained according to the above preparation method is also provided as a homogeneous catalyst for transesterification reaction.
[0031] Optionally, the transesterification reaction is selected from one of the following: transesterification reaction of cyclic carbonates with alcohols, transesterification reaction of chain carbonates with alcohols, transesterification reaction of oxalates with alcohols, and transesterification reaction of acetates with alcohols.
[0032] Optionally, the temperature window for the transesterification reaction is 40–82 °C.
[0033] Optionally, in the aforementioned application, the transesterification reaction is a catalytic transesterification reaction of ethylene carbonate with an alcohol to synthesize diethyl carbonate (DEC).
[0034] Optionally, the application is that the strongly basic ionic liquid D-BEPI is used as a homogeneous catalyst for the transesterification reaction of ethylene carbonate and alcohol to synthesize DEC.
[0035] The beneficial effects that this application can produce include:
[0036] The strongly basic ionic liquid based on the green quaternization of polyethyleneimine provided in this application has an active center of CH3O(C=O)O. ― The negative ion exhibits excellent strong nucleophilicity; the cation is a nitrogen-rich organic quaternary ammonium salt cation. The strongly basic ion of this application possesses high thermal stability, strong basicity, and efficient catalytic ability for transesterification reactions. It is simple to prepare, strongly basic, and exhibits excellent catalytic activity. Furthermore, it demonstrates high catalytic activity and substrate universality in catalyzing various transesterification reactions. Particularly in the transesterification reaction of ethylene carbonate and ethanol, using a D-BPEI ionic liquid catalyst with a ethylene carbonate content of 2% (by mass) achieved an EC conversion of 74.8%, a DEC selectivity and yield of 92.8% and 69.4%, respectively, and a TOF value as high as 120.2 h⁻¹. -1 The strongly alkaline ionic liquid used in this application has extremely strong ring-opening ability of ethylene carbonate and transesterification ability with ethanol, and therefore has important industrial application value in the field of carbonate chemical synthesis. Attached Figure Description
[0037] Figure 1 This is a schematic diagram of the synthesis process of the D-BPEI alkaline ionic liquid catalyst in Example 1 of this application.
[0038] Figure 2 The effect of synthesis temperature on the activity of the prepared D-BPEI alkaline ionic liquid catalyst was investigated.
[0039] Figure 3The effect of synthesis time on the activity of the prepared D-BPEI alkaline ionic liquid catalyst was investigated.
[0040] Figure 4 The effect of the mass ratio of the raw materials on the activity of the prepared strong basic catalyst D-BPEI was investigated.
[0041] Figure 5 NMR of D-BPEI alkaline ionic liquid catalyst 13 C characterization.
[0042] Figure 6 FT-IR characterization of the raw materials B-PEI and D-BPEI alkaline ionic liquid catalysts.
[0043] Figure 7 TG-DTA characterization of the raw materials B-PEI and D-BPEI alkaline ionic liquid catalysts.
[0044] Figure 8 The effect of reaction temperature on the transesterification reaction of EC and EtOH.
[0045] Figure 9 The effect of the amount of D-BPEI basic ionic liquid catalyst on the transesterification reactions of EC and EtOH.
[0046] Figure 10 Stability evaluation of D-BPEI basic ionic liquid catalyst in EC and EtOH transesterification reactions.
[0047] Figure 11 Characterization of the catalytic performance of D-BPEI alkaline ionic liquid catalyst in various transesterification reactions.
[0048] Figure 12 Preparation and evaluation of other carbonate-activated polyethyleneimine ionic liquids. Detailed Implementation
[0049] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0050] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0051] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.
[0052] The specific method for the transesterification reaction of EC and EtOH in the test examples of this application is as follows: 10g EC, 52.3g EtOH, and 0.2g strong basic ionic liquid catalyst are placed in a flask, heated to 82℃, and the reaction is carried out for 150min before sampling and analysis.
[0053] The specific method for the transesterification reaction of DMC and EtOH is as follows: 30g of DMC and 15.3g of EtOH are placed in a flask, and 0.2g of a strong basic ionic liquid catalyst is placed in the flask. The mixture is heated to 82℃ and reacted for 150min before sampling and analysis.
[0054] The specific method for the ester exchange reaction of DEC and MeOH is as follows: Take 30g of DEC and 11.7g of MeOH into a flask, add 0.2g of a strong basic ionic liquid catalyst to the flask, heat to 68℃, react for 150min and then take a sample for analysis.
[0055] The specific method for the transesterification reaction of DMO and EtOH is as follows: 10g of DMO and 34.8g of EtOH are placed in a flask, and 0.2g of a strong basic ionic liquid catalyst is placed in the flask. The mixture is heated to 82℃ and reacted for 150min before sampling and analysis.
[0056] The specific method for the transesterification reaction of DEO and MeOH is as follows: 10g of DEO and 21.9g of MeOH are placed in a flask, and 0.2g of a strong basic ionic liquid catalyst is placed in the flask. The mixture is heated to 68℃ and reacted for 150min before sampling and analysis.
[0057] The specific method for the ester exchange reaction of MAC and EtOH is as follows: 10g of MAC and 62.2g of EtOH are placed in a flask, and 0.2g of a strong basic ionic liquid catalyst is placed in the flask. The mixture is heated to 72℃ and reacted for 150min before sampling and analysis.
[0058] The specific method for the transesterification reaction of PC and EtOH is as follows: 10g of PC and 45.1g of EtOH are placed in a flask, and 0.2g of a strong basic ionic liquid catalyst is placed in the flask. The mixture is heated to 82℃ and reacted for 150min before sampling and analysis.
[0059] The specific method for the transesterification reaction of PC and MeOH is as follows: 10g of PC and 31.4g of MeOH are placed in a flask, and 0.2g of a strong basic ionic liquid catalyst is placed in the flask. The mixture is heated to 68℃ and reacted for 150min before sampling and analysis.
[0060] The specific method for the transesterification reaction of EC and MeOH is as follows: 10g EC and 36.4g MeOH are placed in a flask, and 0.2g of a strong basic ionic liquid catalyst is placed in the flask. The mixture is heated to 68℃ and reacted for 150min before sampling and analysis.
[0061] The calculation methods involved in the test examples of this application are as follows:
[0062] X=100×(na+nb+nc) / (na+nb+nc+nd)
[0063] Sa = 100 × na / (na + nb + nc)
[0064] Sb = 100 × nb / (na + nb + nc)
[0065] Sc = 100 × nc / (na + nb + nc)
[0066] Y = 100 × X × Sa
[0067] TOF = n EC ×X EC ×S DEC / n Cat ×t
[0068] In the formula, X is the conversion rate of ethylene carbonate, %;
[0069] Sa represents the selectivity of diethyl carbonate, %;
[0070] Sb represents the selectivity of 2-hydroxyethyl ethyl carbonate, %;
[0071] Sc represents the selectivity of di-2-hydroxyethyl carbonate, %;
[0072] Y represents the yield of diethyl carbonate, in %.
[0073] n EC The amount of ethylene carbonate is expressed in moles (mol).
[0074] n cat The amount of catalyst is expressed in moles (mol).
[0075] t is the reaction time, in hours (h).
[0076] General preparation method for synthetic strong basic ionic liquids
[0077] The synthesis of a strongly basic ionic liquid catalyst (D-BPEI) is shown in the attached diagram. Figure 1 The steps are as follows:
[0078] (1) Mix polyethyleneimine (B-PEI) and dimethyl carbonate (DMC) in a certain raw material mass ratio (B-PEI:DMC) and transfer them to a reaction vessel. Slowly heat the mixture to a certain synthesis temperature and stir continuously for a certain period of time. After the reaction is completed and cooled to room temperature, release the pressure and collect the discharged gas.
[0079] (2) The liquid collected in the vessel was transferred to a rotary evaporator and rotary evaporated at -0.1 MPa at 50 °C, 60 °C and 70 °C for 30 min, and finally at 80 °C for 1 h. The resulting sample was dried at 70 °C for 24 h to obtain the target strong basic ionic liquid catalyst (D-BPEI).
[0080] Example 1: Specific Preparation of Strongly Basic Ionic Liquids
[0081] The synthesis of a strongly basic ionic liquid catalyst (D-BPEI) is shown in the attached diagram. Figure 1 The steps are shown, and the synthesis process is as shown in Equation III;
[0082]
[0083] (1) Transfer 10g of polyethyleneimine (B-PEI) and 20g of dimethyl carbonate (DMC) to the reactor, slowly heat to 100℃ at a rate of 2℃ / min and stir continuously for 6h. After the reaction is completed and cooled to room temperature, release the pressure and collect the discharged gas.
[0084] (2) The liquid collected in the vessel was transferred to a rotary evaporator and rotary evaporated at -0.1 MPa at 50 °C, 60 °C and 70 °C for 30 min, and finally at 80 °C for 1 h. The resulting sample was dried at 70 °C for 24 h to obtain the target strong basic ionic liquid catalyst (D-BPEI).
[0085] Test Example 1: Effect of Different Synthesis Temperatures on Catalyst Activity
[0086] Using the synthetic example method, the synthesis conditions were controlled as follows: the mass ratio of raw materials (B-PEI:DMC) was 1:3, and the time was 8 hours. Then, the effects of catalysts (D-BPEI) prepared at different synthesis temperatures on the transesterification reaction of EC and EtOH were investigated. Figure 2 As shown in the figure, experimental results indicate that the activity of the synthesis catalyst varies at different temperatures. As the synthesis temperature gradually increases from 70℃ to 100℃, the DEC yield increases from 2.04% to 65.59%, and the TOF value also gradually increases. This is because the increased temperature of the reaction system increases the molecular motion rate of the reactants and the probability of effective intermolecular collisions, leading to a deeper quaternization of B-PEI and thus improving the catalyst activity. When the synthesis temperature is further increased to 110℃, the catalyst activity slightly improves, but the increase in catalytic activity is not significant compared to the catalyst obtained at 100℃. Therefore, considering energy saving and industrial applications, 100℃ is the optimal synthesis temperature.
[0087] Test Example 2: Effect of Different Synthesis Times on Catalyst Activity
[0088] Using the synthetic example method, the synthesis conditions were controlled as follows: the mass ratio of raw materials (B-PEI:DMC) was 1:3, and the temperature was 100℃. The effect of catalysts (D-BPEI) prepared with different synthesis times on the transesterification reaction of EC and EtOH was then investigated. Figure 3 As shown in the figure. The results indicate that as the synthesis time increased from 2 h to 6 h, the DEC yield increased from 35.2% to 73.4%, and the TOF value increased from 24.2 h. -1 Increased to 45.2h -1This is because the degree of quaternization of B-PEI increases with the extension of synthesis time. The degree of quaternization of B-PEI reaches its maximum at a synthesis time of 6 hours. Further extending the synthesis time to 10 hours shows almost no change in the yield of the target product, indicating that the catalytic efficiency of the obtained D-BPEI ionic liquid has reached its maximum at a synthesis time of 6 hours. Therefore, 6 hours can be determined as the optimal synthesis time.
[0089] Test Example 3: Effect of different synthesis feedstock mass ratios on catalyst activity
[0090] The synthesis method was adopted, and the synthesis conditions were controlled as follows: temperature 100℃, time 6h. Then, the effect of catalysts (D-BPEI) prepared with different raw material mass ratios on the transesterification reaction of EC and EtOH was investigated. Figure 4 As shown in the figure. The results indicate that when the raw material mass ratio (B-PEI:DMC) is 1:1, the DEC yield is 0.4% and the TOF value is 0.4 h. -1 This is because a large amount of DMC reacts with the primary and secondary amine groups in B-PEI in the reaction system via methylation, while a very small amount of DMC reacts with the tertiary amine, resulting in low catalyst activity. Further increasing the feed mass ratio to 1:2 resulted in a DEC yield of 72.9% and a TOF value of 84.2 h⁻¹. -1 At this point, the catalyst activity significantly increased. This is because, with the increase of the feed mass ratio, a large amount of tertiary amine in B-PEI reacts with DMC, deepening the quaternization of B-PEI and thus enhancing the catalyst activity. Further increasing the feed mass ratio to 1:3, 1:4, and 1:5 revealed almost no change in EC conversion, DEC selectivity, and DEC yield, indicating that the quaternization of B-PEI reached its maximum at this point. Therefore, the optimal feed mass ratio is 1:2.
[0091] Test Example 4 13 C NMR characterization
[0092] Taking the ionic liquid catalyst (D-BPEI) in Example 1 as an example, D-BPEI's... 13 The C NMR spectrum is as follows Figure 5 As shown. In 13The C10 NMR spectrum showed seven distinct resonance peaks for D-BPEI at 157.15, 62.16, 55.12, 53.20, 51.62, 49.01, and 42.84 ppm. The peaks at chemical shifts of 157.15 ppm and 55.12 ppm were assigned to the carbonyl anion (a) and terminal methyl carbon (c) in the catalyst, respectively. The peak at chemical shift 62.16 ppm was assigned to the carbon at the junction of the adjacent quaternary ammonium cation (b), the peak at chemical shift 53.20 ppm to the carbon at the junction of the adjacent tertiary amine nitrogen (d), the peak at chemical shift 51.62 ppm to the terminal methyl carbon at the junction of the quaternary ammonium cation (e), the peak at chemical shift 49.01 ppm to the carbon near the tertiary amine nitrogen at the junction of the quaternary ammonium cation and the tertiary amine nitrogen (f), and the peak at chemical shift 42.84 ppm to the methyl carbon at the junction of the tertiary amine nitrogen (g). Based on the D-BPEI... 13 C10 NMR analysis confirmed that the structure of the synthesized catalyst was completely consistent with the designed ionic liquid structure.
[0093] Test Example 5: FT-IR Characterization
[0094] Taking the ionic liquid catalyst (D-BPEI) of Example 1 as an example, the infrared spectra of the raw material polyethyleneimine (B-PEI) and the prepared alkaline catalyst (D-BPEI) are as follows: Figure 6 As shown. B-PEI was observed at 3380, 2973, 1599, 1274, 1050 and 880 cm⁻¹. -1 There are obvious characteristic peaks at 3380 cm⁻¹. -1 The absorption peak at 2973 cm⁻¹ is attributed to the stretching vibration of the -OH group. -1 The absorption peak at 1599 cm⁻¹ is attributed to the CH stretching vibration of the -CH₃ group. -1 and 1274cm -1 The absorption peaks at 28 and 1050 cm⁻¹ are attributed to the NH bending vibrations of the primary and secondary amine groups. -1 The absorption peak at the wavenumber is attributed to the bending (stretching) vibration of CN at 34,880 cm⁻¹. -1 The absorption peaks at the wavenumbers are attributed to the in-plane rocking vibrations of the -CH3 group. These peaks are clearly observed at 1704 and 1194 cm⁻¹ in D-BPEI. -1 New functional group characteristic peaks appear at the wavenumber, including 1704 cm⁻¹. -1 The absorption peak at wavenumber is attributed to the stretching vibration of -C=O in the bonded anion (35, 1194 cm⁻¹). -1 The absorption peak at wavenumber 36 is attributed to the CO bending vibration of the bonded anion. The peak at 1599 cm⁻¹ is... -1 The absorption peak of the primary amine group at wavenumber shifts to 1539 cm⁻¹ -1At the wavenumber, this is due to the shift of the absorption peak caused by the formation of hydrogen bonds. 1274 cm -1 The absorption peak at [wavenumber] increases, which is due to the increase in the number of secondary amine groups, resulting in an enhanced absorption peak. 1050 cm -1 The C-N absorption peak at [wavenumber] increases, indicating a deeper degree of quaternization of B-PEI.
[0095] Test Example 6 TG-DTA Characterization
[0096] Taking the ionic liquid catalyst (D-BPEI) in Example 1 as an example, the mass loss of D-BPEI was determined by thermogravimetric analysis in an N2 atmosphere as Figure 7 shown. As the temperature increases, the basic catalyst (D-BPEI) shows three decomposition stages. In the first stage, the weight loss range is from room temperature to 312.7 °C, and the reason for the loss is the volatilization of adsorbed water and residual DMC, with a weight loss rate of approximately 9.3%. The second weight loss range is from 213.7 °C to 289.1 °C, which is due to the decomposition of the bonded anions at high temperature, with a weight loss rate of approximately 23.4%. The third weight loss range is from 289.1 °C to 470.7 °C, mainly due to the degradation of the B-PEI chain, with a weight loss rate of approximately 66.5%. After 470.7 °C, continuous heating results in a remaining mass of approximately 0.8% and remains unchanged, which is due to the carbon deposition generated by the decomposition of D-BPEI at high temperature.
[0097] Test Example 7 Determination of Base Strength and Base Quantity
[0098] Taking the ionic liquid catalyst (D-BPEI) in Example 1 as an example, the base strength and base quantity of D-BPEI prepared under the preferred activation reaction conditions in Example 1 were determined by the Hammett indicator titration method and the national standard GB / T 5760 - 12000, respectively. The base strength of D-BPEI prepared under these conditions was measured to be 9.8 < H < 15.0, and the base quantity was 1.27 mmol / L.
[0099] Test Example 8 Test on the Effect of Reaction Temperature on the Transesterification Reaction of EC and EtOH
[0100] Taking the ionic liquid catalyst (D-BPEI) in Example 1 as an example, the effect of reaction temperature on the transesterification of EC and EtOH was studied as Figure 8 shown. The results show that as the reaction temperature increases, the catalytic ability of D-PEI for the transesterification of EC and EtOH increases. When the reaction temperature rises from 40 °C to 70 °C, the conversion rate of EC and the yield of DEC are relatively low. When the temperature reaches 82 °C, the conversion rate of EC is 74.8%, the yield of DEC is 69.4%, and the TOF value is 120.2 h -1This is because when the reaction system reaches the azeotropic temperature, the frequency and energy of collisions between molecules increase, the reaction rate accelerates, and the DEC yield significantly improves. Therefore, 82℃ can be determined as the optimal reaction temperature.
[0101] Test Example 9: Effect of D-BPEI ionic liquid catalyst dosage on EC and EtOH transesterification reactions
[0102] Using the ionic liquid catalyst (D-BPEI) from Example 1 as a typical example, the effect of catalyst dosage on the transesterification of EC and EtOH was investigated. Figure 9 As shown in the figure, the experimental results indicate that the yield of the target product gradually increases with the increase of catalyst dosage. When the catalyst dosage is 1% of the mass of the raw material EC, the EC conversion rate is 51.4%, the DEC yield is 45.5%, and the TOF value is 157.7 h⁻¹. -1 When the catalyst dosage remained at 2% of the EC mass, the EC conversion reached 74.8%, the DEC yield reached 69.4%, and the TOF value was 120.2 h⁻¹. -1 At this point, the EC conversion and DEC yield significantly increased. This is because with the increase in catalyst dosage, the number of active sites increases, allowing for sufficient contact with the reactants and promoting the forward transesterification reaction between EC and EtOH. Further increasing the catalyst dosage to 3%, 4%, and 5% of the EC mass did not significantly increase the EC conversion, DEC selectivity, and yield. Therefore, the optimal catalyst dosage can be determined to be 2% of the EC mass.
[0103] Test Example 10: Stability evaluation of the catalyst in EC and EtOH transesterification reactions
[0104] Taking the ionic liquid catalyst (D-BPEI) from Example 1 as a typical example, the stability of D-BPEI was studied, and the results are as follows: Figure 10 As shown in the figure, during the initial reuse of D-BPEI, the EC conversion, DEC selectivity, and yield were 79.5%, 90.7%, and 72.1%, respectively. During the sixth reuse, the EC conversion, DEC selectivity, and yield were 73.6%, 88.2%, and 64.9%, respectively. Compared to the initial reuse, the catalytic activity of D-BPEI decreased slightly during the recycling process, mainly due to the loss of a small number of bonded anions during use and catalyst loss caused by multiple samplings during the recycling process. In summary, after six reuses of D-BPEI, the DEC selectivity remained above 85%, and the DEC yield remained above 60%, with no significant deactivation, demonstrating that D-BPEI exhibits good stability and reusability in the EC and EtOH transesterification reactions.
[0105] Test Example 11: Catalytic Performance Testing in Various Transesterification Reactions
[0106] Taking the ionic liquid catalyst (D-BPEI) from Example 1 as an example, the catalytic performance of D-BPEI in various transesterification reactions is as follows: Figure 11 As shown, when D-BPEI catalyzes the transesterification reaction of linear carbonate DMC with EtOH to produce EMC, the conversion rate of DMC is 42.6%, the yield of EMC is 39.2%, and the TOF value is 45.0 h. -1 In the catalytic transesterification reaction of DEC and MeOH to produce EMC, the DEC conversion rate was 37.0%, the EMC yield was 21.2%, and the TOF value was 22.9 h. -1 The results showed that D-BPEI catalyzed a higher yield of EMC in the transesterification reaction of DMC and EtOH. This is because the catalyst generates methoxy anions (CH3O4) through hydrogen bonding with methanol and ethanol, respectively. ― ) and ethoxy anion (CH3CH2O) ― In substitution reactions with carbonyl carbons, the ethoxy group exhibits higher activity. When D-BPEI catalyzes the transesterification reaction of oxalate DMO with EtOH to generate DEO, the DMO conversion is 87.4%, the DEO yield is 28.2%, and the TOF value is 37.7 h⁻¹. -1 When catalytically reacting DEO oxalate with MeOH to produce DMO via transesterification, the DEO conversion was 51.0%, the DMO yield was 9.7%, and the TOF value was 10.5 h⁻¹. -1 Similarly, the higher yield in the catalytic transesterification reaction of DMO and EtOH to generate DEO can be attributed to the higher activity of the ethoxy anion in attacking the carbonyl carbon. In the catalytic transesterification reaction of MAC acetate and EtOH to generate EA, D-BPEI achieved a MAC conversion of 60.5%, and since no other byproducts were generated, the EA yield was 100%, with a TOF value of 128.6 h⁻¹. -1 D-BPEI also exhibits good activity in acetates. In the catalytic transesterification reaction of cyclic carbonate PC with EtOH to produce DEC, D-BPEI achieved a PC conversion of 46.8%, a DEC yield of 44.3%, and a TOF value of 69.8 h⁻¹. -1 When catalytically reacting PC with MeOH for transesterification to produce DMC, the PC conversion rate was 66.3%, the DMC yield was 65.6%, and the TOF value was 103.3 h⁻¹. -1 When catalytically reacting cyclic carbonate EC with EtOH to produce DEC via transesterification, the EC conversion rate was 68.8%, the DEC yield was 65.2%, and the TOF value was 112.9 h. -1 In the catalytic transesterification reaction of EC and MeOH to produce DMC, the EC conversion rate was 78.2%, the DMC yield was 75.7%, and the TOF value was 131.2 h. -1The above results indicate that when different cyclic carbonates (EC and PC) undergo transesterification with the same alcohol, the catalytic activity of EC is significantly higher than that of PC. This is because PC has an additional methyl group (-CH3) in its structure, leading to increased steric hindrance and thus lower catalytic efficiency. When the same cyclic carbonate undergoes transesterification with different alcohols, the catalytic activity with methanol is higher than that with ethanol. This is because the hydroxyl bond energy in methanol is lower than that in ethanol, resulting in the generation of a large number of methoxy anions that catalyze the reaction, allowing the reaction to proceed smoothly in the forward direction.
[0107] Test Example 12: Preparation and Evaluation of Other Carbonate-Activated Polyethyleneimine Ionic Liquids
[0108] Using the ionic liquid catalyst (D-BPEI) from Example 1 as a typical example, the preparation and evaluation of other carbonate-activated polyethyleneimine ionic liquids were studied. Figure 12 As shown in the figure. The results indicate that different types of carbonates can activate polyethyleneimine to obtain a strongly basic ionic liquid catalyst. When B-PEI is activated using DEC, the EC conversion is 75.6%, the DEC yield is 70.5%, and the TOF value is 122.3 h⁻¹. -1 At this point, the catalytic efficiency is similar to that of the D-BPEI ionic liquid, both exhibiting good catalytic activity. When B-PEI is activated using EC, the EC conversion rate is 79.2%, the DEC yield is 75.0%, and the TOF value is 130.0 h⁻¹. -1 When B-PEI was activated using PC, the EC conversion rate was 75.7%, the DEC yield was 69.9%, and the TOF value was 121.1 h. -1 Cyclic carbonates activated polyethyleneimine exhibited good catalytic activity, but EC activated B-PEI ionic liquid showed slightly higher catalytic activity than PC activated B-PEI. The main reason is that PC has one more methyl group in its structure than EC, which increases steric hindrance and makes ring opening difficult during activation, resulting in slightly lower catalytic activity.
[0109] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A strongly basic ionic liquid based on the green quaternization of polyethyleneimine, characterized in that, The strongly alkaline ionic liquid includes cations and anions; The cation is polyethyleneimine containing several quaternary ammonium cation structural units as shown in Formula I. The anion is selected from at least one of the structures shown in Formulas II to V; 2. The strongly alkaline ionic liquid based on the green quaternization of polyethyleneimine according to claim 1, characterized in that, The strong alkaline ionic liquid has an alkalinity of 9.8–15.0 and an alkalinity of 1.0–1.27 mmol / L.
3. The strongly alkaline ionic liquid based on the green quaternization of polyethyleneimine according to claim 1, characterized in that, The anions in the strongly alkaline ionic liquid originate from the raw materials or products of the transesterification reaction.
4. The method for preparing the strongly basic ionic liquid based on the green quaternization of polyethyleneimine according to any one of claims 1 to 3, characterized in that, Includes the following steps: The activated reaction was carried out in a sealed container containing polyethyleneimine and carbonate compounds, followed by rotary evaporation under reduced pressure to obtain the strongly basic ionic liquid based on the green quaternization of polyethyleneimine.
5. The preparation method according to claim 4, characterized in that, The activation reaction conditions include: being carried out under stirring, with an activation reaction temperature of 70–110°C and an activation reaction time of 2–10 h; Preferably, the activation reaction conditions further include: slowly heating to the activation reaction temperature at a rate of 2-3 °C / min.
6. The preparation method according to claim 4, characterized in that, The weight ratio of the polyethyleneimine to the carbonate compound is 1:1 to 5.
7. The preparation method according to claim 4, characterized in that, The conditions for vacuum heating rotary evaporation include: heating to 50-80°C and then rotary evaporating for 3-6 hours under an ambient vacuum of -0.1 to -0.08 Pa.
8. The preparation method according to claim 7, characterized in that, The conditions for vacuum heating rotary evaporation include: maintaining a temperature of 50–80°C for 3–6 hours at an ambient vacuum of -0.1 to -0.08 Pa. Preferably, the conditions for vacuum heating rotary evaporation include: heating sequentially to 50-60°C, 60-70°C, and 70-80°C under an ambient vacuum of -0.1 to -0.08 Pa, and rotary evaporating for 0.5 to 2 hours respectively.
9. The application of the strongly basic ionic liquid based on green quaternization of polyethyleneimine as described in any one of claims 1 to 3, or the strongly basic ionic liquid based on green quaternization of polyethyleneimine obtained by the preparation method according to any one of claims 4 to 8, as a homogeneous catalyst for transesterification reaction.
10. The application according to claim 9, characterized in that, The transesterification reaction is selected from one of the following: transesterification reaction of cyclic carbonates with alcohols, transesterification reaction of chain carbonates with alcohols, transesterification reaction of oxalates with alcohols, and transesterification reaction of acetates with alcohols. Preferably, the temperature window for the transesterification reaction is 40–82°C.