A basic ionic liquid catalyst, its preparation method and its application
By using an alkaline ionic liquid catalyst in synergistic catalysis with H2SO4 to synthesize cyclic carbonates from aliphatic diols and CO2, the problems of poor stability and low catalytic efficiency of traditional catalysts are solved, achieving high catalytic activity and stability. The catalyst system is safe and has good thermal stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENYANG UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2024-09-11
- Publication Date
- 2026-05-26
AI Technical Summary
Existing catalysts suffer from poor stability and low catalytic efficiency in the synthesis of cyclic carbonates from aliphatic diols and CO2.
Using alkaline ionic liquid catalysts [DBUH]phy, [TBDH]phy, and [DBUH]tbd, cyclic carbonates are synthesized from aliphatic diols and CO2 through synergistic catalysis with H2SO4. The ionic liquid anions attack the hydroxyl groups of the aliphatic diols to form carbocations, while the cations form NC bonds with the carbonyl groups of CO2, breaking the carbon-oxygen double bond. H2SO4 abstracts hydrogen from the hydroxyl groups to form oxygen anions, which activate the aliphatic diols to attack the carbonyl carbons to form cyclic carbonates.
It improves the stability and catalytic activity of the catalyst, enhances the conversion rate and selectivity of reactants, and the catalyst system is not easily combustible or explosive at room temperature, exhibiting good thermal and chemical stability.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst technology, and in particular to an alkaline ionic liquid catalyst, its preparation method, and its application. Background Technology
[0002] With the increasing use of natural gas and oil by humans, atmospheric CO2 emissions are rising, leading to the "greenhouse effect" and drawing widespread global attention. As carbon dioxide is an abundant, non-toxic, non-flammable, and inexpensive carbon source, the direct synthesis of chemicals and fuels from it has attracted considerable interest. In the chemical industry, utilizing CO2 chemical conversion reactions to synthesize value-added products is attractive due to its significant economic and environmental benefits. Among chemical conversion processes involving carbon dioxide, the production of dimethyl carbonate, polycarbonate, and cyclic carbonates from CO2 has been actively studied, with some already commercialized. Currently, the cycloaddition of CO2 with epoxides is the most studied due to its green process, and several effective catalysts have been reported. However, this process suffers from the high reactivity, low boiling point, and flammability and explosiveness of epoxides, requiring specialized synthesis techniques and storage and handling requirements. Recently, the carboxylation of aliphatic glycols with CO2 has been considered a green alternative. This reaction produces only water, and the glycols can be produced from biomass, making it renewable. Therefore, the process route for synthesizing carbonates using aliphatic glycols is highly attractive.
[0003] The direct synthesis of cyclic carbonates from aliphatic diols and CO2 is thermodynamically and kinetically unfavorable, requiring high reaction temperatures, pressures, and promoter-induced equilibrium transitions towards the target product. However, existing catalysts, due to their structural properties, still suffer from problems such as catalyst hydrolysis, poor stability, difficulty in separation, low catalytic efficiency, and high catalyst dosage. Therefore, existing catalytic systems require further improvement and enhancement. Summary of the Invention
[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide an alkaline ionic liquid catalyst, its preparation method and its application, in order to solve the problems of poor stability and low catalytic efficiency of traditional catalysts in the prior art.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] In a first aspect, a basic ionic liquid catalyst, wherein the basic ionic liquid catalyst is [DBUH]phy, [TBDH]phy, and [DBUH]tbd, with the following structural formula:
[0007]
[0008] a=[DBUH]phy; b=[TBDH]phy; c=[DBUH]tbd
[0009] Furthermore, the catalyst is an alkaline ionic liquid catalyst obtained by reacting any two of 1,8-diazabicycloundec-7-ene, 1,5,7-triazidobicyclo(4,4,0)dec-5-ene, and phenol.
[0010] Secondly, the preparation method of a basic ionic liquid catalyst is as follows:
[0011] X and Y in a molar ratio of 1.1:1 were added to a reaction vessel, and distilled water was added as a solvent. The mixture was refluxed at 80°C for 12-24 hours under N2 protection. After the reaction was completed, the mixture was washed three times with ethyl acetate and distilled water, and then dried under vacuum at 80°C to obtain an alkaline ionic liquid catalyst. X is one of 1,8-diazabicycloundec-7-ene, 1,5,7-triazidobicyclo(4,4,0)dec-5-ene, and phenol. Y is one of 1,8-diazabicycloundec-7-ene, 1,5,7-triazidobicyclo(4,4,0)dec-5-ene, and phenol. X is not equal to Y.
[0012] Furthermore, the ratio of distilled water to X is 2:1.
[0013] Thirdly, the application of an alkaline ionic liquid catalyst for co-catalyzing the synthesis of cyclic carbonates from aliphatic diols and CO2 with H2SO4; wherein the aliphatic diols include one of ethylene glycol, 1,2-propanediol, 1,3-propanediol, and 1,4-butanediol.
[0014] The technical solution adopted in this invention has the following beneficial effects:
[0015] (1) The catalyst in the system of the present invention is more stable than that of traditional catalysts, requires less catalyst, and can improve reactant conversion rate, reaction selectivity and enhance catalytic activity.
[0016] (2) The catalyst system is based on the properties of ionic liquids. It is a viscous liquid at room temperature, which is not easy to burn, explode, or oxidize, and has good thermal and chemical stability. Attached Figure Description
[0017] Figure 1 The infrared spectra of the catalysts prepared in Examples 1, 2, and 3 are shown below.
[0018] Figure 2 The hydrogen nuclear magnetic resonance spectra of the catalysts prepared in Examples 1, 2, and 3 are shown below.
[0019] Figure 3 The thermogravimetric spectra of the catalysts prepared in Examples 1, 2, and 3 are shown. Detailed Implementation
[0020] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0021] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.
[0022] It should also be noted that the same or similar reference numerals in the accompanying drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the accompanying drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.
[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.
[0024] In a first aspect, an acidic ionic liquid catalyst, wherein the acidic ionic liquid catalyst is a basic ionic liquid catalyst of [DBUH]phy, [TBDH]phy, and [DBUH]tbd, with the chemical formula: .
[0025] Secondly, the preparation method of a basic ionic liquid catalyst is as follows:
[0026] X and Y in a molar ratio of 1.1:1 were added to a reaction vessel, and distilled water was added as a solvent. The mixture was refluxed at 80°C for 12-24 hours under N2 protection. After the reaction was completed, the mixture was washed three times with ethyl acetate and distilled water, and then dried under vacuum at 80°C to obtain an alkaline ionic liquid catalyst. X is one of 1,8-diazabicycloundec-7-ene, 1,5,7-triazidobicyclo(4,4,0)dec-5-ene, and phenol. Y is one of 1,8-diazabicycloundec-7-ene, 1,5,7-triazidobicyclo(4,4,0)dec-5-ene, and phenol. X is not equal to Y.
[0027] The preferred molar ratio of distilled water to X is 2:1.
[0028] Thirdly, the application of an alkaline ionic liquid catalyst for co-catalyzing the synthesis of cyclic carbonates from aliphatic diols and CO2 with H2SO4; wherein the aliphatic diols include one of ethylene glycol, 1,2-propanediol, 1,3-propanediol, and 1,4-butanediol.
[0029] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.
[0030] The catalysts of this invention are [DBUH]phy, [TBDH]phy, and [DBUH]tbd. DBU, TBD, and phenol, two of which react to form an alkaline ionic liquid catalytic system. This catalyst is stable, easy to store, and pollution-free, and exhibits higher selectivity and catalytic activity for the reaction.
[0031] In this invention, DBU and TBD exhibit good catalytic activity for the CO2 reaction, while H2SO4 can activate aliphatic glycols to enhance the synergistic catalytic effect of anions and cations. The principle is that the ionic liquid anion attacks the hydroxyl group on one side of the aliphatic glycol to form a carbocation, while the ionic liquid cation forms an NC bond with the carbonyl carbon group of CO2, breaking the carbon-oxygen double bond and making the carbonyl carbon positively charged. Simultaneously, H2SO4 abstracts hydrogen from the hydroxyl group of the ethylene glycol to form H2O and an oxygen anion. The activated aliphatic glycol simultaneously attacks the positively charged carbonyl carbon and carbonyl oxygen, forming a cyclic carbonate. Compared with other types of catalysts, this effectively improves the selectivity and conversion rate of the catalyst system. Therefore, this invention aims to prepare an alkaline ionic liquid and H2SO4 acid to synergistically catalyze the synthesis of ethylene carbonate from aliphatic glycols and CO2, effectively improving catalytic activity and structural stability.
[0032] Three basic ionic liquids were first prepared to investigate the effect of different Bronsted acids on the catalytic performance of the catalysts.
[0033] Example 1
[0034] DBU and phenol in a molar ratio of 1.1:1 were added to a reaction vessel, followed by distilled water solvent. The mixture was refluxed at 80°C for 24 hours under N2 protection. After the reaction was completed, the mixture was washed three times with ethyl acetate and distilled water, and then dried under vacuum at 80°C for 12 hours to obtain the basic ionic liquid [DBUH]phy.
[0035] Example 2
[0036] TBD and phenol in a molar ratio of 1.1:1 were added to a reaction vessel, followed by distilled water solvent. The mixture was refluxed at 80°C for 24 hours under N2 protection. After the reaction was completed, the mixture was washed three times with ethyl acetate and distilled water, and then dried under vacuum at 80°C for 12 hours to obtain the basic ionic liquid [TBDH]phy.
[0037] Example 3
[0038] DBU and TBD in a molar ratio of 1.1:1 were added to a reaction vessel, followed by distilled water solvent. The mixture was refluxed at 80°C for 24 hours under N2 protection. After the reaction was completed, the mixture was washed three times with ethyl acetate and distilled water, and then dried under vacuum at 80°C for 12 hours to obtain the basic ionic liquid [DBUH]tbd.
[0039] The alkaline ionic liquid catalyst prepared above was used to catalyze the reaction of ethylene glycol and CO2 to synthesize ethylene carbonate.
[0040] The catalytic experimental conditions were as follows: The catalysts prepared in Examples 1-3 were applied to the synthesis of ethylene carbonate from CO2 and ethylene glycol using a batch reactor. The catalyst dosage was 5% of the total raw material mass, with 5g of H2SO4 and 50ml of ethylene glycol. The reactor temperature was 120℃ and the pressure was 3.5MPa, and the reaction was carried out for 12 hours. After the reaction, the mixture was distilled under reduced pressure. The remaining heavy components were the catalyst. The purity of the distillate was determined by gas chromatography. Finally, the conversion, selectivity, and yield were calculated.
[0041] Traditional catalysts CeO2, triethylamine and zinc bromide, and DBU and triethylamine were used to catalyze the reaction of ethylene glycol and CO2 to synthesize ethylene carbonate, respectively, with the catalytic process conditions and procedures described above. The effect of different catalyst types on catalytic performance was investigated, and the catalytic results are shown in Table 1.
[0042] Table 1. Effect of catalyst type on catalytic performance
[0043]
[0044] As can be seen from the data in Table 1, alkaline ionic liquids are superior to CeO2, triethylamine and zinc bromide, DBU and sulfuric acid. Among them, Example 1 has the best catalytic effect, with an ethylene glycol conversion rate of 25.79% and a ethylene carbonate selectivity of 98.89%.
[0045] Example 4
[0046] Taking the catalyst of Example 1 as an example, the performance of catalyzing the synthesis of cyclic carbonates from different aliphatic diols (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, and 1,4-butanediol) and CO2 was evaluated. The catalytic results are shown in Table 2.
[0047] Table 2. Evaluation of catalytic performance of different aliphatic diols
[0048]
[0049] As can be seen from the data in Table 2, the yields of five-membered ring carbonates synthesized from ethylene glycol and 1,2-propylene glycol are relatively high, while the yields of six-membered and seven-membered ring carbonates synthesized from 1,3-propylene glycol and 1,4-butanediol are relatively low. This is because the five-membered ring structure is the most stable and easy to form, while the six-membered and seven-membered rings are less stable.
[0050] The chemical structures of the catalysts prepared in Examples 1-3 were characterized using Fourier transform infrared spectroscopy (FI-IR), and the results are shown in the figure. Figure 1 .
[0051] Figure 1 The figure shows the infrared spectra of the three prepared basic ionic liquid catalysts, where a represents the ionic liquid catalyst [DBUH]phy, b represents the ionic liquid catalyst [TBDH]phy, and c represents the ionic liquid catalyst [DBUH]tbd. The stretching vibration frequency of the OH group on phenol is in the range of 3290 cm⁻¹. -1 The vicinity is not shown in the figure; the CH stretching vibration frequency on the benzene ring of phenol appears at 3045 cm⁻¹. -1 Nearby, the C=C skeletal vibration peak is at 1579 cm⁻¹. -1 692cm -1 Nearby, CO stretching oscillations occurred at 1255 cm⁻¹. -1 Nearby, the NH stretching vibrations on the DBU and TBD occur at 2929 cm⁻¹. -1 Nearby, CH stretching vibrations occur at 2855 cm⁻¹. -1 Nearby. C=N stretching vibration occurs at 1633 cm. -1 Nearby, CN stretching vibration is at 1469 cm. -1 Nearby, the deformation oscillation peak of the DBU and TBD rings is at 1469 cm⁻¹. -1 753 cm -1 The presence of nearby particles confirms the correctness of the catalyst structure. This also confirms the correctness of the structure of this series of catalysts.
[0052] Figure 2The figure shows the proton NMR spectra of the three prepared basic ionic liquid catalysts, where a represents the ionic liquid catalyst [DBUH]phy, b represents the ionic liquid catalyst [TBDH]phy, and c represents the ionic liquid catalyst [DBUH]tbd. In the figure, 1 represents the elution position of hydrogen on the benzene ring of phenol, between 6 and 7.2 ppm, and 2 represents the elution position of hydrogen on the DBU and TBD rings, between 1 and 3.5 ppm. Therefore, this further confirms the correct structure of the basic ionic liquid catalysts.
[0053] Figure 3 The figure shows the thermogravimetric spectra of the three prepared basic ionic liquid catalysts, where a is [DBUH]phy, b is [TBDH]phy, and c is [DBUH]tbd. Catalyst a decomposes slowly below 160 °C. When the temperature reaches about 170 °C, the mass fraction of the sample is still higher than 92%. It decomposes rapidly at about 214 °C, reaching the maximum decomposition rate, and completely decomposes at about 222 °C. Catalyst b decomposes slowly below 190 °C. When the temperature reaches about 200 °C, the mass fraction of the sample is still higher than 90%. It decomposes rapidly at about 264 °C, reaching the maximum decomposition rate, and completely decomposes at about 272 °C. This is because the sample contains low-boiling-point benzene ring compounds that volatilize at high temperatures. Catalyst C decomposes slowly below 280 °C. At approximately 320 °C, the sample mass fraction remains above 80%. Rapid decomposition occurs around 350 °C, reaching the maximum decomposition rate. Decomposition stabilizes around 400 °C, with a sample mass residue close to 20%. The actual reaction temperature is below 160 °C, indicating good thermal stability of the catalyst system.
[0054] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the solutions disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.
Claims
1. A basic ionic liquid catalyst characterized in that, The alkaline ionic liquid catalyst has the chemical formula [DBUH]tbd and the structural formula is: c=[DBUH]tbd; The catalyst is a basic ionic liquid catalyst obtained by the reaction between 1,8-diazabicycloundec-7-ene and 1,5,7-triazidobicyclo(4,4,0)dec-5-ene.
2. A process for the preparation of the basic ionic liquid catalyst according to claim 1, characterized in that, X and Y in a molar ratio of 1.1:1 were added to the reactor, and distilled water was added as a solvent. The mixture was refluxed at 80°C for 12-24 hours under N2 protection. After the reaction was completed, the mixture was washed three times with ethyl acetate and distilled water, and then dried under vacuum at 80°C to obtain an alkaline ionic liquid catalyst, wherein X is 1,8-diazabicycloundec-7-ene and Y is 1,5,7-triazidobicyclo(4,4,0)dec-5-ene.
3. The method for preparing the alkaline ionic liquid catalyst according to claim 2, characterized in that, The ratio of distilled water to X is 2:
1.
4. The application of the alkaline ionic liquid catalyst as described in claim 1, characterized in that, It is used to synergistically catalyze the synthesis of cyclic carbonates from fatty diols and CO2 with H2SO4.
5. The application of the alkaline ionic liquid catalyst according to claim 4, characterized in that, The fatty glycols mentioned include one of ethylene glycol, 1,2-propanediol, 1,3-propanediol, and 1,4-butanediol.