Alkaline ionic liquid catalyst, preparation method and application thereof

Abstract

The invention discloses a basic ionic liquid catalyst as well as a preparation method and application thereof, the structural formula of the basic ionic liquid catalyst is [DBUH] phy, [TBDH] phy and [DBUH] tbd, and the basic ionic liquid catalyst is obtained by reaction of a calculated amount of 1, 8-diazabicyclo undec-7-ene (DBU), a calculated amount of 1, 8-diazabicyclo (4.4. 0) dec-5-ene (TBD) and a calculated amount of phenol. The catalyst is used for cooperating with H2SO4 to catalyze a series of aliphatic diol and CO2 to react to synthesize cyclic carbonate, and has the characteristics of high selectivity and wide applicability; compared with an existing cyclic carbonate synthesis process, the cyclic carbonate synthesis method has the advantages that the reaction process is safer and free of pollution, the catalyst is good in stability, small in dosage, high in selectivity, free of by-products and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a basic ionic liquid catalyst, a preparation method and application thereof. Background Art

[0002] As human beings use natural gas and oil more and more, the amount of CO2 in the atmosphere continues to rise, leading to the "greenhouse effect", which has attracted widespread attention around the world. Since carbon dioxide is an abundant, non-toxic, non-flammable and cheap carbon source, the direct synthesis of chemicals and fuels from carbon dioxide has aroused great interest. In the chemical industry, it is attractive to use chemical conversion reactions of CO2 to synthesize value-added products because such conversions have important economic and environmental effects. Among the chemical conversion processes involving carbon dioxide, the production of dimethyl carbonate, polycarbonate and cyclic carbonates using CO2 has been actively studied, and some of them have been commercialized. At present, the cycloaddition of CO2 with epoxides has been studied the most due to its green process, and a variety of effective catalysts have been reported. However, the problem with this process is that epoxides are highly active, low boiling point, flammable and explosive, and require special synthesis process technology and storage and handling requirements. Recently, the carboxylation of aliphatic diols with CO2 has been considered as a green alternative method. The reaction process only produces water, and the diols can be produced from biomass and are renewable. Therefore, the process route for synthesizing carbonates using aliphatic diols is very attractive.

[0003] The direct use of aliphatic diols and CO2 to synthesize cyclic carbonates is very unfavorable in terms of thermodynamics and kinetics, and requires higher reaction temperature, pressure and additives to induce the equilibrium to shift to the formation of the target product. However, the existing catalysts still have problems such as catalyst hydrolysis, poor stability, difficulty in separation, low catalytic efficiency, and high catalyst dosage due to their own structural properties. Therefore, the existing catalytic system needs to be improved and enhanced. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an alkaline ionic liquid catalyst, a preparation method and application thereof, aiming to solve the problems of poor stability and low catalytic efficiency of traditional catalysts in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In the first aspect, a basic ionic liquid catalyst is provided, wherein the basic ionic liquid catalyst is [DBUH]phy, [TBDH]phy and [DBUH]tbd, and the structural formula is: a=[DBUH]phy; b=[TBDH]phy; c=[DBUH]tbd Furthermore, the catalyst is an alkaline ionic liquid catalyst obtained by reacting any two of 1,8-diazabicycloundec-7-ene, 1,57-triazidobicyclo(4.4.0)dec-5-ene and phenol.

[0006] In the second aspect, a method for preparing a basic ionic liquid catalyst is as follows: Add X and Y in a molar ratio of 1.1:1 to a reaction kettle, add distilled water as a solvent, condense and reflux at 80°C for 12-24h under N2 protection, wash with ethyl acetate and distilled water three times respectively after the reaction, and vacuum dry at 80°C to obtain an alkaline ionic liquid catalyst, wherein 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, and X is not equal to Y.

[0007] Furthermore, the ratio of distilled water to X is 2:1.

[0008] The third aspect is the application of an alkaline ionic liquid catalyst for co-catalyzing with H2SO4 the synthesis of cyclic carbonates from fatty diols and CO2; wherein the fatty diol includes one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, and 1,4-butanediol.

[0009] The technical solution adopted by the present invention has the following beneficial effects: (1) The catalyst of the system of the present invention is more stable than traditional catalysts, requires less catalyst, can improve the conversion rate of reactants, reaction selectivity, and enhance catalytic activity.

[0010] (2) The catalyst system is based on the physical properties of ionic liquids. It is a viscous liquid at room temperature, non-flammable, non-explosive, and non-oxidizable, and has good thermal and chemical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The infrared spectra of the catalysts prepared in Example 1, Example 2 and Example 3 are shown; Figure 2 The hydrogen nuclear magnetic spectra of the catalysts prepared in Example 1, Example 2 and Example 3; Figure 3 The thermogravimetric spectra of the catalysts prepared in Example 1, Example 2, and Example 3 are shown. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0013] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or indirectly on the other component. When a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to the other component.

[0014] It should also be noted that the same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0015] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0016] In the first aspect, an acidic ionic liquid catalyst is provided, wherein the acidic ionic liquid catalyst is a basic ionic liquid catalyst of [DBUH]phy, [TBDH]phy and [DBUH]tbd, and the chemical formula is: .

[0017] In the second aspect, a method for preparing a basic ionic liquid catalyst is as follows: Add X and Y in a molar ratio of 1.1:1 to a reaction kettle, add distilled water as a solvent, condense and reflux at 80°C for 12-24h under N2 protection, wash with ethyl acetate and distilled water three times respectively after the reaction, and vacuum dry at 80°C to obtain an alkaline ionic liquid catalyst, wherein 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, and X is not equal to Y.

[0018] The molar ratio of distilled water to X is preferably 2:1.

[0019] The third aspect is the application of an alkaline ionic liquid catalyst for synergistically catalyzing aliphatic diols and CO2 to synthesize cyclic carbonates with H2SO4; the aliphatic diol includes one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, and 1,4-butanediol.

[0020] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0021] The catalyst of the invention is [DBUH]phy, [TBDH]phy and [DBUH]tbd. DBU, TBD and phenol are reacted to form an alkaline ionic liquid catalyst system. The catalyst is stable in nature, easy to store, pollution-free and has higher selectivity and catalytic activity for the reaction.

[0022] In the present invention, DBU and TBD have good catalytic activity for CO2 reaction, and H2SO4 can activate fatty diols to enhance the synergistic catalytic effect of anions and cations. The principle is that the ionic liquid anions attack the hydroxyl group on the side of the fatty diols to form carbon cations, and at the same time, the ionic liquid cations can form NC bonds with the C in the carbonyl carbon group of CO2, breaking the carbon-oxygen double bond, making the carbonyl carbon positively charged, and at the same time, H2SO4 captures the hydrogen on the hydroxyl group of ethylene glycol to form H2O and oxygen anions, and the activated fatty diols simultaneously attack the positively charged carbonyl carbon and carbonyl oxygen to form cyclic carbonates. Compared with other types of catalysts, the selectivity and conversion rate of the catalyst system can be effectively improved. Therefore, the present invention intends to prepare alkaline ionic liquids and H2SO4 acid to synergistically catalyze fatty diols and CO2 to synthesize ethylene carbonate, effectively improving the catalytic activity and structural stability.

[0023] Firstly, three alkaline ionic liquids were prepared to investigate the effects of different Bronsted acids on the catalytic performance of the catalyst.

[0024] Example 1 DBU and phenol in a molar ratio of 1.1:1 were added to the reactor, and distilled water solvent was added, and condensed and refluxed at 80°C for 24 hours under N2 protection. After the reaction was completed, it was washed with ethyl acetate and distilled water three times, and vacuum dried at 80°C for 12 hours to obtain an alkaline ionic liquid [DBUH]phy.

[0025] Example 2 TBD and phenol in a molar ratio of 1.1:1 were added to the reactor, and distilled water solvent was added, and condensed and refluxed at 80°C for 24 hours under N2 protection. After the reaction was completed, it was washed three times with ethyl acetate and distilled water, and vacuum dried at 80°C for 12 hours to obtain an alkaline ionic liquid [TBDH]phy.

[0026] Example 3 DBU and TBD were added to the reactor at a molar ratio of 1.1:1, and distilled water was added as solvent. The mixture was condensed and 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 vacuum dried at 80°C for 12 hours to obtain the alkaline ionic liquid [DBUH]tbd.

[0027] The alkaline ionic liquid catalyst prepared above is used to catalyze the reaction of ethylene glycol and CO2 to synthesize ethylene carbonate.

[0028] The catalytic experimental conditions are as follows: the catalysts prepared in Examples 1-3 are respectively used in a tank reactor to catalyze the synthesis of ethylene carbonate from CO2 and ethylene glycol. The amount of catalyst used accounts for 5% of the total mass of the raw materials, H2SO4 5g, ethylene glycol 50ml, the reactor temperature is 120°C, and the pressure is 3.5Mpa for 12 hours. After the reaction is completed, the reaction is carried out by vacuum distillation, and the residual heavy component is the catalyst. The distillate is used to determine the product purity by gas chromatography, and finally the conversion rate, selectivity and yield are calculated.

[0029] The conventional catalysts CeO2, triethylamine and zinc bromide, DBU and triethylamine were used to catalyze the reaction of ethylene glycol and CO2 to synthesize ethylene carbonate, respectively, and the catalytic process conditions and process were the same as described above. The effects of different catalyst types on the catalytic performance were investigated, and the catalytic results are shown in Table 1.

[0030] Table 1. Effect of catalyst type on catalytic performance From the data in Table 1, it can be seen that the effects of alkaline ionic liquids are better than CeO2, triethylamine and zinc bromide, DBU and sulfuric acid, among which Example 1 has the best catalytic effect, with an ethylene glycol conversion rate of 25.79% and an ethylene carbonate selectivity of 98.89%.

[0031] Example 4 Taking the catalyst of Example 1 as an example, the performance of catalyzing different fatty diols (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol) and CO2 to synthesize cyclic carbonates was evaluated. The catalytic results are shown in Table 2.

[0032] Table 2. Evaluation of catalytic performance of different fatty diols From the data in Table 2, it can be seen that the yield of the five-membered ring carbonate synthesized from ethylene glycol and 1,2-propylene glycol is higher, and the yield of the six-membered ring carbonate and the seven-membered ring carbonate synthesized from 1,3-propylene glycol and 1,4-butanediol is lower. This is because the structure of the five-membered ring is the most stable and easy to form, while the stability of the six-membered ring and the seven-membered ring is poor.

[0033] The chemical structures of the catalysts prepared in Examples 1-3 were characterized by Fourier transform infrared spectroscopy (FI-IR). Figure 1 .

[0034] Figure 1 The infrared spectra of the three prepared alkaline ionic liquid catalysts are shown in the figure, where a is the ionic liquid catalyst [DBUH]phy, b is the ionic liquid catalyst [TBDH]phy, and c is the ionic liquid catalyst [DBUH]tbd. The OH stretching vibration frequency range of phenol is 3290cm -1 The CH stretching vibration frequency of the phenol benzene ring appears at 3045 cm -1 Nearby, the C=C skeleton vibration peak is at 1579cm -1 、692cm -1 Nearby, CO stretching oscillation appears at 1255 cm -1 Nearby, the NH stretching vibration of DBU and TBD appears at 2929 cm -1 Nearby, CH stretching vibration appears at 2855 cm -1 Nearby. C=N stretching vibration appears at 1633cm -1 Nearby, CN stretching vibration at 1469cm -1 Nearby, the DBU and TBD ring deformation oscillation peaks are at 1469cm -1 、753 cm -1 Nearby, proving that the catalyst structure is correct. Proving that the structure of this series of catalysts is correct.

[0035] Figure 2Shown are the hydrogen nuclear magnetic spectra of the three prepared alkaline ionic liquid catalysts, as shown in the figure, where a is the ionic liquid catalyst [DBUH]phy, b is the ionic liquid catalyst [TBDH]phy, c is the ionic liquid catalyst [DBUH]tbd, where 1 is the peak position of hydrogen on the benzene ring of phenol between 6-7.2ppm, where 2 is the peak position of hydrogen on the DBU and TBD rings between 1-3.5ppm. Therefore, it can be further proved that the structure of the alkaline ionic liquid catalyst is correct.

[0036] Figure 3 Shown are the thermal gravimetric spectra of the three prepared alkaline ionic liquid catalysts, as shown in the figure, where a is the ionic liquid catalyst [DBUH]phy, b is the ionic liquid catalyst [TBDH]phy, and c is the ionic liquid catalyst [DBUH]tbd. When the catalyst a is lower than 160°C, the sample decomposes slowly. When the temperature reaches about 170°C, the sample mass fraction is still higher than 92%. It decomposes rapidly at about 214°C and reaches the maximum decomposition rate. It is completely decomposed at about 222°C. When the catalyst b is lower than 190°C, the sample decomposes slowly. When the temperature reaches about 200°C, the sample mass fraction is still higher than 90%. It decomposes rapidly at about 264°C and reaches the maximum decomposition rate. It is completely decomposed at about 272°C. This is because the sample contains low-boiling benzene ring compounds, which volatilize at high temperature. When the catalyst c is below 280 ℃, the sample decomposes slowly. When the temperature reaches about 320 ℃, the sample mass fraction is still higher than 80%. It decomposes rapidly at about 350 ℃, reaching the maximum decomposition rate. The decomposition tends to be stable at about 400 ℃, and the sample mass residual rate is close to 20%. The actual reaction temperature is lower than 160 ℃. In view of this, it is shown that the catalyst of this system has good thermal stability. In view of this, it is shown that the catalyst of this system has good thermal stability.

[0037] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the schemes disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed in this disclosure. The description and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the claims.

Claims

1. A basic ionic liquid catalyst, characterized in that The chemical formula of the alkaline ionic liquid catalyst is [DBUH]phy, [TBDH]phy and [DBUH]tbd, and the structural formula is: a=[DBUH]phy; b=[TBDH]phy; c=[DBUH]tbd.

2. The alkaline ionic liquid catalyst according to claim 1, characterized in that: The catalyst is a basic ionic liquid catalyst obtained by reacting any two of 1,8-diazabicycloundec-7-ene, 1,57-triazidobicyclo(4.4.0)dec-5-ene and phenol.

3. A method for preparing the alkaline ionic liquid catalyst according to claim 1, characterized in that: Add X and Y in a molar ratio of 1.1:1 to a reaction kettle, add distilled water as a solvent, condense and reflux at 80°C for 12-24h under N2 protection, wash with ethyl acetate and distilled water three times respectively after the reaction, and vacuum dry at 80°C to obtain an alkaline ionic liquid catalyst, wherein 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, and X is not equal to Y.

4. The method for preparing the acidic ionic liquid catalyst according to claim 3, characterized in that: The ratio of distilled water to X is 2:

1.

5. A use of the alkaline ionic liquid catalyst as claimed in claim 1, characterized in that: Used to catalyze the synthesis of cyclic carbonates from aliphatic diols and CO2 in conjunction with H2SO4.

6. The use of the alkaline ionic liquid catalyst according to claim 5, characterized in that: The fatty diol includes one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol and 1,4-butylene glycol.

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