Alkaline forming functional flexible catalyst as well as preparation method and application thereof

Abstract

The invention discloses an alkaline forming functional flexible catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: performing ultrasonic mixing on a precursor A, a precursor B and a precursor C, constructing a microemulsion system by introducing a solution A and a solution B, shearing out tiny reaction particles with different particle sizes from the microemulsion system by regulating and controlling the shearing and stirring speed, and then performing anion regulation and control by utilizing ion exchange to obtain the alkaline forming functional flexible catalyst. A microemulsion system is changed by regulating and controlling the addition amount of a precursor and a solution, a series of formed flexible frames with different particle sizes are created by combining a shearing and stirring process, and then a catalytic material has proper anion-cation active sites by utilizing ion exchange, so that a hydrogen bond acceptor with a substrate recognition effect is obtained; therefore, the alkaline forming functional flexible catalyst which has high catalytic activity and high selectivity and is suitable for catalyzing dimethyl carbonate and ethanol ester exchange to prepare methyl ethyl carbonate is obtained.

Description

Technical Field

[0001] The present invention relates to a basic shaped functional flexible catalyst with high catalytic activity and high selectivity, a preparation method thereof, and an application of the catalyst in the transesterification of dimethyl carbonate and ethanol to prepare ethyl methyl carbonate. Background Art

[0002] Lithium-ion batteries have become the main power source for new energy vehicles due to their excellent performance such as high energy density, long cycle life, and pollution-free, and their sales volume has increased explosively. A lithium-ion battery mainly consists of a positive electrode material (cathode), a negative electrode material (anode), an electrolyte, and a separator. Among them, the cost of the lithium-ion battery electrolyte accounts for 20% of the cost of the lithium battery and is the "blood" of the lithium-ion battery. The lithium-ion battery electrolyte is composed of a carbonate solvent dissolved with a lithium salt. Common carbonate solvents include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc. As a green and environment-friendly solvent, EMC has unique advantages in the field of lithium-ion batteries.

[0003] The main methods for synthesizing ethyl methyl carbonate are: phosgene method, oxidative carbonylation method, and transesterification method. Among them, the phosgene method has been eliminated because the reaction raw material phosgene and the intermediate methyl chloroformate are both highly toxic. The oxidative carbonylation method needs to be carried out under high temperature and high pressure conditions, with harsh reaction conditions and high production costs, making it difficult to achieve large-scale industrial production. In contrast, the transesterification method has significant advantages such as mild reaction conditions, low cost, and environmental friendliness, and is the main method for preparing EMC at present.

[0004] At present, the transesterification reaction of ethanol and dimethyl carbonate catalyzed by sodium methoxide catalyst is a relatively widespread process for preparing ethyl methyl carbonate. Although homogeneous catalysts such as sodium methoxide have high catalytic activity, they have problems such as easy deactivation and difficult recovery, which limit their industrial application in the production of EMC. In contrast, heterogeneous catalysts are insoluble in reactants, do not require subsequent separation, and have high thermal stability and chemical stability, and are expected to replace sodium methoxide. Heterogeneous catalysts mainly include metal oxides, metal-organic framework materials, polyionic liquids, and strongly basic anion resin catalysts, etc. However, the synthesis conditions of these catalysts are harsh, and they mostly exist in the form of powders, which is not conducive to filling and fixing in continuous reaction processes (fixed-bed process, reactive distillation process). For example, patent (CN 116178626A) discloses a method for synthesizing dimethyl carbonate by catalytic transesterification using a basic polyionic liquid. In this method, an imidazole-based ionic liquid is used as the cationic skeleton, and monomers doped with N-containing basic groups are subjected to free radical polymerization to obtain a solid and stable polyionic liquid. However, free radical polymerization can only be carried out under the protection of an inert gas, and the reaction conditions are harsh; moreover, the polyionic liquid exists in the form of powder after drying, which is not conducive to filling and fixing in the fixed-bed process and reactive distillation process, and is not conducive to large-scale industrial application. Patent (CN113636935A) discloses a method for synthesizing ethyl methyl carbonate by catalytic transesterification of ethanol and dimethyl carbonate using a strongly basic anion resin. Although the EMC yield of this method is high, and the synthesized resin exists in the form of small balls, which is convenient for filling and fixing in the fixed-bed process and reactive distillation process, the preparation process of such resin materials is cumbersome, and the cyclic stability is poor in a high-temperature environment (greater than 90°C), and it is still not suitable for large-scale EMC production processes. Therefore, it is necessary to design a class of shaped catalysts with high catalytic activity, high selectivity, simple synthesis method, and stable structure for the fixed-bed process and reactive distillation process to achieve large-scale industrial production of ethyl methyl carbonate. Summary of the Invention

[0005] In order to overcome the problems of low catalytic activity, poor selectivity, harsh synthesis conditions, and existence in the form of powder of heterogeneous catalysts, which are not conducive to filling and fixing in the fixed-bed process and reactive distillation process, the present invention provides a basic shaped functional flexible catalyst and its preparation method. The prepared shaped functional flexible catalyst has the advantages of high catalytic activity, high selectivity, stable structure, easy recovery, etc., and is suitable for catalyzing the transesterification of dimethyl carbonate and ethanol to prepare ethyl methyl carbonate.

[0006] To achieve the above object, the present invention adopts the following technical solutions: The first object of the present invention is to protect a preparation method of a basic shaped functional flexible catalyst, which includes the following steps: 1) Ultrasonically mix precursor A, precursor B, and precursor C, and add solution A and solution B to construct a microemulsion system. After reacting at a certain temperature for a period of time, adjust the rate of shear stirring to shear out tiny reaction particles from the microemulsion system, thus obtaining the shaped flexible framework material. 2) Place the shaped flexible framework material obtained in step 1) in an anionic compound solution, and use acid-base neutralization to conduct anion exchange to construct an alkaline shaped functionalized flexible catalyst.

[0007] Furthermore, the precursor A in step 1) is a coupling structure constructed by polyhalobenzene and 1-vinylimidazole in a molar ratio of 1:10 - 10:1.

[0008] Even further, the polyhalobenzene is one or more of 1,4-p-dichloromethylbenzene, 1,3,5-tris(bromomethyl)benzene, and 1,2,4,5-tetrakis(bromomethyl)benzene.

[0009] Even further, the temperature of the reaction is 50 - 200 °C, and the time is 1 - 48 h.

[0010] Furthermore, the precursor B in step 1) is a nitrogen-containing basic functionalized monomer polymerized from tertiary amine and 4-vinylbenzyl chloride in a molar ratio of 1:5 - 5:1.

[0011] Even further, the tertiary amine is one or more of trimethylamine, triethylamine, and tripropylamine.

[0012] Even further, the temperature of the polymerization reaction is 30 - 100 °C, and the time is 1 - 48 h.

[0013] Furthermore, the molar ratio of precursor A to precursor B used in step 1) is 1:5 - 5:1.

[0014] Furthermore, the precursor C in step 1) is a flexible regulator, which includes one or more of divinylbenzene, divinyl ether, N-N-methylenebisacrylamide, and triallyl isocyanurate.

[0015] Furthermore, the dosage of precursor C in step 1) is 1 - 10% of the total mass of precursor A and precursor B.

[0016] Furthermore, the solution A in step 1) is an aqueous solution of sodium chloride, and its concentration is 0.05 - 2 mol·L -1 。

[0017] Furthermore, the solution B in step 1) is an aqueous solution of polyvinyl alcohol, and its concentration is 1 - 10 mol·L -1 。

[0018] Further, the volume ratio of solution A to solution B used in step 1) is 1-2:1.

[0019] Further, the temperature of the reaction in step 1) is 70-100 °C and the time is 5-24 h.

[0020] Further, the rate of shear stirring in step 1) is 60-500 rpm and the time is 1-48 h.

[0021] Further, the anion compound solution in step 2) is an aqueous solution of one or more of sodium hydroxide, phenol, 1,2,4-triazole, 2-hydroxypyridine, imidazole, and its concentration is 0.1-2 mol·L -1 .

[0022] Further, the time of anion exchange in step 2) is 1-48 h.

[0023] The second object of the present invention is to protect the basic molded functionalized flexible catalyst prepared by the above method.

[0024] The third object of the present invention is to protect the application of the basic molded functionalized flexible catalyst in the transesterification of dimethyl carbonate (DMC) and ethanol (EtOH) to prepare ethyl methyl carbonate.

[0025] Further, the process conditions for using the basic molded functionalized flexible catalyst to catalyze the transesterification of dimethyl carbonate and ethanol to prepare ethyl methyl carbonate are: reaction time 4 h, raw material molar ratio DMC:EtOH = 3:1, catalyst dosage 7% (DMC+EtOH), reaction temperature 90 °C.

[0026] The remarkable advantages of the present invention are as follows: The present invention realizes the improvement of the swelling performance of the catalytic material in the reaction raw materials by regulating the flexibility of the catalytic material, thereby improving the utilization rate of active sites, and shearing out framework materials with different particle sizes from the microemulsion system by regulating the shear stirring rate, and then combining ion exchange to make it obtain appropriate anion-cation active sites to obtain a hydrogen bond acceptor with substrate recognition effect, thereby improving catalytic activity and catalytic selectivity. The synthesis method is rapid and simple, and the obtained catalyst has the advantages of high catalytic activity, high selectivity, stable structure, easy recovery, etc., and can be used to prepare ethyl methyl carbonate in a fixed bed process and a reactive distillation column process.

[0027] The basic forming functional catalyst synthesized by this method can achieve a high EMC yield of 50.83% and a high EMC selectivity of 96.25% under the conditions of a molar ratio of ethanol to dimethyl carbonate of 1:3 in an 85 °C batch reactor for 4 hours. Moreover, it is easy to recover and has high recyclability. It is expected to replace non-renewable basic catalysts such as sodium alkoxide and become an important type of catalytic material in the industrial process of preparing ethyl methyl carbonate. Description of the Drawings

[0028] Figure 1 It is a synthetic route diagram for preparing precursor A using 1,4-dibenzyl chloride and 1-vinylimidazole in Example 1.

[0029] Figure 2 It is a synthetic route diagram for preparing precursor B using 4-vinylbenzyl chloride and trimethylamine in Example 1.

[0030] Figure 3 It is a synthetic route diagram for preparing the basic forming functional flexible catalyst in Example 1.

[0031] Figure 4 It is the X-ray photoelectron spectrum of the basic forming functional flexible catalyst prepared in Example 1, where a is the full XPS spectrum, b is the C 1s spectrum, c is the N 1s spectrum, and d is the O 1s spectrum.

[0032] Figure 5 It is a comparison diagram of the effects of the basic forming functional flexible catalysts prepared with different ratios of precursors A and B in Example 1 for the transesterification of dimethyl carbonate and ethanol to prepare ethyl methyl carbonate.

[0033] Figure 6 It is the infrared spectrum of the basic forming functional flexible catalysts with different particle sizes prepared in Example 2.

[0034] Figure 7 It is a comparison diagram of the effects of the basic forming functional flexible catalysts with different particle sizes prepared in Example 2 for the transesterification of dimethyl carbonate and ethanol to prepare ethyl methyl carbonate.

[0035] Figure 8 It is a diagram of the reuse performance of the basic forming functional flexible catalyst with a particle size of 0.5 mm prepared in Example 2 in the reaction of transesterifying dimethyl carbonate and ethanol to prepare ethyl methyl carbonate. Detailed Embodiments

[0036] A basic forming functional flexible catalyst, the preparation of which includes the following steps: 1) Add precursor A and precursor B in a molar ratio of 1:5 - 5:1, and add precursor C accounting for 1 - 10% of the total mass of precursors A and B. After ultrasonic mixing, add 0.05 - 2 mol·L-1 aqueous sodium chloride solution and 1 - 10 mol·L -1 aqueous solution of polyvinyl alcohol (the volume ratio of the two is 1 - 2:1) to construct a microemulsion system, and then react at 70 - 100 °C for 5 - 24 h. After that, by adjusting the shear stirring rate to 60 - 500 rpm and the time to 1 - 48 h, tiny reaction particles with different particle sizes are sheared out from the microemulsion system, which are the formed flexible framework materials; 2) Place the formed flexible framework material obtained in step 1) in an anion compound solution, and carry out anion exchange for 1 - 48 h by using acid - base neutralization to construct basic formed functionalized flexible catalysts with different particle sizes.

[0037] Among them, in step 1), the precursor A is a coupling structure obtained by adding polyhalogenated benzene and 1 - vinylimidazole in a molar ratio of 1:10 - 10:1 to acetonitrile and reacting at 50 - 200 °C for 1 - 48 h. The polyhalogenated benzene is one or more of 1,4 - p - dibenzyl chloride, 1,3,5 - tris(bromomethyl)benzene, 1,2,4,5 - tetrakis(bromomethyl)benzene. The precursor B is a nitrogen - containing basic functionalized monomer obtained by adding tertiary amine and 4 - vinylbenzyl chloride in a molar ratio of 1:5 - 5:1 to acetone and polymerizing at 30 - 100 °C for 1 - 48 h. The tertiary amine is one or more of trimethylamine, triethylamine, tripropylamine. The precursor C includes one or more of divinylbenzene, divinyl ether, N - N - methylenebisacrylamide, triallyl isocyanurate.

[0038] In step 2), the anion compound solution is an aqueous solution of one or more of sodium hydroxide, phenol, 1,2,4 - triazole, 2 - hydroxypyridine, imidazole, and its concentration is 0.1 - 2 mol·L -1 .

[0039] To make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0040] Example 1: Synthesis of precursor A: Add 1,4 - p - dibenzyl chloride and 1 - vinylimidazole in a molar ratio of 1:2 to acetonitrile, seal it and place it in a water bath at 75 °C for 24 h to obtain a white powder. After drying, it is precursor A (its synthesis route is as Figure 1 shown).

[0041] Synthesis of precursor B: Add 4 - vinylbenzyl chloride and trimethylamine in a molar ratio of 1:1 to acetone, seal it and place it in a water bath at 65 °C for 5 h, then adjust the temperature to 30 °C and continue to react for 24 h to obtain a white powder. After drying, it is precursor B (its synthesis route is as Figure 2as shown).

[0042] The precursor C is selected as divinylbenzene.

[0043] Solution A and solution B are 0.1 mol·L -1 aqueous sodium chloride solution and 1 mol·L -1 aqueous polyvinyl alcohol solution respectively.

[0044] Synthesis of the basic shaped functional flexible catalyst: The precursors A and B are added respectively according to a certain molar ratio (1:0, 1:2, 1:3, 1:4), and 5% of the total mass of the precursors A and B of the precursor C is added for ultrasonic mixing. Then, 50 mL of solution A and 50 mL of solution B are added to construct a microemulsion system. At 85 °C, the reaction is carried out for 24 h at a shear stirring rate of 130 rpm to obtain tiny reaction particles. The obtained tiny reaction particles are placed in a 0.5 mol·L -1 phenol solution, and after reacting at 30 °C for 24 h, they are filtered and dried to obtain the basic shaped functional flexible catalyst (the schematic diagram of its synthesis is as Figure 3 shown).

[0045] The X-ray photoelectron spectrum of the obtained basic shaped functional flexible catalyst is as Figure 4 shown. From Figure 4 it can be seen that in the XPS full spectrum, signal peaks referring to C 1s, N 1s and O 1s appear near 285, 400 and 532 eV respectively, and no signal peak referring to the Cl element appears, indicating the successful synthesis of the basic shaped functional flexible catalyst and the successful anion exchange (a). And it can be seen from the C 1s spectrum that the four catalysts prepared with different ratios all show characteristic peaks referring to C-C, C=C and C-N at 284.80, 286.15 and 287.20 eV, indicating the existence of imidazole groups in the basic shaped functional flexible catalyst (b). In the N1s spectrum, it can be found that the catalyst prepared with the molar ratio of precursor A to precursor B of 1:0 shows a characteristic peak referring to C=N of the imidazole ring on the cationic skeleton at 399.4 eV, indicating the successful attachment of the imidazole cation group. And the catalysts prepared with the molar ratio of precursor A to precursor B of 1:2, 1:3 and 1:4 respectively, in addition to showing a characteristic peak referring to C=N of the imidazole ring on the cationic skeleton at 399.4 eV, also show a characteristic peak referring to -N on the cationic skeleton at 401.6 eV + characteristic peak, indicating... + characteristic peak, and also shows a characteristic peak referring to -N on the cationic skeleton at 401.6 eV +The characteristic peaks indicate the successful grafting of imidazole ionic groups and quaternary ammonium ionic groups (c). In the O 1s spectrum, a C-O characteristic peak representing phenol anions appears at 532.1 eV, further confirming the successful exchange of phenol anions. At the same time, signal peaks appear at 530.3 eV for all four catalysts, which is due to the absorption of H2O in the air (d). In summary, the XPS results indicate the successful preparation of the basic shaped functionalized flexible catalyst.

[0046] Application Example 1: The basic shaped functionalized flexible catalysts prepared from precursor A and precursor B in Example 1 at different molar ratios (1:0, 1:2, 1:3, 1:4) were used in the batch transesterification reaction of dimethyl carbonate (DMC) and ethanol (EtOH). The specific process conditions were as follows: reaction time 4 h, raw material molar ratio DMC:EtOH = 3:1, catalyst dosage 7% (DMC + EtOH), reaction temperature 90 °C. Samples were taken for analysis after 1 h of reaction, and the results are as Figure 5 shown. It can be seen from Figure 5 that when the molar ratio of precursor A to precursor B is 1:3, the catalytic performance is better, the yield of ethyl methyl carbonate can reach 50.83%, and the selectivity of ethyl methyl carbonate can reach 96.25%.

[0047] Example 2: Synthesis of the basic shaped functionalized flexible catalyst: 0.01 mol of precursor A, 0.03 mol of precursor B, and 5% of precursor C based on the total mass of precursor A and precursor B were ultrasonically mixed, and then 50 mL of solution A and 50 mL of solution B were added to construct a microemulsion system. At 85 °C, the reaction was carried out at shear stirring rates of 80, 100, 130, 170, and 220 rpm for 24 h to obtain tiny reaction particles with particle sizes of 1.18, 0.9, 0.5, 0.3, and 0.1 mm respectively; the obtained tiny reaction particles were respectively placed in a phenol solution of 0.5 mol·L -1 After reacting at 30 °C for 24 h, filtration and drying were carried out to obtain basic shaped functionalized flexible catalysts with particle sizes of 1.18, 0.9, 0.5, 0.3, and 0.1 mm respectively.

[0048] The infrared spectra of the obtained basic shaped functionalized flexible catalysts are as Figure 6 shown. It can be found from the figure that stretching vibration peaks of C=N and C-N belonging to the imidazole ring appear at 1258 cm -1 and 1235 cm -1 respectively; a peak representing quaternary ammonium appears at 1028 cm -1 ; a stretching vibration peak of C-H on the benzene ring appears at 865 cm -1 ; at 3030 cm-1 and stretching vibration peaks of C-H and C-O referring to phenol anions appear at 1246 cm -1 respectively, which confirms the successful synthesis of the basic molded functional flexible catalyst.

[0049] Application Example 2: The basic molded functional flexible catalysts with particle sizes of 1.18, 0.9, 0.5, 0.3, and 0.1 mm prepared in the examples were used in the batch transesterification reaction of dimethyl carbonate (DMC) and ethanol (EtOH). The specific process conditions were as follows: reaction time 4 h, raw material molar ratio DMC:EtOH = 3:1, catalyst dosage 7% (DMC + EtOH), reaction temperature 90 °C. Samples were taken for analysis after 1 h of reaction, and the results are as Figure 7 shown. It can be seen from Figure 7 that as the particle size of the catalyst increases, the yield of ethyl methyl carbonate shows a trend of first increasing and then decreasing. This indicates that it is feasible to regulate the catalytic performance of the transesterification of dimethyl carbonate and ethanol to produce ethyl methyl carbonate by controlling the particle size of the catalytic material. Among them, the basic molded functional flexible catalyst with a particle size of 0.5 mm has the best catalytic effect.

[0050] Under the same reaction process conditions (reaction time 4 h, raw material molar ratio DMC:EtOH = 3:1, catalyst dosage 7% (DMC + EtOH), reaction temperature 90 °C), the reusability of the basic molded functional flexible catalyst with a particle size of 0.5 mm was further investigated. The experimental results are as Figure 8 shown. It can be seen from Figure 8 that after 5 cycles of use, the yield of ethyl methyl carbonate only decreased from 50.83% to 47.34%, and the selectivity of ethyl methyl carbonate basically remained stable, indicating that the catalyst has good recyclability and catalytic stability.

[0051] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A preparation method of an alkaline forming functionalized flexible catalyst, characterized in that It includes the following steps: 1) Ultrasonically mix precursor A, precursor B, and precursor C, add solution A and solution B to construct a microemulsion system, and perform shear stirring after the reaction to obtain a shaped flexible framework material; 2) Place the shaped flexible framework material obtained in step 1) in an anionic compound solution for anion exchange to construct the basic shaped functionalized flexible catalyst.

2. The preparation method of the basic molding functionalized flexible catalyst according to claim 1, characterized in that, In step 1), the precursor A is a coupling structure constructed from a polyhalogenated benzene and 1-vinylimidazole in a molar ratio of 1:10 - 10:1, and the polyhalogenated benzene is one or more of 1,4-p-dibenzyl chloride, 1,3,5-tris(bromomethyl)benzene, and 1,2,4,5-tetrakis(bromomethyl)benzene.

3. The preparation method of the basic forming functionalized flexible catalyst according to claim 1, characterized in that, In step 1), the precursor B is a nitrogen-containing basic functionalized monomer polymerized from a tertiary amine and 4-vinylbenzyl chloride in a molar ratio of 1:5 - 5:1, and the tertiary amine is one or more of trimethylamine, triethylamine, and tripropylamine.

4. The preparation method of the basic forming functionalized flexible catalyst according to claim 1, characterized in that, In step 1), the molar ratio of the used precursor A and precursor B is 1:5 - 5:

1.

5. The preparation method of the basic forming functionalized flexible catalyst according to claim 1, characterized in that, In step 1), the precursor C includes one or more of divinylbenzene, divinyl ether, N-N-methylenebisacrylamide, and triallyl isocyanurate; its dosage is 1 - 10% of the total mass of precursor A and precursor B.

6. The preparation method of the basic forming functionalized flexible catalyst according to claim 1, characterized in that, The solution A described in step 1) is an aqueous solution of sodium chloride with a concentration of 0.05 - 2 mol·L -1 ; the solution B is an aqueous solution of polyvinyl alcohol with a concentration of 1 - 10 mol·L -1 ; the volume ratio of the used solution A to solution B is 1~2:

1.

7. The preparation method of the basic molding functionalized flexible catalyst according to claim 1, wherein, In step 1), the temperature of the reaction is 70 - 100 °C and the time is 5 - 24 h.

8. The preparation method of the basic molding functionalized flexible catalyst according to claim 1, characterized in that, In step 1), the rate of the shear stirring is 60 - 500 rpm and the time is 1 - 48 h.

9. The preparation method of the basic forming functional flexible catalyst according to claim 1, characterized in that, The anion compound solution described in step 2) is an aqueous solution of one or more of sodium hydroxide, phenol, 1,2,4-triazole, 2-hydroxypyridine, and imidazole, and its concentration is 0.1-2 mol·L -1 .

10. Application of a basic shaped functionalized flexible catalyst prepared by any of the methods according to claims 1 - 9 in the transesterification of dimethyl carbonate and ethanol to prepare ethyl methyl carbonate.

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