Zinc tetrabromide / imidazolium resin microsphere catalyst for CO2 cycloaddition reaction and preparation method of zinc tetrabromide / imidazolium resin microsphere catalyst

Abstract

The invention discloses a zinc tetrabromide / imidazolium resin microsphere catalyst for CO2 cycloaddition reaction and a preparation method thereof. The catalyst is a heterogeneous catalyst obtained by loading zinc tetrabromide coordination ions on imidazolium modified ion exchange resin microspheres. The catalyst has good activity, can effectively catalyze CO2 and epoxide to synthesize cyclic carbonate without a cocatalyst and a solvent under mild conditions, and can be recycled, and the product is easy to separate and purify. The catalyst carrier-ion exchange resin used in the invention has the characteristics of low cost, easy synthesis, high strength and the like, and can meet the requirements of industrial production.

Description

Technical Field

[0001] The present invention relates to a catalyst, in particular to a catalyst for CO 2 Cycloaddition reaction Tetrabromozinc / imidazolium resin microsphere catalyst and preparation method thereof. Background Art

[0002] Fossil fuels have brought an era of prosperity and development to human society, but the large amounts of CO2 emitted by them have 2 Global warming has led to natural disasters that have seriously threatened human survival and development. It is urgent to achieve the goals of carbon peak and carbon neutrality. 2 It is an important C1 resource. 2 Chemical conversion into fuels or other valuable chemicals not only reduces CO 2 emissions, and can also provide more resources for human development. Due to the high reactivity of the three-membered ring, CO 2 Cyclic carbonates can undergo cycloaddition reactions with epoxy compounds to form cyclic carbonates, which can be widely used as electrolyte solvents for lithium-ion batteries, aprotic polar solvents, precursors of polycarbonates and polyurethanes, and pharmaceutical intermediates. 2 The catalysts for cycloaddition reactions are mainly homogeneous catalysts, which face inherent problems such as difficulty in recycling and reusing the catalysts, difficulty in separating the products, and high costs. 2 Heterogeneous catalysts for cycloaddition reactions with epoxides are of great interest.

[0003] CO 2 The cycloaddition reaction with epoxides is usually achieved under the synergistic action of Lewis acid active centers and nucleophiles. Effective heterogeneous catalysts require the organic integration of suitable Lewis acid sites and nucleophiles. For example, in recent years, a large number of ionic liquid-modified metal-organic framework catalysts have been developed, which contain abundant Lewis acid sites. At the same time, the skeleton of the catalyst is positively charged and can easily load negatively charged nucleophiles. Therefore, a series of metal-organic framework catalysts have been developed. However, this type of catalyst has the disadvantages of high preparation cost, poor stability and low catalytic activity, making it difficult to be truly used in actual production. In addition, fixing highly active homogeneous catalysts on appropriate carriers is also a good way to develop CO 2 An important method for the development of new heterogeneous catalyst systems for cycloaddition reactions. For example, W. Wang et al. synthesized a porous organic polymer containing zinc halide, triphenylphosphine and ionic liquid PPh 3 -ILBr-ZnBr 2@POPS; S. Jayakumar et al. immobilized the cationic zinc porphyrin complex with 3-(trimethoxysilyl)propyl bromide in mesoporous SBA-15; J. Xu et al. used graphene-phase carbon nitride (gC 3 N 4 ) was used as a carrier for immobilizing zinc halides to synthesize ZnBr 2 / gC 3 N 4 Although these heterogeneous catalyst systems exhibit high catalytic activity, they also have problems such as harsh synthesis conditions and high costs, making them difficult to produce on an industrial scale. Summary of the invention

[0004] The present invention is to solve the above-mentioned technical problems existing in the prior art and provide a CO 2 Cycloaddition answer Tetrabromozinc / imidazolium resin microsphere catalyst and preparation method thereof.

[0005] The technical solution of the present invention is: a method for CO 2 Cycloaddition reaction The tetrabromozinc / imidazolium resin microsphere catalyst is a heterogeneous catalyst obtained by loading tetrabromozinc complex ions on imidazolium-modified ion exchange resin microspheres.

[0006] The above is used for CO 2 Cycloaddition reaction The preparation method of tetrabromozinc / imidazolium resin microsphere catalyst is carried out in the following steps: a. Add zinc bromide, tetrabutylammonium bromide and anhydrous ethanol in a beaker in a ratio of 1.8 g: 5.2 g: 4 ml and stir at room temperature for 2 h. Let stand until large crystals appear, then add deionized water and stir. Filter with suction, collect the filter cake and dry it naturally to obtain tetrabromozinc tetrabutylammonium bromide solid; b. Chloromethylated polystyrene resin microspheres, N-alkylimidazole and DMF were added to a beaker in a ratio of 5 g: 3 mmol: 20 ml, and the reaction was carried out at 80 ° C for 24 h. After the reaction, ethanol was added for rinsing, filtered, and the filter cake was collected and dried in vacuo at 80 ° C for 2 h to obtain chloro-imidazolium salt-modified resin microspheres, wherein the N-alkylimidazole is at least one of N-methylimidazole, N-ethylimidazole, N-propylimidazole and N-butylimidazole; c. Add chlorine-modified imidazolium salt-modified resin microspheres, KBr and H into a beaker in a ratio of 2 g: 20 g: 40 ml. 2O, fully stirred at room temperature for 24 h, then filtered, collected the filter cake, and dried it in vacuum at 80 °C for 4 h to obtain bromo-type imidazolium resin microspheres; d. Add chlorine-type imidazolium salt-modified resin microspheres, tetrabromozinc tetrabutylammonium bromide solid and ethanol into a beaker in a dosage ratio of 2 g: 14.3 g: 10 ml, stir thoroughly at room temperature for 24 h, filter with suction, collect the filter cake, add dichloromethane to the filter cake, soak at 40 °C for 1 h, filter with suction, and dry at 50 °C in vacuum for 2 h to obtain tetrabromozinc / imidazolium resin microsphere catalyst.

[0007] The tetrabromozinc / imidazolium resin microsphere heterogeneous catalyst of the present invention has good activity and can effectively catalyze CO under the conditions of no co-catalyst, no solvent and mild conditions. 2 The cyclic carbonate can be synthesized with epoxide, which can be recycled and the product can be easily separated and purified. The catalyst carrier used in the present invention, the ion exchange resin, has the characteristics of low cost, easy synthesis and high strength, and can meet the requirements of industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is ZnBr in the embodiment of the present invention. 4 -Infrared spectrum of Imi-CMPS.

[0009] Figure 2 It is ZnBr in the embodiment of the present invention. 4 -Imi-CMPS and (TBA) 2 ZnBr 4 Photoelectron spectrum.

[0010] Figure 3 It is ZnBr in the embodiment of the present invention. 4 -Thermogravimetric curve of Imi-CMPS.

[0011] Figure 4 It is ZnBr in the embodiment of the present invention. 4 -Imi-CMPS catalyzes the reaction of butylene oxide with CO 2 Schematic diagram of the cyclic test results of the reaction. DETAILED DESCRIPTION Example 1

[0012] The present invention is used for CO 2 The preparation method of tetrabromozinc / imidazolium resin microsphere catalyst for cycloaddition reaction is carried out in the following steps: a. Add 1.8 g zinc bromide, 5.2 g tetrabutylammonium bromide and 4 ml anhydrous ethanol to a beaker, stir thoroughly at room temperature for 2 h, let stand until large crystals appear, add deionized water and stir, filter, collect the filter cake, and dry it naturally to obtain tetrabromozinc tetrabutylammonium bromide solid (TBA)2 ZnBr 4 ), the yield is 68%; b. Add 5 g of chloromethylated polystyrene resin microspheres (CMPS), 3 mmol of N-methylimidazole and 20 ml of DMF into a beaker, react at 80 °C for 24 h, add ethanol to rinse, filter, collect the filter cake, and dry it in vacuum at 80 °C for 2 h to obtain chloro-imidazolium salt-modified resin microspheres (Cl-Imi-CMPS); c. Add 2 g Cl-Imi-CMPS, 20 g KBr and 40 ml H2O into a beaker, stir thoroughly at room temperature for 24 h, filter, collect the filter cake, and dry it under vacuum at 80°C for 4 h to obtain bromo-type imidazolium resin microspheres (Br-Imi-CMPS).

[0013] d. Add 2 g Br-Imi-CMPS and 14.3 g (TBA) into the beaker. 2 ZnBr 4 and 10 ml of ethanol, stirred at room temperature for 24 h, filtered, collected the filter cake, added dichloromethane to the filter cake, soaked at 40 °C for 1 h, filtered, and dried at 50 °C in vacuum for 2 h to obtain tetrabromozinc / imidazolium resin microspheres (ZnBr 4 -Imi-CMPS).

[0014] Experimental Example 1: In order to further characterize the composition of the sample, ZnBr 4 -IMI-CMPS conducted a qualitative analysis. The results are shown in the attached Figure 1 As shown, located at 1571 cm -1 The characteristic absorption peak at 1213 cm -1 and 1159 cm -1 It is attributed to the stretching motion of the imidazole ring, indicating that ZnBr 4 -Successful incorporation of imidazole in Imi-CMPS.

[0015] Through X-ray photoelectron spectroscopy (TBA) 2 ZnBr 4 and ZnBr 4 -Imi-CMPS was qualitatively analyzed. Figure 2 As shown, due to the coordination of four halogen ligands, (TBA) 2 ZnBr 4 The electron density of zinc atoms in ZnCl 2 and ZnBr 2 Compared with the previous study, the binding energy of ZnBr is 1022.0eV, while that of ZnBr is 1022.0eV. 4-The binding energy of zinc atom in Imi-CMPS is 1022.2 eV, which is similar to (TBA) 2 ZnBr 4 Close, indicating that ZnBr 4 The zinc element in Imi-CMPS is [ZnBr 4 ] 2- exists in the form of.

[0016] Experimental Example 2: The heterogeneous catalyst ZnBr prepared in Example 1 was analyzed by thermogravimetric analysis. 4 -Thermal stability of Imi-CMPS, the results are shown in the attached Figure 3 The thermal weight loss before 90℃ can be attributed to ZnBr 4 -Imi-CMPS contains a small amount of ethanol solvent molecules adsorbed in it, and then continues to heat until 230°C before it begins to lose weight significantly. It can be seen that the resin catalyst has excellent thermal stability.

[0017] Experimental Example 3: With butylene oxide and CO 2 The reaction to generate cyclic carbonate 4-ethyl-1,3-dioxane-2-one was used as a reaction model to evaluate the heterogeneous catalyst ZnBr prepared in Example 1 of the present invention. 4 -Performance of Imi-CMPS.

[0018] 3.5 ml of butylene oxide (40 mmol) and ZnBr prepared in Example 1 were added to the autoclave. 4 -Imi-CMPS catalyst. To explore the different amounts of ZnBr 4 -Imi-CMPS for catalytic CO 2 The effect of the reaction of butylene oxide and cyclic carbonate was investigated by charging the reactor with CO 2 , exhaust the air and maintain CO 2 The pressure was 1 MPa, the time was 2 h, and the temperature was 40 °C. The ZnBr prepared in Example 1 4 The amounts of -Imi-CMPS catalyst used were 0.1 g, 0.2 g, 0.3 g, 0.4 g, 0.5 g and 0.6 g, respectively. After the reaction was completed, the catalyst and the product were separated by filtration, and the product was analyzed by gas chromatography. The results are shown in Table 1.

[0019] Table 1 Catalytic performance of CO with different catalyst dosages 2 Reaction with butylene oxide to synthesize cyclic carbonate a

[0020] aReaction conditions: 40 mmol butylene oxide, 1 MPa CO 2 , 40 ℃, 2 h. b The conversion and yield were determined by GC-7890II.

[0021] As can be seen from Table 1, under the conditions of no solvent and co-catalyst, the reaction was carried out at 40°C for 2 h. When the catalyst dosage was increased from 0.1 g to 0.5 g, the conversion rate of butylene oxide gradually increased, the conversion rate of the reaction increased from 21% to 66%, the selectivity was 99%, and the yield increased from 21% to 65%. When the catalyst dosage was 0.6 g, the conversion rate of the reaction increased slightly by 69%. Considering the conversion efficiency and cost factors, the amount of catalyst was determined to be 0.5 g in subsequent experiments.

[0022] Experimental Example 4: To investigate the effect of different temperatures on ZnBr 4 -Imi-CMPS catalyzes CO 2 The effect of the reaction of butylene oxide and cyclic carbonate was investigated by charging CO into the autoclave. 2 , exhaust the air and maintain CO 2 The pressure was 1 MPa, the time was 2 h, the amount of catalyst was 0.5 g, and the reaction temperatures were 40 °C, 60 °C, and 80 °C, respectively. After the reaction was completed, the catalyst and the product were separated by filtration, and the product was analyzed by gas chromatography. The results are shown in Table 2.

[0023] Table 2 ZnBr at different temperatures 4 -Imi-CMPS catalyzes CO 2 Reaction with butylene oxide to synthesize cyclic carbonate a

[0024] a Reaction conditions: 40 mmol butylene oxide, 1 MPa CO 2 , catalyst dosage 0.5 g, 2 h. b The conversion and yield were determined by GC-7890II.

[0025] As can be seen from Table 2, the conversion rate of butylene oxide was 66% and the selectivity was 99% at 40°C after 2 h of reaction without solvent and co-catalyst. As the temperature increased, the conversion rate of butylene oxide gradually increased, the selectivity of the reaction remained at 99%, and the yield gradually increased. When the reaction temperature increased to 80°C, the conversion rate of the reaction increased to 91%. Considering that higher temperatures will affect the mechanical strength of the resin catalyst and damage the life of the catalyst, the operating temperature of the catalyst was set at 80°C in subsequent experiments.

[0026] Experimental Example 5: To explore the ZnBr 4 -Imi-CMPS catalyzes CO 2 The effect of the reaction of butylene oxide and cyclic carbonate was investigated by charging CO into the autoclave. 2 , exhaust the air and maintain CO 2 The pressure was 1 MPa, the amount of catalyst was 0.5 g, the reaction temperature was 80°C, and the reaction time was 1, 2, and 3 h, respectively. After the reaction was completed, the catalyst and the product were separated by filtration, and the product was analyzed by gas chromatography. The results are shown in Table 3.

[0027] Table 3 ZnBr at different times 4 -Imi-CMPS catalyzes CO 2 Reaction with butylene oxide to synthesize cyclic carbonate a

[0028] a Reaction conditions: 40 mmol butylene oxide, 1 MPa CO 2 , reaction temperature 80 ℃, catalyst dosage 0.5 g. b The conversion and yield were determined by GC-7890II.

[0029] It can be seen from Table 3 that under the conditions of no solvent and co-catalyst, the conversion rate of butylene oxide reached 80% and the selectivity was 99% when the reaction time was 1 h at 80 °C. As the reaction time increased, the conversion rate of butylene oxide gradually increased. When the reaction time was 3 h, the conversion rate of the reaction reached 97%.

[0030] Experimental Example 6: Since ZnBr 4 -Imi-CMPS to CO 2 The cycloaddition reaction with butylene oxide showed good catalytic effect. The present invention also investigated ZnBr 4 The catalytic activity of -Imi-CMPS for other epoxy compounds was tested under the following conditions: 40 mmol substrate, 0.5 g catalyst, 1 MPa reaction pressure, 3 h reaction time, and 80 °C reaction temperature. The results are shown in Table 4.

[0031] Table 4 Catalytic CO 2 Reaction with different epoxides to synthesize cyclic carbonates

[0032] a Reaction conditions: 40 mmol substrate, 1 MPa CO 2, catalyst dosage 0.5 g, 3 h. b The conversion rate and yield were determined by GC-7890II. *Reaction conditions: 40 mmol substrate, 1 MPa CO 2 , catalyst dosage 0.5 g, 6 h.

[0033] The experimental results show that the catalyst of the present invention has high catalytic activity for epoxy compounds, and has high conversion rate and yield while maintaining high selectivity. Except for styrene oxide, the conversion rate of other epoxy compounds is above 93%. After 3 hours of reaction, the conversion rate of styrene oxide is only 67%, which may be due to the low reactivity of its β-C atom. When the reaction time is extended to 6 hours, its conversion rate is increased to 98%. The above results show that ZnBr 4 -Imi-CMPS exhibits good catalytic activity for this type of cycloaddition reaction, especially for CO 2 Addition reaction with epoxides.

[0034] Experimental Example 7: ZnBr 4 -Imi-CMPS catalyzes CO 2 Cyclic test of cycloaddition reaction with butylene oxide: After each catalytic reaction, the catalyst was separated, soaked in ethanol for 30 min, and dried in vacuum at 80℃ for 2 h. The regenerated catalyst was directly put into the next reaction. The results of the cyclic test are shown in the attached figure. Figure 4 As shown in the figure, after 5 cycles, the activity of the catalyst did not decrease significantly, indicating that ZnBr 4 -Imi-CMPS has good recyclability.

Claims

1. A method for CO 2 Cycloaddition reaction The tetrabromozinc / imidazolium resin microsphere catalyst is characterized by: A heterogeneous catalyst is obtained by using imidazolium-modified ion exchange resin microspheres to load tetrabromozinc complex ions.

2. The method for use according to claim 1 CO 2 Cycloaddition reaction The method for preparing tetrabromozinc / imidazolium resin microsphere catalyst is characterized in that Follow the steps below: a. Add zinc bromide, tetrabutylammonium bromide and anhydrous ethanol in a beaker in a ratio of 1.8 g: 5.2 g: 4 ml and stir at room temperature for 2 h. Let stand until large crystals appear, then add deionized water and stir. Filter with suction, collect the filter cake and dry it naturally to obtain tetrabromozinc tetrabutylammonium bromide solid; b. Chloromethylated polystyrene resin microspheres, N-alkylimidazole and DMF were added to a beaker in a dosage ratio of 5 g: 3 mmol: 20 ml, and the reaction was carried out at 80 ° C for 24 h. After the reaction, ethanol was added for rinsing, filtered, and the filter cake was collected and dried in vacuo at 80 ° C for 2 h to obtain chloro-imidazolium salt-modified resin microspheres, wherein the N-alkylimidazole is at least one of N-methylimidazole, N-ethylimidazole, N-propylimidazole and N-butylimidazole; c. Add chloro-imidazolium salt-modified resin microspheres, KBr and H2O in a beaker in a ratio of 2 g: 20 g: 40 ml, stir thoroughly at room temperature for 24 h, then filter and collect the filter cake, and dry it in a vacuum oven at 80 °C for 4 h to obtain bromo-imidazolium resin microspheres; d. Add chlorine-type imidazolium salt-modified resin microspheres, tetrabromozinc tetrabutylammonium bromide solid and ethanol into a beaker in a dosage ratio of 2 g: 14.3 g: 10 ml, stir thoroughly at room temperature for 24 h, filter with suction, collect the filter cake, add dichloromethane to the filter cake, soak at 40 °C for 1 h, filter with suction, and dry at 50 °C in vacuum for 2 h to obtain tetrabromozinc / imidazolium resin microsphere catalyst.

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