Method for catalyzing phenol carbon-carbon coupling reaction through confinement membrane

Abstract

The invention discloses a method for catalyzing carbon-carbon coupling reaction of phenols by a confinement membrane, which is carried out based on a membrane component device, a phenolic compound and an oxidizing agent are dissolved in a water phase to form a water solution, the carbon-carbon coupling reaction is realized through a catalytic membrane, the catalytic membrane comprises a substrate and a catalyst layer, the substrate is a filter membrane, and the catalyst layer is a layered catalyst ZnFe-LDH. According to the method, by regulating and controlling the retention time of a substrate between membrane catalyst layers, under the condition of low oxidant dosage, phenols are catalytically oxidized and converted into a carbon-carbon coupling product with high selectivity at the same time, the process is simple, the normal-temperature water phase condition is utilized, and the reaction condition is mild.

Description

Technical Field

[0001] The present invention relates to a method for carbon-carbon coupling reaction, and particularly to a method for confined membrane-catalyzed carbon-carbon coupling reaction of phenols. Background Art

[0002] Organic synthesis mainly constructs molecular skeletons through chemical reactions, among which the formation of carbon-carbon bonds is the core part and can be used to synthesize complex compounds. In the existing technology, the ways to form carbon-carbon bonds usually require site occupancy or pre-functionalization of substrates, and use noble metal catalysts such as palladium or rhodium to achieve carbon-carbon coupling under organic solvent conditions. The reaction conditions are relatively harsh, the raw material utilization rate is low, it is sensitive to air and water, and various by-products are generated, such as carbon-oxygen coupling products and peroxidized ring-opening products, etc.

[0003] The spatial effect of nanoconfinement can significantly change the diffusion and reaction behavior of molecules, and regulate the transition state molecules generated by catalytic reactions at the atomic scale, thereby improving the reaction rate and selectivity. CN119386857 discloses a fixed-bed reactor based on the interlayer confinement effect of hydrotalcite, which constructs the synergistic effect of active metal and interlayer chloride ions to achieve 98% trichloroethylene dechlorination selectivity. Zhang Xiqi et al. from the Institute of Physical Chemistry and Technology of the Chinese Academy of Sciences used multilayer ammoniated graphene membranes to achieve about 100% Knoevenagel condensation reaction in a short time under the drive of pressure difference (Matter. 2023, 6, 1173 - 1187). However, the research on achieving carbon-carbon selective coupling by confined membrane catalysis has not been reported yet. Summary of the Invention

[0004] Object of the Invention: The present invention aims to provide a method for highly selective confined membrane-catalyzed carbon-carbon coupling reaction of phenols with simple process, mild reaction conditions and environmental friendliness.

[0005] Technical Solution: The method for confined membrane-catalyzed carbon-carbon coupling reaction of phenols according to the present invention includes the following steps:

[0006] (1) Dissolve a phenolic compound and persulfate in an aqueous phase to form an aqueous solution, and adjust the pH of the solution to neutral or weakly alkaline;

[0007] (2) Perform a carbon-carbon coupling reaction on the above aqueous solution through a catalytic membrane;

[0008] The catalytic membrane includes a substrate and a catalyst layer. The substrate is a filter membrane, and the catalyst layer is a layered catalyst ZnFe-LDH.

[0009] The catalytic membrane includes a substrate and a catalyst layer. The substrate is a filter membrane, and the catalyst layer is a layered catalyst ZnFe-LDH.

[0010] Preferably, the membrane flux of the solution through the catalytic membrane is 90 - 150 L / (m2 h). As the membrane flux decreases, the removal rate of phenolic compounds increases, but the residence time of phenolic compounds on the membrane increases, resulting in a decrease in the yield of carbon-carbon coupling products. The solution passes through the catalytic membrane at room temperature.

[0011] Preferably, the filter membrane is a PTFE membrane, an MCE membrane or a PES membrane.

[0012] The mixed solution formed by dissolving phenolic compounds and persulfate in ultrapure water is acidic. Under acidic conditions, the removal rate of phenol and the yield of carbon-carbon coupling products are low.

[0013] Preferably, the pH is 7-8.

[0014] Preferably, the loading amount of the layered catalyst ZnFe-LDH in the catalyst membrane is 3 to 6 mg / cm 2 More preferably, the loading amount of the layered catalyst ZnFe-LDH in the catalyst membrane is 3-4 mg / cm 2 .

[0015] Preferably, the molar ratio of the phenolic compound to the persulfate is 1:8-10.

[0016] Preferably, the concentration of the phenolic compound is 0.01 to 1.0 mmol / L.

[0017] Preferably, the persulfate concentration is 0.1 to 10 mmol / L.

[0018] Preferably, the phenolic compound is a phenolic homologue such as phenol, 2-chlorophenol or 2,6-dimethylphenol.

[0019] Preferably, the method for preparing the catalytic membrane is: loading the layered catalyst ZnFe-LDH on the filter membrane by suction filtration.

[0020] Preferably, the preparation method of the layered catalyst ZnFe-LDH is: dispersing zinc salt and iron salt in water, adjusting the pH to 9-10, then aging at 50-80°C for 18-30 hours, washing after the reaction, and freeze-drying to obtain the layered catalyst ZnFe-LDH.

[0021] Preferably, the washing is performed using water and ethanol.

[0022] Invention mechanism: The present invention adopts membrane catalytic reaction. When the substrate phenol molecules flow through the catalytic membrane, a catalytic coupling reaction is carried out, and the reaction products flow away with them, so as to achieve the timely separation of reactants, products and catalysts. Persulfate and phenolic compounds are selectively adsorbed on the ZnFe-LDH membrane. The interlayer nanochannels lead to heterolytic cleavage of the OO bond in the persulfate to generate FeIV =O active species, these Fe IV =O species drive the proton-coupled electron transfer oxidation of phenols to generate phenoxy radicals. By regulating the residence time, the interlayer-confined nanochannels further promote the resonance isomerization of phenoxy radicals to achieve high selectivity of C-C coupling products.

[0023] Advantages: Compared with the prior art, the present invention has the following remarkable advantages: (1) By regulating the residence time of the substrate between the interlayers of the membrane catalyst, while catalytically oxidizing phenols, it is converted into highly selective carbon-carbon coupling products. The process is simple, using ambient temperature aqueous phase conditions, and the reaction conditions are mild; (2) When the membrane flux is 120 L / (m 2 ·h), the removal rate of phenol can reach 50%, the carbon-carbon coupling product yield is 42%, and the selectivity is 84%; (3) The amount of persulfate consumed in the reaction process is relatively low, with the advantages of good conversion effect and high product purity. Description of the Drawings

[0024] Figure 1 XRD pattern of the layered catalyst ZnFe-LDH prepared in Example 1;

[0025] Figure 2 SEM image of the catalytic membrane prepared in Example 1;

[0026] Figure 3 Schematic diagram of the reaction device provided in Example 2;

[0027] Figure 4 Graph of phenol removal, conversion rate and selectivity of coupling products at different membrane fluxes in Example 2;

[0028] Figure 5 UPLC-MS / MS diagram of the conversion of phenol to dihydroxybiphenyl in Example 2;

[0029] Figure 6 EPR diagram using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap in Example 2. Detailed Embodiments

[0030] The technical solution of the present invention will be further described below in conjunction with the embodiments.

[0031] Example 1

[0032] The preparation method of the catalytic membrane of the present invention includes the following steps:

[0033] Dissolve Zn 2+ (2 mmol) and Fe 3+(1 mmol) was added to 50 mL of deionized water and dispersed for 30 minutes. Then, a mixed solution of NaOH and Na₂CO₃ was added to adjust the pH of the solution to 10. Subsequently, it was aged at 65 °C for 24 hours. After the reaction, the solution was naturally cooled to room temperature. The red precipitate was centrifugally washed three times with distilled water and ethanol respectively, and freeze-dried overnight at -50 °C to obtain the layered catalyst ZnFe-LDH;

[0034] The ZnFe-LDH catalyst was ultrasonically dispersed and evenly drawn onto the PTFE membrane using a suction filtration device to obtain a catalytic membrane. The loading amount of the layered catalyst ZnFe-LDH in the catalytic membrane was 4 mg / cm 2 .

[0035] The XRD pattern of the catalyst ZnFe-LDH is as Figure 1 shown.

[0036] The calculation equation for the interlayer spacing is: d = nλ / (2sinθ), where: d is the interlayer spacing, λ is the X-ray wavelength, and Cu Kα radiation is θ represents the diffraction angle.

[0037] From Figure 1 the data calculated, the interlayer spacing of ZnFe-LDH is

[0038] The SEM image of the catalytic membrane is as Figure 2 shown. From Figure 2 it can be seen that a layer of ZnFe-LDH nanosheets is closely packed on the membrane surface, and its cross-sectional thickness is about 40 μm.

[0039] Example 2

[0040] In this embodiment, a simple reaction device (as Figure 2 shown) was used. The water inlet pipe was connected to a peristaltic pump, and the solution was pumped into the pipeline by the peristaltic pump through the catalytic membrane (the catalytic membrane prepared in Example 1). After reaching the water outlet, it was immediately sent for detection. The peristaltic pump was started, and the pump speed of the peristaltic pump was regulated. The effluent was collected at regular intervals, and the phenol concentration in the effluent was measured by ultra-high performance liquid chromatography. The yield of dihydroxybiphenyl was measured by ultra-high performance liquid chromatography-mass spectrometry-mass spectrometry (UPLC-MS / MS), and the conversion rate was calculated.

[0041] The method for confining membrane-catalyzed phenolic carbon-carbon coupling reaction of the present invention includes the following steps:

[0042] (1) Phenol and persulfate were dissolved in water to form an aqueous solution. The initial concentration of the phenol substrate was 1.0 mmol / L, and the concentration of potassium monopersulfate (PMS) was 10 mmol / L. Then, the pH of the solution was adjusted to 8;

[0043] (2) Pass the above aqueous solution through the above membrane filtration device for carbon-carbon coupling reaction. Control the membrane flux to be 30 L / (m 2 ·h), 60 L / (m 2 ·h), 90 L / (m 2 ·h), 120 L / (m 2 ·h), 150 L / (m 2 ·h) by regulating the pump speed, and calculate the removal rate of phenol (C0 - C t ) / C0 * 100, the yield of carbon-carbon coupling product C f / C0 * 100, and the selectivity C f / (C0 - C t ) * 100. In the formula, C0 is the initial concentration of phenol, C t and C f are the concentrations of phenol and carbon-carbon coupling product at a certain reaction time respectively. The results are as Figure 4 shown.

[0044] It can be seen from Figure 4 that when the membrane flux is 30 L / (m 2 ·h), the removal rate of phenol can reach 84%, the yield of the carbon-carbon coupling product dihydroxybiphenyl (the UPLC-MS / MS diagram is as Figure 5 shown) is 27%, and the selectivity is 32%; when the membrane flux is 60 L / (m 2 ·h), the removal rate of phenol can reach 68%, the yield of the carbon-carbon coupling product dihydroxybiphenyl is 32%, and the selectivity is 47%; when the membrane flux is 90 L / (m 2 ·h), the removal rate of phenol can reach 55%, the yield of the carbon-carbon coupling product dihydroxybiphenyl is 39%, and the selectivity is 71%; when the membrane flux is 120 L / (m 2 ·h), the removal rate of phenol can reach 50%, the yield of the carbon-carbon coupling product dihydroxybiphenyl is 42%, and the selectivity is 84%; when the membrane flux is 150 L / (m 2 ·h), the removal rate of phenol can reach 40%, the yield of the carbon-carbon coupling product dihydroxybiphenyl is 33%, and the selectivity is 83%. From the above data, it can be seen that with the decrease of the membrane flux, the removal rate of phenol increases, but the residence time of phenol on the membrane increases, resulting in the decrease of the yield and selectivity of dihydroxybiphenyl. Therefore, when the membrane flux is 120 - 150 L / (m 2 ·h), the effect is better.

[0045] Detect the active species of the confined catalytic membrane system, and the results are as Figure 6 shown.

[0046] It can be seen from Figure 6 that after adding PMS, DMPO-OH· or DMPO-SO4 ·-Signal loss, the appearance of a 7-line spectrum corresponding to DMPOX (5,5-dimethyl-1-pyrrolidone-N-oxy), proves that the IV key role of the Fe

[0047] =O active species in the interlayer-confined ZnFe-LDH membrane system for the removal of PhOH and the generation of carbon-carbon coupling products.

[0048] Based on Example 2, the membrane flux is 120 L / (m 2 ·h), and the catalyst loading is changed to 3 mg / cm 2 , 6 mg / cm 2 . With other conditions unchanged, the test results are shown in Table 1.

[0049] Table 1 Test results under different catalyst loading conditions

[0050]

[0051] As can be seen from Table 1, at a membrane flux of 120 L / (m 2 ·h), with the increase of the catalyst loading, the removal rate of phenol increases, but the C-C coupling yield decreases, resulting in a decrease in the C-C coupling selectivity.

[0052] Example 4

[0053] Based on Example 2, the pH of the aqueous solution in step (1) is changed to 7 and 9, and the other conditions remain unchanged. The test results are shown in Table 2.

[0054] Table 2 Test results under different pH conditions

[0055]

[0056] As can be seen from Table 2, with the increase of pH, the removal rate of phenol increases, the C-C coupling yield decreases, resulting in a decrease in the C-C coupling selectivity.

[0057] Example 5

[0058] Based on Example 2, the membrane flux is 120 L / (m 2 ·h), and the PMS concentration is changed to 8 mM and 12 mM. With other conditions unchanged, the test results are shown in Table 3.

[0059] Table 3 Test results under different PMS addition amounts

[0060]

[0061] As can be seen from Table 3, with the increase of the PMS concentration, the removal rate of phenol increases, the C-C coupling yield decreases, and the selectivity decreases.

Claims

1. A method for the phenolic carbon-carbon coupling reaction catalyzed by a confined membrane, characterized in that, It includes the following steps: (1) Dissolve phenolic compounds and persulfate in an aqueous phase to form an aqueous solution, and adjust the pH of the solution to neutral or weakly alkaline; (2) Conduct a carbon-carbon coupling reaction on the above aqueous solution through a catalytic membrane; the catalytic membrane includes a substrate and a catalyst layer, the substrate is a filter membrane, and the catalyst layer is a layered catalyst ZnFe-LDH.

2. The method for the confined membrane-catalyzed phenolic carbon-carbon coupling reaction according to claim 1, wherein The membrane flux of the solution through the catalytic membrane is 90 - 150 L / (m 2 ·h).

3. The method for catalyzing phenolic carbon-carbon coupling reaction by the confined membrane according to claim 1, wherein The loading amount of the layered catalyst ZnFe-LDH in the catalytic membrane is 3-6 mg / cm 2 .

4. The method for the confinement membrane-catalyzed phenolic carbon-carbon coupling reaction according to claim 1, wherein The molar ratio of the phenolic compound to the persulfate is 1:8 to 10.

5. The method for catalytic phenol carbon-carbon coupling reaction by the confinement membrane according to claim 4, wherein The concentration of the phenolic compound is 0.01 to 1.0 mmol / L.

6. The method for catalyzing phenolic carbon-carbon coupling reaction by a confined membrane according to claim 4, wherein, The concentration of the persulfate is 0.1 to 10 mmol / L.

7. The method for catalytic phenolic carbon-carbon coupling reaction by the confined membrane according to claim 1, wherein The filter membrane is a PTFE membrane, an MCE membrane or a PES membrane.

8. The method for the confined membrane-catalyzed phenolic carbon-carbon coupling reaction according to claim 1, wherein The phenolic compound is phenol, 2-chlorophenol or 2,6-dimethylphenol.

9. The method for catalytic phenol carbon-carbon coupling reaction by a confined membrane according to claim 1, wherein The preparation method of the catalytic membrane is: load the layered catalyst ZnFe-LDH on the filter membrane by suction filtration.

10. The method for the confined membrane-catalyzed phenolic carbon-carbon coupling reaction according to claim 1, characterized in that, The preparation method of the layered catalyst ZnFe-LDH is: disperse zinc salt and iron salt in water, then adjust the pH to 9 to 10, and then age at 50 to 80 °C for 18 to 30 hours. After the reaction, wash and freeze-dry to obtain the layered catalyst ZnFe-LDH.

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