A heterogeneous copper single atom catalyst and its preparation method and application

Abstract

The present application belongs to the technical field of copper catalysts, and in particular, relates to a heterogeneous copper single atom catalyst, a preparation method and an application thereof; the heterogeneous copper single atom catalyst provided by the present application uses carbonized seaweed as a carrier to load copper single atoms, and in the process of catalytic synthesis of aromatic carboxylic acid compounds, the catalytic efficiency can be improved, and the yield of intermediates and product aromatic carboxylic acid compounds is relatively high, thereby improving the effect of current catalysts in catalytic synthesis of aromatic carboxylic acid compounds, and solving the technical problem in the prior art that multiple catalysts need to be used, resulting in reduced catalytic synthesis effect of aromatic carboxylic acid compounds.

Description

Technical Field

[0001] The present application belongs to the technical field of copper catalysts, and in particular relates to a heterogeneous copper single-atom catalyst and a preparation method and application thereof. Background Art

[0002] Aryl carboxylic acid compounds are important chemical raw materials. They can be used as organic molecular skeletons. Through the transformation of carboxylic acids and the introduction of functional groups, they can synthesize a variety of organic compounds. They are widely used in food preservatives, pesticides, dye intermediates, coatings, plasticizers, fragrances and pharmaceuticals.

[0003] In the process of catalytic synthesis of aromatic carboxylic acid compounds, specific catalysts are usually used in each stage of the reaction, which makes the catalytic reaction system for the catalytic synthesis of aromatic carboxylic acid compounds too complicated, reduces the catalytic synthesis effect of aromatic carboxylic acid compounds, and is not conducive to the large-scale catalytic synthesis of aromatic carboxylic acid compounds in the industrial field. Summary of the invention

[0004] In view of this, the present application provides a heterogeneous copper single atom catalyst and a preparation method and application thereof, which are used to solve the technical problem in the prior art that multiple catalysts need to be used, resulting in reduced catalytic synthesis effect of aromatic carboxylic acid compounds.

[0005] In a first aspect, the present application provides a heterogeneous copper single atom catalyst, comprising carbonized seaweed and copper single atoms;

[0006] The carbonized seaweed carries the copper single atom.

[0007] Preferably, the mass ratio of the carbonized seaweed to the copper single atom is 750:0.15-1.5.

[0008] The second aspect of the present application provides a method for preparing a heterogeneous copper single-atom catalyst, which can be used to prepare the heterogeneous copper single-atom catalyst described in the first aspect. The preparation method comprises the steps of:

[0009] Step S1, carbonizing and grinding the seaweed in sequence at high temperature to obtain powdered carbonized seaweed;

[0010] Step S2, adding the carbonized seaweed into the Cu-EDTA solution and stirring until the solvent is completely evaporated, and calcining at high temperature to obtain a heterogeneous copper single atom catalyst.

[0011] Preferably, in step S1, the high-temperature carbonization atmosphere is nitrogen, the heating rate is 5°C / min, the insulation temperature is 600-800°C, and the time is 2-4h.

[0012] Preferably, in step S2, the high temperature calcination is carried out at a temperature of 600 to 800° C. and for a time of 1 to 3 hours.

[0013] The third aspect of the present application provides the use of the heterogeneous copper single-atom catalyst described in the first aspect in the catalytic synthesis of aromatic carboxylic acid compounds.

[0014] Preferably, the application specifically includes:

[0015] Step 1, mixing a reaction substrate aryl olefin solution, biboric acid pinacol ester and a heterogeneous copper single atom catalyst described in the first aspect, and then performing a hydroboration reaction to obtain an aryl borate ester;

[0016] Step 2, mixing an aryl borate ester and an alkaline reagent and hydrolyzing them under alkaline conditions to obtain an aryl alcohol;

[0017] Step 3: Mix the aromatic alcohol and the oxidant and carry out an oxidation reaction to obtain an aromatic carboxylic acid compound.

[0018] Preferably, in step 1, the reaction atmosphere of the hydroboration reaction is nitrogen, the reaction pressure is 0.8-1.2 MPa, the reaction temperature is 80-120° C., and the reaction time is 6-10 h.

[0019] Preferably, in step 2, the reaction temperature of the hydrolysis is 80-120° C., and the reaction time is 6-10 h.

[0020] Preferably, in step 3, the reaction atmosphere of the oxidation reaction is oxygen, the reaction pressure is 0.8-1.2 MPa, the reaction temperature is 80-120° C., and the reaction time is 6-10 h.

[0021] Preferably, in step 1, the reaction substrate aromatic olefin solution used is an isopropanol solution of p-methylstyrene, in step 2, the alkaline reagent used is sodium hydroxide, and in step 3, the oxidant used is hydrogen peroxide.

[0022] In summary, the present application provides a heterogeneous copper single atom catalyst, a preparation method and an application thereof. The heterogeneous copper single atom catalyst provided by the present application comprises: carbonized seaweed and copper single atoms, wherein the carbonized seaweed loads copper single atoms. In the process of catalytic synthesis of aromatic carboxylic acid compounds, in the processes of hydroboration reaction, hydrolysis and oxidation reaction, only the heterogeneous copper single atom catalyst provided by the present application is required, and a complex catalyst system composed of multiple catalysts is not required, thereby simplifying the catalytic process of catalytic synthesis of aromatic carboxylic acid compounds and improving the catalytic efficiency. In addition, the carbonized seaweed has the characteristics of high specific surface area, rich pore structure and active functional groups such as hydroxyl and carboxyl, which can further improve the effect of the heterogeneous copper single atom catalyst in catalytic synthesis of aromatic carboxylic acid compounds, thereby solving the technical problem in the prior art that multiple catalysts need to be used, resulting in reduced catalytic synthesis effect of aromatic carboxylic acid compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a HAADF-STEM characterization image of the heterogeneous copper single atom catalyst provided in Example 1 of the present application;

[0025] Figure 2 This is the XRD characterization diagram of the heterogeneous copper single atom catalyst provided in Example 1 of the present application;

[0026] Figure 3 A schematic diagram of the synthesis route for catalytic synthesis of aromatic carboxylic acid compounds using a heterogeneous copper single atom catalyst provided in Example 1 of the present application;

[0027] Figure 4 The mass spectrum of the intermediate 4,4,5,5-tetramethyl-2-(4-methylphenethyl)-1,3,2-dioxaborane in the catalytic synthesis of aromatic carboxylic acid compounds by the heterogeneous copper single atom catalyst provided in Example 1 of the present application;

[0028] Figure 5 The mass spectrum of the intermediate p-methylphenylethanol in the catalytic synthesis of aromatic carboxylic acid compounds by the heterogeneous copper single atom catalyst provided in Example 1 of the present application;

[0029] Figure 6 This is the mass spectrum of the product p-methylphenylacetic acid in the catalytic synthesis of aromatic carboxylic acid compounds using the heterogeneous copper single atom catalyst provided in Example 1 of the present application. DETAILED DESCRIPTION

[0030] The present application provides a heterogeneous copper single atom catalyst and a preparation method and application thereof, which are used to solve the technical problem in the prior art that multiple catalysts need to be used, resulting in reduced catalytic synthesis effect of aromatic carboxylic acid compounds.

[0031] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0032] In view of the defect that multiple catalysts need to be used in the current catalytic synthesis of aromatic carboxylic acid compounds, resulting in a decrease in the catalytic synthesis effect of aromatic carboxylic acid compounds, the present application provides a heterogeneous copper single-atom catalyst, which comprises carbonized seaweed and copper single atoms, wherein the carbonized seaweed carries copper single atoms; wherein the heterogeneous copper single-atom catalyst can catalyze the hydroboration reaction of aromatic olefins and (bis(boronic acid) pinacol ester) to generate aromatic borate esters, which are hydrolyzed under alkaline conditions to generate aromatic alcohols, and finally oxidized to obtain aromatic carboxylic acids. The entire catalytic process only requires the use of the heterogeneous copper single-atom catalyst provided by the present application, and multiple catalysts are not required in the hydroboration reaction, hydrolysis and oxidation processes, thereby simplifying the catalytic process of catalytic synthesis of aromatic carboxylic acid compounds, improving the catalytic efficiency, and achieving a good catalytic synthesis effect of aromatic carboxylic acid compounds, thereby overcoming the defect that multiple catalysts need to be used in the current catalytic synthesis of aromatic carboxylic acid compounds, resulting in a decrease in the catalytic synthesis effect of aromatic carboxylic acid compounds;

[0033] In addition, the carrier used in the present application is carbonized seaweed, which has a high specific surface area, rich pore structure and active functional groups such as hydroxyl and carboxyl. The high specific surface area and rich pore structure are conducive to promoting the stable dispersion of copper single atom active centers on the carbonized seaweed carrier, and the active functional groups such as hydroxyl and carboxyl form chemical bonds with metallic copper to enhance the binding force between copper single atoms and the carbonized seaweed carrier. Therefore, in the process of catalytic synthesis of carboxylic acid compounds by heterogeneous copper single atom catalyst, the catalytic efficiency of the copper single atom active center is greatly improved, and the copper single atom active center is not easy to fall off from the carbonized seaweed carrier, thereby further improving the effect of the heterogeneous copper single atom catalyst in catalytic synthesis of carboxylic acid compounds.

[0034] The heterogeneous copper single atom catalyst provided in the present application will be specifically described below in combination with embodiments and experimental examples.

[0035] Example 1

[0036] Example 1 of the present application provides a method for preparing a heterogeneous copper single atom catalyst, which includes a step of preparing carbonized seaweed and a step of loading copper single atoms.

[0037] The steps of preparing carbonized seaweed include:

[0038] In a nitrogen atmosphere, the washed and dried seaweed was placed in a tubular furnace for high-temperature carbonization. The conditions for high-temperature carbonization were: heating from 20°C to 700°C at a heating rate of 5°C / min, keeping at 700°C for 3 hours and then cooling to room temperature to obtain carbonized seaweed. The carbonized seaweed was black flocculent particles, which were ground into powder.

[0039] The steps of loading copper single atoms include:

[0040] Add 150 μL of 10 mg / mL Cu-EDTA solution, 750 mg of carbonized seaweed and 30 mL of deionized water into a 50 mL beaker; first stir magnetically at room temperature for 1 hour and then heat to 100°C to remove the solvent water under magnetic stirring; after the solvent is evaporated, move it to a blower dryer and dry it at 70°C for 4 hours to obtain a mixture, then move the mixture to a tubular furnace for high-temperature calcination. The conditions for high-temperature calcination are: heating from 20°C to 700°C at a heating rate of 5°C / min, keeping warm at 700°C for 2 hours and then cooling to room temperature to obtain 716 mg of black powdered heterogeneous copper single-atom catalyst, the copper doping amount in 716 mg of black powder is approximately 0.2wt%, and the heterogeneous copper single-atom catalyst can be recorded as 0.2wt% Cu-N / C.

[0041] In this step, the Cu-EDTA solution used is prepared by the following method: 0.00629 mmol of disodium ethylenediaminetetraacetate EDTA-2Na, 0.00629 mmol of copper nitrate hexahydrate Cu(NO3)2·6H2O and 40 mL of deionized water are mixed, and NaOH is added to adjust the pH to 6-7 to obtain 40 mL, 10 mg / mL Cu-EDTA solution (Cu:EDTA=1:2).

[0042] Experimental Example 1

[0043] Experimental Example 1 of the present application conducts structural and performance tests on the heterogeneous copper single atom catalyst provided in Example 1.

[0044] Among them, the electron microscope image of the heterogeneous copper single atom catalyst is as follows Figure 1 As shown, from Figure 1 It can be clearly seen that there are particles with a size of about 1nm stably dispersed on the surface of carbonized seaweed. Figure 2 It can be seen from the X-ray diffraction pattern that particles with a size of about 1 nm should be single copper atoms, which indicates that in the heterogeneous copper single atom catalyst, the carbonized seaweed carries single copper atoms.

[0045] Among them, the performance test of the heterogeneous copper single atom catalyst was carried out, using p-methylstyrene in aromatic olefins as the reaction substrate to catalyze the synthesis of p-methylphenylacetic acid. The synthesis route is shown in the attached figure. Figure 3 shown.

[0046] The process of catalytic synthesis of p-methylphenylacetic acid comprises: a step of hydroboration reaction, a step of hydrolysis reaction and a step of oxidation reaction.

[0047] The steps of the hydroboration reaction include:

[0048] First, 40 mg of heterogeneous copper single atom catalyst was weighed into a 20 mL high-pressure reactor, and then 0.4 mmol of biboric acid pinacol ester was added, and then 0.2 mmol of p-methylstyrene substrate was added and mixed in 3 mL of isopropanol; then 25 mg of sodium hydroxide solution was added, the reactor was sealed, nitrogen was filled into the reactor six times and discharged, all the air in the reactor was discharged, and then nitrogen was introduced to make the pressure reach 1 MPa, and the reaction was stirred at a temperature of 100° C., the stirring rate was 500 r / min, and the reaction time was 8 h to obtain 0.1928 mmol of the intermediate 4,4,5,5-tetramethyl-2-(4-methylphenethyl)-1,3,2-dioxaborane, and the yield was calculated to be 96%. Its mass spectrum is shown in the attached figure. Figure 4 shown.

[0049] The steps of the hydrolysis reaction include:

[0050] The reactor was opened, and 75 mg of the alkaline reagent sodium hydroxide was directly added thereto, and 5 mL of isopropanol solvent was added. The reactor was sealed and stirred at 100°C with a stirring rate of 500 r / min for 8 h to obtain 0.1619 mmol of the intermediate p-methylphenylethanol. The yield was calculated to be 84%. The mass spectrum is shown in the attached figure. Figure 5 shown.

[0051] The oxidation reaction steps include: opening the reactor, adding 1 mL of oxidant hydrogen peroxide, sealing the reactor, filling the reactor with oxygen six times and discharging it, discharging all the air in the reactor, and then introducing oxygen to make the pressure reach 1 MPa, stirring at a temperature of 100° C., a stirring rate of 500 r / min, and a reaction time of 8 h to obtain 0.089 mmol of p-methylphenylacetic acid, and the calculated yield is 55%. The mass spectrum is shown in the attached figure. Figure 6 shown.

[0052] From the attached Figure 4-6 It can be seen that the heterogeneous copper single-atom catalyst provided in Example 1 of the present application can indeed catalyze the reaction substrate of aromatic olefins to synthesize aromatic carboxylic acid compounds; in the process of catalytic synthesis of aromatic carboxylic acid compounds, a complex catalyst system composed of multiple catalysts is not required, the steps of catalytic synthesis of aromatic carboxylic acid compounds are simple, the catalytic efficiency is high, and the yields of intermediates and products are relatively high, thereby greatly improving the catalytic effect of the current catalytic synthesis of aromatic carboxylic acid compounds.

[0053] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. Application of a heterogeneous copper single atom catalyst in catalytic synthesis of aromatic carboxylic acid compounds, characterized in that: The applications specifically include: Step 1, mixing a reaction substrate aryl olefin solution, biboric acid pinacol ester and a heterogeneous copper single atom catalyst and performing a hydroboration reaction to obtain an aryl borate ester; Step 2, mixing an aryl borate ester and an alkaline reagent and hydrolyzing them under alkaline conditions to obtain an aryl alcohol; Step 3, mixing the aromatic alcohol and the oxidant and performing an oxidation reaction to obtain an aromatic carboxylic acid compound; The preparation method of the heterogeneous copper single-atom catalyst comprises the steps of: Step S1, carbonizing and grinding the seaweed in sequence at high temperature to obtain powdered carbonized seaweed; Step S2, adding carbonized seaweed to a Cu-EDTA solution and stirring until the solvent is completely evaporated, and calcining at high temperature to obtain a heterogeneous copper single atom catalyst; In step S1, the high-temperature carbonization atmosphere is nitrogen, the heating rate is 5°C / min, the insulation temperature is 600-800°C, and the time is 2-4h; In step S2, the high temperature calcination is carried out at a temperature of 600 to 800°C and for a time of 1 to 3 hours.

2. The use of a heterogeneous copper single atom catalyst in catalytic synthesis of aromatic carboxylic acid compounds according to claim 1, characterized in that: In step 1, the reaction atmosphere of the hydroboration reaction is nitrogen, the reaction pressure is 0.8-1.2 MPa, the reaction temperature is 80-120° C., and the reaction time is 6-10 h.

3. The use of a heterogeneous copper single atom catalyst in catalytic synthesis of aromatic carboxylic acid compounds according to claim 1, characterized in that: In step 2, the reaction temperature of the hydrolysis is 80-120° C., and the reaction time is 6-10 hours.

4. The use of a heterogeneous copper single atom catalyst in catalytic synthesis of aromatic carboxylic acid compounds according to claim 1, characterized in that: In step 3, the reaction atmosphere of the oxidation reaction is oxygen, the reaction pressure is 0.8-1.2 MPa, the reaction temperature is 80-120° C., and the reaction time is 6-10 h.

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