Copper monatomic catalyst supported on c3n5, preparation method and application thereof

Abstract

The application discloses a copper monatomic catalyst loaded on C3N5 and a preparation method and application thereof, and belongs to the field of biomass photocatalytic oxidation. The preparation method of the copper monatomic catalyst loaded on C3N5 is as follows: 3-amino-1,2,4-triazole and CuCl2.2H2O are mixed in a certain proportion, ball-milled, and calcined at high temperature, and the copper monatomic catalyst loaded on C3N5 is applied to photocatalytic oxidation reactions of 5-hydroxymethylfurfural and furfural to prepare maleic anhydride. The copper monatomic catalyst loaded on C3N5 is adopted, the photocatalytic activity of C3N5 itself and the change of the band gap of C3N5 caused by Cu are utilized, and the catalytic activity of the catalyst is improved; the catalyst Cu@C3N5 is prepared, the catalyst has the advantages of low cost, simple preparation method, high photocatalytic activity, long service life and stability, and can be recycled and reused.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of biomass photocatalytic oxidation, and particularly relates to a copper monatomic catalyst loaded on C3N5 and a preparation method and application thereof. BACKGROUND

[0002] Cellulose, as the most widely distributed and largest polysaccharide in nature, has the advantages of low price and easy availability. Through a simple catalytic reaction (Ind. Eng. Chem. Res. 2018, 57, 3545−3553; Renew. Sust. Energ. Rev. 2021, 137, 50-56), the most important biomass-based platform compound 5-hydroxymethylfurfural and furfural can be obtained. 5-hydroxymethylfurfural or furfural can be converted into a series of high-value fine chemicals through oxidation, hydrodeoxygenation, hydrolysis and the like. Among them, maleic anhydride is the third largest anhydride raw material in the world in terms of trading volume, only next to phthalic anhydride and acetic anhydride. Maleic anhydride is widely used as a chemical raw material and a chemical product additive, such as the manufacture of unsaturated polyester resins and alkyd resins; it is used as a plasticizer in the plastic industry, a paper treatment agent in the paper industry, and additionally, it can be used in the pharmaceutical industry to manufacture long-acting sulfonamide drugs. It is used as a preservative for fats and oils in the oil and fat industry; and it is used in the organic industry to manufacture fumaric acid and tetrahydrofuran and the like.

[0003] The main methods for industrial synthesis of maleic anhydride include phenoxylation, butene oxidation, butane oxidation and the like. At present, phenoxylation and n-butane oxidation methods are mostly used in production (Clean Technol. Envir. 2019, 21, 1073-1090). The method of obtaining cis-anhydride by using n-butane as a raw material through a n-butane fluidized bed solvent absorption process is gradually replacing the phenoxylation method due to its lower cost. However, the reaction process still requires a high temperature of 400℃ or higher and a large amount of di-n-butyl phthalate as an absorption solvent, which pollutes the environment.

[0004] Researchers have developed various reaction processes for preparing maleic anhydride from biomass platform compounds furfural or 5-hydroxymethylfurfural. In 2012, Manuel Ojeda et al. prepared maleic anhydride from furfural by using VO xChemSusChem 2012, 5, 1984-1990); in 2015, Yinkuowen et al. used 5- hydroxymethylfurfural as raw material, and achieved a yield of about 60% of maleic anhydride under the conditions of 90°C, 1 MPa oxygen atmosphere and heteropoly acid catalysis (ACS Catal. 2015, 5, 2035-2041). Some scholars used hydrogen peroxide as an oxidant and modified titanium silicalite as a catalyst in a reactor containing GVL, water and sulfuric acid solution, and obtained a yield of 70% of maleic anhydride at 115-120°C for about 2 h (Green Chem. 2018, 20, 2845); in 2020, Lu Lin et al. used 5-[(formyloxy)methyl]furfural as raw material, and used sulfuric acid solution and a-MnO2 / Cu(NO3)2 as catalysts, and obtained a yield of 89% of maleic anhydride under the conditions of 90°C for 5 h (ACS Sustain. Chem. Eng. 2020, 8, 7901-7908). In the above processes, the conversion of biomass to maleic anhydride is achieved, but it is difficult to use the above method for large-scale industrial production due to low yield, harsh high temperature and high pressure conditions, and poor environmental friendliness of the oxidant.

[0005] Further, some scholars have developed a milder photocatalytic reaction to oxidize biomass to obtain maleic anhydride. For example, a two-step photocatalytic reaction is used, which first converts furfural into 5-hydroxyfuran-2(5H)-one, and then obtains maleic anhydride through an oxidation process (Angew. Chem. Int. Ed. 2022, 61, e202112618). The catalytic process is complex, and the homogeneous system is not conducive to the recovery of the catalyst. Kailasam et al. used mesoporous carbon nitride as a catalyst, and furfural as a raw material, and obtained a conversion rate of 95% of furfural after 30 h under the irradiation of a simulated sunlight lamp at 100 mW / cm 2 of the photocatalytic reaction, and further improve the yield, while simplifying the catalyst preparation method and shortening the reaction time, have become the direction of further research. H SUMMARY

[0006] ​The present application aims to overcome the deficiencies of the prior art, and provides a copper monatomic catalyst supported on C3N5, a preparation method thereof and a method for preparing maleic anhydride by photocatalytic oxidation of 5-hydroxymethylfurfural and furfural.

[0007] To achieve the above-mentioned object, the technical scheme adopted by the present application is as follows:

[0008] The present application provides a copper monatomic catalyst supported on C3N5, wherein copper is supported on C3N5 in the form of monatomic.

[0009] The present application also provides a preparation method of the copper monatomic catalyst supported on C3N5, comprising the following steps:

[0010] Step one, 3-amino-1,2,4-triazole and CuCl2·2H2O are mixed in a certain proportion, and ball milling treatment is performed to obtain material I;

[0011] Step two, the material I obtained in step one is calcined at high temperature, and the copper monatomic catalyst supported on C3N5, Cu@C3N5, is obtained after natural cooling after calcination.

[0012] Further, the mass ratio of 3-amino-1,2,4-triazole to CuCl2·2H2O in step one is 40-60:0.8-1.2; the ball milling treatment is specifically as follows: stainless steel ball milling tank is used for ball milling, the rotation speed is 250 r / min, forward rotation is 25 min, stop is 5 min, reverse rotation is 25 min, and the cycle is two times.

[0013] Further, the calcination in step two is specifically as follows: nitrogen is used as the protective gas during the calcination process, the heating rate is 5 ℃ / min, the temperature is increased to 500 ℃, and then the calcination is performed at constant temperature for 180 min, and then natural cooling is performed.

[0014] The present application also provides a method for photocatalytic oxidation of 5-hydroxymethylfurfural by using the copper monatomic catalyst supported on C3N5, wherein 5-hydroxymethylfurfural, the catalyst of claim 1 and a solvent are added to a reaction container, and stirring is performed under a certain pressure, a gas atmosphere and visible light irradiation for a certain time, and post-treatment is performed after the reaction is completed.

[0015] Further, the mass ratio of 5-hydroxymethylfurfural, the catalyst of claim 1 and the solvent added above is 4-6:0.8-1.2:80-120.

[0016] Further, the stirring under a certain pressure, a gas atmosphere and visible light irradiation for a certain time is specifically as follows: stirring is performed under 0.1 MPa pressure, an oxygen atmosphere and 413 nm visible light irradiation for 12 h; and the organic solvent is acetonitrile.

[0017] The application also provides a method for photocatalytic oxidation of furfural by using the copper monatomic catalyst supported on C3N5, wherein furfural, the catalyst of claim 1 and a solvent are added into a reaction container, and then the reaction is stirred under a certain pressure, a gas atmosphere and visible light irradiation for a certain time, and after the reaction is completed, post-treatment is performed.

[0018] Further, the mass ratio of the added furfural, the catalyst of claim 1 and the solvent is 4-6:0.8-1.2:80-120.

[0019] Further, the stirring under the certain pressure, the gas atmosphere and the visible light irradiation for the certain time is specifically stirring for 12 h under 0.1 MPa pressure, an oxygen atmosphere and 413 nm visible light irradiation; and the organic solvent is acetonitrile.

[0020] Compared with the prior art, the application has the following beneficial effects:

[0021] Firstly, the copper monatomic catalyst supported on C3N5 is used in the application, and the photocatalytic activity of C3N5 itself and the change of the band gap of C3N5 caused by Cu are utilized to improve the catalytic activity of the catalyst.

[0022] Secondly, the Cu monatomic catalyst prepared by the application has low metal content, cheap raw materials and simple preparation process, and has good stability and recyclability, wherein the Cu is in the form of single atom distributed on the C3N5 carrier material, and the Cu atom content is only 1.8 wt.%, but has excellent catalytic performance.

[0023] Thirdly, a mild reaction system is used in the application, wherein the catalyst, the substrate and the solvent are mixed, and the reaction can occur under visible light. The conversion rates of 5-hydroxymethylfurfural and furfural can be increased to 100%, and the yield of the target product maleic anhydride is as high as 98% and 86% respectively, which has great significance for actual industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0024] Fig. 1a TEM image of the copper monatomic catalyst supported on C3N5 (Cu@C3N5) prepared in Example 1 of the application under a size of 200 nm;

[0025] Fig. 1b TEM image of the copper monatomic catalyst supported on C3N5 (Cu@C3N5) prepared in Example 1 of the application under a size of 100 nm;

[0026] Fig. 1c HAADF image of the copper monatomic catalyst supported on C3N5 (Cu@C3N5) prepared in Example 1 of the application under a size of 200 nm;

[0027] ByFigs. 1a to 1c It can be seen that the Cu@C3N5 is in the form of flake, has a large surface area, provides a basis for excellent photocatalytic activity, and is beneficial to the attachment of copper in the form of single atom, ensures the photocatalytic activity while reducing the loading amount, and improves the dispersity of copper;

[0028] Fig. 2a Mapping diagram of C element distribution of the copper single atom catalyst (Cu@C3N5) supported on C3N5 prepared in Example 1 of the present application;

[0029] Fig. 2b Mapping diagram of N element distribution of the copper single atom catalyst (Cu@C3N5) supported on C3N5 prepared in Example 1 of the present application;

[0030] Fig. 2c Mapping diagram of O element distribution of the copper single atom catalyst (Cu@C3N5) supported on C3N5 prepared in Example 1 of the present application;

[0031] Fig. 2d Mapping diagram of Cu element distribution of the copper single atom catalyst (Cu@C3N5) supported on C3N5 prepared in Example 1 of the present application;

[0032] From the above data, it can be seen that the Cu element is uniformly doped in the catalyst; Figs. 2a to 2d

[0033] Fig. 3 XRD diagram of the copper single atom catalyst (Cu@C3N5) supported on C3N5 prepared in Example 1 of the present application; from the diagram, it can be seen that no diffraction peak of metal Cu is found, indicating that the dispersity of Cu element on the carrier C3N5 is good, and further confirms the single atom structure;

[0034] Fig. 4 PL spectrum diagram of the copper single atom catalyst (Cu@C3N5) supported on C3N5 prepared in Example 1 of the present application; it can be obviously seen that, compared with the ordinary C3N5 catalyst, the prepared Cu@C3N5 has higher fluorescence intensity and higher photocatalytic activity;

[0035] Fig. 5 EXAFS spectrum diagram of the copper single atom catalyst (Cu@C3N5) supported on C3N5 prepared in Example 1 of the present application; no Cu particle signal with sufficient intensity is detected in the sample, and the sample only shows a Cu-C / N single peak signal, indicating that the sample is a single atom structure;

[0036] Fig. 6 Mass spectrum diagram of the organic phase after reaction in Example 2 of the present application; ​

[0037] Fig. 7 The mass spectrum of the organic phase after reaction of Example 3 of the present application. DETAILED DESCRIPTION

[0038] The present application will be further described in conjunction with the following examples.

[0039] Those skilled in the art will appreciate that the following examples are intended to be illustrative only and should not be viewed as limiting the scope of the present application. Wherein no specific technique or condition is specified in the examples, the technique or condition described in the literature or according to the product manual is used. Wherein no manufacturer of the reagent or instrument is specified, it is a conventional product that can be obtained by purchase.

[0040] Example 1: Preparation of catalyst Cu@C3N5

[0041] Step one, 4.2 g of 3-amino-1,2,4-triazole and 85.25 mg of CuCl2·2H2O were weighed and placed in a stainless steel ball mill jar;

[0042] Step two, ball milling was performed using a stainless steel ball mill jar with the following specific requirements: rotation speed 250 r / min, forward rotation for 25 min, stop for 5 min, reverse rotation for 25 min, and cycle twice;

[0043] Step three, the sample after ball milling was taken out and calcined using a tube furnace, nitrogen was used as the protective gas, the heating rate was 5 ℃ / min, after the temperature was raised to 500 ℃, the sample was calcined for 180 min, then naturally cooled to room temperature, taken out, and ground to obtain Cu@C3N5.

[0044] Example 2: Photocatalytic oxidation of 5-hydroxymethylfurfural conversion reaction

[0045]

[0046] 100 mg of 5-hydroxymethylfurfural, 2 mL of acetonitrile and 20 mg of Cu@C3N5 prepared in Example 1 were sequentially added to a glass stoppered reaction tube, and stirred (rotation speed 500 rpm) under an oxygen atmosphere, 0.1 MPa pressure, room temperature and 413 nm visible light irradiation for 12 h; after the reaction was completed, the catalyst and organic phase were separated, and the yield of the target product maleic anhydride was determined by gas chromatography-mass spectrometry to be 98%. The light source used was a LED lamp with a power of 12 W.

[0047] Example 3: Photocatalytic oxidation of furfural conversion reaction

[0048]

[0049] 100 mg of furfural, 2 mL of acetonitrile and 20 mg of Cu@C3N5 were sequentially added into a glass stoppered reaction tube, and stirred (500 rpm) under an oxygen atmosphere, 0.1 MPa pressure, room temperature and 413 nm visible light irradiation for 12 h; after the reaction, the catalyst and organic phase were separated, and the yield of the target product maleic anhydride was determined by gas chromatography-mass spectrometry to be 86%. The light source used was a 12 W LED lamp.

[0050] Example 4: Repeated use of Cu@C3N5 photocatalytic oxidation of 5-hydroxymethylfurfural to prepare maleic anhydride

[0051] 100 mg of 5-hydroxymethylfurfural, 2 mL of acetonitrile and 20 mg of Cu@C3N5 were sequentially added into a glass stoppered reaction tube, and stirred (500 rpm) under an oxygen atmosphere, 0.1 MPa pressure, room temperature and 413 nm visible light irradiation for 12 h; after the reaction, the catalyst was separated by centrifugation, washed with methanol three times and dried. The above process was repeated five times, and the yield of maleic anhydride was determined by gas chromatography-mass spectrometry to be 98%, 97%, 97%, 94% and 92%, respectively.

[0052] The above examples have described the embodiments of the present application in detail, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application. The above description is only the preferred embodiments of the present application, and does not limit the scope of the present application, and equivalent structural changes made by applying the content of the present application are included in the scope of the present application.

Claims

1. A method for preparing a copper monatomic catalyst supported on C3N5, characterized in that, Comprising the following steps: Step one, 3-amino-1, 2, 4-triazole and CuCl2·2H2O are mixed in a certain proportion, ball milling treatment is carried out, and material I is obtained; Step two, the material I obtained in step one is calcined at high temperature, and after calcination, natural cooling is carried out, and the copper monatomic catalyst loaded on C3N5, Cu@C3N5, is obtained. Among them, the copper monatomic catalyst loaded on C3N5, copper is loaded on C3N5 in the form of single atom.

2. The method of claim 1, wherein the method is characterized by: The mass ratio of 3-amino-1, 2, 4-triazole to CuCl2·2H2O in step one is 40-60:0.8-1.2; the ball milling treatment is specifically: using a stainless steel ball milling tank, the rotation speed is 250 r / min, forward rotation for 25 min, stop for 5 min, reverse rotation for 25 min, and the cycle is two times.

3. The method of claim 1, wherein the method is characterized by: The calcination in step two is specifically: nitrogen is used as the protective gas during the calcination process, the heating rate is 5 ℃ / min, the temperature is raised to 500 ℃, and then the calcination is carried out for 180 min, and then the temperature is naturally lowered.

4. A method for photocatalytic oxidation of 5-hydroxymethylfurfural with a catalyst prepared by the method for preparing a copper monatomic catalyst supported on C3N5 according to claim 1, characterized in that: 5-hydroxymethylfurfural, the catalyst prepared by the preparation method of claim 1, and a solvent are added to a reaction container, and stirred under a certain pressure, gas atmosphere, and visible light irradiation for a certain time, and after the reaction is completed, post-treatment is carried out; the mass ratio of 5-hydroxymethylfurfural, the catalyst prepared by the preparation method, and the solvent added is 4-6:0.8-1.2:80-120; the stirring under a certain pressure, gas atmosphere, and visible light irradiation for a certain time is specifically: stirring under 0.1 MPa pressure, oxygen atmosphere, and 413 nm visible light irradiation for 12 h; the solvent is acetonitrile.

5. A method for photocatalytic oxidation of furfural using the catalyst prepared by the method of claim 1, characterized in that: Furfural, the catalyst prepared by the preparation method of claim 1, and a solvent are added to a reaction container, and stirred under a certain pressure, gas atmosphere, and visible light irradiation for a certain time, and after the reaction is completed, post-treatment is carried out; the mass ratio of furfural, the catalyst prepared by the preparation method of claim 1, and the solvent added is 4-6:0.8-1.2:80-120; the stirring under a certain pressure, gas atmosphere, and visible light irradiation for a certain time is specifically: 0.1 MPa pressure, oxygen atmosphere, and 413 nm visible light irradiation for 12 h; the solvent is acetonitrile.

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