N, Se co-doped CuO nanosheet and preparation method and application thereof

Abstract

The application discloses N, Se co-doped CuO nanosheets and a preparation method and application thereof, and relates to a nonmetal element doped metal oxide prepared by a molten salt method and a low-temperature calcination method and used as a catalyst, NaBH4 used as a reducing agent, which can quickly reduce 4-nitrophenol into 4-aminophenol, has excellent reaction rate and nearly 100% product selectivity, and can be recycled for more than 5 times and has good stability. The application not only removes pollutants such as 4-nitrophenol, but also obtains high-value-added chemicals. The catalyst material preparation process is simple and low in cost, and has wide market application prospects in the fields of chemical catalytic organic synthesis and pollutant treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of inorganic nanofunctional materials, and particularly relates to a simple preparation method and application of a selective catalytic reduction nitrophenol catalyst. BACKGROUND

[0002] 4-nitrophenol (4-NP) is one of the most common pollutants in the environment and industrial wastewater, which causes irreversible damage to the kidneys, liver, central nervous system and blood of animals and humans, and is listed as a "priority pollutant" by the US Environmental Protection Agency. Therefore, it is necessary to develop effective methods to treat these pollutants. So far, several strategies have been developed, such as adsorption, microbial degradation, advanced oxidation and catalytic reduction. Among these methods, catalytic reduction has attracted great attention because the reduction of 4-NP to 4-aminophenol (4-AP) with lower toxicity reduces the risk of environmental pollution, and more importantly, the synthesized 4-AP can be widely used for the synthesis of drugs, corrosion inhibitors and developing agents, thereby obtaining considerable economic benefits.

[0003] In the catalytic reduction of 4-NP, NaBH4 is used as a reducing agent, and various catalysts have been designed and prepared. Various catalysts based on noble metals, such as gold, silver and platinum, are widely studied due to their excellent initial activity. Although the efficiency of noble metal catalysts is very high, their wide application is limited due to their high price and limited reserves. While the catalytic efficiency of existing non-noble metal catalysts is generally lower than that of noble metal catalysts. Therefore, it is urgent to develop more efficient, high-yield, high-selectivity and stable non-noble metal catalysts for industrial production to obtain high-value-added compounds. SUMMARY

[0004] This section is intended to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, the abstract and the title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0005] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0006] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art and provide a preparation method of N, Se co-doped CuO nanosheets.

[0007] To solve the above technical problems, the present application provides the following technical solutions: drying copper nitrate to completely melt the copper nitrate to form liquid copper nitrate;

[0008] After the catalyst substrate material is soaked in liquid copper nitrate and kept warm, the in-situ grown basic copper nitrate on the catalyst substrate material is obtained by sequentially ultrasonic treatment in water and anhydrous ethanol, and the basic copper nitrate is vacuum dried;

[0009] The selenium powder is placed in a porcelain boat and placed upstream of the tube furnace; the vacuum-dried basic copper nitrate is placed in another porcelain boat and placed downstream of the tube furnace for calcination; and natural cooling is performed to room temperature to obtain the prepared N, Se co-doped CuO nanosheet.

[0010] As a preferred scheme of the preparation method, the copper nitrate is completely melted by drying the copper nitrate, wherein the drying temperature is 120-160 DEG C, and the time is 0.2-4 h.

[0011] As a preferred scheme of the preparation method, the catalyst substrate material is one or more of carbon paper, foamed nickel, foamed copper and stainless steel mesh, and the size is 4*4 cm.

[0012] As a preferred scheme of the preparation method, after the catalyst substrate material is soaked in liquid copper nitrate and kept warm, wherein the soaking temperature is 120-160 DEG C, and the time is 0.5-3 h.

[0013] As a preferred scheme of the preparation method, the in-situ grown basic copper nitrate on the catalyst substrate material is obtained by sequentially ultrasonic treatment in water and anhydrous ethanol, and the basic copper nitrate is vacuum dried, wherein the ultrasonic treatment time is 10 min, the vacuum temperature is 60 DEG C, and the time is 6 h.

[0014] As a preferred scheme of the preparation method, the selenium powder is placed in a porcelain boat and placed upstream of the tube furnace; the vacuum-dried basic copper nitrate is placed in another porcelain boat and placed downstream of the tube furnace for calcination, wherein the mass ratio of the basic copper nitrate to the selenium powder is 0.1:1-10, the calcination condition is argon, the temperature is 250-350 DEG C, and the time is 1-3 h.

[0015] Still another object of the present application is to provide an N, Se co-doped CuO nanosheet to overcome the deficiencies in the prior art.

[0016] Still another object of the present application is to provide an application of the N, Se co-doped CuO nanosheet in catalytic reduction of 4-nitrophenol (4-NP) to overcome the deficiencies in the prior art.

[0017] As a preferred solution of the preparation method, the catalyst can convert nitrophenol pollutants into amino high value-added chemicals by catalytic hydrogenation, wherein the reaction medium is an aqueous solution containing 4-nitrophenol and sodium borohydride (NaBH4); the concentration of 4-nitrophenol is 5 mM or higher, the concentration of sodium borohydride is 0.05 M or higher, and the amino high value-added chemical is p-aminophenol (4-AP).

[0018] A further object of the present application is to overcome the deficiencies in the prior art and provide an application of N, Se co-doped CuO nanosheets in a hydrogenation reaction system of methylene blue, Congo red and other dyes, hydrogen production by hydrolysis, and catalytic reduction of bromate and other hydrogenation reactions.

[0019] The present application has the following beneficial effects:

[0020] (1) The present application provides a design idea of combining a non-metallic element (Se) with an alkaline copper salt that can be mass-produced to form a nanosheet material. The material is prepared by a molten salt plus calcination method. In the reaction process, a transition metal alkaline salt that can be easily prepared forms an N and Se co-doped metal oxide catalyst material, improving the catalytic activity of the material. The process is simple, has high yield, causes little environmental pollution, has low raw material prices, low production costs, can be mass-produced, and meets the requirements of industrial applications. The prepared material has excellent performance in the field of catalytic reduction of 4-nitrophenol.

[0021] (2) The present application provides a preparation method of the above-mentioned catalyst material, which is prepared by a two-step molten salt method and calcination method. Copper nitrate is placed in a reaction kettle and completely melted at 120-160 DEG C to form liquid copper nitrate. Foam nickel is then soaked in the liquid copper nitrate and incubated at 120-160 DEG C for 0.5-3 h to obtain in-situ grown copper hydroxynitrate (marked as CuHN / NF). The above-mentioned copper hydroxynitrate and a certain amount of selenium powder are then placed in a tube furnace and calcined at 250-350 DEG C in an argon atmosphere for 1-3 h. The prepared catalyst material is obtained after natural cooling to room temperature. The synthesis method is simple and convenient, and is conducive to realizing large-scale industrialized production.

[0022] (3) The present application provides an N and Se co-doped metal oxide catalyst material, which has the unique advantage of being mass-produced and has a wide application prospect in the field of catalytic reduction of nitrobenzene pollutants, especially in the field of catalytic reduction of 4-nitrophenol to prepare 4-aminophenol. The material has excellent conversion rate, high 4-aminophenol selectivity and good stability. In the entire reaction process, the device is simple, so it has a broad market application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings. The catalyst material is N and Se co-doped CuO nanosheet loaded on a nickel foam, which is referred to as N, Se-CuO / NF. Wherein:

[0024] Figure 1 The powder X-ray diffraction pattern of the N, Se-CuO / NF material described in Embodiment 2 of the present application.

[0025] Figure 2 The scanning electron microscope image of the N, Se-CuO / NF material described in Embodiment 3 of the present application.

[0026] Figure 3 The transmission electron microscope and mapping image of the N, Se-CuO / NF material described in Embodiment 3 of the present application.

[0027] Figure 4 The catalytic conversion efficiency diagram, ln(Ct / C0) and reaction time curve diagram and cycle stability diagram of the N, Se-CuO / NF material described in Embodiment 4 of the present application.

[0028] Figure 5 The liquid chromatogram of the product obtained by the N, Se-CuO / NF material described in Embodiment 5 of the present application.

[0029] Figure 6 The reaction real object diagram and reaction mechanism diagram of the Ni, Se-CuO / NF electrode material described in Embodiment 6 of the present application.

[0030] Figure 7 The catalytic conversion efficiency diagram of Embodiments 7-10.

[0031] Figure 8 The catalytic conversion efficiency diagram of Embodiments 10-12.

[0032] Figure 9 The catalytic conversion efficiency diagram of Embodiments 1, 12 and 13 of the present application.

[0033] Figure 10 The catalytic conversion efficiency diagram of Comparative Example 1.

[0034] Figure 11 The catalytic conversion efficiency diagram of Comparative Example 2.

[0035] Figure 12 The catalytic conversion efficiency diagram of Comparative Example 3.

[0036] Figure 13 Catalytic conversion efficiency plot for Comparative Example 4. DETAILED DESCRIPTION

[0037] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, the specific embodiments of the present application will be described in detail below with reference to the embodiments of the present application.

[0038] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0039] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an embodiment that is separate or alternative to other embodiments.

[0040] Reagents and materials: all chemical reagents are commercially available. Copper (II) nitrate trihydrate (Cu(NO3)2·3H2O, 99%) was purchased from Shanghai Titan Science and Technology Co., Ltd. Sodium borohydride (NaBH4, 98%) and selenium powder (Se, 99%) were purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd. Commercial foam nickel was purchased from Suzhou Shengernuo Technology Co., Ltd. 4-nitrophenol (4-NP) and 4-aminophenol (4-AP) were purchased from Shanghai Maikelin Biochemical Co., Ltd.

[0041] Example 1

[0042] The present application provides a preparation method of N and Se co-doped CuO nanosheet material:

[0043] (1) 30 g of copper nitrate was placed in a glass beaker, then placed in an oven, and the copper nitrate was completely melted at 140°C to form a liquid copper nitrate;

[0044] (2) Then place the foam nickel 4*4 cm flat into the beaker, immerse it in the liquid copper nitrate, and incubate at 140°C for 0.5 h. The obtained foam nickel in-situ grown basic copper nitrate (denoted as CuHN / NF) was successively ultrasonically treated in water and anhydrous ethanol for 10 min, and CuHN / NF was placed into a vacuum drying oven and dried at 60°C for 6 h;

[0045] (3) Then 0.2 g of selenium powder was placed in the upstream and downstream two porcelain boats of the tube furnace with CuHN / NF respectively, and calcined at 250°C in an argon atmosphere for 2 h; naturally cooled to room temperature to obtain the prepared catalyst material.

[0046] Example 2

[0047] Crystal structure analysis of the sample prepared in Example 1

[0048] The powder X-ray diffraction was performed on an X-ray powder diffractometer of type D8 of Bruker company in Germany, with a fixed target monochromatic light source Cu-Ka, wavelength The scanning range was 20-60°, and the scanning step was 0.02°. The sample 1# was a typical electrode material prepared in Example 1, as shown in Figure 1 According to the X-ray diffraction pattern obtained by fitting, the prepared precursor material CuHN / NF was Cu2(OH)3(NO3) (PDF: 15-0014) supported on nickel foam, and N, Se-CuO / NF could see the diffraction peak of CuO (PDF: 48-1548), which indicated that through this simple, mild and environmentally friendly condition, the basic copper nitrate could be simply grown in the form of molten salt on the nickel foam in a large scale, and then Se was doped by calcination, so that the regular N and Se co-doped CuO nanosheet material was successfully formed on the substrate.

[0049] Example 3

[0050] Characterization of the morphology of the sample prepared in Example 1

[0051] The morphology of the prepared sample was characterized by SEM and TEM, as shown in Figure 2 Figure 3 The prepared precursor material showed regular nanorod structure as a whole, and the morphology was uniform, as shown in Figure 2 (a) (b) (c); after introducing Se source to form oxide, the original uniform rod structure changed into sheet, as shown in Figure 2 (d) (e) (f); which had rich surface structure, which increased the contact surface of the catalyst and the reaction substrate, exposed more reaction active sites, so as to improve the catalytic activity of the catalyst. In addition, from Figure 3 (a) (b) it could be proved that CuO was generated, Figure 3 (c) it was confirmed that the main elements in the material were Cu, Se, O, N, which further proved that the obtained material was N and Se co-doped CuO.

[0052] Example 4

[0053] Catalytic conversion efficiency diagram of the material, ln(Ct / C0) vs. reaction time curve and cycle stability.

[0054] N,Se-CuO / NF as catalyst, 0.1 M NaBH4 as reductant, 10 mM 4-NP aqueous solution was catalytically reduced. The reaction was continuously stirred during the reaction, 50 μL of reaction solution was absorbed during the reaction, diluted 25 times with ultrapure water, and analyzed by HPLC. Because of the use of an excess of NaBH4 compared with the amount of 4-NP, the catalytic reduction follows a pseudo-first-order reaction. Therefore, the reaction rate constant k (min-1) was calculated according to the kinetic equation ln(Ct / C0) = -kt, in which Ct is the 4-NP concentration at a certain reaction time (t), and C0 is the initial 4-NP concentration. The catalytic conversion efficiency graph and the ln(Ct / C0) vs. reaction time curve are shown in Figure 4 (a) (b) As can be seen from the figure, the N,Se-CuO / NF catalyst has excellent performance for the catalytic reduction of 4-nitrophenol. In order to evaluate the reusability, the catalyst was taken out of the solution and reused in the next cycle without any treatment. As shown in Figure 4 (c), the conversion efficiency of 4-NP remained at 91.7% at the fifth cycle. The results show that N,Se-CuO / NF has good stability and reusability, showing great potential in industrial applications.

[0055] Example 5

[0056] Liquid chromatogram of catalytic reaction

[0057] N,Se-CuO / NF catalytically reduced 50 mL of aqueous solution containing 10 mM 4-NP and 0.1 M NaBH4, and the products obtained at different reaction times were characterized by liquid chromatography, as shown in Figure 5 The residence time of each product in high performance liquid chromatography at different reaction times is shown in

[0058] Example 6

[0059] Mechanism of catalytic reaction

[0060] As shown in Figure 6 (a) (b), the value of k decreases with the increase of 4-NP concentration, and increases with the increase of NaBH4 concentration, indicating that the reduction of 4-NP follows the Langmuir-Hinshelwood mechanism. As shown in Figure 6(c) (d), after adding sodium borohydride, 4-NP is converted into 4-nitrophenolate ion, the solution color changes from light yellow to dark yellow, borohydride and nitrophenolate ion in the aqueous solution are adsorbed on the surface of the catalyst, and a large amount of BH4- provides sufficient H for the subsequent reduction reaction. With the gradual progress of the hydrogenation reaction, 4-nitrophenol is first converted into 4-hydroxyaminophenol intermediate, and finally converted into 4-aminophenol. Finally, the generated 4-AP molecules are desorbed from the surface of the catalyst to provide space for another catalytic cycle. After the complete conversion of 4-nitrophenol, the solution color becomes colorless.

[0061] Example 7

[0062] The difference from Example 1 is that no Se powder is added in step (3), the calcination temperature is 350℃, and the calcination time is 1h.

[0063] Figure 7 The catalytic conversion efficiency diagram of Examples 7-10. The complete conversion of 4-NP is achieved in 40min, and the catalytic efficiency is general.

[0064] Example 8

[0065] The difference from Example 1 is that the mass of Se powder added in step (3) is 0.1g, the calcination temperature is 350℃, and the calcination time is 1h. The complete conversion of 4-NP is achieved in 40min, and the catalytic efficiency is general.

[0066] Example 9

[0067] The difference from Example 1 is that the mass of Se powder added in step (3) is 0.3g, the calcination temperature is 350℃, and the calcination time is 1h. The complete conversion of 4-NP is achieved in 32min, and the catalytic efficiency is general.

[0068] Example 10

[0069] The difference from Example 1 is that the calcination temperature in step (3) is 350℃, and the calcination time is 1h. The complete conversion of 4-NP is achieved in 24min. Compared with Examples 7, 8, and 9, it is shown that under the conditions of a calcination temperature of 350℃ and a calcination time of 1h, the optimal Se powder addition amount is 0.2g.

[0070] Example 11

[0071] The difference from Example 1 is that in step (3), the calcination temperature is 300℃, and the calcination time is 1h. The complete conversion of 4-NP is achieved in 16min, and the catalytic efficiency is general.

[0072] Figure 8 The catalytic conversion efficiency diagram of Examples 10-12.

[0073] Example 12

[0074] The difference from Example 1 is that the calcination time in step (3) is 1 h. The complete conversion of 4-NP is achieved in 10 min, and the catalytic efficiency is better. Compared with Examples 10 and 11, it is shown that the best calcination temperature is 250°C under the condition that the Se powder addition amount is 0.2 g and the calcination time is 1 h.

[0075] Example 13

[0076] The difference from Example 1 is that the calcination time in step (3) is 3 h.

[0077] Figure 9 The catalytic conversion efficiency diagram of Example 1 and Examples 12 and 13 is shown. The complete conversion of 4-NP is achieved in 12 min. Compared with Examples 1 and 12, it is shown that the best calcination time is 2 h under the condition that the Se powder addition amount is 0.2 g and the calcination temperature is 250°C.

[0078] Comparative Example 1

[0079] The difference from Example 1 is that the calcination time in step (3) is 4 h.

[0080] Figure 10 The catalytic conversion efficiency diagram of Comparative Example 1 is shown. The complete conversion of 4-NP is achieved in 16 min. Too long calcination time can cause damage to the material structure and reduce the catalytic efficiency.

[0081] Comparative Example 2

[0082] The difference from Example 1 is that no Se powder is added in step (3).

[0083] Figure 11 The catalytic conversion efficiency diagram of Comparative Example 2 is shown. The complete conversion of 4-NP is achieved in 14 min. The doping of Se can adjust the electronic structure of CuO and promote the adsorption of 4-NP, so that the non-addition of selenium powder can reduce the catalytic efficiency.

[0084] Comparative Example 3

[0085] The difference from Example 1 is that the calcination temperature in step (3) is 200°C.

[0086] Figure 12 The catalytic conversion efficiency diagram of Comparative Example 3 is shown.

[0087] Only about 10% is converted in 20 min, and lower temperature can cause most of the basic copper nitrate to fail to be converted into copper oxide, and the catalytic efficiency is extremely poor.

[0088] Comparative Example 4

[0089] The difference from Example 1 is that the calcination temperature in step (3) is 400°C.

[0090] Figure 13 Catalytic conversion efficiency plot for Comparative Example 4. Complete conversion of 4-NP is achieved in 30 min. Too high a temperature can damage the structure of the material, resulting in a decrease in catalytic conversion efficiency.

[0091] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the present application, and they should be covered in the scope of the present application.

Claims

1. The use of N, Se co-doped CuO nanosheets catalyst in the catalytic reduction of 4-nitrophenol, characterized in that: Comprise; The preparation method of the N, Se co-doped CuO nanosheet catalyst is to dry copper nitrate to completely melt the copper nitrate, forming liquid copper nitrate; After soaking the catalyst substrate material in the liquid copper nitrate and keeping warm, the catalyst substrate material is sequentially ultrasonically treated in water and anhydrous ethanol to obtain the in-situ grown basic copper nitrate on the catalyst substrate material, and the basic copper nitrate is vacuum dried; The selenium powder is placed in a porcelain boat and placed upstream of a tube furnace; the vacuum-dried basic copper nitrate is placed in another porcelain boat and placed downstream of the tube furnace for calcination; and the prepared N, Se co-doped CuO nanosheet is obtained after natural cooling to room temperature. The selenium powder is placed in a porcelain boat and placed upstream of a tube furnace; the vacuum-dried basic copper nitrate is placed in another porcelain boat and placed downstream of the tube furnace for calcination; and the prepared N, Se co-doped CuO nanosheet is obtained after natural cooling to room temperature.

2. Use according to claim 1, characterized in that: The copper nitrate is dried to completely melt the copper nitrate, wherein the drying temperature is 120-160°C, and the time is 0.2-4h.

3. Use according to claim 1, characterized in that: The catalyst substrate material is one or more of carbon paper, foamed nickel, foamed copper, and stainless steel mesh.

4. Use according to claim 3, wherein: After soaking the catalyst substrate material in the liquid copper nitrate and keeping warm, the catalyst substrate material is sequentially ultrasonically treated in water and anhydrous ethanol to obtain the in-situ grown basic copper nitrate on the catalyst substrate material, and the basic copper nitrate is vacuum dried.

5. The use according to claim 1, characterized in that: The catalyst substrate material is one or more of carbon paper, foamed nickel, foamed copper, and stainless steel mesh.

6. The use according to claim 1, characterized in that: After soaking the catalyst substrate material in the liquid copper nitrate and keeping warm, the catalyst substrate material is sequentially ultrasonically treated in water and anhydrous ethanol to obtain the in-situ grown basic copper nitrate on the catalyst substrate material, and the basic copper nitrate is vacuum dried. The catalyst converts nitrophenol pollutants into amino high-value chemicals through catalytic hydrogenation, wherein the reaction medium is an aqueous solution containing 4-nitrophenol and sodium borohydride; the concentration of 4-nitrophenol is 5mM or more, the concentration of sodium borohydride is 0.05M or more, and the amino high-value chemical is p-aminophenol.

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