Preparation method and application of ptni modified zn o catalyst

Abstract

The application relates to a preparation method and application of a PtNi modified ZnO catalyst. Zn(NO3)2.6H2O, Ni(NO3)2.6H2O and CO(NH2)2 are stirred into a mixed solution in deionized water, are transferred into an autoclave, are washed and dried after hydrothermal reaction, and a precursor is obtained; the precursor is calcined in air to obtain NiO-ZnO; H2PtCl6 solution is added to the surface of the NiO-ZnO, is immersed at room temperature, NaBH4 solution is added, is stirred at room temperature, is washed and dried to obtain Pt / NiO-ZnO, and the Pt / NiO-ZnO is calcined in a reducing atmosphere to obtain the PtNi modified ZnO catalyst PtNi / ZnO x . The catalyst is applied to a benzylamine N-formylation reaction participated by carbon dioxide, the conversion rate of the benzylamine substrate can reach 85.0%, and the selectivity of the amide product can reach 99.4%. The preparation process is simple in operation and has good potential for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of photocatalytic organic synthesis, in particular to a preparation method and application of a PtNi modified ZnO catalyst. BACKGROUND

[0002] Excessive carbon dioxide emitted by rapid consumption of a large amount of fossil fuels poses a great threat to the environment, causing a series of serious problems including greenhouse effect and global climate change. It is widely believed that using carbon dioxide as a raw material to produce high-value-added chemicals is an effective solution to reduce carbon dioxide emissions and achieve sustainable development. Among numerous efficient carbon dioxide conversion pathways, the amine N-formylation reaction involving carbon dioxide is closely watched because amide products are widely used in the fields of drug synthesis and industrial solvents. However, due to the structural stability of carbon dioxide itself, its activation and reduction process is very difficult. At present, the amine N-formylation reaction involving carbon dioxide mostly adopts thermal catalytic means to achieve, which usually requires harsh reaction conditions. Compared with traditional thermal catalytic means requiring harsh reaction conditions, the photocatalytic amine N-formylation reaction involving carbon dioxide provides a more energy-saving and environmentally friendly method for converting carbon dioxide into amide products with high added value.

[0003] ZnO has attracted much attention in the field of photocatalytic carbon dioxide conversion due to its suitable energy band structure and moderate carbon dioxide adsorption capacity. However, the narrow light absorption range of single ZnO, fast recombination of photo-generated carriers and slow surface reaction rate limit its further application. Therefore, how to broaden the light absorption range of ZnO, improve the separation efficiency of photo-generated carriers of ZnO and accelerate the surface reaction rate of ZnO is a technical problem to be solved in the field. In order to overcome these problems, the commonly used technical means at present mainly include element doping, heterostructure building, dye sensitization and support of cocatalyst. Among them, the support of cocatalyst has been proved to be an effective method which can broaden the light absorption range of the catalyst, improve the separation efficiency of photo-generated carriers and accelerate the surface reaction rate. As a non-noble metal with abundant reserves, Ni is often used as a cocatalyst to improve the separation efficiency of photo-generated carriers of various photocatalysts due to its good electrical conductivity. At the same time, Ni nanoparticles also have the ability to induce plasmonic resonance effect, which can greatly improve the light response ability of the catalyst. By supporting Pt and other noble metal cocatalysts on the surface of the photocatalyst, a large number of electron traps and active sites can be provided for the photocatalytic reaction, and the surface reaction rate of the catalyst can be accelerated. SUMMARY

[0004] In order to overcome the technical problems of narrow light absorption range of single ZnO, fast recombination of photo-generated carriers and slow surface reaction, the application provides a PtNi modified ZnO catalyst and a preparation method thereof, and the catalyst is applied to a photocatalytic benzylamine N-formylation reaction with carbon dioxide. Through the modification of Pt and Ni on ZnO, the light absorption range of ZnO is widened, the separation and transfer efficiency of photo-generated carriers of ZnO is improved, and the surface reaction rate of ZnO is accelerated, so that the photocatalytic benzylamine N-formylation reaction with carbon dioxide is realized under room temperature, normal pressure and visible light irradiation.

[0005] One of the purposes of the application is to provide a preparation method of a PtNi modified ZnO catalyst, and the specific steps are as follows:

[0006] (1) Zn(NO3)2·6H2O, Ni(NO3)2·6H2O and CO(NH2)2 are stirred in deionized water at room temperature until completely dissolved to obtain a mixed solution, the mixed solution is transferred to an autoclave, and after hydrothermal reaction, washing and drying, a precursor is obtained;

[0007] (2) the precursor obtained in step 1) is calcined in air to obtain NiO-ZnO;

[0008] (3) H2PtCl6 solution is added to the surface of NiO-ZnO, and is immersed at room temperature for 0.5-1h, NaBH4 solution is added, and is stirred at room temperature for 2-4h, and is washed and dried to obtain Pt / NiO-ZnO;

[0009] (4) Pt / NiO-ZnO is calcined in a reducing atmosphere to obtain a PtNi modified ZnO catalyst PtNi / ZnO x .

[0010] In the step (1), the concentration of Zn(NO3)2·6H2O is 0.2-0.3mol / L, the molar ratio of Zn(NO3)2·6H2O to Ni(NO3)2·6H2O is 2-4:1, and the molar ratio of CO(NH2)2 to total metal nitrate is 4-6:1.

[0011] In the step (1), the hydrothermal reaction temperature is 140-200℃, and the hydrothermal reaction time is 1-3h.

[0012] In the step (2), the calcination temperature is 300-500℃, and the calcination time is 1-3h.

[0013] In the step (3), the H2PtCl6 solution is an ethanol solution of H2PtCl6, the concentration is 8-10 mg / mL, and the Pt in the solution is 0.5%-1.5% of the total mass of the NiO-ZnO; the NaBH4 solution is an aqueous solution of NaBH4, the concentration is 0.07-0.08 mol / L, and the volume ratio of the NaBH4 solution to the H2PtCl6 solution is 40-50:1.

[0014] In the step (4), the reducing atmosphere is a mixture of hydrogen and nitrogen, and the volume ratio of the hydrogen to the nitrogen is 0.5-2:1.

[0015] In the step (4), the calcination temperature is 300-500 DEG C, and the calcination time is 3-5 h.

[0016] The PtNi modified ZnO catalyst prepared by the preparation method of the PtNi modified ZnO catalyst has the Ni content of 15%-25% of the total mass of the catalyst and the Pt content of 0.5%-1.5% of the total mass of the catalyst.

[0017] The catalyst PtNi / ZnO prepared according to the method x , the reactant benzylamine and the solvent N,N-dimethylformamide are added into a high-pressure autoclave reactor with a light window, carbon dioxide is filled into the reactor, and the pressure is maintained at 0.1 MPa. The reaction is carried out at room temperature by irradiation with a 300 W xenon lamp with a 420 nm filter (the light intensity is 350 mW / cm 2 ).

[0018] The addition amounts of the catalyst, the reactant and the solvent in the reaction process are all conventional values in the art. The addition amount of the catalyst PtNi / ZnO x is 10-50 mg, the addition amount of the reactant benzylamine is 1-2 mmol, and the addition amount of the solvent N,N-dimethylformamide is 5-10 mL. When the reaction is carried out under the same conditions, the yield of the amide product on the PtNi / ZnO x is 6 times that of the single ZnO; after 24 h of reaction, the conversion rate of the benzylamine substrate on the PtNi / ZnO x is up to 85.0%, and the selectivity of the amide product is up to 99.4%. Meanwhile, the PtNi / ZnO x catalyst also has good cycle stability.

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

[0020] (1) This invention further optimizes the band structure of ZnO by introducing appropriate proportions of Pt and Ni metals to modify ZnO, enhancing its photoresponse capability and improving the separation and transport efficiency of photogenerated carriers. Simultaneously, it accelerates the surface reaction rate of ZnO, overcoming the limitations imposed on its application in the photocatalytic N-formylation of benzylamine involving carbon dioxide, such as narrow light absorption range, rapid recombination of photogenerated carriers, and slow surface reaction. Under the same reaction conditions, PtNi / ZnO... x The yield of amide products can reach 6 times that of single ZnO; after 24 hours of reaction, the yield of PtNi / ZnO... x The conversion rate of benzylamine substrates on PtNi / ZnO can reach 85.0%, and the selectivity of amide products can reach 99.4%. x The catalyst also exhibits good cycle stability.

[0021] (2) The PtNi / ZnO provided by this invention x The catalyst was prepared by impregnation of Pt with hydrogen reduction after the NiO-ZnO precursor was synthesized via a hydrothermal method. This preparation process is simple to operate, has a high yield, strong reproducibility, and good potential for large-scale industrial production.

[0022] (3) The present invention realizes the efficient photocatalytic carbon dioxide-involved N-formylation reaction of benzylamine under visible light irradiation at room temperature and normal pressure. Compared with traditional thermal catalysis, the reaction conditions are milder, which greatly reduces the reaction energy consumption and production cost. Attached Figure Description

[0023] Figure 1 ZnO sample and Pt1Ni prepared in Example 1 20 / ZnO x X-ray diffraction pattern (XRD) of the sample;

[0024] Figure 2 The Pt1Ni prepared in Example 1 20 / ZnO x Transmission electron microscope (TEM) image of the sample;

[0025] Figure 3 ZnO sample and Pt1Ni prepared in Example 1 20 / ZnO x The UV-Vis absorption spectrum (a) and steady-state fluorescence spectrum (b) of the sample;

[0026] Figure 4 ZnO sample and Pt1Ni prepared in Example 1 20 / ZnO xElectrochemical impedance spectroscopy (a) and transient photocurrent response curve (b) of the sample;

[0027] Figure 5 The Pt1Ni prepared in Example 1 20 / ZnO x Catalytic performance of the sample as reaction time increases (a), Pt1Ni prepared in Example 1. 20 / ZnO x Cyclic stability test results of the sample (b) and the Pt1Ni prepared in Example 1 before and after the cyclic test. 20 / ZnO x XRD comparison of the samples (c);

[0028] Figure 6 ZnO sample and PtNi / ZnO prepared in Examples 1-5 x Photocatalytic performance of the sample. Detailed Implementation

[0029] To facilitate understanding of the present invention, the invention will be further described below with reference to specific embodiments. The specific embodiments given are only intended to enable those skilled in the art to better understand the invention and do not constitute a limitation on the invention in any way.

[0030] The materials and reagents used in the following examples are all conventional raw materials in the art and can be obtained commercially unless otherwise specified. The experimental methods used in the following examples are all conventional methods in the art and can be performed according to the techniques and conditions or product instructions provided in the literature in the art unless otherwise specified.

[0031] Example 1

[0032] The synthesis of PtNi-modified ZnO catalysts is carried out through the following steps:

[0033] (1) Weigh 2.558 g of Zn(NO3)2·6H2O and 0.867 g of Ni(NO3)2·6H2O into a beaker, add 40 mL of deionized water, and stir at room temperature for 0.5 h. After the metal salt is completely dissolved, add 3.480 g of CO(NH2)2 and continue stirring at room temperature for 0.5 h. After the CO(NH2)2 is completely dissolved, transfer the mixed solution to a 100 mL autoclave and perform a hydrothermal reaction at 160 °C for 2 h. After the autoclave cools to room temperature, wash the obtained precipitate three times with deionized water and ethanol respectively, and then place it in an oven and dry it at 70 °C for 12 h to obtain the precursor.

[0034] (2) The dried precursor was placed in a muffle furnace and heated to 400°C at a rate of 5°C / min and held for 2 hours to obtain NiO-ZnO.

[0035] (3) 0.3 g of NiO-ZnO was weighed into a beaker, 0.645 mL of H2PtCl6 ethanol solution with a concentration of 10 mg / mL was added, and it was immersed at room temperature for 0.5 h. After the immersion was completed, 30 mL of NaBH4 aqueous solution with a concentration of 0.075 mol / L was slowly added dropwise into the beaker, and it was stirred at room temperature for 2 h. After the obtained precipitate was rinsed with deionized water and ethanol for 3 times respectively, it was placed into a vacuum drying oven and dried at 60°C for 12 h to obtain Pt1 / NiO-ZnO.

[0036] (4) 0.3 g of Pt1 / NiO-ZnO was placed into a tube furnace, and a mixed gas of hydrogen and nitrogen with a volume ratio of 1:1 was passed at a rate of 80 mL / min, and it was heated to 400°C at a rate of 5°C / min and then kept for 4 h. After the tube furnace was cooled to room temperature, nitrogen was continuously blown at a rate of 40 mL / min for 0.5 h to obtain Pt1Ni 20 / ZnO x .

[0037] Figure 1 The XRD patterns of the ZnO sample and the Pt1Ni 20 / ZnO x sample prepared in Example 1 are given. From the XRD pattern of the ZnO sample, it can be seen that it has a hexagonal structure (JCPDS No. 36-1451). In addition to the characteristic peaks of the ZnO phase, the XRD pattern of the Pt1Ni 20 / ZnO x sample prepared in Example 1 also shows peaks of the Ni (JCPDS No. 04-0850) phase, which proves the successful modification of Ni. No characteristic peaks of Pt are observed in the XRD pattern of the Pt1Ni 20 / ZnO x sample prepared in Example 1, which is usually due to its low loading and high dispersion.

[0038] Figure 2 The TEM images of the Pt1Ni 20 / ZnO x sample prepared in Example 1 are given. From Figure 2 (a), it can be seen that the sample as a whole presents a sheet shape. Meanwhile, from Figure 2 (b), lattice fringes with spacings of 0.235, 0.205 and 0.284 nm are also observed, which correspond to the Pt (111), Ni (111) and ZnO (100) crystal planes respectively, which further proves the successful modification of Pt and Ni. In addition, Figure 2 (c) gives the STEM image and EDX element distribution map, which shows that Pt and Ni are uniformly distributed in the Pt1Ni 20 / ZnO xThe sample is uniformly distributed.

[0039] Figure 3 (a) shows the UV-Vis absorption spectra of the ZnO sample and the Pt1Ni 20 / ZnO x The UV-Vis absorption spectra of the samples. As can be seen from the figure, the modification of Pt and Ni on ZnO obviously improves the light response ability of the sample, especially the visible light response is most obvious. Figure 3 (b) shows the UV-Vis absorption spectra of the ZnO sample and the Pt1Ni 20 / ZnO x The steady-state fluorescence spectra of the samples. In general, the weaker the intensity of the corresponding spectral peak of the sample in the steady-state fluorescence spectrum, the weaker the recombination of photo-generated electrons and photo-generated holes, which means that the sample has stronger photo-generated carrier separation ability. As can be seen from the figure, the modification of Pt and Ni on ZnO obviously reduces the fluorescence intensity of the sample, indicating that the modification of the two metals can greatly improve the overall photo-generated carrier separation efficiency of the sample.

[0040] Figure 4 (a) shows the UV-Vis absorption spectra of the ZnO sample and the Pt1Ni 20 / ZnO x The electrochemical impedance spectra of the samples. As can be seen from the figure, the modification of Pt and Ni on ZnO obviously reduces the surface resistance of the sample, and improves the transfer efficiency of the photo-generated carriers on the surface of the sample, which is consistent with the fluorescence results of Figure 3 (b). Figure 4 (b) shows the UV-Vis absorption spectra of the ZnO sample and the Pt1Ni 20 / ZnO x The transient photocurrent response curves of the samples. As can be seen from the figure, the modification of Pt and Ni on ZnO obviously improves the surface photocurrent intensity of the sample, which again proves that the modification of Pt and Ni on ZnO can improve the separation and transfer efficiency of the photo-generated carriers on the surface of the sample.

[0041] Example 2

[0042] The synthesis of the PtNi modified ZnO catalyst, the specific steps are as follows:

[0043] (1) Weigh 2.380 g Zn(N03)2-6H20 and 0.569 g Ni(N03)2-6H20 in a beaker, add 40 mL deionized water, and stir at room temperature for 0.5 h. After the metal salts are completely dissolved, add 3.588 g CO(NH2)2, and continue to stir at room temperature for 0.5 h. After the CO(NH2)2is completely dissolved, transfer the mixed solution into a 100 mL autoclave, and hydrothermally react at 140 °C for 3 h. After the autoclave is cooled to room temperature, rinse the obtained precipitate with deionized water and ethanol for 3 times, respectively, and then place it into an oven to dry at 70 °C for 12 h to obtain a precursor.

[0044] (2) Place the dried precursor into a muffle furnace, heat it to 300 °C at a rate of 5 °C / min, and keep it at this temperature for 3 h to obtain NiO-ZnO(Ni 15 ).

[0045] (3) Weigh 0.3 g NiO-ZnO(Ni 15 ) into a beaker, add 0.645 mL of H2PtCl6 ethanol solution with a concentration of 10 mg / mL, and immerse it at room temperature for 1 h. After the immersion is completed, slowly add 30 mL of NaBH4 aqueous solution with a concentration of 0.075 mol / L into the beaker, and stir at room temperature for 3 h. Rinse the obtained precipitate with deionized water and ethanol for 3 times, respectively, and then place it into a vacuum drying oven to dry at 60 °C for 12 h to obtain Pt1 / NiO-ZnO(Ni 15 ).

[0046] (4) Weigh 0.3 g Pt1 / NiO-ZnO(Ni 15 ) into a tube furnace, pass a mixed gas of hydrogen and nitrogen with a volume ratio of 0.5:1 at a rate of 90 mL / min, heat it to 300 °C at a rate of 5 °C / min, and keep it at this temperature for 5 h. After the tube furnace is cooled to room temperature, continue to pass nitrogen at a rate of 60 mL / min for 0.5 h to obtain Pt1Ni 15 / ZnO x .

[0047] Example 3

[0048] The synthesis of the PtNi modified ZnO catalyst is as follows:

[0049] (1) Weigh 3.570 g of Zn(N03)2-6H20 and 1.613 g of Ni(N03)2-6H20 in a beaker, add 40 mL of deionized water, and stir at room temperature for 0.5 h. After the metal salt is completely dissolved, add 4.216 g of CO(NH2)2, and continue to stir at room temperature for 0.5 h. After the CO(NH2)2is completely dissolved, transfer the mixed solution into a 100 mL autoclave, and hydrothermally react at 160 °C for 2 h. After the autoclave is cooled to room temperature, the obtained precipitate is rinsed with deionized water and ethanol for 3 times respectively, and then placed into an oven to be dried at 70 °C for 12 h to obtain a precursor.

[0050] (2) The dried precursor is placed into a muffle furnace, heated to 400 °C at a rate of 5 °C / min, and then kept at 400 °C for 2 h to obtain NiO-ZnO(Ni 25 ).

[0051] (3) Weigh 0.3 g of NiO-ZnO(Ni 25 ) in a beaker, add 0.645 mL of H2PtCl6 ethanol solution with a concentration of 10 mg / mL, and immerse at room temperature for 0.5 h. After the immersion is completed, slowly add 30 mL of NaBH4 aqueous solution with a concentration of 0.075 mol / L into the beaker, and stir at room temperature for 4 h. The obtained precipitate is rinsed with deionized water and ethanol for 3 times respectively, and then placed into a vacuum drying oven to be dried at 60 °C for 12 h to obtain Pt1 / NiO-ZnO(Ni 25 ).

[0052] (4) Weigh 0.3 g of Pt1 / NiO-ZnO(Ni 25 ) into a tube furnace, and pass a mixed gas of hydrogen and nitrogen with a volume ratio of 2:1 at a rate of 90 mL / min, heat to 400 °C at a rate of 5 °C / min, and then keep at 400 °C for 4 h. After the tube furnace is cooled to room temperature, continue to pass nitrogen at a rate of 30 mL / min for 0.5 h to obtain Pt1Ni 25 / ZnO x .

[0053] Example 4

[0054] The synthesis of the PtNi modified ZnO catalyst is as follows:

[0055] (1) Take 2.558 g Zn(N03)2-6H20 and 0.867 g Ni(N03)2-6H20 in a beaker, add 40 mL deionized water, and stir at room temperature for 0.5 h. After the metal salts are completely dissolved, add 3.480 g CO(NH2)2, and continue to stir at room temperature for 0.5 h. After the CO(NH2)2is completely dissolved, transfer the mixed solution into a 100 mL autoclave, and hydrothermally react at 180 °C for 2 h. After the autoclave is cooled to room temperature, the obtained precipitate is rinsed with deionized water and ethanol for 3 times respectively, and then placed into an oven to be dried at 70 °C for 12 h to obtain a precursor.

[0056] (2) Place the dried precursor into a muffle furnace, heat at a rate of 5 °C / min to 400 °C, and keep the temperature for 2 h to obtain NiO-ZnO.

[0057] (3) Take 0.3 g NiO-ZnO in a beaker, add 0.400 mL H2PtCl6 ethanol solution with a concentration of 8 mg / mL, and immerse at room temperature for 0.5 h. After the immersion is completed, slowly add 20 mL NaBH4 aqueous solution with a concentration of 0.07 mol / L into the beaker, and stir at room temperature for 3 h. The obtained precipitate is rinsed with deionized water and ethanol for 3 times respectively, and then placed into a vacuum drying oven to be dried at 60 °C for 12 h to obtain Pt 0.5 / NiO-ZnO.

[0058] (4) Take 0.3 g Pt 0.5 / NiO-ZnO into a tube furnace, pass in a mixed gas of hydrogen and nitrogen with a volume ratio of 1:1 at a rate of 80 mL / min, heat at a rate of 5 °C / min to 400 °C, and keep the temperature for 4 h. After the tube furnace is cooled to room temperature, pass in nitrogen at a rate of 40 mL / min to continue to purge for 0.5 h to obtain Pt 0.5 Ni 20 / ZnO x .

[0059] Example 5

[0060] Synthesis of PtNi modified ZnO catalyst, the specific steps are as follows:

[0061] (1) Weigh 2.558 g of Zn(NO3)2·6H2O and 0.867 g of Ni(NO3)2·6H2O into a beaker, add 40 mL of deionized water, and stir at room temperature for 0.5 h. After the metal salt is completely dissolved, add 3.480 g of CO(NH2)2 and continue stirring at room temperature for 0.5 h. After the CO(NH2)2 is completely dissolved, transfer the mixed solution to a 100 mL autoclave and perform a hydrothermal reaction at 200 °C for 1 h. After the autoclave cools to room temperature, wash the obtained precipitate three times with deionized water and ethanol respectively, and then place it in an oven and dry it at 70 °C for 12 h to obtain the precursor.

[0062] (2) The dried precursor was placed in a muffle furnace and heated to 500°C at a rate of 5°C / min and held for 1 hour to obtain NiO-ZnO.

[0063] (3) Weigh 0.3 g of NiO-ZnO into a beaker, add 1.065 mL of 9 mg / mL H2PtCl6 ethanol solution, and soak at room temperature for 1 h. After soaking, slowly add 40 mL of 0.08 mol / L NaBH4 aqueous solution to the beaker, and stir at room temperature for 4 h. Rinse the obtained precipitate three times with deionized water and ethanol respectively, and then place it in a vacuum drying oven and dry at 60 °C for 12 h to obtain Pt. 1.5 / NiO-ZnO.

[0064] (4) Weigh 0.3g Pt 1.5 NiO-ZnO was placed in a tube furnace, and a mixture of hydrogen and nitrogen (volume ratio 1:1) was introduced at a rate of 80 mL / min. The temperature was increased to 500 °C at a rate of 5 °C / min and held for 3 h. After the tube furnace cooled to room temperature, nitrogen was introduced at a rate of 40 mL / min for 0.5 h to obtain Pt. 1.5 Ni 20 / ZnO x .

[0065] Example 6

[0066] Photocatalytic reaction performance test of catalyst.

[0067] 50 mg of Pt1Ni prepared in Example 1 was used. 20 / ZnO x The sample, 2 mmol of benzylamine, and 10 mL of N,N-dimethylformamide were added to an 80 mL autoclave reactor equipped with a light window. The reactor was then purged with 0.2 MPa of carbon dioxide (this process was repeated 10 times to remove other gases before the reaction). Finally, the carbon dioxide pressure inside the reactor was maintained at 0.1 MPa, and the reactor was irradiated at room temperature with a 300 W xenon lamp equipped with a 420 nm filter (light intensity 350 mW / cm²). 2) were collected by centrifugation (8000 rpm, 5 min) and the supernatant was removed. The samples were washed with deionized water and ethanol for 3 times, respectively, and then were dried in a vacuum drying oven at 60 °C for 12 h. The products were diluted to constant volume and characterized by gas chromatography-mass spectrometry (GC-Agilent 6890A, MS-Agilent 5973C) and gas chromatography (Nexis GC-2030). 20 / ZnO x The samples were separated from the products, and the Pt1Ni 20 / ZnO x The samples were washed with deionized water and ethanol for 3 times, respectively, and then were dried in a vacuum drying oven at 60 °C for 12 h. The products were diluted to constant volume and characterized by gas chromatography-mass spectrometry (GC-Agilent 6890A, MS-Agilent 5973C) and gas chromatography (Nexis GC-2030).

[0068] Figure 5 (a) shows the catalytic performance of the Pt1Ni 20 / ZnO x samples with the extension of reaction time. As can be seen from the figure, when using the Pt1Ni 20 / ZnO x samples as catalysts, the conversion rate of the substrate benzylamine gradually increased with the increase of reaction time, while the selectivity of the amide product remained basically unchanged. After the reaction reached 24 h, the conversion rate of the substrate benzylamine could reach 85.0%, and the selectivity of the amide product could reach 99.4%. Figure 5 (b) shows the cyclic stability test of the Pt1Ni 20 / ZnO x samples. As can be seen from the figure, after multiple cyclic tests, its performance did not appear obvious decline, proving that the Pt1Ni 20 / ZnO x samples have good stability. Figure 5 (c) shows the XRD comparison of the Pt1Ni 20 / ZnO x samples before and after multiple cyclic tests. As can be seen from the figure, after multiple cyclic tests, the crystal structure of the sample did not change obviously, which further proved that the Pt1Ni 20 / ZnO x samples have good stability.

[0069] Example 7

[0070] Catalytic performance test of the catalyst in photocatalytic reaction.

[0071] 10 mg of the Pt1Ni / ZnO xThe sample, 1 mmol benzylamine and 5 mL N,N-dimethylformamide were added into a 80 mL autoclave reactor with a light window, the autoclave was filled with 0.2 MPa carbon dioxide and then vented (this process was repeated 10 times to remove other gases in the reactor before the reaction), finally the carbon dioxide pressure in the reactor was maintained at 0.1 MPa, and the reaction was carried out at room temperature by irradiation with a 300 W xenon lamp with a 420 nm filter (light intensity was 350 mW / cm 2 After the reaction was completed, the PtNi / ZnO x sample was separated from the product, and the product was characterized by gas chromatography-mass spectrometry (GC-Agilent 6890A, MS-Agilent 5973C) and gas chromatography (Nexis GC-2030) after being diluted to constant volume.

[0072] Figure 6 The photocatalytic performance of the ZnO sample and the PtNi / ZnO x samples prepared in Examples 1-5 is shown in the figure. As can be seen from the figure, the performance of the ZnO sample was poor after 6 h of visible light irradiation (λ>420 nm) at room temperature and normal pressure, and the conversion rate of the benzylamine substrate was only 7.5%, and the selectivity of the amide product was 95.8%. After the ZnO was modified with Pt and Ni, the catalytic activity of the sample was significantly improved, and when the Pt1Ni 20 / ZnO x sample was used as the catalyst, the conversion rate of the benzylamine substrate reached 46.4%, and the selectivity of the amide product reached 99.2%.

[0073] The above several specific embodiments are only to enable those skilled in the art to better understand and implement the present application, but do not constitute any form of limitation on the present application. Those skilled in the art can make other different forms of changes or variations on the basis of the above description, and the changes or variations thus extended do not deviate from the principles or claims of the present application and are still within the protection scope of the present application.

Claims

1. A method for preparing a PtNi-modified ZnO catalyst, characterized by, The method comprises the following steps: (1) stirring Zn(NO3)2·6H2O, Ni(NO3)2·6H2O and CO(NH2)2 in deionized water at room temperature until completely dissolved to obtain a mixed solution, transferring the mixed solution into an autoclave, and washing and drying after hydrothermal reaction to obtain a precursor; (2) calcining the precursor obtained in step 1) in air to obtain NiO-ZnO; (3) adding H2PtCl6 solution to the surface of NiO-ZnO, immersing at room temperature for 0.5-1 h, adding NaBH4 solution, stirring at room temperature for 2-4 h, and washing and drying to obtain Pt / NiO-ZnO; (4) The Pt / NiO-ZnO is placed in a reducing atmosphere for calcination to obtain a PtNi modified ZnO catalyst PtNi / ZnO x .

2. The method of preparing the PtNi-modified ZnO catalyst according to claim 1, characterized in that, In step (1), the concentration of Zn(NO3)2·6H2O is 0.2-0.3 mol / L, the molar ratio of Zn(NO3)2·6H2O to Ni(NO3)2·6H2O is 2-4:1, and the molar ratio of CO(NH2)2 to total metal nitrate is 4-6:

1.

3. The method of claim 1, wherein the PtNi-modified ZnO catalyst is prepared by the steps of: In step (1), the hydrothermal reaction temperature is 140-200℃, and the hydrothermal reaction time is 1-3 h.

4. The method of claim 1, wherein the PtNi-modified ZnO catalyst is prepared by the steps of: In step (2), the calcination temperature is 300-500℃, and the calcination time is 1-3 h.

5. The method of claim 1, wherein the PtNi-modified ZnO catalyst is prepared by the steps of: In step (3), the H2PtCl6 solution is an ethanol solution of H2PtCl6 with a concentration of 8-10 mg / mL, and the Pt content in the solution is 0.5%-1.5% of the total mass of NiO-ZnO; the NaBH4 solution is an aqueous solution of NaBH4 with a concentration of 0.07-0.08 mol / L, and the volume ratio of the NaBH4 solution to the H2PtCl6 solution is 40-50:

1.

6. The method of claim 1, wherein the PtNi-modified ZnO catalyst is prepared by the steps of: In step (4), the reducing atmosphere is a mixture of hydrogen and nitrogen, wherein the volume ratio of hydrogen to nitrogen is 0.5-2:

1.

7. The method of claim 1, wherein the PtNi-modified ZnO catalyst is prepared by the steps of: In step (4), the calcination temperature is 300-500℃, and the calcination time is 3-5 h.

8. A process for the preparation of the PtNi-modified ZnO catalyst of claim 1, the catalyst prepared thereby, characterized in that, The Ni content in the PtNi modified ZnO catalyst is 15%-25% of the total mass of the catalyst, and the Pt content is 0.5%-1.5% of the total mass of the catalyst.

9. The PtNi modified ZnO catalyst of claim 8 is used in a photocatalytic carbon dioxide participating benzylamine N-formylation reaction.

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