Development of uranium-depleted U3O8 catalyst and application of uranium-depleted U3O8 catalyst in synthesis of azobenzene fine chemicals

Abstract

With the sustainable development of nuclear energy technology, how to efficiently utilize and recycle depleted uranium (mainly 238U) has become a key technical problem of environmental protection and sustainable development. In order to solve the problem, the U3O8 catalyst is prepared by taking uranyl nitrate hexahydrate as a raw material and adopting a simple process of combining dissolution, precipitation and roasting, and is successfully applied to a reaction system for synthesizing azobenzene compounds through catalytic oxidation of aniline and derivatives thereof. According to the method, green conversion and high-value utilization of the depleted uranium waste are achieved, new functional attributes are given to the depleted uranium waste, an efficient catalytic path for conversion from aniline to high-value-added fine chemicals is constructed, and good environmental benefits and economic potential are shown.

Description

Technical Field

[0001] The present invention relates to a novel technology for utilizing depleted uranium, in particular to using uranyl nitrate hexahydrate as a raw material to prepare U3O8 for selective catalytic oxidation of aniline or its derivatives to prepare azobenzene (diphenyldiazene) or its derivatives. Technical Background

[0002] Uranium (U), as an important member of the actinide series, is a representative natural radioactive nuclide in nature. Its natural isotope abundance distribution shows a significant non-equilibrium characteristic. 238 U (abundance 99.28±0.01%), 235 U (abundance 0.711±0.001%) and 234 U (abundance 0.0054±0.0002%) is composed of three radioactive isotopes. Its isotopic composition provides key fundamental parameters for nuclear fuel cycle and geochronological studies (see Chemical Science, 2013, Vol. 4, No. 5, pp. 2209-2213). With the continuous expansion and deepening of nuclear energy applications, the proper and safe disposal of the large amounts of depleted uranium waste generated during nuclear reactions and the exploration of its resource utilization have become major challenges in environmental protection and pollution control.

[0003] In the earth's crust, uranium exists mainly in the form of chemical bonds with oxygen, thereby forming uranium oxide (usually UO xIt is worth noting that in addition to conventional stoichiometric compounds, non-stoichiometric compounds and metastable uranium oxides are also widely present. The formation of these special phases has greatly enriched the phase system of uranium oxides (see "Catalysis Today", 2010, Vol. 157, No. 3, 217-222.). A large number of studies have shown that uranium oxides not only have excellent thermal stability, but also exhibit excellent anti-toxic properties. In 1922, James first used uranium oxide for petroleum reforming (see "Chemical and Metallurgical Engineering", 1992, Vol. 26, 209-212.). Its unique crystal structure and rich coordination environment enable it to interact efficiently and precisely with other molecules. Carley et al.'s research on the catalytic reduction of NO using supported uranium oxide demonstrated superior activity and selectivity compared to conventional platinum catalysts: at 400°C, the catalyst achieved 100% NO conversion and 100% N2 selectivity (see Journal of Alloys and Compounds, 2008, Vol. 448, No. 1, pp. 5294-5301). These properties demonstrate unique advantages in uranium oxide for a range of chemical reactions that are difficult to effectively drive using conventional catalytic materials, opening up new research directions and application prospects for the development of catalytic science and technology (see Nature, 2008, Vol. 455, No. 7211, pp. 341-349).

[0004] Azobenzene (diphenyldiazene) and its derivatives are important, high-value-added fine chemicals with a crucial position and economic value in the chemical industry. Traditional industrial synthesis methods (such as the nitro-compound reduction method and the diazo-compound method) are plagued by complex processes, low efficiency, and severe pollution. In recent years, green synthesis processes have garnered widespread attention, with synthetic routes using aniline as the raw material and oxygen as the oxidant gaining popularity due to their simplicity, efficiency, and low cost. In 2008, the Corma research group in Spain developed an Au / TiO2 catalyst, achieving the first oxygen-oxidation synthesis of azobenzene (diphenyldiazene) from aniline (Science, 2008, Vol. 322, pp. 1661-1664). In 2013, the Li Yadong group proposed an Ag / C catalyst system, further advancing this field (Acs Catalysis, 2013, Vol. 3, No. 4, pp. 478-486). However, existing catalytic systems still have problems such as the use of precious metals, low yield, the need for additives, harsh reaction conditions (such as high pressure and high temperature), and poor catalyst reproducibility, which lead to high costs and great safety hazards, limiting their widespread application.

[0005] Uranium oxides exhibit unique catalytic oxidation properties due to the rich oxidation states and thermodynamic properties of the uranium-oxygen system. In response to the demand for resource utilization of depleted uranium in the nuclear industry, this paper proposes to use depleted uranium waste as raw material to construct a valence-controlled uranium-based catalyst to achieve highly selective catalytic oxidation conversion of aniline compounds. By regulating the redox cycle of uranium species, this system is expected to break through the technical bottleneck of the synthesis of azobenzene (diphenyldiazene) and its derivatives. This type of catalytic strategy based on radioactive metal valence state engineering has not been reported in the field of nitrogen-containing heterocyclic compound synthesis. Its successful implementation will provide a dual technical solution for the high-value utilization of depleted uranium waste and the green synthesis of fine chemicals.

[0006] In summary, the traditional nitrobenzene reduction process has inherent defects such as the generation of harmful by-products, and the existing aniline oxidation system has seriously restricted the industrialization process due to factors such as the high cost of precious metal catalysts, poor catalytic selectivity and complex preparation process. In view of this, this study innovatively proposed a new synthesis route using U3O8 as a catalyst, and its preparation process can be completed by a simple precipitation method, which significantly simplifies the process flow. It is particularly noteworthy that the technical solution for the direct catalytic oxidation of aniline to synthesize azobenzene (diphenyldiazene) and its functionalized derivatives based on U3O8 has not been reported in the literature. This breakthrough not only provides a breakthrough for the nuclear industry 238 This research provides an innovative solution for the disposal of U isotope waste and demonstrates significant potential for industrial application in the synthesis of fine chemicals. This research has successfully established a synergistic technology system for "nuclear waste resource utilization and high-value chemical synthesis," combining environmental and economic benefits, and opening up a new path to addressing the challenges of radioactive waste disposal. Summary of the Invention

[0007] The present invention discovers that a U3O8 catalyst prepared using uranyl nitrate hexahydrate as a raw material can catalyze the oxidation of aniline or its derivatives to form azobenzene (diphenyldiazene) or its derivatives. Therefore, the present invention not only provides a new method for utilizing depleted uranium, but also proposes a low-cost, green and efficient method for preparing azobenzene (diphenyldiazene) or its derivatives. The method is simple, low-cost, highly safe, and more in line with the concept of green and friendly chemistry. Specifically, it includes the following contents:

[0008] In a first aspect, the present invention provides a method for preparing a U3O8 catalyst by using uranyl nitrate hexahydrate as a raw material through simple dissolution, precipitation and calcination.

[0009] Preferably, the catalyst preparation method comprises the following steps:

[0010] (1) Preparation of U3O8: Weigh a specific mass of uranyl nitrate hexahydrate, place it in a container, heat and stir, add an appropriate amount of deionized water to completely dissolve the uranyl nitrate to form a transparent uranyl salt solution, then add an appropriate amount of oxidant, continue stirring for several hours, separate the solid product, wash and dry it to obtain UO4·2H2O, and calcine it in air atmosphere for several hours. Its XRD crystal structure is shown in the attached figure. Figure 1 The transmission electron microscope image is shown in the attached Figure 2 The scanning electron microscope image is shown in the attached Figure 3 The pore size distribution curve is shown in the attached figure. Figure 4 shown.

[0011] Preferably, the structural formula of the aniline or its derivative is shown in the following formula (I), and the structural formula of the azobenzene (diphenyldiazene) or its derivative is shown in the following formula (II)

[0012]

[0013] Wherein, R1-R5 are independently selected from any one of hydrogen, halogen, hydroxyl, sulfonic acid, nitro, substituted or unsubstituted straight-chain or branched alkyl, alkoxy, carbonyl, alkenyl, alkynyl, substituted or unsubstituted aryl, amido, and cyano, but are not limited to the above substituents.

[0014] Preferably, R1-R5 are independently selected from hydrogen, methyl, chlorine, bromine, and methoxy.

[0015] Preferably, the aniline or its derivatives include: aniline, o-methylaniline, m-methylaniline, p-methylaniline, p-chloroaniline, p-bromoaniline, and p-methoxyaniline.

[0016] Preferably, the catalyst is U3O8.

[0017] Preferably, the ratio of the catalyst to aniline or its derivatives is 1-60 mg:1 mol.

[0018] Preferably, the ratio of the catalyst to aniline or its derivatives is 10-50 mg:1 mol.

[0019] Preferably, the ratio of the catalyst to aniline or its derivatives is 20-40 mg:1 mol.

[0020] Preferably, the ratio of the catalyst to aniline or its derivatives is 30 mg:1 mol.

[0021] Preferably, the oxidizing agent is tert-butyl hydroperoxide.

[0022] Preferably, the molar ratio of tert-butyl hydroperoxide to aniline or its derivatives is 1-14:1.

[0023] Preferably, the molar ratio of tert-butyl hydroperoxide to aniline or its derivatives is 2-8:1.

[0024] Preferably, the molar ratio of tert-butyl hydroperoxide to aniline or its derivatives is 7:1.

[0025] Preferably, the organic solvent is acetic acid.

[0026] Preferably, the mass ratio of the reaction solvent to aniline or its derivatives is 1-67:1.

[0027] Preferably, the mass ratio of the reaction solvent to aniline or its derivatives is 10-50:1.

[0028] Preferably, the mass ratio of the reaction solvent to aniline or its derivatives is 33:1.

[0029] Preferably, the method comprises: adding aniline or its derivatives, U3O8, and tert-butyl hydroperoxide to a reaction solvent, reacting at 30-120°C for 1-24 hours; filtering, distilling, and recrystallizing to obtain azobenzene (diphenyldiazene) or its derivatives. Preferably, the reaction temperature is 30-120°C.

[0030] Preferably, the reaction temperature is 40-110°C.

[0031] Preferably, the reaction temperature is 60-100°C.

[0032] Preferably, the reaction temperature is 80°C.

[0033] Preferably, the reaction time is 1-24 hours.

[0034] Preferably, the reaction time is 2-20 hours.

[0035] Preferably, the reaction time is 5-15 hours.

[0036] Preferably, the reaction time is 12 hours.

[0037] Compared with the prior art, the method of preparing azobenzene (diphenyldiazene) or its derivatives by catalytic oxidation of aniline or its derivatives of the present invention has the following advantages:

[0038] (1) The present invention uses depleted uranium waste as raw material to prepare the catalyst, effectively solving the problem of safe disposal and reuse of depleted uranium in my country's nuclear energy utilization;

[0039] (2) Aniline or its derivatives used in the present invention are basic raw materials commonly used in industry and are cheap and readily available.

[0040] (3) The present invention uses cheap and readily available tert-butyl hydroperoxide as an oxidant, and the reaction temperature is moderate. Compared with the traditional method using oxidants such as peracetic acid, Pb(OAc)4, Hg(OAc)2, BaMnO4, etc., the cost of the oxidant is greatly reduced, and the problem of toxic substance emissions generated by the use of oxidants is solved.

[0041] (4) The method of the present invention can catalytically oxidize aniline or its derivatives to the corresponding azobenzene (diphenyldiazene) or its derivatives with good specificity and a high yield of the target product.

[0042] The present invention will be further described in detail with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. The raw materials used in the following embodiments are all commercially available unless otherwise specified. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 X-ray diffraction crystal structure of the prepared catalyst U3O8;

[0044] Figure 2 Transmission electron microscopy image of the prepared catalyst U3O8;

[0045] Figure 3 Scanning electron microscopy image of the prepared catalyst U3O8;

[0046] Figure 4 Pore size distribution curve of the prepared U3O8 catalyst;

[0047] Figure 5 Mass spectrum of diphenyldiazene, the product synthesized by the method described in Example 1;

[0048] Figure 6 Mass spectrum of diphenyldiazene, the product synthesized by the method described in Example 2;

[0049] Figure 7 Mass spectrum of diphenyldiazene, the product synthesized by the method described in Example 3;

[0050] Figure 8 Mass spectrum of diphenyldiazene, the product synthesized by the method described in Example 4;

[0051] Figure 9 Mass spectrum of diphenyldiazene, the product synthesized by the method described in Example 5;

[0052] Figure 10 Mass spectrum of diphenyldiazene, the product synthesized by the method described in Example 6;

[0053] Figure 11 Mass spectrum of the product 2,2'-dimethyl-diphenyldiazene synthesized by the method described in Example 7;

[0054] Figure 12 Mass spectrum of the product 3,3'-dimethyldiphenyldiazene synthesized by the method described in Example 7;

[0055] Figure 13 Mass spectrum of the product 4,4'-dimethyl-diphenyldiazene synthesized by the method described in Example 7;

[0056] Figure 14 Mass spectrum of the product 4,4'-dichloro-diphenyldiazene synthesized by the method described in Example 7;

[0057] Figure 15 Mass spectrum of the product 4,4'-dibromo-diphenyldiazene synthesized by the method described in Example 7;

[0058] Figure 16 Mass spectrum of the product 4,4'-dimethoxy-diphenyldiazene synthesized by the method described in Example 7; DETAILED DESCRIPTION

[0059] The present invention will be further described in detail below with reference to specific examples, but the scope of protection of the present invention is not limited thereto. The raw materials used in the following examples are all commercially available unless otherwise specified.

[0060] Example 1 Synthesis of diphenyldiazene using different reaction solvents

[0061] 1. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.66 g of formic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0062] 2. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise while stirring at 80°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0063] 3. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 2.98 g of propionic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0064] 4. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline, 3.66 g of formic acid and acetic acid solvent (mass ratio 1:1), and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise while stirring at 80°C. React for 12 hours, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0065] 5. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline, 3.66 g of formic acid and propionic acid solvent (mass ratio 1:1), and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise while stirring at 80°C. React for 12 hours, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0066] 6. Add 30.0 mg of U₃O₃ catalyst to a 25 mL reaction tube, followed by 0.093 g of aniline, 3.15 g of acetic acid, and propionic acid (1:1 mass ratio). Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% aqueous tert-butyl hydroperoxide solution) dropwise at 80°C while stirring. The mixture was allowed to react for 12 hours. The mixture was then filtered, distilled, and recrystallized to yield the product, diphenyldiazene.

[0067] The product yield of diphenyldiazene obtained by the preparation method described in 1-6 above was calculated, and the results are shown in Table 1 below:

[0068] Table 1 Process parameters of the preparation method described in Example 1 and the yield of the product diphenyldiazene

[0069]

[0070] The mass spectrum of the product synthesized by the above reaction is as follows Figure 5 As shown (the mass spectra of the main products of the six reactions described above are identical, so only one mass spectrum is provided), the structural formula of the product is shown in Formula 1 below. The above results demonstrate that aniline can be catalyzed to synthesize diphenyldiazene using an organic solvent (formic acid, acetic acid, propionic acid, or a combination thereof) as the reaction solvent, tert-butyl hydroperoxide as the oxidant, and U3O8 as the catalyst. Furthermore, using acetic acid as the reaction solvent, the yield of diphenyldiazene can reach up to 91%.

[0071]

[0072] Example 2 Synthesis of diphenyldiazene with different reaction solvent amounts

[0073] 1. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 1.05 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0074] 2. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 2.1 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise while stirring at 80°C. React for 12 hours, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0075] 3. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0076] 4. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 4.2 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 80°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0077] 5. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 5.25 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 80°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0078] 6. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 6.3 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0079] The product yield of diphenyldiazene obtained by the preparation method described in 1-6 above was calculated, and the results are shown in Table 2 below:

[0080] Table 2 Process parameters of the preparation method described in Example 2 and the yield of the product diphenyldiazene

[0081]

[0082] The mass spectrum of the main product obtained from the above reaction is as follows Figure 6 As shown (the mass spectra of the main products of the six reactions described above are identical, so only one mass spectrum is provided), the structural formula of the product is shown in Formula 1 below. The above results demonstrate that the synthesis of diphenyldiazene from aniline can be catalytically performed using acetic acid as the reaction solvent (with a mass ratio of acetic acid to aniline of 1-68:1), tert-butyl hydroperoxide as the oxidant, and U₃O₄ as the catalyst. Furthermore, when the mass ratio of mesitylene to aniline is 22-45:1, the yield of diphenyldiazene obtained in the reaction is consistently above 90%.

[0083]

[0084] Example 3 Synthesis of diphenyldiazene at different reaction temperatures

[0085] 1. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% aqueous tert-butyl hydroperoxide solution) dropwise while stirring at 30°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0086] 2. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise while stirring at 40°C. React for 12 hours, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0087] 3. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 50°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0088] 4. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 60°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0089] 5. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise while stirring at 70°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0090] 6. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0091] 7. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 90°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0092] 8. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 100°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0093] 9. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 110°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazepine.

[0094] 10. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by weight aqueous solution of tert-butyl hydroperoxide) dropwise at 120°C with stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazepine.

[0095] The product yield of diphenyldiazene obtained by the preparation method described in 1-10 above was calculated, and the results are shown in Table 3 below:

[0096] Table 3 Process parameters of the preparation method described in Example 3 and the yield of the product diphenyldiazene

[0097]

[0098] The mass spectrum of the main product obtained from the above reaction is as follows Figure 7 As shown (the mass spectra of the above 10 main products are the same, so only one mass spectrum is provided), the structural formula of the product is shown in Formula 1. The above results show that aniline can be catalyzed to synthesize diphenyldiazene using acetic acid as the reaction solvent, tert-butyl hydroperoxide as the oxidant, and U3O8 as the catalyst at a reaction temperature of 30-120°C; at the same time, when the reaction temperature is 50-90°C, the yield of diphenyldiazene obtained in the reaction is greater than 80%; and when the reaction temperature is 70-80°C, the yield of diphenyldiazene obtained in the reaction is as high as greater than 90%.

[0099]

[0100]

[0101] Example 4 Synthesis of diphenyldiazene with different reaction times

[0102] 1. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise at 80°C while stirring. React for 1 hour, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0103] 2. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 80°C. React for 2 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0104] 3. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 80°C. React for 4 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0105] 4. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 6 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0106] 5. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 8 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0107] 6. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 10 hours, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0108] 7. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 80°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0109] 8. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 14 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0110] 9. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 16 hours, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0111] 10. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by weight aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 18 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0112] 11. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by weight aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 20 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0113] 12. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by weight aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 22 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0114] 13. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by weight aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 24 hours, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0115] The product yield of diphenyldiazene obtained by the preparation method described in 1-13 above was calculated, and the results are shown in Table 4 below:

[0116] Table 4 Process parameters of the preparation method described in Example 4 and the yield of the product diphenyldiazene

[0117]

[0118] The mass spectrum of the main product obtained from the above reaction is as follows Figure 8 As shown (the mass spectra of the main products of the above 13 reactions are the same, so only one mass spectrum is provided), the structural formula of the product is shown in Formula 1 below. The above results indicate that aniline can be catalyzed to synthesize diphenyldiazene using acetic acid as the reaction solvent, tert-butyl hydroperoxide as the oxidant, and U3O8 as the catalyst, with a reaction time of 1-16 h. Furthermore, the yield of diphenyldiazene obtained in the reaction is greater than 80% when the reaction time is 10-24 h, and the yield of diphenyldiazene obtained in the reaction is greater than 93% when the reaction time is 12-24 h.

[0119]

[0120] Example 5 Synthesis of diphenyldiazene with different amounts of tert-butyl hydroperoxide

[0121] 1. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid. Add 1 mmol of tert-butyl hydroperoxide (i.e., 0.137 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0122] 2. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 2 mmol of tert-butyl hydroperoxide (i.e., 0.274 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 80°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0123] 3. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 3 mmol of tert-butyl hydroperoxide (i.e., 0.411 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 80°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0124] 4. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 4 mmol of tert-butyl hydroperoxide (i.e., 0.584 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0125] 5. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0126] 6. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 6 mmol of tert-butyl hydroperoxide (i.e., 0.822 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 80°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0127] 7. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 7 mmol of tert-butyl hydroperoxide (i.e., 0.959 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0128] 8. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 8 mmol of tert-butyl hydroperoxide (i.e., 1.096 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0129] 9. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 9 mmol of tert-butyl hydroperoxide (i.e., 1.233 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0130] 10. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid. Add 10.0 mmol of tert-butyl hydroperoxide (i.e., 1.370 mL of a 70% by weight aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0131] The product yield of diphenyldiazene obtained by the preparation method described in 1-10 above was calculated, and the results are shown in Table 5 below:

[0132] Table 5 Process parameters of the preparation method described in Example 5 and the yield of the product diphenyldiazene

[0133]

[0134] The mass spectrum of the main product obtained from the above reaction is as follows Figure 9 As shown (the mass spectra of the main products of the above 10 reactions are the same, so only one mass spectrum is provided), the structural formula of the product is shown in Formula 1 below. The above results indicate that diphenyldiazene can be synthesized from aniline when the molar ratio of the oxidant tert-butyl hydroperoxide to aniline is 1-14:1, acetic acid is used as the reaction solvent, and U3O8 is used as the catalyst. Furthermore, when the molar ratio of the oxidant tert-butyl hydroperoxide to aniline is 1-6:1, the product yield is greater than 80%. Furthermore, when the molar ratio of the oxidant tert-butyl hydroperoxide to aniline is 6-7:1, the product yield is as high as over 92%.

[0135]

[0136] Example 6 Synthesis of diphenyldiazene with different catalyst addition amounts

[0137] 1. Add 1.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise at 80°C while stirring. React for 12 hours, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0138] 2. Add 5.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 80°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0139] 3. Add 10.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0140] 4. Add 15.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0141] 5. Add 20.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0142] 6. Add 25 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0143] 7. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise with stirring at 80°C. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0144] 8. Add 35.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0145] 9. Add 40.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid, and add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by mass aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0146] 10. Add 45.0 mg of U3O8 catalyst to a 25 mL reaction tube, followed by 0.093 g of aniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by weight aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0147] 11. Add 50.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by weight aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0148] 12. Add 55.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.093 g of aniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by weight aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0149] 13. Add 60.0 mg of U3O8 catalyst to a 25 mL reaction tube, followed by 0.093 g of aniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% by weight aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 h, then filter, distill, and recrystallize to obtain the product diphenyldiazene.

[0150] The product yield of diphenyldiazene obtained by the preparation method described in 1-13 above was calculated, and the results are shown in Table 6 below:

[0151] Table 6 Process parameters of the preparation method described in Example 6 and the yield of the product diphenyldiazene

[0152]

[0153]

[0154] The mass spectrum of the main product obtained from the above reaction is as follows Figure 10As shown (the mass spectra of the main products of the above 13 reactions are the same, so only one mass spectrum is provided), the structural formula of the product is shown in Formula 1 below. The above results show that when acetic acid is used as the reaction solvent, tert-butyl hydroperoxide is used as the oxidant, and U3O8 is used as the catalyst, and the ratio of the catalyst to aniline or its derivative is 1-60 mg:1 mol, aniline can be catalyzed to synthesize diphenyldiazene; and when the ratio of the catalyst to aniline or its derivative is 25-60 mg:1 mol, the yield of diphenyldiazene obtained in the reaction is higher than 80%; and when the ratio of the catalyst to aniline or its derivative is 30-40 mg:1 mol, the yield of diphenyldiazene obtained in the reaction can reach over 91%.

[0155]

[0156] Example 7 Synthesis of diphenyldiazene derivatives using different aniline derivatives

[0157] 1. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.107 g of o-methylaniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise at 80°C while stirring. React for 12 hours, then filter, distill, and recrystallize to obtain the product 2,2'-dimethyl-diphenyldiazene. The mass spectrum of the product is shown in the figure below. Figure 11 As shown, the structural formula is shown in Formula 2 below.

[0158]

[0159] 2. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.107 g of m-methylaniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise at 80°C while stirring. React for 12 hours, then filter, distill, and recrystallize to obtain the product 3,3'-dimethyl-diphenyldiazene. The mass spectrum of the product is shown in the figure below. Figure 12 As shown, the structural formula is shown in Formula 3 below.

[0160]

[0161] 3. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.107 g of p-methylaniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise at 80°C while stirring. React for 12 hours, then filter, distill, and recrystallize to obtain the product 4,4'-dimethyl-diphenyldiazene. The mass spectrum of the product is shown in the figure below. Figure 13 As shown, the structural formula is shown in Formula 4 below.

[0162]

[0163] 4. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.127 g of p-chloroaniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 hours, then filter, distill, and recrystallize to obtain the product 4,4'-dichloro-diphenyldiazene. The mass spectrum of the product is shown in the figure below. Figure 14 As shown, the structural formula is shown in Formula 5 below.

[0164]

[0165] 5. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.172 g of p-bromoaniline and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% tert-butyl hydroperoxide aqueous solution) dropwise at 80°C while stirring. React for 12 hours, then filter, distill, and recrystallize to obtain the product 4,4'-dibromo-diphenyldiazene. The mass spectrum of the product is shown in the figure below. Figure 15 As shown, the structural formula is shown in Formula 6 below.

[0166]

[0167] 6. Add 30.0 mg of U3O8 catalyst to a 25 mL reaction tube, then add 0.123 g of p-anisidine and 3.15 g of acetic acid. Add 5 mmol of tert-butyl hydroperoxide (i.e., 0.685 mL of a 70% aqueous solution of tert-butyl hydroperoxide) dropwise at 80°C while stirring. React for 12 hours, then filter, distill, and recrystallize to obtain the product 4,4'-dimethoxy-diphenyldiazene. The mass spectrum of the product is shown in the figure below. Figure 16 As shown, the structural formula is shown in Formula 7 below.

[0168]

[0169] The product yield of the diphenyldiazene derivative obtained by the preparation method described in 1-6 above was calculated, and the results are shown in Table 7 below:

[0170] Table 7 Process parameters and product yields of the preparation method described in Example 7

[0171]

[0172]

[0173] The mass spectra of the main products in the above reactions 1-6 are as follows: Figure 11-16 The above results show that using acetic acid as the reaction solvent, tert-butyl hydroperoxide as the oxidant, and U3O8 as the catalyst, o-methylaniline can be catalyzed to synthesize 2,2'-dimethyl-diphenyldiazene with a yield of 86%; m-methylaniline can be catalyzed to synthesize 3,3'-dimethyl-diphenyldiazene with a yield of 81%; p-methylaniline can be catalyzed to synthesize 4,4'-dimethyl-diphenyldiazene with a yield of 95%; p-chloroaniline can be catalyzed to synthesize 4,4'-dichloro-diphenyldiazene with a yield of 96%; p-bromoaniline can be catalyzed to synthesize 4,4'-dibromo-diphenyldiazene with a yield of 98%; and p-methoxyaniline can be catalyzed to synthesize 4,4'-dimethoxy-diphenyldiazene with a yield of 92%. Therefore, the method of the present invention can catalyze the synthesis of diphenyldiazene or its derivatives from aniline or its derivatives, and the yield of the target product obtained is high.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention 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 invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. Preparation method of depleted uranium-based U3O8 and its application in catalytic synthesis of azobenzene (diphenyldiazene) or its derivatives.

2. A method for preparing a U3O8 heterogeneous catalyst as claimed in claim 1, characterized in that: Using uranyl nitrate hexahydrate as the starting material, deionized water as the solvent, and a specific oxidant as the auxiliary, UO4·2H2O is prepared, and then calcined for several hours to produce U3O8. The specific steps are as follows: Preparation of U3O8: Weigh a specific mass of uranyl nitrate hexahydrate and place it in a container. While heating and stirring, add an appropriate amount of deionized water to completely dissolve the uranyl nitrate to form a transparent uranyl salt solution. Then, add an appropriate amount of oxidant. After continuous stirring for several hours, separate the solid product, wash and dry it to obtain UO4·2H2O, and calcine it in an air atmosphere for several hours.

3. A method for preparing U3O8 according to claims 1 and 2, characterized in that: The oxidant according to claim 2 is hydrogen peroxide with a mass fraction greater than 25%, wherein the uranyl salt is uranyl nitrate, and the stirring time is 2-25 hours.

4. A method for preparing U3O8 according to claims 1 and 2, characterized in that: The calcination temperature described in claim 2 is 550-700° C. and the calcination time is 1-6 hours.

5. The use of the catalytic synthesis of azobenzene (diphenyldiazene) or its derivatives as claimed in claim 1, characterized in that: The structural formula of the azobenzene (diphenyldiazene) or its derivatives is shown in the following formula (II). The raw material for synthesizing azobenzene (diphenyldiazene) or its derivatives is aniline or its derivatives, and its structural formula is shown in the following formula (I): Wherein, R1-R5 are independently selected from any one of hydrogen, halogen, hydroxyl, sulfonic acid, nitro, substituted or unsubstituted straight-chain or branched alkyl, alkoxy, carbonyl, alkenyl, alkynyl, substituted or unsubstituted aryl, acylamino, and cyano.

6. A method for preparing azobenzene (diphenyldiazene) or a derivative thereof as claimed in claims 1 and 5, said method comprising: A method for preparing azobenzene (diphenyldiazene) or its derivatives, comprising: using aniline or its derivatives as raw materials, acetic acid or a mixture of acetic acid and other organic solvents as a reaction solvent, U3O8 as a catalyst, and tert-butyl hydroperoxide as an oxidant, to synthesize azobenzene (diphenyldiazene) or its derivatives as shown in the following formula (II) through a catalytic oxidation reaction, wherein the organic solvent comprises formic acid, acetic acid, and propionic acid; Wherein, R1-R5 are independently selected from any one of hydrogen, halogen, hydroxyl, sulfonic acid, nitro, substituted or unsubstituted straight-chain or branched alkyl, alkoxy, carbonyl, alkenyl, alkynyl, substituted or unsubstituted aryl, acylamino, and cyano.

7. The synthesis method according to claims 1, 5 and 6, characterized in that The dosage ratio of the catalyst to aniline or its derivative is 1-60 mg:1 mmol; the mass ratio of the reaction solvent to aniline or its derivative is 1-67:1; the volume of the tert-butyl hydroperoxide is 0.1-1.0 mL; the reaction temperature is 30-120° C.; and the reaction time is 1-24 h.

8. The synthesis method according to claim 5-7, characterized in that The R1-R5 are independently selected from hydrogen, methyl, and chlorine. The aniline or its derivatives include: aniline, o-methylaniline, p-methylaniline, p-chloroaniline, o-chloroaniline, and m-chloroaniline.

9. The synthesis method according to any one of claims 5 to 8, characterized in that: Aniline or its derivatives, U3O8 (with a molar ratio of 30 mg:1 mmol to aniline or its derivatives), and TBHP (with a molar ratio of 14:1 to aniline or its derivatives) are added to acetic acid (with a mass ratio of 33:1 to aniline or its derivatives), and the mixture is reacted at 80°C for 12 hours; then azobenzene (diphenyldiazene) or its derivatives is obtained by filtration, distillation, and recrystallization.

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