Use of a physical mixture of zirconium hydroxide and copper oxide catalyst for catalyzing preparation of nitrosobenzene or its derivatives from aniline or its derivatives

Abstract

The application belongs to the technical field of organic synthesis, and particularly relates to application of a physical mixing catalyst of zirconium hydroxide and copper oxide in preparation of nitrosobenzene or a derivative thereof from aniline or a derivative thereof. Aniline or a derivative thereof is used as raw material, hydrogen peroxide is used as oxidant, and in a methanol solvent, zirconium hydroxide is used as catalyst to catalytically oxidize and synthesize azoxybenzene or a derivative thereof. The application finds that a physical mixing catalyst of zirconium hydroxide and copper oxide can catalytically oxidize aniline or a derivative thereof to prepare nitrosobenzene or a derivative thereof without adding an additive or changing a solvent. The zirconium hydroxide and the copper oxide can be directly purchased, or prepared by using a simple precipitation method with a zirconium salt or a copper salt precursor as raw material, and are low in price, and the physical mixing catalyst construction mode of the two is innovative; methanol is used as solvent, hydrogen peroxide is used as oxidant, and no additive is added, which is green and environmentally friendly. The above reaction process is simple, low in cost, high in yield, and easy to industrialize.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to the application of a physical mixed catalyst of zirconium hydroxide and copper oxide in the preparation of nitrosobenzene or its derivatives from aniline or its derivatives. Technical Background

[0002] Nitrobenzene or its derivatives are an extremely important class of fine chemicals, widely used in the synthesis of polymers, pharmaceuticals, dyes, and perfumes. Nitro compounds are also highly valuable chemical intermediates, widely applied in organic synthesis chemistry, such as in the reactions of nitrosoaldehydes with alkenes, cycloaddition reactions, Grignard reagent addition reactions, and the synthesis of indoles and azo aromatics. Furthermore, nitrosene intermediates are readily reduced or oxidized to the corresponding amines and nitrobenzene derivatives. In recent years, nitrosene compounds have also played a crucial role in asymmetric catalysis, serving as important precursors for the synthesis of many asymmetric products.

[0003] In recent years, researchers have been dedicated to developing novel catalytic systems for the production of nitrosamines or their derivatives. Reported synthetic methods include nitrosation of aromatics and organometallic compounds, double bond addition reactions, oxidation of primary amines and hydroxylamines, and reduction reactions of nitroaromatics. However, developing a low-cost, green synthetic route for nitrosamines or their derivatives remains a pressing challenge. This is because nitrosamines or their derivatives are extremely unstable, readily undergoing condensation reactions to form corresponding dimers, or reacting with other intermediates to form azobenzene and oxyazobenzene compounds. Traditionally, nitrosamines or their derivatives are synthesized by oxidizing aniline with large amounts of unstable peracids such as peracetic acid and perbenzoic acid. Therefore, constructing a catalytic system with high conversion and selectivity for the production of nitrosamines or their derivatives using environmentally friendly and inexpensive oxidants, such as hydrogen peroxide, is of significant practical importance. Reported studies on the use of hydrogen peroxide as an oxidant include: a phosphotungsten complex catalyst using hydrogen peroxide as an oxidant to catalyze the oxidation of aniline to nitrosamine or its derivatives (see *Journal of Catalysis*, 2015, Vol. 331, pp. 110-117); and the use of Au / TiO2 as a catalyst and hydrogen peroxide as an oxidant to catalyze the oxidation of aniline to nitrosamine or its derivatives (see *Advanced Synthesis & Catalysis*, 2016, Vol. 358, No. 9, pp. 1500-1508). Furthermore, studies have found that Pt / TiO2 can also catalyze the oxidation of aniline to nitrosamine or its derivatives under light irradiation (see *Acs Catalysis*, 2014, Vol. 4, No. 8, pp. 2418-2425). However, existing catalytic systems suffer from drawbacks such as complex catalyst preparation, high cost, poor activity, low selectivity, limited functional group compatibility, and the need for additives, severely limiting their practical applications. With the increasing demand for nitrosobenzene or its derivatives both domestically and internationally, it is of great significance to develop economical, efficient, and environmentally friendly heterogeneous catalytic systems using readily available and inexpensive hydrogen peroxide as an oxidant, under mild, additive-free, and green solvent reaction conditions, and by controlling the composition of the catalyst. Summary of the Invention

[0004] This invention uses zirconium hydroxide and copper oxide as a physical mixed catalyst to catalyze the oxidation of aniline or its derivatives to generate nitrosamine or its derivatives. Therefore, this invention provides a novel, low-cost, green, and efficient method for preparing nitrosamine or its derivatives. The method is simple, low-cost, safe, and yields a high synthesis rate. Specifically, it includes the following:

[0005] In a first aspect, this invention provides an application of a physically mixed catalyst of zirconium hydroxide and copper oxide in the preparation of nitrosamine or its derivatives from aniline or its derivatives. Both the zirconium hydroxide and copper oxide catalysts are commercially available, or can be prepared using zirconium or copper salt precursors. A certain amount of the metal salt is dissolved in deionized water, sodium hydroxide solution is added dropwise until the pH > 9, and the mixture is stirred for 12 hours. The resulting precipitate is then filtered, washed, dried, and calcined to obtain the desired catalyst. X-ray diffraction patterns of the prepared commercially available zirconium hydroxide and copper oxide physically mixed catalyst, as well as those prepared by the precipitation method, are shown below. Figure 1 As shown.

[0006] Preferably, the zirconium hydroxide and copper oxide catalysts are commercially available directly, or prepared using a simple precipitation method with zirconium or copper salt precursors as raw materials.

[0007] Preferably, the zirconium hydroxide and copper oxide catalysts are purchased directly.

[0008] Preferably, the mass ratio of the physically mixed catalyst zirconium hydroxide to copper oxide is 1:10-10:1.

[0009] Preferably, the mass ratio of the physically mixed catalyst zirconium hydroxide to copper oxide is 1:3-3:1.

[0010] Preferably, the mass ratio of the physically mixed catalyst zirconium hydroxide to copper oxide is 1:2.

[0011] Secondly, the present invention provides an application of a physical mixed catalyst of zirconium hydroxide and copper oxide in the preparation of nitrosamine or its derivatives from aniline or its derivatives. The method comprises: using aniline or its derivatives as shown in formula (I) as raw material, using an organic solvent as a reaction solvent, using zirconium hydroxide and copper oxide as a physical mixed catalyst, and using hydrogen peroxide as an oxidant, to catalytically oxidize and synthesize nitrosamine or its derivatives as shown in formula (II). The organic solvent includes one of methanol, ethanol, water, propanol, butanol, and ethyl acetate.

[0012]

[0013] R1-R5 are selected from any one of hydrogen, halogen, hydroxyl, sulfonic acid group, nitro group, substituted or unsubstituted straight-chain or branched alkyl, alkoxy, carbonyl, alkenyl, alkynyl, substituted or unsubstituted aryl, amide, and cyano groups.

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

[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 a physical mixture of zirconium hydroxide and copper oxide.

[0017] Preferably, the ratio of the catalyst to aniline or its derivative is 5-50 g: 1 mol.

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

[0019] Preferably, the ratio of the catalyst to aniline or its derivative is 20-50 g: 1 mol.

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

[0021] Preferably, the molar ratio of hydrogen peroxide to aniline or its derivative is 2-8:1.

[0022] Preferably, the molar ratio of hydrogen peroxide to aniline or its derivative is 2-5:1.

[0023] Preferably, the molar ratio of hydrogen peroxide to aniline or its derivative is 3:1.

[0024] Preferably, the reaction solvent is methanol.

[0025] Preferably, the mass ratio of the reaction solvent to aniline or its derivative is 2-20:1.

[0026] Preferably, the mass ratio of the reaction solvent to aniline or its derivative is 2-10:1.

[0027] Preferably, the mass ratio of the reaction solvent to aniline or its derivative is 5-10:1.

[0028] Preferably, the mass ratio of the reaction solvent to aniline or its derivative is 5:1.

[0029] Preferably, the method includes: adding aniline or its derivatives, zirconium hydroxide, copper oxide, and hydrogen peroxide to a reaction solvent, reacting at 0-80°C for 0.25-6 hours; filtering, distilling, and recrystallizing to obtain nitrosobenzene or its derivatives.

[0030] Preferably, the reaction temperature is 20-50°C.

[0031] Preferably, the reaction temperature is 30-40°C.

[0032] Preferably, the reaction temperature is 30°C.

[0033] Preferably, the reaction time is 0.5-6 hours.

[0034] Preferably, the reaction time is 1-6 hours.

[0035] Preferably, the reaction time is 2 hours.

[0036] Compared with the prior art, the method for preparing nitrosobenzene or its derivatives by catalytic oxidation of aniline or its derivatives according to the present invention has the following advantages:

[0037] (1) This invention innovatively uses inexpensive zirconium hydroxide and copper oxide as a physical mixed catalyst, without the need for additives or solvent changes. It not only has high activity and good selectivity, but the catalyst can also be directly purchased commercially or prepared by a simple precipitation method. Compared with the precious metal catalysts used in traditional methods, the catalyst cost is greatly reduced.

[0038] (2) The aniline or its derivatives used in this invention are common basic raw materials in industry, and are inexpensive and readily available.

[0039] (3) This invention uses cheap and readily available hydrogen peroxide as an oxidant and has a low reaction temperature. Compared with traditional methods that use chemical peroxides and other oxidants, it significantly reduces the cost of oxidants and solves the problem of toxic emissions generated by the use of oxidants. The reaction system is green and environmentally friendly. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to specific embodiments. The scope of protection of the present invention is not limited thereto. Unless otherwise specified, all raw materials used in the following embodiments can be purchased commercially. Attached Figure Description

[0041] Figure 1 X-ray diffraction patterns of commercially purchased and precipitation-prepared catalysts;

[0042] Figure 2 The 1H NMR spectrum of the nitrosobenzene synthesized by the method described in Example 1;

[0043] Figure 3 The 1H NMR spectrum of the nitrosobenzene synthesized by the method described in Example 2;

[0044] Figure 4 The 1H NMR spectrum of the nitrosobenzene synthesized by the method described in Example 3;

[0045] Figure 5 The 1H NMR spectrum of the nitrosobenzene synthesized by the method described in Example 4;

[0046] Figure 6 The 1H NMR spectrum of the nitrosobenzene synthesized by the method described in Example 5;

[0047] Figure 7 The 1H NMR spectrum of the nitrosobenzene synthesized by the method described in Example 6;

[0048] Figure 8 The 1H NMR spectrum of the o-methylnitrosobenzene synthesized by the method described in Example 7;

[0049] Figure 9 The 1H NMR spectrum of the product m-methylnitrosobenzene synthesized by the method described in Example 7;

[0050] Figure 10 The 1H NMR spectrum of the product p-methylnitrosobenzene synthesized by the method described in Example 7;

[0051] Figure 11 The 1H NMR spectrum of the product p-chloronitrosobenzene synthesized by the method described in Example 7;

[0052] Figure 12 The 1H NMR spectrum of the product p-bromonitrosobenzene synthesized by the method described in Example 7;

[0053] Figure 13 The 1H NMR spectrum of the product p-methoxynitrosobenzene synthesized by the method described in Example 7.

[0054] Example 1: Synthesis of nitrosamines using different preparation methods and different proportions of zirconium hydroxide and copper oxide.

[0055] 1. Add 2.0 g of commercial zirconium hydroxide catalyst and 4.0 g of commercial copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution) dropwise. React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0056] 2. Add 2.0 g of precipitated zirconium hydroxide catalyst and 4.0 g of precipitated copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution) dropwise. React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0057] 3. Add 2.0 g of commercial zirconium hydroxide catalyst and 20.0 g of commercial copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0058] 4. Add 2.0 g of commercial zirconium hydroxide catalyst and 10.0 g of commercial copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0059] 5. Add 2.0 g of commercial zirconium hydroxide catalyst and 2.0 g of commercial copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of butanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0060] 6. Add 2.0 g of commercial zirconium hydroxide catalyst and 1.0 g of commercial copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0061] 7. Add 2.0 g of commercial zirconium hydroxide catalyst and 0.4 g of commercial copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0062] 8. Add 2.0 g of commercial zirconium hydroxide catalyst and 0.2 g of commercial copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0063] The yields of nitrosobenzene products obtained by the preparation methods described in 1-8 above were calculated, and the results are shown in Table 1 below:

[0064] Table 1. Process parameters and yield of nitrosobenzene as described in Example 1.

[0065]

[0066]

[0067] The proton NMR spectrum of the product synthesized by the above reaction is shown below. Figure 2 As shown (the main products of the above 8 reactions have the same 1H NMR spectrum, therefore only one 1H NMR spectrum is provided). The above results indicate that aniline can be catalytically synthesized into nitrosamines using methanol as the reaction solvent, hydrogen peroxide as the oxidant, and zirconium hydroxide and copper oxide as catalysts (the mass ratio of zirconium hydroxide to copper oxide is 1:10-10:1). Furthermore, when the mass ratio of zirconium hydroxide to copper oxide is 1:1-1:10, the yield of nitrosamines obtained is above 70%, and when the mass ratio of zirconium hydroxide to copper oxide is 1:2-1:10, the yield of nitrosamines obtained is as high as 90%, reaching a maximum of 96%.

[0068] Example 2: Synthesis of nitrosobenzene using different reaction solvents

[0069] 1. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0070] 2. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of ethanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0071] 3. Add 2.0g of zirconium hydroxide catalyst and 4.0g of copper oxide catalyst directly to a 500mL container, then add 18.6g of aniline and 93.0g of water. While stirring at 30℃, add 0.6mol of hydrogen peroxide (i.e., 60mL of 30% hydrogen peroxide aqueous solution) dropwise. React for 2 hours, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0072] 4. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 93.0 g of propanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0073] 5. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 93.0 g of butanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0074] 6. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of ethyl acetate. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0075] The yields of nitrosobenzene products obtained by the preparation methods described in 1-6 above were calculated, and the results are shown in Table 2 below:

[0076] Table 2. Process parameters and yield of nitrosobenzene as described in Example 2.

[0077]

[0078] The proton NMR spectrum of the product synthesized by the above reaction is shown below. Figure 3 As shown (the main products of the above six reactions have the same 1H NMR spectrum, therefore only one 1H NMR spectrum is provided). The above results indicate that aniline can be catalytically synthesized into nitrosamine using organic solvents (methanol, ethanol, water, propanol, butanol, ethyl acetate) as reaction solvents, hydrogen peroxide as oxidant, and zirconium hydroxide and copper oxide as catalysts; among them, the yield of nitrosamine synthesis is as high as 96% when methanol is used as the reaction solvent.

[0079] Example 3: Synthesis of nitrosobenzene with different amounts of reaction solvent

[0080] 1. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 37.2 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0081] 2. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0082] 3. Add 2.0g of zirconium hydroxide catalyst and 4.0g of copper oxide catalyst directly into a 500mL container, then add 18.6g of aniline and 148.8g of methanol. While stirring at 30℃, add 0.6mol of hydrogen peroxide (i.e., 60mL of 30% hydrogen peroxide aqueous solution) dropwise. React for 2h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0083] 4. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 186.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0084] 5. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 279.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0085] 6. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 372.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0086] The yields of nitrosobenzene products obtained by the preparation methods described in 1-6 above were calculated, and the results are shown in Table 3 below:

[0087] Table 3. Process parameters and yield of nitrosobenzene as described in Example 3.

[0088]

[0089]

[0090] The proton NMR spectrum of the main product obtained from the above reaction is shown below. Figure 4 As shown (the main products of the above six reactions have the same 1H NMR spectrum, therefore only one 1H NMR spectrum is provided). The above results indicate that aniline can be catalytically synthesized into nitrosamines using methanol as the reaction solvent (methanol to aniline mass ratio of 2-20:1), hydrogen peroxide as the oxidant, and zirconium hydroxide and copper oxide as catalysts. Furthermore, when the methanol to aniline mass ratio is 2-10:1, the yield of nitrosamines obtained is above 80%, and when the methanol to aniline mass ratio is 5-10:1, the yield of nitrosamines obtained is as high as 85%, reaching a maximum of 96%.

[0091] Example 4: Synthesis of nitrosobenzene at different reaction temperatures

[0092] 1. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 0 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution) dropwise. React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0093] 2. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 20 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0094] 3. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0095] 4. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 40 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0096] 5. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 50 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0097] 6. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 60 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0098] 7. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 80 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0099] The yields of nitrosobenzene products obtained by the preparation methods described in 1-7 above were calculated, and the results are shown in Table 4 below:

[0100] Table 4. Process parameters and yield of nitrosobenzene as described in Example 4.

[0101]

[0102] The proton NMR spectrum of the main product obtained from the above reaction is shown below. Figure 5As shown (the main products of the above 8 reactions have the same 1H NMR spectrum, so only one 1H NMR spectrum is provided). The above results indicate that, at a reaction temperature of 0-80℃, using hydrogen peroxide as the oxidant, methanol as the reaction solvent, and zirconium hydroxide and copper oxide as catalysts, aniline can be catalytically synthesized into nitrosamines; at a reaction temperature of 20-50℃, the yield of nitrosamines obtained is above 80%; and at a reaction temperature of 30-40℃, the yield of nitrosamines obtained can reach above 90%.

[0103] Example 5: Synthesis of nitrosobenzene with different reaction times

[0104] 1. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution) dropwise. React for 0.5 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0105] 2. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 1 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0106] 3. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0107] 4. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 4 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0108] 5. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 6 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0109] The yields of nitrosobenzene products obtained by the preparation methods described in 1-6 above were calculated, and the results are shown in Table 5 below:

[0110] Table 5. Process parameters and yield of nitrosobenzene as described in Example 5.

[0111]

[0112]

[0113] The proton NMR spectrum of the main product obtained from the above reaction is shown below. Figure 6 As shown (the main products of the above 6 reactions have the same 1H NMR spectrum, therefore only one 1H NMR spectrum is provided). The above results indicate that, with a reaction time of 0.5-6 h, using hydrogen peroxide as the oxidant, methanol as the reaction solvent, and zirconium hydroxide and copper oxide as catalysts, aniline can be catalytically synthesized into nitrosamines; at a reaction time of 1-6 h, the yield of nitrosamines obtained is above 80%; and at a reaction time of 2-6 h, the yield of nitrosamines obtained can reach above 96%.

[0114] Example 6: Synthesis of nitrosobenzene with different amounts of hydrogen peroxide added.

[0115] 1. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.4 mol of hydrogen peroxide (i.e., 40 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0116] 2. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0117] 3. Add 2.0g of zirconium hydroxide catalyst and 4.0g of copper oxide catalyst directly into a 500mL container, then add 18.6g of aniline and 93.0g of methanol. While stirring at 30℃, add 0.8mol of hydrogen peroxide (i.e., 80mL of 30% hydrogen peroxide aqueous solution) dropwise. React for 2h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0118] 4. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly into a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 1.0 mol of hydrogen peroxide (i.e., 100 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0119] 5. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 1.6 mol of hydrogen peroxide (i.e., 160 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0120] The yields of nitrosobenzene products obtained by the preparation methods described in 1-5 above were calculated, and the results are shown in Table 6 below:

[0121] Table 6 shows the process parameters and yield of the product nitrosobenzene for the preparation method described in Example 6.

[0122]

[0123] The above results indicate that when the molar ratio of hydrogen peroxide to aniline is 2-8:1, methanol is used as the reaction solvent, and zirconium hydroxide and copper oxide are used as catalysts, aniline can be catalytically synthesized into nitrosamines. Furthermore, when the molar ratio of hydrogen peroxide to aniline is 2-8:1, the yield of nitrosamines obtained is above 80%; and when the molar ratio of hydrogen peroxide to aniline is 2-5:1, the yield of nitrosamines obtained is as high as 90% or more.

[0124] Example 7: Synthesis of nitrosobenzene with different catalyst addition amounts

[0125] 1. Add 0.33g of zirconium hydroxide catalyst and 0.67g of copper oxide catalyst directly to a 500mL container, then add 18.6g of aniline and 93.0g of methanol. While stirring at 30℃, add 0.6mol of hydrogen peroxide (i.e., 60mL of 30% hydrogen peroxide aqueous solution) dropwise. React for 2h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0126] 2. Add 0.66 g of zirconium hydroxide catalyst and 1.34 g of copper oxide catalyst directly to a 500 mL container, then add 18.6 g of aniline and 93.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0127] 3. Add 1.32g of zirconium hydroxide catalyst and 2.68g of copper oxide catalyst directly into a 500mL container, then add 18.6g of aniline and 93.0g of methanol. While stirring at 30℃, add 0.6mol of hydrogen peroxide (i.e., 60mL of 30% hydrogen peroxide aqueous solution) dropwise. React for 2 hours, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0128] 4. Add 2.0g of zirconium hydroxide catalyst and 4.0g of copper oxide catalyst directly to a 500mL container, then add 18.6g of aniline and 93.0g of methanol. While stirring at 30℃, add 0.6mol of hydrogen peroxide (i.e., 60mL of 30% hydrogen peroxide aqueous solution). React for 2h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0129] 5. Add 3.3g of zirconium hydroxide catalyst and 6.7g of copper oxide catalyst directly to a 500mL container, then add 18.6g of aniline and 93.0g of methanol. While stirring at 30℃, add 0.6mol of hydrogen peroxide (i.e., 60mL of 30% hydrogen peroxide aqueous solution) dropwise. React for 2h, then filter, distill, and recrystallize to obtain the product nitrosobenzene.

[0130] The yields of nitrosobenzene products obtained by the preparation methods described in 1-5 above were calculated, and the results are shown in Table 7 below:

[0131] Table 7. Process parameters and yield of nitrosobenzene as described in Example 7.

[0132]

[0133] The above results indicate that using hydrogen peroxide as the oxidant, methanol as the reaction solvent, zirconium hydroxide and copper oxide as catalysts, and a catalyst-to-aniline or derivative ratio of 5-50 g:1 mol, aniline can be catalytically synthesized into nitrosamines. Furthermore, when the catalyst-to-aniline or derivative ratio is 10-50 g:1 mol, the yield of nitrosamines obtained is higher than 85%. At the same time, when the catalyst-to-aniline or derivative ratio is 20-50 g:1 mol, the yield of nitrosamines obtained is as high as 92% or more.

[0134] Example 8: Synthesis of nitrosobenzene derivatives using different aniline derivatives

[0135] 1. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 21.4 g of o-methylaniline and 107.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution) dropwise. React for 6 h, then filter, distill, and recrystallize to obtain the product o-methylnitrosobenzene.

[0136] 2. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 21.4 g of m-methylaniline and 107.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product m-methylnitrosobenzene.

[0137] 3. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 21.4 g of p-methylaniline and 107.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product p-methylnitrosobenzene.

[0138] 4. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 25.4 g of p-chloroaniline and 127.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product p-chloronitrosobenzene.

[0139] 5. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 34.4 g of p-bromoaniline and 172.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product p-bromonitrosobenzene.

[0140] 6. Add 2.0 g of zirconium hydroxide catalyst and 4.0 g of copper oxide catalyst directly to a 500 mL container, then add 24.6 g of p-methoxyaniline and 123.0 g of methanol. While stirring at 30 °C, add 0.6 mol of hydrogen peroxide (i.e., 60 mL of 30% hydrogen peroxide aqueous solution). React for 2 h, then filter, distill, and recrystallize to obtain the product p-methoxynitrosobenzene.

[0141] The yields of the nitrosobenzene derivatives obtained by the preparation methods described in 1-6 above were calculated, and the results are shown in Table 8 below:

[0142] Table 8. Process parameters and product yield of the preparation method described in Example 8.

[0143]

[0144] The proton NMR spectra of the main products in reactions 1-6 above are as follows: Figure 8-13 As shown above, the results indicate that using methanol as the reaction solvent, hydrogen peroxide as the oxidant, and zirconium hydroxide and copper oxide as catalysts, o-methylaniline can be catalytically synthesized into o-methylnitrosobenzene with a yield of 89%; m-methylaniline can be catalytically synthesized into m-methylnitrosobenzene with a yield of 90%; p-methylaniline can be catalytically synthesized into p-methylnitrosobenzene with a yield of 92%; p-chloroaniline can be catalytically synthesized into p-chloronitrosobenzene with a yield of 87%; p-bromoaniline can be catalytically synthesized into p-bromonitrosobenzene with a yield of 85%; and p-methoxyaniline can be catalytically synthesized into p-methoxynitrosobenzene with a yield of 93%. Therefore, the method described in this invention can catalytically synthesize nitrosobenzene or its derivatives from aniline or its derivatives, and the yield of the target product is high.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing nitrosobenzene or its derivatives, characterized in that, The method comprises: using aniline or its derivatives as shown in formula (I) as raw material, methanol as reaction solvent, zirconium hydroxide and copper oxide as physical mixed catalysts, and hydrogen peroxide as oxidant, to catalytically oxidize and generate nitrosobenzene or its derivatives as shown in formula (II); wherein R1-R5 are independently selected from any one of hydrogen, halogen, hydroxyl, sulfonic acid group, substituted or unsubstituted straight-chain or branched alkyl, alkoxy, substituted or unsubstituted aryl, amide and cyano groups; the mass ratio of zirconium hydroxide to copper oxide in the physical mixed catalyst is 1:2-1:10; the molar ratio of the total mass of the physical mixed catalyst to the molar ratio of aniline or its derivatives is 10-50 g:1 mol; the molar ratio of hydrogen peroxide to aniline or its derivatives is 2-8:1; and the mass ratio of methanol to aniline or its derivatives is 2-10:

1. 。 2. The preparation method according to claim 1, characterized in that, The physical mixing catalyst is composed of zirconium hydroxide and copper oxide, which are prepared or purchased separately, through physical mixing.

3. The preparation method according to any one of claims 1-2, characterized in that, The mass ratio of zirconium hydroxide to copper oxide in the physically mixed catalyst is 1:

2.

4. The preparation method according to claim 1, characterized in that, The aniline or its derivatives are selected from one of aniline, o-methylaniline, m-methylaniline, p-methylaniline, p-chloroaniline, p-bromoaniline, and p-methoxyaniline.

5. The preparation method according to claim 1, characterized in that, Aniline or its derivatives, zirconium hydroxide and copper oxide were added to methanol, and hydrogen peroxide was added under stirring. The mixture was reacted at 20-50°C for 1-6 hours. After the reaction was completed, the mixture was filtered, distilled and recrystallized to obtain nitrosobenzene or its derivatives.

6. The preparation method according to claim 5, characterized in that, The physical mixed catalyst has a zirconium hydroxide to copper oxide mass ratio of 1:2; the total mass of the physical mixed catalyst to the molar ratio of aniline or its derivative is 30 g: 1 mol; the molar ratio of hydrogen peroxide to aniline or its derivative is 3:1; the mass ratio of methanol to aniline or its derivative is 5:1; the reaction temperature is 30 °C and the reaction time is 2 h.

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