Use of iron oxide-iron sulfide complex as catalyst for catalyzing preparation of aryl hydroxylamine from aryl nitro compound

Abstract

The application belongs to the technical field of organic synthesis, and particularly relates to application of an iron oxide-iron sulfide compound as a catalyst in preparation of aryl hydroxylamine from aryl nitro compounds. The application uses aryl nitro compounds as raw materials, an iron oxide-iron sulfide compound or a composition containing the iron oxide-iron sulfide compound as a catalyst, and hydrazine hydrate as a reducing agent, and aryl hydroxylamine can be synthesized through catalytic reduction reaction; the iron oxide-iron sulfide compound catalyst is simple to prepare, and can be prepared by co-calcination, hydrothermal method or coprecipitation, etc. The patent provides a new method for catalytic reduction of aryl nitro compounds to aryl hydroxylamine, which is simple to operate, low in production cost and small in environmental pollution.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to the application of iron oxide-iron sulfide complex as a catalyst for the preparation of aryl hydroxylamine from aromatic nitro compounds. Technical Background

[0002] Aromatic hydroxylamine compounds are an important class of organic intermediates and raw materials, and they are used as raw materials in many organic reactions such as pesticides, pharmaceuticals, bioactive substances, and cosmetics.

[0003] The selective reduction of aromatic nitro compounds to prepare the corresponding hydroxylamine compounds is an economical and environmentally friendly method. However, because the reduction of nitrobenzene is a continuous process, it is prone to direct over-reduction to aniline, and hydroxylamine is easily disproportionated to form azo compounds (J. Catal., 2010, Vol. 275, pp. 250-256). This reaction must not only ensure high selectivity but also prevent the formation of byproducts.

[0004] Previous reports have shown that additives such as DMSO or organic bases can improve reaction selectivity, but these additives usually come at the cost of sacrificing catalyst activity and increasing the difficulty of subsequent separation processes (Green. Chem., 2009, Vol. 11, 1385-1390). In the study of the catalytic reduction of nitrobenzene compounds to phenyl hydroxylamine compounds, supported noble metal catalysts are the most common reduction catalysts (Catal. Sci. Technol., 2015, Vol. 5, pp. 176-183) (Mol. Catal., 2021, Vol. 514, pp. 11836), such as Ru, Pd, Ag, and Ir. However, noble metal catalysts have disadvantages such as high cost, limited resources, and inability to be used on a large scale, which limits their practical application. Against this backdrop, the use of inexpensive and environmentally friendly non-noble metal catalysts for the reduction synthesis of aromatic hydroxylamines from aromatic nitro compounds has broad application prospects and important practical significance. Summary of the Invention

[0005] Iron-based materials have attracted widespread attention due to their excellent chemical stability, high abundance, low cost, and environmental friendliness. This invention discovers a method for synthesizing aryl hydroxylamines by reducing aromatic nitro compounds using iron-based materials as a catalyst. Therefore, this invention provides a novel, low-cost, green, and efficient catalytic method for preparing aryl hydroxylamines. This method is simple, low-cost, safe, and achieves a high synthesis rate. Specifically, it includes the following:

[0006] In a first aspect, the present invention provides an application of an iron oxide-iron sulfide complex as a catalyst for the preparation of aryl hydroxylamines from aromatic nitro compounds.

[0007] Preferably, the catalyst is an iron oxide-iron sulfide complex or a composition containing an iron oxide-iron sulfide complex.

[0008] Preferably, the catalyst preparation method includes co-calcination, hydrothermal method and precipitation method, but is not limited to these.

[0009] Preferably, the iron salt required for the preparation of the catalyst includes, but is not limited to, ferric nitrate, ferric chloride, ferric sulfate, etc.

[0010] Preferably, the precipitant required for the preparation of the catalyst includes ammonia water, sodium hydroxide solution, sodium carbonate solution, potassium hydroxide solution, potassium carbonate solution, etc., but is not limited to these.

[0011] Preferably, the mass ratio of sulfur to catalyst precursor required for the catalyst preparation method is 0.5 to 2:1.

[0012] Preferably, the calcination temperature of the catalyst is 300–700°C.

[0013] Preferably, the calcination temperature of the catalyst is 600°C.

[0014] Preferably, the structural formula of the above-mentioned aromatic nitro compound is shown in Formula 1 below, and the structural formula of the aryl hydroxylamine is shown in Formula 2 below:

[0015]

[0016] R1-R5 are selected from any one of hydrogen, halogen, sulfonic acid group, nitro group, substituted or unsubstituted straight-chain or branched alkyl group, alkoxy group, carbonyl group, alkenyl group, alkynyl group, substituted or unsubstituted aryl group, amide group, and cyano group, but are not limited to the above substituents.

[0017] Preferably, R1-R5 are selected from hydrogen, bromine, and hydroxymethyl, respectively.

[0018] Secondly, the present invention provides a method for preparing phenylhydroxylamine, wherein the method comprises: using an aromatic nitro compound as shown in Formula 1 as a raw material, using an organic solvent as a reaction solvent, and using an iron oxide-iron sulfide complex as a catalyst, a catalytic reduction reaction is carried out to synthesize an aromatic hydroxylamine as shown in Formula 2.

[0019]

[0020] R1-R5 are selected from any one of hydrogen, halogen, sulfonic acid group, nitro group, substituted or unsubstituted straight-chain or branched alkyl group, alkoxy group, carbonyl group, alkenyl group, alkynyl group, substituted or unsubstituted aryl group, amide group, and cyano group, but are not limited to the above substituents.

[0021] Preferably, R1-R5 are selected from hydrogen, bromine, and hydroxymethyl, respectively.

[0022] Preferably, the aromatic nitro compound includes: nitrobenzene, 4-bromonitrobenzene, and 4-hydroxymethylnitrobenzene.

[0023] Preferably, the molar ratio of hydrazine hydrate to aromatic nitro compound is 10 to 1:1.

[0024] Preferably, the molar ratio of hydrazine hydrate to aromatic nitro compound is 6:1.

[0025] Preferably, the ratio of the catalyst to the aromatic nitro compound is 10-100 g: 1 mol.

[0026] Preferably, the ratio of the catalyst to the aromatic nitro compound is 50 g: 1 mol.

[0027] Preferably, the reaction solvent is one of ethanol, methanol, acetonitrile, toluene, CH2Cl2, CCl4, DMF, DMSO, isopropanol, n-propanol, n-hexane, and cyclohexane, but is not limited thereto.

[0028] Preferably, the reaction solvent is ethanol.

[0029] Preferably, the reaction time is 0.5 to 10 hours.

[0030] Preferably, the reaction time is 2 hours.

[0031] Preferably, the reaction temperature is 0–60°C.

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

[0033] Compared with existing technologies, the method for preparing aryl hydroxylamine from catalytic nitro compounds described in this invention has the following advantages: it innovatively uses an inexpensive iron oxide-iron sulfide complex as a catalyst, requiring no additional additives, exhibiting high activity and selectivity, readily available raw materials, simple preparation, low catalyst cost, and environmental friendliness; it employs a heterogeneous reduction method, making product separation easy and requiring minimal reaction equipment; it uses hydrazine hydrate as a reducing agent, resulting in only N2 and water as products; and the method described in this invention can catalytically reduce nitrobenzene to the corresponding phenylhydroxylamine with good specificity and a high yield of the target product. Attached Figure Description

[0034] Figure 1 XRD patterns of iron oxide-iron sulfide composites synthesized by the methods described in Examples 1, 2, and 3;

[0035] Figure 2 Scanning electron microscope (SEM) images of iron oxide-iron sulfide composites synthesized by the methods described in Examples 1, 2, and 3;

[0036] Figure 3High-performance liquid chromatograms of the phenylhydroxylamine synthesized by the methods described in Examples 4 and 5 (the products are the same, so the same chromatogram was used);

[0037] Figure 4 High-performance liquid chromatography chromatogram of the product 4-bromophenylhydroxylamine synthesized by the method described in Example 6;

[0038] Figure 5 High-performance liquid chromatography chromatogram of the product 4-hydroxymethylphenylhydroxylamine synthesized by the method described in Example 6; Detailed Implementation

[0039] 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.

[0040] Example 1: Preparation of iron oxide precursor in iron oxide-iron sulfide composite catalyst

[0041] 1. Precipitation method

[0042] (1) Solution preparation: Dissolve a certain amount of iron salt (such as ferric nitrate, ferric chloride, ferric sulfate, etc., but not limited to these, the same below) in deionized water and stir for 1-2 hours to fully dissolve the iron salt.

[0043] (2) Precipitation aging: While stirring, slowly add 5-2 times the amount of precipitant (such as ammonia, sodium hydroxide solution, sodium carbonate solution, potassium hydroxide solution, potassium carbonate solution, etc., but not limited to these, the same below) to the iron salt solution until the pH of the solution is 9-11, and stir and age for 10-24 hours.

[0044] (3) Precipitation treatment: The above solution was filtered at normal pressure and washed with deionized water until the pH of the filtrate was 7 to ensure that the ions in the solution were washed away. The precipitate was dried at 50-100℃ to obtain the iron oxide-iron sulfide complex precursor.

[0045] 2. Coprecipitation method

[0046] (1) Preparation of iron salt solution: Dissolve a certain amount of iron salt in deionized water and stir for 1-2 hours to fully dissolve the iron salt. Fill the solution into a constant pressure funnel. Fill another constant pressure funnel with the precipitant.

[0047] (2) Co-precipitation: First, put an equal amount of deionized water into a three-necked flask and stir. At the same time, open the funnel switch for the iron salt solution and the precipitant so that they are dripped into the flask at the same rate. Stir and age for 10-24 hours.

[0048] (3) Precipitation treatment: The above solution was filtered at normal pressure and washed with deionized water until the pH of the filtrate was 7 to ensure that the ions in the solution were washed away. The precipitate was dried at 50-100℃ to obtain the iron oxide-iron sulfide complex precursor.

[0049] 3. Over-precipitation method

[0050] (1) Precipitant: Pour the precipitant solution into a three-necked bottle.

[0051] (2) Adding iron salt solution: Dissolve a certain amount of iron salt in deionized water, stir for 1-2 hours to fully dissolve the iron salt, fill it into a constant pressure funnel, slowly add it to the precipitant, and stir and age for 10-24 hours.

[0052] (3) Precipitation treatment: The above solution was filtered at normal pressure and washed with deionized water until the pH of the filtrate was 7 to ensure that the ions in the solution were washed away. The precipitate was dried at 50-100℃ to obtain the iron oxide-iron sulfide complex precursor.

[0053] It should be noted that the iron oxide-iron sulfide complexes obtained from the precursors prepared by these three methods all exhibit good activity, therefore no detailed distinction has been made. Unless otherwise specified in the following description, the precursors are those obtained by the precipitation method.

[0054] Example 2: Synthesis of phenylhydroxylamine using catalysts prepared with different mass ratios of sulfur to iron oxide precursors.

[0055] 1. Sulfur and the precursor were placed separately in a vertical tube furnace, separated by high-temperature cotton, with a mass ratio of 0.5:1. High-purity nitrogen was continuously introduced, and the furnace was heated to 600℃ at a rate of 3℃ / min, held for 1 hour, and then allowed to cool naturally. 0.05 g of the prepared iron oxide-iron sulfide composite catalyst was added to a 20 mL reaction tube, followed by 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. The reaction was carried out at 30℃ for 2 hours, followed by filtration, extraction, and distillation to obtain the product phenylhydroxylamine.

[0056] 2. Sulfur and the precursor were placed separately in a vertical tube furnace, separated by high-temperature cotton, with a mass ratio of 1:1. High-purity nitrogen was continuously introduced, and the furnace was heated to 600°C at a rate of 3°C / min, held for 1 hour, and then allowed to cool naturally. 0.05 g of the prepared iron oxide-iron sulfide composite catalyst was added to a 20 mL reaction tube, followed by 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. The reaction was carried out at 30°C for 2 hours, followed by filtration, extraction, and distillation to obtain the product phenylhydroxylamine.

[0057] 3. Sulfur and the precursor were placed separately in a vertical tube furnace, separated by high-temperature cotton, with a mass ratio of 1.5:1. High-purity nitrogen was continuously introduced, and the furnace was heated to 600℃ at a rate of 3℃ / min, held for 1 hour, and then allowed to cool naturally. 0.05 g of the prepared iron oxide-iron sulfide composite catalyst was added to a 20 mL reaction tube, followed by 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. The reaction was carried out at 30℃ for 2 hours, followed by filtration, extraction, and distillation to obtain the product phenylhydroxylamine.

[0058] 4. Sulfur and the precursor were placed separately in a vertical tube furnace, separated by high-temperature cotton, with a mass ratio of 2:1. High-purity nitrogen was continuously introduced, and the furnace was heated to 600℃ at a rate of 3℃ / min, held for 1 hour, and then allowed to cool naturally. 0.05g of the prepared iron oxide-iron sulfide composite catalyst was added to a 20mL reaction tube, followed by 2mL of ethanol, 1mmol of nitrobenzene, and 6mmol of hydrazine hydrate. The reaction was carried out at 30℃ for 2 hours, followed by filtration, extraction, and distillation to obtain the product phenylhydroxylamine.

[0059] The yields of styrene obtained by the preparation methods described in 1 to 4 above were calculated, and the results are shown in Table 1 below:

[0060] Table 1. Process parameters and yield of the product phenylhydroxylamine according to the preparation method described in Example 2.

[0061]

[0062] The above results indicate that when the mass ratio of sulfur to precursor is 0.5–2:1, at a reaction temperature of 30°C, with ethanol as the reaction solvent and an iron oxide-iron sulfide complex as the catalyst, and a catalyst dosage of 0.5 g, nitrobenzene can be catalyzed to synthesize phenylhydroxylamine; when the mass ratio of sulfur to precursor is 1:1, the yield of phenylhydroxylamine can reach 99%.

[0063] Example 3: Synthesis of phenylhydroxylamine using catalysts at different calcination temperatures

[0064] 1. Sulfur and the precursor were placed separately in a vertical tube furnace, separated by high-temperature cotton, with a mass ratio of 1:1. High-purity nitrogen was continuously introduced, and the furnace was heated to 300°C at a rate of 3°C / min, held for 1 hour, and then allowed to cool naturally. 0.05 g of the prepared iron oxide-iron sulfide composite catalyst was added to a 20 mL reaction tube, followed by 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. The reaction was carried out at 30°C for 2 hours, followed by filtration, extraction, and distillation to obtain the product phenylhydroxylamine.

[0065] 2. Sulfur and the precursor were placed separately in a vertical tube furnace, separated by high-temperature cotton, with a mass ratio of 1:1. High-purity nitrogen was continuously introduced, and the furnace was heated to 400°C at a rate of 3°C / min, held for 1 hour, and then allowed to cool naturally. 0.05 g of the prepared iron oxide-iron sulfide composite catalyst was added to a 20 mL reaction tube, followed by 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. The reaction was carried out at 30°C for 2 hours, followed by filtration, extraction, and distillation to obtain the product phenylhydroxylamine.

[0066] 3. Sulfur and the precursor were placed separately in a vertical tube furnace, separated by high-temperature cotton, with a mass ratio of 1:1. High-purity nitrogen was continuously introduced, and the furnace was heated to 500°C at a rate of 3°C / min, held for 1 hour, and then allowed to cool naturally. 0.05 g of the prepared iron oxide-iron sulfide composite catalyst was added to a 20 mL reaction tube, followed by 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. The reaction was carried out at 30°C for 2 hours, followed by filtration, extraction, and distillation to obtain the product phenylhydroxylamine.

[0067] 4. Sulfur and the precursor were placed separately in a vertical tube furnace, separated by high-temperature cotton, with a mass ratio of 1:1. High-purity nitrogen was continuously introduced, and the furnace was heated to 600℃ at a rate of 3℃ / min, held for 1 hour, and then allowed to cool naturally. 0.05 g of the prepared iron oxide-iron sulfide composite catalyst was added to a 20 mL reaction tube, followed by 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. The reaction was carried out at 30℃ for 2 hours, followed by filtration, extraction, and distillation to obtain the product phenylhydroxylamine.

[0068] 5. Sulfur and the precursor were placed separately in a vertical tube furnace, separated by high-temperature cotton, with a mass ratio of 1:1. High-purity nitrogen was continuously introduced, and the furnace was heated to 700℃ at a rate of 3℃ / min, held for 1 hour, and then allowed to cool naturally. 0.05 g of the prepared iron oxide-iron sulfide composite catalyst was added to a 20 mL reaction tube, followed by 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. The reaction was carried out at 30℃ for 2 hours, followed by filtration, extraction, and distillation to obtain the product phenylhydroxylamine.

[0069] The yields of phenylhydroxylamine obtained by the preparation methods described in 1-5 above were calculated, and the results are shown in Table 2 below:

[0070] Table 2. Process parameters and styrene yield of the preparation method described in Example 3.

[0071]

[0072] The above results indicate that when the mass ratio of sulfur to precursor is 1:1, the calcination temperature is 300–700 °C, the reaction temperature is 30 °C, ethanol is used as the reaction solvent, iron oxide-iron sulfide composite is used as the catalyst, and the catalyst dosage is 0.5 g, nitrobenzene can be catalyzed to synthesize phenylhydroxylamine; among which, the yield of phenylhydroxylamine synthesis can reach 99% when the calcination temperature is 600 °C.

[0073] Example 4: Synthesis of phenylhydroxylamine with different catalyst addition amounts

[0074] 1. Add 0.01 g of iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0075] 2. Add 0.02 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0076] 3. Add 0.03 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0077] 4. Add 0.04 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0078] 5. Add 0.05 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h. Then, filter, extract, and distill to obtain the product phenylhydroxylamine.

[0079] 6. Add 0.06 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0080] 7. Add 0.07 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0081] 8. Add 0.08 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0082] The yields of phenylhydroxylamine obtained by the preparation methods described in 1 to 8 above were calculated, and the results are shown in Table 3 below:

[0083] Table 3. Process parameters and styrene yield of the preparation method described in Example 4.

[0084]

[0085] The above results indicate that at a reaction temperature of 30°C, using ethanol as the reaction solvent and an iron oxide-iron sulfide composite as the catalyst, with a catalyst dosage of 0.1–0.8 g, nitrobenzene can be catalyzed to synthesize phenylhydroxylamine; and when the catalyst dosage is 0.5–0.8 g, the yield of phenylhydroxylamine obtained from the reaction is 99%.

[0086] Example 5: Synthesis of phenylhydroxylamine using different reaction solvents

[0087] 1. Add 0.05 g of iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of ethanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0088] 2. Add 0.05 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of methanol, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0089] 3. Add 0.05 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of acetonitrile, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0090] 4. Add 0.05 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of toluene, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0091] 5. Add 0.05 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of CH2Cl2, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0092] 6. Add 0.05 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of CCl4, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0093] 7. Add 0.05 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of DMF, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0094] 8. Add 0.05 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of DMSO, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0095] 9. Add 0.05 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of n-hexane, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0096] 10. Add 0.05 g of the iron oxide-iron sulfide composite catalyst to a 20 mL reaction tube, then add 2 mL of cyclohexane, 1 mmol of nitrobenzene, and 6 mmol of hydrazine hydrate. React at 30 °C for 2 h, and then obtain the product phenylhydroxylamine by filtration, extraction, and distillation.

[0097] The yields of phenylhydroxylamine obtained by the preparation methods described in 1 to 10 above were calculated, and the results are shown in Table 4 below:

[0098] Table 4 shows the process parameters and yield of the product phenylhydroxylamine for the preparation method described in Example 5.

[0099]

[0100]

[0101] The above results indicate that nitrobenzene can be catalytically synthesized into phenylhydroxylamine using organic solvents (ethanol, methanol, acetonitrile, etc.) as reaction solvents and iron oxide-iron sulfide complex as catalysts; among them, the yield of phenylhydroxylamine can reach 99% when ethanol is used as the reaction solvent.

[0102] Example 6: Synthesis of substituted aromatic hydroxylamines using different nitrobenzene derivatives

[0103] 1. 0.05 g of the iron oxide-iron sulfide composite catalyst was added to a 20 mL reaction tube, followed by 2 mL of ethanol, 1 mmol of p-bromonitrobenzene, and 6 mmol of hydrazine hydrate. The reaction was carried out at 30 °C for 2 h. The product, 4-bromophenylhydroxylamine, was then obtained by filtration, extraction, and distillation. The liquid chromatogram of the product is shown below. Figure 4 As shown, the structural formula is shown in Equation 3 below.

[0104]

[0105] 2. 0.05 g of the iron oxide-iron sulfide composite catalyst was added to a 20 mL reaction tube, followed by 2 mL of ethanol, 1 mmol of p-methylolnitrobenzene, and 6 mmol of hydrazine hydrate. The reaction was carried out at 30 °C for 2 h. The product, 4-methylolphenylhydroxylamine, was then obtained by filtration, extraction, and distillation. The liquid chromatogram of the product is shown below. Figure 5 As shown, the structural formula is shown in Equation 4 below.

[0106]

[0107] Table 5 shows the process parameters and yield of the aromatic hydroxylamine product prepared in Example 6.

[0108]

[0109] The liquid chromatogram of the product synthesized by the above reaction is shown below. Figures 4-5 As shown above, the results indicate that using ethanol as the reaction solvent, an iron oxide-iron sulfide complex as the catalyst, and a reaction temperature of 30°C for 2 hours, the method can catalyze the synthesis of 4-bromonitrobenzene into 4-bromophenylhydroxylamine with a yield of 93%; and can catalyze the synthesis of 4-methylolnitrobenzene into 4-methylolphenylhydroxylamine with a yield of 89%. Therefore, the method described in this invention can catalyze the synthesis of phenylhydroxylamine or its derivatives from nitrobenzene, and the yield of the target product is quite considerable.

[0110] 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 selectively preparing aryl hydroxylamines, characterized in that, Application of using iron oxide-iron sulfide composite as a catalyst for the catalytic reduction of aromatic nitro compounds to aryl hydroxylamine; the preparation method of the iron oxide-iron sulfide composite catalyst includes the following steps: Iron oxide precursor was prepared by precipitation method; (1) Solution preparation: a certain amount of iron salt was dissolved in deionized water and stirred for 1-2 hours to fully dissolve the iron salt; (2) Precipitation aging: while stirring, 2-5 times the amount of precipitant was slowly added to the iron salt solution until the pH of the solution was 9-11, and the solution was stirred and aged for 10-24 hours; (3) Precipitation treatment: the above solution was filtered at normal pressure and washed with deionized water until the pH of the filtrate was 7 to ensure that the ions in the solution were washed away; the precipitate was dried at 50-100℃ to obtain the product; Sulfur and iron oxide precursors were placed separately into a vertical tube furnace, separated by high-temperature cotton. The mass ratio of the two was 1:1, 1.5:1, or 2:

1. High-purity nitrogen was continuously introduced, and the vertical furnace was heated to 600°C at a rate of 3°C / min. After holding for 1 hour, the temperature was allowed to drop naturally.

2. The method for selectively preparing aryl hydroxylamine according to claim 1, characterized in that, Using the aromatic nitro compound shown in Formula 1 as a raw material, an organic solvent as a reaction solvent, and an iron oxide-iron sulfide complex as a catalyst, an aryl hydroxylamine shown in Formula 2 was synthesized by catalytic reduction reaction: R1-R5 are selected from any one of hydrogen, halogen, sulfonic acid group, substituted or unsubstituted straight-chain or branched alkyl, alkoxy, substituted or unsubstituted aryl, amide and cyano groups.

3. The method for selectively preparing aryl hydroxylamine according to claim 1, characterized in that, The method includes the following steps: adding an iron oxide-iron sulfide composite catalyst to a reaction vessel, then adding an aromatic nitro compound, a solvent, and hydrazine hydrate, reacting at a certain temperature for a certain time, and then obtaining the product aryl hydroxylamine through a separation and purification process.

4. The method for selectively preparing aryl hydroxylamine according to claim 1, wherein the precipitant is selected from ammonia water, sodium hydroxide solution, sodium carbonate solution, potassium hydroxide solution, and potassium carbonate solution; and the iron salt is selected from ferric nitrate, ferric chloride, and ferric sulfate.

5. The method for selectively preparing aryl hydroxylamine according to claim 3, characterized in that, The molar ratio of hydrazine hydrate to aromatic nitro compound is 1 to 10:

1.

6. The method for selectively preparing aryl hydroxylamine according to claim 1, characterized in that, The ratio of the catalyst to the aromatic nitro compound is 50–80 g: 1 mol.

7. The method for selectively preparing aryl hydroxylamine according to claim 1, characterized in that, The organic solvent is selected from one or more of ethanol, methanol, toluene, dichloromethane, carbon tetrachloride, dimethyl sulfoxide, n-hexane or cyclohexane, and the amount of solvent to aromatic nitro compound is 0.1~10L:1mol.

8. The method for selectively preparing aryl hydroxylamine according to claim 1, characterized in that, The reaction temperature is 30~60°C, and the reaction time is 0.5~10 h.

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