A catalyst for the preparation of chloroaromatic amines, its preparation method and application

Abstract

This invention relates to the field of catalyst technology, and discloses a catalyst for the preparation of chloroaromatic amines, comprising palladium-based nanomaterials co-modified with an organophosphorus ligand and a metavanadate. The palladium-based nanomaterials consist of palladium nanoparticles and a carbon support. The palladium nanoparticles include zero-valent palladium and positive-valent palladium. Phosphorus in the organophosphorus ligand forms a palladium-phosphorus coordination bond with the zero-valent palladium, and metavanadate ions in the metavanadate form a vanadium-oxygen-palladium chemical bond with the positive-valent palladium. The catalyst provided by this invention exhibits high conversion and high selectivity in the catalytic hydrogenation of chloronitroaromatic hydrocarbons to prepare chloroaromatic amines, with virtually no formation of byproducts such as chlorohydroxyaromatic amines, azo compounds, and dechlorination products, and the reaction conditions are mild.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a catalyst for preparing chloroaromatic amines, its preparation method, and its application. Background Technology

[0002] Chloroaromatic amines are important raw materials in the organic industry, widely used as synthetic intermediates in pharmaceuticals, dyes, and pesticides. Methods for preparing chloroaromatic amines from chloronitroaromatics include stoichiometric reduction, electrochemical reduction, and catalytic hydrogenation. Because heterogeneous noble metal catalysts (such as palladium and platinum) can continuously activate hydrogen at low temperatures and achieve rapid hydrogenation of the nitro group, they typically exhibit high activity, making catalytic hydrogenation a more efficient route. Furthermore, selectivity is particularly important in the catalytic hydrogenation of the nitro group. On one hand, the catalytic hydrogenation of the nitro group involves multiple intermediates, including nitrosamines, hydroxylamines, azo compounds, azo compounds, and hydrazides. The rate-determining step and the key to the formation of the condensation product are both hydroxylamines; that is, hydroxylamine is crucial to both the hydrogenation conversion rate and selectivity. This is mainly because the hydrogenation rate of hydroxylamine to aniline is very slow, leading to a slower overall reaction rate. Simultaneously, its accumulation increases the extent of the condensation reaction, generating azo byproducts. The accumulation of hydroxylamine is particularly severe when the benzene ring of the nitroaromatic hydrocarbon has an electron-withdrawing group (chlorine). On the other hand, dechlorination occurs during hydrogenation, resulting in byproducts. This is mainly because the adsorption of aromatic rings on the metal surface easily leads to the hydrogenation and breakage of the carbon-chloride chemical bonds. The dehalogenation byproducts (aromatic amines) reduce the purity of the product, and the generated hydrochloric acid is corrosive to the reactor.

[0003] The key to the efficient catalytic hydrogenation of chloronitroaromatic hydrocarbons to chloroaromatic amines lies in overcoming the problems of hydroxylamine accumulation and dechlorination while possessing the high activity of heterogeneous noble metals. For the hydroxylamine accumulation problem, the use of transition metal salts is essential. Compared to the direct hydrogenation of hydroxylamine, introducing catalytically stoichiometric transition metal salt species into the catalytic system can more rapidly convert hydroxylamine to amines via a disproportionation pathway, thus efficiently solving the hydroxylamine accumulation problem. For the dechlorination problem, preventing the flat adsorption of aromatic rings on the metal surface is crucial. The segmentation effect and steric environment formed by the coordination of organic modifiers on the metal surface can effectively manipulate the interaction structure and strength between the substrate and the active site, thereby achieving high selectivity. Commonly used organic ligands include those containing phosphorus, sulfur, and nitrogen.

[0004] In conclusion, if the advantages of both aspects can be combined, high performance of the catalyst will surely be achieved. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a catalyst for the preparation of chloroaromatic amines, its preparation method, and its application. The catalyst is prepared by co-modifying palladium-based nanomaterials with organophosphorus ligands and metavanadates. It exhibits high conversion and high selectivity in the catalytic hydrogenation of chloronitroaromatic hydrocarbons to chloroaromatic amines, with virtually no byproducts such as chlorohydroxyaromatic amines, azo compounds, and dechlorination products (such as aniline). The reaction conditions are mild, the cycle stability is good, and the catalyst can be reused.

[0006] The catalyst provided by this invention for preparing chloroaromatic amines comprises palladium-based nanomaterials co-modified with organophosphorus ligands and metavanadates, wherein the palladium-based nanomaterials are composed of palladium nanoparticles and a carbon support, the palladium nanoparticles include zero-valent palladium and positive-valent palladium, the phosphorus in the organophosphorus ligand forms a palladium-phosphorus coordination bond with the zero-valent palladium, and the metavanadate ion in the metavanadate forms a vanadium-oxygen-palladium chemical bond with the positive-valent palladium.

[0007] The general formula for organophosphine ligands is PR3, where R is one of methyl, ethyl, isopropyl, cyclohexyl, or a substituted or unsubstituted phenyl group.

[0008] In one embodiment, the organophosphorus ligand is triphenylphosphine (PPh3).

[0009] In one embodiment, the palladium content is 3-20 wt% based on the total mass of the palladium nanoparticles, and may further be 3-5 wt% or 5-20 wt%.

[0010] In one embodiment, the palladium nanoparticles comprise a face-centered cubic lattice structure.

[0011] In one embodiment, the palladium nanoparticles have a particle size of less than 10 nm.

[0012] In one embodiment, the metavanadate includes at least one of sodium metavanadate, ammonium metavanadate, and potassium metavanadate.

[0013] In one embodiment, the molar ratio of palladium in the palladium nanoparticles, the organophosphorus ligand, and the metavanadate is 1:(0.1-10):(0.1-10), and may further be 1:(0.1-1):(0.1-5), 1:(0.1-5):(0.1-1), 1:(1-5):(1-5), 1:(1-10):(5-10), or 1:(5-10):(1-10).

[0014] The method for preparing the catalyst provided by the present invention involves dispersing the palladium-based nanomaterial in a first organic solvent, dissolving the organophosphorus ligand in a second organic solvent, dissolving the metavanadate in water, and then mixing them evenly to carry out the reaction, thereby obtaining the catalyst.

[0015] In one embodiment, the first organic solvent and the second organic solvent are each selected from at least one of methanol and ethanol.

[0016] The method for preparing chloroaromatic amines using the catalyst provided by this invention includes the following steps:

[0017] The catalyst and chloronitroaromatic hydrocarbons are added to a reaction vessel. After replacing the air in the reaction vessel with hydrogen, the hydrogen pressure is maintained at 0.1–0.6 MPa, and the reaction temperature is maintained at 20–70°C. The hydrogen pressure can be further selected as 0.1–0.5 MPa, 0.1–0.4 MPa, 0.2–0.5 MPa, 0.2–0.4 MPa, or 0.3–0.5 MPa; the reaction temperature can be further selected as 20–50°C, 20–40°C, 40–70°C, 40–60°C, or 30–50°C.

[0018] In one embodiment, the molar ratio of palladium in the palladium nanoparticles to the chloronitroaromatic hydrocarbon is 1:(10-1000), and may further be 1:(10-600), 1:(10-400), 1:(10-200), 1:(10-100), 1:(10-50), 1:(200-1000), 1:(400-1000), 1:(600-1000), or 1:(800-1000).

[0019] Beneficial effects

[0020] Compared with the prior art, the advantages of the present invention are as follows:

[0021] (1) This invention prepares a catalyst by co-modifying palladium-based nanomaterials with organophosphorus ligands and metavanadates. The palladium nanoparticles in the palladium-based nanomaterials include zero-valent palladium and positive-valent palladium, which form palladium-phosphorus coordination bonds and vanadium-oxygen-palladium chemical bonds, respectively. It exhibits high conversion rate in the catalytic hydrogenation of chloronitroaromatic hydrocarbons to chloroaromatic amines.

[0022] (2) The catalyst provided by the present invention is used to catalyze the reaction of chloronitroaromatic hydrocarbons to prepare chloroaromatic amines. The reaction conditions are mild, and only the chloroaromatic amine product is detected. There is basically no generation of by-products such as chlorohydroxyaromatic amines, azo compounds and dechlorination products, which has high selectivity.

[0023] (3) The catalyst provided by the present invention is used to catalyze the reaction of chloronitroaromatic hydrocarbons to prepare chloroaromatic amines. It has good cycle stability and can be reused. Attached Figure Description

[0024] Figure 1 This is a transmission electron microscope image of a 5 wt% Pd / C catalyst;

[0025] Figure 2 These are high-resolution transmission electron microscope images and corresponding fast Fourier transform analysis diagrams of a 5wt% Pd / C catalyst.

[0026] Figure 3 This is the powder X-ray diffraction pattern of a 5wt% Pd / C catalyst;

[0027] Figure 4 This is the energy dispersive X-ray spectrum of a 5 wt% Pd / C catalyst;

[0028] Figure 5 a is an in-situ X-ray photoelectron spectroscopy (Pd elemental determination) of a 5 wt% Pd / C catalyst, dried, reduced by hydrogen at 400 °C, and oxidized in air at 400 °C. Figure 5 b is an in-situ X-ray photoelectron spectroscopy (O element determination) of a 5wt% Pd / C catalyst that has been dried, reduced by hydrogen at 400°C, and oxidized by air at 400°C.

[0029] Figure 6 The graph shows the changes in conversion and product distribution of p-chloronitrobenzene hydrogenation catalyzed by a 5wt% Pd / C catalyst co-modified with PPh3 and NaVO3 as a function of reaction time.

[0030] Figure 7 The figure shows the experimental results of conversion and selectivity in the cyclic stability test of the hydrogenation of p-chloronitrobenzene catalyzed by the 5wt% Pd / C catalyst co-modified with PPh3 and NaVO3.

[0031] Figure 8 The figure shows the experimental results of the conversion and selectivity of the 5wt% Pd / C catalyst co-modified with PPh3 and NaVO3 under different hydrogen pressures during the hydrogenation of p-chloronitrobenzene.

[0032] Figure 9 The graph shows the experimental results of the conversion and selectivity of the 5wt% Pd / C catalyst co-modified with PPh3 and NaVO3 catalyzing the hydrogenation of p-chloronitrobenzene at different reaction temperatures.

[0033] Figure 10 The figure shows the experimental results of the conversion and selectivity of hydrogenation of p-chloronitrobenzene with different amounts of 5wt% Pd / C catalyst co-modified with PPh3 and NaVO3.

[0034] Figure 11 The figure shows the experimental results of the conversion and selectivity of 5wt% Pd / C catalysts co-modified with PPh3 and NaVO3 prepared according to different palladium elements in palladium nanoparticles and the molar ratio of PPh3 to NaVO3 in the hydrogenation of p-chloronitrobenzene.

[0035] Figure 12The figure shows the experimental results of the conversion and selectivity of hydrogenation of different substrates catalyzed by a 5wt% Pd / C catalyst co-modified with PPh3 and NaVO3.

[0036] Figure 13 The graph shows the changes in conversion and product distribution of p-chloronitrobenzene hydrogenation catalyzed by an unmodified 5wt% Pd / C catalyst over reaction time.

[0037] Figure 14 The graph shows the changes in conversion and product distribution of p-chloronitrobenzene hydrogenation catalyzed by a 5wt% Pd / C catalyst modified with NaVO3 as a function of reaction time.

[0038] Figure 15 This is a graph showing the changes in conversion and product distribution of p-chloronitrobenzene hydrogenation catalyzed by a 5wt% Pd / C catalyst modified with PPh3 as a function of reaction time. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solutions of the present invention, some non-limiting embodiments are further disclosed below to provide a more detailed description of the present invention.

[0040] Terminology Definition

[0041] The term "chloroaromatic hydrocarbons" refers to monosubstituted chloronitrobenzenes (ortho, meta, or para-chloronitrobenzenes) and polysubstituted chloronitrobenzenes (di or trichloronitrobenzenes).

[0042] The term "palladium (Pd)-based nanomaterials (Pd / C catalysts)" refers to palladium nanoparticles (PdNPs) supported on a carbon support. The surface of the carbon support is rich in oxygen species. There is a strong metal-support interaction between the carbon support and the palladium element, involving palladium-oxidation bonds.

[0043] The term "Pd-based nanomaterials co-modified with organophosphorus ligands and metavanadates" refers to the process of dissolving organophosphorus ligands and metavanadates separately in solution, adding them to a dispersion of Pd / C catalyst, and stirring thoroughly to perform modification.

[0044] In this invention, "room temperature" refers to ambient temperature, ranging from approximately 10°C to approximately 40°C. In some embodiments, "room temperature" refers to a temperature ranging from approximately 20°C to approximately 30°C; in other embodiments, "room temperature" refers to a temperature ranging from approximately 25°C to approximately 30°C; and in still other embodiments, "room temperature" refers to 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, etc.

[0045] Regardless of whether words such as "approximately" or "about" are used, all figures disclosed in this invention are approximate values. Based on the disclosed figures, the value of each figure may vary by less than ±10% or by a difference that is considered reasonable by those skilled in the art, such as ±1%, ±2%, ±3%, ±4%, or ±5%.

[0046] The Pd / C catalysts used in the examples with metal loadings of 3 wt%, 5 wt%, and 20 wt% were all purchased from Beijing Bailingwei Technology Co., Ltd.

[0047] Synthesis example 1

[0048] 1 g of Pd / C catalyst with a metal loading of 5 wt% was weighed and placed in a 50 mL beaker, and dried at 90 °C for 24 h in a forced-air drying oven. The Pd / C catalyst was characterized, and the results are as follows.

[0049] Figure 1 These are transmission electron microscope images of the Pd / C catalyst. The results show that PdNPs are uniformly dispersed on the surface of the carbon support, with no large particles present and particle sizes less than 10 nm.

[0050] Figure 2 These are high-resolution transmission electron microscopy images of the Pd / C catalyst and corresponding fast Fourier transform (FFT) analyses. The results show that the (111) interplanar spacing of PdNPs is... It has a face-centered cubic lattice structure and a space group of Fm-3m.

[0051] Figure 3 This is the powder X-ray diffraction pattern of the Pd / C catalyst, from... Figure 3 It can be seen that there are diffraction peaks of carbon materials near the diffraction angle of 27°, and the remaining diffraction peaks correspond to PdNPs with face-centered cubic structure. The nanoparticles are all small in size, and there are no large particles.

[0052] Figure 4 The energy dispersive X-ray spectroscopy (EDS) of the Pd / C catalyst shows that the Pd content is 4.98 wt%, which is close to the theoretical content.

[0053] Figure 5 This is the in-situ X-ray photoelectron spectroscopy (XPS) of the Pd / C catalyst. Among them, from... Figure 5 The curve for 5wt% Pd / C in a shows that PdNPs include both zero-valent and positive-valent Pd. Figure 5 The curve for 5 wt% Pd / C in section b shows that the surface of the Pd / C catalyst contains a relatively large number of oxygen species (-OH and -O-). This in-situ XPS result indicates that the Pd in ​​the Pd / C catalyst is in a mixed valence state and has abundant interfacial PdO. x (x<1) species.

[0054] Synthesis Examples 2 to 3

[0055] The difference between this synthesis example and Pd / C catalyst synthesis example 1 is that the metal loading of the Pd / C catalyst is different. 1g of Pd / C catalyst with a metal loading of 3wt% and 1g of Pd / C catalyst with a metal loading of 20wt% are used to replace 1g of Pd / C catalyst with a metal loading of 5wt% in synthesis example 1.

[0056] Synthesis example 4

[0057] Weigh 1g of the Pd / C catalyst with a metal loading of 5wt% described in Synthesis Example 1 and place it in a crucible. Reduce it in a hydrogen atmosphere at 400°C for 4h in an atmosphere furnace and allow it to cool naturally to room temperature.

[0058] The reduced Pd / C catalyst was characterized, and the in-situ X-ray photoelectron spectroscopy (XPS) of the reduced Pd / C catalyst is shown in the figure. Figure 5 As shown. Figure 5 The curve at 400℃ in section a proves that the PdNPs of the reduced Pd / C catalyst only include zero-valent Pd. Figure 5 The H2 400℃ curve in b confirms that the surface of the reduced Pd / C catalyst contains a relatively large number of -OH species. The above in-situ XPS results indicate that Pd in ​​the reduced Pd / C catalyst is in a low valence state.

[0059] Synthesis example 5

[0060] Weigh 1g of the Pd / C catalyst with a metal loading of 5wt% described in Synthesis Example 1 and place it in a crucible. Oxidize it in a muffle furnace at 400°C in an air atmosphere for 4 hours, and then allow it to cool naturally to room temperature.

[0061] The oxidized Pd / C catalyst was characterized, and the in-situ X-ray photoelectron spectroscopy (XPS) of the oxidized Pd / C catalyst is shown in the figure. Figure 5 As shown. Figure 5 The curve at 400℃ in section a proves that the PdNPs of the oxidized Pd / C catalyst only include high-valence Pd. Figure 5 The air 400℃ curve in b confirms that the surface of the oxidized Pd / C catalyst contains a large number of -O- species. The above in-situ XPS results indicate that Pd in ​​the oxidized Pd / C catalyst is in a high valence state.

[0062] Catalyst Example 1

[0063] At room temperature, 6 mg of the Pd / C catalyst from Synthesis Example 1 was ultrasonically dispersed into 3 mL of ethanol solution in a 48 mL thick-walled, pressure-resistant glass bottle, and stirred thoroughly. 1 mL of an ethanol solution of PPh3 (3.7 mg / mL) and 1 mL of an aqueous solution of NaVO3 (1.7 mg / mL) were added dropwise, and the mixture was stirred thoroughly for 10 min to obtain an ethanol dispersion of the Pd / C catalyst co-modified with PPh3 and NaVO3.

[0064] Catalyst Example 2

[0065] The difference between this embodiment and catalyst embodiment 1 is that after stirring thoroughly for 10 minutes, the dispersion was centrifuged to obtain a solid catalyst, and the solid catalyst was washed three times with a mixed solvent of water and ethanol to remove unmodified PPh3 and NaVO3. The obtained solid catalyst was redispersed in 5 mL of ethanol to obtain an ethanol dispersion of the Pd / C catalyst co-modified with PPh3 and NaVO3.

[0066] Catalyst Example 3

[0067] The difference between this embodiment and Catalyst Example 1 is that the palladium element in the palladium nanoparticles used in the Pd / C catalyst co-modified with PPh3 and NaVO3, and the molar ratio of PPh3 to NaVO3 are adjusted to 1:0.1:0.1, 1:1:5, 1:5:1 and 1:10:10, respectively, to obtain an ethanol dispersion of the Pd / C catalyst co-modified with PPh3 and NaVO3.

[0068] Catalyst Examples 4-5

[0069] The difference between Catalyst Examples 4 and 5 and Catalyst Example 1 is that the Pd / C catalyst (6 mg) prepared in Synthesis Examples 2 and 3 is used instead of the Pd / C catalyst (6 mg) in Synthesis Example 1.

[0070] Catalyst Example 6

[0071] The difference between this embodiment and Catalyst Example 1 is that 3 mL of methanol solution is used instead of 3 mL of ethanol solution in Catalyst Example 1 to obtain an ethanol dispersion of Pd / C catalyst co-modified with PPh3 and NaVO3.

[0072] Catalyst Example 7

[0073] The difference between this embodiment and Catalyst Example 1 is that 1 mL of aqueous solution of NH4VO3 (1.7 mg / mL) was used instead of 1 mL of aqueous solution of NaVO3 (1.7 mg / mL) in Catalyst Example 1 to obtain an ethanol dispersion of Pd / C catalyst co-modified with PPh3 and NH4VO3.

[0074] Catalyst Example 8

[0075] The difference between this embodiment and catalyst embodiment 7 is that, after stirring thoroughly for 10 minutes, the dispersion was filtered to obtain a solid catalyst, and the solid catalyst was washed three times with a mixed solvent of water and ethanol to remove unmodified PPh3 and NH4VO3. The obtained solid catalyst was then redispersed in 5 mL of ethanol to obtain an ethanol dispersion of the Pd / C catalyst co-modified with PPh3 and NH4VO3.

[0076] Catalyst Example 9

[0077] The difference between this embodiment and Catalyst Example 1 is that 1 mL of triethylphosphine ethanol solution (3.7 mg / mL) was used instead of 1 mL of PPh3 ethanol solution (3.7 mg / mL) in Catalyst Example 1 to obtain an ethanol dispersion of Pd / C catalyst co-modified with triethylphosphine and NaVO3.

[0078] Catalyst Comparative Example 1

[0079] At room temperature, 6 mg of the Pd / C catalyst from Synthesis Example 1 was ultrasonically dispersed into 5 mL of ethanol solution in a 48 mL thick-walled glass pressure-resistant bottle, and stirred thoroughly for 10 min to obtain an ethanol dispersion of the unmodified Pd / C catalyst.

[0080] Catalyst Comparative Example 2

[0081] At room temperature, 6 mg of the Pd / C catalyst from Synthesis Example 1 was ultrasonically dispersed into 4 mL of ethanol solution in a 48 mL thick-walled, pressure-resistant glass bottle, and stirred thoroughly. 1 mL of an aqueous solution of NaVO3 (1.7 mg / mL) was added dropwise, and the mixture was stirred thoroughly for 10 min to obtain an ethanol dispersion of the NaVO3-modified Pd / C catalyst.

[0082] Catalyst Comparative Example 3

[0083] At room temperature, 6 mg of the Pd / C catalyst from Synthesis Example 1 was ultrasonically dispersed into 4 mL of ethanol solution in a 48 mL thick-walled, pressure-resistant glass bottle, and stirred thoroughly. 1 mL of an aqueous solution of PPh3 (3.7 mg / mL) was added dropwise, and the mixture was stirred thoroughly for 10 min to obtain an ethanol dispersion of the PPh3-modified Pd / C catalyst.

[0084] Catalyst Comparative Example 4

[0085] At room temperature, 6 mg of the reduced Pd / C catalyst from Synthesis Example 4 was ultrasonically dispersed into 3 mL of ethanol solution in a 48 mL thick-walled, pressure-resistant glass bottle, and stirred thoroughly. 1 mL of PPh3 ethanol solution (3.7 mg / mL) and 1 mL of NaVO3 aqueous solution (1.7 mg / mL) were added dropwise, and the mixture was stirred thoroughly for 10 min to obtain an ethanol dispersion of the reduced Pd / C catalyst co-modified with PPh3 and NaVO3.

[0086] Catalyst Comparative Example 5

[0087] At room temperature, 6 mg of the oxidized Pd / C catalyst from Synthesis Example 5 was ultrasonically dispersed into 3 mL of ethanol solution in a 48 mL thick-walled, pressure-resistant glass bottle, and stirred thoroughly. 1 mL of an ethanol solution of PPh3 (3.7 mg / mL) and 1 mL of an aqueous solution of NaVO3 (1.7 mg / mL) were added dropwise, and the mixture was stirred thoroughly for 10 min to obtain an ethanol dispersion of the oxidized Pd / C catalyst co-modified with PPh3 and NaVO3.

[0088] Catalyst Comparative Example 6

[0089] At room temperature, 6 mg of the Pd / C catalyst from Synthesis Example 1 was ultrasonically dispersed into 3 mL of ethanol solution in a 48 mL thick-walled, pressure-resistant glass bottle, and stirred thoroughly. 1 mL of PPh3 ethanol solution (3.7 mg / mL) and 1 mL of NaVO4 aqueous solution (1.7 mg / mL) were added dropwise, and the mixture was stirred thoroughly for 10 min to obtain an ethanol dispersion of PPh3, NaVO4, and the Pd / C catalyst.

[0090] Example 1 of preparation of chloroaromatic amines

[0091] 1 mL of anhydrous ethanol solution of p-chloronitrobenzene (P-CNB) (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle from Catalyst Example 1. Hydrogen gas at 0.1 MPa was introduced, and the bottle was purged for 1 min to remove air. The pressure-resistant bottle was then sealed, retaining 0.1 MPa of hydrogen gas. The pressure-resistant bottle was heated and maintained at 60°C. The conversion and selectivity of the reaction process were detected using high-performance liquid chromatography (HPLC), and the results are shown in [Figure number missing]. Figure 6 As shown. From Figure 6 As can be seen, P-CNB was basically completely converted within 20 minutes, with a conversion rate of over 99.9%. Even when the reaction time was extended to 40 minutes, no dechlorination product aniline (AN) was detected, and no p-chlorohydroxyaniline (P-CPHA) was detected during the reaction. Only the target product p-chloroaniline (P-CAN) was detected, with a yield of over 99.9%.

[0092] The solid catalyst was recovered by centrifugation and redispersed in 5 mL of ethanol. Under the same conditions, it was repeatedly used in the catalytic reaction of P-CNB, and its cycle stability was tested. The results are as follows: Figure 7 As shown. From Figure 7 As can be seen, the catalyst remained inactive after six cycles, with P-CNB conversion rates all above 99.9% and P-CAN yields all above 99.9%. The catalyst exhibits good cycle stability and can be reused.

[0093] Under the same conditions, hydrogen pressure was adjusted to 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, and 0.6 MPa, respectively, and hydrogenation reactions were carried out accordingly. The conversion rate and selectivity of the reaction process were detected using high-performance liquid chromatography (HPLC). The results are shown in [Figure number missing]. Figure 8 As shown, conversion rate is represented by a bar chart, and selectivity is represented by a scatter plot. From Figure 8 As can be seen, after the reaction proceeded for 30 minutes, the conversion rate of P-CNB was above 99.9%, and the yield of P-CAN was also above 99.9%.

[0094] Under the same conditions, the reaction temperatures were adjusted to 20℃, 30℃, 40℃, 50℃, and 70℃, respectively, for hydrogenation reactions. The conversion rate and selectivity of the reaction process were detected using high-performance liquid chromatography (HPLC). The results are shown in [Figure number missing]. Figure 9 As shown, conversion rate is represented by a bar chart, and selectivity is represented by a scatter plot. From Figure 9 As can be seen, after the reaction proceeded for 30 minutes, the conversion rate of P-CNB was above 99.9%, and the yield of P-CAN was also above 99.9%.

[0095] Under the same conditions, the amount of P-CNB was adjusted so that the molar ratio of Pd to P-CNB in ​​the catalyst was 1:10, 1:50, 1:100, 1:200, 1:400, 1:600, 1:800, and 1:1000, respectively, and hydrogenation reactions were carried out accordingly. The conversion rate and selectivity of the reaction process were detected by high performance liquid chromatography. The results are shown in [Figure number missing]. Figure 10 As shown, conversion rate is represented by a bar chart, and selectivity is represented by a scatter plot. From Figure 10 As can be seen, after 60 minutes of reaction, the conversion rate of P-CNB was above 99.9%, and the yield of P-CAN was also above 99.9%.

[0096] Example 2 of preparation of chloroaromatic amines

[0097] This example differs from Example 1 in that 1 mL of anhydrous ethanol solution of P-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle used in Example 2 for hydrogenation. The conversion and selectivity of the reaction were detected using high-performance liquid chromatography (HPLC). After 40 min of reaction, the conversion rate of P-CNB was above 99.9%, and the yield of the target product P-CAN was also above 99.9%, indicating that good conversion and selectivity can be achieved by co-modifying the Pd / C catalyst with only modified amounts of PPh3 and NaVO3.

[0098] Example 3 of preparation of chloroaromatic amines

[0099] This embodiment differs from Example 1 in that 1 mL of anhydrous ethanol solution of LP-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle used in Example 3 of the catalyst for hydrogenation. The conversion rate and selectivity of the reaction process were detected using high-performance liquid chromatography (HPLC), and the results are shown in [Figure 1]. Figure 11 As shown, conversion rate is represented by a bar chart, and selectivity is represented by a scatter plot. From Figure 11 As can be seen, after 60 minutes of reaction, the conversion rate of P-CNB was above 99.9%, and the yield of P-CAN was also above 99.9%.

[0100] Preparation Examples of Chloroaromatic Amines 4-5

[0101] The difference between Examples 4 and 5 of the preparation of chloroaromatic amines and Example 1 is that 1 mL of anhydrous ethanol solution of P-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottles used in Examples 4 and 5 of the catalyst preparation for hydrogenation reactions. The conversion rate and selectivity of the reaction process were detected using high-performance liquid chromatography (HPLC). After 60 min of reaction, the conversion rate of P-CNB was above 99.9% and the yield of P-CAN was also above 99.9%.

[0102] Example 6 of preparation of chloroaromatic amines

[0103] The difference between this example and Example 1 for the preparation of chloroaromatic amines is that 1 mL of anhydrous ethanol solution of P-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle used in Example 6 for hydrogenation. The conversion rate and selectivity of the reaction were detected using high-performance liquid chromatography (HPLC). After 30 min of reaction, the conversion rate of P-CNB was above 99.9%, and the yield of the target product P-CAN was also above 99.9%, indicating that good conversion rate and selectivity can be achieved using methanol as a solvent.

[0104] Example 7 of preparation of chloroaromatic amines

[0105] This embodiment differs from Example 1 in that 1 mL of anhydrous P-CNB ethanol solution (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle used in Catalyst Example 8 for hydrogenation. The conversion and selectivity of the reaction were detected using high-performance liquid chromatography (HPLC). After 40 min of reaction, the conversion rate of P-CNB was above 99.9%, and the yield of the target product P-CAN was also above 99.9%.

[0106] Example 8 of the preparation of chloroaromatic amines

[0107] This example differs from Example 1 in that 1 mL of anhydrous ethanol solution of P-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle used in Catalyst Example 7 for hydrogenation. The conversion and selectivity of the reaction were detected using high-performance liquid chromatography (HPLC). After 40 min of reaction, the conversion rate of P-CNB was above 99.9%, and the yield of the target product P-CAN was also above 99.9%, indicating that good conversion and selectivity can be achieved by co-modifying the Pd / C catalyst with only modified amounts of PPh3 and NH4VO3.

[0108] Example 9 of the preparation of chloroaromatic amines

[0109] The difference between this example and Example 1 for the preparation of chloroaromatic amines is that 1 mL of anhydrous ethanol solution of P-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle used in Catalyst Example 9 for hydrogenation reaction. The conversion rate and selectivity of the reaction process were detected using high-performance liquid chromatography (HPLC). After 60 min of reaction, the conversion rate of P-CNB was consistently above 99.9%, and the yield of P-CAN was also consistently above 99.9%.

[0110] Example 10 of the preparation of chloroaromatic amines

[0111] This example differs from Example 1 of the preparation of chloroaromatic amines in that the substrates used in the preparation of chloroaromatic amines are different. Anhydrous ethanol solution of o-chloronitrobenzene (1 mL, 157.8 mg / mL), anhydrous ethanol solution of m-chloronitrobenzene (1 mL, 157.8 mg / mL), anhydrous ethanol solution of 2,3-dichloronitrobenzene (1 mL, 192.0 mg / mL), anhydrous ethanol solution of 2,4-dichloronitrobenzene (1 mL, 192.0 mg / mL), anhydrous ethanol solution of 2,5-dichloronitrobenzene (1 mL, 192.0 mg / mL), and anhydrous ethanol solution of 3,5-dichloronitrobenzene (1 mL, 192.0 mg / mL) were used instead of the P-CNB anhydrous ethanol solution (1 mL, 157.8 mg / mL) used in Example 1 of the preparation of chloroaromatic amines for hydrogenation reactions. The conversion rate and selectivity of the reaction process were detected by high performance liquid chromatography, and the results are shown in [Figure 1]. Figure 12As shown, conversion rate is represented by a bar chart, and selectivity is represented by a scatter plot. From Figure 12 As can be seen, the conversion rates of the corresponding chloronitrobenzene are all above 99.9%, and the yields of chloroaniline are also all above 99.9%.

[0112] Preparation of chloroaromatic amines: Comparative Example 1

[0113] The difference between this comparative example and Example 1 for the preparation of chloroaromatic amines is that 1 mL of anhydrous ethanol solution of LP-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle used in Comparative Example 1 for hydrogenation reaction. The conversion rate and selectivity of the reaction process were detected by high performance liquid chromatography, and the results are shown in [Figure 1]. Figure 13 As shown.

[0114] from Figure 13 It can be seen that P-CNB is basically completely converted within 15 minutes. Extending the reaction time to 40 minutes, although the nitro group is rapidly converted, a large amount of the byproduct AN is generated, and dechlorination exceeds 50% at 40 minutes. Simultaneously, a certain amount of P-CPHA is also generated during the reaction. Comparing Examples 1-7 for the preparation of chloroaromatic amines, it can be seen that the co-modification of PPh3 and metavanadate enables the Pd / C catalyst to overcome the problems of hydroxylamine accumulation and dechlorination in the catalytic hydrogenation of chloronitroaromatic hydrocarbons to chloroaromatic amines.

[0115] Preparation of chloroaromatic amines: Comparative Example 2

[0116] The difference between this comparative example and Example 1 for the preparation of chloroaromatic amines is that 1 mL of anhydrous ethanol solution of LP-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle in Comparative Example 2 for hydrogenation reaction. The conversion rate and selectivity of the reaction process were detected by high performance liquid chromatography, and the results are shown in [Figure 1]. Figure 14 As shown.

[0117] from Figure 14 It can be seen that P-CNB is basically completely converted within 20 min. Extending the reaction time to 40 min, although the nitro group is rapidly converted, a large amount of the byproduct AN is generated, and dechlorination exceeds 30% at 40 min. Simultaneously, a small amount of P-CPHA is also generated during the reaction. Comparing Examples 1-7 for the preparation of chloroaromatic amines, it can be seen that the co-modification of PPh3 and metavanadate enables the Pd / C catalyst to overcome the problems of hydroxylamine accumulation and dechlorination in the catalytic hydrogenation of chloronitroaromatic hydrocarbons to chloroaromatic amines, while the single modification effect of NaVO3 is poor.

[0118] Preparation of chloroaromatic amines: Comparative Example 3

[0119] The difference between this comparative example and Example 1 for the preparation of chloroaromatic amines is that 1 mL of anhydrous ethanol solution of LP-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle in Comparative Example 3 for hydrogenation reaction. The conversion rate and selectivity of the reaction process were detected by high performance liquid chromatography, and the results are shown in [Figure 1]. Figure 15 As shown.

[0120] from Figure 15 It can be seen that the conversion rate of P-CNB at 40 min is less than 10%, indicating an excessively low reaction rate, with P-CAN being the main detected product. Comparing Examples 1-7 for the preparation of chloroaromatic amines, it can be seen that the co-modification of PPh3 and metavanadate enables the Pd / C catalyst to overcome the problems of hydroxylamine accumulation and dechlorination during the catalytic hydrogenation of chloronitroaromatic hydrocarbons to chloroaromatic amines, while the effect of PPh3 as a single modification is poor.

[0121] Preparation of chloroaromatic amines: Comparative Example 4

[0122] The difference between this comparative example and Example 1 for the preparation of chloroaromatic amines is that 1 mL of anhydrous ethanol solution of P-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle in Comparative Example 4 for hydrogenation reaction. The conversion rate and selectivity of the reaction process were detected by high performance liquid chromatography. The conversion rate of P-CNB at 40 min was less than 10%, and the reaction rate was too low. The main product detected was P-CPHA, and a small amount of P-CAN was also detected. This indicates that the mixed valence state of Pd in ​​the Pd / C catalyst (containing zero-valent and high-valent Pd) is the key to constructing a high-performance catalyst.

[0123] Preparation of chloroaromatic amines: Comparative Example 5

[0124] The difference between this comparative example and Example 1 for the preparation of chloroaromatic amines is that 1 mL of anhydrous ethanol solution of P-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle in Comparative Example 5 for hydrogenation reaction. The conversion rate and selectivity of the reaction process were detected by high performance liquid chromatography. The conversion rate of P-CNB at 40 min was less than 10%, and the reaction rate was too low. The main product detected was P-CPHA, and a small amount of P-CAN was also detected. This indicates that the mixed valence state of Pd in ​​the Pd / C catalyst (containing zero-valent and high-valent Pd) is the key to constructing a high-performance catalyst.

[0125] Preparation of chloroaromatic amines: Comparative Example 6

[0126] The difference between this comparative example and Example 1 for the preparation of chloroaromatic amines is that 1 mL of anhydrous ethanol solution of P-CNB (157.8 mg / mL) was added to the thick-walled glass pressure-resistant bottle in the catalyst comparative example 6 for hydrogenation reaction. The conversion rate and selectivity of the reaction process were detected by high performance liquid chromatography. The results showed that the conversion rate of P-CNB was extremely low, indicating that NaVO4 cannot coordinate with high-valence Pd like metavanadate, and therefore cannot stabilize high-valence Pd and construct a high-performance catalyst.

[0127] Other experiments have shown that the metavanadate in this invention is also irreplaceable by vanadium pentoxide (V₂O₅), vanadium dioxide (VO₂), vanadium trioxide (V₂O₃), vanadium bis(acetylacetone)oxide (VO(acac)₂), and vanadium acetylacetone (V(acac)₃).

[0128] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A catalyst for the preparation of chloroaromatic amines, characterized in that, This includes palladium-based nanomaterials co-modified with organophosphorus ligands and metavanadates, wherein the palladium-based nanomaterials consist of palladium nanoparticles and a carbon support, and the palladium nanoparticles include zero-valent palladium and positive-valent palladium. The palladium nanoparticles are in a mixed valence state and have abundant interfacial PdO. x Species, where x < 1; The phosphorus in the organophosphorus ligand forms a palladium-phosphorus coordination bond with the zero-valent palladium, and the metavanadate ion in the metavanadate forms a vanadium-oxygen-palladium chemical bond with the positive-valent palladium.

2. The catalyst according to claim 1, characterized in that, Based on the total mass of the palladium nanoparticles, the palladium content is 3~20 wt%.

3. The catalyst according to claim 1, characterized in that, The palladium nanoparticles have a face-centered cubic lattice structure.

4. The catalyst according to claim 1, characterized in that, The palladium nanoparticles have a particle size of less than 10 nm.

5. The catalyst according to claim 1, characterized in that, The metavanadate includes at least one of sodium metavanadate, ammonium metavanadate, and potassium metavanadate.

6. The catalyst according to claim 1, characterized in that, The molar ratio of palladium in the palladium nanoparticles, the organophosphorus ligand, and the metavanadate is 1:(0.1~10):(0.1~10).

7. A method for preparing a catalyst according to any one of claims 1 to 6, characterized in that, The palladium-based nanomaterials were dispersed in a first organic solvent, the organophosphine ligands were dissolved in a second organic solvent, and the metavanadate was dissolved in water. All the solutions were then mixed thoroughly and reacted to obtain the catalyst. The palladium-based nanomaterial is composed of palladium nanoparticles and a carbon support, wherein the palladium nanoparticles include zero-valent palladium and positive-valent palladium.

8. A preparation method as described in claim 7, characterized in that, The first organic solvent and the second organic solvent are each selected from at least one of methanol and ethanol.

9. A method for preparing chloroaromatic amines using the catalyst according to any one of claims 1 to 6, characterized in that, Includes the following steps: The catalyst and chloronitroaromatic hydrocarbons are added to a reaction vessel. After replacing the air in the reaction vessel with hydrogen, the hydrogen pressure is maintained at 0.1~0.6 MPa and the reaction temperature is 20~70℃ to carry out the reaction. The chloronitroaromatic hydrocarbons are selected from p-chloronitrobenzene, o-chloronitrobenzene, m-chloronitrobenzene, 2,3-dichloronitrobenzene, 2,4-dichloronitrobenzene, 2,5-dichloronitrobenzene, and 3,5-dichloronitrobenzene.

10. A method for preparing chloroaromatic amines as described in claim 9, characterized in that, The molar ratio of palladium in the palladium nanoparticles to the chloronitroaromatic hydrocarbon is 1:(10~1000).

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