Method for selective hydrogenation reaction of aromatic nitro compound

Abstract

The invention relates to an aromatic nitro compound selective hydrogenation reaction method, which comprises: in the presence of hydrogen, contacting an aromatic nitro compound with a catalyst to carry out a selective hydrogenation reaction, the catalyst comprises a carbon-coated nickel-molybdenum composite material, the carbon-coated nickel-molybdenum composite material has a core-shell structure, a shell layer is a carbon-coated layer, and an inner core comprises a nickel active component and a molybdenum active component; in the carbon-coated nickel-molybdenum composite material, the atomic ratio of nickel to molybdenum is (1.5-9.0): 1, and the atomic ratio of oxygen to molybdenum is (1.8-3.1): 1. According to the method disclosed by the invention, the selective hydrogenation reaction of the aromatic nitro compound can be carried out in a green, efficient and mild manner under the condition of no additive, and relatively high target product selectivity can be obtained.

Description

Technical Field

[0001] This disclosure relates to the field of selective hydrogenation reactions, and more specifically, to a method for the selective hydrogenation of aromatic nitro compounds. Background Technology

[0002] Aromatic amines are a crucial class of organic intermediates and fine chemical products, widely used in industries such as dyes, pharmaceuticals, pesticides, and polymers. The synthesis of aromatic amines via catalytic hydrogenation of aromatic nitro compounds offers advantages such as high atom economy, stable product quality, and environmental friendliness, making it a primary industrial method for producing aromatic amines. However, selectively hydrogenating nitro groups while retaining other easily reducible groups in nitrobenzenes with multiple substituents remains a research challenge in this field. This selective hydrogenation is particularly difficult when nitro groups and vinyl or acetylene groups are simultaneously present in the reactants.

[0003] For example, patent CN 107216255 B discloses a method for the catalytic hydrogenation of 4-nitrophenylacetylene to 4-aminophenylacetylene using Pt-Zn / SnO2-Sb2O3 as a catalyst. Although the noble metal Pt is used, the reaction pressure still reaches 4 MPa, and the reaction conditions are quite harsh, so there is a need to further improve the catalytic activity.

[0004] As can be seen from the above, providing a green, low-cost catalyst that can selectively hydrogenate nitrostyrene and nitrophenylacetylene compounds to prepare vinylaniline and acetylene aniline compounds has important industrial value for the green synthesis of aromatic amine compounds. Summary of the Invention

[0005] The purpose of this disclosure is to provide a method for the selective hydrogenation of aromatic nitro compounds. This method enables the selective hydrogenation of aromatic nitro compounds under relatively mild conditions without the use of additives, achieving a green and efficient process.

[0006] To achieve the above objectives, this disclosure provides a method for the selective hydrogenation reaction of an aromatic nitro compound, the method comprising: contacting the aromatic nitro compound with a catalyst in the presence of hydrogen to carry out the selective hydrogenation reaction; the catalyst comprising a carbon-coated nickel-molybdenum composite material; The carbon-coated nickel-molybdenum composite material has a core-shell structure, with a carbon coating layer as the shell and a core comprising nickel active components and molybdenum active components. In the carbon-coated nickel-molybdenum composite material, the atomic ratio of nickel to molybdenum is (1.5-9.0):1, and the atomic ratio of oxygen to molybdenum is (1.8-3.1):1; The aromatic nitro compounds include one or more of nitrophenylacetylene compounds and nitrostyrene compounds.

[0007] Optionally, the atomic ratio of nickel to molybdenum is (1.8-8.0):1, and the atomic ratio of oxygen to molybdenum is (1.9-3.0):1.

[0008] Optionally, relative to the total weight of the composite material, the carbon content is 10.0-25.0% by weight, the hydrogen content is 0.5-2.0% by weight, and the total content of oxygen, nickel and molybdenum is 73.0-89.5% by weight.

[0009] Optionally, the nickel active component includes nickel nanoparticles, wherein the average particle size of the nickel nanoparticles is 5-25 nm, preferably 6-16 nm.

[0010] Optionally, the method for preparing carbon-coated nickel-molybdenum composite materials includes the following steps: S1. Mix the nickel source, molybdenum source, organic polyacid and the first solvent to obtain a mixed solution, and then remove the first solvent from the mixed solution to obtain the composite material precursor; S2. The composite material precursor is heat-treated under a processing atmosphere; In step S1, the molar ratio of the nickel source (calculated as nickel) to the molybdenum source (calculated as molybdenum) is (1.5-9.0):1; In step S2, the isothermal temperature of the heat treatment is 500-800℃; The processing atmosphere includes an inert atmosphere and / or a reducing atmosphere.

[0011] Optionally, the nickel source includes one or more of nickel hydroxide, organic salts of nickel, nickel carbonate, and basic nickel carbonate; The molybdenum source includes one or more of ammonium molybdate, molybdenum pentachloride, and molybdenum acetylacetonate; The organic polyacids include one or more of ethylenediaminetetraacetic acid, iminodiacetic acid, diethylenetriaminepentaacetic acid, 1,3-propanediaminetetraacetic acid, citric acid, maleic acid, pyromellitic acid, terephthalic acid, and malic acid. The first solvent includes one or more of water, methanol, and ethanol.

[0012] Optionally, in step S1, the molar ratio of the nickel source (calculated as nickel) to the molybdenum source (calculated as molybdenum) is (1.8-8.0):1; The molar ratio of the nickel source (based on nickel element) to the organic polyacid (based on carboxyl groups) is 1:(2.1-9.0), preferably 1:(3.0-8.0).

[0013] Optionally, in step S2, the heat treatment conditions include: a heating rate of 1-20℃ / min, preferably 2-10℃ / min; and a holding time of 1-360min, preferably 10-180min. The constant temperature for the heat treatment is 500-700℃; The inert atmosphere includes one or more of nitrogen, argon, neon, and helium; The reducing atmosphere includes hydrogen.

[0014] Optionally, the conditions for the selective hydrogenation reaction include: a temperature of 50-140°C, preferably 60-110°C; a pressure of 0.5-5 MPa, preferably 0.8-3 MPa; and a weight ratio of the carbon-coated nickel-molybdenum composite material to the aromatic nitro compound of 1:(1-50).

[0015] Optionally, the selective hydrogenation reaction can be carried out in the presence of a second solvent; The concentration of the aromatic nitro compound in the second solvent is 8-700 g / L; The second solvent includes one or more of water and saturated monohydric alcohols having 1-3 carbon atoms; Preferably, the second solvent is a mixture of isopropanol and water; more preferably, the volume ratio of isopropanol to water is (1-20):1. The nitrophenylacetylene compounds include 3-nitrophenylacetylene and / or 4-nitrophenylacetylene; The nitrostyrene compounds include 3-nitrostyrene and / or 4-nitrostyrene.

[0016] Through the above technical solution, this disclosure uses a carbon-coated nickel-molybdenum composite material with a specific composition and structure as a catalyst to catalyze the selective hydrogenation reaction of aromatic nitro compounds to aromatic amino compounds. Under relatively mild conditions without the use of additives, the selective reduction of nitro groups is achieved, resulting in a high selectivity for the target product.

[0017] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is the X-ray diffraction pattern of the carbon-coated nickel-molybdenum composite material A1 prepared in Preparation Example 1 of this disclosure.

[0019] Figure 2This is a Ni and Mo elemental distribution diagram of the carbon-coated nickel-molybdenum composite material A1 prepared in Preparation Example 1 of this disclosure.

[0020] Figure 3 This is the X-ray diffraction pattern of the carbon-coated nickel-molybdenum composite material A2 prepared in Preparation Example 2 of this disclosure.

[0021] Figure 4 This is the X-ray diffraction pattern of the carbon-coated nickel-molybdenum composite material D1 prepared in Comparative Preparation Example 1 of this disclosure.

[0022] Figure 5 This is the X-ray diffraction pattern of the carbon-coated nickel-molybdenum composite material D2 prepared in Comparative Preparation Example 2 of this disclosure. Detailed Implementation

[0023] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0024] This disclosure provides a method for the selective hydrogenation reaction of an aromatic nitro compound, the method comprising: contacting the aromatic nitro compound with a catalyst in the presence of hydrogen to carry out the selective hydrogenation reaction; the catalyst comprising a carbon-coated nickel-molybdenum composite material; The carbon-coated nickel-molybdenum composite material has a core-shell structure, with a carbon coating layer as the shell and a core comprising nickel active components and molybdenum active components. In the carbon-coated nickel-molybdenum composite material, the atomic ratio of nickel to molybdenum is (1.5-9.0):1, and the atomic ratio of oxygen to molybdenum is (1.8-3.1):1; The aromatic nitro compounds include one or more of nitrophenylacetylene compounds and nitrostyrene compounds.

[0025] The carbon coating layer of the composite material disclosed herein can effectively protect the internal active component core. The material is non-flammable and can be stored in air for a long time. The carbon coating layer can be a graphitized carbon coating layer. The core material includes nickel active components and molybdenum active components with a specific atomic ratio. When used in the selective hydrogenation reaction of aromatic nitro compounds, it can reduce the reduction of carbon-carbon triple bonds and carbon-carbon double bonds, improve the reduction rate of nitro groups under relatively mild conditions without the use of additives, and obtain a high selectivity for the target product.

[0026] According to one embodiment of the present disclosure, in the composite material, the atomic ratio of nickel to molybdenum is (1.8-8.0):1, and the atomic ratio of oxygen to molybdenum is (1.9-3.0):1; the composite material having the above composition is applied to the selective hydrogenation reaction of aromatic nitro compounds, especially the selective hydrogenation reaction of nitrophenylacetylene compounds and nitrostyrene compounds, and can obtain a high selectivity for the target product.

[0027] According to one embodiment of the present disclosure, the carbon content is 10.0-25.0% by weight, the hydrogen content is 0.5-2.0% by weight, and the total content of oxygen, nickel and molybdenum is 73.0-89.5% by weight relative to the total weight of the composite material.

[0028] According to one embodiment of this disclosure, the nickel active component includes nickel nanoparticles, the average particle size of which is 5-25 nm, preferably 6-16 nm, and the average particle size can be calculated using the Scherrer formula for XRD testing.

[0029] According to one embodiment of this disclosure, a method for preparing a carbon-coated nickel-molybdenum composite material includes the following steps: S1. Mix the nickel source, molybdenum source, organic polyacid and the first solvent to obtain a mixed solution, and then remove the first solvent from the mixed solution to obtain the composite material precursor; S2. The composite material precursor is heat-treated under a processing atmosphere; In step S1, the molar ratio of the nickel source (calculated as nickel) to the molybdenum source (calculated as molybdenum) is (1.5-9.0):1; In step S2, the isothermal temperature of the heat treatment is 500-800℃; The processing atmosphere includes an inert atmosphere and / or a reducing atmosphere.

[0030] This disclosure involves mixing a nickel source, a molybdenum source, a multi-component organic acid, and a first solvent to form a homogeneous solution. The first solvent is then removed from the homogeneous solution to obtain a composite material precursor. The precursor is then subjected to high-temperature heat treatment under an inert and / or reducing atmosphere to obtain a carbon-coated nickel-molybdenum composite material. This preparation method is green and efficient, achieving 100% metal atom utilization, and generates no heavy metal wastewater, making it suitable for industrial production. The composite material prepared using this method has a specific nickel-molybdenum and molybdenum-oxygen ratio, uniform core size, and small nickel nanoparticle size, which effectively improves the catalytic activity of the composite material and enables highly selective hydrogenation of aromatic nitro compounds.

[0031] According to one embodiment of this disclosure, the nickel source used is of a type conventional in the art, which can be soluble in a first solvent. Preferably, it includes one or more of nickel hydroxide, organic acid salts and inorganic acid salts. More preferably, it includes one or more of nickel hydroxide, organic acid salts of nickel, nickel carbonate and basic nickel carbonate. When the nickel source includes two or more types, this disclosure does not impose specific restrictions on their proportions.

[0032] According to one embodiment of this disclosure, the type of molybdenum source used is conventional in the art and can be soluble in a first solvent. Preferably, it includes one or more of ammonium molybdate, molybdenum pentachloride, and molybdenum acetylacetonate. When the molybdenum source includes two or more types, this disclosure does not impose specific restrictions on their proportions.

[0033] According to one embodiment of this disclosure, the organic polyacid used is of a type conventional in the art, soluble in a first solvent, and capable of forming a complex with a nickel source and a molybdenum source. The number of carboxyl groups in the organic polyacid can be, for example, 2-4. The organic polyacid preferably includes one or more of ethylenediaminetetraacetic acid, iminodiacetic acid, diethylenetriaminepentaacetic acid, 1,3-propanediaminetetraacetic acid, citric acid, maleic acid, trimesic acid, terephthalic acid, and malic acid. When the organic polyacid includes two or more, this disclosure does not impose specific limitations on their proportions.

[0034] According to one embodiment of this disclosure, the first solvent is of a type conventional in the art, which can form a homogeneous solution with the nickel source, the molybdenum source, and the organic polybasic acid, including one or more of water and saturated monohydric alcohols having 1-3 carbon atoms, preferably including one or more of water, methanol, and ethanol; this disclosure does not impose specific limitations on the amount of the first solvent, as long as it can form a homogeneous solution with the nickel source, the molybdenum source, and the organic polybasic acid.

[0035] In order to further control the ratio of nickel and molybdenum in the composite material and improve the selectivity of the target product, according to one embodiment of the present disclosure, in step S1, the molar ratio of the nickel source (calculated as nickel element) to the molybdenum source (calculated as molybdenum element) is (1.8-8.0):1.

[0036] In order to make the composite material have a suitable size and improve its catalytic activity, according to one embodiment of the present disclosure, the molar ratio of nickel source (calculated as nickel element) to organic polyacid (calculated as carboxyl group) is 1:(2.1-9.0), preferably 1:(3.0-8.0).

[0037] According to one embodiment of this disclosure, the mixing conditions in step S1 are not specifically limited. For example, they may include: a time of 0.1-5 hours, a temperature of 40-125°C, and mixing can be carried out under stirring conditions. The stirring rate is not specifically limited, as long as a homogeneous solution can be formed.

[0038] According to one embodiment of this disclosure, in step S1, the removal of the first solvent from the mixed solution can be performed using any feasible prior art, including freeze drying, oven drying at 100-150°C, or spray drying at 200-230°C.

[0039] To improve the catalytic activity of the composite material, according to one embodiment of this disclosure, in step S2, the heat treatment can be carried out in a tube furnace, with the following conditions: a heating rate of 1-20℃ / min, preferably 2-10℃ / min; and a holding time of 1-360min, preferably 10-180min.

[0040] To further improve the catalytic activity of the composite material, according to one embodiment of this disclosure, the isothermal temperature for heat treatment is 500-700°C.

[0041] According to one embodiment of this disclosure, the type of inert atmosphere is conventional in the art, such as one or more of nitrogen, argon, neon and helium, and the flow rate of the inert atmosphere can be 50-200 mL / min. When the inert atmosphere includes two or more types, this disclosure does not impose specific limitations on their proportions.

[0042] According to one embodiment of this disclosure, the reducing atmosphere includes hydrogen, and the flow rate of the reducing atmosphere can be 2-100 mL / min.

[0043] According to one embodiment of this disclosure, the processing atmosphere includes an inert atmosphere and a reducing atmosphere, wherein the flow rate ratio of the inert atmosphere to the reducing atmosphere is 1:(0.02-1).

[0044] According to one embodiment of this disclosure, the conditions for the selective hydrogenation reaction include: a temperature of 50-140°C, preferably 60-110°C; a pressure of 0.5-5 MPa, preferably 0.8-3 MPa, more preferably 1-2 MPa; and a weight ratio of the carbon-coated nickel-molybdenum composite material to the aromatic nitro compound of 1:(1-50), preferably 1:(2-20).

[0045] According to one embodiment of this disclosure, the selective hydrogenation reaction can be carried out in the presence of a second solvent; the concentration of the aromatic nitro compound in the second solvent is 8-700 g / L.

[0046] According to one embodiment of this disclosure, the second solvent includes one or more of water and saturated monohydric alcohols having 1-3 carbon atoms, preferably a mixed solvent of isopropanol and water, wherein the volume ratio of isopropanol to water is (1-20):1.

[0047] According to one embodiment of this disclosure, the nitrophenylacetylene compound includes 3-nitrophenylacetylene and / or 4-nitrophenylacetylene; the nitrostyrene compound includes 3-nitrostyrene and / or 4-nitrostyrene.

[0048] In this disclosure, the target product of the selective hydrogenation reaction of nitrophenylacetylene compounds is an aminophenylacetylene compound, and the target product of the selective hydrogenation reaction of nitrostyrene compounds is an aminostyrene compound.

[0049] In this disclosure, the selective hydrogenation reaction can be carried out in a reaction vessel.

[0050] The present invention will be described in detail below through embodiments, but is not limited to the following embodiments.

[0051] The surface morphology of the material was characterized by transmission electron microscopy (TEM). The TEM used was a JEM-2100 (Nippon Electron Ltd.), and the TEM testing conditions were: accelerating voltage of 200 kV.

[0052] The analysis of carbon (C), hydrogen (H), and oxygen (O) was performed on an Elementar Micro Cube elemental analyzer. The specific operating methods and conditions are as follows: the sample was combusted at high temperature in the presence of oxygen, converting C and H in the sample into CO2 and H2O, respectively. After removing interfering factors, the reaction gases were carried by the carrier gas into the chromatographic column for separation, and finally detected by a thermal conductivity detector. Oxygen analysis utilized high-temperature decomposition; in the presence of a carbon catalyst, oxygen in the sample was converted into CO, which was then detected using a thermal conductivity detector.

[0053] The total metallic element content is the normalized result after deducting the contents of carbon, hydrogen, oxygen, and nitrogen. The mass ratio of nickel (Ni) and molybdenum (Mo) was measured using a Rigaku ZSX Primus IV wavelength dispersive X-ray fluorescence spectrometer (XRF) in Japan. The method is as follows: After the powder sample is pressed into a pellet, the sample is scanned from the BU on the XRF spectrometer. Based on the intensity of the elements present in the sample obtained from the scan, and the sensitivity of the instrument to pure substances of these elements, the content of each element in the sample is calculated by computer through theoretical calculation and mathematical correction.

[0054] The XRD diffractometer used was an X'Pert Pro model purchased from PA Nalytical in the Netherlands. The test conditions were: Cu target, Kα rays, tube voltage of 40 kV, tube current of 40 mA, and 2θ scan range of 5° to 80°.

[0055] The average particle size was calculated using XRD testing and the Scherrer formula.

[0056] After the reaction was completed, the products were subjected to chromatographic analysis, and the reactant conversion rate and the selectivity of the target product were calculated using the following formulas: Conversion rate (%) = (mass of reactants reacted / mass of reactants added) × 100%; Selectivity (%) = mass of target product / mass of reaction product × 100%.

[0057] Preparation Example 1 S1. Weigh 14.55 g of basic nickel carbonate (nickel content 40.33% by weight), 3.53 g of ammonium molybdate tetrahydrate, and 29.42 g of citric acid monohydrate (the molar ratio of basic nickel carbonate, ammonium molybdate tetrahydrate, and citric acid monohydrate based on carboxyl groups is 5:1:21) and add them to 150 mL of deionized water. Stir at 110 °C for 0.5 h to obtain a homogeneous solution, and continue heating and evaporating for 3 h. Transfer the concentrated solution to a forced-air drying oven and dry at 120 °C for 4 h to remove the deionized water. Grind the obtained solid to obtain the composite material precursor. S2. Take 10 g of the obtained composite material precursor and place it in a ceramic boat. Then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas at a flow rate of 150 mL / min, and heat it to 600℃ at a rate of 10℃ / min. After holding the temperature for 120 min, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain carbon-coated nickel-molybdenum composite material A1. The parameters are listed in Table 1.

[0058] Figure 1 This is the X-ray diffraction pattern of carbon-coated nickel-molybdenum composite material A1. As can be seen from the figure, the main spectral peaks correspond to the diffraction peaks of fcc-Ni.

[0059] Figure 2 This is a distribution diagram of Ni and Mo elements in carbon-coated nickel-molybdenum composite material A1. The diagram shows that the distribution of Ni and Mo elements is relatively consistent.

[0060] Preparation Example 2 S1. Weigh 14.55 g of basic nickel carbonate (nickel content 40.33% by weight), 8.83 g of ammonium molybdate tetrahydrate, and 42.03 g of citric acid monohydrate (the molar ratio of basic nickel carbonate, ammonium molybdate tetrahydrate, and citric acid monohydrate based on carboxyl groups is 2:1:12) and add them to 150 mL of deionized water. Stir at 110 °C for 0.5 h to obtain a homogeneous solution, and continue heating and evaporating for 3 h. Transfer the concentrated solution to a forced-air drying oven and dry at 120 °C for 4 h to remove the deionized water. Grind the obtained solid to obtain the composite material precursor. S2. Take 10 g of the obtained composite material precursor and place it in a ceramic boat. Then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas at a flow rate of 150 mL / min, and heat it to 600℃ at a rate of 10℃ / min. After holding the temperature for 120 min, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain carbon-coated nickel-molybdenum composite material A2. The parameters are listed in Table 1.

[0061] Figure 3 This is the X-ray diffraction pattern of carbon-coated nickel-molybdenum composite material A2. As can be seen from the figure, the main peaks in the spectrum correspond to the diffraction peaks of fcc-Ni.

[0062] Preparation Example 3 Carbon-coated nickel-molybdenum composite material A3 was prepared using the method of Preparation Example 1, except that the molar ratio of basic nickel carbonate (calculated as nickel element), ammonium molybdate tetrahydrate (calculated as molybdenum element), and citric acid monohydrate (calculated as carboxyl group) was 8.5:1:31.5. The parameters of composite material A3 are listed in Table 1.

[0063] Preparation Example 4 Carbon-coated nickel-molybdenum composite material A4 was prepared using the method of Preparation Example 1, except that the isothermal temperature in step S2 was 725℃. The parameters of composite material A4 are listed in Table 1.

[0064] Preparation Example 5 S1. Weigh 14.55g of basic nickel carbonate (nickel content 40.33% by weight), 8.15g of molybdenum acetylacetonate and 31.52g of citric acid monohydrate (the molar ratio of basic nickel carbonate, molybdenum acetylacetonate and citric acid monohydrate based on nickel content, molybdenum content, and carboxyl content is 4:1:18) and add them to 150mL of deionized water. Stir at 110℃ to obtain a homogeneous solution and continue heating to evaporate. Transfer the concentrated solution to a forced-air drying oven and dry at 120℃ to remove the deionized water. Grind the obtained solid to obtain the composite material precursor. S2. Take 10 g of the obtained composite material precursor and place it in a ceramic boat. Then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas at a flow rate of 150 mL / min, and heat it to 600℃ at a rate of 2℃ / min. After holding the temperature for 60 min, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain carbon-coated nickel-molybdenum composite material A5. The parameters are listed in Table 1.

[0065] Comparative Preparation Example 1 S1. Weigh 14.55 g of basic nickel carbonate (nickel content 40.33% by weight), 1.77 g of ammonium molybdate tetrahydrate, and 25.22 g of citric acid monohydrate (the molar ratio of basic nickel carbonate, ammonium molybdate tetrahydrate, and citric acid monohydrate based on carboxyl groups is 10:1:36) and add them to 150 mL of deionized water. Stir at 110 °C for 0.5 h to obtain a homogeneous solution, and continue to heat and evaporate at 110 °C for 3 h. Transfer the concentrated solution to a forced-air drying oven and dry at 120 °C for 4 h to remove the deionized water. Grind the obtained solid to obtain the composite material precursor. S2. Take 10 g of the obtained composite material precursor and place it in a ceramic boat. Then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas at a flow rate of 150 mL / min, and heat it to 600℃ at a rate of 10℃ / min. After holding the temperature for 120 min, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain carbon-coated nickel-molybdenum composite material D1. The parameters are listed in Table 1.

[0066] Figure 4 This is the X-ray diffraction pattern of carbon-coated nickel-molybdenum composite material D1. As can be seen from the figure, the main diffraction peaks are those corresponding to fcc-Ni.

[0067] Comparative Preparation Example 2 Take 10 g of the precursor obtained in Preparation Example 2 and place it in a ceramic boat. Then place the ceramic boat in the constant temperature zone of a tube furnace, introduce nitrogen gas at a flow rate of 150 mL / min, and heat it to 450 °C at a rate of 10 °C / min. After holding the temperature for 120 min, stop heating and cool it to room temperature under a nitrogen atmosphere to obtain carbon-coated nickel-molybdenum composite material D2. The parameters are listed in Table 1.

[0068] Figure 5 This is the X-ray diffraction pattern of carbon-coated nickel-molybdenum composite material D2. As can be seen from the figure, the spectrum mainly contains diffraction peaks corresponding to fcc-Ni, and also contains diffraction peaks corresponding to C.

[0069] Comparative preparation example 3 S1. Weigh 21.01g of citric acid monohydrate and 14.55g of basic nickel carbonate (the molar ratio of basic nickel carbonate based on nickel element to citric acid monohydrate based on carboxylate ion is 1:3) and add them to 150mL of deionized water. Stir at 100℃ to obtain a homogeneous solution, and continue to heat to dryness to remove the deionized water. Grind the obtained solid to obtain the precursor.

[0070] S2. The obtained precursor was placed in a ceramic boat, and then the ceramic boat was placed in the constant temperature zone of a tube furnace. Nitrogen gas was introduced at a flow rate of 100 mL / min, and the temperature was increased to 600℃ at a rate of 10℃ / min. After holding the temperature for 120 min, the heating was stopped, and the mixture was cooled to room temperature under a nitrogen atmosphere to obtain carbon-coated nickel nanocomposite material D3. The parameters are listed in Table 1.

[0071] Example 1 80 mg of carbon-coated nickel-molybdenum composite material A1, 294 mg of 3-nitrophenylacetylene (2 mmol), 27 mL of isopropanol, and 3 mL of water were added to a reactor. After purging the reactor with H2 four times, H2 was introduced again to bring the pressure inside the reactor to 1.0 MPa. The temperature was raised to the predetermined reaction temperature of 80 °C and the reaction was continued for 65 min before heating was stopped. After cooling to room temperature, the pressure was released. The selectivity of the byproduct aminophenyl ethane was 8.0%. Other reaction results are listed in Table 1.

[0072] Example 2 80 mg of carbon-coated nickel-molybdenum composite material A2, 294 mg of 3-nitrophenylacetylene (2 mmol), 27 mL of isopropanol, and 3 mL of water were added to a reactor. After purging the reactor with H2 four times, H2 was introduced again to bring the pressure inside the reactor to 1.0 MPa. The temperature was raised to the predetermined reaction temperature of 80 °C and the reaction was continued for 130 min before heating was stopped. After cooling to room temperature, the pressure was released. The reaction results are listed in Table 1.

[0073] Example 3 80 mg of carbon-coated nickel-molybdenum composite material A1, 294 mg of 3-nitrostyrene (2 mmol), 27 mL of isopropanol, and 3 mL of water were added to a reactor. H2 was introduced to replace the reactor four times, and then H2 was introduced again to bring the pressure inside the reactor to 1.0 MPa. The temperature was raised to the predetermined reaction temperature of 95 °C, and the reaction was continued for 95 min before heating was stopped. After cooling to room temperature, the pressure was released. The reaction results are listed in Table 1.

[0074] Example 4 80 mg of carbon-coated nickel-molybdenum composite material A3, 294 mg of 3-nitrophenylacetylene (2 mmol), 27 mL of isopropanol, and 3 mL of water were added to a reactor. After purging the reactor with H2 four times, H2 was introduced again to bring the pressure inside the reactor to 1.0 MPa. The temperature was raised to the predetermined reaction temperature of 80 °C and the reaction was continued for 60 min before heating was stopped. After cooling to room temperature, the pressure was released. The reaction results are listed in Table 1.

[0075] Example 5 80 mg of carbon-coated nickel-molybdenum composite material A4, 294 mg of 3-nitrophenylacetylene (2 mmol), 27 mL of isopropanol, and 3 mL of water were added to a reactor. After purging the reactor with H2 four times, H2 was introduced again to bring the pressure inside the reactor to 1.0 MPa. The temperature was raised to the predetermined reaction temperature of 80 °C and the reaction was continued for 95 min before heating was stopped. After cooling to room temperature, the pressure was released. The reaction results are listed in Table 1.

[0076] Example 6 80 mg of carbon-coated nickel-molybdenum composite material A5, 294 mg of 3-nitrophenylacetylene (2 mmol), 27 mL of isopropanol, and 3 mL of water were added to a reactor. After purging the reactor with H2 four times, H2 was introduced again to bring the pressure inside the reactor to 1.0 MPa. The temperature was raised to the predetermined reaction temperature of 80 °C and the reaction was continued for 80 min. Heating was then stopped, and the reactor was cooled to room temperature before the pressure was released. The reaction results are listed in Table 1.

[0077] Comparative Example 1 80 mg of carbon-coated nickel-molybdenum composite material D1, 294 mg of 3-nitrophenylacetylene (2 mmol), 27 mL of isopropanol, and 3 mL of water were added to a reactor. After purging the reactor with H2 four times, H2 was introduced again to bring the pressure inside the reactor to 1.0 MPa. The temperature was raised to the predetermined reaction temperature of 65 °C and the reaction was continued for 110 min before heating was stopped. After cooling to room temperature, the pressure was released. The reaction results are listed in Table 1.

[0078] Comparative Example 2 80 mg of carbon-coated nickel-molybdenum composite material D2, 294 mg of 3-nitrophenylacetylene (2 mmol), 27 mL of isopropanol, and 3 mL of water were added to a reactor. After purging the reactor with H2 four times, H2 was introduced again to bring the pressure inside the reactor to 1.0 MPa. The temperature was raised to the predetermined reaction temperature of 80 °C and the reaction was continued for 100 min before heating was stopped. After cooling to room temperature, the pressure was released. The reaction results are listed in Table 1.

[0079] Comparative Example 3 80 mg of carbon-coated nickel nanocomposite material D3, 294 mg of 3-nitrophenylacetylene (2 mmol), 27 mL of isopropanol, and 3 mL of water were added to a reaction vessel. After purging the reaction vessel with H2 four times, H2 was purged again to bring the pressure inside the reaction vessel to 1.0 MPa. The temperature was raised to the predetermined reaction temperature of 120 °C and the reaction was continued for 10 min before heating was stopped. After cooling to room temperature, the pressure was released. The reaction results are listed in Table 1.

[0080] Table 1

[0081] Based on the above data, it can be seen that the carbon-coated nickel-molybdenum composite material prepared by the method of this disclosure can achieve a highly efficient selective hydrogenation reaction of aromatic nitro compounds under relatively mild conditions without the use of additives. Furthermore, based on the comparison of Examples 1, 2 and Example 4, it can be seen that when the atomic ratio of nickel to molybdenum is in the preferred range of (1.8-8.0):1, the catalytic performance of the composite material can be further improved, and higher product selectivity can be obtained.

[0082] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0083] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0084] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for the selective hydrogenation of aromatic nitro compounds, the method comprising: The aromatic nitro compound is contacted with a catalyst in the presence of hydrogen to carry out the selective hydrogenation reaction; characterized in that the catalyst comprises a carbon-coated nickel-molybdenum composite material; The carbon-coated nickel-molybdenum composite material has a core-shell structure, with a carbon coating layer as the shell and a core comprising nickel active components and molybdenum active components. In the carbon-coated nickel-molybdenum composite material, the atomic ratio of nickel to molybdenum is (1.5-9.0):1, and the atomic ratio of oxygen to molybdenum is (1.8-3.1):1; The aromatic nitro compounds include one or more of nitrophenylacetylene compounds and nitrostyrene compounds.

2. The method according to claim 1, wherein, The atomic ratio of nickel to molybdenum is (1.8-8.0):1, and the atomic ratio of oxygen to molybdenum is (1.9-3.0):

1.

3. The method according to claim 1, wherein, Relative to the total weight of the composite material, the carbon content is 10.0-25.0% by weight, the hydrogen content is 0.5-2.0% by weight, and the total content of oxygen, nickel and molybdenum is 73.0-89.5% by weight.

4. The method according to claim 1, wherein, The nickel active component includes nickel nanoparticles, the average particle size of which is 5-25 nm, preferably 6-16 nm.

5. The method according to claim 1, wherein, The method for preparing carbon-coated nickel-molybdenum composite materials includes the following steps: S1. Mix the nickel source, molybdenum source, organic polyacid and the first solvent to obtain a mixed solution, and then remove the first solvent from the mixed solution to obtain the composite material precursor; S2. The composite material precursor is heat-treated under a processing atmosphere; In step S1, the molar ratio of the nickel source (calculated as nickel) to the molybdenum source (calculated as molybdenum) is (1.5-9.0):1; In step S2, the isothermal temperature of the heat treatment is 500-800℃; The processing atmosphere includes an inert atmosphere and / or a reducing atmosphere.

6. The method according to claim 5, wherein, The nickel source includes one or more of nickel hydroxide, organic salts of nickel, nickel carbonate, and basic nickel carbonate; The molybdenum source includes one or more of ammonium molybdate, molybdenum pentachloride, and molybdenum acetylacetonate; The organic polyacids include one or more of ethylenediaminetetraacetic acid, iminodiacetic acid, diethylenetriaminepentaacetic acid, 1,3-propanediaminetetraacetic acid, citric acid, maleic acid, pyromellitic acid, terephthalic acid, and malic acid. The first solvent includes one or more of water, methanol, and ethanol.

7. The method according to claim 5, wherein, In step S1, the molar ratio of the nickel source (calculated as nickel) to the molybdenum source (calculated as molybdenum) is (1.8-8.0):1; The molar ratio of the nickel source (based on nickel element) to the organic polyacid (based on carboxyl groups) is 1:(2.1-9.0), preferably 1:(3.0-8.0).

8. The method according to claim 5, wherein, In step S2, the heat treatment conditions include: a heating rate of 1-20℃ / min, preferably 2-10℃ / min; and a holding time of 1-360min, preferably 10-180min. The constant temperature for the heat treatment is 500-700℃; The inert atmosphere includes one or more of nitrogen, argon, neon, and helium; The reducing atmosphere includes hydrogen.

9. The method according to claim 1, wherein, The conditions for the selective hydrogenation reaction include: a temperature of 50-140℃, preferably 60-110℃; a pressure of 0.5-5MPa, preferably 0.8-3MPa; and a weight ratio of the carbon-coated nickel-molybdenum composite material to the aromatic nitro compound of 1:(1-50).

10. The method according to claim 1, wherein, The selective hydrogenation reaction can be carried out in the presence of a second solvent; The concentration of the aromatic nitro compound in the second solvent is 8-700 g / L; The second solvent includes one or more of water and saturated monohydric alcohols having 1-3 carbon atoms; Preferably, the second solvent is a mixture of isopropanol and water; more preferably, the volume ratio of isopropanol to water is (1-20):

1. The nitrophenylacetylene compounds include 3-nitrophenylacetylene and / or 4-nitrophenylacetylene; The nitrostyrene compounds include 3-nitrostyrene and / or 4-nitrostyrene.

Images