CN110396046B - Method for preparing arylamine by stable and efficient catalytic hydrogenation - Google Patents

Abstract

A stable and efficient method for preparing arylamine by catalytic hydrogenation of aromatic nitro compound is characterized in that the aromatic nitro compound is added with a stabilizer in a reaction solvent, and the aromatic nitro compound and hydrogen are subjected to catalytic hydrogenation reaction under the action of a catalyst in the presence of the stabilizer to obtain the arylamine. The stabilizing agent is added in the preparation process, so that the problem of performance reduction of the hydrogenation catalyst caused by impurities contained in the raw materials is effectively solved, and the stability of the catalyst and the yield of the product are improved.

Description

Method for preparing arylamine by stable and efficient catalytic hydrogenation

Technical Field

The invention relates to a method for preparing arylamine by stable and efficient catalytic hydrogenation, belonging to the technical field of catalytic hydrogenation.

Background

Arylamine is an important organic chemical intermediate, and is widely applied to the fields of medicines, materials, dyes, pesticides and the like.

The method for preparing the arylamine compound by catalytic hydrogenation reduction of the nitroaromatic compound is emphasized and widely applied because of the advantages of environmental friendliness, recyclable catalyst and the like. However, when aromatic amines are prepared from aromatic nitro compounds by catalytic hydrogenation reduction, the performance of hydrogenation catalysts is often affected by impurity compounds contained in industrial raw materials, and the stability of the catalysts is further reduced.

Therefore, there is a need to solve the problem of catalyst performance degradation caused by impurities in the raw materials in the preparation of aromatic amines by catalytic hydrogenation as soon as possible.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a method for preparing arylamine by catalytic hydrogenation with stability and high efficiency, and the method effectively solves the problem of performance reduction of a hydrogenation catalyst caused by raw material impurities by adding a stabilizer in the preparation process, and improves the stability of the catalyst and the product yield.

The technical problem of the invention is solved by the following technical scheme:

the improvement of the method for preparing the arylamine by utilizing the catalytic hydrogenation of the aromatic nitro compound is that a stabilizing agent is added into a reaction solvent, and the aromatic nitro compound shown in the formula (I) and hydrogen react under the action of a catalyst to obtain the arylamine shown in the formula (II) through the catalytic hydrogenation reaction in the presence of the stabilizing agent;

in the formula, -R₁、-R₂、-R₃、-R₄、-R₅Each is independently selected from one of the following groups: -H, -F, -Cl, -Br, -I, -CH₃、-CH₂CH₃、-OH、-NH₂、-OCH₃、-COOCH₃、-COOH、-SO₃H、-NHCH₂CH₃、N(CH₃)₂。

In the stable and efficient method for preparing the arylamine by catalytic hydrogenation, the stabilizer is one of acetic acid, boric acid, formaldehyde, acetaldehyde, hydrogen peroxide, peroxyacetic acid and peroxybenzoic acid.

In the stable and efficient method for preparing the arylamine by catalytic hydrogenation, the using amount of the stabilizer is 0.001-0.5 wt%, preferably 0.002-0.2 wt% of the mass of the aromatic nitro compound.

The method for preparing arylamine by stable and efficient catalytic hydrogenation is characterized in that the catalyst is an activated carbon-loaded bimetallic catalyst, the activated carbon is used as a carrier, a noble metal is used as an active component, Cu is used as an auxiliary agent, and the catalyst is prepared by adopting an isometric multistep dipping method, and specifically comprises the following steps:

a. weighing activated carbon, and preparing a mixed solution containing a noble metal compound, a Cu compound and furfural, wherein the volume of the mixed solution is the same as that of the activated carbon according to the pore volume of the activated carbon;

b. dropwise adding the mixed solution into the activated carbon at 20-30 ℃, and uniformly stirring;

c. vacuum drying the impregnated activated carbon catalyst at 20-30 ℃ for 4-20h to obtain a dried primary catalyst product;

d. preparing a mixed solution containing a noble metal compound, a Cu compound and furfural with the same volume as the pore volume of the activated carbon again, and repeating the step b and the step c;

e. repeatedly dipping for many times to ensure that the content of the metal dipped on the active carbon is consistent with the required load;

f. the finally obtained dried catalyst is added in H₂Reducing for 3-10h at 50-80 ℃ in the atmosphere to obtain the activated carbon loaded bimetallic catalyst.

In the stable and efficient method for preparing arylamine by catalytic hydrogenation, the noble metal compound in the step a is H₂PdCl₄、Pd(NO₃)₂、H₂PtCl₆Or Pt (NO)₃)₂One of (1); the Cu-containing compound is CuCl₂Or Cu (NO)₃)₂。

In the step a, the concentrations of the noble metal, Cu and furfural in the mixed solution are 0.01-0.05 g/ml, 0.01-0.05 g/ml and 0.01-0.05 g/ml respectively.

In the steps e and f, the loading amount of the noble metal in the active carbon loaded bimetallic catalyst is 1-10 wt%, preferably 2-8 wt%; the loading amount of Cu is 1-5 wt%, preferably 2-4 wt%.

In the step a, the granularity of the activated carbon is 100-1000 meshes; the specific surface area is 600-1800 m²(ii)/g; the pore volume is 0.3 to 0.8 ml/g.

According to the method for preparing the arylamine by the stable and efficient catalytic hydrogenation, the dosage of the active carbon supported bimetallic catalyst is 0.1-3.0 wt% of the mass of the aromatic nitro compound.

According to the method for preparing the arylamine by the stable and efficient catalytic hydrogenation, methanol, ethanol or water is used as a reaction solvent in the catalytic hydrogenation reaction, and the addition amount of the catalyst is 0.5-3.0g/g in terms of the mass of the aromatic nitro compound.

The stable and efficient method for preparing the arylamine by the catalytic hydrogenation adopts a kettle type batch reaction process or a kettle type continuous reaction process, and the kettle type batch reaction process specifically comprises the following steps: adding an aromatic nitro compound, a solvent, a catalyst and a stabilizer into a reaction kettle, wherein the feeding mass ratio of the aromatic nitro compound to the solvent to the catalyst to the stabilizer is 1: (0.5-3): (0.1-3.0 wt%): (0.001-0.5 wt%), closing the reaction kettle; replacing air in the reaction kettle with nitrogen, and replacing the nitrogen with hydrogen; then raising the temperature in the reaction kettle to 50-150 ℃, preferably 60-120 ℃, controlling the hydrogen pressure to be 0.4-3 MPa, preferably 0.8-2 MPa, and stirring for reaction; after the reaction is finished, separating to obtain an arylamine product;

the kettle type continuous reaction process specifically comprises the following steps:

a. adding an aromatic nitro compound, a solvent, a catalyst and a stabilizer into a single reaction kettle or a plurality of reaction kettles connected in series in advance, replacing air in the kettle with nitrogen, replacing nitrogen in the kettle with hydrogen, maintaining the pressure of the hydrogen in the reaction kettles at 0.4-3 MPa (preferably 0.8-2 MPa), raising the temperature of materials in the kettles, maintaining the temperature at 50-150 ℃ (preferably 60-120 ℃), and opening a stirrer;

b. continuously inputting a mixture of an aromatic nitro compound, a solvent, a catalyst and a stabilizer into a first hydrogenation reaction kettle through a material pump; if the single-kettle continuous hydrogenation is adopted, the reacted materials are continuously discharged from a discharge hole of the reaction kettle to a gas-liquid separator, and simultaneously, hydrogen is continuously introduced to maintain the reaction pressure; if a plurality of serially connected reaction kettles are used for continuous hydrogenation, the materials continuously overflow from the first hydrogenation reaction kettle to the second hydrogenation reaction kettle in sequence by utilizing the height difference among the kettles until the last hydrogenation reaction kettle is reached, the reacted materials are continuously discharged from the discharge hole of the last reaction kettle to the gas-liquid separator, and simultaneously, hydrogen is continuously introduced into each reaction kettle to maintain the reaction pressure;

c. the separated hydrogen can be used for hydrogenation reaction after being purified, the separated liquid material is filtered, the solid catalyst obtained by filtering is recycled, the liquid product obtained by filtering enters a product storage tank, and the arylamine product is obtained after separation and purification.

The invention has the beneficial effects that:

1) after the stabilizer is added in the preparation process, the influence of impurities in the raw materials on the performance of the hydrogenation catalyst is obviously reduced, and the stability of the catalytic hydrogenation reaction is improved.

2) The stabilizer has wide application range and better applicability to the preparation of arylamine by catalytic hydrogenation of aromatic nitro compounds.

3) The Cu in the active carbon loaded bimetallic catalyst can play a synergistic role with the noble metal, so that the adsorption and activation of the raw material can be promoted during the catalytic hydrogenation reaction, and the content of high activated hydrogen on the noble metal is reduced, so that the catalytic hydrogenation reaction rate is improved, and the high selectivity of a target product is maintained.

4) The catalyst of the invention adopts a multi-step isometric impregnation method, and the concentration of the metal-containing solution is low, so that the metal can be highly dispersed on the surface of the active carbon.

5) The catalyst is prepared by using furfural as an auxiliary agent and directly reducing with hydrogen without alkali liquor precipitation, and has the advantages of small metal particle size, high catalytic activity and good stability.

Detailed Description

The present invention is further illustrated by the following examples.

Preparation of active carbon loaded bimetallic catalyst

Example 1

10g of active carbon with the granularity of 1000 meshes and the specific surface area of 1800m is weighed²The pore volume is 0.6mL/g, 6mL of H-containing solution is prepared first₂PdCl₄、CuCl₂And a mixed solution of furfural (the mixed solution contained Pd of 0.01g, Cu of 0.01g, and furfural of 0.01 g); dropwise adding the mixed solution into the activated carbon, and uniformly stirring; drying the impregnated catalyst at 25 ℃ for 10h in vacuum; preparing 6mL of the same mixed solution, performing equal-volume impregnation, and drying under the same conditions, so as to perform equal-volume impregnation for 5 times in total; the dried catalyst is added in H₂Reducing for 6h at 60 ℃ under the atmosphere to obtain the 3 percent Pd-3 percent Cu/C catalyst.

Example 2

10g of active carbon with the granularity of 100 meshes and the specific surface area of 1000m is weighed²The pore volume is 0.3mL/g, 3mL of H-containing solution is prepared₂PtCl₆、CuCl₂And a mixed solution of furfural (the mass of Pt contained in the mixed solution was 0.02g, the mass of Cu contained in the mixed solution was 0.01g, and the mass of furfural contained in the mixed solution was 0.02 g); dropwise adding the mixed solution into the activated carbon at 25 ℃, and uniformly stirring; drying the impregnated catalyst at 20 ℃ for 20 hours in vacuum; preparing 3mL of the same mixed solution, performing equal-volume impregnation, and drying under the same conditions, wherein the equal-volume impregnation is performed for 10 times in total; the dried catalyst is added in H₂Reducing for 3h at 80 ℃ in the atmosphere to obtain the 6 percent Pt-3 percent Cu/C catalyst.

Example 3

10g of activated carbon with the granularity of 400 meshes and the specific surface area of 1600m is weighed²The pore volume is 0.8mL/g, and 8mL of Pt (NO) is prepared first₃)₂、Cu(NO₃)₂And a mixed solution of furfural (the mixed solution contained Pt by mass 0.01g, Cu by mass 0.01g, and furfural by mass 0.02 g); dropwise adding the mixed solution into the activated carbon at 20 ℃, and uniformly stirring; drying the impregnated catalyst at 20 ℃ for 7 hours in vacuum; preparing 8ml of the same mixed solution, performing equal-volume impregnation, and drying under the same conditions, so as to perform equal-volume impregnation for 5 times in total; the dried catalyst is added in H₂Reducing for 5h at 70 ℃ in the atmosphere to obtain the 4% Pt-4% Cu/C catalyst.

Example 4

10g of active carbon is weighed, the granularity is 800 meshes, and the specific surface area is 600m²The pore volume is 0.3mL/g, 3mL Pd (NO) is first prepared₃)₂、Cu(NO₃)₂And a mixed solution of furfural (the mixed solution contained Pd of 0.05g, Cu of 0.025g, and furfural of 0.05 g); dropwise adding the mixed solution into the activated carbon at 30 ℃, and uniformly stirring; drying the impregnated catalyst at 30 ℃ for 4h in vacuum; preparing 3mL of the same mixed solution, performing equal-volume impregnation, and drying under the same conditions, wherein the equal-volume impregnation is performed for 2 times in total; the dried catalyst is added in H₂Reducing for 9h at 50 ℃ in the atmosphere to obtain the 3 percent Pd-1.5 percent Cu/C catalyst.

Example 5

Weighing 10g of activated carbon, the granularity of 300 meshes and the specific surface area of 1400m²The pore volume is 0.5mL/g, 5mL of H-containing solution is prepared first₂PdCl₄、Cu(NO₃)₂And a mixed solution of furfural (the mass of Pd contained in the mixed solution was 0.04g, the mass of Cu contained in the mixed solution was 0.02g, and the mass of furfural contained in the mixed solution was 0.03 g); dropwise adding the mixed solution into the activated carbon at 25 ℃, and uniformly stirring; drying the impregnated catalyst at 30 ℃ for 5 hours in vacuum; preparing 5mL of the same mixed solution, performing equal-volume impregnation, and drying under the same conditions, so as to perform equal-volume impregnation for 5 times in total; the dried catalyst is added in H₂Reducing for 8h at 60 ℃ under the atmosphere to obtain

10% Pd-5% Cu/C catalyst.

Example 6

10g of active carbon is weighed, the granularity is 300 meshes, and the specific surface area is 1300m²The pore volume is 0.5mL/g, 5mL of H-containing solution is prepared first₂PdCl₄、Cu(NO₃)₂And a mixed solution of furfural (the mixed solution contained Pd of 0.01g, Cu of 0.01g, and furfural of 0.01 g); dropwise adding the mixed solution into the activated carbon at 25 ℃, and uniformly stirring; drying the impregnated catalyst at 30 ℃ for 5 hours in vacuum; 5mL of the sameMixing the solution, performing equal-volume impregnation, and drying under the same conditions, so as to perform equal-volume impregnation for 2 times in total; the dried catalyst is added in H₂Reducing for 5h at 70 ℃ under the atmosphere to obtain the 1 percent Pd-1 percent Cu/C catalyst.

Example 7-example 14

Example 7-example 14 examine the effect of stabilizer species on the performance of hydrogenation catalysts.

Adding 100g of o-chloronitrobenzene, 200mL of ethanol, 0.5g of the 3% Pd-3% Cu/C catalyst prepared in the example 1 into a 500mL stainless steel reaction kettle, adding no stabilizer or 0.01g of the stabilizer, closing the reaction kettle, replacing air in the reaction kettle with nitrogen for three times, and replacing the nitrogen with hydrogen for three times; heating to 60 ℃, controlling the hydrogen pressure to be 2MPa, starting stirring at the stirring speed of 900r/min, and reacting for 1 h; stopping the reaction, cooling to room temperature, taking out the reaction solution, filtering to remove the catalyst, and analyzing the filtrate by gas chromatography. The catalyst obtained by filtering is applied to the next application experiment, and the application experiment conditions are the same as above. The results of the experiment are shown in table 1.

TABLE 1 Effect of stabilizer types on the Performance of hydrogenation catalysts

Example 15 example 20

Example 15-example 20 the hydrogenation performance of different catalysts was examined.

Adding 100g of m-methyl nitrobenzene, 100ml of methanol and 0.5g of activated carbon loaded bimetallic catalyst into a 500ml stainless steel reaction kettle, adding 0.01g of formaldehyde, closing the reaction kettle, replacing air in the reaction kettle with nitrogen for three times, and then replacing with hydrogen for three times; heating to 70 ℃ and hydrogen pressure of 1.0MPa, starting stirring at the stirring speed of 900r/min, and reacting for 1 h; stopping the reaction, cooling to room temperature, taking out the reaction solution, filtering to remove the catalyst, and analyzing the filtrate by gas chromatography. The catalyst obtained by filtering is applied to the next application experiment, and the application experiment conditions are the same as above. The results of the experiment are shown in table 2.

TABLE 2 catalytic hydrogenation performance of different activated carbon loaded bi-metals

Example 21 example 25

The catalytic hydrogenation performance of the stabilizer and the activated carbon loaded bimetallic catalyst when different aromatic nitro compounds are used as raw materials is investigated.

Adding 100g of aromatic nitro compound raw material, 200ml of ethanol, 1g of the second 6% Pt-3% Cu/C catalyst of the embodiment and 0.1g of stabilizer into a 500ml stainless steel reaction kettle, closing the reaction kettle, replacing air in the reaction kettle with nitrogen for three times, and then replacing with hydrogen for three times; heating to 100 ℃ and hydrogen pressure of 1.0MPa, starting stirring at the stirring speed of 900r/min, and reacting for 2 h; stopping the reaction, cooling to room temperature, taking out the reaction solution, filtering to remove the catalyst, and analyzing the filtrate by gas chromatography. The catalyst obtained by filtering is applied to the next application experiment, and the application experiment conditions are the same as above. The results of the experiment are shown in table 3.

TABLE 3 catalytic hydrogenation effect of different aromatic nitro compounds

Example 26

Example 26 investigation of the catalyst application Performance

Adding 100g of methyl p-nitrobenzoate, 200ml of ethanol and 1g of the 6% Pt-3% Cu/C catalyst prepared in example 2 into a 500ml stainless steel reaction kettle, adding 0.05g of benzoic peroxide, closing the reaction kettle, replacing the air in the reaction kettle with nitrogen for three times, and replacing the nitrogen with hydrogen for three times; heating to 100 ℃, controlling the hydrogen pressure to be 1.0MPa, starting stirring at the stirring speed of 900r/min, and reacting for 2 h; stopping the reaction, cooling to room temperature, taking out the reaction solution, filtering to remove the catalyst, and analyzing the filtrate by gas chromatography. The catalyst obtained by filtering is applied to the next application experiment, and the application experiment conditions are the same as above. The results of the experiment are shown in table 4.

TABLE 4 catalyst application Properties

Number of times of application	Catalyst addition/g	Conversion rate	Selectivity (%)
				1	1 (original)	100	99.9
2	0	100	99.9
				3	0	100	99.9
4	0.05	100	100
				5	0	100	99.9
6	0	100	99.8
				7	0.05	100	99.9
8	0	100	99.9
				9	0	100	99.9
10	0.05	100	100
				11	0	100	99.9
12	0	100	99.8
				13	0.05	100	99.9
14	0	100	99.9
				15	0	100	100
16	0.05	100	99.9
				17	0	100	99.9
18	0	100	99.9
				19	0.05	100	99.9
20	0	100	100

Example 27

Investigating the catalytic hydrogenation effect of the kettle type continuous reaction

2 effective volumes are all 5m³The reaction kettles of (1) were connected in series, wherein the first reaction kettle was 0.3m higher than the second reaction kettle, 1.5 tons of 2-chloro-4-methylnitrobenzene, 2.0 tons of ethanol, 10kg of the 4% Pt-4% Cu/C catalyst prepared in example 3, and 8kg of benzoic acid peroxide were previously added to both reaction kettles, the air in the kettles was replaced with nitrogen, the nitrogen in the kettles was replaced with hydrogen, the pressure of the hydrogen in the reaction kettles was maintained at 0.8MPa, the temperature of the materials in the kettles was raised and maintained at 80 ℃, the self-priming agitator was opened and the rotation speed was maintained at 400 rpm; a mixture of an ethanol solution of 2-chloro-4-methylnitrobenzene, the 4% Pt-4% Cu/C catalyst prepared in example 3, and benzoic peroxide in a mass ratio of 1: 2: 0.004: 0.0015, continuously inputting the mixture into a first hydrogenation reaction kettle at a flow rate of 8 tons/h through a material pump, continuously introducing hydrogen into the reaction kettle to maintain a reaction pressure of 0.8MPa, continuously overflowing the material from the first hydrogenation reaction kettle to a second reaction kettle by utilizing the height difference between the two reaction kettles, and continuously discharging the material reacted by the second reaction kettle from a discharge port of the second reaction kettle to a gas-liquid separator; the separated hydrogen can be continuously used for hydrogenation reaction after being purified, the separated liquid material is filtered, the solid catalyst obtained by filtering is continuously recycled, and the liquid product obtained by filtering is analyzed by liquid chromatography. After the continuous stable operation for 2000h, the conversion rate of the raw materials is 100 percent, and the selectivity of the target product is 99.8 percent.

Comparative examples 1 to 3

Comparative examples 1 to 3 examined the catalytic hydrogenation performance of the activated carbon-supported single metal catalyst.

Comparative example 1

10g of active carbon with the granularity of 1000 meshes and the specific surface area of 1800m is weighed²The pore volume is 0.6mL/g, 6mL of H-containing solution is prepared first₂PdCl₄A mixed solution of furfural (the mass of Pd contained in the mixed solution was 0.01g, and the mass of furfural contained in the mixed solution was 0.01 g); dropwise adding the mixed solution into the activated carbon at 25 ℃, and uniformly stirring; the impregnated catalyst is heated to 25 DEG CVacuum drying for 10 h; preparing 6mL of the same mixed solution, performing equal-volume impregnation, and drying under the same conditions, so as to perform equal-volume impregnation for 5 times in total; the dried catalyst is added in H₂Reducing for 6h at 60 ℃ under the atmosphere to obtain the 3 percent Pd/C catalyst.

Adding 100g of m-methyl nitrobenzene, 100mL of methanol and 0.5g of the activated carbon supported palladium catalyst into a 500mL stainless steel reaction kettle, adding 0.01g of formaldehyde, closing the reaction kettle, replacing air in the reaction kettle with nitrogen for three times, and replacing with hydrogen for three times; heating to 70 ℃ and hydrogen pressure of 1.0MPa, starting stirring at the stirring speed of 900r/min, and reacting for 1 h; stopping the reaction, cooling to room temperature, taking out the reaction solution, filtering to remove the catalyst, and analyzing the filtrate by gas chromatography. The catalyst obtained by filtering is applied to the next application experiment, and the application experiment conditions are the same as above. The results of the experiment are shown in Table 5.

Comparative example 2

10g of active carbon with the granularity of 100 meshes and the specific surface area of 1000m is weighed²The pore volume is 0.3mL/g, 3mL of H-containing solution is prepared₂PtCl₆And a mixed solution of furfural (the mass of Pt contained in the mixed solution was 0.02g, and the mass of furfural contained therein was 0.02 g); dropwise adding the mixed solution into the activated carbon at 25 ℃, and uniformly stirring; drying the impregnated catalyst at 20 ℃ for 20 hours in vacuum; preparing 3ml of the same mixed solution, performing equal-volume impregnation, and drying under the same conditions, so as to perform equal-volume impregnation 10 times in total; the dried catalyst is added in H₂Reducing for 3h at 80 ℃ in the atmosphere to obtain the 6 percent Pt/C catalyst.

Adding 100g of m-methyl nitrobenzene, 100mL of methanol and 0.5g of the activated carbon supported platinum catalyst into a 500mL stainless steel reaction kettle, adding 0.01g of formaldehyde, closing the reaction kettle, replacing air in the reaction kettle with nitrogen for three times, and replacing with hydrogen for three times; heating to 70 ℃ and hydrogen pressure of 1.0MPa, starting stirring at the stirring speed of 900r/min, and reacting for 1 h; stopping the reaction, cooling to room temperature, taking out the reaction solution, filtering to remove the catalyst, and analyzing the filtrate by gas chromatography. The catalyst obtained by filtering is applied to the next application experiment, and the application experiment conditions are the same as above. The results of the experiment are shown in Table 5.

Comparative example 3

10g of active carbon with the granularity of 100 meshes and the specific surface area of 1000m is weighed²The pore volume is 0.3mL/g, and 3mL of mixed solution containing CuCl2 and furfural is prepared firstly (the mass of Cu in the mixed solution is 0.01g, and the mass of furfural is 0.02 g); the mixed solution was dropwise added to activated carbon at 25 ℃ and stirred uniformly. The impregnated catalyst was dried under vacuum at 20 ℃ for 20 h. Preparing 3mL of the same mixed solution, performing equal-volume impregnation, and drying under the same conditions, wherein the equal-volume impregnation is performed for 10 times in total; the dried catalyst is added in H₂Reducing for 3h at 80 ℃ in the atmosphere to obtain the 3 percent Cu/C catalyst.

Adding 100g of m-methyl nitrobenzene, 100mL of methanol and 0.5g of the activated carbon supported copper catalyst into a 500mL stainless steel reaction kettle, adding 0.01g of formaldehyde, closing the reaction kettle, replacing air in the reaction kettle with nitrogen for three times, and replacing with hydrogen for three times; heating to 70 ℃ and hydrogen pressure of 1.0MPa, starting stirring at the stirring speed of 900r/min, and reacting for 1 h; stopping the reaction, taking out the reaction liquid after the temperature is reduced to room temperature, filtering to remove the catalyst, and analyzing the filtrate by gas chromatography; the catalyst obtained by filtering is applied to the next application experiment, and the application experiment conditions are the same as above. The results of the experiment are shown in Table 5.

Comparative example 4

Comparative example 4 the hydrogenation performance of the activated carbon supported bimetallic catalyst obtained without furfural addition during the catalyst preparation process was investigated.

10g of active carbon with the granularity of 1000 meshes and the specific surface area of 1800m is weighed²The pore volume is 0.6mL/g, 6mL of H-containing solution is prepared first₂PdCl₄、CuCl₂The mixed solution of (1) (the mass of Pd contained in the mixed solution is 0.01g, and the mass of Cu contained in the mixed solution is 0.01 g); dropwise adding the mixed solution into the activated carbon at 25 ℃, and uniformly stirring; drying the impregnated catalyst at 25 ℃ for 10 hours in vacuum; preparing 6ml of the same mixed solution, performing equal volume impregnation, and drying under the same conditions as above to obtain the final productSoaking for 5 times in total equal volume; the dried catalyst is added in H₂Reducing for 6h at 60 ℃ under the atmosphere to obtain the 3 percent Pd-3 percent Cu/C catalyst.

Adding 100g of m-methyl nitrobenzene, 100mL of methanol and 0.5g of the activated carbon supported bimetallic catalyst into a 500mL stainless steel reaction kettle, adding 0.01g of formaldehyde, closing the reaction kettle, replacing air in the reaction kettle with nitrogen for three times, and replacing with hydrogen for three times; heating to 70 ℃ and hydrogen pressure of 1.0MPa, starting stirring at the stirring speed of 900r/min, and reacting for 1 h; stopping the reaction, cooling to room temperature, taking out the reaction solution, filtering to remove the catalyst, and analyzing the filtrate by gas chromatography. The catalyst obtained by filtering is applied to the next application experiment, and the application experiment conditions are the same as above. The results of the experiment are shown in Table 5.

Comparative example 5

Comparative example 5 investigates the hydrogenation performance of an activated carbon-supported bimetallic catalyst obtained without a multi-step isometric impregnation method during the catalyst preparation process.

10g of active carbon with the granularity of 1000 meshes and the specific surface area of 1800m is weighed²The pore volume is 0.6mL/g, 6mL of H-containing solution is prepared first₂PdCl₄、CuCl₂And a mixed solution of furfural (the mixed solution contained Pd of 0.05g, Cu of 0.05g, and furfural of 0.05 g); the mixed solution was dropwise added to activated carbon at 25 ℃ and stirred uniformly. The impregnated catalyst was dried under vacuum at 25 ℃ for 10 h. And reducing the dried catalyst for 6 hours at 60 ℃ in the atmosphere of H2 to obtain the 3% Pd-3% Cu/C catalyst.

Adding 100g of m-methyl nitrobenzene, 100mL of methanol and 0.5g of the activated carbon supported bimetallic catalyst into a 500mL stainless steel reaction kettle, adding 0.01g of formaldehyde, closing the reaction kettle, replacing air in the reaction kettle with nitrogen for three times, and replacing with hydrogen for three times; heating to 70 ℃ and hydrogen pressure of 1.0MPa, starting stirring at the stirring speed of 900r/min, and reacting for 1 h; stopping the reaction, cooling to room temperature, taking out the reaction solution, filtering to remove the catalyst, and analyzing the filtrate by gas chromatography. The catalyst obtained by filtering is applied to the next application experiment, and the application experiment conditions are the same as above. The results of the experiment are shown in Table 5.

Comparative example 6

Comparative example 6 the hydrogenation performance of the activated carbon supported bimetallic catalyst prepared by precipitation was investigated.

10g of active carbon with the granularity of 1000 meshes and the specific surface area of 1800m is weighed²Adding the mixture into 50mL of deionized water to obtain slurry, wherein the volume of pores is 0.6 mL/g; the preparation was 30mL of a solution containing H₂PdCl₄、CuCl₂And a mixed solution of furfural (the mixed solution contained Pd of 0.01g, Cu of 0.01g, and furfural of 0.01 g); dropwise adding the mixed solution into the active carbon slurry at 25 ℃, and stirring for 120 min; dropwise adding 10 wt% NaOH solution at 25 ℃ to adjust the pH value of the slurry to 7-9, and continuously stirring for 120 min; filtering the slurry; the catalyst obtained after filtration was dried in vacuo at 25 ℃ for 10 h. And reducing the dried catalyst for 6 hours at 60 ℃ in the atmosphere of H2 to obtain the 3% Pd-3% Cu/C catalyst.

Adding 100g of m-methyl nitrobenzene, 100mL of methanol and 0.5g of the activated carbon supported bimetallic catalyst into a 500mL stainless steel reaction kettle, adding 0.01g of formaldehyde, closing the reaction kettle, replacing air in the reaction kettle with nitrogen for three times, and replacing with hydrogen for three times; heating to 70 ℃ and hydrogen pressure of 1.0MPa, starting stirring at the stirring speed of 900r/min, and reacting for 1 h; stopping the reaction, cooling to room temperature, taking out the reaction solution, filtering to remove the catalyst, and analyzing the filtrate by gas chromatography. The catalyst obtained by filtering is applied to the next application experiment, and the application experiment conditions are the same as above. The results of the experiment are shown in Table 5.

Comparative example 7

Comparative example 7 investigated the hydrogenation performance of the activated carbon-supported bimetallic catalyst prepared at higher reduction temperatures.

10g of active carbon with the granularity of 1000 meshes and the specific surface area of 1800m is weighed²The pore volume is 0.6mL/g, 6mL of H-containing solution is prepared first₂PdCl₄、CuCl₂And a mixed solution of furfural (the mixed solution contained Pd of 0.01g, Cu of 0.01g, and furfural of 0.01 g); dropwise adding the mixed solution to the active substanceAnd stirring the mixture evenly in the carbon. The impregnated catalyst was dried under vacuum at 25 ℃ for 10 h. 6mL of the same mixed solution was prepared, and the same volume of impregnation was performed, and drying was performed under the same conditions as above, so that the volume of impregnation was 5 times in total. The dried catalyst is added in H₂Reducing for 6h at 200 ℃ under the atmosphere to obtain the 3 percent Pd-3 percent Cu/C catalyst.

Adding 100g of m-methyl nitrobenzene, 100mL of methanol and 0.5g of the activated carbon supported bimetallic catalyst into a 500mL stainless steel reaction kettle, adding 0.01g of formaldehyde, closing the reaction kettle, replacing air in the reaction kettle with nitrogen for three times, and replacing with hydrogen for three times; heating to 70 ℃ and hydrogen pressure of 1.0MPa, starting stirring at the stirring speed of 900r/min, and reacting for 1 h; stopping the reaction, cooling to room temperature, taking out the reaction solution, filtering to remove the catalyst, and analyzing the filtrate by gas chromatography. The catalyst obtained by filtering is applied to the next application experiment, and the application experiment conditions are the same as above. The results of the experiment are shown in Table 5.

TABLE 5 Performance of catalysts of different comparative examples

Claims (7)

1. A method for preparing arylamine by catalytic hydrogenation is characterized in that aromatic nitro compounds are subjected to catalytic hydrogenation to prepare arylamine: the method comprises the following steps: adding a stabilizer into a reaction solvent, and carrying out catalytic hydrogenation reaction on an aromatic nitro compound shown in a formula (I) and hydrogen under the action of a catalyst in the presence of the stabilizer to obtain arylamine shown in a formula (II);

in the formula, -R₁、-R₂、-R₃、-R₄、-R₅Are respectively selected from one of the following groups: -H, -F, -Cl, -Br, -I, -CH₃、-CH₂CH₃、-OH、-NH₂、-OCH₃、-COOCH₃、-COOH、-SO₃H、-NHCH₂CH₃、N(CH₃)₂；

The stabilizer is one of acetic acid, boric acid, formaldehyde, acetaldehyde, hydrogen peroxide, peroxyacetic acid and peroxybenzoic acid;

the catalyst is an activated carbon loaded bimetallic catalyst, is prepared by using activated carbon as a carrier, noble metal as an active component and Cu as an auxiliary agent and adopting an isometric multistep impregnation method, and specifically comprises the following steps:

a. weighing activated carbon, and preparing a mixed solution containing a noble metal compound, a Cu compound and furfural, wherein the volume of the mixed solution is the same as that of the activated carbon according to the pore volume of the activated carbon;

b. dropwise adding the mixed solution into the activated carbon at 20-30 ℃, and uniformly stirring;

c. vacuum drying the impregnated activated carbon catalyst at 20-30 ℃ for 4-20h to obtain a dried primary catalyst product;

d. preparing a mixed solution containing a noble metal compound, a Cu compound and furfural with the same volume as the pore volume of the activated carbon again, and repeating the step b and the step c;

e. repeatedly dipping for many times to ensure that the content of the metal dipped on the active carbon is consistent with the required load;

f. the finally obtained dried catalyst is added in H₂Reducing for 3-10h at 50-80 ℃ in the atmosphere to obtain an activated carbon loaded bimetallic catalyst;

the noble metal compound in the step a is H₂PdCl₄、Pd(NO₃)₂、H₂PtCl₆Or Pt (NO)₃)₂One of (1); the Cu-containing compound is CuCl₂Or Cu (NO)₃)₂。

2. A process for the preparation of aromatic amines by catalytic hydrogenation according to claim 1, characterized in that: the dosage of the stabilizer is 0.001-0.5% of the mass of the aromatic nitro compound.

3. A process for the preparation of aromatic amines by catalytic hydrogenation according to claim 2, characterized in that: in the step a, the concentrations of the noble metal, Cu and furfural in the mixed solution are 0.01-0.05 g/ml, 0.01-0.05 g/ml and 0.01-0.05 g/ml respectively.

4. A process for the preparation of aromatic amines by catalytic hydrogenation according to claim 3, characterized in that: in the steps e and f, the loading amount of the noble metal in the activated carbon loaded bimetallic catalyst is 1-10 wt%; the loading amount of Cu is 1-5 wt%.

5. A process for the preparation of aromatic amines by catalytic hydrogenation according to claim 4, characterized in that: the dosage of the active carbon supported bimetallic catalyst is 0.1-3.0% of the mass of the aromatic nitro compound.

6. A process for the preparation of aromatic amines by catalytic hydrogenation according to claim 5, characterized in that: the catalytic hydrogenation reaction takes methanol, ethanol or water as a reaction solvent, and the addition amount of the methanol, the ethanol or the water is 0.5 to 3.0g/g based on the mass of the aromatic nitro compound.

7. A process for the preparation of aromatic amines by catalytic hydrogenation according to claim 6, characterized in that: the method adopts a kettle type batch reaction process or a kettle type continuous reaction process, and the kettle type batch reaction process specifically comprises the following steps: adding an aromatic nitro compound, a solvent, a catalyst and a stabilizer into a reaction kettle, wherein the feeding mass ratio of the aromatic nitro compound to the solvent to the catalyst to the stabilizer is 1: (0.5-3): (0.1-3.0%): (0.001-0.5%), closing the reaction kettle; replacing air in the reaction kettle with nitrogen, and replacing the nitrogen with hydrogen; then, raising the temperature in the reaction kettle to 50-150 ℃, controlling the hydrogen pressure to be 0.4-3 MPa, and stirring for reaction; after the reaction is finished, separating to obtain an arylamine product;

the kettle type continuous reaction process specifically comprises the following steps:

a. adding an aromatic nitro compound, a solvent, a catalyst and a stabilizer into a single reaction kettle or a plurality of reaction kettles connected in series in advance, replacing air in the kettle with nitrogen, replacing nitrogen in the kettle with hydrogen, maintaining the pressure of the hydrogen in the reaction kettles at 0.4-3 Mpa, raising the temperature of materials in the kettles, maintaining the reaction temperature at 50-150 ℃, and opening a stirrer;

b. continuously inputting a mixture of an aromatic nitro compound, a solvent, a catalyst and a stabilizer into a first hydrogenation reaction kettle through a material pump; if the single-kettle continuous hydrogenation is adopted, the reacted materials are continuously discharged from a discharge hole of the reaction kettle to a gas-liquid separator, and simultaneously, hydrogen is continuously introduced to maintain the reaction pressure; if a plurality of serially connected reaction kettles are used for continuous hydrogenation, the materials continuously overflow from the first hydrogenation reaction kettle to the second hydrogenation reaction kettle in sequence by utilizing the height difference among the kettles until the last hydrogenation reaction kettle is reached, the reacted materials are continuously discharged from the discharge hole of the last reaction kettle to the gas-liquid separator, and simultaneously, hydrogen is continuously introduced into each reaction kettle to maintain the reaction pressure;

c. the separated hydrogen can be used for hydrogenation reaction after being purified, the separated liquid material is filtered, the solid catalyst obtained by filtering is recycled, the liquid product obtained by filtering enters a product storage tank, and the arylamine product is obtained after separation and purification.