Structured alloy catalyst for hydrogenation of nitrobenzene to aniline, its preparation method and application

Abstract

The application belongs to the technical field of catalyst preparation, and particularly relates to a structured alloy catalyst for producing aniline by hydrogenation of nitrobenzene and a preparation method and application thereof. The catalyst is obtained by anchoring loaded metal ions in a solution on the surface of a foamed nickel through growth of a poly-o-phenylenediamine film, centrifugation, washing, drying and calcination. The poly-o-phenylenediamine is generated by polymerization of o-phenylenediamine and dilute hydrochloric acid containing ammonium persulfate, and the loaded metal includes one or more of Cu, Mo and Fe. The structured alloy catalyst is loaded in a fixed bed reactor and used in a process for continuous production of aniline by hydrogenation of nitrobenzene. The structured alloy catalyst has the advantages of high activity, good selectivity, low reaction temperature, excellent heat and mass transfer performance and long service life, the conversion rate of nitrobenzene reaches more than 90%, and the selectivity of aniline is higher than 99.5%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation, in particular to a structured alloy catalyst for producing aniline by hydrogenation of nitrobenzene and a preparation method and application thereof. BACKGROUND

[0002] Aniline is an important organic chemical raw material, widely used in dye, medicine, pesticide, rubber additive and fine chemical industries, and is the main raw material for producing polyurethane raw material MDI (diphenyl methane diisocyanate), and MDI can account for about 80% of the downstream products of aniline. In recent years, with the continuous development of MID industry, aniline has great market development potential. Therefore, the selective hydrogenation reaction of aromatic nitro compounds has always been favored by researchers. At present, the industrial production of aniline and its derivatives mainly depends on the hydrogenation reaction of aromatic nitro compounds, but the activity, selectivity and atomic economy of the catalyst used in the production process still need to be improved, because a certain amount of intermediates and by-products are produced. Therefore, the development of more efficient, high-selectivity and environmentally friendly catalysts is of great importance to the basic research and industrial application of aniline production.

[0003] At present, the production process of aniline at home and abroad is relatively mature, and the main methods are: nitrobenzene catalytic hydrogenation, phenol amination and nitrobenzene iron powder reduction. With the continuous breakthrough and progress of hydrogenation process and catalyst, catalytic hydrogenation is easier to control, safer and has less impact on the environment, so the production of aniline by catalytic hydrogenation of nitrobenzene has become the method used by most enterprises, which can account for more than 90% of the global aniline production capacity, while the iron powder reduction method and the phenol amination method have been gradually replaced due to environmental costs and other problems.

[0004] The nitrobenzene catalytic hydrogenation method includes fixed bed gas phase catalytic hydrogenation, fluidized bed gas phase catalytic hydrogenation and nitrobenzene liquid phase catalytic hydrogenation. The core of hydrogenation reaction is catalyst. The fixed bed gas phase hydrogenation process generally uses CuO / SiO2 catalyst with copper supported on silica carrier, which provides high selectivity of aniline by virtue of the weak hydrogenation ability of copper metal itself. The advantages of this type of catalyst are low cost and good selectivity, and the disadvantages are poor resistance to toxicity and trace organic sulfides can easily poison the catalyst. At present, the improvement of this catalyst focuses on the carrier and additive to improve the activity, stability and life of the catalyst, but the heat exchange problem can only be solved by using tubular heat exchanger. The fluidized bed gas phase hydrogenation process improves the heat transfer problem of fixed bed, but the catalyst wear and process cost also restrict the development of the process. Compared with the above two methods, the reaction conditions of liquid phase catalytic hydrogenation are more moderate, and the development potential is greater. At present, the catalysts used for the production of aniline by liquid phase hydrogenation of nitrobenzene mainly include noble metal catalysts and nickel-based catalysts. However, the recovery cost of noble metal catalysts is too high, and nickel-based catalysts have become a research hotspot at home and abroad due to their good catalytic activity and low price.

[0005] Patent CN117123238A discloses Raney nickel composite catalyst, which has high nitrobenzene hydrogenation activity, and the conversion rate is as high as 99.5%, but the heat transfer capacity of Raney nickel catalyst is poor and the microporous structure is developed, a large amount of heat is generated in the pores at the moment of reaction and cannot be conducted in time, which is easy to cause micropore collapse, and the service life of the catalyst is short.

[0006] Patent CN115301261A discloses Ni / SiC-B x Catalyst, which reduces the cost of the catalyst by reducing the loading of the active component, and keeps the conversion rate of nitrobenzene and the selectivity of aniline both above 99%, but the thermal conductivity of the carrier is poor, causing local hot spots, leading to excessive hydrogenation of nitrobenzene to generate a series of by-products, and the stability of the catalyst is poor.

[0007] Traditional supported nickel-based catalysts usually use alumina, silica and other inert oxide powders as carriers, and use the high specific surface area of the powder to promote the uniform dispersion of the active component to improve the catalytic efficiency. However, in large-scale industrial production, the shortcomings of powder carriers in heat and mass transfer are magnified, especially for high flux and strong thermal effect reaction processes. Powder catalyst bed often has high pressure drop, uneven distribution of reactants and heat, etc., leading to increased industrial cost, decreased product quality, etc. In recent years, foam metal has been developed into various structured catalysts and applied to the field of catalysis due to its low density, high porosity, high heat / mass transfer performance, high mechanical strength and other characteristics.

[0008] Therefore, in view of the shortcomings and defects of the existing catalysts for the production of aniline from nitrobenzene liquid phase hydrogenation, based on the characteristics of low density, high porosity, high heat / mass transfer performance, high mechanical strength of foam metal, and the superior performance of nickel-based catalyst in hydrogenation reaction, a high-performance foam nickel structured catalyst for the production of aniline from nitrobenzene hydrogenation is designed by adopting the design concept of structured catalyst. SUMMARY

[0009] Therefore, the present application provides a structured alloy catalyst for the production of aniline from nitrobenzene hydrogenation, its preparation method and application, which solves the problems of low selectivity, high bed pressure drop and poor heat transfer of traditional nickel-based catalysts in the prior art.

[0010] To achieve the above-mentioned purpose, the present application provides the following technical solution: a structured alloy catalyst for the production of aniline from nitrobenzene hydrogenation, which uses foam nickel with a nickel hydroxide coating structure as a substrate, and grows a poly-o-phenylenediamine film on the surface of the substrate to anchor the loaded metal ions in the solution, and then obtains the catalyst after centrifugation, washing, drying and calcination.

[0011] Preferably, the poly-o-phenylenediamine film is formed by polymerization of o-phenylenediamine in dilute hydrochloric acid containing ammonium persulfate.

[0012] Preferably, the supported metal includes one or more of Cu, Mo, Fe, and the poly-o-phenylenediamine film-grown nickel foam is placed in a solution of the supported metal salt for a period of time, and the structured alloy catalyst is obtained by washing, drying, and calcining the supported metal.

[0013] Preferably, the supported metal is added in an amount of 1-10 wt% of the mass of the nickel foam substrate.

[0014] Preferably, the nickel foam substrate is a cubic sheet of 1-5 mm x 1-5 mm x 1-5 mm or a circular sheet of 1-5 mm in diameter and 1-5 mm in thickness.

[0015] In a second aspect, the present application also provides a method for preparing a structured alloy catalyst for the production of aniline by hydrogenation of nitrobenzene, comprising the following steps:

[0016] S1. Taking a nickel foam raw material, cutting it into pieces of a certain size, cleaning it with dilute hydrochloric acid, ethanol, and deionized water, and drying it;

[0017] S2. First, o-phenylenediamine is added to dilute hydrochloric acid, and after the o-phenylenediamine is fully dissolved, the nickel foam is added, and ultrasonic waves are used to disperse the solution uniformly on the surface of the nickel foam. Then, dilute hydrochloric acid containing ammonium persulfate is added dropwise. In the presence of the oxidant ammonium persulfate, the o-phenylenediamine grows on the surface of the nickel foam by polymerization to obtain PoPD@Ni-foam.

[0018] S3. Dissolve the supported metal in deionized water to prepare a metal ion solution, and then add the PoPD@Ni-foam to the metal ion solution and stir thoroughly at room temperature to allow the metal ions to be fully adsorbed on the surface of the poly-o-phenylenediamine. Then, wash with deionized water, dry, and calcine to obtain a structured alloy catalyst for the production of aniline by hydrogenation of nitrobenzene.

[0019] Preferably, in step S2, the mass ratio of the nickel foam, ammonium persulfate, and o-phenylenediamine is (0.5-1):(2-5):1, the concentration of the dilute hydrochloric acid is 0.5-2 mol / L, and the self-polymerization reaction time at room temperature is 12-24 h.

[0020] Preferably, in step S3, the supported metal includes one or more of Cu, Mo, and Fe, wherein the Mo source ion solution is any one or several of ammonium tetrathiomolybdate, ammonium molybdate tetrahydrate, molybdenum acetylacetonate, and molybdenum hexacarbonyl; the Cu source ion solution is any one or several of copper nitrate, copper chloride, and copper sulfate; the Fe source ion solution is any one or several of iron nitrate, iron chloride, and iron sulfate; the stirring time is 6-24 h; during the calcination process, the calcination temperature is 500-900°C, the calcination time is 2-4 h, and the calcination atmosphere is any one of nitrogen, argon, and helium.

[0021] In another aspect, the application also provides a use of the structured alloy catalyst for producing aniline by hydrogenation of nitrobenzene.

[0022] Further preferably, the structured alloy catalyst is loaded in a fixed bed reactor, and after loading the structured alloy catalyst, hydrogen is first introduced for reduction, and the reduction conditions are as follows: temperature 300-500 DEG C, pressure 0.5-10 MPa, hydrogen space velocity 200-600 h-1. -1 Then 5wt%-30wt% of the nitrobenzene reaction raw material is introduced for hydrogenation reaction of the nitrobenzene, and the hydrogenation reaction conditions are as follows: temperature 80-200 DEG C, pressure 0.5-10 MPa, mass space velocity of the nitrobenzene 0.5-4 h-1, and molar ratio of hydrogen to nitrobenzene 6:1-30:1. -1

[0023] Compared with the prior art, the application provides the structured alloy catalyst for producing aniline by hydrogenation of nitrobenzene, and a preparation method and use thereof, and has the following beneficial effects:

[0024] The structured alloy catalyst for producing aniline by hydrogenation of nitrobenzene utilizes the three-dimensional porous structure of the foam nickel as a substrate, and grows a poly-o-phenylenediamine (PoPD) film on the surface of the foam nickel, so that the adsorption capacity for metal ions is increased, and the conversion rate of the nitrobenzene is improved.The metals on the surface of the alloy catalyst exist in an oxidized state, and after hydrogen reduction in the reactor, the metals exist in different valence states on the surface of the catalyst, so that the electronic structure can be effectively adjusted, the adsorption and activation capacity of the active metals for hydrogen is ensured, the defects generated by the electron conduction between the alloys can capture the electron-rich groups of the nitro groups, so that the adsorption capacity for the nitro groups is improved, the adsorption of the benzene rings is reduced, the excessive hydrogenation of the nitrobenzene is prevented, and the selectivity of the aniline is improved. The structured alloy catalyst is constructed by constructing an alloy structure on the surface of the foam nickel, so that the problems of the loss of the active components of the traditional supported catalysts, the large bed pressure drop of the traditional catalysts in the reactor, and the poor heat transfer of the traditional catalysts can be solved, and the structured alloy catalyst has the advantages of high activity, good selectivity, long service life, and easy recovery.

[0025] The structured alloy catalyst for producing aniline by hydrogenation of nitrobenzene has good hydrogenation activity of the nitrobenzene and selectivity of the aniline, the conversion rate of the nitrobenzene reaches more than 90%, and the selectivity of the aniline reaches more than 99.5%. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0027] Figure 1 The SEM image of the foamed nickel after cleaning in step (1) in the present application embodiment 1-4;

[0028] Figure 2 The SEM image of the catalyst prepared in the present application embodiment 2. DETAILED DESCRIPTION

[0029] The catalyst and the preparation method thereof described in the present application will be further described in the following specific embodiments to help the skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solutions of the present application. It should be pointed out that the description of the process flow and parameters in the embodiments is exemplary, and is not intended to limit the scope of protection of the present application. The test methods described in the following embodiments are conventional methods unless otherwise specified. The instruments and materials mentioned are commercially available unless otherwise specified. For example, the foamed nickel material has a thickness of 1-5 mm, a surface density of 150-600 g / m2, an average pore size of 0.1-0.3 mm, and a porosity of 80-97%. 2

[0030] Embodiment 1

[0031] (1) Take commercially available foamed nickel material, cut it into 2mm x 2mm x 2mm cubic particles, clean it with dilute hydrochloric acid, ethanol and deionized water, and then dry it at 80℃ for 12h;

[0032] (2) 100g of o-phenylenediamine was added to 10L of 1mol / L dilute hydrochloric acid in a beaker, and ultrasonic treatment was performed for 30min until the o-phenylenediamine was fully dissolved. Then, 100g of foamed nickel was added and ultrasonic treatment was performed for 30min to make it uniformly dispersed. Then, 200g of ammonium persulfate was added to the dilute hydrochloric acid, and stirring was performed at room temperature for 24h. After the polymerization reaction was completed, filtration, washing and drying at 70℃ under vacuum for 6h were performed to obtain PoPD@Ni-foam.

[0033] ​(3) 220 g of PoPD@Ni-foam was added into a beaker, then 5 L of deionized water and 4.5 L of absolute ethanol were added, and it was uniformly dispersed by ultrasonic for 15 min, then 100 g of ammonium tetrathiomolybdate was added, and after stirring for 24 h, the Mo source metal ions not anchored on the surface of PoPD@Ni-foam were removed by centrifugation, and after centrifugation and washing for 3 times, the sample was dried at 70 °C under vacuum for 6 h to obtain a sample, the sample was poured into a magnetic boat and placed in a tube furnace, and the temperature was raised to 700 °C at a temperature rising rate of 2 °C / min under a nitrogen atmosphere for 2 h, and after natural cooling, the catalyst precursor was obtained. Catalyst 1 was obtained.

[0034] The structured alloy catalyst 1 prepared in this example can be used in the continuous production process of aniline by liquid phase hydrogenation of nitrobenzene, and the process uses a fixed bed reactor. The conversion rate of nitrobenzene and the selectivity of aniline are determined by gas chromatography (HP-5 chromatographic column, FID detector) using peak area normalization method.

[0035] Specifically, 100 g of catalyst 1 was filled in a fixed bed reactor, and before the activity test, the catalyst 1 was first reduced and activated under a hydrogen atmosphere, and the temperature was raised to 350 °C at a temperature rising rate of 2 °C / min under a hydrogen space velocity of 400 h -1 -1 and a pressure of 2 MPa. Then a 20 wt% nitrobenzene solution was introduced, the solvent of the nitrobenzene solution was tetrahydrofuran, and the evaluation of the catalyst was carried out under the conditions of a nitrobenzene mass space velocity of 2 h -1 -1, a hydrogen / nitrobenzene molar ratio of 12:1, a temperature of 160 °C and a pressure of 2 MPa.

[0036] After stable operation, the conversion rate of nitrobenzene was 97.4%, and the selectivity of aniline was 99.8%.

[0037] Example 2

[0038] (1) A commercially available nickel foam material was cut into 2 mm x 2 mm x 2 mm cubic particles, and then washed with dilute hydrochloric acid, ethanol and deionized water, and then dried at 80 °C for 12 h.

[0039] (2) 100 g of o-phenylenediamine was added to 10 L of 1 mol / L dilute hydrochloric acid in a beaker, and after ultrasonic for 30 min until the o-phenylenediamine was dissolved, 100 g of nickel foam was added and ultrasonic for 30 min to make it uniformly dispersed, then 200 g of ammonium persulfate was added dropwise in dilute hydrochloric acid and stirred at room temperature for 24 h, after the polymerization reaction was completed, the product was filtered, washed and dried at 70 °C under vacuum for 6 h to obtain PoPD@Ni-foam.

[0040] (3) To a beaker, 220 g of PoPD@Ni-foam was added, followed by 5 L of deionized water and 4.5 L of absolute ethanol, and then ultrasonicated for 15 min to make it uniformly dispersed. Then, 100 g of ammonium molybdate tetrahydrate was added, and stirred for 24 h. After that, the Mo source metal ions not anchored on the surface of PoPD@Ni-foam were removed by centrifugation. After centrifugation and washing for 3 times, the sample was dried at 70 °C under vacuum for 6 h. The sample was poured into a magnetic boat and placed in a tube furnace, and then heated to 700 °C at a heating rate of 2 °C / min under nitrogen atmosphere for 2 h. After natural cooling, the catalyst precursor was obtained. Catalyst 2 was obtained.

[0041] Figure 1 The SEM image of the surface of the nickel foam after cleaning in step (1) of Example 1-4 is shown in Figure 1. Figure 2 The SEM image of the surface of the nickel foam after treatment in step (3) of this example is shown in Figure 2. Figure 1 As can be seen from Figure 2, the surface of the nickel foam is smooth, without any oxide and oil residue. Figure 2 As can be clearly seen from Figure 3, Mo is distributed on the surface of the nickel foam, which can prevent the aggregation of nickel metal particles and improve the selectivity of aniline.

[0042] The structured alloy catalyst 2 prepared in this example can be used in the continuous production process of aniline by liquid phase hydrogenation of nitrobenzene. The process uses a fixed bed reactor, and the conversion of nitrobenzene and the selectivity of aniline are determined by gas chromatography (HP-5 chromatographic column, FID detector) using peak area normalization method.

[0043] Specifically, 100 g of catalyst 2 was filled in a fixed bed reactor. Before the activity test, the catalyst 2 was first reduced and activated under hydrogen atmosphere, and then the temperature was raised to 350 °C at a rate of 2 °C / min under a hydrogen space velocity of 400 h -1 -1, a pressure of 2 MPa, and a constant temperature for 2 h. Then, a 20 wt% nitrobenzene solution was introduced, the solvent of which was tetrahydrofuran. The evaluation of the catalyst was carried out under the conditions of a nitrobenzene mass space velocity of 1 h -1 -1, a hydrogen / nitrobenzene molar ratio of 12:1, a temperature of 160 °C, and a pressure of 2 MPa.

[0044] After stable operation, the conversion of nitrobenzene was 99.4%, and the selectivity of aniline was 99.6%.

[0045] Example 3

[0046] (1) Commercially available nickel foam material was cut into circular thin slices with a diameter of 2 mm and a thickness of 2 mm, and then cleaned with dilute hydrochloric acid, ethanol, and deionized water, and then dried at 80 °C for 12 h.

[0047] (2) Add 100g of o-phenylenediamine to 10L of 1mol / L dilute hydrochloric acid in a beaker, sonicate for 30min until the o-phenylenediamine is fully dissolved, add 100g of nickel foam and sonicate for 30min to disperse it evenly, then add dilute hydrochloric acid containing 200g of ammonium persulfate and stir at room temperature for 24h. After the polymerization reaction is completed, filter, wash and dry under vacuum at 70℃ for 6h to obtain PoPD@Ni-foam.

[0048] (3) Add 220g of PoPD@Ni-foam to a beaker, then add 5L of deionized water and 4.5L of anhydrous ethanol. Sonicate for 15min to disperse the mixture evenly. Add 200g of ammonium molybdate tetrahydrate and stir for 24h. Centrifuge to remove Mo source metal ions not anchored on the surface of PoPD@Ni-foam. After centrifugation and washing three times, dry the sample under vacuum at 70℃ for 6h. Pour the sample into a magnetic boat and place it in a tube furnace. Heat the furnace to 700℃ at a rate of 2℃ / min under a nitrogen atmosphere and maintain the temperature for 2h. After natural cooling, remove the sample to obtain the catalyst precursor. Catalyst 3 is obtained.

[0049] The structured alloy catalyst 3 prepared in this embodiment can be used in the continuous production of aniline by liquid-phase hydrogenation of nitrobenzene. The process adopts a fixed-bed reactor, and the conversion rate of nitrobenzene and the selectivity of aniline are determined by gas chromatography (HP-5 column, FID detector) using the peak area normalization method.

[0050] Specifically, 100g of catalyst 3 was packed into a fixed-bed reactor. Before the activity test, catalyst 3 was first reduced and activated in a hydrogen atmosphere at a hydrogen space velocity of 400h⁻¹. -1 The temperature was increased to 350℃ at a programmed rate of 2℃ / min under a pressure of 2 MPa and held at that temperature for 2 hours. Then, a 20 wt% nitrobenzene solution was introduced, with tetrahydrofuran as the solvent. At 160℃ and 2 MPa, the mass hourly space velocity (HSV) of the nitrobenzene solution was 1 h⁻¹. -1 The catalyst was evaluated under the condition that the hydrogen / nitrobenzene molar ratio was 12:1.

[0051] After stabilization, the nitrobenzene conversion rate was 92.7%, and the aniline selectivity was 99.5%.

[0052] Example 4

[0053] (1) Take commercially available nickel foam material, cut it into 2mm×2mm×2mm cubic particles, clean it with dilute hydrochloric acid, ethanol and deionized water, and then dry it at 80℃ for 12h.

[0054] (2) 100 g of o-phenylenediamine was added into 10 L of 1 mol / L dilute hydrochloric acid in a beaker, and ultrasonic treatment was performed for 30 min until o-phenylenediamine was fully dissolved. Then, 100 g of nickel foam was added and ultrasonic treatment was performed for 30 min until the nickel foam was uniformly dispersed. Then, 200 g of ammonium persulfate was added in dilute hydrochloric acid, and stirring was performed at room temperature for 24 h. After the polymerization reaction was completed, filtration, washing, and drying at 70°C under vacuum for 6 h were performed to obtain PoPD@Ni-foam.

[0055] (3) 220 g of PoPD@Ni-foam was added into a beaker, and then 5 L of deionized water and 4.5 L of anhydrous ethanol were added. Ultrasonic treatment was performed for 15 min until the PoPD@Ni-foam was uniformly dispersed. Then, 100 g of copper nitrate trihydrate was added, and stirring was performed for 24 h. Centrifugation was performed to remove Cu source metal ions that were not anchored on the surface of the PoPD@Ni-foam. After centrifugation and washing for 3 times, drying was performed at 70°C under vacuum for 6 h to obtain a sample. The sample was poured into a magnetic boat and placed in a tube furnace. The temperature was raised to 700°C at a temperature raising rate of 2°C / min under a nitrogen atmosphere, and maintained for 2 h. After natural cooling, the catalyst precursor was obtained. Catalyst 4 was obtained.

[0056] The structured alloy catalyst 4 prepared in this example can be used in a continuous process for producing aniline by liquid-phase hydrogenation of nitrobenzene. The process uses a fixed bed reactor, and the conversion rate of nitrobenzene and the selectivity of aniline are determined by gas chromatography (HP-5 chromatographic column, FID detector) using the peak area normalization method.

[0057] Specifically, 100 g of catalyst 4 was filled into a fixed bed reactor. Before the activity test, the catalyst 4 was reduced and activated under a hydrogen atmosphere. The temperature was raised to 350°C at a temperature raising rate of 2°C / min under a hydrogen space velocity of 400 h-1 and a pressure of 2 MPa, and maintained for 2 h. Then, a 20 wt% nitrobenzene solution was introduced, the solvent of the nitrobenzene solution was tetrahydrofuran, and the evaluation of the catalyst was performed under the conditions of a nitrobenzene mass space velocity of 1 h-1, a hydrogen / nitrobenzene molar ratio of 12:1, a temperature of 160°C, and a pressure of 2 MPa. -1 -1

[0058] After the operation was stable, the conversion rate of nitrobenzene was 77.6%, and the selectivity of aniline was 99.5%.

[0059] Example 5

[0060] The structured alloy catalyst 2 prepared in Example 2 can be used in a continuous process for producing aniline by liquid-phase hydrogenation of nitrobenzene. The process uses a fixed bed reactor, and the conversion rate of nitrobenzene and the selectivity of aniline are determined by gas chromatography (HP-5 chromatographic column, FID detector) using the peak area normalization method.

[0061] ​​The catalyst activation conditions were changed, specifically, 100 g of catalyst 2 was filled in a fixed bed reactor, and before the activity test, the catalyst 2 was first reduced and activated under a hydrogen atmosphere, and was programmed to increase the temperature to 450°C at a rate of 2°C / min under a hydrogen space velocity of 300 h -1 -1, a pressure of 4 MPa, and a constant temperature for 2 h. Then, a 20 wt% nitrobenzene solution was introduced, the solvent of the nitrobenzene solution was tetrahydrofuran, and the catalyst was evaluated under the conditions of a nitrobenzene mass space velocity of 1 h -1 -1, a hydrogen / nitrobenzene molar ratio of 12:1, a temperature of 160°C, and a pressure of 2 MPa.

[0062] After stable operation, the nitrobenzene conversion rate was 91.4%, and the aniline selectivity was 99.6%.

[0063] Example 6

[0064] The structured alloy catalyst 2 prepared in Example 2 can be used in a continuous nitrobenzene liquid-phase hydrogenation process for producing aniline, and the process uses a fixed bed reactor. The nitrobenzene conversion rate and the aniline selectivity are determined by gas chromatography (HP-5 chromatographic column, FID detector) using the peak area normalization method.

[0065] The activity evaluation conditions were changed, specifically, 100 g of catalyst 2 was filled in a fixed bed reactor, and before the activity test, the catalyst 2 was first reduced and activated under a hydrogen atmosphere, and was programmed to increase the temperature to 350°C at a rate of 2°C / min under a hydrogen space velocity of 400 h -1 -1, a pressure of 2 MPa, and a constant temperature for 2 h. Then, a 20 wt% nitrobenzene solution was introduced, the solvent of the nitrobenzene solution was tetrahydrofuran, and the catalyst was evaluated under the conditions of a nitrobenzene mass space velocity of 1 h -1 -1, a hydrogen / nitrobenzene molar ratio of 12:1, a temperature of 200°C, and a pressure of 2 MPa.

[0066] After stable operation, the nitrobenzene conversion rate was 98.4%, and the aniline selectivity was 99.5%.

[0067] Example 7

[0068] The structured alloy catalyst 2 prepared in Example 2 can be used in a continuous nitrobenzene liquid-phase hydrogenation process for producing aniline, and the process uses a fixed bed reactor. The nitrobenzene conversion rate and the aniline selectivity are determined by gas chromatography (HP-5 chromatographic column, FID detector) using the peak area normalization method.

[0069] The activity evaluation conditions were changed, specifically, 100 g of catalyst 2 was filled in a fixed bed reactor, and before the activity test, the catalyst 2 was first reduced and activated under a hydrogen atmosphere, and was programmed to increase the temperature to 350°C at a rate of 2°C / min under a hydrogen space velocity of 400 h -1at 2 MPa, and then 20 wt% nitrobenzene solution was introduced into the reactor, the solvent of the nitrobenzene solution was tetrahydrofuran, the reaction was carried out at 160 °C and 2 MPa, and the mass space velocity of the nitrobenzene was 1 h -1 The catalyst was evaluated under the conditions of a hydrogen / nitrobenzene molar ratio of 24:1.

[0070] After the system was stable, the conversion of nitrobenzene was 95.1%, and the selectivity of aniline was 99.6%.

[0071] Comparative Example 1

[0072] A commercially available foamed nickel material was cut into 2 mm x 2 mm x 2 mm cubic particles, washed with dilute hydrochloric acid, ethanol, and deionized water, and then dried at 80 °C for 12 h to obtain catalyst 5.

[0073] The catalyst 5 prepared in this example was used in the continuous production of aniline from nitrobenzene in a liquid phase hydrogenation process. The process used a fixed bed reactor, and the conversion of nitrobenzene and the selectivity of aniline were determined by gas chromatography (HP-5 column, FID detector) using peak area normalization.

[0074] Specifically, 100 g of catalyst 5 was filled into a fixed bed reactor, and before the activity test, the catalyst 5 was reduced and activated in a hydrogen atmosphere at a hydrogen space velocity of 400 h -1 at 2 MPa, and then 20 wt% nitrobenzene solution was introduced into the reactor, the solvent of the nitrobenzene solution was tetrahydrofuran, the reaction was carried out at 160 °C and 2 MPa, and the mass space velocity of the nitrobenzene was 1 h -1 The catalyst was evaluated under the conditions of a hydrogen / nitrobenzene molar ratio of 24:1.

[0075] After the system was stable, the conversion of nitrobenzene was 95.1%, and the selectivity of aniline was 99.6%.

[0076] Comparative Example 2

[0077] (1) A commercially available foamed nickel material was cut into 2 mm x 2 mm x 2 mm cubic particles, washed with dilute hydrochloric acid, ethanol, and deionized water, and then dried at 80 °C for 12 h;

[0078] (2) 2 L of concentrated ammonia and 0.5 L of hydrogen peroxide were diluted in 3 L of distilled water, mixed well, and 300 g of the foamed nickel material treated in step (1) was placed in the obtained mixed solution, and hydrothermal etching was carried out at 100 °C for 18 h. The foamed nickel was washed with deionized water and dried at 100 °C for 6 h to obtain catalyst 6.

[0079] The catalyst 6 prepared in the example was used in a continuous liquid phase hydrogenation process of nitrobenzene to aniline, which used a fixed bed reactor. The conversion of nitrobenzene and the selectivity of aniline were determined by gas chromatography (HP-5 column, FID detector) using the peak area normalization method.

[0080] Specifically, 100 g of the catalyst 6 was filled in a fixed bed reactor. Before the activity test, the catalyst 6 was reduced and activated under a hydrogen atmosphere. The temperature was raised to 350°C at a rate of 2°C / min under a hydrogen space velocity of 400 h -1 -1 and a pressure of 2 MPa. Then, a 20 wt% nitrobenzene solution was introduced, the solvent of which was tetrahydrofuran. The evaluation of the catalyst was carried out at 160°C and a pressure of 2 MPa, under a nitrobenzene mass space velocity of 1 h -1 -1 and a hydrogen / nitrobenzene molar ratio of 12:1.

[0081] After the operation was stable, the conversion of nitrobenzene was 56.8% and the selectivity of aniline was 95.9%.

[0082] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, for those skilled in the art, the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions claimed by the present application.

Claims

1. A structured alloy catalyst for the hydrogenation of nitrobenzene to aniline, characterized in that, This structured alloy catalyst uses nickel foam with a nickel hydroxide coating structure as a substrate, on which a poly(o-phenylenediamine) film is grown to anchor the loaded metal ions in the solution. The catalyst is then obtained by centrifugation, washing, drying, and calcination. The supported metals include one or more of Cu, Mo, and Fe. The foamed nickel with a poly(o-phenylenediamine) film grown on it is placed in a solution of supported metal salts for a period of time, and the structured alloy catalyst is obtained by washing, drying, and calcining the anchored metal.

2. The structured alloy catalyst for the hydrogenation of nitrobenzene to aniline according to claim 1, characterized in that, Poly(o-phenylenediamine) films are formed by the polymerization and growth of o-phenylenediamine in dilute hydrochloric acid containing ammonium persulfate.

3. The structured alloy catalyst for the hydrogenation of nitrobenzene to aniline according to claim 2, characterized in that, The amount of the loaded metal added is 1-10 wt% of the mass of the nickel foam substrate.

4. The structured alloy catalyst for the hydrogenation of nitrobenzene to aniline according to any one of claims 1-3, characterized in that, Nickel foam substrate is It consists of cubic sheets or circular sheets with a diameter of 1-5 mm and a thickness of 1-5 mm.

5. A method for preparing a structured alloy catalyst for the hydrogenation of nitrobenzene to aniline as described in claim 4, characterized in that, Includes the following steps: S1. Take the nickel foam raw material, cut it into fragments of a certain size, clean it with dilute hydrochloric acid, ethanol and deionized water, and dry it; S2. First, o-phenylenediamine is added to dilute hydrochloric acid. After the o-phenylenediamine is fully dissolved, nickel foam is added and ultrasonically dispersed evenly on the surface of the nickel foam. Then, dilute hydrochloric acid containing ammonium persulfate is added dropwise. Under the condition of the oxidant ammonium persulfate, o-phenylenediamine grows on the surface of the nickel foam through polymerization to obtain PoPD@Ni-foam. S3. Dissolve the supported metal in deionized water to prepare a metal ion solution. Add PoPD@Ni-foam to the metal ion solution and stir thoroughly at room temperature to allow the metal ions to be fully adsorbed on the surface of poly(o-phenylene diamine). Then wash with deionized water, dry and calcine to obtain the structured alloy catalyst for the hydrogenation of nitrobenzene to produce aniline.

6. The method for preparing the structured alloy catalyst for the hydrogenation of nitrobenzene to aniline according to claim 5, characterized in that, In step S2, the mass ratio of nickel foam, ammonium persulfate and o-phenylenediamine is (0.5-1):(2-5):1; the concentration of dilute hydrochloric acid is 0.5-2 mol / L; and the self-polymerization reaction is carried out at room temperature for 12-24 h.

7. The method for preparing the structured alloy catalyst for the hydrogenation of nitrobenzene to aniline according to claim 5, characterized in that, In step S3, the loaded metal includes one or more of Cu, Mo, and Fe. The Mo source ion solution is any one or more of ammonium tetrathiomolybdate solution, ammonium molybdate tetrahydrate solution, molybdenum acetylacetonate solution, and molybdenum hexacarbonyl solution. The Cu source ion solution is any one or more of copper nitrate solution, copper chloride solution, and copper sulfate solution. The Fe source ion solution is any one or more of ferric nitrate solution, ferric chloride solution, and ferric sulfate solution. The stirring time is 6-24 h. During the calcination process, the calcination temperature is 500-900℃, the calcination time is 2-4 h, and the calcination atmosphere is any one of nitrogen, argon, and helium.

8. The application of a structured alloy catalyst for the hydrogenation of nitrobenzene to aniline, wherein the catalyst is prepared using the structured alloy catalyst for the hydrogenation of nitrobenzene to aniline according to any one of claims 1-4 or by the preparation method according to any one of claims 5-7, characterized in that, This catalyst is used for the continuous hydrogenation of nitrobenzene to produce aniline.

9. The application of the structured alloy catalyst for the hydrogenation of nitrobenzene to aniline according to claim 8, characterized in that, The structured alloy catalyst needs to be activated by hydrogen reduction first. The reduction conditions are: temperature 300-500℃, pressure 0.5-10MPa, and hydrogen space velocity 200-600h⁻¹. -1 The reduction time is 2-6 hours. After activation, a raw material with a nitrobenzene content of 5-30 wt% is introduced to carry out the nitrobenzene hydrogenation reaction. The hydrogenation reaction conditions are: temperature 80-200℃, pressure 0.5-10 MPa, and nitrobenzene mass hourly space velocity 0.5-4 h⁻¹. -1 The molar ratio of hydrogen to nitrobenzene is 6:1-30:1.

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