Method for preparing eggshell catalyst for continuous selective hydrogenation of nitrobenzene to anilines and use thereof

Abstract

The application belongs to the technical field of catalyst preparation, and discloses a method for preparing an eggshell type catalyst for continuously and selectively hydrogenating nitrobenzene with a substituent group into an aniline with a substituent group and application thereof. A hydrothermal synthesis method is used to produce petal type hydrotalcite-like lamellas in situ on the surface of γ-Al2O3 balls, and a bimetallic oxide eggshell type catalyst γ-Al2O3@NiFe-MMO is obtained by calcining in an O / Ar gas atmosphere. The active metal of the catalyst is highly dispersed and uniformly dispersed on the surface of the ball, and the catalyst can be safely, continuously and stably operated on a fixed bed, and has good heat transfer effect. The catalyst has a low non-noble metal loading, and still has high activity, selectivity and stability under relatively mild reaction conditions. The preparation process is simple, the carrier and active metal are abundant and cheap and easy to obtain, the synthesis cost is greatly reduced, and the catalyst has the potential to replace noble metal catalysts and good industrial promotion value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst preparation, and particularly relates to a preparation method of an eggshell type catalyst for continuously selectively hydrogenating a substituted nitrobenzene to prepare a substituted aniline and application thereof. BACKGROUND

[0002] The preparation of a corresponding substituted aniline by hydrogenation of a substituted nitrobenzene is a very important chemical process. The substituted aniline is an important component of fine chemicals and bulk chemicals, and can be used to manufacture polyurethane, dyes, medicines, pesticides, rubber vulcanizing agents, gasoline additives, etc. The early production process of the substituted aniline is an iron powder reduction method, but it has been eliminated because of the huge consumption of iron powder, serious equipment corrosion, slow reaction rate, difficult product separation, serious pollution and other problems that do not meet the requirements of green chemical production. The second is a phenol ammoniation method, but it has been gradually eliminated because of high energy consumption, large capital investment and high production process cost. The electrochemical reduction method is restricted in large-scale production application because of high energy consumption. The catalytic hydrogenation reduction method meets the requirements of green chemistry because of controllable production, high product purity, high catalyst utilization rate and good atom economy.

[0003] Patents CN116272964A and CN115254167A disclose a catalyst doped with phosphorus, sulfur and nitrogen elements for catalyzing o-chloronitrobenzene and p-chloronitrobenzene to prepare the corresponding aniline. However, the preparation of the catalyst is relatively complicated, and the use of phosphorus-containing organic matter in the preparation pollutes the environment and is difficult to handle, which does not meet the requirements of green chemistry. The reaction is carried out in a reaction kettle, which is not conducive to continuous production. The use of noble metals is high in cost and difficult to recycle and separate, which is not conducive to large-scale promotion and utilization.

[0004] Patents CN111871415A and CN101333169A disclose the application of o-chloronitrobenzene to generate o-chloroaniline. However, the amine dehalogenation inhibitor added during the reaction is difficult to remove in the product, which increases the treatment cost and reduces the product purity.

[0005] Patents CN115739080A, CN110407707A and CN104672094A disclose a method for preparing a corresponding aniline by hydrogenation of a substituted nitrobenzene in a fixed bed. However, these catalysts have small particle sizes, and when applied to a fixed bed liquid phase reaction, the pressure difference is large. At the same time, the reactants enter the inside of the catalyst to react and release heat, which easily forms hot spots to cause sintering and polymerization of the active metal, resulting in an increase in particle size and a decrease in conversion rate and selectivity. SUMMARY

[0006] The application provides a shell catalyst for continuously and selectively hydrogenating substituted nitrobenzene to prepare substituted aniline, and aims to solve the problems existing in the prior art of preparing substituted aniline from substituted nitrobenzene, i.e., (1) organic pollutants such as phosphorus and sulfur are used in the preparation process of the catalyst; (2) other additives are added in the reaction process, which is difficult to separate and increases the cost; (3) a small particle size catalyst carrier is selected, so that the pressure difference of the reaction is large; and (4) the heat generated in the reaction cannot be quickly diffused in the fixed bed, so that the temperature rise of the reaction is difficult to control.

[0007] The technical scheme of the application is as follows:

[0008] A method for preparing a shell catalyst for continuously and selectively hydrogenating substituted nitrobenzene to prepare substituted aniline, and the steps are as follows:

[0009] (1) carrier pretreatment: γ-Al2O3 carriers with a particle size of 1-2 mm are placed in a muffle furnace and calcined at 400-600 DEG C for 2-6 h;

[0010] (2) catalyst precursor synthesis: nickel salt, iron salt, urea and ammonium nitrate with a molar ratio of (0.1-1) : (0.2-1) : (1-5) : 1 are sequentially added to deionized water and stirred and dissolved, wherein the concentration of ammonium nitrate is 0.2 mol / L; the carrier obtained in step (1) is added to the prepared solution, and is aged at room temperature for 4-6 h, and then is transferred to a high-pressure hydrothermal reaction kettle and reacted at 80-160 DEG C for 8-24 h; the sample is separated and washed to neutral, and is dried in an oven at 60-80 DEG C for 12-24 h, thereby obtaining a γ-Al2O3@NiFe-LDHs precursor;

[0011] (3) catalyst calcination: the γ-Al2O3@NiFe-LDHs precursor prepared in step (2) is calcined at 300-600 DEG C for 2-6 h, thereby obtaining a nickel-iron bimetallic oxide shell catalyst (γ-Al2O3@NiFe-MMO).

[0012] The nickel salt is one or more than two kinds of mixture of nickel nitrate, nickel acetate and nickel acetylacetone, and the iron salt is one or more than two kinds of mixture of iron nitrate, iron chloride, ferrous chloride and iron acetylacetone.

[0013] The application of an eggshell type catalyst for preparing substituted aniline by continuously selecting hydrogenation of substituted nitrobenzene: the eggshell type (γ-Al2O3@NiFe-MMO) catalyst needs to be in-situ reduced and activated in a fixed bed before hydrogenation of substituted nitrobenzene; the activation conditions are as follows: H2 pressure 0.5-6 MPa, H2 flow rate 20-200 mL / min, activation degree 300-500 DEG C, and activation time 2-6 h; and the reaction conditions are as follows: reaction pressure 1-6 MPa, reaction temperature 60-160 DEG C, hydrogen / oil ratio 100-600, and raw material volume flow rate 0.05-1 mL / min.

[0014] The substituted nitrobenzene includes o-chloronitrobenzene, p-chloronitrobenzene, p-bromonitrobenzene, p-nitrotoluene, m-nitrophenol and nitrobenzene.

[0015] The preparation method of the eggshell type catalyst for hydrogenation of substituted nitrobenzene in the application can obtain the eggshell type catalyst with active metal highly dispersed and uniformly dispersed on the surface of γ-Al2O3 balls with a suitable particle size without using organic phosphorus and sulfur precursor salts, the catalyst can be safely and continuously and stably operated on a fixed bed, and the heat transfer effect is good; no inhibitor needs to be added, the separation cost is reduced; the catalyst still has high activity, selectivity and stability under the conditions of low non-noble metal loading and relatively mild reaction conditions. The preparation process is simple, the carrier and active metal are abundant and cheap and easy to obtain, the synthesis cost is greatly reduced, and the application is convenient for industrialization. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 (a) is a physical picture of the eggshell type catalyst of example 1;

[0017] Figure 1 (b) is a cross-sectional view of the eggshell type catalyst of example 1.

[0018] Figure 2 (a) is a line scanning graph of the EPMA nickel element of the eggshell type catalyst of example 1;

[0019] Figure 2 (b) is a line scanning graph of the EPMA iron element of the eggshell type catalyst of example 1;

[0020] Figure 2 (c) is a partial surface scanning graph of the EPMA nickel element of the eggshell type catalyst of example 1;

[0021] Figure 2 (d) is a partial surface scanning graph of the EPMA iron element of the eggshell type catalyst of example 1. DETAILED DESCRIPTION

[0022] The application will be described in detail through examples, but the application is not limited to the examples.

[0023] Example 1

[0024] Preparation of a γ-Al2O3@Ni3Fe1-MMO eggshell type catalyst with a nickel-iron molar ratio of 3:1

[0025] Nickel nitrate, iron nitrate, urea, and ammonium nitrate with a molar ratio of 0.75:0.25:3:1 were sequentially added to 50 ml of deionized water and stirred to dissolve, wherein the concentration of ammonium nitrate was 0.2 mol / L; 2 g of calcined γ-Al2O3 was added to the prepared solution, and after static aging at 30°C for 4 h, it was loaded into a high-pressure reaction kettle and reacted at 110°C for 12 h. After the reaction was completed, it was naturally cooled to room temperature, the sample was taken out and ultrasonically washed, and then placed in an 80°C oven for 12 h to dry, thereby obtaining γ-Al2O3@Ni3Fe1-LDHs.

[0026] The dried precursor was heated to 450°C at a heating rate of 5°C / min, calcined in an O2:Ar (v / v) = 1:2 atmosphere for 4 h, thereby obtaining a γ-Al2O3@Ni3Fe1-MMO eggshell type catalyst with a nickel-iron molar ratio of 3:1.

[0027] Example 2

[0028] Preparation of a γ-Al2O3@Ni2Fe1-MMO eggshell type catalyst with a nickel-iron molar ratio of 2:1

[0029] Nickel nitrate, iron nitrate, urea, and ammonium nitrate with a molar ratio of 0.66:0.33:2:1 were sequentially added to 50 ml of deionized water and stirred to dissolve, wherein the concentration of ammonium nitrate was 0.2 mol / L; 2 g of calcined γ-Al2O3 was added to the prepared solution, and after static aging at 30°C for 4 h, it was loaded into a high-pressure reaction kettle and reacted at 110°C for 12 h. After the reaction was completed, it was naturally cooled to room temperature, the sample was taken out and ultrasonically washed, and then placed in an 80°C oven for 12 h to dry, thereby obtaining γ-Al2O3@Ni2Fe1-LDHs.

[0030] The dried precursor was heated to 450°C at a heating rate of 5°C / min, calcined in an O2:Ar (v / v) = 1:2 atmosphere for 4 h, thereby obtaining a γ-Al2O3@Ni2Fe1-MMO eggshell type catalyst with a nickel-iron molar ratio of 2:1.

[0031] Example 3

[0032] Preparation of a γ-Al2O3@Ni1Fe1-MMO eggshell type catalyst with a nickel-iron molar ratio of 1:1

[0033] Nickel nitrate, iron nitrate, urea and ammonium nitrate with a molar ratio of 0.5:0.5:1:1 were sequentially added into 50 ml of deionized water for stirring and dissolving, wherein the concentration of ammonium nitrate was 0.2 mol / L; 2 g of γ-Al2O3 after calcination was added into the prepared solution, and after static aging at 30℃ for 4 h, it was loaded into a high-pressure reaction kettle for reaction at 110℃ for 12 h; after the reaction was completed, it was naturally cooled to room temperature, the sample was taken out for ultrasonic washing, and was placed into a 80℃ oven for drying for 12 h to obtain γ-Al2O3@Ni1Fe1-LDHs.

[0034] The dried precursor was heated to 450℃ at a heating rate of 5℃ / min, and was calcined in an O2:Ar (v / v) = 1:2 atmosphere for 4 h to obtain a γ-Al2O3@Ni1Fe1-MMO eggshell type catalyst with a nickel-iron molar ratio of 1:1.

[0035] Example 4

[0036] Preparation of a γ-Al2O3@NiO eggshell type catalyst

[0037] Nickel nitrate, urea and ammonium nitrate with a molar ratio of 0.75:3:1 were sequentially added into 50 ml of deionized water for stirring and dissolving, wherein the concentration of ammonium nitrate was 0.2 mol / L; 2 g of γ-Al2O3 after calcination was added into the prepared solution, and after static aging at 30℃ for 4 h, it was loaded into a high-pressure reaction kettle for reaction at 110℃ for 12 h; after the reaction was completed, it was naturally cooled to room temperature, the sample was taken out for ultrasonic washing, and was placed into a 80℃ oven for drying for 12 h to obtain γ-Al2O3@NiAl-LDHs.

[0038] The dried precursor was heated to 450℃ at a heating rate of 5℃ / min, and was calcined in an O2:Ar (v / v) = 1:2 atmosphere for 4 h to obtain a metal oxide eggshell type catalyst γ-Al2O3@NiO.

[0039] Example 5

[0040] Preparation of a γ-Al2O3@Fe2O3 eggshell type catalyst

[0041] Ferrous chloride, urea and ammonium nitrate with a molar ratio of 0.25:3:1 were sequentially added into 50 ml of deionized water for stirring and dissolving, wherein the concentration of ammonium nitrate was 0.2 mol / L; 2 g of γ-Al2O3 after calcination was added into the prepared solution, and after static aging at 30℃ for 4 h, it was loaded into a high-pressure reaction kettle for reaction at 110℃ for 12 h; after the reaction was completed, it was naturally cooled to room temperature, the sample was taken out for ultrasonic washing, and was placed into a 80℃ oven for drying for 12 h to obtain γ-Al2O3@FeAl-LDHs.

[0042] The dried precursor was heated to 450 °C at a heating rate of 5 °C / min, and calcined in an O2:Ar (v / v) = 1:2 atmosphere for 4 h to obtain the metal oxide eggshell catalyst γ-Al2O3@Fe2O3.

[0043] Example 6

[0044] 1 g of the metal oxide eggshell catalyst in Example 1-5 was uniformly mixed with 20-40 mesh quartz sand, and then loaded into the middle part of the fixed bed reactor tube. The upper and lower parts of the reactor tube were filled with 40-80 mesh quartz sand. The catalyst was reduced in situ, and the fixed bed reactor furnace was set to heat to 400 °C at a rate of 5 °C / min and maintained for 4 h. The reaction pressure was set to 2 MPa, and the hydrogen flow rate was set to 40 ml / min. After reduction, the reactor was naturally cooled to 80 °C, the reactor furnace was adjusted to maintain the reactor at 80 °C, the pressure was maintained at 2 MPa, and the system was adjusted to a steady state. The feed pump was turned on, the feed rate was adjusted to 0.2 ml / min, and a 1% o-chloronitrobenzene ethanol solution was pumped in. After 12 hours of reaction, the sample was discarded after 50 min, and a sample was taken for analysis after 10 min.

[0045]

[0046] Example 7

[0047] The precursor γ-Al2O3@Ni3Fe1-LDHs prepared in Example 1 was heated to 350 °C at a heating rate of 5 °C / min, and calcined in an O2:Ar (v / v) = 1:2 atmosphere for 4 h to obtain the γ-Al2O3@Ni3Fe1-MMO eggshell catalyst with a nickel-iron molar ratio of 3:1.

[0048] 1 g of the metal oxide eggshell catalyst in Example 1 was uniformly mixed with 20-40 mesh quartz sand, and then loaded into the middle part of the fixed bed reactor tube. The upper and lower parts of the reactor tube were filled with 40-80 mesh quartz sand. The catalyst was reduced in situ, and the fixed bed reactor furnace was set to heat to 400 °C at a rate of 5 °C / min and maintained for 4 h. The reaction pressure was set to 2 MPa, and the hydrogen flow rate was set to 40 ml / min. After reduction, the reactor was naturally cooled to 80 °C, the reactor furnace was adjusted to maintain the reactor at 80 °C, the pressure was maintained at 2 MPa, and the system was adjusted to a steady state. The feed pump was turned on, the feed rate was adjusted to 0.2 ml / min, and a 1% o-chloronitrobenzene ethanol solution was pumped in. After 12 hours of reaction, the sample was discarded after 50 min, and a sample was taken for analysis after 10 min.

[0049] Example 8

[0050] The precursor γ-Al2O3@Ni3Fe1-LDHs prepared in Example 1 was heated to 450℃ at a heating rate of 5℃ / min, and calcined in an O2:Ar (v / v) = 1:2 atmosphere for 4h, to obtain γ-Al2O3@Ni3Fe1-MMO eggshell type catalysts with a nickel-iron molar ratio of 3:1, respectively.

[0051] The reaction conditions were the same as in Example 7.

[0052] Example 9

[0053] The precursor γ-Al2O3@Ni3Fe1-LDHs prepared in Example 1 was heated to 550℃ at a heating rate of 5℃ / min, and calcined in an O2:Ar (v / v) = 1:2 atmosphere for 4h, to obtain γ-Al2O3@Ni3Fe1-MMO eggshell type catalysts with a nickel-iron molar ratio of 3:1, respectively.

[0054] The reaction conditions were the same as in Example 7.

[0055] The reaction results of catalysts at different calcination temperatures are as follows:

[0056]

[0057] Example 10 (catalyst applicability test)

[0058] 1g of the metal oxide eggshell type catalyst in Example 1 was weighed, mixed with 20-40 mesh quartz sand, and then loaded into the middle part of the fixed bed reactor tube. The upper and lower parts of the reactor tube were filled with 40-80 mesh quartz sand. The catalyst was reduced in situ, and the fixed bed reactor heating furnace was set to heat at a rate of 5℃ / min to 400℃ and maintained for 4h. The reaction pressure was set to 2MPa, and the hydrogen flow was set to 40ml / min. After reduction, the reactor was naturally cooled to 80℃, the reactor heating furnace was adjusted to maintain the reactor at 80℃, the pressure was maintained at 2MPa, and the system was adjusted to a steady state. The feed pump was opened, and the feed rate was adjusted to 0.2ml / min. The 1% p-chloronitrobenzene ethanol solution, the p-nitrophenol ethanol solution, the p-nitrotoluene ethanol solution, and the nitrobenzene ethanol solution were pumped in, respectively. After 12 hours of reaction, the sample was discarded after 50min, and the sample was taken for analysis after 10min.

[0059] Number Conversion (%) Selectivity (%) p-Chloronitrobenzene 95.3 97.1 p-Bromonitrobenzene 94.6 95.6 p-Nitrotoluene 97.4 99.0 m-Nitrophenol 94.5 99.5 Nitrobenzene 96.1 99.1

[0060] As can be seen from the experimental results, the eggshell type catalyst prepared by the present application has good conversion rate and selectivity under mild reaction conditions, and has certain applicability to different substituted nitrobenzene.

Claims

1. Use of an eggshell type catalyst for the continuous selective hydrogenation of a nitro-substituted benzene to an amino-substituted benzene, characterized in that, The preparation steps of the eggshell type catalyst are as follows: (1) carrier pretreatment: the γ-Al2O3 carrier with a particle size of 1-2 mm is placed in a muffle furnace and calcined at 400-600°C for 2-6h; (2) catalyst precursor synthesis: nickel salt, iron salt, urea and ammonium nitrate with a molar ratio of (0.1-1):(0.2-1):(1-5):1 are sequentially added to deionized water and stirred to dissolve, wherein the concentration of ammonium nitrate is 0.2mol / L; the carrier obtained in step (1) is added to the prepared solution, and is aged at room temperature for 4-6h; after aging, it is transferred to a high-pressure hydrothermal reaction kettle and reacted at 80-160°C for 8-24h; the sample is separated and washed to neutral, and is dried in an oven at 60-80°C for 12-24h, thereby obtaining the γ-Al2O3@NiFe-LDHs precursor; (3) catalyst calcination: the γ-Al2O3@NiFe-LDHs precursor prepared in step (2) is calcined at 300-600°C for 2-6h, thereby obtaining the eggshell type catalyst γ-Al2O3@NiFe-MMO of nickel-iron bimetallic oxide; The eggshell type γ-Al2O3@NiFe-MMO catalyst of nickel-iron bimetallic oxide needs to be activated in situ by reduction in a fixed bed before the hydrogenation of the substituted nitrobenzene; the activation conditions are as follows: H2 pressure 0.5-6MPa, H2 flow rate 20-200mL / min, activation temperature 300-500°C, and activation time 2-6h; the reaction conditions are as follows: reaction pressure 1-6MPa, reaction temperature 60-160°C, hydrogen / oil ratio 100-600, and raw material volume flow rate 0.05-1mL / min.

2. Use according to claim 1, characterized in that, The nickel salt is one or a mixture of two or more of nickel nitrate, nickel acetate and nickel acetylacetone.

3. Use according to claim 1, characterized in that, The iron salt is one or a mixture of two or more of iron nitrate, iron chloride and iron acetylacetone.

4. Use according to claim 1, characterized in that, The substituted nitrobenzene includes o-chloronitrobenzene, p-chloronitrobenzene, p-bromonitrobenzene and p-nitrotoluene.

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