Application of solid acid catalyst in catalyzing nitrobenzene hydrogenation to prepare p-aminophenol

Abstract

The application relates to application of a solid acid catalytic catalyst in preparation of p-aminophenol through nitrobenzene hydrogenation. The application comprises the following steps: adding a solid acid catalyst, cetyltrimethylammonium bromide, deionized water and nitrobenzene into a high-pressure reactor, and reacting under magnetic stirring for 0-24 hours at 25-150 DEG C to obtain the product p-aminophenol. The activated carbon for preparing the solid acid catalyst is coconut shell activated carbon, the series of activated carbon has the advantages of large specific surface area, rich micropores and strong adsorption capacity, and the coconut shell activated carbon solid acid with different acidities is prepared to catalyze the nitrobenzene hydrogenation reaction. The application avoids using traditional liquid acid sulfuric acid to provide the acidic active sites required by the reaction, greatly alleviates the problems of equipment corrosion, environmental unfriendliness, catalyst and product separation difficulty and the like. The catalyst used has good performance, the conversion rate of nitrobenzene is up to 100%, and the yield of p-aminophenol is up to 81.17%.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering, specifically relating to the application of a solid acid catalyst in the hydrogenation of nitrobenzene to prepare p-aminophenol. Background Technology

[0002] p-Aminophenol (4-AP) is an important chemical raw material and pharmaceutical intermediate, widely used in pharmaceuticals (production of acetaminophen), dyes (synthesis of sulfur dyes, acid dyes, fur dyes and azo dyes, etc.), rubber (synthesis of phenylenediamine antioxidants), pesticides (synthesis of the plant growth regulator p-chlorophenoxyacetic acid), and photosensitive materials (manufacturing developing agents).

[0003] The process routes for preparing 4-AP can be classified according to the raw materials as follows: phenol-aniline coupling method (lower raw material cost, but high consumption, large emissions of waste, and complex low-temperature diazotization process, rarely used industrially), p-chloronitrobenzene method (severe pollution, difficult waste treatment), hydroquinone amination method (raw material price is much higher than 4-AP price, no industrial significance), p-nitrophenol method (iron powder reduction method is simple, with few side reactions, but cumbersome operation, producing large amounts of iron sludge and wastewater, causing severe pollution; catalytic hydrogenation method has high 4-AP yield, few by-products, and low waste liquid and residue emissions), nitrobenzene reduction method (metal reduction method, using Al, Fe reduces nitrobenzene (NB) to 4-AP under acidic conditions with high yield, but consumes a large amount of single metal and causes serious environmental pollution. Electrochemical reduction has the advantages of short process flow, high product purity, low cost and low pollution, but there are problems such as the selection of electrode plate materials and regeneration after electrode deactivation. Catalytic hydrogenation, under acidic conditions, uses a hydrogenation catalyst to catalyze the hydrogenation rearrangement of NB to generate 4-AP. This method has a short process flow and low pollution.

[0004] NB is produced by selectively catalytically hydrogenating NB to the intermediate phenylhydroxylamine (PHA) under acidic conditions and with a hydrogenation catalyst, followed by Bamberger rearrangement to obtain 4-AP. Several foreign companies have already put this method into production, and many domestic institutions are conducting research and development on this process. This method often uses highly concentrated sulfuric acid (mass fraction > 10%) as the acid catalyst for the PHA rearrangement, which leads to problems such as severe equipment corrosion, environmental unfriendliness, and difficulty in separating the catalyst from the product.

[0005] Therefore, developing non-traditional liquid acids to replace concentrated sulfuric acid and designing green reaction processes have become key research areas and hot topics. This invention uses high-quality coconut shells as a carbon source to prepare a series of solid acid catalysts with different acidities to replace traditional liquid sulfuric acid, using Pt / C or Pd / C as hydrogenation catalysts, and applies them to the catalytic hydrogenation of NB to prepare 4-AP. Summary of the Invention

[0006] The purpose of this invention is to provide a solid acid catalyst preparation method and its application in the catalytic hydrogenation of nitrobenzene to p-aminophenol. The catalyst uses Pt as the active component and is prepared as a coconut shell activated carbon solid acid catalyst via a sol-gel method. The solid acid in the catalyst can also work with the CO2 / H2O system to provide the necessary acid for the Bamberger rearrangement in the reaction.

[0007] The main technical solution of this invention is an application of a solid acid catalyst for the hydrogenation of nitrobenzene to p-aminophenol, characterized in that: a solid acid catalyst, a surfactant, water, and nitrobenzene are added to a high-pressure reactor, and a hydrogenation reaction is carried out under magnetic stirring to obtain the product p-aminophenol; the solid acid catalyst uses coconut shell activated carbon as a support, and is sulfonated with sulfuric acid of different concentrations to obtain solid acid catalysts with different acidities having a certain amount of platinum metal loaded as the hydrogenation active component; the solid acid in the catalyst can, together with the CO2 / H2O system, provide the required acid for the Bamberger rearrangement in the catalytic hydrogenation reaction of nitrobenzene.

[0008] Furthermore, the CO2 / H2O system is as follows: nitrobenzene, solid acid catalyst, surfactant, and water are added to the batch reaction high-pressure reactor. The high-pressure reactor is then sealed, and CO2 is introduced to replace the air inside the reactor, maintaining the pressure at 4-6 MPa to form a CO2 / H2O system. The system is heated and stirred. Once the temperature stabilizes, H2 is introduced into the reactor to raise the pressure to 4.5-6.5 MPa for hydrogenation reaction.

[0009] Furthermore, the weight ratio of nitrobenzene to water is 1:10 to 40, the weight ratio of solid acid catalyst to nitrobenzene is 1:20 to 50, and the mass ratio of surfactant to nitrobenzene is 1:100.

[0010] Furthermore, the surfactant is hexadecylammonium bromide.

[0011] Furthermore, the hydrogenation reaction temperature is 100–150°C, and the reaction time is 4–7 hours.

[0012] The preparation method of the solid acid catalyst of the present invention is as follows: the coconut shell activated carbon particles that have been ground and sieved are pretreated, washed and dried to obtain a coconut shell activated carbon carrier; sulfuric acid of different concentrations is prepared, and the prepared chloroplatinic acid solution is added to the sulfuric acid solution of different concentrations under stirring, and then the coconut shell activated carbon carrier is added, followed by filtration, washing, drying and calcination to obtain the solid acid catalyst.

[0013] Furthermore, the Pt mass content in the solid acid catalyst is 2-5%.

[0014] Furthermore, the sulfuric acid concentrations range from 0.2 to 0.8 mol / L.

[0015] Furthermore, the size of the coconut shell activated carbon particles is 60-80 mesh.

[0016] Preferably, the preparation method of the solid acid catalyst includes the following steps:

[0017] The first step is to grind and sieve the coconut shell activated carbon into granules;

[0018] The second step is to remove metal oxide ash impurities from the coconut shell activated carbon particles, wash until the pH is neutral, and then vacuum dry to obtain the coconut shell activated carbon carrier.

[0019] The third step involves mixing and stirring anhydrous ethanol and water to obtain solution A; then, under vigorous stirring, chloroplatinic acid solution is added dropwise to anhydrous ethanol, followed by rapid addition of dilute sulfuric acid to obtain solution B.

[0020] Fourth step: Add coconut shell activated carbon carrier to solution B under vigorous stirring, continue stirring, then add solution A dropwise to solution B. After the addition is complete, continue stirring, let stand, filter, wash with water and anhydrous ethanol, and vacuum dry.

[0021] The fifth step involves calcining the material obtained in the fourth step under a nitrogen atmosphere, then cooling it and maintaining it in an air atmosphere to obtain a solid acid catalyst.

[0022] More preferably, in the second step, coconut shell activated carbon is added to hydrochloric acid of appropriate concentration and boiled at normal pressure for 2 hours to remove iron, sodium metal oxides, ash impurities, etc. from the activated carbon. The solid-liquid mixture is filtered and washed with deionized water until the pH of the filtrate is neutral. The solution is tested with silver nitrate solution until no chloride ions are detected. Finally, the washed coconut shell activated carbon particles are vacuum dried at 60°C for 12 hours to obtain coconut shell activated carbon carrier.

[0023] More preferably, in the fourth step, coconut shell activated carbon carrier is added to solution B under vigorous stirring, and stirring is continued for 30 minutes. Then, solution A is added dropwise to solution B. After the addition is complete, stirring is continued for 30 minutes. Then, the mixture is allowed to stand for 2.5 hours, filtered, washed with water and anhydrous ethanol, and vacuum dried at 60°C for 12 hours.

[0024] More preferably, in the fifth step, the material obtained in the fourth step is passed through a muffle furnace with nitrogen gas at a flow rate of 100 mL / min for protection, and the temperature is raised to 400 ℃, 500 ℃ and 600 ℃ respectively at a heating rate of 10 ℃ / min. The material is then calcined at this temperature for 3 h, and then naturally cooled to 250 ℃. The nitrogen protection is then stopped, and the material is kept at 250 ℃ in an air atmosphere for 3 h to obtain a coconut shell activated carbon solid acid catalyst.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] Compared with the traditional sulfuric acid process, this invention avoids the corrosion of equipment and environmental pollution caused by sulfuric acid. Based on surfactants, it improves the solubility of organic matter in the aqueous phase, allowing the aqueous and organic phases to come into full contact. At the same time, it enables phase transfer catalytic reactions between the liquid and gas phases, accelerating the reaction rate and improving the selectivity of para-aminophenol. The addition of the main active component Pt supported on coconut shell activated carbon catalyst solves the shortcomings of insufficient acidity and low selectivity in the CO2 / H2O system, and the preparation process is simple. Implementation

[0027] The detailed information included in the following examples is for further illustration of the technical solutions of the present invention, but is not limited thereto. Unless otherwise specified, the experimental methods described in the following examples are conventional methods. Unless otherwise specified, the chemical reagents and materials described are commercially available. Example

[0028] Preparation of solid acid catalysts:

[0029] The coconut shell activated carbon particles, after being ground and sieved, are pretreated, washed, and dried to obtain a coconut shell activated carbon carrier. Sulfuric acid of different concentrations is prepared, and the prepared chloroplatinic acid solution is added to the sulfuric acid solution of different concentrations under stirring. Then the coconut shell activated carbon carrier is added, followed by filtration, washing, drying, and calcination to obtain a solid acid catalyst.

[0030] Preparation of p-aminophenol by hydrogenation of nitrobenzene:

[0031] Nitrobenzene, a solid acid catalyst, a surfactant, and water are added to a batch reaction high-pressure reactor. The weight ratio of nitrobenzene to water is 1:10–40, and the weight ratio of the solid acid catalyst to nitrobenzene is 1:20–50. The high-pressure reactor is sealed, and CO2 is introduced to replace the air in the reactor 3–5 times. The CO2 pressure is 4–6 MPa to form a CO2 / H2O system. The temperature is raised to 100–160°C, and stirring is started. After the temperature stabilizes, H2 is introduced into the reactor to raise the pressure to 4.5–6.5 MPa. The reaction is carried out for 4–7 hours. Example 1

[0032] Preparation of solid acid catalysts:

[0033] The first step is to grind the coconut shell activated carbon granules and sieve them to obtain particles of 60-80 mesh size for later use.

[0034] The second step involves adding coconut shell activated carbon to a suitable concentration of hydrochloric acid and boiling it under normal pressure for 2 hours to remove impurities such as iron, sodium, and other metal oxides. The solid-liquid mixture is then filtered and washed with deionized water until the pH of the filtrate is neutral, and tested with silver nitrate solution until no chloride ions are detected. Finally, the washed coconut shell activated carbon particles are vacuum dried at 60 °C for 12 hours to obtain the coconut shell activated carbon carrier used in the experiment.

[0035] Third, measure 25 mL of anhydrous ethanol and 8 mL of water, mix and stir to prepare a solution A; measure 50 mL of anhydrous ethanol into a beaker, add 15 mL of chloroplatinic acid solution dropwise while stirring vigorously, and then quickly add 0.8 mol / L dilute sulfuric acid to prepare another solution B.

[0036] Fourth, under vigorous stirring, add 6 g of coconut shell activated carbon carrier to solution B and continue stirring for 30 min. Then, add solution A dropwise to solution B, and continue stirring for 30 min after the addition is complete. Then let it stand for 2.5 h. Filter by suction, wash several times with water and anhydrous ethanol, and vacuum dry at 60 ℃ for 12 h.

[0037] The fifth step involves placing the sample in a muffle furnace and introducing nitrogen gas at a flow rate of 100 mL / min for protection. The temperature is then raised to 400 °C, 500 °C, and 600 °C at a heating rate of 10 °C / min, respectively, and calcined at these temperatures for 3 h. After calcination, the sample is allowed to cool naturally to 250 °C, and the nitrogen protection is stopped. The sample is then kept at 250 °C in air for 3 h to obtain the coconut shell activated carbon solid acid catalyst.

[0038] Preparation of p-aminophenol by hydrogenation of nitrobenzene:

[0039] 2.45 g of nitrobenzene, 0.14 g of solid acid catalyst, 0.02 g of hexadecyltrimethylammonium bromide, and 50 mL of water were added to a batch high-pressure reactor. The reactor was sealed, and CO2 was introduced to replace the air in the reactor 3-5 times at a pressure of 5.5 MPa to form a CO2 / H2O system. The temperature was raised to 160 °C, and stirring was started at 700 rpm / min. After the temperature stabilized, H2 was introduced into the reactor to raise the pressure to 6 MPa, and the reaction was carried out for 7 hours. After the reaction was completed, the high-pressure reactor was cooled to room temperature, and the pressure in the reactor was released. Finally, the reaction liquid in the reactor was filtered, and the filter cake was used to recover and reuse the catalyst. The components and contents of the filtrate were analyzed by high-performance liquid chromatography. The analysis results showed that the conversion rate of nitrobenzene was 71.2%, and the selectivity for p-aminophenol was 30.2%. Example 2

[0040] The other steps are the same as in Example 1, except that different carbon dioxide pressures are applied.

[0041] 2.45 g nitrobenzene, 0.06 g solid acid catalyst, 0.02 g CTAB, stirring speed: 1000 rpm, temperature: 130 °C, H₂O: 50 mL; reaction time: 5 h, hydrogen pressure: 0.5 MPa. The results showed that the nitrobenzene conversion was 100% at CO₂ pressures of 3.5 MPa and 4 MPa, with 0% selectivity for aminophenol. At a CO₂ pressure of 5.5 MPa, the nitrobenzene conversion was 21.5%, and the selectivity for aminophenol was 51.6%. Example 3

[0042] The other steps are the same as in Example 1, except for the reaction temperature.

[0043] 2.45 g of nitrobenzene, 0.06 g of solid acid catalyst, 0.02 g of CTAB, 50 mL of H2O, and CO2 and H2 pressures of 5.5 and 0.5 MPa respectively were used. The stirring speed was 700 rpm, and the reaction time was 6 h. The results showed that at 130℃, the nitrobenzene conversion was 21.5% and the selectivity for p-aminophenol was 51.6%. At 150℃, the nitrobenzene conversion was 21.6% and the selectivity for p-aminophenol was 70.1%. At 160℃, the nitrobenzene conversion was 68.1% and the selectivity for p-aminophenol was 55.3%. Example 4

[0044] The other steps are the same as in Example 1, except for the amount of catalyst used.

[0045] 2.45 g nitrobenzene, 0.02 g CTAB, 50 mL H₂O, CO₂ and H₂ pressures of 5.5 MPa and 0.5 MPa respectively, stirring speed of 700 rpm, reaction temperature of 150 °C, reaction time of 7 h. The results showed that when the catalyst dosage was 0.06 g of solid acid catalyst, the nitrobenzene conversion was 21.6% and the selectivity for p-aminophenol was 70.1%. When the catalyst dosage was 0.12 g of solid acid catalyst, the nitrobenzene conversion was 62.8% and the selectivity for p-aminophenol was 81.1%. Example 5

[0046] The other steps are the same as in Example 1, except for the reaction time.

[0047] The reaction mixture consisted of 2.45 g nitrobenzene, 0.06 g solid acid catalyst, 0.02 g CTAB, 50 mL H₂O, and CO₂ and H₂ pressures of 5.5 and 0.5 MPa, respectively. The stirring speed was 700 rpm, and the reaction temperature was 150 °C. The results showed that after 5 h, the nitrobenzene conversion was 16.1% and the selectivity for aminophenol was 59.1%; after 6 h, the conversion was 21.6% and the selectivity for aminophenol was 70.1%; and after 7 h, the conversion was 60.1% and the selectivity for aminophenol was 64.2%. Example 6

[0048] The other steps are the same as in Example 1, except for the amount of glacial acetic acid used.

[0049] 2.45 g nitrobenzene, 0.06 g solid acid catalyst, 0.02 g CTAB, 50 mL H₂O, CO₂ and H₂ pressures of 4 and 0.3 MPa respectively, stirring speed of 1000 rpm, reaction time of 6 h, 110 °C. The results showed that when 5 mL of glacial acetic acid was used, the nitrobenzene conversion rate was 32.8% and the selectivity for p-aminophenol was 10.6%; when 10 mL of glacial acetic acid was used, the nitrobenzene conversion rate was 78.5% and the selectivity for p-aminophenol was 12.7%.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] Compared with the traditional sulfuric acid process, this invention avoids the corrosion of equipment and environmental pollution caused by sulfuric acid. Based on surfactants, it improves the solubility of organic matter in the aqueous phase, allowing the aqueous and organic phases to come into full contact. At the same time, it enables phase transfer catalytic reactions between the liquid and gas phases, accelerating the reaction rate and improving the selectivity of para-aminophenol. The addition of the main active component Pt supported on coconut shell activated carbon catalyst solves the shortcomings of insufficient acidity and low selectivity in the CO2 / H2O system, and the preparation process is simple.

[0052] Matters not covered in this invention are common knowledge.

Claims

1. An application of a solid acid catalyst in the hydrogenation of nitrobenzene to p-aminophenol, characterized in that: A solid acid catalyst, surfactant, water, and nitrobenzene were added to a high-pressure reactor. The weight ratio of nitrobenzene to water was 1:10 to 40, the weight ratio of solid acid catalyst to nitrobenzene was 1:20 to 50, and the mass ratio of surfactant to nitrobenzene was 1:

100. The hydrogenation reaction was carried out under magnetic stirring to obtain the product p-aminophenol. The solid acid catalyst uses coconut shell activated carbon as a support and is sulfonated with sulfuric acid of different concentrations to obtain solid acid catalysts with different acidities that are loaded with a certain amount of platinum metal as the hydrogenation active component. The preparation method of the solid acid catalyst includes the following steps: The first step is to grind and sieve the coconut shell activated carbon into granules; The second step involves adding coconut shell activated carbon granules into hydrochloric acid of appropriate concentration and boiling them under normal pressure for 2 hours to remove iron, sodium metal oxides, ash impurities, etc. from the activated carbon. The solid-liquid mixture is then filtered and washed with deionized water until the pH of the filtrate is neutral. The solution is tested with silver nitrate solution until no chloride ions are detected. Finally, the washed coconut shell activated carbon granules are vacuum dried at 60°C for 12 hours to obtain the coconut shell activated carbon carrier. The third step involves mixing and stirring anhydrous ethanol and water to obtain solution A; then, under vigorous stirring, chloroplatinic acid solution is added dropwise to anhydrous ethanol, followed by rapid addition of dilute sulfuric acid to obtain solution B. Fourth step: Add coconut shell activated carbon carrier to solution B under vigorous stirring, continue stirring, then add solution A dropwise to solution B. After the addition is complete, continue stirring, let stand, filter, wash with water and anhydrous ethanol, and vacuum dry. The fifth step involves calcining the material obtained in the fourth step under a nitrogen atmosphere, cooling it, and then maintaining it in an air atmosphere to obtain a solid acid catalyst. The solid acid in the catalyst can work together with the CO2 / H2O system to provide the required acid for the Bamberger rearrangement in the catalytic hydrogenation of nitrobenzene; The CO2 / H2O system is as follows: Nitrobenzene, solid acid catalyst, surfactant, and water are added to a batch reaction high-pressure reactor. The high-pressure reactor is then sealed, and CO2 is introduced to replace the air inside the reactor, maintaining the pressure at 4–6 MPa to form a CO2 / H2O system. The system is heated and stirred. Once the temperature stabilizes, H2 is introduced into the reactor to raise the pressure to 4.5–6.5 MPa for hydrogenation reaction. The hydrogenation reaction temperature is 100–160°C, and the reaction time is 4–7 hours.

2. The application according to claim 1, characterized in that: The surfactant is hexadecyltrimethylammonium bromide.

3. The application according to claim 1, characterized in that: The Pt content in the solid acid catalyst is 2-5% by mass.

4. The application according to claim 1, characterized in that: The different concentrations of sulfuric acid range from 0.2 to 0.8 mol / L.

5. The application according to claim 1, characterized in that: The size of the coconut shell activated carbon particles is 60-80 mesh.

6. The application according to claim 1, characterized in that: the solid acid catalyst preparation step: In the fourth step, coconut shell activated carbon carrier is added to solution B under vigorous stirring. Stirring is continued for 30 minutes. Then solution A is added dropwise to solution B. After the addition is complete, stirring is continued for 30 minutes. Then, the mixture is allowed to stand for 2.5 hours, filtered, washed with water and anhydrous ethanol, and vacuum dried at 60°C for 12 hours. In the fifth step, the material obtained in the fourth step is placed in a muffle furnace and protected with nitrogen gas at a flow rate of 100 mL / min. The temperature is raised to 400 ℃, 500 ℃ and 600 ℃ respectively at a heating rate of 10 ℃ / min, and calcined at this temperature for 3 h. Then, it is naturally cooled to 250 ℃, the nitrogen protection is stopped, and it is maintained at 250 ℃ in air atmosphere for 3 h to obtain the coconut shell activated carbon solid acid catalyst.