Catalyst for continuous production of m-aminobenzenesulfonic acid, its preparation method and application

Abstract

The application discloses a kind of catalyst for m-aminobenzenesulfonic acid continuous production and its preparation method and application, the catalyst preparation method includes: after active carbon is pretreated by acid oxidation, nitrogen doping treatment is carried out, and nitrogen-doped active carbon carrier is obtained;Platinum precursor, cerium precursor and complexing agent are dissolved in solvent, and prepared into composite solution;Spraying mode is uniformly loaded on the surface of nitrogen-doped active carbon carrier after preheating, dried, and load type solid material is obtained;Reduction treatment is carried out in reducing atmosphere, and Pt-Ce bimetallic catalyst precursor is obtained;It is placed in the modification atmosphere containing organosilane passivation agent and carried out passivation treatment and obtains.The catalyst is matched with fixed bed continuous reaction system, can realize the complete conversion of raw material under mild reaction condition, the ultra-high selectivity of target product and the extremely low impurity rate, and has excellent long-term running stability, product is easy to separate, safety is good, cost is significantly reduced, and easy to industrial application.

Description

Technical Field

[0001] This invention belongs to the field of catalytic hydrogenation technology, specifically relating to a catalyst for the continuous production of m-aminobenzenesulfonic acid, its preparation method, and its application. Background Technology

[0002] m-Aminobenzenesulfonic acid is an important fine chemical intermediate widely used in the production of dyes, pesticides, pharmaceuticals, and fluorescent whitening agents. Its traditional production processes mainly include the intermittent iron powder reduction method and the sodium sulfide reduction method. However, these traditional methods have inherent drawbacks such as large emissions of "three wastes" (waste gas, wastewater, and waste residue), serious environmental pollution, unstable product quality, and low production efficiency, making it difficult to meet the requirements of modern green chemical engineering and sustainable development.

[0003] Catalytic hydrogenation technology, especially heterogeneous catalytic hydrogenation using noble metals as active components, has become the mainstream development direction to replace traditional reduction processes due to its significant advantages such as high atom economy, environmental friendliness, high product purity, and ease of continuous production. Currently, commonly used industrial hydrogenation catalysts include Pd / C and Raney Ni. However, applying these traditional catalysts to the hydrogenation reaction of sodium m-nitrobenzenesulfonate still faces a series of technical challenges: Poor selectivity and high impurity content: When using traditional catalysts such as Pd / C, side reactions such as dechlorination are prone to occur during the process of reducing nitro groups to amino groups, generating toxic impurities such as aniline.

[0004] Harsh reaction conditions: To achieve high conversion rates, traditional processes typically require high reaction temperatures (>100℃) and high hydrogen pressures (>3MPa). This not only significantly increases energy consumption and equipment investment costs but also places higher demands on production safety and increases operational risks.

[0005] Insufficient catalyst stability and short lifespan: During long-term operation, traditional Pd / C or Raney Ni catalysts are prone to migration and agglomeration of active metal components, or deactivation due to carbon buildup or feedstock poisoning, resulting in a short catalyst lifespan (typically only a few hundred hours). Frequent catalyst replacements not only increase production costs but also lead to unplanned downtime of the production line, reducing overall production efficiency.

[0006] Catalyst preparation processes are complex and costly: Existing catalyst preparation methods, such as impregnation, often lack precise control over the dispersion and particle size distribution of active metals, resulting in low utilization rates of precious metals. Furthermore, complex post-processing steps are sometimes required to suppress side reactions, keeping the overall catalyst preparation cost high.

[0007] Developing a novel catalyst and its supporting process that can achieve high conversion rate, high selectivity, low impurity rate, and excellent long-term stability under mild reaction conditions is of great industrial value and practical significance for promoting the green and efficient upgrading of m-aminobenzenesulfonic acid production technology. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a catalyst for the continuous production of m-aminobenzenesulfonic acid, its preparation method and application. By using nitrogen-doped activated carbon to support Pt-Ce bimetallic active components, a composite catalyst is prepared by HMDS gas-phase grafting technology. This catalyst, when paired with a fixed-bed continuous reaction system, can achieve complete conversion of raw materials, ultra-high selectivity of target products and extremely low impurity rate under mild reaction conditions. It also has excellent long-term operational stability, easy product separation, good safety, significantly reduced cost, and is easy to industrialize.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, a method for preparing a catalyst for the continuous production of m-aminobenzenesulfonic acid is provided, comprising: Step (1): After acid oxidation pretreatment, activated carbon is placed in an ammonia atmosphere for nitrogen doping treatment to obtain nitrogen-doped activated carbon carrier N-AC; Step (2): Dissolve the platinum precursor, cerium precursor and complexing agent in a solvent to prepare a composite solution; Step (3): The composite solution is uniformly loaded onto the surface of the preheated N-AC carrier by spraying, and then dried to obtain the loaded solid material. Step (4): The supported solid material is placed in a reducing atmosphere for reduction treatment to obtain the Pt-Ce bimetallic catalyst precursor; Step (5): The Pt-Ce bimetallic catalyst precursor is placed in a modified atmosphere containing organosilanes as passivating agents for passivation treatment to obtain the Pt-Ce / N-AC bimetallic composite catalyst.

[0010] In some embodiments, in step (1), the activated carbon is columnar activated carbon, preferably with a particle size of 20-40 mesh.

[0011] In some embodiments, in step (1), the acid is at least one of nitric acid, hydrochloric acid, and sulfuric acid. In some embodiments, the mass concentration of the acid is 5-15%. In some embodiments, in step (1), the activated carbon undergoes acid oxidation pretreatment by immersing the activated carbon in an acid with a mass concentration of 5%-15% for 6-12 hours, then washing it with water until neutral and drying it at 100-120°C. In some embodiments, in step (1), the nitrogen doping treatment refers to heating the activated carbon to 500-800°C, preferably 600-700°C, at a heating rate of 3-8°C / min in an ammonia atmosphere, and then isothermally treating the activated carbon for 3-8 hours, preferably 4-6 hours.

[0012] In some embodiments, in step (2), the platinum precursor is chloroplatinic acid or chloroplatinate. In some embodiments, the chloroplatinate is selected from at least one of ammonium chloroplatinate, potassium chloroplatinate, and sodium chloroplatinate.

[0013] In some embodiments, in step (2), the cerium precursor is cerium nitrate or cerium ammonium nitrate.

[0014] In some embodiments, in step (2), the complexing agent is disodium ethylenediaminetetraacetate (EDTA disodium) or citric acid.

[0015] In some embodiments, in step (2), the solvent is ultrapure water, methanol, ethanol, 95% ethanol, or deionized water. In some embodiments, in the composite solution, the Pt atom concentration is 15~30 g / L, the Ce atom concentration is 5~12 g / L, and the complexing agent concentration is 0.05~0.15 mol / L.

[0016] In some embodiments, in step (3), the spraying method involves rolling the N-AC carrier at a speed of 20-40 rpm in a coating machine while simultaneously spraying the composite solution evenly onto the surface of the N-AC carrier. In some embodiments, the drying process includes pre-drying at 60-80°C for 1-3 hours, followed by drying at 100-120°C for 4-6 hours. In some embodiments, the N-AC carrier needs to be preheated to 30-70°C before spraying. In some embodiments, the mass-to-volume ratio of the N-AC carrier to the composite solution is 100 g / L.

[0017] In some embodiments, in step (4), the reducing atmosphere includes nitrogen and hydrogen in a volume ratio of (19~27):1. In some embodiments, in step (4), the temperature of the reduction treatment is 270~370℃, preferably 300~350℃, and the time is 3~6h, preferably 4~6h.

[0018] In some embodiments, the organosilane passivating agent is hexamethyldisiloxane (HMDS).

[0019] In some embodiments, the modified atmosphere consists of an inert gas carrying organosilane passivating agent vapor; the passivation treatment temperature is 85-135°C, preferably 100-120°C, and the time is 2-3 hours. In some embodiments, the inert gas is nitrogen or argon. In some embodiments, the volume ratio of hexamethyldisiloxane vapor to inert gas is 1:(20-50). In some embodiments, the mass of the hexamethyldisiloxane vapor is 2-5% of the mass of the Pt-Ce bimetallic catalyst precursor. In some embodiments, the passivation treatment temperature is 100-120°C, and the time is 2-3 hours.

[0020] Secondly, a Pt-Ce / N-AC bimetallic composite catalyst is provided, which is prepared according to the method described in this invention.

[0021] In some embodiments, the catalyst has a platinum loading of (15~30) g / 100g support and a cerium loading of (5~12) g / 100g support.

[0022] Thirdly, a method for the continuous production of m-aminobenzenesulfonic acid is provided, comprising:

[0023] Sodium m-nitrobenzenesulfonate solution is mixed with hydrogen gas, preheated, and then introduced into a fixed-bed reactor filled with the Pt-Ce / N-AC bimetallic composite catalyst described in this invention for hydrogenation reaction.

[0024] In some embodiments, the preheating temperature is 70~180°C, preferably 70~90°C.

[0025] In some embodiments, the reaction temperature of the fixed-bed reactor is 60~200℃, preferably 70~90℃, the reaction pressure is 0.5~3MPa, and the hourly feed mass to catalyst packing mass space velocity ratio is 2.5~8.0 h⁻¹. -1 The dwell time is 0.1 to 10 minutes, preferably 1.5 to 3.0 minutes.

[0026] In some embodiments, the mass concentration of the sodium m-nitrobenzenesulfonate solution is 10-50%, preferably 15-25%.

[0027] In some embodiments, the solvent used in the sodium m-nitrobenzenesulfonate solution is any one of water, methanol, ethanol, or 95% ethanol by mass concentration.

[0028] In some embodiments, the molar ratio of sodium m-nitrobenzenesulfonate to hydrogen is 1:(3~10), preferably 1:(3.0~4.0).

[0029] Fourthly, a reaction system for the continuous hydrogenation of sodium m-nitrobenzenesulfonate to m-aminobenzenesulfonic acid is provided, comprising: The raw material supply unit is used to provide sodium m-nitrobenzenesulfonate solution and hydrogen gas; A mixing unit, connected to the raw material supply unit, is used to mix the sodium m-nitrobenzenesulfonate solution with hydrogen gas; A preheating unit, connected to the mixing unit, is used to preheat the mixed materials to 70~90℃; A fixed-bed reactor, connected to the preheating unit, is filled with the Pt-Ce / N-AC bimetallic composite catalyst prepared by the method of the present invention or the Pt-Ce / N-AC bimetallic composite catalyst of the present invention, for carrying out hydrogenation reaction at 60~200℃, preferably 70~90℃, and 0.5~3MPa. The product post-processing unit is connected to the fixed-bed reactor and is used to condense and separate the reaction liquid from gas.

[0030] In some embodiments, the gas-liquid mixing preheater is any one of a static mixer, a T-type mixer, a Y-type mixer, or a cross-type mixer, preferably a static mixer or a T-type mixer.

[0031] In some embodiments, the product post-processing unit includes a condenser, a back pressure valve, and a gas-liquid separator, wherein the back pressure value of the back pressure valve is set to 0.5~1.5MPa.

[0032] In some embodiments, the system further includes an online analysis unit, which includes an immersion Raman spectroscopy probe or an online microfluidic sampling-chromatographic analysis system for real-time monitoring of the concentrations of raw materials, products and impurities in the reaction solution.

[0033] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: This invention provides a catalyst for the continuous production of m-aminobenzenesulfonic acid, its preparation method, and its application. Compared with traditional technologies, this method optimizes reaction conditions and catalyst performance, achieving efficient, green, and continuous production of m-aminobenzenesulfonic acid, significantly improving production efficiency and product quality.

[0034] The catalyst prepared by this invention is characterized by modifying activated carbon through "nitric acid pretreatment + nitrogen doping in ammonia atmosphere", achieving uniform co-loading of Pt and Ce bimetals through spraying, and constructing a protective layer on the catalyst surface that selectively inhibits side reactions through "organosilane vapor passivation".

[0035] Extremely high selectivity and extremely low impurity rate: The Pt-Ce / N-AC catalyst prepared by this invention can achieve a 100.00% feed conversion rate and a selectivity of up to 99.50% for the target product m-aminobenzenesulfonic acid in the continuous hydrogenation reaction of sodium m-nitrobenzenesulfonate, with the specific impurity rate controlled below 0.03%. These performance indicators are far superior to existing technologies, representing a major technological breakthrough in this field.

[0036] Mild reaction conditions, safe and economical: This invention can achieve efficient hydrogenation under mild conditions of 80℃ and 1MPa, which significantly reduces energy consumption and equipment investment, improves the safety of the production process, and is in line with the development concept of green chemical industry.

[0037] The catalyst exhibits good stability and long lifespan: Through nitrogen doping support, Pt-Ce bimetallic synergy, and unique organosilanes passivation treatment, the catalyst of this invention has excellent resistance to sintering and poisoning, and demonstrates good stability during long-term operation. The catalyst lifespan is significantly extended, reducing production costs.

[0038] The preparation process is controllable and facilitates scale-up: This invention achieves high dispersion and uniform distribution of active components through spray loading and precise control of reduction and passivation conditions, thereby improving the utilization rate of precious metals and reducing catalyst costs. Furthermore, this preparation process is easily automated and suitable for large-scale industrial production.

[0039] The preparation of m-aminobenzenesulfonic acid in this invention adopts a continuous production method, which greatly shortens the production time per batch, enables the production line to operate continuously, and significantly increases output. At the same time, it reduces multiple feeding and unloading operations, reduces human error, and further improves the stability and consistency of production. Attached Figure Description

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] Figure 1 This is a BET test curve of the catalyst obtained in Example 1 of the present invention. In the figure, the green curve represents the differential pore size distribution curve; the red curve is the cumulative pore volume curve. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0043] General Method 1 A method for preparing a catalyst for the continuous production of m-aminobenzenesulfonic acid, comprising: Step 1: Vector pretreatment Columnar activated carbon of 20-40 mesh was selected as the carrier raw material. First, the activated carbon was soaked in a 5%-15% nitric acid solution for 6-12 hours to introduce oxygen-containing functional groups onto the surface. Then, it was repeatedly washed with deionized water until neutral and dried at 100-120℃. Next, the dried activated carbon was placed in a tube furnace, ammonia gas was introduced, and the temperature was raised to 500-800℃ at a rate of 3-8℃ / min, and held at this temperature for 3-8 hours. The ammonia gas underwent high-temperature decomposition to generate active nitrogen free radicals, which chemically reacted with the oxygen-containing functional groups on the activated carbon surface to graft onto the surface nitrogen-containing groups. Simultaneously, some active nitrogen atoms were embedded into the carbon framework lattice to achieve bulk doping, thus preparing a nitrogen-doped activated carbon carrier (N-AC). Finally, it was naturally cooled to room temperature to obtain the N-AC carrier. In this step, the concentration and treatment time of nitric acid, as well as the temperature and holding time of the ammonia gas treatment, all affect the type and quantity of surface functional groups on the final carrier, thereby affecting the subsequent loading and dispersion of active metals.

[0044] Step 2: Preparation of the composite solution: A platinum precursor, a cerium precursor, and a complexing agent are weighed, dissolved in a solvent, and ultrasonically dissolved to obtain a homogeneous and stable composite solution. The platinum precursor is preferably chloroplatinic acid or chloroplatinate, the cerium precursor is preferably cerium nitrate or cerium ammonium nitrate, the complexing agent is preferably disodium ethylenediaminetetraacetate (EDTA disodium) or citric acid, and the solvent is preferably ultrapure water or deionized water. The complexing agent can form stable complexes with Pt and Ce ions, preventing hydrolysis or precipitation during subsequent loading and drying processes, ensuring uniform co-loading of the bimetallic compounds. In the composite solution, the Pt atom concentration is 15-30 g / L, the Ce atom concentration is 5-12 g / L, and the complexing agent concentration is 0.05-0.15 mol / L.

[0045] Step 3 Spray load: The N-AC carrier obtained in step 1 is placed in a coating machine, with a rolling speed set to 20-40 rpm. Before spraying, the N-AC carrier needs to be preheated to 30-70°C. The composite solution prepared in step 2 is sprayed evenly onto the surface of the rolling carrier in an atomized form using a spraying device. The spraying process lasts approximately 0.5-2 hours, ensuring the solution evenly covers the carrier surface and pore openings. After spraying, the loaded material is pre-dried at 60-80°C for 1-3 hours, and then dried at 100-120°C for 4-6 hours to obtain the loaded solid material. The mass-to-volume ratio of the N-AC carrier to the composite solution is 100 g / L. Compared to the traditional equal-volume impregnation method, the spraying method effectively avoids the "coffee ring effect" of the active components during the drying process, achieving a more uniform distribution and higher dispersion, thus more effectively leveraging the synergistic effect of the Pt-Ce bimetallic compound.

[0046] Step 4: Restore The dried supported solid material from step 3 was placed in a tube furnace, and a mixed reducing atmosphere of nitrogen and hydrogen was introduced, with a nitrogen to hydrogen volume ratio of (19~27):1. The temperature was increased to 270~370℃ at a heating rate of 3~8℃ / min, and the temperature was maintained for reduction for 3~6 hours. During this process, the Pt and Ce precursors were reduced to metals or low-valence oxides, forming catalytically active Pt-Ce bimetallic nanoparticles. After reduction, the material was cooled to room temperature under nitrogen protection to obtain the Pt-Ce bimetallic catalyst precursor.

[0047] Step 5 Passivation: The Pt-Ce bimetallic catalyst precursor obtained in step 4 is placed in a tube furnace and passivated for 2-3 hours at 85-135°C under a mixed modified atmosphere of inert gas (such as nitrogen or argon) carrying organosilane passivating agent vapor. The organosilane passivating agent is preferably hexamethyldisiloxane. During this process, hexamethyldisiloxane molecules undergo chemical adsorption or reaction on the catalyst surface, forming a hydrophobic organosilicon protective layer. This protective layer effectively inhibits the non-selective adsorption of reactants or intermediates on the catalyst surface, thereby significantly suppressing side reactions such as dechlorination and improving the selectivity of the target product. The volume ratio of hexamethyldisiloxane vapor to inert gas is 1:(20-50). The mass of the hexamethyldisiloxane vapor is 2-5% of the mass of the Pt-Ce bimetallic catalyst precursor obtained after reduction.

[0048] General Method 2 This invention also provides the application of the Pt-Ce bimetallic catalyst in the continuous hydrogenation of sodium m-nitrobenzenesulfonate to prepare m-aminobenzenesulfonic acid, employing the following continuous flow reaction system: This system includes a material mixing device, a T-junction, a preheater, a fixed-bed reactor, a condenser, a back pressure valve, and a gas-liquid separator. The reaction process is as follows: Under nitrogen protection, a sodium m-nitrobenzenesulfonate solution with a mass concentration of 10%~50% is placed in the material mixing device and mixed evenly, and preheated to 70~180°C. The preheated sodium m-nitrobenzenesulfonate solution and hydrogen (molar ratio of 1:(3.0~10)) are simultaneously fed into the T-junction for mixing. The mixed material is preheated again to 70~180°C and then enters a fixed-bed reactor pre-filled with the Pt-Ce / N-AC catalyst prepared according to this invention. The temperature of the fixed-bed reactor is controlled at 60~200℃, the reaction pressure is 0.5~3MPa, and the hourly space velocity (WHSV) of the reactant mass to the catalyst charge is 2.5~8.0 h⁻¹. -1 The residence time is 0.1 to 10 minutes. The reaction liquid flowing out of the fixed bed reactor enters the condenser for condensation, and then flows into the gas-liquid separator through the back pressure valve (back pressure value set to 1 to 3 MPa). The separated liquid phase is the reaction liquid containing the target product m-aminobenzenesulfonic acid, which can be further separated and purified.

[0049] Example 1 A method for preparing a catalyst for the continuous production of m-aminobenzenesulfonic acid, comprising: Step 1: Support Pretreatment: Take 100g of 30-mesh columnar activated carbon, soak it in 8% nitric acid for 8 hours, wash it with water until neutral, and dry it at 110℃. Place the dried activated carbon in a tube furnace, introduce NH3 atmosphere for nitrogen doping, heat it to 650℃ at a heating rate of 5℃ / min, hold it at that temperature for 5 hours, and then allow it to cool naturally to room temperature to obtain the N-AC support.

[0050] Step 2: Preparation of composite solution: Weigh chloroplatinic acid containing 22g platinum, cerium nitrate containing 8g cerium, and 0.11mol disodium EDTA, dissolve them in 1L of ultrapure water, and sonicate for 30 minutes to obtain the composite solution.

[0051] Step 3: Spray Loading: Place 100g of N-AC carrier in a coating machine and roll it at 30rpm, preheating it to 70℃. Spray the composite solution evenly onto the surface of the rolling N-AC carrier for 1 hour. Pre-dry the loaded material at 70℃ for 2 hours, then dry it at 110℃ for 5 hours to obtain the loaded solid material.

[0052] Step 4 Reduction: Place the dried material in a tube furnace, introduce a mixture of nitrogen and hydrogen (volume ratio 22:1), heat to 320°C at a heating rate of 5°C / min, reduce at a constant temperature for 5 hours, and then cool to room temperature to obtain the Pt-Ce bimetallic catalyst precursor.

[0053] Step 5 Passivation: The Pt-Ce bimetallic catalyst precursor is placed in a tube furnace under a nitrogen atmosphere carrying hexamethyldisiloxane vapor. The amount of hexamethyldisiloxane is 3% of the mass of the Pt-Ce bimetallic catalyst precursor, and the volume ratio of hexamethyldisiloxane vapor to inert gas is 1:30. Passivation is carried out at 110°C for 2.5 hours to obtain the final Pt-Ce / N-AC catalyst.

[0054] The BET test chromatogram of the catalyst is shown below. Figure 1 As shown, the pore size of the obtained catalyst is concentrated in the range of 10-12 nm, which is typical of decongestant materials. This indicates that the catalyst prepared in this invention is very suitable for the entry and exit channels of aromatic reactants such as sodium m-nitrobenzenesulfonate, is not prone to pore blockage, and can effectively maintain the catalytic performance of the catalyst.

[0055] Example 2 The difference from Example 1 is that the amount of disodium EDTA is adjusted, while the rest is the same as in Example 1.

[0056] Table 1 Adjustment of EDTA disodium dosage

[0057] Example 3 The difference from Example 1 is that the reduction temperature is different, but the rest is the same as Example 1.

[0058] Table 2 Reduction Temperature Adjustment

[0059] Example 4 The difference from Example 1 is that the passivation conditions are different, but the rest is the same as Example 1.

[0060] Table 3 Passivation Condition Adjustment

[0061] Example 5 The difference from Example 1 is that the nitrogen doping temperature is adjusted, but otherwise it is the same as Example 1.

[0062] Table 4 Nitrogen Doping Temperature Adjustment

[0063] Example 6 The difference from Example 1 is that the nitric acid treatment parameters were adjusted, but the rest is the same as in Example 1.

[0064] Table 5 Adjustment of Nitric Acid Treatment Parameters

[0065] Example 7 The difference from Example 1 is that the reducing atmosphere is adjusted, but the rest is the same as Example 1.

[0066] Table 6 Adjustment of reducing atmosphere

[0067] Example 8 The difference from Example 1 is that the Pt / Ce ratio is adjusted, while the rest is the same as Example 1.

[0068] Table 7 Pt / Ce Ratio Adjustment

[0069] Comparative Example 1 The difference from Example 1 is that the spraying method in step 3 is replaced by an equal-volume impregnation method. Specifically, 1L of the composite solution prepared in step 2 is slowly added dropwise to 100g of the N-AC support obtained in step 1, with continuous stirring during the addition process, until the support surface is just wetted and there is no excess liquid, at which point the addition is stopped. Then, the solution is allowed to stand for 2 hours to allow it to fully penetrate the pores of the support. The remaining drying, reduction, and passivation steps are the same as in Example 1.

[0070] Comparative Example 2 The difference from Example 1 is that hexamethyldisiloxane was not present in the atmosphere of the passivation step in step 5. That is, the reduced catalyst was passivated at 110°C for 2.5 hours under nitrogen protection, and then cooled to room temperature before being used directly in the reaction. The remaining steps were the same as in Example 1.

[0071] Comparative Example 3 The difference from Example 1 is that ammonia gas was not introduced in step 1 for nitrogen doping. The remaining steps are the same as in Example 1.

[0072] Comparative Example 4 The difference from Example 1 is that, in the preparation of the composite solution, only the Pt precursor was used, and the Ce precursor was not added, to prepare the Pt / N-AC catalyst. The remaining steps were the same as in Example 1.

[0073] Comparative Example 5 It is a commercially available Pd / C catalyst (Merck).

[0074] Example 1 Under nitrogen protection, a 20% (w / w) sodium m-nitrobenzenesulfonate solution was mixed thoroughly in a material mixing device and preheated to 80°C. The preheated sodium m-nitrobenzenesulfonate solution and hydrogen (molar ratio 1:3.5) were simultaneously fed into a T-junction for mixing. The mixed material was preheated again to 80°C and then fed into a fixed-bed reactor pre-loaded with catalyst. The temperature of the fixed-bed reactor was controlled at 80°C, the reaction pressure at 1 MPa, and the hourly space velocity (WHSV) of the reactant to the catalyst charge was 3.5 h⁻¹. -1 The residence time was 2.0 minutes. The reaction liquid flowing from the fixed-bed reactor was condensed in the condenser, and then flowed into the gas-liquid separator through a back pressure valve (back pressure set to 1 MPa). The separated liquid phase was the reaction liquid containing the target product, m-aminobenzenesulfonic acid, which could be further separated and purified. The detection results are shown in Table 8.

[0075] Table 8 Test Results

[0076] Note: When using commercially available Pd / C catalysts, the optimal reaction conditions for hydrogenation catalysis are: temperature 100℃ and reaction pressure 3MPa.

[0077] As shown in Table 8, the catalysts prepared in Examples 1-8 of this invention, when used for the continuous production of m-aminobenzenesulfonic acid, exhibit significantly better selectivity than the comparative examples, and the impurity content is significantly lower. Changes in some catalyst preparation parameters have little impact on catalyst performance.

[0078] Compared to Example 1, the use of the equal-volume impregnation method in Comparative Example 1 resulted in decreased selectivity and increased impurity rate. This indicates that the spray loading method can achieve a more uniform distribution and higher dispersion of the active components, thereby more effectively leveraging the synergistic effect of the Pt-Ce bimetallic compound, suppressing side reactions, and improving selectivity.

[0079] Compared to Example 1, Comparative Example 2, by omitting the passivating agent, resulted in a sharp decrease in selectivity and a surge in the impurity rate of over 16 times (from 0.03% to 0.50%). This irrefutably demonstrates the decisive role of the hexamethyldisiloxane vapor passivation step in suppressing side reactions such as dechlorination and achieving ultra-high selectivity and ultra-low impurity rate. The hydrophobic protective layer constructed on the catalyst surface by the passivation layer effectively prevents the non-specific adsorption of reaction intermediates or byproducts, which is a key guarantee for the superior performance of the technical solution of this invention.

[0080] Compared to Example 1, Comparative Example 3, which omitted the nitrogen doping step, resulted in decreased selectivity and a significantly increased impurity rate. This indicates that the nitrogen-containing functional groups introduced onto the support surface by the high-temperature nitrogen doping treatment in an NH3 atmosphere are crucial for anchoring active metals, enhancing metal-support interactions, and improving selectivity.

[0081] Compared to Example 1, Comparative Example 4, which omitted the Ce promoter, resulted in a significant decrease in selectivity and a sharp increase in impurity rate. This fully demonstrates that Ce, as a co-catalyst, plays an indispensable core role in suppressing dechlorination side reactions and achieving high selectivity. The electronic synergistic effect between the Pt-Ce bimetals is key to the high selectivity of the catalyst of this invention.

[0082] Even under more demanding reaction conditions, commercial Pd / C catalysts exhibit significantly lower conversion rates, selectivity, and impurity control compared to the catalyst of this invention. This highlights the advanced and original nature of the catalyst formulation and preparation process of this invention.

[0083] As can be seen from the above examples and comparative examples, the Pt-Ce / N-AC catalyst, its preparation method, and its application provided by the present invention, through the support modification of "nitric acid pretreatment + nitrogen doping in ammonia atmosphere", the loading method of "EDTA disodium-assisted spray co-impregnation", the formulation design of "Pt-Ce bimetallic synergy" and the post-treatment process of "hexamethyldisiloxane vapor passivation", produce a significant synergistic effect among the steps, which can achieve efficient and highly selective continuous hydrogenation of sodium m-nitrobenzenesulfonate under mild conditions, and has extremely high industrial application value and significant technological progress.

[0084] Example 2 Using the Pt-Ce / N-AC catalyst prepared in Example 1, the catalytic reaction was carried out for 168 h, following the catalytic process of Example 1, and the catalytic effect of the catalyst was evaluated. The results are shown in Table 9.

[0085] Table 9 Catalyst Performance Study

[0086] As can be seen from the data in Table 9, the catalytic effect remains almost unchanged within 168 hours, and the purity and yield remain stable. The method of this invention enables the catalyst to operate continuously and stably in a fixed bed for more than 168 hours without degradation.

[0087] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing a catalyst for the continuous production of m-aminobenzenesulfonic acid, characterized in that, include: Step (1): After acid oxidation pretreatment, activated carbon is placed in an ammonia atmosphere for nitrogen doping treatment to obtain nitrogen-doped activated carbon support; Step (2): Dissolve the platinum precursor, cerium precursor and complexing agent in a solvent to prepare a composite solution; Step (3): The composite solution is uniformly loaded onto the surface of the preheated nitrogen-doped activated carbon carrier by spraying, and then dried to obtain the loaded solid material. Step (4): The supported solid material is placed in a reducing atmosphere for reduction treatment to obtain the Pt-Ce bimetallic catalyst precursor; Step (5): The Pt-Ce bimetallic catalyst precursor is placed in a modified atmosphere containing organosilanes as passivating agents for passivation treatment to obtain the Pt-Ce / N-AC bimetallic composite catalyst.

2. The preparation method according to claim 1, characterized in that, In step (1), the activated carbon is columnar activated carbon with a particle size of 20-40 mesh; Alternatively, the acid is at least one of nitric acid, hydrochloric acid, and sulfuric acid; Alternatively, the mass concentration of the acid is 5-15%; Alternatively, in step (1), the activated carbon undergoes acid oxidation pretreatment by soaking the activated carbon in an acid with a mass concentration of 5% to 15% for 6 to 12 hours, then washing it with water until neutral and drying it at 100 to 120°C. Alternatively, in step (1), the nitrogen doping treatment refers to heating the activated carbon to 500-800°C in an ammonia atmosphere at a heating rate of 3-8°C / min, and then treating it at a constant temperature for 3-8 hours.

3. The preparation method according to claim 1, characterized in that, In step (2), the platinum precursor is chloroplatinic acid or chloroplatinate; Alternatively, in step (2), the cerium precursor is cerium nitrate or cerium ammonium nitrate; Alternatively, in step (2), the complexing agent is disodium ethylenediaminetetraacetate or citric acid; Alternatively, in step (2), the solvent is ultrapure water, methanol, ethanol, 95% ethanol, or deionized water; Alternatively, in the composite solution, the concentration of Pt atoms is 15~30 g / L, the concentration of Ce atoms is 5~12 g / L, and the concentration of the complexing agent is 0.05~0.15 mol / L.

4. The preparation method according to claim 1, characterized in that, In step (3), the spraying method involves rolling the nitrogen-doped activated carbon carrier at a speed of 20-40 rpm in a coating machine while simultaneously spraying the composite solution evenly onto the surface of the nitrogen-doped activated carbon carrier; or, the drying treatment includes pre-drying at 60-80℃ for 1-3 hours and then drying at 100-120℃ for 4-6 hours; or, the nitrogen-doped activated carbon carrier needs to be preheated to 30-70℃ before spraying; or, the mass-to-volume ratio of the nitrogen-doped activated carbon carrier to the composite solution is 100 g / L.

5. The preparation method according to claim 1, characterized in that, In step (4), the reducing atmosphere includes nitrogen and hydrogen, with a volume ratio of (19~27):1; or, in step (4), the temperature of the reduction treatment is 270~370℃ and the time is 3~6 hours. Alternatively, the organosilane passivating agent is hexamethyldisiloxane; or, the modified atmosphere consists of an inert gas carrying organosilane passivating agent vapor; the passivation treatment temperature is 85~135℃, and the time is 2~3 hours; or the inert gas is nitrogen or argon; or, the mass of the hexamethyldisiloxane vapor is 2~5% of the mass of the Pt-Ce bimetallic catalyst precursor; or, the volume ratio of the hexamethyldisiloxane vapor to the inert gas is 1:(20~50); or, the passivation treatment temperature is 100~120℃, and the time is 2~3 hours.

6. A Pt-Ce / N-AC bimetallic composite catalyst, characterized in that, Prepared according to the method described in any one of claims 1 to 5.

7. The catalyst according to claim 6, characterized in that, In the catalyst, the platinum loading is 15~30g / 100g support, and the cerium loading is 5~12g / 100g support.

8. A method for continuous production of m-aminobenzenesulfonic acid, characterized in that, include: Sodium m-nitrobenzenesulfonate solution is mixed with hydrogen gas, preheated, and then introduced into a fixed-bed reactor filled with the Pt-Ce / N-AC bimetallic composite catalyst prepared by any one of claims 1 to 5 or the Pt-Ce / N-AC bimetallic composite catalyst of claim 6 for hydrogenation reaction.

9. The method according to claim 8, characterized in that, The preheating temperature is 70~180℃; Alternatively, the fixed-bed reactor may have a reaction temperature of 60–200°C, a reaction pressure of 0.5–3 MPa, and a space velocity ratio of the hourly feed mass of the reactants to the hourly catalyst loading mass of 2.5–8.0 h⁻¹. -1 The stay time is 0.1 to 10 minutes; Alternatively, the mass concentration of the sodium m-nitrobenzenesulfonate solution is 10-50%, preferably 15-25%; the solvent used in the sodium m-nitrobenzenesulfonate solution is any one of water, methanol, ethanol, or 95% ethanol; the molar ratio of sodium m-nitrobenzenesulfonate to hydrogen is 1:(3-10), preferably 1:(3.0-4.0).

10. A reaction system for the continuous hydrogenation of sodium m-nitrobenzenesulfonate to m-aminobenzenesulfonic acid, characterized in that, include: The raw material supply unit is used to provide sodium m-nitrobenzenesulfonate solution and hydrogen gas; A mixing unit, connected to the raw material supply unit, is used to mix the sodium m-nitrobenzenesulfonate solution with hydrogen gas; A preheating unit, connected to the mixing unit, is used to preheat the mixed materials to 70~90℃; A fixed-bed reactor, connected to the preheating unit, is filled with a Pt-Ce / N-AC bimetallic composite catalyst prepared by any one of claims 1 to 5 or the Pt-Ce / N-AC bimetallic composite catalyst of claim 6, for use in hydrogenation reactions; The product post-processing unit is connected to the fixed-bed reactor and is used to condense and separate the reaction liquid from gas.

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