Preparation method and application of a continuous platinum-based catalyst for hydrogenation to prepare aminophenol

Abstract

The application discloses a kind of continuous hydrogenation preparation method and application of platinum-based catalyst for amino phenol, and the method comprises the following steps: surface modification is carried out to activated carbon with organic amine, material separation and drying treatment are carried out, and amine-modified activated carbon material is obtained;Amine-modified activated carbon material is mixed with binder and liquid medium, granulation forming is carried out, then drying, high-temperature carbonization and activation treatment are carried out, and activated carbon carrier is obtained;Platinum precursor and auxiliary metal precursor are prepared into mixed solution, then the mixed solution is loaded on the activated carbon carrier, and calcination treatment is carried out after drying treatment, and platinum-based catalyst is prepared.The application solves the technical problems that catalyst is easy to be poisoned and deactivated, selectivity is decreased and service life is short in the process of fixed-bed continuous hydrogenation, and achieves the effects of high catalytic selectivity, excellent anti-poisoning performance and long service life.

Description

Technical Field

[0001] This invention relates to the field of platinum-based catalyst preparation technology, specifically a method for preparing and applying a platinum-based catalyst for continuous hydrogenation to aminophenol. Background Technology

[0002] Aminophenols (including o-aminophenol, m-aminophenol, and p-aminophenol, collectively referred to as AP) are important aromatic intermediates in the fine chemical industry. Their molecular structure possesses both amino and phenolic hydroxyl groups, exhibiting excellent chemical reactivity and wide applications in pharmaceuticals, dyes, rubber additives, coatings, pesticide synthesis, and polymer modification. p-Aminophenol is a key raw material for the synthesis of antipyretic and analgesic drugs such as acetaminophen, and is also used in the preparation of sulfur dyes, acid dyes, rubber antioxidants, photosensitive materials, and antioxidants. o-Aminophenol is mainly used in the synthesis of dye intermediates, pharmaceutical bactericides, and fluorescent whitening agents. m-Aminophenol is widely used in high-end dyes, resin curing agents, and fine organic synthesis.

[0003] Traditional aminophenol production processes mainly involve nitrophenol chemical reduction, iron powder reduction, and sodium sulfide reduction. These processes have low technological barriers and require minimal equipment investment, but they generate large amounts of hazardous waste pollutants such as iron sludge, saline wastewater, and organic waste residue. The cost of treating these three types of waste is high, and environmental pollution problems are prominent. With the continuous upgrading of environmental regulations, the high-pollution and high-energy-consumption traditional reduction processes are gradually being restricted and phased out, while green catalytic hydrogenation technology has become the mainstream alternative technology in the industry.

[0004] The liquid-phase catalytic hydrogenation reduction of nitrophenol to aminophenol is a green synthesis process that uses nitrophenol as a raw material and selectively reduces the nitro group (-NO2) to the amino group (-NH2) while retaining the phenolic hydroxyl structure under a catalyst and hydrogen atmosphere. This process produces only water as a byproduct, generates no solid waste, and features high atom utilization, cleanliness, high product purity, and simple post-processing. Currently, catalytic hydrogenation technology is widely used in high-end aminophenol production abroad, and leading domestic companies are gradually completing process iterations. However, the industry as a whole still faces technical challenges such as high catalyst costs, insufficient selectivity, susceptibility to over-hydrogenation, and poor stability in continuous production. Therefore, there is still a reliance on imports for high-end, high-purity aminophenol products.

[0005] The core reaction in the hydrogenation of nitrophenol to aminophenol is the selective catalytic hydrogenation reduction of aromatic nitro groups. The reaction process involves the sequential hydrogenation of the nitro group to generate a nitroso group, a hydroxylamine intermediate, and finally reduction to an amino group. Throughout the process, side reactions such as phenolic hydroxyl group removal, excessive hydrogenation of the benzene ring, excessive reduction of the amino group, and molecular coupling must be strictly avoided. Compared to the hydrogenation reaction of ordinary nitrobenzene, the phenolic hydroxyl group in the nitrophenol molecule has a strong electron-withdrawing effect and polar adsorption characteristics, which easily leads to catalyst active site poisoning, carbon deposition and deactivation, and exacerbates side reactions, making process control more difficult.

[0006] Fixed-bed continuous hydrogenation technology has become a mainstream direction for industrial upgrading in recent years. It employs a tubular fixed-bed reactor, where shaped granular catalyst is packed inside the bed to achieve continuous feeding of nitrophenol feedstock and hydrogen, continuous reaction at constant temperature and pressure, and continuous discharge. Compared to batch reactor processes, fixed-bed processes offer advantages such as continuous production, high capacity, low labor costs, uniform product quality, and stable operating conditions, making them suitable for large-scale production. However, fixed-bed processes still face the following technical bottlenecks: First, nitrophenol is highly polar and prone to crystallization, requiring high-level pretreatment of the feedstock, which can easily lead to catalyst bed blockage and increased pressure drop, affecting the stability of continuous production. Second, shaped catalysts suffer from high mass transfer resistance and surface active sites being encapsulated, resulting in a slight decrease in activity compared to powdered catalysts. Third, phenolic hydroxyl groups are easily adsorbed onto the catalyst surface, leading to catalyst carbonization, coking, poisoning, and deactivation over long-term operation, resulting in short catalyst regeneration cycles and insufficient stability in continuous operation. Fourth, the operating parameters are highly coupled; the matching accuracy of space velocity, hydrogen-to-feed ratio, temperature, and pressure directly affects the reaction effect, making process control difficult.

[0007] The catalyst is the core of the hydrogenation technology of nitrophenol to aminophenol, directly determining the selectivity of nitro reduction, feed conversion rate, product purity, and production cost. The core technical challenge of this reaction is to efficiently reduce the nitro group while suppressing side reactions such as phenolic hydroxyl group removal, benzene ring hydrogenation, amino oxidation, and intermediate coupling, while also being resistant to phenolic hydroxyl group adsorption poisoning and possessing excellent hydrothermal stability and anti-carbon deposition capabilities. Currently, the industry's catalyst systems are mainly divided into two categories: precious metal catalysts and non-precious metal catalysts. Precious metal catalysts, with palladium, platinum, and ruthenium as core active components, have advantages such as high activity at low temperatures, fast reaction rates, strong substrate adaptability, and fewer side reactions. However, precious metal resources are scarce and expensive, resulting in high catalyst preparation costs. Furthermore, phenolic hydroxyl groups easily adsorb strongly on the catalyst surface, leading to active site coverage, carbon deposition, and deactivation over long-term operation, thus limiting the catalyst's cycle life. Non-precious metal catalysts mainly use inexpensive transition metals such as nickel, copper, and cobalt as active components, resulting in low raw material costs. However, their overall activity and low-temperature reaction performance are weaker than those of precious metal catalysts, requiring higher reaction temperatures and pressures. Furthermore, they generally suffer from the problem of "difficulty in achieving both activity and selectivity," and their compatibility with high-end products is insufficient.

[0008] Therefore, developing a catalyst with high selectivity, long lifespan, strong resistance to poisoning, and suitable for continuous hydrogenation of nitrophenol to aminophenol in a fixed bed is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] The purpose of this application is to provide a method for preparing a platinum-based catalyst for continuous hydrogenation to aminophenol and its application, which has high catalytic selectivity, excellent anti-poisoning performance and long service life.

[0010] This application provides a method for preparing a platinum-based catalyst for the continuous hydrogenation production of aminophenols, specifically including the following steps: S100: Activated carbon is surface modified with organic amines, and after material separation and drying, amine-modified activated carbon material is obtained. S200: Amine-modified activated carbon material is mixed with binder and liquid medium, granulated, and then dried, carbonized at high temperature and activated to obtain activated carbon carrier; S300: A platinum-based catalyst is prepared by mixing a platinum precursor with an auxiliary metal precursor, loading the mixture onto an activated carbon support, drying it, and then calcining it.

[0011] Furthermore, in S100, the organic amine is selected from at least one of triethylamine, methylamine, and ethylenediamine.

[0012] Furthermore, in S100, the organic amine is an organic amine solution, and the mass fraction of the organic amine solution is 1%-5%.

[0013] Furthermore, in S200, the binder is selected from at least one of carboxymethyl cellulose, starch paste, and calcium lignosulfonate.

[0014] Furthermore, in S200, the mass ratio of the binder to the liquid medium is 1:(2-10).

[0015] Furthermore, in S200, granulation is carried out on a disc granulator, and the disc tilt angle is controlled at 40°-50° and the disc rotation speed is controlled at 30r / min-50r / min.

[0016] Furthermore, in S200, the spherical granulation specifically includes: forming mother sphere seed crystals by rolling and agglomerating powder, then continuously adding carbon powder and intermittently supplying a binder aqueous solution to obtain spherical activated carbon particles.

[0017] Furthermore, in S200, the particle size of the spherical activated carbon particles is between 1 mm and 5 mm.

[0018] Furthermore, in S200, the high-temperature carbonization temperature is controlled at 650℃-750℃ and the time is 6h-12h.

[0019] Furthermore, in S200, high-temperature carbonization is carried out under the protection of an inert gas.

[0020] Furthermore, in S200, the activation treatment temperature is controlled at 900℃-1000℃ and the time is controlled at 1h-6h.

[0021] Furthermore, in S200, the activation treatment is carried out in an activation atmosphere containing water vapor.

[0022] Furthermore, in S300, the platinum precursor is selected from at least one of chloroplatinic acid, platinum acetate, and platinum nitrate.

[0023] Furthermore, in S300, the platinum loading is 0.1wt%-5wt% based on the mass of the activated carbon carrier.

[0024] Furthermore, in S300, when the platinum precursor is prepared as a liquid system, the molar concentration of platinum in the platinum-containing liquid system is 0.1 mol / L-2 mol / L.

[0025] Furthermore, in S300, the auxiliary metal precursor is selected from at least one of indium nitrate, cadmium nitrate, and zinc nitrate.

[0026] Furthermore, in S300, the molar amount of auxiliary metal is 10%-100% of the molar amount of platinum, in terms of elemental molars.

[0027] Furthermore, in S300, the calcination treatment temperature is controlled at 200℃-400℃ and the time is controlled at 1h-5h.

[0028] Furthermore, in S300, the calcination process is carried out under inert gas protection.

[0029] Furthermore, in S100, the drying process is controlled at a temperature of 90℃-120℃ and a time of 12h-24h.

[0030] Furthermore, in S300, the drying process is controlled at a temperature of 90℃-120℃ and a time of 12h-24h.

[0031] Furthermore, this application also proposes an application of a platinum-based catalyst for the continuous hydrogenation production of aminophenol. The platinum-based catalyst prepared is applied to the continuous hydrogenation production of aminophenol from nitrophenol in a fixed bed, specifically including the following steps: Platinum-based catalyst was packed into a fixed-bed reactor, and hydrogen was introduced into the fixed-bed reactor to pretreat the platinum-based catalyst with hydrogen. Then, nitrophenol feedstock liquid and hydrogen were continuously introduced into the fixed-bed reactor to carry out catalytic hydrogenation under hydrogenation reaction conditions. Finally, the reaction effluent was solvent-separated to obtain the aminophenol product.

[0032] Furthermore, the hydrogen pretreatment temperature is controlled at 100℃-300℃, the time at 1h-6h, and the pressure at 0.1MPa-2MPa.

[0033] Furthermore, the nitrophenol raw material solution is obtained by mixing the raw material and the solvent. The raw material is selected from at least one of o-nitrophenol, m-nitrophenol, and p-nitrophenol, and the solvent is selected from at least one of ultrapure water, methanol, and ethanol.

[0034] Furthermore, the mass fraction of nitrophenol in the nitrophenol feedstock solution is 1%-30%.

[0035] Furthermore, the catalytic hydrogenation reaction is controlled at a temperature of 80℃-150℃, a pressure of 0.1MPa-3MPa, and a feed mass hourly space velocity of 0.1g / g. cat h-1.2g / g cat The molar ratio of hydrogen to nitrophenol raw material is 5-100.

[0036] As can be seen from the above, the preparation method and application of a platinum-based catalyst for continuous hydrogenation to aminophenol provided in this application enhance the hydrophilicity of the activated carbon support by modifying the surface of organic amines to suppress the strong adsorption of phenolic hydroxyl groups. Combined with the optimized granulation process, the mass transfer efficiency is improved and the encapsulation of active sites is reduced. At the same time, the loading and calcination parameters are precisely controlled to ensure the high dispersion of platinum-based active components. This effectively solves the technical problems of easy catalyst poisoning and deactivation, decreased selectivity and short lifespan in the fixed-bed continuous hydrogenation process. It has high catalytic selectivity, excellent anti-poisoning performance and long service life. Detailed Implementation

[0037] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0038] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or server that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or modules not explicitly listed or inherent to such processes, methods, products, or devices.

[0039] Traditional aminophenol production processes generate significant amounts of hazardous waste, incur high costs for waste treatment, and cause substantial environmental pollution. While green catalytic hydrogenation has become the mainstream alternative technology, the industry as a whole still faces technical challenges such as high catalyst costs, insufficient selectivity, susceptibility to over-hydrogenation, and poor stability in continuous production. Particularly in the continuous hydrogenation process of nitrophenol in a fixed bed, the strong electron-withdrawing effect and polar adsorption characteristics of the phenolic hydroxyl group easily lead to catalyst active site poisoning, carbon deposition, and deactivation. Furthermore, molded catalysts suffer from high mass transfer resistance and insufficient stability during continuous operation, resulting in continued reliance on imports for high-end, high-purity aminophenol products.

[0040] To address this issue, this application proposes a method for preparing a platinum-based catalyst for continuous hydrogenation to aminophenol, aiming to solve the aforementioned technical problems. The method specifically includes the following steps: S100: Surface modification of activated carbon with an organic amine, followed by material separation and drying, yielding amine-modified activated carbon material; S200: Mixing the amine-modified activated carbon material with a binder and a liquid medium, granulating, and then drying, high-temperature carbonizing, and activation treatment to obtain an activated carbon support; S300: Preparing a platinum precursor and an auxiliary metal precursor into a mixed solution, then loading the mixed solution onto the activated carbon support, drying, and calcining to obtain the platinum-based catalyst.

[0041] For ease of understanding, the following explains some key terms in this embodiment: Continuous hydrogenation to aminophenol refers to a green synthesis process that uses nitrophenol as a raw material, and selectively reduces the nitro group to an amino group while retaining the phenolic hydroxyl structure, under a catalyst and hydrogen atmosphere, through continuous feeding, continuous reaction, and continuous discharge. This process is typically carried out in a fixed-bed reactor to achieve large-scale production.

[0042] Platinum-based catalysts are catalyst systems that use platinum as the main active component and may contain other auxiliary metals or supports. As a noble metal, platinum exhibits high activity and selectivity in hydrogenation reactions, making it key to the efficient conversion of nitrophenols.

[0043] Surface modification of activated carbon with organic amines refers to the interaction between organic amine molecules and functional groups on the surface of activated carbon, altering its surface chemical properties, pore structure, or polarity. This modification aims to optimize the interaction between the activated carbon support and the active metal component, and to adjust the adsorption characteristics of the support for reactants (such as the phenolic hydroxyl groups in nitrophenol), thereby improving the catalyst's resistance to poisoning and its stability.

[0044] Activated carbon support refers to activated carbon materials with specific physicochemical properties obtained through organic amine modification, granulation, drying, high-temperature carbonization, and activation treatment. This support provides a dispersion substrate for active metal components and influences the catalyst's mechanical strength, mass transfer performance, and resistance to carbon deposition.

[0045] Auxiliary metal precursors are compounds used to introduce auxiliary metal components. The auxiliary metal forms a bimetallic system with platinum, which, through a synergistic effect, modulates the electronic and geometric structures of the catalyst, thereby optimizing the catalyst's activity and selectivity, and enhancing its ability to suppress side reactions and resist poisoning.

[0046] The preparation method of this application includes the following steps: In step S100, activated carbon undergoes surface modification with an organic amine, followed by material separation and drying to obtain amine-modified activated carbon material. Surface modification of activated carbon can be carried out in various ways. For example, activated carbon can be impregnated in an organic amine solution, allowing the organic amine to be adsorbed or chemically bonded to the activated carbon surface; alternatively, the organic amine can be uniformly applied to the surface of activated carbon particles by spraying. The organic amine can be of various types, including primary, secondary, or tertiary amines. The modified material needs to be separated, for example, by filtration or centrifugation to separate the solid material from the liquid. Subsequently, the separated material is dried, for example, by hot air drying in an oven to remove moisture and residual solvent.

[0047] In step S200, the amine-modified activated carbon material is mixed with a binder and a liquid medium, then granulated, dried, carbonized at high temperature, and activated to obtain an activated carbon carrier. The mixing of the amine-modified activated carbon material with the binder and liquid medium can be carried out by stirring, kneading, etc., to form a homogeneous mixture. The binder can be a variety of polymeric or inorganic materials, such as polyvinyl alcohol, silica sol, etc. The liquid medium is usually water or an organic solvent. The mixture is then granulated, using methods such as extrusion molding, sheet molding, or roller molding to obtain particles with specific shapes and sizes. The granulated particles are first dried to remove most of the moisture. Subsequently, high-temperature carbonization is performed, such as heat treatment in a high-temperature furnace at a specific temperature, to improve the material's mechanical strength and pore structure. Finally, activation is performed, such as heat treatment in an atmosphere containing an activating agent, to further expand the pore volume and specific surface area, forming an activated carbon carrier with excellent adsorption and catalytic properties.

[0048] In step S300, a platinum precursor and an auxiliary metal precursor are prepared into a mixture, which is then loaded onto an activated carbon support, dried, and calcined to obtain a platinum-based catalyst. The platinum precursor can be any soluble platinum salt, such as chloroplatinic acid or platinum nitrate. The auxiliary metal precursor can be any soluble metal salt, such as indium nitrate or zinc chloride. The selected platinum precursor and auxiliary metal precursor are dissolved in a suitable solvent to prepare a homogeneous mixture. Subsequently, the mixture is loaded onto the prepared activated carbon support using methods such as impregnation, spraying, or chemical vapor deposition, ensuring that the metal components are uniformly dispersed on the support surface and in the pores. After loading, the support loaded with the metal precursor is dried to remove the solvent. Finally, calcination is performed, for example, heat treatment at a specific temperature under an inert or reducing atmosphere, to decompose the metal precursor and convert it into a catalytically active metal or metal oxide, thereby obtaining the platinum-based catalyst.

[0049] The preparation method of this application involves surface modification of activated carbon with organic amines, which effectively adjusts the surface properties of the support, weakens the strong adsorption of phenolic hydroxyl groups to active sites, and enhances the catalyst's resistance to poisoning. Simultaneously, through granulation and subsequent high-temperature carbonization and activation treatments, an activated carbon support with specific pore structure and mechanical strength is constructed, reducing mass transfer resistance and ensuring the structural stability of the catalyst in the fixed-bed continuous hydrogenation process. Therefore, the prepared platinum-based catalyst exhibits high selectivity, long lifetime, and excellent continuous operation stability in the fixed-bed continuous hydrogenation of nitrophenol to aminophenol.

[0050] In some of the above-mentioned schemes of this application, it is proposed to use organic amines to modify the surface of activated carbon to prepare catalyst supports. However, in practical applications, if the type and concentration of organic amines used for modification are not precisely defined, it may lead to uneven distribution of functional groups on the surface of activated carbon or insufficient modification, which in turn affects the uniformity of loading and anchoring effect of subsequent platinum-based active components. This results in the easy loss or unreasonable distribution of active sites in the catalyst during continuous hydrogenation reactions, making it difficult to meet the industrial requirements of high selectivity and long life.

[0051] In this regard, this application further proposes that in S100, the organic amine is selected from at least one of triethylamine, methylamine, and ethylenediamine; and / or, the organic amine is an organic amine solution, and the mass fraction of the organic amine solution is 1%-5%.

[0052] Organic amines, as surface modifiers for activated carbon supports, play a crucial role in modulating the chemical properties of the activated carbon surface by introducing nitrogen-containing functional groups. These nitrogen-containing functional groups serve as effective anchoring sites, enhancing the adsorption capacity of the activated carbon support for subsequently loaded platinum precursors and auxiliary metal precursors. Specifically, triethylamine, a tertiary amine, possesses strong basicity due to the lone pair electrons on its nitrogen atom, enabling it to interact with acidic functional groups on the activated carbon surface. This alters the charge distribution on the support surface, facilitating the uniform adsorption of metal precursors. Methylamine, a primary amine, has a small molecular structure and high activity, allowing it to penetrate deep into the microporous structure of activated carbon and form stable chemical bonds or hydrogen bonds with oxygen-containing functional groups on the surface, providing abundant anchoring sites. Ethylenediamine, a diamine, contains two amino groups in its molecule, enabling it to form chelate structures and exhibit stronger complexation capabilities for metal ions. This promotes high dispersion of metal components on the support surface and effectively inhibits the aggregation of metal particles during subsequent high-temperature treatment. By selecting organic amines with different steric hindrances and basicity, the surface modification effect of the support can be flexibly controlled according to the specific surface characteristics of activated carbon and the performance requirements of the target catalyst.

[0053] Preparing organic amines into solution form and precisely controlling their mass fraction within the range of 1%-5% is crucial to ensuring uniform and appropriate modification effects. Solution form allows organic amine molecules to fully wet the pore structure of activated carbon, guaranteeing the homogeneity of the modification process. If the mass fraction of the organic amine solution is below 1%, the number of active anchoring sites formed on the activated carbon surface is insufficient, resulting in weak metal precursor loading and easy agglomeration during subsequent calcination, affecting the catalyst's activity and stability. If the mass fraction of the organic amine solution is above 5%, it may lead to excessive adsorption or polymerization of organic amines on the activated carbon surface, not only occupying the pore structure of the activated carbon, reducing its specific surface area and pore volume, but also hindering the diffusion of reactant molecules, thus limiting the overall performance of the catalyst. Therefore, controlling the mass fraction within the range of 1%-5% ensures sufficient anchoring site formation while maximally maintaining the original pore structure and specific surface area of ​​the activated carbon support, ensuring the catalyst possesses excellent mass transfer performance and accessibility of active sites.

[0054] Through the above technical solution, this application can precisely control the surface chemical properties of the activated carbon support. Specifically, by selecting specific organic amines (such as triethylamine, methylamine, and ethylenediamine) for surface modification, the amino functional groups in these organic amine molecules interact with the oxygen-containing functional groups or defect sites on the activated carbon surface, effectively enhancing the adsorption capacity of the support for platinum precursors and auxiliary metal precursors. This ensures that the metal components are highly dispersed on the support surface, thereby preventing the agglomeration of metal particles during subsequent calcination and significantly improving the utilization rate of the catalyst's active sites. Simultaneously, by precisely controlling the mass fraction of the organic amine solution within the range of 1% to 5%, a balance is achieved between the degree of modification and the maintenance of the support's pore structure, avoiding the problems of insufficient anchoring points due to excessively low concentration or pore blockage due to excessively high concentration. This precise surface modification strategy enables the prepared platinum-based catalyst to exhibit superior metal dispersion, higher active site stability, and stronger resistance to poisoning in the continuous hydrogenation reaction to aminophenol, thereby effectively suppressing side reactions, extending catalyst lifespan, and meeting the industrial production demand for highly selective and long-life catalysts.

[0055] In some of the embodiments described above in this application, it is proposed to mix amine-modified activated carbon material with binder and liquid medium for granulation. However, in the actual preparation process, if the binder is not properly selected or the ratio of binder to liquid medium is unbalanced, the activated carbon carrier may experience problems such as insufficient strength, overfilling of pore structure or low particle formation rate during the forming process, which in turn affects the loading effect of subsequent catalysts and the mechanical stability in the fixed bed reactor.

[0056] In this regard, this application further proposes that in S200, the adhesive is selected from at least one of carboxymethyl cellulose, starch paste, and calcium lignosulfonate; and / or, the mass ratio of the adhesive to the liquid medium is 1:(2-10).

[0057] Specifically, the binder here acts as an auxiliary material to bind the amine-modified activated carbon particles together, forming carrier particles with a certain shape and strength. These binders are typically polymeric compounds that provide the necessary adhesion during granulation, ensuring particle integrity. Carboxymethyl cellulose is a water-soluble polymer with good adhesive and film-forming properties, effectively improving the mechanical strength of the particles. Starch paste is a natural polymeric binder with moderate viscosity, easy to handle, and can be carbonized in subsequent high-temperature treatment, reducing clogging of the pore structure. Calcium lignosulfonate, a byproduct of wood pulping wastewater, has excellent adhesive and dispersing properties, promoting uniform particle formation. Besides the above-mentioned binders, those skilled in the art can select other types of binders, such as polyvinyl alcohol, silica sol, and bentonite, to achieve similar bonding effects depending on specific needs.

[0058] Meanwhile, the mass ratio of binder to liquid medium is a key parameter controlling the rheological properties of granulated materials. The liquid medium, typically water or other solvent, is used to dissolve or disperse the binder and wet the activated carbon material, giving it plasticity. This ratio directly affects the material's viscosity, wettability, and flowability, thus determining the particle formation efficiency, shape uniformity, and the final mechanical strength and pore structure of the carrier during granulation. For example, if the proportion of liquid medium is too low, the material may be too dry, making it difficult to agglomerate and form particles, resulting in insufficient particle strength or the formation of a large amount of dust; if the proportion of liquid medium is too high, the material may be too thin, making it difficult to maintain particle shape, and may form excessively large pores during drying, reducing the carrier's bulk density and mechanical strength. By precisely controlling this ratio, it is possible to ensure that the material reaches an optimal plastic state during granulation, thereby forming dense, uniform activated carbon carrier particles with sufficient mechanical strength. Specifically, the mass ratio of the adhesive to the liquid medium is 1:(2-4); or, the mass ratio of the adhesive to the liquid medium is 1:(5-7); or, the mass ratio of the adhesive to the liquid medium is 1:(8-10).

[0059] Through the above technical solution, this application effectively solves the problems of insufficient strength, overfilling of pores, or low particle formation rate that may occur in activated carbon carriers during the molding process by limiting the type of binder and the mass ratio of binder to liquid medium in step S200. Specifically, carboxymethyl cellulose, starch paste, or calcium lignosulfonate are selected as binders. These polymeric materials can provide excellent adhesion properties, promoting the formation of tight aggregates in amine-modified activated carbon materials and ensuring the initial strength of the carrier particles. At the same time, these binders can be moderately decomposed or transformed into a carbon skeleton during subsequent high-temperature carbonization and activation treatment, avoiding permanent blockage of the inherent pore structure of activated carbon, thereby ensuring that the carrier has sufficient specific surface area to efficiently load platinum-based active components. In addition, precisely controlling the mass ratio of binder to liquid medium within the range of 1:2 to 1:10 can optimize the rheology and wettability of the granulated material, enabling the material to form uniform, dense particles with good mechanical strength during the granulation process. This precise proportioning avoids uneven granulation and increased debris caused by insufficient liquid medium, while also preventing problems such as difficulty in maintaining particle shape and excessive porosity and reduced mechanical strength after drying caused by excessive liquid medium. Ultimately, the prepared activated carbon support possesses excellent physical structure and mechanical strength, providing a solid foundation for the stable loading of subsequent platinum-based catalysts. This significantly improves the catalyst's resistance to crushing and its long-term operational stability during continuous hydrogenation in a fixed bed, thereby ensuring the efficiency and product quality of continuous production.

[0060] In some of the above-mentioned schemes of this application, activated carbon supports are prepared by granulation to support the catalyst. However, in the actual fixed-bed continuous hydrogenation process, if the physical structure parameters of the shaped catalyst are not properly controlled, it will lead to uneven accumulation of catalyst particles in the reactor, excessive mass transfer resistance or insufficient mechanical strength, which in turn will cause problems such as increased bed pressure drop, uneven material distribution and easy breakage and pulverization of the catalyst, seriously affecting the stability and catalytic efficiency of continuous production.

[0061] In this regard, this application further proposes that in step S200, the granulation is carried out on a disc granulator, and the disc tilt angle is controlled at 40°-50° and the disc rotation speed is controlled at 30r / min-50r / min; and / or, the spherical granulation specifically includes: forming mother sphere seed crystals by rolling and agglomerating powder, then continuously adding carbon powder and intermittently supplying a binder aqueous solution to obtain spherical activated carbon particles; and / or, the particle size of the spherical activated carbon particles is 1mm-5mm.

[0062] Specifically, granulation is performed on a disc granulator, with the disc's tilt angle controlled between 40° and 50° and its rotational speed between 30 and 50 rpm. A disc granulator is a device that forms granules by the rolling, collision, and agglomeration of materials within a tilting, rotating disc. The disc's tilt angle and rotational speed are key parameters affecting the quality of the granules. For example, in addition to the 40°–50° tilt angle range, in actual operation, the tilt angle can also be adjusted by modifying the disc's support structure or hydraulic system, for example, by setting it to 35°–45° or 45°–55° to accommodate the flowability and adhesion of different materials. The rotational speed, besides the 30–50 rpm range, can also be precisely adjusted using a variable frequency motor or mechanical speed changer, for example, by setting it to 25–45 rpm or 40–60 rpm to optimize the density and uniformity of the granules. By precisely controlling these parameters, it is possible to ensure that the particles are subjected to uniform stress during growth, thereby obtaining a carrier with a dense structure and regular shape, and avoiding local flow channel blockage caused by uneven molding.

[0063] The ball-rolling granulation specifically includes: forming mother sphere seed crystals by rolling and agglomerating powder, then continuously adding carbon powder and intermittently supplying a binder aqueous solution to obtain spherical activated carbon granules. Ball-rolling granulation is a method of gradually agglomerating and growing materials into spherical granules during rolling. The mother sphere seed crystals can be formed by pre-mixing some carbon powder with a small amount of binder and initially rolling it in the granulator to form small particles as seed crystals; or by controlling the initial feed rate and binder spraying rate to allow some powder to rapidly agglomerate and form seed crystals in the early stages of granulation. Continuous or semi-continuous addition of carbon powder can be achieved using a screw conveyor, vibrating feeder, or other methods. Intermittent supply of the binder aqueous solution can be achieved through a spray system, dripping system, or other methods, periodically or as needed, sprayed onto the rolling material according to particle growth and humidity requirements. This layer-by-layer coating method makes the internal structure of the particles more compact, helping to improve the mechanical strength of the carrier, making it less prone to breakage under the impact of high-pressure fluid in a fixed bed, and reducing bed pressure drop fluctuations caused by pulverization.

[0064] The spherical activated carbon particles have a particle size of 1mm-5mm. Particle size is a measure of particle dimensions, and for catalyst supports, a suitable particle size range is crucial for their performance in a fixed-bed reactor. Particle size control can be achieved by adjusting process parameters such as granulation time, disc rotation speed, tilt angle, binder dosage, and carbon powder replenishment rate. Furthermore, the granulated particles can be graded using sieving equipment to remove excessively large or small particles, thus obtaining products within the target particle size range. Particle size can be detected using laser particle size analyzers, sieving methods, etc. Controlling the particle size of spherical activated carbon particles within a specific range is key to balancing the catalyst's specific surface area and bed porosity. Specifically, the particle size of spherical activated carbon particles is 1mm-2mm; or 2.5mm-3.5mm; or 4mm-5mm.

[0065] By employing the above technical solution and using a disc granulator with precise control over the disc's tilt angle and rotation speed, uniform stress on the particles during growth is ensured, resulting in a dense and regularly shaped activated carbon carrier. This effectively avoids localized flow channel blockage caused by uneven molding, thus guaranteeing uniform material flow within the fixed-bed reactor. Simultaneously, the granulation method, which involves rolling agglomeration to form mother spherical seed crystals and continuous replenishment of carbon powder while intermittently supplying a binder aqueous solution, allows the particles to achieve a more compact internal structure through layer-by-layer encapsulation. This growth mechanism significantly enhances the mechanical strength of the activated carbon carrier, making it less prone to breakage under the impact of high-pressure fluid in the fixed bed. This reduces pressure drop fluctuations in the bed caused by pulverization, improving the catalyst's crush resistance and lifespan. Furthermore, precisely controlling the particle size of the spherical activated carbon particles within the range of 1mm-5mm achieves an optimized balance between the catalyst's specific surface area and bed porosity. This particle size range ensures sufficient exposure of active sites to maintain high catalytic activity while providing suitable bed porosity, effectively reducing mass transfer resistance as the fluid passes through the bed. This ensures sufficient diffusion and reaction between the nitrophenol feedstock and hydrogen on the catalyst surface, thereby improving the overall stability and catalytic efficiency of the continuous operation of the catalytic hydrogenation process. In summary, the activated carbon support prepared in this application possesses excellent physical structure and hydrodynamic properties, effectively solving problems such as uneven catalyst stacking, high mass transfer resistance, and insufficient mechanical strength in fixed-bed continuous hydrogenation processes, significantly improving the stability and catalytic efficiency of the catalyst in continuous production.

[0066] In some of the embodiments described above in this application, activated carbon supports are prepared by granulation. However, in the process of continuous hydrogenation in a fixed bed, if the activated carbon support is not sufficiently structurally strengthened and its surface properties are not properly controlled, it is very easy for the mechanical strength to decrease, the pore structure to collapse, or the carbon on the surface to deactivate under the high temperature and high pressure reaction environment. This leads to an increase in the pressure drop of the catalyst bed and the covering of active sites, thereby limiting the long-term operational stability and service life of the catalyst.

[0067] In this regard, this application further proposes that in step S200, the activated carbon support undergo high-temperature carbonization and activation treatment. Specifically, the high-temperature carbonization is controlled at a temperature of 650℃-750℃ for a time of 6h-12h; and / or, the high-temperature carbonization is carried out under inert gas protection; and / or, the activation treatment is controlled at a temperature of 900℃-1000℃ for a time of 1h-6h; and / or, the activation treatment is carried out in an activation atmosphere containing water vapor.

[0068] The high-temperature carbonization process, controlled at 650℃-750℃ for 6-12 hours, aims to remove organic impurities and volatiles from the activated carbon material through pyrolysis, and promote the rearrangement and densification of the carbon skeleton. Precisely controlling the temperature within the range of 650℃ to 750℃ and maintaining it for 6-12 hours ensures that the carbon material undergoes sufficient carbonization under appropriate thermodynamic conditions, thereby forming a stable carbon skeleton structure and laying the foundation for subsequent activation treatment. For example, the granulated activated carbon material can be placed in a tube furnace or box furnace, gradually heated to the target temperature under programmed temperature control, and held at that temperature; alternatively, a rotary kiln can be used for continuous carbonization, controlling the carbonization conditions by adjusting the kiln rotation speed and the temperature distribution in the heating zone. Specifically, the high-temperature carbonization is controlled at a temperature of 730℃-750℃ for 6-7 hours; or at a temperature of 650℃-680℃ for 10-12 hours; or at a temperature of 690℃-710℃ for 6-8 hours.

[0069] Meanwhile, the high-temperature carbonization is carried out under inert gas protection, which is a key measure to prevent the carbon material from undergoing oxidation at high temperatures. During high-temperature carbonization, carbon materials are highly susceptible to oxidation with oxygen in the air, leading to burn-off of the carbon skeleton, collapse of the pore structure, and a decrease in mechanical strength. Using inert gases, such as nitrogen or argon, can effectively isolate oxygen, thereby maintaining the integrity and stability of the carbon skeleton and ensuring that the carrier possesses good mechanical strength and structural stability. For example, high-purity nitrogen or argon can be continuously introduced into the carbonization furnace to maintain positive pressure and remove oxygen; or, airlocks can be installed at the inlet and outlet of the carbonization equipment, and the inside of the equipment can be evacuated before being filled with inert gas to create an oxygen-free environment.

[0070] Furthermore, controlling the activation treatment temperature at 900℃-1000℃ and the time at 1h-6h is a key step in imparting a high specific surface area and well-developed pore structure to the activated carbon support. By controlling the temperature within the relatively high range of 900℃ to 1000℃ and maintaining it for 1h to 6h, a moderate gasification reaction can be promoted in the carbon skeleton, thereby forming abundant micropores, mesopores, and macropores within the carbon material. The selection of this temperature range and time window aims to achieve controllable development of the pore structure, effectively increasing the specific surface area and pore volume while avoiding excessive activation that would lead to excessive burning of the carbon skeleton and a significant decrease in mechanical strength. For example, the carbonized activated carbon support can be placed in an activation furnace, heated to the target temperature under programmed temperature control, and held at that temperature; or, a fluidized bed reactor can be used for activation, with the degree of activation precisely controlled by adjusting the fluidizing gas flow rate and reaction temperature. Specifically, the activation treatment temperature is controlled at 940℃-960℃ for 1h-3h; or the activation treatment temperature is controlled at 990℃-1000℃ for 1h-2h; or the activation treatment temperature is controlled at 940℃-960℃ for 4h-6h.

[0071] Furthermore, the activation treatment is carried out in an activation atmosphere containing water vapor. Water vapor, as a mild and efficient activator, reacts with carbon materials at high temperatures through a vaporization reaction, selectively etching the carbon skeleton to form a uniform and rationally distributed pore structure. Compared to other activators, water vapor activation effectively avoids introducing additional impurities and helps form specific oxygen-containing functional groups on the surface of the carbon material. These functional groups play a positive role in the subsequent loading and anchoring of platinum-based active components. By controlling the concentration and flow rate of water vapor, the degree of activation and pore structure characteristics can be precisely controlled. For example, preheated water vapor is introduced into the activation furnace and mixed with an inert gas to form an activation atmosphere; or, water vapor is generated by a steam generator, and its flow rate and temperature are precisely controlled before it enters the activation reactor. Specifically, the activation atmosphere containing water vapor is a mixture of water vapor and nitrogen; or, the activation atmosphere containing water vapor is saturated water vapor.

[0072] Through the above technical solution, this application aims to construct a support framework with high mechanical strength, suitable pore size distribution, and excellent chemical stability by precisely controlling the high-temperature carbonization and activation treatment of the activated carbon support, thereby improving the catalyst's resistance to pressure and carbon deposition in a fixed-bed reactor. High-temperature carbonization at 650℃ to 750℃ under inert gas protection effectively removes binders introduced during granulation and impurities within the activated carbon, causing deep condensation of the carbon framework. This significantly enhances the mechanical strength of the support, preventing breakage and bed blockage under high-pressure fluid impact in the fixed bed. Simultaneously, activation treatment at 900℃ to 1000℃ in a water vapor atmosphere allows for controlled etching of the carbon framework, forming abundant micropores and mesopores on the support surface. This optimized pore structure not only increases the loading space for platinum-based active components but also effectively promotes the diffusion of reactants and products, reduces mass transfer resistance, and enhances the anchoring effect of the support on the active components by adjusting the distribution of surface functional groups, inhibiting the migration and aggregation of active components during the reaction process. The synergistic effect of the aforementioned carbonization and activation processes ensures that the support maintains a stable physical morphology under the harsh conditions of nitrophenol hydrogenation, while also mitigating carbon deposition and deactivation caused by phenolic hydroxyl adsorption through optimized pore structure. This, in turn, guarantees the continuous operational stability of the catalyst from the support structure level and extends the catalyst's service life.

[0073] In some embodiments described above in this application, a platinum precursor is supported on an activated carbon support to prepare a catalyst. However, in the process of hydrogenating nitrophenol to aminophenol, a single platinum metal active site is easily poisoned and deactivated by the strong adsorption of phenolic hydroxyl groups. Furthermore, in the process of reducing nitro groups, a single metal is difficult to simultaneously achieve high selectivity and high activity, which can easily lead to side reactions such as excessive hydrogenation of the benzene ring or excessive reduction of the amino group, thus limiting the cycle life of the catalyst.

[0074] To address this issue, this application further proposes an optimized method for preparing platinum-based catalysts. Specifically, in step S300, the catalyst composition is finely designed to solve the aforementioned problems. The method includes: a platinum precursor selected from at least one of chloroplatinic acid, platinum acetate, platinum nitrate, and chloroplatinic acid; and / or, based on the mass of the activated carbon support, the platinum loading is 0.1 wt% to 5 wt%; and / or, when the platinum precursor is prepared as a liquid phase system, the molar concentration of platinum in the platinum-containing liquid phase system is 0.1 mol / L to 2 mol / L; and / or, an auxiliary metal precursor selected from at least one of indium nitrate, cadmium nitrate, and zinc nitrate; and / or, based on elemental molar amounts, the molar amount of the auxiliary metal is 10% to 100% of the molar amount of platinum.

[0075] The platinum precursor is selected from at least one of chloroplatinic acid, platinum acetate, platinum nitrate, and chloroplatinic acid. These precursors are compounds that provide the active metal platinum, and their selection is crucial for the dispersibility of the active component and the final performance of the catalyst. For example, chloroplatinic acid, as an inorganic platinum precursor, has good water solubility and stability, and is easily and uniformly dispersed on the support surface; or, platinum acetate or platinum nitrate, as organic or inorganic platinum precursors, have relatively low decomposition temperatures, which helps to form highly dispersed platinum nanoparticles under mild conditions and reduce impurity residues.

[0076] Based on the mass of the activated carbon support, the platinum loading ranges from 0.1 wt% to 5 wt%. This loading range is designed to balance catalyst activity and cost. Specifically, the platinum loading can be any value from 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, to 5 wt%, or a continuous range between any two values.

[0077] When platinum precursors are prepared as liquid systems, the molar concentration of platinum in the platinum-containing liquid system is between 0.1 mol / L and 2 mol / L. Controlling this concentration range helps ensure good solubility and dispersibility of the platinum precursor in the liquid phase, thus affecting its uniform distribution on the support. For example, a solution of the desired concentration can be prepared by dissolving an appropriate amount of platinum precursor in deionized water or an organic solvent, supplemented by heating and stirring, to ensure uniform distribution of platinum ions in the solution, which is beneficial for penetration and distribution during subsequent impregnation processes. Alternatively, the concentration of the liquid system can be optimized according to the adsorption characteristics of the support and the target loading to achieve the ideal impregnation depth and distribution of the platinum component within the pores of the activated carbon support.

[0078] The auxiliary metal precursor is selected from at least one of indium nitrate, cadmium nitrate, and zinc nitrate. The introduction of an auxiliary metal is one of the key innovations of this application, aiming to overcome the limitations of single platinum catalysts by forming a bimetallic or multimetallic synergistic system. For example, indium nitrate, as a precursor, can introduce indium elements that can regulate the electronic structure of platinum through electronic effects, thereby weakening the strong adsorption of phenolic hydroxyl groups at active sites and promoting the reduction of nitro groups; or, cadmium nitrate or zinc nitrate, as precursors, can introduce cadmium or zinc elements that can form alloys with platinum or interact with it, optimizing the adsorption and reduction pathways of nitro groups while reducing the excessive hydrogenation activity on the benzene ring and effectively suppressing the occurrence of side reactions.

[0079] The molar amount of the auxiliary metal, measured in molar amounts, is 10% to 100% of the molar amount of platinum. Precise control of this molar ratio is crucial to ensuring optimal bimetallic synergistic effects. For example, by accurately calculating and weighing the amounts of the auxiliary metal precursor and the platinum precursor to achieve the target molar ratio in the mixture, ideal intermetallic interactions can be formed in the catalyst to achieve the best synergistic catalytic effect. Alternatively, when preparing the mixture, the ratio of the auxiliary metal to platinum can be adjusted based on experimental data and theoretical models to significantly improve the catalyst's resistance to carbon deposition and operational stability during continuous hydrogenation while maintaining its low-temperature activity. Specifically, the molar ratio of platinum to the auxiliary metal is (1-2):1; or (4-6):1; or (8-10):1.

[0080] Through the above technical solution, this application effectively solves the problems of single noble metal catalysts being easily poisoned and deactivated by strong adsorption of phenolic hydroxyl groups during the hydrogenation of nitrophenols, and the frequent side reactions caused by insufficient selectivity, by introducing an auxiliary metal to form a bimetallic or multimetallic synergistic system with platinum. Specifically, by selecting appropriate platinum precursors and auxiliary metal precursors, and precisely controlling the platinum loading, the concentration of the platinum-containing liquid phase system, and the molar ratio of the auxiliary metal to platinum, good dispersion and uniform distribution of the active components on the activated carbon support can be ensured. The introduced auxiliary metals, such as indium, cadmium, or zinc, can adjust the electronic structure of the platinum surface through electronic or geometric effects, thereby significantly weakening the strong adsorption of phenolic hydroxyl groups at the active sites and effectively inhibiting catalyst poisoning. At the same time, this synergistic effect optimizes the adsorption and reduction pathway of nitro groups, effectively inhibiting the occurrence of side reactions such as excessive hydrogenation of benzene rings and excessive reduction of amino groups, thereby improving the selectivity of nitro group reduction. Furthermore, this bimetallic system enhances the catalyst's resistance to carbon deposition and hydrothermal stability during continuous hydrogenation, extends the catalyst's cycle life, and provides a more efficient and stable catalyst solution for the continuous hydrogenation of nitrophenol to aminophenol via a fixed bed.

[0081] In some embodiments described above in this application, a scheme is proposed to load platinum precursors and auxiliary metal precursors onto an activated carbon support. However, in the subsequent calcination process, if there is a lack of precise control over temperature and atmosphere, the active components are prone to agglomeration, sintering, or surface oxidation, which reduces the dispersion of active sites on the catalyst and affects the initial activity and long-term operational stability of the catalyst in continuous hydrogenation reactions.

[0082] In this regard, this application further proposes to optimize the calcination treatment in the preparation method of the platinum-based catalyst, specifically including: controlling the calcination treatment temperature at 200℃-400℃ and the time at 1h-5h; and / or, the calcination treatment is carried out under inert gas protection.

[0083] Specifically, calcination is a crucial step in catalyst preparation. Its purpose is to transform the platinum precursor and auxiliary metal precursor supported on the activated carbon support into catalytically active metal species and stabilize their dispersion on the support. Precisely controlling the calcination temperature within the range of 200℃ to 400℃ ensures sufficient decomposition of the precursors, forming highly dispersed metal nanoparticles or their oxides, while effectively preventing migration, agglomeration, or excessive interaction between the metal particles and the support due to excessively high temperatures. For example, precise temperature control can be achieved by using a muffle furnace or tube furnace with programmed temperature rise. Simultaneously, controlling the calcination time to 1 to 5 hours provides sufficient heat treatment time for the metal components to reach a stable loading state on the activated carbon support, promoting their phase transformation or structural rearrangement, while avoiding excessive sintering that may result from prolonged high-temperature treatment. For example, the optimal calcination time can be determined by setting the operating time of the heating equipment or by monitoring the physicochemical properties of the catalyst online. Specifically, the calcination treatment is controlled at a temperature of 380℃-400℃ for 1-2 hours; or at a temperature of 200℃-250℃ for 4-5 hours; or at a temperature of 280℃-320℃ for 1.5-3.5 hours.

[0084] Furthermore, the calcination process is carried out under an inert gas atmosphere to effectively prevent the active metal components from reacting with oxygen in the air during the high-temperature calcination process, which could lead to oxidation deactivation or the formation of valence states unfavorable to the catalytic reaction. For example, high-purity nitrogen or argon can be used as the inert gas, continuously introduced into the calcination furnace at a certain flow rate to ensure an inert atmosphere inside the furnace, thereby protecting the active components.

[0085] Through the above technical solutions, this application aims to optimize the state of the active components of the catalyst on the support surface by precisely defining the calcination process parameters. By controlling the calcination temperature within the range of 200℃ to 400℃, it is possible to ensure the complete decomposition and transformation of the precursor into active metal species, while effectively preventing the migration, agglomeration, or excessive interaction between metal particles and the support due to excessively high temperatures. This maintains the high dispersion of the active components and ensures that the catalyst has sufficient active sites. By controlling the calcination time within 1 hour to 5 hours, the sufficiency of the heat treatment process is ensured, allowing the metal components to reach a stable loading state within the pores of the support. Calcination under inert gas protection effectively isolates oxygen and prevents the metal components from being oxidized at high temperatures, thereby maintaining the reduced state or specific valence state of the metal components. This is crucial for maintaining high selectivity in the hydrogenation reaction of nitrophenol. This synergistic control of the calcination environment and thermodynamic conditions significantly improves the structural stability of the catalyst, enabling it to maintain good catalytic activity and resistance to deactivation even when faced with the strong polar adsorption of nitrophenol. This provides a key process guarantee for achieving long-term stability in fixed-bed continuous production.

[0086] In some of the above-mentioned schemes of this application, a process for preparing catalysts by surface modification, granulation and metal loading is proposed. However, in these preparation processes, the drying conditions of intermediate and final products are not finely controlled, resulting in insufficient stability of the catalyst support surface structure. Furthermore, if the drying process after metal loading is not properly controlled, it can easily cause uneven distribution or agglomeration of active components on the support surface, thereby affecting the activity and lifespan of the catalyst in continuous hydrogenation reaction.

[0087] In this regard, this application further proposes that in S100, the drying process is controlled at a temperature of 90℃-120℃ and a time of 12h-24h; and / or, in S300, the drying process is controlled at a temperature of 90℃-120℃ and a time of 12h-24h.

[0088] Specifically, in step S100, when drying the amine-modified activated carbon material, the temperature is controlled within the range of 90°C to 120°C, and the processing time is maintained between 12 and 24 hours. This drying step aims to effectively remove moisture and residual solvents from the amine-modified activated carbon material while avoiding adverse effects on the pore structure and surface chemical properties of the activated carbon. For example, a hot air circulation drying oven can be used to ensure uniform heating of the material; alternatively, a vacuum drying device can be used to dry under reduced pressure to achieve a gentler and more thorough solvent removal. By precisely controlling the drying temperature and time, it is possible to ensure that the organic amine modifier is uniformly distributed and stably adhered to the activated carbon surface, providing a structurally stable carrier precursor with excellent surface properties for subsequent granulation.

[0089] In step S300, after the mixture of platinum precursor and auxiliary metal precursor is loaded onto an activated carbon support, it is also dried, with the temperature controlled between 90°C and 120°C and the time between 12 and 24 hours. This drying step is crucial to ensuring the uniform dispersion of the active metal component on the support. For example, a constant-temperature oven can be used for slow heating and drying to avoid the "coffee ring effect" and metal component migration and aggregation caused by rapid solvent evaporation; alternatively, freeze-drying technology can be used to remove the solvent by sublimation to maximize the preservation of the original dispersion state of the metal component within the pores of the support. By precisely controlling the drying conditions at this stage, uneven distribution or aggregation of platinum and auxiliary metal precursors during the drying process can be effectively prevented, thereby ensuring a high degree of dispersion of the active sites.

[0090] Through the above technical solutions, this application aims to optimize the physicochemical structure of the catalyst and improve its overall performance in continuous hydrogenation processes by strictly limiting the parameters of key drying steps in the catalyst preparation process. In the S100 modified activated carbon drying step, controlling the temperature between 90°C and 120°C for 12 to 24 hours ensures sufficient and gentle removal of moisture and solvent from the activated carbon after organic amine modification. This controlled drying process avoids pore structure collapse or uneven distribution of the modifier due to excessively rapid heating, providing a carrier precursor with good pore structure and surface chemical properties for subsequent granulation, thereby enhancing the mechanical strength of the carrier and the anchoring ability of the subsequently loaded metal. In the S300 metal-loaded post-drying step, the same temperature range of 90°C to 120°C and a drying time of 12 to 24 hours are used; this characteristic is crucial for the uniform distribution of the active components. Slow and uniform solvent evaporation effectively prevents platinum and auxiliary metal precursors from migrating to the support surface and forming large particle agglomerates during the drying process, ensuring that the metal active sites are highly dispersed within the pores and on the surface of the activated carbon support. This refined drying process not only improves the utilization rate of the active components but also enhances the catalyst's resistance to poisoning and structural stability in the face of strong nitrophenol adsorption by improving the interaction between the metal and the support, laying the foundation for long-term continuous and stable operation of the fixed-bed reactor.

[0091] Traditional aminophenol production processes generate significant amounts of hazardous waste, incur high costs for waste treatment, and cause substantial environmental pollution. While green catalytic hydrogenation has become the mainstream alternative technology, the industry as a whole still faces technical challenges such as high catalyst costs, insufficient selectivity, susceptibility to over-hydrogenation, and poor stability in continuous production. Particularly in the continuous hydrogenation process of nitrophenol in a fixed bed, the strong electron-withdrawing effect and polar adsorption characteristics of the phenolic hydroxyl group easily lead to catalyst active site poisoning, carbon deposition, and deactivation. Furthermore, molded catalysts suffer from high mass transfer resistance and insufficient stability during continuous operation, resulting in continued reliance on imports for high-end, high-purity aminophenol products.

[0092] In this regard, this application proposes an application of a platinum-based catalyst for the continuous hydrogenation of aminophenol. The platinum-based catalyst prepared by the method is applied to the continuous hydrogenation of nitrophenol to aminophenol in a fixed bed, specifically including the following steps: packing the platinum-based catalyst into a fixed bed reactor, introducing hydrogen into the fixed bed reactor to pretreat the platinum-based catalyst with hydrogen, then continuously introducing nitrophenol feedstock liquid and hydrogen into the fixed bed reactor, carrying out a catalytic hydrogenation reaction under hydrogenation reaction conditions, and finally separating the reaction effluent with solvent to obtain the aminophenol product.

[0093] In some embodiments described above, a method of packing platinum-based catalysts into a fixed-bed reactor was proposed. However, during implementation, the active sites on the catalyst surface are easily covered by phenolic hydroxyl adsorption, leading to insufficient initial activity. To address this, this application further proposes a specific implementation step of hydrogen pretreatment: introducing hydrogen into the fixed-bed reactor to pretreat the platinum-based catalyst. This step activates the active sites on the catalyst surface through hydrogen reduction and removes impurities that may have been adsorbed during packing, ensuring that the catalyst is in its optimal active state before entering the formal reaction. This effectively avoids the selectivity decrease problem caused by the covering of active sites in the early stages of the reaction.

[0094] Furthermore, this application implements an operation process of continuously introducing nitrophenol feedstock liquid and hydrogen. Specifically, during the catalytic hydrogenation reaction under hydrogenation reaction conditions, the selective hydrogenation capability of the platinum-based catalyst for nitro groups is utilized. While ensuring the reduction of nitro groups to amino groups, the structural characteristics of the catalyst suppress side reactions such as phenolic hydroxyl group removal and excessive hydrogenation of the benzene ring. This process strictly controls the space velocity, hydrogen-to-feed ratio, and temperature and pressure parameters, causing the nitro group (-NO2) in the nitrophenol molecule to successively pass through the nitroso and hydroxylamine intermediate stages, and finally be selectively reduced to amino groups (-NH2). The process avoids side reactions such as phenolic hydroxyl group removal, excessive hydrogenation of the benzene ring, and molecular coupling throughout, thereby significantly improving the purity of the product.

[0095] Furthermore, this application achieves effective recovery of both product and solvent by separating the reaction effluent from the solvent. This step not only simplifies the post-processing flow but also reduces production costs through solvent recycling, ensuring the cleanliness and efficiency of the entire hydrogenation process. Compared to traditional batch reactor processes, the continuous operation of a fixed bed ensures stable contact between the nitrophenol feedstock and the catalyst, effectively solving the bed blockage problem caused by the high polarity and easy crystallization of the feedstock liquid, while also reducing mass transfer resistance and ensuring the stability of continuous production.

[0096] The core innovation of this embodiment lies in combining a specially formulated platinum-based catalyst with a fixed-bed continuous hydrogenation process. Specifically, by activating the active sites on the catalyst surface through a hydrogen pretreatment step and optimizing continuous feed conditions, the catalyst effectively suppresses phenolic hydroxyl adsorption poisoning and carbon deposition deactivation, achieving a significant extension of catalyst lifespan while maintaining high selectivity. This application successfully solves the technical problems of catalyst susceptibility to phenolic hydroxyl adsorption poisoning and carbon deposition deactivation in the fixed-bed continuous hydrogenation process of nitrophenol, as well as poor continuous operation stability and the difficulty in balancing high selectivity and long lifespan. It provides a reliable technical path for the domestic mass production of high-end aminophenol.

[0097] In some embodiments of this application, a method for preparing a platinum-based catalyst for the hydrogenation reduction of nitrophenol is proposed. However, when this catalyst is applied to a fixed-bed continuous production process, the complexity of the nitrophenol feedstock, the fluctuation of the reaction conditions, and the interaction between the active sites on the catalyst surface and the reactants often lead to problems such as active site poisoning, carbon deposition and deactivation, and increased bed pressure drop in actual operation. This makes it difficult to maintain the stability of continuous production and to accurately control the reaction parameters to balance conversion and selectivity.

[0098] In this regard, this application further proposes an application of a platinum-based catalyst for the continuous hydrogenation production of aminophenol, specifically including: the hydrogen pretreatment temperature controlled at 100℃-300℃, time at 1h-6h, and pressure at 0.1MPa-2MPa; and / or, the nitrophenol feedstock solution is obtained by mixing feedstock and solvent, wherein the feedstock is selected from at least one of o-nitrophenol, m-nitrophenol, and p-nitrophenol, and the solvent is selected from at least one of ultrapure water, methanol, and ethanol; and / or, the mass fraction of nitrophenol in the nitrophenol feedstock solution is 1%-30%; and / or, the catalytic hydrogenation reaction temperature controlled at 80℃-150℃, pressure at 0.1MPa-3MPa, and feed mass hourly space velocity at 0.1g / g. cat h-1.2g / g cat The molar ratio of hydrogen to nitrophenol raw material is 5-100.

[0099] To ensure optimal catalyst performance in continuous hydrogenation reactions, this application optimizes the hydrogen pretreatment conditions. Specifically, the hydrogen pretreatment temperature is controlled between 100℃ and 300℃. This temperature range effectively promotes the reduction of active components (such as platinum) on the catalyst surface, transforming them from an oxidized state to a catalytically active metallic state. It also helps remove impurities that may have been adsorbed during catalyst preparation, while avoiding sintering or loss of active components due to excessively high temperatures. The pretreatment time is controlled between 1 h and 6 h. This time range is sufficient to ensure adequate catalyst activation, fully exposing its active sites and thus exhibiting excellent catalytic performance in subsequent reactions. It also avoids increased energy consumption or excessive changes in catalyst structure that may result from prolonged pretreatment. The pretreatment pressure is controlled between 0.1 MPa and 2 MPa. This pressure range ensures that hydrogen can effectively penetrate the catalyst's pore structure and fully contact the active sites, achieving efficient reduction activation while avoiding the equipment requirements and operational complexity caused by excessively high pressures.

[0100] In the preparation of the nitrophenol feedstock solution, this application employs a specific combination of feedstock and solvent. The feedstock is selected from at least one of o-nitrophenol, m-nitrophenol, and p-nitrophenol. These nitrophenol isomers are key precursors for the preparation of the corresponding aminophenols, and they have similar nitro functional groups in structure, making them suitable for the catalytic hydrogenation system provided in this application. The solvent is selected from at least one of ultrapure water, methanol, and ethanol. These solvents are all polar solvents, capable of effectively dissolving nitrophenol and reducing the viscosity of the feedstock solution, thereby ensuring good flowability of the feedstock solution in the fixed-bed reactor and preventing bed blockage due to excessive viscosity or crystallization. Furthermore, these solvents are relatively stable under hydrogenation reaction conditions and are less prone to side reactions. The mass fraction of nitrophenol in the nitrophenol feedstock solution is 1%-30%. This concentration range has been optimized to ensure reaction efficiency and yield while effectively avoiding crystallization and blockage problems that may occur during the transport and reaction of high-concentration nitrophenol, thus maintaining the stability of continuous production.

[0101] This application also features refined control of the operating parameters for the catalytic hydrogenation reaction. The reaction temperature is controlled between 80℃ and 150℃. This temperature range provides sufficient activation energy to ensure rapid conversion of nitrophenols while effectively suppressing side reactions such as phenolic hydroxyl removal and excessive hydrogenation of the benzene ring, thus guaranteeing the selectivity of the aminophenol product. The reaction pressure is controlled between 0.1 MPa and 3 MPa. This pressure range facilitates the dissolution and diffusion of hydrogen in the liquid phase, ensuring a sufficient supply of hydrogen during the reaction, thereby promoting complete reduction of the nitro group and helping to suppress side reactions such as intermediate coupling. The feed mass hourly space velocity is controlled at 0.1 g / g. cat h-1.2g / g catThe space velocity range of h ensures that the reactants have an appropriate residence time in the catalyst bed, allowing nitrophenol to fully contact the active sites of the catalyst and complete the conversion, while avoiding excessive hydrogenation or catalyst deactivation that may result from excessively low space velocities. The molar ratio of hydrogen to nitrophenol feedstock is controlled between 5 and 100. This molar ratio ensures a sufficient hydrogen source for the reaction, effectively avoiding incomplete reactions or increased side reactions due to insufficient hydrogen, thereby further improving the yield and selectivity of aminophenol.

[0102] By precisely defining the pretreatment, feedstock preparation, and reaction conditions in the fixed-bed continuous hydrogenation process, this application constructs a complete process operation system aimed at solving the problems of catalyst stability and reaction selectivity during long-term operation. Specifically, by subjecting the aforementioned platinum-based catalyst to hydrogen pretreatment within a specific temperature, time, and pressure range, the platinum-based active sites on the catalyst surface can be effectively activated, and impurities or oxidized species that may remain from the preparation process can be removed. This allows the catalyst to reach its optimal reduced-state activity before entering the formal reaction, thereby significantly enhancing its initial catalytic ability for nitro hydrogenation and laying a stable foundation for subsequent continuous reactions. Simultaneously, by mixing the nitrophenol feedstock with solvents such as ultrapure water, methanol, or ethanol, and precisely controlling the mass fraction of nitrophenol, the viscosity of the feedstock solution can be effectively reduced, and crystallization of nitrophenol can be prevented during transport and reaction. This avoids blockage or abnormal pressure drop in the fixed-bed reactor bed, ensuring uniform distribution and continuous flow of materials within the bed, and greatly improving the stability of continuous production. Furthermore, precise control of reaction kinetics was achieved through the coordinated control of temperature, pressure, feed mass hourly space velocity (MHSV), and the molar ratio of hydrogen to nitrophenol in the catalytic hydrogenation reaction. Within a specific temperature and pressure range, the reaction rate and side reactions can be effectively balanced, avoiding selectivity reduction issues such as phenolic hydroxyl group removal or excessive benzene ring hydrogenation caused by excessively high temperatures. By limiting the feed MHSV, sufficient residence time of the reactants in the catalyst bed is ensured for complete conversion. Simultaneously, by controlling the molar ratio of hydrogen to nitrophenol, a sufficient hydrogen source is guaranteed for the hydrogenation reaction, effectively suppressing side reactions such as intermediate coupling. Thus, while ensuring high conversion rates, the selectivity of the aminophenol product is significantly improved. Overall, the above technical solution, combined with the prepared platinum-based catalyst, effectively solves problems such as catalyst deactivation, bed blockage, and difficulty in selectivity control in continuous production, ensuring the long-term stable operation of the aminophenol production process and the high quality of the product.

[0103] The following describes the scheme of this application with specific experiments and experimental data: Reagents used in the examples: The activated carbon was commercially available powdered activated carbon; triethylamine, methylamine, ethylenediamine, calcium lignosulfonate, carboxymethyl cellulose, starch paste, chloroplatinic acid, indium nitrate, cadmium nitrate, zinc nitrate, ortho / m / p-nitrophenol, methanol, and ethanol were all industrial-grade chemical reagents; nitrogen purity ≥99.99%, hydrogen purity ≥99.99%.

[0104] Example 1: This embodiment provides a method for preparing a platinum-based catalyst for continuous hydrogenation to aminophenol, and the specific preparation method is as follows: S100: Prepare 500g of 1% triethylamine aqueous solution, add 100g of powdered activated carbon to the above triethylamine solution, impregnate at room temperature for 3h, filter after impregnation to obtain amine-modified activated carbon filter cake; place the filter cake in a 90℃ oven to dry for 24h to obtain amine-modified activated carbon material.

[0105] S200: Calcium lignosulfonate and deionized water were mixed at a mass ratio of 1:2 and stirred for 3 hours to prepare an aqueous binder solution. Disc granulation conditions: Disc inclination angle approximately 45°, rotation speed 30 r / min; Granulation process: A small amount of amine-modified activated carbon material was first added, followed by atomized spraying of the binder solution. The powder rolled and agglomerated on the disc surface to form small mother sphere seed crystals. Amine-modified activated carbon material was continuously and uniformly added, while the binder solution was intermittently atomized and sprayed. The granulation time was 15 min, resulting in spherical carbon particles with a diameter of approximately 1 mm. The spherical carbon particles were dried in a 90℃ oven for 24 hours, controlling the particle moisture content to <2%. Subsequently, they were carbonized at 650℃ for 12 hours under a nitrogen protective atmosphere. After carbonization, the temperature was raised to 900℃, and saturated steam was introduced for activation for 6 hours. After cooling, spherical activated carbon carriers with a diameter of 1 mm were obtained.

[0106] S300: Weigh chloroplatinic acid and indium nitrate according to 0.1% platinum element based on the mass of spherical activated carbon support, with a platinum to indium molar ratio of 10:1, and add water to prepare a platinum-indium mixed precursor solution; atomize the mixed solution and spray it onto the surface of the spherical activated carbon support; after loading, dry in an oven at 90℃ for 24h; calcine at 400℃ for 1h under a nitrogen atmosphere, and cool to obtain the finished catalyst A (0.1% Pt-In / C).

[0107] Example 2: This embodiment provides a method for preparing a platinum-based catalyst for continuous hydrogenation to aminophenol, and the specific preparation method is as follows: S100: Prepare 500g of 5% (w / w) methylamine aqueous solution, add 100g of powdered activated carbon to the above methylamine solution, impregnate at room temperature for 3h, filter after impregnation to obtain amine-modified activated carbon filter cake; place the filter cake in an oven at 120℃ and dry for 12h to obtain amine-modified activated carbon material.

[0108] S200: Carboxymethyl cellulose and deionized water were mixed at a mass ratio of 1:10 and stirred for 1 hour to prepare an aqueous binder solution. Disc granulation conditions: Disc inclination angle approximately 45°, rotation speed 30 r / min; Granulation process: A small amount of amine-modified activated carbon material was first added, followed by atomized spraying of the binder solution. The powder rolled and agglomerated on the disc surface to form small mother sphere seed crystals. Amine-modified activated carbon material was continuously and uniformly added, while the binder solution was intermittently atomized and sprayed. The granulation time was 60 minutes, resulting in spherical carbon particles with a diameter of approximately 5 mm. The spherical carbon particles were dried in a 120℃ oven for 12 hours, controlling the particle moisture content to <2%. Subsequently, they were carbonized at 750℃ for 6 hours under a nitrogen protective atmosphere. After carbonization, the temperature was raised to 1000℃, and saturated steam was introduced for activation for 1 hour. After cooling, spherical activated carbon carriers with a diameter of 5 mm were obtained.

[0109] S300: Based on 5% platinum element of the spherical activated carbon support, weigh chloroplatinic acid and cadmium nitrate, with a platinum to cadmium metal molar ratio of 5:1, and add water to prepare a platinum-cadmium mixed precursor solution; atomize the mixed solution and spray it onto the surface of the spherical activated carbon support; after loading, dry in an oven at 120℃ for 12h; calcine at 200℃ for 5h under a nitrogen atmosphere, and cool to obtain the finished catalyst B (5%Pt-Cd / C).

[0110] Example 3: This embodiment provides a method for preparing a platinum-based catalyst for continuous hydrogenation to aminophenol, and the specific preparation method is as follows: S100: Prepare 500g of 3% ethylenediamine aqueous solution, add 100g of powdered activated carbon to the above ethylenediamine solution, impregnate at room temperature for 3h, filter after impregnation to obtain amine-modified activated carbon filter cake; place the filter cake in an oven at 110℃ and dry for 15h to obtain amine-modified activated carbon material.

[0111] S200: Mix starch paste and deionized water at a mass ratio of 1:4 and stir for 1 hour to prepare a binder aqueous solution. Disc granulation conditions: Disc inclination angle approximately 45°, rotation speed 50 r / min; Granulation process: First, add a small amount of amine-modified activated carbon material, then atomize and spray the binder aqueous solution. The powder rolls and agglomerates on the disc surface to form small mother sphere seed crystals; continuously and uniformly add amine-modified activated carbon material, while intermittently atomizing and spraying the binder solution, for a rolling time of 30 min, to obtain spherical carbon particles with a particle size of 2 mm. Place the spherical carbon particles in a 110℃ oven to dry for 12 hours, controlling the particle moisture content to <2%; then carbonize at 700℃ for 6 hours under a nitrogen protective atmosphere; after carbonization, raise the temperature to 950℃ and introduce saturated steam for activation for 2 hours. After cooling, obtain spherical activated carbon carriers with a particle size of 2 mm.

[0112] S300: Based on 1% platinum element of the spherical activated carbon support, weigh chloroplatinic acid and zinc nitrate, with a platinum to zinc metal molar ratio of 1:1, and add water to prepare a platinum-zinc mixed precursor solution; atomize the mixed solution and spray it onto the surface of the spherical activated carbon support; after loading, dry in an oven at 110℃ for 12h; calcine at 300℃ for 2h under a nitrogen atmosphere, and cool to obtain the finished catalyst C (1%Pt-Zn / C).

[0113] Example 4: Catalyst A for the fixed-bed hydrogenation of p-nitrophenol to prepare p-aminophenol 1. Reaction conditions: 80g of catalyst A was loaded into a 200mL fixed-bed reactor, followed by hydrogen pretreatment. Hydrogen pretreatment conditions: temperature 130℃, pressure 1MPa, treatment time 6h.

[0114] After pretreatment, a 20% (w / w) p-nitrophenol (4-NP) feed solution was prepared using methanol as the solvent and continuously fed. Feed conditions: mass hourly space velocity (HHSV) 0.1 g / g cat The reaction conditions were: ·h, hydrogen to p-nitrophenol molar ratio 5, reaction temperature 80℃, and reaction pressure 3MPa.

[0115] 2. Detection method: (1) Sample pretreatment: After sampling the hydrogenation reaction solution, centrifuge to remove the solid catalyst and take the supernatant; dilute with water / methanol to a suitable ratio and filter through a 0.45μm organic filter membrane.

[0116] Note: Samples should be stored away from light and should not be left out for extended periods; if the pH of the system is alkaline, p-aminophenol (4-AP) is easily oxidized and turns black.

[0117] (2) HPLC instrument conditions: Column: C18, 250mm × 4.6mm, 5μm; Detector: UV-DAD, detection wavelength 230nm or 245nm (both 4NP and 4AP have strong absorption); Mobile phase: methanol-water (containing 0.1% formic acid), volume ratio 40:60; isocratic elution; Flow rate: 1.0 mL / min; Column temperature: 35℃-40℃; Injection volume: 10 μL; Running time: 20 minutes.

[0118] (3) Calculation method: A standard curve was plotted using the external standard method, and the conversion rate and selectivity were calculated. Conversion rate = 1 - (remaining molar amount of p-nitrophenol / molar amount of p-nitrophenol fed in). Selectivity = molar amount of p-aminophenol produced / molar amount of p-nitrophenol converted.

[0119] 3. Test results: The conversion rate of p-nitrophenol in the raw material is >99.9%, and the selectivity of the target product p-aminophenol is >99.5%; the catalyst has been running stably in the reactor for more than 1000 hours.

[0120] Example 5: Catalyst B for the fixed-bed hydrogenation of o-nitrophenol to o-aminophenol 1. Reaction conditions: 100g of catalyst B was loaded into a 300mL fixed-bed reactor, followed by hydrogen pretreatment. Hydrogen pretreatment conditions: temperature 300℃, pressure 0.5MPa, treatment time 1h.

[0121] After pretreatment, a 1% (w / w) o-nitrophenol feed solution was prepared using ultrapure water as the solvent and fed continuously. Feed conditions: mass hourly space velocity (WHSV) 1.2 g / g cat The reaction conditions were: ·h, hydrogen to o-nitrophenol molar ratio 100, reaction temperature 150℃, and reaction pressure 0.5MPa.

[0122] 2. Product testing The product analysis method is the same as in Example 4.

[0123] 3. Test results: o-nitrophenol conversion rate > 99.9%, o-aminophenol selectivity > 99.5%; the catalyst can operate continuously and stably for more than 800 hours.

[0124] Example 6: Catalyst C for the fixed-bed hydrogenation of m-nitrophenol to prepare m-aminophenol 1. Reaction conditions: 500g of catalyst C was loaded into a 2000mL fixed-bed reactor, followed by hydrogen pretreatment. Hydrogen pretreatment conditions: temperature 200℃, pressure 2MPa, treatment time 3h.

[0125] After pretreatment, a 10% m-nitrophenol feedstock solution was prepared using ethanol as a solvent and continuously fed. Feed conditions: mass hourly space velocity (WHSV) 0.8 g / g cat • h, the molar ratio of hydrogen to m-nitrophenol is 20; the reaction temperature is 120℃ and the reaction pressure is 1MPa.

[0126] 2. Product testing The product analysis method is the same as in Example 4.

[0127] 3. Test results: m-nitrophenol conversion rate > 99.9%, m-aminophenol selectivity > 99.8%; the catalyst can operate continuously and stably in the reactor for more than 2000 hours.

[0128] Example 7: Catalyst B used in high-concentration p-nitrophenol hydrogenation and catalyst regeneration experiments 1. Reaction conditions: 100g of catalyst B was loaded into a 300mL fixed-bed reactor, followed by hydrogen pretreatment. Hydrogen pretreatment conditions: temperature 200℃, pressure 2MPa, treatment time 2h.

[0129] After pretreatment, a 30% p-nitrophenol feedstock solution was prepared using a 50 vol% ethanol-water mixture as the solvent and fed continuously. Feed conditions: mass hourly space velocity (WHSV) 1.2 g / g. cat The reaction conditions were: ·h, hydrogen to p-nitrophenol molar ratio 6, reaction temperature 130℃, and reaction pressure 1.0MPa.

[0130] 2. Product testing The product analysis method is the same as in Example 4.

[0131] 3. Test results: p-nitrophenol conversion rate > 99.9%, p-aminophenol selectivity > 99.7%, and the catalyst can operate stably for more than 800 hours.

[0132] After 1200 hours of continuous operation, the catalyst exhibited performance degradation: the conversion rate of p-nitrophenol decreased to 99.1%, and the selectivity of p-aminophenol decreased to 98.5%. Feeding was stopped, and hydrogen was used to replace the materials in the reactor system. The temperature was raised to 200°C, and the hydrogen pressure was increased to 2 MPa. This temperature and pressure were maintained for 5 hours to perform in-situ hydrogen activation and regeneration of the catalyst bed.

[0133] After regeneration, the feed was restored. Under the same process conditions, the test results showed that the conversion rate of p-nitrophenol was restored to 99.8% and the selectivity of p-aminophenol was restored to 99.7%, proving that the catalyst of this invention can achieve the recovery of the active part through in-situ hydrogen activation.

[0134] Comparative Example 1: This embodiment provides a spherical Pt-In / C catalyst that does not undergo organic amine modification, and the preparation method is as follows: S100: Add 100g of powdered activated carbon to pure water and soak for 3 hours. After soaking, filter to obtain activated carbon filter cake. Place the filter cake in a 90℃ oven and dry for 24 hours to obtain activated carbon material.

[0135] Steps S200 and S300 are the same as in Example 1, and catalyst D is finally obtained.

[0136] Catalyst D was used for the fixed-bed hydrogenation of p-nitrophenol to prepare p-aminophenol, following the same steps as in Example 4.

[0137] The test results are as follows (the product analysis method is the same as in Example 4): p-nitrophenol conversion rate is 99.2%, p-aminophenol selectivity is 98.1%; after the catalyst runs for 220 hours, the conversion rate drops rapidly to 92%, the support is not modified with organic amines, and the resistance to phenolic hydroxyl poisoning and carbon deposition is significantly worse.

[0138] Comparative Example 2: This embodiment provides a spherical Pt / C catalyst supported only on platinum, without the addition of indium as a cooperating metal. The preparation method is as follows: Steps S100 and S200 are the same as in Example 1.

[0139] S300: Weigh chloroplatinic acid according to 0.1% platinum element based on the mass of spherical activated carbon support, add water to prepare a platinum precursor solution; atomize the platinum precursor solution and spray it onto the surface of spherical activated carbon support; after loading, dry in an oven at 90℃ for 24h; calcine at 400℃ for 1h under nitrogen atmosphere, and cool to obtain the finished catalyst E.

[0140] Catalyst E was used for the fixed-bed hydrogenation of p-nitrophenol to prepare p-aminophenol, following the same steps as in Example 4.

[0141] The test results are as follows (the product analysis method is the same as in Example 4): p-nitrophenol conversion rate is 99.8%, and p-aminophenol selectivity is 97.3%; by-products have increased significantly, and selectivity declines rapidly with long-term operation.

[0142] In summary, this invention modifies the surface of activated carbon with organic amines to obtain nitrogen, followed by disc rolling, carbonization, and steam activation to obtain a spherical activated carbon support. Platinum and auxiliary metals (In, Cd, Zn) are then loaded onto this support to obtain a platinum-based spherical catalyst. This catalyst is used for the continuous hydrogenation of nitrophenols in a fixed bed to produce aminophenols. It is compatible with various substrates including ortho-, meta-, and para-nitrophenols, achieving a feed conversion rate >99.9% and an aminophenol product selectivity >99.5% over a wide process window. The catalyst exhibits good resistance to poisoning and carbon deposition, enabling long-term continuous operation for 800-2000 hours. Furthermore, the catalyst's performance can be partially restored through in-situ hydrogen regeneration after performance degradation. Comparative studies confirm that organic amine support modification and synergistic effects with auxiliary metal components are essential technical means to achieve the aforementioned excellent catalytic performance.

[0143] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than those in the embodiments and still achieve the desired results. Additionally, in some implementations, multitasking and parallel processing are possible or may be advantageous.

[0144] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0145] This specification is merely an illustrative description of this application and is intended to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Therefore, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A method for preparing a platinum-based catalyst for continuous hydrogenation to aminophenol, characterized in that, Specifically, the following steps are included: S100: Activated carbon is surface modified with organic amines, and after material separation and drying, amine-modified activated carbon material is obtained. S200: The amine-modified activated carbon material is mixed with a binder and a liquid medium, granulated, and then dried, carbonized at high temperature, and activated to obtain an activated carbon carrier. S300: A platinum precursor and an auxiliary metal precursor are formulated into a mixture, which is then loaded onto the activated carbon support, dried, and calcined to obtain the platinum-based catalyst.

2. The preparation method according to claim 1, characterized in that, In S100, The organic amine is selected from at least one of triethylamine, methylamine, and ethylenediamine; and / or, The organic amine is an organic amine solution, and the mass fraction of the organic amine solution is 1%-5%.

3. The preparation method according to claim 1, characterized in that, In S200, The binder is selected from at least one of carboxymethyl cellulose, starch paste, and calcium lignosulfonate; and / or, The mass ratio of the adhesive to the liquid medium is 1:(2-10).

4. The preparation method according to claim 1, characterized in that, In S200, The granulation process is performed on a disc granulator, with the disc tilt angle controlled at 40°–50° and the disc rotation speed at 30 r / min–50 r / min; and / or, The spherical granulation specifically includes: forming mother spherical seed crystals by rolling and agglomerating powder, then continuously adding carbon powder and intermittently supplying a binder aqueous solution to obtain spherical activated carbon particles; and / or, The particle size of the spherical activated carbon particles is 1mm-5mm.

5. The preparation method according to claim 1, characterized in that, In S200, The high-temperature carbonization is controlled at a temperature of 650℃-750℃ and a time of 6h-12h; and / or, The high-temperature carbonization is carried out under inert gas protection; and / or, The activation treatment is controlled at a temperature of 900℃-1000℃ and a time of 1h-6h; and / or, The activation process is carried out in an activation atmosphere containing water vapor.

6. The preparation method according to claim 1, characterized in that, In S300, The platinum precursor is selected from at least one of chloroplatinic acid, platinum acetate, and platinum nitrate; and / or Based on the mass of the activated carbon support, the platinum loading is 0.1 wt%-5 wt%; and / or, When the platinum precursor is prepared into a liquid phase system, the molar concentration of platinum in the platinum-containing liquid phase system is 0.1 mol / L-2 mol / L; and / or, The auxiliary metal precursor is selected from at least one of indium nitrate, cadmium nitrate, and zinc nitrate; and / or, In terms of elemental molars, the molar amount of auxiliary metals is 10%-100% of the molar amount of platinum.

7. The preparation method according to claim 1, characterized in that, In S300, The calcination treatment is controlled at a temperature of 200℃-400℃ and a time of 1h-5h; and / or, The calcination process is carried out under inert gas protection.

8. The preparation method according to any one of claims 1-7, characterized in that, In step S100, the drying process is controlled at a temperature of 90℃-120℃ and a time of 12h-24h; and / or, In S300, the drying process is controlled at a temperature of 90℃-120℃ and a time of 12h-24h.

9. An application of a platinum-based catalyst for continuous hydrogenation to aminophenol, characterized in that, The platinum-based catalyst prepared by the method according to any one of claims 1-8 is applied to the continuous hydrogenation of nitrophenol to aminophenol in a fixed bed, specifically including the following steps: The platinum-based catalyst was packed into a fixed-bed reactor, and hydrogen was introduced into the fixed-bed reactor to pretreat the platinum-based catalyst with hydrogen. Then, nitrophenol feedstock liquid and hydrogen were continuously introduced into the fixed-bed reactor to carry out catalytic hydrogenation under hydrogenation reaction conditions. Finally, the reaction effluent was solvent-separated to obtain the aminophenol product.

10. The application of the platinum-based catalyst for continuous hydrogenation to aminophenol as described in claim 9, characterized in that, The hydrogen pretreatment is controlled at a temperature of 100℃-300℃, a time of 1h-6h, and a pressure of 0.1MPa-2MPa; and / or, The nitrophenol feedstock solution is obtained by mixing a feedstock and a solvent. The feedstock is selected from at least one of o-nitrophenol, m-nitrophenol, and p-nitrophenol, and the solvent is selected from at least one of ultrapure water, methanol, and ethanol; and / or The mass fraction of nitrophenol in the nitrophenol feedstock solution is 1%-30%; and / or The catalytic hydrogenation reaction is controlled at a temperature of 80℃-150℃, a pressure of 0.1MPa-3MPa, and a feed mass hourly space velocity of 0.1g / g. cat h-1.2g / g cat The molar ratio of hydrogen to nitrophenol raw material is 5-100.