Catalyst for fixed bed anti-dehalogenation nitro hydrogenation, and preparation process and application thereof

Abstract

The invention provides a catalyst for fixed bed anti-dehalogenation nitro hydrogenation as well as a preparation process and application thereof. The preparation process comprises the following steps: (1) pretreatment: preparing an alkaline precursor solution; carrier pretreatment; preparing a metal precursor solution; (2) preparing a catalyst precursor by spraying; and (3) performing microwave-assisted crystallization treatment to prepare the catalyst. According to the application, the prepared catalyst is used for a fixed bed anti-dehalogenation nitro hydrogenation reaction, and then it is verified that the catalyst has the stable halogen bonding capacity and can efficiently prevent dehalogenation. The catalyst disclosed by the invention can stably run for 1000 hours in a fixed bed, and the activity of the catalyst is almost not attenuated; the preparation process of the catalyst is friendly to equipment and conforms to the green chemical principle; the catalyst is used for hydrogenation reaction, and the obtained product has high conversion rate and selectivity.

Description

Technical Field

[0001] This invention relates to the field of catalytic hydrogenation technology, specifically to a catalyst for fixed-bed dehalogenation nitro hydrogenation, its preparation process, and its application. Background Technology

[0002] Halogenated nitro compounds are important intermediates in the synthesis of pharmaceuticals, pesticides, and fine chemicals. During the hydrogenation process to prepare haloanilines, halogens (Cl, Br) are easily removed at acidic sites or under strong reducing conditions, leading to decreased product purity and catalyst deactivation. Existing technologies, platinum-based, palladium-based, or nickel-based catalysts suffer from low halogen retention (typically <95%) and short catalyst lifetimes.

[0003] Some related technologies disclose solutions. For example, CN107626329B discloses a platinum / alumina catalyst, wherein the components of the platinum / alumina catalyst, by mass percentage, include: 0.05-1.0% platinum, 0.1-2.0% iron, 0.5-5.0% germanium dioxide, and 99.35-92.0% alumina, prepared by directly impregnating the support in a metal compound solution. CN112642425A discloses a dehalogenation prevention catalyst for the nitro reduction of halogenated aromatic nitro compounds. By adding an auxiliary component B (alkali metal or oxides such as Ba and Sr) to suppress the adsorption of halide ions at the acid sites of the catalyst, and simultaneously using alkanolamines or amide solvents during the loading process to regulate the acid sites, the dehalogenation rate is reduced to <0.1% due to the dual effect. However, the preparation cost using alkanolamines or amide solvents is high, resulting in poor economic efficiency.

[0004] Therefore, developing a high-efficiency, dehalogenation-resistant, long-life, and low-cost fixed-bed hydrogenation catalyst has significant industrial value. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a catalyst, its preparation process, and its application for preventing dehalogenation nitro hydrogenation in a fixed-bed reactor. The catalyst possesses the ability to stabilize halogen bonds, effectively preventing dehalogenation. It can operate stably in a fixed bed for up to 1000 hours with almost no activity decay. The catalyst preparation process is equipment-friendly and conforms to green chemistry principles. When used to prevent dehalogenation nitro hydrogenation, this catalyst yields products with high conversion rates and selectivity.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: On the one hand, a process for preparing a catalyst for fixed-bed dehalogenation nitro hydrogenation is provided, comprising the following steps: (1) Pretreatment: Preparation of alkaline precursor solution: Dissolve inorganic base in deionized water, add polyvinylpyrrolidone (PVP), and stir magnetically until completely dissolved to obtain an aqueous solution of inorganic base containing PVP. Carrier pretreatment: The carrier is calcined in a muffle furnace to remove impurities; Preparation of metal precursor solution: Take active metal precursor, auxiliary metal precursor and PVP and add them to ethanol-water mixed solvent, stir and mix until completely dissolved to obtain metal precursor solution containing PVP. (2) Spray treatment (2-1) First spray: The pretreated carrier is preheated in a fluidized bed, and an alkaline precursor solution is sprayed onto the surface of the carrier under a nitrogen protective atmosphere and dried to obtain a carrier containing an alkaline layer. (2-2) Transition treatment: The carrier containing the alkaline layer is treated with ethanol vapor; (2-3) Second spray: The metal precursor solution is sprayed onto the surface of the support containing the alkaline layer, and H2 / N2 mixed gas is introduced into the fluidized bed for reduction during the spraying process. After the reduction is completed, the solution is cooled to obtain the catalyst precursor. (3) Microwave-assisted crystallization treatment The catalyst precursor obtained by microwave treatment is then obtained as the catalyst.

[0007] In some embodiments, during the spraying process, a laser particle size analyzer is used to control the D50 of the spray droplets to be between 15-25 μm, preferably 22 μm.

[0008] In some embodiments, in the aqueous solution of the inorganic alkali containing PVP, the mass concentration of PVP is 0.1-0.5 wt%, and the concentration of the inorganic alkali is 5 wt%. By adding PVP to the inorganic alkali solution (e.g., K₂CO₃), sodium or potassium ions are prevented from being released into the solution. + Local aggregation is achieved by controlling ion distribution with a low concentration of PVP (0.3%). The inorganic alkali solution is prepared using a pure water system to maximize the solubility of the inorganic alkali (e.g., K₂CO₃), facilitating subsequent spray dispersion. Spraying the inorganic alkali onto the carrier surface reduces acidic sites and inhibits halogen removal during subsequent applications.

[0009] In some embodiments, the molecular weight of the PVP is 8000-40000, preferably PVPK30 or PVPK40.

[0010] In some embodiments, the inorganic base is potassium carbonate or sodium carbonate.

[0011] In some embodiments, the carrier is selected from at least one of alumina and silicon oxide; or at least one of spherical alumina and silicon oxide with a diameter of 1-5 mm or at least one of strip-shaped alumina and silicon oxide with a size of 1-10 mm.

[0012] In some embodiments, the calcination temperature is 300-500℃ and the calcination time is 4 hours; preferably, the calcination temperature is 300℃, 350℃, 400℃, 450℃, or 500℃.

[0013] In some embodiments, the PVP-containing metal precursor solution contains PVP at a mass concentration of 0.5-0.8 wt%, an active metal precursor at a concentration of 1-5 wt%, and a co-metal precursor at a concentration of 0.1-0.5 wt%. Adding PVP to the metal solution facilitates control of the metal particle size (4-6 nm). High PVP concentrations (0.5%) can regulate the nanoparticles attached to the support surface, which is beneficial for subsequent spray dispersion. By utilizing the active metal and co-metal spray to adhere to the support surface, a strong metal-support interaction is formed, which is beneficial for stabilizing halogen bonds during subsequent applications, resulting in a significantly improved halogen retention rate compared to catalysts prepared by conventional processes (such as catalysts prepared by impregnation).

[0014] In some embodiments, the active metal precursor is selected from chloroplatinic acid or platinum nitrate.

[0015] In some embodiments, the auxiliary metal precursor is selected from at least one of ferric chloride, nickel chloride, and cobalt chloride.

[0016] In some embodiments, the mass ratio of ethanol to water in the ethanol-water mixed solvent is 3:7. Using a 3:7 ethanol-water solvent system balances surface tension and metal solubility, which is beneficial for subsequent spraying.

[0017] In some embodiments, the pH of the PVP-containing metal precursor solution is adjusted to 4-5, preferably 4.5, with 0.1 mol / L nitric acid.

[0018] In some embodiments, in the first spray, the atomization pressure is 0.5-1.0 bar, the feed rate is 5-10 mL / min, the spraying time is 20-40 min, the spray drying temperature is 160-190℃, and the drying time is 25-40 min, preferably 30 min. In some embodiments, after the first spray, drying continues until the residual moisture content is <1%; the residual moisture content is controlled to avoid affecting the second spray; the spraying time is short and the moisture content is high; 25-30 min is optimal; a near-infrared moisture meter is used to provide real-time feedback on the drying progress. After the first spray, the resulting product needs to be thoroughly dried (moisture content <1%), and gentle drying is performed at 160-190℃ to avoid migration of alkaline components.

[0019] In some embodiments, the transition treatment involves treating the product with ethanol vapor at 80-100°C for 15-30 min, with an ethanol flow rate of 50 mL / min; preferably, the product is treated at 90°C for 20 min. This transition treatment with ethanol vapor enables rapid setting of the obtained product.

[0020] In some embodiments, the second spraying involves spraying a metal precursor solution onto the surface of the obtained product at an atomization pressure of 1.0-1.5 bar, a feed rate of 10-15 mL / min, and a spraying time of 15-30 min to obtain a catalyst precursor. Short spraying times result in insufficient dispersion and are time-consuming, which is not conducive to cost reduction; 20-25 min is optimal. The second spraying step prevents the metal from penetrating too deeply and achieves uniform nanoscale dispersion of the metal components on the support, resulting in a metal particle size of 4-6 nm for the prepared catalyst.

[0021] The spatial distribution of the catalyst is controlled by two-step spraying, constructing an ordered "alkaline layer-metal layer" structure, forming atomic-level interfacial bonding (e.g., K-Pd-O), reducing the chance of halogens contacting acidic sites, improving the conversion and selectivity of the reaction raw materials, and reducing the dehalogenation rate.

[0022] In some embodiments, the volume percentage of H2 in the H2 / N2 mixture is 5-10%.

[0023] In some embodiments, the reduction temperature is 190-210°C (preferably 200°C), and the residence time is 1-2 hours (preferably 2 hours). In some embodiments, the product after reduction treatment is cooled at a rate of 5°C / min. By synchronously reducing the product to a metallic state through simultaneous spraying, particle size growth can be controlled within a reasonable range.

[0024] In some embodiments, microwave-assisted crystallization is performed: the obtained catalyst precursor is treated at 2.45 GHz and 200-400 W (preferably 300 W) for 5-15 min, preferably 10 min, to obtain the catalyst. Microwave crystallization promotes the formation of strong interactions between the metal and the support, induces dipole polarization, forms electron-rich metal centers, and improves the catalytic activity against dehalogenation and nitro hydrogenation reactions.

[0025] In some embodiments, during the spraying process, a laser particle size analyzer is used to control the D50 of the spray droplets to be between 15-25 μm, preferably 22 μm.

[0026] In a second aspect, a catalyst for fixed-bed dehalogenation nitro hydrogenation is provided, which is prepared by the method described in the first aspect.

[0027] Thirdly, the application of a catalyst prepared by the method described in the first aspect in the dehalogenation nitro hydrogenation reaction is provided.

[0028] In some embodiments, the process of the application includes: packing the catalyst into a fixed-bed reactor, introducing hydrogen gas for pretreatment, introducing a nitro compound for hydrogenation reaction, and separating the product from the solvent to obtain the corresponding amino compound.

[0029] In some embodiments, the pretreatment temperature is 100-200°C, the pressure is 0.1-2 MPa, and the treatment time is 2-10 h.

[0030] In some embodiments, the nitro-containing compound includes one of chloronitrobenzene, 3,4-dichloronitrobenzene, 2,4-dichloronitrobenzene, 2,5-dichloronitrobenzene, 2,3-dichloronitrobenzene, 3,5-dichloronitrobenzene, and 2,6-dichloronitrobenzene.

[0031] In some embodiments, the solvent is one of methanol, ethanol, tetrahydrofuran, and isopropanol.

[0032] In some embodiments, the hydrogenation reaction is carried out at a temperature of 60-80°C, a pressure of 0.5-2 MPa, and a feed space velocity of 0.1-1.2 h⁻¹. -1 The hydrogen ratio is 3-50. Feed space velocity refers to the feed mass / (catalyst mass × hour). The hydrogen ratio refers to the molar ratio of hydrogen to feed.

[0033] Compared with the prior art, one of the above technical solutions has the following advantages or beneficial effects: In preparing the catalyst according to this invention, an alkaline layer is loaded on the surface of the support to reduce the acidic sites on the support, which is beneficial for inhibiting halogen removal in subsequent catalytic applications.

[0034] In preparing the catalyst, the present invention achieves stable halogen bonding during catalytic application by using active metals and auxiliary metals to interact with the support, thereby significantly improving the halogen retention rate.

[0035] In preparing the catalyst, the present invention achieves double coverage of the alkali layer and the metal layer by spraying the support twice. On the one hand, this reduces the acidic sites of the catalyst, and on the other hand, it helps to stabilize halogen bonds during the application of the catalyst, so that the dehalogenation rate in the nitro hydrogenation reaction is ≤0.05%.

[0036] In preparing the catalyst, this invention optimizes the catalyst preparation process conditions to achieve a highly efficient and green catalyst that prevents dehalogenation nitro hydrogenation. This significantly improves the production efficiency and product quality of nitro hydrogenation, reduces the generation of dechlorination byproducts, and is more friendly to production equipment.

[0037] The catalyst prepared by the method of this invention can be applied to fixed-bed dehalogenation nitro hydrogenation, achieving a feed conversion rate of greater than 99.99%, a selectivity of halogenated aniline greater than 99%, and a dehalogenation rate of ≤0.05%. Furthermore, the catalyst prepared by the method of this invention can operate continuously in a fixed bed for more than 1000 hours with almost no decrease in catalyst activity and stable selectivity, making it suitable for highly selective hydrogenation of chloronitrobenzene and polyhalogenated nitro compounds. Detailed Implementation

[0038] The following provides various embodiments or examples to enable those skilled in the art to implement the invention based on the description. These are merely examples and not intended to limit the invention. The endpoints and values ​​of the ranges disclosed herein are not limited to precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0040] Examples 1-5: Preparation of Catalysts (1) Pretreatment: Preparation of alkaline precursor solution: Weigh 5.0g of inorganic base and add water to a total mass of 100g, add 0.1-0.5g of PVPK30, stir magnetically for 2 hours until completely dissolved, to obtain a 5wt% inorganic base aqueous solution containing 0.1-0.5wt% PVPK30; Carrier pretreatment: The carrier is calcined in a muffle furnace at 300-500℃ for 4 hours to remove impurities; Preparation of metal precursor solution: Take 1g of active metal precursor, 0.2g of auxiliary metal precursor, and 0.5-0.8g of PVPK30 and add them to 98.3g of ethanol-water mixed solvent. The mass ratio of ethanol to water in the mixed solvent is 3:7. Stir for 2 hours until completely dissolved. Adjust the pH to 4.5 with 0.1mol / L nitric acid to obtain a metal precursor solution containing 0.5-0.8wt% PVPK30. (2) Preparation of catalyst precursor by spraying First spray: The pretreated carrier is preheated to 120°C in a fluidized bed. Under a nitrogen protective atmosphere, the alkaline precursor solution is sprayed onto the carrier surface. The atomization pressure is 0.5-1.0 bar, the feed rate is 5-10 mL / min, the spraying time is 20-40 min, the spray drying temperature is 160-190°C, and the drying time is 25-40 min, preferably 30 min, until the residual moisture content is <1%. A near-infrared moisture meter is used to provide real-time feedback on the drying progress. Transition treatment: Treat the product with ethanol vapor at 80-100℃ for 15-30 min, with an ethanol flow rate of 50 mL / min; Second spray: The metal precursor solution is sprayed onto the surface of the obtained product at an atomization pressure of 1.0-1.5 bar, a feed rate of 10-15 mL / min, and a spraying time of 15-30 min. During this spraying process, a H2 / N2 mixed gas (H2 volume percentage of 5-10%) is introduced into the fluidized bed. The product is reduced in situ at 190-210 °C for 1-2 h. After the reduction is completed, the product is cooled at a rate of ≤5 °C / min to obtain the catalyst precursor. (3) Preparation of catalyst Microwave-assisted crystallization treatment: The obtained reduced catalyst precursor is treated with microwave at 2.45 GHz and 200-400 W for 5-15 minutes to obtain the catalyst.

[0041] The component parameters for each embodiment are shown in Table 1 below: Table 1. Details of each embodiment

[0042] Comparative Example 1 The difference from Example 1 is that PVPK30 was not added during the preparation process; the remaining processes, components, and amounts were the same as in Example 1. The prepared catalyst a contained metal particles with a diameter of 7.5 nm, and the particle size distribution was uneven.

[0043] Comparative Example 2 The difference from Example 1 is that a one-step spray method is used to load alkaline and metallic substances, while the remaining processes, components, and amounts are the same as in Example 1. Specifically, the alkaline precursor solution and the metallic precursor solution are first mixed, and then the mixed solution is sprayed onto the pretreated carrier surface using the second spray method of Example 1.

[0044] The metal particles in the prepared catalyst b have a diameter of 8.8 nm.

[0045] Comparative Example 3 The difference from Example 1 is that an impregnation method is used to load alkaline and metallic substances, while the remaining processes, components, and amounts are the same as in Example 1. The specific impregnation process is as follows: The pretreated carrier was first immersed in an alkaline precursor solution for 30 minutes, dried, and then subjected to a transition treatment. The resulting product was then immersed in a metal precursor solution for 20 minutes.

[0046] The prepared catalyst c has a metal particle size of 10.7 nm and a non-uniform particle size distribution, with a CV > 30%.

[0047] Comparative Example 4 The difference from Example 1 is that the alkaline precursor solution spraying process was omitted, and the prepared catalyst lacked an alkaline layer. The rest of the preparation process, components, and amounts were consistent with Example 1. The prepared catalyst was catalyst d.

[0048] Comparative Example 5 The difference from Example 1 is that the auxiliary metal precursor is missing; the remaining components, preparation process, and amounts are the same as in Example 1. The prepared catalyst is catalyst e.

[0049] Comparative Example 6 The difference from Example 1 is that the active metal precursor is missing; the remaining components, preparation process, and amounts are the same as in Example 1. The prepared catalyst is catalyst f.

[0050] Application of catalysts in the examples 10g of catalyst A was packed into a 20mL fixed bed reactor with an inner diameter of 10mm and a catalyst packing height of 20mm. After purging the reactor with hydrogen, the mixture was preheated to 100-200℃, and the hydrogen pressure was increased to 0.1-2MPa. This temperature and pressure were maintained for 2-5 hours. 100g of the feedstock was then dissolved in 1000g of solvent to prepare a 10wt% solution; the mass hourly space velocity (WHSV) was 0.1-1.2h. -1 The hydrogen ratio was 3.5-50, the catalytic temperature was 55-80℃, and hydrogen gas was introduced at a pressure of 0.5-2 MPa. Samples were taken every 24 hours, and the initial conversion rate, initial selectivity of the target product, and initial dehalogenation rate of the hydrogenation liquid were obtained by gas chromatography analysis, as shown in Table 2. After the catalyst had been running stably for a certain period of time, the feed conversion rate, target product selectivity, and dehalogenation rate were as shown in Table 2.

[0051] Table 2 Application of the catalysts prepared in the examples

[0052] As shown in Table 3, the catalysts used in the examples can operate continuously for over 1000 hours in fixed-bed dehalogenation nitro hydrogenation, exhibiting high conversion rates and selectivity for chloronitrobenzene. Examples 6-8 show that different catalysts all demonstrated good catalytic performance. Examples 9-11 show that the catalyst prepared in Example 1 exhibited good catalytic performance for different reaction substrates.

[0053] Example 12 The difference from Example 6 is that the raw material is 2-chloronitrobenzene and the product is 2-chloroaniline.

[0054] Example 13 The difference from Example 6 is that the raw material is 2,5-dichloronitrobenzene and the product is 2,5-dichloroaniline.

[0055] Example 14 The difference from Example 6 is that the raw material is 2,6-dichloronitrobenzene and the product is 2,6-dichloroaniline.

[0056] The dehalogenation rate of Examples 12-14 is ≤0.05%, and the selectivity of the target amine is >99%.

[0057] Comparative Examples 7-12 The process of applying the catalyst is the same as in Example 6, except that a different catalyst is used. Details are shown in Table 3 below: Table 3. Catalyst application in comparative examples

[0058] As can be seen from Tables 1, 2, and 3, the addition of PVPK30 can effectively control ion distribution and the metal particle size of the catalyst, thereby improving catalyst performance. Multi-step spraying not only prevents the migration of alkaline components but also prevents excessive metal penetration, achieving particle size control of the metal catalyst within 4-6 nm and enhancing catalyst performance. The catalyst prepared in the examples, after 1000 hours of operation, effectively prevents dehalogenated nitro hydrogenation, and the resulting product exhibits good conversion and selectivity with a low dehalogenation rate.

[0059] As can be seen from Comparative Examples 7-9, different preparation processes result in different catalysts. The catalysts used in these examples exhibit low conversion and selectivity for halogenated nitrobenzene, but high dehalogenation rates. The catalytic application results from Examples 6-8 and Comparative Example 7 show that the catalyst prepared with added PVPK30 has superior performance, and its particle size is also more favorable. The catalytic application results from Examples 6-12 and Comparative Examples 8-9 show that the catalyst prepared via multi-step spraying yields products with good conversion and selectivity, but low dehalogenation rates.

[0060] As can be seen from Comparative Examples 10-12, the catalysts prepared with missing components exhibit poor conversion rates, selectivity, and dehalogenation rates when used for hydrogenation catalysis. Further, the catalysts prepared in the embodiments of this invention undergo a first spray treatment to prepare an alkaline layer. This alkaline pretreatment of the support reduces acidic sites and inhibits halogen removal during catalysis. A second spray treatment prepares a metal layer, enabling bimetallic-support interaction, stabilizing halogen bonds, and significantly improving halogen retention. When applied to a fixed bed, the catalyst operates stably for over 1000 hours with virtually no activity decay, a selectivity >99%, and a dehalogenation rate <0.1%.

[0061] Although the above embodiments have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the above descriptions are merely embodiments of the present invention and do not limit the scope of patent protection of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A process for preparing a catalyst for fixed-bed dehalogenation nitro hydrogenation prevention, characterized in that, Includes the following steps (1) Pretreatment: Preparation of alkaline precursor solution: Dissolve inorganic base in deionized water, add polyvinylpyrrolidone, and stir magnetically until completely dissolved to obtain an aqueous solution of inorganic base containing polyvinylpyrrolidone. Carrier pretreatment: The carrier is calcined in a muffle furnace to remove impurities; Preparation of metal precursor solution: Take active metal precursor, auxiliary metal precursor and polyvinylpyrrolidone and add them to ethanol-water mixed solvent, stir and mix until completely dissolved to obtain metal precursor solution containing polyvinylpyrrolidone. (2) Spray treatment (2-1) First spray: The pretreated carrier is preheated in a fluidized bed, and an alkaline precursor solution is sprayed onto the surface of the carrier under a nitrogen protective atmosphere and dried to obtain a carrier containing an alkaline layer. (2-2) Transition treatment: The carrier containing the alkaline layer is treated with ethanol vapor; (2-3) Second spray: The metal precursor solution is sprayed onto the surface of the support containing the alkaline layer, and H2 / N2 mixed gas is introduced into the fluidized bed for reduction during the spraying process. After the reduction is completed, the solution is cooled to obtain the catalyst precursor. (3) Microwave-assisted crystallization treatment The catalyst precursor obtained by microwave treatment is then obtained as the catalyst.

2. The preparation process according to claim 1, characterized in that, In an aqueous solution containing polyvinylpyrrolidone (PVP), the mass concentration of PPVP is 0.1-0.5 wt%, and the concentration of the inorganic alkali is 5 wt%. The inorganic base is potassium carbonate or sodium carbonate; The polyvinylpyrrolidone is K30 or K40; The carrier is selected from alumina or silicon dioxide; The roasting temperature is 300-500℃, and the roasting time is 4 hours.

3. The preparation process according to claim 1, characterized in that, In the polyvinylpyrrolidone-containing metal precursor solution, the mass concentration of polyvinylpyrrolidone is 0.5-0.8 wt%, the concentration of the active metal precursor is 1-5 wt%, and the concentration of the auxiliary metal precursor is 0.1-0.5 wt%. The active metal precursor is selected from chloroplatinic acid or platinum nitrate; The auxiliary metal precursor is selected from at least one of ferric chloride, nickel chloride, and cobalt chloride.

4. The preparation process according to claim 1, characterized in that, The mass ratio of ethanol to water in the ethanol-water mixed solvent is 3:7; the pH of the metal precursor solution containing polyvinylpyrrolidone is adjusted to 4-5 with 0.1 mol / L nitric acid.

5. The preparation process according to claim 1, characterized in that, In the first spray, the atomization pressure is 0.5-1.0 bar, the feed rate is 5-10 mL / min, the spraying time is 20-40 min, the spray drying temperature is 160-190℃, and the drying time is 25-40 min.

6. The preparation process according to claim 1, characterized in that, The transition treatment involves treating the carrier containing the alkaline layer with ethanol vapor at 80-100℃ for 15-30 minutes, with an ethanol flow rate of 50 mL / min.

7. The preparation process according to claim 1, characterized in that, The second spraying process involves spraying the metal precursor solution onto the surface of the resulting support containing an alkaline layer. The atomization pressure is 1.0-1.5 bar, the feed rate is 10-15 mL / min, and the spraying time is 15-30 min, yielding the catalyst precursor. In the H2 / N2 mixture, H2 accounts for 5-10% of the total volume. The reduction temperature is 190-210℃, and the residence time is 1-2 hours.

8. The preparation process according to claim 1, characterized in that, Microwave-assisted crystallization treatment: The obtained catalyst precursor was treated at 2.45 GHz and 200-400 W for 5-15 min.

9. A catalyst for fixed-bed dehalogenation nitro hydrogenation prevention, characterized in that, It is prepared by the preparation process described in any one of claims 1-8.

10. The application of a catalyst prepared by the process according to any one of claims 1-8 or the catalyst according to claim 9 in the dehalogenation nitro hydrogenation reaction.

Images