Preparation method and application of nitrogen and phosphorus doped carbon-coated metal structure catalyst

Abstract

The application discloses a preparation method and application of a nitrogen and phosphorus doped carbon coated metal structure catalyst, and comprises the following steps: according to the mass ratio of microorganisms, biomass and water, 0.1-10 g:10-50 g:10-50 g of corresponding substances are weighed and mixed and stirred, and a metal impregnation solution (for example, [PdCl4] 2‑ , [NiCl4] 2‑ , [CoCl4] 2‑ , [RuCl4] 2‑ , etc.) is added, and then a nitrogen and phosphorus doped carbon coated metal palladium catalyst (the total loading amount of N and P of the catalyst is 1.0-6.0%, and the loading amount of the metal is 0.5-8%) is obtained through hydrothermal carbonization, pyrolysis or microwave, etc. The application adopts the biomass and microorganism interaction to further form a nitrogen and phosphorus doped carbon coating layer, and the nitrogen and phosphorus doped carbon coating layer has a stronger interaction with palladium or other metals, and shows the characteristics of high activity, selectivity and acid resistance in a chloronitrobenzene hydrogenation reaction.

Description

Technical Field

[0001] This invention belongs to the field of metal structure catalyst preparation, specifically relating to a method for preparing and applying a nitrogen-phosphorus-doped carbon-coated metal structure catalyst. Background Technology

[0002] Halogenated anilines are basic raw materials and important intermediates in the chemical industry, including pharmaceuticals, pesticides, dyes, and daily necessities.

[0003] Currently, various methods for preparing aromatic anilines have been developed, such as catalytic transfer hydrogenation, direct catalytic hydrogenation, and photoelectrocatalytic hydrogenation. Among these, the heterogeneous catalytic hydrogenation method, using hydrogen as the hydrogen source, produces water as the reduction product. It operates under mild conditions, generates minimal waste, and is considered the most sustainable and green process, exhibiting strong competitiveness among various synthetic methods. This method uses aromatic nitro compounds as raw materials, first generating the intermediate hydroxylamine under the action of a hydrogenation catalyst, followed by further hydrogenation to produce the final product. However, due to the high hydrogenation activity of the catalyst, deep hydrogenation and dehalogenation of the carbon-halogen bonds can occur, generating byproducts such as aniline. This reduces the selectivity of haloanilines, and the generated HCl easily forms an acidic environment, leading to the loss of the metal-type hydrogenation catalyst, resulting in reduced activity and poor cycle stability.

[0004] To address the aforementioned issues, Chinese Patent 201711340016.7 discloses a method for preparing a Pt / TiO2 / SBA-15 catalyst, which exhibits good platinum dispersion and synergistic catalysis with the support, achieving reactant conversion and p-chloroaniline selectivity as high as 99%. However, the catalyst's cycle stability is not mentioned. Chinese Patent 202111454144.0 proposes a method for preparing p-chloroaniline via the hydrogenation of p-chloronitrobenzene using an activated carbon-pentametallic catalyst from the perspective of active metals. The conversion rate of p-chloronitrobenzene hydrogenation is 82.43%–99.98%, and the selectivity for p-chloroaniline is 79.42%–96.53%. However, the recovery of the pentametallic alloy is challenging.

[0005] Chinese Patent 201810842345.X discloses a method for catalyzing the preparation of p-chloroaniline from p-chloronitrobenzene using carbon-coated nickel nanocomposite material as a catalyst and hydrogen as a hydrogen source; Chinese Patent 202211000483.6 uses platinum nanoparticles encapsulated by SOD-type molecular sieves as a catalyst, which greatly reduces the diffusion of p-chloronitrobenzene in the catalyst by utilizing the hydrogen overflow effect combined with the encapsulation effect of the SOD cage, thereby weakening the hydrogenation capacity by inhibiting the direct contact between p-chloronitrobenzene and platinum.

[0006] Chinese patent 202111679212.3 discloses a method for preparing a supported carbon-encapsulated bimetallic catalyst by combining sugars as a carbon source with a commercial catalyst. The patent proposes that using heteroatom-doped carbon as the encapsulation layer would better facilitate the interaction between the encapsulation layer and hydrogen gas; however, carbon was not doped in this patent. This method of encapsulating the metal with a support not only improves the selectivity of the target product but also reduces metal loss in acidic environments, thus ensuring the catalyst's activity.

[0007] In view of the above factors, and in response to the problems of severe loss of catalyst metal components and the use of additives, this invention provides a method for preparing an acid-resistant nitrogen-phosphorus doped carbon-coated metal structure catalyst and its application in the hydrogenation of p-chloronitrobenzene to p-aminoaniline. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing and applying a nitrogen-phosphorus doped carbon-coated metal structure catalyst, in order to solve the problems mentioned in the background art.

[0009] This invention provides a method for preparing a nitrogen-phosphorus-doped carbon-coated metal structure catalyst. The catalyst prepared by this method has a total N and P loading of 1.0-6.0% and a M loading of 0.5-8%, and forms a coated structure.

[0010] The second objective of this invention is to provide a catalyst that exhibits high selectivity for halogenated anilines and good catalyst stability in the hydrogenation of halogenated nitrobenzene to halogenated anilines.

[0011] The objective of this invention is achieved through the following technical solution: a method for preparing a nitrogen-phosphorus doped carbon-coated metal structure catalyst, comprising the following steps;

[0012] Step 1), Preparation of metal impregnation solution:

[0013] Weigh the palladium precursor into a container, add concentrated hydrochloric acid, dilute with water to prepare a metal impregnation solution with a concentration of 0.1-0.8 g / mL. The amount of concentrated hydrochloric acid added is 20-30 mL / 100 mL. The metal solution is then ready for use.

[0014] Step 2), Preparation of nitrogen and phosphorus doped carbon-coated metal catalysts:

[0015] Biomass, water, and microorganisms are added and left to stand for a certain period of time. They are then thoroughly mixed with the metal solution from step 1 and carbonized under different treatment methods and conditions to obtain nitrogen and phosphorus-doped carbon-coated metal catalysts.

[0016] The total loading of N and P in the catalyst is 1.0–6.0%, and the loading of metal is 0.5–8%.

[0017] Furthermore, the palladium precursor in step 1 is any one of PdCl2, PdBr2, Pd(CH3COO)2, or Pd(NO3)2.

[0018] Furthermore, the biomass mentioned in step 2 is any one or two of starch, flour, lotus root starch, or rice flour.

[0019] Furthermore, the microorganisms mentioned in step 2 are any one or more of Bacillus subtilis, probiotics, or yeast.

[0020] Furthermore, the mass ratio of microorganisms:biomass:water in step 2 is 0.1-10g:10-50g:10-50g.

[0021] Furthermore, the processing method described in step 2 includes any one of hydrothermal, pyrolysis, or microwave methods;

[0022] The microwave or pyrolysis atmosphere mentioned in step 2 is any one of air, nitrogen or argon.

[0023] A method for preparing nitrogen-phosphorus doped carbon-coated metal structure catalysts includes the following steps;

[0024] Weigh out the appropriate amount of material according to the mass ratio of microorganisms:biomass:water of 0.1-10g:10-50g:10-50g, mix and stir, let stand for a certain period of time, and then add 1-10mL of metal impregnation solution with a concentration of 0.1-0.8g / mL (e.g., [PdCl4)). 2- [NiCl4] 2- [CoCl4] 2- [RuCl4] 2- The catalyst is stirred evenly and then carbonized by hydrothermal, pyrolysis or microwave methods to obtain a nitrogen-phosphorus doped carbon-coated metal catalyst, wherein the total loading of N and P in the catalyst is 1.0 to 6.0% and the loading of metal is 0.5 to 8%.

[0025] The catalyst prepared by the above method is washed with 1-3 mol / L hydrochloric acid and then used to synthesize the corresponding haloaniline in halonitrobenzene compounds to investigate its acid resistance. The application of a method for preparing a nitrogen-phosphorus doped carbon-coated metal structure catalyst includes the following steps:

[0026] Weigh p-chloronitrobenzene into a high-pressure reactor, add the nitrogen-phosphorus-doped carbon-coated metal structure catalyst and solvent prepared above according to a certain feeding ratio, and purge with about 0.5 MPa H2 to replace the air each time, for a total of 5 times. Finally, p-chloroaniline is purged with hydrogen gas at a pressure of 0.3-1.2 MPa. React at 80-130℃ and 600-1500 r / min for 100-150 min to generate p-chloroaniline.

[0027] Further, the solvent is any one or more of water, ethanol, or hexane; wherein, the feed ratio of catalyst: p-chloronitrobenzene: solvent is 0.01-0.05g: 4-10mol: 20-50mL.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The catalyst preparation process of this invention is simple, using biomass as the carbon source, which is renewable and low-cost. Microbial pretreatment of the biomass effectively introduces heteroatom doping and creates pores in the carbon material, and the metal does not require reduction with a reducing agent. Furthermore, the catalyst has a heteroatom-doped carbon-encapsulated metal structure, thus exhibiting good acid resistance and stability. In the process of hydrogenating halonitrobenzenes to prepare haloanilines, it demonstrates high activity and high selectivity for haloanilines under relatively mild reaction conditions. Most importantly, this preparation method eliminates the need for surfactants or other additives, improving production conditions, reducing production costs, and enhancing catalyst performance.

[0030] The catalyst prepared by this invention has a total N and P loading of 1.0-6.0% and a M loading of 0.5-8%, and forms a coating structure. The coating layer is formed by the interaction of biomass and microorganisms, which has a stronger interaction with palladium or other metals. It is low in cost, green and environmentally friendly, and exhibits high activity, selectivity and acid resistance in the hydrogenation reaction of p-chloronitrobenzene. Attached Figure Description

[0031] Figure 1 This is a TEM image of the catalyst in Example 1 of the present invention;

[0032] Figure 2 This is the catalyst element mapping diagram for Example 1 of the present invention;

[0033] Figure 3 The Raman spectra of the catalysts prepared in Example 1 and Comparative Example 1 of this invention are shown. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] like Figure 1-3 As shown, the present invention will be further described below with reference to embodiments.

[0036] A method for preparing a nitrogen-phosphorus doped carbon-coated metal structure catalyst includes the following steps;

[0037] Step 1), Preparation of metal impregnation solution:

[0038] Weigh the palladium precursor into a container, add concentrated hydrochloric acid, dilute with water to prepare a metal impregnation solution with a concentration of 0.1-0.8 g / mL. The amount of concentrated hydrochloric acid added is 20-30 mL / 100 mL. The metal solution is then ready for use.

[0039] Step 2), Preparation of nitrogen and phosphorus doped carbon-coated metal catalysts:

[0040] Biomass, water, and microorganisms are added and left to stand for a certain period of time. They are then thoroughly mixed with the metal solution from step 1 and carbonized under different treatment methods and conditions to obtain nitrogen and phosphorus-doped carbon-coated metal catalysts.

[0041] The catalyst prepared by this method has a total N and P loading of 1.0 to 6.0% and a M loading of 0.5 to 8%, and forms a coated structure. Specific Implementation Example 1:

[0043] Weigh 0.15g of dry yeast, add 16g of deionized water, stir well at room temperature, then add 21g of flour and stir well again. Let stand for 30 minutes, then add 2mL of 0.5mg / L palladium chloroacetic acid solution (1% palladium loading) and stir for 30 minutes. Heat to 850℃ in a nitrogen atmosphere at a heating rate of 5℃ / min and maintain for 10 hours to obtain a nitrogen-phosphorus-doped carbon-coated palladium catalyst.

[0044] The preparation methods of specific embodiments 2-12 are the same as those of specific embodiment 1, except that the parameters are different, as shown in Table 1.

[0045] Table 1 shows the different proportions, metal loading, stirring time, carbonization methods, and condition parameters;

[0046]

[0047]

[0048]

[0049]

[0050] Note: Metal ions in the impregnation solution are in the form of [PdCl4]. 2- [NiCl4] 2- [CoCl4] 2- [RuCl4] 2- .

[0051] Comparative Example 1:

[0052] Weigh 0.1g of dry yeast, add 10g of deionized water, stir well at room temperature, then add 10g of flour and stir well again. Let stand for 0.5h, then heat to 800℃ in a nitrogen atmosphere at a heating rate of 5℃ / min to obtain carbon material. Further, take 1g of this carbon material, add a certain amount of deionized water, incubate in an 80℃ water bath, then add chloropalladium acid solution to adjust the pH to 12, and stir for 5h. Filter and wash until neutral to obtain a 1% palladium-supported nitrogen-phosphorus-doped carbon catalyst.

[0053] Comparative Example 2:

[0054] The difference from Comparative Example 1 is that the catalyst was added to 1 mol / L hydrochloric acid and stirred for 2 h, then filtered, washed, and dried under vacuum at 80 °C for 10 h.

[0055] Comparative Example 1:

[0056] Weigh 1g of commercial activated carbon, add a certain amount of deionized water, incubate in an 80℃ water bath, then add chloropalladium acid solution to adjust the pH to 12, and stir for 5 hours. Filter and wash until neutral to obtain a 1% palladium-supported carbon catalyst. Specific Implementation Example 13:

[0058] The catalyst from Example 1 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and water were mixed in a ratio of 0.01 g: 4 mol: 20 mL. Air was replaced by purging with approximately 0.5 MPa H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 0.8 MPa was introduced, and the reaction was carried out at 100 °C and 1000 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 110 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 99.2%. Specific Implementation Example 14:

[0060] The catalyst from Example 2 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and ethanol were mixed in a ratio of 0.02 g: 6 mol: 25 mL. Air was replaced by purging with approximately 0.5 MPa of H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.0 MPa was introduced, and the reaction was carried out at 110 °C and 1200 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 110 min, the conversion rate was 96.5%, and the selectivity for p-chloroaniline was 98.1%. Specific Implementation Example 15:

[0062] The catalyst from Example 3 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and hexane were mixed in a ratio of 0.01 g: 4 mol: 20 mL. Air was replaced with approximately 0.5 MPa H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.1 MPa was introduced, and the reaction was carried out at 100 °C and 1200 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 110 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 98.0%. This shows that acid washing has no effect on the activity and selectivity of the coated catalyst. Specific Implementation Example 16:

[0064] The catalyst from Example 4 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and water were reacted at a ratio of 0.02 g: 8 mol: 20 mL. Air was replaced by purging with approximately 0.5 MPa of H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.2 MPa was introduced. The reaction was carried out at 90 °C and 1200 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 120 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 99.1%. Specific Implementation Example 17:

[0066] The catalyst from Example 5 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and ethanol were mixed in a ratio of 0.01 g: 6 mol: 25 mL. Air was replaced with approximately 0.5 MPa H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.0 MPa was introduced, and the reaction was carried out at 110 °C and 1200 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 115 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 96.1%. Specific Implementation Example 18:

[0068] The catalyst from Example 6 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and hexane were reacted at a ratio of 0.02 g: 4 mol: 25 mL. Air was replaced by purging with approximately 0.5 MPa H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.0 MPa was introduced, and the reaction was carried out at 110 °C and 1500 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 115 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 95.4%. Specific Implementation Example 19:

[0070] The catalyst from Example 7 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and water were mixed in a ratio of 0.03 g: 6 mol: 25 mL. Air was replaced by purging with approximately 0.5 MPa of H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.0 MPa was introduced, and the reaction was carried out at 120 °C and 1500 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 135 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 95.9%. Specific Implementation Example 20:

[0072] The catalyst from Example 8 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and water were mixed in a ratio of 0.03 g: 4 mol: 20 mL. Air was replaced by purging with approximately 0.5 MPa of H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.0 MPa was introduced, and the reaction was carried out at 110 °C and 1200 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 115 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 96.5%. Specific Implementation Example 21:

[0074] The catalyst from Example 9 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and ethanol were mixed in a ratio of 0.02 g: 8 mol: 50 mL. Air was replaced with approximately 0.5 MPa H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.2 MPa was introduced, and the reaction was carried out at 100 °C and 1000 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 150 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 97.5%. Specific Implementation Example 22:

[0076] The catalyst from Example 10 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and ethanol were mixed in a ratio of 0.01 g: 6 mol: 25 mL. Air was replaced with approximately 0.5 MPa H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.1 MPa was introduced, and the reaction was carried out at 110 °C and 1200 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 115 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 99.0%. Specific Implementation Example 23:

[0078] The catalyst from Example 11 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and hexane were mixed in a ratio of 0.03 g: 8 mol: 50 mL. Air was replaced with approximately 0.5 MPa H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.1 MPa was introduced, and the reaction was carried out at 110 °C and 1500 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 135 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 95.5%. Specific Implementation Example 24:

[0080] The catalyst from Example 12 was placed in a 50 mL autoclave. The catalyst, p-chloronitrobenzene, and water were mixed in a ratio of 0.02 g: 10 mol: 35 mL. Air was replaced by purging with approximately 0.5 MPa of H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.0 MPa was introduced, and the reaction was carried out at 90 °C and 1300 rpm. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 135 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 97.0%. Specific Implementation Example 25:

[0082] The catalyst of Comparative Example 1 was placed in a 50 mL autoclave, and the ratio of catalyst, p-chloronitrobenzene, and water was 0.01 g: 4 mol: 20 mL. Air was replaced by purging with approximately 0.5 MPa H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.0 MPa was introduced, and the reaction was carried out at 100 °C and 1000 r / min. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 100 min, the conversion rate was 100%, and the selectivity for p-chloroaniline was 89.9%. This shows that nitrogen and phosphorus doped carbon-coated metal structures exhibit higher selectivity. Specific Implementation Example 26:

[0084] The catalyst of Comparative Example 2 was placed in a 50 mL autoclave, and the ratio of catalyst, p-chloronitrobenzene, and water was 0.01 g: 4 mol: 20 mL. Air was replaced by purging with approximately 0.5 MPa H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.0 MPa was introduced, and the reaction was carried out at 100 °C and 1300 r / min. The hydrogenation product was analyzed using an Agilent 7890A gas chromatograph. The reaction time was 100 min, the conversion rate was 55%, and the selectivity for p-chloroaniline was 96.9%. It is evident that the activity of the supported catalyst decreased significantly after acid washing. Specific Implementation Example 27:

[0086] The catalyst of Comparative Example 1 was placed in a 50 mL autoclave, and the ratio of catalyst, p-chloronitrobenzene, and ethanol was 0.02 g: 6 mol: 25 mL. Air was replaced by purging with approximately 0.5 MPa of H2 each time, for a total of 5 times. Finally, hydrogen gas at a pressure of 1.2 MPa was introduced, and the reaction was carried out at 100 °C and 1200 r / min. The hydrogenation products were analyzed using an Agilent 7890A gas chromatograph. The reaction time was 115 min, the conversion rate was 99%, and the selectivity for p-chloroaniline was 82.9%. It is evident that when pure carbon is used as the support, the catalyst activity and selectivity are lower than those of the catalyst supported by nitrogen and phosphorus doped carbon. Specific Implementation Example 28:

[0088] After recovering, washing, and recycling the catalyst from Example 13 10 times, the conversion rate of chloronitrobenzene was 100% and the selectivity for chloroaniline was 99.0%.

[0089] It is worth noting that the preparation method mentioned in this invention not only includes palladium, nickel, cobalt and ruthenium, but can also be extended to other precious and base metals. Therefore, any technology and means that modify this method will fall within the protection scope of this patent.

[0090] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0091] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a nitrogen-phosphorus-doped carbon-coated metal structure catalyst, characterized in that: Includes the following steps; Step 1), Preparation of metal impregnation solution: Weigh the palladium precursor into a container, add concentrated hydrochloric acid, dilute with water to prepare a metal impregnation solution with a concentration of 0.1–0.8 g / mL. The amount of concentrated hydrochloric acid added is 20–30 mL / 100 mL. The metal solution is then ready for use. Step 2), Preparation of nitrogen and phosphorus-doped carbon-coated metal catalysts: According to microorganisms: The biomass:water mass ratio is 0.1-10 g:10-50 g:10-50 g. Weigh the corresponding substances, mix and stir, let stand for a certain time, then add 1-10 mL of metal impregnation solution with a concentration of 0.1-0.8 g / mL, stir evenly, and then carbonize by hydrothermal, pyrolysis or microwave to obtain nitrogen and phosphorus doped carbon-coated palladium catalyst, wherein the total loading of N and P in the catalyst is 1.0-6.0%; and the loading of metal is 0.5-8%. The biomass mentioned in step 2 is any one or two of starch, flour, lotus root starch, or rice flour; The microorganism mentioned in step 2 is yeast.

2. The preparation method of the nitrogen-phosphorus doped carbon-coated metal structure catalyst as described in claim 1, characterized in that: The palladium precursor in step 1 is any one of PdCl2, PdBr2, Pd(CH3COO)2 or Pd(NO3)2.

3. The preparation method of the nitrogen-phosphorus doped carbon-coated metal structure catalyst as described in claim 2, characterized in that: The microwave or pyrolysis atmosphere mentioned in step 2 is any one of air, nitrogen or argon.

4. The application of a catalyst prepared by the method for preparing a nitrogen-phosphorus doped carbon-coated metal structure catalyst as described in any one of claims 1-3, characterized in that: The catalyst prepared by the method according to any one of claims 1-3 is washed with 1-3 mol / L hydrochloric acid and then used to synthesize the corresponding haloaniline from halonitrobenzene compounds to examine its acid resistance.

5. The application of the catalyst prepared by the method for preparing nitrogen-phosphorus-doped carbon-coated metal structure catalyst as described in claim 4, characterized in that: Includes the following steps: Weigh p-chloronitrobenzene into a high-pressure reactor, add the nitrogen-phosphorus-doped carbon-coated metal structure catalyst and solvent according to a certain feeding ratio, and purge the air with 0.5 MPa H2 each time for a total of 5 times. Finally, p-chloroaniline is generated by purging with hydrogen gas at a pressure of 0.3-1.2 MPa. React at 80-130 ℃ and 600-1500 r / min for 100-150 min.

6. The application of the catalyst prepared by the method for preparing nitrogen-phosphorus-doped carbon-coated metal structure catalyst as described in claim 5, characterized in that: The solvent is any one or more of water, ethanol, and hexane; wherein the catalyst is p-chloronitrobenzene: the ratio of the solvent to the catalyst is 0.01-0.05 g: 4-10 mol: 20-50 mL.

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