A preparation method and application of porous microspheres and a reduction method of nitro compounds

Abstract

The present invention discloses a method for preparing porous microspheres for supporting catalysts, which are obtained by hot pressing inorganic materials and resins and then sintering. The microspheres are inorganic nanoporous microspheres, which are strong and have many holes and can absorb a large amount of catalysts. The present invention also discloses that the porous microspheres supporting the catalyst of the present invention are used for catalytic hydrogenation reactions in fixed bed reactors, and are applied to nitro reduction reactions of nitro compounds, especially reduction of dinitro compounds and polynitro compounds. The obtained amino compounds have high purity and high conversion rate, and the catalyst has strong durability and can be recycled for multiple times and for a long time.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemistry, and in particular to a preparation method and application of porous microspheres and a reduction method of nitro compounds. Background Art

[0002] Common amino compounds such as 4,4-diaminodiphenyl ether (ODA) are important organic chemical products, mainly used to synthesize high-performance polyimide. Early industrial production usually used iron powder catalytic reduction, but the yield was low, the cost was high, and a large amount of iron mud and wastewater that were difficult to handle were produced, causing serious environmental pollution. Currently, catalytic hydrogenation reduction is mostly used in industrial production, but most of them still use reactor-type intermittent catalytic hydrogenation reduction. For example, patent 201110330139.9. The intermittent process operation is complicated and the production cost is high.

[0003] The fixed bed hydrogenation process is simpler in terms of process and equipment structure. The flow of the fluid can be regarded as an ideal displacement flow, so the chemical reaction rate is faster. When the same production capacity is achieved, the required catalyst dosage and reactor volume are smaller. However, the disadvantage is that fine-particle catalysts cannot be used, and the active inner surface of the catalyst cannot be fully utilized. To realize the fixed bed continuous process, the catalyst must have high activity, high selectivity, high activity stability, and appropriate mechanical strength. Among them, the activity and stability of the catalyst are the key to determining whether the fixed bed process can be successfully implemented and industrialized.

[0004] Chinese patent application 2019105721199 discloses a method for continuous synthesis of 2-amino-2-methyl-1-propanol, in which 2-nitro-2-methyl-1-propanol is catalytically reduced in a fixed bed reactor, discharged and rectified after the reaction, to obtain high-purity 2-amino-2-methyl-1-propanol. However, the catalytic effect of the iron / aluminum catalyst used in the patented technical solution is poor, and a catalyst with higher catalytic efficiency is required. Such as porous microsphere loading, but the high-strength and high-stability porous microsphere loaded catalyst obtained by the prior art is expensive, and it is necessary to develop a high-strength and high-stability porous microsphere loaded catalyst.

[0005] The fixed bed catalyst preparation method currently used in industry is complex and costly. Chinese patent application 201810080547.5 discloses a common preparation method for porous alumina microspheres, which comprises dissolving polyvinyl pyrrolidone in anhydrous ethanol to obtain a dispersed alcohol solution; adding ammonium aluminum carbonate and sodium chloride to the dispersed alcohol solution, stirring evenly to form a uniform suspension; placing the suspension in a vacuum distillation reactor for vacuum distillation reaction for about 200 minutes to obtain a viscous concentrated solution; adding the viscous concentrated solution to a mold and slowly heating it until the ethanol is completely removed to obtain an alumina spherical precursor; placing the alumina spherical precursor in a muffle furnace for sintering, and naturally cooling to obtain a porous alumina sphere; finally, placing the porous alumina sphere in deionized water for ultrasonic reaction for 3-4 hours, taking it out and drying it to obtain porous alumina microspheres. This method is a commonly used method for preparing alumina microspheres at this stage. The process steps are multi-step, the mold molding efficiency is low, and the solvent volatilization is large and not environmentally friendly. The prepared alumina microspheres are insufficient in strength and are difficult to be used in fixed bed reactors. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing porous microspheres. The porous microspheres obtained by the preparation method of the present invention have many holes and high strength, and can be used for catalytic purposes of fixed bed hydrogenation reduction. The present invention also discloses a method for preparing amino compounds using the porous microsphere fixed bed of the present invention, which has high reaction conversion rate and high product purity.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for preparing porous microspheres, comprising the following steps: (1) mixing 20-60 parts of resin, 40-80 parts of inorganic material and 2-10 parts of auxiliary agent by weight; (2) grinding after mixing evenly, and hot pressing to form microspheres at a temperature higher than the melting temperature of the resin after grinding, or adding a curing agent to cure the microspheres in a mold; (3) sintering at a temperature higher than the decomposition temperature of the resin to obtain porous microspheres; the weight ratio of the resin to the inorganic material is (1:3) to (1:1); the resin is selected from one or more of polystyrene, polyvinyl chloride, polyethylene, acrylic resin, polyurethane, epoxy resin, isocyanate, etc.; the inorganic material is selected from one or more powders of silicon carbide, silicon, silicon dioxide, titanium dioxide, aluminum nitride, aluminum oxide, silicon nitride, calcium fluoride, magnesium oxide, zinc oxide, zirconium oxide, etc.; the auxiliary agent is selected from one or more of polyvinyl pyrrolidone, polyethylene glycol, and sodium dodecylbenzene sulfonate.

[0009] Preferably, step (2) is performed by hot pressing the microspheres at a temperature higher than the melting temperature of the resin after grinding. The porous microspheres obtained by using the preferred technology have higher strength and higher specific surface area.

[0010] Alternatively, curing may be performed by adding a curing agent in the mold, wherein the curing agent may be an aliphatic amine curing agent.

[0011] The resin, inorganic material and surfactant are mixed evenly in solution, and the polymer / inorganic composite microspheres are formed by hot molding of the resin and inorganic material. The purpose is that the inorganic material can form a discontinuous two-phase separation structure with the resin, and finally the continuous porous structure of the inorganic material is formed after the resin is removed by sintering. The ratio of the resin material to the inorganic material is 1:3~1:1. The preparation process can regulate the pore size and adsorption performance of the inorganic material, so that the specific surface area is increased and a better adsorption catalyst effect is obtained.

[0012] The porous microspheres obtained by the above preparation method are used to load catalysts, specifically, they can be used to load one or more of Pd (palladium) catalysts, Ni (nickel) catalysts, Ag (silver) catalysts, Rh (rhodium) catalysts, Ru (ruthenium) catalysts, and Pt (platinum) catalysts.

[0013] Its continuous pore structure gives it excellent adsorption function, so it has the characteristic of being able to adsorb metal catalyst substances. The porous microspheres are used to load catalysts, wherein the catalyst adsorption process can be a combination of one or more of precipitation method, impregnation method, and hydrothermal synthesis method, and the active components contained are selected from one or more of nitrate metal salts, acetate metal salts, and ammonium metal salts, and then the porous microspheres are reduced to obtain active metal nanoparticle catalysts.

[0014] Specifically, for loading Pd catalyst, the porous microspheres prepared as above are immersed in a palladium chloride solution with a mass concentration of 8-15% for 1-3 hours, taken out and dried, and then reduced with NaBH4 to obtain a loaded Pd catalyst.

[0015] Another type of the porous microspheres is used to load Ni (nickel) catalysts. The porous microspheres prepared above are immersed in a 0.15-0.25 mol / L nickel nitrate solution for 2-5 hours, taken out and dried, and then reduced with a formaldehyde aqueous solution to obtain a loaded Ni catalyst after drying.

[0016] A method for reducing the nitro group of a nitro-containing compound using the above-mentioned supported catalyst comprises the following steps: adding the above-mentioned supported Pd catalyst, the nitro-containing compound and the reaction solvent into a fixed bed reactor, carrying out a reduction reaction at 40-100° C. and 1.5-5 MPa hydrogen pressure, with a raw material liquid space velocity of 0.02-0.3 L / h; exhausting hydrogen after the reaction is completed; filtering to obtain the amino-containing compound and the reaction solvent; and then performing a distillation process to obtain the amino-containing compound.

[0017] Specifically, the reaction solvent is selected from methanol, ethanol, dimethylformamide, dimethylacetamide, tetrahydrofuran, and the weight ratio of the reaction solvent to the nitro-containing compound is 1:1 to 10:1.

[0018] When the loaded Ni catalyst is used instead of the loaded Pd catalyst, the reaction solvent is DMF, the reaction temperature is 110-160°C, the hydrogen pressure is 2.5-5MPa, and the raw material liquid space velocity is 0.02-0.3L / h.

[0019] The dinitro compound is selected from at least one of dinitrotoluene, dinitrochlorobenzene, 4,4-dinitrodiphenyl ether, dinitrobenzene and bisphenol A dinitrodiphenyl ether; the mononitro compound is selected from at least one of nitrobenzene and p-nitrophenol; and the polynitro compound is selected from at least one of trinitrotoluene and trinitrophenol.

[0020] The present invention has the following beneficial effects

[0021] The present invention discloses a method for preparing porous microspheres, which are obtained by hot pressing and sintering resin and inorganic materials. Compared with the porous microspheres obtained in the prior art, the porous microspheres of the present invention not only have more holes on the surface, but also have higher strength, and can meet the application of fixed bed catalysts. The present invention also discloses a method for fixed bed catalytic reduction of nitro compounds, which uses the porous microspheres loaded with catalysts of the present invention, has high reaction conversion rate, high product purity, and can be repeatedly used for a long time (300 hours).

[0022] The porous microspheres of the present invention can be adjusted in pore size and can be used to prepare different types of catalysts. The carrier microspheres have many advantages such as high physical and chemical stability, large specific surface area, large adsorption capacity, good selectivity, low cost, etc., and they have very outstanding advantages in the preparation of supported catalysts. DETAILED DESCRIPTION

[0023] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0024] The raw materials used in the present invention are derived from commercially available products:

[0025] 4,4-Dinitrodiphenyl ether: purity 99.5%;

[0026] m-Dinitrobenzene: purity 99.5%;

[0027] Bisphenol A dinitroether: purity 99.5%

[0028] Polyethylene glycol: average molecular weight 10000;

[0029] Polyethylene: average molecular weight 150000;

[0030] Epoxy resin: average molecular weight 400;

[0031] Polyvinylpyrrolidone: average molecular weight 50000;

[0032] Silica powder: 50 mesh;

[0033] Alumina powder: 5 microns;

[0034] Titanium dioxide powder: 50nm;

[0035] Curing agent: aliphatic amine curing agent;

[0036] 0.2 mol / L nickel nitrate solution: homemade;

[0037] 1 mol / L chloroplatinic acid: Homemade:

[0038] DMF: analytical grade;

[0039] THF: analytical grade;

[0040] The purity of the prepared product was tested by gas chromatography.

[0041] Comparative Example 1A:

[0042] Weigh 10 grams of polystyrene and dissolve it in 30 milliliters of tetrahydrofuran, add 10 grams of silica powder and 0.5 grams of polyvinyl pyrrolidone, stir evenly, then slowly add it into a coagulation bath formed by 100 milliliters of water, stir to form microspheres, then filter out the aqueous solution to form polystyrene / silica composite microspheres. Then sinter at 500°C in a high-temperature muffle furnace to obtain a porous silica / C composite material.

[0043] Preparation of porous silica / C composite microspheres adsorbing Pd catalyst: The above silica / C composite microsphere particles were immersed in a 10% palladium chloride solution for 2 hours, then dried, and then reduced with NaBH4. The mass fraction of Pd in ​​the Pd / Al2O3 catalyst was 10%.

[0044] Fixed bed catalytic hydrogenation reduction process:

[0045] The prepared supported palladium catalyst was added to a fixed bed reactor. The solvent was methanol. The mass ratio of methanol to 4,4-dinitrodiphenyl ether was 2:1. The reaction liquid space velocity was 0.02 L / h. The reaction temperature was 45° C. and the reaction pressure was 3 MPa. After reduction, the pressure was reduced to separate hydrogen. The diaminodiphenyl ether and methanol solvent were subjected to a continuous distillation process to separate methanol and high-purity diaminodiphenyl ether. Gas chromatography analysis showed that the purity of diaminodiphenyl ether was 99.5%, and the conversion rate of 4,4-dinitrodiphenyl ether was 96%.

[0046] Comparative Example 1B:

[0047] Activity after 300 hours of circulation:

[0048] The reaction was continued in the fixed bed reactor for 300 hours, the solvent was methanol, the mass ratio of methanol to 4,4-dinitrodiphenyl ether was 2:1, the reaction liquid space velocity was 0.02 L / h, the reaction temperature was 45°C, the reaction pressure was 3 MPa, and the pressure was reduced after reduction to separate hydrogen. The diaminodiphenyl ether and methanol solvents were subjected to a continuous distillation process to separate methanol and high-purity diaminodiphenyl ether. Gas chromatography analysis showed that the purity of diaminodiphenyl ether was 85%, and the conversion rate of 4,4-dinitrodiphenyl ether was 82%.

[0049] Summary: It can be seen from Comparative Example 1A / B that the porous silica / C composite microsphere palladium catalyst obtained by the above method has low strength and is difficult to maintain long-term and repeated use.

[0050] Example 1A:

[0051] Preparation of porous alumina microspheres:

[0052] 30 grams of polyethylene and 60 grams of alumina powder were added with 3 grams of polyethylene glycol, mixed evenly and ground, hot pressed into microspheres at 180°C in a mold, and then sintered at 500°C to form porous microspheres of alumina. The prepared porous microspheres were immersed in a 0.2 mol / L nickel nitrate solution for 4 hours, then dried, and then reduced with a formaldehyde aqueous solution, and then dried to obtain an alumina-supported Ni catalyst.

[0053] Fixed bed catalytic hydrogenation reduction process:

[0054] The prepared loaded Ni catalyst was added into a fixed bed reactor, the solvent was DMF, the mass ratio of DMF to 4,4-dinitrodiphenyl ether was 5:1, the hydrogen pressure was 3 MPa, the reaction temperature was 120°C, the reaction liquid space velocity was 0.03 L / h, and the pressure was reduced after the reaction to separate the hydrogen. The diaminodiphenyl ether and DMF solvent were subjected to a continuous distillation process to separate DMF and high-purity diaminodiphenyl ether. Gas chromatography analysis showed that the purity of diaminodiphenyl ether was 99.9%, and the conversion rate of 4,4-dinitrodiphenyl ether was 99.8%.

[0055] Example 1B:

[0056] Activity after 300 hours of circulation:

[0057] The reaction was continued in the fixed bed reactor for 300 hours, the solvent was DMF, the mass ratio of DMF to 4,4-dinitrodiphenyl ether was 5:1, the hydrogen pressure was 3 MPa, the reaction temperature was 120°C, the reaction liquid space velocity was 0.2 L / h, and after the reaction was completed, the pressure was reduced to separate the hydrogen. The diaminodiphenyl ether and DMF solvent were subjected to a continuous distillation process to separate DMF and high-purity diaminodiphenyl ether. Gas chromatography analysis showed that the purity of diaminodiphenyl ether was 99.9%, and the conversion rate of 4,4-dinitrodiphenyl ether was 99.5%.

[0058] Summary: The alumina porous microsphere Ni catalyst obtained by the porous microsphere preparation method of the present invention has high strength and can be used for long-term and repeated catalytic use, which fully meets the use of fixed bed catalysts.

[0059] Example 2A:

[0060] 1 gram of aliphatic amine curing agent was added to 50 grams of epoxy resin / 50 grams of titanium dioxide powder (weight ratio of 1:1), mixed evenly, and cured in a mold to form epoxy resin / titanium dioxide microspheres, which were sintered and cured at a high temperature of 600°C to obtain porous titanium dioxide microspheres. The above microspheres were immersed in a 1 mol / L chloroplatinic acid solution for 2 hours, and reduced with hydrazine hydrate to obtain a platinum-loaded titanium dioxide catalyst with a platinum content of 2%.

[0061] The prepared supported platinum catalyst was added to a fixed bed reactor, the solvent was DMF, the mass ratio of DMF to 4,4-dinitrodiphenyl ether was 2:1, the hydrogen pressure was 5 MPa, the reaction temperature was 100°C, the reaction liquid space velocity was 0.1 L / h, and after the reaction was completed, the pressure was reduced to separate the hydrogen. The diaminodiphenyl ether and DMF solvent were subjected to a continuous distillation process to separate DMF and high-purity diaminodiphenyl ether. Gas chromatography analysis showed that the purity of diaminodiphenyl ether was 99.9%, and the conversion rate of 4,4-dinitrodiphenyl ether was 100%.

[0062] Example 2B:

[0063] Activity after 300 hours of circulation:

[0064] The reaction was continued in the fixed bed reactor for 300 hours, the solvent was DMF, the mass ratio of DMF to 4,4-dinitrodiphenyl ether was 2:1, the hydrogen pressure was 5 MPa, the reaction temperature was 100°C, the reaction liquid space velocity was 0.05 L / h, and the pressure was reduced after the reaction to separate the hydrogen. The diaminodiphenyl ether and DMF solvent were subjected to a continuous distillation process to separate DMF and high-purity diaminodiphenyl ether. Gas chromatography analysis showed that the purity of diaminodiphenyl ether was 99.8%, and the conversion rate of 4,4-dinitrodiphenyl ether was 99.8%.

[0065] Summary: The titanium dioxide porous microsphere platinum catalyst obtained by the method for preparing porous microspheres of the present invention has high strength, can be used for long-term and repeated catalytic use, and fully meets the use of fixed bed catalysts.

[0066] Example 3A:

[0067] 3 g of sodium dodecylbenzene sulfonate was added to the micropowder of 50 g epoxy resin / 100 g alumina (weight ratio of 1:2), and a fatty amine curing agent was added, mixed evenly, and cured in a mold to form epoxy resin / alumina microspheres, which were sintered and cured at a high temperature of 600°C to obtain porous microspheres of alumina. The above microspheres were immersed in a solution of 1 mol / L chloroplatinic acid for 6 hours, and reduced with hydrazine hydrate to obtain a platinum-loaded alumina catalyst with a platinum content of 2%.

[0068] The prepared supported platinum catalyst was added into a fixed bed reactor, the solvent was DMF, the mass ratio of DMF to bisphenol A dinitrodiphenyl ether was 2:1, the hydrogen pressure was 5 MPa, the reaction temperature was 100°C, the reaction liquid space velocity was 0.1 L / h, and the pressure was reduced after the reaction to separate the hydrogen. The bisphenol A diaminodiphenyl ether and DMF solvent were subjected to a continuous distillation process to separate DMF and high-purity bisphenol A diaminodiphenyl ether. Gas chromatography analysis showed that the purity of bisphenol A diaminodiphenyl ether was 98.5%, and the conversion rate of bisphenol A dinitrodiphenyl ether was 100%.

[0069] Example 3B:

[0070] Activity after 300 hours of use:

[0071] The reaction was continued in the fixed bed reactor for 300 hours, the solvent was DMF, the mass ratio of DMF to bisphenol A dinitrodiphenyl ether was 2:1, the hydrogen pressure was 5 MPa, the reaction temperature was 100°C, the reaction pressure was 5 MPa, the reaction liquid space velocity was 0.1 L / h, and the pressure was reduced after the reaction to separate the hydrogen. The bisphenol A diaminodiphenyl ether and DMF solvent were subjected to a continuous distillation process to separate DMF and high-purity bisphenol A diaminodiphenyl ether. Gas chromatography analysis showed that the purity of bisphenol A diaminodiphenyl ether was 99.7%, and the conversion rate of bisphenol A dinitrodiphenyl ether was 100%.

[0072] Summary: The alumina porous microsphere platinum catalyst obtained by the method for preparing porous microspheres of the present invention has high strength, can be used for long-term and repeated catalytic use, and fully meets the use of fixed bed catalysts.

[0073] Example 4A:

[0074] 50 g of isocyanate / 50 g of alumina powder were mixed evenly, and a polyether polyol equivalent to the isocyanate was added, and the mixture was cured in a mold to form polyurethane / alumina microspheres, which were sintered and cured at a high temperature of 600°C to obtain porous microspheres of alumina. The microspheres were immersed in a 1 mol / L chloroplatinic acid solution for 4 hours, and reduced with hydrazine hydrate to obtain a platinum-loaded alumina catalyst with a platinum content of 2%.

[0075] The prepared supported platinum catalyst was added into a fixed bed reactor, the solvent was DMAc, the mass ratio of DMAc to m-dinitrobenzene was 2:1, the hydrogen pressure was 3 MPa, the reaction temperature was 100°C, and the pressure was reduced after the reaction to separate the hydrogen. The m-phenylenediamine and DMF solvent were subjected to a continuous distillation process to separate DMF and high-purity m-phenylenediamine. Gas chromatography analysis showed that the purity of m-phenylenediamine was 99.9%, and the conversion rate of m-dinitrobenzene was 100%.

[0076] Example 4B:

[0077] Activity after 300 hours of circulation:

[0078] The reaction was continued in the fixed bed reactor for 300 hours, the solvent was DMAc, the mass ratio of DMAc to m-dinitrobenzene was 2:1, the hydrogen pressure was 3 MPa, the reaction temperature was 100°C, and after the reaction was completed, the pressure was reduced to separate the hydrogen. The m-phenylenediamine and DMF solvents were subjected to a continuous distillation process to separate DMF and high-purity m-phenylenediamine. Gas chromatography analysis showed that the purity of m-phenylenediamine was 99.9%, and the conversion rate of m-dinitrobenzene was 99.8%.

[0079] Summary: The alumina porous microsphere platinum catalyst obtained by the method for preparing porous microspheres of the present invention has high strength, can be used for long-term and repeated catalytic use, and fully meets the use of fixed bed catalysts.

[0080] Example 5A:

[0081] Preparation of porous alumina microspheres:

[0082] 30g of polyvinyl chloride, 60g of alumina powder, 3g of polyethylene glycol were added, mixed evenly and ground, hot pressed into microspheres at 180°C, and then sintered at 500°C to form porous microspheres of alumina. The microspheres were immersed in a 0.2mol / L palladium chloride solution for 4 hours, then dried, reduced with a formaldehyde aqueous solution, and then dried to obtain an alumina-supported palladium catalyst.

[0083] Fixed bed catalytic hydrogenation reduction process:

[0084] The prepared loaded Pd catalyst was added into a fixed bed reactor. The solvent was DMF. The mass ratio of DMF to 4,4-dinitrodiphenyl ether was 2:1. The hydrogen pressure was 3 MPa. The reaction temperature was 120°C and the reaction pressure was 3 MPa. After the reaction, the pressure was reduced to separate the hydrogen. The diaminodiphenyl ether and DMF solvent were subjected to a continuous distillation process to separate ethanol and high-purity diaminodiphenyl ether. Gas chromatography analysis showed that the purity of diaminodiphenyl ether was 99.9%, and the conversion rate of 4,4-dinitrodiphenyl ether was 99.8%.

[0085] Example 5B:

[0086] Activity after 300 hours of circulation:

[0087] The reaction was continued in the fixed bed reactor for 300 hours, the solvent was DMF, the mass ratio of DMF to 4,4-dinitrodiphenyl ether was 2:1, the reaction temperature was 120°C, the reaction pressure was 3 MPa, the crude diaminodiphenyl ether was first decompressed to separate hydrogen, and the diaminodiphenyl ether and DMF solvent were subjected to a continuous distillation process to separate ethanol and high-purity diaminodiphenyl ether. Gas chromatography analysis showed that the purity of diaminodiphenyl ether was 99.9%, and the conversion rate of 4,4-dinitrodiphenyl ether was 99.5%.

[0088] Summary: The alumina porous microsphere Pd catalyst obtained by the preparation method of the porous microsphere of the present invention has high strength, can be used for a long time and repeatedly for catalysis, and fully meets the use of fixed bed catalyst.

Claims

1. A method for reducing a nitro compound, characterized in that: The loaded Pd catalyst, the nitro compound and the reaction solvent are added to a fixed bed reactor, and a reduction reaction is carried out at 40-100° C. and 1.5-5 MPa hydrogen pressure. After the reaction is completed, the hydrogen is discharged, and a mixture of the amino compound and the reaction solvent is obtained by filtration, and then a rectification process is performed to obtain the amino compound; The preparation method of the loaded Pd catalyst is as follows: immersing the porous microspheres in a palladium chloride solution with a mass concentration of 8-15% for 1-6 hours, taking them out and drying them, and then reducing them with NaBH4 to obtain the loaded Pd catalyst; The preparation method of porous microspheres comprises the following steps: (1) mixing 20-60 parts of resin, 40-80 parts of inorganic material and 2-10 parts of auxiliary agent by weight; (2) grinding after uniform mixing, and hot pressing into microspheres at a temperature higher than the melting temperature of the resin after grinding; (3) sintering at a temperature higher than the decomposition temperature of the resin to obtain porous microspheres; the weight ratio of the resin to the inorganic material is (1:3)-(1:1); the resin is selected from one of polystyrene, polyvinyl chloride, polyethylene, acrylic resin, polyurethane, and epoxy resin; the inorganic material is selected from one or more powders of silicon carbide, silicon, silicon dioxide, titanium dioxide, aluminum nitride, aluminum oxide, silicon nitride, calcium fluoride, magnesium oxide, zinc oxide, and zirconium oxide; the auxiliary agent is selected from one or more of polyvinyl pyrrolidone, polyethylene glycol, and sodium dodecylbenzene sulfonate.

2. The method for reducing a nitro compound according to claim 1, characterized in that: The reaction solvent is selected from one or more of methanol, ethanol, dimethylformamide, dimethylacetamide, and tetrahydrofuran, and the weight ratio of the reaction solvent to the nitro compound is 1:1 to 10:

1.

3. The method for reducing a nitro compound according to claim 1, characterized in that: The nitro compound is selected from at least one of a mononitro compound and a polynitro compound.

4. The method for reducing a nitro compound according to claim 3, characterized in that: The polynitro compound is selected from dinitro compounds, and the dinitro compound is selected from at least one of dinitrotoluene, dinitrochlorobenzene, 4,4-dinitrodiphenyl ether, dinitrobenzene, and bisphenol A dinitrodiphenyl ether; the mononitro compound is selected from at least one of nitrobenzene and p-nitrophenol.

5. The method for reducing a nitro compound according to claim 3, characterized in that: The polynitro compound is selected from at least one of trinitrotoluene and trinitrophenol.

6. A method for reducing a nitro compound, characterized in that: The loaded Ni catalyst, dimethylformamide and nitro compound are added to a fixed bed reactor, and then a reduction reaction is carried out at a reaction temperature of 110-160° C. and a hydrogen pressure of 2.5-5 MPa. After the reaction is completed, the hydrogen is discharged, and a mixture of an amino compound and a reaction solvent is obtained by filtration, and then a rectification process is performed to obtain an amino compound; The preparation method of the loaded Ni catalyst is as follows: immersing the porous microspheres in a 0.15-0.25 mol / L nickel nitrate solution for 1-6 hours, taking them out and drying them, reducing them with a formaldehyde aqueous solution, and drying them to obtain the loaded Ni catalyst; The preparation method of porous microspheres comprises the following steps: (1) mixing 20-60 parts of resin, 40-80 parts of inorganic material and 2-10 parts of auxiliary agent by weight; (2) grinding after uniform mixing, and hot pressing into microspheres at a temperature higher than the melting temperature of the resin after grinding; (3) sintering at a temperature higher than the decomposition temperature of the resin to obtain porous microspheres; the weight ratio of the resin to the inorganic material is (1:3)-(1:1); the resin is selected from one of polystyrene, polyvinyl chloride, polyethylene, acrylic resin, polyurethane, and epoxy resin; the inorganic material is selected from one or more powders of silicon carbide, silicon, silicon dioxide, titanium dioxide, aluminum nitride, aluminum oxide, silicon nitride, calcium fluoride, magnesium oxide, zinc oxide, and zirconium oxide; the auxiliary agent is selected from one or more of polyvinyl pyrrolidone, polyethylene glycol, and sodium dodecylbenzene sulfonate.

7. The method for reducing a nitro compound according to claim 6, characterized in that: The nitro compound is selected from at least one of a mononitro compound and a polynitro compound.

8. The method for reducing a nitro compound according to claim 7, characterized in that: The polynitro compound is selected from dinitro compounds, and the dinitro compound is selected from at least one of dinitrotoluene, dinitrochlorobenzene, 4,4-dinitrodiphenyl ether, dinitrobenzene, and bisphenol A dinitrodiphenyl ether; the mononitro compound is selected from at least one of nitrobenzene and p-nitrophenol.

9. The method for reducing a nitro compound according to claim 7, characterized in that: The polynitro compound is selected from at least one of trinitrotoluene and trinitrophenol.