Reduction-state catalyst suitable for preparing aniline through nitrobenzene gas-phase hydrogenation as well as preparation and application of reduction-state catalyst

Abstract

The invention discloses a reduction-state catalyst suitable for preparing aniline through nitrobenzene gas-phase hydrogenation as well as a preparation method and application of the reduction-state catalyst, and belongs to the technical field of catalysts. The catalyst is used in a reaction for preparing aniline through nitrobenzene gas phase hydrogenation, the induction period is shorter than 3 h, the total amount of by-products in the induction period is lower than 120 ppm, and during stable operation in the induction period, phenol in an aniline product is lower than 40 ppm, and cyclohexanol in the aniline product is lower than 15 ppm; in the reduction process of the catalyst, the catalyst can tolerate rapid reduction of high-concentration hydrogen or pure hydrogen, does not influence the activity and selectivity of an induction period, has the condition that the catalyst is supplemented into a fluidized bed device in production in an oxidation state to be rapidly reduced and put into use in a high-concentration hydrogen environment in the bed, and does not influence the quality of an aniline product.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, and particularly relates to a reduced catalyst suitable for preparing aniline from gaseous nitrobenzene by hydrogenation and a preparation method and application thereof. BACKGROUND

[0002] Aniline is one of the most important dye intermediates in the dye industry, and is mainly used for producing various dyes and dye intermediates, printing and dyeing aniline black cloth, and manufacturing rubber aids. The manufacturing methods of aniline include iron powder reduction method, hydrogenation reduction method, phenol ammonolysis method, and chlorination amination method.

[0003] At present, the fluidized bed nitrobenzene hydrogenation method is the mainstream route for aniline production. The fluidized bed gaseous phase catalytic hydrogenation is usually carried out at 260-280℃ and 0.05-0.1 MPa, and the selectivity of aniline is greater than 99%. This method has good heat transfer condition, avoids local overheating, reduces the occurrence of side reactions, and prolongs the service life of the catalyst. Under normal circumstances, the process for replacing the fluidized bed nitrobenzene hydrogenation catalyst is as follows: after the service period of the catalyst ends, first, the catalyst is stopped and regenerated, then the regenerated catalyst is unloaded to the catalyst storage tank, then the regenerated catalyst in the catalyst storage tank and the fresh catalyst added are blown into the fluidized bed together through compressed air, and finally, after reduction in the bed, the next period of feeding operation can be carried out. In this process, after the catalyst is reduced in the bed each time, there is an induction period of 1-3 days when feeding. During the induction period, the catalyst has more side reactions, and the by-products are in the order of by-product amount as follows: phenol > cyclohexanol > cyclohexanone ≈ cyclohexane ≈ cyclohexylamine, and the total amount is usually 300-2000 ppm. These by-products have a significant impact on the quality of aniline products during the induction period. Therefore, the frequent replacement and regeneration of the catalyst and the long induction period time become the main factors affecting the aniline production in the industrial device.

[0004] CN115532300A provides a copper-based aniline catalyst supported on silica, which can reduce the content of phenol in the crude aniline product to below 20 ppm after 72 hours of operation, and has a longer induction period. CN11930663A provides a method for preparing aniline by gaseous hydrogenation, and Co / Ce is added as an additive in the copper-based silica aniline catalyst. However, the patent does not mention how to solve the problem of the induction period of the catalyst. SUMMARY

[0005] In view of the fact that the aniline production device is frequently regenerated and catalyst is added intermittently at present, and after adding catalyst each time, there is a long induction period, the first object of the present application is to provide a reduced state catalyst suitable for preparing aniline from nitrobenzene by gas phase hydrogenation, which has a short induction period, less by-products and high hydrogen reduction resistance. The catalyst is used in the reaction of preparing aniline from nitrobenzene by gas phase hydrogenation, the induction period is less than 3h, the total amount of by-products during the induction period is less than 120ppm, when the induction period is passed and the system is stably operated, the phenol in the aniline product is less than 40ppm, and the cyclohexanol is less than 15ppm; during the reduction process of the catalyst, high concentration hydrogen or pure hydrogen can be tolerated for rapid reduction, without affecting the induction period activity and selectivity, the catalyst can be added in the form of oxidation state into the fluidized bed device being produced, and rapidly reduced in the high concentration hydrogen environment in the bed to be put into use, without affecting the quality of aniline product.

[0006] The present application is realized by the following technical solutions:

[0007] A reduced state catalyst suitable for preparing aniline from nitrobenzene by gas phase hydrogenation is composed of the following raw materials in mass fraction:

[0008] The active component is 5.0-15.0%, the modified silicon carrier is 84.0-94.0%, and the additive is 0.5-1%;

[0009] The active component is copper;

[0010] The additive is chromium sesquioxide.

[0011] A preparation method of a reduced state catalyst suitable for preparing aniline from nitrobenzene by gas phase hydrogenation is carried out by using an excess impregnation method, and includes the following steps:

[0012] S1, selecting a commercially available ordinary silicon carrier to be modified and treated by hydrothermal hole expansion in a chromium-containing precursor aqueous solution to obtain a chromium-containing carrier;

[0013] S2, after the chromium-containing carrier is treated by wet reduction and air drying, a modified silicon carrier containing chromium sesquioxide is obtained;

[0014] S3, by using an excess impregnation method, a copper precursor is loaded onto the modified silicon carrier containing chromium sesquioxide, and after drying and calcination, an oxidation state catalyst is obtained;

[0015] S4, the oxidation state catalyst is reduced to obtain an active reduced state aniline catalyst.

[0016] As a preferred, in the S1, the silicon carrier is an ordinary macroporous silica gel particle;

[0017] The chromium-containing precursor aqueous solution is any one of a chromium nitrate aqueous solution, a chromium chloride aqueous solution and a potassium chromate aqueous solution; preferably, the chromium nitrate aqueous solution;

[0018] The molar concentration of the chromium-containing precursor aqueous solution is 0.2-0.5 mol / L; preferably 0.25-0.45 mol / L;

[0019] The volume ratio of the silicon carrier to the chromium-containing precursor aqueous solution is 1:1.5-4.0; preferably 1:2.0-2.5;

[0020] The hydrothermal hole-expanding modification process is as follows: the ordinary silicon carrier and the chromium-containing precursor aqueous solution are added to a stainless steel reaction kettle of a hydrothermal device, an acid-base regulator is added to adjust the pH value to 3-4, the temperature is maintained after sealing and heating, then the temperature is lowered, the carrier is taken out and drained, and the chromium-containing carrier is obtained;

[0021] The acid-base regulator is oxalic acid;

[0022] The hydrothermal pressure in the hydrothermal device is the autogenous pressure of water vapor;

[0023] The temperature of the sealing and heating is 120-180℃, and the time length is 2-8h; preferably the temperature is 140-160℃, and the time length is 4-6h.

[0024] As a preference, the ordinary macroporous silica gel particles are prepared by an air method or an oil method; preferably prepared by an oil method;

[0025] In the total mass of the ordinary macroporous silica gel particles, the particle size is normally distributed in the range of 150-830μm; preferably the particle size is normally distributed in the range of 180-250μm, and the proportion is not less than 70% in the total mass.

[0026] As a preference, in S2, the process of the wet reduction and the air drying treatment is as follows:

[0027] The chromium-containing carrier is soaked in an excess of an aqueous sodium borohydride solution, after complete reaction, the carrier is taken out and dried in flowing air to obtain a modified silicon carrier containing Cr2O3;

[0028] The molar concentration of the aqueous sodium borohydride solution is 0.05 mol / L;

[0029] The soaking time in the excess of the aqueous sodium borohydride solution is 1-1.2h, and the soaking frequency is 3-4 times;

[0030] In the air drying treatment, the drying temperature is 80-160℃, and the time length is 6-10h; preferably the drying temperature is 120-240℃, and the time length is 7-9h.

[0031] As a preference, in S3, the precursor of copper is a copper-ammonium complex ion solution;

[0032] The copper-ammonium complex ion solution is obtained by complexing copper nitrate solution with excess ammonia gas in the solution;

[0033] The molar concentration of the copper nitrate solution is 0.3-1.5 mol / L; preferably 0.5-1.0 mol / L;

[0034] The pH value of the copper-ammonium complex ion solution is 8-14; preferably 9-11;

[0035] The process for loading the copper precursor onto the modified silicon carrier containing chromium trioxide is as follows: the modified silicon carrier containing chromium trioxide is soaked in excess copper-ammonium complex ion solution, and after being taken out, is dried at 80-160 DEG C for 6-10 h and calcined at 200-400 DEG C for 1-6 h to obtain an oxidized state catalyst; preferably, after being taken out, it is dried at 110-120 DEG C for 7-9 h and calcined at 300-380 DEG C for 1.5-2.0 h to obtain an oxidized state catalyst;

[0036] The soaking temperature is 30-80 DEG C, and the soaking time is 1-5 h; preferably, the temperature is 35-55 DEG C, and the time is 2.5-3.5 h.

[0037] As preferred, in S4, the reduction treatment is a reduction treatment with hydrogen at 150-280 DEG C.

[0038] A use method of a reduced state catalyst suitable for preparing aniline from nitrobenzene by gas phase hydrogenation, wherein the induction period of the catalyst in the reaction of preparing aniline from nitrobenzene by gas phase hydrogenation is less than 3 h, the total amount of by-products in the induction period is less than 120 ppm, the phenol in the aniline product is less than 40 ppm and the cyclohexanol is less than 15 ppm when the catalyst is stably operated after passing through the induction period.

[0039] The use of a reduced state catalyst suitable for preparing aniline from nitrobenzene by gas phase hydrogenation in preparing fluidized bed on-line supplemental oxidized state catalyst, wherein the reduced state catalyst is obtained by the preparation method.

[0040] Compared with the prior art, the present application has at least the following technical effects:

[0041] The present application provides a reduced state catalyst suitable for preparing aniline from nitrobenzene by gas phase hydrogenation, wherein the induction period of the catalyst in the reaction of preparing aniline from nitrobenzene by gas phase hydrogenation is less than 3 h, the total amount of by-products in the induction period is less than 120 ppm, the phenol in the aniline product is less than 40 ppm and the cyclohexanol is less than 15 ppm when the catalyst is stably operated after passing through the induction period; the catalyst can tolerate high concentration hydrogen or pure hydrogen rapid reduction in the reduction process without affecting the induction period activity and selectivity, has the condition of being supplemented in the form of an oxidized state into a fluidized bed device in production and being rapidly reduced in a high concentration hydrogen environment in the bed for use without affecting the aniline product quality. DETAILED DESCRIPTION

[0042] The embodiments of the present application will be described in detail with examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not mentioned the manufacturer are all conventional products that can be purchased on the market.

[0043] Example 1

[0044] A preparation method of a reduced state catalyst suitable for preparing aniline by gas phase hydrogenation of nitrobenzene, which is carried out by using an excess impregnation method, comprising the following steps:

[0045] 94 g of macroporous silica gel and 300 mL of 0.3 mol / L aqueous solution of chromium nitrate were added to a stainless steel reaction kettle, and the pH value was adjusted to 4.0 with oxalic acid. After being sealed and heated to 150℃ for 6 h, the solid was taken out, drained, and soaked in 300 mL of 0.05 mol / L sodium borohydride solution for 1 h. The solid was taken out and drained, and then soaked in 300 mL of fresh 0.05 mol / L sodium borohydride solution for 1 h. The above operation was repeated 4 times until there was no obvious gas bubble when the solid was soaked in sodium borohydride.

[0046] The soaked solid was taken out and dried at 130℃ for 8 h to obtain a dried carrier.

[0047] 300 mL of 0.5 mol / L copper nitrate solution was prepared, and the temperature of the solution was maintained at 40℃. Excess ammonia gas was introduced into the solution through a gas distributor until a blue precipitate was formed, and then the blue precipitate was dissolved to form a uniform blue solution. The amount of ammonia gas introduced was adjusted to control the pH value of the solution to be 10. The soaked solid was added to the solution and soaked for 3 h, and then taken out. The solid was dried at 120℃ for 8 h, and then calcined at 350℃ for 2 h to obtain an oxidized state catalyst, which was recorded as sample 1.

[0048] It was determined that the copper oxide was converted into elemental copper by removing oxygen, and then the copper content in sample 1 was 5.3%, the silicon dioxide content was 93.8%, and the chromium oxide content was 0.9% based on the total mass of the catalyst after removing the oxygen in the copper oxide.

[0049] Example 2

[0050] A preparation method of a reduced state catalyst suitable for preparing aniline by gas phase hydrogenation of nitrobenzene, which is carried out by using an excess impregnation method, comprising the following steps:

[0051] Put 90g macroporous silica gel and 250mL 0.25mol / L chromium nitrate aqueous solution into a stainless steel reactor, adjust pH value to 3.0 with oxalic acid, seal and heat to 160℃ for 5h, then take out the solid, and then put the obtained solid into 250mL 0.1mol / L sodium borohydride solution for 1h, take out and drain, then put it into 250mL fresh 0.1mol / L sodium borohydride solution for 1h, repeat 4 times until no obvious bubbles are generated when put into sodium borohydride.

[0052] Take out the soaked solid, and dry it at 130℃ for 8h to obtain the dried carrier.

[0053] Put 280mL 0.75mol / L copper nitrate solution into a stainless steel reactor, maintain the solution temperature at 55℃, and then pass excess ammonia gas into the solution through a gas distributor until blue precipitate is generated, then until the blue precipitate is dissolved to form a uniform blue solution, and then adjust the amount of ammonia gas to control the pH value of the solution to 9. Put the soaked solid into the solution, soak for 3.5h, then take out, dry at 110℃ for 10h, and then calcine at 380℃ for 1.5h to obtain the oxidized catalyst, which is recorded as sample 2.

[0054] After measurement, the copper oxide is converted into elemental copper, and then the copper content in sample 2 is 10.1%, the silicon dioxide content is 89.4%, and the chromium oxide content is 0.5% after normalization with the total mass of the catalyst without the oxygen in the copper oxide.

[0055] Example 3:

[0056] A preparation method of a reduced state catalyst suitable for preparing aniline by gas phase hydrogenation of nitrobenzene, which is carried out by using excess impregnation method, comprising the following steps:

[0057] Put 85g macroporous silica gel and 250mL 0.45mol / L chromium nitrate aqueous solution into a stainless steel reactor, adjust pH value to 3.5 with oxalic acid, seal and heat to 140℃ for 4h, then take out the solid, and then put the obtained solid into 250mL 0.2mol / L sodium borohydride solution for 1h, take out and drain, then put it into 250mL fresh 0.2mol / L sodium borohydride solution for 1h, repeat 4 times until no obvious bubbles are generated when put into sodium borohydride.

[0058] Take out the soaked solid, and dry it at 140℃ for 7h to obtain the dried carrier.

[0059] Take 260 mL of 1.0 mol / L copper nitrate solution, maintain the solution temperature at 35°C, and pass excess ammonia gas through the solution via a gas distributor until a blue precipitate is formed, then until the blue precipitate dissolves to form a uniform blue solution, and adjust the amount of ammonia gas passed to control the solution pH value to 11. Add all the soaked solid to the solution, soak for 2.5 h, then take out, dry at 110°C for 6 h, and then calcine at 300°C for 2 h to obtain an oxidized catalyst, which is recorded as sample 3.

[0060] Determination shows that, after converting the copper oxide to elemental copper by removing oxygen and normalizing to the total mass of the catalyst after removing oxygen from the copper oxide, the copper content in sample 3 is 14.8%, the silicon dioxide content is 84.2%, and the chromium oxide content is 1.0%.

[0061] Example 4:

[0062] A preparation method of a reduced-state catalyst suitable for the gas-phase hydrogenation of nitrobenzene to prepare aniline, which is performed by using an excess impregnation method, and includes the following steps:

[0063] Add 92 g of macroporous silica gel and 270 mL of 0.3 mol / L chromium nitrate aqueous solution to a stainless steel reaction kettle, adjust the pH value to 3.0 with oxalic acid, seal and heat to 160°C, maintain for 5 h, then take out the solid, drain the solid, add to 300 mL of 0.2 mol / L sodium borohydride solution, soak for 1 h, take out and drain, then re-soak in 300 mL of fresh 0.2 mol / L sodium borohydride solution for 1 h, repeat for 4 times, until no obvious bubbles are generated when the solid is soaked in the sodium borohydride.

[0064] Take out the soaked solid, dry at 130°C with blast drying for 8 h to obtain a dried carrier.

[0065] Take 300 mL of 0.6 mol / L copper nitrate solution, maintain the solution temperature at 40°C, pass excess ammonia gas through the solution via a gas distributor until a blue precipitate is formed, then until the blue precipitate dissolves to form a uniform blue solution, and adjust the amount of ammonia gas passed to control the solution pH value to 9.5. Add all the soaked solid to the solution, soak for 3.5 h, then take out, dry at 120°C for 8 h, and then calcine at 365°C for 1.75 h to obtain an oxidized catalyst, which is recorded as sample 4.

[0066] Determination shows that, after converting the copper oxide to elemental copper by removing oxygen and normalizing to the total mass of the catalyst after removing oxygen from the copper oxide, the copper content in sample 4 is 7.4%, the silicon dioxide content is 92.0%, and the chromium oxide content is 0.6%.

[0067] Example 5:

[0068] A preparation method of a reduced-state catalyst suitable for the gas-phase hydrogenation of nitrobenzene to prepare aniline, which is performed by using an excess impregnation method, and includes the following steps:

[0069] 87g macroporous silica gel and 310mL of 0.2mol / L aqueous solution of chromium nitrate were added into a stainless steel reactor, and the pH value was adjusted to 4.0 with oxalic acid. The reactor was sealed and heated to 140℃ for 4h, and then cooled to take out the solid. The obtained solid was drained and soaked in 300mL of 0.1mol / L sodium borohydride solution for 1h. The solid was taken out and drained, and then soaked in 300mL of fresh 0.1mol / L sodium borohydride solution for 1h. The soaking was repeated for 4 times until no obvious bubbles were generated in the sodium borohydride solution.

[0070] The soaked solid was taken out and dried at 130℃ for 8h to obtain the dried carrier.

[0071] 300mL of 0.8mol / L copper nitrate solution was prepared, and the temperature of the solution was maintained at 45℃. Excess ammonia gas was introduced into the solution through a gas distributor until a blue precipitate was generated, and then the blue precipitate was dissolved to form a uniform blue solution. The amount of ammonia gas introduced was adjusted to control the pH value of the solution to be 10.5. The soaked solid was added into the solution and soaked for 3h, and then taken out. The solid was dried at 110℃ for 9h, and then calcined at 325℃ for 2h to obtain the catalyst in oxidation state, which was recorded as sample 5.

[0072] It was determined that the copper oxide was converted into elemental copper by removing oxygen, and then the copper content in sample 5 was normalized by the total mass of the catalyst after removing oxygen from the copper oxide. The copper content was 10.9%, the silicon dioxide content was 88.2%, and the chromium oxide content was 0.9%.

[0073] Comparative Example 1

[0074] A preparation method of a reduced state catalyst suitable for preparing aniline by gas phase hydrogenation of nitrobenzene, which was carried out by using excess impregnation method, and included the following steps:

[0075] According to the preparation steps of Example 5, the aqueous solution of chromium nitrate was replaced by deionized water, and other steps were unchanged to obtain Comparative Example 1.

[0076] It was determined that the copper oxide was converted into elemental copper by removing oxygen, and then the copper content in Comparative Example 1 was normalized by the total mass of the catalyst after removing oxygen from the copper oxide. The copper content was 11.3%, the silicon dioxide content was 88.7%, and the chromium oxide content was 0%.

[0077] Comparative Example 2

[0078] A preparation method of a reduced state catalyst suitable for preparing aniline by gas phase hydrogenation of nitrobenzene, which was carried out by using excess impregnation method, and included the following steps:

[0079] According to the preparation steps of Example 5, the macroporous silica gel and the aqueous solution of chromium nitrate were added into the stainless steel reactor without heating for 4h, and the hydrothermal step was cancelled, and other steps were unchanged to obtain Comparative Example 2.

[0080] The copper oxide was converted into elemental copper by removing oxygen, and the copper content was 10.9%, the silicon dioxide content was 88.2%, and the chromium oxide content was 0.9% in Comparative Example 2, based on the total mass of the catalyst after removing oxygen from the copper oxide.

[0081] Evaluation data:

[0082] An application of a reduced catalyst suitable for the gas phase hydrogenation of nitrobenzene to aniline. Specifically, the evaluation was performed in a fixed bed reactor.

[0083] The hydrogen pressure was 0.2 MPa, the initial temperature was 160°C, the catalyst loading was 10 ml, the nitrobenzene flow rate was 0.25 ml / min, the hydrogen tail gas reading was 300 ml / min, and the product content was analyzed by gas chromatography.

[0084] Table 1 Sample 5 data for the gas phase hydrogenation of nitrobenzene to aniline

[0085]

[0086] The above catalyst was reduced using pure hydrogen at 270°C for 10 min.

[0087] Results: The catalyst prepared according to the present application was resistant to reduction with pure hydrogen, and the induction period was short. The test showed that the catalyst entered the stable period after about 2.5 hours, and the product was essentially free of cyclohexylamine, cyclohexane, and cyclohexanone. The main byproducts, phenol and cyclohexanol, were maintained at less than 100 ppm and 35 ppm during the induction period, and at less than 40 ppm and 15 ppm during the stable period.

[0088] Table 2 Example sample and comparative example data for the gas phase hydrogenation of nitrobenzene to aniline byproducts

[0089]

[0090] The above catalyst was reduced using pure hydrogen at 270°C for 10 min.

[0091] Results: The five examples were all resistant to reduction with pure hydrogen, and entered the stable period within 3 hours. The sample of Comparative Example 1, which was hydrothermally treated in deionized water, entered the stable period after 48 hours, but the aniline conversion rate and selectivity were slightly lower during the stable period. Comparative Example 2, which was not hydrothermally treated and did not contain the additive, had poor activity and selectivity after 48 hours, and could not be used for industrial production.

[0092] Finally, it should be noted that the above description is only a preferred embodiment of the present application and is not intended to limit the protection scope of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A reduced catalyst suitable for preparing aniline by gas-phase hydrogenation of nitrobenzene, characterized in that: It is composed of the following raw materials by mass fraction: Active component 5.0-15.0%, modified silicon carrier 84.0-94.0% and auxiliary agent 0.5-1%; The active component is copper; The auxiliary agent is chromium trioxide.

2. A method for preparing a reduced catalyst suitable for preparing aniline by gas-phase hydrogenation of nitrobenzene as claimed in claim 1, characterized in that: The method is carried out by an excessive impregnation method, comprising the following steps: S1. Select a commercially available common silicon support and perform a hydrothermal pore expansion modification treatment in a chromium-containing precursor aqueous solution to obtain a chromium-containing support; S2, subjecting the chromium-containing support to wet reduction and air drying to obtain a modified silicon support containing chromium trioxide; S3, using an excess impregnation method to load a copper precursor onto the modified silicon support containing chromium trioxide, and then drying and calcining to obtain an oxidized catalyst; S4. The oxidized catalyst is subjected to reduction treatment to obtain an active reduced aniline catalyst.

3. The method for preparing a reduced catalyst suitable for preparing aniline by gas-phase hydrogenation of nitrobenzene according to claim 2, characterized in that: In S1, the silicon carrier is ordinary macroporous silica gel particles; The chromium-containing precursor aqueous solution is any one of a chromium nitrate aqueous solution, a chromium chloride aqueous solution, and a potassium chromate aqueous solution; preferably a chromium nitrate aqueous solution; The molar concentration of the chromium-containing precursor aqueous solution is 0.2 to 0.5 mol / L, preferably 0.25 to 0.45 mol / L; The volume ratio of the silicon carrier to the chromium-containing precursor aqueous solution is 1:1.5-4.0; preferably 1:2.0-2.5; The hydrothermal pore expansion modification process is as follows: adding a common silicon carrier and a chromium-containing precursor aqueous solution into a stainless steel reactor of a hydrothermal device, adding an acid-base regulator to adjust the pH value to 3-4, sealing and heating, maintaining the temperature, then cooling, taking out the carrier and draining it to obtain the chromium-containing carrier; The acid-base regulator is oxalic acid; The hydrothermal pressure in the hydrothermal equipment is the autogenous pressure of water vapor; The sealing heating temperature is 120-180° C. for 2-8 hours; preferably, the temperature is 140-160° C. for 4-6 hours.

4. The method for preparing a reduced catalyst suitable for preparing aniline by gas-phase hydrogenation of nitrobenzene according to claim 3, characterized in that: The ordinary macroporous silica gel particles are prepared by an air method or an oil method; preferably, they are prepared by an oil method; The ordinary macroporous silica gel particles have a particle size normally distributed in the range of 150 to 830 μm in the total mass; preferably, the particle size is normally distributed in the range of 180 to 250 μm, accounting for no less than 70% of the total mass.

5. The method for preparing a reduced catalyst suitable for preparing aniline by gas-phase hydrogenation of nitrobenzene according to claim 2, characterized in that: In S2, the process of wet reduction and air drying is as follows: The chromium-containing support is added to an excess of sodium borohydride aqueous solution and soaked. After the reaction is complete, the support is taken out and dried in flowing air to obtain a modified silicon support containing Cr2O3. The molar concentration of the sodium borohydride aqueous solution is 0.05 mol / L; The soaking time in the excess sodium borohydride aqueous solution is 1 to 1.2 hours, and the number of soaking times is 3 to 4 times; during the air drying treatment, the drying temperature is 80 to 160° C., and the time is 6 to 10 hours; preferably, the drying temperature is 120 to 240° C., and the time is 7 to 9 hours.

6. The method for preparing a reduced catalyst suitable for preparing aniline by gas-phase hydrogenation of nitrobenzene according to claim 2, characterized in that: In said S3, the copper precursor is a cuprammonium complex ion solution; The cuprammonium complex ion solution is obtained by complexing a copper nitrate solution with excess ammonia gas in the solution; The molar concentration of the copper nitrate solution is 0.3 to 1.5 mol / L, preferably 0.5 to 1.0 mol / L; The pH value of the cuprammonium complex ion solution is 8 to 14, preferably 9 to 11; The process of loading the copper precursor onto the modified silicon support containing chromium trioxide is as follows: soaking the modified silicon support containing chromium trioxide in an excess of cuprammonium complex ion solution, drying it at 80-160° C. for 6-10 hours, and calcining it at 200-400° C. for 1-6 hours to obtain an oxidized catalyst; preferably, drying it at 110-120° C. for 7-9 hours, and calcining it at 300-380° C. for 1.5-2.0 hours to obtain an oxidized catalyst; The soaking temperature is 30-80° C., and the soaking time is 1-5 hours; preferably, the temperature is 35-55° C., and the soaking time is 2.5-3.5 hours.

7. The method for preparing a reduced catalyst suitable for preparing aniline by gas-phase hydrogenation of nitrobenzene according to claim 2, characterized in that: In the above S4, the reduction treatment is a reduction treatment at 150-280° C. using hydrogen.

8. A method for using the reduced catalyst suitable for preparing aniline by gas-phase hydrogenation of nitrobenzene as claimed in claim 1, characterized in that: When the catalyst is used in the gas-phase hydrogenation of nitrobenzene to produce aniline, the induction period is less than 3 hours, the total amount of by-products during the induction period is less than 120 ppm, and when the catalyst operates stably after the induction period, the phenol content in the aniline product is less than 40 ppm, and the cyclohexanol content is less than 15 ppm.

9. Use of a reduced catalyst suitable for preparing aniline by gas-phase hydrogenation of nitrobenzene in the preparation of an oxidized catalyst for online addition in a fluidized bed, characterized in that: The reduced catalyst is obtained by the preparation method according to any one of claims 2 to 7.

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