A catalyst for preparing aniline by gas phase hydrogenation of nitrobenzene and a preparation method and application thereof

Abstract

This invention provides a catalyst for the gas-phase hydrogenation of nitrobenzene to aniline, its preparation method, and its application. A coarse-porous silica gel is etched using an alkaline solution. The etched sodium silicate, along with the active components and auxiliary agents, is deposited on the surface and inside the pores of the treated coarse-porous silica gel after temperature-controlled treatment. The etched support structure is stable and has a suitable pore structure, which is beneficial for improving the shape selectivity of the product while promoting heat dissipation during the reaction, thereby improving the activity, selectivity, and stability of the catalyst and further extending its lifetime. The nitrobenzene gas-phase hydrogenation catalyst prepared by this invention achieves a 100% nitrobenzene conversion and a 99.90% aniline selectivity, exhibiting excellent activity, selectivity, and stability, which is beneficial for industrial application and promotion.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a catalyst for the gas-phase hydrogenation of nitrobenzene to aniline, its preparation method, and its application. Background Technology

[0002] Aniline (C6H7N) is an important organic chemical raw material intermediate, mainly used in the production of diphenylmethane diisocyanate (MDI), a raw material for polyurethane, and in the chemical industry, including dyes, pesticides, pharmaceuticals, specialty fibers, rubber additives, and organic intermediates. Currently, the mainstream method for aniline production is the catalytic hydrogenation of nitrobenzene. This method is further divided into liquid-phase hydrogenation and gas-phase hydrogenation. The liquid-phase catalytic hydrogenation process requires high pressure, necessitates separation of reactants, catalysts, and solvents, results in high equipment operating costs, expensive catalysts, and excessively high catalyst activity leading to numerous byproducts. In contrast, the fluidized bed gas-phase catalytic hydrogenation method involves heating and vaporizing the nitrobenzene raw material, mixing it with hydrogen, and then introducing it into a fluidized bed reactor containing a catalyst for the reaction. This improves heat transfer and avoids localized overheating. According to the reported literature, the catalytic systems for the catalytic hydrogenation of nitrobenzene to produce aniline mainly include the Cu / SiO2 system with copper supported on a silica support, noble metal catalysts with metals such as Pt, Pd, and Rh supported on supports such as alumina and activated carbon, and other catalytic systems.

[0003] The gas-phase hydrogenation reaction of nitrobenzene mainly uses Cu / SiO2 catalysts, which have the advantages of inexpensive and readily available raw materials, simple and feasible preparation methods, and good selectivity. However, they have disadvantages such as poor resistance to poisoning and the susceptibility of trace amounts of organic sulfides to catalyst poisoning. A common preparation method for Cu / SiO2 catalysts involves impregnating the active component, copper, onto coarse-porous silica gel using ammonia stripping. During use, some of the active component detaches, and the support strength decreases significantly during catalyst regeneration in the fluidized bed reaction, causing blockage in the subsequent cyclone separation and affecting the catalyst's single-pass lifespan.

[0004] Patent CN 115999548 A discloses a catalyst for the hydrogenation of nitrobenzene to aniline, its preparation method, and its application. The method involves treating coarse-porous silica gel with a polycarboxylic acid and using excess ammonia to form a copper-ammonia complex with copper nitrate, promoting the uniform distribution of the active component copper within the coarse-porous silica gel. The decomposition of the polycarboxylic acid during calcination pre-reduces the active component of the catalyst. Therefore, when applied to the hydrogenation reaction of nitrobenzene, the catalyst does not require reduction activation, and the reaction can reach equilibrium quickly, significantly shortening the catalyst's induction period.

[0005] Patent CN 117899890 A discloses a copper-based catalyst, its preparation method, and its application. The catalyst is prepared by utilizing the interaction between silicates and silicon dioxide and metal (copper, zinc, and manganese) ions, combined with an optimized aging process. The preparation method only requires simple mixing and drying, which can effectively enhance the bonding strength between the active species copper and the support silica. It does not require high-temperature (>250°C) treatment, thus avoiding the sintering of the active species or their detachment from the support at high temperatures. Summary of the Invention

[0006] To address a series of problems in existing Cu / SiO2 catalyst systems, such as poor resistance to poisoning, insufficient support strength, and short single-pass catalyst lifespan, this application proposes a catalyst for the gas-phase hydrogenation of nitrobenzene to aniline, its preparation method, and its application. An alkaline solution is used to etch coarse-porous silica gel. The etched sodium silicate, along with the active component and additive precipitate, is then deposited on the surface and inside the pores of the treated coarse-porous silica gel under controlled temperature. Cu, as the active component, is deposited on the surface and inside the pores of the coarse-porous silica gel support in the form of co-precipitation, strengthening the interaction between the support and the active component. The main function of the additive Mn is to anchor the active component Cu and promote its dispersion, preventing its migration during use and thus avoiding copper grain growth. The etched support has a stable structure and suitable pore structure, which is beneficial for improving the shape selectivity of the product while promoting heat dissipation during the reaction, thereby improving the catalyst's activity, selectivity, and stability, and further extending the catalyst lifespan.

[0007] A method for preparing a catalyst for the gas-phase hydrogenation of nitrobenzene to aniline includes the following steps: (1) under ultrasonic conditions, coarse-porous silica gel is added to an alkaline solution for etching; (2) copper salt and manganese salt are added, and the temperature is controlled; (3) the product from step (2) is poured out, washed, filtered, dried, and calcined to obtain the catalyst for the gas-phase hydrogenation of nitrobenzene to aniline. The ratio of coarse-porous silica gel, copper salt, and manganese salt is (85-92):(8-24):(10-21).

[0008] The catalysts described above, by mass percentage, contain 85-92% coarse-porous silica gel as the support, 5-10% CuO as the active component, and 3-5% MnO2 as the auxiliary agent.

[0009] In step (1) above, the alkaline solution is any aqueous solution of sodium hydroxide or potassium hydroxide; the concentration of the alkaline solution is [value missing].

[0010] The diameter of the coarse-pore silicone after etching in step (1) above is 150-600 μm, and the specific surface area is 400-500 m². 2 / g, with an average pore size of 2-5nm.

[0011] The ultrasonic conditions for step (1) above are an ultrasonic frequency of 50-100kHz, a time of 20-50min, and a temperature of 45-65℃. The ultrasonic time affects parameters such as the pore size of the etched coarse-pore silicone. The parameters of the coarse-pore silicone when the time is less than 20min or more than 50min can be determined by BET testing, as shown in Table 1.

[0012] In step (2) above, the copper salt can be any one of copper nitrate, copper sulfate, or copper chloride.

[0013] The manganese salt in step (2) above is either manganese nitrate or manganese sulfate.

[0014] The temperature control conditions for step (2) above are 65-85℃ and 1-2h.

[0015] The drying temperature in step (3) above is 100-120℃, and the drying time is 20-24h; the calcination temperature is 350-450℃, and the calcination time is 2-6h. The washing operation is a routine operation, and deionized water is generally used for washing.

[0016] When the catalyst prepared by the above method is applied to the gas-phase hydrogenation of nitrobenzene to aniline, the reaction conditions are as follows: reaction temperature 140-180℃, reaction pressure atmospheric pressure, hydrogen flow rate 250-400 ml / min, and liquid hourly space velocity of nitrobenzene 0.4-1.2 h⁻¹. -1 .

[0017] This application has the following advantages over the prior art:

[0018] (1) The present invention uses alkaline etching to make the coarse-porous silica support have a more suitable pore structure, which is conducive to the diffusion of reaction raw materials and products and improves the strength of the support; the etched support part is redeposited on the support with active components and additives, thereby strengthening the interaction between the support and active components, avoiding the active components from falling off during use, and further improving the catalyst life.

[0019] (2) By adding additives, the dispersion of active components can be further improved, their interaction with the support can be strengthened, and the crystal growth caused by them during use can be limited, thereby improving the catalyst activity.

[0020] The catalyst for the gas-phase hydrogenation of nitrobenzene to aniline provided by this invention involves etching coarse-porous silica gel with an alkaline solution. Under ultrasonic treatment, an active component and auxiliary agent salt solution are continuously added to the alkaline solution to form fine precipitates of the active component and auxiliary agent. These precipitates are then deposited together with sodium silicate in the solution on the surface and within the pores of the etched coarse-porous silica gel. This design of the invention enables the catalyst to obtain a suitable pore structure while also ensuring a more uniform and robust dispersion of the active component, thereby guaranteeing the catalyst's activity, selectivity, and stability.

[0021] The catalyst prepared by this invention is applied to the gas-phase hydrogenation reaction of nitrobenzene to aniline, and the aniline conversion rate reaches 100% and the aniline selectivity reaches 99.90%, that is, the prepared catalyst has excellent activity, selectivity and stability. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] Catalyst Preparation Example 1

[0024] Step 1) Weigh 20g of NaOH and dissolve it in 200ml of deionized water to prepare an alkaline solution. Weigh 85g of coarse-porous silica gel and add it to the alkaline solution under the action of ultrasound. Control the solution temperature at 60℃ and the treatment time at 40min.

[0025] Step 2) Weigh 23.5g of copper nitrate and 20.6g of manganese nitrate solution (concentration 50%), prepare 100ml of solution, and add the copper nitrate and manganese nitrate mixed solution to the pore-expanding silica gel solution treated in step 1) under the action of ultrasound, control the temperature at 70℃, and add the material for 1.5h.

[0026] Step 3) The catalyst precursor obtained in Step 2) is washed, filtered, dried at 100°C for 24 h, and calcined at 400°C for 4 h to obtain catalyst C1.

[0027] ICP testing revealed that the catalyst C1 contained 85 wt% support, 10 wt% CuO active component, and 5 wt% MnO2 auxiliary agent.

[0028] Catalyst Preparation Example 2

[0029] Step 1) Weigh 20g of NaOH and dissolve it in 200ml of deionized water to prepare an alkaline solution. Weigh 90g of coarse-porous silica gel and add it to the alkaline solution under the action of ultrasound. Control the solution temperature at 65℃ and the treatment time at 20min.

[0030] Step 2) Weigh 11.8g of copper nitrate and 20.6g of manganese nitrate solution (concentration 50%), prepare 100ml of solution, and add the copper nitrate and manganese nitrate solution to the pore-expanding silica gel solution treated in Step 1) under the action of ultrasound, control the temperature at 85℃, and add the materials for 1 hour.

[0031] Step 3) The catalyst precursor obtained in Step 2) is directly dried, cooled, washed, filtered, dried at 100℃ for 24h, and calcined at 450℃ for 2h to obtain catalyst C2.

[0032] ICP testing revealed that the catalyst C2 contained 90 wt% support, 5 wt% CuO as the active component, and 5 wt% MnO2 as the auxiliary agent.

[0033] Catalyst Preparation Example 3

[0034] Step 1) Weigh 28g of KOH and dissolve it in 200ml of deionized water to prepare an alkaline solution. Weigh 92g of coarse-porous silica gel and add it to the alkaline solution under the action of ultrasound. Control the solution temperature at 45℃ and the treatment time at 50min.

[0035] Step 2) Weigh 11.8g of copper nitrate and 12.36g of manganese nitrate solution (concentration 50%), prepare 100ml of solution, and add the copper nitrate and manganese nitrate solution to the pore-expanding silica gel solution treated in Step 1) under the action of ultrasound, control the temperature at 65℃, and add the materials for 2 hours.

[0036] Step 3) The catalyst precursor obtained in Step 2) is directly dried, cooled, washed, filtered, dried at 120℃ for 20h, and calcined at 350℃ for 6h to obtain catalyst C3.

[0037] The catalyst C3 contains 92 wt% support, 5 wt% active component CuO, and 3 wt% auxiliary agent MnO2.

[0038] Catalyst Preparation Example 4

[0039] Step 1) Weigh 28g of KOH and dissolve it in 200ml of deionized water to prepare an alkaline solution. Weigh 88g of coarse-porous silica gel and add it to the alkaline solution under the action of ultrasound. Control the solution temperature at 50℃ and the treatment time at 30min.

[0040] Step 2) Weigh 16g of copper sulfate and 16.48g of manganese nitrate solution (concentration 50%), prepare 100ml of solution, and add the copper sulfate and manganese nitrate solution to the pore-expanding silica gel solution treated in Step 1) under the action of ultrasound, control the temperature at 75℃, and add the materials for 1.5h.

[0041] Step 3) The catalyst precursor obtained in Step 2) is directly dried, cooled, washed, filtered, dried at 110℃ for 22h, and calcined at 400℃ for 5h to obtain catalyst C4.

[0042] ICP testing revealed that the catalyst C4 contained 88 wt% support, 8 wt% CuO as the active component, and 4 wt% MnO2 as the auxiliary agent.

[0043] Catalyst Preparation Example 5

[0044] Step 1) Weigh 28g of KOH and dissolve it in 200ml of deionized water to prepare an alkaline solution. Weigh 90g of coarse-porous silica gel and add it to the alkaline solution under the action of ultrasound. Control the solution temperature at 45℃ and the treatment time at 50min.

[0045] Step 2) Weigh 11.81g of copper chloride and 10.5g of manganese sulfate solution (concentration 50%), prepare 100ml of solution, and add the copper chloride and manganese sulfate solution to the pore-expanding silica gel solution treated in step 1) under the action of ultrasound, control the temperature at 75℃, and add the materials for 1.5h.

[0046] Step 3) The catalyst precursor obtained in Step 2) is directly dried, cooled, washed, filtered, dried at 120°C for 20 h, and calcined at 350°C for 3 h to obtain catalyst C5.

[0047] ICP testing revealed that catalyst C5 contained 90 wt% support, 7 wt% CuO as the active component, and 3 wt% MnO2 as the auxiliary agent.

[0048] Catalyst Preparation Example 6

[0049] Step 1) Weigh 20g of NaOH and dissolve it in 200ml of deionized water to prepare an alkaline solution. Weigh 85g of coarse-porous silica gel and add it to the alkaline solution under the action of ultrasound. Control the solution temperature at 55℃ and the treatment time at 25min.

[0050] Step 2) Weigh 16.88g of copper chloride and 10.5g of manganese sulfate solution (concentration 50%), prepare 100ml of solution, add copper chloride and manganese sulfate solution to the expanded silica gel solution treated in step 1) under the action of ultrasound, control the temperature at 80℃, and add the material for 2 hours.

[0051] Step 3) The catalyst precursor obtained in Step 2) is directly dried, cooled, washed, filtered, dried at 110℃ for 22h, and calcined at 350℃ for 4h to obtain catalyst C6.

[0052] ICP testing revealed that the C6 catalyst contained 85 wt% support, 10 wt% CuO as the active component, and 3 wt% MnO2 as the auxiliary agent.

[0053] Catalyst Preparation Example 7

[0054] Step 1) Weigh 28g of KOH and dissolve it in 200ml of deionized water to prepare an alkaline solution. Weigh 92g of coarse-porous silica gel and add it to the alkaline solution under the action of ultrasound. Control the solution temperature at 60℃ and the treatment time at 30min.

[0055] Step 2) Weigh 11.8g of copper nitrate and 12.36g of manganese nitrate solution (concentration 50%), prepare 100ml of solution, and add the copper nitrate and manganese nitrate solution to the pore-expanding silica gel solution treated in Step 1) under the action of ultrasound, control the temperature at 85℃, and add the materials for 1 hour.

[0056] Step 3) The catalyst precursor obtained in Step 2) is directly dried, cooled, washed, filtered, dried at 100℃ for 24h, and calcined at 420℃ for 6h to obtain catalyst C7.

[0057] ICP testing revealed that the catalyst C7 contained 92 wt% support, 5 wt% CuO as the active component, and 3 wt% MnO2 as the auxiliary agent.

[0058] Catalyst Preparation Comparative Example 1

[0059] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not perform the alkaline treatment operation in step (1). Catalyst DC1 is obtained.

[0060] ICP testing revealed that catalyst DC1 contained 94 wt% support, 5 wt% CuO as the active component, and 1 wt% MnO2 as the auxiliary agent.

[0061] Catalyst Preparation Comparative Example 2

[0062] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses hierarchical porous activated carbon as raw material. Catalyst DC2 was obtained.

[0063] ICP testing revealed that the catalyst DC2 contained 85 wt% support, 10 wt% CuO as the active component, and 5 wt% MnO2 as the auxiliary agent.

[0064] Catalyst preparation Comparative Example 3

[0065] The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, step 1) of silica gel modification is as follows: the raw silica gel is washed with deionized water and then placed in a reactor containing deionized water. The reactor temperature is controlled at 120°C and the reaction pressure at 0.45 MPa. Nitric acid solution is added to adjust the acidity of the solution. The treatment time is 2 hours, and then it is washed with deionized water until the pH of the washing solution is 7.0. Catalyst DC3 is obtained.

[0066] ICP testing revealed that the catalyst DC3 contained 90 wt% support, 7 wt% CuO as the active component, and 3 wt% MnO2 as the auxiliary agent.

[0067] Catalyst preparation Comparative Example 4

[0068] The difference between Comparative Example 4 and Example 1 is that Comparative Example 4 did not add manganese nitrate solution. Catalyst DC4 was obtained.

[0069] ICP testing revealed that the support content in catalyst DC4 was 90 wt%, and the content of the active component CuO was 10 wt%.

[0070] The silicone materials after comparative treatment in some embodiments were tested, and the parameters of the coarse-pore silicone materials obtained by BET testing are shown in Table 1 below:

[0071] Table 1

[0072]

[0073] Test Example 1: Catalyst Activity Evaluation Test

[0074] Take 10 ml of C1-C7 and DC1-DC3 catalysts and pack them into a fixed-bed reactor. Before the reaction, reduce the catalyst at 180℃, 0.2 MPa, and a 5% hydrogen concentration nitrogen-hydrogen atmosphere for 12 h, then cool to 160℃. The reaction pressure is atmospheric pressure, and the nitrobenzene feed rate is 0.6 h. -1 The H2 flow rate was 250 ml / min, and the results are shown in Table 2.

[0075] Table 2

[0076]

[0077]

[0078] As can be seen from the data in Table 1, when the catalyst designed by the technical solution of this invention is applied to the gas-phase hydrogenation reaction of nitrobenzene to aniline, the conversion rate of nitrobenzene reaches 100% and the selectivity of aniline reaches more than 99%, indicating that the catalyst has good performance.

[0079] Test Example 2: Evaluation of Catalyst Activity Based on Reaction Conditions

[0080] Take 10 ml of C1 catalyst and fill it into a fixed-bed reactor. Before the reaction, reduce the catalyst at 180℃, 0.2 MPa and 5% hydrogen concentration in a nitrogen-hydrogen atmosphere for 12 h. Then change the reaction conditions and test the results. The results are shown in Table 3.

[0081] Table 3

[0082]

[0083] Based on the above test results, it can be seen that using alkaline etching on coarse-porous silica supports can give the supports a more suitable pore structure, which is conducive to the diffusion of reactants and products and improves the strength of the supports. The etched support portion is then redeposited on the supports with active components and additives, thereby strengthening the interaction between the supports and active components, preventing the active components from falling off during use, and further improving the catalyst life.

[0084] The addition of additives further improves the dispersion of active components, strengthens their interaction with the support, and limits the grain growth caused during use, thereby improving catalyst activity.

[0085] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing a catalyst for the gas phase hydrogenation of nitrobenzene to aniline, characterized in that Includes the following steps: (1) Under ultrasonic conditions, coarse-pore silica gel was added to an alkaline solution for etching; (2) Continue adding copper and manganese salt solutions and control the temperature. (3) Pour out the product from step (2), wash, filter, dry and calcine to obtain the catalyst for the gas-phase hydrogenation of nitrobenzene to aniline.

2. The preparation method according to claim 1, characterized in that: The weight ratio of the coarse-pore silica gel, copper salt, and manganese salt is (85-92):(8-24):(10-21).

3. The preparation method according to claim 1, characterized in that: The alkaline solution in step (1) is any aqueous solution of sodium hydroxide or potassium hydroxide; the concentration of the alkaline solution is 2.5 mol / L.

4. The preparation method according to claim 1, characterized in that: The diameter of the coarse hole of the silica gel after the step (1) etching is 150-600 μm, the specific surface area is 400-500 m 2 / g, and the average pore size is 2-5 nm.

5. The preparation method according to claim 1, characterized in that: The ultrasonic conditions for step (1) are an ultrasonic frequency of 50-100kHz, a time of 20-50min, and a temperature of 45-65℃.

6. The preparation method according to claim 1, characterized in that: The copper salt in step (2) is any one of copper nitrate, copper sulfate, and copper chloride; the manganese salt in step (2) is any one of manganese nitrate and manganese sulfate.

7. The preparation method according to claim 1, characterized in that: The temperature control conditions for step (2) are 65-85℃ and 1-2h.

8. The preparation method according to claim 1, characterized in that: The drying temperature in step (3) is 100-120℃ and the drying time is 20-24h; the calcination temperature is 350-450℃ and the calcination time is 2-6h.

9. The catalyst prepared by the method according to any one of claims 1-8, characterized in that: The catalyst, by mass percentage, comprises 85-92% coarse-porous silica gel support, 5-10% CuO active component, and 3-5% MnO2 auxiliary agent.

10. The application of the catalyst according to claim 9 in the gas-phase hydrogenation of nitrobenzene to aniline.

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