A process for the gas phase hydrogenation of nitrobenzene to aniline

Abstract

The present application relates to a kind of gas phase hydrogenation preparation aniline method, including nitrobenzene, hydrogen is reacted under the action of catalyst to obtain aniline;The carrier of the catalyst includes modified silica gel, active component includes Cu, and auxiliary active component includes Co and / or Ce;The modification method of the modified silica gel includes that silica gel is treated with alkali;The catalyst is prepared by the following method, and active component Cu and auxiliary active component are supported on modified silica gel, then heat treatment is carried out under ammonia atmosphere, and the catalyst is obtained.The carrier silica gel of the catalyst is modified by alkali treatment in the present application, the surface and pore structure of carrier are optimized, and copper is used as active component and Ce and / or Co are used as catalyst additive, and the catalyst is modified by ammonia heat treatment;The catalyst is used for the gas phase reduction of nitrobenzene and hydrogen to prepare aniline, and it has excellent nitrobenzene conversion rate and aniline selectivity, reduces the energy consumption and cost of aniline post-processing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aromatic amine synthesis, and particularly relates to a method for preparing aniline by gas-phase hydrogenation. BACKGROUND

[0002] Aniline, also known as aminobenzene, is an organic compound with the chemical formula C6H7N, which is a colorless oily liquid and decomposes at 370 DEG C, slightly soluble in water, and easily soluble in organic solvents such as ethanol and diethyl ether. Aniline is one of the most important amine substances. It is mainly used for the manufacture of dyes, drugs, resins, and can also be used as a rubber vulcanization accelerator, etc. It can also be used as a black dye. Its derivative methyl orange can be used as an indicator for acid-base titration.

[0003] Common preparation methods of aniline include gas-phase hydrogenation of nitrobenzene and liquid-phase hydrogenation of nitrobenzene. The liquid-phase hydrogenation method, such as a method for preparing aniline by liquid-phase hydrogenation of nitrobenzene with low phenol yield disclosed in the prior art, relates to a method for preparing aniline by liquid-phase hydrogenation of nitrobenzene with low phenol yield. The raw material nitrobenzene is fed into a tower reactor at different heights, the concentration of nitrobenzene in the raw material liquid at the bottom of the reactor is controlled to be below 50%, and the mass ratio of nitrobenzene to hydrogen at the bottom of the reactor is between 6:1 and 10:1, thereby reducing the generation of by-product phenol from the raw material benzene, and further reducing the generation of phenol. The gas-phase hydrogenation method, such as a coupling reaction device and reaction method for preparing aniline by hydrogenation of nitrobenzene disclosed in the prior art, utilizes three reaction zones to finely control the reaction, and solves the problem of online regeneration and activation of coked catalyst by using the setting of two degassing tanks, thereby achieving the technical scheme of low nitrobenzene content in crude aniline, continuous reaction, long-period production target of regeneration and activation, and better solving the above technical problems, which can be applied to industrial production of aniline by hydrogenation of nitrobenzene. The gas-phase hydrogenation method, as one of the mainstream methods, still has problems such as insufficient activity of the gas-phase hydrogenation catalyst, long required period of reaction temperature, and many by-products.

[0004] Therefore, it is still of great significance to further improve the composition and structure of the catalyst, thereby optimizing the activity and selectivity of the catalyst, and further reducing the energy consumption and cost of subsequent separation of aniline. SUMMARY

[0005] The present application aims to provide a method for preparing aniline by gas-phase hydrogenation, which comprises using nitrobenzene and hydrogen as raw materials, and using a specific catalyst to catalyze the reaction to obtain aniline, wherein the catalyst uses modified silica gel treated with alkali as a carrier, modifies active components Co and / or Ce with Cu, and is prepared by ammonia thermal treatment modification; the catalyst is used for preparing aniline by gas-phase hydrogenation of nitrobenzene, has excellent nitrobenzene conversion rate and aniline selectivity, and reduces the energy consumption and cost of aniline post-treatment.

[0006] In order to achieve the object of the present application, the following technical scheme is adopted:

[0007] The application provides a method for preparing aniline by gas phase hydrogenation, comprising reacting nitrobenzene and hydrogen under the action of a catalyst to obtain aniline; a carrier of the catalyst comprises modified silica gel, an active component comprises Cu, and a promoter active component comprises Co and / or Ce.

[0008] The modification method of the modified silica gel comprises alkali treatment of silica gel.

[0009] The catalyst is prepared by the following method: loading the active component Cu and the promoter active component on the modified silica gel, and then performing heat treatment under an ammonia atmosphere to obtain the catalyst.

[0010] The synthesis of aniline by gas phase method with nitrobenzene and hydrogen as raw materials is one of main routes for synthesizing aniline at present, and silica gel loaded with Cu is generally used as a catalyst in the traditional method, but due to the performance of the catalyst itself, there are still problems such as low reaction efficiency, many by-products, high separation cost of light components, high energy consumption and the like; based on the research on the above problems, the application provides a preparation method of aniline improved based on a specific catalyst composition; the catalyst uses alkali-treated modified silica gel as a carrier, optimizes the surface and internal pore structure of the silica gel, and adds the promoter active component Co and / or Ce to form a synergistic effect with the active component Cu, thereby optimizing the selectivity of aniline in the reaction process and reducing the by-products of phenol and other components.

[0011] Preferably, the loading amount of Cu is selected from 10wt%-15wt% based on 100% of the mass of the modified silica gel, for example, 11wt%, 12wt%, 13wt% or 14wt%, and the loading amount of the promoter active component is selected from 5wt%-10wt%, for example, 6wt%, 7wt%, 8wt% or 9wt%.

[0012] In the catalyst, the loading amount of the active component and the promoter active component is selected within the above range, and the catalyst has good catalytic conversion rate and aniline selectivity.

[0013] Preferably, the alkali treatment method comprises: heat treating the silica gel under an inert atmosphere gas; and the heat treatment temperature is selected from 300°C-400°C, for example, 320°C, 350°C or 370°C.

[0014] Then, the silica gel is immersed in an ammonia water solution, and then washed and dried to obtain the modified silica gel.

[0015] Preferably, the concentration of the ammonia water solution is selected from 15wt%-30wt%, for example, 16wt%, 18wt%, 20wt%, 22wt%, 25wt% or 28wt%.

[0016] Preferably, the temperature of the impregnation in the aqueous ammonia solution is 15℃ to 30℃, such as 18℃, 20℃, 22℃, 25℃ or 28℃, etc.

[0017] Preferably, the time of the impregnation in the aqueous ammonia solution is 0.5h to 1.5h, such as 0.5h, 1h, 1.5h, etc.

[0018] Preferably, the silica gel is selected from coarse-pore silica gel, preferably coarse-pore bulk silica gel.

[0019] The conventional nitrobenzene reduction catalyst Cu / SiO2 has a transition period at the initial stage of the catalytic reaction, and the selectivity of the reaction to aniline is low and the amount of by-products such as phenol is large during the transition period. After a period of time, the selectivity of the reaction to aniline is improved, and it is found that the pore structure of the catalyst changes at this time, which indicates that the surface and pore structure of the catalyst carrier have a great influence on the catalytic performance. It is found by the present application that the above-mentioned alkali treatment operation on the silica gel carrier before loading the active component is beneficial to optimizing the surface and pore structure of the catalyst, and in combination with the loading of the active component and the specific active component, it is beneficial to improving the reaction selectivity of the catalyst.

[0020] Preferably, the catalyst is prepared by a method comprising the following steps:

[0021] (1) The silica gel is subjected to alkali treatment to obtain modified silica gel.

[0022] (2) The silica gel is immersed in a mixed solution of copper salt and auxiliary metal salt and dried.

[0023] (3) The product of step (2) is calcined at 200℃ to 300℃ (exemplary values include 220℃, 250℃ or 270℃, etc.) under an inert atmosphere, and then treated by passing ammonia gas to obtain the catalyst.

[0024] Preferably, the copper salt is selected from water-soluble copper salt, preferably copper nitrate.

[0025] Preferably, the temperature of the treatment by passing ammonia gas is selected from 200℃ to 300℃, such as 220℃, 250℃ or 270℃.

[0026] Preferably, the time of the treatment by passing ammonia gas is selected from 1h to 2h, such as 1.2h, 1.5h or 1.8h, etc.

[0027] In the present application, during the preparation of the catalyst, after the alkali-treated modified silica gel carrier is immersed in copper salt and auxiliary metal salt, it is then calcined under the protection of inert atmosphere, and the active component and the auxiliary active component are highly dispersed on the surface and in the pore structure of the carrier. Then, the modified catalyst is obtained by treating it by passing ammonia gas for reduction and surface modification. Finally, the catalyst is shaped by grinding and sieving to obtain the granular catalyst.

[0028] The catalyst is calcined under inert atmosphere, and modified by ammonia heat treatment reduction, which optimizes the interaction between the main active component, the auxiliary active component and the carrier, further improves the selectivity of the catalyst to aniline in the catalytic reaction process, and reduces the generation of by-products.

[0029] Preferably, the molar ratio of the nitrobenzene and the hydrogen is 1:5-15, such as 1:7, 1:10 or 1:13, etc.

[0030] Preferably, the auxiliary active component is selected from Co; the loading ratio of Cu to Co is 1.5-2.5:1, such as 1.6:1, 1.8:1, 2:1, 2.2:1 or 2.4:1, etc.

[0031] or the auxiliary active component is selected from Ce, and the loading ratio of Cu to Ce is 1.5-2.5:1, such as 1.6:1, 1.8:1, 2:1, 2.2:1 or 2.4:1, etc.

[0032] Preferably, the reaction of the nitrobenzene and the hydrogen is carried out in a fluidized bed reactor or a fixed bed reactor.

[0033] Preferably, the particle size of the catalyst is selected from 60-80 mesh, such as 60-70 mesh or 70-80 mesh, etc.

[0034] Preferably, the reaction temperature of the nitrobenzene and the hydrogen is selected from 150-210℃, such as 160℃, 170℃, 180℃, 190℃ or 200℃, etc.

[0035] Preferably, the reaction pressure of the nitrobenzene and the hydrogen is selected from 0.05-0.3MPa, such as 0.06MPa, 0.07MPa, 0.08MPa, 0.09MPa, 0.1MPa, 0.15MPa, 0.2MPa or 0.25MPa, etc.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] In the aniline preparation method, the carrier silica gel of the catalyst is modified by alkali treatment, which optimizes the surface and pore structure of the carrier, and copper is used as the active component and Ce and / or Co is used as the catalyst additive; the catalyst is modified by ammonia heat treatment, and the catalyst is used for the reduction of nitrobenzene and hydrogen to prepare aniline, which has excellent nitrobenzene conversion rate and aniline selectivity, and reduces the energy consumption and cost of aniline post-treatment. DETAILED DESCRIPTION

[0038] The technical solutions of the present application are further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations on the present application.

[0039] Catalyst preparation example 1

[0040] The composition of the catalyst in this embodiment is as follows: the mass ratio of the carrier, Cu and Co is 1:0.125:0.06;

[0041] The catalyst is prepared by the following method, which comprises:

[0042] (1) In a tube furnace, the coarse-pored silica gel is heat-treated at 350°C for 20 min under a nitrogen atmosphere; then it is immersed in an ammonia water solution with a concentration of 25% at room temperature for 1 h, filtered, washed with deionized water, and dried to obtain modified silica gel;

[0043] (2) A mixed salt solution of copper nitrate and cobalt nitrate is prepared, and the above modified silica gel is immersed in the mixed salt solution, and then dried;

[0044] (3) The dried product in step (2) is calcined at 250°C for 2 h under a nitrogen atmosphere; then ammonia gas is introduced, and reduction modification is carried out at 250°C for 1.5 h to obtain a modified catalyst; and the catalyst is ground and sieved to obtain catalyst particles with a size of 60-80 mesh.

[0045] Catalyst preparation example 2

[0046] The difference between this embodiment and example 1 is only that the loading amount of the auxiliary active component is replaced by Ce instead of Co, and cerium nitrate is used as the raw material in the preparation process. The other parameters and conditions are exactly the same as in example 1.

[0047] Catalyst preparation example 3

[0048] The difference between this embodiment and example 1 is only that the composition of the catalyst in this embodiment is as follows: the mass ratio of the carrier, Cu and Co is 1:0.14:0.08; the corresponding material parameters are adaptively adjusted in the preparation process, and the other parameters and conditions are exactly the same as in example 1.

[0049] Catalyst preparation example 4

[0050] The difference between this embodiment and example 1 is only that the composition of the catalyst in this embodiment is as follows: the mass ratio of the carrier, Cu and Co is 1:0.2:0.13; the corresponding material parameters are adaptively adjusted in the preparation process, and the other parameters and conditions are exactly the same as in example 1.

[0051] Catalyst preparation comparative example 1

[0052] The embodiment differs from example 1 only in that the calcination under nitrogen atmosphere in step (3) is replaced by calcination under air atmosphere, and the ammonia reduction is replaced by hydrogen reduction; other parameters and conditions are exactly the same as in example 1.

[0053] Catalyst preparation comparative example 2

[0054] The comparative example differs from comparative example 1 only in that the operation in step (1) is not performed, and other parameters and conditions are exactly the same as in comparative example 1.

[0055] Catalyst preparation comparative example 3

[0056] The comparative example differs from comparative example 1 only in that the catalyst does not contain a promoter component, and other parameters and conditions are exactly the same as in comparative example 1.

[0057] Example:

[0058] A method for preparing aniline by gas phase hydrogenation, specifically, the catalyst prepared in the catalyst preparation examples and catalyst preparation comparative examples is added in a fixed bed reactor, the particle size of the catalyst is selected from 60 mesh to 80 mesh, the catalyst loading volume is 5 mL, the inlet temperature of the feed is 180°C, the pressure is set to 0.25 MPa; the molar ratio of nitrobenzene to hydrogen in the feed composition is 1:10; the feed flow rate of nitrobenzene is 0.2 ml / min. After the reaction is stable for 40 min, the gas composition after the reaction is tested by gas chromatography, and the conversion rate of nitrobenzene and the yield of aniline are calculated. The test results are shown in Table 1.

[0059] Table 1

[0060] Catalyst Nitrobenzene conversion (%) Aniline selectivity (%) Catalyst Preparation Example 1 99.3 99.1 Catalyst Preparation Example 2 99.6 99.5 Catalyst Preparation Example 3 99.5 99.2 Catalyst Preparation Example 4 98.8 98.7 Catalyst Preparation Comparative Example 1 91.4 92.1 Catalyst Preparation Comparative Example 2 88.1 91.5 Catalyst Preparation Comparative Example 3 84.1 89.4

[0061] As can be seen from the above test results, the catalyst described in the present application has good catalytic activity and aniline selectivity, the catalyst described in the present application optimizes the pore channel and surface structure of the carrier by alkali modification of the carrier, and combines the promoter component and ammonia reduction to modify the active component and the promoter component, so that the catalytic activity of the catalyst is significantly improved; as can be seen from the above table, after the reaction is stable for 40 min, the selectivity of nitrobenzene can be as high as 99.6%, and the selectivity of aniline can be as high as 98.7% or more, and further preferably as high as 99% or more, which reduces the generation of by-product components, and is conducive to reducing the subsequent purification cost and energy consumption of the product; and the catalyst used in the preparation method described in the present application has a simple composition and low preparation cost.

[0062] The applicant states that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by those skilled in the art, and all of them fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing aniline by gas-phase hydrogenation, comprising reacting nitrobenzene and hydrogen in the presence of a catalyst to obtain aniline; characterized in that: The catalyst carrier includes modified silica gel, the active component includes Cu, and the co-active component includes Co and / or Ce; The modified silica gel modification method includes subjecting the silica gel to alkali treatment; the alkali treatment method includes: subjecting the silica gel to heat treatment under an inert atmosphere; the heat treatment temperature is selected from 300° C. to 400° C.; then immersing the silica gel in an ammonia solution, and then washing and drying the silica gel to obtain the modified silica gel; The catalyst is prepared by the following method: loading the modified silica gel with the active component Cu and the co-active component, and then heat-treating the modified silica gel under an ammonia atmosphere to obtain the catalyst; the method comprises the following steps: (1) treating silica gel with alkali to obtain modified silica gel; (2) Immersing the silica gel in a mixed solution of copper salt and metal salt of the co-active component and drying; (3) The product of step (2) is calcined at 200° C. to 300° C. under an inert atmosphere, and then ammonia is introduced for heat treatment to obtain the catalyst.

2. The method for preparing aniline by gas phase hydrogenation according to claim 1, characterized in that: Based on the mass of the modified silica gel as 100%, the loading amount of Cu is selected from 10wt% to 15wt%; the loading amount of the co-active component is selected from 5wt% to 10wt%.

3. The method for preparing aniline by gas phase hydrogenation according to claim 1, characterized in that: The silica gel is selected from coarse pore silica gel.

4. The method for preparing aniline by gas phase hydrogenation according to claim 1, characterized in that: The molar ratio of the nitrobenzene to the hydrogen is 1:5-15.

5. The method for preparing aniline by gas phase hydrogenation according to claim 1 or 2, characterized in that: The co-active component is selected from Co; the loading ratio of Cu to Co is 1.5-2.5:1; Or the co-active component is selected from Ce, and the loading ratio of Cu to Ce is 1.5-2.5:

1.

6. The method for preparing aniline by gas phase hydrogenation according to claim 1, characterized in that: The nitrobenzene and the hydrogen react in a fluidized bed reactor and / or a fixed bed reactor; The particle size of the catalyst is selected from 60 to 80 meshes.

7. The method for preparing aniline by gas phase hydrogenation according to claim 1, characterized in that: The reaction temperature of the nitrobenzene and the hydrogen is selected from 150° C. to 210° C.

8. The method for preparing aniline by gas-phase hydrogenation according to claim 1, wherein the reaction pressure of the nitrobenzene and the hydrogen is selected from 0.05 to 0.3 MPa.