Method for producing diphenylamine

Abstract

The present invention belongs to the technical field of fine chemical engineering, and specifically relates to a method for producing diphenylamine. The method comprises: in the presence of an olefin, allowing aniline to come into contact with a catalyst, and performing a condensation reaction, wherein therea re 2-4 carbon atoms in the olefin. By means of introducing an olefin into a reaction system, the method for producing diphenylamine provided in the present invention can effectively improve the conversion rate of aniline and the stability of the reaction, where the conversion rate of aniline can reach a maximum of 40.2 mol% while maintaining relatively high selectivity.

Description

Method for producing diphenylamine

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application 202311712987.5 filed on December 13, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The invention belongs to the technical field of fine chemicals, and particularly relates to a method for producing diphenylamine. Background Art

[0004] Diphenylamine is a widely used chemical product, with important applications in rubber additives, dyes, explosives stabilizers, fruit preservatives, and pharmaceuticals. Currently, there are over 20 methods for synthesizing diphenylamine. Raw materials include aniline, phenol, cyclohexanone, N-cyclohexylaniline, and dicyclohexylamine, and catalysts primarily include aluminum trichloride, boron trifluoride, activated alumina, and zeolite molecular sieves. Among these methods, the method using only aniline as a raw material offers the best atom economy, the strongest feasibility for large-scale production, and has already been industrialized. The production processes for synthesizing diphenylamine from aniline include batch, gas-phase, and liquid-phase continuous methods, with the liquid-phase continuous method currently being the most advanced. However, these processes suffer from low aniline conversion rates, severely limiting the efficiency of these processes and presenting a major challenge in the current industrial production of diphenylamine.

[0005] CN1186802A discloses a process for the continuous synthesis of diphenylamine from aniline using hydrogen. This process uses refined gas (approximately 75% hydrogen and 25% nitrogen) from a synthetic ammonia plant as the hydrogen source, and a gas-phase circulation system is constructed between the diphenylamine plant and the synthetic ammonia compression section. This process has the advantage of fully utilizing hydrogen resources, effectively increasing the aniline conversion rate and extending the catalyst life in the diphenylamine production process. Although this hydrogenation effect is relatively significant, the aniline conversion rate still does not exceed 30%.

[0006] CN103044270A also reports a process for continuously synthesizing diphenylamine from aniline using hydrogen, which aims to improve the conversion rate of aniline by developing a hydrogen-dissolving process. This process focuses on contacting the aniline feedstock with hydrogen before it enters the reactor, dissolving the hydrogen into the aniline feedstock. The hydrogen-dissolved aniline feedstock then enters the aniline continuous diphenylamine synthesis reactor, where the aniline-to-diphenylamine reaction proceeds. This method has the advantage of improving the efficiency of diphenylamine synthesis from aniline by dissolving hydrogen. However, dissolving hydrogen does not effectively improve the conversion rate of aniline. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the problems of low aniline conversion and poor reaction stability in the prior art and provide a method for producing diphenylamine. The method of the present invention has the characteristics of high aniline conversion and good reaction stability and has good industrial application prospects.

[0008] The present invention provides a method for producing diphenylamine, which comprises: contacting aniline with a catalyst in the presence of an olefin to carry out a condensation reaction; wherein the number of carbon atoms in the olefin is 2-4.

[0009] In existing aniline condensation reactions to prepare diphenylamine, the aniline condensation reaction is carried out in the presence of hydrogen and / or nitrogen. However, the inventors of the present invention have discovered that, while this method can suppress side reactions to a certain extent and improve the selectivity of diphenylamine, it is difficult to promote the aniline condensation reaction, and the aniline conversion rate remains low. Furthermore, CN106631829A discloses a method for increasing the diphenylamine conversion rate by introducing isopropyl alcohol into the reaction system. However, the aniline conversion rate still cannot exceed 30%. Furthermore, when isopropyl alcohol consumes the ammonia produced by the aniline condensation reaction, it produces water, which may poison the catalyst and hinder the long-term operation of the reaction. Furthermore, the introduction of liquid isopropyl alcohol also increases the operational complexity.

[0010] The method for producing diphenylamine provided by the present invention can effectively improve the conversion rate of aniline and the stability of the reaction by introducing olefins into the reaction system. Compared with the existing preparation method, the aniline conversion rate can reach a maximum of 40.2 mol% while maintaining the same selectivity level. DETAILED DESCRIPTION

[0011] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0012] The present invention provides a method for producing diphenylamine, which comprises: contacting aniline with a catalyst in the presence of an olefin to carry out a condensation reaction; wherein the number of carbon atoms in the olefin is 2-4.

[0013] The inventors discovered that introducing C2-C4 olefins into the reaction system effectively increases the conversion of aniline, resulting in a high overall selectivity for the target product. Furthermore, compared to the prior art method of introducing isopropyl alcohol to consume ammonia, the method provided by the present invention does not produce water, thus preventing catalyst poisoning and improving reaction stability.

[0014] According to the present invention, the olefin is selected from at least one of ethylene, propylene, 1-butene, 2-butene and isobutylene, preferably ethylene and / or propylene.

[0015] According to some particularly preferred embodiments of the present invention, the olefin is propylene. Adopting the above preferred embodiments is beneficial to further improve the aniline conversion rate and reaction stability.

[0016] According to some preferred embodiments of the present invention, the molar ratio of olefin to aniline is 1:(1-5), and can be, for example, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, and other specific but non-limiting ratios. Preferably, the molar ratio of olefin to aniline is 1:(1.5-3). Adopting the above preferred embodiment is conducive to further ensuring the selectivity of diphenylamine in the reaction solution and reducing the occurrence of side reactions.

[0017] According to the present invention, preferably, the olefin is present in gaseous form during the condensation reaction. In this preferred embodiment, the olefin gas can both act as a stripping agent, removing ammonia generated by the aniline condensation reaction from the reaction system, and also consume a small amount of the generated ammonia, thereby facilitating improved aniline conversion and diphenylamine selectivity.

[0018] According to some preferred embodiments of the present invention, the temperature of the condensation reaction is 130-220°C, preferably 150-200°C, and the liquid hourly volume space velocity of aniline is 0.01-1h -1 , preferably 0.05-0.5h -1 , the reaction pressure is 1-5 MPa, preferably 3-5 MPa. In the present invention, all pressures involved are gauge pressures. The reaction temperature for preparing diphenylamine using existing liquid-phase continuous processes is typically above 300°C. Compared to the prior art, the method provided by the present invention can significantly reduce the reaction temperature for diphenylamine synthesis. At the same time, at lower temperatures and lower space velocities, it achieves higher aniline conversion and diphenylamine selectivity.

[0019] According to the present invention, the contact reaction can be carried out in any conventional reactor in the art. Preferably, the contact reaction is carried out in a fixed bed reactor which is filled with a catalyst.

[0020] The present invention does not particularly limit the feeding method of olefins and aniline, and those skilled in the art may adjust the feeding method based on the actual reactor conditions and specific needs. For example, both olefins and aniline may be fed into the fixed-bed reactor using a top-feed method and passed through the catalyst bed; alternatively, both olefins and aniline may be fed into the fixed-bed reactor using a bottom-feed method and passed through the catalyst bed; or alternatively, olefins may be fed into the fixed-bed reactor using a bottom-feed method and aniline may be fed into the fixed-bed reactor using a top-feed method and passed through the catalyst bed.

[0021] In order to further improve the conversion rate of aniline, preferably, both olefin and aniline are fed into the fixed bed reactor in a bottom feeding manner and pass through the catalyst bed.

[0022] The present invention does not particularly limit the type and composition of the catalyst. Any catalyst conventionally used in the art for the condensation reaction of aniline to prepare diphenylamine can be used in the present invention. The present invention also does not particularly limit the source of the catalyst. The catalyst can be purchased commercially or prepared by any method known in the art.

[0023] According to some preferred embodiments of the present invention, the catalyst includes beta zeolite and a metal component.

[0024] According to the present invention, preferably, the molar ratio of silicon oxide to aluminum oxide in the beta zeolite is 20-100, preferably 50-70.

[0025] Preferably, the beta zeolite is H beta zeolite.

[0026] The present invention has a wide selection range for the metal component. In order to further improve the conversion rate of aniline, preferably, the metal component is selected from at least one of alkali metals, more preferably at least one of lithium, sodium and potassium.

[0027] According to some preferred embodiments of the present invention, based on the total mass of the catalyst, the content of the beta zeolite is 50-90wt%, for example, it can be 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt% or the like, or a range between any two thereof; the content of the metal component in terms of element is 0.1-40wt%, for example, it can be 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt% or the like, or a range between any two thereof.

[0028] More preferably, the beta zeolite content is 65-75 wt% based on the total mass of the catalyst, and the metal component content, calculated as an element, is 1-30 wt%. This preferred embodiment helps ensure a conversion rate of the raw material aniline exceeding 30%, and, under certain process conditions, suppresses side reactions, thereby producing more high-value-added products.

[0029] In the present invention, the content of metal components in the catalyst is measured by inductively coupled plasma optical emission spectrometer (ICP-OES).

[0030] According to some preferred embodiments of the present invention, the catalyst further comprises a binder to obtain a shaped catalyst body. The present invention provides a wide range of binders for selection; any binder that can be used for catalyst molding in the art can be used in the present invention. Preferably, the binder is alumina and / or silica, more preferably alumina.

[0031] Preferably, based on the total mass of the catalyst, the beta zeolite content is 50-90wt%, preferably 65-75wt%, the alkali metal content, calculated as metal elements, is 0.1-40wt%, preferably 1-30wt%, and the binder content is 0.5-49.9wt%, preferably 5-30wt%. This preferred composition is conducive to ensuring a raw material aniline conversion rate exceeding 30%, and under certain process conditions, suppressing side reactions, thereby obtaining more high-value-added products.

[0032] The present invention has no particular limitation on the shape of the catalyst, and those skilled in the art can select the size and morphology of the catalyst according to actual needs.

[0033] Preferably, the catalyst is in the form of strips or spherical particles. When in the form of strips, the cross-section can be cylindrical, clover-shaped or four-leaf-shaped. The cross-sectional width of the strip particles is 0.5-3.0 mm, preferably 1.0-2.0 mm. When in the form of spheres, the particle diameter is 0.5-5.0 mm, preferably 1.0-3.0 mm.

[0034] The present invention does not particularly limit the source of the catalyst, and the catalyst may be purchased commercially or prepared by any method known in the art. For example, the catalyst may be prepared by the method disclosed in CN200510047489.9. For example, the catalyst of the present invention may be prepared by the following method:

[0035] (1) contacting Hβ zeolite with a solution of a soluble compound of a metal component;

[0036] (2) subjecting the mixture obtained in step (1) to solid-liquid separation, washing and drying;

[0037] (3) The modified Hβ zeolite obtained in step (2), the binder and / or the binder precursor and the processing aid (such as an extrusion aid and a peptizing agent) are fully mixed and kneaded, and then formed into a mold, and then dried and calcined.

[0038] Preferably, the contact temperature of step (1) is 15-35° C. and the contact time is 0.5-2 h. For example, it can be carried out at room temperature.

[0039] Preferably, the concentration of the solution of the soluble compound of the metal component is 0.05-4 mol / L.

[0040] The present invention does not particularly limit the operating methods and conditions for the solid-liquid separation and washing, and those skilled in the art can select them according to actual needs. The solid-liquid separation can be performed, for example, by filtration. The present invention does not particularly limit the number of washing times, and can be adjusted according to actual washing conditions. The detergent used for the washing can be water.

[0041] The present invention has no particular limitation on the drying conditions in step (2). Preferably, the drying temperature is 100-130° C. and the drying time is 8-12 h.

[0042] In the present invention, the binder precursor refers to any substance that can be calcined to obtain the binder. For example, the precursor of aluminum oxide can be pseudo-boehmite and / or aluminum hydroxide, which are well known to those skilled in the art.

[0043] The present invention does not particularly limit the processing aid, and any conventional method in the art can be used. The present invention also does not particularly limit the amount of the processing aid, and those skilled in the art can select the appropriate amount based on actual needs. The extrusion aid can be, for example, sesbania powder, and the peptizing agent can be, for example, dilute nitric acid and / or citric acid. The concentration of the dilute nitric acid can generally be 3-15 wt%.

[0044] The present invention has no particular limitation on the molding method, and those skilled in the art can select the molding method according to actual needs, for example, it can be extrusion molding, tablet molding, ball molding, etc.

[0045] Preferably, the drying temperature in step (3) is 100-130° C. and the drying time is 8-12 h.

[0046] Preferably, the calcination temperature in step (3) is 450-550° C. and the calcination time is 6-8 h.

[0047] Another aspect of the present invention provides a method for producing diphenylamine from aniline, the method comprising: contacting aniline with a catalyst in the presence of propylene;

[0048] The temperature of the contact reaction is 130-220°C, preferably 150-200°C, and the liquid hourly volume space velocity of aniline is 0.01-1h -1 , preferably 0.05-0.5h -1 , the reaction pressure is 1-5MPa, preferably 3-5MPa.

[0049] The present invention will be described in detail below through examples.

[0050] In the following examples and comparative examples, unless otherwise specified, all raw materials used were commercially available.

[0051] In the following examples and comparative examples, the calculation methods for the conversion of aniline and the selectivity of diphenylamine are as follows:

[0052] Aniline molar conversion:

[0053] Wherein, ω: aniline molar conversion, mol%; n0: molar number of aniline in the raw material, mol; n2: molar number of aniline in the reaction solution, mol.

[0054] Diphenylamine molar selectivity:

[0055] Wherein, ε1: molar selectivity of diphenylamine, mol%; n1: molar number of each product component in the reaction solution, mol; n3: molar number of diphenylamine in the reaction solution, mol.

[0056] The reaction liquid refers to the mixed liquid phase obtained after the reaction. The "product" in the above formulas does not include aniline. The composition of the reaction liquid is analyzed with reference to standard HG / T5534-2019.

[0057] The catalysts used in the examples and comparative examples were prepared by the following method:

[0058] (1) contacting Hβ zeolite with a sodium chloride solution;

[0059] (2) filtering, washing and drying the mixture obtained in step (1);

[0060] (3) The modified Hβ zeolite obtained in step (2), the alumina binder precursor, the extrusion aid, and the peptizing agent are fully mixed and kneaded, and then extruded to obtain a strip catalyst with a diameter of 2 mm and a length of 2-3 mm, which is then dried and calcined.

[0061] The contact temperature of step (1) is 20°C and the contact time is 1.5 hours. The concentration of the sodium chloride solution is 0.5 mol / L. Step (2) is dried at 120°C for 10 hours, step (3) is dried at 120°C for 10 hours, and calcined at 500°C for 6 hours. The binder used is aluminum hydroxide, and the zeolite used is commercially available Hβ zeolite, with a specific surface area of ​​650m 2 / g, particle size 1.5-2mm.

[0062] The properties of the catalysts are listed in Table 1.

[0063] Table 1

[0064] Example 1

[0065] A stainless steel fixed-bed reactor with an inner diameter of 20 mm and a length of 1000 mm was loaded with 100 mL of catalyst. Aniline and propylene (commercially available, purity >99%) were introduced into the reactor via a bottom-feed system. The reaction product, exiting the reactor top, was cooled and then passed into a separator. The reaction was carried out for 48 hours according to the reaction conditions in Table 2. The composition of the reaction product was analyzed by gas chromatography, and the product distribution is shown in Table 2 below.

[0066] Examples 2-7

[0067] The method of Example 1 was followed, except that the feeding method and reaction conditions were as shown in Table 2. After 48 hours of reaction, the composition of the reaction product was analyzed by gas chromatography, and the product distribution was shown in Table 2.

[0068] Examples 8-11

[0069] The method of Example 1 was followed, except that the feeding method and reaction conditions were as shown in Table 3. After 48 hours of reaction, the composition of the reaction product was analyzed by gas chromatography, and the product distribution was shown in Table 3.

[0070] Example 12

[0071] The method of Example 1 was followed, except that propylene was replaced by an equal molar amount of ethylene.

[0072] The composition of the reaction products was analyzed by gas chromatography, and the measured product distribution is shown in Table 3 below.

[0073] Comparative Example 1

[0074] The method of Example 1 was followed, except that propylene was replaced with an equimolar amount of hydrogen. The specific reaction conditions and results are shown in Table 3.

[0075] Comparative Example 2

[0076] Diphenylamine was synthesized according to the method of CN106631829A, with a molar ratio of isopropyl alcohol to aniline of 1:1. The specific reaction conditions and results are shown in Table 3.

[0077] Table 2

[0078] Table 3

[0079] Examples 13-14

[0080] A stainless steel fixed-bed reactor with an inner diameter of 20 mm and a length of 1000 mm was loaded with 100 mL of catalyst. Aniline and propylene (commercially available, purity >99%) were introduced into the reactor via a bottom-feed system. The reaction product exited the reactor top, cooled, and then passed into a separator. The reaction conditions and product distribution are shown in Table 4.

[0081] Comparative Example 3

[0082] The method of Example 12 was followed, except that propylene was replaced with an equimolar amount of hydrogen.

[0083] The specific reaction conditions and results are shown in Table 4.

[0084] Comparative Example 4

[0085] Diphenylamine was synthesized according to the method of CN106631829A, with a molar ratio of isopropyl alcohol to aniline of 1:1. The specific reaction conditions and results are shown in Table 4.

[0086] Table 4

[0087] From the results of the above examples and comparative examples, it can be seen that the method provided by the present invention can effectively improve the conversion rate of aniline and the stability of the reaction by introducing olefins into the reaction system. While maintaining a high selectivity, the aniline conversion rate can reach a maximum of 40.2 mol%.

[0088] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for producing diphenylamine, characterized in that: The method comprises: contacting aniline with a catalyst in the presence of olefin to carry out a condensation reaction; Wherein, the number of carbon atoms in the olefin is 2-4.

2. The method according to claim 1, wherein: The olefin is selected from at least one of ethylene, propylene, 1-butene, 2-butene and isobutylene, preferably ethylene and / or propylene, more preferably propylene.

3. The method according to claim 1 or 2, wherein: The molar ratio of the olefin to the aniline is 1:(1-5), preferably 1:(1.5-3).

4. The method according to any one of claims 1 to 3, wherein: During the condensation reaction, the olefin is present in gaseous form; Preferably, the conditions of the condensation reaction include: a reaction temperature of 130-220°C, preferably 150-200°C, a liquid hourly volume space velocity of aniline of 0.01-1h -1 , preferably 0.05-0.5h -1 , the reaction pressure is 1-5MPa, preferably 3-5MPa.

5. The method according to any one of claims 1 to 4, wherein: The contact reaction is carried out in a fixed bed reactor.

6. The method according to claim 5, wherein: Olefins and aniline are fed into the fixed bed reactor by top feeding and pass through the catalyst bed; or, Olefins and aniline are fed into the fixed bed reactor and passed through the catalyst bed by bottom feeding; or, Olefins are fed into the fixed bed reactor in a bottom feeding manner, and aniline is fed into the fixed bed reactor in an top feeding manner and passes through the catalyst bed.

7. The method according to any one of claims 1 to 6, wherein: The catalyst includes beta zeolite and a metal component.

8. The method according to claim 7, wherein: The molar ratio of silicon oxide to aluminum oxide in the beta zeolite is 20-100; Preferably, the beta zeolite is H beta zeolite; Preferably, the metal component is selected from at least one of alkali metals, preferably at least one of lithium, sodium and potassium.

9. The method according to claim 7 or 8, wherein: Based on the total mass of the catalyst, the content of the beta zeolite is 50-90wt%, and the content of the metal component in terms of element is 0.1-40wt%; Preferably, based on the total mass of the catalyst, the content of the beta zeolite is 65-75 wt%, and the content of the metal component in terms of element is 1-30 wt%.

10. The method according to any one of claims 7 to 9, wherein: The catalyst further contains a binder, preferably, the binder is alumina and / or silica, more preferably alumina; Preferably, based on the total mass of the catalyst, the content of the beta zeolite is 50-90wt%, preferably 65-75wt%, the content of the alkali metal component in terms of metal element is 0.1-40wt%, preferably 1-30wt%, and the content of the binder is 0.5-49.9wt%, preferably 5-30wt%.

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