A process for the synthesis of diphenylamine from aniline

Abstract

The application discloses a method for synthesizing diphenylamine from aniline. μ -H)3IrCp*][X] (Cp*: pentamethylcyclopentadiene; X: BF4 — , PF6 — , BPh4 — , CF3SO3 — ) as a catalyst, and diphenylamine is obtained under the conditions of a reaction temperature of 100-300 DEG C and a reaction pressure of 0.5-4.0 MPa. The method has high aniline conversion rate and good diphenylamine selectivity, and the catalyst can be recovered through solvent polarity adjustment after the reaction is completed.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, specifically relating to a method for synthesizing diphenylamine from aniline. Background Technology

[0002] Diphenylamine is a widely used chemical product with important applications in rubber additives, dyes, explosive stabilizers, fruit preservatives, and pharmaceuticals. Currently, there are approximately 20 methods for synthesizing diphenylamine, using raw materials such as aniline, phenol, cyclohexanone, N-cyclohexylaniline, and dicyclohexyl, and catalysts such as aluminum trichloride, boron trifluoride, activated alumina, and zeolite molecular sieves. Among these methods, the method using aniline as a single raw material to produce diphenylamine has the best atom economy and the strongest feasibility for large-scale production, and has already been industrialized. The production processes for synthesizing diphenylamine from aniline are divided into batch processes, gas-phase continuous processes, and liquid-phase continuous processes, with the liquid-phase continuous process currently being the most advanced. However, the low aniline conversion rate in these processes severely limits the production efficiency of the aniline-to-diphenylamine synthesis process, which is also the main problem currently faced in the industrial production of diphenylamine.

[0003] US4100195 discloses a method for the batch synthesis of diphenylamine from aniline. This method involves preparing a slurry of raw materials (including fresh and recycled aniline) and ammonium fluoroborate, which is then added to a stainless steel reactor. The reaction is carried out continuously for 4 hours at a temperature of 345°C and a pressure of 3.85 MPa. After the reaction, the ammonia gas in the reactor is released, and the catalyst is recovered. The crude product is separated to obtain diphenylamine. In this process, the aniline conversion rate is 35.4%, and the diphenylamine selectivity is 93.6%. This process is a traditional method for synthesizing diphenylamine from aniline, but it has low aniline conversion and diphenylamine selectivity, and it causes severe corrosion to the production equipment, making it unsuitable for industrial applications.

[0004] The literature J. Porous. Mat., 2021-09-05 (10.1007 / s10934-021-01139-4GE2521293) reports a method for synthesizing diphenylamine from aniline using an Hβ molecular sieve / bentonite composite material. Small-scale experimental studies show that under reaction conditions of 315℃~320℃ and 2.0MPa, the average aniline conversion is less than 35%, with a selectivity reaching a maximum of approximately 97%. Compared to the method reported in US4100195, although this method exhibits relatively better selectivity for diphenylamine, the aniline conversion is relatively low, and the problem of low reaction efficiency in the synthesis of diphenylamine from aniline still exists. Summary of the Invention

[0005] The problem this invention aims to solve is to provide an efficient method for synthesizing diphenylamine. This method uses aniline as the raw material and employs a hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][X](Cp*: pentamethylcyclopentadiene; X: BF4). — PF6 — BPh4 — CF3SO3 — Using a catalyst, diphenylamine can be obtained under relatively mild reaction conditions. This method has a high aniline conversion rate and good diphenylamine selectivity. After the reaction is complete, the catalyst can be recovered by adjusting the solvent polarity.

[0006] This invention is achieved through the following technical solution:

[0007] A method for synthesizing diphenylamine from aniline, comprising the following:

[0008] Using aniline as the reactant and a hydrogen-bridged binuclear iridium complex as the catalyst, the reaction was carried out at a reaction temperature of 100℃~300℃ and a reaction pressure of 0.5MPa~4.0MPa to obtain a product containing diphenylamine, wherein the molar ratio of aniline to catalyst was 1:0.005~0.1.

[0009] Furthermore, the general structural formula of the binuclear iridium complex catalyst is as follows:

[0010]

[0011] X is BF4 — PF6 — BPh4 — CF3SO3 — Any one of them.

[0012] Furthermore, the binuclear iridium complex catalyst can be synthesized according to the method described in J. Am. Chem. Soc. 1985, 107, 3502-3507.

[0013] Furthermore, the reaction temperature is 150℃~300℃, preferably 200℃~250℃.

[0014] Furthermore, the reaction pressure is 1.0 MPa to 3.0 MPa.

[0015] Furthermore, the reaction time is 0.5 to 5.0 hours, preferably 1.0 to 3.0 hours.

[0016] Furthermore, the molar ratio of aniline to catalyst is 1:0.01 to 0.05.

[0017] Furthermore, the method described in this invention further includes: after the reaction is complete, the catalyst can be recovered and reused by adding a weakly polar solvent to the reaction system, followed by filtration and drying. The weakly polar solvent is selected from one or more of n-pentane, n-hexane, petroleum ether, benzene, toluene, etc.

[0018] Furthermore, in the synthesis method described in this invention, the diphenylamine product can be obtained by recrystallization, thin-layer chromatography, column chromatography, or vacuum distillation of the filtrate obtained after filtration and catalyst recovery.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. The method of this invention provides a highly efficient hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][X](Cp*: pentamethylcyclopentadienyl; X: BF4) — PF6 — BPh4 — CF3SO3 — This invention provides a method for the catalytic synthesis of diphenylamine from aniline. Compared with existing methods, the method of this invention features milder reaction conditions, simpler operation, better diphenylamine selectivity, and higher aniline conversion. The molar conversion of aniline can reach 38%–45%, and the molar selectivity of diphenylamine can reach 97.5%–98.5%.

[0021] 2. In addition, the catalyst used in this method can be recycled and reused, and has good prospects for industrial production applications. Detailed Implementation

[0022] The method of the present invention will be described in more detail below with reference to specific embodiments.

[0023] This invention provides a highly efficient method for synthesizing diphenylamine. This method utilizes a hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][X](Cp*: pentamethylcyclopentadienyl; X: BF4). — PF6 — BPh4 — CF3SO3 — Using aniline as a raw material and employing a catalyst, a high-pressure autoclave reaction is carried out at a temperature of 100℃–300℃, a pressure of 0.5MPa–4.0MPa, and a reaction time of 0.5–5.0 hours. The molar ratio of aniline to catalyst is 1:0.005–0.1. After the reaction is complete, a weakly polar solvent (preferably n-hexane or n-pentane) is added to the reaction solution, followed by filtration. The filter cake, which is the catalyst, can be recovered and reused. The resulting filtrate is then separated by column chromatography or vacuum distillation to obtain diphenylamine. The molar conversion of aniline is 38%–45%, and the molar selectivity of diphenylamine is 97.5%–98.5%.

[0024] The reaction equation for the method of this invention is as follows:

[0025]

[0026] Example 1

[0027] 30 mL of aniline was added to a 100 mL stainless steel high-pressure reactor, followed by the addition of a hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][BF4] (Cp* being pentamethylcyclopentadienyl) at a molar ratio of 1:0.1. The reactor was sealed and purged with nitrogen at room temperature for 1 hour. The pressure was then increased to 4.0 MPa, and nitrogen was continuously introduced for protection. Once the pressure stabilized, the reaction temperature was slowly increased. When the internal temperature reached 150 °C, heating was maintained for 5.0 hours. After the reaction, the reactor was cooled under nitrogen purging. When the internal temperature returned to room temperature, nitrogen purging was stopped and the pressure was slowly released. The obtained reaction solution was analyzed by gas chromatography; the aniline conversion and diphenylamine selectivity are shown in Appendix Table 1. Add 100 mL of n-pentane to the reaction solution, and the precipitated yellow solid is the catalyst. After filtration and drying, it can be reused. After vacuum distillation of the reaction solution, diphenylamine product can be obtained.

[0028] Example 2

[0029] The specific operation process is the same as in Example 1. The catalyst is a hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][PF6] (Cp* is pentamethylcyclopentadienyl). The molar ratio of aniline to catalyst is 1:0.05. The reaction pressure is 3.5 MPa, the reaction temperature is 180 °C, and the reaction time is 4.5 hours. The reaction solution obtained from the product is analyzed by gas chromatography. The aniline conversion rate and diphenylamine selectivity are shown in Appendix Table 1. The catalyst can be recovered by adding n-hexane to the reaction solution according to the method in Example 1.

[0030] Change the catalyst, the amount of catalyst, the reaction temperature, and the reaction time.

[0031] Example 3

[0032] The specific operation process is the same as in Example 1. The catalyst is a hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][PF6] (Cp* is pentamethylcyclopentadienyl). The molar ratio of aniline to catalyst is 1:0.015. The reaction pressure is 1.5 MPa, the reaction temperature is 280 °C, and the reaction time is 1.0 hour. The reaction solution obtained from the product is analyzed by gas chromatography. The aniline conversion rate and diphenylamine selectivity are shown in Appendix Table 1. The catalyst can be recovered by adding toluene to the reaction solution according to the method in Example 1.

[0033] Example 4

[0034] The specific operation process is the same as in Example 1. The catalyst is a hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][BPh4] (Cp* is pentamethylcyclopentadienyl), the molar ratio of aniline to catalyst is 1:0.04, the reaction pressure is 3.0 MPa, the reaction temperature is 200 °C, and the reaction time is 3.5 hours. The reaction solution obtained from the product is analyzed by gas chromatography. The aniline conversion rate and diphenylamine selectivity are shown in Appendix Table 1. The catalyst can be recovered by adding benzene to the reaction solution according to the method in Example 1.

[0035] Example 5

[0036] The specific operation process is the same as in Example 1. The catalyst is a hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][BPh4] (Cp* is pentamethylcyclopentadienyl). The molar ratio of aniline to catalyst is 1:0.005. The reaction pressure is 0.5 MPa, the reaction temperature is 300 °C, and the reaction time is 0.5 hours. The reaction solution obtained from the product is analyzed by gas chromatography. The aniline conversion rate and diphenylamine selectivity are shown in Appendix Table 1. The catalyst can be recovered by adding diethyl ether to the reaction solution according to the method in Example 1.

[0037] Example 6

[0038] The specific operation process is the same as in Example 1. The catalyst is a hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][CF3SO3] (Cp* is pentamethylcyclopentadienyl). The molar ratio of aniline to catalyst is 1:0.02. The reaction pressure is 2.0 MPa, the reaction temperature is 250 °C, and the reaction time is 1.5 hours. The reaction solution obtained from the product is analyzed by gas chromatography. The aniline conversion rate and diphenylamine selectivity are shown in Appendix Table 1. The catalyst can be recovered by adding n-hexane to the reaction solution according to the method in Example 1.

[0039] Table 1

[0040]

Claims

1. A method for synthesizing diphenylamine from aniline, comprising the following steps: reacting aniline with a hydrogen-bridged dinuclear iridium complex as a catalyst at a reaction temperature of 100 ℃ to 300 ℃ and a reaction pressure of 0.5 MPa to 4.0 MPa to obtain a product containing diphenylamine; wherein the molar ratio of aniline to the catalyst is 1:0.005 to 0.1; the hydrogen-bridged dinuclear iridium complex catalyst has the following general structure: ， X is any one of BF4 — , PF6 — , BPh4 — , CF3SO3 — .

2. The process for the synthesis of diphenylamine from aniline according to claim 1, characterized in that, the reaction temperature is 150 ℃ to 300 ℃.

3. The process for the synthesis of diphenylamine from aniline according to claim 1, characterized in that, the reaction pressure is 1.0 MPa to 3.0 MPa.

4. The process for the synthesis of diphenylamine from aniline according to claim 1, characterized in that, the reaction time is 0.5 to 5.0 hours.

5. The process for synthesis of diphenylamine from aniline as claimed in claim 1 wherein, the molar ratio of aniline to the catalyst is 1:0.01 to 0.

05.

6. The process for the synthesis of diphenylamine from aniline according to claim 1, characterized in that, the method further comprises: after the reaction, adding a weak polar solvent to the post-reaction system, and then filtering and drying to obtain the recovered catalyst.

7. The process for the synthesis of diphenylamine from aniline according to claim 6, characterized in that, the obtained filtrate is separated by recrystallization, thin layer chromatography, column chromatography or vacuum distillation to obtain the diphenylamine product.

8. The process for synthesizing diphenylamine from aniline according to claim 6, wherein, the weak polar solvent is selected from one or more of n-pentane, n-hexane, petroleum ether, benzene and toluene.

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