Method for synthesizing diphenylamine from aniline

Abstract

The invention discloses a method for synthesizing diphenylamine from aniline. According to the method, aniline is taken as a synthesis raw material, a hydrogen-bridged binuclear iridium complex [Cp * Ir (mu-H) 3IrCp *] [X] (Cp *: pentamethylcyclopentadiene, X: BF4 <->, PF6 <->, BPh4 <-> and CF3SO3 <->) is taken as a catalyst, and the diphenylamine product is obtained under the conditions that the reaction temperature is 100-300 DEG C and the reaction pressure is 0.5-4.0 MPa. According to the method, the aniline conversion rate is high, the diphenylamine selectivity is good, and after the reaction is completed, the catalyst can be recycled in a solvent polarity blending mode.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemicals, and in particular relates to a method for synthesizing diphenylamine from aniline. Background Art

[0002] Diphenylamine is a widely used chemical product, and has important applications in rubber additives, dyes, explosive stabilizers, fruit preservatives, medicines, etc. Up to now, there are more than 20 methods for synthesizing diphenylamine, and the raw materials are aniline, phenol, cyclohexanone, N-cyclohexylaniline, dicyclohexyl, etc., and the catalysts are mainly aluminum chloride, boron trifluoride, activated alumina, zeolite molecular sieves, etc. Among these methods, the method of producing diphenylamine with single aniline as raw material has the best atomic economy and the strongest feasibility for large-scale production, and has been industrialized. The production process of synthesizing diphenylamine from aniline is divided into intermittent method, gas phase continuous method, and liquid phase continuous method, among which the liquid phase continuous method is the most advanced production process at present. However, the aniline conversion rate in the above production process is low, which seriously limits the production efficiency of the process of synthesizing diphenylamine from aniline, which is also the main problem faced in the current industrial production process of diphenylamine.

[0003] US4100195 reports a method for batch synthesis of diphenylamine from aniline, wherein raw materials (including fresh aniline and recovered aniline) and ammonium fluoroborate are prepared into a slurry and added to a stainless steel reactor, and the reaction is continued for 4 hours at a reaction temperature of 345°C and a pressure of 3.85MPa. After the reaction is completed, the ammonia in the reactor is released, and the catalyst is recovered. The crude reaction product is separated to obtain a diphenylamine product, and 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, and the aniline conversion rate and diphenylamine selectivity are low, and the production equipment is severely corroded, which is not suitable for industrial application.

[0004] The document J.Porous.Mat., 2021-09-05, (10.1007 / s10934-021-01139-4GE2521293) reports a method for synthesizing diphenylamine from aniline catalyzed by Hβ molecular sieve / bentonite composite materials. Small-scale experimental studies have shown that under the conditions of reaction temperature of 315℃~320℃ and reaction pressure of 2.0MPa, the average conversion rate of aniline is less than 35%, and the selectivity can reach up to about 97%. Compared with the method reported in US4100195, although the selectivity of diphenylamine in this method is relatively good, the conversion rate of aniline is relatively low, and the problem of low reaction efficiency of aniline to diphenylamine still exists. Summary of the invention

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

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for synthesizing diphenylamine from aniline comprises the following contents:

[0008] Aniline is used as a reaction raw material, a hydrogen-bridged binuclear iridium complex is used as a catalyst, and a reaction is carried out at a reaction temperature of 100° C. to 300° C. 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.

[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 .

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

[0013] Furthermore, the reaction temperature is 150°C to 300°C, preferably 200°C to 250°C.

[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 the catalyst is 1:0.01 to 0.05.

[0017] Furthermore, the method of the present invention further comprises: after the reaction is completed, the catalyst can be recovered and reused by adding a weak polar solvent to the system after the reaction, filtering and drying. The weak polar solvent is selected from one or more of n-pentane, n-hexane, petroleum ether, benzene, toluene, etc.

[0018] Furthermore, in the synthesis method of the present invention, the filtrate obtained after filtering and recovering the catalyst is separated by recrystallization, thin layer chromatography, column chromatography or reduced pressure distillation to obtain the diphenylamine product.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The method of the present invention provides a highly efficient hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][X] (Cp*: pentamethylcyclopentadienyl; X: BF4 — PF6 — ,BPh4 — CF3SO3 — ) A method for catalyzing aniline to synthesize diphenylamine. Compared with the existing method, the method of the present invention has milder reaction conditions, simple operation, good diphenylamine selectivity, high aniline conversion rate, aniline molar conversion rate can reach 38% to 45%, and diphenylamine molar selectivity can reach 97.5% to 98.5%.

[0021] 2. In addition, the catalyst used in this method can be recycled and reused, and has good industrial production application prospects. DETAILED DESCRIPTION

[0022] The method of the present invention is described in more detail below in conjunction with specific embodiments.

[0023] The present invention provides a method for efficiently synthesizing diphenylamine. The method uses a hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][X] (Cp*: pentamethylcyclopentadienyl; X: BF4 — PF6 — ,BPh4 — CF3SO3 — ) as a catalyst, aniline as a raw material, an autoclave reaction, a reaction temperature of 100°C to 300°C, a reaction pressure of 0.5MPa to 4.0MPa, a reaction time of 0.5 to 5.0 hours, and a molar ratio of aniline to the catalyst of 1:0.005 to 0.1. After the reaction is completed, a weak polar solvent (preferably n-hexane or n-pentane) is added to the reaction solution and filtered. The filter cake is a catalyst that can be recycled and reused. The obtained filtrate can be separated by column chromatography or reduced pressure distillation to obtain diphenylamine. The molar conversion of aniline is 38% to 45%, and the molar selectivity of diphenylamine is 97.5% to 98.5%.

[0024] The reaction equation of the method of the present invention is:

[0025]

[0026] Example 1

[0027] 30 mL of aniline was added to a 100 mL stainless steel autoclave, and a hydrogen-bridged binuclear iridium complex [Cp*Ir(μ-H)3IrCp*][BF4] (Cp* is pentamethylcyclopentadienyl) was added at a molar ratio of 1:0.1. After the autoclave was sealed, it was purged and replaced with nitrogen at room temperature. After purging for 1 hour, the pressure of the autoclave was raised to 4.0 MPa, and nitrogen was continuously introduced for protection. When the pressure of the autoclave was stable, the reaction temperature was slowly increased. When the temperature inside the autoclave rose to 150°C, the heating was maintained and the reaction was continued for 5.0 hours. After the reaction was completed, the temperature was lowered under the condition of nitrogen introduction. When the temperature inside the autoclave dropped to room temperature, the nitrogen introduction was stopped and the pressure was slowly released. The obtained reaction solution was analyzed by gas chromatography. The aniline conversion rate and diphenylamine selectivity are shown in Appendix 1. Add 100 mL of n-pentane to the reaction solution, and the precipitated yellow solid is the catalyst, which can be reused after filtration and drying. After the reaction solution is subjected to reduced pressure distillation, the diphenylamine product can be obtained.

[0028] Example 2

[0029] The specific operation process is the same as that of 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 the catalyst is 1:0.05, the reaction pressure is 3.5 MPa, the reaction temperature is 180°C, the reaction time is 4.5 hours, the reaction liquid obtained by the product is subjected to gas chromatography analysis, and the aniline conversion rate and diphenylamine selectivity are shown in Appendix 1. The catalyst can be recovered by adding n-hexane to the reaction liquid according to the method in Example 1.

[0030] Change different catalysts, catalyst dosage, reaction temperature and reaction time.

[0031] Example 3

[0032] The specific operation process is the same as that of 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 the catalyst is 1:0.015, the reaction pressure is 1.5 MPa, the reaction temperature is 280°C, the reaction time is 1.0 hour, the reaction liquid obtained by the product is subjected to gas chromatography analysis, and the aniline conversion rate and diphenylamine selectivity are shown in Appendix 1. The catalyst can be recovered by adding toluene to the reaction liquid according to the method in Example 1.

[0033] Example 4

[0034] The specific operation process is the same as that of 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 the catalyst is 1:0.04, the reaction pressure is 3.0 MPa, the reaction temperature is 200°C, the reaction time is 3.5 hours, the reaction liquid obtained by the product is subjected to gas chromatography analysis, and the aniline conversion rate and diphenylamine selectivity are shown in Appendix 1. The catalyst can be recovered by adding benzene to the reaction liquid according to the method in Example 1.

[0035] Example 5

[0036] The specific operation process is the same as that of 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 the catalyst is 1:0.005, the reaction pressure is 0.5 MPa, the reaction temperature is 300°C, the reaction time is 0.5 hour, the reaction solution obtained by the product is subjected to gas chromatography analysis, and the aniline conversion rate and diphenylamine selectivity are shown in Appendix 1. The catalyst can be recovered by adding ether to the reaction solution according to the method in Example 1.

[0037] Example 6

[0038] The specific operation process is the same as that of 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 the catalyst is 1:0.02, the reaction pressure is 2.0 MPa, the reaction temperature is 250°C, the reaction time is 1.5 hours, the reaction liquid obtained by the product is subjected to gas chromatography analysis, and the aniline conversion rate and diphenylamine selectivity are shown in Appendix 1. The catalyst can be recovered by adding n-hexane to the reaction liquid according to the method in Example 1.

[0039] Table 1

[0040]

Claims

1. A method for synthesizing diphenylamine from aniline, comprising the following contents: Aniline is used as the reaction raw material, hydrogen-bridged binuclear iridium complex is used as the catalyst, and the reaction temperature is 100℃~ The reaction is carried out under the conditions of 300° C. 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.

2. The method for synthesizing diphenylamine from aniline according to claim 1, characterized in that: The general structural formula of the hydrogen-bridged binuclear iridium complex catalyst is as follows: X is BF4 — PF6 — ,BPh4 — CF3SO3 — Any one of .

3. The method for synthesizing diphenylamine from aniline according to claim 1, characterized in that: The reaction temperature is 150°C to 300°C, preferably 200°C to 250°C.

4. The method for synthesizing diphenylamine from aniline according to claim 1, characterized in that: The reaction pressure is 1.0MPa~3.0MPa.

5. The method for synthesizing diphenylamine from aniline according to claim 1, characterized in that: The reaction time is 0.5 to 5.0 hours, preferably 1.0 to 3.0 hours.

6. The method for synthesizing diphenylamine from aniline according to claim 1, characterized in that: The molar ratio of aniline to the catalyst is 1:0.01-0.

05.

7. The method for synthesizing diphenylamine from aniline according to claim 1, characterized in that: The method further comprises: after the reaction is finished, adding a weak polar solvent to the post-reaction system, filtering and drying to obtain a recovered catalyst.

8. The method for synthesizing diphenylamine from aniline according to claim 7, characterized in that: The filtrate obtained by filtration is separated by recrystallization, thin layer chromatography, column chromatography or reduced pressure distillation to obtain the diphenylamine product.

9. The method for synthesizing diphenylamine from aniline according to claim 7, characterized in that: The weak polar solvent is selected from at least one of n-pentane, n-hexane, petroleum ether, benzene and toluene.

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