Catalysts for the synthesis of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, methods of preparation and use thereof

Abstract

The application discloses a catalyst for synthesizing 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, a preparation method and application thereof. Single-atom Pd is loaded on a nitrogen-doped biomass pyrolysis carbon carrier to catalyze synthesis of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, so that the product 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl has a higher yield under the condition that the loading amount of the active metal Pd is lower, and the use cost of the catalyst is reduced. The catalyst has a long service life, and the product still has a high yield after being repeated for more than 30 times, and the catalyst has good stability. In addition, the raw material biomass has low cost and a wide source, and the prepared carrier has a large specific surface area and pore distribution, which is beneficial to cost saving and improvement of the activity of the catalyst.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalyst preparation, and particularly relates to a catalyst for synthesizing 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, a preparation method and application thereof. BACKGROUND

[0002] 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl is an excellent material chemical intermediate product, and is also one of important raw materials for synthesizing soluble polyimide. Due to the two trifluoromethyl groups at the 2,2'-position in the molecular structure, the space steric hindrance effect causes a torsion angle between the two benzene rings of biphenyl, resulting in a non-planar structure. Therefore, the polyimide film material of the diamine monomer with TFDB as the core has many special properties, such as high solubility, light color, high thermal stability, good mechanical strength and good light transmittance. Therefore, it has great industrial value to study the large-scale production method of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl.

[0003] The most studied method at present is through rearrangement of 3,3'-bis(trifluoromethyl) diphenylhydrazine, that is, m-nitrotrifluoromethylbenzene is used as a raw material, and 3,3'-bis(trifluoromethyl) diphenylhydrazine can be prepared by zinc powder or catalytic hydrogenation in alkaline solution. The synthesis method reported in Chinese patent CN101525294A uses alcohol and aromatic hydrocarbon as solvents, and m-nitrotrifluoromethylbenzene is reduced by Zn powder to prepare 3,3'-bis(trifluoromethyl) diphenylhydrazine in an inorganic alkaline solution, and then rearranged by an inorganic acid, the solvent is recovered by liquid separation, the water phase is neutralized, and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl is obtained by recrystallization. The industrial zinc powder reduction has problems of large amount of zinc powder, large amount of waste alkaline solution and zinc oxide solid waste, etc. The three wastes problems lead to high environmental protection cost, and the product has many impurities and low yield, which is not conducive to industrial production. The method of using palladium-carbon catalyst can solve the problem of large amount of waste water produced by zinc powder reduction. Chinese patent CN109232273A uses m-nitrotrifluoromethylbenzene as a raw material, uses phase transfer catalyst, auxiliary catalyst and Pd / C as a catalytic system, uses aromatic hydrocarbon as a solvent, and synthesizes 3,3'-bis(trifluoromethyl) diphenylhydrazine by hydrogenation reaction in an inorganic alkaline solution. 3,3'-bis(trifluoromethyl) diphenylhydrazine is rearranged in an inorganic acid aqueous solution to obtain 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl.

[0004] This method uses hydrogen as a reducing agent and Pd / C as a catalyst. The loading amount of Pd is high, and Pd is seriously detached after the reaction is repeated for several times, resulting in waste of the catalyst and inability to reuse. Moreover, Pd is a noble metal catalyst and belongs to a rare resource, which is expensive, leading to high cost and being not suitable for industrial production. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art, and to provide a catalyst for 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl with high activity, long service life, low loading and cost advantage, and a preparation method thereof.

[0006] A catalyst for synthesizing 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, the catalyst has a nitrogen-doped biomass pyrolysis carbon as a carrier, and metal monatomic Pd is dispersed in the carrier; the mass percentage of the metal monatomic Pd in the catalyst is 0.01-1wt%, preferably 0.01-0.2wt%, and further preferably 0.08-0.2wt%.

[0007] According to an embodiment of the present application, the nitrogen doping amount in the catalyst is 1-5wt%.

[0008] According to an embodiment of the present application, the precursor of the biomass pyrolysis carbon is biomass, and preferably one or more of peanut shell, coconut shell, cotton shell and corn cob.

[0009] According to an embodiment of the present application, the catalyst is prepared by a one-pot method using biomass, a palladium salt and a nitrogen dopant as raw materials.

[0010] The second object of the present application is to provide a preparation method of the catalyst, which specifically comprises the following steps:

[0011] (1) placing biomass and a nitrogen dopant in a palladium salt solution for soaking treatment;

[0012] (2) filtering, drying and calcining under an inert atmosphere to obtain the catalyst.

[0013] According to an embodiment of the present application, the nitrogen dopant is one or more of urea, melamine and amino acid.

[0014] According to an embodiment of the present application, the palladium salt is one or more of palladium chloride, palladium acetate and palladium nitrate.

[0015] According to an embodiment of the present application, the solvent of the palladium salt solution is one or more of methanol, ethanol, water and DMF; and the concentration of the palladium salt solution is 1-10wt%.

[0016] According to an embodiment of the present application, the soaking temperature is 10-50℃, and the soaking time is 1-10h.

[0017] According to an embodiment of the present application, the calcination temperature is 300-1000℃, and preferably 700-900℃; and the calcination time is 2-8h.

[0018] According to an embodiment of the present application, the inert atmosphere is nitrogen or argon.

[0019] A third object of the present application is to provide the use of the above-mentioned catalyst or the catalyst prepared by the above-mentioned preparation method in the synthesis of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl.

[0020] According to an embodiment of the present application, the above-mentioned synthesis method comprises the following steps:

[0021] S1, dissolving m-nitro-trifluorotoluene in an organic solvent and adding the catalyst thereto, placing it in a high-pressure reactor, adding an aqueous inorganic base solution, introducing H2, and stopping the reaction when H2 is no longer absorbed, to prepare 3,3'-bis(trifluoromethyl) diphenylhydrazine;

[0022] S2, under the protection of nitrogen, using 3,3'-bis(trifluoromethyl) diphenylhydrazine as a raw material, and under the action of an inorganic acid, a rearrangement reaction occurs to prepare 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl.

[0023] The reaction scheme is as follows:

[0024]

[0025] According to an embodiment of the present application, in step S1, the reaction temperature is 10-100℃, preferably 50-70℃; the reaction pressure is 0.1-1Mpa, preferably 0.3-0.6Mpa.

[0026] According to an embodiment of the present application, in step S1, the organic solvent is one or more of methanol, ethanol, and DMF, preferably methanol.

[0027] According to an embodiment of the present application, in step S2, the inorganic acid is hydrochloric acid or sulfuric acid.

[0028] Beneficial effects:

[0029] The present application uses nitrogen-doped biomass pyrolysis carbon to load single-atom Pd to catalytically synthesize 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, which realizes a high yield (first yield higher than 68%) of the product 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl under the condition of a low loading amount of active metal Pd (lower than 1wt%, even lower than 0.2wt%), reduces the use cost of the catalyst. The catalyst has a long service life, and can still ensure a high yield (higher than 64%) of the product after being repeated for more than 30 times, and has good stability. The raw material biomass has a low cost and a wide source, and the prepared carrier has a large specific surface area and pore distribution, which is conducive to cost saving and improving the activity of the catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Figure a is a TEM characterization of the peanut shell pyrolysis carbon in the catalyst prepared in Preparation Example 1;

[0031] Figure 1 Figure b is a TEM characterization of the monatomic palladium in the catalyst prepared in Preparation Example 1;

[0032] Figure 2 Figure c is a spherical aberration electron microscopy of the monatomic palladium loaded peanut shell pyrolysis carbon catalyst in the catalyst prepared in Preparation Example 1;

[0033] Figure 3 Figure d is an XRD of the monatomic palladium loaded peanut shell pyrolysis carbon catalyst in the catalyst prepared in Preparation Example 1. DETAILED DESCRIPTION

[0034] The following detailed description of the present disclosure is described in detail. It should be understood that the specific implementation described herein is only for illustration and explanation of the present disclosure, and is not intended to limit the present disclosure. It should also be understood that the following examples are only used to further illustrate the present application, and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present application are within the scope of protection of the present application. The following examples of specific process parameters are only one example in the appropriate range, i.e. those skilled in the art can select within the appropriate range according to the description herein, and are not limited to the specific values of the following examples.

[0035] The present application provides a catalyst for synthesizing 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, the catalyst is a nitrogen-doped biomass pyrolysis carbon as a carrier, and metal monatomic Pd is dispersed in the carrier; the mass percentage of metal monatomic Pd in the catalyst is 0.01-1wt%, preferably 0.01-0.2wt%, further preferably 0.08-0.2wt%, and specifically can be 0.08wt%, 0.09wt%, 0.10wt%, 0.11wt%, 0.12wt%, 0.13wt%, 0.14wt%, 0.15wt%, 0.16wt%, 0.17wt%, 0.18wt%, 0.19wt%, 0.20wt%.

[0036] According to one embodiment of the present application, the nitrogen doping amount in the above-mentioned catalyst is 1-5wt%, preferably 3-5wt%.

[0037] According to one embodiment of the present application, the precursor of the above-mentioned biomass pyrolysis carbon is biomass, preferably one or more of peanut shell, coconut shell, cotton shell, and corn cob.

[0038] According to an embodiment of the present application, the catalyst is prepared by one-pot method using biomass, palladium salt and nitrogen dopant as raw materials.

[0039] A second object of the present application is to provide a method for preparing the catalyst, which comprises the following steps:

[0040] (1) soaking biomass and nitrogen dopant in a palladium salt solution;

[0041] (2) filtering, drying and calcining under inert atmosphere to obtain the catalyst.

[0042] According to an embodiment of the present application, the nitrogen dopant is one or more of urea, melamine, thiourea and amino acid.

[0043] According to an embodiment of the present application, the palladium salt is one or more of palladium chloride, palladium acetate and palladium nitrate.

[0044] According to an embodiment of the present application, the solvent of the palladium salt solution is one or more of methanol, ethanol, water and DMF; and the concentration of the palladium salt solution is 1-10 wt%.

[0045] According to an embodiment of the present application, the soaking temperature is 10-50℃ and the soaking time is 1-10 h.

[0046] According to an embodiment of the present application, the calcining temperature is 300-1000℃, preferably 700-900℃; and the calcining time is 2-8 h.

[0047] According to an embodiment of the present application, the inert atmosphere is nitrogen or argon.

[0048] A third object of the present application is to provide the use of the catalyst or the catalyst prepared by the method as described above in the synthesis of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl.

[0049] According to an embodiment of the present application, the synthesis method comprises the following steps:

[0050] S1, dissolving m-nitro-trifluoromethylbenzene in an organic solvent and adding the catalyst thereto, placing it in a high-pressure reactor, adding an aqueous inorganic base solution, passing in H2, and stopping the reaction when H2 is no longer absorbed, to prepare 3,3'-bis(trifluoromethyl)hydrazobenzene;

[0051] S2, under nitrogen protection, using 3,3'-bis(trifluoromethyl)hydrazobenzene as a raw material, and under the action of an inorganic acid, to undergo a rearrangement reaction to prepare 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl.

[0052] According to an embodiment of the present application, in step S1, the reaction temperature is 10-100°C, preferably 50-70°C; the reaction pressure is 0.1-1Mpa, preferably 0.3-0.6Mpa.

[0053] According to an embodiment of the present application, in step S1, the organic solvent is one or more of methanol, ethanol, and DMF, preferably methanol.

[0054] According to an embodiment of the present application, in step S2, the inorganic acid is hydrochloric acid or sulfuric acid.

[0055] The present application is further illustrated by the following examples, but the present application is not limited in any way by the examples. The instruments and reagents used in the examples are conventional for those skilled in the art, unless otherwise specified.

[0056] Preparation Example 1

[0057] The active component, palladium chloride, was prepared into a 5wt% methanol solution. Peanut shells and urea were placed in the palladium chloride solution and soaked at 25°C for 6h. After filtration and drying, the catalyst was calcined at 700°C under an argon atmosphere for 5h to obtain a Pd-N-C-1 single-atom catalyst. The mass fraction of the active component Pd in the catalyst was 0.08wt%, and the doping amount of N was 5wt%. The obtained catalyst was characterized, and it was found through the characterization analysis that the support had a rich pore structure, and the atomic palladium was uniformly dispersed on the support, which could well support the palladium atoms and provide a stable coordination environment for the palladium atoms.

[0058] Figure 1 FIG. a of the drawing is a TEM characterization diagram of the peanut shell pyrolytic carbon in the catalyst prepared in Preparation Example 1;

[0059] Figure 1 FIG. b of the drawing is a TEM characterization diagram of the single-atom palladium in the catalyst prepared in Preparation Example 1;

[0060] Figure 2 FIG. is a spherical aberration electron microscope diagram of the single-atom palladium loaded peanut shell pyrolytic carbon catalyst in the catalyst prepared in Preparation Example 1;

[0061] Figure 3 FIG. is an XRD diagram of the single-atom palladium loaded peanut shell pyrolytic carbon catalyst in the catalyst prepared in Preparation Example 1.

[0062] Preparation Example 2

[0063] The active component palladium nitrate was prepared into a 5wt% solution, and the coconut shell and melamine were placed in the palladium nitrate solution, soaked at 25°C for 6h, filtered, dried, and calcined at 900°C under a nitrogen atmosphere for 5h to obtain the Pd-N-C-2 monatomic catalyst; the mass fraction of the active component Pd in the catalyst was 0.12wt%, and the doping amount of N was 3wt%.

[0064] Preparation Example 3

[0065] The active component palladium nitrate was prepared into a 5wt% solution, and the coconut shell and melamine were placed in the palladium nitrate solution, soaked at 25°C for 6h, filtered, dried, and calcined at 900°C under a nitrogen atmosphere for 5h to obtain the Pd-N-C-2 monatomic catalyst; the mass fraction of the active component Pd in the catalyst was 0.12wt%, and the doping amount of N was 3wt%.

[0066] Preparation Example 4

[0067] The active component palladium nitrate was prepared into a 5wt% solution, and the coconut shell and melamine were placed in the palladium nitrate solution, soaked at 25°C for 6h, filtered, dried, and calcined at 900°C under a nitrogen atmosphere for 5h to obtain the Pd-N-C-2 monatomic catalyst; the mass fraction of the active component Pd in the catalyst was 0.12wt%, and the doping amount of N was 3wt%.

[0068] Preparation Example 5

[0069] The active component palladium nitrate was prepared into a 5wt% solution, and the coconut shell and melamine were placed in the palladium nitrate solution, soaked at 25°C for 6h, filtered, dried, and calcined at 900°C under a nitrogen atmosphere for 5h to obtain the Pd-N-C-2 monatomic catalyst; the mass fraction of the active component Pd in the catalyst was 0.12wt%, and the doping amount of N was 3wt%.

[0070] Example 1

[0071] In a 1000mL autoclave, 43.8g (0.225mol) of m-nitro-trifluoromethylbenzene was dissolved in 100.0mL of methanol, 1g of monatomic catalyst Pd-N-C-1 was added, 13.7g of 40% sodium hydroxide aqueous solution was added, H2 was introduced, the pressure was increased to 0.4MPa, and the reaction was carried out at 65°C with vigorous stirring for 2.5h until no hydrogen was absorbed, the stirring was stopped, the monatomic catalyst Pd-N-C-1 was recovered by filtration, and 42g of 3,3'-bis(trifluoromethyl)hydrazinylbenzene methanol solution was obtained, with a GC content of 99.5%.

[0072] Into a 1000mL three-necked flask, 120g of 30wt% hydrochloric acid solution was added under nitrogen protection, stirring was started, and all of the 42g of 3,3'-bis(trifluoromethyl)hydrazinylmethanol solution obtained in the above process was added dropwise at 20°C, and the reaction was allowed to proceed for 3h. Sampling was performed for high performance liquid chromatography analysis after standing. After the reaction was completed, 25wt% NaOH solution was prepared for neutralization, and the p H was adjusted to 9-10. A large amount of yellowish solid was precipitated in the solution, which was filtered and washed with water, and then recrystallized with ethanol to obtain white crystal product 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, with a yield of 68.8wt%.

[0073] Examples 2-5

[0074] The other conditions were the same as in Example 1, except that the catalysts added were the catalysts prepared in Preparation Examples 2-5, and the specific parameters and results are shown in Table 1.

[0075] Comparative Example 1

[0076] The other conditions were the same as in Example 1, except that the catalyst added was the catalyst Pd-C-D1 prepared in Comparative Example 1, and the specific parameters and results are shown in Table 1.

[0077] Comparative Example 2

[0078] The other conditions were the same as in Example 1, except that the catalyst added was a commercially available palladium-carbon catalyst with a Pd loading of 5wt%, and the specific parameters and results are shown in Table 1.

[0079] Table 1

[0080]

[0081] As can be seen from Table 1, the yield of the catalyst prepared in the application is greatly improved compared to the catalyst without nitrogen doping. Compared with the palladium-carbon catalyst of the corresponding technology, it can be realized that under the condition of lower active metal palladium loading, it has higher catalytic activity and service life.

[0082] The process of Example 1-5 was repeated, and the same catalysts Pd-N-C-1 to Pd-N-C-5 were reused for 30 times, and the yield structure is shown in Table 2:

[0083] Table 2

[0084]

[0085]

[0086] As can be seen from Table 2, the catalyst of the present application has a low loading (0.01-1% by mass) and can be repeated for 30 times or more with a high yield.

Claims

1. The application of a catalyst in the synthesis of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, characterized in that, The catalyst uses nitrogen-doped biomass pyrolysis char as a support, with single-atom Pd metal dispersed in the support; the single-atom Pd metal accounts for 0.01-1 wt% of the catalyst by mass. The precursor of the biomass pyrolysis char is one or more of peanut shells, coconut shells, cotton hulls, and corn cobs; The nitrogen doping content in the catalyst is 1-5%wt.

2. The application according to claim 1, characterized in that, The mass percentage of the single-atom Pd in ​​the catalyst is 0.01-0.2 wt%.

3. The application according to claim 2, characterized in that, The mass percentage of the single-atom Pd in ​​the catalyst is 0.08-0.2 wt%.

4. The application according to any one of claims 1-3, characterized in that, The preparation method of the catalyst specifically includes the following steps: (1) Place the biomass and nitrogen dopant in a palladium salt solution and soak them; (2) The catalyst was obtained by filtering, drying and calcining under an inert atmosphere.

5. The application according to claim 4, characterized in that, The nitrogen dopant is one or more of urea, melamine, and amino acids.

6. The application according to claim 4, characterized in that, The palladium salt is one or more of palladium chloride, palladium acetate, and palladium nitrate.

7. The application according to claim 4, characterized in that, The calcination temperature is 300-1000℃; the calcination time is 2-8h.

8. The application according to claim 7, characterized in that, The calcination temperature is 700-900℃.

9. The application according to claim 4, characterized in that, The inert atmosphere is nitrogen or argon.

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