Reduction process of 2, 2-dinitrobibenzyl

Abstract

The invention relates to the technical field of chemical synthesis, and particularly discloses a reduction process of 2, 2-dinitrobibenzyl. The porous iron particles with the cavities are prepared by taking iron oxide as a raw material and adopting spray drying and hydrogen reduction sintering modes, and the porous iron particles are applied to the reduction reaction of 2, 2-dinitrobibenzyl as a reducing agent. The porous iron particles have larger specific surface area than commercially available reduced iron powder, and the cavities in the particles can enable the reduction reaction of 2, 2-dinitrobibenzyl to mainly occur on the sides, close to the surfaces, of the porous iron particles, so that the diffusion path of reactants is shortened, the higher yield can be achieved after the reaction is carried out for 1.5-2 hours, and the method is suitable for industrial production. And the production efficiency of 2, 2-diaminobiphenyl can be fully improved.

Description

Technical Field

[0001] The present application relates to the technical field of chemical synthesis, and more specifically, to a reduction process of 2,2-dinitrobibenzyl. Background Art

[0002] Iminostilbene is an organic compound with a wide range of uses. Iminostilbene has high physiological activity and can prevent and treat hepatitis C. It can also be used as an intermediate for the synthesis of anti-epileptic drugs carbamazepine and oxcarbazepine and antidepressant imipramine. In the field of catalysts, iminostilbene can stabilize the anion complex of rhodium catalysts and can be used to synthesize automobile exhaust catalysts. In addition, iminostilbene is also an important synthetic raw material in genetic engineering and materials science, for example, it can be used as a synthetic raw material for porphyrin compounds.

[0003] According to the current mainstream synthesis process, iminostilbene needs to be synthesized using 2,2-diaminobibenzyl as an intermediate, and 2,2-diaminobibenzyl is usually obtained by reducing 2,2-dinitrobibenzyl. In the related art, there is a reduction process for 2,2-dinitrobibenzyl, which includes the following steps: mixing 2,2-dinitrobibenzyl, reduced iron powder, distilled water and ammonium chloride, stirring and heating to the reaction temperature and then keeping the temperature, filtering the product after the insulation, adding phosphoric acid to the filtrate, filtering again and washing the filter residue with ethyl acetate, and drying the filter residue to obtain 2,2-diaminobibenzyl.

[0004] Regarding the above-mentioned related technologies, the inventors believe that although the methods in the related technologies can reduce 2,2-dinitrobiphenyl to 2,2-diaminobiphenyl, it usually takes more than 3 hours to obtain a high yield, resulting in difficulty in further improving the production efficiency of 2,2-diaminobiphenyl. Summary of the invention

[0005] In the related art, the reduction reaction of 2,2-dinitrobiphenyl usually takes more than 3 hours to obtain a high yield, which makes it difficult to further improve the production efficiency of 2,2-diaminobiphenyl. In order to improve this defect, the present application provides a reduction process of 2,2-dinitrobiphenyl.

[0006] The present application provides a reduction process of 2,2-dinitrobibenzyl, which adopts the following technical solution: A reduction process for 2,2-dinitrobibenzyl comprises the following steps: (1) adding iron oxide powder, a binder, a defoamer and a surfactant into water to mix into a slurry, spray granulating the slurry to obtain iron oxide pellets, and subjecting the iron oxide pellets to hydrogen reduction sintering at a sintering temperature of 500-600° C. to obtain porous iron particles; in this step, the iron oxide pellets have cavities inside; (2) Mix 2,2-dinitrobibenzyl, porous iron particles, a solvent and ammonium chloride to obtain a reaction solution, heat the reaction solution at 80-95° C. for 1.5-2 h, filter the reaction solution with a sand core funnel covered with diatomaceous earth, and then rinse the diatomaceous earth with methanol to obtain a filtrate; evaporate the filtrate under reduced pressure, then add dichloromethane to dissolve and filter, and evaporate the newly obtained filtrate under reduced pressure to obtain 2,2-diaminobibenzyl.

[0007] By adopting the above technical scheme, the present application first uses iron oxide powder as raw material, and spray granulation is carried out with the assistance of a binder, a defoamer and a surfactant. During the spray drying process, water vapor evaporates on the surface of the droplets formed by spray dispersion, the water inside the droplets moves to the surface, and organic matter such as adhesives and part of the iron oxide powder also migrate and arrange to the surface of the droplets, and form a shell with a certain microporous structure on the surface of the droplets. As the temperature of the droplets increases, the evaporation of water cannot completely dry the particles, the water inside the droplets vaporizes, and a hollow structure is formed inside the droplets through volume expansion, thereby obtaining an iron oxide agglomerate with a solid shell with micropores on the outside and a cavity on the inside. After the iron oxide agglomerates are sintered and reduced by hydrogen, the organic matter undergoes thermal decomposition, and the iron oxide powder is reduced to iron powder by hydrogen, and the internal cavity is also retained. With the growth of grains during the reduction process, point contact and mechanical bite between adjacent iron powders are transformed into surface contact and grain boundary bonding, and the particles are sintered to form a mesh structure. After the hydrogen reduction sintering is completed, porous iron particles with cavities inside can be obtained. The porous iron particles prepared according to the conditions of this application have a larger specific surface area than commercially available reduced iron powder, and the cavities formed during the spray drying process can also be retained, so that the reduction reaction of 2,2-dinitrobibenzyl mainly occurs on the side of the porous iron particles close to the surface, shortening the diffusion path of the reactants, so that a higher yield can be achieved when the reaction is carried out for 1.5-2 hours, which helps to fully improve the production efficiency of 2,2-diaminobiphenyl.

[0008] Preferably, in step (1) of the process, the sintering temperature is 500-550°C.

[0009] By adopting the above technical solution, the present application optimizes the temperature of hydrogen reduction sintering. By selecting a lower range within the range of 500-600°C, the bonding tightness between the iron powder particles can be limited, which helps to obtain porous iron particles with a larger specific surface area.

[0010] Preferably, in step (1) of the process, the hydrogen reduction sintering is carried out at the sintering temperature for 4-5 hours.

[0011] By adopting the above technical solution, the present application optimizes the time of hydrogen reduction sintering, which can limit the bonding tightness between iron powder particles while fully reducing the iron oxide, and is helpful to obtain porous iron particles with relatively ideal specific surface area.

[0012] Preferably, in step (1) of the process, the iron oxide powder used has a D 50 The particle size is 300-350nm.

[0013] By adopting the above technical solution, the present application preferably selects the D of the iron oxide powder. 50 Particle size range: within the above particle size range, the iron oxide powder can fully contact with hydrogen and undergo a reduction reaction, and the prepared porous iron particles can have a relatively ideal specific surface area.

[0014] Preferably, in step (1) of the process, the average particle size of the iron oxide agglomerates obtained by spray granulation is 47-76 μm.

[0015] By adopting the above technical solution, the present application optimizes the specific surface area of ​​the iron oxide particles.

[0016] Preferably, the ratio between the average diameter of the cavities inside the iron oxide agglomerates and the average particle size of the iron oxide agglomerates is 0.38-0.51.

[0017] By adopting the above technical solution, the porous iron particles can have a sufficiently large cavity inside, which is helpful to obtain porous iron particles with relatively ideal reduction performance.

[0018] Preferably, in step (2) of the process, the solvent used is a mixture of water and ethanol.

[0019] By adopting the above technical solution, the role of water in the reduction reaction is to provide proton hydrogen and transfer heat, and mixing water with ethanol can promote the reduction reaction and help improve the reaction efficiency.

[0020] Preferably, in step (2) of the process, the solvent used is a mixture of water and ethanol in a volume ratio of 2:1.

[0021] By adopting the above technical solution, the present application optimizes the volume ratio of water and ethanol, which helps to fully improve the reaction efficiency.

[0022] Preferably, in step (2) of the process, the reaction solution is heated at 87-92°C.

[0023] By adopting the above technical solution, within the range of 80-95°C, the reaction yield shows a trend of increasing first and then decreasing as the temperature rises. This is because when the temperature is too low, the iron powder has low reactivity and does not participate in the reaction; when the temperature is too high, the side reactions increase, resulting in a decrease in the yield. In the preferred temperature range of the present application, the iron powder has a higher reactivity and is not prone to side reactions, which helps to obtain a higher product yield.

[0024] Preferably, the molar ratio between the iron element and 2,2-dinitrobibenzyl in the porous iron particles is (6.5-7.5):1.

[0025] By adopting the above technical solution, the present application optimizes the molar ratio between the iron element and 2,2-dinitrobibenzyl, which helps to obtain a more ideal yield in a shorter time.

[0026] In summary, this application has the following beneficial effects: 1. This application uses iron oxide as a raw material, and adopts the method of spray drying followed by hydrogen reduction sintering to prepare porous iron particles with cavities, and applies the porous iron particles as a reducing agent to the reduction reaction of 2,2-dinitrobibenzyl. The porous iron particles of this application have a larger specific surface area than commercially available reduced iron powder, and the cavities inside the particles make the reduction reaction of 2,2-dinitrobibenzyl mainly occur on the side of the porous iron particles close to the surface, shortening the diffusion path of the reactants. Therefore, a high yield can be achieved when the reaction is carried out for 1.5-2 hours, which helps to fully improve the production efficiency of 2,2-diaminobiphenyl.

[0027] 2. The temperature and time of hydrogen reduction sintering are preferably selected in the present application, which can limit the bonding tightness between the iron powder particles while fully reducing the iron oxide, and help to obtain porous iron particles with a relatively ideal specific surface area. DETAILED DESCRIPTION

[0028] The present application is further described in detail below in conjunction with the embodiments, comparative examples and comparative examples. The raw materials involved in the present application can all be obtained commercially. Example

[0029] Examples 1-5 The following description is given by taking Example 1 as an example.

[0030] Example 1 In this embodiment, the D 50 The particle size is 300 nm (referred to as iron oxide powder particle size in Table 1), the binder is polyvinyl alcohol (CAS: 9002-89-5), and the defoamer is a mixture of tributyl phosphate, Span 20, and n-octanol in a weight ratio of 4:3:3.

[0031] This embodiment provides a reduction process of 2,2-dinitrobibenzyl, comprising the following steps: (1) Add iron oxide powder, binder, defoamer and surfactant into water and mix them into slurry. After the slurry is subjected to airflow spray granulation, iron oxide agglomerates with an average particle size of 76 μm (referred to as iron oxide agglomerate particle size in Table 1) are obtained. Turn on the power of the carbon selenium rod furnace, set the heating rate to 20°C / min, adjust the heating rate to 30°C / min after reaching 300°C, add the iron oxide agglomerates into the furnace body when the furnace temperature reaches 400°C, continue to heat to 600°C, and then continue to heat the furnace body. The iron oxide pellets were subjected to hydrogen reduction sintering at a sintering temperature of 600° C. for 5 h to obtain porous iron particles; in this step, the iron oxide pellets had cavities inside, and the ratio between the average diameter of the cavities and the average particle size of the iron oxide pellets was 0.51 (referred to as the cavity diameter ratio in Table 1); in this step, the weight of the iron oxide powder accounted for 40% of the total weight of the slurry, the amount of the binder was 3% of the total weight of the iron oxide powder, and the amount of the defoamer was 0.5% of the total weight of the iron oxide powder; (2) 2,2-dinitrobibenzyl, porous iron particles, a solvent and ammonium chloride are mixed to obtain a reaction solution, the reaction solution is heated at 80° C. for 2 h (referred to as the reaction time in Table 1), the reaction solution is filtered using a sand core funnel covered with diatomaceous earth, and the diatomaceous earth is rinsed with methanol for 3 times to obtain a filtrate; the filtrate is subjected to vacuum rotary evaporation, and then dichloromethane is added to dissolve the filter residue, and the filtrate is filtered again, and the filtrate is subjected to vacuum rotary evaporation to obtain 2,2-diaminobibenzyl; in this step, the solvent is distilled water, and the ratio of the amount of 2,2-dinitrobibenzyl to the solvent is 1 g:135 mL; the molar ratio of ammonium chloride to 2,2-dinitrobibenzyl is 0.4:1, and the molar ratio of the iron element in the porous iron particles to the 2,2-dinitrobibenzyl is 6.5:1 (referred to as the reaction ratio in Table 1).

[0032] As shown in Table 1, the differences between Examples 1-5 mainly lie in the different production and processing parameters.

[0033] Table 1 Production and processing parameters sample Example 1 Example 2 Example 3 Example 4 Example 5 Iron oxide powder particle size / nm 350 339 327 314 300 Iron oxide particle size / μm 76 68 62 54 47 Cavity diameter ratio 0.38 0.41 0.43 0.45 0.51 Reaction time / min 90 100 110 110 120 Reaction ratio 6.5:1 6.8:1 7:1 7.3:1 7.5:1 Embodiment 5-9 As shown in Table 2, the difference between Examples 5-9 is that in step (1), the hydrogen reduction sintering is carried out at different sintering temperatures.

[0034] Table 2 Sintering temperature sample Sintering temperature / ℃ Example 5 600 Example 6 580 Example 7 550 Example 8 530 Example 9 500 Examples 9-11 As shown in Table 3, the difference between Examples 9-11 is that, in step (1), the time for hydrogen reduction sintering at the sintering temperature is different.

[0035] Table 3 Sintering time sample Sintering time / h Example 9 5 Example 10 4.5 Embodiment 11 4 Example 12 The difference between this embodiment and embodiment 11 is that in step (2), the solvent used is a mixed solution obtained by mixing water and ethanol in a volume ratio of 1:1.

[0036] Embodiment 13 The difference between this embodiment and the embodiment is that in step (2), the solvent used is a mixed solution obtained by mixing water and ethanol in a volume ratio of 2:3.

[0037] Embodiment 14 The difference between this embodiment and the embodiment is that in step (2), the solvent used is a mixed solution obtained by mixing water and ethanol in a volume ratio of 2:1.

[0038] Examples 14-18 As shown in Table 4, the difference between Examples 14-18 is that in step (2), the reaction solution is heated at different temperatures (referred to as reaction temperature in Table 4).

[0039] Table 4 Reaction temperature sample Reaction temperature / ℃ Embodiment 14 80 Embodiment 15 87 Example 16 90 Embodiment 17 92 Embodiment 18 95 Comparative Example 1 The difference between this comparative example and Example 16 is that in step (1), the time for hydrogen reduction sintering at the sintering temperature is 5.5 hours.

[0040] Comparative Example 2 The difference between this comparative example and Example 16 is that the iron oxide powder used has a D 50 The particle size is 420nm.

[0041] Comparative Example 3 The difference between this comparative example and Example 16 is that the spray granulation method is adjusted from airflow spray granulation to centrifugal spray granulation, and the obtained iron oxide agglomerates are solid particles with an average particle size of 41 μm. Such iron oxide agglomerates are used to prepare porous iron particles.

[0042] Comparative Example 4 The difference between this comparative example and Example 16 is that the molar ratio between the iron element and 2,2-dinitrobibenzyl in the porous iron particles is 6:1.

[0043] Comparative Example Comparative Example 1 The present comparative example provides a reduction process of 2,2-dinitrobibenzyl, comprising the following steps: mixing 2,2-dinitrobibenzyl, reduced iron powder, distilled water and ammonium chloride to obtain a mixed solution, stirring and heating the mixed solution at 90° C. for 3 hours, suction filtering the mixed solution with a sand core funnel covered with diatomaceous earth, and then washing the diatomaceous earth with methanol for 3 times to obtain a filtrate; performing vacuum rotary evaporation on the filtrate, then adding dichloromethane to dissolve the filter residue, filtering again, and performing vacuum rotary evaporation on the filtrate to obtain 2,2-diaminobibenzyl.

[0044] In this comparative example, the specific surface area of ​​the reduced iron powder used is 11.32 g / m 2 The ratio of 2,2-dinitrobibenzyl to distilled water is 1 g:135 mL; the molar ratio of ammonium chloride to 2,2-dinitrobibenzyl is 0.4:1, and the molar ratio of iron element in the porous iron particles to 2,2-dinitrobibenzyl is 7:1.

[0045] Comparative Example 2 The difference between this comparative example and comparative example 1 is that the time for stirring and heating the mixed liquid in the reduction process is 1.5 h.

[0046] Comparative Example 3 The difference between this comparative example and Example 1 is that the iron oxide pellets are subjected to hydrogen reduction sintering at a sintering temperature of 650°C.

[0047] Performance testing methods According to the dosage of 2,2-dinitrobibenzyl, the theoretical yield of 2,2-diaminobibenzyl is calculated according to the following overall reaction formula: 2C 14 H 12 N2O4+9Fe+4H2O→2C 14 H 16 N2+3Fe3O4. The yield of 2,2-diaminobibenzyl was calculated based on the theoretical yield and actual yield of 2,2-diaminobibenzyl. The results are shown in Table 5.

[0048] Table 5 sample Yield / % sample Yield / % Example 1 71.28 Embodiment 14 88.32 Example 2 73.17 Embodiment 15 91.77 Example 3 74.24 Example 16 93.15 Example 4 75.93 Embodiment 17 91.26 Example 5 78.42 Embodiment 18 89.23 Example 6 79.25 Comparative Example 1 87.38 Example 7 80.13 Comparative Example 2 91.27 Example 8 80.77 Comparative Example 3 82.56 Example 9 81.35 Comparative Example 4 80.64 Example 10 82.07 Comparative Example 1 92.35 Embodiment 11 83.86 Comparative Example 2 56.82 Example 12 85.71 Comparative Example 3 64.56 Embodiment 13 86.62 / / Combining Example 1 and Comparative Examples 1-2 and Table 5, it can be seen that the yield measured in Example 1 is lower than the yield measured in Comparative Example 1, and higher than the yield measured in Comparative Example 2, while the reaction times of Example 1 and Comparative Example 2 are both 1.5 h, and the reaction time of Comparative Example 1 is 3 h, indicating that the process of the present application has a higher reaction efficiency, and a yield of more than 70% can be obtained in 1.5 h, which can more fully save the time for preparing 2,2-diaminobibenzyl compared with Comparative Example 1.

[0049] Combining Example 1 and Comparative Example 3 and Table 5, it can be seen that the yield measured in Example 1 is higher than that in Comparative Example 3. This is because when the temperature of hydrogen reduction sintering is too high, the iron powders are too tightly bound together, resulting in a decrease in specific surface area, which affects the reduction effect of the porous iron particles.

[0050] Combining Examples 1-5 and Table 5, it can be seen that among Examples 1-5, the reaction time of Example 5 is only 2 hours, and a yield close to 80% has been obtained.

[0051] Combining Examples 5-9 and Table 5, it can be seen that the yields measured in Examples 7-9 are relatively high, indicating that when the iron oxide pellets are subjected to hydrogen reduction sintering at 500-550° C., the obtained porous iron particles have a good promoting effect on the reduction of 2,2-dinitrobibenzyl.

[0052] It can be seen from Examples 9-11 and Table 5 that when the iron oxide pellets are subjected to hydrogen reduction sintering at 500° C. for 4-5 h, the prepared porous iron particles have a good promoting effect on the reduction of 2,2-dinitrobibenzyl.

[0053] It can be seen from Examples 11-14 and Table 5 that, compared with using water alone as a solvent, using a mixture of ethanol and water as a solvent is more helpful in accelerating the reduction of 2,2-dinitrobibenzyl. When the solvent is a mixture of water and ethanol in a volume ratio of 2:1, the reduction reaction of 2,2-dinitrobibenzyl can be carried out with higher efficiency, and a higher product yield can be obtained in the same time.

[0054] It can be seen from Examples 14-18 and Table 5 that when 2,2-dinitrobibenzyl undergoes reduction reaction at 87-92° C., the reduction reaction efficiency is higher and a higher product yield can be obtained within the same time.

[0055] It can be seen from Example 16, Comparative Example 1 and Table 5 that after the hydrogen reduction sintering time was adjusted to 5.5 h on the basis of the example, the measured yield decreased, indicating that too long sintering time is not conducive to improving the reactivity of the porous iron particles.

[0056] Combining Example 16 and Comparative Example 2, it can be seen that when the D of the iron oxide powder 50 When the particle size exceeds 350 nm, the reduction reaction efficiency of 2,2-dinitrobibenzyl is low, and the total amount of product obtained in the same time is small.

[0057] Combining Example 16 and Comparative Example 3, it can be seen that when the iron oxide particles are solid particles, the reduction reaction efficiency of 2,2-dinitrobibenzyl is low, and the total amount of product obtained in the same time is less.

[0058] Combining Example 16 and Comparative Example 4, it can be seen that when the molar ratio between the iron element in the porous iron particles and 2,2-dinitrobibenzyl is lower than 6.5:1, the reduction reaction efficiency of 2,2-dinitrobibenzyl is low, and the total amount of product obtained in the same time is less.

[0059] The above embodiments are merely explanations of the present application and are not limitations of the present application. After reading this specification, those skilled in the art may make modifications to the embodiments of the present application without any creative contribution as needed. However, as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A reduction process for 2,2-dinitrobibenzyl, characterized in that: The following steps are involved: (1) adding iron oxide powder, a binder, a defoamer and a surfactant into water to mix into a slurry, spray granulating the slurry to obtain iron oxide pellets, and subjecting the iron oxide pellets to hydrogen reduction sintering at a sintering temperature of 500-600° C. to obtain porous iron particles; in this step, the iron oxide pellets have cavities inside; (2) Mix 2,2-dinitrobibenzyl, porous iron particles, a solvent and ammonium chloride to obtain a reaction solution, heat the reaction solution at 80-95° C. for 1.5-2 h, filter the reaction solution with a sand core funnel covered with diatomaceous earth, and then rinse the diatomaceous earth with methanol to obtain a filtrate; evaporate the filtrate under reduced pressure, then add dichloromethane to dissolve and filter, and evaporate the newly obtained filtrate under reduced pressure to obtain 2,2-diaminobibenzyl.

2. The reduction process of 2,2-dinitrobibenzyl according to claim 1, characterized in that: In step (1) of the process, the sintering temperature is 500-550°C.

3. The reduction process of 2,2-dinitrobibenzyl according to claim 2, characterized in that: In step (1) of the process, the hydrogen reduction sintering is carried out at the sintering temperature for 4-5 hours.

4. The reduction process of 2,2-dinitrobibenzyl according to claim 1, characterized in that: In step (1) of the process, the iron oxide powder used is D 50 The particle size is 300-350nm.

5. The reduction process of 2,2-dinitrobibenzyl according to claim 4, characterized in that: In step (1) of the process, the average particle size of the iron oxide agglomerates obtained by spray granulation is 47-76 μm.

6. The reduction process of 2,2-dinitrobibenzyl according to claim 5, characterized in that: The ratio between the average diameter of the cavities inside the iron oxide agglomerates and the average particle size of the iron oxide agglomerates is 0.38-0.

51.

7. The reduction process of 2,2-dinitrobibenzyl according to claim 1, characterized in that: In step (2) of the process, the solvent used is a mixture of water and ethanol.

8. The reduction process of 2,2-dinitrobibenzyl according to claim 7, characterized in that: In step (2) of the process, the solvent used is a mixture of water and ethanol in a volume ratio of 2:

1.

9. The reduction process of 2,2-dinitrobibenzyl according to claim 1, characterized in that: In step (2) of the process, the reaction solution is heated at 87-92°C.

10. The reduction process of 2,2-dinitrobibenzyl according to claim 1, characterized in that: The molar ratio between the iron element and 2,2-dinitrobibenzyl in the porous iron particles is (6.5-7.5):1.