Method for preparing paranitroaniline and paranitrosoaniline
By using organic and inorganic base catalysts in polar and nonpolar solvents and controlling the moisture content of the reaction system, the problem of difficult-to-control selectivity of p-nitrosoaniline in the reaction of urea and nitrobenzene was solved, and efficient synthesis of p-nitrosoaniline was achieved.
Patent Information
- Application Number
- CN202511027842.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-24
- Publication Date
- 2025-11-04
AI Technical Summary
In existing technologies, the selectivity of the reaction between urea and nitrobenzene to produce p-nitrosoaniline is difficult to control, resulting in high hydrogen consumption and long reaction time.
In a mixed solvent of polar and nonpolar solvents, using organic and inorganic base catalysts, and by controlling the water content in the reaction system, highly selective synthesis of p-nitrosoaniline and p-nitroaniline can be achieved.
This improved the yield and selectivity of p-nitrosoaniline, while reducing hydrogen consumption and reaction time.
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Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to the field of chemical preparation, and in particular, to a method for preparing p-nitrosaniline and p-nitrosoaniline. BACKGROUND
[0002] Both p-nitrosaniline and p-nitrosoaniline are widely used chemical intermediates. For example, a mixture of p-nitrosaniline and p-nitrosoaniline can be generated by reacting urea and nitrobenzene, and the mixture does not need to be separated and can be directly reduced to prepare p-phenylenediamine. In the preparation of p-phenylenediamine, a high content of p-nitrosaniline can reduce hydrogen consumption and reaction time, and reduce energy consumption. However, the selectivity of p-nitrosaniline in the reaction process of urea and nitrobenzene is difficult to control. SUMMARY
[0003] The present disclosure provides a method for preparing p-nitrosaniline and p-nitrosoaniline, comprising the following steps:
[0004] In a mixed solvent of a polar solvent and a non-polar solvent, urea and nitrobenzene are reacted in the presence of a base catalyst to obtain p-nitrosaniline and p-nitrosoaniline. DETAILED DESCRIPTION
[0005] The present disclosure will be described in detail below with specific examples. The following examples will help those skilled in the art to further understand the present disclosure, but do not limit the present disclosure in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present disclosure. These are all within the scope of protection of the present disclosure.
[0006] In some embodiments of the present disclosure, a method for preparing p-nitrosaniline and p-nitrosoaniline can comprise the following steps: in a mixed solvent of a polar solvent and a non-polar solvent, urea and nitrobenzene are reacted in the presence of a base catalyst to obtain p-nitrosaniline and p-nitrosoaniline.
[0007] In some embodiments of the present disclosure, both polar solvents and non-polar solvents exist in the reaction system, wherein the polar solvent can be used to dissolve urea, and the non-polar solvent can be used for azeotropic distillation with water existing in the reaction system to control the moisture content in the reaction system. In addition, in some embodiments of the present disclosure, the use of non-polar solvents can also improve the yield and selectivity of p-nitrosaniline.
[0008] In some embodiments of the present disclosure, the base catalyst can include an organic base catalyst and an inorganic base catalyst.
[0009] In some embodiments of the present disclosure, the use of both organic base catalyst and inorganic base catalyst can improve the product yield and selectivity to nitrosaniline. This can be due to the synergistic catalysis of the organic base catalyst and inorganic base catalyst, combined with the mass transfer enhancement of the non-polar solvent, the inhibition of side reactions, and the resulting synergistic effect.
[0010] In some embodiments of the present disclosure, the molar ratio of base catalyst to nitrobenzene can be 1.5:1-0.5:1.
[0011] In some embodiments of the present disclosure, the molar ratio of base catalyst to nitrobenzene can be any value or a range formed by any combination of values in 1.5:1-0.5:1, for example, 1.5-1:1, 1-0.8:1, 0.9-0.6:1, 0.7-0.5:1, 1.4:1, 1.2:1, 1.1:1, 1.0:1, 0.9:1, 0.8:1, 0.7:1, 0.6:1, etc.
[0012] In some embodiments of the present disclosure, the molar ratio of organic base catalyst to inorganic base catalyst can be 0.6:1-1.5:1.
[0013] In some embodiments of the present disclosure, the molar ratio of organic base catalyst to inorganic base catalyst can be any value or a range formed by any combination of values in 0.6:1-1.5:1, for example, 0.6-0.8:1, 0.7-1:1, 0.9-1.5:1, 1.4:1, 1.2:1, 0.8:1, 0.7:1, etc.
[0014] In some embodiments of the present disclosure, the organic base catalyst can include an aqueous solution of tetraalkylammonium hydroxide.
[0015] Those skilled in the art can understand that the organic base catalyst including an aqueous solution of tetraalkylammonium hydroxide is only exemplary, and the anhydrous tetraalkylammonium hydroxide and water can be added to the reaction system respectively to form the aqueous solution of tetraalkylammonium hydroxide.
[0016] In some embodiments of the present disclosure, the organic base catalyst includes an aqueous solution of tetramethylammonium hydroxide, tetraethylammonium hydroxide, benzyltrimethylammonium hydroxide, and / or triethylmethylammonium hydroxide.
[0017] In some embodiments of the present disclosure, the inorganic base catalyst can include any one or a combination of several of alkali metal hydroxides (e.g., sodium hydroxide, potassium hydroxide, etc.), alkali metal oxides (e.g., sodium oxide, potassium oxide, etc.), alkaline earth metal hydroxides (e.g., magnesium hydroxide, etc.), or alkaline earth metal oxides (e.g., calcium oxide, etc.).
[0018] In some preferred embodiments of the present disclosure, the inorganic base catalyst can include alkali metal hydroxides, such as sodium hydroxide, potassium hydroxide, and the like.
[0019] In some embodiments of the present disclosure, the inorganic base catalyst can be added to the reaction in the form of an aqueous solution, for example, using an aqueous potassium hydroxide solution, to ensure that the inorganic base catalyst with strong alkalinity can be fully dissolved.
[0020] In some embodiments of the present disclosure, the polar solvent, non-polar solvent, urea, and base catalyst are mixed, and then nitrobenzene is added. When the nitrobenzene is added, the water content in the reaction system is maintained at no more than 10% by mass ratio.
[0021] In some embodiments of the present disclosure, when the nitrobenzene is added, the water content in the reaction system can be any value or a range formed by any combination of values in the range of no more than 10% by mass ratio, for example, 1%-3%, 1%-5%, 1%-8%, 2%-5%, 2%-8%, 3%-5%, 3%-8%, 4%-7%, 4%-10%, 5%-8%, 5%-10%, 6%-7%, 7%-9%, 8%-10%, 9%-10%, 1%, 2%, 3%, 5.5%, 7.5%, 8%, 9.5%, and the like.
[0022] In some embodiments of the present disclosure, the method for preparing p-nitrosaniline and p-nitroaniline can include controlling the water content in the reaction system in stages, including: a first stage: mixing the polar solvent, non-polar solvent, urea, and base catalyst, and then adding nitrobenzene. When the nitrobenzene is added, the water content in the reaction system is maintained at 8%-15% by mass ratio; a second stage: after the nitrobenzene is completely added to the reaction system, the water content in the reaction system is maintained at 5%-10% by mass ratio; a third stage: when the remaining amount of nitrobenzene (the amount of unreacted nitrobenzene) in the reaction system is 30%-60% of the total amount of nitrobenzene added, the water content in the reaction system is maintained at no more than 3% by mass ratio.
[0023] In some embodiments of the present disclosure, the water content in the reaction system is controlled in stages, which can achieve a balance between the amination efficiency and selectivity. For example, at the initial stage of the reaction, the appropriate water content in the reaction system can promote the catalytic reaction. The water, inorganic base catalyst, and organic base catalyst in the reaction system can cooperatively maintain strong alkaline conditions, accelerate the reduction and amination reaction of nitrobenzene, and inhibit the generation of by-products such as azobenzene. At the middle stage of the reaction, the water content in the reaction system is reduced, which promotes the reaction to generate p-nitrosaniline and p-nitroaniline. At the late stage of the reaction, the water content in the reaction system is further reduced, which inhibits the oxidation of the nitroso intermediate (-NO), maintains the high selectivity and stability of p-nitrosaniline, and the like.
[0024] In some embodiments of the present disclosure, in the first stage, the water content in the reaction system can be maintained at any value in the range of 8-15% or a range formed by any combination of values in the range, such as 8-10%, 8-12%, 9-10%, 9-5%, 10-15%, 9%, 10%, 12%, 14%, and the like, in terms of mass ratio.
[0025] In some embodiments of the present disclosure, in the second stage, the water content in the reaction system can be maintained at any value in the range of 5-10% or a range formed by any combination of values in the range, such as 5-8%, 7-10%, 6%, 7%, 8%, 9%, and the like, in terms of mass ratio.
[0026] In some embodiments of the present disclosure, in the third stage, the water content in the reaction system can be maintained at any value in the range of 0-3% or a range formed by any combination of values in the range, such as 0-1%, 0-1.5%, 0-2%, 0-2.5%, 0.5-1%, 0.5-2%, 0.5%, 1%, 1.5%, 2%, 2.5%, and the like, in terms of mass ratio.
[0027] In some embodiments of the present disclosure, in the third stage, the residual amount of nitrobenzene in the reaction system can be 30-60% or a range formed by any combination of values in the range, such as 30-40%, 30-50%, 40-50%, 40-60%, 50-60%, 30%, 45%, 55%, 60%, and the like, of the total amount of nitrobenzene added.
[0028] In some embodiments of the present disclosure, the mass-volume ratio of urea to polar solvent is 1 g / 2 ml-1 g / 100 ml.
[0029] In some embodiments of the present disclosure, the volume of non-polar solvent accounts for 40-70% of the total volume of polar solvent and non-polar solvent.
[0030] In some embodiments of the present disclosure, the polar solvent can include dimethyl sulfoxide, N,N-dimethylformamide, acetone, acetonitrile, tetrahydrofuran, or a protic alcohol solvent.
[0031] In some embodiments of the present disclosure, the protic alcohol solvent can include methanol, ethanol, propanol, ethylene glycol, propylene glycol, or glycerol.
[0032] In some embodiments of the present disclosure, the non-polar solvent can include an aliphatic hydrocarbon solvent or an aromatic hydrocarbon solvent.
[0033] In some embodiments, the aliphatic hydrocarbon solvent can include cyclohexane, etc. The aromatic hydrocarbon solvent can include benzene, toluene, or xylene, etc.
[0034] In some embodiments of the present disclosure, the polar solvent can be N,N-dimethylformamide; the non-polar solvent can be toluene.
[0035] In some embodiments of the present disclosure, the reaction pressure can be 0.005-0.3 MPa, and the reaction temperature can be 50-150°C.
[0036] In some embodiments of the present disclosure, the molar ratio of urea to nitrobenzene can be 1.5:1-3:1.
[0037] The present application will be described in detail below with specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present application. The methods, reagents and materials used in the examples are conventional in the art unless otherwise specified. The raw materials in the examples can be purchased through commercial channels.
[0038] Example 1
[0039] Into a reactor equipped with a stirrer, a thermometer, a water separator (Dean-Stark device) and a reflux condenser, 120 g (2 mol) of urea and 396 ml of N,N-dimethylformamide were added, stirred, and after the urea was dissolved, 164.6 g (containing 0.45 mol of tetramethylammonium hydroxide) of a 25% by mass tetramethylammonium hydroxide aqueous solution was added, followed by the slow addition of 19.5 g (0.35 mol) of solid powdered potassium hydroxide, stirring for about 30 minutes, the addition of 333 ml of toluene, heating at normal pressure, and the control of the temperature at 85-90°C. The water condenser was opened, and the toluene and water azeotrope was separated through the water separator to control the water content in the reaction system to be no more than 10%. The temperature was lowered to 75-80°C, and nitrobenzene was added dropwise while stirring. The total amount of nitrobenzene added was 123 g (1 mol). The reaction was completed when the reaction system was substantially free of nitrobenzene. The reaction product was analyzed by liquid chromatography, and the yield of sulfanilamide and the yield of p-nitroaniline based on nitrobenzene (both yields were calculated based on nitrobenzene) are shown in Table 1.
[0040] Comparative Example 1
[0041] This example is the same as Example 1, except that 291.2 g (containing 0.8 mol of tetramethylammonium hydroxide) of a 25% by mass tetramethylammonium hydroxide solution was added, and no potassium hydroxide was added.
[0042] Comparative Example 2
[0043] This example is the same as Example 1, except that no tetramethylammonium hydroxide was added, and 44.8 g (0.8 mol) of potassium hydroxide was dissolved in 165 ml of water to form a potassium hydroxide aqueous solution, which was then added to the reactor.
[0044] Comparative Example 3
[0045] This example is the same as Example 1, except that the aqueous solution of tetramethylammonium hydroxide having a mass concentration of 25% is first distilled to remove water until the mass concentration is 35%, and when the nitrobenzene is added, the water content in the reaction system is controlled to be 7.47% by mass. No toluene is added to the reaction system.
[0046] Example 2
[0047] This example is the same as Example 1, except that the inorganic base is sodium hydroxide, and 13.9 g (0.35 mol) of solid powdered sodium hydroxide is added.
[0048] Example 3
[0049] This example is the same as Example 1, except that the organic base is tetraethylammonium hydroxide, and 265.9 g of an aqueous solution of tetraethylammonium hydroxide having a mass concentration of 25% (containing 0.45 mol of tetraethylammonium hydroxide) is added.
[0050] Example 4
[0051] Into a reactor equipped with a stirrer, a thermometer, a water separator (Dean-Stark apparatus), and a reflux condenser, 108 g (1.8 mol) of urea and 356 ml of N,N-dimethylformamide were added, and stirred until the urea was dissolved. Then, 167.2 g of an aqueous solution of tetramethylammonium hydroxide having a mass concentration of 25% (containing 0.46 mol of tetramethylammonium hydroxide) was added, followed by the slow addition of 30.3 g (0.54 mol) of solid powdered potassium hydroxide. After stirring for about 30 minutes, 535 ml of benzene was added, and heated until the temperature reached 69-70°C. The benzene and water azeotrope was separated by opening the water separator, and the water content in the reaction system was controlled to be not more than 10%. The temperature was then increased to 70-75°C, and nitrobenzene was added dropwise while stirring. The total amount of nitrobenzene added was 123 g (1 mol). When the reaction system was substantially free of nitrobenzene, the reaction was terminated.
[0052] Example 5
[0053] Into a reactor equipped with a stirrer, a thermometer, a Dean-Stark apparatus and a reflux condenser, 168 g (2.8 mol) of urea and 504 ml of dimethyl sulfoxide were added, stirred, and after the urea was dissolved, 191.1 g (0.53 mol) of a 25% by mass aqueous solution of tetramethylammonium hydroxide was added, followed by the slow addition of 49 g (0.88 mol) of solid powdered potassium hydroxide, stirring for about 30 minutes, the addition of 424 ml of toluene, heating, and the adjustment of the temperature to 85-90°C. The water condenser was opened, and the toluene and water azeotrope was separated through the Dean-Stark apparatus, the water content of the reaction system was controlled to be not more than 10%, the temperature was lowered to 75-80°C, and the nitrobenzene was started to be added dropwise while stirring. The reaction was completed when the reaction system was substantially free of nitrobenzene.
[0054] Example 6
[0055] This example is the same as Example 1, except that after the water content of the reaction system was controlled to be not more than 10%, the temperature was lowered to 65°C, the reaction pressure was controlled to be 0.01 MPa, and the nitrobenzene was started to be added dropwise. The reaction was completed when the reaction system was substantially free of nitrobenzene.
[0056] Example 7
[0057] This example is the same as Example 1, except that after the water content of the reaction system was controlled to be not more than 10%, the temperature was raised to 120°C, the reaction pressure was controlled to be 0.3 MPa, and the nitrobenzene was started to be added dropwise. The reaction was completed when the reaction system was substantially free of nitrobenzene.
[0058] Example 8
[0059] The reaction was divided into three stages.
[0060] First stage: Into a reactor equipped with a stirrer, a thermometer, a Dean-Stark apparatus and a reflux condenser, 120 g (2 mol) of urea and 396 ml of N,N-dimethylformamide were added, stirred, and after the urea was dissolved, 164.6 g (0.45 mol) of a 25% by mass aqueous solution of tetramethylammonium hydroxide was added, followed by the slow addition of 19.5 g (0.35 mol) of solid powdered potassium hydroxide, stirring for about 30 minutes, the addition of 333 ml of toluene, heating under normal pressure, and the adjustment of the temperature to 85-90°C. The water condenser was opened, and the toluene and water azeotrope was separated through the Dean-Stark apparatus, the water content of the reaction system was controlled to be not more than 10%, the temperature was lowered to 75-80°C, and the nitrobenzene was started to be added dropwise while stirring. The nitrobenzene was added in a total amount of 60 g in this stage.
[0061] Second stage: cooling to 75-80°C, adding the rest of nitrobenzene, the total amount of nitrobenzene added in the first and second stages is 123g (1mol), after the addition of nitrobenzene is completed, the water content in the reaction system is maintained at 7% by mass.
[0062] Third stage: when the residual amount of nitrobenzene in the reaction system is 48% of the total amount of nitrobenzene added, the water content in the reaction system is maintained at no more than 2% by mass until the end of the reaction.
[0063] Example 9
[0064] This example is the same as Example 8, except that in the first stage, 274.3g of 15% tetramethylammonium hydroxide aqueous solution (containing 0.45mol of tetramethylammonium hydroxide) is added to control the water content in the reaction system to 15% by mass; in the second stage, the water content in the reaction system is maintained at 10% by mass; and in the third stage, the water content in the reaction system is maintained at no more than 3% by mass.
[0065] Example 10
[0066] This example is the same as Example 8, except that in the first stage, the water content in the reaction system is controlled to 8%; in the second stage, the water content in the reaction system is maintained at 5% by mass; and in the third stage, the water content in the reaction system is maintained at no more than 1.5% by mass.
[0067] Table 1: Reaction results of each example
[0068]
[0069]
[0070] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the specific embodiments described above, and various modifications or changes can be made by those skilled in the art within the scope of the claims, which do not affect the essential content of the present application.
Claims
1. A method for preparing p-nitrosoaniline and p-nitroaniline, characterized in that, Includes the following steps: In a mixed solvent of polar and nonpolar solvents, urea and nitrobenzene react in the presence of an alkaline catalyst to yield p-nitrosoaniline and p-nitrobenzene.
2. The method for preparing p-nitrosoaniline and p-nitroaniline according to claim 1, characterized in that, The base catalyst includes organic base catalysts and inorganic base catalysts; and / or The molar ratio of the alkaline catalyst to the nitrobenzene is 1.5:1–0.5:
1.
3. The method for preparing p-nitrosoaniline and p-nitroaniline according to claim 2, characterized in that, The molar ratio of the organic base catalyst to the inorganic base catalyst is 0.6:1 to 1.5:
1.
4. The method for preparing p-nitrosoaniline and p-nitroaniline according to claim 1, characterized in that, The organic base catalyst comprises an aqueous solution of tetraalkylammonium hydroxide; and / or The inorganic base catalyst includes alkali metal hydroxides, alkali metal oxides, alkaline earth metal hydroxides, and / or alkaline earth metal oxides.
5. The method for preparing p-nitrosoaniline and p-nitroaniline according to any one of claims 2-4, characterized in that, The organic base catalyst includes tetramethylammonium hydroxide, tetraethylammonium hydroxide, benzyltrimethylammonium hydroxide and / or triethylmethylammonium hydroxide.
6. The method for preparing p-nitrosoaniline and p-nitroaniline according to claim 1, characterized in that, A polar solvent, a non-polar solvent, urea, and an alkaline catalyst are mixed, and nitrobenzene is added last. When adding nitrobenzene, the water content in the reaction system is maintained at no more than 10% by mass.
7. The method for preparing p-nitrosoaniline and p-nitroaniline according to claim 1, characterized in that, This includes controlling the water content in the reaction system in stages, including: First stage: Mix polar solvent, non-polar solvent, urea and alkaline catalyst, and finally add nitrobenzene. When adding nitrobenzene, maintain the water content in the reaction system at 8%-15% by mass. Second stage: After all nitrobenzene is added to the reaction system, the water content in the reaction system is maintained at 5%-10% by mass. Third stage: When the remaining amount of nitrobenzene in the reaction system is 30%-60% of the total amount of nitrobenzene added, the water content in the reaction system should be maintained at no more than 3% by mass.
8. The method for preparing p-nitrosoaniline and p-nitroaniline according to claim 1, characterized in that, The mass-to-volume ratio of the urea to the polar solvent is 1 g / 2 ml to 1 g / 100 ml; and / or The volume of the non-polar solvent accounts for 40%-70% of the total volume of the polar solvent and the non-polar solvent.
9. The method for preparing p-nitrosoaniline and p-nitroaniline according to claim 1, characterized in that, The polar solvent includes dimethyl sulfoxide, N,N-dimethylformamide, acetone, acetonitrile, tetrahydrofuran, or protic alcohol solvents; and / or The nonpolar solvent includes hydrocarbon solvents or aromatic hydrocarbon solvents.
10. The method for preparing p-nitrosoaniline and p-nitroaniline according to claim 9, characterized in that, The polar solvent is N,N-dimethylformamide; and The nonpolar solvent is toluene.
11. The method for preparing p-nitrosoaniline and p-nitroaniline according to claim 1, characterized in that, Reaction pressure 0.005MPa-0.3MPa, reaction temperature 50℃-150℃; and / or The molar ratio of urea to nitrobenzene is 1.5:1–3:1.