The invention relates to a solvent-free synthesis method of 4, 4apos; process for the preparation of-dinitrodiphenyl ethers

Abstract

The invention discloses a method for solvent-free synthesis of 4, 4 '-dinitrodiphenyl ether, and belongs to the field of organic synthesis. The synthesis method comprises the working procedures of feeding dehydration, condensation reaction, reduced pressure distillation, steam distillation, water washing, reduced pressure suction filtration and drying, and the 4, 4 '-dinitrodiphenyl ether is synthesized by taking sodium p-nitrophenolate and p-nitrochlorobenzene as raw materials through solvent-free condensation reaction under the catalysis of potassium chloride. The method provided by the invention has the advantages of direct contact of reactants, short reaction time, high efficiency, energy saving, environmental protection, low production cost, high product yield and good product quality, also avoids the use of organic solvent nitrobenzene, reduces the environmental pollution problem, and realizes green production.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis, and specifically relates to a method for synthesizing 4,4'-dinitrodiphenyl ether without solvent. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] 4,4'-Dinitrodiphenyl ether is an important organic synthesis intermediate. It is mainly used to prepare 4,4'-diaminodiphenyl ether and its derivatives in the field of chemical production. It is a key raw material for the production of various high-end dyes, heat-resistant polymer materials, etc. It has a wide range of uses. With the continuous expansion of the application scope of 4,4'-dinitrodiphenyl ether in many fields, the market demand and output of 4,4'-dinitrodiphenyl ether are increasing year by year, and the performance requirements are getting higher and higher. Its synthesis technology is also receiving more and more attention. Therefore, it is of great significance to carry out research on new methods for the synthesis of 4,4'-dinitrodiphenyl ether.

[0004] The existing synthesis technologies of 4,4'-dinitrodiphenyl ether mainly include diphenyl ether nitration method, p-dinitrobenzene condensation method, p-nitrochlorobenzene condensation method, and condensation method of p-nitrochlorobenzene and p-nitrophenol or phenol salt. Among them, the diphenyl ether nitration method will obtain a 2,4-position mixed dinitration product. This method has many by-products and a low yield of 4,4'-dinitrodiphenyl ether; the p-dinitrobenzene condensation method has a simple process, but it will produce nitrogen oxides as by-products, causing pollution to the ecological environment, and the recovery process of the non-protonic polar organic solvent used is complicated; the p-nitrochlorobenzene condensation method requires the use of nitrite catalysis and a large amount of carbonate auxiliary catalysis, both of which are consumables and cannot be reused, resulting in excessively high salt concentrations in wastewater discharge, causing a serious environmental burden; the p-nitrochlorobenzene and p-nitrophenol or phenol salt condensation method is a traditional process for producing 4,4'-dinitrodiphenyl ether. When p-nitrophenol is used as a raw material, a strong base is required as an auxiliary material. After the reaction is completed, the waste liquid needs to be neutralized with acid, thereby producing a higher concentration of sodium salt wastewater, which puts great pressure on environmental emissions, while p-nitrophenol salt can be directly condensed.

[0005] At present, the most commonly used method in actual production is the condensation method of p-nitrochlorobenzene and sodium p-nitrophenolate, using potassium chloride as a catalyst and nitrobenzene as a solvent to generate 4,4'-dinitrodiphenyl ether through the condensation reaction between p-nitrochlorobenzene and sodium p-nitrophenolate. However, the organic solvent nitrobenzene in this production process is highly toxic, has a long reaction time, consumes a lot of heat energy, and results in a long production cycle, high investment cost, and low yield. Therefore, it is urgent to develop a new synthesis method to achieve the green production of 4,4'-dinitrodiphenyl ether. Summary of the invention

[0006] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a method for solvent-free synthesis of 4,4'-dinitrodiphenyl ether. The method provided by the present invention is efficient, energy-saving, environmentally friendly, low in production cost, good in product quality, and high in yield. It also avoids the use of organic solvent nitrobenzene, reduces environmental pollution problems, and achieves green production. At the same time, the reactants are in direct contact, which can improve production efficiency, shorten reaction time, and increase production capacity.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] On the one hand, the present invention provides a method for synthesizing 4,4'-dinitrodiphenyl ether without solvent, comprising the steps of feeding dehydration, condensation reaction, reduced pressure distillation, steam distillation, water washing, reduced pressure filtration and drying, wherein sodium p-nitrophenolate and p-nitrochlorobenzene are used as raw materials, and 4,4'-dinitrodiphenyl ether is synthesized by solvent-free condensation reaction under the catalysis of potassium chloride.

[0009] In one or more embodiments, the dehydration and condensation reaction steps are both carried out under a nitrogen atmosphere. The nitrogen pressure is adjusted to ensure a moderate nitrogen filling rate, and the crystal water of sodium p-nitrophenolate and free water carried by the raw materials are removed by the nitrogen flow.

[0010] In one or more embodiments, the molar ratio of sodium p-nitrophenolate, p-nitrochlorobenzene and potassium chloride is 1:(2-5):(0.05-0.3), preferably 1:(2-5):(0.1-0.3), and more preferably 1:(2.5-4):(0.1-0.2). The excess p-nitrochlorobenzene helps to accelerate the reaction, so that the reactant sodium p-nitrophenolate is completely converted into 4,4'-dinitrodiphenyl ether, thereby improving the reaction efficiency.

[0011] In one or more embodiments, the dehydration temperature is 130-150°C.

[0012] In one or more embodiments, the temperature of the condensation reaction is 210-230°C, preferably 220-230°C.

[0013] In one or more embodiments, the condensation reaction time is 4 to 8 hours, preferably 6 to 8 hours.

[0014] In one or more embodiments, the steam distillation temperature is 160-170°C.

[0015] In one or more embodiments, the water washing temperature is 40-90°C.

[0016] In one or more embodiments, the number of water washings is 3 to 8 times.

[0017] In one or more embodiments, the specific process steps of the method are: strictly measuring sodium p-nitrophenolate, p-nitrochlorobenzene and potassium chloride in a ratio, and heating and dehydrating under a nitrogen atmosphere; after the dehydration is completed, heating the reaction system to the condensation temperature for reaction until a brown product is obtained; subjecting the reactant mixture to vacuum distillation to remove excess p-nitrochlorobenzene, and when no p-nitrochlorobenzene droplets flow out, the vacuum distillation process is completed; obtaining a crude product by steam distillation, and washing with water for multiple times to remove sodium chloride and potassium chloride, and finally obtaining pure 4,4'-dinitrodiphenyl ether by vacuum filtration and vacuum drying.

[0018] The vacuum distillation can effectively separate p-nitrochlorobenzene, and has the advantage of energy saving due to the low operating temperature. In addition, the p-nitrochlorobenzene obtained by the vacuum distillation can be directly used for the next batch of condensation reactions, thereby improving the conversion rate of p-nitrochlorobenzene.

[0019] The invention adopts a solvent-free reaction, avoids the use of an organic solvent (such as nitrobenzene), and realizes green production; in the dehydration process after the raw materials are put in, firstly, replacement is carried out by vacuuming and filling with nitrogen, then heating and dehydration are carried out, and then the temperature is raised to the condensation temperature for reaction; after the reaction is completed, vacuum distillation and steam distillation are carried out to obtain a crude product of 4,4'-dinitrodiphenyl ether; finally, sodium chloride and potassium chloride are removed by washing with water to obtain high-purity 4,4'-dinitrodiphenyl ether.

[0020] One or some of the above technical solutions have the following advantages or beneficial effects:

[0021] 1. The use of solvent-free reaction technology solves the main pollution problem in traditional synthesis methods, avoids the use of organic solvents (such as nitrobenzene), and the production process is green and environmentally friendly.

[0022] 2. Short reaction time, energy saving and high efficiency, effectively reducing the generation of tar.

[0023] 3. Nitrogen protection is used during the reaction process to avoid impurities from mixing, ensure that the reaction is not disturbed, and further reduce the production of tar.

[0024] 4. The condensation reaction is complete, making the subsequent washing process more convenient and reducing the amount of sewage discharge.

[0025] 6. The condensation product 4,4'-dinitrodiphenyl ether has a high yield (95.6%) and good purity (99.9%).

[0026] 7. The raw materials and catalysts required for the condensation reaction are strictly measured and added at one time, which is accurate and easy to control, saving time and labor and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 4,4'-dinitrodiphenyl ether prepared in Example 7 of the present invention 1 H-NMR nuclear magnetic spectrum;

[0029] Figure 2 This is a high pressure liquid chromatogram of 4,4'-dinitrodiphenyl ether prepared in Example 7 of the present invention. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0031] Example 1

[0032] To a 250mL three-necked flask equipped with a reflux condenser, a dehydration device, an electric stirrer and a thermometer, 27.72g of sodium p-nitrophenolate, 75.63g of p-nitrochlorobenzene and 1.79g of potassium chloride were added in sequence. Nitrogen was replaced at room temperature, heated to 140°C for dehydration under a nitrogen flow, and then heated to 220°C for reaction for 4 hours. Excess p-nitrochlorobenzene was removed from the reactants by vacuum distillation. The remaining small amount of p-nitrochlorobenzene was further separated by steam distillation to obtain a crude product. Finally, the inorganic salt impurities were removed by 90°C hot water washing agent, vacuum filtered, and dried in a vacuum oven to obtain a light yellow crystalline product with a yield of 75.4% and a purity of 95.6%.

[0033] Example 2

[0034] To a 250mL three-necked flask equipped with a reflux condenser, a dehydration device, an electric stirrer and a thermometer, 27.72g of sodium p-nitrophenolate, 75.63g of p-nitrochlorobenzene and 1.79g of potassium chloride were added in sequence. Nitrogen was replaced at room temperature, heated to 140°C for dehydration under a nitrogen flow, and then heated to 220°C for reaction for 6 hours. Excess p-nitrochlorobenzene was removed from the reactants by vacuum distillation. The remaining small amount of p-nitrochlorobenzene was further separated by steam distillation to obtain a crude product. Finally, the inorganic salt impurities were removed by 90°C hot water washing agent, vacuum filtered, and dried in a vacuum oven to obtain a light yellow crystalline product with a yield of 93.6% and a purity of 99.7%.

[0035] Example 3

[0036] To a 250mL three-necked flask equipped with a reflux condenser, a dehydration device, an electric stirrer and a thermometer, 27.72g of sodium p-nitrophenolate, 75.63g of p-nitrochlorobenzene and 1.79g of potassium chloride were added in sequence. Nitrogen was replaced at room temperature, heated to 140°C for dehydration under a nitrogen flow, and then heated to 220°C for reaction for 8 hours. Excess p-nitrochlorobenzene was removed from the reactants by vacuum distillation. The remaining small amount of p-nitrochlorobenzene was further separated by steam distillation to obtain a crude product. Finally, the inorganic salt impurities were removed by 90°C hot water washing agent, vacuum filtered, and dried in a vacuum oven to obtain a light yellow crystalline product with a yield of 92.7% and a purity of 99.5%.

[0037] Example 4

[0038] To a 250mL three-necked flask equipped with a reflux condenser, a dehydration device, an electric stirrer and a thermometer, 27.72g of sodium p-nitrophenolate, 75.63g of p-nitrochlorobenzene and 0.75g of potassium chloride were added in sequence. Nitrogen was replaced at room temperature, heated to 140°C for dehydration under a nitrogen flow, and then heated to 220°C for reaction for 6 hours. Excess p-nitrochlorobenzene was removed from the reactants by vacuum distillation. The remaining small amount of p-nitrochlorobenzene was further separated by steam distillation to obtain a crude product. Finally, the inorganic salt impurities were removed by 90°C hot water washing agent, vacuum filtered, and dried in a vacuum oven to obtain a light yellow crystalline product with a yield of 53.8% and a purity of 87.8%.

[0039] Example 5

[0040] To a 250mL three-necked flask equipped with a reflux condenser, a dehydration device, an electric stirrer and a thermometer, 27.72g of sodium p-nitrophenolate, 75.63g of p-nitrochlorobenzene and 2.24g of potassium chloride were added in sequence. Nitrogen was replaced at room temperature, heated to 140°C for dehydration under a nitrogen flow, and then heated to 220°C for reaction for 6 hours. Excess p-nitrochlorobenzene was removed from the reactants by vacuum distillation. The remaining small amount of p-nitrochlorobenzene was further separated by steam distillation to obtain a crude product. Finally, the inorganic salt impurities were removed by 90°C hot water washing agent, vacuum filtered, and dried in a vacuum oven to obtain a light yellow crystalline product with a yield of 95.6% and a purity of 99.9%.

[0041] Example 6

[0042] To a 250mL three-necked flask equipped with a reflux condenser, a dehydration device, an electric stirrer and a thermometer, 27.72g of sodium p-nitrophenolate, 56.73g of p-nitrochlorobenzene and 2.24g of potassium chloride were added in sequence. Nitrogen was replaced at room temperature, heated to 140°C for dehydration under a nitrogen flow, and then heated to 220°C for reaction for 6 hours. Excess p-nitrochlorobenzene was removed from the reactants by vacuum distillation. The remaining small amount of p-nitrochlorobenzene was further separated by steam distillation to obtain a crude product. Finally, the inorganic salt impurities were removed by 90°C hot water washing agent, vacuum filtered, and dried in a vacuum oven to obtain a light yellow crystalline product with a yield of 88.7% and a purity of 99.2%.

[0043] Example 7

[0044] To a 250mL three-necked flask equipped with a reflux condenser, a dehydration device, an electric stirrer and a thermometer, 27.72g of sodium p-nitrophenolate, 94.53g of p-nitrochlorobenzene and 2.24g of potassium chloride were added in sequence. Nitrogen was replaced at room temperature, heated to 140°C for dehydration under a nitrogen flow, and then heated to 220°C for reaction for 6 hours. Excess p-nitrochlorobenzene was removed from the reactants by vacuum distillation. The remaining small amount of p-nitrochlorobenzene was further separated by steam distillation to obtain a crude product. Finally, the inorganic salt impurities were removed by 90°C hot water lotion, vacuum filtered, and dried in a vacuum oven to obtain a light yellow crystalline product with a yield of 95.3% and a purity of 99.9%.

[0045] Example 8

[0046] To a 250mL three-necked flask equipped with a reflux condenser, a dehydration device, an electric stirrer and a thermometer, 27.72g of sodium p-nitrophenolate, 75.63g of p-nitrochlorobenzene and 1.79g of potassium chloride were added in sequence. Nitrogen was replaced at room temperature, heated to 140°C for dehydration under a nitrogen flow, and then heated to 210°C for reaction for 6 hours. Excess p-nitrochlorobenzene was removed from the reactants by vacuum distillation. The remaining small amount of p-nitrochlorobenzene was further separated by steam distillation to obtain a crude product. Finally, the inorganic salt impurities were removed by 90°C hot water lotion, vacuum filtered, and dried in a vacuum oven to obtain a light yellow crystalline product with a yield of 90.8% and a purity of 99.6%.

[0047] Example 9

[0048] To a 250mL three-necked flask equipped with a reflux condenser, a dehydration device, an electric stirrer and a thermometer, 27.72g of sodium p-nitrophenolate, 75.63g of p-nitrochlorobenzene and 1.79g of potassium chloride were added in sequence. Nitrogen was replaced at room temperature, heated to 140°C for dehydration under a nitrogen flow, and then heated to 230°C for reaction for 6 hours. Excess p-nitrochlorobenzene was removed from the reactants by vacuum distillation. The remaining small amount of p-nitrochlorobenzene was further separated by steam distillation to obtain a crude product. Finally, the inorganic salt impurities were removed by 90°C hot water lotion, vacuum filtered, and dried in a vacuum oven to obtain a light yellow crystalline product with a yield of 94.7% and a purity of 99.8%.

[0049] Comparative Example 1: Traditional Synthesis Method of 4,4'-Dinitrodiphenyl Ether

[0050] The difference from Example 7 is that nitrobenzene is used as the solvent, and the other steps are the same as those of Example 7. The condensation reaction time is 22 hours to obtain 4,4'-dinitrodiphenyl ether with a yield of 93%.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for solvent-free synthesis of 4,4'-dinitrodiphenyl ether, characterized in that: The method comprises the steps of feeding and dehydration, condensation reaction, vacuum distillation, steam distillation, water washing, vacuum filtration and drying, and uses sodium p-nitrophenolate and p-nitrochlorobenzene as raw materials, and obtains 4,4'-dinitrodiphenyl ether through solvent-free condensation reaction under the catalysis of potassium chloride.

2. The method according to claim 1, characterized in that The dehydration and condensation reaction steps were carried out under a nitrogen atmosphere.

3. The method according to claim 1, characterized in that The molar ratio of sodium p-nitrophenolate, p-nitrochlorobenzene and potassium chloride is 1:(2-5):(0.05-0.3), preferably 1:(2-5):(0.1-0.3), and more preferably 1:(2.5-4):(0.1-0.2).

4. The method according to claim 1, characterized in that: The dehydration temperature is 130-150°C.

5. The method according to claim 1, characterized in that The temperature during the condensation reaction is 210 to 230°C, preferably 220 to 230°C.

6. The method according to claim 1, characterized in that The condensation reaction time is 4 to 8 hours, preferably 6 to 8 hours.

7. The method according to claim 1, characterized in that The steam distillation temperature is 160-170°C.

8. The method according to claim 1, characterized in that: The water washing temperature is 40-90°C.

9. The method according to claim 1, characterized in that: The number of water washings is 3 to 8 times.

10. The method according to claim 1, characterized in that The specific process steps of the method are: strictly measuring sodium p-nitrophenolate, p-nitrochlorobenzene and potassium chloride in a ratio, heating and dehydrating in a nitrogen atmosphere; after the dehydration is completed, heating the reaction system to a condensation temperature for reaction until a brown product is obtained; performing vacuum distillation on the reactant mixture to remove excess p-nitrochlorobenzene, and completing the vacuum distillation process when no p-nitrochlorobenzene droplets flow out; obtaining a crude product through steam distillation, and removing sodium chloride and potassium chloride through multiple water washings, and finally obtaining a pure 4,4'-dinitrodiphenyl ether through vacuum filtration and vacuum drying.

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