Process for the synthesis of 2,4-dinitroanisole based on a continuous flow channel
The continuous flow synthesis of 2,4-dinitroanisole using a microchannel reactor solves the problems of long reaction time, high energy consumption, and safety hazards in traditional batch reactors, achieving efficient and safe production of 2,4-dinitroanisole.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV OF SCI & TECH
- Filing Date
- 2024-11-27
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies for producing 2,4-dinitroanisole suffer from problems such as long reaction time, high energy consumption, significant safety hazards, and difficulties in subsequent processing. Furthermore, traditional batch reactors are difficult to achieve efficient and safe continuous production.
2,4-dinitroanisole was synthesized in a continuous flow using a microchannel reactor. By controlling the temperature, flow rate, and molar ratio, the mixed reaction of 2,4-dinitrochlorobenzene and sodium hydroxide aqueous solution was achieved. The reaction temperature was 60–70 °C, the retention time was 3–9 s, and the reaction was cooled with ice water and then filtered and dried.
High conversion and high yield of 2,4-dinitroanisole were achieved, with high product purity, good safety, and suitability for industrial production.
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Figure CN122102913A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical synthesis and relates to a method for synthesizing 2,4-dinitroanisole based on a channel-type continuous flow. Background Technology
[0002] TNT, as a traditional cast explosive, has wide applications in the military industry. However, it suffers from inherent defects such as expansion, brittleness, and oil leakage, making it unsuitable for current international standards and requirements for insensitive munitions. Researchers have been dedicated to developing alternatives. Studies have shown that 2,4-dinitroanisole, with a melting point of 94–96°C and suitable performance, can be used to develop a new type of low-sensitivity cast explosive for IM applications, making it a promising alternative to TNT.
[0003] Currently, the industrial production of 2,4-dinitroanisole is still in the stage of batch process, which mostly adopts the method of heating 2,4-dinitrochlorobenzene with methanol and inorganic base. However, in order to obtain high-quality 2,4-dinitroanisole (DNAN), the heating reaction will cause methanol to volatilize, resulting in incomplete reaction. The reaction time is 1 to 5 hours, which is long and energy-intensive. At the same time, the subsequent processing after the reaction is quite difficult.
[0004] Chinese patent application CN1146450A discloses a method for preparing 2,4-dinitroanisole using 2,4-dinitrochlorobenzene (CDNB). The reaction is carried out using a 40% sodium hydroxide aqueous solution as an acid-binding agent at a reaction temperature of 50–55°C. The yield of 2,4-dinitroanisole obtained is 95%. However, the content of 2,4-dinitrophenol in the product is not further specified.
[0005] Chinese patent application CN102391126A discloses a method for preparing 2,4-dinitroanisole and 2,4-dinitrophenol using 2,4-dinitrochlorobenzene as a raw material. The method uses a 10% to 40% sodium hydroxide solution as an acid-binding agent for the reaction, and the reaction temperature is 55 to 70°C to obtain a mixture of 2,4-dinitroanisole and 2,4-dinitrophenol, which are then separated to obtain their respective products.
[0006] Etherification reactions play a crucial role in the pharmaceutical and chemical industries. However, these reactions are often exothermic, and batch reactors are difficult to control, posing safety hazards. Achieving continuous and safe production of etherification reactions is currently a research hotspot. In recent years, microchannel reactors, with their millimeter-scale channel size, have gained significant attention in hazardous processes due to their ability to increase the surface area of material contact, achieve thorough mixing, provide accurate temperature control, offer excellent mass and heat transfer, and eliminate the scale-up effects that can occur in traditional batch reactors during industrial production.
[0007] The market needs a method to produce high-quality 2,4-dinitroanisole using green and environmentally friendly micro-reaction technology, while also solving the safety issues caused by the high reaction temperature and intense exothermic reaction during the etherification synthesis of 2,4-dinitroanisole by CDNB, as well as the difficulties in subsequent reaction processing. Summary of the Invention
[0008] The purpose of this invention is to provide a method for synthesizing 2,4-dinitroanisole based on a continuous flow channel, which has high CDNB conversion rate, high yield and high quality of 2,4-dinitroanisole, and the synthesis process is environmentally friendly and safe.
[0009] The technical solution for achieving the objective of this invention is as follows:
[0010] The method for synthesizing 2,4-dinitroanisole based on a continuous flow channel is described in the following reaction equation:
[0011]
[0012] The specific steps are as follows:
[0013] (1) Dissolve 2,4-dinitrochlorobenzene in methanol to obtain the first mixture;
[0014] (2) Use a 5% sodium hydroxide aqueous solution as the second mixture;
[0015] (3) Control the preheating temperature of the microchannel reactor at 60-70℃, control the molar ratio of 2,4-dinitrochlorobenzene and sodium hydroxide at 1:1.2-1.5, adjust the flow rate of the first mixture and the second mixture, and pump them into the nitration reaction microchannel reactor for mixing and reaction. The pressure of the mixing module is 1.8-3.0 bar, the reaction temperature is 60-70℃, and the reaction retention time is 3-9 s.
[0016] (4) After the reactants flow out of the microchannel reactor, they are cooled with ice water to precipitate the product, which is then filtered and dried to obtain 2,4-dinitroanisole.
[0017] Further, in step (1), in the first mixture, m(2,4-dinitrochlorobenzene):v(methanol) = 1.01g:15mL.
[0018] Furthermore, in step (3), the preheating temperature of the microchannel reactor is controlled at 65°C, the pressure of the mixing module is 2.0 bar, the reaction temperature is 65°C, and the reaction retention time is 3 s.
[0019] Further, in step (3), the flow rate of the first mixture is 22.9 to 45.8 mL / min, and the flow rate of the second mixture is 7.1 to 14.2 mL / min, preferably the flow rate of the first mixture is 45.8 mL / min and the flow rate of the second mixture is 14.2 mL / min.
[0020] Furthermore, in step (3), the molar ratio of 2,4-dinitrochlorobenzene to sodium hydroxide is 1:1.3.
[0021] Compared with the prior art, the present invention has the following advantages:
[0022] (1) This invention uses microchannel continuous flow to generate 2,4-dinitroanisole. The microchannel reaction plates are at the millimeter level, which greatly increases the specific surface area of material contact and shortens the reaction time from 1 hour in a traditional batch reactor to less than 30 seconds. The microchannel reactor has accurate temperature control, avoiding the generation of by-products caused by inaccurate temperature control in batch reactors, and improving product selectivity. The method is in a flow state, which can discharge the water generated during the reaction in time, thereby effectively improving the yield of 2,4-dinitroanisole and achieving complete conversion of 2,4-dinitrochlorobenzene. The good heat transfer effect of the microchannel reactor reduces the reaction temperature and energy consumption.
[0023] (2) Since the commonly used sodium methoxide-methanol reagent is difficult to dissolve the sodium chloride produced after the reaction, it cannot meet the conditions for entering the microchannel reactor (no solids present). This invention uses an aqueous sodium hydroxide solution instead of the sodium methoxide-methanol reagent, and by adjusting the mass fraction of the aqueous sodium hydroxide solution, the sodium chloride produced after the reaction is completely dissolved, thus meeting the conditions for entering the microchannel reactor.
[0024] (3) Since the 2,4-dinitroanisole obtained in a conventional batch reaction is a solid, it cannot meet the conditions for entering the microchannel reactor (no solid is present). This invention increases the amount of methanol and the reaction temperature, so that the 2,4-dinitroanisole obtained after the reaction can be completely dissolved, and the whole system is in a liquid state, which meets the conditions for entering the microchannel reactor.
[0025] (4) The method of the present invention has the characteristics of short reaction time, high efficiency, high conversion rate of 2,4-dinitrochlorobenzene, high yield and purity of 2,4-dinitroanisole, high safety and environmental friendliness, and is suitable for industrial production. Attached Figure Description
[0026] Figure 1 This is a liquid chromatogram of the pure 2,4-dinitroanisole obtained in this invention. Detailed Implementation
[0027] The present invention will be further explained below with reference to embodiments and comparative examples.
[0028] Example 1
[0029] (1) Dissolve 5.05g CDNB in 75mL of methanol to obtain the first mixture;
[0030] (2) Use 40 mL of sodium hydroxide aqueous solution with a mass fraction of 5% as the second mixture;
[0031] (3) Control the preheating temperature of the microchannel reactor at 65℃, adjust the flow rate of the first mixture at 45.8mL / min, and adjust the flow rate of the second mixture at 14.2mL / min (n(CDNB):n(NaOH)=1:1.3), and pump them into the nitration reaction microchannel reactor for mixing and reaction. The pressure of the mixing module is 2bar, the reaction temperature is 65℃, and the reaction retention time is 3s.
[0032] (4) After the reactants flow out of the microchannel reactor, they are cooled with ice water to precipitate the product. The product is then filtered and dried to obtain 2,4-dinitroanisole with a purity of 99.43% and a reaction yield of 96.18%.
[0033] Example 2
[0034] (1) Dissolve 5.05g CDNB in 75mL of methanol to obtain the first mixture;
[0035] (2) Use 40 mL of sodium hydroxide aqueous solution with a mass fraction of 5% as the second mixture;
[0036] (3) Control the preheating temperature of the microchannel reactor at 60℃, adjust the flow rate of the first mixture at 45.8mL / min, and adjust the flow rate of the second mixture at 14.2mL / min (n(CDNB):n(NaOH)=1:1.3), and pump them into the nitration reaction microchannel reactor for mixing and reaction. The pressure of the mixing module is 2bar, the reaction temperature is 60℃, and the reaction retention time is 3s.
[0037] (4) After the reactants flow out of the microchannel reactor, they are cooled with ice water to precipitate the product. The product is then filtered and dried to obtain 2,4-dinitroanisole with a purity of 98.87% and a reaction yield of 94.85%.
[0038] Table 1 Effect of temperature on the reaction
[0039]
[0040]
[0041] Table 1 shows that the purity and yield of the DNAN product were significantly lower at 60℃. When the temperature was increased to 65℃, both the purity and yield reached their highest levels, with a purity of 99.43% and a reaction yield of 96.18%. However, further increases in temperature promoted the conversion of 2,4-dinitroanisole to 2,4-dinitrophenol, leading to a decrease in the DNAN yield. Therefore, a reaction temperature of 65℃ is optimal.
[0042] Example 3
[0043] (1) Dissolve 5.05g CDNB in 75mL of methanol to obtain the first mixture;
[0044] (2) Use 40 mL of sodium hydroxide aqueous solution with a mass fraction of 5% as the second mixture;
[0045] (3) Control the preheating temperature of the microchannel reactor at 65℃, adjust the flow rate of the first mixture at 45.8mL / min, and adjust the flow rate of the second mixture at 14.2mL / min (n(CDNB):n(NaOH)=1:1.3), and pump them into the nitration reaction microchannel reactor for mixing and reaction. The pressure of the mixing module is 2bar, the reaction temperature is 65℃, and the reaction retention time is 6s.
[0046] (4) After the reactants flow out of the microchannel reactor, they are cooled with ice water to precipitate the product. The product is then filtered and dried to obtain 2,4-dinitroanisole with a purity of 98.95% and a reaction yield of 94.50%.
[0047] Example 4
[0048] (1) Dissolve 5.05g CDNB in 75mL of methanol to obtain the first mixture;
[0049] (2) Use 40 mL of sodium hydroxide aqueous solution with a mass fraction of 5% as the second mixture;
[0050] (3) Control the preheating temperature of the microchannel reactor at 65℃, adjust the flow rate of the first mixture at 45.8mL / min, and adjust the flow rate of the second mixture at 14.2mL / min (n(CDNB):n(NaOH)=1:1.3), and pump them into the nitration reaction microchannel reactor for mixing and reaction. The pressure of the mixing module is 2bar, the reaction temperature is 65℃, and the reaction retention time is 9s.
[0051] (4) After the reactants flow out of the microchannel reactor, they are cooled with ice water to precipitate the product. The product is then filtered and dried to obtain 2,4-dinitroanisole with a purity of 98.70% and a reaction yield of 92.37%.
[0052] Table 2 Effect of residence time on the reaction
[0053]
[0054] As shown in Table 2, the product purity and yield are both highest when the residence time is 3 s. Increasing the residence time to 6 s actually reduces both product purity and yield. Further increasing the residence time to 9 s results in a significant decrease in product yield. Therefore, a residence time of 3 s is optimal.
[0055] Example 5
[0056] (1) Dissolve 5.05g CDNB in 75mL of methanol to obtain the first mixture;
[0057] (2) Use 40 mL of sodium hydroxide aqueous solution with a mass fraction of 5% as the second mixture;
[0058] (3) Control the preheating temperature of the microchannel reactor at 65℃, adjust the flow rate of the first mixture at 45.8mL / min, and adjust the flow rate of the second mixture at 14.2mL / min (n(CDNB):n(NaOH)=1:1.3), and pump them into the nitration reaction microchannel reactor for mixing and reaction. The pressure of the mixing module is 2bar, the reaction temperature is 65℃, and the reaction retention time is 6s.
[0059] (4) After the reactants flow out of the microchannel reactor, they are cooled with ice water to precipitate the product. The product is then filtered and dried to obtain 2,4-dinitroanisole with a purity of 98.95% and a reaction yield of 94.50%.
[0060] Example 6
[0061] (1) Dissolve 5.05g CDNB in 75mL of methanol to obtain the first mixture;
[0062] (2) Use 40 mL of sodium hydroxide aqueous solution with a mass fraction of 5% as the second mixture;
[0063] (3) Control the preheating temperature of the microchannel reactor at 65℃, adjust the flow rate of the first mixture at 22.9mL / min, and adjust the flow rate of the second mixture at 7.1mL / min (n(CDNB):n(NaOH)=1:1.3), and pump them into the nitration reaction microchannel reactor for mixing and reaction. The pressure of the mixing module is 2bar, the reaction temperature is 65℃, and the reaction retention time is 6s.
[0064] (4) After the reactants flow out of the microchannel reactor, they are cooled with ice water to precipitate the product. The product is then filtered and dried to obtain 2,4-dinitroanisole with a purity of 98.47% and a reaction yield of 93.37%.
[0065] Table 3 Effect of flow rate on reaction Table 3 shows that the reaction flow rate has little effect on the purity of the DNAN product, which can reach 98.0% in all cases. However, under the condition of a reaction time of 6 s, the DNAN yield reaches the highest level of 94.50% when the flow rate of the first mixture is 45.8 mL / min and the flow rate of the second mixture is 14.2 mL / min. Therefore, the optimal flow rate is set at 45.8 mL / min for the first mixture and 14.2 mL / min for the second mixture.
[0066] Example 7
[0067] (1) Dissolve 5.05g CDNB in 75mL of methanol to obtain the first mixture;
[0068] (2) Use 40 mL of sodium hydroxide aqueous solution with a mass fraction of 5% as the second mixture;
[0069] (3) Control the preheating temperature of the microchannel reactor at 65℃, adjust the flow rate of the first mixture at 46.6mL / min, and adjust the flow rate of the second mixture at 13.4mL / min (n(CDNB):n(NaOH)=1:1.2), and pump them into the nitration reaction microchannel reactor for mixing and reaction. The pressure of the mixing module is 2bar, the reaction temperature is 65℃, and the reaction retention time is 3s.
[0070] (4) After the reactants flow out of the microchannel reactor, they are cooled with ice water to precipitate the product. The product is then filtered and dried to obtain 2,4-dinitroanisole with a purity of 98.04% and a reaction yield of 93.48%.
[0071] Example 8
[0072] (1) Dissolve 5.05g CDNB in 75mL of methanol to obtain the first mixture;
[0073] (2) Use 40 mL of sodium hydroxide aqueous solution with a mass fraction of 5% as the second mixture;
[0074] (3) Control the preheating temperature of the microchannel reactor at 65℃, adjust the flow rate of the first mixture at 45.0 mL / min, and adjust the flow rate of the second mixture at 15.0 mL / min (n(CDNB):n(NaOH)=1:1.4), and pump them into the nitration reaction microchannel reactor for mixing and reaction. The pressure of the mixing module is 2 bar, the reaction temperature is 65℃, and the reaction retention time is 3s.
[0075] (4) After the reactants flow out of the microchannel reactor, they are cooled with ice water to precipitate the product. The product is then filtered and dried to obtain 2,4-dinitroanisole with a purity of 98.04% and a reaction yield of 93.18%.
[0076] Table 4 Effect of molar ratio on the reaction As shown in Table 4, the product purity and yield are both highest when the reactant molar ratio is 1:1.3. When the molar ratio is decreased to 1:1.2, the product purity and yield decrease. When the molar ratio is increased to 1:1.4, the product yield decreases significantly. Therefore, a molar ratio of 1:1.3 is optimal.
Claims
1. A method for synthesizing 2,4-dinitroanisole based on a continuous flow channel, characterized in that, The specific steps are as follows: (1) Dissolve 2,4-dinitrochlorobenzene in methanol to obtain the first mixture; (2) Use a 5% sodium hydroxide aqueous solution as the second mixture; (3) Control the preheating temperature of the microchannel reactor at 60~70℃, control the molar ratio of 2,4-dinitrochlorobenzene and sodium hydroxide at 1:1.2~1.5, adjust the flow rate of the first mixture and the second mixture, and pump them into the nitration reaction microchannel reactor for mixing and reaction. The pressure of the mixing module is 1.8~3.0 bar, the reaction temperature is 60~70℃, and the reaction retention time is 3~9s. (4) After the reactants flow out of the microchannel reactor, they are cooled with ice water to precipitate the product, which is then filtered and dried to obtain 2,4-dinitroanisole.
2. The method according to claim 1, characterized in that, In step (1), in the first mixture, m(2,4-dinitrochlorobenzene):v(methanol) = 1.01g:15mL.
3. The method according to claim 1, characterized in that, In step (3), the preheating temperature of the microchannel reactor is controlled at 65°C, the pressure of the mixing module is 2.0 bar, the reaction temperature is 65°C, and the reaction retention time is 3 s.
4. The method according to claim 1, characterized in that, In step (3), the flow rate of the first mixture is 22.9~45.8 mL / min, and the flow rate of the second mixture is 7.1~14.2 mL / min.
5. The method according to claim 1, characterized in that, In step (3), the molar ratio of 2,4-dinitrochlorobenzene to sodium hydroxide is 1:1.3.