Methylhydrazine aqueous solution synthesis method

Abstract

The invention belongs to the technical field of methylhydrazine preparation, and particularly relates to a synthetic method of a methylhydrazine aqueous solution, which comprises the following steps of: mixing hydrazine hydroiodate serving as an initial raw material with water under the catalysis of hydroiodic acid to generate a hydrazine hydroiodate hydroiodic acid aqueous solution; preheating the hydrazine hydroiodate hydroiodic acid aqueous solution and methanol to 80-90 DEG C, continuously pumping into the microchannel reactor at a stable pumping speed, carrying out an alkylation reaction to obtain a reaction generation solution, and carrying out removal, dissociation, evaporation and rectification on the reaction generation solution to obtain a methylhydrazine aqueous solution. Compared with an existing method, the method has higher reaction selectivity and product stability, by-products are few, the alkylation reaction rate can be effectively increased by adding the hydrazinodic acid aqueous solution and the methanol at a stable pump speed, the safety problem caused by the violent reaction process is effectively solved, and the method is suitable for industrial production. And the stability and the yield of the product can be effectively improved, so that the mass production of the methylhydrazine aqueous solution is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of methylhydrazine preparation, and specifically relates to a method for synthesizing an aqueous solution of methylhydrazine. Background Art

[0002] The alkylation reaction is a high-risk process in the methylhydrazine synthesis process because the reaction process is relatively violent and difficult to control. In traditional methylhydrazine synthesis, the alkylation reaction mainly uses intermittent batch reactions. This reaction method requires manual operation according to the on-site situation, with a high risk factor. Moreover, manual control will inevitably bring uncertainties, and it is extremely easy to cause safety accidents due to non-standard operations. It is also difficult to ensure the quality of the final product. Therefore, the intermittent alkylation reaction method not only affects the production efficiency of methylhydrazine but also limits the large-scale production of methylhydrazine and cannot meet the growing market demand.

[0003] To solve the problems existing in the intermittent alkylation reaction method, microchannel reactions are currently used. Through the automated control technology of microchannel reactors, it is beneficial for data traceability. It can not only improve the selectivity, conversion rate, and production efficiency of the chemical production process but also effectively reduce pollutant emissions and the danger of the production process. Moreover, compared with traditional batch reactors, it has many advantages such as high heat and mass transfer capabilities, continuous and controllable reaction processes, small volume, low energy consumption, and high safety. However, due to the usually small scale of microchannel reactors, it is difficult to achieve large-scale industrial production, and it is also difficult to adapt to the violent reaction environment in the methylhydrazine production process.

[0004] There are studies in the prior art on the difficulty of microchannel reactors to meet the production requirements of methylhydrazine. For example, in patent application CN114133339A - A continuous flow microchannel alkylation method for methylhydrazine, it prepares methylhydrazine by continuously alkylating hydrazine hydrochloride and methanol in a microreactor. Although it can improve the selectivity and conversion rate of the reaction to a certain extent, there are still problems of more by-products, and it is difficult to ensure the reaction rate during the alkylation reaction, so the stability and yield of the product cannot be effectively improved, thus affecting the mass production of the aqueous solution of methylhydrazine. For this reason, a new technical solution is needed to further improve the existing continuous flow microchannel alkylation method for methylhydrazine. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for synthesizing an aqueous solution of methylhydrazine to solve the problems in the above-mentioned background art that there are still more by-products in the current continuous flow microchannel alkylation method for methylhydrazine, and it is difficult to ensure the reaction rate during the alkylation reaction, so the stability and yield of the product cannot be effectively improved, thus affecting the mass production of the aqueous solution of methylhydrazine.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A method for synthesizing an aqueous solution of methylhydrazine, and its specific steps are as follows: First, using hydrazine hydriodide as the starting material, it is first mixed with water under the catalysis of hydroiodic acid to form an aqueous solution of hydrazine hydriodide hydroiodide, wherein the mass concentration ratio of hydrazine hydriodide to hydroiodic acid is 75-85%: 0.5%. Second, preheat the aqueous solution of hydrazine hydriodide hydroiodide and methanol to 80-90 °C and continuously pump them into the microchannel reactor at stable pump rates of 47-55 g / min and 47-55 g / min respectively, and carry out an alkylation reaction at 110-120 °C and 0.7-0.8 MPa for 30-35 min to obtain a reaction product solution. Among them, the mass ratio of the aqueous solution of hydrazine hydriodide hydroiodide to methanol is 1:0.92-1, and the specific reaction process is as follows: ; Third, first distill the reaction product solution at normal pressure at 60-130 °C to recover the methanol mixture containing methanol, water, methyl iodide and hydrogen iodide, and then remove the remaining methanol and water from the reaction product solution by thin-film evaporation at a temperature of 110-115 °C and a pressure of -0.09 MPa to -0.11 MPa. Then, add hydrazine hydrate with a concentration of 78-80% to the reaction product solution at 80-85 °C to liberate methylhydrazine. Among them, the amount of hydrazine in the hydrazine hydrate is 1.05 times the amount of hydrazine hydriodide, and the specific reaction process is as follows: ; Then, the reaction product solution from which methylhydrazine has been liberated is subjected to vacuum thin-film evaporation at 60-150 °C to obtain crude methylhydrazine. Finally, the crude methylhydrazine is continuously rectified at normal pressure at 104-105 °C to obtain an azeotrope of methylhydrazine and water, that is, an aqueous solution of methylhydrazine.

[0007] Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention adopts the design that hydrazine hydriodide reacts with water under the catalysis of hydriodic acid to generate a reaction precursor and then undergoes an alkylation reaction, effectively reducing the generation of common by-products in the existing continuous-flow microchannel alkylation method of methylhydrazine. Compared with hydrazine hydrachloride used in the existing continuous-flow microchannel alkylation method of methylhydrazine, hydrazine hydriodide shows higher reaction selectivity and product stability under the catalytic condition of hydriodic acid, thus significantly reducing the content of by-products (such as dimethylhydrazine, etc.), effectively improving the purity of methylhydrazine, and enabling the purity of methylhydrazine in the finally obtained aqueous solution of methylhydrazine to reach more than 99.5%, meeting the market demand for high-quality products. By utilizing the advantages of the microchannel reactor in continuous-flow reactions (such as high heat and mass transfer capabilities, continuous and controllable reaction process, etc.), it ensures that the alkylation reaction proceeds under constant and optimized conditions. Then, by precisely controlling the pumping flow rate of the reaction materials, the accurate regulation of the reaction rate is achieved, effectively avoiding safety problems caused by violent reaction processes, effectively improving the stability and yield of the product, and thus ensuring the mass production of the aqueous solution of methylhydrazine; 2. The present invention optimizes the reaction system by setting the mass concentration ratio of hydrazine hydriodide to hydriodic acid, making the reaction more efficient and controllable, and providing a good foundation for the subsequent alkylation reaction. By optimizing the mass ratio of the aqueous solution of hydrazine hydriodide, hydriodic acid and methanol, not only the purity and yield of the product are improved, but also the generation of by-products is reduced, making the reaction process more efficient and environmentally friendly. Then, by setting the preheating temperature of the aqueous solution of hydrazine hydriodide, hydriodic acid and methanol and precisely controlling its flow rate into the microchannel reactor, the uniform mixing and stable supply of the reaction materials are achieved, which helps to ensure that the reaction proceeds under the best conditions, thereby improving the reaction selectivity and yield; 3. The present invention uses a microchannel reactor to carry out the alkylation reaction. By precisely regulating the pump speed, reaction temperature, pressure and time, the continuous, stable and controllable reaction process is achieved, not only improving the reaction efficiency, but also reducing the safety risk, making the reaction process safer and more reliable. Compared with the traditional batch alkylation method, the reaction time is greatly shortened, the production efficiency is significantly improved, and at the same time, the emission of pollutants is effectively reduced, which is more in line with the concept of green chemistry and sustainable development. At the same time, the limitations of the microchannel reactor in the production process of methylhydrazine are successfully overcome, and the stable mass production of the aqueous solution of methylhydrazine is realized, which not only meets the increasing market demand for the aqueous solution of methylhydrazine, but also promotes the innovation and upgrading of the methylhydrazine production technology; 4. The present invention adopts techniques such as atmospheric distillation to recover the methanol mixture, thin-film evaporation to remove residues, and the use of hydrazine hydrate to liberate methylhydrazine for separation and purification. It not only effectively removes impurities in the reaction system, but also improves the extraction efficiency and purity of methylhydrazine, laying a solid foundation for the subsequent continuous rectification to prepare aqueous methylhydrazine solution. At the same time, it also solves the problems of many by-products, difficult to ensure the reaction rate, low product stability and yield in the existing continuous-flow microchannel alkylation method of methylhydrazine, realizing the high-efficiency and stable mass production of aqueous methylhydrazine solution. Detailed implementation mode

[0008] The following examples are used to further illustrate the content of the present invention and do not limit the application of the present invention. Example 1:

[0009] This example provides a method for synthesizing aqueous methylhydrazine solution, and the specific steps are as follows: First, hydrazine hydriodide with a mass concentration of 75% (hydrazine hydriodide is obtained by the acid-base neutralization reaction of hydrazine hydrate (N2H4·H2O) and hydriodic acid (HI), and its chemical equation is It is mixed with water under the catalysis of hydroiodic acid with a mass concentration of 0.5% to prepare an aqueous solution of hydrazine hydriodide and hydroiodic acid. Then, an aqueous solution of hydrazine hydriodide and hydroiodic acid with a mass ratio of 1:0.92 and methanol are preheated to 80 - 90 °C (the preheated aqueous solution of hydrazine hydriodide and hydroiodic acid will be in a fluid state). First, methanol is pumped into the microchannel reactor at a pump speed of 47 g / min (for the relevant parameters of the microchannel reactor, please refer to the content of the patent application with the publication number CN114133339A and the application name "A continuous flow microchannel alkylation method of methylhydrazine" filed on January 5, 2022, which will not be elaborated here) to fill the microchannels. Then, the aqueous solution of hydrazine hydriodide and hydroiodic acid is pumped into the microchannels of the microchannel reactor at a rate of 51 g / min, enabling the aqueous solution of hydrazine hydriodide and hydroiodic acid to continuously react with methanol at 110 °C and 0.8 MPa for 35 min to generate a reaction product solution, which is collected. After detection, the alkylation reaction rate reaches 91.80%. Then, the collected reaction product solution is distilled under normal pressure at 60 - 130 °C to recover a methanol mixture containing methanol, water, methyl iodide, and hydrogen iodide. Next, the reaction product solution is subjected to thin-film evaporation at a temperature of 110 - 115 °C and a pressure of -0.09 MPa to -0.11 MPa to remove the residual methanol and water. Then, the temperature is controlled at 80 - 85 °C, and hydrazine hydrate with a concentration of 78 - 80% is added in a flowing manner for liberation, such that the amount of substance of hydrazine in hydrazine hydrate is 1.05 times the amount of substance of hydrazine hydriodide, liberating methylhydrazine (dimethylhydrazine will also be liberated). Then, the reaction product solution containing the liberated methylhydrazine is subjected to vacuum thin-film evaporation at -0.085 to -0.099 MPa and 60 - 150 °C to obtain a crude product of methylhydrazine (the crude product of methylhydrazine contains dimethylhydrazine, methylhydrazine, hydrazine hydrate, and water, and the residue is hydrazine hydriodide). Finally, an azeotrope of methylhydrazine and water is obtained by continuous distillation under normal pressure at 104 - 105 °C, which is the aqueous solution of methylhydrazine. After detection, the reaction selectivity in this example is 99.01% and the yield is 92.70%. Hydrazine hydrate will remain in the distillation kettle. The remaining hydrazine hydrate does not need to be taken out, but it needs to be recovered by vacuum distillation at 60 - 70 °C and -0.095 MPa. The recovered hydrazine hydrate can be reused in the production of methylhydrazine. Example 2:

[0010] This embodiment provides a method for synthesizing aqueous methylhydrazine. The specific steps are as follows: First, hydrazine hydriodide with a mass concentration of 85% is mixed with water under the catalysis of hydriodic acid with a mass concentration of 0.5% to prepare an aqueous solution of hydrazine hydriodide and hydriodic acid. Then, the aqueous solution of hydrazine hydriodide and hydriodic acid with a mass ratio of 1:1 and methanol are preheated to 80 - 90 °C. First, methanol is pumped into the microchannel reactor at a pump speed of 55 g / min to fill the microchannels, and then the aqueous solution of hydrazine hydriodide and hydriodic acid is pumped into the microchannels of the microchannel reactor at a rate of 55 g / min, enabling the aqueous solution of hydrazine hydriodide and hydriodic acid to continuously react with methanol at 120 °C and 0.7 MPa for 30 min to generate a reaction product solution, which is collected. After detection, the alkylation reaction rate reaches 92.60%. Then, the collected reaction product solution is distilled under normal pressure at 60 - 130 °C to recover a methanol mixture containing methanol, water, methyl iodide, and hydrogen iodide. Next, the reaction product solution is subjected to thin-film evaporation at a temperature of 110 - 115 °C and a pressure of -0.09 MPa to -0.11 MPa to remove the remaining methanol and water. Then, the temperature is controlled at 80 - 85 °C, and hydrazine hydrate with a concentration of 78 - 80% is added dropwise for liberation, such that the amount of hydrazine in hydrazine hydrate is 1.05 times the amount of hydrazine hydriodide, liberating methylhydrazine (dimethylhydrazine will also be liberated). Then, the reaction product solution containing liberated methylhydrazine is subjected to vacuum thin-film evaporation at -0.085 to -0.099 MPa and 60 - 150 °C to obtain crude methylhydrazine (the crude methylhydrazine contains dimethylhydrazine, methylhydrazine, hydrazine hydrate, and water, and the residue is hydrazine hydriodide). Finally, an azeotrope of methylhydrazine and water is obtained by continuous distillation under normal pressure at 104 - 105 °C, which is the aqueous methylhydrazine solution. After detection, the reaction selectivity in this embodiment is 99.40% and the yield is 94.30%. Hydrazine hydrate will remain in the distillation kettle. The remaining hydrazine hydrate does not need to be drawn out, but it needs to be recovered by vacuum distillation at 60 - 70 °C and -0.095 MPa. The recovered hydrazine hydrate can be reused in the production of methylhydrazine. Example 3:

[0011] This embodiment provides a method for synthesizing aqueous methylhydrazine, and the specific steps are as follows: First, hydrazine hydriodide with a mass concentration of 80% is mixed with water under the catalysis of hydriodic acid with a mass concentration of 0.5% to prepare an aqueous solution of hydrazine hydriodide and hydriodic acid. Then, the aqueous solution of hydrazine hydriodide and hydriodic acid and methanol with a mass ratio of 1:0.96 are preheated to 80 - 90 °C. First, methanol is pumped into the microchannel reactor at a pump speed of 49.7 g / min to fill the microchannels, and then the aqueous solution of hydrazine hydriodide and hydriodic acid is pumped into the microchannels of the microchannel reactor at a pump speed of 51.8 g / min, so that the aqueous solution of hydrazine hydriodide and hydriodic acid can continuously react with methanol at 115 °C and 0.75 MPa for 32.5 min to generate a reaction product solution, which is collected. After detection, the alkylation reaction rate reaches 92.40%. Then, the collected reaction product solution is distilled under normal pressure at 60 - 130 °C to recover a methanol mixture containing methanol, water, methyl iodide, and hydrogen iodide. Then, the reaction product solution is subjected to thin-film evaporation at a temperature of 110 - 115 °C and a pressure of -0.09 MPa to -0.11 MPa to remove the remaining methanol and water. Then, the temperature is controlled at 80 - 85 °C, and hydrazine hydrate with a concentration of 78 - 80% is added dropwise for liberation, so that the amount of substance of hydrazine in hydrazine hydrate is 1.05 times the amount of substance of hydrazine hydriodide, and methylhydrazine (dimethylhydrazine hydrate will also be liberated) is liberated. Then, the reaction product solution containing liberated methylhydrazine is subjected to vacuum thin-film evaporation at -0.085 to -0.099 MPa and 60 - 150 °C to obtain crude methylhydrazine (the crude methylhydrazine contains dimethylhydrazine, methylhydrazine, hydrazine hydrate, and water, and the residue is hydrazine hydriodide). Finally, an azeotrope of methylhydrazine and water is obtained by continuous distillation under normal pressure at 104 - 105 °C, which is the aqueous methylhydrazine solution. After detection, the reaction selectivity in this embodiment is 99.27%, and the yield is 93.60%. There will be residual hydrazine hydrate in the distillation kettle, and the residual hydrazine hydrate does not need to be taken out, but it needs to be recovered by vacuum distillation at 60 - 70 °C and -0.095 MPa. The recovered hydrazine hydrate can be reused in the production of methylhydrazine. Example 4:

[0012] The method for synthesizing aqueous methylhydrazine in this embodiment is the same as that in Example 1, except that the pump speeds of the aqueous solution of hydrazine hydriodide and hydriodic acid and methanol are inconsistent, that is, both the aqueous solution of hydrazine hydriodide and hydriodic acid and methanol are pumped into the microchannel reactor at a pump speed of 49 g / min for alkylation reaction. After detection, the alkylation reaction rate in this embodiment reaches 90.20%, the reaction selectivity is 99.37%, and the yield is 93.80%.

[0013] Comparative Example 1: The method for synthesizing aqueous methylhydrazine in this comparative example is the same as that in Example 3, except that the reaction equipment is inconsistent, that is, an intermittent batch reactor process is used for 4 h of alkylation reaction. After detection, the reaction rate in this comparative example is only 78.60%, the reaction selectivity is 80.34%, and the yield is 79.40%.

[0014] The following is a statistical table of the reaction rate, reaction selectivity, and yield of Examples 1-4 and Comparative Example 1: ; As can be seen from the above table, for the alkylation reaction carried out using a microchannel reactor, it is superior to the alkylation reaction carried out using an intermittent batch reactor in terms of reaction rate, reaction selectivity, or yield. Adding the aqueous solution of hydrazine hydriodide and methanol at a stable pump speed can effectively increase the rate of the alkylation reaction, effectively avoid safety problems caused by the violent reaction process, and can also effectively improve the stability and yield of the product, thus ensuring the mass production of aqueous methylhydrazine.

Claims

1. A method for synthesizing aqueous methylhydrazine solution, characterized in that, Using hydrazine hydriodide as the starting material, it is first mixed with water under the catalysis of hydriodic acid to form an aqueous solution of hydrazine hydriodide hydriodic acid, and then the aqueous solution of hydrazine hydriodide hydriodic acid and methanol are preheated to 80-90 °C and continuously pumped into a microchannel reactor at a stable pump rate for an alkylation reaction to obtain a reaction product solution. Then, the reaction product solution is subjected to removal, liberation, evaporation, and rectification to obtain an aqueous solution of methylhydrazine.

2. The method for synthesizing an aqueous solution of methylhydrazine according to claim 1, wherein The mass concentration ratio of hydrazine hydriodide to hydriodic acid is 75-85%: 0.5%.

3. A method for synthesizing aqueous methylhydrazine according to claim 1, characterized in that, The mass ratio of the aqueous solution of hydrazine hydriodide hydriodic acid to methanol is 1: 0.92-1.

4. A method for synthesizing an aqueous solution of methylhydrazine according to claim 3, characterized in that, The pump rate of the aqueous solution of hydrazine hydriodide hydriodic acid is 47-55 g / min, and the pump rate of methanol is 47-55 g / min.

5. A method for synthesizing an aqueous solution of methylhydrazine according to claim 1, characterized in that, The temperature, pressure, and time of the alkylation reaction are 110-120 °C, 0.7-0.8 MPa, and 30-35 min, respectively.

6. A method for synthesizing an aqueous solution of methylhydrazine according to claim 1, characterized in that, Before the removal, the reaction product solution also needs to be distilled under normal pressure at 60-130 °C to recover a methanol mixture containing methanol, water, methyl iodide, and hydrogen iodide.

7. A method for synthesizing an aqueous solution of methylhydrazine according to claim 6, characterized in that, The reaction product solution is removed of residual methanol and water by thin-film evaporation at a temperature of 110-115 °C and a pressure of -0.09 MPa to -0.11 MPa.

8. A method for synthesizing aqueous methylhydrazine according to claim 1, characterized in that, The liberation is carried out by adding a hydrazine hydrate solution with a concentration of 78-80% to the reaction product solution at 80-85 °C to liberate methylhydrazine. Among them, the amount of hydrazine in the hydrazine hydrate is 1.05 times the amount of hydrazine hydriodide.

9. A method for synthesizing an aqueous solution of methylhydrazine according to claim 8, characterized in that, The reaction product solution from which methylhydrazine has been liberated is subjected to vacuum thin-film evaporation at 60-150 °C to obtain a crude product of methylhydrazine.

10. A method for synthesizing aqueous methylhydrazine according to claim 9, characterized in that, The crude product of methylhydrazine is continuously rectified under normal pressure at 104-105 °C to obtain an azeotrope of methylhydrazine and water, that is, an aqueous solution of methylhydrazine.