A continuous catalytic process for the synthesis of methylhydrazine

Abstract

The application belongs to the technical field of chemical synthesis, and particularly relates to a continuous catalytic synthesis process of methylhydrazine, which specifically comprises two steps: S1, preparation of hydrazine hydrochloride solution; and S2, mixing of hydrazine hydrate, hydrochloric acid and methanol in a micro-channel reactor under continuous catalytic reaction of zinc chloride to obtain methylhydrazine with a molar conversion rate of 40-42%. The application has a more mild reaction environment, is more convenient to operate, has low requirements on equipment, and solves the problems of long time consumption in auxiliary operations such as loading and packing of manual operation kettle type reactors or pressure reaction containers, process discontinuity in the auxiliary operation process, unstable product quality, small heat exchange area and low control ability on strong exothermic reactions, realizes continuous catalysis of methylhydrazine in the actual sense in the synthesis reaction process, shortens the reaction time, improves the reaction efficiency, and ensures large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the technical field of chemical synthesis, specifically relating to a continuous catalytic synthesis process for methylhydrazine. Background Technology

[0002] Chemicals refer to pure substances and mixtures composed of various elements. Methylhydrazine is a highly toxic chemical. There are many processes for synthesizing it. The earliest process used was the chloramine method (which involves reacting sodium hypochlorite with ammonia and then reacting it with monomethylamine to produce monomethylhydrazine, or simply methylhydrazine). This method has a low yield of the target product and high energy consumption and cost. Currently, with the continuous expansion of the application fields and the continuous growth of production of hydrazine hydrate, research on hydrazine hydrate derivatives is also ongoing, and the process of methylhydrazine is also being improved accordingly. One method is to use hydrazine hydrate as a raw material to condense with benzaldehyde to form benzylene triazine, and then to obtain methylhydrazine through a methylation reaction. This process is relatively complex, with high raw material costs and high energy consumption, which is not conducive to large-scale industrial production. The second method is to use methanol-hydrazine hydrate as a raw material, and hydrochloric acid and chloromethane as methylation reagents as catalysts to prepare methylhydrazine under conditions of 0.7-1.3 MPa. Although this method is low in cost and has a high product selectivity, and no further processing is required in the downstream stage, the product conversion rate is low, the equipment requirements are relatively high (i.e., a reaction vessel with good corrosion resistance and high pressure resistance is required), and the equipment maintenance cost is high.

[0003] Existing technologies include research on the cost and large-scale industrial production of methylhydrazine synthesis processes, such as patent applications CN115232023A (a new process for catalytic synthesis of methylhydrazine) and CN105037196A (a new method for catalytic synthesis of methylhydrazine under atmospheric pressure). These technologies address the high cost and unsuitability for large-scale industrial production of methylhydrazine by using hydrazine hydrate as a raw material in a one-step reaction with methanol or with chloromethane. However, existing methylhydrazine synthesis processes utilize batch reactors or pressure vessels, requiring manual operation for packing and temperature control. Precise control of reaction temperature, time, and material ratios is difficult. Large-scale industrial production necessitates cyclic reactions, resulting in long reaction times and failing to achieve truly continuous catalytic reactions. Therefore, a new technical solution is needed to address these issues. Summary of the Invention

[0004] The purpose of this invention is to provide a continuous catalytic synthesis process for methylhydrazine, which solves the technical problems mentioned in the background art. The current methylhydrazine synthesis process still requires manual operation such as loading and heating / cooling, making it difficult to accurately control the reaction temperature, time, and material ratio. For large-scale industrial production, it still needs to be achieved through a cyclic reaction, which results in a long reaction time and cannot achieve a truly continuous catalytic reaction.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a continuous catalytic synthesis process for methylhydrazine, comprising the following specific steps:

[0006] S1. Add hydrazine hydrochloride to water, heat to 70-90℃ and stir to dissolve. When the pH value is adjusted to 3, add hydrochloric acid and stir thoroughly to prepare a hydrazine hydrochloride solution with a hydrazine hydrochloride content of 80%. Hydrazine hydrochloride and water are mixed and dissolved in a mass ratio of 4:1 to obtain hydrazine hydrate.

[0007] S2. Methanol is first added to the microchannel reactor via a feed pump at a feed rate of 10–12 ml / min and heated to 90–110°C. Then, hydrazine hydrochloride solution is slowly and gradually added via a feed pump at a feed rate of 6–8 ml / min, so that the feed ratio of methanol to hydrazine hydrochloride solution is 2:1. The temperature and pressure inside the microchannel reactor are maintained at 60–80°C, 100–175°C, and 70–80°C. The inlet pressure is 0–1.2 MPa, the outlet pressure is 0.80–0.90 MPa, and the residence time is 3–6 min. Methylhydrazine with a molar conversion rate of 40–42% is obtained under continuous catalytic reaction of zinc chloride.

[0008] Furthermore, in S2, methanol reacts with hydrochloric acid in a hydrazine hydrochloride solution under the catalysis of zinc chloride to yield the methylating agent chloromethane, as shown in the following reaction equation: In this process, methanol and zinc chloride are mixed to form a zinc chloride methanol solution with a concentration of 2-8%.

[0009] Compared with the prior art, the beneficial effects of the present invention are:

[0010] 1. This invention employs a synthesis process for methylhydrazine using a mixture of hydrazine hydrate, hydrochloric acid, and methanol. This process creates a milder reaction environment and facilitates operation, effectively reducing equipment requirements. Utilizing the characteristics of a microchannel reactor, it allows for precise control of the reaction temperature, time, and material ratio. It also offers high standards of controllability in terms of safety and environmental protection. Furthermore, it alters the internal fluid flow state, effectively reducing fluid dispersion and resulting in faster mass and heat transfer efficiency. This process provides strong continuity over a short time, effectively avoiding the problems associated with manual operation of batch reactors or pressure reaction vessels, such as long loading times, discontinuous processes, unstable product quality, and low control over strongly exothermic reactions due to small heat exchange areas. Thus, it achieves practical continuous catalysis of methylhydrazine during the synthesis process, effectively shortening the reaction time, improving reaction efficiency, and ensuring large-scale industrial production.

[0011] 2. The present invention uses methanol hydrogen chloride to produce methylhydrazine. The reaction mechanism is simple, making its source and transportation more convenient than other chemicals, effectively saving transportation costs and improving economic benefits. The gas-liquid phase method with zinc chloride as catalyst makes the reaction environment milder, the operation more convenient, and the equipment easier to operate, effectively improving the reaction rate.

[0012] 3. This invention utilizes a microchannel environment to form a methylating agent, chloromethane, from a mixture of hydrochloric acid and methanol. This chloromethane then reacts continuously with hydrazine hydrate to generate the target product, methylhydrazine (i.e., monomethylhydrazine). This allows the two-step reaction of catalytic synthesis of the alkylating agent chloromethane and the reaction with chloromethane and hydrazine hydrate to produce methylhydrazine to be continuous, effectively shortening the reaction time, improving the reaction efficiency, and ensuring large-scale industrial production. Detailed Implementation

[0013] The present invention will be further described below with reference to embodiments, but this does not limit the present invention in any way. Example 1:

[0014] Continuous catalytic synthesis of methylhydrazine:

[0015] S1. Prepare hydrazine hydrochloride solution: Add 4 kg of hydrazine hydrochloride to 1 kg of water, heat in a water bath to 80 degrees Celsius, stir to dissolve and obtain hydrazine hydrate, and check pH=3; add 125 g of 30% hydrochloric acid, stir thoroughly, and wait for feeding; prepare methanol: add 5 kg of methanol to the mixing tank, and wait for feeding;

[0016] S2. In the microchannel reactor, first add 5 kg of methanol using a feed pump at a feed rate of 10–12 ml / min, and heat thoroughly to 90–110°C. Then, slowly and gradually add hydrazine hydrochloride solution using a feed pump at a feed rate of 6–8 ml / min, maintaining a methanol to 64% hydrazine hydrochloride solution feed ratio of 2:1. Maintain the temperature and pressure within the microchannel reactor, ensuring the feed temperature is 60–80°C, the reaction temperature is 168°C, and the discharge temperature is 7°C. The microchannel reactor was operated at 0–80℃ with an inlet pressure of 0–1.2 MPa and an outlet pressure of 0.8 MPa. The residence time was 5 min. The HPLC area ratio of hydrazine hydrate to methylhydrazine was 0.93–0.94. Following continuous catalysis with zinc chloride, methylhydrazine with a molar conversion of 40.84%–41.81% was obtained. Specifically, methanol reacted with hydrochloric acid in the hydrazine hydrochloride solution under zinc chloride catalysis to yield the methylating agent chloromethane. The reaction equation is as follows: Methanol and zinc chloride were mixed to form a 4% zinc chloride methanol solution, and the flow rate ratio of the methanol solution to the 64% hydrazine hydrochloride solution in the microchannel reactor was set to 2:1 per minute.

[0017] When the molar ratio of hydrazine hydrate obtained in S1 to methylhydrazine obtained in S2 is set to 1:1, the area ratio of hydrazine hydrate to methylhydrazine in HOLC under high performance liquid chromatography (HPLC) is 0.47.

[0018] In addition, the equipment used in the above synthesis process includes one set of microchannel reactor (C1-20-4 (i.e., single module liquid holding capacity 20ml, 4 sets)), two horizontal flow pumps (0-200ml / min, PTFE pump head), one high and low temperature integrated machine (-30-200℃, 6kw, VCO-HL30), one temperature display (4 channels), one pressure shut-off valve (PTFE lined), one cooling coil (Φ=3mm, stainless steel tube), two raw material bottles (hydrazine hydrochloride, zinc chloride, methanol feed bottles (200ml), several receiving bottles (200ml), and one water bath. Among them, the equipment of microchannel reactor must also meet the following conditions: two feed pumps (one room temperature pump, one maximum operating temperature 40 degrees), maximum flow rate 20ml / min, maximum raw material tank volume 10L, other consumables, 40 sample (100ml) and 4 storage tanks (5L);

[0019] The operating procedure for the above equipment is as follows: First, prepare 500g of hydrazine hydrochloride aqueous solution and 500g of 4% zinc chloride methanol solution; second, start the horizontal flow pump and rinse the microchannel reactor with pure water; third, turn on the high and low temperature integrated machine to raise the temperature to above 120 degrees Celsius; then, start feeding until the microchannel reactor is full, and adjust the feed rate of the horizontal flow pump, the high and low temperature integrated machine and the pressure shut-off valve to control the feed ratio, residence time, reaction temperature and reaction pressure respectively; finally, conduct orthogonal experiments on the feed ratio, residence time, reaction temperature, reaction pressure and zinc chloride methanol concentration respectively. Example 2:

[0020] The continuous catalytic synthesis process in this embodiment is the same as that in Example 1, except that when the molar ratio of hydrazine hydrate to methylhydrazine is set to 2:1, the area ratio of HOLC of hydrazine hydrate to methylhydrazine under high performance liquid chromatography (HPLC) is 1.14. Example 3:

[0021] The continuous catalytic synthesis process in this embodiment is the same as that in Example 1, except that when the molar ratio of hydrazine hydrate to methylhydrazine is set to 4:1, the area ratio of HOLC of hydrazine hydrate to methylhydrazine under high performance liquid chromatography (HPLC) is 2.63. Example 4:

[0022] The continuous catalytic synthesis process in this embodiment is the same as that in Example 1, except that when the molar ratio of hydrazine hydrate to methylhydrazine is set to 6:1, the area ratio of HOLC of hydrazine hydrate to methylhydrazine under high performance liquid chromatography (HPLC) is 4. Example 5:

[0023] The continuous catalytic synthesis process in this embodiment is the same as that in Example 1, except that when the molar ratio of hydrazine hydrate to methylhydrazine is set to 8:1, the area ratio of HOLC of hydrazine hydrate to methylhydrazine under high performance liquid chromatography (HPLC) is 6.24. Example 6:

[0024] The continuous catalytic synthesis process in this embodiment is the same as that in Example 1, except that when the molar ratio of hydrazine hydrate to methylhydrazine is set to 10:1, the area ratio of HOLC of hydrazine hydrate to methylhydrazine under high performance liquid chromatography (HPLC) is 7.3.

[0025] Comparative Example 1:

[0026] The synthesis process of this comparative example is the same as that of Example 1, except that the reaction temperature in the microchannel reactor is 160°C, the flow rate ratio of 64% hydrazine hydrochloride solution to 4% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute, the outlet pressure is 0.8 MPa, the inlet pressure is 1.12 MPa, the residence time is 5.3 min, and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 3.77, and the molar conversion rate of methylhydrazine is measured to be 15.6%.

[0027] Comparative Example 2:

[0028] The synthesis process of this comparative example is the same as that of Example 1, except that the reaction temperature in the microchannel reactor is 164°C, the flow rate ratio of 64% hydrazine hydrochloride solution and 4% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute, the outlet pressure is 0.8 MPa, the inlet pressure is 1.12 MPa, the residence time is 5.3 min, and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 2.3, and the molar conversion rate of methylhydrazine is measured to be 21.7%.

[0029] Comparative Example 3:

[0030] The synthesis process of this comparative example is the same as that of Example 1, except that the reaction temperature in the microchannel reactor is 170°C, the flow rate ratio of 64% hydrazine hydrochloride solution to 4% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute, the outlet pressure is 0.8 MPa, the inlet pressure is 1.12 MPa, the residence time is 5.3 min, and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 2.67, and the molar conversion rate of methylhydrazine is measured to be 19.43%.

[0031] Comparative Example 4:

[0032] The synthesis process of this comparative example is the same as that of Example 1, except that: the outlet pressure in the microchannel reactor is 0.4 MPa, the flow rate ratio of 64% hydrazine hydrochloride solution and 4% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute, the reaction temperature is 168°C, the inlet pressure is 1.2 MPa, the residence time is 5.3 min, and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 1.92, and the molar conversion rate of methylhydrazine is measured to be 25.44%.

[0033] Comparative Example 5:

[0034] The synthesis process of this comparative example is the same as that of Example 1, except that: the outlet pressure in the microchannel reactor is 0.6 MPa, the flow rate ratio of 64% hydrazine hydrochloride solution and 4% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute, the reaction temperature is 168°C, the inlet pressure is 1.2 MPa, the residence time is 5.3 min, and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 1.65, and the molar conversion rate of methylhydrazine is measured to be 28.74%.

[0035] Comparative Example 6:

[0036] The synthesis process of this comparative example is the same as that of Example 1, except that: the outlet pressure in the microchannel reactor is 1.0 MPa, the flow rate ratio of 64% hydrazine hydrochloride solution and 4% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute, the reaction temperature is 168°C, the inlet pressure is 1.2 MPa, the residence time is 5.3 min, and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 0.91, and the molar conversion rate of methylhydrazine is 42.14%.

[0037] Comparative Example 7:

[0038] The synthesis process of this comparative example is the same as that of Example 1, except that the flow rate ratio in the microchannel reactor is set to 3:1, and the reaction temperature is 168°C with 63% hydrazine hydrochloride solution and 4% zinc chloride methanol solution, the outlet pressure is 0.82 MPa, the inlet pressure is 1.12 MPa, the residence time is 5.3 min, and the area ratio of hydrazine hydrate to methylhydrazine under high performance liquid chromatography (HPLC) is 0.82, and the molar conversion rate of methylhydrazine is 44.89%.

[0039] Comparative Example 8:

[0040] The synthesis process of this comparative example is the same as that of Example 1, except that the flow rate ratio in the microchannel reactor is set to 1:1, and the reaction temperature is 168°C with 63% hydrazine hydrochloride solution and 4% zinc chloride methanol solution, the outlet pressure is 0.82 MPa, the inlet pressure is 1.12 MPa, the residence time is 5.3 min, and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 5.4, and the molar conversion rate of methylhydrazine is 11.64%.

[0041] Comparative Example 9:

[0042] The synthesis process of this comparative example is the same as that of Example 1, except that the flow rate ratio in the microchannel reactor is set to 1:3, and the reaction temperature is 168°C with 63% hydrazine hydrochloride solution and 4% zinc chloride methanol solution, the outlet pressure is 0.82 MPa, the inlet pressure is 1.12 MPa, the residence time is 5.3 min, and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 43.7, and the molar conversion rate of methylhydrazine is 1.75%.

[0043] Comparative Example 10:

[0044] The synthesis process of this comparative example is the same as that of Example 1, except that: the concentration of zinc chloride methanol solution is 2%, and the flow rate ratio of 65% hydrazine hydrochloride solution to 2% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute; the reaction temperature is 168°C; the outlet pressure is 0.84 MPa; the inlet pressure is 1.12 MPa; the residence time is 5.3 min; and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 4.9, and the molar conversion rate of methylhydrazine is 12.5%.

[0045] Comparative Example 11:

[0046] The synthesis process of this comparative example is the same as that of Example 1, except that: the concentration of zinc chloride methanol solution is 6%, and the flow rate ratio of 65% hydrazine hydrochloride solution to 6% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute; the reaction temperature is 168°C; the outlet pressure is 0.84 MPa; the inlet pressure is 1.12 MPa; the residence time is 5.3 min; and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 2.5, and the molar conversion rate of methylhydrazine is measured to be 20.6%.

[0047] Comparative Example 12:

[0048] The synthesis process of this comparative example is the same as that of Example 1, except that: the concentration of zinc chloride methanol solution is 8%, and the flow rate ratio of 65% hydrazine hydrochloride solution to 4% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute; the reaction temperature is 168°C; the outlet pressure is 0.84 MPa; the inlet pressure is 1.12 MPa; the residence time is 5.3 min; and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 2.3, and the molar conversion rate of methylhydrazine is 21.6%.

[0049] Comparative Example 13:

[0050] The synthesis process of this comparative example is the same as that of Example 1, except that: the residence time in the microchannel reactor is 3 min, the flow rate ratio of 65% hydrazine hydrochloride solution to 4% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute, the reaction temperature is 168°C, the outlet pressure is 0.84 MPa, the inlet pressure is 1.12 MPa, and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 0.975, and the molar conversion rate of methylhydrazine is 40.4%.

[0051] Comparative Example 14:

[0052] The synthesis process of this comparative example is the same as that of Example 1, except that: the residence time in the microchannel reactor is 4 min, the flow rate ratio of 65% hydrazine hydrochloride solution to 4% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute, the reaction temperature is 168°C, the outlet pressure is 0.84 MPa, the inlet pressure is 1.12 MPa, and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 1.755, and the molar conversion rate of methylhydrazine is measured to be 26.4%.

[0053] Comparative Example 15:

[0054] The synthesis process of this comparative example is the same as that of Example 1, except that: the residence time in the microchannel reactor is 6 min, the flow rate ratio of 65% hydrazine hydrochloride solution to 4% zinc chloride methanol solution in the microchannel reactor is set to 2:1 per minute, the reaction temperature is 168°C, the outlet pressure is 0.84 MPa, the inlet pressure is 1.12 MPa, and the HPLC area ratio of hydrazine hydrate to methylhydrazine is 0.89, and the molar conversion rate of methylhydrazine is 44.42%.

[0055] Comparative Example 16:

[0056] The synthesis process of this comparative example is the same as that of Example 1, except that the reaction equipment is a traditional batch reactor.

[0057] In conjunction with Examples 1-6, the area ratios of hydrazine hydrate and methylhydrazine in high-performance liquid chromatography (HPLC) at different molar ratios were investigated, and the results are shown in the table below:

[0058] , As can be seen from the table, the molar ratio of hydrazine hydrate to methylhydrazine directly affects the area ratio of HOLC of hydrazine hydrate and methylhydrazine.

[0059] In conjunction with Example 1 and Comparative Examples 1-3, the effect of different reaction temperatures on the conversion rate of methylhydrazine was investigated in a microchannel reactor with a flow rate ratio of 2:1 (64% hydrazine hydrochloride solution, 4% zinc chloride methanol solution), an outlet pressure of 0.8 MPa, an inlet pressure of 1.12 MPa, and a residence time of 5.3 min. The results are shown in the table below:

[0060] , As can be seen from the table, the conversion rate is highest at 168℃ as the reaction temperature increases. After that, the conversion rate decreases linearly with further increases in reaction temperature. Therefore, choosing a reaction temperature of 168℃ is more appropriate.

[0061] In conjunction with Example 1 and Comparative Examples 4-6, the effect of different outlet pressures on the conversion rate of methylhydrazine was investigated in a microchannel reactor with a flow rate ratio of 2:1 (64% hydrazine hydrochloride solution, 4% zinc chloride methanol solution), a reaction temperature of 168°C, an inlet pressure of 1.2 MPa, and a residence time of 5.3 min. The results are shown in the table below:

[0062] , As can be seen from the table, as the export pressure increases, a conversion rate of 0.8 MPa is relatively high. However, the higher pressure experimental conditions required to achieve a higher conversion rate are not yet achievable. From a safety perspective, an export pressure of 0.8 MPa is more appropriate.

[0063] In conjunction with Example 1 and Comparative Examples 7-9, the effect of different flow rates of methanol to hydrazine hydrochloride solution on the conversion rate of methylhydrazine was investigated at a reaction temperature of 168°C, an outlet pressure of 0.82 MPa, an inlet pressure of 1.12 MPa, and a residence time of 5.3 min, using 3% hydrazine hydrochloride solution, 4% zinc chloride methanol solution, and other conditions. The results are shown in the table below.

[0064] , As can be seen from the table, as the feed ratio of methanol to hydrazine hydrochloride solution changes continuously, a feed ratio of 2:1 for methanol to hydrazine hydrochloride is more appropriate based on experimental data and the excess level of the bound material.

[0065] In conjunction with Example 1 and Comparative Examples 10-12, the effect of different zinc chloride methanol solution concentrations on the conversion rate of methylhydrazine was investigated in a microchannel reactor with a flow rate ratio of 2:1 per minute in a 65% hydrazine hydrochloride solution, a reaction temperature of 168°C, an outlet pressure of 0.84 MPa, an inlet pressure of 1.12 MPa, and a residence time of 5.3 min. The results are shown in the table below:

[0066] , As can be seen from the table, the conversion rate is highest when the concentration of zinc chloride methanol solution increases to 4%. After that, the conversion rate will decrease slightly with further increases in the concentration of zinc chloride methanol solution. Therefore, a 4% concentration of zinc chloride methanol solution is more suitable.

[0067] In conjunction with Example 1 and Comparative Examples 13-15, the effect of different residence times on the conversion rate of methylhydrazine was investigated in a microchannel reactor with a flow rate ratio of 2:1 (65% hydrazine hydrochloride solution to 4% zinc chloride methanol solution), a reaction temperature of 168°C, an outlet pressure of 0.84 MPa, and an inlet pressure of 1.12 MPa. The results are shown in the table below:

[0068] , As can be seen from the table, the conversion rate is higher when the residence time is extended to 5 minutes. However, the higher pressure experimental conditions required to achieve a higher conversion rate are not yet achievable. From a safety perspective, a residence time of 5 minutes is more appropriate.

[0069] Based on Example 1 and Comparative Example 16, the effect of different reactor equipment on the conversion rate of methylhydrazine was investigated when the methylhydrazine synthesis process was the same. The results are shown in the table below:

[0070] , As can be seen from the table, Example 1 uses a microchannel reactor as the reaction equipment for synthesizing methylhydrazine, which makes the operation simpler and more convenient. The conversion rate of the target product is significantly improved by more than 50%, and the conversion rate of by-products is significantly reduced. Therefore, the use of a microchannel reactor can solve the problems of long time consumption, discontinuous process, unstable product quality, and low control of strong exothermic reaction caused by manual operation of batch reactors such as loading and packing. Thus, it realizes the actual continuous catalysis of methylhydrazine in the synthesis reaction process, effectively shortens the reaction time, improves the reaction efficiency, and ensures large-scale industrial production.

Claims

1. A continuous catalytic synthesis process for methylhydrazine, characterized in that, The specific steps are as follows: S1. Add hydrazine hydrochloride to water, heat to 70-90℃ and stir to dissolve. When the pH value is adjusted to 3, add hydrochloric acid and stir thoroughly to prepare a hydrazine hydrochloride solution. Hydrazine hydrochloride and water are mixed and dissolved in a mass ratio of 4:1 to obtain hydrazine hydrate. S2. In a microchannel reactor, methanol is first added via a feed pump at a rate of 10–12 ml / min, and the mixture is heated to 90–110°C. Then, hydrazine hydrochloride solution is gradually added via a feed pump at a rate of 6–8 ml / min, while maintaining the temperature and pressure within the microchannel reactor. Methylhydrazine with a molar conversion rate of 40–42% is obtained under the continuous catalytic reaction of zinc chloride. The feed ratio of methanol to hydrazine hydrochloride solution is 2:

1. The reaction of methanol with hydrochloric acid in the hydrazine hydrochloride solution yields chloromethane, a methylating agent, under the catalysis of zinc chloride. The reaction equation is as follows: Methanol and zinc chloride are mixed to form a 2-8% zinc chloride methanol solution. The feed temperature in the microchannel reactor is 60-80℃, the reaction temperature in the microchannel reactor is 100-175℃, the discharge temperature in the microchannel reactor is 70-80℃, the inlet pressure in the microchannel reactor is 0-1.2MPa, the outlet pressure in the microchannel reactor is 0.80-0.90MPa, and the reaction residence time in the microchannel reactor is 3-6min.

2. The continuous catalytic synthesis process for methylhydrazine according to claim 1, characterized in that, In S1, the hydrazine hydrochloride aqueous solution contains 80% hydrazine hydrochloride.