A continuous production process for methylhydrazine

Abstract

The present application relates to chemical intermediate preparation technology, and aims to provide a continuous production method of methylhydrazine. The method comprises the following steps: continuously feeding liquid hydrazine hydrochloride after heating and melting, methanol and a catalyst into a continuous flow reactor, and continuously reacting by heating; the reaction liquid overflows from the upper part of the continuous flow reactor, is subjected to free treatment of hydrazine hydrate, and methylhydrazine and monomethylhydrazine are separated; the single-pass conversion rate and the selectivity of hydrazine hydrochloride are controlled by adjusting the feeding proportion of hydrazine hydrochloride, methanol and the catalyst. The liquid-liquid reaction in the existing tank type production process is changed into a gas-liquid reaction, and the self-limiting reaction is realized in space by strengthening mass transfer to reduce excessive side reactions. Compared with the prior art, the reaction efficiency is significantly improved, the reaction selectivity is greatly improved, the equipment cost is significantly reduced, the operation safety and stability are improved, and the continuous production can be realized.

Description

Technical Field

[0001] This invention belongs to the field of chemical intermediate preparation technology, specifically relating to a continuous production method for methylhydrazine. Background Technology

[0002] Methylhydrazine is an important chemical intermediate widely used in pesticides, pharmaceuticals, energy, and other fields. Currently, there are several methods for synthesizing methylhydrazine, such as the hydrazine-benzaldehyde condensation method, the dimethyl phosphite method, the dimethyl carbonate method, the dimethyl sulfate method, and the urea method.

[0003] In current industrial production, methylhydrazine is mainly prepared using the chloramine process and the hydrazine hydrochloride-methanol process. The chloramine process, also known as the Raschig process, typically involves reacting sodium hypochlorite with ammonia to produce chloramine, which is then reacted with methylamine to obtain methylhydrazine. This method has a relatively mature process route. Chinese patents CN103263884A, CN203303953U, CN206715925U, CN206715356U, and CN206951175U have improved the reaction and post-processing equipment for methylhydrazine production using the chloramine process. However, these methods cannot fundamentally solve the problems of low product yield, high energy consumption, and the generation of large amounts of saline waste, thus limiting their effectiveness in green and sustainable production. The hydrazine hydrochloride-methanol process is a method developed by Japan Hydrazine Co., Ltd. It uses methanol and hydrazine hydrochloride as reactants and hydrogen chloride or chloromethane as catalysts to react under certain temperature and pressure to produce methylhydrazine hydrochloride, which is then obtained through a free reaction (UK Patent application GB 2090828A).

[0004]

[0005] Although subsequent literature and patents have optimized the hydrazine hydrochloride-methanol process of Japan Hydrazine Corporation, such as in journals (Coal and Chemical Industry, 2021, 44(9), 135-137; Liming Chemical Industry, 1990, 4, 10-13) and Chinese patent CN 109503418 A and CN101402586A, etc., but cannot solve the shortcomings of the pressurized batch reaction in principle. The main shortcomings are reflected in the following aspects: (1) Under the reaction pressure conditions (1.0~1.6MPa), methanol mainly exists in liquid form. Liquid methanol and hydrazine hydrochloride are immiscible, which leads to limited mass transfer between reactants and low reaction efficiency; (2) In order to enhance mass transfer, a large amount of water is added to the system to make the system homogeneous, but this greatly increases the energy consumption for subsequent water removal; at the same time, after adding water, the system becomes a homogeneous reaction, which makes the generated methylhydrazine hydrochloride very easy to continue to react with methanol to generate unsymmetrical dimethylhydrazine hydrochloride, reducing selectivity. Therefore, the current process needs to control the single-pass conversion rate of hydrazine hydrochloride to not be too high, otherwise a large amount of unsymmetrical dimethylhydrazine hydrochloride will be generated, which is an irreconcilable contradiction; (3) The aqueous solution of hydrazine hydrochloride is extremely corrosive. In industry, glass-lined reactors are usually used, but the pressure (1.0~1.6MPa) in the reaction brings great safety risks to the glass-lined reactor, requiring multiple safety interlocking measures.

[0006] Given that existing technologies generally suffer from high raw material costs, large quantities of unsymmetrical dimethylhydrazine (UDMH) produced, complex processes, and significant safety or environmental burdens, they are insufficient to meet the demands for large-scale, continuous industrial production of methylhydrazine. Therefore, developing a safe, highly selective, and continuous method for the large-scale production of methylhydrazine is of significant practical importance. Summary of the Invention

[0007] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide a continuous production method for methylhydrazine. This invention fundamentally reconstructs the reaction mechanism and mass transfer pathway, significantly improving reaction efficiency and solving the problem of low reaction efficiency in previous processes. It also enhances the overall industrialization level while improving process safety and environmental friendliness.

[0008] To solve the technical problem, the solution of the present invention is:

[0009] A continuous production method for methylhydrazine is provided, characterized by comprising: continuously feeding heated and melted liquid hydrazine hydrochloride, methanol, and a catalyst into a continuous flow reactor for continuous reaction; the reaction liquid overflowing from the top of the continuous flow reactor (containing methylhydrazine hydrochloride, unsymmetrical dimethylhydrazine hydrochloride, and hydrazine hydrochloride) is first treated with hydrazine hydrate for free treatment, and then separated by distillation to obtain methylhydrazine and unsymmetrical dimethylhydrazine, while recovering hydrazine hydrate; the single-pass conversion rate and selectivity of hydrazine hydrochloride are controlled by adjusting the feed ratio of hydrazine hydrochloride, methanol, and catalyst.

[0010] As a preferred embodiment of the present invention, the molar ratio of the reaction raw materials hydrazine hydrochloride, methanol and catalyst is 1:0.3-4.0:0.03-0.20.

[0011] As a preferred embodiment of the present invention, the catalyst is hydrogen chloride gas, hydrochloric acid, hydrazine dihydrochloride, or chloromethane; the catalyst is pre-mixed with liquid hydrazine hydrochloride and then fed into the reactor, or fed into the reactor through a separate pipeline.

[0012] As a preferred embodiment of the present invention, hydrazine hydrochloride is heated to 100-150 °C to form liquid hydrazine hydrochloride, which is then fed into the bottom of the reactor; liquid methanol is heated to form gaseous methanol, which is then fed into the bottom of the reactor.

[0013] As a preferred embodiment of the present invention, it further includes delivering an appropriate amount of liquid methanol into the reactor through a pipeline, and using the liquid methanol to regulate the temperature inside the reactor.

[0014] As a preferred embodiment of the present invention, the reaction temperature inside the reactor is 100-150°C; the pressure inside the reactor is atmospheric pressure or slightly positive pressure to ensure that methanol is in a vaporized state.

[0015] As a preferred embodiment of the present invention, the reaction liquid overflowing from the tower reactor first enters the reaction liquid storage tank, and then is sent to the free reaction vessel through the pipeline, with hydrazine hydrate as the free agent; the reaction liquid obtained from the free treatment is sent to the distillation column for distillation treatment, and hydrazine hydrochloride is recovered from the bottom of the distillation column as a reaction raw material for reuse. The fraction at the top of the distillation column is separated by a condenser to obtain unsymmetrical dimethylhydrazine, methylhydrazine and hydrazine hydrate, wherein hydrazine hydrate is used as the free agent for reuse.

[0016] As a preferred embodiment of the present invention, the gas discharged from the top of the tower reactor first passes through a condenser to separate and recover unreacted liquid methanol, while the non-condensable waste gas is sent to the tail gas treatment device.

[0017] As a preferred embodiment of the present invention, the continuous flow reactor is a tower reactor or a tubular reactor; wherein, the tower reactor includes a gas distributor at the bottom, packing inside the tower, an external heating jacket, a bottom feed inlet, an upper discharge outlet and a top gas outlet; the tubular reactor includes an internal static mixer, an external heating jacket, a bottom feed inlet, an upper discharge outlet and a top gas outlet.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] Based on the principle of engineering process intensification, this invention proposes a novel reaction mechanism: transforming the liquid-liquid reaction into a gas-liquid reaction (enhancing mass transfer) and achieving a "self-limiting reaction" in space to reduce the occurrence of excessive side reactions (reducing the contact between methylhydrazine hydrochloride and methanol), fundamentally solving the problems of low reaction efficiency, low selectivity, and high safety risks.

[0020] (1) Significantly improved reaction efficiency: In traditional pressurized autoclave reactions, liquid hydrazine hydrochloride and liquid methanol have poor miscibility, limiting mass transfer and resulting in low reaction efficiency. This invention converts methanol from liquid to gas, transforming the reaction system from a pressurized liquid-liquid two-phase reaction to an atmospheric pressure gas-liquid two-phase reaction. Gaseous methanol is introduced into the bottom of the reaction tower and further dispersed by a gas distributor. It then comes into continuous turbulent gas-liquid contact with liquid hydrazine hydrochloride in the reactor, ensuring thorough mixing of the gas and liquid and promoting the reaction. This fundamentally reconstructs the reaction mechanism and mass transfer path, greatly improving reaction efficiency and solving the problem of low reaction efficiency in traditional processes.

[0021] (2) Significantly improved reaction selectivity: In a batch reaction system, the raw materials and products are in a state of complete backmixing for a long time, with methylhydrazine hydrochloride and methanol coexisting, making it difficult to suppress the over-methylation reaction. In this invention, the reaction liquid flows from bottom to top along the tower, and methanol is gradually consumed from bottom to top, effectively reducing the contact between methylhydrazine hydrochloride and a large amount of methanol, reducing the collision probability between methylhydrazine hydrochloride molecules and methanol molecules, effectively suppressing the formation of by-products such as unsymmetrical dimethylhydrazine hydrochloride, and realizing a "space-limited reaction". This fundamentally solves the problem of excessive cascade side reactions, which is an effect that batch reaction cannot achieve.

[0022] (3) Significantly reduced equipment investment: In traditional batch reactor processes, the reaction usually needs to be carried out under conditions of 1.0 to 1.6 MPa, requiring the use of pressure-resistant equipment; however, the extremely corrosive nature of hydrazine hydrochloride makes it impossible to use conventional alloy equipment, and currently industrial production uses pressure-resistant glass-lined reactors. This invention adopts continuous tower reactor operation, which allows the reaction to be carried out under normal pressure or slightly positive pressure conditions, avoiding the risks of corrosion leakage and overpressure explosion caused by high pressure, reducing the requirements for equipment materials and pressure resistance performance, and significantly saving equipment investment.

[0023] (4) Improved operational safety and stability: The gas distributor and internal components of the tower reactor of this invention enhance gas-liquid mixing, eliminating the need for dynamic equipment such as mechanical stirring, thus improving the safety and stability of production operation.

[0024] (5) Achieving continuous production: Compared with the traditional intermittent batch process, the present invention achieves continuous production of methylhydrazine, which significantly improves production efficiency, reduces production costs, and has great value for large-scale industrial production. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the continuous production apparatus for methylhydrazine in this invention.

[0026] The reference numerals in the figure are as follows: 1. Tower reactor; 2. Gas distributor; 3. Sampling point; 4. Temperature sensor; 5. Hydrazine hydrochloride melting vessel; 6. Methanol vaporization tank; 7. Reaction liquid storage tank; 8. Free reaction vessel; 9. Condenser; 10. Light phase receiving tank; 11. Distillation column; 12. Hydrazine hydrochloride receiving tank; 13. Condenser; 14. Unsymmetrical dimethylhydrazine receiving tank; 15. Methylhydrazine receiving tank; 16. Hydrazine hydrate receiving tank. Detailed Implementation

[0027] To more clearly illustrate the technical solution of the present invention, the following description is provided in conjunction with embodiments.

[0028] Part 1: Overview of the Technical Solution of the Invention (Taking a Tower Reactor as an Example)

[0029] (a) Continuous production method of methylhydrazine

[0030] 1. Raw material pretreatment and feeding

[0031] The continuous production of methylhydrazine according to the present invention uses raw materials including hydrazine hydrochloride, methanol, and a catalyst, with a molar ratio of 1:0.3-4.0 (0.3-1.0 is preferred, more preferably 0.4-0.6):0.03-0.20 (preferably 0.08-0.10). The catalyst is hydrogen chloride gas, hydrochloric acid, hydrazine dihydrochloride, or chloromethane; the water content in the hydrazine hydrochloride does not exceed 20% of the hydrazine hydrochloride mass percentage to avoid excessive water affecting the vaporization state of methanol in the tower reactor.

[0032] Hydrazine hydrochloride is heated to 100–150°C (preferably 120–130°C) and then fed to the bottom of the tower reactor. Liquid methanol is heated and vaporized to obtain methanol vapor, which is then piped to the bottom of the tower reactor. The catalyst is pre-mixed with liquid hydrazine hydrochloride and added to the tower, or it is fed into the tower through a separate pipeline from the bottom. Alternatively, a suitable amount of liquid methanol can be piped into the bottom of the tower reactor to regulate the temperature inside the tower.

[0033] 2. Methylation reaction and discharge

[0034] Liquid hydrazine hydrochloride, heated and melted, is fed together with methanol vapor and catalyst into the bottom of a tower reactor. The reaction liquid undergoes a methylation reaction as it flows upwards within the tower. The tower temperature is controlled at 100–150°C (preferably 120–130°C); the tower pressure is maintained at atmospheric pressure or slightly positive pressure to keep the methanol in a vaporized state. The gas is discharged from the top of the tower reactor; the reaction liquid overflows from the upper part of the tower reactor and is a mixture of methylhydrazine hydrochloride, unsymmetrical dimethylhydrazine hydrochloride, and hydrazine hydrochloride.

[0035] 3. Post-processing of reaction products

[0036] The reaction solution is fed into a free reaction vessel through a pipeline, where hydrazine hydrate is used as a freeing agent (deprotonating agent) to release methylhydrazine and unsymmetrical dimethylhydrazine from the hydrazine salt. As an example, the molar ratio of hydrazine hydrate to methylhydrazine hydrochloride in the reaction solution during the free reaction is 1–4 (preferably 2:1); fresh hydrazine hydrate and hydrazine hydrate recovered through distillation can be combined and used as a freeing agent in the free reaction vessel.

[0037] The gas is then fed into a distillation unit for separation. Hydrazine hydrochloride is recovered from the bottom of the distillation column and reused as a feedstock. The fraction at the top of the distillation column is condensed and separated according to the difference in boiling points to obtain unsymmetrical dimethylhydrazine, methylhydrazine, and hydrazine hydrate. The hydrazine hydrate can be returned to the free reaction vessel as a free agent. The gas at the top of the tower reactor first passes through a condenser to separate unreacted liquid methanol, which is sent to a light phase receiving tank. The waste gas is sent to a tail gas treatment unit.

[0038] Through the innovative continuous production process of this invention, the single-pass conversion rate of hydrazine hydrochloride can reach more than 40%, and the reaction selectivity of methylhydrazine hydrochloride can reach more than 95%.

[0039] The core of the continuous production process of this invention lies in the innovative coupling of raw material pretreatment, methylation reaction, and reaction apparatus. The separation process of the reaction products obtained from continuous production is existing technology (such as free reaction, distillation separation, condensation separation, etc.). Those skilled in the art can make selections that meet the requirements of industrial production based on publicly available literature and existing production experience; this invention does not impose any special requirements.

[0040] Part Two: Specific Implementation Examples and Comparative Analysis

[0041] Example 1

[0042] In this embodiment, the specific steps for the continuous production of methylhydrazine are as follows:

[0043] 1. Add 200 kg of solid hydrazine hydrochloride to a hydrazine hydrochloride melting vessel and heat it to 95°C to melt the solid hydrazine hydrochloride into liquid hydrazine hydrochloride. Then, introduce 8.5 kg of hydrogen chloride gas (8% of the molar amount of hydrazine hydrochloride) as a catalyst into the liquid hydrazine hydrochloride.

[0044] 2. The hydrazine hydrochloride, after being acidified with hydrogen chloride, is further heated to 120-130℃ and then pumped into the bottom of the tower reactor at a flow rate of 52.1 kg / h.

[0045] 3. Methanol is heated in the methanol vaporization tank to form high-temperature methanol vapor, which is then metered by a gas flow meter and introduced into the bottom of the tower reactor. By adjusting the gas flow rate, the methanol feed rate is controlled at 11.6 kg / h (0.5 equivalent of the molar amount of hydrazine hydrochloride feed).

[0046] 4. Liquid hydrazine hydrochloride and gaseous methanol are separately introduced into the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. The temperature inside the tower is maintained at 120-130℃ by heat transfer oil in the outer jacket of the tower reactor, thus allowing the methylation reaction to proceed under atmospheric pressure.

[0047] 5. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor. Methanol is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port and enters the reaction liquid storage tank. The sampling analysis results show that the single-pass conversion rate of hydrazine hydrochloride is 46%, and the reaction selectivity of methylhydrazine hydrochloride is 97.4%.

[0048] 6. The reaction solution in the storage tank is continuously fed into the free reaction vessel, where hydrazine hydrate is added for the free reaction. Hydrazine hydrate (commercially available concentration 80%) is continuously added to the free reaction vessel at a flow rate of 41.9 kg / h. The mixture after the free reaction is sent to a distillation unit, where it is separated to obtain 0.52 kg / h of unsymmetrical dimethylhydrazine, 37.6 kg / h of a 40% methylhydrazine aqueous solution, and 17.5 kg / h of recovered hydrazine hydrate. The residual hydrazine hydrochloride from the free reaction vessel is returned to the hydrazine hydrochloride melting vessel for use in the next cycle of methylation reaction.

[0049] 7. The gas discharged from the top of the tower reactor is separated by a condenser to obtain unreacted liquid methanol, which is sent to a light phase receiving tank, while the waste gas is sent to a tail gas treatment device.

[0050] Example 2:

[0051] In this embodiment, the specific steps for the continuous production of methylhydrazine are as follows:

[0052] 1. Add solid hydrazine hydrochloride (200 kg) into the hydrazine hydrochloride melting kettle, heat it to 120-130℃ to form molten hydrazine hydrochloride, and then pump it into the bottom of the tower reactor at a flow rate of 50 kg / h.

[0053] 2. Methanol is heated in a methanol vaporization tank to form high-temperature methanol vapor, which is then metered by a gas flow meter and introduced into the bottom of the tower reactor. By adjusting the gas flow rate, the methanol feed rate is controlled at 11.6 kg / h (0.5 equivalent of the molar amount of hydrazine hydrochloride feed).

[0054] 3. Liquid hydrazine hydrochloride and gaseous methanol are separately introduced into the bottom of the tower reactor; simultaneously, hydrogen chloride gas, acting as a catalyst, is introduced into the bottom of the tower reactor at a rate of 2.1 kg / h (15% of the molar amount of hydrazine hydrochloride); the three materials are thoroughly mixed and contacted within the tower. The temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature inside the tower at 120-130℃, thus allowing the methylation reaction to proceed under atmospheric pressure.

[0055] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor. Methanol is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port and enters the reaction liquid storage tank. The sampling analysis results show that the single-pass conversion rate of hydrazine hydrochloride is 45%, and the reaction selectivity of methylhydrazine hydrochloride is 97.7%.

[0056] 5. The reaction solution in the storage tank is continuously fed into the free reaction vessel, where hydrazine hydrate is added for the free reaction. Hydrazine hydrate (commercially available concentration 80%) is continuously added to the free reaction vessel at a flow rate of 41.9 kg / h. The mixture after the free reaction is sent to a distillation unit, where it is separated to obtain 0.53 kg / h of unsymmetrical dimethylhydrazine, 37.8 kg / h of a 40% methylhydrazine aqueous solution, and 15.2 kg / h of recovered hydrazine hydrate. The residual hydrochloric acid after the free reaction is returned to the hydrazine hydrochloride melting vessel for use in the next cycle of methylation reaction.

[0057] 6. The gas discharged from the top of the tower reactor is separated by a condenser to obtain unreacted liquid methanol, which is sent to a light phase receiving tank, while the waste gas is sent to a tail gas treatment device.

[0058] Example 3

[0059] In this embodiment, the specific steps for the continuous production of methylhydrazine are as follows:

[0060] 1. Add 200 kg of solid hydrazine hydrochloride to a hydrazine hydrochloride melting vessel and heat it to 95°C to melt the solid hydrazine hydrochloride into liquid hydrazine hydrochloride. Then, introduce 3.2 kg of hydrogen chloride gas as a catalyst into the liquid hydrazine hydrochloride (3% of the molar amount of hydrazine hydrochloride).

[0061] 2. The hydrazine hydrochloride, after being acidified with hydrogen chloride, is further heated to 130-140℃ and then pumped into the bottom of the tower reactor at a flow rate of 50.8 kg / h.

[0062] 3. Methanol is heated in the methanol vaporization tank to form high-temperature methanol vapor, which is then metered by a gas flow meter and introduced into the bottom of the tower reactor. By adjusting the gas flow rate, the methanol feed rate is controlled at 7.0 kg / h (0.3 equivalents of the feed molar amount of hydrazine hydrochloride).

[0063] 4. Liquid hydrazine hydrochloride and gaseous methanol are separately introduced into the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. The temperature inside the tower is maintained at 130-140℃ by heat transfer oil in the outer jacket of the tower reactor, thus allowing the methylation reaction to proceed under atmospheric pressure.

[0064] 5. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor. Methanol is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port and enters the reaction liquid storage tank. Sampling analysis results show that the single-pass conversion rate of hydrazine hydrochloride is 27.8% (0.3 equivalent of methanol, the theoretical maximum single-pass conversion rate of hydrazine hydrochloride is 30%), and the reaction selectivity of methylhydrazine hydrochloride is 99.1%.

[0065] 6. The reaction solution in the storage tank is continuously fed into the free reaction vessel, where hydrazine hydrate is added for the free reaction. Hydrazine hydrate (commercially available concentration 80%) is continuously added to the free reaction vessel at a flow rate of 31.7 kg / h. The mixture after the free reaction is sent to a distillation unit, where it is separated to obtain unsymmetrical dimethylhydrazine (0.1 kg / h), a 40% aqueous solution of methylhydrazine (23.1 kg / h), and recovers 16.3 kg / h of hydrazine hydrate. The residual hydrochloric acid after the free reaction is returned to the hydrazine hydrochloride melting vessel for use in the next cycle of methylation reaction.

[0066] 7. The gas discharged from the top of the tower reactor is separated by a condenser to obtain unreacted liquid methanol, which is sent to a light phase receiving tank, while the waste gas is sent to a tail gas treatment device.

[0067] Example 4

[0068] In this embodiment, the specific steps for the continuous production of methylhydrazine are as follows:

[0069] 1. Add 200 kg of solid hydrazine hydrochloride to a hydrazine hydrochloride melting vessel and heat it to 95°C to melt the solid hydrazine hydrochloride into liquid hydrazine hydrochloride. Then, introduce hydrogen chloride gas as a catalyst into the liquid hydrazine hydrochloride at a rate of 21.3 kg (20% of the molar amount of hydrazine hydrochloride).

[0070] 2. The hydrazine hydrochloride, after being acidified with hydrogen chloride, is further heated to 110-120℃ and then pumped into the bottom of the tower reactor at a flow rate of 55.3 kg / h.

[0071] 3. Methanol is heated in the methanol vaporization tank to form high-temperature methanol vapor, which is then metered by a gas flow meter and introduced into the bottom of the tower reactor. By adjusting the gas flow rate, the methanol feed rate is controlled at 23.4 kg / h (1.0 equivalent of the molar amount of hydrazine hydrochloride feed).

[0072] 4. Liquid hydrazine hydrochloride and gaseous methanol are separately introduced into the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. The temperature inside the tower is maintained at 110-120℃ by heat transfer oil in the outer jacket of the tower reactor, thus allowing the methylation reaction to proceed under atmospheric pressure.

[0073] 5. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor. Methanol is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port and enters the reaction liquid storage tank. The sampling analysis results show that the single-pass conversion rate of hydrazine hydrochloride is 41.8%, and the reaction selectivity of methylhydrazine hydrochloride is 95.3%.

[0074] 6. The reaction solution in the storage tank is continuously fed into the free reaction vessel, where hydrazine hydrate is added for the free reaction. Hydrazine hydrate (commercially available concentration 80%) is continuously added to the free reaction vessel at a flow rate of 38.1 kg / h. The mixture after the free reaction is sent to a distillation unit, where it is separated to obtain 0.86 kg / h of unsymmetrical dimethylhydrazine, 33.4 kg / h of a 40% methylhydrazine aqueous solution, and 17.9 kg / h of recovered hydrazine hydrate. The residual hydrochloric acid after the free reaction is returned to the hydrazine hydrochloride melting vessel for use in the next cycle of methylation reaction.

[0075] 7. The gas discharged from the top of the tower reactor is separated by a condenser to obtain unreacted liquid methanol, which is sent to a light phase receiving tank, while the waste gas is sent to a tail gas treatment device.

[0076] Example 5

[0077] In this embodiment, the specific steps for the continuous production of methylhydrazine are as follows:

[0078] 1. Add solid hydrazine hydrochloride (200 kg) and dihydrazine hydrochloride (7.6 kg, which is 10% of the molar amount of hydrazine hydrochloride) as a catalyst into the hydrazine hydrochloride melting vessel, heat to 130-140℃, and then pump into the bottom of the tower reactor at a flow rate of 51.9 kg / h.

[0079] 2. Methanol is heated in a methanol vaporization tank to form high-temperature methanol vapor, which is then metered by a gas flow meter and introduced into the bottom of the tower reactor. By adjusting the gas flow rate, the methanol feed rate is controlled at 58.4 kg / h (2.5 times the molar amount of hydrazine hydrochloride feed).

[0080] 4. Liquid hydrazine hydrochloride and gaseous methanol are separately introduced into the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. The temperature inside the tower is maintained at 130-140℃ by heat transfer oil in the outer jacket of the tower reactor, thus allowing the methylation reaction to proceed under atmospheric pressure.

[0081] 5. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor. Methanol is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port and enters the reaction liquid storage tank. The sampling analysis results show that the single-pass conversion rate of hydrazine hydrochloride is 42.4%, and the reaction selectivity of methylhydrazine hydrochloride is 95.2%.

[0082] 6. The reaction solution in the storage tank is continuously fed into the free reaction vessel, where hydrazine hydrate is added for the free reaction. Hydrazine hydrate (commercially available concentration 80%) is continuously added to the free reaction vessel at a flow rate of 48.4 kg / h. The mixture after the free reaction is sent to a distillation unit, where it is separated to obtain 0.89 kg / h of unsymmetrical dimethylhydrazine, 33.9 kg / h of a 40% methylhydrazine aqueous solution, and 27.5 kg / h of recovered hydrazine hydrate. The residual hydrochloric acid after the free reaction is returned to the hydrazine hydrochloride melting vessel for use in the next cycle of methylation reaction.

[0083] 7. The gas discharged from the top of the tower reactor is separated by a condenser to obtain unreacted liquid methanol, which is sent to a light phase receiving tank, while the waste gas is sent to a tail gas treatment device.

[0084] Example 6

[0085] In this embodiment, the specific steps for the continuous production of methylhydrazine are as follows:

[0086] 1. Put solid hydrazine hydrochloride (200 kg) into the hydrazine hydrochloride melting kettle, heat it to 95°C to melt the solid hydrazine hydrochloride into liquid hydrazine hydrochloride, continue heating to 120-130°C, and then pump it into the bottom of the tower reactor at a flow rate of 50 kg / h.

[0087] 3. Methanol is heated in the methanol vaporization tank to form high-temperature methanol vapor, which is then metered by a gas flow meter and introduced into the bottom of the tower reactor. By adjusting the gas flow rate, the methanol feed rate is controlled at 18.7 kg / h (0.8 equivalent of the molar amount of hydrazine hydrochloride feed).

[0088] 4. Liquid hydrazine hydrochloride and gaseous methanol are separately introduced into the bottom of the tower reactor. Simultaneously, chloromethane gas, acting as a catalyst, is introduced into the bottom of the tower reactor at a rate of 2.9 kg / h (8% of the molar amount of hydrazine hydrochloride). The mixture is thoroughly mixed and contacted within the tower via a gas distributor. The temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature within the tower at 120-130℃, thus allowing the methylation reaction to proceed under atmospheric pressure.

[0089] 5. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor. Methanol is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port and enters the reaction liquid storage tank. The sampling analysis results show that the single-pass conversion rate of hydrazine hydrochloride is 41.3%, and the reaction selectivity of methylhydrazine hydrochloride is 97.4%.

[0090] 6. The reaction solution in the storage tank is continuously fed into the free reaction vessel, where hydrazine hydrate is added for a free reaction. Hydrazine hydrate (commercially available concentration 80%) is continuously added to the free reaction vessel at a flow rate of 37.7 kg / h. The mixture after the free reaction is sent to a distillation unit, where it is separated to obtain 0.47 kg / h of unsymmetrical dimethylhydrazine, 33.8 kg / h of a 40% methylhydrazine aqueous solution, and 15.4 kg / h of recovered hydrazine hydrate. The residual hydrazine hydrochloride from the free reaction vessel is returned to the hydrazine hydrochloride melting vessel for use in the next cycle of methylation reaction.

[0091] 7. The gas discharged from the top of the tower reactor is separated by a condenser to obtain unreacted liquid methanol, which is sent to a light phase receiving tank, while the waste gas is sent to a tail gas treatment device.

[0092] Example 7

[0093] In this embodiment, the specific steps for the continuous production of methylhydrazine are as follows:

[0094] 1. Add 200 kg of solid hydrazine hydrochloride to a hydrazine hydrochloride melting vessel and heat it to 95°C to melt the solid hydrazine hydrochloride into liquid hydrazine hydrochloride. Then, introduce 28.5 kg of hydrochloric acid (30% by mass) as a catalyst (8% of the molar amount of hydrazine hydrochloride) into the liquid hydrazine hydrochloride.

[0095] 2. The hydrazine hydrochloride, after being acidified with hydrochloric acid, is further heated to 110-120℃ and then pumped into the bottom of the tower reactor at a flow rate of 57.1 kg / h.

[0096] 3. Methanol is heated in the methanol vaporization tank to form high-temperature methanol vapor, which is then metered by a gas flow meter and introduced into the bottom of the tower reactor. By adjusting the gas flow rate, the methanol feed rate is controlled at 11.6 kg / h (0.5 equivalent of the molar amount of hydrazine hydrochloride feed).

[0097] 4. Liquid hydrazine hydrochloride and gaseous methanol are separately introduced into the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. The temperature inside the tower is maintained at 110-120℃ by heat transfer oil in the outer jacket of the tower reactor, thus allowing the methylation reaction to proceed under atmospheric pressure.

[0098] 5. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor. Methanol is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port and enters the reaction liquid storage tank. The sampling analysis results show that the single-pass conversion rate of hydrazine hydrochloride is 46.8%, and the reaction selectivity of methylhydrazine hydrochloride is 96.5%.

[0099] 6. The reaction solution in the storage tank is continuously fed into the free reaction vessel, where hydrazine hydrate is added for a free reaction. Hydrazine hydrate (commercially available concentration 80%) is continuously added to the free reaction vessel at a flow rate of 41.9 kg / h. The mixture after the free reaction is sent to a distillation unit, where it is separated to obtain 0.71 kg / h of unsymmetrical dimethylhydrazine, 37.9 kg / h of a 40% methylhydrazine aqueous solution, and 21.9 kg / h of recovered hydrazine hydrate. The residual hydrazine hydrochloride from the free reaction vessel is returned to the hydrazine hydrochloride melting vessel for use in the next cycle of methylation reaction.

[0100] 7. The gas discharged from the top of the tower reactor is separated by a condenser to obtain unreacted liquid methanol, which is sent to a light phase receiving tank, while the waste gas is sent to a tail gas treatment device.

[0101] Example 8

[0102] In this embodiment, the specific steps for the continuous production of methylhydrazine are as follows:

[0103] 1. Add 200 kg of solid hydrazine hydrochloride to a hydrazine hydrochloride melting vessel and heat it to 95°C to melt the solid hydrazine hydrochloride into liquid hydrazine hydrochloride. Then, introduce 5.3 kg of hydrogen chloride gas (5% of the molar weight of hydrazine hydrochloride) as a catalyst into the liquid hydrazine hydrochloride.

[0104] 2. The hydrazine hydrochloride, after being acidified with hydrogen chloride, is further heated to 100-110℃ and then pumped into the bottom of the tower reactor at a flow rate of 51.3 kg / h.

[0105] 3. Methanol is heated in the methanol vaporization tank to form high-temperature methanol vapor, which is then metered by a gas flow meter and introduced into the bottom of the tower reactor. By adjusting the gas flow rate, the methanol feed rate is controlled at 93.4 kg / h (4.0 equivalents of the feed molar amount of hydrazine hydrochloride).

[0106] 4. Liquid hydrazine hydrochloride and gaseous methanol are separately introduced into the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. The temperature inside the tower is maintained at 100-110℃ by heat transfer oil in the outer jacket of the tower reactor, thus allowing the methylation reaction to proceed under atmospheric pressure.

[0107] 5. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor. Methanol is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port and enters the reaction liquid storage tank. The sampling analysis results show that the single-pass conversion rate of hydrazine hydrochloride is 43.5%, and the reaction selectivity of methylhydrazine hydrochloride is 95.0%.

[0108] 6. The reaction solution in the storage tank is continuously fed into the free reaction vessel, where hydrazine hydrate is added for a free reaction. Hydrazine hydrate (commercially available concentration 80%) is continuously added to the free reaction vessel at a flow rate of 49.6 kg / h. The mixture after the free reaction is sent to a distillation unit, where it is separated to obtain 0.95 kg / h of unsymmetrical dimethylhydrazine, 34.7 kg / h of a 40% methylhydrazine aqueous solution, and 25.9 kg / h of recovered hydrazine hydrate. The residual hydrazine hydrochloride from the free reaction vessel is returned to the hydrazine hydrochloride melting vessel for use in the next cycle of methylation reaction.

[0109] 7. The gas discharged from the top of the tower reactor is separated by a condenser to obtain unreacted liquid methanol, which is sent to a light phase receiving tank, while the waste gas is sent to a tail gas treatment device.

[0110] Example 9

[0111] In this embodiment, the specific steps for the continuous production of methylhydrazine are as follows:

[0112] 1. Add 200 kg of solid hydrazine hydrochloride to a hydrazine hydrochloride melting vessel and heat it to 95°C to melt the solid hydrazine hydrochloride into liquid hydrazine hydrochloride. Then, introduce 8.5 kg of hydrogen chloride gas (8% of the molar amount of hydrazine hydrochloride) as a catalyst into the liquid hydrazine hydrochloride.

[0113] 2. The hydrazine hydrochloride, after being acidified with hydrogen chloride, is further heated to 140-150℃ and then pumped into the bottom of the tower reactor at a flow rate of 52.1 kg / h.

[0114] 3. Liquid methanol is fed into the bottom of the reaction tower using a transfer pump and a flow meter. The methanol feed rate is controlled at 11.6 kg / h (0.5 times the molar amount of hydrazine hydrochloride feed). The liquid methanol absorbs heat from the high-temperature hydrazine hydrochloride at the bottom of the tower and turns into gaseous methanol. At the same time, the temperature of the hydrazine hydrochloride is reduced to a suitable reaction temperature range. The temperature is then controlled by the heat transfer oil in the outer jacket of the tower reactor to maintain the reaction temperature in the tower at 140-150℃.

[0115] 4. Liquid hydrazine hydrochloride and gaseous methanol are thoroughly mixed and contacted in the tower through a gas distributor, thereby carrying out the methylation reaction under normal pressure.

[0116] 5. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor. Methanol is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port and enters the reaction liquid storage tank. The sampling analysis results show that the single-pass conversion rate of hydrazine hydrochloride is 44.6%, and the reaction selectivity of methylhydrazine hydrochloride is 96.1%.

[0117] 6. The reaction solution in the storage tank is continuously fed into the free reaction vessel, where hydrazine hydrate is added for a free reaction. Hydrazine hydrate (commercially available concentration 80%) is continuously added to the free reaction vessel at a flow rate of 41.9 kg / h. The mixture after the free reaction is sent to a distillation unit, where it is separated to obtain unsymmetrical dimethylhydrazine (UDMH) at a flow rate of 0.76 kg / h, a 40% aqueous solution of methylhydrazine at a flow rate of 35.9 kg / h, and hydrazine hydrate at a flow rate of 18.2 kg / h. The residual hydrazine hydrochloride from the free reaction vessel is returned to the hydrazine hydrochloride melting vessel for use in the next cycle of methylation reaction.

[0118] 7. The gas discharged from the top of the tower reactor is separated by a condenser to obtain unreacted liquid methanol, which is sent to a light phase receiving tank, while the waste gas is sent to a tail gas treatment device.

[0119] Comparative Example 1

[0120] Compared to Example 1, the reaction apparatus is a batch reactor, and the feed ratio, reaction time, and post-treatment are all the same:

[0121] 1. Add solid hydrazine hydrochloride (50 kg) into a high-pressure reactor, add liquid methanol (11.6 kg), and start stirring; introduce hydrogen chloride gas (2.1 kg) through a conduit.

[0122] 2. The high-pressure reactor is heated to an internal temperature of 120-130 degrees Celsius using heat transfer oil, and then kept at that temperature for 1.5 hours.

[0123] 3. The pressure rises to a maximum of 1.2 MPa during the reaction (the tower reaction is at atmospheric pressure).

[0124] 4. After the reaction was completed, the sampling analysis results showed that the single-pass conversion rate of hydrazine hydrochloride was only 36.9%, and the reaction selectivity of methylhydrazine hydrochloride was 93.1%.

[0125] 5. The reaction solution is transferred to a free reaction vessel, and hydrazine hydrate (41.9 kg) is added to the free reaction vessel at once to carry out the free reaction. The mixture after the free reaction is sent to a distillation unit, and after distillation separation, 1.11 kg / h of unsymmetrical dimethylhydrazine, 28.8 kg / h of 40% methylhydrazine aqueous solution, and 14.2 kg / h of hydrazine hydrate are obtained.

[0126] Analysis of the reaction revealed that the significantly increased pressure in the batch reactor led to increased safety risks and equipment investment. Furthermore, because the materials were completely backmixed during the single-batch reaction, the reaction selectivity decreased, and the content of the byproduct unsymmetrical dimethylhydrazine increased. In addition, the corresponding data also show that the continuous production method of methylhydrazine of this invention significantly surpasses the traditional batch reactor process in terms of single-pass conversion rate of hydrazine hydrochloride, reaction selectivity of methylhydrazine hydrochloride, and yield of the target product methylhydrazine.

[0127] It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of this invention. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations.

Claims

1. A continuous production method for methylhydrazine, characterized in that, include: The heated and melted liquid hydrazine hydrochloride, along with methanol and a catalyst, is continuously fed into a continuous flow reactor for continuous heating and reaction. The reaction liquid overflows from the top of the continuous flow reactor and is treated with hydrazine hydrate to separate methylhydrazine and unsymmetrical dimethylhydrazine. The single-pass conversion rate and selectivity of hydrazine hydrochloride are controlled by adjusting the feed ratio of hydrazine hydrochloride, methanol and catalyst.

2. The method according to claim 1, characterized in that, The molar ratio of the reactants hydrazine hydrochloride, methanol, and catalyst is 1:0.3–4.0:0.03–0.

20.

3. The method according to claim 1, characterized in that, The catalyst is hydrogen chloride gas, hydrochloric acid, hydrazine dihydrochloride, or chloromethane; the catalyst is pre-mixed with liquid hydrazine hydrochloride before being fed into the reactor, or fed into the reactor through a separate pipeline.

4. The method according to claim 1, characterized in that, Hydrazine hydrochloride is heated to 100–150 °C to form liquid hydrazine hydrochloride, which is then fed into the bottom of the reactor; liquid methanol is heated to form gaseous methanol, which is also fed into the bottom of the reactor.

5. The method according to claim 1, characterized in that, Further, it includes feeding an appropriate amount of liquid methanol into the reactor through a pipeline, and using the liquid methanol to regulate the temperature inside the reactor.

6. The method according to claim 1, characterized in that, The reaction temperature inside the reactor is 100–150°C; the pressure inside the reactor is atmospheric pressure or slightly positive pressure to ensure that methanol is in a vaporized state.

7. The method according to claim 1, characterized in that, The reaction liquid overflowing from the tower reactor first enters the reaction liquid storage tank, and then is sent to the free reaction vessel through pipeline, with hydrazine hydrate as the free agent. The reaction liquid obtained from the free treatment is sent to the distillation column for distillation treatment. Hydrazine hydrochloride is recovered from the bottom of the distillation column and reused as a reaction feedstock. The fraction at the top of the distillation column is separated by a condenser to obtain unsymmetrical dimethylhydrazine, methylhydrazine and hydrazine hydrate, with hydrazine hydrate being reused as the free agent.

8. The method according to claim 1, characterized in that, The gas discharged from the top of the tower reactor first passes through a condenser to separate unreacted liquid methanol for recycling, while the non-condensable waste gas is sent to the tail gas treatment device.

9. The method according to claim 1, characterized in that, The continuous flow reactor is a tower reactor or a tubular reactor; wherein, the tower reactor includes a gas distributor at the bottom, packing inside the tower, an external heating jacket, a bottom feed inlet, an upper discharge outlet, and a top gas outlet; the tubular reactor includes an internal static mixer, an external heating jacket, a bottom feed inlet, an upper discharge outlet, and a top gas outlet.

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