Continuous catalysis system and method for synthesizing methylhydrazine
By applying a continuous catalytic system and a multi-element synergistic catalyst, the high pressure risk and product quality fluctuation problems in the synthesis of methylhydrazine were solved, a safe and efficient production process was achieved, the activity and stability of the catalyst were improved, and the range of applicable raw materials was expanded.
Patent Information
- Application Number
- CN202512019058.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-10
AI Technical Summary
Existing methylhydrazine synthesis technologies suffer from problems such as high pressure risk, high hazard factor, large fluctuations in product quality, difficulty in controlling by-products, insufficient catalyst activity and stability, poor raw material compatibility, and low degree of automation control, which limit their industrial-scale promotion.
A continuous catalytic system is adopted, including raw material pretreatment, continuous reaction, post-treatment purification and catalyst circulation units. Combined with gradient temperature rise, back pressure regulation and real-time parameter monitoring, suitable solid acid, metal and ionic liquid catalysts are used to achieve multi-element synergistic catalysis and form a closed-loop system.
It improves the safety and purity of methylhydrazine synthesis, reduces catalyst consumption costs, expands the range of applicable raw materials, and achieves a highly efficient and stable production process to meet the needs of high-end applications.
Smart Images
Figure CN121819722A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of methylhydrazine synthesis technology, and in particular to a continuous catalytic system and method for synthesizing methylhydrazine. Background Technology
[0002] Methylhydrazine, as a key chemical raw material, is widely used in pharmaceutical synthesis, pesticide production, fine chemicals, and aerospace propellants, with consistently stable market demand. Currently, common industrial methods for synthesizing methylhydrazine include the chloramine method, the benzaldehyde condensation method of hydrazine hydrate, the dimethyl sulfate method of hydrazine hydrate, and the hydrochloric acid-methanol-hydrazine hydrate method. However, all of these methods have significant drawbacks: the chloramine method has low product yield, high energy consumption, and is difficult to separate; the benzaldehyde condensation method of hydrazine hydrate is complex and has high raw material costs, hindering industrial application; the dimethyl sulfate method of hydrazine hydrate uses highly toxic dimethyl sulfate, posing significant safety hazards and producing difficult-to-treat sodium salts; and the hydrochloric acid-methanol-hydrazine hydrate method has low reaction yield and requires large equipment investment.
[0003] Current mainstream industrial production uses the hydrazine hydrate process, which, while clean, energy-efficient, and produces relatively high-quality products, involves alkylation reactions at pressures as high as 0.9-1.3 MPa, posing significant potential safety risks. Furthermore, it often employs batch reactors with volumes of 2000L or 3000L, leading to high hazard levels, significant product quality fluctuations, and difficulties in controlling byproducts. Although continuous catalytic synthesis technology has been gradually applied in the chemical industry, its application in methylhydrazine synthesis still faces core technological bottlenecks: a lack of efficient and inexpensive catalysts suitable for continuous flow reactions; insufficient catalyst activity and stability; difficulty in catalyst recovery; imperfect reaction parameter coupling and control logic, resulting in lower mass and heat transfer efficiency; poor compatibility between continuous reaction systems and raw material characteristics, with impurities in industrial-grade raw materials easily affecting reaction stability; and low levels of automation throughout the process, making precise closed-loop control of process parameters difficult, resulting in a trade-off between product purity and production safety, thus hindering the technological upgrading and sustainable development of methylhydrazine production. Summary of the Invention
[0004] To address the technical problems existing in the prior art, embodiments of the present invention provide a continuous catalytic system and method for synthesizing methylhydrazine. The technical solution is as follows:
[0005] A continuous catalytic system and method for synthesizing methylhydrazine are provided, including a raw material pretreatment unit, a raw material preparation unit, a continuous reaction unit, a post-treatment purification unit, a catalyst recycling unit, and a whole-process control unit. Each unit is connected sequentially according to the process flow to form a closed-loop system.
[0006] The raw material pretreatment unit includes an adsorption column and a light component removal tower, which are connected by pipelines to adapt to the purification treatment of industrial-grade methanol raw materials; the raw material preparation unit includes a hydrazine hydrochloride dissolution vessel and a methanol catalytic solution preparation vessel, which are respectively equipped with a stirring module and an acidity adjustment component for the preparation of the corresponding raw material solution.
[0007] The continuous reaction unit consists of a microchannel reactor connected in series with a subsequent reaction section, and is equipped with a gradient heating module and a back pressure regulating component to achieve continuous catalytic alkylation of materials;
[0008] The post-processing purification unit includes a methanol distillation column, a free reaction vessel, and a vacuum distillation column. The vacuum distillation column is equipped with a side-stream sampling component to complete the purification of the reaction product liquid.
[0009] The catalyst recycling unit includes a solid-liquid separation component, a washing module, a drying module, and an active component replenishment vessel. It is connected to the raw material preparation unit through pipelines to realize the recycling and reuse of the catalyst.
[0010] The entire process control unit includes flow, temperature, pressure and component monitoring modules, which are electrically connected to the execution components of each functional unit;
[0011] Includes the following steps:
[0012] Preparation of S1 raw material system: Hydrazine hydrochloride and pure water were mixed and heated in a water bath. The mixture was stirred until the solid was completely dissolved to form a clear and transparent solution. Hydrochloric acid solution was added at set intervals and stirred continuously until the system was homogeneous to obtain hydrazine hydrochloride raw material solution. Methanol and solid acid catalyst were mixed, and hydrochloric acid was added and stirred until the components were evenly dispersed to obtain methanol catalyst solution.
[0013] S2 Continuous Catalytic Alkylation: Hydrazine hydrochloride feedstock and methanol catalyst are simultaneously fed to a continuous reaction unit connected in series with a microchannel and subsequent reaction section through a dual-feed system. The heating system is started to increase the temperature gradient, and the system pressure is adjusted by the back pressure valve to control the residence time of the material in the unit, thus completing the continuous catalytic alkylation reaction.
[0014] S3 post-treatment purification: The reaction product liquid is first subjected to atmospheric distillation to remove methanol and recover it. Liquid alkali is added to the residual liquid, stirred and allowed to stand for separation. The organic phase is then subjected to vacuum distillation, and the target fraction is collected to obtain the methylhydrazine product.
[0015] Beneficial effects
[0016] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:
[0017] By combining gradient heating and precise pressure regulation technology, stable control of reaction pressure is achieved. The small-volume continuous flow design replaces the traditional large-volume batch reactor reaction, solving the core problems of high pressure risk and high hazard factor in traditional processes. This improves the intrinsic safety level of methylhydrazine synthesis and meets the industry demand for improved intrinsic safety in hazardous chemical enterprises.
[0018] By screening and modifying suitable catalysts such as solid acids, metals, and ionic liquids, a multi-element synergistic catalytic structure is formed. Combined with the directional control of feed liquid acidity and catalyst recycling process, the long-term maintenance of catalytic activity and low-cost reuse are achieved. This solves the problems of insufficient activity, poor selectivity, and difficulty in recovery of traditional catalysts, and improves the catalytic efficiency and economy of the process.
[0019] By monitoring key reaction parameters in real time and dynamically adapting them, and combining the efficient mass and heat transfer characteristics of continuous flow reactions, precise temperature, pressure, and time control can be achieved in the synthesis of methylhydrazine. This solves the defects of large product quality fluctuations and numerous by-product accumulation in traditional batch processes, improves product purity and production stability, and meets the product quality requirements of high-end applications.
[0020] By adding a methanol pretreatment step, the process combines adsorption dehydration with the removal of light components to adapt to the characteristics of industrial-grade raw materials. This avoids the damage of moisture and impurities to the active sites of the catalyst, solving the problems of stringent requirements for raw material quality and limited application scenarios in traditional processes. It expands the process's adaptability to raw materials of different purities and its prospects for industrial application, while reducing raw material loss. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 This is a process flow diagram of a continuous catalytic system and method for synthesizing methylhydrazine, provided as an embodiment of this application. Detailed Implementation
[0023] The technical solution provided in this application will now be described in conjunction with the accompanying drawings.
[0024] To facilitate understanding of the embodiments of this application, the following points will be explained first:
[0025] First, in this application, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates an "or" relationship between the preceding and following related objects, but does not exclude the possibility of indicating an "and" relationship. The specific meaning can be understood in the context. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c" can represent: a, b, c; a and b; a and c; b and c; or a and b and c. Here, a, b, and c can be single or multiple.
[0026] Second, in this application, the use of prefixes such as "first" and "second" is merely for the purpose of distinguishing and describing different things belonging to the same name category, and does not constrain the order, size, or quantity of things. For example, "first message" and "second message" are simply different messages, and there is no temporal sequence, size, or priority relationship between them.
[0027] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.
[0028] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.
[0029] like Figure 1 As shown, this application provides a continuous catalytic method for synthesizing methylhydrazine, comprising the following steps:
[0030] Preparation of S1 raw material system: Hydrazine hydrochloride and pure water were mixed and heated in a water bath. The mixture was stirred until the solid was completely dissolved to form a clear and transparent solution. Hydrochloric acid solution was added at set intervals and stirred continuously until the system was homogeneous to obtain hydrazine hydrochloride raw material solution. Methanol and solid acid catalyst were mixed, and hydrochloric acid was added and stirred until the components were evenly dispersed to obtain methanol catalyst solution.
[0031] S2 Continuous Catalytic Alkylation: Hydrazine hydrochloride feedstock and methanol catalyst are simultaneously fed to a continuous reaction unit connected in series with a microchannel and subsequent reaction section through a dual-feed system. The heating system is started to increase the temperature gradient, and the system pressure is adjusted by the back pressure valve to control the residence time of the material in the unit, thus completing the continuous catalytic alkylation reaction.
[0032] S3 post-treatment purification: The reaction product liquid is first subjected to atmospheric distillation to remove methanol and recover it. Liquid alkali is added to the residual liquid, stirred and allowed to stand for separation. The organic phase is then subjected to vacuum distillation, and the target fraction is collected to obtain the methylhydrazine product.
[0033] As an optional embodiment, in step S1, the screening and modification method of the solid acid catalyst is as follows: screening catalysts suitable for continuous flow reactions from solid acid, metal, and ionic liquid catalysts, and modifying the screened catalysts by physical or chemical means to adjust their active site distribution and structural stability; the catalyst recovery method is as follows: after the reaction, the catalyst is collected by solid-liquid separation, washed with deionized water to remove surface residues, dried, immersed in active component replenishment solution, dried again, and returned to step S1 for recycling.
[0034] As an optional embodiment, in S2, the operation method of the continuous reaction system is as follows: after the material enters the microchannel reactor, the components are rapidly mixed and initially reacted by utilizing the flow field characteristics within the channel, and then the reaction continues to advance in the subsequent reaction section; both the microchannel reactor and the subsequent reaction section are heated by gradient heating to control the temperature difference between each reaction zone within a set range; the material residence time is dynamically adjusted according to the catalyst activity cycle and the reaction progress to ensure sufficient reaction and avoid the accumulation of side reactions.
[0035] As an optional embodiment, in S2, the method for controlling the reaction temperature, system pressure, and material flow rate is as follows: the reaction temperature is maintained within the appropriate range between the microchannel reactor and the subsequent reaction section; the system pressure is adjusted to the set range through the back pressure valve; and the delivery flow rates of the hydrazine hydrochloride feed solution and the methanol catalyst solution are synchronously controlled in a fixed ratio. Based on the changes in material composition during the reaction process, the flow rate ratio and residence time are dynamically fine-tuned to adapt to changes in catalyst activity.
[0036] As an optional embodiment, in S1, the acidity adjustment method of the hydrazine hydrochloride feed solution is as follows: by controlling the amount and interval of hydrochloric acid solution added, the acidity of the system is made to be within the range suitable for the active sites of the solid acid catalyst; this acidity condition matches the characteristics of the active sites of the catalyst, promotes the adsorption of hydrazine hydrochloride molecules on the catalyst surface, and at the same time blocks the reaction pathway of secondary alkylation of methyl hydrazine and methanol.
[0037] As an optional embodiment, in the methanol distillation stage of S3, after the distillation operation is completed, the solid acid catalyst after the reaction is separated by filtration, the surface adsorbed reaction residues and impurities are removed by washing with deionized water multiple times, the structure is restored by drying treatment, and then the active components are replenished by immersion in a mixed replenishment solution of metal ion salt and non-metal acid salt. After drying, it is returned to step S1 to prepare methanol catalyst solution.
[0038] As an optional embodiment, the reduced pressure distillation method of S3 is as follows: a packed distillation column is used for distillation operation, a side-stream outlet is set at a set position in the distillation section, and the distillation vacuum degree and the column top temperature are adjusted to form an adaptive relationship, so that the heavy components at the bottom of the column are refluxed to the middle section of the distillation column in a set proportion; the opening timing and extraction rate of the side-stream outlet are dynamically adjusted according to the column top temperature, the stable state of the vacuum degree and the separation process of the components in the column.
[0039] As an optional embodiment, the method further includes a process parameter monitoring and control step: a flow monitoring module is set in the dual-feed system, a temperature and pressure monitoring module is set in the continuous reaction system, and a component monitoring module is set in the distillation column. Each module continuously collects corresponding parameter data at a set frequency. After receiving the collected data, the control module analyzes the parameter deviation in real time and adjusts the feed pump speed of the dual-feed system, the heating power of the continuous reaction system, and the opening of the reflux valve of the distillation column to maintain the stability of each process parameter.
[0040] As an optional embodiment, a methanol pretreatment step is added to step S1: industrial methanol is first passed into an adsorption column for dehydration treatment. The type of adsorbent filled in the adsorption column is determined according to the water content in the methanol and the water tolerance characteristics of the solid acid catalyst. The dehydrated methanol is then passed into a light component removal tower, where low-boiling-point impurities and trace harmful components are removed by distillation. The operating parameters of the distillation process are adjusted according to the type of impurities and their boiling point characteristics.
[0041] This invention also proposes a continuous catalytic system for the synthesis of methylhydrazine, comprising a raw material pretreatment unit, a raw material preparation unit, a continuous reaction unit, a post-treatment purification unit, a catalyst circulation unit, and a full-process control unit, wherein each unit is connected sequentially according to the process flow to form a closed-loop system;
[0042] The raw material pretreatment unit includes an adsorption column and a light component removal tower, which are connected by pipelines to adapt to the purification treatment of industrial-grade methanol raw materials; the raw material preparation unit includes a hydrazine hydrochloride dissolution vessel and a methanol catalytic solution preparation vessel, which are respectively equipped with a stirring module and an acidity adjustment component for the preparation of the corresponding raw material solution.
[0043] The continuous reaction unit consists of a microchannel reactor connected in series with a subsequent reaction section, and is equipped with a gradient heating module and a back pressure regulating component to achieve continuous catalytic alkylation of materials;
[0044] The post-processing purification unit includes a methanol distillation column, a free reaction vessel, and a vacuum distillation column. The vacuum distillation column is equipped with a side-stream sampling component to complete the purification of the reaction product liquid.
[0045] The catalyst recycling unit includes a solid-liquid separation component, a washing module, a drying module, and an active component replenishment vessel. It is connected to the raw material preparation unit through pipelines to realize the recycling and reuse of the catalyst.
[0046] The whole process control unit includes flow, temperature, pressure and component monitoring modules, which are electrically connected to the execution components of each functional unit.
[0047] Example
[0048] I. Basic Experimental Conditions
[0049] 1. Raw material specifications;
[0050] Hydrazine hydrochloride: Industrial grade, purity not less than 98%, mixed with pure water to prepare a homogeneous aqueous solution according to process requirements;
[0051] Methanol: Industrial grade, purity not less than 99.0%, after pretreatment the purity is increased to not less than 99.9%, and the moisture content is controlled at a low level;
[0052] Hydrochloric acid: Industrial grade, mass fraction is the commonly used industrial specification;
[0053] Liquid caustic soda: Industrial grade, mass fraction is the commonly used industrial specification;
[0054] catalyst:
[0055] Solid acid catalyst: Using HZSM-5 molecular sieve as support, it is modified stepwise by metal ion salt solution and non-metal acid salt solution to form a multi-component synergistic catalytic structure;
[0056] Metal catalyst: Pd / Al2O3 type, active components are loaded according to catalytic requirements;
[0057] Ionic liquid catalyst: 1-Butyl-3-methylimidazolium hydrogen sulfate, with a purity of not less than 99%.
[0058] 2. Experimental equipment;
[0059] Raw material pretreatment unit: molecular sieve adsorption column, stainless steel light component removal tower, and matching flow control and temperature regulation components;
[0060] Raw material preparation unit: hydrazine hydrochloride dissolving kettle (equipped with water bath heating device and mechanical stirrer), methanol catalyst preparation kettle (equipped with acidity online monitoring component);
[0061] Continuous reaction unit: high borosilicate glass microchannel reactor (composed of coarse channel plate and medium channel plate), subsequent reaction section (TA2 material coil or iron-lined PTFE tube), integrated cold and hot circulation unit, back pressure regulating component;
[0062] Post-processing purification unit: methanol distillation column, free reaction vessel, corrugated packed vacuum distillation column (with side feed outlet), and matching reflux and temperature control components;
[0063] Catalyst circulation unit: solid-liquid separation component, washing module, vacuum drying oven, active component replenishment vessel;
[0064] The entire process control unit includes a flow sensor, temperature sensor, pressure sensor, online component monitoring module, and PLC control host, enabling real-time parameter acquisition and closed-loop control.
[0065] Comparative equipment: Traditional batch reactor (equipped with a stirrer and electric heating elements) is a commonly used equipment in current industrial production.
[0066] II. Implementation Examples
[0067] Example 1: Solid acid-modified catalyst + microchannel + TA2 coil continuous system
[0068] Raw material pretreatment: Industrial methanol is first passed through a molecular sieve adsorption column to remove moisture, and then enters a light component removal tower to remove low-boiling-point impurities. After pretreatment, the purity of methanol meets the requirements of subsequent catalytic reactions.
[0069] Preparation of raw material system:
[0070] Hydrazine hydrochloride feedstock solution: Hydrazine hydrochloride and pure water are mixed according to the process ratio, heated in a water bath to a suitable temperature and continuously mechanically stirred until the solid is completely dissolved to form a clear and transparent solution; hydrochloric acid solution is added in portions at set intervals, and stirring is maintained after each addition until the system is homogeneous; the acidity of the system is adjusted to the range suitable for the active sites of the solid acid catalyst to obtain hydrazine hydrochloride feedstock solution;
[0071] Methanol catalyst solution: Pretreated methanol and solid acid modified catalyst are mixed in an appropriate ratio, and an appropriate amount of hydrochloric acid is added. The mixture is stirred in a staged stirring mode. First, the components are initially dispersed by stirring at low speed, and then the mixture is stirred at medium speed to ensure uniform mixing, so as to obtain a stable methanol catalyst solution.
[0072] Continuous catalytic alkylation:
[0073] Dual-feed control: The hydrazine hydrochloride feedstock and methanol catalyst are synchronously fed to the continuous reaction unit at an appropriate flow rate ratio through a dual-feed system;
[0074] Reaction parameter control: Start the heating system and raise the temperature to the set reaction temperature in a gradient heating mode. Adjust the system pressure to a stable range through the back pressure valve to control the residence time of the material in the microchannel reactor and TA2 coil to ensure that the reaction proceeds fully.
[0075] Full-process control: Each monitoring module collects flow, temperature, and pressure data at a set frequency, transmits them to the PLC control host, and adjusts the operating parameters of relevant components in real time to maintain stable process conditions;
[0076] Post-processing purification:
[0077] Methanol recovery: The methanol in the reaction product liquid is removed by atmospheric distillation and collected for recovery;
[0078] Free reaction: Add liquid alkali to the residual liquid after methanol removal, stir evenly, let stand to separate the layers, and separate to obtain the organic phase;
[0079] Vacuum distillation: The organic phase is fed into a corrugated packed vacuum distillation column, the vacuum degree and the top temperature of the column are adjusted, and the column is operated according to the set reflux ratio. The target fraction is collected through the side stream outlet to obtain the methylhydrazine product.
[0080] Catalyst recycling: During the methanol distillation stage, the solid acid catalyst after the reaction is separated by the solid-liquid separation component. It is washed multiple times with deionized water to remove surface residues and impurities. After drying to restore structural stability, it is immersed in the active component replenishment solution, dried, and returned to the raw material preparation unit for recycling.
[0081] Example 2: Metal catalyst + microchannel + iron-lined PTFE tubing continuous system
[0082] The raw material pretreatment and hydrazine hydrochloride raw material solution preparation steps are the same as in Example 1;
[0083] Methanol catalyst solution: Pretreated methanol and metal catalyst are mixed in an appropriate ratio, and an appropriate amount of hydrochloric acid is added. The mixture is stirred in the same staged stirring mode as in Example 1 until all components are uniformly dispersed to obtain the methanol catalyst solution.
[0084] Continuous catalytic alkylation:
[0085] Dual-feed control: The two raw material liquids are synchronously conveyed at an appropriate flow rate ratio through a dual-feed system to maintain a stable feed ratio;
[0086] Reaction parameter control: The heating system is raised to the set reaction temperature in a gradient heating mode. The PTFE-lined iron tube is heated by a heating tape to maintain a stable temperature. The system pressure is adjusted to the set range by the back pressure valve to control the residence time of the material in the microchannel reactor and the PTFE-lined iron tube.
[0087] Full-process control: The control logic is consistent with that of Example 1, ensuring that the fluctuations of each process parameter are controlled within the allowable range;
[0088] The post-processing purification steps are the same as in Example 1;
[0089] Catalyst recycling: After being washed and dried, the separated metal catalyst is immersed in the corresponding active component replenishment solution, dried, and then returned to the raw material preparation unit for recycling.
[0090] Example 3: Ionic liquid catalyst + microchannel + TA2 coil continuous system
[0091] The raw material pretreatment and hydrazine hydrochloride raw material solution preparation steps are the same as in Example 1;
[0092] Methanol catalyst solution: Pretreated methanol and ionic liquid catalyst are mixed in an appropriate ratio, and an appropriate amount of hydrochloric acid is added. The mixture is stirred in stages until the components are evenly dispersed to obtain the methanol catalyst solution.
[0093] Continuous catalytic alkylation:
[0094] Dual-feed control: Two raw material liquids are synchronously fed through a dual-feed system at an appropriate flow rate ratio;
[0095] Reaction parameter control: The heating system rises to the set reaction temperature in a gradient heating mode, and the system pressure is adjusted to the set range through the back pressure valve to control the residence time of the material in the continuous reaction unit;
[0096] Full-process control: The control logic is consistent with that of Example 1, ensuring stable process conditions;
[0097] The post-processing purification steps are the same as in Example 1;
[0098] Catalyst recycling: The ionic liquid catalyst is recovered by vacuum distillation, purified, and then returned to the raw material preparation unit for recycling.
[0099] Example 4: Stability verification of solid acid catalysts for recycling;
[0100] Using the process route and core parameters of Example 1, the recovered solid acid catalyst is continuously recycled multiple times;
[0101] After each cycle, key indicators such as the specific surface area of the catalyst, the density of active sites, product purity, and by-product content are measured.
[0102] During the cycle, the impregnation time and process parameters of the active component replenishment solution are finely adjusted according to the catalyst activity decay. Other operating steps are the same as in Example 1.
[0103] III. Comparative Example
[0104] Raw material preparation: The preparation method of hydrazine hydrochloride raw material solution is the same as in Example 1. Methanol is directly used as industrial grade raw material (without pretreatment) and mixed evenly with unmodified solid acid catalyst;
[0105] Intermittent alkylation: Hydrazine hydrochloride feedstock and methanol catalyst are added to the batch reactor at one time, the temperature is raised to the set reaction temperature, the pressure is adjusted to the range commonly used in traditional processes, the stirrer is turned on to carry out the intermittent reaction, and the reaction continues for the set time.
[0106] Post-treatment: Methanol was removed by atmospheric distillation, liquid alkali was added to the residual liquid to carry out the free reaction, and after standing and separation, the organic phase was collected and the fraction was collected by vacuum distillation.
[0107] Catalyst disposal: After the reaction is completed, the catalyst is discarded directly and is not recycled.
[0108] IV. Experimental Results and Comparative Analysis
[0109] 1. Comparison Table of Key Technical Indicators
[0110]
[0111] The embodiment adopts a continuous flow reaction system. Through the structural characteristics of the microchannel reactor, gradient temperature control, and precise pressure regulation by the back pressure valve, the system pressure is kept stable, avoiding the pressure fluctuation problem of traditional batch reactor processes. Combined with the design of small-volume reactors and full-process automated control, the high-risk is reduced from the process itself, which is in line with the project's core R&D goal of "improving the intrinsic safety level of hazardous chemical enterprises".
[0112] The example utilizes the efficient mass and heat transfer characteristics of continuous flow reaction to significantly shorten the total reaction time and improve efficiency significantly compared to traditional batch process. At the same time, through the directional catalytic effect of catalyst, synergistic control of process parameters, and precise operation of post-processing purification, the product purity is stable and the by-product content is controlled at a low level, solving the defects of large product quality fluctuation and insufficient purity of traditional process.
[0113] The catalysts used in the examples all have good recycling performance and can maintain high catalytic activity after multiple cycles, which greatly reduces the cost of catalyst consumption; the methanol recovery rate is maintained at a high level, which reduces raw material loss and waste emissions, and meets the industrial development needs of cost reduction, efficiency improvement and green environmental protection.
[0114] The closed-loop control system ensures that all process parameters are maintained within a stable range, resulting in minimal fluctuations in product quality. Furthermore, all process parameters can be collected and traced in real time, facilitating industrial production management. The reaction system and equipment selection adopt commonly used industrial specifications and materials, and the process route is simple and controllable, possessing excellent prospects for industrial scale-up.
[0115] While an overview of the subject matter has been described with reference to specific example embodiments, various modifications and changes can be made to these embodiments without departing from the broader scope of embodiments of this disclosure. Such embodiments of the subject matter are referred to herein, individually or collectively, as inventions, for convenience only, and if more than one disclosure or concept is disclosed in fact, it is not intended to limit the scope of this application to any single disclosure or concept.
[0116] The embodiments described herein have been described in sufficient detail to enable those skilled in the art to practice the disclosed teachings. Other embodiments may be used and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. Therefore, the detailed description should not be construed as limiting, and the scope of the various embodiments is defined only by the appended claims and the full scope of their equivalents.
Claims
1. A continuous catalytic method for synthesizing methylhydrazine, characterized in that, Includes the following steps: S1 raw material system preparation: Hydrazine hydrochloride and pure water are mixed and heated in a water bath. Stirring is carried out until the solid is completely dissolved to form a clear and transparent solution. Hydrochloric acid solution is added at set intervals and stirring is continued until the system is homogeneous to obtain hydrazine hydrochloride raw material solution. Methanol was mixed with a solid acid catalyst, and hydrochloric acid was added. The mixture was stirred until all components were evenly dispersed to obtain a methanol catalytic solution. S2 Continuous Catalytic Alkylation: Hydrazine hydrochloride feedstock and methanol catalyst are simultaneously fed to a continuous reaction unit connected in series with a microchannel and subsequent reaction section through a dual-feed system. The heating system is started to increase the temperature gradient, and the system pressure is adjusted by the back pressure valve to control the residence time of the material in the unit, thus completing the continuous catalytic alkylation reaction. S3 post-treatment purification: The reaction product liquid is first subjected to atmospheric distillation to remove methanol and recover it. Liquid alkali is added to the residual liquid, stirred and allowed to stand for separation. The organic phase is then subjected to vacuum distillation, and the target fraction is collected to obtain the methylhydrazine product.
2. The continuous catalytic method for synthesizing methylhydrazine as described in claim 1, characterized in that, In step S1, the screening and modification method of the solid acid catalyst is as follows: a catalyst suitable for continuous flow reaction is screened from solid acid, metal and ionic liquid catalysts, and the screened catalyst is modified by physical or chemical means to adjust its active site distribution and structural stability. The catalyst recovery method is as follows: after the reaction, the catalyst is collected by solid-liquid separation, the surface residue is removed by washing with deionized water, the catalyst is dried and then immersed in the active component replenishment solution, dried again and returned to step S1 for recycling.
3. The continuous catalytic method for synthesizing methylhydrazine as described in claim 2, characterized in that, In S2, the operation method of the continuous reaction system is as follows: after the material enters the microchannel reactor, the components are rapidly mixed and initially reacted by utilizing the flow field characteristics within the channel, and then the reaction continues to advance in the subsequent reaction section; both the microchannel reactor and the subsequent reaction section are heated by gradient heating to control the temperature difference between each reaction zone within a set range; the material residence time is dynamically adjusted according to the catalyst activity cycle and the reaction progress to ensure sufficient reaction and avoid the accumulation of side reactions.
4. The continuous catalytic method for synthesizing methylhydrazine as described in claim 3, characterized in that, In S2, the reaction temperature, system pressure, and material flow rate are controlled as follows: the reaction temperature is maintained within the appropriate range between the microchannel reactor and the subsequent reaction section; the system pressure is adjusted to the set range through the back pressure valve; and the delivery flow rates of the hydrazine hydrochloride feed solution and the methanol catalyst solution are synchronously controlled in a fixed ratio. Based on the changes in material composition during the reaction process, the flow rate ratio and residence time are dynamically fine-tuned to adapt to changes in catalyst activity.
5. The continuous catalytic method for synthesizing methylhydrazine as described in claim 4, characterized in that, In S1, the acidity adjustment method of the hydrazine hydrochloride feed solution is as follows: by controlling the amount and interval of hydrochloric acid solution added, the acidity of the system is made to be within the range suitable for the active sites of the solid acid catalyst; this acidity condition matches the characteristics of the active sites of the catalyst, promotes the adsorption of hydrazine hydrochloride molecules on the catalyst surface, and at the same time blocks the reaction pathway of secondary alkylation of methyl hydrazine and methanol.
6. The continuous catalytic method for synthesizing methylhydrazine as described in claim 5, characterized in that, In the methanol distillation stage of S3, after the distillation operation is completed, the solid acid catalyst after the reaction is separated by filtration, and the surface adsorbed reaction residues and impurities are removed by washing with deionized water multiple times. After drying to restore structural stability, it is immersed in a mixed replenishing solution of metal ion salt and non-metal acid salt to replenish the active components. After drying, it is returned to step S1 to prepare methanol catalyst solution.
7. The continuous catalytic method for synthesizing methylhydrazine as described in claim 6, characterized in that, The reduced pressure distillation method of S3 is as follows: a packed distillation column is used for distillation operation, a side stream outlet is set at a set position in the distillation section, and the distillation vacuum degree and the column top temperature are adjusted to form an appropriate relationship, so that the heavy components at the bottom of the column are refluxed to the middle section of the distillation column in a set proportion. The timing and rate of opening the side-stream extraction outlet are dynamically adjusted based on the tower top temperature, the stable state of the vacuum, and the separation process of components within the tower.
8. The continuous catalytic method for synthesizing methylhydrazine as described in claim 1, characterized in that, The process also includes a full-process parameter monitoring and control step: a flow monitoring module is set in the dual-feed system, a temperature and pressure monitoring module is set in the continuous reaction system, and a component monitoring module is set in the distillation column. Each module continuously collects corresponding parameter data at a set frequency. After receiving the collected data, the control module analyzes the parameter deviation in real time and adjusts the feed pump speed of the dual-feed system, the heating power of the continuous reaction system, and the opening of the reflux valve of the distillation column to maintain the stability of each process parameter.
9. The continuous catalytic method for synthesizing methylhydrazine as described in claim 2, characterized in that, In step S1, a methanol pretreatment step is added: industrial methanol is first passed into an adsorption column for dehydration treatment. The type of adsorbent filled in the adsorption column is determined according to the water content in the methanol and the water tolerance characteristics of the solid acid catalyst. The dehydrated methanol is then passed into a light component removal tower, where low-boiling-point impurities and trace harmful components are removed by distillation. The operating parameters of the distillation process are adjusted according to the type of impurities and their boiling point characteristics.
10. A continuous catalytic system for synthesizing methylhydrazine, applicable to the continuous catalytic method for synthesizing methylhydrazine according to any one of claims 1 to 9, characterized in that, It includes a raw material pretreatment unit, a raw material preparation unit, a continuous reaction unit, a post-treatment purification unit, a catalyst circulation unit, and a whole-process control unit. Each unit is connected in sequence according to the process flow to form a closed-loop system. The raw material pretreatment unit includes an adsorption column and a light component removal tower, which are connected by pipelines to adapt to the purification treatment of industrial-grade methanol raw materials; the raw material preparation unit includes a hydrazine hydrochloride dissolution vessel and a methanol catalytic solution preparation vessel, which are respectively equipped with a stirring module and an acidity adjustment component for the preparation of the corresponding raw material solution. The continuous reaction unit consists of a microchannel reactor connected in series with a subsequent reaction section, and is equipped with a gradient heating module and a back pressure regulating component to achieve continuous catalytic alkylation of materials; The post-processing purification unit includes a methanol distillation column, a free reaction vessel, and a vacuum distillation column. The vacuum distillation column is equipped with a side-stream sampling component to complete the purification of the reaction product liquid. The catalyst recycling unit includes a solid-liquid separation component, a washing module, a drying module, and an active component replenishment vessel. It is connected to the raw material preparation unit through pipelines to realize the recycling and reuse of the catalyst. The whole process control unit includes flow, temperature, pressure and component monitoring modules, which are electrically connected to the execution components of each functional unit.