A system for the continuous flow preparation of chloroacetaldehyde bisalkyl acetal

Abstract

This application provides a system for the continuous flow preparation of chloroacetaldehyde dialkyl alcohols, relating to the field of chloroacetaldehyde dialkyl alcohol preparation equipment. The system includes a precooling module, a tubular reactor, an alcoholysis reactor, and a post-treatment module. The precooling module cools the raw materials, and the cooling chamber within the tubular reactor is circulated with a refrigerant to ensure that vinyl acetate and chlorine react at an ideal temperature, effectively suppressing side reactions. The main reaction chamber is equipped with turbulent impellers; the rotation of the impellers generates high shear force, enabling efficient molecular-level mixing of the materials. The circulating reaction chamber extends the reaction time, ensuring complete reaction. The post-treatment module employs a stepped temperature design to avoid the decomposition of heat-sensitive substances. This application solves the problem of numerous side reactions in existing technologies through an integrated design of precooling-tubular reaction-circulating chlorination-alcoholization-distillation.

Description

Technical Field

[0001] This application relates to the field of equipment for the preparation of chloroacetaldehyde dialkyl alcohols, and more particularly to a system for the continuous flow preparation of chloroacetaldehyde dialkyl alcohols. Background Technology

[0002] Chloroacetaldehyde dimethyl acetal (systematic name: 2-chloro-1,1-dimethoxyethane) is widely used in the synthesis of fragrances, pharmaceuticals, and pesticides, and is also an important organic synthesis reagent. As an important organic compound, it has wide applications in organic synthesis, chemical separation, analytical chemistry, pharmaceuticals, and pesticides. Early disclosures of the preparation of chloroacetaldehyde dimethyl acetal include patents US2803668 and US 4130592, both using vinyl chloride as a starting material. Chlorine gas is first passed through an aqueous solution, and then the solution reacts with vinyl chloride to obtain an aqueous solution of chloroacetaldehyde.

[0003]

[0004] However, this method generates a large amount of 1,1,2-trichloroethane as a byproduct during the preparation of chloroacetaldehyde, leading to yield loss and high production costs. Furthermore, vinyl chloride has been classified as a Group 1 carcinogen by the World Health Organization, posing a significant safety risk as a starting material.

[0005] Method 2: This method primarily uses acetaldehyde or chloroacetaldehyde trimer as the main raw material, obtained by direct chlorination in methanol. Literature supporting the use of acetaldehyde or trichloroacetaldehyde as raw materials includes: CN106397081; WO2018005328; EP0456157; EP0368613. However, the preparation of chloroacetaldehyde is complex, requiring large amounts of solvent and concentrated sulfuric acid, and the low yield makes this method difficult to industrialize.

[0006] Method 3: Using vinyl acetate compounds as raw materials, a dichloro intermediate is first obtained by chlorination, and then condensed with methanol to obtain the product chloroacetaldehyde dimethyl acetal. References: US4642398; JP2003073322; CN10795486; all use this method to prepare the finished product.

[0007]

[0008] However, they all share the common feature of introducing chlorine gas into a mixture of vinyl acetate and alcohol, which inevitably generates a large number of side reactions, affecting industrial applications. Furthermore, because the chlorine flow rate cannot be precisely controlled, and the addition reaction between chlorine and vinyl acetate is very rapid, it easily leads to the generation of over-chlorinated impurities I, II, and III, as shown in the figure below, resulting in the inability to obtain high-purity products.

[0009]

[0010] Therefore, the existing methods for preparing chloroacetaldehyde dialkyl acetals have the technical problem of generating a large number of side reactions. There is an urgent need for a system that can be used for the continuous flow preparation of chloroacetaldehyde dialkyl acetals. Utility Model Content

[0011] The purpose of this application is to provide a system for the continuous preparation of chloroacetaldehyde dialkyl alcohols, which can solve the problem of a large number of side reactions generated in the preparation of chloroacetaldehyde dialkyl alcohols in the prior art.

[0012] This application provides a system for the continuous flow preparation of chloroacetaldehyde dialkyl acetals, employing the following technical solution: A system for the continuous flow preparation of chloroacetaldehyde dialkyl acetals, comprising...

[0013] The precooling module includes a refrigeration unit with a built-in spiral coil. A first feed inlet is provided at the front end of the spiral coil. The cavity between the refrigeration unit and the spiral coil is filled with a refrigerant. The rear end of the spiral coil is connected to a tubular reactor.

[0014] The tubular reactor includes a main reaction chamber and a circulating reaction chamber. The front end of the main reaction chamber is provided with a second feed port and a third feed port. The third feed port is connected to the rear end of the spiral coil. An internal stirring shaft is provided, and turbulent blades are fixed to the outer wall of the stirring shaft. The circulating reaction chamber is connected in series at the rear end of the main reaction chamber.

[0015] The alcoholysis reactor includes a fourth inlet, a fifth inlet, and an outlet. The fourth inlet is connected in series with the rear end of the circulating reaction chamber.

[0016] The post-processing module includes, in sequence, a layering tank, a magnesium sulfate drying tank, a vacuum distillation column, and a rectification column.

[0017] Furthermore, the turbulent impeller has a three-bladed helical structure with three blades evenly distributed around the circumference. The blades are tilted at a 45° angle and their surfaces are coated with polytetrafluoroethylene. The speed is adjustable by connecting a drive motor to the left end.

[0018] Furthermore, the spiral coil of the precooling module is covered with a thermally conductive silicone grease layer, and the refrigerant is liquid nitrogen.

[0019] Furthermore, the circulating reaction chamber is 10m long and 50mm in inner diameter, with a cooling chamber on the outer wall, which is connected to the refrigerant circulation system.

[0020] Furthermore, the middle section of the distillation column is equipped with a structured packing layer with a packing height of 1.5m, which can reduce the wall flow effect.

[0021] Furthermore, the top of the stratified tank is equipped with a liquid alkali addition port and an online pH monitor. The liquid alkali addition port is connected to a metering pump, and the metering pump is linked with the online pH monitor to achieve automatic adjustment of the pH value to 7-8.

[0022] Furthermore, the alcoholysis reactor is equipped with two sets connected in parallel, with a volume three times that of the main reaction chamber of the tubular reactor. The two sets of reactors are switched by valves to achieve alternating continuous feeding.

[0023] In summary, this application includes at least one of the following beneficial technical effects:

[0024] This system for the continuous flow preparation of chloroacetaldehyde dialkyl alcohols solves the problem of numerous side reactions in existing technologies through an integrated design of precooling-tubular reaction-cyclic chlorination-alcoholization-distillation; and improves the yield by first chlorinating vinyl acetate directly and then adding methanol for alcoholysis. Attached Figure Description

[0025] Figure 1 This is a system composition diagram of this application.

[0026] Figure 2 This is an overall schematic diagram of this application;

[0027] Figure 3 This is a schematic diagram of the tubular reactor structure of this application.

[0028] Figure 4 This is a schematic diagram of the turbulent blade structure of this application.

[0029] In the picture:

[0030] 1-Precooling module, 2-Tube reactor, 3-Stirring shaft, 4-Turbulent impeller, 5-Alcohololysis reactor, 6-Separated tank, 7-Magnesium sulfate drying tank, 8-Vacuum distillation column, 9-Distillation column, 10-Main reaction chamber, 11-Circulating reaction chamber, 12-Second feed inlet, 13-Third feed inlet. Detailed Implementation

[0031] The following is in conjunction with the appendix Figure 1 -Appendix Figure 2 This application will be described in further detail below.

[0032] like Figure 1 As shown, a system for the continuous flow preparation of chloroacetaldehyde dialkyl alcohol includes a precooling module 1, a tubular reactor 2, an alcoholysis reactor 5, and a post-processing module. The precooling module 1 includes a refrigeration unit with a built-in spiral coil. A first inlet is located at the front end of the spiral coil, connected to a pumped vinyl acetate. The cavity between the refrigeration unit and the spiral coil is filled with a refrigerant to cool the vinyl acetate to -10°C to 0°C. The rear end of the spiral coil is connected to the tubular reactor.

[0033] The tubular reactor 2 includes a main reaction chamber 10 and a circulating reaction chamber 11. The main reaction chamber 10 is a tubular structure with an inner diameter of 50 mm and a length of 10 m. A second inlet 12 and a third inlet 13 are located at the front end of the main reaction chamber 10. The second inlet 12 is connected to a chlorine injection unit equipped with a flow controller to control the chlorine feed rate at 170–187 g / min. The third inlet 13 is connected to the rear end of a spiral coil to introduce vinyl acetate cooled by the pre-cooling module 1, with the feed rate controlled at 200–220 g / min. The reaction chamber 10 has a built-in stirring shaft 3, which is a cantilever structure. The left end is connected to the drive motor. The outer wall of the stirring shaft 3 is fixed with a turbulent impeller 4 with an inclination angle of 45°. The rear end of the main reaction chamber 10 is connected in series with a circulating reaction chamber 11. The circulating reaction chamber 11 consists of 9 straight cylindrical reaction chambers connected in series by a bent pipe, with a total length of 10m, which can extend the reaction time by ≥20min. The outer walls of the main reaction chamber 10 and the circulating reaction chamber 11 are equipped with cooling chambers with temperature sensors and a cooling medium to maintain the reaction temperature from -10℃ to 10℃, ultimately producing dichloroacetic acid ester.

[0034] Two alcoholysis reactors, 5, are used alternately in a cyclic cycle. One reactor includes a fourth inlet, a fifth inlet, and a discharge outlet. The fourth inlet is connected in series with the rear end of the circulating reaction chamber 11. The fifth inlet is connected to methanol. The weight ratio of dichloroacetate to methanol is 2.88–3.168:2.95–3.05. The alcoholysis reactor 5 is equipped with a reflux condenser and an online pH monitor. Its volume is three times that of the tubular reactor 2, allowing for a reflux reaction time of at least 2.85 hours. Its discharge outlet is connected to a post-treatment module. The post-treatment module includes, and is sequentially connected to, a layered tank 6, a magnesium sulfate drying tank 7, a vacuum distillation column 8, and a rectification column 9. Liquid alkali is added to the intermediate through the feed inlet in the separator 6 to make the pH of the intermediate 7-8. After separation, the organic phase flows into the magnesium sulfate drying tank 7 and the reaction is carried out for no less than 1.85 hours. After the reaction is completed, the mixture is filtered, in which the weight ratio of magnesium sulfate to the separated intermediate is 0.1:10. The filtrate is fed into the vacuum distillation column 8 and the low-boiling solvent is removed by vacuum distillation at 30℃-40℃. Then it is fed into the rectification column 9 and the fraction is collected by rectification at 50℃-60℃ to obtain chloroacetaldehyde dialkyl acetal.

[0035] With the above setup, the precooling module 1 cools the raw materials, and the cooling chamber in the tubular reactor 2 is circulated with a refrigerant to allow vinyl acetate and chlorine to react at an ideal temperature, effectively suppressing side reactions. The main reaction chamber 10 is equipped with turbulent impellers 4, which generate high shear force through impeller rotation, enabling efficient molecular-level mixing of materials at -10℃ to 10℃. The circulating reaction chamber 11 is 10m long, which can extend the reaction time by ≥20min to ensure complete reaction. The post-treatment module adopts stepped temperature (30℃~40℃ for vacuum distillation and 50℃~60℃ for rectification) to avoid decomposition of heat-sensitive substances.

[0036] Turbulent blade 4 has a three-bladed helical structure. Figure 2 The blades are arranged in three evenly distributed circumferences with a 45° inclination angle. Their surfaces are coated with polytetrafluoroethylene (PTFE). The rotation speed is adjustable via a drive motor connected to the left end, ranging from 200 r / min to 500 r / min. The 45° inclination angle generates vortex flow during rotation, disrupting laminar flow and improving mixing uniformity. Compared to traditional vertical blades, this reduces energy consumption and increases the reaction rate. It achieves efficient material mixing, and the PTFE coating simultaneously reduces the coefficient of friction, minimizing frictional heat and directly suppressing side reactions. The spiral coil of the pre-cooling module 1 is covered with a thermally conductive silicone grease layer, solving the contact thermal resistance problem between the metal coil and the cooling chamber. The refrigerant is liquid nitrogen, with a temperature control accuracy of ±0.5℃, achieving precise temperature control. The circulating reaction chamber 11 is 10m long with an inner diameter of 50mm. A cooling chamber is located on the outer wall, connected to the refrigerant circulation system, controlling the reaction temperature between -10℃ and 10℃. The distillation column 9 contains a structured packing layer with a specific surface area ≥500m². 2 / m 3 The packing height is 1.5m (traditional processes use 1m packing), which reduces wall flow effects and improves separation efficiency. The top of the stratification tank 6 is equipped with a liquid alkali addition port and an online pH monitor. The liquid alkali addition port is connected to a metering pump, which is linked to the online pH monitor. The pumping rate of the metering pump is controlled by the online pH monitor to achieve automatic pH adjustment between 7 and 8. The alcoholysis reactor 5 has two sets connected in parallel, with a volume three times that of the main reaction chamber 10 of the tubular reactor 2. The two sets of reactors are switched by valves to achieve alternating continuous feeding, ensuring a reflux reaction time of no less than 2.85 hours, enabling continuous and uninterrupted production. Through the integrated design of precooling-tubular reaction-circulating chlorination-alcoholization-distillation, the problem of numerous side reactions generated by existing technologies is solved.

[0037] During production, vinyl acetate is pumped into the first inlet of the spiral coil in the pre-cooling module 1. The cavity between the refrigeration unit and the spiral coil is filled with -10°C liquid nitrogen, which cools the vinyl acetate to -10°C through heat exchange in the spiral coil. The vinyl acetate then enters the main reaction chamber 10 through the spiral coil outlet via the third inlet 13, with the feed rate controlled at 200 g / min by a flow controller. Chlorine gas is fed into the main reaction chamber 10 through the second inlet 12, with a flow rate controlled at 170 g / min by a flow controller. The mixture then enters the circulating reaction chamber 11, where it circulates for 30 minutes. Liquid nitrogen at -10°C is circulated in the cooling chamber to maintain both the reaction and circulating reaction temperatures at -10°C. Subsequently, the mixture enters the alcoholysis reactor 5 through the fourth inlet at a flow rate of 200 g / min via a metering pump, and is continuously collected for 24 hours, yielding approximately 525 kg of dichloroacetic acid ester. Methanol 375 kg is added through the fifth inlet, and the mixture is heated and refluxed for 3 hours. The mixture was then transferred to a separating tank 6, where liquid alkali was added to adjust the pH to 7, causing separation. The organic phase flowed into a magnesium sulfate drying tank 7, where 10.0 kg of magnesium sulfate was added and the mixture was dried for 2 hours. After filtration, the filtrate entered a vacuum distillation column 8, where low-boiling-point solvents were removed by vacuum distillation at 40°C. Subsequently, the mixture entered a rectification column 9, where the temperature was slowly increased, and the fraction distilled at 60°C was collected. 342 kg of the correct product of chloroacetaldehyde diol condensate was obtained, with a yield of 82.3%.

[0038] GC detection data:

[0039] GC purity % 0.20％ 0.03％ 99.5％

[0040] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. A system for the continuous flow preparation of chloroacetaldehyde dialkyl alcohols, characterized in that: include The precooling module (1) includes a refrigeration unit with a built-in spiral coil. The front end of the spiral coil is provided with a first feed port. The cavity between the refrigeration unit and the spiral coil is filled with a refrigeration medium. The rear end of the spiral coil is connected to a tubular reactor (2). The tubular reactor (2) includes a main reaction chamber (10) and a circulating reaction chamber (11). The front end of the main reaction chamber (10) is provided with a second feed port (12) and a third feed port (13). The third feed port (13) is connected to the rear end of the spiral coil. A stirring shaft (3) is built in, and a turbulent impeller (4) is fixed to the outer wall of the stirring shaft (3). The circulating reaction chamber (11) is connected in series at the rear end of the main reaction chamber (10). The alcoholysis reactor (5) includes a fourth inlet, a fifth inlet and an outlet, with the fourth inlet connected in series with the rear end of the circulating reaction chamber (11); The post-processing module includes, in sequence, a layered tank (6), a magnesium sulfate drying tank (7), a vacuum distillation column (8), and a rectification column (9). The inlet of the layered tank (6) is connected to the outlet of the alcoholysis reactor (5).

2. The system for continuous flow preparation of chloroacetaldehyde dialkyl alcohols according to claim 1, characterized in that: The turbulent blade (4) has a three-bladed helical structure with three blades evenly distributed on the circumference. The blades are tilted at 45° and coated with polytetrafluoroethylene. The speed is adjustable by connecting the drive motor at the left end.

3. The system for continuous flow preparation of chloroacetaldehyde dialkyl alcohols according to claim 2, characterized in that: The spiral coil of the precooling module (1) is covered with a thermally conductive silicone grease layer, and the cooling medium is liquid nitrogen.

4. The system for continuous flow preparation of chloroacetaldehyde dialkyl alcohols according to claim 3, characterized in that: The length of the circulating reaction chamber (11) is 10m, the inner diameter is 50mm, and the outer wall is provided with a cooling chamber, which is connected to the refrigeration medium circulation system.

5. The system for continuous flow preparation of chloroacetaldehyde dialkyl alcohols according to claim 4, characterized in that: The middle section of the distillation column (9) has a built-in structured packing layer with a packing height of 1.5m, which can reduce the wall flow effect.

6. The system for continuous flow preparation of chloroacetaldehyde dialkyl alcohols according to claim 1, characterized in that: The top of the layered tank (6) is equipped with a liquid alkali addition port and a pH online monitoring instrument. The liquid alkali addition port is connected to a metering pump, and the metering pump is linked with the pH online monitoring instrument to achieve automatic adjustment of pH value from 7 to 8.

7. The system for continuous flow preparation of chloroacetaldehyde dialkyl alcohols according to claim 1, characterized in that: The alcoholysis reactor (5) is equipped with two sets in parallel, with a volume three times that of the main reaction chamber of the tubular reactor (2). The two sets of reactors are switched by valves to achieve alternating continuous feeding.

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