Apparatus for azeotropic distillation for purification of perchloromethyl mercaptan
By combining vacuum distillation and azeotropic rectification with an azeotropic distillation apparatus and using dichloroethane as an azeotropic agent, the carbon tetrachloride content in perchloromethane mercaptan is reduced, solving the problem of substandard captan products and achieving efficient purification and energy saving.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- INNER MONGOLIA GUANSHIDA CHEM CO LTD
- Filing Date
- 2025-07-17
- Publication Date
- 2026-06-19
AI Technical Summary
In existing technologies, the carbon tetrachloride content in perchloromethanethiol is too high, resulting in the synthesized captan product failing to meet export standards and incurring high production costs.
An azeotropic distillation apparatus is used, combining vacuum distillation and azeotropic rectification. The carbon tetrachloride content in perchloromethane is reduced by forming a binary azeotrope with the azeotropic agent dichloroethane and carbon tetrachloride. Multiple coolers and reflux tanks are used to improve separation efficiency, and the latent heat of liquefaction is recovered through a feed preheater to reduce energy consumption.
It significantly reduces the carbon tetrachloride content in perchloromethanethiol to below 100 ppm, meeting export standards, reducing production costs, improving the product quality and purification efficiency of captan, and achieving savings in equipment investment and energy consumption.
Smart Images
Figure CN224370695U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of captan production technology, and in particular to an azeotropic distillation apparatus for the purification of perchloromethanethiol. Background Technology
[0002] Captan is a broad-spectrum protective organosulfur fungicide, mainly used as a spray. It has good control effects on many diseases of crops such as barley, wheat, oats, rice, corn, cotton, vegetables, fruit trees, melons, and tobacco. Captan technical grade is a yellow or off-white powder; the pure product is colorless crystals. It has a melting point of 177℃ (decomposes), is almost insoluble in water, slightly soluble in organic solvents, stable in a dry state, slowly hydrolyzes when moist at room temperature, and rapidly hydrolyzes in alkaline solutions. Hydrolysis accelerates with increasing temperature.
[0003] The domestic synthesis of captan technical material mainly uses water as a solvent method. Tetrahydrophthalamide is reacted with sodium hydroxide in water to produce its sodium salt, which is then condensed with perchloromethanethiol to obtain captan. The by-product sodium chloride is dissolved in water, and the product is heated, filtered, and dried to obtain solid captan.
[0004] Currently, the main production processes for captan used in exports are: 1. Using carbonate as an acid-binding agent and dichloroethane as a solvent, perchloromethane is added dropwise to a mixture of tetrahydrophthalimide, dichloroethane, acid-binding agent, and catalyst under the catalysis of a quaternary ammonium salt phase transfer catalyst; 2. Liquid alkali is added dropwise to a mixture of tetrahydrophthalimide, dichloroethane, perchloromethane, and a quaternary ammonium salt phase transfer catalyst. These two methods are largely similar, both being improvements on organic synthesis processes. By adding a large amount of dichloroethane to dilute carbon tetrachloride, the concentration of carbon tetrachloride in wet captan is reduced. Although this method can barely reduce the carbon tetrachloride content to acceptable levels, the problems of significant solvent loss and high production costs remain unresolved.
[0005] Therefore, there is an urgent need to develop a device for purifying perchloromethanethiol, so as to significantly reduce the carbon tetrachloride content in perchloromethanethiol, thereby enabling the synthesized captan to meet export standards. Utility Model Content
[0006] This invention provides an azeotropic distillation apparatus for the purification of perchloromethanethiol that can significantly reduce carbon tetrachloride content and has a simple process and operation. It solves the problem that the high carbon tetrachloride content in perchloromethanethiol leads to excessive carbon tetrachloride in its synthetic product, captan, which fails to meet export standards.
[0007] Specifically, this utility model provides an azeotropic distillation apparatus for the purification of perchloromethanethiol, comprising: a distillation kettle and an azeotropic distillation column; the feed inlet of the distillation kettle is connected to a perchloromethanethiol storage tank, the distillation outlet at the top of the distillation kettle is connected to a carbon tetrachloride storage tank via a vacuum pump, and the discharge outlet at the bottom of the distillation kettle is connected to the feed inlet of the azeotropic distillation column via a feed pump; a dichloroethane storage tank is also connected to the feed inlet of the azeotropic distillation column; the bottom discharge outlet of the azeotropic distillation column is connected to a captan synthesis kettle, and the top discharge outlet of the azeotropic distillation column is connected to an azeotropic product storage tank.
[0008] Furthermore, a first cooler is provided between the vacuum pump and the carbon tetrachloride storage tank.
[0009] Furthermore, a second cooler and a reflux tank are provided between the top outlet of the azeotropic distillation column and the azeotropic storage tank. The outlet of the reflux tank is connected to the inlet of the azeotropic storage tank and the reflux port at the top of the azeotropic distillation column via a reflux pump.
[0010] Furthermore, a third cooler is provided between the reflux tank and the azeotropic storage tank.
[0011] Furthermore, a phase separator is also provided between the third cooler and the azeotropic storage tank. The bottom outlet of the phase separator is connected to the azeotropic storage tank, and the water outlet at the top of the phase separator is connected to the sewage tank.
[0012] Furthermore, a feed preheater is installed between the distillation vessel and the perchloromethane mercaptan storage tank, and the heat source for the feed preheater is steam.
[0013] Furthermore, a feed preheater is installed between the distillation vessel and the perchloromethane mercaptan storage tank, and the heat source inlet of the feed preheater is connected to the top outlet of the azeotropic distillation column; the feed preheater is connected in series or in parallel with the second cooler.
[0014] Furthermore, when the feed preheater and the second cooler are connected in series, the heat source outlet of the feed preheater is connected to the inlet of the second cooler.
[0015] Furthermore, when the feed preheater and the second cooler are connected in parallel, the heat source outlet of the feed preheater is connected to the inlet of the reflux tank.
[0016] The azeotropic distillation apparatus for the purification of perchloromethanethiol provided by this utility model effectively reduces equipment investment and energy consumption by combining vacuum distillation and azeotropic rectification, achieving efficient purification of perchloromethanethiol and reducing the carbon tetrachloride content in perchloromethanethiol to below 100 ppm, so that the quality of captan synthesized from perchloromethanethiol meets the standards of the Food and Agriculture Organization of the United Nations (FAO).
[0017] The azeotropic distillation apparatus has a simple operation and process flow, low maintenance cost, high separation efficiency, and good purification effect. By forming a binary azeotrope with carbon tetrachloride, the volatility of carbon tetrachloride is increased, thereby reducing the operational difficulty of removing carbon tetrachloride by distillation and effectively reducing its separation energy consumption as well as the equipment and operating costs of the distillation process.
[0018] This device produces stable output, has high purification efficiency, and the azeotropic agent used in the purification process can be reused. It can also recover the latent heat of liquefaction of the gaseous material at the top of the azeotropic distillation column through the feed preheater, which improves energy utilization efficiency and has significant energy-saving and consumption-reducing effects, making it suitable for large-scale industrial application. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 A schematic diagram of the azeotropic distillation apparatus for the purification of perchloromethanethiol provided in one embodiment of this utility model;
[0021] Figure 2 A schematic diagram of an azeotropic distillation apparatus for the purification of perchloromethanethiol, provided as another embodiment of this utility model;
[0022] Figure 3 A schematic diagram of the azeotropic distillation apparatus for the purification of perchloromethanethiol provided in another embodiment of this utility model;
[0023] Figure 4 A schematic diagram of an azeotropic distillation apparatus for the purification of total chloromethanethiol, provided as another embodiment of this utility model.
[0024] Explanation of reference numerals in the attached figures:
[0025] 101. Distillation vessel; 102. Perchloromethane mercaptan storage tank; 103. Vacuum pump; 104. Carbon tetrachloride storage tank; 105. Feed pump; 106. First cooler; 201. Azeotropic distillation column; 202. Dichloroethane storage tank; 203. Captan synthesis vessel; 204. Azeotropic material storage tank; 205. Second cooler; 206. Reflux tank; 207. Reflux pump; 301. Third cooler; 302. Phase separator; 303. Feed preheater; 304. Wastewater tank. Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions in the embodiments of this utility model are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are also within the protection scope of this utility model.
[0027] like Figure 1 This utility model provides an azeotropic distillation apparatus for the purification of perchloromethanethiol, comprising: a distillation kettle 101 and an azeotropic distillation column 201; the feed inlet of the distillation kettle 101 is connected to a perchloromethanethiol storage tank 102, the distillation outlet at the top of the distillation kettle 101 is connected to a carbon tetrachloride storage tank 104 via a vacuum pump 103, and the discharge outlet at the bottom of the distillation kettle 101 is connected to the feed inlet of the azeotropic distillation column 201 via a feed pump 105; a dichloroethane storage tank 202 is also connected to the feed inlet of the azeotropic distillation column 201; the bottom discharge outlet of the azeotropic distillation column 201 is connected to a captan synthesis kettle 203, and the top discharge outlet of the azeotropic distillation column 201 is connected to an azeotropic product storage tank 204.
[0028] The carbon tetrachloride content in the perchloromethane mercaptan from storage tank 102 is 1%-5%. Perchloromethane mercaptan has a boiling point of 147°C, while carbon tetrachloride has a boiling point of 76.8°C. Vacuum distillation is performed in distillation kettle 101 under vacuum pump 103, which distills away most of the carbon tetrachloride from the perchloromethane mercaptan and sends it to carbon tetrachloride storage tank 104 for temporary storage. When the carbon tetrachloride content in the perchloromethane mercaptan is below 1%, the relative volatility of perchloromethane mercaptan and carbon tetrachloride is low, making it more difficult to further reduce the carbon tetrachloride content. This portion of the material needs to be fed into azeotropic distillation column 201 via feed pump 105. Simultaneously, the azeotropic agent dichloroethane from storage tank 202 is fed into azeotropic distillation column 201. Carbon tetrachloride and dichloroethane form a binary azeotrope, increasing the volatility of carbon tetrachloride and significantly reducing the difficulty of separating it. After azeotropic distillation, carbon tetrachloride and dichloroethane are distilled off as a binary azeotrope and temporarily stored in azeotropic tank 204. The purity of the distilled perchloromethanethiol is significantly improved, and the carbon tetrachloride content is reduced to below 100 ppm. It can then be directly fed into captan synthesis reactor 203 to participate in the synthesis reaction.
[0029] The device first recovers a portion of carbon tetrachloride through vacuum distillation, then adds dichloroethane for azeotropic distillation. This effectively removes almost all carbon tetrachloride from perchloromethane mercaptan, significantly improving the quality of captan, the synthetic product of perchloromethane mercaptan, and making it meet export standards. Even if a certain amount of dichloroethane remains at the bottom of the azeotropic distillation column 201, it has no impact on the synthesis process because dichloroethane is required as a solvent in the captan synthesis process.
[0030] like Figure 1 Furthermore, a first cooler 106 is provided between the vacuum pump 103 and the carbon tetrachloride storage tank 104. The first cooler 106 cools the carbon tetrachloride material extracted by the vacuum pump 103 before storing it in the carbon tetrachloride storage tank 104 for later use. The distillation vessel 101 is preferably a vacuum distillation unit to reduce heat consumption. The distillation vessel 101 is conventionally equipped with a heater to heat the material in the distillation vessel 101, causing the material to vaporize. For example, the heater can be a heating metal ring surrounding the inside of the distillation vessel 101, or a steam jacket surrounding the outside of the distillation vessel 101, but is not limited to these.
[0031] like Figure 1 Furthermore, a second cooler 205 and a reflux tank 206 are provided between the top outlet of the azeotropic distillation column 201 and the azeotropic storage tank 204. The outlet of the reflux tank 206 is connected to the inlet of the azeotropic storage tank 204 and the reflux port at the top of the azeotropic distillation column 201 via a reflux pump 207. The operation of the azeotropic distillation column 201 is conventional in the art. The second cooler 205 and the reflux tank 206 facilitate reflux in the azeotropic distillation column 201, improving the distillation efficiency and promoting the distillation separation effect, thereby obtaining higher purity perchloromethanethiol. The azeotropic distillation column 201 is also equipped with a reboiler, which is a conventional setting. The reboiler is used to provide a gas phase to the azeotropic distillation column 201 to promote the evaporation and distillation separation of the materials in the column.
[0032] like Figure 2 Furthermore, a third cooler 301 is provided between the reflux tank 206 and the azeotropic storage tank 204. Multiple coolers in this device are used for cooling the materials, and their cold sources can be the same or different. For example, the cold source for the second cooler 205 is preferably circulating cooling water (20℃-35℃), and the cold sources for the first cooler 106 and the third cooler 301 are preferably low-temperature chilled water (5℃-10℃).
[0033] like Figure 2Furthermore, a phase separator 302 is provided between the third cooler 301 and the azeotropic storage tank 204. The bottom outlet of the phase separator 302 is connected to the azeotropic storage tank 204, and the upper outlet of the phase separator 302 is connected to the wastewater tank 304. The azeotrope delivered by the reflux pump 207 is cooled again by the third cooler 301, preferably to room temperature, which is beneficial to improving the subsequent phase separation effect. The azeotrope enters the phase separator 302 to drain water. The upper aqueous phase obtained by separation is sent to the wastewater tank 304 for purification treatment, and the lower organic phase enters the azeotropic storage tank 204 for further recovery and reuse. The azeotrope can be further separated and purified. The obtained carbon tetrachloride is temporarily stored for later use, while dichloroethane can be sent to the azeotropic distillation column 201 for reuse to reduce operating costs.
[0034] like Figure 2 Furthermore, a feed preheater 303 is installed between the distillation vessel 101 and the perchloromethane mercaptan storage tank 102. The heat source for the feed preheater 303 is steam. The feed preheater 303 is used to preheat the perchloromethane mercaptan material to be processed, thereby improving the processing efficiency of the distillation vessel 101 and also helping to reduce its energy consumption.
[0035] like Figure 3 or Figure 4 Furthermore, a feed preheater 303 is installed between the distillation vessel 101 and the perchloromethane mercaptan storage tank 102. The heat source inlet of the feed preheater 303 is connected to the top outlet of the azeotropic distillation column 201. The feed preheater 303 is connected in series or in parallel with the second cooler 205. The heat source of the feed preheater 303 is the top outlet of the azeotropic distillation column 201, which can recover and utilize the latent heat of liquefaction of the gaseous material at the top of the column, greatly reducing the heat consumption of the entire unit, improving energy utilization efficiency, and playing a role in energy saving and consumption reduction.
[0036] like Figure 3 Furthermore, when the feed preheater 303 is connected in series with the second cooler 205, the heat source outlet of the feed preheater 303 is connected to the inlet of the second cooler 205.
[0037] like Figure 4 Furthermore, when the feed preheater 303 and the second cooler 205 are connected in parallel, the heat source outlet of the feed preheater 303 is connected to the inlet of the return tank 206.
[0038] The present invention will be further described in detail below with reference to specific embodiments. Example 1
[0039] Azeotropic distillation apparatus for the purification of perchloromethanethiol, such as Figure 1In practice, perchloromethanethiol (97.5% purity, 2.3% carbon tetrachloride, and 0.2% other impurities) from perchloromethanethiol storage tank 102 is fed into distillation vessel 101. The heater in distillation vessel 101 heats the vessel, while vacuum pump 103 is activated to evacuate it. The perchloromethanethiol undergoes vacuum distillation in distillation vessel 101. The temperature at the distillation outlet of distillation vessel 101 is maintained below 84°C. Carbon tetrachloride vaporizes and is extracted from the distillation outlet. After passing through vacuum pump 103, it is cooled and liquefied by first cooler 106, and finally stored in carbon tetrachloride storage tank 104.
[0040] When the carbon tetrachloride content in the material in the distillation vessel 101 is less than 1%, the material in the distillation vessel 101 is fed into the azeotropic distillation column 201 by the feed pump 105, and at the same time, the azeotropic agent - dichloroethane from the dichloroethane storage tank 202 is fed into the azeotropic distillation column 201. After azeotropic distillation, carbon tetrachloride and dichloroethane are distilled off as a binary azeotrope. The azeotrope enters the second cooler 205 from the top outlet of the azeotropic distillation column 201 for cooling and liquefaction. After liquefaction, it enters the reflux tank 206 and is transported by the reflux pump 207. Part of it enters the azeotropic distillation column 201 through the reflux port at the top of the azeotropic distillation column 201 for reflux, while the other part is sent to the azeotropic storage tank 204 for temporary storage. The purity of the perchloromethanethiol after distillation is significantly improved, and the carbon tetrachloride content is reduced to below 100 ppm. It can be directly sent to the captan synthesis reactor 203 to participate in the synthesis reaction. Example 2
[0041] like Figure 2 Based on the above embodiments, this embodiment also includes: a third cooler 301 is provided between the reflux tank 206 and the azeotropic storage tank 204. The azeotropic material delivered by the reflux pump 207 is cooled again by the third cooler 301, and the temperature is preferably reduced to room temperature, which is beneficial to improving the subsequent phase separation effect.
[0042] This embodiment also includes: a phase separator 302 is provided between the third cooler 301 and the azeotropic storage tank 204. The azeotrope enters the phase separator 302 to drain water. The bottom outlet of the phase separator 302 is connected to the azeotropic storage tank 204. The lower organic phase enters the azeotropic storage tank 204 to wait for further recycling and reuse. The water outlet at the top of the phase separator 302 is connected to the sewage tank 304. The separated upper aqueous phase is sent to the sewage tank 304 for purification treatment. Example 3
[0043] like Figure 2Based on the above embodiments, this embodiment further includes: a feed preheater 303 is provided between the distillation kettle 101 and the perchloromethane mercaptan storage tank 102, and the heat source of the feed preheater 303 is steam. The feed preheater 303 is used to preheat the perchloromethane mercaptan material to be processed, thereby improving the processing efficiency of the distillation kettle 101 and also helping to reduce its energy consumption. Example 4
[0044] like Figure 3 Based on the above embodiments, this embodiment further includes: a feed preheater 303 is provided between the distillation kettle 101 and the perchloromethane mercaptan storage tank 102, the heat source inlet of the feed preheater 303 is connected to the top outlet of the azeotropic distillation column 201; the heat source outlet of the feed preheater 303 is connected to the inlet of the second cooler 205. Example 5
[0045] like Figure 4 Based on the above embodiments, this embodiment further includes: a feed preheater 303 is installed between the distillation kettle 101 and the perchloromethanethiol storage tank 102; the heat source inlet of the feed preheater 303 is connected to the top outlet of the azeotropic distillation column 201; the heat source outlet of the feed preheater 303 is connected to the inlet of the reflux tank 206. The heat source of the feed preheater 303 is the top outlet of the azeotropic distillation column 201, which is consistent with the purpose of Embodiment 4. It can recover and utilize the latent heat of liquefaction of the gaseous material at the top of the column, greatly reducing the heat consumption of the entire unit, improving energy utilization efficiency, and playing a role in energy saving and consumption reduction.
[0046] It should be noted that the detailed structure of some devices in this utility model is not described in detail, but belongs to the prior art known to those skilled in the art, and therefore will not be described again here. In addition, the parts of this device not described are the same as or can be implemented using existing technology.
[0047] It should be noted that those skilled in the art, under the guidance of this utility model, can also make some modifications to the design of the above system. For example, the equipment in the system is also equipped with level gauges, overflow / nitrogen pipelines, etc.; pumps, pressure sensors, flow meters or temperature sensors are installed on the conveying pipelines inside the system in different units or devices, and different valves, such as pressure relief valves, pressure regulating valves, safety valves, pneumatic valves, etc., are also installed to regulate and stabilize the pressure of the entire system, and the opening degree of the valves can also be adjusted to regulate the flow rate of materials in the pipeline, etc.
[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it; although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.
Claims
1. An azeotropic distillation apparatus for the purification of perchloromethanethiol, characterized in that, include: The distillation vessel comprises a distillation kettle and an azeotropic distillation column; the inlet of the distillation kettle is connected to a perchloromethanethiol storage tank, the distillation outlet at the top of the distillation kettle is connected to a carbon tetrachloride storage tank via a vacuum pump, and the outlet at the bottom of the distillation kettle is connected to the inlet of the azeotropic distillation column via a feed pump; a dichloroethane storage tank is also connected to the inlet of the azeotropic distillation column; the bottom outlet of the azeotropic distillation column is connected to a captan synthesis kettle, and the top outlet of the azeotropic distillation column is connected to an azeotropic product storage tank.
2. The azeotropic distillation apparatus for the purification of total chloromethanethiol according to claim 1, characterized in that, A first cooler is provided between the vacuum pump and the carbon tetrachloride storage tank.
3. The azeotropic distillation apparatus for the purification of total chloromethanethiol according to claim 1, characterized in that, A second cooler and a reflux tank are provided between the top outlet of the azeotropic distillation column and the azeotropic storage tank. The outlet of the reflux tank is connected to the inlet of the azeotropic storage tank and the reflux port at the top of the azeotropic distillation column respectively through a reflux pump.
4. The azeotropic distillation apparatus for the purification of total chloromethanethiol according to claim 3, characterized in that, A third cooler is also provided between the reflux tank and the azeotropic storage tank.
5. The azeotropic distillation apparatus for the purification of total chloromethanethiol according to claim 4, characterized in that, A phase separator is also provided between the third cooler and the azeotropic tank. The bottom outlet of the phase separator is connected to the azeotropic tank, and the water outlet at the top of the phase separator is connected to the sewage tank.
6. The azeotropic distillation apparatus for the purification of total chloromethanethiol according to any one of claims 1-5, characterized in that, A feed preheater is provided between the distillation vessel and the total chloromethane mercaptan storage tank, and the heat source of the feed preheater is steam.
7. The azeotropic distillation apparatus for the purification of total chloromethanethiol according to claim 3, characterized in that, A feed preheater is provided between the distillation vessel and the total chloromethane mercaptan storage tank, and the heat source inlet of the feed preheater is connected to the top outlet of the azeotropic distillation column; the feed preheater is connected in series or in parallel with the second cooler.
8. The azeotropic distillation apparatus for the purification of total chloromethanethiol according to claim 7, characterized in that, When the feed preheater is connected in series with the second cooler, the heat source outlet of the feed preheater is connected to the inlet of the second cooler.
9. The azeotropic distillation apparatus for the purification of total chloromethanethiol according to claim 7, characterized in that, When the feed preheater is connected in parallel with the second cooler, the heat source outlet of the feed preheater is connected to the inlet of the reflux tank.