A system and process for the production of dichlorobutadiene

Abstract

The application discloses a dichlorobutadiene production system and process, and belongs to the technical field of chloroprene rubber production. The dichlorobutadiene production system and process take trichlorobutene as raw material, dechlorinate to obtain a dichlorobutadiene mixed solution under the action of a sodium methoxide solution, remove methanol and sodium chloride through water extraction, and then make the raffinate pass through coalescence dehydration and negative pressure rectification in sequence to obtain a dichlorobutadiene product with a purity of greater than or equal to 99.5%, and meanwhile, the methanol in the extraction liquid is recycled through a recovery tower. The process uses sodium methoxide cyclic continuous reaction to replace NaOH emulsification intermittent production, combines negative pressure rectification to reduce heat load and avoid high-temperature polymerization, and uses water extraction-coalescence dehydration continuous process to reduce the material loss of traditional emulsification and water stripping, so that the device energy consumption and raw material cost are reduced, the treatment difficulty of by-products and three wastes is reduced, the problems of unstable product quality and difficult treatment of waste liquid are solved.

Description

Technical Field

[0001] This invention relates to the field of chloroprene production technology, specifically to a dichlorobutadiene production system and process. Background Technology

[0002] Chloroprene rubber is widely used in adhesives, industrial rubber products, wires and cables, and automobile manufacturing due to its excellent flame retardancy, oil resistance, chemical corrosion resistance, sealing properties, and flexural strength. For some core properties, there are currently no completely replaceable materials. The mainstream production processes for chloroprene rubber are the acetylene method and the butadiene method. Due to raw material costs, the acetylene method has become the mainstream production route in China. During the acetylene method for producing chloroprene rubber, dichlorobutene is continuously produced as a byproduct of chloroprene monomer production. Based on a daily production of 24-27 m³ of chloroprene, approximately 1-1.5 m³ of dichlorobutene is produced daily, and this byproduct increases proportionally with capacity expansion. The mainstream approach in the industry is to convert dichlorobutene to dichlorobutadiene, and then copolymerize it with chloroprene to prepare special chloroprene rubber. Introducing dichlorobutadiene into the structure breaks the regularity of the polychloroprene molecular chain, giving the rubber excellent anti-crystallization, weather resistance, and aging resistance. The resulting products are suitable for various applications such as low-temperature conditions, automotive seals, cable accessories, and miscellaneous rubber parts.

[0003] Currently, cold-resistant chloroprene rubber with sulfur regulation has been successfully developed abroad. Although relevant research institutions in China have also conducted research on this type of rubber, and its various properties have met the technical requirements, commercial production is impossible due to the lack of high-purity and high-stability dichloroprene raw materials. Therefore, preparing high-purity dichloroprene using dichlorobutene, a byproduct of chloroprene, as raw material has significant practical implications. However, existing dichloroprene preparation processes have the following technical problems: First, the traditional process involves chlorinating dichlorobutene to generate trichlorobutene, followed by removing H₂ under the action of NaOH. + Cl - Dichlorobutadiene is obtained. Since the reaction is exothermic, dichlorobutadiene is prone to self-polymerization when heated (above 80℃), and the concentration of NaOH in the batch reactor is difficult to control during the reaction, easily generating byproducts such as trichlorobutadiene. Overall, the conversion rate from raw material dichlorobutene to dichlorobutadiene is only about 30%, resulting in extremely high production costs and a product purity that can only be maintained at around 98%. Secondly, to ensure the smooth progress of the dechlorination reaction, traditional processes require the addition of a certain amount of emulsifier to fully mix the reaction system. The resulting mixture needs to be steam-distilled to obtain crude dichlorobutadiene. Steam distillation produces a large volume of waste liquid containing large amounts of polychlorinated hydrocarbons, polychlorinated olefins, polymerization inhibitors, wood tar, and phenothiazine, with high COD concentration, poor biodegradability, and severe odor, making it difficult to dispose of. Currently, the pretreatment cost is as high as 600-700 yuan / ton of waste liquid.

[0004] In summary, traditional batch dichlorobutadiene preparation processes suffer from problems such as low product purity, unstable quality, numerous byproducts, difficult waste treatment, and high energy and material losses. Furthermore, the separation process easily leads to material self-polymerization and decomposition, further reducing product yield and quality. Therefore, developing a new refining process that can operate continuously, at low cost, with low energy consumption, and stably produce high-purity dichlorobutadiene has significant market value and practical implications. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned shortcomings by providing a dichlorobutadiene production system and process that achieves high purity, high yield, low energy consumption, and methanol recycling of dichlorobutadiene, significantly reducing production costs and the difficulty of waste treatment. To achieve the above objective, this invention provides the following technical solution: A dichlorobutadiene production system includes a reaction complex unit, a purification and separation unit, and a recovery unit. The reaction complex unit is connected to the purification and separation unit. In the reaction complex unit, trichlorobutene reacts with sodium methoxide to form a reaction mixture that is then purified into dichlorobutadiene product by the purification and separation unit, and methanol is separated out. The reaction mixture of dichlorobutadiene is then purified into dichlorobutadiene product by the purification and separation unit, and methanol is separated out. The recovery unit is connected to both the purification and separation unit and the reaction complex unit, and is used to recover methanol from the purification and separation unit and return it to the reaction complex unit for recycling.

[0006] Furthermore, the reaction complex unit includes a sodium methoxide reaction tower and a dechlorination reaction vessel; the discharge end of the sodium methoxide reaction tower is connected to the feed end of the dechlorination reaction vessel, and the top is connected to the recovery unit; the discharge end of the dechlorination reaction vessel is connected to the purification and separation unit; the dechlorination reaction vessel is equipped with a stirring mechanism, and the outer shell is equipped with a cooling liquid jacket.

[0007] Furthermore, the refining and separation unit includes a water extraction tower, a dehydration coalescer, and a refining tower; the dechlorination reactor, water extraction tower, dehydration coalescer, and refining tower are connected in series to sequentially treat the dichlorobutadiene reaction mixture produced in the dechlorination reactor by water extraction, dehydration, and vacuum distillation; the top of the water extraction tower is connected to a recovery unit, which sends the separated methanol to the recovery unit; the top of the refining tower is equipped with a condenser and a vacuum pump, and the bottom of the tower is equipped with a reboiler, and a portion of the dichlorobutadiene obtained in the condenser is sent back to the top of the refining tower for reflux.

[0008] Furthermore, the recovery unit includes a methanol recovery tower, a compressor, and a reboiler; the top of the methanol recovery tower is connected to the lower part of the sodium methoxide reaction tower and the upper part of the methanol recovery tower respectively; a compressor is installed on the pipeline connecting the top of the methanol recovery tower and the lower part of the sodium methoxide reaction tower; a compressor and a reboiler are sequentially installed on the pipeline connecting the top of the methanol recovery tower and the upper part of the methanol recovery tower; the bottom of the methanol recovery tower is connected to the shell-side inlet of the reboiler through a pipeline, and the shell-side outlet of the reboiler is connected to the lower part of the methanol recovery tower through a pipeline.

[0009] A dichlorobutadiene production process, using the above-mentioned dichlorobutadiene production system, includes the following steps: S1. Prepare sodium methoxide solution; S2, dechlorination reaction; S3, Refining and Separation.

[0010] Furthermore, in step S1, methanol and NaOH solution are fed into the sodium methoxide reaction tower from the top of the tower, and react continuously with methanol vapor fed into the tower from the bottom of the sodium methoxide reaction tower to produce sodium methoxide and methanol solution.

[0011] Furthermore, in step S2, trichlorobutene, sodium methoxide and methanol solution obtained in step S1 are fed into a dechlorination reactor for dechlorination reaction to obtain a reaction mixture containing dichlorobutadiene.

[0012] Furthermore, before step S2, a polymerization inhibitor is added to the dechlorination reactor. The polymerization inhibitor is prepared in advance in a polymerization inhibitor preparation tank by diphenylamine sulfide and diethylhydroxylamine in a certain ratio.

[0013] Furthermore, in step S3, the purification and separation includes the following steps: S31. Water extraction to remove impurities: The dichlorobutadiene reaction mixture obtained in step S2 is fed into a water extraction tower. In the water extraction tower, water is used as the extractant to extract and remove methanol and sodium chloride from the reaction mixture.

[0014] S32, coalescence and dehydration: The dichlorobutadiene reaction mixture after water extraction and impurity removal in S31 is sent to the dehydration and coalescence unit to remove water from the reaction mixture through coalescence and dehydration.

[0015] S33. Vacuum distillation: The dichlorobutadiene reaction mixture after water removal in S32 is sent to a purification tower. The dichlorobutadiene is purified by vacuum distillation using the boiling point difference between dichlorobutadiene and other reaction byproducts to obtain the dichlorobutadiene monomer product.

[0016] Furthermore, it also includes methanol recycling; the methanol recycling is carried out after the sodium methoxide solution preparation step and after the water extraction and impurity removal step; the methanol and water mixture vapor discharged from the top of the sodium methoxide reaction tower is extracted by the water extraction tower and sent to the methanol recovery tower for distillation separation. The anhydrous methanol obtained is discharged from the top of the methanol recovery tower and sent back to the sodium methoxide reaction tower for recycling via a compressor. The other part is discharged from the top of the methanol recovery tower and then condensed in the reboiler after being compressed and releasing heat before flowing back into the methanol recovery tower. The methanol liquid at the bottom of the methanol recovery tower is vaporized after being heated by the reboiler and then enters the methanol recovery tower for distillation separation again.

[0017] The beneficial effects of this invention are: This invention discloses a dichlorobutadiene production process that uses trichlorobutene as a raw material. Dichlorobutadiene is obtained by dechlorination in a sodium methoxide solution. The resulting dichlorobutadiene mixture is then subjected to water extraction to remove methanol and NaCl, before being fed into a methanol recovery tower for methanol recycling. The raffinate phase is crude dichlorobutadiene, which is dehydrated in a dehydration coalescer and then purified using a vacuum distillation column to obtain a high-purity dichlorobutadiene product. This process uses a continuous sodium methoxide cycle reaction instead of intermittent NaOH emulsification, improving the conversion rate of dichlorobutadiene, reducing operational difficulty and process safety risks. It also combines negative pressure distillation to reduce heat load and avoid high-temperature polymerization, and utilizes a continuous water extraction-coalescing dehydration process to reduce material losses associated with traditional emulsification and water stripping. Furthermore, it improves the product quality of dichlorobutadiene, reduces energy consumption and raw material costs, reduces byproducts and the difficulty of waste treatment, and solves the problems of unstable product quality and difficult waste treatment. This process possesses significant market value and practical significance. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the dichlorobutadiene production system of the present invention; In the attached diagram: 1-Sodium methoxide reaction tower, 2-Dechlorination reactor, 3-Water extraction tower, 4-Dehydration coalescer, 5-Refining tower, 6-Methanol recovery tower, 7-Compressor, 8-Reboiler, 9-Transfer pump, 10-Condenser, 11-Vacuum pump, 12-Preheater, 13-Cooling liquid jacket, 14-Stirring mechanism, 15-Flow meter. Detailed Implementation

[0019] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0020] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also mean including the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0021] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0022] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "over," etc. The meaning of such spatial relative terms includes different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure is flipped, then an element described as "below other elements or features" or "below other elements or features" will subsequently be oriented "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in the text will be interpreted accordingly.

[0023] The core reaction process of this invention involves using trichlorobutene obtained by chlorinating dichlorobutene as a raw material, and then dechlorinating it in the presence of sodium methoxide solution to obtain dichlorobutadiene. The main reaction equation is as follows: CH2=CCl-CHCl-CH2Cl+CH3ONa→CH2=CCl-CCl=CH2+NaCl+CH3OH.

[0024] Example 1: See attached Figure 1 This invention discloses a dichlorobutadiene production system, comprising a reaction and compounding unit, a purification and separation unit, and a recovery unit. The reaction and compounding unit is connected to the purification and separation unit. The reaction and compounding unit generates a mixture containing dichlorobutadiene using trichlorobutene and sodium methoxide solution as raw materials. This mixture is then purified in the purification and separation unit through water extraction, coalescence dehydration, and vacuum distillation to obtain a high-purity (≥99.5%) dichlorobutadiene monomer product. The recovery unit is connected to both the purification and separation unit and the reaction and compounding unit, recovering methanol from both units. This methanol is then purified by distillation and returned to the reaction and compounding unit for recycling. This invention achieves continuous production, improves conversion rate and product purity, reduces energy consumption, raw material costs, and the difficulty of waste treatment, and solves the problems of low product purity, unstable quality, and difficult waste treatment in existing intermittent dichlorobutadiene production using NaOH emulsification.

[0025] Specifically, the reaction complex unit includes a sodium methoxide reaction tower 1 and a dechlorination reactor 2. The sodium methoxide reaction tower 1 contains internal components such as a distributor and packing material, and its outlet is connected to the inlet of the dechlorination reactor 2 via a pipeline. Methanol and NaOH solution are fed into the inlet of the sodium methoxide reaction tower 1, where they react to produce sodium methoxide and a methanol solution. The resulting sodium methoxide and methanol solution enter the dechlorination reactor 2 from the outlet at the bottom of the sodium methoxide reaction tower 1. Trichlorobutene is fed into the dechlorination reactor 2, where it is dechlorinated under the action of the sodium methoxide solution to obtain a dichlorobutadiene reaction mixture. A stirring mechanism 14 is installed inside the dechlorination reactor 2 to fully stir the materials inside the reactor during operation, ensuring uniform mixing and complete reaction of trichlorobutene and sodium methoxide solution. A cooling jacket 13 is installed on the outer shell of the dechlorination reactor 2. Since the dechlorination reaction is exothermic, the heat generated by the reaction can be removed in time by introducing a cooling medium into the jacket, effectively controlling the temperature inside the reactor and preventing the self-polymerization and decomposition of dichlorobutadiene due to excessive temperature, thus ensuring a stable reaction. The top of the sodium methoxide reaction tower 1 is connected to the recovery unit to send the methanol-water mixture vapor discharged from the top of the tower to the recovery unit for methanol recovery. The discharge end of the dechlorination reactor 2 is connected to the purification and separation unit to send the dichlorobutadiene reaction mixture generated by the dechlorination reaction to the subsequent purification process. Flow meters 15 are also installed on the inlet pipes of the sodium methoxide reaction tower 1 and the dechlorination reactor 2 to accurately control the reaction ratio.

[0026] Specifically, the refining and separation unit includes a water extraction tower 3, a dehydration coalescer 4, and a refining tower 5. The discharge end of the dechlorination reactor 2, the water extraction tower 3, the dehydration coalescer 4, and the refining tower 5 are connected in series via pipelines to sequentially perform water extraction, dehydration, and vacuum distillation on the dichlorobutadiene reaction mixture produced in the dechlorination reactor 2, completing the purification and upgrading operations step by step. A transfer pump 9 is installed on the pipeline connecting the dechlorination reactor 2 and the water extraction tower 3. The generated dichlorobutadiene reaction mixture is sent to the water extraction tower 3 for water extraction. Utilizing the characteristic that water is essentially insoluble with dichlorobutadiene but completely miscible with methanol and NaCl, methanol is extracted from the dichlorobutadiene mixture, thus achieving the separation of methanol and dichlorobutadiene. The extraction tower is divided into upper and lower sedimentation / mass transfer sections, with internal components using a random packing structure. To improve the extraction effect, distributors are arranged between the packing section and the feed pipe. Meanwhile, to reduce axial back mixing in the tower, baffles are arranged between the packings to divide the tower cross section into several independent areas. The upper and lower baffles are staggered by 90° to make the liquid in the tower tend to flow in an ideal plunger flow. After water extraction, the dichlorobutadiene reaction mixture enters the dehydration coalescer 4. Since the boiling point of dichlorobutadiene at normal pressure is 98℃, which is very close to the boiling point of water, it is difficult to separate the small amount of water (about 0.5% to 0.6% wt) in dichlorobutadiene by distillation. The dehydration coalescer 4 has a built-in coalescing element. The coalescing block is supported by a stainless steel wire mesh demister and the surface is sintered and coated with PTFE material. The coalescing block with special hydrophobicity intercepts the tiny water droplets carried in dichlorobutadiene on the top of the coalescing block. The tiny water droplets continuously accumulate into water droplets, and the larger water droplets rise due to their own buoyancy. The oil phase substances such as dichlorobutadiene settle due to their own gravity, thereby realizing the coalescence and dehydration of dichlorobutadiene to obtain crude dichlorobutadiene. When the liquid in the dehydration coalescer 4 reaches a certain level, it is discharged as waste liquid. A transfer pump 9 and a preheater 12 are sequentially installed on the pipeline connecting the dehydration coalescer 4 and the refining tower 5. The crude dichlorobutadiene in the dehydration coalescer 4 is preheated by the preheater 12 under the action of the transfer pump 9 and then enters the refining tower 5 for vacuum distillation. By utilizing the boiling point difference between dichlorobutadiene and high-boiling-point impurities such as trichloro-1-butene and trichloro-1,3-butadiene, the high-boiling-point byproducts such as trichloro-1-butene and trichloro-1,3-butadiene in the crude dichlorobutadiene are separated.The refining column 5 is a packed column. A condenser 10 and a vacuum pump 11 are installed at the top of the column, and a reboiler 8 is installed at the bottom. The vacuum pump 11 continuously extracts air from the column to create a negative pressure environment, lowering the operating temperature under reduced pressure to effectively prevent the thermal polymerization of dichlorobutadiene. The reboiler 8 uses steam as a heat source, continuously providing a stable upward steam flow to the refining column 5, providing energy for mass and heat transfer between the gas and liquid phases within the column. This serves as the power source for continuous distillation separation. The liquid from the bottom of the column circulates into the reboiler 8 for heating, reducing the boiling point of the dichlorobutadiene. The dichlorobutadiene preferentially vaporizes to form a gas-liquid mixture, which is then sent back to the bottom of the purification tower 5 for gas-liquid separation. The separated dichlorobutadiene vapor rises to the top of the tower and is condensed and liquefied by the condenser 10. Part of the condensed liquid dichlorobutadiene flows back from the top of the purification tower 5, forming a countercurrent contact mass and heat transfer between the gas and liquid phases in the packing layer. This enriches the dichlorobutadiene at the top of the tower and the high-boiling-point substances at the bottom, maintaining stable distillation conditions within the tower and improving separation and purification efficiency. The remaining portion is collected as high-purity (≥99.5%) dichlorobutadiene product. A flow meter 15 is installed at the bottom of the purification tower 5. When the liquid in the bottom reaches a certain level, a portion of the bottom liquid is discharged as organic waste. In addition, the top of the water extraction tower 3 is connected to the recovery unit to send the methanol-containing extract separated by water extraction to the recovery unit for methanol recovery.

[0027] Specifically, the recovery unit includes a methanol recovery tower 6, a compressor 7, and a reboiler 8. The methanol recovery tower 6 is a packed tower with two pipelines at the top. One pipeline connects to the lower part of the sodium methoxide reaction tower 1, and the compressor 7 is installed on this pipeline. The other pipeline connects the compressor 7 and the reboiler 8 sequentially, then returns to the upper part of the methanol recovery tower 6. Additionally, the bottom of the methanol recovery tower 6 is connected to the shell-side inlet of the reboiler 8 via a pipeline, and the shell-side outlet of the reboiler 8 is connected to the lower part of the methanol recovery tower 6. The methanol-water mixture vapor discharged from the top of the sodium methoxide reaction tower 1, as well as the methanol material separated from the water extraction tower 3, are uniformly fed into the methanol recovery tower 6 for distillation and purification. A portion of the purified anhydrous methanol is pressurized and heated by the compressor 7 and then sent back to the sodium methoxide reaction tower 1 for reuse in preparing sodium methoxide solution, achieving medium recycling. The other portion of the anhydrous methanol is sent to the reboiler 8 via the compressor 7, where it enters the shell side of the reboiler 8 for condensation and heat release, providing heat for the bottom liquid. The condensed methanol liquid then flows back to the upper part of the methanol recovery tower 6. Meanwhile, the methanol liquid at the bottom of methanol recovery tower 6 enters reboiler 8 to absorb heat and vaporize. The vaporized material is then returned to methanol recovery tower 6 to participate in distillation, ensuring the continuous and stable operation of methanol purification, thus achieving "self-regenerative distillation". In addition, a flow meter 15 is also installed at the bottom of methanol recovery tower 6. When the liquid in methanol recovery tower 6 reaches a certain level, it is discharged as waste liquid.

[0028] Example 2: A dichlorobutadiene production process, using the dichlorobutadiene production system in Example 1, includes the following steps: S1, preparing sodium methoxide solution; S2, dechlorination reaction; S3, purification and separation.

[0029] Step S1: Preparation of sodium methoxide solution. Methanol and NaOH solution are fed into the sodium methoxide reaction tower 1 from the top, and react continuously countercurrently with methanol vapor fed into the tower from the bottom. The mole fraction of water in the liquid phase gradually decreases from the top to the bottom, while the mole fraction of water in the vapor phase gradually increases from the bottom to the top, reaching vapor-liquid equilibrium at the top. The mixed vapor of methanol and water is discharged from the top and sent to methanol recovery tower 6 for distillation separation. The sodium methoxide and methanol solution (sodium methoxide content 20%–30% wt) produced in sodium methoxide reaction tower 1 are discharged from the bottom and sent as raw materials to dechlorination reactor 2.

[0030] The main reaction equation in sodium methoxide reaction tower 1 is as follows: CH3OH + NaOH → CH3ONa + H2O (reversible reaction).

[0031] The main process operating conditions of sodium methoxide reaction tower 1 are as follows: tower top pressure, 0.005~0.01MPaG; tower bottom pressure, 0.01~0.02MPaG; tower top temperature, 70~100℃; tower bottom temperature, 90~120℃; reflux ratio, 2~15.

[0032] Step S2: Dechlorination Reaction. First, diphenylamine sulfide and diethylhydroxylamine are mixed in a certain ratio in an inhibitor preparation tank to prepare an inhibitor, which is then added to the dechlorination reactor 2. Next, trichlorobutene obtained from the upstream chlorination reaction is fed into the dechlorination reactor 2, where it comes into contact with the sodium methoxide and methanol mixture from the previous step. Under the stirring action of the stirring mechanism 14, the trichlorobutene and sodium methoxide are fully contacted and undergo a dechlorination reaction. After the trichlorobutene removes Cl- and H+, a reaction mixture containing dichlorobutadiene, methanol, sodium chloride, and a small amount of byproducts is obtained. The dechlorination reaction is exothermic; the released heat can be removed by the chilled water in the cooling jacket 13 on the outer shell, controlling the reaction temperature within a set range to inhibit the self-polymerization of dichlorobutadiene. Simultaneously, the inhibitor in the dechlorination reactor 2 also inhibits the self-polymerization and thermal decomposition of dichlorobutadiene upon heating.

[0033] The main reaction equation in dechlorination reactor 2 is as follows: CH2=CCl-CHCl-CH2Cl (trichlorobutene) + CH3ONa (sodium methoxide) → CH2=CCl-CCl=CH2 (dichlorobutadiene) + NaCl + CH3OH; CH2=CCl-CHCl-CH2Cl (trichlorobutene) + NaOH → CH2=CCl-CCl=CH2 (dichlorobutadiene) + NaCl + H2O; Main side reactions: CH3ONa + H2O → CH3OH + NaOH; CH2Cl-CHCl-CHCl-CH2Cl (tetrachlorobutane) + NaOH → CH2Cl-CHCl-CCl=CH2 (trichloro-1-butene) + NaCl + H2O; CHCl2-CHCl-CHCl-CH2Cl (pentachlorobutane) + 2NaOH → CHCl=CCl-CCl=CH2 (trichloro-1,3-butadiene) + 2NaCl + 2H2O.

[0034] The main process operating conditions of dechlorination reactor 2 are as follows: reaction pressure, 0.005~0.01MPaG; reaction inlet temperature, 20~100℃; temperature rise of dechlorination reactor 2, ≤5~15℃.

[0035] Step S3: Refining and separation specifically includes the following sub-steps: S31 Water Extraction for Impurity Removal. The dichlorobutadiene reaction mixture obtained from the dechlorination reaction in step S2 is fed into water extraction tower 3. In water extraction tower 3, water is used as the extractant. Taking advantage of the fact that water is essentially insoluble with dichlorobutadiene but completely miscible with methanol and sodium chloride, methanol and sodium chloride are extracted and removed from the reaction mixture. The raffinate obtained after extraction is crude dichlorobutadiene, which is sent to the next dehydration process. The extract is an aqueous solution containing methanol, which is piped from the top of water extraction tower 3 to methanol recovery tower 6 for methanol recovery. The main process operating conditions of water extraction tower 3 are: space velocity (VHSV), volumetric hourly space velocity (VHSV), 0.1~0.4 (h⁻¹); operating pressure, 0.6~2.0 MPaG; dispersed phase (oil phase) feed temperature, ≤40℃; continuous phase (aqueous phase) feed temperature, ≤40℃.

[0036] S32 Coalescing and Dehydration. The crude dichlorobutadiene, after water extraction and impurity removal in step S31, is fed into dehydration coalescer 4 for deep dehydration treatment to remove residual water from the system, obtaining crude dichlorobutadiene material with low moisture content, which is then sent to the next step of vacuum distillation. The main process operating conditions of dehydration coalescer 4 are: space velocity (VHSV), volumetric hourly space velocity (VHSV), 0.1~0.4 (h⁻¹); operating pressure, 0.6~1.0 MPaG; pressure drop, ≤0.1~0.3 MPa; outlet water content, ≤200 ppm.

[0037] S33 Vacuum Distillation. The crude dichlorobutadiene, after dehydration in step S32, is fed into refining column 5. Refining column 5 is maintained under reduced pressure by vacuum pump 11. Gas-liquid mass transfer separation is performed within the column, utilizing the boiling point difference between dichlorobutadiene and other reaction byproducts (such as trichloro-1-butene, trichloro-1,3-butadiene, etc.). The dichlorobutadiene vapor distilled at the top of the column enters condenser 10 and is condensed into liquid. A portion is returned to refining column 5 from the top as reflux, and the other portion is collected as product, yielding high-purity dichlorobutadiene monomer product with a purity ≥99.5%. The main operating conditions of refining column 5 are: top pressure, 10~60 kPa; bottom pressure, 10~60 kPa; top temperature, 10~40℃; bottom temperature, 60~150℃; reflux ratio, 2~30.

[0038] The process of this invention also includes a methanol recycling step. Methanol recycling is performed after the preparation of the sodium methoxide solution and after the water extraction and impurity removal step.

[0039] The methanol-water mixed vapor discharged from the top of sodium methoxide reaction tower 1 and the methanol-containing extract discharged from the top of water extraction tower 3 are respectively sent to methanol recovery tower 6 for rectification and separation via pipelines. In methanol recovery tower 6, methanol and water are separated by rectification. The anhydrous methanol obtained from the rectification separation is discharged from the top of methanol recovery tower 6. Part of it is pressurized by compressor 7 and sent back to the lower part of sodium methoxide reaction tower 1 via pipeline as raw material for the preparation of sodium methoxide solution; the other part is compressed by compressor 7 and enters the shell side of reboiler 8, where it condenses and releases latent heat. This heat is used to heat the material in the bottom of methanol recovery tower 6, causing the liquid in the bottom of the tower to vaporize and generate rising steam to maintain the rectification operation. The condensed methanol liquid flows out from the shell side outlet of reboiler 8 and flows back to the upper part of methanol recovery tower 6 to participate in rectification and separation again. The methanol-water mixture in the bottom of methanol recovery tower 6 enters the tube side of reboiler 8 via pipeline. After being heated by high-temperature methanol vapor in the shell side, it partially vaporizes. The gas-liquid mixture returns to the lower part of methanol recovery tower 6. The residual wastewater (with extremely low methanol content) in the bottom of the tower is periodically discharged and sent to a wastewater treatment plant. Through this complete methanol recycling process, continuous methanol recovery and reuse are achieved, reducing both raw material consumption and pollutant emissions, significantly lowering methanol feedstock consumption.

[0040] Through the connection and process operation of the dichlorobutadiene production system of this invention, continuous production of dichlorobutadiene is achieved. The continuous series operation of the sodium methoxide reaction tower and the dechlorination reactor ensures the immediate preparation of the sodium methoxide solution and the continuous conduction of the dechlorination reaction. The stirring mechanism and cooling jacket within the dechlorination reactor ensure uniform reaction and effective temperature control. The sequential series connection of the dechlorination reactor, water extraction tower, dehydration coalescer, and purification tower allows the reaction mixture to undergo extraction and removal of methanol and sodium chloride, removal of water, and vacuum distillation purification of the high-purity product, ultimately obtaining dichlorobutadiene with a purity ≥99.5%. The combined configuration and corresponding connection of the methanol recovery tower, compressor, and reboiler achieve efficient methanol recovery and self-heating utilization, reducing energy consumption. The condenser and vacuum pump at the top of the purification tower work in tandem to ensure stable operation of vacuum distillation and smooth product extraction. The entire system forms a closed-loop cycle, fully recovering and utilizing methanol, and easily treating wastewater, achieving clean production.

[0041] All technical features in this embodiment can be freely combined according to actual needs. The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

[0042] The above embodiments are preferred implementations of the present invention. In addition, other implementations are also included. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A dichlorobutadiene production system, characterized in that: The system includes a reaction complex unit, a purification and separation unit, and a recovery unit. The reaction complex unit is connected to the purification and separation unit. In the reaction complex unit, trichlorobutene reacts with sodium methoxide to form a reaction mixture that is converted into dichlorobutadiene. This mixture is then purified into dichlorobutadiene product by the purification and separation unit, and methanol is separated from it. The reaction mixture of dichlorobutadiene is also purified into dichlorobutadiene product by the purification and separation unit, and methanol is separated from it. The recovery unit is connected to both the purification and separation unit and the reaction complex unit, and is used to recover methanol from both units and return it to the reaction complex unit for recycling.

2. The dichlorobutadiene production system according to claim 1, characterized in that: The reaction complex unit includes a sodium methoxide reaction tower (1) and a dechlorination reactor (2); the discharge end of the sodium methoxide reaction tower (1) is connected to the feed end of the dechlorination reactor (2), and the top is connected to the recovery unit; the discharge end of the dechlorination reactor (2) is connected to the purification and separation unit; the dechlorination reactor (2) is equipped with a stirring mechanism (14) and a cooling liquid jacket (13) on its outer shell.

3. The dichlorobutadiene production system according to claim 2, characterized in that: The refining and separation unit includes a water extraction tower (3), a dehydration coalescer (4), and a refining tower (5); the dechlorination reactor (2), water extraction tower (3), dehydration coalescer (4), and refining tower (5) are connected in series to sequentially perform water extraction, dehydration, and vacuum distillation on the dichlorobutadiene reaction mixture; the top of the water extraction tower (3) is connected to the recovery unit, and the separated methanol is sent to the recovery unit; the top of the refining tower (5) is equipped with a condenser (10) and a vacuum pump (11), and the bottom of the tower is equipped with a reboiler (8). The dichlorobutadiene obtained in the condenser (10) is sent back to the top of the refining tower (5) for reflux.

4. The dichlorobutadiene production system according to claim 3, characterized in that: The recovery unit includes a methanol recovery tower (6), a compressor (7), and a reboiler (8); the top of the methanol recovery tower (6) is connected to the lower part of the sodium methoxide reaction tower (1) and the upper part of the methanol recovery tower (6); the compressor (7) is installed on the pipeline connecting the top of the methanol recovery tower (6) to the lower part of the sodium methoxide reaction tower (1); the compressor (7) and the reboiler (8) are sequentially installed on the pipeline connecting the top of the methanol recovery tower (6) to the upper part of the methanol recovery tower (6); the bottom of the methanol recovery tower (6) is connected to the shell-side inlet of the reboiler (8) through a pipeline, and the shell-side outlet of the reboiler (8) is connected to the lower part of the methanol recovery tower (6) through a pipeline.

5. A dichlorobutadiene production process, employing the dichlorobutadiene production system as described in claim 4, characterized in that: Includes the following steps: S1. Prepare sodium methoxide solution; S2, dechlorination reaction; S3, Refining and Separation.

6. The dichlorobutadiene production process according to claim 5, characterized in that: In step S1, methanol and NaOH solution are fed into the sodium methoxide reaction tower (1) from the top of the tower and react continuously with methanol vapor fed into the tower from the bottom of the sodium methoxide reaction tower (1) to produce sodium methoxide and methanol solution.

7. The dichlorobutadiene production process according to claim 6, characterized in that: In step S2, trichlorobutene, sodium methoxide and methanol solution obtained in step S1 are fed into dechlorination reactor (2) for dechlorination reaction to obtain reaction mixture containing dichlorobutadiene.

8. The dichlorobutadiene production process according to claim 7, characterized in that: Before step S2, a polymerization inhibitor is added to the dechlorination reactor (2). The polymerization inhibitor is prepared in advance in the polymerization inhibitor preparation tank by diphenylamine sulfide and diethylhydroxylamine in a certain ratio.

9. The dichlorobutadiene production process according to claim 7 or 8, characterized in that: In step S3, the purification and separation includes the following steps: S31. Water extraction to remove impurities: The dichlorobutadiene reaction mixture obtained in step S2 is sent to the water extraction tower (3). In the water extraction tower (3), water is used as the extractant to extract and remove methanol and sodium chloride from the reaction mixture. S32, coalescence and dehydration: The dichlorobutadiene reaction mixture after water extraction and impurity removal in S31 is sent to the dehydration coalescer (4) to remove water from the reaction mixture through coalescence and dehydration. S33, vacuum distillation: The dichlorobutadiene reaction mixture that has been dehydrated in S32 is sent to the purification tower (5). The dichlorobutadiene is purified by vacuum distillation using the difference in boiling point between dichlorobutadiene and other reaction byproducts to obtain the dichlorobutadiene monomer product.

10. The dichlorobutadiene production process according to claim 9, characterized in that: It also includes methanol recycling; the methanol recycling is carried out after the preparation of sodium methoxide solution and after the water extraction and impurity removal step; the methanol and water mixed vapor discharged from the top of the sodium methoxide reaction tower (1) is extracted from the methanol in the water extraction tower (3) and sent to the methanol recovery tower (6) for distillation separation. The anhydrous methanol obtained is discharged from the top of the methanol recovery tower (6) and sent back to the sodium methoxide reaction tower (1) for recycling via the compressor (7). The other part is discharged from the top of the methanol recovery tower (6) and then enters the reboiler (8) via the compressor (7) to condense and release heat before flowing back into the methanol recovery tower (6). The methanol liquid at the bottom of the methanol recovery tower (6) is vaporized after being heated by the reboiler (8) and enters the methanol recovery tower (6) again for distillation separation.

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