A multi-kettle series solvent circulation reaction device for preparing dichlorobutene by liquid phase chlorination of butadiene

Abstract

The utility model provides a kind of for butadiene liquid phase chlorination preparation dichlorobutene's multiple kettle series connection solvent circulation reaction device, including one mixing tank, multiple series connection's stirred reaction kettle assembly, chlorine gas feed main pipe and solvent reflux main pipe.Solvent reflux main pipe's discharge end is communicated with mixing tank, and this mixing tank is used for butadiene, solvent, catalyst and condensed reflux solvent mixture.Each stirred reaction kettle assembly independently includes reaction kettle and condensation separation component;Reaction kettle is provided with gas distributor and stirrer, and reactor bottom is provided with reaction material outlet, and kettle top is provided with material inlet, chlorine gas feed port and volatile solvent discharge port, and solvent volatilized from reaction kettle is handled after condensation separation component and enters solvent reflux main pipe;Chlorine gas feed main pipe is simultaneously communicated with the chlorine gas feed port of each reaction kettle.

Description

Technical Field

[0001] This utility model relates to the field of dichlorobutene preparation technology, specifically to a multi-reactor series solvent circulation reaction device for the liquid-phase chlorination of butadiene to prepare dichlorobutene. Background Technology

[0002] Chloroprene rubber is an elastomer polymerized from chloroprene monomers. It has excellent mechanical properties, oil resistance, heat resistance, flame retardancy and ozone aging resistance, and is widely used in adhesives, cable sheaths, conveyor belts and other fields.

[0003] Currently, the industrial production of chloroprene mainly employs two process routes: the acetylene process and the butadiene process. The butadiene process is widely used due to its low raw material cost and good production safety. This method includes three steps: chlorination, isomerization, and dehydrochlorination, with chlorination being the key step. The butadiene liquid-phase chlorination method has recently become a research hotspot due to its high yield, low production cost, and safety and environmental friendliness.

[0004] Under liquid-phase conditions, at 25-100℃ and with the aid of a catalyst, butadiene reacts with chlorine to produce the target product dichlorobutene (3,4-dichloro-1-butene, cis-1,4-dichloro-2-butene, and trans-1,4-dichloro-2-butene). Dichlorobutene further reacts with chlorine to produce tetrachlorobutane as a byproduct. Chlorination is a strongly exothermic and rapid reaction; the technical challenges lie in controlling the heat of reaction and improving selectivity. Existing techniques typically add a large amount of solvent to the liquid phase to reduce the heat effect of the reaction and simultaneously improve selectivity. Furthermore, to increase selectivity and improve reaction safety, butadiene is usually in excess of chlorine to ensure complete reaction of the chlorine.

[0005] To address the aforementioned issues, existing technologies have actively explored new approaches. For example, patents US5077443 and CN1026484C disclose an evaporation-condensation reactor for liquid-phase butadiene chlorination. This reactor employs a single-bottle continuous stirred reactor equipped with a condensation reflux device to remove the heat of reaction through evaporative cooling. At 25-100°C, under pressure ensuring the reaction remains in the liquid phase, butadiene reacts with chlorine gas in solvents such as 1,2-dichlorotetrafluoroethane and n-pentane using quaternary ammonium chloride and quaternary phosphorus chloride as catalysts. The heat of reaction is removed through solvent evaporation, and the vapor is condensed by a condenser installed at the top of the reactor before being returned to the reactor. The aforementioned patents offer convenient heat removal and simple temperature control. However, the reactor in this patent is a fully mixed reactor, resulting in severe product backmixing. It is unsuitable for tandem reaction systems where the target product is an intermediate. During the chlorination reaction, tetrachlorobutane is easily generated as a tandem byproduct, leading to poor reaction selectivity and making it very difficult to improve it. The patent uses a large amount of solvent, with a solvent-to-chlorine ratio as high as 6-10, resulting in low product content in the reaction solution and high energy consumption for subsequent separation. In this patent, the solvent is returned to the reactor after evaporation and condensation, serving only as a heat transfer medium, and the heat of reaction in the chlorination reaction is not utilized. In this patent, butadiene, solvent, and catalyst are introduced into the reactor separately, resulting in uneven mixing. In some areas, the ratio of butadiene, solvent, and chlorine is lower than the set value. Since the chlorination reaction is a fast reaction, it does not meet the high requirements for raw material premixing, leading to poor reaction selectivity.

[0006] Patent JP2008247770A proposes a loop reactor using C5-C7 hydrocarbon solvents, with the reaction temperature controlled by an external heat exchanger. However, butadiene chlorination is a strongly exothermic reaction, and traditional heat exchange methods struggle to achieve precise temperature control, easily leading to localized overheating and increasing the risk of byproduct formation. Patent CN114505021B proposes a spiral plate multi-stage reactor for the liquid-phase chlorination of butadiene to produce dichlorobutene. However, this reactor cannot achieve isothermal temperature control, and the heat of reaction is not utilized effectively.

[0007] In summary, existing butadiene liquid-phase chlorination equipment has the following problems:

[0008] 1. The reactor is a fully mixed structure with severe backmixing. It is not compatible with the reaction system that has a series of side reactions in the chlorination reaction, resulting in poor reaction selectivity, a large amount of tetrachlorobutane byproducts, and making it very difficult to improve the reaction selectivity.

[0009] 2. The large amount of solvent used results in a low content of reaction products in the reaction solution, leading to high energy consumption in subsequent separation.

[0010] 3. The heat of reaction is removed through solvent evaporation and condensation or continuous heat exchange, and the heat of reaction is not utilized rationally;

[0011] 4. Butadiene, solvent, and catalyst are fed into the reactor separately, which leads to incomplete mixing. The reaction with chlorination is a fast reaction, which does not meet the requirements for high premixing of raw materials. Summary of the Invention

[0012] This invention addresses the aforementioned problems and aims to overcome the shortcomings of the above-mentioned butadiene liquid-phase chlorination reaction apparatus for preparing dichlorobutene, thereby proposing a new butadiene liquid-phase chlorination reaction apparatus for preparing dichlorobutene.

[0013] The technical solution of this utility model is based on the following concept:

[0014] (1) A multi-stage series stirred reactor device is adopted. Butadiene, solvent and catalyst are mixed and added at once from the first stage reactor. Chlorine gas is divided into multiple streams and enters each stage reactor, thereby effectively suppressing backmixing, adapting to the requirements of the reaction system with series side reactions in the chlorination reaction, and improving the reaction selectivity.

[0015] (2) By dividing chlorine gas into multiple streams in equal or certain proportions and introducing them into each stage of the reactor, the ratio of butadiene to chlorine gas and solvent to chlorine gas in the reactor is greatly increased, thereby improving the selectivity of the reaction.

[0016] (3) Provide a mixing tank to fully mix butadiene, solvent and catalyst and send it to the first-stage reactor to meet the high requirements of raw material premixing for chlorination reaction;

[0017] (4) The stirred reactor operation mode of bubble point reaction is adopted. The heat released by the reaction is mainly carried away by solvent evaporation. All the solvent after evaporation and condensation in each reactor is returned to the mixing tank to realize the recycling of solvent. It also increases the ratio of solvent to chlorine in the reactor. At the same time, the solvent evaporation makes full use of the heat of reaction, increases the content of reaction products in the reaction liquid, and reduces the energy consumption of subsequent separation process.

[0018] Based on the above ideas and considering the characteristics of butadiene liquid-phase chlorination, a multi-reactor series solvent circulation reactor and reaction method suitable for the preparation of dichlorobutene by butadiene liquid-phase chlorination are proposed. The aim is to improve reaction selectivity, reduce material consumption, fully utilize reaction heat, and reduce subsequent separation energy consumption. The specific technical solution is as follows:

[0019] In a first aspect, this utility model provides a multi-tank series solvent circulation reaction device for the liquid-phase chlorination of butadiene to prepare dichlorobutene, comprising a mixing tank, multiple stirred reaction vessel assemblies connected in series, a chlorine gas feed main pipe, and a solvent reflux main pipe.

[0020] The solvent reflux main outlet is connected to the mixing tank, which is used to mix butadiene, solvent, catalyst, and refluxed solvent. Each stirred reactor assembly independently includes a reactor and a condensation separation assembly. The reactor is equipped with a gas distributor and a stirrer. The bottom of the reactor has a reactant outlet, and the top of the reactor has a material inlet, a chlorine inlet, and a volatile solvent outlet. The solvent volatilized from the reactor is processed by the condensation separation assembly and then enters the solvent reflux main. The chlorine inlet main is also connected to the chlorine inlet of each reactor.

[0021] Preferably, in the multi-tank series solvent circulation reaction device for preparing dichlorobutene by liquid-phase chlorination of butadiene provided by this utility model, the top of the mixing tank is provided with a feed pipe and the solvent reflux main pipe, and the feed pipe is simultaneously equipped with feed valves for butadiene, solvent and catalyst; the inside of the mixing tank is provided with a stirrer, and the bottom end is connected to the material inlet of the first-stage reaction vessel through a centrifugal pump.

[0022] Preferably, in the multi-stage series solvent circulation reaction device for the liquid-phase chlorination of butadiene to prepare dichlorobutene provided by this utility model, the stirred reaction vessel assembly consists of 3 to 5 stages in series, and adjacent stages of the reaction vessels are connected by a centrifugal pump; the stirrer type of the reaction vessel is turbine, paddle or propeller type, and the stirring speed is 100 to 500 r / min; the volume of the mixing tank is 2 to 5 times the volume of the reaction vessel.

[0023] Preferably, in the multi-reactor series solvent circulation reaction device for the liquid-phase chlorination of butadiene to prepare dichlorobutene provided by this utility model, each stage of the condensation and separation component includes a condenser, a gas-liquid separation tank and a solvent circulation pump installed on the pipeline. The gas-liquid separation tank is equipped with a back pressure valve, and the pressure inside the reaction vessel is regulated by adjusting the pressure of the gas-liquid separator.

[0024] Preferably, in the multi-reactor series solvent circulation reaction device for preparing dichlorobutene by liquid-phase chlorination of butadiene provided by this utility model, the chlorine gas feed main pipe is connected to the chlorine gas feed port of each reactor through a regulating valve. The chlorine gas is evenly divided into multiple streams according to the number of reactors and enters each stage of stirred reactor, or distributed in a manner that gradually reduces the chlorine gas feed amount of each stage of reactor according to the flow direction of the reactants.

[0025] In a second aspect, this invention provides a method for preparing dichlorobutene using the aforementioned multi-stage series solvent circulation reactor. The main steps are as follows: Butadiene, solvent, catalyst, and refluxed solvent are mixed in a mixing tank, and the mixed material is sequentially passed through each stage of stirred reactor by a centrifugal pump; chlorine gas is divided into multiple streams according to the number of reactors and enters each stage of stirred reactor in a bubbling manner through a gas distributor to react with butadiene; the temperature inside the stirred reactor is the bubble point temperature of the reaction mixture, and the heat released by the reaction is carried away by solvent evaporation; the solvent evaporated in each stage of reactor is condensed by a condenser and enters a gas-liquid separator, and then is circulated back to the mixing tank by a centrifugal pump; the output from each stage of reactor is pumped, and after continuous reaction in multiple reactors, the reaction product is discharged from the last stage of reactor and enters the subsequent separation section.

[0026] Preferably, the molar ratio of butadiene feed to total chlorine feed is 1.4-2; the solvent is n-butane, and the molar ratio of n-butane feed to butadiene feed is 3-5; the catalyst is pyridine, and the amount of pyridine used is controlled at 100-200 ppm based on the mass of the solvent in the mixing tank; the heat exchange medium in the condenser is selected from -10℃ ethylene glycol circulating liquid.

[0027] Preferably, the effective liquid holding capacity of each reactor is maintained between 1 / 2 and 2 / 3 of the reactor volume; the residence time of the liquid phase material in each reactor is 2 to 10 minutes, and the stirring speed of each reactor is the same; the bubble point reaction temperature in each stirred reactor is controlled at 40 to 60°C, and the reaction temperature of each stage reactor is the same, or the bubble point reaction temperature of each stage reactor gradually decreases according to the flow direction of the reactants.

[0028] The beneficial protections and effects of this utility model are as follows:

[0029] Compared with the existing reactor structure and reaction method of liquid-phase chlorination, this invention has the following technical advantages:

[0030] (1) This invention adopts a multi-reactor series structure to form an approximate plug flow reaction environment. By connecting multiple reactors in series, material backmixing is effectively suppressed. Compared with a single-reactor continuous stirred reactor, it has a larger reactant concentration gradient and a stronger reaction driving force, thereby controlling the reaction path more precisely, significantly reducing the overchlorination side reaction, improving the selectivity of the target product dichlorobutene, and reducing material consumption.

[0031] (2) This utility model adopts a segmented chlorine feeding method, and independently controls the chlorine flow rate of each segment through a mass flow meter. This not only effectively reduces the local heat effect, avoids local overheating and side reactions, and improves the safety and efficiency of the reaction, but also increases the ratio of butadiene to chlorine and solvent to chlorine, effectively inhibiting the further chlorination of dichlorobutene, thereby improving the selectivity of the reaction.

[0032] (3) This utility model sets up a mixing tank to pre-mix butadiene, solvent and catalyst thoroughly before conveying the mixture to the first reaction vessel. Pre-mixing feed can ensure the uniformity of materials in the reaction vessel, avoid local solvent ratios that are too low due to uneven mixing of materials, and thus enhance the stability of the entire reaction process.

[0033] (4) This invention utilizes the characteristic that the reaction takes place below the boiling point of the material, and uses the heat absorbed by the vaporization of the solvent to remove the heat of reaction, and condenses the vaporized steam back to the mixing tank for recycling. This process not only makes full use of the heat of reaction and evaporates the solvent to increase the product concentration, but also significantly reduces the energy consumption of the subsequent separation process and improves the energy efficiency of the entire process; at the same time, the recycled solvent also increases the proportion of solvent in the upper reaction vessel, further improving the selectivity of the reaction.

[0034] In summary, the multi-reactor series solvent circulation reaction apparatus for the liquid-phase chlorination of butadiene to prepare dichlorobutene provided by this invention has a simple process, flexible operation, and precise thermal control, making it suitable for the liquid-phase chlorination reaction of butadiene. This method has significant advantages in improving reaction selectivity, reducing energy consumption, and enhancing safety, and has promising prospects for industrial application. Attached Figure Description

[0035] Figure 1 This invention relates to a schematic diagram of a three-reactor series structure of a multi-reactor series solvent circulation reaction device for the liquid-phase chlorination of butadiene to prepare dichlorobutene.

[0036] Figure 2 This invention relates to a schematic diagram of a five-reactor series structure of a multi-reactor series solvent circulation reaction device for the liquid-phase chlorination of butadiene to prepare dichlorobutene.

[0037] In the diagram: 1-mixing tank; 2, 8, 14, 20, 29, 35-transfer centrifugal pumps; 3-first reaction vessel; 4, 10, 16, 25, 31-condensers; 5, 11, 18, 27, 33-gas-liquid separators; 6, 12, 17, 26, 32-back pressure valves; 7, 13, 19, 28, 34-solvent circulation pumps; 9-second reaction vessel; 15-third reaction vessel; 21, 22, 23, 36, 37-gas distributors; 24-fourth reaction vessel; 30-fifth reaction vessel. Detailed Implementation

[0038] The following embodiments further illustrate the present invention and should not be construed as limiting the present invention. The embodiments do not include a detailed description of conventional methods, which are well known to those skilled in the art and described in numerous publications.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention, and the preferred embodiments and materials described in the specific implementation are for illustrative purposes only.

[0040] Unless otherwise specified, the experimental methods described in the following examples are generally performed under standard conditions or as recommended by the manufacturer.

[0041] I. Multi-reactor series solvent circulation device for the liquid-phase chlorination of butadiene to prepare dichlorobutene

[0042] This utility model provides a multi-stage series solvent circulation reaction device for the liquid-phase chlorination of butadiene to prepare dichlorobutene. It includes a mixing tank and multiple stirred reaction vessels connected in series. Each reaction vessel is equipped with an independent gas distributor, stirring device, condenser, gas-liquid separator, and back pressure valve. The liquid stream is transported by a centrifugal pump. The three-stage and five-stage series structures are described below.

[0043] Figure 1 This diagram illustrates a three-reactor series solvent circulation system for the liquid-phase chlorination of butadiene to produce dichlorobutene: Butadiene, solvent, catalyst, and refluxed solvent are mixed in mixing tank 1 and then conveyed to the first reactor 3 by centrifugal pump 2. The material exits from the bottom of the first reactor 3 and sequentially enters the second reactor 9 and the third reactor 15 via centrifugal pumps 8 and 14, respectively, before being conveyed to the subsequent separation section by centrifugal pump 20. By adjusting the flow rates of each centrifugal pump, the effective liquid holdup in each reactor is maintained between 1 / 2 and 2 / 3 of its volume. Simultaneously, chlorine gas is uniformly or proportionally divided into three streams and enters the first reactor 3, the second reactor 9, and the third reactor 15 via gas distributors 21, 22, and 23, respectively, to react with the butadiene. The heat generated by the reaction is primarily removed through solvent vaporization. The vaporized solvents from the first reactor 3, the second reactor 9, and the third reactor 15 are condensed by condensers 4, 10, and 16, respectively, and then enter gas-liquid separators 5, 11, and 18. Subsequently, the condensed solvents are transported back to the mixing tank 1 by solvent circulation pumps 7, 13, and 19.

[0044] Figure 2This diagram illustrates a five-reactor series solvent circulation system for the liquid-phase chlorination of butadiene to produce dichlorobutene: Butadiene, solvent, catalyst, and refluxed solvent are mixed in mixing tank 1 and then conveyed to the first reactor 3 by centrifugal pump 2. The material exits from the bottom of the first reactor 3 and sequentially enters the second reactor 9, third reactor 15, fourth reactor 24, and fifth reactor 30 via centrifugal pumps 8, 14, 20, and 29, respectively, before being finally conveyed to the subsequent separation section by centrifugal pump 35. By adjusting the flow rates of each centrifugal pump, the effective liquid holdup in each reactor is maintained between 1 / 2 and 2 / 3 of its volume. Simultaneously, chlorine gas is uniformly or proportionally divided into five streams, which enter the first reactor 3, second reactor 9, third reactor 15, fourth reactor 24, and fifth reactor 30 via gas distributors 21, 22, 23, 36, and 37, respectively, to react with the butadiene. The heat generated by the reaction is primarily removed through solvent vaporization. The vaporized solvents from the first reactor 3, the second reactor 9, the third reactor 15, the fourth reactor 24, and the fifth reactor 30 are condensed by condensers 4, 10, 16, 25, and 31, respectively, and then enter gas-liquid separators 5, 11, 18, 27, and 33. Subsequently, solvent circulation pumps 7, 13, 19, 28, and 34 transport the condensed solvents back to the mixing tank 1.

[0045] II. Specific Application Examples

[0046] A multi-reactor series solvent circulation pilot-scale apparatus for the liquid-phase chlorination of butadiene to prepare dichlorobutene, the process is as follows: Figure 1 , 2 As shown, the components selected for the two devices are as follows:

[0047] Mixing tank 1 has a volume of 5L; stirred reaction vessels 3, 9, 15, 24, and 30 each have a volume of 1L, with paddle-type agitators; gas-liquid separators 5, 11, 18, 27, and 33 each have a volume of 2L; and condensers 4, 10, 16, 25, and 31 have a heat exchange area of ​​0.16m². 2 The cooling medium is ethylene glycol. The mixing tank, gas-liquid separator, and solvent circulation pumps 7, 13, 19, 28, and 34 are connected by seamless steel pipes with a diameter of φ12.7 mm; the mixing tank, each reaction vessel, and centrifugal transfer pumps 2, 8, 14, 20, 29, and 35 are connected by seamless steel pipes with a diameter of φ9.5 mm; gas distributors 21, 22, 23, 36, and 37 are connected by straight pipes with a diameter of φ6.35 mm to a ring pipe with eight evenly distributed φ1 mm vertically downward holes. All other pipelines use seamless steel pipes with a diameter of φ6.35 mm.

[0048] Example 1

[0049] A pilot-scale three-reactor series solvent circulation apparatus for the liquid-phase chlorination of butadiene to prepare dichlorobutene, such as... Figure 1 As shown, the device dimensions are illustrated in a specific application example.

[0050] The flow rate of butadiene was 20 ml / min, the flow rate of fresh solvent n-butane was 100 ml / min, and the amount of catalyst pyridine was based on 100 ppm of the solvent mass in mixing tank 1. These raw materials were premixed with refluxed n-butane (approximately 90 ml) in mixing tank 1, with the mixing tank stirring speed at 200 r / min. The mixed material was then fed into the first reactor 3 via centrifugal pump 2 at a flow rate of 210 ml / min. The residence times of the liquid phase in reactors 3, 9, and 15 were 3 min, 4 min, and 5 min, respectively. Correspondingly, the flow rates of centrifugal pumps 8, 14, and 20 were set to 180 ml / min, 150 ml / min, and 120 ml / min, respectively, to control the liquid holdup in each reactor between 500 and 650 ml. The stirring speed of each reactor was set to 400 r / min. By adjusting back pressure valves 6, 12, and 17, the pressures of reactors 3, 9, and 15 are controlled at 0.43 MPa, 0.41 MPa, and 0.37 MPa, respectively, corresponding to a boiling point of approximately 45°C for the materials inside the reactors. The chlorine feed temperature is 25°C, the pressure is 0.50 MPa, and the total chlorine flow rate is 2600 ml / min (STP). After being proportionally distributed, the chlorine enters each reactor via gas distributors 21, 22, and 23 to react with butadiene. The heat released from the reaction is mainly removed through solvent vaporization. The vaporized vapor from each reactor is condensed by condensers 4, 10, and 16 (heat exchange medium is -10°C ethylene glycol circulating liquid) and then enters gas-liquid separators 5, 11, and 18, before being transported back to mixing tank 1 by solvent circulation pumps 7, 13, and 19. After continuous reaction in the three reactors, the reaction product is discharged from the third reactor 15 and transported to the subsequent separation section by centrifugal pump 20. After the system stabilized, the chlorine conversion rate reached 100%. Chromatographic analysis of the reaction products showed that the yield of dichlorobutene was 96%, and the by-product rate of tetrachlorobutane was 3.2%.

[0051] Example 2

[0052] A five-reactor series solvent circulation pilot-scale apparatus for the liquid-phase chlorination of butadiene to prepare dichlorobutene is shown in the flow chart below. Figure 2 As shown, the device dimensions are illustrated in a specific application example.

[0053] The flow rate of butadiene was 20 ml / min, the flow rate of fresh solvent n-butane was 100 ml / min, and the amount of catalyst pyridine was based on 200 ppm of the solvent mass in mixing tank 1. These raw materials were premixed with refluxed n-butane (approximately 90 ml) in mixing tank 1, with the mixing tank stirring speed at 200 r / min. The mixed material was then fed into the first reactor 3 via centrifugal pump 2 at a flow rate of 210 ml / min. The residence times of the liquid phase in reactors 3, 9, 15, 24, and 30 were 3 min, 3.5 min, 4 min, 4.5 min, and 5 min, respectively. Correspondingly, the flow rates of centrifugal pumps 8, 14, 20, 29, and 35 were set to 190 ml / min, 170 ml / min, 150 ml / min, 135 ml / min, and 120 ml / min, respectively, to control the liquid holdup in each reactor at 500–650 ml. The stirring speed of each reactor was set to 400 r / min. By adjusting back pressure valves 6, 12, 17, 26, and 32, the pressures of reactors 3, 9, 15, 24, and 30 are controlled at 0.44 MPa, 0.43 MPa, 0.415 MPa, 0.4 MPa, and 0.375 MPa, respectively, corresponding to a boiling point of approximately 45°C for the materials inside the reactors. The chlorine feed temperature is 25°C, the pressure is 0.50 MPa, and the total chlorine flow rate is 2600 ml / min (STP). After being distributed in a 9:9:8:7:6 ratio, the chlorine enters each reactor through gas distributors 21, 22, 23, 36, and 37 to react with butadiene. The heat released during the reaction is mainly removed through solvent vaporization. The vaporized vapors from each reactor are condensed in condensers 4, 10, 16, 25, and 31 (heat exchange medium is -10℃ ethylene glycol circulating liquid), and then enter gas-liquid separators 5, 11, 18, 27, and 33. From there, they are pumped back to mixing tank 1 by solvent circulation pumps 7, 13, 19, 28, and 34. After continuous reaction in five reactors, the reaction product is discharged from reactor 30 and transported to the subsequent separation section by centrifugal pump 35. Once the operation stabilizes, the chlorine conversion rate reaches 100%. Chromatographic analysis of the reaction products shows that the dichlorobutene yield is 97.5%, and the tetrachlorobutane byproduct rate is 2.1%.

[0054] In summary, the multi-reactor series solvent circulation reactor of this invention for the liquid-phase chlorination of butadiene to prepare dichlorobutene has the following advantages:

[0055] 1. By employing multiple reactors connected in series to form an approximate plug flow, chlorine is injected in stages and reacts with the premixed materials. This not only suppresses backmixing but also significantly increases the molar ratio of butadiene to chlorine and the molar ratio of solvent to chlorine, thereby greatly improving the selectivity of the reaction products. The dichlorobutene selectivity of the three-reactor series unit is increased from 93% in CN1026484C to 96%, and after five reactors are connected in series, it increases by another 1.5%, eventually stabilizing at 97.5%.

[0056] 2. The heat of reaction is carried away by the vaporization of the solvent inside the reactor. After the vapor phase is condensed, it is sent back to the mixing tank by the solvent circulation pump. No external steam reboiling is required. This method can recover about 70% of the solvent in the reaction product, which significantly reduces the energy consumption of the subsequent separation section.

[0057] The undescribed parts of this utility model are the same as or implemented using existing technology. The applicant declares that this utility model is illustrated through the above embodiments, but it is not limited to the above detailed methods, meaning that this utility model does not necessarily rely on the above detailed methods for implementation. Those skilled in the art should understand that any improvements to this utility model, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this utility model.

Claims

1. A multi-tank series solvent circulation reactor for the liquid-phase chlorination of butadiene to prepare dichlorobutene, characterized in that, It includes a mixing tank, multiple stirred reactor assemblies connected in series, a chlorine feed main, and a solvent reflux main. The outlet end of the solvent reflux manifold is connected to the mixing tank, which is used for mixing butadiene, solvent, catalyst, and condensed reflux solvent. Each stirred reactor assembly independently includes a reactor and a condensation separation assembly; the reactor is equipped with a gas distributor and a stirrer, the bottom of the reactor is equipped with a reactant outlet, the top of the reactor is equipped with a material inlet, a chlorine inlet and a volatile solvent outlet, and the solvent volatilized from the reactor is processed by the condensation separation assembly and then enters the solvent return main; The chlorine gas feed manifold is simultaneously connected to the chlorine gas feed port of each reactor.

2. The multi-tank series solvent circulation reactor for the liquid-phase chlorination of butadiene to prepare dichlorobutene according to claim 1, characterized in that: in, The top of the mixing tank is equipped with a feed pipe and a solvent reflux main pipe, and the feed pipe is also equipped with feed valves for butadiene, solvent and catalyst. The mixing tank is equipped with an agitator inside, and its bottom is connected to the material inlet of the first-stage reactor via a centrifugal pump.

3. The multi-tank series solvent circulation reactor for the liquid-phase chlorination of butadiene to prepare dichlorobutene according to claim 1, characterized in that: in, The stirred reactor assembly consists of 3 to 5 stages connected in series, with adjacent stages connected by a centrifugal pump. The agitator of the reactor is a turbine, paddle, or propeller type, with a stirring speed of 100~500 r / min.

4. The multi-tank series solvent circulation reactor for the liquid-phase chlorination of butadiene to prepare dichlorobutene according to claim 1, characterized in that: in, Each stage of the condensation and separation assembly includes a condenser, a gas-liquid separator, and a solvent circulation pump installed on the pipeline. The gas-liquid separator is equipped with a back pressure valve, and the pressure inside the reactor is regulated by adjusting the pressure of the gas-liquid separator.

5. The multi-tank series solvent circulation reactor for the liquid-phase chlorination of butadiene to prepare dichlorobutene according to claim 1, characterized in that... ； The chlorine feed main is connected to the chlorine inlet of each reactor via a regulating valve; the chlorine is evenly divided into multiple streams according to the number of reactors and enters each stage of stirred reactor, or distributed in a manner that gradually decreases the chlorine feed rate of each stage of reactor according to the flow direction of the reactants.

Images