A method and system for preparing glycerol chlorination to prepare dichloropropanol

Abstract

The application provides a preparation method and a production system for preparing dichloropropanol by glycerol chlorination, and belongs to the technical field of compound preparation. The method adopts multistage series connection of reaction kettles for reaction, and precisely controls the chlorination reaction process by controlling the reaction temperature and the dehydration amount. In the reaction, hydrogen chloride gas is kept in communication with all the reactors, glycerol and a catalyst are fed into a first-stage reaction kettle for reaction, liquid-phase products are transferred into a next-stage reaction kettle for continuous reaction, and gas-phase products are transferred into the original reaction kettle for continuous reaction after dehydration. The method provided by the application can not only precisely and efficiently solve the water inhibition problem in the reaction process, but also can improve the chlorination reaction efficiency, the selectivity and the yield of dichloropropanol, and the purity of the product.

Description

Technical Field

[0001] This invention belongs to the field of compound preparation technology, and particularly relates to a preparation method and production system for dichloropropanol prepared by glycerol chlorination. Background Technology

[0002] Epichlorohydrin is an important organic chemical raw material and intermediate, mainly used in the production of epoxy resins, synthetic glycerol, and other chemical products. The glycerol process, as a green process for producing epichlorohydrin, has attracted widespread attention due to its high atom economy. The core step of this process is the chlorination reaction of glycerol with hydrogen chloride in the presence of a catalyst, producing the intermediate dichloropropanol. This chlorination reaction is reversible and involves the formation of water. However, the presence of water severely inhibits the shift of the reaction equilibrium to the right, leading to problems such as slow reaction rate, insufficient chlorination depth (i.e., high monochloropropanediol content and low dichloropropanol yield), and reduced equipment capacity.

[0003] Chinese patent CN101693646B discloses a method for preparing dichloropropanol using a catalytically catalyzed, water-absorbing, strongly acidic polymeric resin or a combination of resin and carboxylic acid. During the preparation process, the efficiency of glycerol chlorination is improved by vacuum distillation to remove water and by dehydrating and recycling the catalyst, but the production process is complex. In the method disclosed in patent CN101255099B, the efficiency of the chlorination reaction is effectively improved by utilizing an external circulation dehydration system and a dehydrating agent. Chinese patent CN102887816A develops a pervaporation coupling method for preparing dichloropropanol. After coupling pervaporation with the chemical reaction, the water generated in the reaction is removed in time, and the chlorination reaction proceeds efficiently under the impetus of chemical equilibrium. However, this method uses a cationic resin as a catalyst, which is expensive, and the permeate membrane needs frequent replacement. Therefore, developing a glycerol-based process for preparing dichloropropanol with a reasonable process flow, high product yield, and environmental friendliness has significant industrial application value. Summary of the Invention

[0004] This invention provides a method and production system for preparing dichloropropanol by chlorination of glycerol. The method provided by this invention can not only accurately and efficiently solve the problem of water inhibition during the reaction process, but also improve the chlorination reaction efficiency, the selectivity and yield of dichloropropanol, and improve the purity of the product.

[0005] To achieve the above objectives, the present invention provides a method for preparing dichloropropanol by chlorination of glycerol, which uses a multi-stage series reactor for the reaction. Hydrogen chloride gas is introduced into each stage of the reactor, and glycerol and a catalyst are introduced into the first stage reactor for the reaction. Liquid and gas phases are obtained in each stage of the reactor, respectively.

[0006] The liquid phase obtained from the upper reactor is transferred to the lower reactor for reaction. The gas phase obtained from each reactor is dehydrated, and the dehydrated product is transferred back to the original reactor for reaction.

[0007] Among them: the moisture content of the material in the first-stage reactor is controlled at 5~15 wt%;

[0008] The moisture content of the material in the intermediate stage reactor is controlled at 2-5 wt%.

[0009] The moisture content of the material in the final stage reactor is controlled to be ≤2 wt%, and the moisture content of the material in the next stage reactor is lower than that of the material in the previous stage reactor.

[0010] Preferably, the glycerol is preheated to 80-120°C before being introduced into the reactor.

[0011] Preferably, the catalyst is adipic acid, azelaic acid, sebacic acid, or octanoic acid.

[0012] Preferably, the multi-stage series reactor consists of 2 to 6 series reactors.

[0013] Preferably, the pressure in each reactor is controlled at 0~0.5 MPa; the temperature in each reactor is controlled at 90~140℃, and the temperature of the upper reactor does not exceed the reaction temperature of the lower reactor; the reaction time in each reactor is 1.5~4 h, and the total residence time of the reaction in the multi-stage reactor is 4~12 h.

[0014] Preferably, the gas phase obtained from the last stage reactor is dehydrated by concentrated sulfuric acid dehydration, molecular sieve adsorption dehydration, or pervaporation membrane separation dehydration; the gas phase obtained from other reactors is dehydrated by condensation dehydration.

[0015] Preferably, when the multi-stage series reactor consists of two reactors connected in series, the temperature of the first-stage condensation and dehydration is 40~60℃, and the second-stage dehydration is carried out by concentrated sulfuric acid dehydration, molecular sieve adsorption dehydration, or pervaporation membrane separation dehydration; when the multi-stage series reactor consists of three to six reactors connected in series, the temperature of the first-stage condensation and dehydration is 40~60℃, and the temperature of the last-stage condensation and dehydration is -5~5℃.

[0016] Preferably, the final stage of dehydration includes a gas-phase condensation pretreatment process; when concentrated sulfuric acid or molecular sieve adsorption is used for dehydration, the temperature of the gas-phase condensation pretreatment is -5°C, and when pervaporation membrane separation is used for dehydration, the temperature of the gas-phase condensation pretreatment is room temperature.

[0017] This invention provides a dichloropropanol production system according to any one of the above claims, comprising a multi-stage reactor connected in series, wherein:

[0018] The liquid outlet at the bottom of the upper reactor is connected to the liquid inlet at the top of the lower reactor via a conveying pipeline, forming a multi-stage series reactor; the gas inlet at the bottom of each reactor is connected to a hydrogen chloride gas conveying pipeline.

[0019] The gas outlet at the side of each stage reactor is connected to the inlet of a dehydration device via a pipeline, and a gas phase valve is installed on the pipeline connecting the gas outlet and the inlet of the dehydration device; the gas outlet of the dehydration device is connected to the inlet at the side of the reactor via a pipeline.

[0020] Preferably, the reactor also includes a glycerol storage tank and a finished product storage tank. The glycerol storage tank is connected to the feed inlet at the top of the first-stage reactor via a conveying pipeline, and the discharge outlet at the bottom of the last-stage reactor is connected to the finished product storage tank via a pipeline.

[0021] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0022] (1) High yield of dichloropropanol: The preparation method for dichloropropanol by glycerol chlorination provided in this invention adopts a multi-stage reactor series process, which ensures uniform gas-liquid contact, reduces backmixing, and achieves high reaction efficiency. At the same time, it adopts segmented dehydration for precise control, breaking the equilibrium limitation: Through the "segmented dehydration" strategy, the thermodynamic and kinetic characteristics of each reaction stage are precisely matched. Strong dehydration is carried out in the later stage of the reaction, which most effectively breaks the reaction equilibrium, significantly improves the reaction conversion rate and depth, and ensures a high yield of the final product, dichloropropanol.

[0023] (2) Optimize energy consumption and improve economic efficiency: Avoid unnecessary strong dehydration in the early stage of reaction, save energy consumption, reduce operating costs, and make the whole process more economical and green.

[0024] (3) Suppressing side reactions and improving selectivity: By controlling the water content in the early stage, the intense exothermic reaction in the early stage of the reaction is mitigated, the risk of side reactions such as glycerol polymerization and dehydration to produce acrolein is reduced, and the selectivity of the reaction and the safety of the system are improved.

[0025] (4) The dichloropropanol production system provided by this invention can not only significantly improve the yield and purity of dichloropropanol to meet the requirements of industrial production, but also has a simple process flow, low energy consumption, and can realize continuous large-scale production. At the same time, the production system can also realize the efficient utilization of hydrogen chloride and the recycling of by-products, reducing production costs and environmental burden. Attached Figure Description

[0026] Figure 1 Schematic diagram of the production system for preparing dichloropropanol by chlorination of glycerol;

[0027] Wherein: 1-First stage reactor, 2-Second stage reactor, 3-Third stage reactor, 4-First stage dehydration device, 5-Second stage dehydration device, 6-Third stage dehydration device, 7-Glycerin storage tank, 8-Finished product storage tank, 9-Gas phase valve, 10-Pretreatment condenser. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides a method for preparing dichloropropanol by chlorination of glycerol, which uses a multi-stage series reactor for the reaction. Hydrogen chloride gas is introduced into each stage of the reactor, and glycerol and a catalyst are introduced into the first stage reactor for the reaction. Liquid and gas phases are obtained in each stage of the reactor, respectively.

[0030] The liquid phase obtained from the upper reactor is transferred to the lower reactor for reaction. The gas phase obtained from each reactor is dehydrated, and the dehydrated product is transferred back to the original reactor for reaction.

[0031] Among them: the moisture content of the material in the first-stage reactor is controlled at 5~15 wt%;

[0032] The moisture content of the material in the intermediate stage reactor is controlled at 2-5 wt%.

[0033] The moisture content of the material in the final stage reactor is controlled to be ≤2 wt%, and the moisture content of the material in the next stage reactor is lower than that of the material in the previous stage reactor.

[0034] The multi-stage series reactors are preferably 2 to 6 reactors in series. In this invention, it is preferable to preheat the glycerol to 80 to 120°C before introducing it into the reactors. In this invention, the purity of the glycerol is preferably 90 wt% to 99.5 wt%, more preferably 98 wt% to 99 wt%. This invention does not have a special limitation on the source of the glycerol; conventional commercially available products are acceptable. To save costs, biomass-derived glycerol is preferred. In this invention, the catalyst is preferably adipic acid, azelaic acid, sebacic acid, or octanoic acid.

[0035] In this invention, during the reaction, the volume of the reaction liquid in each reactor is preferably controlled at 40%. Controlling the reaction liquid volume at this level ensures sufficient gas-liquid contact while maintaining safe operation of the apparatus. In this invention, the pressure in each reactor is preferably controlled between 0 and 0.5 MPa; the temperature in each reactor is preferably controlled between 90 and 140°C, and the temperature of the upper reactor does not exceed the reaction temperature of the lower reactor. Controlling the reaction temperature within this range ensures efficient chlorination while minimizing side reactions. Based on the kinetics and thermodynamics of the two-step chlorination reaction, controlling the chlorination temperature at a lower level in the initial stage effectively reduces the formation of 2-chloro-1,3-propanediol, while the subsequent higher chlorination temperature effectively promotes the conversion of the monochloro product to the dichloro product.

[0036] In this invention, the reaction time in each reactor is preferably 1.5 to 4 h, and the total residence time of the reaction in the multi-stage reactor is preferably 4 to 12 h, more preferably 6 to 8 h.

[0037] In this invention, the gas phase obtained from the last-stage reactor is preferably dehydrated by concentrated sulfuric acid, molecular sieve adsorption, or pervaporation membrane separation, more preferably by molecular sieve adsorption; the gas phase obtained from other reactors is preferably dehydrated by condensation. That is, condensation is used for all stages except the last, and concentrated sulfuric acid, molecular sieve adsorption, or pervaporation membrane separation is the preferred method for the last stage. For example, when using a three-stage series reactor, the gas phase obtained from the first and second stages is dehydrated by condensation, while the gas phase obtained from the third stage is dehydrated by concentrated sulfuric acid, molecular sieve adsorption, or pervaporation membrane separation. In this invention, when pervaporation membrane separation is used, the main components of the dehydration product are hydrogen chloride and dichloropropanol; the main component of the dehydration product obtained by other dehydration methods is HCl. In this invention, when the multi-stage series reactor consists of two reactors connected in series, the preferred temperature for the first-stage condensation and dehydration is 40~60℃, and the second-stage dehydration is carried out by concentrated sulfuric acid dehydration, molecular sieve adsorption dehydration, or permeate evaporation membrane separation dehydration; when the multi-stage series reactor consists of 3~6 reactors connected in series, the preferred temperature for the first-stage condensation and dehydration is 40~60℃, and the preferred temperature for the last-stage condensation and dehydration is -5~5℃.

[0038] In this invention, the final stage of dehydration preferably includes a gas-phase condensation pretreatment process. When concentrated sulfuric acid or molecular sieve adsorption is used for dehydration, the temperature of the gas-phase condensation pretreatment is -5°C; when pervaporation membrane separation is used for dehydration, the temperature of the gas-phase condensation pretreatment is room temperature. In this invention, performing gas-phase condensation pretreatment in the final stage of dehydration can effectively remove most of the water, reduce operating costs, and extend the operating time of the dehydrator.

[0039] Specifically, in this invention, when concentrated sulfuric acid is used for the final stage of dehydration, most of the water, glycerol, and chloroglycerol are removed through pretreatment by vapor-phase condensation (condensation temperature -5℃). The condensate then enters a distillation column for separation and utilization. The vapor components enter a concentrated sulfuric acid absorption tower, and the exiting gas re-particulates in the chlorination reaction. In this invention, 92% concentrated sulfuric acid is used as the desiccant in the concentrated sulfuric acid absorption tower, the temperature inside the tower is controlled at 25~45℃, and the HCl water content at the exiting tower is <200 ppm.

[0040] In this invention, when molecular sieve adsorption is used for the final stage of dehydration, most of the water, glycerol, and chloroglycerol are removed through gas-phase condensation pretreatment (condensation temperature -5℃). The condensate is then separated and utilized in a distillation column. The gas phase enters the molecular sieve for adsorption dehydration, and the dried HCl gas after dehydration re-enters the chlorination reactor to participate in the reaction. In this invention, when molecular sieve adsorption dehydration is used, the molecular sieve adsorption device is preferably filled with a mixture of molecular sieve and color-changing silica gel. In this invention, the preferred volume ratio of the molecular sieve to silica gel is 3:1. In this invention, the molecular sieve is preferably 3A molecular sieve; the silica gel is preferably color-changing silica gel. In this invention, using a mixture of molecular sieve and silica gel for dehydration facilitates timely replacement and regeneration of the molecular sieve by utilizing the indicating effect of the color-changing silica gel. The introduction of silica gel can protect the molecular sieve and reduce dehydration costs. The HCl water content after molecular sieve adsorption dehydration is <10 ppm.

[0041] In this invention, when the final stage of dehydration uses a pervaporation membrane for separation, a pretreatment process involving gas-phase condensation (at room temperature) is first performed to remove most of the water, HCl, glycerol, and chloroglycerol. The gas phase then enters the pervaporation membrane for dehydration. The pervaporation temperature is 60-90°C, and the pervaporation membrane is an acid-resistant inorganic or organic-inorganic pervaporation membrane. The feed pressure is 0.15-0.3 MPa, and the discharge pressure is 0.5-3 kPa. The residual liquid from the pervaporation is returned to the chlorination reactor for further reaction.

[0042] In this invention, the amount of water removed is controlled by adjusting the opening degree of the gas phase valve connected to the dehydration pipeline and the temperature at the top of the condenser tower. The opening degree of the gas phase valve can be adjusted arbitrarily from 0% to 100%. When the valve opening degree is constant, the gas composition will change during the reaction process. As the water content increases, the amount of water removed by condensation and dehydration also increases, thus making the water content in the reactor relatively stable. In actual production, if the water content varies greatly, the valve opening degree can be adjusted according to the real-time water content.

[0043] The chlorination reaction for the preparation of dichloropropanol from glycerol is reversible and involves water formation. The presence of water severely inhibits the shift of the reaction equilibrium to the right, leading to slow reaction rates, insufficient chlorination depth (i.e., high monochloropropanediol content and low dichloropropanol yield), and reduced equipment capacity. Traditional processes typically employ non-dehydration, one-time, or continuous constant dehydration methods, which cannot match the dynamic changes in the reaction process. In the initial stage of the reaction, the glycerol concentration is high, and the demand for dehydration is relatively low; forced deep dehydration may lead to localized overheating and catalyst coking. In the middle and later stages of the reaction, the water volume increases sharply; if the dehydration intensity is insufficient, the reaction rate rapidly decreases, and side reactions intensify.

[0044] The present invention provides a method for preparing dichloropropanol by glycerol chlorination, employing a segmented dehydration control method: For the first-stage reactor: weak or no dehydration is performed, controlling the dehydration intensity to maintain a relatively high water content in the reactor (5 wt%~15 wt%). The main objective of this stage is to utilize the high concentration of glycerol and HCl for a rapid reaction to generate dichloropropanediol. A moderately high water content helps suppress side reactions caused by overly vigorous reactions and saves energy. For the intermediate-stage reactor (if an intermediate-stage reactor exists): moderate-intensity dehydration is performed, controlling the dehydration intensity to reduce the water content in the reactor to an intermediate level (2 wt%~5 wt%). At this stage, the reactant concentration decreases, and the inhibitory effect of water begins to appear, driving the reaction towards the formation of dichloropropanol through dehydration. For the final-stage reactor: intensified dehydration is performed. The dehydration intensity is controlled to reduce the water content in the reactor to a minimum (≤ 2 wt%). At this stage, the reaction is close to equilibrium, and the driving force of the reaction is small. Strong dehydration is the key to breaking the equilibrium, achieving deep chlorination, and maximizing the yield of dichloropropanol.

[0045] This invention employs a multi-stage reactor series process, which ensures uniform gas-liquid contact, reduces backmixing, and achieves high reaction efficiency, while significantly improving the selectivity of glycerol dichloride. The segmented temperature-controlled dehydration process reduces the amount of 2-MCH and acrolein generated due to excessively high temperatures in the initial stage of the chlorination reaction. On the other hand, segmented dehydration can more effectively remove the water content generated during the chlorination reaction, thus promoting the chlorination reaction.

[0046] This invention provides a dichloropropanol production system according to any one of the above claims, comprising a multi-stage reactor connected in series, wherein:

[0047] The liquid outlet at the bottom of the upper reactor is connected to the liquid inlet at the top of the lower reactor via a conveying pipeline, forming a multi-stage series reactor; the gas inlet at the bottom of each reactor is connected to a hydrogen chloride gas conveying pipeline.

[0048] The gas outlet at the side of each stage reactor is connected to the inlet of a dehydration device via a pipeline, and a gas phase valve is installed on the pipeline connecting the gas outlet and the inlet of the dehydration device; the gas outlet of the dehydration device is connected to the inlet at the side of the reactor via a pipeline.

[0049] In this application, Figure 1 As shown: A three-stage reactor system is formed by connecting three reactors in series: a first-stage reactor 1, a second-stage reactor 2, and a third-stage reactor 3. The gas outlets at the sides of the first-stage reactor 1, second-stage reactor 2, and third-stage reactor 3 are connected via pipelines to the inlets of the first-stage dehydration unit 4, second-stage dehydration unit 5, and third-stage dehydration unit 6, respectively. The gas outlets at the first-stage dehydration unit 4, second-stage dehydration unit 5, and third-stage dehydration unit 6 are also connected via pipelines to the inlets at the sides of the first-stage reactor 1, second-stage reactor 2, and third-stage reactor 3, respectively. A gas phase valve 9 is installed on the pipeline connecting the gas outlet to the inlet of the dehydration unit, thereby allowing for the control of the dehydration rate.

[0050] The present invention does not impose any special limitations on the specific structure of the reaction vessel; conventional products in the field can be used.

[0051] The present invention does not impose any special limitations on the specific structure of the separation equipment used in the concentrated sulfuric acid dehydration scheme, the molecular sieve adsorption dehydration scheme, and the pervaporation membrane separation; conventional commercially available products in the field can be used.

[0052] In this invention, a pretreatment condenser 10 is preferably also provided. The gas inlet of the pretreatment condenser 10 is connected to the gas outlet at the side of the last stage reactor via a pipeline, and the gas outlet of the pretreatment condenser 10 is connected to the inlet of the last stage dehydration device.

[0053] In this invention, when the final stage of dehydration employs molecular sieve adsorption, the final stage dehydration device preferably includes 2-3 dehydrators connected in parallel. By using 2-3 dehydrators in parallel, multiple dehydrators can be operated simultaneously during operation, thereby improving dehydration efficiency. Alternatively, one dehydrator can be operated while the others remain on standby. When a dehydrator requires drying, maintenance, or other operations, it can be shut down, and other dehydrators can be switched on, ensuring an uninterrupted reaction process and further improving dehydration efficiency.

[0054] In this invention, such as Figure 1As shown, to facilitate the storage and transportation of glycerol and the finished product, a glycerol storage tank 7 and a finished product storage tank 8 are preferably included. The glycerol storage tank 7 is connected to the feed inlet at the top of the first-stage reactor 1 via a conveying pipeline, and the discharge outlet at the bottom of the last-stage reactor is connected to the finished product storage tank 8 via a pipeline. In this invention, when the glycerol storage tank 7 is provided, it is preferable to first mix and heat the catalyst and glycerol in the glycerol storage tank.

[0055] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] The chlorination of glycerol was carried out using a three-stage series reactor, with each reactor connected to a dehydration device. Adipic acid was used as a catalyst in the chlorination reaction. The specific operation is as follows:

[0058] The catalyst was added to the glycerol storage tank at a catalyst-to-glycerol mass ratio of 1:25. Glycerol and catalyst were then pumped into the first-stage reactor, maintaining the reaction liquid volume at 40%. Hydrogen chloride gas, three times the molar amount of glycerol, was introduced into the first-stage reactor. The operating temperature of the first-stage reactor was 100℃, and the pressure was atmospheric pressure. The hot steam generated in the first-stage reactor during the reaction was transferred to a first-stage dehydration unit for dehydration treatment. The dehydrator was a condenser tower, with the top temperature controlled at 45℃. The dehydrated gas obtained after dehydration was returned to the first-stage reactor for further reaction, and the dehydrated liquid phase was separated by distillation for reuse. The gas phase valve of the dehydration pipeline was opened at 30% to maintain the water content in the reactor at (10±0.5)%.

[0059] The second-stage reactor receives the liquid material generated in the first-stage reactor. The operating temperature of the second-stage reactor is controlled at 115℃, and the pressure inside the reactor is regulated to 0.2 MPa using HCl. The hot steam generated in the second-stage reactor during the reaction is transferred to a second-stage dehydration unit for dehydration treatment. The dehydrator is a condenser tower, and the top temperature of the tower is controlled at 5℃. The resulting gaseous material after dehydration is transferred back to the second-stage reactor for further reaction, and the dehydrated liquid phase is separated by distillation for reuse. The opening degree of the gas phase valve entering the dehydration pipeline is controlled at 75%, reducing the water content inside the reactor to (4.5±0.3)%.

[0060] The third-stage reactor receives the liquid material generated in the second-stage reactor. The operating temperature of the third-stage reactor is controlled at 120℃, and the pressure inside the reactor is regulated to 0.3 MPa using HCl. During the reaction, the hot steam generated in the third-stage reactor first enters the condenser in the third-stage dehydration unit for gas-phase condensation pretreatment (condensation pretreatment temperature is -5℃). After gas-phase condensation pretreatment, dehydration is performed (the third-stage dehydration unit has two dehydrators connected in parallel; the upper part of the pipe of each dehydrator is filled with 3A molecular sieve, and the lower part is filled with color-changing silica gel, with a volume ratio of 3A molecular sieve to color-changing silica gel of 3:1. After the color-changing silica gel at the bottom of the dehydrator changes color, it is switched to the other dehydrator. After the dehydrator absorbs water, it is disassembled, purged with nitrogen, dried, and reused). The dehydrated material obtained after dehydration is transferred back to the third-stage reactor for further reaction. The opening degree of the gas phase valve entering the dehydration pipeline is controlled at 90%, and the molecular sieve gas-phase pretreatment temperature is -5℃, reducing the water content in the reactor to (0.5±0.1)%. The glycerol feed rate was adjusted to maintain the reaction liquid volume in the reactor at 40%. The reaction liquid in each reactor was allowed to remain for 2 hours to allow for a complete chlorination reaction. The chlorination reaction in the three-stage series reactors took a total of 6 hours. After the reaction was completed, the solution was pumped into the finished product storage tank.

[0061] Example 2

[0062] The chlorination of glycerol was carried out using a three-stage series reactor, with each reactor connected to a dehydration device. Azelaic acid was used as a catalyst in the chlorination reaction. The specific operation is as follows:

[0063] The catalyst was added to the glycerol storage tank at a catalyst-to-glycerol mass ratio of 1:25. The glycerol (98% purity) in the storage tank was heated to 100°C. The preheated glycerol and catalyst were then pumped into the first-stage reactor, maintaining the reaction liquid volume in the reactor at 40%. Hydrogen chloride gas, three times the molar amount of glycerol, was introduced into the first-stage reactor. The operating temperature of the first-stage reactor was 110°C, and the pressure was atmospheric pressure. The hot steam generated in the first-stage reactor during the reaction was transferred to the first-stage dehydration unit for dehydration treatment. The dehydrator was a condenser tower, and the top temperature of the tower was controlled at 40°C. The dehydrated gas obtained after dehydration was returned to the first-stage reactor for further reaction, and the dehydrated liquid phase was separated by distillation for reuse. The opening degree of the gas phase valve entering the dehydration pipeline was controlled at 70%, maintaining the water content in the reactor at (5.5±0.3)%.

[0064] The second-stage reactor receives the liquid material generated in the first-stage reactor. The operating temperature of the second-stage reactor is controlled at 120℃, and the pressure inside the reactor is regulated to 0.2 MPa using HCl. The hot steam generated in the second-stage reactor during the reaction is transferred to a second-stage dehydration unit for dehydration treatment. The dehydrator is a condenser tower, and the top temperature of the tower is controlled at 5℃. The resulting gaseous material after dehydration is transferred back to the second-stage reactor for further reaction. The dehydrated liquid phase is then separated by distillation for reuse. The opening degree of the gas phase valve entering the dehydration pipeline is controlled at 85%, reducing the water content inside the reactor to (3±0.2)%.

[0065] The third-stage reactor receives the liquid material generated in the second-stage reactor. The operating temperature of the third-stage reactor is controlled at 120℃, and the pressure inside the reactor is regulated to 0.3 MPa using HCl. During the reaction, the hot steam generated in the third-stage reactor first enters the condenser in the third-stage dehydration unit for gas-phase condensation pretreatment (condensation pretreatment temperature is -5℃). After gas-phase condensation pretreatment, dehydration is performed (the third-stage dehydration unit is a concentrated sulfuric acid absorption tower, using 92% concentrated sulfuric acid as the absorbent, and the temperature inside the tower is controlled at 30℃). The opening of the gas phase valve entering the dehydration pipeline is controlled to 95%, reducing the water content in the reactor to (1±0.1)%. After dehydration, the water is transferred to the third-stage reactor for further reaction. The glycerol feed rate is adjusted to maintain the reaction liquid volume in the reactor at 40%. The reaction liquid in each reactor remains for 2 hours for complete chlorination. The total chlorination reaction in the three-stage series reactors requires 6 hours. After the reaction is completed, the liquid is pumped into the finished product storage tank.

[0066] Example 3

[0067] Glycerol chlorination was carried out using a two-stage series reactor, with each reactor connected to a dehydration device. Sebacic acid was used as a catalyst in the chlorination reaction. The specific operation is as follows:

[0068] The catalyst was added to the glycerol storage tank at a catalyst-to-glycerol mass ratio of 1:25. The glycerol (98% purity) in the storage tank was heated to 120°C. The preheated glycerol and catalyst were then pumped into the first-stage reactor, maintaining the reaction liquid volume in the reactor at 40%. Hydrogen chloride gas, three times the molar amount of glycerol, was introduced into the first-stage reactor. The operating temperature of the first-stage reactor was 120°C, and the pressure was 0.05 MPa. The hot steam generated in the first-stage reactor during the reaction was transferred to the first-stage dehydration unit for dehydration treatment. The dehydrator was a condenser tower, and the top temperature of the tower was controlled at 50°C. The dehydrated gas obtained after dehydration was returned to the first-stage reactor for further reaction, and the dehydrated liquid phase was separated by distillation for reuse. The opening degree of the gas phase valve entering the dehydration pipeline was controlled at 10%, maintaining the water content in the reactor at (14.5±0.5)%.

[0069] The second-stage reactor receives the liquid material generated in the first-stage reactor. The operating temperature of the second-stage reactor is controlled at 140℃, and the pressure inside the reactor is regulated to 0.5 MPa using HCl. During the reaction, the hot steam generated in the second-stage reactor first enters the condenser in the second-stage dehydration unit for gas-phase condensation pretreatment (the condensation pretreatment temperature is room temperature). After gas-phase condensation pretreatment, dehydration is performed (the second-stage dehydration unit is a pervaporation membrane separator; the pervaporation temperature is 70℃, the permeation membrane is a molecular sieve permeation membrane with a pore size of 0.41 nm, the feed pressure is 0.3 MPa, and the discharge pressure is 3 kPa). The opening of the gas phase valve entering the dehydration pipeline is controlled to 90%, reducing the water content in the reactor to (1.7 ± 0.2)%. After dehydration, the water is transferred back to the second-stage reactor for further reaction. The glycerol feed rate is adjusted to maintain the reaction liquid volume in the reactor at 40%. The reaction liquid in each reactor is left to stand for 2 hours to allow for a full chlorination reaction. The chlorination reaction in the two-stage series reactors takes a total of 4 hours. After the reaction is completed, the solution is pumped into the finished product storage tank.

[0070] Example 4

[0071] Glycerol chlorination was carried out using a three-stage series reactor, with each reactor connected to a dehydration device. Octanoic acid was used as a catalyst in the chlorination reaction. The specific operation is as follows:

[0072] The catalyst was added to the glycerol storage tank at a catalyst-to-glycerol mass ratio of 1:25. The glycerol (98% purity) in the storage tank was heated to 80°C. The preheated glycerol and catalyst were then pumped into the first-stage reactor, maintaining the reaction liquid volume in the reactor at 40%. Hydrogen chloride gas, three times the molar amount of glycerol, was introduced into the first-stage reactor. The operating temperature of the first-stage reactor was 100°C, and the pressure was atmospheric pressure. The hot steam generated in the first-stage reactor during the reaction was transferred to the first-stage dehydration unit for dehydration treatment. The dehydrator was a condenser tower, and the top temperature of the tower was controlled at 45°C. The dehydrated gas obtained after dehydration was returned to the first-stage reactor for further reaction, and the dehydrated liquid phase was separated by distillation for reuse. The opening degree of the gas phase valve entering the dehydration pipeline was controlled at 40%, maintaining the water content in the reactor at (8±0.5)%.

[0073] The second-stage reactor receives the liquid material generated in the first-stage reactor. The operating temperature of the second-stage reactor is controlled at 115℃, and the pressure inside the reactor is regulated to 0.2 MPa using HCl. The hot steam generated in the second-stage reactor during the reaction is transferred to a second-stage dehydration unit for dehydration treatment. The dehydrator is a condenser tower, and the top temperature of the tower is controlled at 5℃. The resulting gaseous material after dehydration is transferred back to the second-stage reactor for further reaction. The dehydrated liquid phase is then separated by distillation for reuse. The opening degree of the gas phase valve entering the dehydration pipeline is controlled at 80%, reducing the water content inside the reactor to (4±0.3)%.

[0074] The third-stage reactor receives the liquid material generated in the second-stage reactor. The operating temperature of the third-stage reactor is controlled at 120℃, and the pressure inside the reactor is regulated to 0.3 MPa using HCl. During the reaction, the hot steam generated in the third-stage reactor first enters the condenser in the third-stage dehydration unit for gas-phase condensation pretreatment (condensation pretreatment temperature -5℃). After gas-phase condensation pretreatment, dehydration treatment is performed (the third-stage dehydration unit has two parallel dehydrators; the upper part of the pipe of each dehydrator is filled with 3A molecular sieve, and the lower part is filled with color-changing silica gel, with a volume ratio of 3A molecular sieve to color-changing silica gel of 3:1. After the color-changing silica gel at the bottom of the dehydrator changes color, it is switched to the other dehydrator. After the dehydrator absorbs water, it is disassembled, purged with nitrogen, dried, and reused). The dehydrated material obtained after dehydration is transferred back to the third-stage reactor for further reaction. The opening degree of the gas phase valve entering the dehydration pipeline is controlled at 95%, reducing the water content in the reactor to (1±0.1)%. The glycerol feed rate was adjusted to maintain the reaction liquid volume in the reactor at 40%. The reaction liquid in each reactor was allowed to remain for 4 hours to allow for a complete chlorination reaction. The chlorination reaction in the three-stage series reactors took a total of 12 hours. After the reaction was completed, the solution was pumped into the finished product storage tank.

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 1 is that the gas flow rate to the three dehydrators is controlled to be 0, that is, no dehydration is performed at all, and the generated hot steam is directly returned to the reactor.

[0077] Comparative Example 2

[0078] The difference between this comparative example and Example 1 is that the reaction temperature of all three reactors is set to 120°C, and the opening degree of the gas valves leading to the three dehydration devices is controlled to 100%, that is, to maximize the dehydration operation.

[0079] Comparative Example 3

[0080] The difference between this comparative example and Example 1 is that the opening degree of the air valves leading to the three dehydration devices is controlled to 100%, that is, to maximize the dehydration operation.

[0081] A continuous chlorination reaction was carried out, and samples were taken after 72 hours of reaction for testing and analysis. The test results were used to evaluate the performance of each chlorination reaction scheme. The specific evaluation indicators and results are shown in Table 1.

[0082] Table 1

[0083]

[0084] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing dichloropropanol by chlorination of glycerol, characterized in that, The reaction was carried out using a multi-stage series reactor. Hydrogen chloride gas was introduced into each stage of the reactor, and glycerol and catalyst were introduced into the first stage reactor to react. Liquid and gas phases were obtained in each stage of the reactor, respectively. The liquid phase obtained from the upper reactor is transferred to the lower reactor for reaction. The gas phase obtained from each reactor is dehydrated, and the dehydrated product is transferred back to the original reactor for reaction. Among them: the moisture content of the material in the first-stage reactor is controlled at 5~15 wt%; The moisture content of the material in the intermediate stage reactor is controlled at 2-5 wt%. The moisture content of the material in the final stage reactor is controlled at ≤2wt%, and the moisture content of the material in the next stage reactor is lower than that of the material in the previous stage reactor. The pressure in each reactor is controlled at 0~0.5 MPa; the temperature in each reactor is controlled at 90~140℃, and the temperature of the upper reactor does not exceed the reaction temperature of the lower reactor; the reaction time in each reactor is 1.5~4 h, and the total residence time of the reaction in the multi-stage reactor is 4~12 h.

2. The preparation method according to claim 1, characterized in that, Before introducing glycerol into the reactor, preheat the glycerol to 80-120°C.

3. The preparation method according to claim 1, characterized in that, The catalyst is adipic acid, azelaic acid, sebacic acid, or octanoic acid.

4. The preparation method according to claim 1, characterized in that, The multi-stage series reactor consists of 2 to 6 reactors connected in series.

5. The preparation method according to claim 4, characterized in that, The gas phase obtained from the last stage reactor is dehydrated by concentrated sulfuric acid dehydration, molecular sieve adsorption dehydration, or pervaporation membrane separation dehydration; the gas phase obtained from other reactors is dehydrated by condensation dehydration.

6. The preparation method according to claim 5, characterized in that, When the multi-stage series reactor consists of two reactors connected in series, the temperature of the first-stage condensation and dehydration is 40~60℃, and the second-stage dehydration is carried out by concentrated sulfuric acid dehydration, molecular sieve adsorption dehydration, or pervaporation membrane separation dehydration. When the multi-stage series reactor consists of 3~6 reactors connected in series, the temperature of the first-stage condensation and dehydration is 40~60℃, and the temperature of the last-stage condensation and dehydration is -5~5℃.

7. The preparation method according to claim 5, characterized in that, The final stage of dehydration always includes a gas-phase condensation pretreatment process. When concentrated sulfuric acid or molecular sieve adsorption is used for dehydration, the temperature of the gas-phase condensation pretreatment is -5°C. When pervaporation membrane separation is used for dehydration, the temperature of the gas-phase condensation pretreatment is room temperature.

8. The preparation method according to claim 1, characterized in that, The liquid outlet at the bottom of the upper stage reactor in the multi-stage series reactor is connected to the liquid inlet at the top of the lower stage reactor via a conveying pipeline; the gas inlet at the bottom of each reactor is connected to a hydrogen chloride gas conveying pipeline. The gas outlet at the side of each stage reactor is connected to the inlet of a dehydration device via a pipeline, and a gas phase valve is installed on the pipeline connecting the gas outlet and the inlet of the dehydration device; the gas outlet of the dehydration device is connected to the inlet at the side of the reactor via a pipeline.

9. The preparation method according to claim 8, characterized in that, It also includes a glycerol storage tank and a finished product storage tank. The glycerol storage tank is connected to the feed inlet at the top of the first-stage reactor via a conveying pipeline, and the discharge outlet at the bottom of the last-stage reactor is connected to the finished product storage tank via a pipeline.

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