CN109721571B

CN109721571B - Epichlorohydrin production method and epichlorohydrin production system

Info

Publication number: CN109721571B
Application number: CN201711034533.1A
Authority: CN
Inventors: 刘中清; 周丽娜; 罗一斌; 舒兴田
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2017-10-30
Filing date: 2017-10-30
Publication date: 2022-07-15
Anticipated expiration: 2037-10-30
Also published as: CN109721571A

Abstract

The invention discloses a production method and a production system of epichlorohydrin, wherein the production method comprises the following steps: carrying out chlorohydrination reaction on chloropropene to obtain a chlorohydrination reaction mixture containing dichloropropanol; separating dichloropropanol from the chlorohydrination reaction mixture; and (3) delivering the dichloropropanol into an alkali chamber of a bipolar membrane electrodialyzer for bipolar membrane electrodialysis to obtain an alkali chamber effluent containing the epichlorohydrin. According to the production method, no or almost no wastewater and waste residue are generated in the epoxidation reaction process, so that the amount of the waste generated in the whole process flow is greatly reduced, and the treatment burden of the wastewater and the waste residue is reduced; in the production method, the epoxidation step does not adopt a catalyst, so that the production cost is reduced; the method has low separation cost and simple operation method.

Description

Epichlorohydrin production method and epichlorohydrin production system

Technical Field

The invention relates to a production method of epichlorohydrin, and the invention further relates to an epichlorohydrin production system.

Background

Epichlorohydrin is an important basic organic chemical raw material and intermediate, and is widely applied to synthesis of epoxy resin, glycerol, epichlorohydrin rubber, medicines, pesticides, surfactants, plasticizers and other products.

At present, the process commonly adopted in China industry is a propylene high-temperature chlorination method, which comprises the steps of preparing chloropropene by propylene high-temperature chlorination, performing hypochlorination on the chloropropene to generate dichloropropanol, performing saponification on the dichloropropanol to prepare epoxy chloropropane, and performing rectification and other procedures to obtain the product epoxy chloropropane. The method has the advantages of flexible production process, mature process and stable operation, and has the defects of serious equipment corrosion caused by the raw material chlorine, high requirements on propylene purity and reactor materials, high energy consumption, high chlorine consumption, a plurality of byproducts and low product yield. Meanwhile, the amount of sewage containing calcium chloride and organic chloride generated in the saponification process is large, the sewage seriously harms the environment, and the investment for treating the waste water usually accounts for 15-20% of the total investment.

In addition, the epichlorohydrin can also be synthesized by adopting a vinyl acetate method, including the synthesis of vinyl acetate by propylene, the preparation of allyl alcohol by the hydrolysis of the vinyl acetate, the preparation of dichloropropanol by the addition of the allyl alcohol, and the saponification of the dichloropropanol to generate the epichlorohydrin. The method has the advantages of mild reaction conditions, easy control, no coking and stable operation, reduces the consumption of propylene, calcium hydroxide and chlorine, the discharge amount of reaction byproducts and calcium chloride-containing wastewater, and can easily obtain high-purity allyl alcohol which cannot be obtained by the prior art. However, this method has disadvantages of a long process flow, a short catalyst life, the need for a stainless steel material for preventing acetic acid corrosion, the need for preventing explosion of the allyl alcohol unit mixture, and a relatively high investment cost.

With the shortage of global petroleum resources, especially the stricter and stricter environmental requirements, the inherent defects of the current industrial production method become more and more obvious, and the development of new processes is promoted.

CN101157670A discloses a method for synthesizing epichlorohydrin, which comprises the following steps:

1) using byproduct glycerol in the production process of biodiesel as a raw material, and reacting the raw material with a chlorinating agent in the presence of a catalyst to generate 1, 3-dichloropropanol when the solvent is present or absent, wherein the molar ratio of the catalyst to the glycerol is (0.1-0.5): 1, the mol ratio of chlorine to glycerin which can participate in the reaction in the chlorinating agent is 2-6: 1; neutralizing with alkali after the reaction is finished, filtering to obtain 1, 3-dichloropropanol, and directly using in cyclization reaction without purification;

2) dehydrochlorination of 1, 3-dichloropropanol to epichlorohydrin in water under base catalysis, the molar ratio of 1, 3-dichloropropanol to water or organic solvent being 1: the molar ratio of 8-15, 1, 3-dichloropropanol to the base catalyst is 1: 1-1.5; and (3) evaporating the product by using water vapor at any time in the reaction process, standing for layering, and rectifying an organic layer to obtain the high-purity epichlorohydrin.

However, this process requires the product to be distilled off with steam at any time during the reaction in the epoxidation step, which increases the complexity of the operation on the one hand and the operating cost on the other hand.

CN101172970A discloses a method for preparing epichlorohydrin by direct epoxidation of chloropropene, which takes a mixture of chloropropene, hydrogen peroxide and a solvent as a raw material, wherein the solvent is acetonitrile, methanol, acetone or tertiary butanol, and the molar ratio of chloropropene to hydrogen peroxide is 1-7: 1, the weight ratio of the solvent to the chloropropene is 1-6: 1, wherein the temperature is 35-85 ℃ and the space velocity of chloropropene is 0.1-6 hours^-1Under the condition, the raw material is subjected to chloropropene oxidation catalytic reaction in a fixed bed reactor with heat insulation and catalyst existence to prepare epichlorohydrin, the catalyst is a molding mixture consisting of a titanium-silicon molecular sieve and inert silica, the titanium-silicon molecular sieve is a titanium-containing molecular sieve with a topological structure of MFI or MWW, and the weight ratio of the titanium-silicon molecular sieve to the inert silica is 7: 3.

however, due to the catalyst and H used in the process₂O₂High cost, solvent used in the reaction process and increased energy consumption for separation.

In conclusion, it is necessary to develop a green epoxy chloropropane production technology suitable for sustainable development.

Disclosure of Invention

The invention aims to overcome the defects of the existing epichlorohydrin production process and provide an epichlorohydrin production technology which is green and environment-friendly and is suitable for sustainable development.

According to a first aspect of the present invention, there is provided a process for producing epichlorohydrin, which comprises:

(1) carrying out chlorohydrination reaction on chloropropene to obtain a chlorohydrination reaction mixture containing dichloropropanol;

(2) separating the dichloropropanol from the chlorohydrination reaction mixture;

(3) and (3) delivering the dichloropropanol into an alkali chamber of a bipolar membrane electrodialyzer for bipolar membrane electrodialysis to obtain an alkali chamber effluent containing epichlorohydrin.

According to a second aspect of the present invention, the present invention provides an epichlorohydrin production system, which includes a chlorohydrination reaction unit, a chlorohydrination reaction mixture separation unit and an epoxidation reaction unit, wherein a dichloropropanol output port of the chlorohydrination reaction unit is communicated with a to-be-separated material input port of the chlorohydrination reaction mixture separation unit, and a dichloropropanol output port of the chlorohydrination reaction mixture separation unit is communicated with a dichloropropanol input port of the epoxidation reaction unit;

the chlorohydrination reaction unit is used for carrying out chlorohydrination reaction on chloropropene to obtain a chlorohydrination reaction mixture containing dichloropropanol, the chlorohydrination reaction mixture separation unit is used for separating the dichloropropanol from the chlorohydrination reaction mixture,

The epoxidation reaction unit comprises a bipolar membrane electrodialyzer and is used for carrying out bipolar membrane electrodialysis on the dichloropropanol in an alkali chamber of the bipolar membrane electrodialyzer to obtain an alkali chamber effluent liquid containing the epichlorohydrin.

According to the epichlorohydrin production method of the invention, dichloropropanol is epoxidized in the alkali chamber of the bipolar membrane electrodialyzer to prepare epichlorohydrin, and compared with the existing epichlorohydrin production method, the method of the invention has the following advantages:

(1) compared with the traditional propylene high-temperature chlorination method and the acetate propylene ester method, the epoxidation reaction step of the production method does not generate or basically does not generate waste water and waste residue;

(2) compared with a chloropropene direct epoxidation method, the epoxidation reaction step of the production method does not adopt a catalyst, so that the production cost is reduced; in addition, according to the epoxidation reaction step of the method, water is used as a solvent instead of an organic solvent, and the reaction liquid containing epoxy chloropropane can be separated into an organic phase rich in epoxy chloropropane and a water phase poor in epoxy chloropropane by settling separation methods such as standing, centrifuging and the like, so that the separation cost is reduced;

(3) according to the method, in the epoxidation reaction process, the product is not required to be distilled by methods such as steam distillation and the like, and the operation method is simple.

Drawings

Fig. 1 is a view for explaining one embodiment of a membrane unit of a bipolar membrane electrodialyzer used in the epoxidation step in the process for producing epichlorohydrin according to the present invention.

Fig. 2 is a diagram for illustrating a preferred embodiment of the membrane unit of a bipolar membrane electrodialyzer used in the epoxidation step of the process for the production of epichlorohydrin according to the invention.

Fig. 3 is a diagram illustrating one embodiment of an epichlorohydrin production system according to this invention.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

(2) Separating dichloropropanol from the chlorohydrination reaction mixture;

According to the production process of the present invention, step (1) is used to provide dichloropropanol, and chloropropenes may be chlorohydrinated using conventional methods. In one embodiment, the chloropropene is contacted with hypochlorous acid, thereby converting the chloropropene to dichloropropanol. The hypochlorous acid is preferably generated in situ during the contacting. In particular, chloropropenes may be contacted with water and chlorine under chlorohydrination reaction conditions to give a chlorohydrination reaction mixture containing dichloropropanol. The chlorohydrination reaction conditions of the present invention are not particularly limited, and may be carried out under conditions known to those skilled in the art. Preferably, the chloropropenes are in excess of the stoichiometric ratio with respect to chlorine to ensure complete conversion of chlorine, and unreacted chloropropenes can be recycled, for example: the mole ratio of chloropropene to chlorine may be 1: 0.8 to 0.98, preferably 1: 0.9-0.95. Water is used as a raw material for converting chlorine gas into hypochlorous acid and as a reaction medium, and the amount of the water is based on the function of the chlorine gas. The chloropropene may be contacted with water and chlorine at a temperature of from 50 to 90 deg.c, preferably from 60 to 80 deg.c. The contacting of the chloropropene with water and chlorine can be carried out at atmospheric pressure (i.e., 1 atm).

The chlorohydrination reaction mixture may be separated by conventional means to give dichloropropanol. In one embodiment, the dichloropropanol may be separated from the chlorohydrination reaction mixture by a process comprising the steps of:

(A) carrying out gas-liquid separation on the chlorohydrination reaction mixture to obtain a gas-phase material flow and a liquid-phase material flow;

(B) and contacting the liquid phase material flow with an extracting agent for extraction and separation to obtain the dichloropropanol.

The chlorohydrination reaction mixture can contain unreacted chloropropene and/or chlorine besides dichloropropanol, and the chlorohydrination reaction mixture is subjected to gas-liquid separation, so that the content of gas substances in a liquid phase can be reduced, and the safety of subsequent reaction is improved; on the other hand, unreacted chloropropene and/or chlorine can be recycled for chlorohydrination reaction, so that the raw material utilization rate of the method is further improved.

The chlorohydrination reaction mixture may be subjected to a flash distillation to separate the chlorohydrination reaction mixture into a vapor stream and a liquid stream.

The liquid phase material flow is contacted with an extracting agent to carry out extraction separation, thereby separating the dichloropropanol. The extractant may be a substance that is commonly extracted from dichloropropanol. Preferably, the extractant is chloropropene. The chloropropene is used as an extracting agent, so that the dichloropropanol can be separated from the liquid phase material flow with high extraction efficiency, and no additional impurity is introduced.

The dichloropropanol is enriched in the extract liquid by extraction separation, and the dichloropropanol can be separated from the extract liquid by a conventional method and the recovered extractant can be obtained at the same time. The recovered extractant can be recycled as the extractant. Specifically, the extract may be subjected to distillation to obtain recovered chloropropene and dichloropropanol, and at least part of the recovered chloropropene may be recycled as the extractant.

And raffinate phase obtained by extraction and separation can be output. When chloropropene is contacted with chlorine and water for chlorohydrination reaction, the raffinate phase contains hydrochloric acid aqueous solution which can be directly output and sent to downstream procedures for producing hydrochloric acid.

According to the production method of the present invention, in step (3), dichloropropanol is fed into the alkali chamber of the bipolar membrane electrodialyzer and reacts with hydroxyl ions (OH) produced by the bipolar membrane electrodialysis^-) And carrying out in-situ instant reaction to obtain the epoxy chloropropane.

The arrangement form of the membrane unit in the bipolar membrane electrodialyzer takes the realization of the above functions as the standard.

In one embodiment, the bipolar membrane electrodialyzer is a two-compartment bipolar membrane electrodialyzer, i.e. the membrane units of the bipolar membrane electrodialyzer comprise an acid compartment and an alkali compartment. As a preferred example of the two-compartment bipolar membrane electrodialyzer, as shown in fig. 1, the bipolar membrane electrodialyzer comprises an anode, a cathode and at least one membrane unit disposed between the anode and the cathode, the membrane unit comprising bipolar membranes and anion exchange membranes arranged at intervals, the space between an anion exchange layer of an anion exchange membrane and an anion exchange layer of an adjacent bipolar membrane being an alkali compartment, and the space between an anion exchange membrane and a cation exchange layer of an adjacent other bipolar membrane being an acid compartment.

According to this embodiment, in carrying out bipolar membrane electrodialysis, water enters the acid compartment and an aqueous solution containing dichloropropanol enters the base compartment, and the bipolar membrane dissociates the water into hydrogen ions (H) under the action of the direct current electric field⁺) And hydroxide ion (OH)^-)，OH^-The effluent enters an alkali chamber through an anion exchange layer of a bipolar membrane and is in contact reaction with dichloropropanol to form epichlorohydrin, so that the effluent of the alkali chamber containing the epichlorohydrin is obtained from the alkali chamber; h⁺Cl entering the acid compartment through the cation exchange layer of the bipolar membrane and entering the acid compartment through the anion exchange membrane^-Combining to form HCl, thereby obtaining an acid chamber effluent containing hydrochloric acid from the acid chamber.

Although the bipolar membrane electrodialyzer shown in fig. 1 has only one pair of acid compartments and base compartments, it is well known to those skilled in the art that the number of the acid compartments and the base compartments is not limited to one pair, and the bipolar membrane electrodialyzer may have a plurality of acid compartments and base compartments in pairs, as long as the number of bipolar membranes and anion exchange membranes is increased accordingly. Specifically, in this embodiment, the bipolar membrane electrodialyzer may have 1 to 1000 pairs of acid and base compartments, preferably 5 to 500 pairs of acid and base compartments, more preferably 8 to 300 pairs of acid and base compartments, and still more preferably 10 to 100 pairs of acid and base compartments.

In a more preferred embodiment, the bipolar membrane electrodialyzer is a three-compartment bipolar membrane electrodialyzer, i.e. the membrane units of the bipolar membrane electrodialyzer comprise an acid compartment, a base compartment and a salt compartment. When the bipolar membrane electrodialyzer is a three-chamber bipolar membrane electrodialyzer, the output port of the salt chamber is communicated with the input port of the alkali chamber, so that the effluent of the salt chamber is used as the feed of the alkali chamber. According to this preferred embodiment, the salt chamber is preferably arranged between the acid chamber and the base chamber, and the effluent of the salt chamber enters the base chamber, the dichloropropanol reacts in the base chamber to form epichlorohydrin, and the concentration of epichlorohydrin in the salt chamber is low, so that the concentration of epichlorohydrin in the acid chamber can be further reduced, and the product yield can be further improved.

The bipolar membrane, the cation-exchange membrane and the anion-exchange membrane may be arranged in combination to obtain a bipolar membrane electrodialyzer having three chambers. In a preferred example, as shown in fig. 2, the bipolar membrane electrodialyzer comprises an anode, a cathode, and at least one membrane unit disposed between the anode and the cathode, the membrane unit comprising a first bipolar membrane, a second bipolar membrane, an anion exchange membrane and a cation exchange membrane, the anion exchange membrane and the cation exchange membrane being adjacently arranged and disposed between the first bipolar membrane and the second bipolar membrane, the first bipolar membrane and the second bipolar membrane being partitioned, a space between the cation exchange membrane and an anion exchange layer of the adjacent first bipolar membrane being an alkali compartment, a space between the anion exchange membrane and a cation exchange layer of the adjacent second bipolar membrane being an acid compartment, a space between the adjacently arranged anion exchange membrane and a cation exchange membrane being a salt compartment, an output port of the salt compartment being in communication with an input port of the alkali compartment.

According to this preferred embodiment, in the bipolar membrane electrodialysis, the aqueous solution containing dichloropropanol passes from the salt compartment into the alkaline compartment and the water passes into the acid compartment, the bipolar membrane dissociating the water into hydrogen ions (H) under the action of the DC electric field⁺) And hydroxide ion (OH)^-)，OH^-The effluent enters an alkali chamber through an anion exchange layer of a bipolar membrane and is in contact reaction with dichloropropanol to form epichlorohydrin, so that the effluent of the alkali chamber containing epichlorohydrin is obtained from the alkali chamber; h⁺Cl which passes through the cation exchange layer of the bipolar membrane into the acid compartment and through the anion exchange membrane on the salt compartment side and finally into the acid compartment^-Combining to form HCl, thereby obtaining an acid compartment effluent from the acid compartment containing hydrochloric acid.

Although the bipolar membrane electrodialyzer shown in fig. 2 has only one set of acid compartments, salt compartments and base compartments, it is well known to those skilled in the art that the number of the acid compartments, the salt compartments and the base compartments is not limited to one set, and the bipolar membrane electrodialyzer may have a plurality of acid compartments, salt compartments and base compartments in sets as long as the number of bipolar membranes, cation exchange membranes and anion exchange membranes is increased accordingly. Specifically, in this embodiment, the bipolar membrane electrodialyzer may have 1 to 1000 groups of acid compartments, salt compartments and base compartments, preferably 5 to 500 groups of acid compartments, salt compartments and base compartments, more preferably 8 to 300 groups of acid compartments, salt compartments and base compartments, and further preferably 10 to 100 groups of acid compartments, salt compartments and base compartments.

According to the production process of the present invention, the electrode liquid used in the cell of the bipolar membrane electrodialyzer is an aqueous solution containing an electrolyte. The electrolyte may be an inorganic electrolyte and/or an organic electrolyte, and specific examples thereof may include, but are not limited to, one or more of ammonium sulfate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate, sodium dihydrogen phosphate, potassium nitrate, potassium phosphate, potassium hydrogen phosphate, potassium dihydrogen phosphate, sodium hydroxide, potassium hydroxide, formic acid, acetic acid, sodium formate, potassium formate, and quaternary ammonium type electrolytes. Preferably, the electrolyte is an inorganic electrolyte. More preferably, the electrolyte is sodium sulfate and/or ammonium sulfate.

Generally, the electrolyte content in the polar liquid may be 1 to 15% by weight, preferably 3 to 10% by weight.

According to the production process of the present invention, the kinds and contents of electrolytes in the polar liquids fed to the cathode chamber and the anode chamber of the bipolar membrane electrodialyzer may be the same or different. From the viewpoint of ease of operation, the types and contents of electrolytes in the polar liquids introduced into the cathode chamber and the anode chamber of the bipolar membrane electrodialyzer are the same.

According to the production method of the present invention, in the bipolar membrane electrodialysis, the voltage applied to each membrane unit may be 0.5 to 2.5V, preferably 0.6 to 2.3V, more preferably 0.8 to 2.2V, and further preferably 1 to 2.1V. The bipolar membrane electrodialysis may be carried out at a temperature of 5-45 ℃, preferably at a temperature of 10-42 ℃, more preferably at a temperature of 25-40 ℃.

In the step (3), the amount of dichloropropanol used is not particularly limited, and may be selected according to the throughput of the bipolar membrane electrodialyzer. In general, the dichloropropanol content may range from 1 to 80 wt.%, preferably from 3 to 60 wt.%, more preferably from 5 to 50 wt.%, even more preferably from 7 to 40 wt.%, even more preferably from 8 to 30 wt.% and particularly preferably from 10 to 20 wt.%, based on the total amount of feed to the caustic chamber.

According to the production process of the present invention, step (3), preferably comprises carrying out an adjustment operation in the bipolar membrane electrodialysis process, said adjustment operation bringing the pH of the alkaline compartment effluent to a value of 5.5-10, which enables a significant improvement in the selectivity for epichlorohydrin and/or in the conversion of dichloropropanol. For example: the adjustment operation is performed such that the pH of the alkaline chamber effluent is 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, or 10. The pH of the effluent from the caustic chamber is measured by an operation that causes the effluent to flow out of the caustic chamber without changing the pH of the effluent. In practice, the pH value measured at the outlet end of the base chamber can be used as the pH value of the effluent of the base chamber.

In one embodiment, the adjusting operation results in a pH of the caustic chamber effluent of 8 to 10. According to the embodiment, under the condition that higher selectivity of epoxy chloropropane can be obtained, higher conversion rate of dichloropropanol can be obtained.

In a further embodiment, the adjustment is performed such that the pH of the effluent from the caustic chamber is in the range of 6 to below 8, such as 6.5-7.9, preferably 7-7.8, more preferably 7.2-7.6. According to this more preferred embodiment, a higher selectivity to epichlorohydrin is obtained under conditions such that a higher conversion of dichlorohydrin is obtained.

The adjustment operation may be an operation capable of adjusting the pH of the effluent of the caustic chamber. Preferably, said adjustment operation comprises adjusting the amount of dichloropropanol entering the alkaline chamber. Increasing the amount of dichloropropanol when the pH of the effluent of the caustic chamber is above the range, thereby adjusting the pH of the effluent of the caustic chamber to be within the range; when the pH of the effluent from the caustic chamber is below the above range, the amount of dichloropropanol is reduced, thereby adjusting the pH of the effluent from the caustic chamber to be within the above range.

According to the production process of the present invention, in step (3), the bipolar membrane electrodialysis is preferably carried out in the presence of at least one additive selected from the group consisting of water-soluble alkali metal salts and water-soluble ammonium salts, which is effective in improving the operating efficiency of the bipolar membrane electrodialyzer. In the present invention, the terms "water-soluble alkali metal salt" and "water-soluble ammonium salt" mean that the alkali metal salt and the ammonium salt have a solubility of 1g or more in 100g of water at 25 ℃ and 1 atm.

The additive may be one or more of alkali metal chloride, alkali metal sulfate, alkali metal nitrate, alkali metal carboxylate, alkali metal phosphate, ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium carboxylate, ammonium phosphate, ammonium hydrogen phosphate and ammonium dihydrogen phosphate. Specific examples of the additives may include, but are not limited to: one or more of sodium chloride, potassium chloride, lithium chloride, sodium sulfate, potassium sulfate, sodium nitrate, potassium nitrate, lithium nitrate, sodium formate, sodium acetate, potassium acetate, sodium phosphate, potassium phosphate, sodium hydrogen phosphate, potassium hydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium phosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium acetate.

The additive is preferably selected from the group consisting of sodium chloride, potassium chloride and ammonium chloride from the viewpoint of further reducing the cost on the premise of improving the operation efficiency of the bipolar membrane electrodialyzer.

Generally, the additive is added to the base compartment feed (salt compartment feed, hereinafter abbreviated as "base compartment feed/salt compartment feed" when salt compartments are present) of a bipolar membrane electrodialyzer. Preferably, the additive is added to an aqueous solution containing dichloropropanol. Specifically, the additive can be mixed with an aqueous solution containing dichloropropanol, and then the mixture enters a bipolar membrane electrodialyzer, so that the bipolar membrane electrodialysis is carried out in the presence of the additive.

The amount of the additive in the feed to the base compartment/feed to the salt compartment may be selected according to the desired current density. Although small amounts of additives are introduced in the feed to the base/salt compartment of a bipolar membrane electrodialyser, for example: the content of the additive in the alkali compartment feed/salt compartment feed of 0.01 wt% can achieve an improvement in the operating efficiency of the bipolar membrane electrodialyzer, but the inventors of the present invention have found in the course of their studies that if the content of the additive in the alkali compartment feed/salt compartment feed is further increased, the selectivity for epichlorohydrin can be further improved.

Thus, according to the production process of the invention, the additive may be present in the alkali/salt compartment feed in an amount of from 0.01% by weight up to the weight percentage of the additive when saturated in water, such as from 0.02 to 35% by weight, preferably from 0.05 to 30% by weight. The weight percent of the additive when saturated in water is the weight percent of the additive when forming a saturated solution in water at a temperature of 25 ℃.

According to the production process of the present invention, in one embodiment, the content of the additive in the feed to the alkali compartment/feed to the salt compartment of the bipolar membrane electrodialyzer is from 0.01% by weight to less than 5% by weight, preferably from 0.02 to 4.5% by weight, more preferably from 0.05 to 4% by weight, still more preferably from 0.1 to 3.5% by weight. According to the embodiment, the operation efficiency of the bipolar membrane electrodialyzer can be obviously improved.

In a more preferred embodiment, the additive is contained in an amount of 5% by weight or more, such as 5.5 to 28% by weight, in the feed to the alkali compartment/feed to the salt compartment of the bipolar membrane electrodialyzer. Preferably, the additive is present in the alkali/salt compartment feed in an amount of 6 wt% or more, such as 8-25 wt%, more preferably 10-20 wt%. According to this more preferred embodiment, a higher selectivity to epichlorohydrin is obtained.

According to the production method of the present invention, in a particularly preferred embodiment, the bipolar membrane electrodialysis is carried out in the presence of the additive while the conditioning operation is carried out in the bipolar membrane electrodialyzer process. According to this particularly preferred embodiment, the content of said additive in the alkali/salt compartment feed is preferably above 5 wt.%, such as 5.5-28 wt.%, more preferably above 6 wt.%, such as 8-25 wt.%, even more preferably 10-20 wt.%.

According to the production method, water is used as a dispersion medium of the dichloropropanol, and the effluent of the alkali chamber is also the effluent of the water as the dispersion medium, so that the effluent of the alkali chamber can be separated into an organic phase rich in the epichlorohydrin and an aqueous phase rich in the unreacted dichloropropanol through settling separation. The settling separation may be a standing separation, a centrifugal separation, or a combination of a standing separation and a centrifugal separation, for example: the effluent from the base chamber may be first centrifuged and then allowed to stand to separate the effluent from the base chamber into an organic phase rich in epichlorohydrin and an aqueous phase rich in unreacted dichloropropanol.

According to the production method, after the bipolar membrane electrodialysis is finished, the effluent of the alkaline chamber is separated to obtain an organic phase rich in epoxy chloropropane.

According to the production process of the present invention, from the viewpoint of further improving the selectivity of epichlorohydrin, preferably during bipolar membrane electrodialysis, an organic phase rich in epichlorohydrin is separated from the effluent of the base compartment, and the remaining liquid phase from which the organic phase is separated, and optionally fresh dichloropropanol, are recycled into the base compartment of the bipolar membrane electrodialyzer. The alkaline chamber feed/salt chamber feed can be the residual liquid phase or a mixture of the residual liquid phase and fresh dichloropropanol. For example: in the case of bipolar membrane electrodialysis carried out in a batch mode, the alkaline compartment feed/salt compartment feed may be the residual liquid phase; when bipolar membrane electrodialysis is carried out in a continuous manner, the alkaline compartment feed/salt compartment feed may be a mixture of the retentate phase and fresh dichloropropanol. The intermittent mode is that a certain amount of aqueous solution containing dichloropropanol is added at the beginning of each bipolar membrane electrodialysis, and after the bipolar membrane electrodialysis is carried out for a preset time, all alkaline chamber effluent liquid is discharged. The continuous mode is that a certain amount of aqueous solution containing dichloropropanol is added at the beginning of the bipolar membrane electrodialysis, and in the bipolar membrane electrodialysis process, at least part of epichlorohydrin is discharged and fresh dichloropropanol is replenished.

According to the production process of the invention, the effluent of the alkaline chamber is subjected to a settling separation into an organic phase rich in epichlorohydrin and an aqueous phase, the aqueous phase being the upper liquid phase and the organic phase being the lower liquid phase. When bipolar membrane electrodialysis is carried out in the presence of the additive, the content of the additive in the aqueous solution containing dichloropropanol is more than 25 wt%, the effluent of the alkaline chamber is subjected to sedimentation separation to obtain two phases, wherein the upper liquid phase is an organic phase rich in epichlorohydrin, and the lower liquid phase is an aqueous phase.

The organic phase rich in epichlorohydrin, separated from the base chamber effluent, can be exported. According to the production method of the present invention, preferably, the method further comprises refining the organic phase rich in epichlorohydrin to obtain an epichlorohydrin product.

The purification method of the present invention is not particularly limited, and a commonly used purification method of a crude epichlorohydrin product may be used, for example: the organic phase rich in epichlorohydrin can be rectified, so as to obtain the epichlorohydrin product.

The organic phase rich in the epichlorohydrin also contains unreacted dichloropropanol, and preferably also comprises the recovery of the unreacted dichloropropanol in the refining process, wherein at least part of the recovered dichloropropanol is preferably recycled into an alkali chamber of the bipolar membrane electrodialyzer so as to further improve the utilization rate of the dichloropropanol and further reduce the amount of waste liquid generated by the method.

The organic phase rich in epichlorohydrin may also contain by-products such as glycerol, which are preferably recovered during the purification process according to the process of the invention. The recovered by-products can be exported.

According to a second aspect of the present invention, there is provided an epichlorohydrin production system including a chlorohydrination reaction unit, a chlorohydrination reaction mixture separation unit, and an epoxidation reaction unit.

According to the epoxy chloropropane production system, the dichloropropanol output port of the chlorohydrination reaction unit is communicated with the material to be separated input port of the chlorohydrination reaction mixture separation unit, and the dichloropropanol output port of the chlorohydrination reaction mixture separation unit is communicated with the dichloropropanol input port of the epoxidation reaction unit.

The chlorohydrination reaction unit is used for carrying out chlorohydrination reaction on chloropropene to obtain a chlorohydrination reaction mixture containing dichloropropanol. The chlorohydrination reaction unit can adopt a conventional reaction device to chlorohydrate chloropropene to obtain dichloropropanol.

The chlorohydrination reaction mixture separation unit is for separating dichloropropanol from the chlorohydrination reaction mixture. In a preferred embodiment, the chlorohydrination reaction mixture separation unit comprises a gas-liquid separation device, an extraction device, and a dichloropropanol recovery device.

The gas-liquid separation device receives a chlorohydrination reaction mixture output by the chlorohydrination reaction unit and separates the chlorohydrination reaction mixture into a gas-phase material flow and a liquid-phase material flow. The gas-liquid separation device may employ a device having a common gas-liquid separation function, for example: and (4) a flash tower.

The extraction device contacts the liquid phase stream with an extracting agent to separate dichloropropanol from the liquid phase stream. The extraction apparatus may be a conventional extraction column. The extractant may be fed from the upper part of the extraction column and the liquid stream from the middle or lower part of the extraction column so that the extractant and the liquid stream are brought into countercurrent contact to obtain an extract enriched in dichloropropanol.

The dichloropropanol recovery device is used for recovering dichloropropanol from the extract liquor. The dichloropropanol recovery device can adopt a device which is enough to recover the dichloropropanol from the extraction liquid, such as: and (4) a flash tower.

The gas phase material flow separated by the gas-liquid separation device can be circularly used in the chlorohydrination reaction unit, the chlorohydrination reaction mixture separation unit is preferably provided with a corresponding pipeline to communicate the gas phase material flow output port of the gas-liquid separation device with the raw material input port of the chlorohydrination reaction unit, so that the gas phase material flow separated by the gas-liquid separation device is circularly sent into the chlorohydrination reaction unit.

The membrane unit of the bipolar membrane electrodialyzer contains an alkali chamber and an acid chamber.

The membrane unit of the bipolar membrane electrodialyzer may contain only an alkali compartment and an acid compartment, i.e., the bipolar membrane electrodialyzer may be a two-compartment bipolar membrane electrodialyzer. In one embodiment, the two-compartment bipolar membrane electrodialyzer comprises an anode, a cathode and at least one membrane unit disposed between the anode and the cathode, as shown in fig. 1, the membrane unit comprising bipolar membranes and anion exchange membranes arranged alternately, the space between an anion exchange layer of an anion exchange membrane and an adjacent bipolar membrane being an alkali compartment, and the space between an anion exchange layer of an anion exchange membrane and a cation exchange layer of an adjacent other bipolar membrane being an acid compartment.

Preferably, the bipolar membrane electrodialyzer is a three-chamber bipolar membrane electrodialyzer, a membrane unit of the bipolar membrane electrodialyzer comprises an alkali chamber, a salt chamber and an acid chamber, an output port of the salt chamber is communicated with an input port of the alkali chamber, an aqueous solution containing dichloropropanol enters the alkali chamber from the salt chamber and is combined with hydroxide ions generated by bipolar membrane electrodialysis in the alkali chamber to react to form epichlorohydrin, and then an alkali chamber effluent containing epichlorohydrin is obtained from the alkali chamber; simultaneously, an acid chamber effluent containing HCl is obtained in the acid chamber.

In one embodiment, the three-compartment bipolar membrane electrodialyzer comprises an anode, a cathode and at least one membrane unit disposed between the anode and the cathode, as shown in fig. 2, the membrane unit comprising a first bipolar membrane, a second bipolar membrane, an anion exchange membrane and a cation exchange membrane, the anion exchange membrane and the cation exchange membrane being adjacently arranged and disposed between the first bipolar membrane and the second bipolar membrane, and separating the first bipolar membrane from the second bipolar membrane, the space between the cation exchange membrane and the anion exchange layer of the adjacent first bipolar membrane being an alkali compartment, the space between the anion exchange membrane and the cation exchange layer of the adjacent second bipolar membrane being an acid compartment, the space between the adjacently arranged anion exchange membrane and the cation exchange membrane being a salt compartment, an output port of the salt compartment being in communication with an input port of the alkali compartment.

The epoxidation reaction unit also comprises an alkali chamber effluent settling tank, wherein the alkali chamber effluent settling tank is communicated with an alkali chamber effluent output port of the bipolar membrane electrodialyzer and is used for receiving alkali chamber effluent of the bipolar membrane electrodialyzer and feeding at least part of the alkali chamber effluent and optional fresh dichloropropanol into the bipolar membrane electrodialyzer as alkali chamber feed.

In a preferred embodiment, the alkali chamber effluent settling tank comprises an alkali chamber effluent input port, a fresh dichloropropanol input port, an alkali chamber feed output port and an organic phase output port, the alkali chamber effluent input port is communicated with the alkali chamber effluent output port of the bipolar membrane electrodialyzer, the alkali chamber feed output port is communicated with the alkali chamber feed input port of the bipolar membrane electrodialyzer (the salt chamber feed input port when a salt chamber exists), a partition is arranged inside the alkali chamber effluent settling tank to divide the inner space of the alkali chamber effluent settling tank into a first liquid phase zone and a second liquid phase zone, the lower parts of the first liquid phase zone and the second liquid phase zone are adjoined by the partition, the upper parts of the first liquid phase zone and the second liquid phase zone are communicated, the alkali chamber effluent input port is arranged in the first liquid phase zone (preferably arranged in the upper part of the first liquid phase zone), the fresh dichloropropanol inlet is arranged in the second liquid phase zone (preferably in the upper part of the second liquid phase zone), the alkali chamber feed outlet is arranged in the lower part of the second liquid phase zone, and the organic phase outlet is arranged in the first liquid phase zone (preferably in the lower part and/or the upper part of the first liquid phase zone).

According to the preferred embodiment, when the system is operated, the effluent of the alkali chamber output by the alkali chamber of the bipolar membrane electrodialyzer enters the first liquid phase zone from the effluent input port of the alkali chamber, part of the stream entering the first liquid phase zone overflows from the top of the partition plate to enter the second liquid phase zone, and the effluent of the alkali chamber retained in the first liquid phase zone is subjected to sedimentation separation to obtain an organic phase rich in epichlorohydrin, and the organic phase rich in epichlorohydrin is output through the organic phase output port. According to this preferred embodiment, it is possible to separate the organic phase rich in epichlorohydrin from the alkaline compartment effluent during bipolar membrane electrodialysis, thus further increasing the epichlorohydrin selectivity.

According to this preferred embodiment, the height of the partition is such that it is possible to ensure that the quantity of material in the second liquid-phase zone meets the feed requirements of the bipolar membrane electrodialyser and that a sufficient quantity of the alkaline compartment effluent is retained for separation.

In this preferred embodiment, the organic phase output port is disposed in a lower portion and/or an upper portion of the first liquid phase region. In a preferred embodiment, organic phase output ports are provided in both the lower and upper portions of the first liquid phase zone, so that depending on the relative positions of the organic phase and the remaining liquid phase separated by settling of the alkaline chamber effluent, the selection of whether to open the upper organic phase output port or the lower organic phase output port will allow the organic phase to be output.

According to the production system, in the starting stage, an aqueous solution containing dichloropropanol can be filled in an effluent settling tank (comprising a first liquid phase region and a second liquid phase region, namely a second liquid phase region) of the alkali chamber to be used as the feeding of the alkali chamber/the feeding of the salt chamber; and filling water in an effluent storage tank of the acid chamber to serve as a feed of the acid chamber. Where the alkaline chamber effluent settling tank comprises the first liquid phase zone and the second liquid phase zone as described previously, an aqueous solution comprising dichloropropanol is filled into the second liquid phase zone. The aqueous solution comprising dichloropropanol preferably contains at least one additive as described hereinbefore.

The epoxidation reaction unit also includes an acid chamber effluent storage tank. The acid chamber effluent storage tank is communicated with the acid chamber of the bipolar membrane electrodialyzer and is used for receiving the acid chamber effluent of the bipolar membrane electrodialyzer and providing feed for the acid chamber of the bipolar membrane electrodialyzer. During the start-up phase, the acid chamber effluent storage tank may be filled with water as the feedstock for the acid chamber.

According to the production system provided by the invention, the organic phase rich in the epoxy chloropropane can be output, and can be further refined to obtain an epoxy chloropropane product. Preferably, the production system according to the invention further comprises a refining unit for receiving the organic phase rich in epichlorohydrin and output from the effluent settling tank of the alkali chamber and refining the organic phase to obtain an epichlorohydrin product.

The refining unit can adopt various devices capable of recovering the epichlorohydrin from the organic phase rich in the epichlorohydrin. In one embodiment, the refining unit comprises a rectifying tower, the organic phase rich in the epichlorohydrin enters the rectifying tower for rectification to obtain an epichlorohydrin product, and simultaneously recovers unreacted dichloropropanol and glycerol which may exist as by-products, the recovered unreacted dichloropropanol is circularly sent to an alkali chamber of a bipolar membrane electrodialyzer for bipolar membrane electrodialysis, and the recovered epichlorohydrin product and the by-products are respectively output.

The production system according to the present invention preferably further comprises a storage tank for the dichloropropanol for providing the initial feedstock to the alkaline chamber effluent settling tank and replenishing fresh dichloropropanol when required.

According to the production system of the present invention, a conditioning operation is preferably performed in performing the bipolar membrane electrodialysis. Specifically, a flow valve may be provided on the connection line between the storage tank for storing dichloropropanol and the effluent settling tank of the alkaline chamber to adjust the amount of dichloropropanol entering the effluent settling tank of the alkaline chamber.

The production system of the present invention may be operated in a batch mode or a continuous mode, and is not particularly limited.

Fig. 3 shows an embodiment of the production system according to the present invention, and the production system according to the embodiment and the production method based on the production system will be described in detail below with reference to fig. 3.

As shown in fig. 3, the epichlorohydrin production system according to this embodiment includes a chlorohydrination reaction unit, a chlorohydrination reaction mixture separation unit, an epoxidation reaction unit, and a purification unit. The epoxidation reaction unit comprises a bipolar membrane electrodialyzer, an alkaline chamber effluent liquid settling tank, an acid chamber effluent liquid storage tank and a refining unit. The bipolar membrane electrodialyzer is a two-compartment bipolar membrane electrodialyzer, the membrane unit of which has an alkali compartment and an acid compartment. And a partition plate is arranged in the alkaline chamber effluent settling tank to divide the internal space of the alkaline chamber effluent settling tank into a first liquid phase area and a second liquid phase area. The refining unit comprises a rectification column.

When the system operates, chlorine, water and chloropropene enter a chlorohydrination reactor to perform contact reaction in a chlorohydrination reaction unit to obtain a chlorohydrination reaction mixture. The chlorohydrination reaction mixture then enters an extraction column of an extraction unit to contact the extractant, resulting in an extract enriched in dichloropropanol, which then enters a flash column (not shown in figure 3) to separate the dichloropropanol and recover the extractant. At least part of the recovered extractant is sent to the extraction tower for recycling. The separated dichloropropanol and water are filled into a second liquid phase zone to obtain an aqueous solution containing dichloropropanol. The acid chamber effluent storage tank was filled with water. Starting an alkali chamber feeding output port of an alkali chamber effluent settling tank and an acid chamber feeding output port of an acid chamber effluent storage tank, correspondingly starting a pump on a pipeline, respectively pumping aqueous solution containing dichloropropanol and water into an alkali chamber and an acid chamber of a bipolar membrane electrodialyzer, after stable logistics circulation is established, starting the bipolar membrane electrodialyzer to perform bipolar membrane electrodialysis, enabling the generated alkali chamber effluent to enter a first liquid phase area, and overflowing into a second liquid phase area when the height of a material in the first liquid phase area exceeds the height of a partition plate. And settling and separating the liquid phase retained in the first liquid phase region to obtain an organic phase rich in epichlorohydrin, and outputting the organic phase through an output port of the organic phase. In the bipolar membrane electrodialysis process, depending on the mode of operation, for example in a continuous mode, fresh dichloropropanol can be fed to the second liquid phase zone via a fresh dichloropropanol inlet. An acid compartment effluent containing HCl produced by bipolar membrane electrodialysis is circulated between the acid compartment and an acid compartment effluent reservoir.

And (3) the organic phase which is output from the first liquid phase region and is rich in the epichlorohydrin enters a rectifying tower of a refining unit for rectification to obtain an epoxypropane product and byproducts such as glycerol, and the separated unreacted dichloropropanol is sent to the second liquid phase region for recycling.

According to the embodiment shown in fig. 3, during operation, an adjustment operation is preferably performed.

In the embodiment shown in FIG. 3, the bipolar membrane electrodialyzer is a two-compartment bipolar membrane electrodialyzer, which can be replaced by a three-compartment bipolar membrane electrodialyzer as will be understood by those skilled in the art, such as the three-compartment bipolar membrane electrodialyzer described above.

The following examples are given in detail, but are not intended to limit the scope of the present invention.

In the following examples, the composition of the obtained alkali chamber effluent was analyzed by gas chromatography, and the dichlorohydrin conversion and the epichlorohydrin selectivity were calculated by the following formulas, respectively, on the basis of this:

dichloropropanol conversion (%) × (molar amount of added dichloropropanol-molar amount of unreacted dichloropropanol)/molar amount of added dichloropropanol ] × 100%;

epichlorohydrin selectivity (%) × 100% for the molar amount of epichlorohydrin produced by the reaction/(molar amount of dichloropropanol added-molar amount of unreacted dichloropropanol).

In the following embodiments, an on-line pH meter is disposed on a pipeline connecting an output port of an alkali chamber of a bipolar membrane electrodialyzer and an input port of an effluent storage tank of the alkali chamber to detect the pH of the effluent of the alkali chamber.

Examples 1-28 are intended to illustrate the invention.

Example 1

(1) Chlorohydrination reaction step

Chloropropene and chlorine are mixed according to a molar ratio of 1: 0.9 into a chlorohydrination reactor to contact with water for chlorohydrination reaction, wherein the reaction temperature is 80 ℃ and the pressure in the reactor is normal pressure (i.e. 1 atm). And carrying out gas-liquid separation on the obtained reaction mixture, extracting and separating the obtained liquid phase by adopting chloropropene as an extracting agent, enriching dichloropropanol in the extraction liquid, and carrying out flash evaporation on the extraction liquid to obtain the dichloropropanol.

The obtained dichloropropanol and sodium chloride were dispersed in water to obtain an aqueous solution containing dichloropropanol in which the concentration of dichloropropanol was 20% by weight and the content of sodium chloride was 10% by weight as raw materials for the epoxidation step.

(2) Step of epoxidation reaction

The bipolar membrane used in this example was a homogeneous bipolar membrane (model BP-1) available from Hebei Guangya, and the anion exchange membrane was an anion exchange membrane (model AHA) available from Aston, Japan.

This example carried out bipolar membrane electrodialysis in a batch manner using the production system shown in FIG. 3 (but without a rectification column and without a partition in the alkaline compartment effluent settling tank), which was a two-compartment bipolar membrane electrodialyzer having 10 membrane units as shown in FIG. 1.

Feeding 2000g of aqueous solution containing dichloropropanol as a raw material into an alkali chamber effluent settling tank, and feeding 2000g of deionized water into an acid chamber effluent storage tank, wherein an alkali chamber effluent inlet port of the alkali chamber effluent settling tank is communicated with an alkali chamber discharge outlet port of a bipolar membrane electrodialyzer, and an alkali chamber feed outlet port of the alkali chamber effluent settling tank is communicated with an alkali chamber feed inlet port of the bipolar membrane electrodialyzer; an acid chamber effluent inlet port of the acid chamber effluent storage tank is communicated with an acid chamber effluent outlet port of the bipolar membrane electrodialyzer, and an acid chamber feed outlet port of the acid chamber effluent storage tank is communicated with an acid chamber feed inlet port of the bipolar membrane electrodialyzer. An aqueous sodium sulfate solution (sodium sulfate content: 5% by weight) was fed as a polar liquid to the polar liquid tank.

And opening an alkali chamber feeding output port of the alkali chamber effluent settling tank, an acid chamber feeding output port of the acid chamber effluent storage tank and an output port of the polar liquid tank, and respectively feeding aqueous solution containing dichloropropanol, water and polar liquid into an alkali chamber, an acid chamber and a polar chamber of the bipolar membrane electrodialyzer to establish stable material input and output circulation.

The power supply of the bipolar membrane electrodialyzer was turned on, a voltage was applied to the membrane units of the bipolar membrane electrodialyzer, the voltage applied to each membrane unit was adjusted to 1.5V and a constant voltage operation was maintained while controlling the temperatures of the acid chamber and the base chamber to 35 ℃. During the bipolar membrane electrodialysis, the pH value of the alkaline chamber effluent liquid is gradually increased, and the bipolar membrane electrodialysis is stopped when the pH value of the alkaline chamber effluent liquid reaches 8.5.

After the bipolar membrane electrodialysis is finished, gas chromatography analysis is carried out on the water phase and the organic phase of the effluent liquid of the alkali chamber, and the conversion rate of the dichloropropanol is 99% and the selectivity of the epichlorohydrin is 82% determined by calculation.

Example 2

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 1, except that the aqueous solution containing dichloropropanol as a raw material contained 20% by weight of sodium chloride.

After the bipolar membrane electrodialysis is finished, gas chromatography analysis is carried out on the water phase and the organic phase of the effluent liquid of the alkali chamber, and the conversion rate of the dichloropropanol is 99% and the selectivity of the epichlorohydrin is 85% determined by calculation.

Example 3

Bipolar membrane electrodialysis was carried out to produce epichlorohydrin using the same procedure as in example 1, except that: the concentration of sodium chloride in the starting aqueous solution containing dichloropropanol was 25 wt%.

After the bipolar membrane electrodialysis is finished, gas chromatography analysis is carried out on the water phase and the organic phase of the effluent liquid of the alkali chamber, and the conversion rate of the dichloropropanol is 99% and the selectivity of the epichlorohydrin is 87% determined by calculation.

Example 4

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 1, except that the concentration of sodium chloride in the dichloropropanol-containing aqueous solution as the starting material was 5 wt%.

After the bipolar membrane electrodialysis is finished, gas chromatography analysis is carried out on a water phase and an organic phase of an effluent liquid of the alkali chamber, and the conversion rate of dichloropropanol is 99% and the selectivity of epichlorohydrin is 77% through calculation and determination.

Example 5

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 1, except that the concentration of sodium chloride in the dichloropropanol-containing aqueous solution as the raw material was 3 wt%.

After the bipolar membrane electrodialysis is finished, gas chromatography analysis is carried out on the water phase and the organic phase of the effluent liquid of the alkali chamber, and the conversion rate of dichloropropanol is 99 percent and the selectivity of epichlorohydrin is 69 percent according to calculation and determination

Example 6

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 1, except that the concentration of sodium chloride in the dichloropropanol-containing aqueous solution as the raw material was 0.5 wt%.

After the bipolar membrane electrodialysis is finished, gas chromatography analysis is carried out on the water phase and the organic phase of the effluent liquid of the alkali chamber, and the conversion rate of the dichloropropanol is 99% and the selectivity of the epichlorohydrin is 64% determined by calculation.

Example 7

(1) Chlorohydrination reaction step

Chloropropene and chlorine are mixed according to a molar ratio of 1: 0.95 part of the crude product was introduced into a chlorohydrination reactor and contacted with water to conduct a chlorohydrination reaction, wherein the reaction temperature was 60 ℃ and the pressure in the reactor was atmospheric (i.e., 1 atm). And carrying out gas-liquid separation on the obtained reaction mixture, extracting and separating the obtained liquid phase by adopting chloropropene as an extracting agent, enriching dichloropropanol in the extraction liquid, and carrying out flash evaporation on the extraction liquid to obtain the dichloropropanol.

The obtained dichloropropanol and ammonium chloride were dispersed in water to obtain an aqueous solution containing dichloropropanol in which the concentration of dichloropropanol was 10% by weight and the content of ammonium chloride was 18% by weight as starting materials for the epoxidation step.

(2) Step of epoxidation reaction

This example employed the same production system and bipolar membrane electrodialyzer as in example 1, but the bipolar membrane electrodialysis was carried out in a continuous manner, and a partition plate was provided in the alkali compartment effluent settling tank to divide the alkali compartment effluent settling tank into a first liquid-phase zone and a second liquid-phase zone.

(2-1) feeding 2000g of aqueous solution containing dichloropropanol as a raw material into an alkali chamber effluent settling tank, and feeding 2000g of deionized water into an acid chamber effluent storage tank, wherein an alkali chamber effluent inlet port of the alkali chamber effluent settling tank is communicated with an alkali chamber discharge outlet port of a bipolar membrane electrodialyzer, and an alkali chamber feed outlet port of the alkali chamber effluent settling tank is communicated with an alkali chamber feed inlet port of the bipolar membrane electrodialyzer; an acid chamber effluent inlet port of the acid chamber effluent storage tank is communicated with an acid chamber effluent outlet port of the bipolar membrane electrodialyzer, and an acid chamber feed outlet port of the acid chamber effluent storage tank is communicated with an acid chamber feed inlet port of the bipolar membrane electrodialyzer. An aqueous sodium sulfate solution (sodium sulfate content: 8% by weight) was fed as an electrode liquid to the electrode liquid tank.

And opening an alkali chamber feeding output port of an alkali chamber effluent settling tank, an acid chamber feeding output port of an acid chamber effluent storage tank and an output port of a polar liquid tank, and respectively feeding aqueous solution, water and polar liquid containing dichloropropanol into an alkali chamber, an acid chamber and a polar chamber of the bipolar membrane electrodialyzer to establish stable material input and output circulation.

The power supply of the bipolar membrane electrodialyzer was turned on, a voltage was applied to the membrane units of the bipolar membrane electrodialyzer, the voltage applied to each membrane unit was adjusted to 1.5V and a constant voltage operation was maintained, while the temperatures of the acid chamber and the alkali chamber were controlled to 30 ℃.

(2-2) enabling an alkali chamber effluent liquid output by the bipolar membrane electrodialyzer to enter a first liquid phase area, enabling the effluent liquid to overflow into a second liquid phase area when the height of a material in the first liquid phase area exceeds the height of a partition plate, and enabling the material in the second liquid phase area and fresh dichloropropanol to circulate together to enter an alkali chamber of the bipolar membrane electrodialyzer for bipolar membrane electrodialysis. And (3) carrying out sedimentation separation on the liquid phase retained in the first liquid phase region to obtain an organic phase rich in epichlorohydrin, wherein the organic phase is arranged at the lower layer of the first liquid phase region of the alkaline chamber effluent liquid sedimentation tank, and after a certain amount of organic phase is accumulated, discharging the organic phase from the first liquid phase region of the alkaline chamber effluent liquid sedimentation tank.

And performing bipolar membrane electrodialysis for 24 hours, wherein in the bipolar membrane electrodialysis process, the pH value of the alkaline chamber effluent is controlled to be 8.5 by adjusting the adding amount of fresh dichloropropanol. And (3) performing gas chromatography analysis on the effluent liquid of the alkali chamber, wherein the conversion rate of the dichloropropanol is 97% and the selectivity of the epichlorohydrin is 83% by calculation.

Example 8

The bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 7, except that the pH of the alkaline chamber effluent was controlled to 10.0 by adjusting the amount of fresh dichloropropanol added during the bipolar membrane electrodialysis.

After the bipolar membrane electrodialysis is finished, carrying out gas chromatography analysis on the effluent liquid of the alkali chamber, and calculating to determine that the conversion rate of the dichloropropanol is 99% and the selectivity of the epichlorohydrin is 73%.

Example 9

The bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 7, except that the pH of the alkaline chamber effluent was controlled to 5.7 by adjusting the amount of fresh dichloropropanol added during the bipolar membrane electrodialysis.

After the bipolar membrane electrodialysis is finished, carrying out gas chromatography analysis on the effluent liquid of the alkali chamber, and calculating to determine that the conversion rate of the dichloropropanol is 80% and the selectivity of the epichlorohydrin is 96%.

Example 10

The bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 7, except that the pH of the alkaline chamber effluent was controlled to 7.2 by adjusting the amount of fresh dichloropropanol added during the bipolar membrane electrodialysis.

After the bipolar membrane electrodialysis is finished, carrying out gas chromatography analysis on the effluent liquid of the alkali chamber, and calculating to determine that the conversion rate of the dichloropropanol is 93% and the selectivity of the epichlorohydrin is 89%.

Example 11

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 10, except that the content of ammonium chloride in the dichloropropanol-containing aqueous solution as the starting material was 11 wt%.

After the bipolar membrane electrodialysis is finished, carrying out gas chromatography analysis on the effluent liquid of the alkali chamber, and calculating to determine that the conversion rate of the dichloropropanol is 91% and the selectivity of the epichlorohydrin is 87%.

Example 12

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 10, except that the content of ammonium chloride in the dichloropropanol-containing aqueous solution as the raw material was 3.5 wt%.

After the bipolar membrane electrodialysis is finished, carrying out gas chromatography analysis on the effluent liquid of the alkali chamber, and calculating to determine that the conversion rate of the dichloropropanol is 88% and the selectivity of the epichlorohydrin is 73%.

Example 13

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 10, except that the aqueous solution containing dichloropropanol as the raw material contained no ammonium chloride.

After the bipolar membrane electrodialysis is finished, the effluent liquid of the alkali chamber is subjected to gas chromatography analysis, and the conversion rate of the dichloropropanol is determined by calculation to be 8.9%, and the selectivity of the epichlorohydrin is 65%.

Example 14

(1) Chlorohydrination reaction step

Dichloropropanol was prepared in the same manner as in example 7, except that the aqueous solution containing dichloropropanol as the starting material for the epoxidation step contained 10% by weight of dichloropropanol and 12% by weight of ammonium chloride.

(2) Step of epoxidation reaction

The bipolar membrane used in this example was a homogeneous bipolar membrane (model No. BP-1) available from north-Henshima, the anion exchange membrane was an anion exchange membrane (model No. AHA) available from Asia Stoneley, Japan, and the cation exchange membrane was a cation exchange membrane (model No. CMX) available from Asia Stoneley, Japan.

This example employed a production system shown in fig. 3 (but no rectifying column was provided, and no partition was provided in the alkali chamber effluent settling tank) to perform bipolar membrane electrodialysis in a batch manner, and the bipolar membrane electrodialyzer employed was a three-compartment bipolar membrane electrodialyzer having 12 membrane units as shown in fig. 2.

Feeding 2000g of aqueous solution containing dichloropropanol as a raw material into an alkali chamber effluent liquid settling tank, and feeding 2000g of deionized water into an acid chamber effluent liquid storage tank, wherein an alkali chamber effluent liquid input port of the alkali chamber effluent liquid settling tank is communicated with an alkali chamber discharge output port of a bipolar membrane electrodialyzer, an alkali chamber feed output port of the alkali chamber effluent liquid settling tank is communicated with a salt chamber feed input port of the bipolar membrane electrodialyzer, and a salt chamber effluent output port is communicated with an alkali chamber; an acid chamber effluent inlet port of the acid chamber effluent storage tank is communicated with an acid chamber effluent outlet port of the bipolar membrane electrodialyzer, and an acid chamber feed outlet port of the acid chamber effluent storage tank is communicated with an acid chamber feed inlet port of the bipolar membrane electrodialyzer. An aqueous sodium sulfate solution (sodium sulfate content: 5% by weight) was fed as an electrode liquid to the electrode liquid tank.

And opening an alkali chamber feeding output port of the alkali chamber effluent settling tank, an acid chamber feeding output port of the acid chamber effluent storage tank and an output port of the electrode liquid tank, respectively feeding aqueous solution containing dichloropropanol, water and electrode liquid (wherein the salt chamber effluent is used as alkali chamber feeding) into a salt chamber, an acid chamber and an electrode chamber of the bipolar membrane electrodialyzer, and establishing stable material input and output circulation.

The power supply of the bipolar membrane electrodialyzer was turned on, a voltage was applied to the membrane units of the bipolar membrane electrodialyzer, the voltage applied to each membrane unit was adjusted to 1.5V and a constant voltage operation was maintained while controlling the temperature inside the membrane unit to 40 ℃. During the bipolar membrane electrodialysis, the pH value of the alkaline chamber effluent liquid is gradually increased, and the bipolar membrane electrodialysis is stopped when the pH value of the alkaline chamber effluent liquid reaches 8.5.

After the bipolar membrane electrodialysis is finished, gas chromatography analysis is carried out on the water phase and the organic phase of the effluent liquid of the alkali chamber, and the conversion rate of the dichloropropanol is 99% and the selectivity of the epichlorohydrin is 84% determined by calculation.

Example 15

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 14, except that the concentration of ammonium chloride in the dichloropropanol-containing aqueous solution as the raw material was 18% by weight.

Example 16

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 14, except that the concentration of ammonium chloride in the dichloropropanol-containing aqueous solution as the raw material was 24 wt%.

After the bipolar membrane electrodialysis is finished, gas chromatography analysis is carried out on the water phase and the organic phase of the effluent liquid of the alkali chamber, and the conversion rate of the dichloropropanol is 99% and the selectivity of the epichlorohydrin is 90% determined by calculation.

Example 17

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 14, except that the concentration of ammonium chloride in the dichloropropanol-containing aqueous solution as the raw material was 6 wt%.

After the bipolar membrane electrodialysis is finished, gas chromatography analysis is carried out on the water phase and the organic phase of the effluent liquid of the alkali chamber, and the conversion rate of the dichloropropanol is 99% and the selectivity of the epichlorohydrin is 80% determined by calculation.

Example 18

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 14, except that the concentration of ammonium chloride in the dichloropropanol-containing aqueous solution as the raw material was 2.5 wt%.

After the bipolar membrane electrodialysis is finished, gas chromatography analysis is carried out on the water phase and the organic phase of the effluent liquid of the alkali chamber, and the conversion rate of the dichloropropanol is 99% and the selectivity of the epichlorohydrin is 70% determined by calculation.

Example 19

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 14, except that the concentration of ammonium chloride in the dichloropropanol-containing aqueous solution as the raw material was 0.1 wt%.

After the bipolar membrane electrodialysis is finished, gas chromatography analysis is carried out on the water phase and the organic phase of the effluent liquid of the alkali chamber, and the conversion rate of the dichloropropanol is 99% and the selectivity of the epichlorohydrin is 68% determined by calculation.

Example 20

(1) Chlorohydrination reaction step

Dichloropropanol was prepared in the same manner as in example 7, except that the aqueous solution containing dichloropropanol as the starting material for the epoxidation step was an aqueous solution containing dichloropropanol and potassium chloride, wherein the content of dichloropropanol was 15% by weight and the content of potassium chloride was 10% by weight.

(2) Step of epoxidation reaction

This example employed the same production system and bipolar membrane electrodialyzer as in example 14, but the bipolar membrane electrodialysis was carried out in a continuous manner, and a partition plate was provided in the alkali compartment effluent settling tank to divide the alkali compartment effluent settling tank into a first liquid-phase zone and a second liquid-phase zone.

(2-1) feeding 2000g of aqueous solution containing dichloropropanol as a raw material into an alkali chamber effluent settling tank, and feeding 2000g of deionized water into an acid chamber effluent storage tank, wherein an alkali chamber effluent inlet port of the alkali chamber effluent settling tank is communicated with an alkali chamber discharge outlet port of a bipolar membrane electrodialyzer, an alkali chamber feed outlet port of the alkali chamber effluent settling tank is communicated with a salt chamber feed inlet port of the bipolar membrane electrodialyzer, and a salt chamber effluent outlet port is communicated with an alkali chamber; an acid chamber effluent inlet port of the acid chamber effluent storage tank is communicated with an acid chamber effluent outlet port of the bipolar membrane electrodialyzer, and an acid chamber feed outlet port of the acid chamber effluent storage tank is communicated with an acid chamber feed inlet port of the bipolar membrane electrodialyzer. An aqueous sodium sulfate solution (sodium sulfate content: 7% by weight) was fed as an electrode liquid to the electrode liquid tank.

The power supply of the bipolar membrane electrodialyzer was turned on, a voltage was applied to the membrane units of the bipolar membrane electrodialyzer, the voltage applied to each membrane unit was adjusted to 1.4V and a constant voltage operation was maintained while controlling the temperature inside the membrane unit to 35 ℃.

(2-2) enabling an alkali chamber effluent liquid output by the bipolar membrane electrodialyzer to enter a first liquid phase area, when the height of a material in the first liquid phase area exceeds the height of a partition plate, overflowing the material into a second liquid phase area, and enabling the material in the second liquid phase area and fresh dichloropropanol to circularly enter an alkali chamber of the bipolar membrane electrodialyzer to carry out bipolar membrane electrodialysis. And (3) settling and separating the liquid phase retained in the first liquid phase region to obtain an organic phase rich in epichlorohydrin, allowing the organic phase to be in the lower layer of the first liquid phase region of the effluent liquid settling tank of the alkali chamber, and discharging the organic phase from the first liquid phase region of the effluent liquid settling tank of the alkali chamber after a certain amount of the organic phase is accumulated.

And performing bipolar membrane electrodialysis for 36 hours, wherein in the bipolar membrane electrodialysis process, the pH value of the alkaline chamber effluent is controlled to be 8.0 by adjusting the adding amount of fresh dichloropropanol. The effluent of the alkali chamber is analyzed by gas chromatography, and the conversion rate of the dichloropropanol is 87% and the selectivity of the epichlorohydrin is 85% by calculation.

Example 21

The bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 20, except that, during the bipolar membrane electrodialysis, the pH of the effluent of the base compartment was controlled to 7.4 by adjusting the amount of fresh dichloropropanol added.

And (3) carrying out gas chromatography analysis on the effluent liquid of the alkali chamber, wherein the conversion rate of the dichloropropanol is 84% and the selectivity of the epichlorohydrin is 90% through calculation and determination.

Example 22

The bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 20, except that, during the bipolar membrane electrodialysis, the pH of the effluent of the base compartment was controlled to 5.7 by adjusting the amount of fresh dichloropropanol added.

And (3) carrying out gas chromatography analysis on the effluent of the alkali chamber, and calculating to determine that the conversion rate of the dichloropropanol is 75% and the selectivity of the epichlorohydrin is 95%.

Example 23

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 21, except that the content of potassium chloride in the dichloropropanol-containing aqueous solution as the raw material was 16% by weight.

And (3) carrying out gas chromatography analysis on the effluent of the alkali chamber, wherein the conversion rate of the dichloropropanol is 86% and the selectivity of the epichlorohydrin is 91% by calculation.

Example 24

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 21, except that the content of potassium chloride in the dichloropropanol-containing aqueous solution as the starting material was 22 wt%.

And (3) performing gas chromatography analysis on the effluent of the alkali chamber, and calculating to determine that the conversion rate of the dichloropropanol is 89% and the selectivity of the epichlorohydrin is 93%.

Example 25

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 21, except that the content of potassium chloride in the dichloropropanol-containing aqueous solution as the raw material was 6% by weight.

The effluent of the alkali chamber is analyzed by gas chromatography, and the conversion rate of the dichloropropanol is 82 percent and the selectivity of the epichlorohydrin is 84 percent.

Example 26

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 21, except that the content of potassium chloride in the dichloropropanol-containing aqueous solution as the raw material was 3% by weight.

And (3) performing gas chromatography analysis on the effluent liquid of the alkali chamber, wherein the conversion rate of the dichloropropanol is 80% and the selectivity of the epichlorohydrin is 74% by calculation.

Example 27

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 21, except that the content of potassium chloride in the dichloropropanol-containing aqueous solution as the raw material was 0.05 wt%.

And (3) performing gas chromatography analysis on the effluent of the alkali chamber, wherein the conversion rate of the dichloropropanol is 78% and the selectivity of the epichlorohydrin is 72% by calculation.

Example 28

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 21, except that the aqueous solution containing dichloropropanol as a starting material contained no potassium chloride.

The effluent of the alkali chamber is subjected to gas chromatography analysis, and the conversion rate of the dichloropropanol is determined to be 9.1 percent and the selectivity of the epichlorohydrin is determined to be 69 percent.

The results of examples 1 to 28 demonstrate that, with the process of the invention, dichloropropanol fed into the alkaline compartment of a bipolar membrane electrodialyzer for bipolar membrane electrodialysis can be converted into epichlorohydrin; in addition, no solid waste residue and no or almost no waste liquid are generated in the epoxidation reaction process, so that the method is green and environment-friendly. In addition, in the epoxidation reaction step in the method, a catalyst is not required to be additionally added, and a product is not required to be distilled out in the epoxidation reaction process, so that the operation is simple.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A process for producing epichlorohydrin, the process comprising:

(3) feeding the dichloropropanol into an alkali chamber of a bipolar membrane electrodialyzer for bipolar membrane electrodialysis to obtain an alkali chamber effluent containing epichlorohydrin, the bipolar membrane electrodialysis is carried out in the presence of at least one additive selected from one or more of alkali metal chlorides, alkali metal sulfates, alkali metal nitrates, alkali metal carboxylates, alkali metal phosphates, ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium carboxylates, ammonium phosphate, ammonium hydrogen phosphate, and ammonium dihydrogen phosphate, the additive is contained in the alkaline chamber feed in an amount of 8-25 wt%, and in the bipolar membrane electrodialysis, the voltage applied to each membrane unit is 0.5-2.5V, the method also comprises an adjusting operation carried out in the bipolar membrane electrodialysis process, wherein the adjusting operation leads the pH value of the alkaline chamber effluent to be 7-9;

the process also comprises separating an organic phase rich in epichlorohydrin from the effluent of the base chamber and feeding the remaining liquid phase from which the organic phase has been separated, and optionally fresh dichloropropanol, into the base chamber of a bipolar membrane electrodialyser, the organic phase being separated from the effluent of the base chamber by settling separation.

2. The production process according to claim 1, wherein the chlorohydrination of chloropropenes comprises: under the chlorohydrination reaction condition, chloropropene is contacted with water and chlorine to obtain a chlorohydrination reaction mixture containing dichloropropanol.

3. The production process according to claim 2, wherein the process for separating dichloropropanol from the chlorohydrination reaction mixture comprises:

(A) carrying out gas-liquid separation on the chlorohydrination reaction mixture to obtain a gas phase material flow and a liquid phase material flow;

4. The production process according to claim 3, wherein the extractant is chloropropene.

5. The production process according to claim 4, wherein the dichloropropanol is enriched in the extraction liquid.

6. The production process according to claim 5, wherein the extract is subjected to distillation to obtain recovered chloropropenes and dichloropropanol, and at least part of the recovered chloropropenes is recycled as extractant.

7. The production process according to claim 3, wherein at least part of the gas phase stream is recycled for the chlorohydrination reaction.

8. The production process according to claim 1, wherein the bipolar membrane electrodialyzer comprises an anode, a cathode and at least one membrane unit comprising an alkali compartment and an acid compartment disposed between the anode and the cathode; or

The bipolar membrane electrodialyzer comprises an anode, a cathode and at least one membrane unit arranged between the anode and the cathode, wherein the membrane unit comprises an alkali chamber, an acid chamber and a salt chamber, an output port of the salt chamber is communicated with an input port of the alkali chamber, and dichloropropanol enters the alkali chamber from the salt chamber.

9. The production method according to claim 1, wherein the additive is selected from the group consisting of sodium chloride, potassium chloride and ammonium chloride.

10. The production method according to claim 1 or 9, wherein the bipolar membrane electrodialysis is carried out at a temperature of 5-45 ℃.

11. The production process according to claim 1 or 9, wherein the adjustment operation comprises adjusting the dichloropropanol content entering the alkaline chamber.

12. The production process according to claim 1 or 9, wherein the adjustment operation is such that the pH of the effluent of the caustic chamber is 7 to less than 8.

13. The production process according to claim 12, wherein the adjustment operation is carried out so that the pH of the effluent from the alkali chamber is 7 to 7.9.

14. The production process according to claim 13, wherein the adjustment operation is carried out so that the pH of the effluent from the alkali chamber is 7 to 7.8.

15. The process according to claim 1 or 9, wherein in step (3), the dichloropropanol content is between 1 and 80% by weight, based on the total amount of feed to the caustic chamber.

16. The production method according to claim 1, wherein the settling separation is one of a standing separation, a centrifugal separation, or a combination of both.

17. The process according to claim 1, wherein it further comprises refining the organic phase rich in epichlorohydrin to obtain an epichlorohydrin product.