CN109721570B

CN109721570B - Method for producing epoxy chloropropane

Info

Publication number: CN109721570B
Application number: CN201711034532.7A
Authority: CN
Inventors: 刘中清; 罗一斌; 周丽娜; 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: CN109721570A

Abstract

The invention discloses a method for producing epoxy chloropropane, which comprises the following steps: contacting chloropropene with water and chlorine, carrying out gas-liquid separation on the obtained chlorohydrination reaction mixture containing dichloropropanol to obtain gas-phase material flow and liquid-phase material flow, contacting the liquid-phase material flow with an extracting agent to obtain extraction liquid rich in dichloropropanol, and separating the dichloropropanol from the extraction liquid; feeding dichloropropanol, an additive selected from water-soluble alkali metal salt and water-soluble ammonium salt and water into an alkali chamber of a bipolar membrane electrodialyzer to carry out bipolar membrane electrodialysis to obtain an alkali chamber effluent containing epichlorohydrin. According to the production method, no or basically no waste water or waste residue is generated, and the production method is environment-friendly; no catalyst is adopted, so that the production cost is reduced; according to the method, the separation cost is low, and the operation method is simple. The method for preparing the epoxy chloropropane can obtain higher raw material conversion rate and higher production efficiency.

Description

Method for producing epoxy chloropropane

Technical Field

The invention relates to a method for producing epoxy chloropropane.

Background

Epichlorohydrin is an important basic organic chemical raw material and intermediate, and is widely applied to synthesis of various products such as epoxy resin, glycerol, chlorohydrin rubber, medicines, pesticides, surfactants, plasticizers and the like.

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 existing industrial production method become more and more obvious, and the development of new processes is promoted to be strengthened.

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 exists or does not exist, 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 costs 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 tert-butyl alcohol, 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 process₂O₂The cost is high, and the reaction process needs to use a solvent, so that the energy consumption for separation is increased.

In summary, it is necessary to develop a green epichlorohydrin 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.

The invention provides a method for producing epoxy chloropropane, which comprises the following steps:

(1) under the chlorohydrination reaction condition, chloropropene is contacted with water and chlorine to obtain a chlorohydrination reaction mixture containing dichloropropanol

(2) Carrying out gas-liquid separation on the chlorohydrination reaction mixture to obtain a gas-phase material flow and a liquid-phase material flow, contacting the liquid-phase material flow with an extracting agent to obtain an extraction liquid rich in the dichloropropanol, and separating the dichloropropanol from the extraction liquid rich in the dichloropropanol;

(3) feeding dichloropropanol into an alkali chamber of a bipolar membrane electrodialyzer, and carrying out bipolar membrane electrodialysis in the presence of at least one additive to obtain an alkali chamber effluent containing epichlorohydrin, wherein the additive is one or more than two selected from water-soluble alkali metal salts and water-soluble ammonium salts.

Compared with the existing production method of epoxy chloropropane, the production method of the invention has the following advantages that the epoxy chloropropane is prepared by epoxidizing dichloropropanol in the alkali chamber of a bipolar membrane electrodialyzer:

(1) compared with the traditional propylene high-temperature chlorination method and the acetate propylene ester method, 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 production method does not adopt a catalyst, so that the production cost is reduced; in addition, according to the method, water is used as a solvent instead of an organic solvent, and the reaction liquid containing the epoxy chloropropane can be separated into an organic phase rich in the epoxy chloropropane and a water phase poor in the epoxy chloropropane by adopting settling separation methods such as standing, centrifuging and the like, so that the separation cost is reduced;

(3) according to the method, in the 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.

The production method of epichlorohydrin according to the invention, which carries out the epoxidation reaction of dichloropropanol in the presence of at least one additive, can obtain obviously improved raw material conversion rate and production efficiency, and can also improve the selectivity of epichlorohydrin.

Drawings

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

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

Fig. 3 serves to illustrate one embodiment of the process for the manufacture of epichlorohydrin according to the invention.

Detailed Description

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

According to the production process of the present invention, step (1) is used to provide dichloropropanol, the chloropropenes may be chlorohydrinated under conditions well 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: 0.8-0.98, 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 gas at a temperature of from 50 to 90 c, preferably from 60 to 80 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 contain unreacted chloropropene and/or chlorine besides dichloropropanol, and in the step (2), the chlorohydrination reaction mixture is subjected to gas-liquid separation, so that on one hand, the content of gas substances in a liquid phase can be reduced, and the safety of subsequent reactions is improved; on the other hand, unreacted chloropropene and/or chlorine can be recycled for chlorohydrination reaction, so that the utilization rate of the raw materials 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 conventional substance capable of extracting dichloropropanol. Preferably, the extractant is chloropropene. Chloropropene is used as an extracting agent, so that dichloropropanol can be separated from the liquid phase material flow with high extraction efficiency, and no extra 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. In particular, the extract may be subjected to distillation to obtain chloropropene and dichloropropanol, and at least part of the 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 process of the present invention, in step (3), the bipolar membrane electrodialysis is carried out in the presence of at least one additive, and the operation efficiency of the bipolar membrane electrodialyzer can be effectively improved.

The additive is one or more than two selected from water-soluble alkali metal salt and water-soluble ammonium salt. 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.

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

The amount of the additive may be selected according to the desired current density. Although a small amount of additives are introduced into the alkaline compartment of the bipolar membrane electrodialyzer, for example: the improvement of the operation efficiency of the bipolar membrane electrodialyzer can be achieved with the content of the additive of 0.01 wt% based on the total amount of the additive, dichloropropanol and water entering the alkaline chamber, but the inventors of the present invention found in the course of their research that if the content of the additive is further increased, the selectivity to epichlorohydrin can be further improved.

Thus, according to the process of the invention, the additive may be present in an amount of from 0.01% by weight up to the weight percentage of the additive saturated in water, such as from 0.02 to 40% by weight, preferably from 0.05 to 35% by weight, based on the total amount of additive, dichloropropanol and water entering the caustic chamber. The weight percent of the additive when saturated in water refers to the weight percent of the additive when forming a saturated solution in water at a temperature of 25 ℃.

In one embodiment of the process according to the invention, the additive is present in an amount of 0.01 to less than 5 wt.%, preferably 0.02 to 4.6 wt.%, more preferably 0.05 to 4.2 wt.%, and even more preferably 0.1 to 3.8 wt.%, based on the total amount of additive, dichloropropanol and water entering the base chamber. According to this embodiment, the operation efficiency of the bipolar membrane electrodialyzer can be significantly improved.

In a more preferred embodiment of the process according to the invention, the additive is present in an amount of more than 5 wt.%, such as 5.5-30 wt.%, based on the total amount of additive, dichloropropanol and water entering the base chamber. Preferably, the additive is present in an amount of 6 wt.% or more, such as 8-26 wt.%, more preferably 10-20 wt.%, based on the total amount of additive, dichloropropanol and water entering the caustic chamber. According to this more preferred embodiment, a higher selectivity to epichlorohydrin is obtained.

According to the process of the present invention, the additive may be added to the feed to the base compartment (salt compartment feed, hereinafter abbreviated as "base compartment feed/salt compartment feed" when salt compartments are present) of the bipolar membrane electrodialyzer. In general, the bipolar membrane electrodialysis can be carried out in the presence of the additive by preparing an aqueous solution of dichloropropanol and the additive and feeding the aqueous solution into the alkaline compartment (the salt compartment when present) of the bipolar membrane electrodialysis device. According to the process of the present invention, the additive may be introduced into the initial charge of the bipolar membrane electrodialyzer, and the additive may not be supplemented during the cycling reaction, but it will be understood by those skilled in the art that the additive may be supplemented when the content of the additive is insufficient during the cycling reaction.

According to the process of the invention, the dichloropropanol may be present in an amount of 1 to 80 wt.%, preferably 3 to 60 wt.%, more preferably 5 to 50 wt.%, even more preferably 7 to 40 wt.%, even more preferably 8 to 30 wt.%, and particularly preferably 10 to 20 wt.%, based on the total amount of additive, dichloropropanol and water entering the base chamber. According to the process of the invention, the dichloropropanol may be 1, 3-dichloro-2-propanol and/or 2, 3-dichloro-1-propanol.

According to the method of the invention, dichloropropanol is fed into the alkaline chamber of a bipolar membrane electrodialyser and reacts with hydroxide ions (OH) generated by bipolar membrane electrodialysis^-) And carrying out in-situ instant reaction to obtain the epichlorohydrin. The arrangement form of the membrane units in the bipolar membrane electrodialyzer takes the principle that the above functions can be realized.

In one embodiment, the bipolar membrane electrodialyzer is a two-compartment bipolar membrane electrodialyzer, i.e. the membrane units of the bipolar membrane electrodialyzer contain an acid compartment and a base 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 one bipolar membrane and one anion exchange membrane, the anion exchange membrane and the bipolar membrane being alternately arranged, a space between the anion exchange membrane and an anion exchange layer of an adjacent bipolar membrane being an alkali compartment, and a space between the anion exchange membrane and a cation exchange layer of an adjacent other bipolar membrane being an acid compartment.

According to this embodiment, in the bipolar membrane electrodialysis, water is fed into the acid compartment and an aqueous solution containing dichloropropanol and additives is fed into the base compartment, and the bipolar membrane dissociates 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⁺Then enters the acid compartment through the cation exchange layer of the bipolar membrane and the Cl 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.

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 acid compartments, base compartments and salt compartments. 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.

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 one example, the membrane unit of the bipolar membrane electrodialyzer comprises a bipolar membrane, an anion exchange membrane, a first cation exchange membrane and a second cation exchange membrane, the space between the first cation exchange membrane and the anion exchange layer of the adjacent bipolar membrane is an alkali chamber, the space between the cation exchange layer of the bipolar membrane and the adjacent anion exchange membrane is an acid chamber, the space between the anion exchange membrane and the adjacent second cation exchange membrane is a salt chamber, and the output port of the salt chamber is communicated with the input port of the alkali chamber. In another example, the membrane unit of the bipolar membrane electrodialyzer comprises a bipolar membrane, a cation exchange membrane, a first anion exchange membrane and a second anion exchange membrane, the space between the first anion exchange membrane and the cation exchange layer of the adjacent bipolar membrane is an acid chamber, the space between the anion exchange layer of the bipolar membrane and the adjacent cation exchange membrane is an alkali chamber, the space between the cation exchange membrane and the adjacent second anion exchange membrane is a salt chamber, and the output port of the salt chamber is communicated with the input port of the alkali chamber.

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. In the preferred embodiment, the salt chamber is arranged between the acid chamber and the alkali chamber, the feed of the salt chamber enters the alkali chamber, the dichloropropanol reacts in the alkali chamber to generate the epichlorohydrin, and the concentration of the epichlorohydrin in the salt chamber is low, so that the concentration of the epichlorohydrin in the acid chamber can be further reduced, and the product yield is further improved.

According to this more preferred embodiment, in carrying out bipolar membrane electrodialysis, water enters the acid compartment, an aqueous solution containing dichloropropanol and additives enters the salt compartment and from there enters the base compartment, and the bipolar membrane dissociates 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 chamber effluent containing hydrochloric acid from the acid chamber.

Although the bipolar membrane electrodialyzer shown in fig. 1 and 2 has only one membrane unit, it is well known to those skilled in the art that the number of membrane units is not limited to one group, and the bipolar membrane electrodialyzer may have a plurality of membrane units. Specifically, the bipolar membrane electrodialyzer may have 1 to 1000 membrane units, preferably 5 to 500 membrane units, more preferably 8 to 300 membrane units, further preferably 10 to 100 membrane units.

According to the process of the present invention, the polar liquid employed in the polar compartments 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 process of the present invention, the types 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 process of the invention, it is preferred to carry out, during the bipolar membrane electrodialysis, an adjustment operation which brings the pH of the alkaline compartment effluent to a value between 5.5 and 10, which makes it possible to significantly improve the selectivity for epichlorohydrin and/or 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 base chamber is measured by the operation of flowing out from the base 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 alkaline chamber effluent 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 alkali 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 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 ℃.

According to the 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 sedimentation separation. The settling separation may be stationary separation, centrifugal separation, or a combination of stationary separation and 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 method, after the bipolar membrane electrodialysis is completed, the alkaline chamber effluent liquid can be separated to obtain an organic phase rich in epoxy chloropropane.

From the viewpoint of further improving the selectivity of epichlorohydrin, it is preferred that in the bipolar membrane electrodialysis process, 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 to the base compartment of the bipolar membrane electrodialysis apparatus. 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 and additives is added at the beginning of bipolar membrane electrodialysis each time, and after bipolar membrane electrodialysis is carried out for a preset time, all alkaline chamber effluent is discharged. The continuous mode is that a certain amount of aqueous solution containing dichloropropanol and additives is added at the beginning of bipolar membrane electrodialysis, and at least part of epichlorohydrin is discharged and fresh dichloropropanol is supplemented in the bipolar membrane electrodialysis process.

According to the 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, as a rule, the upper liquid phase and the organic phase being the lower liquid phase. However, when the content of the additive in the alkali chamber feed and/or the salt chamber feed is more than 25 wt%, the effluent of the alkali 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 enriched in epichlorohydrin separated from the base chamber effluent can be exported. According to the method of the present invention, preferably, the method further includes refining the organic phase rich in epichlorohydrin to obtain an epichlorohydrin product. The method for purification in the present invention is not particularly limited, and a commonly used method for purification of a crude epichlorohydrin product may be used, for example: the organic phase rich in the epoxy chloropropane can be rectified, so that an epoxy chloropropane product is obtained.

When the organic phase rich in the epichlorohydrin also contains unreacted dichloropropanol, the refining process preferably also comprises the recovery of the unreacted dichloropropanol, and 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 waste liquid amount generated by the method. The organic phase rich in epichlorohydrin may also contain by-products such as glycerol, which are preferably recovered during the refining process. The recovered by-products can be exported.

The process for producing epichlorohydrin according to the present invention may be carried out in a production system including a chlorohydrination reaction unit, a chlorohydrination reaction mixture separation unit, and an epoxidation reaction unit. The output port of the dichloropropanol of the chlorohydrination reaction unit is communicated with the input port of the material to be separated of the chlorohydrination reaction mixture separation unit, and the output port of the dichloropropanol of the chlorohydrination reaction mixture separation unit is communicated with the input port of the dichloropropanol 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 used for separating the dichloropropanol from the chlorohydrination reaction mixture and 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 extraction 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 counter-current 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 extract 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 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 epichlorohydrin.

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 chamber and an acid chamber, i.e., the bipolar membrane electrodialyzer may be a two-chamber bipolar membrane electrodialyzer preferably having the membrane unit shown in fig. 1. Preferably, the bipolar membrane electrodialyzer is a three-chamber bipolar membrane electrodialyzer, a membrane unit of the three-chamber bipolar membrane electrodialyzer comprises a base chamber, a salt chamber and an acid chamber, an outlet port of an effluent of the salt chamber is communicated with an inlet port of the base chamber, an aqueous solution containing dichloropropanol and an additive enters the base chamber from the salt chamber and is combined with hydroxide ions generated by bipolar membrane electrodialysis in the base chamber to react to form epichlorohydrin, and an effluent of the base chamber containing epichlorohydrin is obtained from the base chamber; simultaneously, an acid chamber effluent containing HCl is obtained in the acid chamber. The three-compartment bipolar membrane electrodialyzer preferably has the membrane units shown in FIG. 2.

The epoxidation reaction unit also comprises an alkali chamber effluent settling tank which is communicated with the alkali chamber of the bipolar membrane electrodialyzer and is used for receiving the 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/salt 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 arranged at the upper part of the second liquid phase zone), the alkali chamber feed outlet is arranged in the second liquid phase zone (preferably arranged at the lower part of the second liquid phase zone), and the organic phase outlet is arranged in the first liquid phase zone (preferably arranged at the lower part and/or the upper part of the first liquid phase zone). The height of the partition plate is based on the principle that the material quantity in the second liquid phase area can meet the feeding requirement of the bipolar membrane electrodialyzer, and enough alkaline chamber effluent liquid can be reserved for separation.

According to the preferred embodiment, when the system is operated, the alkali chamber effluent outputted by the alkali chamber of the bipolar membrane electrodialyzer enters the first liquid phase zone from the alkali chamber effluent input port, when the height of the material entering the first liquid phase zone exceeds that of the partition plate, part of the material overflows from the top of the partition plate and enters the second liquid phase zone, the alkali chamber effluent remained 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 outputted through the organic phase output port. According to this embodiment, it is possible to separate the organic phase rich in epichlorohydrin from the alkaline chamber effluent during bipolar membrane electrodialysis, thereby further increasing the epichlorohydrin selectivity.

In this preferred embodiment, the organic phase output port is preferably disposed at a lower portion and/or an upper portion of the first liquid phase region. In a preferred embodiment, an organic phase outlet port is 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 the alkaline chamber effluent settling, the upper organic phase outlet port or the lower organic phase outlet port can be selectively opened to output the organic phase.

In the start-up phase of the production system, an aqueous solution containing dichloropropanol and at least one additive can be filled in an effluent settling tank of the alkali chamber as the feeding of the alkali chamber/the feeding of the salt chamber; and filling water in the effluent storage tank of the acid chamber as a raw material 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 and additives is filled into the second liquid phase zone.

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 further comprises a refining unit, and the refining unit is used for receiving the organic phase rich in epichlorohydrin and output from the alkali chamber effluent settling tank, 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 to be rectified to obtain the epichlorohydrin product, and simultaneously, unreacted dichloropropanol and glycerol which may exist as by-products are recovered, the recovered unreacted dichloropropanol is circularly sent into an alkali chamber of a bipolar membrane electrodialyzer to carry out bipolar membrane electrodialysis, and the recovered epichlorohydrin product and the by-products are respectively output.

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

The production system is preferably subjected to a conditioning operation in the course of conducting 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 may be operated in a batch manner or a continuous manner, and is not particularly limited.

Fig. 3 shows an embodiment of the process for the manufacture of epichlorohydrin according to the invention, which is 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 refining 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-chamber bipolar membrane electrodialyzer, and a membrane unit of the electrodialyzer contains an alkali chamber and an acid chamber. And a partition plate is arranged in the effluent liquid settling tank of the alkali chamber to divide the inner space of the effluent liquid settling tank of the alkali chamber into a first liquid phase area and a second liquid phase area. The refining unit comprises a rectifying tower.

When the system is operated, 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 is then passed into an extraction column of an extraction unit to contact the extractant, resulting in an extract enriched in dichlorohydrin, which is then passed into a flash column (not shown in FIG. 3) to separate the dichlorohydrin and recover the extractant. At least part of the recovered extractant is sent to the extraction tower for recycling. The separated dichloropropanol, water and additives enter a second liquid phase zone, so that an aqueous solution containing the dichloropropanol and the additives is obtained. The acid chamber effluent storage tank was filled with water. Starting a feeding output port of the alkali chamber and a feeding output port of the acid chamber of an acid chamber effluent storage tank, correspondingly starting a pump on a pipeline, respectively pumping aqueous solution containing dichloropropanol and additives and water into the alkali chamber and the acid chamber of the bipolar membrane electrodialyzer, establishing stable logistics circulation, 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 materials in the first liquid phase area exceeds the height of a partition plate. And carrying out sedimentation separation on the liquid phase remained in the first liquid phase region to obtain an organic phase rich in the epichlorohydrin, and outputting the organic phase through an output port of the organic phase. During the bipolar membrane electrodialysis, 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. In a continuous mode, whether the additive is supplemented or not can be determined according to the system loss in the system operation process, the additive can not be supplemented when the system loss is low, and the additive can be supplemented when the system loss is high.

And 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 propylene oxide products, glycerin and other byproducts, 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 as will be understood by those skilled in the art may be replaced by a three-compartment bipolar membrane electrodialyzer, such as the three-compartment bipolar membrane electrodialyzer described hereinbefore.

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

In the following examples and comparative examples, the bipolar membrane used was a homogeneous bipolar membrane (model BP-1) available from Hebei Guangzhou company, the anion-exchange membrane was an anion-exchange membrane (model AHA) available from Japan Asia Stoneley, and the cation-exchange membrane was a cation-exchange membrane (model CMX) available from Japan Asia Stoneley.

In the following examples and comparative examples, the composition of the obtained alkaline chamber effluent was analyzed by gas chromatography, on the basis of which the dichloropropanol conversion and the epichlorohydrin selectivity were calculated by the following formulae:

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 alkali chamber effluent storage tank, and is used to detect the pH value of the alkali chamber effluent.

Examples 1-26 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 (namely 1 standard atmospheric pressure). 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 and additives, wherein the concentration of the dichloropropanol in the aqueous solution was 20% by weight and the content of the sodium chloride was 10% by weight, as a raw material for the epoxidation step.

(2) Step of epoxidation reaction

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 carry out bipolar membrane electrodialysis in a batch manner, and the bipolar membrane electrodialyzer employed was a two-chamber bipolar membrane electrodialyzer having 10 membrane units as shown in fig. 1.

Feeding 2000g of aqueous solution containing dichloropropanol and an additive serving as a raw material into an effluent settling tank of an alkali chamber, and feeding 2000g of deionized water into an effluent storage tank of an acid chamber, wherein an alkali chamber effluent input port of the alkali chamber effluent settling tank is communicated with an alkali chamber effluent output port of a bipolar membrane electrodialyzer, and an alkali chamber feed output port of the alkali chamber effluent settling tank is communicated with an alkali chamber feed input 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 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 and additives 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 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 a water phase and an organic phase of an effluent liquid of the alkali chamber, and it is determined that the conversion rate of dichloropropanol is 99% and the selectivity of epichlorohydrin is 82%.

Example 2

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 1, except that the content of sodium chloride in the aqueous solution containing dichloropropanol and the additive as a raw material was 20 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 85% determined by calculation.

Example 3

Bipolar membrane electrodialysis was carried out to produce epichlorohydrin using the same method as in example 1, except that: in the aqueous solution containing dichloropropanol and the additive as the raw material, the concentration of sodium chloride was 25% by weight. 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 87% through calculation and determination.

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 aqueous solution containing dichloropropanol and the additive as the raw material was 5% by weight. 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 77% determined by calculation.

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 aqueous solution containing dichloropropanol and the additive 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 the dichloropropanol is 99% and the selectivity of the epichlorohydrin is 69% determined by calculation.

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 aqueous solution containing dichloropropanol and the additive as a 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 and additives, wherein the concentration of the dichloropropanol in the aqueous solution was 10 wt% and the content of the ammonium chloride was 18 wt%, as a raw material 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 cell effluent settling tank to partition the alkali cell effluent settling tank into a first liquid phase zone and a second liquid phase zone.

(2-1) feeding 2000g of an aqueous solution containing dichloropropanol and an additive 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 effluent 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 a polar liquid to the polar 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 and additives 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, 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 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, and determining that the conversion rate of the dichloropropanol is 97% and the selectivity of the epichlorohydrin is 83%.

Example 8

The bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 7, except that, during the bipolar membrane electrodialysis, the pH of the effluent of the base compartment was controlled to 10.0 by adjusting the amount of fresh dichloropropanol added. 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 to be 99%, and the selectivity of the epichlorohydrin is determined to be 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 determining 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, during the bipolar membrane electrodialysis, the pH of the effluent of the base compartment was controlled to 7.2 by adjusting the amount of fresh dichloropropanol added. After the bipolar membrane electrodialysis is finished, performing gas chromatography analysis on the effluent liquid of the alkali chamber, and determining 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 aqueous solution containing dichloropropanol and additives as a raw 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 determining that the conversion rate of dichloropropanol is 91% and the selectivity of 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 aqueous solution containing dichloropropanol and additives as a raw material was 3.5 wt%. After the bipolar membrane electrodialysis is finished, performing gas chromatography analysis on the effluent of the alkali chamber, and determining that the conversion rate of the dichloropropanol is 88% and the selectivity of the epichlorohydrin is 73%.

Comparative example 1

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 10, except that the aqueous solution containing dichloropropanol and the additive 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 to be 8.9%, and the selectivity of the epichlorohydrin is determined to be 65%.

Example 13

(1) Chlorohydrination reaction step

Dichloropropanol was produced in the same manner as in example 7, except that the aqueous solution containing dichloropropanol and the additive 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

This example carried out bipolar membrane electrodialysis in a batch mode 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 three-compartment bipolar membrane electrodialyzer having 10 membrane units as shown in FIG. 2.

Feeding 2000g of 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 effluent liquid 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 the salt chamber effluent liquid output port is communicated with the alkali chamber feed input port; 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 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, respectively feeding an aqueous solution containing dichloropropanol and an additive, water and polar liquid (wherein the salt chamber effluent is used as the alkali chamber feeding) into a salt chamber, an acid chamber and a polar 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 the temperature inside the membrane unit was controlled 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 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 84% through calculation and determination.

Example 14

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 13, except that the concentration of ammonium chloride in the aqueous solution containing dichloropropanol and the additive as a raw material was 18 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 it is determined that the conversion rate of dichloropropanol is 99% and the selectivity of epichlorohydrin is 87%.

Example 15

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 13, except that the concentration of ammonium chloride in the aqueous solution containing dichloropropanol and the additive as the raw material was 24% by weight. 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 90% through calculation and determination.

Example 16

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 13, except that the concentration of ammonium chloride in the aqueous solution containing dichloropropanol and the additive as a raw material was 6 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 80% through calculation and determination.

Example 17

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 13, except that the concentration of ammonium chloride in the aqueous solution containing dichloropropanol and the additive 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 18

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 13, except that the concentration of ammonium chloride in the aqueous solution containing dichloropropanol and the additive as the raw material was 0.1 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 68% through calculation and determination.

Example 19

(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 13, 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 an aqueous solution containing dichloropropanol and an additive, which is taken 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 input port of the alkali chamber effluent settling tank is communicated with an alkali chamber effluent output port of a bipolar membrane electrodialyzer, an alkali chamber feed output port of the alkali chamber effluent settling tank is communicated with a salt chamber feed input port of the bipolar membrane electrodialyzer, and the salt chamber effluent output port is communicated with the alkali chamber feed input port; 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 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 electrode liquid tank, respectively feeding an aqueous solution containing dichloropropanol and an additive, water and an electrode liquid (wherein the salt chamber effluent is used as the alkali chamber feeding) into a salt chamber, an acid chamber and an electrode chamber of the bipolar membrane electrodialyzer, and establishing a stable material input-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 1.4V 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, enabling overflow to enter 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 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. And (3) performing gas chromatography analysis on the effluent liquid of the alkali chamber, and determining that the conversion rate of the dichloropropanol is 87% and the selectivity of the epichlorohydrin is 85%.

Example 20

The bipolar membrane electrodialysis was carried out to produce epichlorohydrin by the same method as in example 19, except that, during the bipolar membrane electrodialysis, the pH of the alkaline chamber effluent was controlled to 7.4 by adjusting the amount of fresh dichloropropanol added. The effluent of the alkali chamber is analyzed by gas chromatography, and the conversion rate of the dichloropropanol is 84 percent and the selectivity of the epichlorohydrin is 90 percent.

Example 21

The bipolar membrane electrodialysis was carried out to produce epichlorohydrin by the same method as in example 19, except that, during the bipolar membrane electrodialysis, the pH of the alkaline chamber effluent 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 22

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 20, except that the content of potassium chloride in the aqueous solution containing dichloropropanol and the additive 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 23

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 20, except that the content of potassium chloride in the aqueous solution containing dichloropropanol and the additive as the raw material was 22% by weight. 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 24

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 20, except that the content of potassium chloride in the aqueous solution containing dichloropropanol and the additive 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 25

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 20, except that the content of potassium chloride in the aqueous solution containing dichloropropanol and the additive as the raw material was 3% by weight. The effluent of the alkali chamber is analyzed by gas chromatography, and the conversion rate of the dichloropropanol is 80 percent and the selectivity of the epichlorohydrin is 74 percent.

Example 26

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 20, except that the content of potassium chloride in the aqueous solution containing dichloropropanol and the additive as the raw material was 0.05 wt%. The effluent of the alkali chamber is analyzed by gas chromatography, and the conversion rate of the dichloropropanol is 78 percent and the selectivity of the epichlorohydrin is 72 percent.

Comparative example 2

Bipolar membrane electrodialysis was performed to produce epichlorohydrin by the same method as in example 20, except that the aqueous solution containing dichloropropanol and the additive as the raw 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 1-26 demonstrate that by using the process of the present invention to feed dichloropropanol into the alkaline compartment of a bipolar membrane electrodialyzer for bipolar membrane electrodialysis, not only can dichloropropanol be converted into epichlorohydrin, but also higher raw material conversion and product selectivity can be achieved. Meanwhile, according to the method disclosed by the invention, no solid waste residue is generated, no waste liquid is generated or basically generated, and the method is green and environment-friendly. In addition, the method of the invention does not need to distill the product out in the epoxidation reaction process, and 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 various technical features being combined 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 manufacturing epichlorohydrin, the process comprising:

(3) feeding an aqueous solution containing dichloropropanol and an additive into an alkali chamber of a bipolar membrane electrodialyzer, carrying out bipolar membrane electrodialysis in the presence of at least one additive to obtain an alkali chamber effluent containing epichlorohydrin, wherein the additive is one or more selected from 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, the content of the additive is 16-26 wt% based on the total amount of the additive, dichloropropanol and water entering the alkali chamber, the voltage applied to each membrane unit in the bipolar membrane electrodialysis is 0.5-2.5V,

The method also comprises an adjusting operation carried out in the bipolar membrane electrodialysis process, wherein the adjusting operation enables the pH value of the effluent of the alkali chamber to be 7-8.5;

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

2. The production process according to claim 1, wherein the separation of dichloropropanol from the dichloropropanol-rich extract comprises: distilling the extract liquor to obtain recovered chloropropene and dichloropropanol, and recycling at least part of recovered chloropropene as an extracting agent.

3. The production process according to claim 1 or 2, wherein the extractant is chloropropene.

4. The production process according to claim 1, wherein at least part of the gas phase stream is recycled for chlorohydrination reactions.

5. The production method according to claim 1, wherein the additive is one or more selected from the group consisting 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.

6. The production method according to claim 1, wherein the additive is one or two or more selected from the group consisting of sodium chloride, ammonium chloride and potassium chloride.

7. The production method according to any one of claims 1, 5 and 6, wherein in the bipolar membrane electrodialysis, a voltage of 1-2.1V is applied to each membrane unit.

8. The production method according to any one of claims 1, 5 and 6, wherein the bipolar membrane electrodialysis is performed at a temperature of 5-45 ℃.

9. The production process according to any one of claims 1, 5 and 6, wherein the bipolar membrane electrodialyzer comprises an anode, a cathode, and at least one membrane unit comprising a base compartment and an acid compartment, disposed between the anode and the cathode; or alternatively

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 acid chamber, an alkali chamber and a salt chamber, an output port of the salt chamber is communicated with an input port of the alkali chamber, and an aqueous solution containing dichloropropanol and an additive enters the alkali chamber from the salt chamber.

10. The production process according to any one of claims 1, 2 and 4 to 6, wherein the dichloropropanol content in the aqueous solution containing dichloropropanol and the additive is 1 to 80% by weight.

11. The production process according to claim 10, wherein the aqueous solution containing dichloropropanol and the additive has a dichloropropanol content of 5-50 wt%.

12. The production process according to any one of claims 1, 2 and 4 to 6, wherein the dichloropropanol is 1, 3-dichloro-2-propanol and/or 2, 3-dichloro-1-propanol.

13. 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.

14. The process according to any one of claims 1, 2, 4 to 6 and 13, wherein it further comprises refining the organic phase rich in epichlorohydrin to obtain an epichlorohydrin product.