WO2021129377A1

WO2021129377A1 - Method for treating byproduct hydrogen chloride in fluorine-containing olefin production process

Info

Publication number: WO2021129377A1
Application number: PCT/CN2020/134501
Authority: WO
Inventors: 李宏峰; 周黎旸; 万金儒; 徐晓波; 黄雪浩; 张伟
Original assignee: 李宏峰
Priority date: 2019-12-27
Filing date: 2020-12-08
Publication date: 2021-07-01
Also published as: CN111138384A

Abstract

A method for treating byproduct hydrogen chloride in a fluorine-containing olefin production process, comprising the following steps: (1) reacting hydrogen chloride with glycerol in fluorine-containing olefin cracking gas under the action of a catalyst so as to obtain a gas phase reaction product and a dichloropropanol crude product; (2) rectifying the dichloropropanol crude product obtained in step (1) to obtain dichloropropanol and a tower kettle liquid, and returning the tower kettle liquid to step (1) for continuous reaction; and (3) performing saponification and cyclization reactions on dichloropropanol obtained in step (2) and an inorganic alkali, performing neutralizing, water vapor distilling, condensing and layering on a reaction product, drying an obtained liquid phase, and performing reduced pressure distillation to obtain an epichlorohydrin product. The method has the advantages of being environmentally friendly and good in economic benefit.

Description

Method for treating by-product hydrogen chloride in fluorine-containing olefin production process

Technical field

The invention belongs to the technical field of environmental protection and petrochemical industry, and specifically relates to a method for treating by-product hydrogen chloride in the production process of fluorine-containing olefins.

Background technique

In industry, fluorinated olefins are mainly produced by cracking methods, and a large amount of by-product hydrogen chloride will be produced during the production process. For example, the production of tetrafluoroethylene adopts the difluoro-chloromethane cracking method, and the composition of the fluoroolefin cracking gas is complex, including a large amount of by-product hydrogen chloride, unreacted difluoro-chloromethane (HCFC-22), tetrafluoroethylene ( TFE), hexafluoropropylene (HFP), steam (if dry cracking does not contain steam), and hydrogen chloride must be sold after being converted into hydrochloric acid. The price of hydrochloric acid is low, especially when the hydrochloric acid contains a small amount of hydrofluoric acid. It can be sold after removing fluoride ions. At present, there are mainly tetrafluoroethylene steam cracking method and tetrafluoroethylene dry cracking method in the domestic production of tetrafluoroethylene by cracking of difluorochloromethane. Most of the domestic production of tetrafluoroethylene by the cracking of difluorochloromethane is the tetrafluoroethylene steam cracking method. The by-product hydrochloric acid is dilute hydrochloric acid, which needs to be concentrated before it can be sold. Therefore, the steam cracking of tetrafluoroethylene is produced The cost of hydrochloric acid treatment is higher than the cost required for tetrafluoroethylene dry cracking water to absorb hydrogen chloride to produce concentrated hydrochloric acid. Therefore, it is neither economical nor environmentally friendly to convert a large amount of by-product hydrogen chloride into hydrochloric acid and then sell it. It is urgent to find a green, economical and safe treatment method for the by-product hydrogen chloride in the tetrafluoroethylene production process.

Epichlorohydrin is an important fine chemical product and synthetic organism. It is widely used in chemical, light industry, medicine, electronic appliances and other industries. It is mainly used in the production of epoxy resin, adhesives, positive ion exchange resins and glass fiber reinforced plastics. Chlorohydrin rubber, insulation products, explosives, etc. At present, the production methods of epichlorohydrin include propylene high temperature chlorination method, propylene acetate method, glycerin method and so on. The first two methods are difficult to treat wastewater, high energy consumption, high investment cost, and are very dependent on petroleum resources. With the increasing scarcity of global crude oil resources, biodiesel renewable energy will continue to vigorously develop, which ensures the continuous increase in the supply of biodiesel by-product glycerin at home and abroad, and the price of glycerin is greatly reduced. The glycerin process has become epichlorohydrin production. The main development direction of technology.

In industry, glycerin and hydrogen chloride are reacted to produce dichloropropanol, which is then saponified with inorganic lye to produce epichlorohydrin. Therefore, there is no doubt that if the hydrogen chloride produced by the cracking of difluoromonochloromethane is directly reacted with glycerin to produce epichlorohydrin, it will be a very economical in-situ disposal of the by-product hydrogen chloride produced by tetrafluoroethylene, but it contains fluorine. The composition of olefin cracking gas is complex. In addition to hydrogen chloride, there are a large number of other products. When reacting with glycerol, the process is difficult to control.

Summary of the invention

The purpose of the present invention is to aim at the existing shortcomings and provide a method for treating the by-product hydrogen chloride in the production process of fluoroolefins with simple process, green environmental protection and good economic benefits.

In order to achieve the above-mentioned object, the technical solution adopted by the present invention is: a method for treating by-product hydrogen chloride in the production process of fluoroolefin, including the following steps:

(1) The hydrogen chloride and glycerin in the fluorine-containing olefin cracked gas are reacted under the action of a catalyst to obtain the gas phase reaction product and the crude dichloropropanol;

(2) The crude dichloropropanol obtained in step (1) is rectified to obtain dichloropropanol and tower still liquid, and the tower still liquid is returned to step (1) to continue the reaction;

(3) The dichloropropanol obtained in step (2) is subjected to a saponification and cyclization reaction with an inorganic base, the reaction product is neutralized, steam distilled, condensed, and layered, the liquid phase obtained is dried and then distilled under reduced pressure The epichlorohydrin product is obtained.

As a preferred embodiment of the present invention, the gas-phase reaction product described in step (1) can be condensed and then subjected to gas-liquid separation to obtain a gas phase and a liquid phase, and the gas phase is fed into the post-fluorine-containing olefin production system. The liquid phase is separated to obtain an inorganic phase and an organic phase, and the organic phase is returned to step (1) to continue the reaction.

As a preferred embodiment of the present invention, the temperature of the reaction in step (1) is 100-150°C, the pressure of the reaction is 0.1-0.3 MPa, and the reaction time is 5-30h, and the fluorine-containing olefin cracked gas The molar ratio of hydrogen chloride to glycerin is 2-8:1, and the amount of the catalyst is 3-20% of the molar amount of glycerol.

As a preferred embodiment of the present invention, the catalyst described in step (1) is one of acetic acid, propionic acid, succinic acid, adipic acid, sebacic acid, suberic acid, benzoic acid, and terephthalic acid . The catalyst is more preferably one of adipic acid, suberic acid and sebacic acid.

As a preferred embodiment of the present invention, the temperature of the saponification and cyclization reaction in step (3) is 40-80°C, the reaction time is 20-80s, and the molar ratio of the inorganic base to dichloropropanol is 0.5～1.4:1.

As a preferred embodiment of the present invention, the inorganic base described in step (3) is at least one of NaOH, Ca(OH) ₂ , KOH, Mg(OH) ₂ and Na ₂ CO ₃ . The inorganic base is more preferably Ca(OH) ₂ or NaOH.

As a preferred embodiment of the present invention, the fluorine-containing olefin cracked gas is a mixed gas produced by steam cracking of difluorochloromethane to produce tetrafluoroethylene or a mixed gas produced by dry cracking of difluorochloromethane to produce tetrafluoroethylene.

The method for treating the by-produced hydrogen chloride in the production process of fluorine-containing olefins of the present invention reacts hydrogen chloride in the fluorine-containing olefin cracking gas with glycerin to produce dichloropropanol, and then dichloropropanol is saponified and cyclized to produce epichlorohydrin . In actual production, the fluorine-containing olefin cracking gas can be continuously passed into the dichloropropanol reactor, such as a bubbling stirred reactor or a packed reaction tower. The dichloropropanol reactor can be pre-filled with glycerin and catalyst, or it can be combined with The fluorine-containing olefin cracking gas is introduced at the same time. The dichloropropanol reactor can be single or multiple, and the reaction will be more complete when multiple reactors are used for the reaction in series. Taking the bubbling packing reaction tower as an example, glycerin and catalyst flow in series from top to bottom in the reaction tower, and fluorine-containing olefin cracking gas is fed in parallel from the bottom of each reaction tower through a gas distributor, and glycerin and cracking Gas countercurrent contact reaction, the steam in the cracked gas, unreacted hydrogen chloride, product dichloropropanol, and a small amount of intermediate product monochloropropanediol are cooled from the upper outlet of the reaction tower through the condenser to the separation equipment such as gas-liquid/oil-water separator. The liquid is stratified in the gas-liquid/oil-water separator. The lower layer is mainly dichloropropanol and monochloropropanediol and returned to the bubbling packing reaction tower. The upper layer is an aqueous solution mainly composed of hydrochloric acid, which can be discharged continuously or intermittently. Difluorochloromethane, tetrafluoroethylene, hexafluoropropylene and other low-boiling substances in the fluoroolefin cracking gas enter the post-fluoroolefin production system through the upper outlet of the gas-liquid/oil-water separator. The crude difluoropropanol from the bottom of the reaction tower enters the rectification system to first extract a small amount of low boilers and water from the top of the tower, and then extract dichloropropanol, catalyst, unreacted glycerin, and intermediate monochloride from the top of the tower. Propanol can be returned to the bubbling packing reaction tower from the bottom of the rectification tower.

In the present invention, when the saponification and cyclization reaction produces epichlorohydrin, dichloropropanol removes one molecule of water under the action of lye to generate epichlorohydrin, and at the same time, epichlorohydrin and water are used to form an azeotrope at 85°C , Use steam to separate the product from the reaction system. In the saponification process, a slight excess of lye is enough, too much alkaline lye, epichlorohydrin is easily hydrolyzed into glycerol, and the cyclization time should not be too long to avoid excessive side reactions; Increasing the cyclization reaction temperature speeds up the evaporation rate of epichlorohydrin, which is beneficial to increase the yield of epichlorohydrin. The lye can be various inorganic alkali aqueous solutions, but from the viewpoint of economy and reaction effect, dilute sodium hydroxide aqueous solutions can be used, and milder calcium hydroxide aqueous solutions are more preferred.

The fluorine-containing olefin cracking gas applicable to the present invention may or may not contain water vapor. Take the use of steam to crack difluorochloromethane to produce tetrafluoroethylene as an example. The cracked gas contains a lot of water vapor. Since water can inhibit the reaction to a certain extent, the water can be removed in time through the gas-liquid/oil-water separator. Separate out. When dry cracking of difluorochloromethane is used, the cracked gas does not contain water vapor, and the other components are the same as the steam cracked gas, which is also applicable to the present invention.

The invention directly converts the hydrogen chloride in the fluorine-containing olefin cracking mixed gas into higher-value epichlorohydrin, instead of converting the hydrogen chloride in the fluorine-containing olefin production tail gas into hydrochloric acid for low price sale. Therefore, the present invention is a very economical and effective method for disposing of the by-product hydrogen chloride in the production of fluorine-containing olefins.

Compared with the prior art, the present invention has the following advantages:

1. Good economic benefits. The present invention directly converts the hydrogen chloride in the fluorine-containing olefin cracking mixed gas into higher-value epichlorohydrin, instead of converting the hydrogen chloride in the fluorine-containing olefin production tail gas into hydrochloric acid for low price. Significant economic benefits;

2. Green and environmental protection. The present invention directly converts the hydrogen chloride in the fluorine-containing olefin cracking mixed gas into higher-value epichlorohydrin, realizing the in-situ green environmental protection treatment of the by-product hydrogen chloride in the fluorine-containing olefin production process, and preparing dichloride The catalyst and unreacted glycerin in the propanol process can be returned to the reactor for recycling, further reducing costs and reducing the emissions of three wastes;

3. The yield and product purity are high. The highest yield for preparing dichloropropanol in the present invention can reach 93%, and the highest yield for preparing epichlorohydrin can reach 92%.

Detailed ways

Hereinafter, the present invention will be further described in detail through examples, but the present invention is not limited to these examples.

Example 1

(1) The mixed solution of 5kg glycerol and 238g adipic acid (accounting for 3% of the glycerol mole content) is added to the dichloropropanol reactor (single bubbling packing tower, packing 4x4mm polytetrafluoroethylene Pall ring) from the top ), and at the same time, at the bottom of the packed tower, pass the difluoro-chloromethane cracking gas (water-containing steam, wherein the mole content of hydrogen chloride is 17%) through the gas distributor at a flow rate of 18L/min to start the bubbling reaction, and control the reaction pressure to 0.1MPa. The reaction temperature is 110°C, the reaction time lasts for 20 hours, and the molar ratio of hydrogen chloride to glycerin in the difluorochloromethane cracked gas is 3:1. During the reaction, steam, hydrogen chloride, part of the product dichloropropanol, and a small amount of intermediate product monochloropropanediol are cooled from the top of the bubbling packing tower through the condenser to the gas-liquid/oil-water separator. After the liquid phase is stratified, the lower layer is mainly dichloride Propanol and monochloropropanediol are returned to the reaction tower, and the upper layer is an aqueous solution dominated by hydrochloric acid, which is released intermittently. Other low-boiling gases such as difluorochloromethane, tetrafluoroethylene, and hexafluoropropylene in the fluorine-containing olefin cracking gas enter the post-tetrafluoroethylene production system through the upper part of the gas-liquid/oil-water separator. After the reaction was completed, the bottom of the tower was discharged to obtain crude dichloropropanol. Sampling and analysis showed that the yield of dichloropropanol was 71% (based on glycerin).

(2) The crude dichloropropanol from the bottom of the bubbling packing tower enters the rectification tower. A small amount of low-boiling substances and water are first extracted from the top of the tower, and then dichloropropanol with a purity of 99.5% is obtained. The catalyst adipic acid and unreacted glycerin and monochloropropanediol are used to return the catalyst adipic acid, unreacted glycerin and monochloropropanediol to the dichloropropanol reactor.

(3) Add the dichloropropanol obtained in step (2) into the epichlorohydrin reactor, add 10wt% NaOH aqueous solution to react, the molar ratio of NaOH to dichloropropanol is 1.1, the reaction temperature is 50°C, and the reaction time After 30s, the reaction product was neutralized with hydrochloric acid and then steam distilled. The distillation temperature was controlled at 92°C. The mixed steam was condensed and separated into layers. After the lower layer was dried with anhydrous calcium chloride, the product was collected by distillation under reduced pressure. Sampling and analysis showed that the yield of epichlorohydrin was 75% (based on dichloropropanol).

Example 2

(1) After mixing glycerol and sebacic acid (8% of the glycerol molar amount), continuously add the dichloropropanol reactor from the upper part (a group of bubbling packing towers with three towers in series), and the mixture of glycerol and sebacic acid is from The top of the tower is sprayed down by a liquid distributor, while the difluoro-chloromethane cracking gas (water vapor, in which the mole content of hydrogen chloride is 17%) is respectively passed from the bottom of the three towers through the gas distributor to the countercurrent contact reaction with glycerin. The reaction temperature is 130℃, the reaction pressure is 0.2MPa, the reaction liquid material enters from the first bubble packing tower, and the third bubble packing tower exits. The reaction time lasts for 10 hours. The moles of hydrogen chloride and glycerin in the difluorochloromethane cracking gas The ratio is 8:1. During the reaction, steam, hydrogen chloride, part of the product dichloropropanol, and a small amount of intermediate product monochloropropanediol are cooled from the top of the reaction tower to the gas-liquid/oil-water separator through the condenser. After the liquid phase is separated, the lower layer is mainly dichloropropanol and The monochloropropanediol is returned to the reaction tower, and the upper layer is an aqueous solution dominated by hydrochloric acid, which is continuously released. Other low-boiling gases such as difluoromonochloromethane, tetrafluoroethylene, and hexafluoropropylene in the cracked gas enter the post-tetrafluoroethylene production system through the upper part of the gas-liquid/oil-water separator. The crude dichloropropanol was continuously produced from the outlet of the third bubbling packing tower, and sampling and analysis from the outlet of the third bubbling packing tower showed that the yield of dichloropropanol was 89%.

(2) The crude dichloropropanol from the outlet of the third bubbling packing tower enters the rectification tower. A small amount of low-boiling substances and water are first extracted from the top of the tower, and then 99.5% of dichloropropanol is obtained. The catalyst sebacic acid, unreacted glycerin and monochloropropanediol are obtained, and the catalyst sebacic acid, unreacted glycerin and monochloropropanediol are returned to the dichloropropanol reactor.

(3) Add the dichloropropanol obtained in step (2) into the epichlorohydrin reactor, add 20wt% Ca(OH) ₂ aqueous solution to react, the molar ratio of _{Ca(OH) 2 to dichloropropanol is} 0.65, reaction temperature 70°C, reaction time 60s, the reaction product was neutralized with hydrochloric acid and then steam distilled. The distillation temperature was controlled at 92°C. The mixed steam was condensed and separated into layers. The lower layer was dried with anhydrous calcium chloride and then decompressed. The product is collected by distillation. Sampling analysis showed that the yield of epichlorohydrin was 92% (based on dichloropropanol).

Example 3

(1) Mix 5kg of glycerol and 473g of suberic acid (5% of the molar amount of glycerol) into the dichloropropanol reactor (single bubbling stirred reactor), difluoromonochloromethane cracking gas (dry cracking gas) , Without water vapor, hydrogen chloride molar content is about 45%) through the bottom of the gas distributor bubbling and stirring, the pyrolysis gas flow rate is 9L/min, the stirring speed is 400 rpm, the control reaction temperature is 150℃, and the reaction pressure is 0.3 MPa, the reaction time lasts 30h, and the molar ratio of hydrogen chloride to glycerin in the difluoro-chloromethane cracked gas is 6:1. The steam, hydrogen chloride, part of the product dichloropropanol and a small amount of intermediate product monochloropropanediol produced during the reaction are cooled from the top of the reactor through the condenser to the gas-liquid/oil-water separator. After the liquid phase is stratified, the lower layer is mainly dichloride The propanol and monochloropropanediol are returned to the reaction kettle, and the upper layer is an aqueous solution mainly containing hydrochloric acid, which is discharged intermittently. Other low-boiling gases such as difluoromonochloromethane, tetrafluoroethylene, and hexafluoropropylene in the cracked gas enter the post-tetrafluoroethylene production system through the upper part of the gas-liquid/oil-water separator. After the reaction, the bottom of the kettle was discharged to obtain the crude dichloropropanol, and the yield of the dichloropropanol was 90%.

(2) The crude dichloropropanol from the outlet of the third bubbling packing tower enters the rectification tower. A small amount of low-boiling substances and water are first extracted from the top of the tower, and then 99.5% of dichloropropanol is obtained. The catalyst suberic acid, unreacted glycerin and monochloropropanediol are obtained, and the catalyst suberic acid, unreacted glycerin and monochloropropanediol are returned to the bubbling stirring reactor.

(3) Add the dichloropropanol obtained in step (2) into the epichlorohydrin reactor, add 20wt% Ca(OH) ₂ aqueous solution to react, the molar ratio of _{Ca(OH) 2 to dichloropropanol is} 0.7, reaction temperature 40°C, reaction time 80s, the reaction product is neutralized with hydrochloric acid and then steam distilled. The distillation temperature is controlled at 92°C. The mixed steam is condensed and separated into layers. The lower layer is dried with anhydrous calcium chloride and then decompressed. The product is collected by distillation. Sampling analysis showed that the yield of epichlorohydrin was 77% (based on dichloropropanol).

Example 4

(1) After mixing glycerol and sebacic acid (20% of the glycerol molar amount), add the dichloropropanol reactor (a group of bubbling packing towers in series with three towers) continuously from the upper part, and the mixture of glycerol and sebacic acid is from The top of the tower is sprayed down by a liquid distributor, while the difluoro-chloromethane cracking gas (water vapor, in which the mole content of hydrogen chloride is 17%) is respectively passed from the bottom of the three towers through the gas distributor to the countercurrent contact reaction with glycerin. The reaction temperature is controlled at 120℃, the reaction pressure is 0.2MPa, the reaction liquid material enters from the first bubble packing tower, and the third bubble packing tower exits. The reaction time lasts for 5h. The moles of hydrogen chloride and glycerin in the difluorochloromethane cracked gas The ratio is 8:1. During the reaction, steam, hydrogen chloride, part of the product dichloropropanol, and a small amount of intermediate product monochloropropanediol are cooled from the top of the reaction tower to the gas-liquid/oil-water separator through the condenser. After the liquid phase is separated, the lower layer is mainly dichloropropanol and The monochloropropanediol is returned to the reaction tower, and the upper layer is an aqueous solution dominated by hydrochloric acid, which is continuously released. Other low-boiling gases such as difluoromonochloromethane, tetrafluoroethylene, and hexafluoropropylene in the cracked gas enter the post-tetrafluoroethylene production system through the upper part of the gas-liquid/oil-water separator. The crude dichloropropanol was continuously produced from the outlet of the third bubbling packing tower, and sampling and analysis from the outlet of the third bubbling packing tower showed that the yield of dichloropropanol was 93%.

(3) Add the dichloropropanol obtained in step (2) into the epichlorohydrin reactor, add 20wt% Ca(OH) ₂ aqueous solution to react, the molar ratio of _{Ca(OH) 2 to dichloropropanol is} 0.65, reaction temperature 80°C, reaction time 60s, the reaction product was neutralized with hydrochloric acid and then steam distilled. The distillation temperature was controlled at 92°C. The mixed steam was condensed and separated into layers. The lower layer was dried with anhydrous calcium chloride and then decompressed. The product is collected by distillation. Sampling analysis showed that the yield of epichlorohydrin was 91% (based on dichloropropanol).

Claims

A method for treating by-product hydrogen chloride in the production process of fluorinated olefins, which is characterized in that it comprises the following steps:

(1) The hydrogen chloride and glycerin in the fluorine-containing olefin cracked gas are reacted under the action of a catalyst to obtain the gas phase reaction product and the crude dichloropropanol;

(2) The crude dichloropropanol obtained in step (1) is rectified to obtain dichloropropanol and tower still liquid, and the tower still liquid is returned to step (1) to continue the reaction;

(3) The dichloropropanol obtained in step (2) is subjected to a saponification and cyclization reaction with an inorganic base, the reaction product is neutralized, steam distilled, condensed, and layered, the liquid phase obtained is dried and then distilled under reduced pressure The epichlorohydrin product is obtained.
The method for treating by-product hydrogen chloride in the fluoroolefin production process according to claim 1, wherein the gas-phase reaction product in step (1) is condensed and then subjected to gas-liquid separation to obtain a gas phase and a liquid phase. Enter the post-production system of fluoroolefins.
The method for treating by-product hydrogen chloride in the production process of fluorine-containing olefins according to claim 2, characterized in that the liquid phase is separated to obtain an inorganic phase and an organic phase, and the organic phase is returned to step (1) to continue the reaction .
The method for treating by-product hydrogen chloride in the production of fluoroolefins according to claim 1, wherein the reaction temperature in step (1) is 100-150°C, and the reaction pressure is 0.1-0.3 MPa, The reaction time is 5-30h, the molar ratio of hydrogen chloride to glycerin in the fluorine-containing olefin cracked gas is 2-8:1, and the amount of the catalyst is 3-20% of the glycerol molar amount.
The method for treating by-product hydrogen chloride in the production process of fluorine-containing olefins according to claim 1, wherein the catalyst in step (1) is acetic acid, propionic acid, succinic acid, adipic acid, sebacic acid One of, suberic acid, benzoic acid and terephthalic acid.
The method for treating by-product hydrogen chloride in the production process of fluorine-containing olefins according to claim 5, wherein the catalyst is one of adipic acid, suberic acid and sebacic acid.
The method for treating by-product hydrogen chloride in the production of fluoroolefins according to claim 1, wherein the temperature of the saponification and cyclization reaction in step (3) is 40-80°C, and the reaction time is 20- 80s, the molar ratio of the inorganic base to dichloropropanol is 0.5-1.4:1.
The method for treating by-product hydrogen chloride in the production process of fluorine-containing olefins according to claim 1, wherein the inorganic base in step (3) is NaOH, Ca(OH) 2 , KOH, Mg(OH) 2 , At least one of Na 2 CO 3.
The method for treating by-product hydrogen chloride in the production process of fluorine-containing olefins according to claim 8, wherein the inorganic base is Ca(OH) 2 or NaOH.
The method for treating by-product hydrogen chloride in the production process of fluorine-containing olefins according to claim 1, wherein the fluorine-containing olefin cracking gas is a mixed gas of difluoro-chloromethane to produce tetrafluoroethylene through steam cracking or two Fluorine-chloromethane dry cracking to produce mixed gas of tetrafluoroethylene.