CN1583693A

CN1583693A - Treating method and apparatus for perfluoro-isobutene methanol absorbing liquid

Info

Publication number: CN1583693A
Application number: CN 200410024921
Authority: CN
Inventors: 应德雄; 粟小理
Original assignee: Shanghai 3F New Materials Co Ltd
Current assignee: Shanghai Huayi Sanaifu New Material Co ltd
Priority date: 2004-06-04
Filing date: 2004-06-04
Publication date: 2005-02-23
Anticipated expiration: 2024-06-04
Also published as: CN1250499C

Abstract

A process for treating the perfluoroisobuten methanol absorbing liquid includes such steps as pretreating by the aqueous solution of alkali, separating out supernatant, and reacting between the residual solution and the aqueous solution of alkal. Its equipment is composed of tubular treating apparatus, static separator, and coarse product tank.

Description

Method and equipment for treating perfluoroisobutylene methanol absorption liquid

Technical Field

The invention relates to a method for treating a perfluoroisobutylene methanol absorption liquid and equipment for treating the perfluoroisobutylene methanol absorption liquid.

Background

The pyrolysis process for producing tetrafluoroethylene and hexafluoropropylene (for example, the pyrolysis process of tetrafluoroethylene produces hexafluoropropylene) generates Perfluoroisobutylene (PFIB), which is a valuable chemical raw material, so how to effectively and comprehensively utilize perfluoroisobutylene is a common concern in the field of global fluorine chemical industry.

CF at position β in perfluoroisobutylene molecule₃The strong electron-withdrawing effect of the compound causes the electrophilicity of the C ═ C double bond to be greatly higher than that of perfluorobutene-1, perfluorobutene-2, hexafluoropropylene and tetra-butylenePerfluoroisobutylene has a large chemical activity and high toxicity because of the C ═ C double bond in the vinyl fluoride molecule (Lct)₅₀0.87mg min/L, ten times greater than phosgene), and is volatile (boiling point 6.4 ℃), odorless, and tasteless, and once leaked in the air, it is not easily detected. Perfluoroisobutylene belongs to pneumophilic virulent gas, and acute lung injury can be caused by the fact that a human body inhales the perfluoroisobutylene gas.

The high toxicity, difficult prevention and difficult cure of perfluoroisobutylene limit the direct utilization of perfluoroisobutylene. In order to improve the safety of the process of producing hexafluoropropylene by a tetrafluoroethylene pyrolysis method, in the prior art, a method for selectively absorbing perfluoroisobutylene by methanol is adopted to eliminate virulent perfluoroisobutylene in the process of producing hexafluoropropylene by the tetrafluoroethylene pyrolysis method. Therefore, the technology of comprehensively utilizing the perfluoroisobutylene is developed into the technology of comprehensively utilizing the perfluoroisobutylene methanol absorption liquid.

When a pyrolysis gas containing perfluoroisobutylene generated in hexafluoropropylene production by a tetrafluoroethylene pyrolysis method or a high boiling product of the pyrolysis gas containing perfluoroisobutylene is brought into contact with an excessive amount of methanol to react, a methanol mixed solution mainly containing octafluoroisobutyl methyl ether, heptafluoroisobutylene methyl ether (in a small amount), perfluoroolefin compounds, hydrogen fluoride and the like (which may further contain perfluoroisobutylene) is generated (hereinafter, collectively referred to as a perfluoroisobutylene methanol absorbent solution). The perfluoroisobutylene methanol absorption liquid has complex components, and the original absorption-dissolution balance can be destroyed along with the change of components and external conditions when the perfluoroisobutylene methanol absorption liquid is treated, so that toxic gas dissolved in the perfluoroisobutylene methanol absorption liquid is released. Therefore, the comprehensive utilization difficulty of the perfluoroisobutylene methanol absorption liquid is high, and the common treatment method is still incineration at present.

However, the existing incineration disposal has the great defects that firstly useful resources are wasted, secondly, waste gas generated by incineration needs to be treated again, and the tail gas and waste residues thereof still pollute the environment. Therefore, a comprehensive treatment method of the perfluoroisobutylene methanol absorption liquid is needed.

Heptafluoroisobutylene methyl ether is an important chemical raw material, and for example, it can be used for producing hexafluoroacetone, heptafluoroether, hexafluoroisobutylene and the like. In addition, the storage stability of heptafluoroisobutylene methyl ether is better than that of octafluoroisobutyl methyl ether.

Susumu Misaki discloses in Journal of Fluorine Chemistry (Journal of Fluorine Chemistry, 29(1985)471-474) a process for dehydrofluorination degradation of octafluoroisobutylmethyl ether to heptafluoroisobutylene methyl ether and 2-trifluoromethyl-3-methoxy-1-perfluoropropene in the presence of a base such as 25-50% potassium hydroxide according to the following chemical reaction scheme:

reaction conditions and results for removing hydrogen fluoride from compounds using liquid base

Kind of base	Amount of base used (relative to) At 1 mol of octafluoro Isobutyl methyl ether)	Reaction temperature Degree of rotation (℃)	Reaction time (hours)	Octafluoroisobutyl Methyl ether Conversion rate of (2)	Heptafluoroisobutyl Alkenyl methyl ethers Yield of (2)	2-trifluoromethyl- 3-methoxy-1- Process for producing perfluoropropene Yield of
Kind of base		Reaction temperature Degree of rotation (℃)	Reaction time (hours)	Octafluoroisobutyl Methyl ether Conversion rate of (2)	Heptafluoroisobutyl Alkenyl methyl ethers Yield of (2)		KOH	2	65-85	1.5	100	80.3	4.2
KOH	1.1	65-85	1.5	97.4	83.3	7.1	KOH	2	65-85	1.5	100	80.3	4.2
KOH	1.1	65-85	1.5	97.4	83.3	7.1	NaOH	1.1	65-85	1.8	86.1	77.7	3.2
Ca(OH)₂ +KOH	0.5 1.1	65-85	1.5	100	79.5	0.9	NaOH	1.1	65-85	1.8	86.1	77.7	3.2

Note: the concentration of alkali is 50%

Whereas Susumu Misaki discloses the dehydrofluorination of octafluoroisobutyl methyl ether to heptafluoroisobutylene methyl ether and 2-trifluoromethyl-3-methoxy-1-perfluoropropene in the presence of a base (e.g., 25-50% potassium hydroxide), several methods of treating perfluoroisobutylene methanol absorption solutions have been proposed in the art to obtain the important chemical feedstock, heptafluoroisobutylene methyl ether:

1) directly alkalizing perfluoroisobutylene methanol absorption liquid, and then distilling and separating;

2) directly distilling perfluoroisobutylene methanol absorption liquid, and intercepting the fraction with high content of octafluoroisobutyl methyl ether for alkalization to prepare heptafluoroisobutylene methyl ether;

3) the perfluoroisobutylene methanol absorption liquid is directly washed by water to remove a large amount of methanol, other water-soluble substances and fluoride gas, and then reacts with alkaline solution with the equivalent concentration of 25-50%.

However, these methods have drawbacks. For example,

method 1 a direct alkalization method was used, according to the method disclosed by Susumu Misaki, the concentration of the aqueous alkali solution used for alkalization should be 25-50%. If the methanol absorption solution is directly alkalized, the alkali can directly react with the hydrogen fluoride or the octafluoroisobutyl methyl ether in the methanol absorption solution, the heat release amount is large, and the reaction is difficult to control. In addition, since a high concentration (25 to 50% in equivalent concentration) of an aqueous alkali solution is used, the alkali solution itself is insufficient to dissolve the formed fluoride, and as a result, the fluoride is deposited on the wall of the reactor or distillation column, so that the reaction or distillation process cannot be continued;

the method 2 adopts a method of firstly distilling and separating and then alkalifying, and has the defects that the raw material with strong acidity (due to the dissolved hydrogen fluoride) seriously corrodes a distillation tower;

the method 3 adopts direct water washing of the perfluoroisobutylene methanol absorption solution to remove a large amount of methanol and other water-soluble substances and fluoride gas, and then the reaction is carried out with an alkaline solution with 25-50% of equivalent concentration. Since water washing produces a strongly acidic aqueous solution, this method requires high washing equipment, thereby increasing the cost of treatment.

Therefore, it is necessary to develop a method and a device for continuously and simply treating the perfluoroisobutylene methanol absorption liquid with different components and different phase states.

Disclosure of Invention

The invention aims to provide a method and equipment for continuously and simply treating perfluoroisobutylene methanol absorption liquid with different components and different phase states.

Therefore, the invention provides a method for treating a perfluoroisobutylene methanol absorption liquid, which comprises the following steps:

1) pretreating a perfluoroisobutylene methanol absorption liquid by using an alkaline water solution with the equivalent concentration of 1-25%;

2) separating and removing the supernatant liquid in which the fluoride, the methanol and other water-soluble substances formed by the reaction are dissolved;

3) reacting the lower layer solution separated in step 2) with an aqueous alkali solution of 25-50% of equivalent concentration.

The invention also provides equipment for treating the perfluoroisobutylene methanol absorption liquid, which comprises equipment (pretreatment equipment) for pretreating the perfluoroisobutylene methanol absorptionliquid by using an alkaline aqueous solution with the equivalent concentration of 1-25% to obtain a crude product of the octafluoroisobutyl methyl ether and equipment (pretreatment equipment) for treating the crude product by using an alkaline aqueous solution with the equivalent concentration of 25-50%, and is characterized in that the equipment (pretreatment equipment) for pretreating the perfluoroisobutylene methanol absorption liquid by using the alkaline aqueous solution with the equivalent concentration of 1-25% to obtain the crude product of the octafluoroisobutyl methyl ether comprises:

the tubular processor is provided with a lower part dilute alkali liquid inlet, a middle part perfluoroisobutylene methanol absorption liquid inlet, a lower part octafluoroisobutyl methyl ether crude product outlet, an upper part supernatant fluid overflow outlet and an upper part gas escape outlet.

The pretreatment equipment of the invention can also comprise a second static separator, the upper part of the second static separator is connected with the outlet of the octafluoroisobutyl methyl ether at the lower part of the tubular processor, and the lower part of the second static separator is connected with a crude product storage tank through a crude product pipeline.

Drawings

The invention is further described below with reference to the accompanying drawings. In the drawings:

FIG. 1 is a process flow diagram for treating a perfluoroisobutylene methanol absorption liquid;

FIG. 2 is a schematic diagram of a baffled agitator column used as a tube processor in a preferred embodiment of the present invention.

Detailed Description

Herein, unless otherwise specified, the concentrations of the aqueous alkali solutions are equivalent concentrations.

The method for treating the perfluoroisobutylene methanol absorption liquid to recover the target product of the heptafluoroisobutylene methyl ether mainly comprises the following three steps:

1. pretreatment of perfluoroisobutylene methanol absorption liquid with 1-25% equivalent concentration aqueous alkali

The purpose of pretreating the perfluoroisobutylene methanol-absorbed solution with a 1-25% equivalent concentration aqueous alkali solution is to remove as much as possible of impurities other than octafluoroisobutyl methyl ether and heptafluoroisobutylene methyl ether in the perfluoroisobutylene methanol-absorbed solution. After the aqueous alkali solution is added, the hydrogen fluoride dissolved in the perfluoroisobutylene methanol absorption liquid reacts with the alkali to form water-soluble fluoride. And since the added aqueous alkali solution is a dilute alkali solution containing a large amount of water, the water-soluble fluoride formed can be dissolved in the aqueous phase together with methanol. It follows that the concentration of aqueous alkaline solution added in this step should not be too high, otherwise the water content in the system is not sufficient to dissolve the fluoride formed in the aqueous phase, and the resulting fluoride precipitate can have an adverse effect on the subsequent reaction step.

The concentration of the alkali solution added in this step is not more than 25% at the most, preferably not more than 20% at the most, more preferably not more than 15% at the most.

In addition, under the action of alkali, part of olefin contained in the perfluoroisobutylene methanol absorption liquid is decomposed to form metal fluoride which enters a water phase, so that the content of impurity fluorine compounds is further reduced. In addition, the alkali also has the function of neutralizing acidic ions in the perfluoroisobutylene methanol absorption liquid so as to prevent the acidic ions from corroding equipment. Therefore, the concentration of the added aqueous alkali solution cannot be too low. The concentration of the alkali solution added in this step is at least 1%, preferably at least 3%, more preferably at least 5%.

The base suitable for use in the process of the present invention is not particularly limited as long as it is water-soluble and does not adversely affect the subsequent reaction step. In a preferred embodiment of the invention, the base may be selected from the group consisting of soluble bases formed from group IA or IIA elements of the periodic Table, or strong bases and weak acid salts, such as lithium hydroxide, potassium hydroxide, sodium hydroxide, barium hydroxide, sodium carbonate, potassium carbonate, and the like. Potassium hydroxide and potassium carbonate are preferably used because the final product potassium fluoride is highly soluble in water.

Without wishing to be bound by theory, the inventors believe that the following physico-chemical changes occur primarily when the perfluoroisobutylene methanol absorption solution is pretreated with a 1-25% equivalent concentration aqueous alkali:

1) hydrogen fluoride reacts exothermically with a base (such as potassium hydroxide) to produce potassium fluoride;

2) reacting a portion of the octafluoroisobutyl methyl ether with a base (e.g., potassium hydroxide) exothermically to form heptafluoroisobutyl methyl ether and potassium fluoride;

3) low boiling point fluoride gas partially dissolved in the perfluoroisobutylene methanol absorption liquid, namely perfluorobutene-1, perfluorobutene-2, perfluorobutadiene and perfluorocyclobutane (if the methanol pre-absorption process is also dissolved with hexafluoropropylene and tetrafluoroethylene) are desorbed due to the balance being destroyed and released in a gas form;

4) the methanol is extracted by water, and metal fluoride (such as potassium fluoride) is dissolved in water, and a small amount of octafluoroisobutyl methyl ether, heptafluoroisobutylene methyl ether and deeply defluorinated derivatives thereof are dissolved in water, so that wastewater containing organic fluorides such as octafluoroisobutyl methyl ether, heptafluoroisobutylene methyl ether and derivatives thereof, potassium fluoride, methanol and the like is formed.

In the present invention, the amount of the aqueous alkaline solution to be used relative to the perfluoroisobutylene methanol-absorbing liquid depends on the concentration of impurities other than octafluoroisobutyl methyl ether and heptafluoroisobutylene methyl ether in the methanol-absorbing liquid. The amount of aqueous base added can be readily determined by one of ordinary skill in the art based on the particular perfluoroisobutylene methanol absorption solution. In a preferred embodiment of the present invention, the weight feed ratio of the perfluoroisobutylene methanol-absorbing liquid to the aqueous alkali solution is 1: 0.5 to 12, preferably 1: 0.5 to 5, more preferably 1: 0.5 to 3.

In addition, as described above, after addition of a dilute alkali solution having an equivalent concentration of 1 to 25%, a portion of the octafluoroisobutyl methyl ether reacts exothermically with a base (e.g., potassium hydroxide) to form heptafluoroisobutyl methyl ether and potassium fluoride. If the reaction amount is too high, the temperature of the reaction system may rapidly rise. Therefore, in a preferred embodiment of the present invention, the temperature of the reaction system is controlled to 100 ℃ or lower, preferably 56 ℃ or lower, more preferably 30 ℃ or lower by, for example, cooling. The cooling method is not particularly limited, and a person of ordinary skill in the art can easily determine a suitable cooling method, for example, water cooling, air cooling, etc., according to his or her expert knowledge.

In addition, it is permissible to add some substances related to the system, such as potassium fluoride, organofluorine compounds, and the like, to the aqueous alkali solution. The existence of the substances is allowed, and the recycling of the process water is facilitated.

2. Separating and removing fluoride gas dissolved in the methanol absorption liquid, and supernatant liquid of potassium fluoride and methanol

Since the specific gravity of the crude octafluoroisobutyl methyl ether (containing a small amount of heptafluoroisobutylene methyl ether) is about 1.5, it is larger than that of the supernatant. Meanwhile, the crude product of the octafluoroisobutyl methyl ether (containing a small amount of heptafluoroisobutylene methyl ether) and the supernatant can hardly be mutually dissolved. Therefore, another feature of the present invention is to separate the supernatant containing impurities and the solution containing crude octafluoroisobutyl methyl ether by using the difference in specific gravity of the solutions. The separation step of the present invention is not particularly limited and may be any separation step known in the art. For example, a separatory funnel may be used to separate the two solutions. In the present invention, the term "supernatant" refers to the liquid in the upper part of the crude octafluoroisobutylmethyl ether (containing a small amount of heptafluoroisobutylmethyl ether) regardless of whether it is clear and transparent.

The crude octafluoroisobutyl methyl ether obtained can optionally be further purifiedto obtain a fine octafluoroisobutyl methyl ether product. The purification method may be a method well known in the art, and for example, a distillation method may be employed.

3. Reacting the separated organic phase with 25-50% of alkali aqueous solution

Such as Susumu Misaki inJournal of fluorine chemistry(Journal of Fluorine Chemistry, 29(1985)471-474) A method for dehydrofluorination of octafluoroisobutylmethyl ether to heptafluoroisobutylene methyl ether and 2-trifluoromethyl-3-methoxy-1-perfluoropropene in the presence of an aqueous alkali solution of 25-50% equivalent concentration, the chemical reaction formula of which is as follows:

the base used in this step may be selected from soluble bases formed from group IA or IIA elements of the periodic Table, or strong base weak acid salts, such as lithium hydroxide, potassium hydroxide, sodium hydroxide, barium hydroxide, sodium carbonate, potassium carbonate, and the like. The base may be the same as or different from the base used in step 1).

The reaction of the octafluoroisobutyl methyl ether to degrade into heptafluoroisobutylene methyl ether is an exothermic reaction, and therefore, it is necessary to control the reaction rate or to control the temperature of the reaction system using a cooling system, for example. One of ordinary skill in the art, after reading this disclosure, in combination with his or her expertise, can readily take appropriate measures to control the temperature of the reaction system.

The invention also provides equipment for the method for treating the perfluoroisobutylene methanol absorption liquid, which comprises equipment for pretreating the perfluoroisobutylene methanol absorption liquid by using an alkaline aqueous solution with the equivalent concentration of 1-25 percent to obtain a crude product of the octafluoroisobutyl methyl ether (hereinafter referred to as pretreatment equipment for short) and equipment for treating the crude product by using an alkaline solution with the equivalent concentration of 25-50 percent. As shown in figure 1, the equipment for pre-treating the perfluoroisobutylene methanol absorption liquid by using the alkaline water solution with the equivalent concentration of 1-25% to obtain the crude octafluoroisobutyl methyl ether comprises:

the tubular processor 1 is provided with a lower part dilute alkali liquid inlet 2, a middle part perfluoroisobutylene methanol absorption liquid inlet 3, a lower part octafluoroisobutyl methyl ether outlet 10 and an upper part supernatant fluid overflow outlet 6.

In a preferred embodiment of the invention, the apparatus comprises a second static separator 4, the upper part of which is connected to the outlet 10 for octafluoroisobutylmethyl ether in the lower part of the tube processor 1 and the lower part of which is connected to the crude storage tank 5 through a crude conduit 18.

In a preferred embodiment of the present invention, the pipe processor 1 further comprises a central return inlet 19; the pretreatment equipment also comprises a first static separator 9, the upper part of which is connected with the supernatant overflow outlet 6 at the upper part of the tubular processor 1, the middle part of which is connected with a wastewater storage tank 11 through a wastewater pipeline 17, and the lower part of which is connected with a middle return inlet 19 of the tubular processor 1 through a valve 16. The purpose of the first static separator 9 is to further separate and recover crude octafluoroisobutyl methyl ether entrained in the supernatant to be discarded, so as to improve the recovery efficiency of the product.

In another preferred embodiment of the invention, the tube processor 1 is further provided with an upper boiling gas outlet 8, and the pretreatment apparatus further comprises a condenser 7, the inlet of which is connected to the upper boiling gas outlet 8 of the tube processor 1. An off-gas outlet pipe 15 of the waste water storage tank 11 is connected with an inlet of the condenser 7. The purpose of the condenser 7 is to condense and recover the high temperature fraction entrained in the boiling gas, so as to improve the recovery of the product.

During operation, metered dilute alkali liquor enters the tubular reactor from the lower dilute alkali liquor inlet 2 of the tubular reactor 1 through the pipeline 13; metered perfluoroisobutylene methanol absorption liquid enters the tubular reactor 1 from a middle perfluoroisobutylene methanol absorption liquid inlet 3 of the tubular reactor through a pipeline 12. The perfluoroisobutylene methanol absorption liquid entering the tubular reactor generates the following processes under the action of dilute alkaline water:

1) since the compatibility of water with methanol is greater than that of octafluoroisobutylmethyl ether (containing a small amount of heptafluoroisobutylene methyl ether) with methanol, the methanol dissolved in octafluoroisobutylmethyl ether (containing a small amount of heptafluoroisobutylene methyl ether) can be extracted with water by micronizing the mixed liquid of octafluoroisobutylmethyl ether (containing a small amount of heptafluoroisobutylene methyl ether) -methanol under the action of strong dispersion such as a stirrer or the like. The specific gravity (1.5) of the crude octafluoroisobutyl methyl ether (containing a small amount of heptafluoroisobutylene methyl ether) is greater than that of the methanol-water solution, and the crude octafluoroisobutyl methyl ether naturally settles; enters the second static separator 4 via the lower octafluoroisobutylmethyl ether outlet 10. Along with the increase of the amount of the crude product entering the second static separator 4, the crude product of octafluoroisobutyl methyl ether accumulated in the static separator automatically enters an octafluoroisobutyl methyl ether crude product collecting tank (crude ether storage tank) 5 through a pipeline 18 under the action of static pressure;

2) the low boiling point (boiling point below normal temperature) fluoride (other than hydrogen fluoride) dissolved in octafluoroisobutyl methyl ether (containing a small amount of heptafluoroisobutylene methyl ether) will be released in the form of gas to form bubbles. The fluoride has good compatibility with the octafluoroisobutyl methyl ether, and the octafluoroisobutyl methyl ether with lower boiling point (bp 56 ℃) is easy to carry out. Therefore, the bubbles are made fine by a strong dispersing action of a stirrer or the like, and the octafluoroisobutylmethyl ether carried in the gas in the bubbles is brought into contact with water. Due to the effect of specific gravity, octafluoroisobutyl methyl ether in water precipitates and separates from other fluoride gases. In a preferred embodiment of the present invention, the remaining low boiling point (boiling point below room temperature) fluoride gas which is insoluble in water is introduced into a condenser 7 from an upper boiling gas outlet 8 of the tube processor 1, and after a part of the higher boiling point material is removed by the condenser, the resulting product is taken out of the system for treating the methanol absorbent solution of perfluoroisobutylene via a line 14. The gas which leaves can be further comprehensively utilized;

3) 1-25% of alkaline water reacts with hydrogen fluoride and part of octafluoroisobutyl methyl ether in an exothermic way, so that the temperature of the system rises, and octafluoroisobutyl methyl ether with low boiling point (bp 56 ℃) is volatilized, so that ina better embodiment of the invention, the system needs to be cooled and exhaust gas is condensed;

4) in order to improve the recovery rate of crude octafluoroisobutyl methyl ether, in a preferred embodiment of the present invention, wastewater containing methanol-potassium fluoride aqueous solution and a small amount of crude octafluoroisobutyl methyl ether and the like is made to overflow from the supernatant overflow port 6 at the upper part of the tubular reactor 1 to the first static separator 9, and further separated crude octafluoroisobutyl methyl ether is made to overflow into the wastewater storage tank 11 through the pipeline 17; when a certain amount of crude octafluoroisobutyl methyl ether has accumulated in the first static separator 9, the valve 16 in the lower part of the first static separator 9 is opened and the crude ether is returned to the pipestill 1.

FIG. 2 is a schematic representation of a preferred embodiment of a tube processor 1 according to the invention, which is a baffled agitator tower comprising a plurality of parallel paddles 30 rotating about a central axis and a plurality of parallel longitudinal baffles 31 extending radially from the tower wall. As shown in FIG. 2, the methanol absorption liquid enters the stirring tower through the inlet 3, and the dilute alkali solution enters the stirring tower through the inlet 2, and the methanol absorption liquid and the dilute alkali solution are mixed under the stirring action of the paddle 30. The longitudinal baffles 31 may enhance mass transfer and prolong the fluid path.

In a preferred embodiment of the invention, the aspect ratio of the tube processor is greater than 1, preferably greater than 5, and most preferably greater than 10. The tubular processor with large length-diameter ratio is beneficial to full contact of the methanol absorption liquid of the perfluoroisobutylene and the dilute alkaline water and full separation of the crude octafluoroisobutyl methyl ether and the supernatant;

the pipe processor of the present invention may be installed vertically, but it may be installed obliquely as long as it does not affect its reaction and separation effect. In a preferred embodiment of the invention, the length of the tube processor is angled, for example, from 30 to 150 °, preferably from 60 to 120 °, from horizontal. However, increasing the vertical length of the tube processor facilitates adequate separation of crude octafluoroisobutyl methyl ether from the supernatant.

THE ADVANTAGES OF THE PRESENT INVENTION

The invention can continuously and simultaneously carry out reaction, gas phase extraction, liquid phase extraction, gas-liquid separation and liquid-liquid separation integration on the perfluoroisobutylene methanol absorption liquid with different components and different phase states, thereby simplifying the treatment process and equipment;

the invention can continuously and hermetically treat the high-toxicity perfluoroisobutylene methanol absorption liquid, and separates out high-toxicity and low-boiling-point fluorides in the perfluoroisobutylene methanol absorption liquid to form tail gas, so that the separated out medium-toxicity octafluoroisobutyl methyl ether crude product can be further comprehensively utilized;

the invention utilizes the chemical principle to automatically separate and convey substances, saves manpower and energy and realizes the automatic production process with low energy consumption;

the invention uses two liquid reverse continuous full contact processes, greatly reduces the water usage amount and the wastewater discharge amount, and saves the wastewater treatment cost;

the invention uses the dilute alkali solution to continuously and fully contact the perfluoroisobutylene methanol absorption liquid for a long time, effectively removes the corrosive substance hydrogen fluoride in the perfluoroisobutylene methanol absorption liquid, prevents the hydrogen fluoride from corroding condensers, pipelines, reactors and the like of materials such as metal or glass lining and the like, widens the range of materials used by equipment, and greatly reduces the cost of implementation projects.

The present invention is further illustrated by the following examples.

Example 1

The pretreatment apparatus shown in FIG. 1 was used. The tubular processor used was a 316L stainless steel packed tower 2 meters long and 60 mm in inside diameter, loaded with 3X 3 316L stainless steel wound packing (packing loading 2.0 kg). The upper end of the stainless steel packed tower is provided with an upper boiling gas outlet 8 and an upper supernatant overflow outlet 6. The overflow outlet is connected with a first static separator 9 which is made of 316L stainless steel and is 0.5 meter long and 80 mm in inner diameter, and the middle lower part of the packed tower is provided with a feed inlet 19 which is connected with the discharge outlet of the first static separator 9 through a valve; the lower end of the packed tower is provided with a lower dilute alkali liquor inlet 2 and a lower octafluoroisobutyl methyl ether outlet 10; a lower octafluoroisobutyl methyl ether outlet 10 is connected with a 316L stainless steel second static separator with the length of 0.5 meter and the inner diameter of 80 millimeters; there is an inlet 3 for methanol absorption liquid at the length 1/2 of the packed column tube.

Introducing a potassium carbonate solution with the equivalent concentration of 10% into a dilute alkali liquor inlet 2 at the lower part of the packed tower; the perfluoroisobutylene methanol absorption liquid is introduced into the methanol absorption liquid inlet 3 at the position 1/2 of the length of the tube. The condenser is filled with cold water with the temperature of 0-5 ℃. When the weight ratio of the potassium hydroxide solution with the equivalent concentration of 10% to the absorption liquid of the perfluoroisobutylene methanol is 1.2: 1, the crude octafluoroisobutyl methyl ether is automatically discharged from the second static separator, and the content analysis condition of the crude octafluoroisobutyl methyl ether is 68% of the octafluoroisobutyl methyl ether, 10% of the heptafluoroisobutylene methyl ether and 0.9% of the methanol.

When the first static separator is visually observed to have liquid stratification, the lower valve of the first static separator is opened and the lower liquid is returned to the pipe processor.

After running for a period of time, the tubular processor is opened, and no fluoride deposition or obvious corrosion phenomenon is found on the tube wall.

Example 2

The packed column of example 1 was replaced with a flap agitator column of the configuration of fig. 2. The paddle type stirring is used, the length of the paddle is 17mm, the width of the paddle is 10mm, and the rotating speed is 300 r/m. The content analysis conditions of the crude octafluoroisobutyl methyl ether are 66 percent of octafluoroisobutyl methyl ether, 12 percent of heptafluoroisobutylene methyl ether and 0.3 percent of methanol.

When the liquid stratification phenomenon in the first static separator is observed by naked eyes, a lower valve of the first static separator is opened, and the lower liquid is returned to the tubular processor.

After running for a period of time, the tubular processor is opened, and no fluoride deposition or obvious corrosion phenomenon is found on the tubewall.

Example 3

In the same manner as in example 1 except that the alkali solution added was a potassium hydroxide solution having a concentration of 1% by weight, which was 10 times that of example 1, the crude octafluoroisobutyl methyl ether was automatically discharged from the second static separator and analyzed in terms of the contents of 70% octafluoroisobutyl methyl ether, 8% heptafluoroisobutyl methyl ether and 0.7% methanol.

Example 4

The same procedure as in example 2 was followed, except that the alkali solution was 25% strength by weight potassium carbonate solution and the weight feed ratio of the aqueous alkali solution to the methanol-absorbed solution was 3: 1.

Comparative example 1

1050 g of perfluoroisobutylene methanol absorption liquid is introduced into a 2000ml three-necked flask with a stirrer and a condenser, and the condenser tube is cooled by water at 0-3 ℃. 200 g of 85% solid KOH is put into a three-neck flask in batches, the reaction temperature is controlled to be 20-25 ℃, the reaction is continued for 5 hours, and 330 g of gas phase is lost.

The reaction solution was poured into a 2000ml distillation flask and distilled to obtain 150 g of heptafluoroisobutylene methyl ether having a purity (chromatography) of 91%, 450 g of a front fraction, a yellowish white solid adhered to the wall of the distillation flask and a large amount of water was required to rinse off the yellow white solid, thereby producing a large amount of F-containing substance^-The methanol wastewater.

Comparative example 2

Repeating the above experiment, washing the reaction solution with 6 times of water for three times, separating the lower layer solution each time, and washing the upper layer solution containing F^-The methanol wastewater. The lower layer was dried over anhydrous magnesium sulfate and distilled in a distillation flask to obtain 190 g of heptafluoroisobutylene methyl ether having a purity of 91.5%, wherein the front cut was 350 g, and almost no solid matter but a residual liquid was contained in the distillation flask.

Comparative example 3

Introducing 1000 g of perfluoroisobutylene methanol absorption liquid into a 2000ml distillation flask for direct distillation, and distilling by using water with the temperature of 0-3 ℃ as cooling water to obtain:

fraction at 20-50 ℃ of 150 g

520 g of fraction at 51-65 DEG C

Fraction at 66-80 ℃ of 100 g

20 g of residual liquid

Loss of 210 grams

The material was found to be very corrosive to the distillation equipment.

300 g of 50% KOH solution was charged into a 1000 three-necked flask equipped with 520 g (51-65 ℃ cut) equipped with a stirrer and a condenser, and the condenser tube was cooled with water at 0-3 ℃. The reaction is carried out for 2 hours at 54 ℃, the reaction solution can not be separated, more than 2 times of water is needed to be added to separate out an organic phase, and the organic phase is washed twice by 4 times of water to obtain 350 g of a crude product of the heptafluoroisobutylene methyl ether, and the chromatographic analysis shows that the heptafluoroisobutylene methyl ether is 64 percent and the octafluoroisobutyl methyl ether is 14 percent.

Comparative example 4

The procedure of comparative example 3 was repeated, but KOH was changed to NaOH to produce NaF having low solubility after the reaction, resulting in that NaF fine particles were mixed with the underlying liquid and were difficult to separate from each other, and it was necessary to dissolve NaF by ten times or more of water, thereby generating a large amount of F-containing solution^-The methanol wastewater.

Comparative example 5

1000 g of perfluoroisobutylene methanol absorption liquid is added into a 2000ml three-necked bottle (the loss of materials exists), 600 g of 50 percent KOH solution is added, the reaction is carried out for 3 hours at 54 ℃, 3 times of water is added after the reaction is finished, and 420 g of lower organic phase can be separated. But the lower layer still contains about 14% of unconverted octafluoroisobutyl methyl ether and 1% of methanol.

Comparative example 6

Introducing 1000 g of perfluoroisobutylene methanol absorption liquid into a 2000ml three-neck flask which is filled with 2 times of water and is provided with a stirrer and a condenser within 2 hours, cooling a condenser pipe by using water with the temperature of 0-3 ℃, and controlling the mixing temperature to be below 15-20 ℃. 510 g of a lower layer liquid is separated, wherein the lower layer liquid contains 70% of octafluoroisobutyl methyl ether, 5% of heptafluoroisobutylene methyl ether, 1.9% of methanol and other fluorine-containing compounds. However, both liquids were found to be acidic and the glass flask corroded.

Comparative example 7

1000 g of perfluoroisobutylene methanol absorption solution was introduced into a 2000ml three-necked flask containing 1000 g of 20% wt KOH solution, a water-cooled equilibrium condenser tube at 0 to 3 ℃ was cooled, and the evolved gas was collected by a-78 ℃ cold well. Controlling the mixing temperature below 15 ℃, and adding the perfluoroisobutylene methanol absorption liquid after 2 hours. Stirring for 2 hours, standing for 2 hours, and separating the lower layer liquid. Then, 3 times of water was added thereto and the mixture was washed twice to obtain 513 g of a lower layer solution. Wherein the content of octafluoroisobutyl ether is 48.8%, the content of heptafluoroisobutylene methyl ether is 37.9%, and the content of methanol is 1.3%. 279 g of volatile material was collected in the cold well.

Claims

1. A method for treating perfluoroisobutylene methanol absorption liquid comprises the following steps:

2. The process according to claim 1, characterized in that in step 1) an aqueous alkali solution with an equivalent concentration of 3 to 20% is added; preferably, in step 1), an aqueous alkali solution having an equivalent concentration of 5 to 15% is added.

3. The process according to any one of claims 1-2, wherein the base added in step 1) and step 3) is the same or different and is selected from the group consisting of soluble bases formed from elements of group IA or IIA of the periodic table, or salts of strong bases and weak acids.

4. The process according to any one of claims 1 to 2, wherein in step 1), the weight feed ratio of the perfluoroisobutylene methanol-absorbing liquid to the aqueous alkali solution is 1: 0.5 to 12; preferably 1: 0.5-3.

5. A process according to claim 3, characterised in that the base is selected from lithium hydroxide, potassium hydroxide, sodium hydroxide, barium hydroxide, sodium carbonate, potassium carbonate.

6. An apparatus for use in the method of claim 1, comprising a pretreatment apparatus and an apparatus for treating said crude product with an alkaline solution having an equivalent concentration of 25 to 50%, wherein said pretreatment apparatus comprises:

the tubular processor (1) is provided with a lower part dilute alkali liquid inlet (2), a middle part perfluoroisobutylene methanol absorption liquid inlet (3), a lower part octafluoroisobutyl methyl ether outlet (10) and an upper part supernatant overflow outlet (6).

7. The apparatus according to claim 6, characterized in that it further comprises a second static separator (4) connected at its upper part to the outlet (10) for the octafluoroisobutylmethyl ether in the lower part of the tube processor (1) and at its lower part to the crude storage tank (5) through a crude conduit (19).

8. The apparatus according to claim 6 or 7, characterized in that the pipe processor (1) further comprises a central return inlet (20); the pretreatment equipment also comprises a first static separator (9), the upper part of the first static separator is connected with an upper supernatant overflow outlet (6) of the tubular processor (1), the middle part of the first static separator is connected with a wastewater storage tank (11) through a wastewater pipeline (18), and the lower part of the first static separator is connected with a middle reflux inlet (20) of the tubular processor (1) through a valve (17).

9. The plant as claimed in claim 6 or 7, characterized in that the tube processor (1) is further provided with an upper boiling gas outlet (8), and the pretreatment plant further comprises a condenser (7) whose inlet is connected to the upper boiling gas outlet (8) of the tube processor (1) and whose outlet is connected via a line (14) to an inlet line (15) of the waste water reservoir (11) and to a tail gas outlet line (16).

10. The apparatus according to claim 6 or 7, characterized in that the tube processor (1) comprises a baffled agitator tower comprising a plurality of mutually parallel blades (30) rotating about a central axis and a plurality of mutually parallel longitudinal baffles (31) extending radially on the tower wall.

11. The apparatus according to claim 6 or 7, characterized in that the length to diameter ratio of the tube processor (1) is greater than 1; preferably greater than 10.

12. A tubular processor is provided with a lower dilute alkali liquid inlet (2), a middle perfluoroisobutylene methanol absorption liquid inlet (3), a lower octafluoroisobutyl methyl ether outlet (10) and an upper supernatant liquid overflow outlet (6), and also comprises a plurality of mutually parallel blades (30) rotating around a central shaft and a plurality of mutually parallel longitudinal baffles (31) radially extending on the tower wall.