JP2000128522A - Removing method and recovering method of boron trifluoride using lithium fluoride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing boron trifluoride from fluid containing boron trifluoride or the complex with high efficiency by a means economical and free from the generation of environmental pollution and a method for recovering re-utilizable boron trifluoride. SOLUTION: In this removing method of boron trifluoride, the fluid containing boron trifluoride or the complex is allowed to contact with lithium fluoride at <=160 deg.C. The recovering method of boron trifluoride is for obtaining boron trifluoride and lithium fluoride by heating tetra fluoroboric acid lithium salt produced by the removing method to 100-600 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for selectively separating and removing boron trifluoride from a fluid containing boron trifluoride or a complex thereof, and a method for recovering the same. Boride can be reused.

[0002]

2. Description of the Related Art Boron trifluoride or a boron trifluoride complex comprising a boron trifluoride and a complexing agent (also called a ligand) is used for various chemical reactions such as alkylation, isomerization, polymerization, decomposition, dehydration and the like. It is widely used industrially as a catalyst in reactions. These catalysts are used alone or in a form in which various complexing agents are coordinated with boron trifluoride at an appropriate ratio depending on the reaction to be treated.

After completion of these reactions using boron trifluoride or its complex catalyst, it is necessary to deactivate the boron trifluoride. For this purpose, usually, after neutralization with an aqueous solution of a basic substance such as ammonia, caustic soda and lime,
The method of washing with water is adopted. However, since the neutralization and washing processes discharge wastewater containing alkali and fluoride, which is a neutralized product of boron trifluoride, take measures to remove them in consideration of environmental pollution in recent years. Is desired. In addition, because boron trifluoride is expensive,
It is economically advantageous to recover and reuse the removed boron trifluoride, and several proposals have conventionally been made from the viewpoint of removal and recovery and reuse.

[0004] For example, a method is known in which a product of an oligomerization reaction is brought into contact with silica to remove boron trifluoride contained therein. Morgenson et al. U.S. Pat.
No. 9,177, and Madgavkar et al., US Pat.
No. 3,001 and U.S. Pat. No. 4,308,414 also use silica as an absorbent for absorbing boron trifluoride after the oligomerization reaction. Madgavkar
U.S. Pat. No. 4,394,296 discloses the use of hydrous silica as a cocatalyst with boron trifluoride as a catalyst in an oligomerization process, followed by filtration and recycling of the silica.

[0005] However, according to experiments performed by the present inventors,
When silica was used, it was found that boron trifluoride once adsorbed was decomposed at the time of separation, and it was difficult to recover it as boron trifluoride. Therefore, it is difficult to separate and collect boron trifluoride using silica and to repeatedly use it.

As another method for removing boron trifluoride, Tycer et al., US Pat. No. 4,981,578, disclose the oligomer product stream in solid or aqueous KF, NaF.
Alternatively, a method of removing boron trifluoride by contact with NH ₄ F is disclosed.

[0007] All of these methods are only intended to remove boron trifluoride from the product stream, and are not intended to recover reusable boron trifluoride. In addition, the ability to absorb boron trifluoride is not always sufficient. The above KF, Na
Sodium tetrafluoroborate (NaBF ₄ ) and potassium salts produced by reacting with boron trifluoride when recovering and reusing by a method of removing boron trifluoride using F or NH ₄ F (KBF ₄ ) has a high thermal decomposition temperature of 650 ° C. or higher and 750 ° C. or higher, respectively. In order to recover boron trifluoride, these must be thermally decomposed, and practical application is difficult in view of the energy cost for heating. Further, NH ₄ F itself is very unstable to heat, and may be decomposed into NH ₃ and HF even at the stage of adsorbing boron trifluoride. Therefore, the above KF, NaF or NH ₄
It is extremely difficult to implement a method of removing boron trifluoride using F.

As in the prior art described above, several methods for extracting boron trifluoride from a production process using boron trifluoride or a complex thereof have been proposed and much effort has been made to develop them. Is understood. However, a method of recovering reusable boron trifluoride by means that is economical and does not cause environmental pollution has not been proposed so far.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to convert expensive and harmful boron trifluoride from a fluid containing boron trifluoride or its complex by means of an economical and environmentally friendly means. Moreover, it is an object of the present invention to provide a method of removing boron trifluoride with high efficiency and a method of recovering reusable boron trifluoride.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above-mentioned object, and as a result, have been able to remove boron trifluoride from a fluid containing boron trifluoride or a complex thereof, and further reuse the fluid. The inventors have found an epoch-making method for recovering a suitable boron trifluoride, and have completed the present invention. That is, the first aspect of the present invention is to form a fluid containing boron trifluoride or a boron trifluoride complex at a temperature of 160 ° C. or lower by lithium fluoride (L
iF) and a method for removing boron trifluoride. The second aspect of the present invention relates to the method for removing boron trifluoride according to the first aspect of the present invention, wherein the contact temperature is 100 ° C. or lower. A sixth aspect of the present invention relates to a method for recovering boron trifluoride comprising the following steps. (Step 1) a step of bringing a fluid containing boron trifluoride or a boron trifluoride complex into contact with lithium fluoride at a temperature of 160 ° C. or lower, and (Step 2) a lithium tetrafluoroborate salt produced in Step 1 ( LiBF ₄ ) in a temperature range of 100 to 600 ° C. to obtain boron trifluoride and lithium fluoride. A seventh aspect of the present invention is the sixth aspect of the present invention, wherein the heating temperature of the lithium tetrafluoroborate salt in Step 2 is 160
The present invention relates to a method for recovering boron trifluoride at a temperature in the range of ~ 500 ° C. An eighth aspect of the present invention is the sixth aspect of the present invention, wherein the step 1
And a contact temperature of 100 ° C. or lower. Third and ninth aspects of the present invention are the boron trifluoride complex according to the first and sixth aspects of the present invention, wherein the boron trifluoride complex is a complex formed of boron trifluoride and an organic or inorganic polar compound. And a method for recovering boron trifluoride. Fourth and tenth aspects of the present invention are the third and ninth aspects of the present invention, wherein the organic or inorganic polar compound is selected from oxygen-containing compounds, nitrogen-containing compounds, sulfur-containing compounds, phosphorus-containing compounds, and inorganic acids. The present invention relates to a method for removing boron trifluoride and a method for recovering boron trifluoride. Fifth and eleventh aspects of the invention are the fourth and tenth aspects of the invention, wherein the oxygen-containing compound is water, alcohols, ethers,
Phenols, ketones, aldehydes, esters,
The present invention relates to a method for removing boron trifluoride selected from organic acids and acid anhydrides and a method for recovering boron trifluoride. According to the method of the present invention, by using lithium fluoride as an adsorbent for boron trifluoride, boron trifluoride can be selectively adsorbed and separated with high efficiency even in the form of a complex. Since boron can be desorbed and recovered with high efficiency and high purity without decomposing boron trifluoride, boron trifluoride can be effectively reused.

Hereinafter, the present invention will be further described. Boron trifluoride or boron trifluoride complex composed of boron trifluoride and complexing agent, AlCl _3, FeCl ₃ as catalysis, is classified into a so-called Friedel-Crafts catalyst containing sulfuric acid, AlCl _3, It is known that it exhibits excellent catalytic performance in that it has an effect of suppressing side reactions other than the main reaction as compared with FeCl ₃ , sulfuric acid and the like. Therefore, boron trifluoride and its various complexes, alkylation, isomerization,
It is widely used industrially as a catalyst in various chemical reactions such as polymerization, decomposition and dehydration.

For example, boron trifluoride has been used in the production of ethylbenzene from ethylene and benzene obtained from naphtha crackers by gas phase alkylation. Similarly, the production of alkylbenzenes, which have a large market for applications such as synthetic detergents and antioxidants, is carried out by liquid-phase alkylation of lower olefins and aromatics. Boron trifluoride or its complexes have been used. A low molecular weight hydrocarbon resin obtained by polymerizing a C ₉ aromatic olefin fraction and a C ₅ diolefin fraction from naphtha crackers singly or in combination with an acid catalyst is generally called a petroleum resin, Agent,
Widely used in fields such as printing inks. Boron trifluoride or a complex thereof is also widely used industrially as a polymerization catalyst during the production of this resin. In addition, boron trifluoride or a complex thereof is also used in the synthesis of terracol, which is an intermediate when producing spandex of synthetic fibers. As described above, boron trifluoride or a complex thereof is used for a variety of applications as a production catalyst in the chemical industry, but is also widely used in the fields of medicine, semiconductors, and the like.

In the above-mentioned reaction such as alkylation, a fluid as a reaction mixture containing boron trifluoride or a complex thereof flows out of the reaction step after the reaction. A typical example of the fluid containing boron trifluoride or its complex used in the present invention is a fluid flowing out of a production process using boron trifluoride or its complex as a catalyst as described above. In general, the fluid is composed of a liquid or gas that does not form a complex with boron trifluoride, and as long as it does not form a complex, air, a gas such as nitrogen, an organic compound such as a hydrocarbon, alcohol, ether, ketone, ester, etc. Liquids or vapors thereof can be used. In this fluid, boron trifluoride, its complex and possibly both are present in the form of a solution or dispersion. However, if a fluid that dissolves lithium fluoride or lithium tetrafluoroborate (a reaction product of lithium fluoride and boron trifluoride) used in the step of removing and absorbing boron trifluoride is used, the above-described adsorption step can be performed. It is not preferable because it becomes difficult to perform. Specific examples of the fluid that is not suitable in the present invention include a fluid composed of an ammonium salt or hydrofluoric acid or a fluid containing these fluids.

As the object of the treatment of the present invention, a fluid containing a boron trifluoride complex can be used in addition to a fluid containing boron trifluoride itself. And, even with a complex, it is possible to selectively adsorb only boron trifluoride by treating according to the method of the present invention.
Therefore, examples of the fluid that can be a target of the treatment of the present invention include, for example, an organic liquid mixture in which boron trifluoride or a complex thereof is dispersed or dissolved in an organic liquid, An organic liquid mixture in which the vapor of boron or its complex is dissolved or dispersed,
Alternatively, a mixed gas containing a vapor of boron trifluoride or a complex thereof in a gas, for example, an exhaust gas, or the like can be given.

As the complexing agent for forming a boron trifluoride-based complex suitable for the present invention, specific polar compounds, for example, alcohols, ethers, phenols, ketones, aldehydes, esters Organic or inorganic polar compounds such as organic compounds, oxygen-containing compounds such as acid anhydrides, nitrogen-containing compounds, sulfur-containing compounds, phosphorus-containing compounds and inorganic acids.

Specifically, the alcohols include aromatic or C _{1 to} C ₂₀ aliphatic alcohols.
The C ₁ -C ₂₀ carbon skeleton may be a linear alkyl group or a branched alkyl group, an n-, sec- or tert-alkyl group or an alicyclic alkyl group, or an alkyl group containing an alicyclic ring. No problem. More specifically, examples include, but are not limited to, methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, benzyl alcohol, and cyclohexanol. Further, polyhydric alcohols such as diol and triol may be used.

As ethers, aromatic or C ₁
Ether is used having an aliphatic hydrocarbon group -C _20, carbon skeleton of the C ₁ -C ₂₀ may be either branched alkyl group with a straight chain alkyl group, n-, sec-or tert-
An alkyl group or an alicyclic alkyl group, or an alkyl group containing an alicyclic ring may be used. Specifically, dimethyl ether, diethyl ether, methyl ethyl ether, dipropyl ether, methyl propyl ether,
Ethyl propyl ether, dibutyl ether, methyl butyl ether, ethyl butyl ether, propyl butyl ether, dipentyl ether, or phenyl methyl ether, phenyl ethyl ether, diphenyl ether, cyclohexyl methyl ether, cyclohexyl ethyl ether, and the like.

As the phenols, 1-3 phenols are suitable, and specifically, phenol, cresol and the like are preferable.

Ketones include aromatic or C ₁ -C ₆
Ketones having a hydrocarbon group of C _{1 to} C ₆
May be a linear alkyl group or a branched alkyl group, and may be an n-, sec- or tert-alkyl group, an alicyclic alkyl group, or an alkyl group containing an alicyclic ring. Specifically, methyl ethyl ketone,
Examples thereof include diethyl ketone, methyl butyl ketone, and cyclohexanone.

As the esters, aromatic or C ₁
~ C ₆ aliphatic alcohol component and aromatic or C ₁
That form an ester bond with an aliphatic carboxylic acid or phosphoric acid component -C ₆ is used, the C ₁ -C ₆
May be a linear alkyl group or a branched alkyl group, and may be an n-, sec- or tert-alkyl group, an alicyclic alkyl group, or an alkyl group containing an alicyclic ring. Specifically, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate, hexyl acetate, ethyl hexanoate,
Ethyl benzoate and the like, and complete esters of phosphoric acid such as tributyl phosphate and the like can be mentioned.

The organic acids are aromatic or C _1-
C ₆ aliphatic carboxylic acids, their halogen-substituted products,
Phosphoric acid or a partial ester of phosphoric acid and an aromatic or C _{1 to} C ₆ aliphatic alcohol component is used, and the C _{1 to} C ₆ carbon skeleton may be a linear alkyl group or a branched alkyl group. , An n-, sec- or tert-alkyl group or an alicyclic alkyl group, or an alkyl group containing an alicyclic ring. Specifically, formic acid, acetic acid,
And propionic acid, oxalic acid, malonic acid, benzoic acid, diethyl phosphate and the like. Phosphoric acid, hydrochloric acid, and the like are used as the inorganic acids.

One of these complexing agents may be used alone in each of the complex systems, or two or more thereof may be used by mixing at an appropriate ratio. These complexes themselves can be produced according to a conventionally known method. For example, it can be prepared in advance as a complex,
Alternatively, boron trifluoride and one or more complexing agents may be separately or simultaneously added to the reaction system at a predetermined ratio to form a boron trifluoride complex in the reaction solution.

In the complex to be treated in the present invention, the molar ratio of boron trifluoride to the complexing agent is not particularly limited, and any molar ratio can be treated. Is in the range from 0.01 to 100.

When the boron trifluoride contained in the fluid is a complex as described above, the concentration as boron trifluoride may be considerably high. However, in order to improve the removal efficiency, it is usually preferable to use a dilute fluid of boron trifluoride. Specifically, the content of boron trifluoride is 10% by weight or less, more preferably 5% by weight or less. The lower the concentration, the higher the removal efficiency, and therefore the lower limit of the concentration is not particularly limited. It can be appropriately diluted so as to be not more than the above concentration. As the diluting fluid, any fluid can be used as long as it does not form a complex with boron trifluoride, and for example, it can be selected from the liquids described above.

In the present invention, lithium fluoride used for the adsorption of boron trifluoride is a substance which is used in a large amount in various industries such as a phosphor, an optical glass, a ceramics filter, a welding flux, and a glaze. In the present invention, any of natural products, synthetic products, and products obtained from industrial wastes may be used. As a natural product, it is desirable to select a natural product that has been purified to a high purity so as to contain 98% or more of lithium fluoride.

It is known that lithium fluoride or lithium carbonate can be synthesized with hydrofluoric acid according to the reaction of the following formula (1) or (2). Synthetic products can also be used. Lithium fluoride synthesized by these reactions may be used as it is, separated by natural sedimentation or filtration, etc. It is more preferable to use those that have been washed and then dried by heating. HF + LiOH → LiF + H ₂ O (1) 2HF + Li ₂ CO ₃ → 2LiF + H ₂ O + CO _2. .... Equation (2)

Further, in a manufacturing process using water fluoride or the like as a catalyst, neutralization of hydrogen fluoride may be performed as in the above formula (1) or (2) in order to deactivate the catalyst. At that time, lithium fluoride is by-produced as industrial waste. Such lithium by-product can also be used.

Next, the step of adsorbing boron trifluoride on lithium fluoride will be described. First, when boron trifluoride or a complex thereof comes into contact with lithium fluoride, the reaction of the following formula (3) or (4) proceeds easily, and lithium tetrafluoroborate (LiBF ₄ ) is generated. The produced lithium tetrafluoroborate salt is usually poorly soluble in the fluid to be treated. By the generation of the lithium tetrafluoroborate salt, only boron trifluoride can be selectively captured and removed from the fluid. BF ₃ + LiF → LiBF ₄ (3) BF _3- (ligand) + LiF → LiBF ₄ + (ligand) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Formula (4)

In order to adsorb and remove boron trifluoride from a fluid containing boron trifluoride or a complex thereof, the fluid is brought into contact with lithium fluoride at a temperature of 160 ° C. or lower.
In this temperature range, the chemical adsorption efficiency of boron trifluoride is high, so that any temperature of 160 ° C. or less can be adopted. Considering changes in the composition and chemical structure of the product, the more preferred adsorption temperature is in the range of 100 ° C. or lower. The fluid at the time of contact may be any of a gas phase, a liquid phase, or a mixed phase including both.

Regarding the crystal structure of the adsorbent, lithium fluoride is a colorless cubic system, and lithium tetrafluoroborate formed after adsorbing boron trifluoride is a colorless orthorhombic system. Are known. Both are very stable inorganic crystalline materials. The state of the change in the crystal form before and after the adsorption can be easily observed by X-ray diffraction analysis.

The method for contacting the fluid with lithium fluoride is not particularly limited. For example, a fluid containing boron trifluoride or a complex thereof can be brought into contact with a fixed bed filled with lithium fluoride alone or filled with an inert inorganic filler containing lithium fluoride.
Examples of the inert inorganic filler include activated carbon and stainless steel packing, but the material is not limited to this, and the shape is arbitrary. Lithium fluoride does not need to be completely calcined,
When the collected boron trifluoride is reused for the purpose of avoiding moisture, it is preferable to use the one obtained by firing lithium fluoride to remove the moisture.

The particle size of lithium fluoride to be used is not particularly limited. For example, commercially available lithium fluoride is a fine particle having a particle size distribution in the range of 1 to 10 μm. Those having an appropriate particle size distribution may be used.
In order to further increase the adsorption efficiency of boron trifluoride, it is preferable to increase the surface area of lithium fluoride as an adsorbent. From this viewpoint, the finer the particle size, the better. However, the particle size is appropriately selected in consideration of the ease of the adsorption operation and the like.

The shape of the lithium fluoride is not particularly limited. For example, in addition to a normal circular cross-sectional shape, a hollow shape or a special porous shape may be used. It is preferable to select appropriately according to the purpose.

The contact operation for the adsorption can be carried out by any of a flow type using a suction tube or a column filled with lithium fluoride particles or the like as described above, and a batch type. The contact time is not particularly limited, and can be determined as appropriate. Usually, in the flow type, the space velocity can be selected from the range of 0.01 to 10 hr ^-1 .
The amount of lithium fluoride for completely removing boron trifluoride in a batch system needs to be at least equimolar to the boron trifluoride in the target fluid. In order to improve the removal efficiency, it is preferable to use a larger amount of lithium fluoride, but the amount used can be appropriately selected.

By bringing a fluid containing boron trifluoride or a complex thereof into contact with lithium fluoride according to the method described above, boron trifluoride in the fluid is chemically adsorbed on lithium fluoride and separated from the fluid. Removed. After the adsorption, the lithium fluoride adsorbing the boron trifluoride can be separated from the system by an appropriate method. The desorption operation described below can be performed in an adsorption tube or an adsorption tower, or can be performed by transferring to a separate device.

Next, in order to desorb the adsorbed boron trifluoride from lithium fluoride and recover it in a reusable state, the lithium tetrafluoroborate salt generated by the adsorption is heated. That is, in the desorption, it is possible to return to the form of pure boron trifluoride gas and the original lithium fluoride by advancing the reaction of the following formula (5). LiBF ₄ → BF ₃ + LiF Equation (5)

As a heating method for the above desorption, in addition to simple heating, the heating may be performed in the presence of an appropriate inert gas, for example, nitrogen. It is also possible to heat in a suitable inert organic solvent. An essential requirement is that the desorption of the boron trifluoride gas be performed at a temperature of 100 ° C. or higher, and a temperature range of 160 ° C. or higher is desirable in order to sufficiently increase the desorption speed. The upper limit of the desorption temperature is not particularly limited, since lithium fluoride itself is a stable crystal that does not melt until about 850 ° C., and the higher the temperature, the faster the desorption proceeds. However, a high temperature exceeding 600 ° C. is not preferable because problems such as an increase in energy cost, decomposition of an organic solvent, and corrosion of the device by boron trifluoride gas at a high temperature occur. Therefore, the desorption is preferably performed at a temperature of 600 ° C. or less.

The time for desorption of boron trifluoride is not particularly limited as long as it is within the above temperature range. The longer the heating time, the higher the desorption rate of boron trifluoride, but it is uneconomical to spend an excessively long time. When lithium fluoride as an adsorbent is used repeatedly, it is preferable from an economic viewpoint that the desorption rate of boron trifluoride be kept at an appropriate level. By the above heating operation, boron trifluoride is recovered in the form of high-purity boron trifluoride without undergoing decomposition or the like. Also, the adsorbent is restored to the original high-purity lithium fluoride. Therefore, lithium fluoride on which boron trifluoride has been adsorbed or desorbed by the method of the present invention can be repeatedly used as necessary.

Since the desorbed boron trifluoride has high purity, it is recovered by an appropriate means and used in an appropriate process. For example, it can be reused in a process in which a fluid to be treated is discharged. Further, the desorbed boron trifluoride can be appropriately absorbed or adsorbed by a solid alkali or the like and discarded.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to examples.

EXAMPLES The specification of the desorbed boron trifluoride gas in this example was carried out according to the following analytical method well known in the art. <Specification of Desorbed Boron Trifluoride Gas> When boron trifluoride or a complex thereof is reacted with an aqueous solution of calcium chloride, 1 mol of boron trifluoride is converted to 3 mol of hydrochloric acid and 1 mol of calcium trichloride according to the reaction of the following formula (6). Molar boric acid is generated, and the generated hydrochloric acid is neutralized and titrated with an aqueous alkali solution having a known normality such as sodium hydroxide or potassium hydroxide, so that the concentration of existing fluorine can be known. Further, by measuring boric acid produced according to the reaction of the following formula (6) in accordance with the boric acid content test method of Japanese Industrial Standard JIS K8863-1991, it is possible to know the concentration of boron present. it can. In other words, this is a method that utilizes the property of boric acid to form a water-soluble strong acidic complex with mannitol.It is necessary to know the boric acid content by neutralizing and titrating the resulting strong acidic complex with an aqueous alkali solution of normality. The concentration of boron present is determined from the value. 2BF ₃ + 3CaCl ₂ + 6H ₂ O → 2H ₃ BO ₃ + 6HCl + 3CaF ₂ Equation (6)

The method for specifying boron trifluoride used in the present invention is as follows. First, after boron trifluoride is adsorbed on lithium fluoride from a fluid containing boron trifluoride or a complex thereof to form a lithium tetrafluoroborate salt, the adsorbed salt is heated to release the trifluoride. Boron fluoride is absorbed in a solution such as water, lower alcohol or diethyl ether. Next, an aqueous solution of calcium chloride is added to the absorption solution, and the above-described two-stage neutralization titration is performed, the contents of fluorine and boron are examined, and the atomic molar ratio of both elements and the concentration of boron trifluoride are determined. By the above method, the free gas obtained from the embodiment of the present invention has, in each case, an atomic molar ratio of fluorine to boron of 3: 1 and retains the form of boron trifluoride (BF ₃ ). Confirmed that.

Example 1 (Adsorption Removal of Boron Trifluoride) A dispersion (boron trifluoride) in which boron trifluoride diethyl etherate was dispersed in hexane was placed in a conical flask equipped with a stir bar under a nitrogen stream. 100 g of boron (0.25% by weight) was charged, and while stirring at a constant temperature of 25 ° C., 1.91 g of a commercially available special-grade reagent, lithium fluoride (purity: 99% or more, manufactured by Soegawa Rikagaku Co., Ltd.)
(Equivalent to 20 times the molar amount of boron trifluoride), and the mixture was stirred for 30 minutes under a nitrogen stream. By stopping the stirring and allowing the dispersion to stand, the adsorbent and the organic liquid phase were separated into two phases by a difference in specific gravity, and the organic phase was separated into different containers by decantation. An aqueous calcium chloride solution was added to the organic phase, and the concentration of boron trifluoride remaining in the organic phase was measured by an analytical method using the reaction of the above formula (6). The residual boron trifluoride concentration was zero. It was confirmed that boron trifluoride was completely absorbed and removed. Next, the adsorbent was filtered off and dried under reduced pressure to check the change in weight. As a result of determining the difference from the weight before the adsorption of boron trifluoride, it was found that the amount of boron trifluoride adsorbed and held in the added lithium fluoride was 13.1 g / 100 g-lithium fluoride. did. Furthermore, the composition of the organic phase separated by decantation was analyzed by gas chromatography, and it was found that all of the diethyl ether corresponding to the input amount of the boron trifluoride diethyl etherate complex had moved to the organic phase. confirmed. When the lithium fluoride adsorbent on which boron trifluoride was adsorbed and dried was subjected to X-ray diffraction analysis, two types of lithium fluoride (LiF) and lithium tetrafluoroborate (LiBF ₄ ) were obtained. The crystal structure was confirmed.

(Heating Desorption) A lithium fluoride adsorbent adsorbing and holding boron trifluoride was filled in a stainless steel tubular container, and nitrogen was supplied at a flow rate of 1 ml / min (standard state) to heat the supplied nitrogen. Was started and the temperature was maintained at 270 ° C. The nitrogen flowing out of the outlet was introduced into a pre-cooled diethyl ether solution. In this state, nitrogen from the outlet was observed, and the introduction of heated nitrogen was continued until no white smoke due to boron trifluoride was observed. Then, when the weight of the adsorbent powder remaining after cooling was weighed, the residual amount of boron trifluoride was zero, and the amount of adsorbed boron trifluoride was 1
It was confirmed that 00% was desorbed. Further, when X-ray diffraction analysis was performed on the remaining powder in the same manner as at the time of adsorption,
Only the crystal structure of lithium fluoride was observed, confirming that it had been restored to its original form. Further, an aqueous calcium chloride solution was added to the diethyl ether solution having absorbed the desorbed gas by heating, and the above-mentioned two-stage neutralization titration was performed to examine the contents of fluorine and boron. The atomic molar ratio between fluorine and boron was calculated from the obtained value, and the amount of boron trifluoride was determined at the same time. The atomic molar ratio between fluorine and boron was 3: 1 and the form of boron trifluoride was determined. Was confirmed, and it was found that the amount of boron trifluoride present in the diethyl ether solution was 0.24 g. As a result, it was confirmed that 96% of the boron trifluoride charged during the adsorption could be recovered in the form of reusable boron trifluoride. Table 1 shows the above results.

<Example 2> (Adsorption removal of boron trifluoride) 18.00 g (694 mmol) of lithium fluoride used in Example 1 was added to a sample having a diameter of 20 m.
m and a length of 200 mm in a stainless steel tubular container. Example 1 was maintained at a constant temperature of 25 ° C.
A dispersion in which boron trifluoride diethyl etherate is dispersed in hexane in the same manner as described above (0.2 as boron trifluoride)
5 wt%) at 10 ml / hr (16.5 as boron trifluoride)
(mg / hr). The concentration of boron trifluoride in the outlet fluid was zero, and it was confirmed that boron trifluoride was completely absorbed and removed. Further, the adsorption operation was continued, and 120 hours after the supply of the dispersion solution was started, when the detection of a trace amount of boron trifluoride from the outlet fluid was confirmed, the supply of the dispersion solution was stopped. After the supply of the dispersion solution was stopped, nitrogen was supplied into the filling tube to dry the organic medium attached to the adsorbent, and then the weight of the filling tube was measured. As a result of obtaining a difference from the weight before the supply of the boron trifluoride solution measured in advance, the amount of boron trifluoride absorbed and held in the filled lithium fluoride was 11.0 g / 100 g-lithium fluoride. . In addition, when the X-ray diffraction analysis of the adsorbent that adsorbed and held the air-dried boron trifluoride was performed, two crystal structures of lithium fluoride and lithium tetrafluoroborate were confirmed as in Example 1. .

(Heating Desorption) Nitrogen was supplied at a flow rate of 1 ml / min (standard state) to the lithium fluoride filled tube on which boron trifluoride was adsorbed as described above, and heating of the filled tube was started. The temperature was maintained at 270.degree. The nitrogen flowing out of the outlet was introduced into precooled diethyl ether. In this state, nitrogen from the outlet was observed, and heating of the filling tube and introduction of nitrogen were continued until almost no white smoke due to boron trifluoride was recognized. Thereafter, the mixture was cooled and the weight of the filled tube was weighed. The residual amount of boron trifluoride was 0.1 g / 100 g.
It was g-lithium fluoride, and it was confirmed that 99.1% of the adsorbed boron trifluoride was desorbed. Further, an aqueous solution of calcium chloride was added to the diethyl ether solution having absorbed the desorbed gas by heating, and the contents of fluorine and boron were examined in the same manner as in Example 1. It was confirmed that the amount of boron trifluoride present in the ether solution was 1.88 g. As a result, 95% of the boron trifluoride
It was possible to confirm that a% equivalent could be recovered in the form of reusable boron trifluoride.

Example 3 A dispersion obtained by changing the boron trifluoride dietherate used in Example 1 to a boron trifluoride phenolate complex and dispersing it in hexane (0.25% by weight as boron trifluoride) ) Was carried out in the same manner as in Example 1, except that boron trifluoride was adsorbed and desorbed. Table 1 shows the results.

Example 4 A boron trifluoride diethyl etherate used in Example 1 was changed to a boron trifluoride ethyl alcohol complex and dispersed in hexane (a boron trifluoride of 0.1%). (25% by weight), and an experiment of adsorption and desorption of boron trifluoride was performed in the same manner as in Example 1. Table 1 shows the results.

<Example 5> Table 1 shows the results of adsorption and desorption of boron fluoride performed in Example 1 except that only the temperature condition for thermal desorption was changed from 270 ° C to 400 ° C.

[0049]

[Table 1]

An X-ray diffraction analysis of the adsorbents adsorbing and holding boron trifluoride was performed on Examples 3 to 5, and as in Example 1, lithium fluoride and lithium tetrafluoroborate salt were obtained. Were confirmed. In addition, it was confirmed that all gases desorbed when the adsorbed salt was heated retained the form of boron trifluoride.

<Example 6> In Example 1, an olefin component in a C ₉ aromatic mixture was replaced with a boron trifluoride phenol complex catalyst in place of the dispersion obtained by dispersing boron trifluoride diethyl etherate in hexane. When the adsorption and desorption of boron trifluoride were carried out in the same manner except that a reaction mixture obtained by polymerization (containing 0.25% by weight as boron trifluoride) was used, 13.1 g / 100 g-fluorine was obtained. Boron trifluoride could be completely separated and removed by the amount of lithium chloride adsorbed. By further processing at a high temperature of 270 ° C., 93% of the adsorbed boron trifluoride was recovered. The olefin component in the C ₉ aromatic mixture refers to C ₉ α-methylstyrene, vinyltoluene, indene, etc., which are by-produced during thermal cracking or catalytic cracking of petroleum light hydrocarbons such as naphtha and butane. Is a mixture of aromatic olefins.

Example 7 In Example 1, the olefin component in the C ₄ mixture was polymerized with a boron trifluoride ethyl alcohol complex catalyst in place of the dispersion obtained by dispersing boron trifluoride etherate in hexane. The adsorption and desorption of boron trifluoride was carried out in the same manner except that the reaction mixture (boron trifluoride 0.25% by weight) obtained as described above was used, and complete adsorption was performed with 13.1 g / 100 g-lithium fluoride adsorption. Was able to adsorb and remove boron trifluoride. 2 more
By treating at a high temperature of 70 ° C., 96% of the adsorbed boron trifluoride was recovered. The C ₄ mixture is
Is a C ₄ raffinate containing isobutene (butadiene raffinate from ethylene cracker), its composition is as follows (wt%).

Example 8 (Adsorption Removal of Boron Trifluoride) 18.00 g (694 mmol) of lithium fluoride used in Example 1 was charged into the stainless steel tubular container used in Example 2. The tube was maintained at a constant temperature of 25 ° C., and free unreacted boron trifluoride gas (boron trifluoride concentration: 70%) discharged during the polymerization of the olefin component in the C ₉ aromatic mixture described in Example 6 was used.
(0 to 900 ppm by volume) was passed through the tube at a flow rate of 30 l / hr (73 mg / hr as an average flow rate of boron trifluoride). The concentration of boron trifluoride in the outlet fluid was zero, and it was confirmed that boron trifluoride was completely absorbed and removed. Further, the adsorption operation was continued, and the supply was stopped 32 hours after the supply of the exhaust gas was started, when the detection of a trace amount of boron trifluoride from the outlet fluid was confirmed. After the supply of the exhaust gas was stopped, nitrogen was supplied into the filling tube to dry and remove the organic medium attached to the adsorbent, and then the weight of the filling tube was measured. As a result of obtaining a difference from the weight before the supply of the boron trifluoride solution measured in advance, the amount of boron trifluoride absorbed and held in the filled lithium fluoride was 13.
It was 0 g / 100 g-lithium fluoride. When the thus obtained adsorbed material was subjected to heat desorption treatment in the same procedure as in Example 2, 97% of the adsorbed boron trifluoride was recovered.

Comparative Example 1 5% by weight of acrylonitrile
1% by weight, based on acrylonitrile, of tert-butyl peroxide and 0.5% of acrylonitrile as a polymerization initiator were added to a toluene solution.
By weight, thiourea was dissolved, and the obtained solution was impregnated with 60-80 mesh activated carbon previously dried at 150 ° C., and heated at 100 ° C. for 2 hours in a nitrogen stream to perform polymerization. After the heating was completed, washing with toluene heated to the boiling point was performed to remove unreacted acrylonitrile and low-polymerized products. In place of lithium fluoride in Example 1, adsorption of boron trifluoride was carried out in the same manner except that the same weight of activated carbon carrying the acrylonitrile polymer obtained above was filled. When the adsorption amount of boron trifluoride was determined, it was 2.6 g / 100 g-activated carbon, and it was confirmed that the adsorption efficiency was low.

<Comparative Example 2> (Adsorption removal of boron trifluoride) In Example 1, instead of lithium fluoride, 4.29 g of the same molar amount of powdered potassium fluoride (20 parts of boron trifluoride charged) was used. (Equivalent to double molar amount) was added, and boron trifluoride was adsorbed in the same manner. As a result, boron trifluoride was 0.9 g / 100.
It was adsorbed at the ratio of g-potassium fluoride, confirming that the adsorption efficiency was low. (Heat Desorption) In the same manner as in Example 1, a potassium fluoride adsorbent partially adsorbing and holding boron trifluoride was subjected to heat desorption. Although the heating temperature was initially maintained at 270 ° C., almost no white smoke due to boron trifluoride was observed from the outlet. Therefore, when the heating temperature was gradually increased,
When the temperature reached about 700 ° C., white smoke was detected from the outlet.

<Comparative Example 3> (Adsorption removal of boron trifluoride) In Example 1, instead of lithium fluoride, 1.91 g of silica gel of the same weight was used.
Was added, and boron trifluoride was adsorbed in the same manner as in Example 1. As a result, 5.1 g of boron trifluoride
Although adsorbed at a ratio of / 100 g-silica gel, the released boron trifluoride complex was detected in the organic phase, confirming that the adsorption efficiency was low. Furthermore, it was confirmed that HF gas was released in the gas phase of the organic phase during the adsorption. Also,
Photoelectron spectroscopy (ESCA) analysis of the silica gel adsorbent, which is believed to have adsorbed and retained boron trifluoride, revealed that the adsorbent contained fluorine and boron in an atomic molar ratio of 2: 1.
And it was confirmed that the form of boron trifluoride was not retained. These can react silanol groups in silica gel at adsorption (-SiOH) is a boron trifluoride, probably because decomposed into HF gas free and ₂ group -SiOBF, recovery of reusable boron trifluoride Confirmed that it was difficult.

[0057]

According to the present invention, by using lithium fluoride as an adsorbent, boron trifluoride contained in a fluid can be selectively adsorbed and separated with high efficiency. Highly efficient boron trifluoride can be desorbed and recovered with high efficiency, and can be reused as needed.

Claims (11)

[Claims] 1. A method for removing boron trifluoride, comprising bringing a fluid containing boron trifluoride or a boron trifluoride complex into contact with lithium fluoride (LiF) at a temperature of 160 ° C. or lower. 2. The method for removing boron trifluoride according to claim 1, wherein the temperature of the contact is 100 ° C. or lower. 3. The method for removing boron trifluoride according to claim 1, wherein the boron trifluoride complex is a complex formed of boron trifluoride and an organic or inorganic polar compound. 4. The removal of boron trifluoride according to claim 3, wherein the organic or inorganic polar compound is selected from an oxygen-containing compound, a nitrogen-containing compound, a sulfur-containing compound, a phosphorus-containing compound and an inorganic acid. Method. 5. The oxygen-containing compound according to claim 4, wherein the oxygen-containing compound is selected from water, alcohols, ethers, phenols, ketones, aldehydes, esters, organic acids and acid anhydrides. A method for removing boron trifluoride. 6. A method for recovering boron trifluoride comprising the following steps: (Step 1) converting a fluid containing boron trifluoride or a boron trifluoride complex into lithium fluoride (LiF) at a temperature of 160 ° C. or lower. (Step 2) Lithium tetrafluoroborate salt (Li) produced in Step 1
A step of heating BF ₄ ) in a temperature range of 100 to 600 ° C. to obtain boron trifluoride and lithium fluoride. 7. The method for recovering boron trifluoride according to claim 6, wherein the heating temperature of the lithium tetrafluoroborate salt in the step 2 is in a range of 160 to 500 ° C. 8. The contact temperature in the step 1 is 100 ° C.
The method for recovering boron trifluoride according to claim 6, which is as follows. 9. The method for recovering boron trifluoride according to claim 6, wherein the boron trifluoride complex is a complex formed of boron trifluoride and an organic or inorganic polar compound. 10. The recovery of boron trifluoride according to claim 9, wherein the organic or inorganic polar compound is selected from an oxygen-containing compound, a nitrogen-containing compound, a sulfur-containing compound, a phosphorus-containing compound and an inorganic acid. Method. 11. The method according to claim 10, wherein the oxygen-containing compound is selected from water, alcohols, ethers, phenols, ketones, aldehydes, esters, organic acids, and acid anhydrides. A method for recovering boron trifluoride.