JPH0210081B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying hydrochloric acid, and more particularly to a method for purifying hydrochloric acid, which comprises bringing a specific silane compound into contact with hydrochloric acid containing hydrogen fluoride.

Generally, fluorinated halogenated hydrocarbons are
For example, when producing fluorinated chlorinated hydrocarbons,
Hydrogen chloride is produced as a by-product in an amount equal to the hydrogen fluoride that contributed to the reaction. This hydrogen chloride is used as by-product hydrochloric acid, but it is well known that hydrogen fluoride, silicon fluoride, etc. are mixed into this. Since these mixed fluorides pose a great harm to the effective use of by-product hydrochloric acid, the method for removing them is an extremely important issue, and many methods have been proposed to date. For example, US Patent No. 3411879
No. 50-110999 describes a method for removing fluorine ions using silica gel. However, these methods using silica gel are unsuitable for effectively purifying hydrochloric acid containing a high concentration of hydrogen fluoride.

As a result of repeated research on the purification method of hydrochloric acid, the present inventors discovered that a specific silicon compound reacts with hydrogen fluoride and hydrogen fluoride can be effectively removed, leading to the completion of the present invention. .

That is, one gist of ^the present invention is to prepare hydrochloric acid ^containing hydrogen fluoride with ^the formula: R ¹ R ² R ³ SiX () [wherein, ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ each represent an alkyl group having 1 to 4 carbon atoms or a phenyl group. ] A method for purifying hydrochloric acid characterized by removing hydrogen fluoride by contacting with a silicon compound shown in the following.

Among the silicon compounds () used in the present invention, preferred are compounds in which R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are each a methyl group, ethyl group, n-propyl group or phenyl group. Particularly preferred are trimethylchlorosilane, triethylchlorosilane, methyldiphenylchlorosilane,
tri-n-propylsilanol and hexamethyldisiloxane. In particular, trimethylchlorosilane reacts with hydrogen fluoride and is converted to trimethylfluorosilane with a boiling point of 16°C, so it is very easy to separate from hydrochloric acid.

The silicon compound () may be used in an amount equivalent to at least 1 to 10 times the amount of hydrogen fluoride, and there is no upper limit to the amount used. 1
-5 times equivalent, especially 1-2 times equivalent is industrially preferable.

Contacting takes place at 0-110°C. The contact time may be determined depending on other conditions such as the amount of silicon compound () used and the temperature.

The silicon compound () reacts with hydrogen fluoride to form the formula: R ¹ R ² R ³ SiF or R ⁴ R ⁵ R ⁶ SiF () [wherein R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ have the same meanings as above. ] It produces the compound shown below.

The hydrochloric acid from which hydrogen fluoride has been removed is thus separated from the fluorosilane () formed and unreacted silicon compounds, if present. This separation can be carried out by evaporating the latter or by liquid-liquid separation.

On the other hand, regarding the reuse of fluorosilane (), if the generated fluorosilane () has a low boiling point, it will naturally evaporate during the hydrogen fluoride removal operation, so it is necessary to collect and reuse it. Can be done. If it has a high boiling point, it separates into liquid from hydrochloric acid along with any unreacted silicon compounds () that may be present. The mixture of fluorosilane () and the silicon compound can be further separated by distillation and reused, or it can be directly subjected to hydrolysis and, if necessary, condensation, which will be described later, and then reused.

That is, fluorosilane () can be hydrolyzed to form the formula: R ¹ R ² R ³ SiOH or R ⁴ R ⁵ R ⁶ SiOH () [wherein R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ has the same meaning as above. ] It can be converted to the silanol represented by the formula, and this can be reused for the removal of hydrogen fluoride. Hydrolysis can be carried out at 0 to 90°C under neutral or alkaline conditions.

Since silanol () is generally unstable, it can be further treated with acid (e.g. hydrochloric acid) and condensed to form the formula: R ¹ R ² R ³ SiOSiR ⁴ R ⁵ R ⁶ , (R ¹ R ² R ³ Si ) ₂ O or (R ⁴ R ⁵ R ⁶ S
i) ₂ O [wherein R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ have the same meanings as above. ] It can also be recovered by converting it into disiloxane shown in the following. This can be reused for removing hydrogen fluoride. The condensation is 0 under acidic conditions.
Can be carried out at temperatures of ~90 °C.

According to the purification method of the present invention, even hydrochloric acid containing a relatively large amount of hydrogen fluoride can be effectively purified, and 99%
The above amount of hydrogen fluoride can be removed. There is little contamination of hydrochloric acid by the removal agent, and there is no removal agent in purified hydrochloric acid.
Contains less than 10ppm. Further, in the present invention, it is possible to reuse the removing agent.

Next, the present invention will be explained in detail with reference to Examples.

Example 1 500 g of 20.7% hydrochloric acid containing 2650 ppm of hydrogen fluoride
was placed in a polyethylene reaction vessel, 10g of trimethylchlorosilane was added under stirring, and then
Stirring was continued for 1 hour at 25°C. After standing for 30 minutes, separate the upper organic layer using a separating funnel and add purified hydrochloric acid.
Got 495g. The hydrogen fluoride concentration in this hydrochloric acid is
8 ppm, and the removal rate was 99.7%.

Example 2 Purified hydrochloric acid was obtained by repeating the same procedure as in Example 1 except that 15 g of triethylchlorosilane was used instead of trimethylchlorosilane and the mixture was stirred at 25° C. for 3 hours. Hydrogen fluoride concentration: 18ppm.

Removal rate: 99.3%.

Example 3 In Example 1, 30 g of diphenylmethylchlorosilane was used instead of trimethylchlorosilane,
Purified hydrochloric acid was obtained by repeating the same procedure as in Example 1 except for stirring at 25°C for 3 hours. Hydrogen fluoride concentration: 37ppm. Removal rate: 98.6%.

Example 4 500 g of 20.7% hydrochloric acid containing 2650 ppm of hydrogen fluoride was placed in a polyethylene reaction vessel equipped with a reflux condenser, a dropping funnel, and a magnetic stirrer, and the temperature of the hydrochloric acid was maintained at 90°C in a hot water bath while stirring. At the same time, 10 g of hexamethyldisiloxane was added from the dropping funnel. After reacting under reflux for 5 hours, the mixture was allowed to stand for 30 minutes, cooled to room temperature, and the upper organic layer was separated using a separating funnel to obtain 495 g of purified hydrochloric acid.
Hydrogen fluoride concentration is 10ppm, removal rate is 99.6%
It was hot.

Example 5 In Example 4, the gas generated from the top of the reflux condenser during the reaction was passed through two gas scrubbing towers (arranged in series) each containing 500 g of 10% potassium hydroxide solution using a vinyl chloride tube. did. After repeating the reaction of Example 4 10 times, the organic layer formed on the potassium hydroxide solution was separated and stirred with 100 g of 5% hydrochloric acid for 1 hour. After standing for 30 minutes, the organic layer was separated to obtain 48.3 g of hexamethyldisiloxane. Using this, hydrochloric acid was treated in the same manner as in Example 4, and similar results were obtained.

Example 6 In Example 4, the gas generated from the top of the reflux condenser during the reaction was led to a cold trap cooled with an acetone dry ice bath and collected. The liquid collected when the reaction in Example 4 was repeated 10 times was dissolved in 300 ml of ethyl ether, and while stirring while cooling with a salt-ice cold agent, the phenolphthalene was kept neutral using 1N-NaOH, and about It was added slowly over 30 minutes. The organic layer was separated, the aqueous layer was extracted with ether, and both organic layers were combined and purified using a glass rectification column to obtain 50.6 g of trimethylsilanol.

Example 7 Purified hydrochloric acid was obtained by repeating the same procedure as in Example 1 except that 10 g of trimethylsilanol was used instead of trimethylchlorosilane. Hydrogen fluoride concentration 6ppm. Removal rate 99.8%.

Similar results were obtained using trimethylsilanol obtained in Example 6.

Claims (1)

[Claims] 1 Hydrochloric acid containing hydrogen fluoride Formula: R ¹ R ² R ³ SiX [In the formula, X is chlorine, a hydroxyl group, or a group represented by OSiR ⁴ R ⁵ R ⁶ , R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ each represent an alkyl group having 1 to 4 carbon atoms or a phenyl group. ] A method for purifying hydrochloric acid, characterized by removing hydrogen fluoride by contacting with a silicon compound represented by the following. 2. The purification method according to claim 1, wherein X is chlorine. 3. The purification method according to claim 2, wherein R ¹ , R ² and R ³ are all methyl groups or ethyl groups. 4. The purification method according to claim 1, wherein X is a hydroxyl group. 5. The purification method according to claim 4, wherein R ¹ , R ² and R ³ are all n-propyl groups. 6. The purification method according to claim 1, wherein X is a group represented by OSiR ⁴ R ⁵ R ⁶ . 7. The purification method according to claim 6, wherein all of R ¹ to R ⁶ are methyl groups. 8 To hydrochloric ^{acid containing} hydrogen ^fluoride Formula: ^{R 1} R ^{2 R 3} SiX [In ^the formula ^, , R ⁵ and R ⁶ each represent an alkyl group having 1 to 4 carbon atoms or a phenyl group. ] A step of contacting a silicon compound represented by the formula: R ¹ R ² R ³ SiF produced in the step [wherein R ¹ , R ² and R ³ have the same meanings as above. ] Hydrolyzing the compound represented by the formula: R ¹ R ² R ³ SiOH [wherein R ¹ , R ² and R ³ have the same meanings as above. ] If necessary, the silanol is condensed to give the formula: R ¹ R ² R ³ SiOSiR ⁴ R ⁵ R ⁶ [In the formula: R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ has the same meaning as above. ] Including the step of converting into disiloxane shown by
A method for purifying hydrochloric acid, characterized in that silanol and/or disiloxane obtained in a later step is resupplied to an earlier step.