JP3912969B2 - Method for recovering fluoroalkylsulfonic acid - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for recovering fluoroalkylsulfonic acid, which is a substance useful as a catalyst for medical and organic synthesis reactions.
[0002]
[Prior art and problems to be solved]
In general, anhydrous fluoroalkylsulfonic acid can be obtained by adding phosphorus pentoxide to fluoroalkylsulfonic acid, followed by distillation after reaction. For example, in the production of trifluoromethanesulfonic anhydride, as shown by the following formula, crude trifluoromethanesulfonic acid is obtained by adding phosphorus pentoxide to trifluoromethanesulfonic acid and reacting and then distilling.
6CF ₃ SO ₃ H + P ₂ O ₅ → 3 (CF ₃ SO ₂ ) ₂ O + 2H ₃ PO ₄
Furthermore, a method for producing pure trifluoromethanesulfonic anhydride by rectifying these crude products is known.
[0003]
Thus, the production of trifluoromethanesulfonic anhydride is performed by a dehydration reaction of trifluoromethanesulfonic acid with phosphorus pentoxide. Since this reaction becomes extremely slow when the reaction rate progresses by about 60%, the actual situation is that the reaction is substantially stopped at this point. Therefore, about 40% of unreacted trifluoromethanesulfonic acid is present in the reaction residue, and it is necessary to recover and use this unreacted component industrially. However, most of the reaction residue is solid phosphorus pentoxide, and it is difficult to extract from the reactor. In this state, trifluoromethanesulfonic acid is not recovered even if distillation under reduced pressure is performed. Processing of the reaction residue is a problem. Further, there is a similar problem with the treatment of waste liquid containing fluoromethanesulfonic acid and phosphoric acid.
[0004]
[Specific means for solving the problem]
As a result of intensive studies in view of these problems of the prior art, the inventors have added a metal hydroxide or a metal carbonate that forms an insoluble phosphate to a solution containing a fluoroalkylsulfonic acid and a phosphoric acid component. The inventors have found that the fluoroalkylsulfonic acid contained in the solution can be efficiently recovered by removing the precipitate of the generated insoluble metal phosphate compound, and the present invention has been achieved.
[0005]
That is, the present invention has the general formula _{C n F 2n + 1 SO 3} H (n = 1~8) at a fluoroalkyl sulfonic acid and phosphorus pentoxide by the reaction shown, to produce a fluoroalkyl sulfonic acid anhydride by distillation At the time, the pH of the distillation residual solution containing the fluoroalkylsulfonic acid and the phosphoric acid content is 5 to 13, a metal hydroxide or a metal carbonate that forms an insoluble phosphate is added, and the insoluble phosphoric acid that is formed A method for recovering a fluoroalkylsulfonic acid, characterized by removing an insoluble metal phosphate from a metal salt and a soluble fluoroalkylsulfonate produced together , and the soluble fluoroalkylsulfone obtained by the method Sulfuric acid is added to the acid salt and distilled, or the soluble fluoroalkyl sulfonate obtained by the method is added with potassium hydroxide or sodium hydroxide. It is to provide a method for efficiently recover a fluoroalkyl sulfonic acid by the addition of potassium.
[0006]
In the present invention, as the metal hydroxide or metal carbonate for generating the insoluble phosphate, hydroxides or carbonates such as alkaline earth metals, lanthanide metals, and transition metals can be used. Calcium carbonate and calcium hydroxide that are inexpensive and easily available are preferred.
[0007]
Further, the insoluble phosphate referred to herein means one having a solubility of 1% or less. However, it can be used even if the solubility is higher than that, but it is not preferable because the recovery rate is lowered.
[0008]
In order to produce insoluble phosphate, the pH is preferably controlled in the range of 5-13. A pH of 5 or lower is not preferable because it becomes a soluble phosphate or the like and the recovery rate is lowered. On the other hand, when the pH is 13 or more, excessive salt is added, resulting in deterioration of filterability and the like.
[0009]
Next, the amount of the metal hydroxide or the metal carbonate is preferably in the range of the theoretical molar ratio M / P = 0.5 to 3 (M represents a metal). If the amount is less than this amount, the recovery rate is unfavorable. If added too much, it solidifies and is not very economical. Moreover, the addition method of a metal hydroxide or a metal carbonate may be added by either a powder or an aqueous solution thereof.
[0010]
Further, the reaction temperature is preferably in the range of 20 to 100 ° C., and if it exceeds this range, mist and the like are scattered, which is not preferable.
[0011]
The reaction solution (fluoroalkylsulfonic acid) concentration is preferably in the range of 1 to 25%, and the phosphoric acid concentration is preferably in the range of 1 to 50% (as P ₂ O ₅ ). If it is thinner than this concentration, the recovery rate is lowered and it is not industrial. On the other hand, if it exceeds this range, solidification occurs and stirring becomes impossible.
[0012]
Next, in general, a fluoroalkylsulfonic acid is obtained by subjecting a fluoroalkylsulfonic acid salt to sulfuric acid decomposition. That is, it can be obtained by adding sulfuric acid to a fluoroalkylsulfonate and distilling it. The soluble fluoroalkyl sulfonate obtained by the present invention becomes a dilute solution because washing water or the like is used to increase the recovery rate. However, in order to increase the efficiency of sulfuric acid decomposition, it is preferable to carry out concentration drying and the like to obtain a salt having a low water content. Also, if the water content is high, a hydrated salt of fluoroalkyl sulfonic acid is generated, which has an adverse effect such as blockage in the system. Therefore, it is effective to use fuming sulfuric acid together.
[0013]
The distillation temperature is preferably in the range of 150 to 250 ° C., and the distillation pressure is preferably in the range of 0.07 MPa to 0.099 MPa. When the distillation temperature is low, the recovery rate is lowered, which is not preferable. When the distillation temperature is higher than this range, decomposition or the like is not preferable.
[0014]
For example, in the case of calcium trifluoromethanesulfonate as the soluble fluoroalkyl sulfonate obtained in the present invention, when sulfuric acid is decomposed and distilled as it is, calcium sulfate or the like is generated, which may cause inconvenience in the process. In such a case, potassium trifluoromethanesulfonate or sodium trifluoromethanesulfonate is easy to handle in the process by adding potassium hydroxide or sodium hydroxide to calcium trifluoromethanesulfonate in advance and removing the calcium salt as calcium hydroxide. Can be recovered. Thus, fluoroalkylsulfonic acid can be recovered by selecting a salt to be recovered depending on the purpose of use.
[0015]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
[0016]
Example 1
Reacts trifluoromethanesulfonic acid (CF ₃ SO ₃ H) with phosphorus pentoxide, and after distillation, contains 13% trifluoromethanesulfonic acid and 60% phosphoric acid concentration (as P ₂ O ₅ ) as a distillation residue. 200 g of the solution was collected in a 1 L beaker. A mixed slurry of 270 g of industrial calcium carbonate and 230 g of water was added thereto while slowly stirring. After stirring for 2 hours, the entire amount was filtered using a membrane filter (pore diameter 0.45 μm) to obtain 95 g of a filtrate. The filtrate had a pH of 6.6 (23 ° C.).
[0017]
Then, in order to collect | recover the trifluoromethanesulfonate adhering to the filtration residue, the residue was wash | cleaned 3 times with 100 ml of pure water, and 301g of washing | cleaning liquids were obtained. The S and P contents of the filtrate and washing solution were measured with an ICP emission spectroscopic analyzer. As a result, 97% of trifluoromethanesulfonate was recovered. Moreover, the analytical value of P was 20 ppm or less, which is the lower limit of analytical quantification.
[0018]
Example 2
Reacts trifluoromethanesulfonic acid (CF ₃ SO ₃ H) with phosphorus pentoxide, and after distillation, contains 13% trifluoromethanesulfonic acid and 60% phosphoric acid concentration (as P ₂ O ₅ ) as a distillation residue. 200 g of the solution was collected in a 1 L beaker. A mixed slurry of 203 g of industrial calcium hydroxide and 330 g of water was added thereto while slowly stirring. After stirring for 2 hours, the entire amount was filtered using a membrane filter (pore diameter 0.45 μm) to obtain 211 g of filtrate. The pH of the filtrate was 12.2 (23 ° C.).
[0019]
Thereafter, the filtration residue was washed with 100 ml of pure water three times to obtain 297 g of a washing liquid. The S and P contents of the filtrate and the washing solution were measured with an ICP emission spectroscopic analyzer. As a result, 98% of trifluoromethanesulfonate was recovered. Moreover, the analytical value of P was 20 ppm or less, which is the lower limit of analytical quantification.
[0020]
Example 3
Reacts trifluoromethanesulfonic acid (CF ₃ SO ₃ H) with phosphorus pentoxide, and after distillation, contains 13% trifluoromethanesulfonic acid and 60% phosphoric acid concentration (as P ₂ O ₅ ) as a distillation residue. 2 kg of the solution was collected in a 10 LPTFE container. A mixed slurry of 2 kg of industrial calcium hydroxide and 3 kg of water was added thereto while slowly stirring. After stirring for 2 hours, the whole amount was filtered using a membrane filter (pore diameter 0.45 μm). The filtration residue was washed 3 times with 3 kg of pure water to obtain a filtrate and a cleaning liquid of 3.22 kg. This liquid was heated with a rotary evaporator and concentrated in vacuo to obtain 278 g of calcium salt of trifluoromethanesulfonic acid. As a result of analyzing the amount of S and Ca of this calcium salt of trifluoromethanesulfonic acid with an ICP emission spectroscopic analyzer, it contained 87% of calcium salt of trifluoromethanesulfonic acid and 3.5% of calcium hydroxide. 200 g of this calcium salt of trifluoromethanesulfonic acid was put into a four-necked flask of a glass distillation apparatus, and 120 g of 96% concentrated sulfuric acid and 150 g of fuming sulfuric acid (30% SO ₃ ) were added and reacted. Distillation under reduced pressure was performed to obtain about 100 g of a distillate. This distillate was analyzed by FT-NMR and confirmed to be trifluoromethanesulfonic acid.
[0021]
Example 4
Reacts trifluoromethanesulfonic acid (CF ₃ SO ₃ H) with phosphorus pentoxide, and after distillation, contains 13% trifluoromethanesulfonic acid and 60% phosphoric acid concentration (as P ₂ O ₅ ) as a distillation residue. 200 g of the solution was collected in a 1 L beaker. A mixed slurry of 203 g of industrial calcium hydroxide and 330 g of water was added thereto while slowly stirring. Furthermore, 20 g of 95% strength potassium hydroxide was added thereto and stirred for 2 hours, and then the whole amount was filtered using a membrane filter (pore diameter 0.45 μm).
[0022]
This filtrate was heated with a rotary evaporator and concentrated in vacuo to obtain 32 g of potassium salt of trifluoromethanesulfonic acid. When the amount of Ca and P in this potassium salt was analyzed with an ICP emission spectroscopic analyzer, both were 200 ppm or less.
Example 5
C ₄ F ₉ SO ₃ H and phosphorus pentoxide are reacted, and after distillation, a solution containing 21% C ₄ F ₉ SO ₃ H and 57% phosphoric acid concentration (as P ₂ O ₅ ) as a distillation residue 200 g was collected in a 1 L beaker. A mixed slurry of 195 g of industrial calcium hydroxide and 320 g of water was added thereto while slowly stirring. Furthermore, after adding 17 g of 95% strength potassium hydroxide and stirring for 2 hours, the whole amount was filtered using a membrane filter (pore diameter 0.45 μm).
[0023]
The filtrate was heated with a rotary evaporator and concentrated in vacuo to obtain 45 g of C ₄ F ₉ SO ₃ K. When the amount of Ca and P in this potassium salt was analyzed with an ICP emission spectroscopic analyzer, both were 200 ppm or less.
[0024]
Example 6
A solution containing C ₈ F ₁₇ SO ₃ H and phosphoric acid concentration 54% (as P ₂ O ₅ ) as a distillation residue after reacting C ₈ F ₁₇ SO ₃ H with phosphorus pentoxide 200 g was collected in a 1 L beaker. A mixed slurry of 182 g of industrial calcium hydroxide and 300 g of water was added thereto while slowly stirring. Further, 12 g of 95% strength potassium hydroxide was added and stirred for 2 hours, and the whole was filtered using a membrane filter (pore diameter 0.45 μm).
[0025]
The filtrate was heated with a rotary evaporator and concentrated in vacuo to obtain 51 g of C ₈ F ₁₇ SO ₃ K. When the amount of Ca and P in this potassium salt was analyzed with an ICP emission spectroscopic analyzer, both were 200 ppm or less.
[0026]
Comparative Example 1
Reacts trifluoromethanesulfonic acid (CF ₃ SO ₃ H) with phosphorus pentoxide, and after distillation, contains 13% trifluoromethanesulfonic acid and 60% phosphoric acid concentration (as P ₂ O ₅ ) as a distillation residue. 200 g of the solution was collected in a 1 L beaker. A solution obtained by dissolving 110 g of 95% strength potassium hydroxide in 216 g of pure water was added thereto while slowly stirring. After stirring for 2 hours, the entire amount was filtered using a membrane filter (pore size 0.45 μm) to obtain 367 g of filtrate and 148 g of crystals. The pH of the filtrate was 6.2 (24 ° C.).
[0027]
The S and P contents of this filtrate were measured with an ICP emission spectroscopic analyzer. As a result, the P content in the filtrate was 8.4%, and the S content was 1.4%, which was a mixture of trifluoromethanesulfonic acid and phosphoric acid solution and could not be separated.
[0028]
Comparative Example 2
Reacts trifluoromethanesulfonic acid (CF ₃ SO ₃ H) with phosphorus pentoxide, and after distillation, contains 13% trifluoromethanesulfonic acid and 60% phosphoric acid concentration (as P ₂ O ₅ ) as a distillation residue. 10 g of the solution and 390 g of pure water were collected in a 1 L beaker. A mixed slurry of 14 g of industrial calcium carbonate and 30 g of water was added thereto while slowly stirring. After stirring for 2 hours, the entire amount was filtered using a membrane filter (pore size 0.45 μm) to obtain 418 g of filtrate and 9 g of crystals. The pH of the filtrate was 4.2 (23 ° C.).
[0029]
The amount of S and P of the filtrate was measured with an ICP emission spectroscopic analyzer. As a result, the P content in the filtrate was 0.4%, and the S content was 0.3%, which was a mixed solution of trifluoromethanesulfonic acid and phosphoric acid solution and could not be separated.
[0030]
【The invention's effect】
By the method of the present invention, the fluoroalkylsulfonic acid in the distillation residue can be efficiently recovered.

Claims (3)

When an anhydrous fluoroalkylsulfonic acid is produced by reacting a fluoroalkylsulfonic acid represented by the general formula C _n F _{2n + 1} SO ₃ H (n = 1 to 8) with phosphorus pentoxide, In addition, a metal hydroxide or a metal carbonate that forms an insoluble phosphate is added to the residual distillation solution containing the phosphoric acid content and the insoluble phosphate metal salt that is formed together with the pH. A method for recovering a fluoroalkylsulfonic acid, comprising removing an insoluble metal phosphate from a soluble fluoroalkylsulfonic acid salt .   A method for recovering fluoroalkylsulfonic acid, comprising adding sulfuric acid to the soluble fluoroalkylsulfonic acid salt obtained by the method according to claim 1 and distilling the sulfuric acid.   A method for recovering fluoroalkylsulfonic acid, comprising adding potassium hydroxide or sodium hydroxide to the soluble fluoroalkylsulfonic acid salt obtained by the method according to claim 1.