RU2203271C1 - Method of synthesis of trifluoromethane sulfoacid - Google Patents

Abstract

FIELD: organic chemistry, chemical technology. SUBSTANCE: invention relates to the improved method of synthesis of trifluoromethane sulfoacid used in synthesis of derivatives of trifluoro- methane sulfoacid, in fine organic synthesis, production of drugs, fungicides, surface-active substances, engine fuel. Method involves treatment of trifluoromethane sulfoacid salt with silicon dioxide, sulfuric acid in the concentration 99.5-100.5% followed by distillation off of crude trifluoromethane sulfoacid from reaction mixture at feeding inert gas to mixture and the following fractional distillation of crude trifluoro- methane sulfoacid in the presence of silicon dioxide under reduced pressure and at inert gas feeding and utilization of by-side fractions of fractional distillate. Method ensures to decrease consumptions of reagents, enhance quality of trifluoromethane sulfoacid and to except formation of cakes in reactor of acid synthesis. EFFECT: improved method of synthesis. 5 cl, 1 tbl

Description

 The invention relates to a technology for the production of organofluorine compounds, in particular to a technology for producing perfluoroalkanesulfonic acids. Trifluoromethanesulfonic acid (hereinafter TFMSK) is widely used in fine organic synthesis, in the production of pharmaceuticals, fungicides, insecticides, surfactants, motor fuels, etc.

A known method for producing TFMSC by hydrogen peroxide oxidation of bis (trifluoromethylthio) mercury obtained from trifluoromethyl iodide and sulfur in the presence of mercury, followed by conversion of the resulting trifluoromethanesulfonic acid monohydrate (CF ₃ SO ₃ H • H ₂ O) into the barium salt of TFMSC, which is treated with concentrated sulfuric acid (RN Haszeldine and JM Kidd, J. Chem. Soc., P. 4228-4232, 1954).

 There is also a known method for producing TFMSC from trifluoromethyl bromide with its conversion to the sodium salt of trifluoromethyl sulfinic acid, which is converted by oxidation to the sodium salt of trifluoromethanesulfonic acid with further processing of the latter with concentrated sulfuric acid (France, patent 2593808, 1988). These methods are suitable for the synthesis of TFMSC in laboratory conditions.

The industry mainly uses the method for producing TFMSC by reacting its dehydrated salts of alkali or alkaline earth metals with an excess of 100% sulfuric acid, followed by distillation of TFMSC (US, Patent 2732298, 1956) - a prototype. In this method, the TFMSC salt obtained by hydrolysis of trifluoromethanesulfofluoride in an aqueous solution of an alkali or alkaline earth metal hydroxide is thoroughly dehydrated and treated with 100% sulfuric acid with a mass ratio of salt to H ₂ SO ₄ 1: 1, TFMSC is distilled from the reaction mixture. The disadvantage of this method is the increased consumption of reagents, the increased content of impurities in the synthesized TFMSK, the formation of difficult to remove sintered waste from the synthesis reactor TFMSK.

 An object of the invention is to reduce the consumption of reagents, improving the quality of TFMSK, the exclusion of cakes in the synthesis reactor TFMSK.

The problem is solved in that when receiving TFMSC by treating its dehydrated salt with an excess of concentrated sulfuric acid by heating and distilling TFMSC from the reaction mixture, silicon dioxide is added to the dehydrated salt, sulfuric acid with a concentration of 99.5-100.5%, which added with 1.5-2.1 - fold excess of the stoichiometry of the reaction mixture, by being supplied with a mixture of inert gas raw TFMSK distilled at atmospheric pressure to its selection at a vapor temperature of the reaction mixture to 180-190 ^o C, to the raw TF SK is added silica and the resulting mixture was refluxed under vacuum (absolute pressure of 550-600 mm Hg) while supplying inert gas into the mixture, followed by distillation, and collecting the desired fraction with a vapor temperature of 145-152 ^o C, side fractions are returned either to the head of the process (as an additive to H ₂ SO ₄ ), or used as an additive to the raw TFMSK, or subjected to distillation (separately or together with the raw TFMSK), or sent for hydrolysis in an alkaline solution of metal hydroxide for disposal and triflate ion. The method provides TFMSK with the content of the main substance according to NMR analysis nuclei F ¹⁹ is not below 99.9% by mole and the content of F ^- is not higher than 10 ppm, SO ₄ ^2- is not greater than 100 ppm to form particulate removed easily bottoms during synthesis TFMSK , on the neutralization of residual acidity which is spent less alkaline or carbonate reagent. The rationale for the proposed method is as follows.

In the synthesis of TFMSC in the reaction mixture there are reactions:
(CF ₃ SO ₃ ) ₂ Ва + H ₂ SO ₄ = BaSO ₄ + 2СF ₃ SO ₃ Н (1) - the main reaction.

Adverse reactions involving impurities, intermediates and starting reagents:
BaF ₂ + H ₂ SO ₄ = BaSO ₄ + 2HF (2)
HF + SO ₃ = HSO ₃ F (3)
see J. Simons. Fluorine and its compounds. - M .: Inlit, 1953

H ₂ SO ₄ + HF = HSO ₃ F + H ₂ O (4)
see there.

НSO ₃ F + CF ₃ SO ₃ H -> CF ₃ SO ₃ CF ₃ + СF ₃ OSO ₂ F (5)
see J. of Org Chem., 52, 19, 1987.

НSO ₃ F + 2 CF ₃ SO ₃ H = СF ₃ SO ₃ CF ₃ + SO ₂ + HF + H ₂ SO ₄ (6)
see "Synthesis", 1976, p. 319-320.

SO ₃ + 2 CF ₃ SO ₃ H = CF ₃ SO ₃ CF ₃ + SO ₂ + H ₂ SO ₄ (7)
see Tetrahedron Letters, vol. 22, p. 65-68, 1981.

SiO ₂ + 6HF = H ₂ SiF ₆ + 2H ₂ O (8)
see N. S. Nikolaev, S.N. Suvorov et al. Analytical chemistry of fluorine. - M: Science, 1970.

H ₂ SiF ₆ + H ₂ SO ₄ = 2HSO ₃ F + SiF ₄ + 2H ₂ O (9)
see V.A. Zaitsev, A.A. Novikov et al. Production of fluoride compounds in the processing of phosphate raw materials. -M .: Chemistry, 1982.

2HSО ₃ F + 2Н ₂ О = 2H ₂ SO ₄ + 2HF (10)
see there.

SiО ₂ + 4HSО ₃ F = SiF ₄ + 2H ₂ SO ₄ + 2SO ₃ (11)
see N. Ishikawa, E. Kobayashi. Fluorine, chemistry and application. - M.: Mir, 1982.

SiO ₂ + 2H ₂ SO ₄ + 2BaF ₂ = SiF ₄ + 2BaSO ₄ + 2H ₂ O (12)
in the same place.

The presence of the indicated fluorine-containing impurities in TFMSC was confirmed by us by NMR analyzes on ¹⁹ F and IR nuclei.

1. For the main reaction (1):
(CF ₃ SO ₃ ) ₂ Ba + H ₂ SO ₄ = BaSO ₄ + 2CF ₃ SO ₃ H
The theoretical mass ratio of the TFMSC salt to H ₂ SO ₄ is 1: 0.225. In the prototype, the mass ratio of salt to acid is 1: 1, which corresponds to a 3.5-4.5-fold excess of sulfuric acid relative to stoichiometry. Empirically, we found that for the treatment of salt, sulfuric acid must be added in an amount exceeding stoichiometry by 1.5-2.1 times. With a large excess of acid there will be an overspending of sulfuric acid, additional costs for the neutralization of waste. With a smaller excess, sulfuric acid is not enough to create a homogeneous mixture, the yield of TFMSC is reduced. In addition, solid wastes after distillation of crude TFMSC at the indicated ratio (1.5-2.1-fold excess from stoichiometry) have the consistency of a loose, unsintered mass that can be easily removed from the reactor. With a greater or lesser amount of sulfuric acid, hard-to-remove clay-like or vitrified cakes are formed in the reactor. Stirring of the reaction mixture is a prerequisite for the complete transfer of the triflate ion from the salt to TFMSC. In the absence of mixing, a “gang” occurs with a significant amount of unreacted components.

1. Reaction (2): BaF ₂ + H ₂ SO ₄ = BaSO ₄ + 2HF
always takes place, since the presence of metal fluoride (BaF ₂ ) in the TFMSC salt is due to the hydrolysis of trifluoromethanesulfofluoride [СF ₃ SO ₂ F + Ва (ОН) ₂ = Ва (СF ₃ SO ₃ ) ₂ + BaF ₂ ] and the technological features of the production process salts of TFMSC associated with dilution of the initial alkali with water (the greater the dilution with water, the more crystals of metal fluoride will go into the solution, which after evaporation is filtered) and the fine particles of insoluble metal fluoride will slip through the filter when filtering the hydrolyzed solution.

2. Reaction (3): HF + SO ₃ = HSO ₃ F
passes easily and quantitatively in vapors distilled from the reaction mixture. The source of SO ₃ is the concentrated sulfuric acid used. It is known that a mixture of H ₂ SO ₄ and H ₂ O with an acid content of 98.3 wt.% Corresponds to the azeotropic composition, the vapor pressure of H ₂ O and SO ₃ above it is minimal. From this point of view it should be used. But the presence of moisture in the reaction mixture dramatically reduces the yield of TFMSC due to the formation of TFMSC monohydrate (CF ₃ SO ₃ H • H ₂ O), which remains almost completely in the bottom residue. At a concentration of sulfuric acid of 99.5-100.5%, the yield of TFMSC increases. The use of sulfuric acid with a concentration above 100.5% due to an increase in the vapor pressure of SO ₃ above it leads to an increase in the content of TFMSC trifluoromethyl ether, fluoride and sulfate ions in the reaction mixture (reactions 6, 7):
НSO ₃ F + 2 СF ₃ SO ₃ Н = СF ₃ SO ₃ СF ₃ + SO ₂ + HF + H ₂ SO ₄ (6)
SO ₃ + 2 CF ₃ SO ₃ H = CF ₃ SO ₃ CF ₃ + SO ₂ + H ₂ SO ₄ (7).

3. Fluorosulfonic acid (see reactions 3, 4, 9) boils in the same temperature range as TFMSC, it is distilled off with it. Subsequently (during the distillation of the raw TFMSC), its slow decomposition by reactions 5, 6, 10 and intensive decomposition by reaction (11) occurs with removal of SiF ₄ from the system.

4. The addition of silicon dioxide at the stages of the treatment of the TFMSC salt with sulfuric acid and the distillation of the crude TFMSC promotes the conversion of HF and HCO ₃ F to easily removable silicon tetrafluoride (reactions 8, 9, 11, 12).

 5. The supply of inert gas to the reaction volume during the distillation of the raw TFMSK helps to remove easily boiling impurities from the reaction volume, and also prevents contact of the selected distillation fractions with atmospheric air.

In connection with the foregoing, the proposed method for producing TFMSK is as follows. The dried TFMSC salt (for example, barium trifluoromethanesulfonate) and silicon dioxide are loaded into the reactor, the mixer is turned on, and 99.5-100.5% sulfuric acid is added in an amount exceeding stoichiometry according to the main reaction equation (1) by 1.5-2 , 1 time, turn on the heating, open the nitrogen supply to the reaction space and distill the crude TFMSK at atmospheric pressure and select it to the temperature of the vapor of the distilled mixture 180-190 ^o C. The distilled vapors are condensed in a refrigerator cooled by water, the condensed raw TFMSK is collected in a reception room capacity. Upon reaching a vapor temperature of 190 ^o With the heating of the reactor is turned off, the waste is unloaded, neutralized and sent for disposal. At this stage, they are freed from excess sulfuric acid in the system. At a vapor temperature above 190 ^o With in the raw material will come in significant quantities of sulfuric acid. If you turn off the heating when the vapor temperature is below 180 ^o C, the output TFMSK in raw will decrease. The raw TFMSC is loaded into a reactor equipped with a reflux condenser, silicon dioxide is added there, a cold water supply is opened into the jacket of the reflux condenser, and heating is turned on. An inert gas (nitrogen) is supplied to the system, the system is placed under vacuum (absolute pressure 550-600 mm Hg), the mixture is kept at boiling for 2 hours (at this stage, decomposition of fluorosulfonic acid occurs, removal of the bulk of low-boiling impurities: HF , SiF ₄ , CF ₃ SO ₃ CF ₃ , CF ₃ OSO ₂ F), after which the water supply to the reflux condenser is closed and the selection of I fraction begins. Finish its selection at a vapor temperature of 148 ^o C. At a vapor temperature of 148-152 ^o With selected II (target) fraction. Then, the III fraction is taken to a vapor temperature of 155 ^o C. At a vapor temperature of 155 ^o C, the heating of the distillation cube is turned off, the system is filled with nitrogen to atmospheric pressure, the I and III fractions are combined, subjected to either distillation under conditions similar to the distillation of the raw TFMSK to obtain an additional target amount fractions, or added to the raw TFMSK before distillation, (it is also possible to use trifluoromethanesulfonic acid used to treat the dehydrated salt as an additive to sulfuric acid), and the bottom part is hydrolyzed in internal solution to recover therefrom the triflate ion. Nitrogen, both in the synthesis of raw TFMSK and in its distillation, is supplied in an amount of 7-10% of the volume of distilled vapors. Below are examples of the method (see table).

Claims (5)

1. A method of producing trifluoromethanesulfonic acid by treating a dehydrated salt of trifluoromethanesulfonic acid by heating with an excess of concentrated sulfuric acid and distilling trifluoromethanesulfonic acid from the reaction mixture, characterized in that silicon dioxide is added to the dehydrated salt, and sulfuric acid with a concentration of 99.5-100 is used to treat the salt mixture with silicon dioxide , 5%, from the reaction mixture under stirring and under inert gas feed raw distilled trifluoromethanesulfonic vapor to temperature 180-190 ^o C at atmospheric pressure, to the raw trifluoromethanesulfonic acid was added silica and the resulting mixture was subjected to boiling under vacuum and supplying an inert gas into it to return the evaporated products with a reflux condenser, followed by distillation of the mixture is subjected to distillation side-stream disposal.  2. The method according to p. 1, characterized in that sulfuric acid for processing a mixture of salt and silicon dioxide is added in an amount exceeding stoichiometry by 1.5-2.1 times. 3. The method according to claims 1 and 2, characterized in that the distillation of the crude trifluoromethanesulfonic acid is carried out at an absolute pressure of 550-600 mm Hg. with the selection of the target fraction at a vapor temperature of 145-152 ^o C.  4. The method according to claims 1 to 3, characterized in that the inert gas is fed into the reaction mixture during synthesis and during distillation of the crude trifluoromethanesulfonic acid in an amount equal to 10% of the volume of distilled vapor of the reaction mixture.  5. The method according to claims 1 to 4, characterized in that the side fractions of the distillation of the crude trifluoromethanesulfonic acid are utilized by distillation or by addition to sulfuric acid at the initial stage of the process, or by hydrolysis of them in an alkaline earth metal hydroxide.

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