CA2067077A1 - Process for the preparation of perfluoroethercarboxylic acids - Google Patents
Process for the preparation of perfluoroethercarboxylic acidsInfo
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- CA2067077A1 CA2067077A1 CA 2067077 CA2067077A CA2067077A1 CA 2067077 A1 CA2067077 A1 CA 2067077A1 CA 2067077 CA2067077 CA 2067077 CA 2067077 A CA2067077 A CA 2067077A CA 2067077 A1 CA2067077 A1 CA 2067077A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
- B01J19/1812—Tubular reactors
- B01J19/1837—Loop-type reactors
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/04—Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid halides
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Abstract
Abstract Process for the preparation of perfluoroethercarboxylic acids The invention relates to a process for the preparation of perfluoroethercarboxylic acids of the formula (I) Rf-COOH
from perfluoroetheracyl fluorides of the formula (II):
(II) Rf-COF
where Rf is equal to CmF2m+1-O-(C3F60)n-CF(CF3)-, in which m = 1 - 8 and n = O - 8, in which the acyl fluorides (II) are diluted with 0.5 to 5 times the amount by weight of a fluorinated inert solvent and the diluted mixture is then intensively mixed with 2-15 mol of water per mole of acyl fluoride and the organic phase obtained after phase separation is freed from the solvent by distillation.
from perfluoroetheracyl fluorides of the formula (II):
(II) Rf-COF
where Rf is equal to CmF2m+1-O-(C3F60)n-CF(CF3)-, in which m = 1 - 8 and n = O - 8, in which the acyl fluorides (II) are diluted with 0.5 to 5 times the amount by weight of a fluorinated inert solvent and the diluted mixture is then intensively mixed with 2-15 mol of water per mole of acyl fluoride and the organic phase obtained after phase separation is freed from the solvent by distillation.
Description
2~7~
HOECHST AKq~IENGESELLSCH~q~ HOE 91/F 121 Dr.~/Pl Description Proce~ for the preparation of perfluoroethercarboxylic ac:ids The invention relates to a process for the preparation of perfluoroethercarboxylic acids of the formula (I) Rr-COOH
from perfluoroetheracyl fluorides of the formula (II):
(II) Rr-COF
where Rr i8 equal to CmF~l-O-(C3F60)n-CF(CF3)-, in which m = 1 - 8 and n = 0 - 8.
Perfluoroethercarboxylic acids are important inter-mediatec for the preparation of non-combustible, tempera-ture-stable perfluoropolyether~, which are used as inert liquids (US Patent 3 665 041, US Patent 3 250 808). They sre further u~ed as surfactants and hydrophoblzing a~ents.
The preparation of perfluoroalkanoic acids by electro-fluorination of acyl fluorides and subsequent hydrolysis of the resulting perfluoroalkanoyl fluorides is already known (US Patent 4 022 824, US Patent 4 927 962~.
It is also already known to prepare perfluoroether-carboxylic acids by oligomerization of perfluorinated epoxides and hydrolysis of the re~ulting perfluoroether-acyl fluoride~ (US Patent 3 274 239, US Patent 3 250 808). However, in US Patent 3 274 239 it i8 not stated in more detail by which method the hydrolysis ~hould be carried out. According to Examples 7 and 9 of US Patent 3 250 8~8, for this purpo~e, perfluoroether-acyl fluorides are dissolved in perfluorodimethylcyclo-butane and hydrolyzed with a 60-fold exce~s of water. The example6 mentioned show that thi~ process result~ in low yields of 65 or 25% and that comparatively large amount~
. . ., ' ': , ` . ~ , .
2~a77 of water and solvent and also long reaction times (60 min to 60 hours) are required. The process i8 therefore little suited for industrial application.
What ha~ not been mentioned i8 that the perfluoroether-carboxylic acids obtained in such a manner containfluoride ion~ (since aqueous hydrofluoric acid results from the reaction), which lead to corrosion of the distillation apparatus used ~ubsequently.
A process has now been found which permits by simple means - and thus also on an industrial scale - perfluoro-ethercarboxylic acids which are low in fluoride and free from by-products to be obtained from the perfluoro-etheracyl fluorides.
The invention relates to a process for the preparation of perfluoroethercarboxylic acids of the formula (I) R~-COOH
from perfluoroetheracyl fluorides of the formula (II):
~II) R~-COF
where Rr is equsl to CmF2~l-O-(C3F6O)n-CF(CF3)-, in wh~ch m z 1 - 8 and n = O - 8, which comprises diluting the acyl fluorides (II) with 0.5 to 5 times the amount by weight of a fluorinated inert solvent and then intensively mixing the dilution with 2-15 mol of water per mole of acyl fluoride and, after phase separation, freeing the resulting organic phase from the solvent by distillation.
The perfluoroetheracyl fluoride i8 thus hydrolyzed to give the corresponding acid (I):
RrCOF + HzO > R~COOH + HF aq.
Two phases are then obtained: a light aqueous phase, which comprises a diluted aqueous hydrofluoric acid, and a heavy organic phase which comprises 20~7~
perfluoroethercarboxylic acid and solvent. The organic phase is separated off by simple phase separation. The fluoride content of the organic phase i8 dependent on the n~olecular weight of the acid (I); it is between 10 and ';00 ppm. If it i~ over 100 ppm, it is advantageous to reduce it to a value below 100 ppm by a ~imple aqueous e~xtraction of the organic phase.
Thi~ value i8 low enough to permit corrosion-free distil-lation of the organic phase in conventional stainless steel apparatuses to separate the solvent and perfluoro-ethercarboxylic acid (I).
By distillation of the organic phase, if necessary after extraction, the acid is obtained in a purity > 99% and virtually free from fluoride. The fluoride content is generally < 10 ppm; only with a low molecular weight of the carboxylic acid is it between 10 and 30 ppm.
If a single acid fluoride (II) was used for the hydrolysis, there is no need for a distillation of the acid obtained in thi~ way, ~ince the acid, following 8eparation by distillation (preferably using a thin film evaporator) of the lower boiling solvent, only contains water in an amount between 1 and 5% by weight. This water content is without significance for most applications.
However, if a mixture of a plurality of acid fluorides (II) is hydrolyzed, a solution is obtained of a mixture of the corresponding acids (I), which, following distil-lation off of the solvent, must still be separated into the individual acids by distillation.
Fluorinated inert solvents suitable for the process are:
l-H-perfluorohexane C6F13H, Perfluoroalkanes of the formula C~F2~2 where a = 5 - 12, Chlorofluoroalkanes of the formula C2Cl3F3 and C3Cl2F5H, Fluorinated ethers and polyethers of the formula 2~67~77 ~ 3 F ~ O ~C F - C ~ 2 -- o ~ C F - C F ~ O - C F C F 1 ~) C
where b - 0-4 and c - 0-4 01- .
,, . , _ . . _ ,, , .. _ ... . . ..
C3~7-0 ~C~ - CF2 - 0~ CFdHe c~3 S where b 0-4 and d = 1, e = 1 or d ~ 2, e 0 The fluorinated alkanes mentioned are described in A.M. Lovelace, Aliphatic Fluorine Compounds, Reinhold Publ. Corp., New York, 1958, and the mentioned fluorinated ethers and polyethers are de6cribed in German Offenlegungsschrift 3 828 848 and US Patent 3 250 808.
Particular preference i~ given to 1,1,2-trichloro-1,2,2-trifluoroethane, perfluorohexane, perfluoropropyl ethyl ether, perfluoropropyl tetrafluoroethyl ether and 1-H-perfluorohexane, but especially to chlorofluorocarbon F 113 (1,1,2-trichloro-1,2,2-trifluoroethane) because of its favorable boiling point of 47C and its low price.
0.5 to 2 times the weight of solvent, relative to perfluoroetheracyl fluoride (II) are preferably used. For the hydrolysis, 9 to 12 mol of water per mole of per-fluoroetheracyl fluoride are preferably u~ed. This amount of water i6 lower by a factor of 5 to 7 than according to the abovementioned US Patent 3 250 808. The preferred roughly 9-12-fold excess of water over the stoichiometric amount has proved to be advantageous, in order to separate off the resulting hydrogen fluoride in the form of approximately 10% ~trength aqueous hydrofluoric acid.
For the abovementioned extraction of fluoride from the .
- 5 ~ 7~
organic phase, which, if necessary, is carried out prior to removal of the solvent, the 0.1- to 0.5-fold quantity o~ water is added directly to the organic phase from the llydrolysis - solvent and acid (I).
~rhe aqueous extract obtained by extraction of the organic phase contains up to 1% by weight of perfluoroether-carboxylic acid~ (I) and in a continuous operation is advantageously reused for the hydrolysis of the perfluoroetheracyl fluorides (II).
By this means the yield i6 increased and residues are avoided. The total yield of acid is then greater than 97%.
The preparation of the perfluoroetheracyl fluorides can be carried out by oligomerization of hexafluoropropena oxide (HFP0) (US Patent 3 247 239 and US Patent 3 250 808). In this case, a mixture of oligomeric acid fluorides (II) results, which can be used in the hydrolysis according to the reaction without previous ~eparation of the oligomers.
For the industrial-~cale implementation of the hydrolysis and - where carried out - the extraction, all apparatuses are in principle suitable which permit a good mixing of organic and aqueous phase during the hydroly6is, for example by means of mechanical stirrers, by means of a centrifugal pump, by mean6 of flow mixer6 or by means of ultrasound.
For discontinuous hydrolysi6, a stirred tank has proved advantageous; for a continuous process, a flow tube equipped with mixing elements, or a loop reactor having a rapidly-rotating pump for mixing are well suited. The extraction can be carried out in the same appaxatuses;
however, a mixer-settler and a vibrated base column have proved to be expedient.
Materials for the apparatuses which are particularly suitable are pla6tics, such as polyethylene, polypropylene, PVC, plastic-clad steel and those metals 2067~77 which are resistant to fluoride-containing acids, such as Hastelloy steels. Glass can also be u~ed as the material for the extraction apparatus.
The process described has the following advantages:
It permits short reaction times and gives high space-time yields of 0.5 kg/(h l) in the stirred tank, 2.0 kg/(h l) in the flow mixer and 30 kg(h l) in the pumped mixer, compared with 0.1 kq/(h l) according to the process described in US Patent 3 250 808. Using the preferred low amount of solvent (0.5- to 2-fold amount) and with recycling of solvent and, where appropriate, extraction water, yields ~ 97% and high purities are achieved.
The process permits in particular the preparation of high boiling point, perfluoroethercarboxylic acids of limited thermal stability in a pure form, since following the hydrolysis of the corresponding individual acid fluoride only the low boiling point solvent mu~t be removed and no distillation of the acid i~ required.
A particular embodiment of the process allows conversion of a mixture of perfluoroetheracyl fluorides of the formula ~II), in which m equals 3 and n equals 0, 1, 2 or 3, as obtained by catalytic oligomerization of hexa-fluoropropene oxide (US Patent 4 874 557), into the corresponding individual perfluoroethercarbGxylic acids.
By hydrolysis of the mentioned acid fluoride mixture in trichlorotrifluoroethane and extraction of fluoride (as described above), a ~olution of the corresponding carboxylic acids (I) is obtained which contains 50 to 100 ppm of fluoride and 3-4~ by weight of water.
Small amounts of solid or high boiling point impurities from the oligomerization catalyst, such as for example potassium salt and adiponitrile, can, during the direct fractionation of this solution by rectification in vacuo, lead to a portion of the carboxylic acids being decomposed. Preferably, therefore, a procedure is u~ed such that, in one distillation step under mild thermal conditions using a thin film evaporator, the low boiling point solvent i~ first separated o~f and then the perfluoroethercarboxylic acids are separated off from the eolid or high boiling point impurities. The perfluoro-et:hercarboxylic acids are then separated from each other by fractional vacuum distillation and are obtained without decomposition in a form free from chloride.
Examples The percentage figures mentioned below are percentages by weight, where not otherwise stated or obvious. 1,1,2-Trichloro-1,2,2-trifluoroethane is termed in short trichlorotrifluoroethane.
Comparison Example 1 200 g of water (11.1 mol) were introduced into a 1 1 polyethylene vessel equipped with stirrer, dropping funnel, reflux cooler and lnternal thermometer and cooled using an ice/water cooling bath to 10-15C. 498 g (1.0 mol) of C3F7-O- ( C3F60 ) ~CF ( CF3 ) -COF were added dropwi~e with vigorous stirring. The two resulting phases were separated. The organic phase (460 g) contained 90.5% of C3F,-0-(C3F60)-CF(CF3)-C00~ (yield 83.9%), 9.4% water and 1370 ppm of fluoride. V4A steel was corroded by this organic phase. This shows that in a hydrolysis without organic solvent the perfluoroether-carboxylic acid formed has a very high fluoride content.
Example 1 800 g of water (44.4 mol) were introduced into a 1 1 polyethylene ves6el equipped with stirrer~ dropping funnel, reflux cooler and internal thermometer and were cooled with stirring to 10-15C. A 601ution of 2000 g of C3F7-O- ( C3F60 ) -CF ( CF3 ) -COF ( 4.0 mol) in 2000 g of tri-chlorotrifluoroethane was added dropwise in the course of 1 h, where the internal temperature did not rise above 25C. After completion of addition, the mixture was 20g7~77 ~tirred for 5 min; the two phases resulting were then ~eparated. From the organic phase, after removal of the E~olvent in vacuo at 25C, 2035 g of C3F,-O-(C3F6O)-CF(CF3)-COOH were o~tained, having a water content of 3.5~ and a fluoride content of 30 ppm. The yield was 98.5%. A
aorrosion test showed no erosion on V4A steel.
~xample 2 Analogously to Example 1, 2000 g of C3F,-O-(C3F6O)2-CF(CF3)-COF t3.0 mol) in 2000 g of trichlorotri-fluoroethane were reacted with 600 g of water (33.3 mol).
2010 g of C3F,-O-(C3F6O)2-CF(CF3)-COOH were obtained having a water content of 1.2% and a fluoride content of 15 ppm.
The yield wa~ 99.6%.
Example 3 Analogously to Example 1, 2000 g of C3F,-O-CF(CF3)-COF
(6.0 mol) in 2000 g of trichlorotrifluoroethane were reacted with 1200 g of water (66.6 mol). 2082 g of C3F,-O-CF~CF3)-COOH were obtained having a water content of 5.5%
and a fluoride content of 190 ppm. After distillation at atmospheric pressure, 1942 g of C3F,-O-CF(CF3)-COOH were obtained, having a boiling point of 143C, a water content < 0.3% and a fluoride content of 18 ppm. The yield was 97.1%.
Example 4 30 g of C3F,-O-(C3F6O)-CF(CF3)-COF (60 mmol) were dissolved in 30 g of perfluoro-2-methylpentane in a 100 ml poly-ethylene vessel. 11 g of water (0.61 mol) were added in the course of 5 min with intensive stirring. Subsequent phase separation gave 30 g of organic phase, which contained 29 g of C3F7-O-(C3F6O)-CF(CF3)-COOH, 1 g of water and 65 ppm of fluoride.
Example 5 The apparatus used was a loop reactor (Fig. 1) which comprised a centrifugal pump (1) (output 60 l/h) for mixing the reactants, two metering pumps (2) and (3), a 2067~77 g water cooler (4) (length 20 cm) and a controllable valve (5), which were connected together in a ring by plastic tubing (6) (diameter 0.8 cm) and which were connected, by means of a bleeder valve (7), with a separator vessel (8). The reaction volume of the loop reactor was 200 ml.
In the cour~e of 15 min, 1500 g of C3F,-O-(C3F6O)-CF(CF3)-COF (3.0 mol), diluted with 1500 g of trichlorotrifluoro-ethane, and 580 g of water (32.2 mol) were pumped into the apparatus via the metering pumps (2) and (3). The product was continuously removed via the bleeder valve (7) into the separator vessel (8) and was there separated into an aqueous and an organic phase. 1480 g of C3F7-O-(C3F6O)-CF(CF3)-COOH having a water content of 1% and a fluoride content of 70 ppm were obtained as the organic phase. The yield was 98.1%.
Example 6 250 g of C3F7-O-(C3F6O)-CF(CF3)-COF (0.5 mol) in 200 g of trichlorotrifluoroethane and 100 g of water (5.5 mol) were simultaneously pumped in the course of 15 min, with the aid of two membrane pumps, through a 30-cm-long plastic tube (internal diameter 18 mm, volume 76 cm3) which contained flow mixer elements. After phase ~eparation, 240 g of C3F,-O-(C3F6O)-CF(CF3)-COO~ were obtained with complete conversion.
Example 7 360 g of a mixture (organic phase) obtained by oligomeri-zation of hexafluoropropene oxide and subsequent hydrolysis according to the invention and composed of trichlorotrifluoroethane and perfluoroethercarboxylic acids of the formula C3F7-O-(C3F6O)A-CF(CF3)-COO~ (com-position: 8% carboxylic acid having n = 0; 28% having n = l; 8.7% having n = 2; 54% trichlorotrifluoroethane) having a fluoride content of 440 ppm and a water content of 3.5% were mixed in a stirred vessel for 10 min with 120 g of water for fluoride extraction. By means of phase separation, 348 g of organic phase having a fluoride content of 77 ppm were obtained. This was separated via 2~7~77 a thin film evaporator (glass, steel blade; heating temperature 80~C, pressure 1008 mbar) into 1;79 g of distillate (trichlorotrifluoroethane) and 162 g of bottom product. The bottom product was separated at 130C and 10 mbar via the same thin film evaporator into 2.2 g of solid residue, 2.9 g of residual trichlorotrifluoro-ethane (in the cold tr~p) and 154 g of distillate. The distillate was separated ~y fractional vacuum distil-lation on a packed column into 25 g of C3F7-O-CF(CF3)-COOH
(boiling point 65C/40 mbar; purity 99.1%, fluoride content 14 ppm), 94 g of C3F7-O-(C3F6O~-CF(CF3)-COOH
(boiling point 87C/20 mbar; purity 99.6%, fluoride content 4 ppm) and 27 g of C3F7-O-(C3F6O)2-CF(CF3)-COOH
(boiling point 129C/20 mbar; purity 99.4~, fluoride content l.S ppm).
Example 8 350 g of C3F7-O-(C3F60)3-CF(CF3)-COF (42.1 mmol) were diluted with 350 g of trichlorotrifluoroethane, and 84 g of water (4.7 mol) were added to the mixture in a polyethylene vessel with stirring. After phase separation and removal of the solvent at 25C in vacuo, 332 g of C3F7-O-(C3F6O)3-CF(CF3)-COOH were obtained.
Example 9 60 kg of extraction water from a previous extraction batch were introduced, via pipe (13) and metering pump (14), into a recirculation reactor ~Fig. 2), comprising a 600 1 polyethylene vessel (9) having a cooling jacket, centrifugal pump (10) (3 m3/h), Hastelloy cooler (11) and circuit piping (12), and the extraction water was pumped round the circuit. 160 kg of a mixture of oligomeric per-fluoroetheracyl fluorides of the formula C3F7-O-(C3F6O) n~
CF(CF3)-COF (n equals 0, 1, and 2), which was prepared by oligomerization of HFPO, was diluted with 155 kg of trichlorotrifluoroethane and pumped (approximately 110 kg/h) into the reaction vessel (9) via the pipe (15), metering pump (16) and circuit piping (12). At the same time, 60 kg of extraction water (20 kg~h) was pumped in 2~67~7 via pipe (17). 30 min after completion of addition, the circulation pump ~10) was turned off and the two phases resulting were separated in the vessel (9). The organic phase was transferred via valve (18) and pipe (19) into a vibrated base column (20) composed of glass (length m, internal diameter 50 mm) and extracted there with 60 kg of water, to reduce the chloride content. 320 kg of perfluoroethercarboxylic acid solution (organic phase) having a water content of 3.5% and a fluoride content of 97 ppm were obtained in this case via pipe (21). Material tests were carried out using 1 l of this solution on V4A, Hastelloy C4 and Hastelloy C22 steels over several days under hot conditions. All materials were resistant to the solution, so that further work-up could be carried out by distillation in a conventional steel apparatus. The fluoride contents of the distilled acids were 20 ppm (C3F~-O-CF(CF3)-COOH), 7 ppm (C3F,-O-(C3F6O)-CF(CF3)-COOH) and 4 ppm (C3F7-O-(C3F6O)2-CF(CF3)-COOH).
HOECHST AKq~IENGESELLSCH~q~ HOE 91/F 121 Dr.~/Pl Description Proce~ for the preparation of perfluoroethercarboxylic ac:ids The invention relates to a process for the preparation of perfluoroethercarboxylic acids of the formula (I) Rr-COOH
from perfluoroetheracyl fluorides of the formula (II):
(II) Rr-COF
where Rr i8 equal to CmF~l-O-(C3F60)n-CF(CF3)-, in which m = 1 - 8 and n = 0 - 8.
Perfluoroethercarboxylic acids are important inter-mediatec for the preparation of non-combustible, tempera-ture-stable perfluoropolyether~, which are used as inert liquids (US Patent 3 665 041, US Patent 3 250 808). They sre further u~ed as surfactants and hydrophoblzing a~ents.
The preparation of perfluoroalkanoic acids by electro-fluorination of acyl fluorides and subsequent hydrolysis of the resulting perfluoroalkanoyl fluorides is already known (US Patent 4 022 824, US Patent 4 927 962~.
It is also already known to prepare perfluoroether-carboxylic acids by oligomerization of perfluorinated epoxides and hydrolysis of the re~ulting perfluoroether-acyl fluoride~ (US Patent 3 274 239, US Patent 3 250 808). However, in US Patent 3 274 239 it i8 not stated in more detail by which method the hydrolysis ~hould be carried out. According to Examples 7 and 9 of US Patent 3 250 8~8, for this purpo~e, perfluoroether-acyl fluorides are dissolved in perfluorodimethylcyclo-butane and hydrolyzed with a 60-fold exce~s of water. The example6 mentioned show that thi~ process result~ in low yields of 65 or 25% and that comparatively large amount~
. . ., ' ': , ` . ~ , .
2~a77 of water and solvent and also long reaction times (60 min to 60 hours) are required. The process i8 therefore little suited for industrial application.
What ha~ not been mentioned i8 that the perfluoroether-carboxylic acids obtained in such a manner containfluoride ion~ (since aqueous hydrofluoric acid results from the reaction), which lead to corrosion of the distillation apparatus used ~ubsequently.
A process has now been found which permits by simple means - and thus also on an industrial scale - perfluoro-ethercarboxylic acids which are low in fluoride and free from by-products to be obtained from the perfluoro-etheracyl fluorides.
The invention relates to a process for the preparation of perfluoroethercarboxylic acids of the formula (I) R~-COOH
from perfluoroetheracyl fluorides of the formula (II):
~II) R~-COF
where Rr is equsl to CmF2~l-O-(C3F6O)n-CF(CF3)-, in wh~ch m z 1 - 8 and n = O - 8, which comprises diluting the acyl fluorides (II) with 0.5 to 5 times the amount by weight of a fluorinated inert solvent and then intensively mixing the dilution with 2-15 mol of water per mole of acyl fluoride and, after phase separation, freeing the resulting organic phase from the solvent by distillation.
The perfluoroetheracyl fluoride i8 thus hydrolyzed to give the corresponding acid (I):
RrCOF + HzO > R~COOH + HF aq.
Two phases are then obtained: a light aqueous phase, which comprises a diluted aqueous hydrofluoric acid, and a heavy organic phase which comprises 20~7~
perfluoroethercarboxylic acid and solvent. The organic phase is separated off by simple phase separation. The fluoride content of the organic phase i8 dependent on the n~olecular weight of the acid (I); it is between 10 and ';00 ppm. If it i~ over 100 ppm, it is advantageous to reduce it to a value below 100 ppm by a ~imple aqueous e~xtraction of the organic phase.
Thi~ value i8 low enough to permit corrosion-free distil-lation of the organic phase in conventional stainless steel apparatuses to separate the solvent and perfluoro-ethercarboxylic acid (I).
By distillation of the organic phase, if necessary after extraction, the acid is obtained in a purity > 99% and virtually free from fluoride. The fluoride content is generally < 10 ppm; only with a low molecular weight of the carboxylic acid is it between 10 and 30 ppm.
If a single acid fluoride (II) was used for the hydrolysis, there is no need for a distillation of the acid obtained in thi~ way, ~ince the acid, following 8eparation by distillation (preferably using a thin film evaporator) of the lower boiling solvent, only contains water in an amount between 1 and 5% by weight. This water content is without significance for most applications.
However, if a mixture of a plurality of acid fluorides (II) is hydrolyzed, a solution is obtained of a mixture of the corresponding acids (I), which, following distil-lation off of the solvent, must still be separated into the individual acids by distillation.
Fluorinated inert solvents suitable for the process are:
l-H-perfluorohexane C6F13H, Perfluoroalkanes of the formula C~F2~2 where a = 5 - 12, Chlorofluoroalkanes of the formula C2Cl3F3 and C3Cl2F5H, Fluorinated ethers and polyethers of the formula 2~67~77 ~ 3 F ~ O ~C F - C ~ 2 -- o ~ C F - C F ~ O - C F C F 1 ~) C
where b - 0-4 and c - 0-4 01- .
,, . , _ . . _ ,, , .. _ ... . . ..
C3~7-0 ~C~ - CF2 - 0~ CFdHe c~3 S where b 0-4 and d = 1, e = 1 or d ~ 2, e 0 The fluorinated alkanes mentioned are described in A.M. Lovelace, Aliphatic Fluorine Compounds, Reinhold Publ. Corp., New York, 1958, and the mentioned fluorinated ethers and polyethers are de6cribed in German Offenlegungsschrift 3 828 848 and US Patent 3 250 808.
Particular preference i~ given to 1,1,2-trichloro-1,2,2-trifluoroethane, perfluorohexane, perfluoropropyl ethyl ether, perfluoropropyl tetrafluoroethyl ether and 1-H-perfluorohexane, but especially to chlorofluorocarbon F 113 (1,1,2-trichloro-1,2,2-trifluoroethane) because of its favorable boiling point of 47C and its low price.
0.5 to 2 times the weight of solvent, relative to perfluoroetheracyl fluoride (II) are preferably used. For the hydrolysis, 9 to 12 mol of water per mole of per-fluoroetheracyl fluoride are preferably u~ed. This amount of water i6 lower by a factor of 5 to 7 than according to the abovementioned US Patent 3 250 808. The preferred roughly 9-12-fold excess of water over the stoichiometric amount has proved to be advantageous, in order to separate off the resulting hydrogen fluoride in the form of approximately 10% ~trength aqueous hydrofluoric acid.
For the abovementioned extraction of fluoride from the .
- 5 ~ 7~
organic phase, which, if necessary, is carried out prior to removal of the solvent, the 0.1- to 0.5-fold quantity o~ water is added directly to the organic phase from the llydrolysis - solvent and acid (I).
~rhe aqueous extract obtained by extraction of the organic phase contains up to 1% by weight of perfluoroether-carboxylic acid~ (I) and in a continuous operation is advantageously reused for the hydrolysis of the perfluoroetheracyl fluorides (II).
By this means the yield i6 increased and residues are avoided. The total yield of acid is then greater than 97%.
The preparation of the perfluoroetheracyl fluorides can be carried out by oligomerization of hexafluoropropena oxide (HFP0) (US Patent 3 247 239 and US Patent 3 250 808). In this case, a mixture of oligomeric acid fluorides (II) results, which can be used in the hydrolysis according to the reaction without previous ~eparation of the oligomers.
For the industrial-~cale implementation of the hydrolysis and - where carried out - the extraction, all apparatuses are in principle suitable which permit a good mixing of organic and aqueous phase during the hydroly6is, for example by means of mechanical stirrers, by means of a centrifugal pump, by mean6 of flow mixer6 or by means of ultrasound.
For discontinuous hydrolysi6, a stirred tank has proved advantageous; for a continuous process, a flow tube equipped with mixing elements, or a loop reactor having a rapidly-rotating pump for mixing are well suited. The extraction can be carried out in the same appaxatuses;
however, a mixer-settler and a vibrated base column have proved to be expedient.
Materials for the apparatuses which are particularly suitable are pla6tics, such as polyethylene, polypropylene, PVC, plastic-clad steel and those metals 2067~77 which are resistant to fluoride-containing acids, such as Hastelloy steels. Glass can also be u~ed as the material for the extraction apparatus.
The process described has the following advantages:
It permits short reaction times and gives high space-time yields of 0.5 kg/(h l) in the stirred tank, 2.0 kg/(h l) in the flow mixer and 30 kg(h l) in the pumped mixer, compared with 0.1 kq/(h l) according to the process described in US Patent 3 250 808. Using the preferred low amount of solvent (0.5- to 2-fold amount) and with recycling of solvent and, where appropriate, extraction water, yields ~ 97% and high purities are achieved.
The process permits in particular the preparation of high boiling point, perfluoroethercarboxylic acids of limited thermal stability in a pure form, since following the hydrolysis of the corresponding individual acid fluoride only the low boiling point solvent mu~t be removed and no distillation of the acid i~ required.
A particular embodiment of the process allows conversion of a mixture of perfluoroetheracyl fluorides of the formula ~II), in which m equals 3 and n equals 0, 1, 2 or 3, as obtained by catalytic oligomerization of hexa-fluoropropene oxide (US Patent 4 874 557), into the corresponding individual perfluoroethercarbGxylic acids.
By hydrolysis of the mentioned acid fluoride mixture in trichlorotrifluoroethane and extraction of fluoride (as described above), a ~olution of the corresponding carboxylic acids (I) is obtained which contains 50 to 100 ppm of fluoride and 3-4~ by weight of water.
Small amounts of solid or high boiling point impurities from the oligomerization catalyst, such as for example potassium salt and adiponitrile, can, during the direct fractionation of this solution by rectification in vacuo, lead to a portion of the carboxylic acids being decomposed. Preferably, therefore, a procedure is u~ed such that, in one distillation step under mild thermal conditions using a thin film evaporator, the low boiling point solvent i~ first separated o~f and then the perfluoroethercarboxylic acids are separated off from the eolid or high boiling point impurities. The perfluoro-et:hercarboxylic acids are then separated from each other by fractional vacuum distillation and are obtained without decomposition in a form free from chloride.
Examples The percentage figures mentioned below are percentages by weight, where not otherwise stated or obvious. 1,1,2-Trichloro-1,2,2-trifluoroethane is termed in short trichlorotrifluoroethane.
Comparison Example 1 200 g of water (11.1 mol) were introduced into a 1 1 polyethylene vessel equipped with stirrer, dropping funnel, reflux cooler and lnternal thermometer and cooled using an ice/water cooling bath to 10-15C. 498 g (1.0 mol) of C3F7-O- ( C3F60 ) ~CF ( CF3 ) -COF were added dropwi~e with vigorous stirring. The two resulting phases were separated. The organic phase (460 g) contained 90.5% of C3F,-0-(C3F60)-CF(CF3)-C00~ (yield 83.9%), 9.4% water and 1370 ppm of fluoride. V4A steel was corroded by this organic phase. This shows that in a hydrolysis without organic solvent the perfluoroether-carboxylic acid formed has a very high fluoride content.
Example 1 800 g of water (44.4 mol) were introduced into a 1 1 polyethylene ves6el equipped with stirrer~ dropping funnel, reflux cooler and internal thermometer and were cooled with stirring to 10-15C. A 601ution of 2000 g of C3F7-O- ( C3F60 ) -CF ( CF3 ) -COF ( 4.0 mol) in 2000 g of tri-chlorotrifluoroethane was added dropwise in the course of 1 h, where the internal temperature did not rise above 25C. After completion of addition, the mixture was 20g7~77 ~tirred for 5 min; the two phases resulting were then ~eparated. From the organic phase, after removal of the E~olvent in vacuo at 25C, 2035 g of C3F,-O-(C3F6O)-CF(CF3)-COOH were o~tained, having a water content of 3.5~ and a fluoride content of 30 ppm. The yield was 98.5%. A
aorrosion test showed no erosion on V4A steel.
~xample 2 Analogously to Example 1, 2000 g of C3F,-O-(C3F6O)2-CF(CF3)-COF t3.0 mol) in 2000 g of trichlorotri-fluoroethane were reacted with 600 g of water (33.3 mol).
2010 g of C3F,-O-(C3F6O)2-CF(CF3)-COOH were obtained having a water content of 1.2% and a fluoride content of 15 ppm.
The yield wa~ 99.6%.
Example 3 Analogously to Example 1, 2000 g of C3F,-O-CF(CF3)-COF
(6.0 mol) in 2000 g of trichlorotrifluoroethane were reacted with 1200 g of water (66.6 mol). 2082 g of C3F,-O-CF~CF3)-COOH were obtained having a water content of 5.5%
and a fluoride content of 190 ppm. After distillation at atmospheric pressure, 1942 g of C3F,-O-CF(CF3)-COOH were obtained, having a boiling point of 143C, a water content < 0.3% and a fluoride content of 18 ppm. The yield was 97.1%.
Example 4 30 g of C3F,-O-(C3F6O)-CF(CF3)-COF (60 mmol) were dissolved in 30 g of perfluoro-2-methylpentane in a 100 ml poly-ethylene vessel. 11 g of water (0.61 mol) were added in the course of 5 min with intensive stirring. Subsequent phase separation gave 30 g of organic phase, which contained 29 g of C3F7-O-(C3F6O)-CF(CF3)-COOH, 1 g of water and 65 ppm of fluoride.
Example 5 The apparatus used was a loop reactor (Fig. 1) which comprised a centrifugal pump (1) (output 60 l/h) for mixing the reactants, two metering pumps (2) and (3), a 2067~77 g water cooler (4) (length 20 cm) and a controllable valve (5), which were connected together in a ring by plastic tubing (6) (diameter 0.8 cm) and which were connected, by means of a bleeder valve (7), with a separator vessel (8). The reaction volume of the loop reactor was 200 ml.
In the cour~e of 15 min, 1500 g of C3F,-O-(C3F6O)-CF(CF3)-COF (3.0 mol), diluted with 1500 g of trichlorotrifluoro-ethane, and 580 g of water (32.2 mol) were pumped into the apparatus via the metering pumps (2) and (3). The product was continuously removed via the bleeder valve (7) into the separator vessel (8) and was there separated into an aqueous and an organic phase. 1480 g of C3F7-O-(C3F6O)-CF(CF3)-COOH having a water content of 1% and a fluoride content of 70 ppm were obtained as the organic phase. The yield was 98.1%.
Example 6 250 g of C3F7-O-(C3F6O)-CF(CF3)-COF (0.5 mol) in 200 g of trichlorotrifluoroethane and 100 g of water (5.5 mol) were simultaneously pumped in the course of 15 min, with the aid of two membrane pumps, through a 30-cm-long plastic tube (internal diameter 18 mm, volume 76 cm3) which contained flow mixer elements. After phase ~eparation, 240 g of C3F,-O-(C3F6O)-CF(CF3)-COO~ were obtained with complete conversion.
Example 7 360 g of a mixture (organic phase) obtained by oligomeri-zation of hexafluoropropene oxide and subsequent hydrolysis according to the invention and composed of trichlorotrifluoroethane and perfluoroethercarboxylic acids of the formula C3F7-O-(C3F6O)A-CF(CF3)-COO~ (com-position: 8% carboxylic acid having n = 0; 28% having n = l; 8.7% having n = 2; 54% trichlorotrifluoroethane) having a fluoride content of 440 ppm and a water content of 3.5% were mixed in a stirred vessel for 10 min with 120 g of water for fluoride extraction. By means of phase separation, 348 g of organic phase having a fluoride content of 77 ppm were obtained. This was separated via 2~7~77 a thin film evaporator (glass, steel blade; heating temperature 80~C, pressure 1008 mbar) into 1;79 g of distillate (trichlorotrifluoroethane) and 162 g of bottom product. The bottom product was separated at 130C and 10 mbar via the same thin film evaporator into 2.2 g of solid residue, 2.9 g of residual trichlorotrifluoro-ethane (in the cold tr~p) and 154 g of distillate. The distillate was separated ~y fractional vacuum distil-lation on a packed column into 25 g of C3F7-O-CF(CF3)-COOH
(boiling point 65C/40 mbar; purity 99.1%, fluoride content 14 ppm), 94 g of C3F7-O-(C3F6O~-CF(CF3)-COOH
(boiling point 87C/20 mbar; purity 99.6%, fluoride content 4 ppm) and 27 g of C3F7-O-(C3F6O)2-CF(CF3)-COOH
(boiling point 129C/20 mbar; purity 99.4~, fluoride content l.S ppm).
Example 8 350 g of C3F7-O-(C3F60)3-CF(CF3)-COF (42.1 mmol) were diluted with 350 g of trichlorotrifluoroethane, and 84 g of water (4.7 mol) were added to the mixture in a polyethylene vessel with stirring. After phase separation and removal of the solvent at 25C in vacuo, 332 g of C3F7-O-(C3F6O)3-CF(CF3)-COOH were obtained.
Example 9 60 kg of extraction water from a previous extraction batch were introduced, via pipe (13) and metering pump (14), into a recirculation reactor ~Fig. 2), comprising a 600 1 polyethylene vessel (9) having a cooling jacket, centrifugal pump (10) (3 m3/h), Hastelloy cooler (11) and circuit piping (12), and the extraction water was pumped round the circuit. 160 kg of a mixture of oligomeric per-fluoroetheracyl fluorides of the formula C3F7-O-(C3F6O) n~
CF(CF3)-COF (n equals 0, 1, and 2), which was prepared by oligomerization of HFPO, was diluted with 155 kg of trichlorotrifluoroethane and pumped (approximately 110 kg/h) into the reaction vessel (9) via the pipe (15), metering pump (16) and circuit piping (12). At the same time, 60 kg of extraction water (20 kg~h) was pumped in 2~67~7 via pipe (17). 30 min after completion of addition, the circulation pump ~10) was turned off and the two phases resulting were separated in the vessel (9). The organic phase was transferred via valve (18) and pipe (19) into a vibrated base column (20) composed of glass (length m, internal diameter 50 mm) and extracted there with 60 kg of water, to reduce the chloride content. 320 kg of perfluoroethercarboxylic acid solution (organic phase) having a water content of 3.5% and a fluoride content of 97 ppm were obtained in this case via pipe (21). Material tests were carried out using 1 l of this solution on V4A, Hastelloy C4 and Hastelloy C22 steels over several days under hot conditions. All materials were resistant to the solution, so that further work-up could be carried out by distillation in a conventional steel apparatus. The fluoride contents of the distilled acids were 20 ppm (C3F~-O-CF(CF3)-COOH), 7 ppm (C3F,-O-(C3F6O)-CF(CF3)-COOH) and 4 ppm (C3F7-O-(C3F6O)2-CF(CF3)-COOH).
Claims (9)
1. A process for the preparation of a perfluoroether-carboxylic acid of the formula (I) Rf-COOH from a perfluoroetheracyl fluoride of the formula (II) R1-COF
where R1 is equal to CmF2m+1-O-(C3F6O)n-CF(CF3)-in which m = 1 - 8 and n = 0-8.
which comprises diluting the acyl fluoride (II) with 0.5 to 5 times the amount by weight of a fluorinated inert solvent and then intensively mixing the dilution with 2-15 mol of water per mole of acyl fluoride and, after phase separation, freeing the resulting organic phase from the solvent by distillation.
where R1 is equal to CmF2m+1-O-(C3F6O)n-CF(CF3)-in which m = 1 - 8 and n = 0-8.
which comprises diluting the acyl fluoride (II) with 0.5 to 5 times the amount by weight of a fluorinated inert solvent and then intensively mixing the dilution with 2-15 mol of water per mole of acyl fluoride and, after phase separation, freeing the resulting organic phase from the solvent by distillation.
2. The process as claimed in claim 1, wherein the solvent used is a chlorofluoroalkane of the formula C2Cl3F3 or C3Cl2F5H.
3. The process as claimed in claim 1, wherein the solvent used is a fluorinated ether or polyether of the formula where b = 0-4 and c = 0-4 or where b = 0-4 and d = 1, e = 1 or d = 2, e = O.
4. The process as claimed in claim 1, wherein the solvent used is a perfluoroalkane of the formula CaF2a+2 where a = 5 - 12.
5. The process as claimed in claim 1, wherein the solvent used is 1,1,2-trichloro-1,2,2-trifluoro-ethane, perfluorohexane, perfluoropropyl ethyl ether, perfluoropropyl tetrafluoroethyl ether or 1-H-perfluorohexane.
6. The process as claimed in claim 1, wherein the solvent used is 1,1,2-trichloro-1,2,2-trifluoro-ethane.
7. The process as claimed in one of claims 1 to 6, wherein the organic phase obtained after the hydrolysis is extracted with water, before it is freed from the solvent by distillation.
8. The process as claimed in one of claims 1 to 6, wherein a mixture of perfluoroetheracyl fluorides of the formula (II) having m = 3 and n = 0, 1, 2 or 3 is used, the organic phase obtained after the hydrolysis is extracted with water and the solvent is then eliminated by multi-stage fractional distil-lation under mild thermal conditions and the result-ing perfluoroethercarboxylic acids of the formula (I) having m = 3 and n = 0, 1, 2 or 3 are separated from each other.
9. The process as claimed in one of claims 1 to 8, wherein the hydrolysis is carried out continuously in a loop reactor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4113620.9 | 1991-04-26 | ||
| DE4113620 | 1991-04-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2067077A1 true CA2067077A1 (en) | 1992-10-27 |
Family
ID=6430386
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2067077 Abandoned CA2067077A1 (en) | 1991-04-26 | 1992-04-24 | Process for the preparation of perfluoroethercarboxylic acids |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0510596A3 (en) |
| JP (1) | JPH06128189A (en) |
| CA (1) | CA2067077A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2432836A (en) * | 2005-12-01 | 2007-06-06 | 3M Innovative Properties Co | Fluorinated surfactant |
| CN102131759A (en) * | 2008-09-08 | 2011-07-20 | 大金工业株式会社 | Process for preparing fluorocarboxylic acid |
| CN113840649A (en) * | 2019-05-16 | 2021-12-24 | 日曹工程股份有限公司 | Chemical reaction system and device suitable for small-flow reaction |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19540645A1 (en) * | 1995-10-31 | 1997-05-07 | Basf Ag | Process and device for the continuous production of N-acylaminocarboxylic acids and N-acylaminosulfonic acids and their alkali metal salts |
| JPWO2003037842A1 (en) * | 2001-11-02 | 2005-02-17 | 旭硝子株式会社 | Process for producing purified fluorine-containing compound |
| DE10201689A1 (en) * | 2002-01-17 | 2003-07-31 | Merck Patent Gmbh | Continuous process for the hydrolysis of a solvent-containing organic compound |
| WO2004029008A2 (en) * | 2002-09-25 | 2004-04-08 | E.I. Du Pont De Nemours And Company | Process for preparing fluorocarboxylic acids |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3250808A (en) * | 1963-10-31 | 1966-05-10 | Du Pont | Fluorocarbon ethers derived from hexafluoropropylene epoxide |
| JP2503591B2 (en) * | 1987-06-02 | 1996-06-05 | ダイキン工業株式会社 | Halogen-containing polyether and its applications |
| US4889656A (en) * | 1987-10-30 | 1989-12-26 | Minnesota Mining And Manufacturing Company | Perfluoro(cycloaliphatic methyleneoxyalkylene) carbonyl fluorides and derivatives thereof |
-
1992
- 1992-04-22 EP EP19920106858 patent/EP0510596A3/en not_active Withdrawn
- 1992-04-23 JP JP10500292A patent/JPH06128189A/en not_active Withdrawn
- 1992-04-24 CA CA 2067077 patent/CA2067077A1/en not_active Abandoned
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2432836A (en) * | 2005-12-01 | 2007-06-06 | 3M Innovative Properties Co | Fluorinated surfactant |
| CN102131759A (en) * | 2008-09-08 | 2011-07-20 | 大金工业株式会社 | Process for preparing fluorocarboxylic acid |
| CN102131759B (en) * | 2008-09-08 | 2013-12-11 | 大金工业株式会社 | Process for preparing fluorocarboxylic acid |
| US8624060B2 (en) | 2008-09-08 | 2014-01-07 | Daikin Industries, Ltd. | Process for preparing fluorocarboxylic acid |
| CN113840649A (en) * | 2019-05-16 | 2021-12-24 | 日曹工程股份有限公司 | Chemical reaction system and device suitable for small-flow reaction |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0510596A2 (en) | 1992-10-28 |
| JPH06128189A (en) | 1994-05-10 |
| EP0510596A3 (en) | 1993-01-20 |
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