Aug. 22, 1950 J. H. SIMONs 2,519,983 ELECTROCHEMICAL PROCESS OF MAKING FLUORINE-CONTAINING CARBON-COMPOUNDS Filed Nov. 29, 1948

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344,42.277zaz75 Patented Aug. 22, 1950 2519,983

- UNITED STATES PATENT OFFICE 2,519,983 ELECTROCEMICAL PROCESS OF MAKNG FJOR NE-CONTAINING CARBON COM POUNDS Joseph H. Simons, State College, Pa., assignor to Minnesota Mining & Manufacturing Company, St. Paul, Minn, a corporation of Delaware Application November 29, 1948, Serial No. 62,496 20 Claims, (C. 204-62) This application is a continuation-in-part of ditives to permit of electrolyzing liquid hydrogen my copending application Ser. No. 677,407 (filled fluoride solutions thereof admixed with rela June 17, 1946), since abandoned. The latter was tively insoluble organic starting compounds, such filed as a continuation-in-part of the following as alkanes, which do not provide adequate con prior applications which thereafter were aban ductivity. Pure anhydrous liquid hydrogen fluo doned in its favor: Ser. Nos. 384,729 (filed March ride, per se, is non-conductive. The electrolyte 22, 1941), 569,265 (filed December 21, 1944), and is free from water in more than a small pro 626,434 (filed November 2, 1945). portion but need not be anhydrous in a strict This invention relates to my discovery of a Sense. basically new process of making fluorocarbons O Excellent results can be obtained with simple and other fluorine-containing carbon compounds. single compartment electrolytic cell arrange The process is simple in operation, does not in ments. No diaphragm is needed between elec volve the use or formation of free fluorine at any trodes. Fluorination can be completed in one stage, and has great versatility in enabling the step to directly obtain fully fluorinated product direct production of many types of product com 15 compounds which are relatively insoluble and pounds using organic starting compounds which either evolve with the cell gases or settle to the are readily available and relatively inexpensive. bottom of the cell from which they can be It is an electrochemical process and its utility drained, depending upon their boiling points. has been demonstrated by extensive pilot plant The process is suitable for continuous as well as operations employing a 2000-ampere cell, as well batch operation. The cell can be operated at as by many laboratory experiments. atmospheric pressure. The cell and the cathodes This process was publicly disclosed in the oral can be made of iron or steel, and the anodes of presentation on September 15, 1948, at the Port nickel, and such cells have been satisfactorily land, Oregon, session of the 114th meeting of the operated at 5 to 8 volts, D.C., in producing a wide American Chemical Society, of five papers aur variety of product compounds. thored by me and my assistants. Abstracts of The reaction mechanism is not fully under these papers had been previously published in stood but the electrolyzing process apparently the advance 'Abstracts of Papers' volume issued transforms the organic starting compounds at or by the society (pp. 42-0 to 45-0). News items adjacent to the anode and may be regarded as an relating thereto and briefly describing the process 30 anodic process. Hydrogen is evolved at the cath have been published in the society's magazine ode, being derived from the hydrogen fluoride; Chemical and Engineering News, vol. 26, p. 2428 and will also evolve in the cell by derivation from (Aug. 16, 1948) and pp. 2878-9 (Sept. 27, 1948). other hydrogen-containing compounds which These papers were subsequently published in the may be present. Fluorine is not evolved, and the Journal of the Electrochemical Society, vol. 95, 35 reaction mechanism does not involve the forma No. 2, pp. 47-67 (Feb. 1949). tion of molecular (free elemental) fluorine as an Briefly stated, this new and useful electro intermediate agent. chemical process involves electrolyzing a liquid Product compounds are obtainable (both cyclic hydrogen fluoride (HF) Solution containing a and non-cyclic) which have the same number of fluorinatable organic starting compound, at an 40 carbon atoms and same carbon skeletal structure electrolyzing potential which is insufficient to as do the starting compounds, but with partial generate free fluorine under the existing condi or total fluorine atom replacement of hydrogen tions, but which is sufficient to cause the pro atoms and other atoms and radicals bonded to duction of fluorine-containing carbon compound the carbon skeleton of the molecule. Fluorine products at a useful rate. A wide variety of 45 addition occurs in the case of unsaturated and organic compounds are soluble in anhydrous aromatic types of starting compounds to produce liquid hydrogen fluoride and provide adequate fully saturated product compounds. Non-cyclic electrolytic conductivity. Use can also be made compounds (in addition to cyclic compounds) of soluble organic and inorganic conductivity ad having the same number of carbon atoms are ob

a,b10,088 3 tainable from cyclic starting compounds as the fewer or more carbon atoms than the paren result of bond cleavage and fluorine addition. hydrocarbon groups can also be obtained from Also, the use of polycarbon cyclic and non-cyclic such compounds. A feature of the present proc starting compounds generally results in appre ess is that it provides a simple and economical cable yields of product compounds having fewer procedure for making normally liquid fluorocar carbon atoms in the molecule, due to fragmenta ition of the carbon skeleton and fluorine addition. bons, having five or more carbon atoms in the Compounds having a greater number of carbon molecule. atoms than the starting compounds are obtain The formation of fluorocarbons is accompanied able as the result of coupling of carbon radicals bypartially the formation fluorinated of hydrocarbons, fluorocarbon duehydrides to income and formed in the solution. The kinds and relative plete hydrogen replacement in the case of one proportions of product compounds obtainable in molecules. The proportions depend upon the any given case will depend upon the starting conditions. The fluorocarbon monohydrides and compound and the operating conditions. By ... dihydrides are of particular value because they proper selection it is possible to obtain excellent 15 have a high degree of thermal stability and yields of desired products, which can be readily chemical inertness and are non-combustible, and separated by fractional distillation from each yet the hydrogen atoms offer points of attack for other and from low-yield by-product compounds. the synthesis of fluorocarbon derivatives. Thus In commercial operations, use can be made of the these fluorocarbon hydrides can be thermally production of multiple products in building up chlorinated and brominated to yield the corre stocks of many useful compounds from a much. sponding fluorocarbon chlorides and bromides, as more limited number of starting compounds. disclosed in a paper published in the Journal of In some cases resinous material is formed in the American Chemical Society, vol. 88, pp. 968 the cell but is generally soluble in the electrolyte 989 (June 1946) of which I was a co-author. olution and does not interfere with the opera Saturated fluorocarbons and fluorocarbon de ton. Resinous products containing combined rivatives are obtainable in good yields ranging fluorine in proportions up to 60% have been ob from the simplest compound, CP, which is a low ... tained. In many cases no solid residual mate ... boiling gas, up to high-boiling compounds hav rials are found even after extended use of the ring eight or more carbon atoms in the molecule cell. In general, there is little or no corrosion of and having boiling points above 100 C. the electrodes...... The fluorocarbon and related compounds ob To briefly indicate at this point the versatility tainable by this process have utility for many of the process in enabling the production of purposes. The saturated fluorocarbons, fluoro fluorocarbon derivatives, mention is made (for carbon hydrides, fluorocarbon ethers, and tri illustration and not limitation) of the following fluorocarbon amines, for example, have a high types designated by generic formulae wherein R degree of thermal stability and chemical inert represents saturated fluorocarbon radicals (cycle ness, they do not burn, and they have uniquely or non-cyclic) consisting solely of carbon and low refractive indices and dielectric constants fluorine atoms: R'OR' (obtainable from ethers), as compared with ordinary organic compounds. R'R'R''N (obtainable from tertiary amines), 40 The liquid compounds (containing five or more R'R''N (obtainable from secondary annes), carbon atoms) have exceptionally low surface RN (obtainable from primary amines), RCO tensions and viscosities, coupled with high densi (obtainable from monocarboxylic acids), ties. These and other compounds can be used for such purposes (depending upon boiling RicooR' points) as refrigerants, fire extinguishers, inert solvents and diluents, heat exchange fluids, tur (obtainable from esters), RCN (obtainable from bine impellents, dielectrics, hydraulic mechanism nitriles) and RSF (obtainable from mercaptains). fluids, and lubricants. The products of this proc Fluorocarbon compounds which contain con ess can also be used as intermediates in the syn bined chlorine can be obtained from chlorine thesis of other chemical compounds. In particu containing starting compounds (e. g., chloroe lar, the fluorocarbon acid fluorides (RCOF) pro acetic acid). Heterocyclic compounds contain vide the reactive starting compounds for making ing one or more oxygen or nitrogen atoms in the a vast number of derivative compounds contain ring can be obtained by replacement of the ing a fluorocarbon radical and having unique hydrogen atoms by fluorine atons in starting SS properties on that account. compounds of corresponding structure. All organic compounds potentially capable of True fluorocarbons (carbon fluorides contain reacting with fluorine can be employed to pro in only carbon and fluorine atoms) can be duce fluorine-containing carbon compound prod directly obtained from hydrocarbon starting ucts by the present process. Fluorine is the most compounds, and also by electrolyzing solutions chemically active substance. No organic mate of various hydrocarbon derivatives, to obtain rial is completely resistant to fluorine except car substantial yields of fluorocarbons having the bon tetrafluoride (CF). Even the polycarbon same number of carbon atoms as the starting saturated fluorocarbons can react by carbon Compounds. For example, alkanes, alcohols and carbon bond cleavage and fluorine addition, the monocarboxylic acids can be employed to yield stable end product being CF. fluorocarbons having the same number of carbon As a practical matter in respect to the con atoms. In addition, fluorocarbons having fewer mercial utilization of the process, the hydrogen and more carbon atoms are produced. Fluoro containing organic compounds which contain at carbons having fewer carbon atoms than the least one hydrogen aton bonded to a carbon aton starting compound can also be produced from O in the molecule are of main interest. These can hetero compounds wherein carbon atoms are all be used for making fluorocarbons, and other hinked by non-carbon atoms, as in the case of fluorine-containing carbon compounds which ethers; and secondary and tertiary amines; the contain at least one fluorine atom bonded to a hydrocarbon groups being released to form cor carbon atom in the molecule. The sub-classes responding fluorocarbons. Fluorocarbons having s of these organic starting compounds of particu

a,519,983 lar value for making fluorocarbons, and fluoro for the generation of free fluorine (a) is ap carbon derivatives of chief commercial interest, proximately 3 volts. The reason why total cell are the hydrocarbons (which contain only car voltages higher than this can be used in actual bon and hydrogen), and the compounds which practice of the process without causing free fluo are oxygen-containing or nitrogen-containing in rine formation is because a substantial part of addition to being hydrogen-containing. Exem the total cell voltage (measured across external plary of the latter are the cyclic and non-cyclic anode and cathode connections) is utilized under organic acids, alcohols, ethers, esters, ketones, the existing conditions in overcoming the resist aldehydes, nitriles, amines, amides, etc. These ances of the electrodes, the resistance of the elec oxygen-containing and nitrogen-containing or 0. trolyte between the electrodes, and the blocking ganic starting compounds are soluble in anhy resistances of electrode polarization films. drous liquid hydrogen fluoride and provide ade In an experiment using a carbon-anode cell it quate conductivity, no conductivity additive being was found that electrolysis of a hydrogen fluoride needed. The hydrocarbons (which are relatively solution of acetic acid resulted in the formation insoluble) can be employed when use is made of S of fluoromethane (CHF) at a cell voltage as low a conductivity additive, as explained in some as about 0.5 volt. In another experiment using a detail later on. These sub-classes embrace the nickel-anode cell, a hydrogen fluoride Solution of readily available and relatively inexpensive al acetonitrile (CH3CN) was electrolyzed for five kanes, alcohols, ethers, carboxylic acids (includ days at a cell voltage of 1.7 volts and the prod ing the anhydride forms), and amines, both ucts included CFCN, CF3H, CF, CFs and CaFs. cyclic and non-cyclic, which can all be efficiently 920 These cell voltage values were very substantially employed in the preparation of fluorocarbons and lower than the minimum cell voltage (approxi of other fluorine-containing carbon compounds. mately 3 volts) required for generation of molec Conjoint use can be made of two or more ular fluorine even under ideal conditions. Hence organic starting compounds and in some cases 25 these experiments conclusively demonstrate the this will result in improving the operating eff utility of electrolyzing potentials which are in ciency. For example, the efficiency of the elec sufficient to generate free fluorine and yet are trolysis of a solution of hexyl ether can be im sufficient to cause the production of fluorine proved by including propionic acid as a second containing carbon compounds. Organic starting compound. 30 . In a review paper written by me and published The proportion of the organic starting mate in 1931 (Chemical Reviews, vol. 8), long prior to rial relative to the hydrogen fluoride can vary the discovery of the present process, I referred Over a wide range and it can be either a minor to and summarized previously published experi component or a major component of the solution. mental data of Fredenhagen and Cadenbach on As previously mentioned, this process does not the solubilities and equivalent conductivities cf involve the use or generation of free (molec various inorganic and organic compounds dis ular) fluorine at any stage. It is fundamentally solved in anhydrous liquid hydrogen fluoride' (p. different from processes wherein free fluorine is 223, et seq.). The well-known laboratory pro reacted with organic compounds which are dis cedure for measuring conductivities of Solutions solved in or mixed with liquid hydrogen fluoride, 40 employs a small cell provided with platinum as by introducing gaseous fluoride into the re electrodes and utilizes a rapidly reversing cur action zone. For any given cell arrangement rent (A. C.) of 1,000 cycles or more per second and charging stock there is a minimum cell volt to substantially eliminate electrode polarization age at and above which molecular fluorine (free effects and to cause momentarily formed elec elementary fluorine) is formed from the hydrogen As trode products to revert with each alternation fluoride, but the resultant effects are quite dif of electrode polarity rather than to escape from ferent from those obtained in the present process the electrodes as free products. In Such experi and can be easily recognized. When the cell volt ments the current is passed, for each measure age is raised to this critical value or higher, the ment of voltage versus current flow, during a onset of free fluorine formation manifests itself very short time interval (a few minutes at most unmistakably by a marked change in product and often a few seconds or less), for otherwise formation due to the rapid and powerful de accurate values for a desired temperature cannot composition and fragmentation effects on the be obtained due to heating of the electrolyte and organic compounds in the cell; extensive cor for other reasons. rosion of the electrodes occurs; some gaseous Fredenhagen and Cadenbach stated in their fluorine escapes and can be detected in the exit paper (Z. physikal. Chem., Abt. A., vol. 146, pp. gas mixture even when present in trace amounts; 245-80) that they employed a conductivity cell and minor and even major explosions occur. vessel made of a gold-platinum alloy, which Satisfactory yields of fluorinated compounds served as one electrode, and the other electrode having a substantial number of carbon atoms in was a platinum capillary tube extending through the molecule cannot be obtained. the stopper down into the vessel. The cell was The present process is based upon my dis a small one and contained 20.7 cc. of solution covery that liquid hydrogen fluoride solutions (approximately 1.3 cubic inches) when making a containing organic compounds can be efficiently measurement. That they employed alternating electrolyzed to produce fluorocarbons and other current is made clear by the absence of any de fluorine-containing carbon compounds, by using scription of an unconventional procedure and a cell voltage which in any given case is below by their use of a telephone receiver in balanc the minimum voltage required for free fluorine ing the bridge. Nothing was said to suggest that generation. For example, when using nickel the total time of current flow for any given Solu anode types of cells for which operating volt 70 tion amounted to more than a few minutes at ages in the range of 5 to 8 are quite satisfactory, most, even when several measurements were it has been found that the voltage must be in made at intervals. Each solution had served its creased to at least 10 to 12 before evidence of purpose and was discarded when the measure free fluorine generation occurs. ment work had been completed. There was no The minimum theoretical cell voltage required 76 suggestion that detectable trace amounts of free 8,510,088 7 8 molecular hydrogen or other electrolysis prod not only fluorocarbons and fluorocarbon hydrides ucts were produced. That none were formed is ibut also fluorine-containing carbon compound to be expected since precision conductivity meas which contain oxygen or nitrogen atoms in the urement procedures are deliberately designed to molecule. avoid the irreversible production of free elec Commercial anhydrous liquid hydrogen falo trolysis products, as indicated above, which would ride normally contains a trace of dissolved water, consume energy and thus render the voltage-cur and traces of water are readily absorbed when rent relation inaccurate as a measure of the elec there is contact with a moist atmosphere. Such trolyte resistance, as well as altering the come water can be readily renoved or reduced to a Very position of the solution being tested. These O low value by passing current through the liquid authors speculated as to the manner of ionic hydrogen fluoride prior to adding the startins dissociation of the organic compounds when dis compound, the water being consumed by the solved in the anhydrous liquid hydrogen fluoride, formation of hydrogen, oxygen fluoride (O) and on the possible formation of reaction prod and oxygen which evolve as gases. In actual ucts resulting therefron, in commenting upon s the various conductivity values, since the mag practice, the first few hours of electrolysis of the nitudes of the latter would depend upon what it hydrogen fluoride solution containing the soul was whose conductivity was actually being meas ble organic starting compound will generally ured. This had reference only to substances cause the proportion of water to dininah to 0.1 formed as the result of dissolving the original or less and it is not necessary to subject Coan organic compounds in the anhydrous liquid hy mercial anhydrous hydrogen fluoride to a prelian drogen fluoride and not to the formation of free inary water-removal treatment. The expression electrolysis products. "anhydrous liquid hydrogen fluoride" as used A mere scientific conductivity determination is herein is employed, except when otherwise stated. not a useful process for making electrolysis prod to include liquid hydrogen fluoride which Con lucts from a solution of a starting compound tains traces of water not exceeding 1% by weight whose conductivity is being measured, and the Liquid hydrogen fluoride containing 1% water objectives are antithetical. It will be understood has a low conductivity, being about 0.06 Enho that no attempt is being made herein to claim (reciprocal ohm) per centimeter cube at O' C. . mere conductivity measurements. The conductivity when there is a 0.1% water Con When laboratory size cells are used in perform tent is about 0.006 inho. ing batch experiments on the present process, the When the proportion of dissolved water in the runs continue for periods of hours (generally for liquid hydrogen fluoride is increased substan a day or more). Likewise the commercial oper tially above 1% there is a material decrease in ation of the process using large cells requires the operating efficiency of the process in various electrolyzing the cell charge for a period of many respects. While a small proportion of water can hours in order to obtain a commercially desirable be used to advantage as a means of increasing yield ratio of product compounds from the start the conductivity, a point shortly to be discussed ing material, and a cell will normally be continu in connection with the use of conductivity add Ously operated for days before being shut down, 40 tives, the presence of water in proportions ex the hydrogen fluoride and starting material being ceeding 10% by weight of the total of Water and replenished during Operation. hydrogen fluoride results in such marked inef Alternating currents can be usefully employed ciency that it should be avoided for economical in practicing the present process when polariz operation of the process and the obtaining of able electrodes (e.g., nickel electrodes) and a rel 45 desirable yields of fluorocarbon compounds atively low frequency (e. g., 60 cycles) are used. Water in amount substantially exceeding 10% In this case each electrode alternately functions also gives rise to serious explosion hazards due as an anode and as a cathode, but the operating to the evolution of readily explosive gas mixtures conditions permit the release of free electrolysis containing substantial proportions of oxygen flu products at the electrodes. The use of direct 50 oride and oxygen mixed with hydrogen. Some currents is greatly preferred. The eficiency of organic starting compounds may contain dis alternating currents is much inferior and greater solved water in the commercial forms employed heating of the electrolyte is produced. In the (as in the case of ethyl alcohol), and in such cases case of normal direct current operation each the starting compounds should be employed in cathode and anode electrode continuously func proportions which will not result in there being tions as such at a uniform voltage (which may be more than 10% by weight of water relative to the varied during the run for optimal operation), and total weight of water, and hydrogen fluoride. It the cathodes and anodes can be made of different will be understood that the generic term "liquid materials adapted to produce the most eficient hydrogen fluoride,' when not restricted by the results. Pulsating unidirectional currents, un "anhydrous' adjective, includes not only anhy filtered rectified A. C., and superimporsed A. C. drous liquid hydrogen fluoride but also solutions On D. C., can also be used and are to be regarded thereof which contain small proportions of water as types of direct currents. in excess of 1% as above indicated. As previously mentioned, pure anhydrous liquid Some organic compounds, such as acetic acid, hydrogen fluoride is non-conductive but a wide react with liquid hydrogen fluoride to form an variety of organic starting compounds are solu equilibrium mixture containing water and the ble therein and provide adequate electrolytic anhydride of the starting compound, such as conductivity to permit the passage of effective acetic anhydride. In such cases the theoretical electrolyzing currents. The starting compounds total amount of water capable of being formed of chief commercial interest in this respect are 70 from the starting compound may exceed the the oxygen-containing and nitrogen-containing 10% value previously mentioned without causing organic compounds which have at least one an uneconomically low operating eficiency, since hydrogen aton attached to a carbon aton in the it is not the mere equivalent of free water added beenmolecule, given, of and which on various these examples ther can have be obtaine already " all atGuid once hydrogeniuoride to the liquid hydrogen containing fluoride. a man 2,519,988. 10 proportion of dissolved water, as described above, process is not an equivalent of direct fluorination is also entirely different in other respects from processes but is an entirely different kind of proc the aqueous solutions of hydrogen fluoride which ess which does not involve the use or evolution are sold in bottles and are commonly referred to of free (molecular) fluorine and which produces as hydrofluoric acid. These contain less than 5 product compounds that cannot be obtained in 50% by weight of hydrogen fluoride as normally significant proportions by direct fluorination sold. Such solutions cannot be kept in glass or with free fluorine, metal containers and if introduced into elec The exact mechanism of the electrolyzing proc trolysis cells such as are used in the present proc ess remains a mystery. The gases and heat ess (for example, a steel cell having nickel 0. evolved in the cell vigorously agitate the cell con anodes and iron Cathodes) would cause rapid tents so that a mixture of the insoluble organic corrosion of the metals contacted even in the starting compound and the liquid hydrogen flu absence of current flow. Whereas the boiling oride electrolyte solution is present at the anode, points of hydrofluoric acid solutions containing and it is a fact that the existing conditions cause 50% by weight of hydrogen fluoride or less are 5 the formation of fluorine-containing carbon com in the range of 100 to 114 C., the boiling point pounds, including fluorocarbons, at the anode. of pure anhydrous liquid hydrogen fluoride is , The conductivity additives fall into two general 19.5° C. and the presence of 10% by weight of groups, Organic and inorganic. water results in a boiling point of about 32 C. The Organic conductivity additives are com The specific gravity of aqueous solutions in 20 pounds which can themselves be employed as creases with increase of hydrogen fluoride from starting compounds, and numerous examples 1.0 to a maximum value of about 1.26 at about . have already been indicated. The most impor 75% hydrogen fluoride and then rapidly de tant are the oxygen-containing and nitrogen creases to a value of 1.0 for anhydrous liquid hy containing organic compounds which contain at drogen fluoride (measured at 0° C.). The con 25 least one hydrogen atom attached to a carbon ductivity decreases as the hydrogen fluoride per atom of the molecule, Illustrative examples are: centage increases above 75%, and rapidly SO as acetic anhydride, acetic acid, propionic acid, ca the percentage increases above 90%. These data proic acid, methyl alcohol, diethyl ether, tri are of interest as showing that liquid hydrogen ethyl amine, pyridine, and 2-fluoropyridine, fluoride, both when anhydrous and when Con 30 which have all been employed in experiments taining a small proportion of dissolved water, as wherein hydrocarbon starting compounds were employed in the present process, differs radically converted into fluorocarbons and fluorocarbon in physical as well as chemical properties from hydrides. The proportion of the conductivity ad hydrofluoric acid solutions which contain a large ditive to the hydrogen fluoride can be relatively proportion of water and which cannot be em small, e. g., 42 to 5%, but much higher propor ployed in the present process. tions can be used. These additives are them The present process is not limited to the use of selves converted during operation of the process, organic starting compounds which are soluble in and hence the fluorine-containing carbon com anhydrous liquid hydrogen fluoride and provide pound reaction products are derived in part from adequate electrolytic conductivity to permit of 40 the soluble conductivity additive and in part from effective electrolysis. I have made the surpris the insoluble organic starting compound. Thus, ing discovery that the necessary electrolytic con in effect, there are two types of organic starting ductivity can be provided by a third component compounds utilized in this procedure, one being olute which can be either organic or inorganic, soluble and serving also as a conductivity addi so that organic starting compounds which are in 45 tive and the other being insoluble. For example, soluble in the liquid hydrogen fluoride can be ef when hexane is employed in admixture with fectively employed in admixture with liquid hy liquid hydrogen fluoride which contains dis drogen fluoride solutions containing a dissolved solved pyridine, both the hexane and the pyridine conductivity additive. This feature of the ge are converted to produce fluorine-containing neric process greatly extends its versatility and 50 carbon product compounds, including fluorocar usefulness. Thus it makes possible the use of bons. Another example of an organic conduc very cheap organic compounds, such as the hy tivity additive is mercuric cyanide, which also ill drocarbons, as starting materials for producing lustrates organic starting compounds that do not fluorocarbons and fluorocarbon hydrides. contain hydrogen. Examples of hydrocarbon starting compounds 55. The inorganic conductivity additives are inor which can be effectively utilized when a conduc ganic compounds which are soluble in liquid hy tivity additive is employed, are the alkanes (both drogen fluoride and provide effective electrolytic cyclic and non-cyclic). The aromatic com conductivity. The soluble fluorides, such as so pounds, such as benzene and toluene, can also dium fluoride and potassium fluoride, can be used be employed. Moreover, this procedure permits 60 and have the advantage of not decomposing and of good yields of fluorocarbon compounds having not being consumed. Ammonia can be used but is the same number of carbon atoms as the starting gradually consumed, yielding nitrogen trifluoride compound. Thus hexane can be used for mak (NF) which is a low-boiling relatively insoluble ing C6F14 (tetradecafluorohexane), a normally liquid fluorocarbon. As in the procedures uti 65 gas and is evolved. Water can be used in limited lizing soluble organic starting compounds, the amount. The proportion of water in the liquid electrolyzing potential employed is insufficient to . hydrogen fluoride Solution should not exceed a generate free fluorine. In contrast, if it were small proportion because otherwise there will be attempted to fluorinate hexane (as an admixture poor efficiency and a poor yield of desired COm dispersed in liquid hydrogen fluoride) with free 70 pounds. Effective results can be obtained using fluorine, the reaction would be a violent one and as little as 1 to 2% of added water. The water is fragmentation would be so severe that there gradually consumed, yielding Oxygen fluoride would be no substantial yield of polycarbon full (OF), carbon dioxide (CO2), oxygen and hydlo orocarbons and little if any CoF14 could be ob gen, and must be replenished during extended tained. This illustrates again that the present 75 runs. Some organic conductivity additives also s,819,088 2 provide water so that their use actually involves Suspended from the cover, so as to be located both organic and inorganic additives. Thus ace within the cell when the cover is in position, is tic acid is dehydrated by hydrogen fluoride to the electrode pack consisting of a series of anode produce acetic anhydride and water, and alco plates and an alternating series of intermeshed hols may contain a small amount of dissolved cathode plates. An extreme outward anode plate water. Further illustrative examples are sulfuric and cathode plate 7 are shown, the other plates acid and phosphoric acid. The illustrative inor being to the rear and not visible in the drawing. ganic additives named above have all been em The anode plates are connected and held in ployed in experiments wherein hydrocarbon spaced relation by a cross bar connector 8 to starting compounds were converted into fluoro O which the tabs of the plates are welded; and sini carbons and fluorocarbon hydrides, including sig larly the cathode plates are joined by connector nificant yields of fully fluorinated product com . The connectors are suspended from anode pounds having the same number of carbon atoms conductor rod and cathode conductor rod , as the starting compound. Thus CaFis has been respectively. These rods pass through the cell made from octane, and CF4 and CFs from tolu 5 cover, being insulated therefrom and sealed by ene, for example, concentric insulating material, and external con Various combinations of two or more conduc nection is made to them from the power source. tivity additives can be employed. Thus an or The cell body can be conveniently made of ganic additive and an inorganic additive can be steel. Iron cathode plates and nickel anode jointly employed. 20 plates are suitable, and the cross bars and con In some cases the soluble conductivity additive ductor rods call be made of the same metals as (depending upon the kind and amount used) will the electrode plates served by them. The plates function as a mutual solvent so as to cause an can be closely spaced, a spacing distance between . otherwise insoluble organic starting material to adjacent anode and cathode surfaces of the order be appreciably soluble in the electrolyte solution. 25 of 6 to % inch being quite satisfactory. "Teflon." This action does not appear to be necessary to (polytetrafluoroethylene) is a very satisfactory the operation of the process, since useful results non-corroding material for insulating and seal are obtained notwithstanding the insolubility of ing the conductor rods from the cover and for the starting compound, providing a gasket between the cover and body The principle of using a conductivity additive 30 flange of the cell. can also be employed to increase the efficiency The bottom of the cell is provided with an out even when the organic starting compound is sufi let pipe 2 having a valve 8, used for draining ciently soluble so that it could be used without the cell. This can be used during operation for such expedient. This is helpful in the case of draining liquid products which settle to the bot starting compounds of limited solubility in anhy tom of the cell. drous liquid hydrogen fluoride and which do not The cell cover is provided with a vertica inlet provide an efficient conductivity. pipe 4 (which connects to the bottom of the hy Another expedient is to change the operating drogen fluoride condenser shortly to be describe) temperature or pressure or both to cause a more and a charging inlet pipe is, having a valve I, favorable solubility relation. Thus a starting 40 connects thereto to permit of introducing into compound which is poorly soluble or relatively the cell the liquid hydrogen fluoride, the organic insoluble in liquid hydrogen fluoride at 0° C. may starting compound, and any other substance (such be made much more soluble therein by substan as a conductivity additive) which is to be pres tally increasing the temperature, while the solu ent. This inlet pipe extends down into the cell bility of normally gaseous compounds can be in AS a sufficient distance so that its lower end will be creased by using lower temperatures. . well below the surface of the liquid solution dur The accompanying drawing is a diagrammatic ing normal operation, thereby making a liquid sectional elevation of an illustrative apparatus for seal. It is located in front of the electrode pack carrying out the process and also serves as a flow and is spaced therefrom. sheet. The drawing has been simplified in the The cell cover is also provided with a vertical interest of clarity by omitting heat-insulating outlet pipe 7, for gaseous products evolved in jackets and coverings, couplings, etc., and by en the cell, which connects to the hydrogen fluoride ploying conventionalized representations as com condenser located above the cell. This con monly used in schematic chemical drawings. The denser has a jacket 19 to permit of circulating a apparatus as shown is suitable for laboratory ex coolant liquid for maintaining a desired low tem periments and can also in larger form be en perature. The pipe 7 extends down into the con ployed for pilot plant or small-scale commercial denser short of the bottom, and may be in the use. A large commercial plant would necessarily form of a spiral for better heat transfer. The be designed on more complex lines, as chemical bottom of the condenser vessel is connected, engineers will understand, but would embody the through valve 2, with the aforesaid vertical inlet basic principles of the invention as illustrated pipe of the cell. This permits the liquid con and described. densate to drain back into the cell. Referring to the drawing, the heart of the ap The top of this condenser is connected by tube paratus is the electrolysis cell , which is pro 2 to the reactor vessel 22, the tube extending vided with a cooling jacket 2 having an inlet down into the vessel, which is filled with a 15% and outlet for flow of a coolant liquid (such as ... sodium hydroxide solution. The top of the reac an aqueous Solution of ethylene glycol or meth tor is in turn connected by tube 23 to the drier anol) which is pumped through the jacket and vessel 24, the tube extending down into the vessel. recycled through a refrigerator (not shown), so This vessel is filled with a drying medium, such as as to maintain a desired cels operating tempera 70 potassium hydroxide pellets, for removing water ture. An operating temperature in the neighbor from the gaseous mixture passing therethrough. hood of 0°C. is convenient and permits of simple The top of the drier is connected by tube 25, operation at substantially atmospheric pressure. having valve 2, to the product condenser vessel boltedThe cell to hasan outwarda removable top flange cover of5 whichthe ce: can hrs. be The27, the tube tube can extending be spiraled down so short as to of improve the bottom. he

8,519,988 13 14 transfer. This vessel is provided with a remov the sodium hydroxide bubbler for removal of able liquid-air cooling jacket 28, for maintaining residual hydrogen fluoride from the gas stream. in the condenser a very low temperature sufficient Oxygen fluoride (OFa), formed when water is for condensing even such low-boiling product present in the electrolyte solution of the cell, can compounds as carbon tetrafluoride (CFA) and is be removed from the gas stream by bubbling fluoroform (CFH), but insufficient to condense through an aqueous potassium-sulfite-iodide so the accompanying hydrogen. lution contained in a reactor vessel included in The top of this condenser is provided with an the train ahead of the drier. When nitrogen-con outlet tube 29, having a valve 30, for Conducting taining organic starting compounds are being the hydrogen gas to the gas meter 3, the latter 10 processed, the gas stream will contain some nitro being used for measuring the hydrogen produc gen trifluoride (NE3). This is a stable low-boiling tion. The outlet tube is provided with a branch gas and can be separated from the product com tube 32, having a valve 33, which connects on the pounds by fractionation. upstream side of valve 30. During normal opera A further alternative is to remove the residual tion valve 26 and 30 are open and valve 33 is 15 traces of hydrogen fluoride from the gas strean closed. However, valves 26 and 30 can be closed leaving the hydrogen fluoride condenser by pass and valve 33 opened to withdraw the condensate ing through a vessel packed with sodium fluoride compounds, the latter being vaporized by warm pellets. It is not necessary to remove CO2, OF2 ing in the absence of the liquid air; and during and NF3 from the gas stream, and the use of this period the gaseous products from the cell 20 aqueous purifying Solutions can be omitted. The can be diverted to an alternate recovery system gas stream from the Sodium fluoride vessel can (not shown) if continuous cell operation is in go directly to the product condenser in this case progress. The withdrawn products can be led as no drying is needed. The CO2 (and any OFa to a fractional distillation system (not shown) and NF3 present) can be separated from the for separating the various product compounds 25 products by distillation. This procedure is espe which have been formed. cially useful when reactive fluorocarbon deriva The gaseous mixture evolved from the cell will tives (such as fluorocarbon acid fluorides made normally contain some hydrogen fluoride (evap from carboxylic acids) are contained in the gas orated in the cell) in addition to hydrogen and to stream. volatile fluorine-containing carbon product com 30 The principal non-volatile products of interest pounds. If an oxygen-containing organic start are insoluble" in the hydrogen fluoride electrolyte ing compound is employed this will also result in solution and settle to the bottom of the cell from the formation of some CO2. The hydrogen fluo which they can be drained. The immiscible ride condenser f8 is maintained at a temperature liquid drained from the cell may include nor of about minus 40° C. and serves to condense out 35 mally Solid compounds dissolved therein. This most of the hydrogen fluoride, which is returned liquid can be washed with potassium hydroxide to the cell. The other constituents of the gas solution to remove traces of hydrogen fluoride mixture are substantially insoluble in the liquid and then fractionally distilled. Soluble product hydrogen fluoride condensate and are carried materials which remain in the electrolyte solu along in vapor phase in the hydrogen gas stream. 40 tion can be recovered by distillation following Wapors from any higher-boiling fluorine-contain the run. Some product compounds (of interme ing carbon product compounds formed in the cell diate volatility) will be recovered in part from will also condense and return to the cell; such the gaseous mixture evolved from the cell and compounds in the main settling to the bottom of in part from the imniscible liquid which is the cell. 45 drained from the bottom of the cell. The sodium hydroxide reactor 22 serves to re The body of the electrolysis cell can be used move from the gas stream any residual HF and as a cathode, being connected to the cathodes also any CO2 which is present. The drier 24 in the cell, or, as is generally preferable, it can Serves to remove water vapor which has been simply "float,' not being electrically connected picked up in the reactor. The fluorocarbons and 50 or grounded. other fluorine-containing carbon product com The cathode elements do not need to be made pounds are separated from the hydrogen by being of iron or steel. Any metallic conducting mate frozen out in the product condenser 27, from rial which resists the corrosive action of the which they can be withdrawn in the manner al hydrogen fluoride solution can be used, includ ready indicated. 56 ing copper, magnesium, aluminum, nickel, nickel Other means can be used for separating the alloys, etc. Anode elements can be made of hydrogen from the purified gaseous product com nickel alloys as well as of nickel, or of Monel pounds. A condenser cooled by a mixture of metal, silicon carbide, carbon, etc. solid-CO2 and acetone can be included ahead of Using iron Cathodes and nickel anodes, operat the liquid-air condenser to preliminarily condense 60 ing cell voltages in the range of 5 to 8 volts have out the higher-boiling product compounds. In been found generally suitable for most efficient stead of using a liquid-air condenser, the gaseous results, with 5 to 6 volts usually being the opti mixture can be compressed and refrigerated so mum. Current densities as high as 20 amperes as to condense out the product compounds. This or higher per square foot of anode surface are can be done in Several stages so as to first con obtainable. A 50-ampere cell, having about 350 dense out the bulk of the higher-boiling com sq. in. of anode surface, has proved quite satis pounds and then, at a lower temperature or high factory for general laboratory research use and er pressure (or both), condense out the remain permits of making substantial quantities of ing product compounds. The hydrogen can also product compounds for study of properties and be separated by chemical means, as by passing 70 for preliminary use evaluation. The compact the gas stream through heated copper oxide. ness of the cells per unit of power is an advan The aforesaid purifying and recovery system tageous feature of the process. Operating tem has a wide application but can be readily modi peratures in the range of about minus 20° C. to fled as desired. For example, an aqueous calcium plus 80° C. have proved highly effective. Within chloride bubbler can be inserted in series before this range, temperatures of about 0° C. to 20° C. 2,519,088 5 readily permit of convenient operation at about products at a useful rate, and recovering one or atmospheric pressure (the boiling point of hy more fluorine-containing carbon compound prod drogen fluoride being 19.5 C. and being raised ucts of the process. by dissolved compounds), and the necessary cool In order to further illustrate the invention by ing can be readily effected. specific examples, the following table is presented It is to be understood, however, that the in as a convenient summarization of the results of vention is not restricted to the operating condi a large number of experiments. This table is not tions noted above. Under appropriate conditions intended to set forth all compounds that have been cell voltages as low as about a volt can be used. made or can be made, and serves for illustration While higher cell voltages than those mentioned ) rather than limitation. It lists a considerable can be used under some circumstances without number of different fluorine-containing carbon causing free fluorine generation, arrangements product compounds which have been made by this utilizing cell voltages not exceeding 8 volts are process from soluble organic starting compounds much preferred since the use of a higher voltage dissolved in anhydrous liquid hydrogen fluoride. means that much energy is being lost in Over s Boiling point values for most of the compounds coming current blocking conditions in the cell. are given in the left-hand column. These are to A wide range of operating temperatures and be regarded as approximate values. Many of pressures can be employed. Thus temperatures these values were determined at about 740 mm. as low as minus 80 C. and higher than plus 75 pressure and have not been corrected to stand C. have actually been used in experiments. The 20 ard condition (760 nm.) values, and hence are freezing point of pure hydrogen fluoride is minus somewhat lower (1 to 3) than the latter. These 83 C. and a still lower freezing point results when compounds were separated and clearly identified it contains dissolved material. Thus the liquid by physical and chemical properties. In all nec state of liquid hydrogen fluoride solutions can essary cases the content of fluorine and of other be maintained at very low temperatures. Tem non-carbon elements present was determined by peratures higher than about 20° C. generally re analysis. In some cases where compounds of the quire operation at superatmospheric vapor pres same series or of an analogous series had pre sures in order to elevate the boiling point of the viously been obtained and identified, it was not solution. However, the necessary pressure can considered necessary to chemically analyze the be minimized and even atmospheric pressure can 30 product compounds for unambiguous identifica be utilized by employing solutes which markedly tion; the physical and chemical properties, to lower the hydrogen fluoride vapor pressure, as gether with knowledge of the starting compound by dissolving potassium or sodium fluoride in employed, being quite sufficient to enable definite relatively large proportion in the hydrogen identification. In some cases derivatives were fluoride. Superatmospheric cell pressures are 35 made and identified, further corroborating the needed in some cases to maintain the starting identification of the cell product. Infrared abs compound in liquid phase or to prevent rapid sorption spectra determinations have been made evaporation, even though a low operating tem on various series of these compounds to supply perature is employed. This is especially true in further identification corroboration. Several the case of low-boiling starting compounds which 40 compounds were analyzed by the mass spectro are not dissolved in the liquid hydrogen fluoride. graph method. To take an extreme illustration, ethane has a boiling point of minus 88 C. at atmospheric Under the listing of each product compound pressure and hence the cell must be operated at there is listed in the indented column one or more an elevated pressure in order to maintain ethane HF-soluble starting compounds from which it was in a liquid state in the cell at temperatures above made. No attempt has been made at complete this value. ness in the latter respect-thus carbon tetrafluo It will be evident from the foregoing descrip ride (CF) and fluoroform (CFH) were presun tion that this invention pertains to a basically ably produced in substantially all experiments. new unit process in chemistry and is not a mere The product compounds are those which were re process for producing a particular type of com garded as of particular significance in the ex pound from a particular type of starting mate periments on the listed starting compounds. rial. Practically all organic materials can be Some starting compounds have produced signifi utilized as starting compounds, whether or not cant yields of two or more types of compounds, soluble in liquid hydrogen fluoride, and the proc 5 5 as for example, the ethers have yielded both fluo ess provides a new general method by which they rocarbons and fluorocarbon oxides, the amines can be transformed into a great variety of have yielded fully fluorinated nitrogen-contain fluorine-containing carbon product compounds, ing carbon compounds as well as fluorocarbons, including many novel compounds not hitherto the carboxylic acids have yielded fluorocarbon made by any other process. . () acid fluorides as well as fluorocarbons, etc. Most In all cases the basic generic principle of the of these product compounds have been, and all present invention is employed, namely, the useful of them could be, produced with the type of cell electrochemical preparation of fluorine-contain arrangement which has been described in con ing carbon product compounds from fluorinatable nection with the drawing, utilizing iron cathodes organic starting compounds, by electrolyzing for and nickel anodes and cell voltages below 8 volts a period of hours a current-conducting mixture D. C., and operating temperatures in the neigh of liquid hydrogen fluoride solution and the or borhood of O' C. The solubilities of these start ganic starting material (either dissolved or ad ing compounds in anhydrous liquid hydrogen flu mixed), which is free from water in more than oride at O' C. permitted use of starting solutions a small proportion, at a temperature and pressure 70 containing at least about a 1 to 10 ratio by weight at which a liquid state is maintained and at an of the starting compound to the hydrogen fluo electrolyzing potential which is insufficient to ride and in many cases a substantially higher generate free fluorine under the existing condi ratio was actually used. Thus in some experi tions, but which is sufficient to cause the produc ments using acetic acid, the initial amount there tion of fluorine-containing carbon compound 75 of exceeded that of the hydrogen fluoride.

2,519,988 17 8 Flourine-Containing Carbon Product Compounds made B.P., Flourine-Containing Carbon Product Compoun from the under-listed organic compounds front the under-listed organic SERE made - - - - -e- - - - - CF (carbon tetrafluoride 138 CFOCsCEOCE (d-undecafluoroamyl (damyl Seyy ether) CHOHEO 'EY(ethyl alcohol alcohol) 172 CHCOOH (acetic acid) . CaFQ9 (d-tridecafluorohexyl ether) CHCOONa (sodium acetate) CHOCH (dihexyether) CHCOCs (acetone) 35 CFOCE ESSEE ether) CHCOCl (acetyl chloride) HOCECHöethylenegoi nonobutyl ether) CHCN (acetonitrile) 14 CF36ESSESSEE2V decatoro-glyco 8 ether CHCOOHCHCOOBI &E(butyrie acid)acid) CHOCHCHOCH E. y (CI)NCEOCH (trimeth SEESP ine) Hg(CN) (mercuric cyanide) 97 CFOCFCFOCFCFOCF (octafluorodiethylene gly CF (hexafluoroethane) cold-petafluoroethylether) - CHCN (acetonitrile) CH3CHCHOCH2CHOOHdiethyl ether) (diethylene glycol CHOHCCOO (ethyl i. alcohol) acid) CFOCF (undecafluorocyclohexyl trifluoromethyl CHOH (propyl alcohol) ether) CHCOOH (butyric acid) CHOCH (anisole) CHOCH (diethyl ether) CaFO (octafluorotetranethylene oxide) (CH)N (triethylamine) CHO (tetramethylenre oxide) CF (octafluoropronane) CFgO (decafluoropentanethylene oxide) (CH)2CHOH (isopropyl alcohol) CO (pentamethylene oxide) SE:33HCOOH (propionic (disopropylacid) ether) 20 C.HCOOH (butyric acid) QCF.gFCF (hexafluoropropylene oxide-1,2) CECHO (butyraldehyde (CH3)3CCOOH (piyalic d) (CH)N (tripropylamine) OCHCHCHCl (epichlorohydrin) CF (decafluorobutane) CEOH (butyl alcohol) CsCOOH (butyric acid) . 25 CH3COOCE (butyl acetate) CFOOF (trifluoroacetyl fluoride) CHNCO (butyl isocyanate) CFCOFCHCOOH (pentafluoropropionyl (acetic acid) fluoride) CHgSE (butyl mercaptan) CsCOOH (propionic acid) Ci)(COOH)2 (adipic acid) CFCOF (heptafluorobutyryl fluoride) HOE (any alcohol) CHCOOH (butyric acid) CHOCH (diabutyl ether) CsIFCOF (undecafluorocaproyl fluoride) (CH)NH (dibutylamine) CHCOOH (caproic acid) (CH)sN(tributylamine) CFCOE (pentadecafluorocaprylyl flyoride) (C5H1)N(triannylamine) CBsCOOH. (caprylic acid) CE.1 (dodecafuoropentane) CFCOF (nonadecafluorocapryl fluoride) Cs1OH (any alcohol) CE COOE (capric acid) CsIOC5H1 (diaIny ether) CFCOF (undeeafluorocyclohexanecarboxylic acid CE COOH (caproic acid) fluoride) V CEOE (phenol) CHCOOH (benzoic acid) (CH2)(COOH) (sebasic acid) CFCFCOF (tridecafluorocyclohexyacetyl fluoride) CHN (trianyamine) CCHCOOH (phenylacetic aci) IN (pyridine) CHCHCOOH (cyclohexylacetic acid) 52 CF1 (dodecafluorocyclohexane) CFCN (trifluoroacetonitrile) CsIOE (phenol) CHCN (acetonitrile) CHNBataniline FCHN (2-fluoropyridine) CF (tetradecafluorohexane) CHN (pyridine) CEO (hexyl alcohol) 40 CFNF (tridecafluorocyclohexylamine) CECOOH9H1399E (caproic(hexyl ether) acid) CNE (aniline) CHCOOH (benzoic acid) CFNF (undecafiuoropiperidine) 82 C7F1s (hexadecafluoroheptane) CssN (pyridine) CHCOOH (benzoic acid) (CF)N(tritifluoromethylanine) CHCOOH (caprylic acid) (CIs)..N (trimethylamine 104 CEF1s (octadecafluorooctane) (CFS)N(tri-pentafluoroethylamine) CH10COOE (capric acid) 45 (CEN(CBs)N(triethylamine) (triheptafluoropropylamine) y CH2)(COOH)sing (octylamine) (sebacic acid) (CHN (tripropylamine) CHCN (caprylonitrile) (CE)N(trinonafluorobutylamine) CHISH (octyl mercaptan) (CHN (tributylamine) o CFOctadecafluoropropylcyclohexane) 216 CEN (quinoline) (CFSsils Selectorylamin) iannylamine CoE (eicosafluorononane) 5 (CFS),NCF (N,N-di-trifluoromethyl-undecafluorocy CH2)(COOH) (sebacic acid) HCOOH (capric acid) exity22 ls (dimethylaniline)imethylanl CoF (docosafluorodecane) 65 (CF).NCFCF (N,N-dipentafluoroethyltridecafluo CHCOOH (capric acid) rocyclohexylmethylamie) CoENE (decylamine) (CHNCHCH (diethylbenzylanine) CHF (fluoromethane) 93 (CF).NCF (N,N-di-pentafluoroethyl-heptafluoropro CH3COOH (acetic acid) pylanline) CFB (difluoromethane) 55 (CEs). NCB (diethylpropylamine) CHCOOH (acetic acid) 13 (CF).NCF (N,N-dipentatiuoroethyl-nonafluorobu CF3H (fluoroform) tylamine) . . . CEO (methyl alcohol) (CENCF (diethylbutylamine) CH3COOH (acetic acid) 111 (CFNöFON,N-diheptafluoropropyl-pentafluoroeth CHCOONa (sodium acetate) ylamine) CH3COCl (acetylchloride) CH5NCHs (dipropylethylanine) CHSCOCH (acetone) 08 (-c.5 NCF (SSEEpyl-pentafluoro CHOCH (dimethylether) 60 ethylamine) CHCOOH (butyric acid) (CHSCH. (diisopropylethylamine) CH3CN (acetonitrile) 159 CFCFSF (octadecafluorooctyl mercaptan) (CHS)N (trimethylamine) HCCH)SH (octyl mercaptan) CFI (tetrafiuoroethane) CHCOOH (propionic acid) CHCOCs (methyl ethylketone) CFH (pentafluoroethane) Many of the product compounds listed in the CHCOOH (propionic acid) foregoing table have not been disclosed in prior CHCOOH (butyric acid) publications or patents and are believed to be CHSOCHs (methyl ethyl ketone) novel. Some of them are claimed as new Con Cs FHCHCN (hexafluoropropane) (acetonitrile) - positions of matter in the following applications CHCOOH (butyric acid) CIFE (heptafluoropropane) of which I am in each case the Sole or a joint CHCOOH(EEE : O applicant, and which describe their preparation CFOCF(CH3)2CHOCH(CH) (di-trifluoromethyl (diisopropyl ether) ether) by the present process and give further informa CHOCH (dimethyl ether) CFOCFs (di-pentafluoroethylether) tion on their physical and chemical properties, CH5OCH (diethyl ether) viz.: Ser. Nos. 29,955 (filed May 28, 1948), now CFQCF (dinonafluorobutyl ether) abandoned, 38,751 and 38.752 (both fied July 14, CHOCH (dibutyl ether) 1948), 39.999 (filed July 21, 1948), 48,777 (filed 2,519,983 19 September 10, 1948) and 70,154 (filed January 10, 1949). Ser. Nos. 38,751 and 38,752 have since is Boiling range, Quantity, Mol. Formula sued as Patents Nos. 2,490,098 and 2,490,099, dated Cut o C, grains wit. Identity purewt. comp. of December 6, 1949, and Ser. No. 39,999 as Patent No. 2,500,388, dated March 14, 1950. The following examples are based on actual 1------133 to -48 60 experiments and further serve to illustrate the i2------48 to -42 20 i3------42 to -41. 80 invention. Additional detailed examples have 4------4 to -38 280 been set forth in my aforesaid parent applica 5------39 to -23 60 O 6------23 to -16 70 170 CFE.--- 170 tions, Ser. Nos. 384,729, 569,265, 626,434; and 7------16 to -4 50 165 Intercut------677,407, to which reference may be made, but in 8------4 to -2 30 152 CFBI. 152 the interest of brevity have not been set forth 9------2 to -18 30 150 Residue.------in the present specification. It will be evident from the above table that the Eacample I gaseous mixture contained a large proportion of In this experiment use was made of a 100 fluorocarbon compounds having three carbon ampere cell. The casing was a rectangular steel atoms in the molecule, i. e. CFs (octafluoropro box having a removable steel cover plate bolted pane), CFH (heptafluoropropane) and CFH a to the flanged top of the casing. The conductor (hexafluoropropane). rods were insulated and Sealed from the cover After several runs using this same charge plate by means of "Saran' (polyvinylidene chlo (without replenishment of the butyric acid) the ride) tubing, which was also employed in sheet following materials were collected from the gas form as a gasket between the cover and the cas mixture: Boiling below -38 C., 1141 grams; at ing flange. Eight anode plates of nickel and approximately -38 C., 1988 grams; between seven interleaving cathode plates of iron were -38 and -17 C., 182 grams; between -17 and used, spaced so that the distance between adja -4 C., 1183 grams; above - 4 C., 972 grams. cent electrode surfaces was 0.29'. The dimen The residual solution in the cell, after an ex sions of each plate were 18' x 11%' x is'. The tended period of electrolysis, was found to con distance between the outer anode plate surfaces tain 2.27 kg. (5 pounds) of organic material and the cell walls was 0.40'. The cell casing 30 which contained about 40% by weight of com served as a cathode element and was connected. bined fluorine. Thus non-gaseous fluorine-con to the cathode plates. The anode plates had a taining carbon compounds were also produced by total operating area of 23 sq. ft. (21,400 sq. cm.). the process and remained in the cell. The cell was maintained at a temperature during Other experiments have demonstrated the for operation of from minus 5° C. to plus 10° C. by nation from butyric acid of a substantial yield means of a chilled brine bath. of C4F10 (decafluorobutane), having a boiling This cell was charged with 4.45 kg. (50.5 mols) point close to 0°C., as well as other compounds, of n-butyric acid (approximately 10 pounds) and including the fluorocarbon acid fluoride con with 27.5 kg. (1375 mols) of commercial anhy pound C3FCOF. drous liquid hydrogen fluoride (approximately 61 - O pounds). The applied cell voltage was 5.3 volts, Eacample II which produced an average current of 100 am peres, the average current density being about A Small laboratory cell was used. The cell 4.4 amps./sq. ft. body was constructed of a one-foot length of The exit gas mixture from the cell was con 45 iron pipe (3' diameter) having an iron plate ducted through a tube (connected to the cover brazed to one end to form the bottom. An iron plate) to a condenser where the bulk of the HF rod ('%' dia.) was brazed to the center of the was condenser and drained back to the cell, then bottom and extended upwardly to near the top. through a sodium fluoride tube for further re The pipe and this center rod constituted the moval of HF, then through a potassium hydrox 50 cathodes. An iron cover plate was secured to a ide bubbler to remove CO2 and any residual HF, flange at the upper end of the pipe. Through a potassium iodide and sodium thiosulfate bub the center of the cover passed an anode con bler to remove OF2, a liquid air trap to condense ductor Support rod sealed and insulated there the fluorocarbon compounds, and lastly a wet from, to which was fastened a cylinder of sheet test meter for measuring the quantity of hydro 55 nickel (1%' dia.) surrounding the iron center gen. rod and forming the anode. "Saran' was used The materials collected in the liquid air trap for Sealing and gasketing. An outlet tube was during a portion of the run were transferred to connected to the upper end of the pipe for with a gas holder over water. The weight of this puri drawing gaseous products. The cell was cooled fied condensate was 745 grams, produced during 60 in an ice bath to maintain an operating temper an operating period of 54.4 hours, with 232 fara ature in the neighborhood of 0° C. days being passed. This material was fraction The cell was charged with 400 grams (20 mois) ated into nine portions with yields as shown in of commercial. anhydrous liquid hydrogen fluo the following table. Molecular weights of the ride, 93 grams (1 mol) of toluene, and 5 grams fractions were obtained by using a gas density (0.3 mol) of added water, Serving as a conductiv balance and applying the ideal gas law; they rep ity additive. The toluene was substantially in resent approximate weighted averages in the Soluble in the hydrogen fluoride Solution but be case of fractions boiling over an appreciable came admixed therewith during operation. range. The weight amount of each fraction was Electroylsis proceeded at 5 volts and 1.1 ann obtained from the pressure of the gas when the 70 peres for a period of 12 days, during which 88 fraction was allowed to vaporize into a receptacle liters of gas were evolved which yielded 11 grams of known volume, applving the ideal gas law. of condensate in a liquid air trap. The conden The first cut was a mixture of CF4, CFH and Sate was distilled to yield a 0.5 gram portion boil C2Fs. Other cuts consisted of relatively pure ing below -80 C., a 0.5 gram portion boiling at Single compounds, as shown. 75 about 0. C., and a principal fraction of 10 grams

9,519,088 2. 22 boiling above room temperature. The latter was Eacample IV redistilled in a fractionating column and the fol A Small copper Cell having a nickel anode was lowing fractions were separated: charged with acetic acid and KF3HF in the Weight (grams) ratio of 1 to 3.4 by weight. Current was passed Boiling range ( C.) : through the cell at about 8 volts and 9 amperes 57-60 ------1.6 until 6 faradays had passed. The operation was 60-63 ------1.6 conducted at atmospheric pressure and a tem 63-64 ------3.2 perature averaging 75° C. This operating pres Residue ------0.7 O Sure was possible, despite the elevated tempera The 63-64 C. fraction had a molecular weight ture, due to the low vapor pressure of the com of 383, corresponding to a 7-carbon fluorocar plex of potassium fluoride and hydrogen fluoride, bon. which remained in a non-boiling liquid state. Using the same cell arrangement, the forma The products included CF4 and CF3H. tion of fluorocarbons from n-octane, using wa 5 A similar experiment, using a cell charge of ter as a conductivity additive, was demonstrated. Sodium acetate and KF3HF in the ratio of 1 to The cell was charged with 550 grams (27.5 mols) 6.8 by weight, was conducted under similar con of commercial anhydrous liquid hydrogen fluo ditions and with similar results. ride, 160 grams (1.4 mols) of n-octane, and 10 - Eacample V grams (0.6 mol) of added water. An electrolysis 20 Use was made of an iron laboratory cell con proceeded during the 600 hour run period, a total taining nickel anodes and iron cathodes, operat of 440 additional grams of hydrogen fluoride and ing at atmospheric pressure and a temperature of 60 grams of water were added from time to time 0° C. The initial cell charge consisted of 7,500 to replenish the hydrogen fluoride and to main grams of highly anhydrous liquid hydrogen fluo tain the conductivity. The cell voltage varied 25 ride and 700 grams of dried pyridine. Additional from 6.5 to 7.7 volts and the cell current varied pyridine was added during the run to make a in the range of 1.5 to 3.0 amperes. A total of total of about 2,000 grams. The pyridine emi 47.3 faradays passed. Fractionation of the prod ployed was dried over solid sodium hydroxide uct mixture demonstrated that the Original and then distilled. Current was passed for a octane had been (to a large extent) converted to 3) period of four days, at an average cell voltage fluorocarbon compounds, of which more than of approximately 6.0. A total of 447 faradays was one-third was CaF18. Substantial yields of Cils paSSed. and C6F14 were also obtained. The liquid cell product mixture was drained The production of fluorocarbons from n-Octane from the bottom of the cell, treated with lime to was also demonstrated in experiments using am remove residual HF, and was fractionally dis monia, mercuric cyanide, and pyridine, as con tilled. There was obtained about 250 grams of a ductivity additives. In the absence of the n liquid fraction which was identified as relatively octane, a solution of mercuric cyanide in anhy pure C5FoNF (undecafluoropiperidine), a cyclic drous liquid hydrogen fluoride yielded CF4 and compound having the following measured prop NF3 when subjected to a cell potential of about 4) erties: 7.5 volts, and with the liberation of free mer cury. Boiling point (at about 740 mm.) ----C 48 Eacample III Refractive index (at 20° C.) ------1.281 Density (grams/cc. at 20° C.) ------1.744 A cell of the type described in the preceding Y Surface tension (dynes/cm. at 20° C.) -- 13.6 example was charged with 205 grams (5 mols) Molecular weight (from vapor density) -- 285 of acetonitrile (CH3CN) and 785 grams (39.3 Per cent F------73.4 mols) of anhydrous liquid hydrogen fluoride Fer cent N ------4.87 (which initially contained a substantial trace of The values for the pure compound as calculated water). Current was passed for five days at an () from the formula are: molecular weight, 283; average of 5.5 amperes. The cell voltage aver Per cent F, 73.1; Per cent N, 4.95. aged 1.7 volts and remained close to this value Other products included 2-fluoropyridine, during this five day period. Fluorocarbon com C5F12 and NF3 pounds were formed during the entire run. The The CsIF12 (dodecafluoropentane) is formed by identified products included OF2, CF3H, CF4, 5 cleavage of the ring (eliminating N) and fluorine C2F5H, CFs and CF3CN. replacement and addition to produce the satu The C2F5H and CF3CN appeared to form an rated open chain. Substantially all of the C5F12 azeotropic mixture and separation by distillation formed from pyridine is of the normal, straight was not accomplished. This mixture fraction. chain type. A highly purified sample (obtained (boiling in the range of -73 to -48 C.) was (t) from another experiment in which pyridine was chemically treated to identify the CF3CN in the used) having a molecular Weight value (deter following way: The gaseous mixture was passed mined from vapor density) of 288, in agreement through 50% aqueous potassium hydroxide at with the formula weight of 288, and which was 60-70° C., then into a standard HCl acid solu estimated from the freezing point range to be at tion, through a drying tube, and, recondensed in least 99.5 mol per cent pure, was found to have a liquid air trap. Titration of the acid indicated the following physical properties: that 3.2 grams of CF3CN had been hydrolyzed, equivalent to 5.1 g. of CF3COOK. The basic solu Boiling point (at 760 mm.) ------C- 27.9 tion was neutralized with HCl and evaporated to Freezing point ------C -125.65 dryness. The residue was then dried and was 70 Dielectric constant (at 20° C.). ------. .68 Subjected to an analytical procedure which dem onstrated the presence of 5.1 g. of CF3COOK. Eacample VI The gas from the liquid air trap was found to Use was made of an iron-cathode nickel-anode have a molecular weight range of 118 to 124 and cell of the type shown in the drawing, operating was mainly C2F5H (formula wt. 120). 5 at atmospheric pressure and a temperature of 2,519,988 23 24 about 0° C. The initial cell charge consisted of erate free fluorine under the txisting couditions 1800 grams of anhydrous liquid hydrogen fluoride but which is sufficient to cause the production of and 400 grams of di-n-butyl ether. Additional fluorine-containing carbon compound products ether was added during the run to replenish that at a useful rate, and recovering at least one fluo consumed. The cell voltage was in the range of rine-containing carbon compound product of 4 to 6 volts and produced a current density of the proceSS. about 20 amperes per square foot of anode Sur 2. A new and useful electrochemical process face. of making carbon compounds which have at least At the end of 60 hours, 1355 grams of immis one fluorine atom bonded to a carbon atom in the cible liquid was recovered from the bottom of the O molecule, which comprises electrolyzing for a cell, and this was washed with potassium hy period of hours a current-conducting mixture of droxide solution to remove traces of HF, and liquid hydrogen fluoride free from water in more was then fractionally distilled to yield a liquid than a small proportion and an organic starting fraction which was identified as relatively pure compound having at least one hydrogen atom normal CAF'-O-CF9 (di-n-nonafluorobutyl s bonded to a carbon atom in the molecule, at a ether). This fraction had the following measured temperature and pressure at which a liquid state properties: is maintained and at a cell voltage which is in Boiling point (at 741 mm.) ------°C 100.7 sufficient to generate free fluorine under the ex Refractive index (at 25 C.) ------1.26. isting conditions but which is sufficient to cause 20 the production of fluorine-containing carbon Density (grams/cc. at 34 C.) ------1689 compound products at a useful rate, and recover Dielectric constant (at 20° C.) ------82 ing a carbon compound product of the process Molecular weight (from vapor density) -- 459 which has at least one fluorine atom bonded to a The formula weight of the pure compound is carbon atom in the molecule. 454. 3. A new and useful electrochemical process This compound has boiling point, refractive of making carbon compounds which have at least index, and density values which are slightly but one fluorine atom bonded to a carbon atom in appreciably lower than those of the normal the molecule, which comprises electrolyzing a CF1s fluorocarbon (mol, wt. 438) which have current-conducting mixture of liquid hydrogen been found to be 104° C., ii.267, and 1.765, re 30 fluoride free from water in more than a small spectively, and may be compared with the values proportion and an organic starting compound given above. having at least one hydrogen atom bonded to a This butyl ether starting compound also pro carbon atom in the molecule, by passing direct duces a substantial yield of the CF10 fluorocar current through the Solution for a period of hours bon, and lesser yields of lower fluorocarbon Com at an electrolyzing potential which is insufficient pounds. Minor yields of fluorocarbon ethers to generate free fluorine under the existing con aving fewer than eight carbon atoms are also ditions but which is Sufficient to cause the pro produced. Some material is also produced which duction of fluorine-containing carbon compound is higher boiling than the CF-O-C4F9 prod products at a useful rate, the temperature and uct. There is Some evidence for the formation 40 pressure being Such as to maintain a liquid state, CF18, presumably formed by the combination and recovering a carbon Compound product of of C4Fg radicals in the solution. the process which has at least One fluorine atom The fluorocarbon ethers are so stable that di bonded to a carbon atom in the molecule. rect analytical determination of the oxygen con 4. A process according to claim 3 wherein an tent is extremely difficult. The formation of oxygen-containing starting Compound is en Such compounds from hydrocarbon ether start ployed which has at least One hydrogen atom ing compounds has been further Substantiated attached to a carbon atom in the molecule. by homologous series runs down to and including 5. A process according to claim 3 wherein a the production of CF3-O-CF3 and carboxylic acid Starting Compound is employed. 50 6. A process according to claim 3 wherein a nitrogen-containing starting compound is en from dimethyl ether and diethyl ether, respec ployed which has at least One hydrogen atom tively. These products were found to have boil attached to a carbon atom in the molecule. ing points of minus 59° C. and plus 1 C., respec 7. A process according to claim 3 wherein an tively, and the measured molecular weights amine starting compound is employed. (vapor density method) were the same as the for 8. A process according to claim 3 wherein a mula weights. Their identification was further hydrocarbon starting compound is employed. confirmed by mass spectrograph analyses which 9. A process according to claim 3 wherein an admit of no doubt since the mass numbers of the alkane starting compound is employed. ionic fragments were measured with ample pre 10. A new and useful electrochemical process cision. of making fluorine-containing carbon compounds Having described various embodiments and ex from fluorinatable hydrogen-containing organic amples of my novel process for purposes of illus starting compounds which are readily soluble in tration rather than limitation, what I claim is as anhydrous liquid hydrogen fluoride to form elec follows: trolytically conducting Solutions, which com 1. A new and useful electrochemical process of prises electrolyzing in a nickel-anode cell a making fluorine-containing carbon compounds current-conducting Solution of the Organic start from fluorinatable organic starting compounds, ing material in anhydrous liquid hydrogen which comprises electrolyzing for a period of fluoride by passing direct current through the hours a current-conducting mixture of the or O solution for a period of hours at an electrolyzing ganic starting material in liquid hydrogen fluo potential which is insufficient to generate free ride free from water in more than a small pro fluorine under the existing conditions but which portion as herein described, at a temperature and is sufficient to cause the production of fluorine pressure at which a liquid state is maintained containing carbon compound products at a use and at a cell voltage which is insufficient to gen ful rate, the temperature and pressure being such 2,519,983 25 26 as to maintain a liquid state, and recovering at 18. A process according to claim 12 wherein a least one fluorine-containing carbon compound soluble fluoride Salt is employed as a conductivity product of the process. additive. 11. A process according to claim 10 wherein 19. A new and useful electrochemical process the temperature is maintained in the range of for making fluorine-containing carbon con about minus 20 to plus 80 C., and the total s pounds, which comprises electrolyzing in a cell potential does not exceed 8 volts. nickel-anode cell a current-conducting Solution 12. A new and useful electrochemical process essentially consisting of liquid hydrogen fluoride of making fluorine-containing carbon compounds containing a dissolved conductivity additive and from fluorinatable organic starting compounds, also containing an admixed and undissolved which comprises electrolyzing for a period of fluorinatable hydrogen-containing Organic start hours a current-conducting solution essentially ing compound and which is free from Water in consisting of liquid hydrogen fluoride containing more than a small proportion as herein described, a dissolved conductivity additive and also con by passing direct current through the Solution taining an admixed undissolved organic starting for a period of hours at an electrolyzing poten compound and which is free from water in more tial which is insufficient to generate free fluorine than a small proportion as herein described, at under the existing conditions but which is Sufi a temperature and pressure at which a liquid cient to cause the production of fiuorine-contain state is maintained and at an electrolyzing ing carbon compound products at a useful rate, potential which is insufficient to generate free the temperature and pressure being Such as to fluorine under the existing conditions but which 20 maintain a liquid state, and recovering at least is sufficient to cause the production of fluorine one fluorine-containing carbon compound prod containing carbon compound products at a use uct of the process. ful rate, and recovering at least one fluorine 20. A process according to claim 19 wherein containing carbon compound product of the anhydrous liquid hydrogen fluoride, and a hydro proceSS. carbon starting compound, are employed. 13. A process according to claim 12 wherein a JOSEPH. H. SIMONS. soluble organic compound is employed as a con ductivity additive. REFERENCES CITED 14. A process according to claim 12 wherein a 30 The following references are of record in the soluble oxygen-containing Organic compound file of this patent: which contains at least one hydrogen atom bonded to a carbon atom in the molecule is en UNITED STATES PATENTS ployed as a conductivity additive. Number . Name Date 15. A process according to claim 12 wherein a 2,186,917 Gaylor ------Jan. 9, 1940 soluble monocarboxylic acid is employed as a 35 2,220,713 Grosse et al. ------Nov. 5, 1940 conductivity additive. OTHER REFERENCES 16. A process according to claim 12 wherein a soluble nitrogen-containing organic compound Simons: Chemical Reviews, vol. 8 (1931), pp. which contains at least One hydrogen atom 223-230. bonded to a carbon atom in the molecule is em 40 Getman et al.: Outlines of Theoretical Chem ployed as a conductivity additive. istry, 6th ed., (1937), pp. 367, 368, 473. 17. A process according to claim 12 wherein a Porter: Chemical and Metallurgical Engineer Soluble inorganic compound is employed as a ing (July 1946), p. 107. conductivity additive. 45