May 12, 1970 H. M. Fox ETAL 3,511,760 ELECTROCHEMICAL FLUORINATION OF ORGANIC COMPOUNDs . Filed Nov. 2, 1967 3. Sheets-Sheet l

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A 77OAPWAYS May 12, 1970 H. M. FOX ETAL 3,511,760 ELECTROCHEMICAL FLUORINATION OF ORGANIC COMPOUNDS 3. Sheets-Sheet 2

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ATTOARWAYS May 12, 1970 H. M. Fox ETAL 3,511,760 ELECTROCHEMICAL FLUORINATION OF ORGANIC COMPOUNDS Faled Nov. 2, 1967 3. Sheets-Sheet 5

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INVENTORS : H. M. FOX BY F. N. RUEHLEN %ry /42.47 a 77OARWAYS 3,511,760 United States Patent Office Patented May 12, 1970

1. 2 veniently preparing fluorine-containing compounds. In 3,511,760 ELECTROCHEMICAL FLUORNATION OF our process the extent of fluorination of the fluorinatable ORGANIC COMPOUNDS compound can be readily controlled. Consequently, our Homer M. Fox and Forrest N. Ruehlen, Bartlesville, process is capable of producing a wide variety of fluorine Okla., assignors to Phillips Petroleum Company, a cor containing products with high efficiency and good selec poration of Delaware tivity. Compared with the fluorination processes of the Continuation-in-part of application Ser. No. 435,263, prior art, the reaction conditions utilized in our process Feb. 25, 1965. This application Nov. 2, 1967, Ser. are mild, and the yields of product per kilowatt hour or No. 683,089 per unit of anode area are extraordinarily high. Further Int, C. B.01k 3/00 more, as discussed further hereinafter, we have found that U.S. C. 204-59 20 Claims () we can introduce more fluorine into a fluorinatable com pound per kilowatt hour or per unit of anode area (in the order of at least 100 times as much or more in some ABSTRACT OF THE DISCLOSURE instances) than can be accomplished in processes of the Fluorinatable feedstocks are electrochemically fluori 5 prior art. nated in an electrolysis cell provided with a porous Another surprising result or advantage of our inven anode and using an anhydrous liquid hydrogen fluoride tion is that the primary products obtained in our process electrolyte. The fluorination is carried out under condi are predominantly partially fluorinated materials. It is tions such that it occurs within the pores of the anode. difficult to obtain such materials in the methods of the 20 prior art and, as stated above, even more difficult to pro duce moderately fluorinated hydrocarbons containing This application is a continuation-in-part of our co fluorine atoms in certain specific locations in the mole pending application Ser. No. 435,263, filed Feb. 25, 1965, cule. It is the reactive nature of fluorine to bind itself to now abandoned. a carbon atom to which one or more previous fluorine This invention relates to electrochemical fluorination. atoms have already been bound. Thus, any difluoro com In one aspect this invention relates to a process for pre pounds made by direct fluorination techniques of the paring fluorine-containing compounds by electrochemi prior art almost invariably have both the fluorine atoms cal fluorination of a fluorinatable compound. attached to the same carbon atom. This has made it Fuorine-containing organic compounds are known to necessary to employ indirect methods such as the prep possess value in many fields of industrial chemistry. For 30 aration of appropriate chloro- or hydroxy-analogs foll example, many of the lower molecular weight compounds lowed by replacement of such groups with fluorine. Our are useful as refrigerants, dielectrics, fire extinguishing invention provides a direct fluorination process which un materials, and as aerosol propellants. Many fluorine-con expectedly produces good yields of difluoro compounds taining compounds are also useful as intermediates for in which the two fluorine atoms are not on the same car the production of plastics and synthetic elastomers. A bon atom. As specific examples, 1,2-difluoroethane and numer of techniques are known for producing fluorine 1,4-difluorobutane can be easily and directly produced in containing organic compounds. These include pyrolysis good yields by the process of our invention. Thus, in one techniques in which fluorine-containing materials are pyr aspect, our invention provides a direct process for the olyzed in the presence of carbon or carbon-containing production of such materials directly from a hydrocar materials to obtain a mixture of fluorinated compounds. bon starting material in a one-step process. Another technique is to electrolyze a mixture of an elec Broadly speaking, the process of our invention com trolyzable fluoride having the compound to be fluorinated prises electrolyzing a current-conducting essentially an dissolved therein. In many instances, a wider commercial hydrous liquid hydrogen fluoride electrolyte in an electro application of fluorine-containing organic compounds has lysis cell provided with a cathode and a porous anode, in been limited due to difficulties in their preparation. Many 45 troducing a fluorinatable organic compound into the pores of the prior art processes for preparing such compounds of said anode and therein at least partially fluorinating involve several chemical and mechanical steps and re at least a portion of said organic compound within said quire the utilization of costly starting materials. Further pores of said anode, and recovering fluorinated compound more, when employing the methods of the prior art it products from said cell. is difficult to produce moderately or only partially fluori 50 An object of this invention is to provide an improved nated products in satisfactory yields. It is even more dif electrochemical process for the production of fluorine ficult to produce moderately or partially fluorinated prod containing compounds. Another object of this invention ucts, e.g., fluorinated hydracarbons, containing fluorine is to provide an electrochemical process for the produc atoms in certain specific locations in the molecule. It is tion of fluorine-containing organic compounds in good also difficult to produce fluorinated products electrochem 55 yields and with good selectivity. Another object of this ically at high rates of conversion and avoid the formation invention is to provide an improved electrochemical proc of Substantial amounts of cleavage products. ess for the production of fluorine-containing compounds The present invention provides a solution for the which is economical, commercially feasible, provides for above-described difficulties. We have now discovered an the maximum utilization of the starting fluorinatable ma improved electrochemical process for efficiently and con 60 terial, and is accompanied by the minimum formation of 3,511,760 3. 4. undesirable by-products. Another object of this invention Since fluorine is so reactive, no list of practical length is to provide an improved electrochemical process for the could include all starting materials which can be used production of fluorine-containing organic compounds in the practice of our invention. However, representative which process can be readily controlled to yield products examples of the above-described starting materials in having a desired fluorine content. Still another object of clude, among others, the following: methane; ethane; this invention is to provide an improved electrochemical 5 propane; butane; isobutane; pentane; n-hexane; n-octane: . fluorination process for the production of partially fluori cyclopropane; cyclopentane; cyclohexane; cyclooctane; nated fluorine-containing compounds, such as difluoro 1,2-dichloroethane; 1-fluoro-2-chloro-3-methylheptane; compounds, wherein the two fluorine atoms are attached ethylene; propylene; cyclobutene; cyclohexene; 2-meth to different carbon atoms. Other aspects, objects, and ad ylpentene-1; 2,3-dimethylhexene-2; butadiene; vinyl chlo vantages of the invention will be apparent to those skilled 10 ride; 3-fluoropropylene; acetylene; methylacetylene; vinyl in the art in view of this disclosure. acetylene; 3,3-dimethylpentyne-1; allyl chloride; methyl Thus, according to the invention, there is provided a amine; ethylamine; diethylamine; 2-amino-3-ethylpentane; process for the electrochemical fluorination of a fluorina 3-bromopropylamine; triethylamine; dimethyl ether; di table organic compound, which process comprises: Pass 5 ethyl ether; methyl ethyl ether; methyl vinyl ether; 2-iodo ing an electric current through a current-conducting es ethyl methyl ether; di-n-propyl ether; methyl formate; sentially anhydrous liquid hydrogen fluoride electrolyte methyl acetate; ethyl butyrate; ethyl formate; n-amyl contained in an electrolysis cell provided with a cathode acetate; methyl 2-chloroacetate; methyl mercaptan; ethyl and a porous anode; passing said organic compounds into mercaptan; n - propyl mercaptan; 2 - mercaptohexane; the pores of said anode and therein into contact with 20 2-methyl-3-mercaptoheptane; acetonitrile; propionitrile; the fluorinating species produced by said electrolyzing; n-butyronitrile; acrylonitrile; n-hexanonitrile; methanol; and recovering fluorinated organic compound as product ethanol; isopropanol; n-hexanol; 2,2-dimethylhexanol-3; of the process. n-butanol; ethylenebromohydrin; benzene; toluene, cu Very few organic compounds are resistant to fluorina mene; o-xylene; p-xylene; and monochlorobenzene. tion. Consequently, a wide variety of feed materials, both The electrochemical process of the invention is carried normally liquid and normally gaseous compounds, can be out in a medium of hydrogen fluoride electrolyte. Al used in the practice of this invention. Organic compounds though said hydrogen fluoride electrolyte can contain which are normally gaseous or which can be introduced small amounts of water, such as up to about 5 weight per in gaseous state into the pores of a porous anode under cent, it is preferred that said electrolyte be essentially an the conditions employed in the electrolysis cell, and which 30 hydrous. Generally speaking, it is preferred that said elec are capable of reacting with fluorine, are presently pre trolyte contain not more than about 0.1 weight percent ferred as starting materials in the practice of the invent water. However, commercial anhydrous liquid hydrogen tion to produce fluorine-containing compounds. However, fluoride which normally contains dissolved water in it is within the scope of the invention to utilize starting amounts ranging from a trace (less than, 0.1 weight per materials which are introduced into the pores of the anode 35 cent) up to about 1 percent by weight can be used in in liquid state. Generally speaking, desirable organic the practice of the invention. Thus, as used herein and starting materials which can be used are those containing in the claims, the term "essentially anhydrous liquid hy from 1 to 8, preferably 1 to 6, carbon atom per molecule. drogen fluoride," unless otherwise specified, includes liquid However, it is within the scope of the invention to utilize hydrogen fluoride which can contain water not exceeding reactants which contain more than 6 or 8 carbon atoms. 40 up to about 1 weight percent. As the electrolysis reac If desired, suitable feed materials having boiling points tion proceeds, any water contained in the hydrogen fluo above cell operating temperatures can be passed into ride electrolyte is slowly decomposed and said electro the pores of the porous anode in gaseous state by utilizing lyte concomitantly approaches the anhydrous state. In a suitable carrier gas. Thus, a suitable carrier gas can be the practice of the invention, when using one of the more saturated with the feed reactant (as by bubbling said car expensive feed materials, one preferred method of op rier gas through the liquid reactant), and then passing eration when startining a cell with a new electrolyte which the saturated carrier gas into the pores of the porous contains traces of water is to electrolyze said electrolyte anode. Suitable carrier gases include the inert gases such for a few hours while using an inexpensive feed material as helium, xenon, argon, neon, krypton, nitrogen, etc. It such as methane, prior to introducing the more expen is also within the scope of the invention to utilize normally 50 sive feed material so as to remove said water. The hy gaseous materials such as hydrocarbons containing from 1 drogen fluoride electrolyte is consumed in the reaction to 4 carbon atoms as carrier gases. These latter gases will and must be either continuously or intermittently placed react, but in many instances this will not be objection in the cell. able. It is also within the scope of the invention to utilize Pure anhydrous liquid hydrogen fluoride is nonconduc the above-described carrier gases, and particularly said 55 tive. The essentially anhydrous liquid hydrogen fluorides inert gases, as diluents for the feedstocks which are nor described above have a low conductivity which, gener mally gaseous at cell operating conditions. ally speaking, is lower than desired for practical opera Some general types of starting materials which can be tion. To provide adequate conductivity in the electrolyte, used include, among others, the following: alkanes, and to reduce the hydrogen fluoride vapor pressure at cell alkenes, alkynes, amines, ethers, esters, mercaptans, ni 60 operating conditions, an inorganic additive can be in triles, alcohols, aromatic compounds, and partially halo corporated in the electrolyte. Examples of suitable addi genated compounds of both the aliphatic and aromatic tives are inorganic compounds which are soluble in liquid series. It will be understood that the above-named types hydrogen fluoride and provide effective electrolytic con of compounds can be either straight chain, branched ductivity. The presently preferred additives are the alkali chain, or cyclic compounds. Partially chlorinated and the 65 metal (sodium, potassium, lithium, rubidium, and cesium) partially fluorinated compounds are the preferred partially fluorides and ammonium fluoride. Other additives which halogenated compounds. The presently preferred starting can be employed are sulphuric acid and phosphoric acid. materials are the saturated and unsaturated hydrocarbons Potassium fluoride, cesium fluoride, and rubidium fluoride (alkanes, alkenes, and alkynes) containing from 1 to 6 are the presently preferred additives. Potassium fluoride carbon atoms per molecule. The presently more preferred 70 is the presently most preferred additive. Said additives starting materials are the normally gaseous organic com can be utilized in any suitable molar ratio of additive to pounds, and particularly said saturated and unsaturated hydrogen fluoride within the range of from 1:4.5 to 1:1, hydrocarbons, containing from 1 to 4 carbon atoms per preferably 1:4 to 1:2. The presently most preferred elec molecule. 75 trolytes are those which correspond approximately to the 3,511,760 5 6 formulas KF•2HF, KF.3HF, or KF4HF. Such electro temperatures sometimes tend to promote fragmentation lytes can be conveniently prepared by adding the required of the product molecules. quantity of hydrogen fluoride to KF-HF (potassium bi Pressures substantially above or below atmospheric can fluoride). In general, said additives are not consumed in be employed if desired, depending upon the vapor pressure the process and can be used indefinitely. Said additives of the electrolyte as discussed above. In all instances, the are frequently referred to as conductivity additives for 5 cell pressure will be sufficient to maintain the electrolyte convenience. in liquid phase. Generally speaking, the process of the The cell body and the electrodes in the cell must be fab invention is conveniently carried out at substantially at ricated of materials which are resistant to the action of mospheric pressure. It should be pointed out that a valu the contents of the cell under the reaction conditions. able feature of the invention is that the operating condi Materials such as steel, iron, nickel, polytetrafluoroethyl O tion of temperature and pressures within the limitations ene (Teflon), carbon, and the like, can be employed for discussed above are not critical and are essentially inde the cell body. The cathode can be fabricated in any suit pendent of the type of feed employed in the process. able shape or design and can be made of any suitable An outstanding advantage of the invention is that the conducting material such as iron, steel, nickel, alloys of process does not depend upon the solubility of the feed said metals, and carbon. The anode must be porous. Said material in the electrolyte. Vigorous agitation or the use of anode can be fabricated from any suitable conducting chemical solubilizers, such as required in some prior art material which is compatible with the system, e.g., nickel, processes, are not necessary. In some instances, however, iron, various metal alloys, and carbon, which is not wet a mild stirring or agitation for purposes of aiding in tem ted by the electrolyte. By "not wetted' we mean that the 20 perature control is beneficial. It should be particularly contact angle between the electrolyte and the anode must noted that the porous anode is not merely a sparger for exceed 90° in order that anticapillary forces will prevent introducing the feedstock into the electrolyte as in some substantial invasion of the small pores of the anode by the electrolytic processes of the prior art. In the preferred electrolyte. Porous carbon, which is economical and read manner of practicing our invention, we avoid contact ily available in ordinary channels of commerce, is pres between the main body of the electrolyte and the feed ently preferred for the anode. Porous carbon impregnated stock and/or fluorinated products. with a suitable metal such as nickel can also be used as For purposes of efficiency and economy, the rate of the anode. Various grades of porous carbon can be used direct current flow through the cell is maintained at a in the practice of the invention. It is preferred to employ rate which will give the highest practical current densities porous carbon which has been made from carbon pro 30 for the electrodes employed. Generally speaking, the cur duced by pyrolysis, and not graphitic carbon. Types of rent density will be high enough so that anodes of moder commercially available porous carbon are described here ate size can be employed, yet low enough so that said inafter. Said anode can be fabricated in any suitable shape anode is not corroded or disintegrated under the given cur or design, but must be arranged or provided with a suit rent flow. Current densities within the range of from 30 able means for introducing the feed reactant material to 1000, or more, preferably 50 to 500 milliamps per into the pores thereof and into contact with the fluorinat square centimeter of anode geometric surface area can be ing species within said pores. used. Current densities less than 30 milliamps per square Except for the limitations described above, any con centimeter of anode geometric surface area are not prac venient cell configuration or electrode arrangement can tical because the rate of fluorination is too slow. The volt be employed. The cell must be provided with a vent or 40 age which is employed will vary depending upon the vents through which by-product hydrogen can escape particular cell configuration employed and the current and through which volatile cell products can be removed density employed. In all cases, under normal operating and recovered. If desired or necessary, a drain can be pro conditions, however, the cell voltage or potential will be vided on the bottom of the cell for removal of heavier less than that required to evolve or generate free or ele nonvolatile products. The cell can contain an ion perme mental fluorine. Voltages in the range of from 4 to 12 able membrane or divider, if desired, for dividing the cell volts are typical. The maximum voltage will not exceed into an anode compartment and a cathode compartment. 20 volts per unit cell. Thus, as a guide in practicing the It is frequently preferred to employ such a membrane or invention, voltages in the range of 4 to 20 volts per unit divider to prevent hydrogen generated at the cathode from cell can be used. mixing with the volatile fluorinated products produced As used herein and in the claims, unless otherwise at the anode. This is done to simplify the purification and Specified, the term "anode geometric surface" refers to isolation of the fluorine-containing products. Any conven the outer geometric surface area of the anode which is ex tionally known resistant membrane or divider material posed to electrolyte and does not include the pore Sur can be employed for this purpose. When the anode prod faces. For example, in FIG. 1 the anode geometric sur lucts are withdrawn from the cell through a conduit means face is the vertical cylindrical side wall. directly connected to the anode, as described further here The feed rate of the fluorinatable material being in inafter, said divider can be omitted. troduced through the pores of the anode is an important The electrochemical conversion can be effectively and process variable in that, for a given current flow or cur conveniently carried out over a broad range of tempera rent. density, the feed rate controls the degree of con tures and pressures limited only by the freezing point 60 Version. Similarly, for a given feed rate, the amount of and the vapor pressure of the electrolyte. Generally speak current flow or current density can be employed to con ing, the process of the invention can be carried out at trol the degree of conversion. Feed rates which can be temperatures within the range of from minus 80° to 500 employed in the practice of the invention will preferably C. at which the vapor pressure of the electrolyte is not be in the range of from 0.5 to 10 milliliters per minute excessive, e.g., less than 250 mm. Hg. It is preferred to 65 per square centimeter of anode geometric surface area. operate at temperatures such that the vapor pressure of With the higher feed rates, higher current density and the electrolyte is less than about 50 mm. Hg. As will be cent rates are employed. Since the anode can have a understood by those skilled in the art, the vapor pressure Wide variety of geometrical shapes, which will affect the of the electrolyte at a given temperature will be dependent geometrical surface area, a sometimes more useful Way upon the composition of said electrolyte. It is well known 70 of Xpressing the feed rate is in terms of anode cross. that additives such as potassium fluoride cause the vapor Sectional area (taken perpendicular to the direction of pressure of liquid hydrogen fluoride to be decreased an flow). For the anode employed in several of the examples unusually great amount. A presently preferred range of and illustrated in FIG. 1, the above range would be 25 to 500 milliliters per minute per square centimeter of temperature is from about 60 to about 1050 C. Higher 75 CrOSS-Sectional area. 3,511,760 7 8 The actual feed rate employed will depend upon the The above-described pressure balance will permit some type of carbon used in fabricating the porous anode as invasion of the pores of the anode by the hydrogen well as several other factors including the nature of the fluoride electrolyte. The amount of said invasion will de feedstock, the conversion desired, current density, etc., pend upon the inlet pressure of the feedstock and the pore | because all these factors are interrelated and a change in size. The larger size pores are more readily invaded. We one will affect the others. In all instances, however, the have found that porous carbon anodes as described herein feed rate will be such that the feedstock is passed into can be successfully operated when up to 40 to 50 percent the pores of the anode, and into contact with the fluorinat of the pores have been invaded by liquid HF electrolyte. ing species therein, at a flow rate such that the inlet pres The degree of conversion significantly affects the type sure of said feedstock into said pores is essentially less or identity of the predominating products. Low degrees than the sum of (a) the hydrostatic pressure of the elec of conversion favor the production of partially fluorinated trolyte at the level of entry of the feedstock into said products whereas high degrees of conversion produce pores and (b) the exit pressure of any unreacted feed more highly fluorinated products. An important feature stock and fluorinated products from said pores into the of our invention is that the residence time of the feed electrolyte. Said exit pressure is defined as the pressure materials in the cell is uniform and very low. While the required to form a bubble on the outer surface of the actual residence time of the feed and fluorinated product anode and break said bubble away from said surface. in the reaction zone of the cell is difficult to determine, Said exit pressure is independent of hydrostatic pressure. it appears the maximum residence time is in the order Under these flow rate conditions there is established a of 0.01 to 2 minutes, probably less than 1 minute. Pref pressure balance between the feedstock entering the pores 20 erably, the residence time within the pores of the anode of the anode from one direction and electrolyte attempt will be in the range of from 0.2 to 2 minutes, more pref ing to enter the pores from another and opposing direc erably within the range of 0.25 to 0.5 minute. The actual tion. This pressure balance provides an important and residence time will depend upon the amount of invasion distinguishing feature of our invention in that essentially of the anode pores by the electrolyte. This is in marked none of the feed leaves the anode to form bubbles which 25 contrast to the prior art processes wherein the feed ma escape into the main body of the electrolyte. Essentially terial is dissolved in the electrolyte and the resulting solu all of the feedstock travels within the carbon anode via tion then electrolyzed over a period of hours. Conse the pores therein until it reaches a collection zone within quently, controlling the conversion in the process of our the anode from which it is removed via a conduit, or invention makes possible a much closer control of the until it exits from the anode, preferably at a point above 30 products of the invention as compared to said prior art the surface of the electrolyte. processes, whose "batch type' operation tends to produce The more permeable carbons will permit higher flow excessive quantities of fragmented, completely fluorinated rates than the less permeable carbons. Any suitable por products. Thus, in the practice of the invention when it ous carbon which will permit operation within the limits is desired to utilize a specific feed for the purpose of ob of the above-described pressure balance can be employed 35 taining a predominantly specific product, or a predomi in the practice of the invention. Thus, broadly speaking, nating range of products, a porous anode is chosen which porous carbons having a permeability within the range will be capable of operating at high current densities and of from 0.5 to 75 darcys and average pore diameters thus suitable for passing the required quantity of feed within the range of from 1 to 150 microns can be em into and within the pores thereof at a rate which will ployed in the practice of the invention. Generally speak 40 utilize its porosity to maximum advantage. ing, carbons having a permeability within the range of In the practice of the invention, the feed material and from about 2 to about 30 darcys and an average pore the products obtained therefrom are retained in the cell diameter within the range of from about 20 to about 75 for a period of time which is generally less than one microns are preferred. minute. The fluorinated products, and the unconverted Similarly, anode shapes, anode dimensions, and manner feed are passed from the cell and then are subjected to of disposal of the anode in the electrolyte will also have conventional separation techniques such as fractionation, a bearing on the flow rate. Thus, owing to the many dif. Solvent extraction, adsorption, and the like, for separation ferent types of carbon which can be employed and the of unconverted feed and reaction products. Unconverted almost infinite number of combinations of anode shapes, or insufficiently converted feed materials can be recycled dimensions, and methods of disposal of anode in the elec 50 to the cell for the production of more highly fluorinated trolyte, there are no really fixed numerical limits on the products, if desired. Perfluorinated products, or other flow rates which can be used in the practice of the inven products which have been too highly fluorinated, can be tion. Broadly speaking, the upper limit on the flow rate burned to recover hydrogen fluoride which can be re will be that at which "breakout' of feedstock and/or turned to the cell, if desired. By-product hydrogen can fluorinated product begins in a region other than within 55 be burned to provide heat energy or can be utilized in the top portion of the anode when operating with a to hydrogen-consuming processes such as hydrogenation, tally immersed anode as in FIG. 1 or along the im etc. mersed portion of the anode when the anode is provided It will be noted that in the process of the invention the with an internal collection zone as in FIG. 2 or the top reactant fluorinatable compound or substance is intro of the anode is above the surface of the electrolyte as in 60 duced into the pores of a porous anode and the fluorina FIG. 4. Herein and in the claims, unless otherwise speci tion of said reactant is carried out within said pores. fied, "breakout' is defined as the formation of bubbles of While it is not intended to limit the invention by any feedstock and/or fluorinated product on the outer im theory as to its reaction mechanism, it is presently be mersed surface of the anode with subsequent detachment lieved that fluorine-containing anion from the HF electro of said bubbles wherein they pass into the main body of lyte migrates into the pores of the porous anode where it the electrolyte. Broadly speaking, the lower limit of the discharges an electron and forms a free radical intermedi feed rate will be determined by the requirement to supply ate. It is believed this free radical adsorbs to the surface the minimum amount of feedstock sufficient to furnish of the anode pores forming a surface complex which is enough hydrogen values to prevent evolution of free 70 the actual fluorinating species capable of fluorinating said fluorine. As a practical guide to those skilled in the art reactant. We have established that free or elemental who desire to practice the invention, the flow rates can fluorine is not the fluorinating species. This is shown by be within the range of from 3 to 600, preferably 12 to the fact that in the normal operation of the process of the 240, cc. per minute per square centimeter of cross-sec invention no free or elemental fluorine can be detected tional area (taken perpendicular to the direction of flow). 75 in the cell or in the reaction products. 3,511,760 9 10 Such a system wherein the fluorination takes place short period of time, usually about 2 to 10 minutes, An within the pores of the anode differs markedly from the other way of overcoming polarization is to reverse the systems of the prior art wherein (a) the reactant to be current for a short period of time. fluorinated is dissolved or emulsified to some extent in In prior art processes utilizing hydrogen fluoride elec the electrolyte, or (b) said reactant is fed through a trolytes and which depend upon the solubility of the re porous or perforated sparger into the electrolyte. In such 5 actant feed material in the electrolyte, the maximum prior art systems fluorination occurs in the electrolyte and amount of current density which can be employed without the solubility of the reactant, usually very low or of only excessive anode corrosion and product degradation oc limited solubility at best, has a marked effect upon the curring is in the order of 20 milliamps per square centi reaction and limits the maximum rate of exhaustion or 10 meter of anode surface. In other prior art processes, utilization of the fluorinating species or complex and attempts have been made to overcome lack of solubility thus limits the amount of current density which can be of the feed in the electrolyte by employing a porous or employed in the process. This limit is not present in the perforated anode as a sparger to supply feed continu present invention because the reactant feedstock is con ously to the electrolyte. In these processes extensive tinually transported to the fluorinating species within the 5 amounts of cleavage products and other by-products are pores of the anode and solubility of the feedstock in the formed. In contrast, in the process of our invention the electrolyte is not a controlling factor. This makes possible preferred minimum current density is 50 milliamps per the utilization of much higher current densities with a square centimeter of anode surface. In our process, even resultant great increase in overall efficiency of the process. when employing these high current densities, essentially This increased efficiency is reflected in the unusually high 20 no cleavage products are produced, even when an un amounts of fluorinated product produced per kilowatt saturated feed such as ethylene is used. hour, the unusually high amount of fluorine introduced FIG. 1 is a view in cross section illustrating one form into said product (converted feedstock) per kilowatt of electrolysis cell which can be employed in the practice hour, and the unusually high amount of fluorine intro of the invention. duced into the product (converted feedstock) per square 25 FIG. 2 is a view in cross section illustrating one form centimeter of anode surface per hour, as illustrated by of anode assembly which can be employed in the prac the examples given hereinafter. Other outstanding advan tice of the invention. tages of our proccss include a markcd reduction in car FIG. 3 is a diagrammatic flow sheet illustrating various bon chain cleavage and corresponding reduction in the processing embodiments of the invention. amount of cleavage products, and a preponderance of the 30 FIG. 4 is a schematic illustration of another cell ar more valuable partially fluorinated products. rangement and anode assembly which can be employed Based on said examples, it is within the scope of the in the practice of the invention. invention to introduce into thc converted feedstock FIG. 5 is a schematic illustration of another cell ar (fluorinated product) an amount of fluorine within the rangement and anode assembly which can be employed in range of from 0.01 to 0.7 gram per square centimeter of the practice of the invention. anode geometric surface per hour, or more. When operat FIG. 6 is a view in cross section along the line 6-6 ing in accordance with the preferred conditions set forth of FIG.S. herein, the amount of fluorine which can be introduced Referring now to the drawings, the invention will be into said converted feedstock is within the range of from more fully explained. In FIG. 1, there is illustrated an 0.02 to 0.4 gram per square centimeter of anode geometric 40 electrolysis cell designated generally by the reference nu surface per hour. The above amounts of introduced fluo meral 10. Said cell comprises a generally cylindrical con rine which can be obtained by the process of the inven tainer 12 which is closed at the bottom and open at the tion are far greater than can be obtained by processes top. Said container can be fabricated from any suitable of the prior art. material which is resistant to the electrolyte employed Stated in terms of electrical power, it is within the therein. A removable top closure member 14 is adapted Scope of the invention to introduce into the converted to cooperatively engage the upper portion of said con feedstock (fluorinated product) an amount of fluorine tainer and close same. As here shown, said closure mem within the range of from 15 to 1000 grams per kilowatt ber comprises a rubber stopper which has been inserted hour, or more. When operating in accordance with the into the upper portion of the container. It will be preferred conditions set forth herein, the amount of 50 understood that any other suitable type of closure mem fluorine which can be introduced into said converted ber which engages the upper edges or upper portion of feedstock is within the range of from 30 to 590 grams the container, e.g., a threaded closure member can be per kilowatt hour. The above amounts of introduced employed. A first opening is centrally disposed in and fluorine which can be obtained by the process of the in extends through said closure member, as shown. While vention represent a much greater efficiency in use of elec 5 5 said opening is here shown as being centrally disposed trical power than is obtained by processes of the prior art. for convenience, it will be understood it is not essential An outstanding advantage of the process of the inven that said opening be centrally disposed. A first conduit tion is the comparative freedom of the process from 18, conveniently fabricated from stainless steel, mild polarization difficulties as compared to prior art processes steel, or other conductive material, extends through utilizing hydrogen fluoride electrolytes. This contributes 60 said first opening into the interior of said container 12. to and makes possible the above-described great increase A suitable insulation 20, such as Teflon tape, is dis in overall efficiency of the invention process. Polarization posed around the outer wall of said first conduit and is sometimes referred to as the anodic effect. When this between same and the wall of said first opening. An happens the ohmic resistance of the cell increases anode 16 comprising a cylinder of porous carbon, closed markedly. In severe cases the cell for all practical purposes 65 at one end thereof, is connected at the other end to the becomes nonconductive and inoperable. Polarization is end of said conduit 18 which extends into said con aggravated by more than trace amounts of water in the tainer. Preferably, the top and bottom surfaces of said hydrogen fluoride electrolyte. Breakout of the feedstock carbon cylinder are sealed with a suitable plastic or from the anode into the main body of the electrolyte, other resistant cement 22. In the cell illustrated in FIG. e.g., when the feedstock is passed through the pores of the 70 1, said anode 16 has an outside diameter of about one anode and bubbles into the electrolyte as in some prior art inch. The remainder of the elements of said cell are, in processes, increases polarization. When polarization does general, proportional in size. These dimensions are given 9ccur, infrequently, in the operation of our process, we by Way of example only and are not limiting on the in have found the cell can be restored to operation by vention. Any suitable type of porous carbon from among applying high voltage (about 80 volts) thereto for a 75 the Several grades commercially available can be em. 8,511,760 11 2 ployed for fabricating said anode. One presently pre with only one opening such as 32, 34, or 36 and to re ferred type of porous carbon is known commercially as move all of the cell effluents through said one opening. Stackpole 139 carbon. This carbon has a pore volume In the operation of the cell illustrated in FIG. 1, said of about 0.2 to about 0.3 cc. per gram with the pore cell is first charged with a suitable electrolyte such as diameters ranging from 0.1 to 10 microns. Another suit essentially anhydrous liquid hydrogen fluoride and po able porous carbon is that known commercially as Na: tassium fluoride in a mole ratio of KF•2HF. In the tional Carbon Grade 60 which has a pore volume of event said electrolyte contains traces of water, it is pre about 0.3 to about 0.5 cc. per gram with the pores rang ferred to first electrolyze the electrolyte by connecting ing from 10 to 60 microns in diameter. The actual values said first conduit 18 and said thermocouple well 30 to a of said pore volumes will depend upon the specific 0 suitable source of direct current and passing said cur method employed for determining same. Thus, preferred rent through the cell for a period of time sufficient to re- . porous carbons for fabricating anodes employed in the move essentially all of the water. A fluorinatable or practice of the invention include those having a pore ganic compound, e.g., a gaseous hydrocarbon, is then volume within the range of about 0.2 to about 0.5 cc. passed through conduit 18 into the interior of anode 16, per gram with the pores ranging from 0.1 to 60 microns 5 and then passed into the pores of said anode and into in diameter. contact with the fluorinating species therein. Fluorina As shown, a recess is provided in the bottom wall of tion occurs within the pores of said anode. As shown by said closure member 14 and surrounds said first open examples given hereinafter, the unreacted feedstock and ing in said bottom wall. A substantially cylindrical dia fluorinated products move upward through the connect phragm holder 28 is positioned with the upper end there 20 ing pores of the anode and exit from said anode adjacent of mounted in said recess and the lower end thereof ex the top thereof where the hydrostatic pressure of the tending downwardly around said first conduit 18. A electrolyte is least. The fluorinated products enter the substantially cylindrical diaphragm 26 is positioned with space above the electrolyte and are withdrawn from the its upper end mounted in said diaphragm holder 28 and anode compartment via the conduit inserted into opening its lower end extending downwardly around said anode 25 34. Hydrogen is withdrawn from the cathode compart 16. Said diaphragm can be fabricated from any suitable ment via opening 36. The effluents from the cell will ion permeable membrane or divider material. As here contain some HF, depending upon the temperature at shown, said diaphragm has been fabricated from an acid which the cell is operated, and this HF can be removed washed filter paper. Other diaphragm materials which from said effluents by scrubbing with a suitable scrubbing can be employed include grids or screens made of vari 30 agent such as Ascarite (sodium hydroxide supported on ous metals such as nickel or nickel alloys, etc. The use asbestos), or if recovery of the HF is desired the scrub of a diaphragm such as diaphragm 26 is not essential bing agent can be sodium fluoride or potassium fluoride. in the practice of the invention but is sometimes pre In many instances, said HF can be separated from the ferred in that said diaphragm divides the interior of the cell effluents by fractional distillation. Temperature con container into an anode compartment and a cathode 35 trol of the cell contents is maintained by placing the cell compartment. The division of said container into said in an oil bath provided with heat exchange means. compartments separates the anode products from the hy In the above description, the top of anode 16 has been drogen produced at the cathode and facilitates the re positioned below the electrolyte level in the cell. If de covery and separation of said anode products. While sired, the anode can be raised so that the top portion said diaphragm is shown as extending to the bottom of 40 thereof is above the electrolyte level, and fluorinated prod said container 12, it will be understood there is no con uct and any remaining unfluorinated feedstock are passed nection therebetween and liquid electrolyte is free to from within the pores of the anode directly into the space flow between said compartments. Also, while not shown, above the surface of the electrolyte within the cell. it will be understood that the bottom or bottom portion While the cell in FIG. 1 has been illustrated as being of said container can be provided with an outlet conduit. substantially cylindrical in shape, any other suitable con A second opening 34 is provided in and extends figuration can be employed. Also, it is within the scope of through said closure member 14 into communication the invention to employ any other suitable electrolysis with said anode - compartment. This opening provides cell incorporating the general features of the above-de means for withdrawing the anode products from the Scribed cell of FIG. 1. It is also within the scope of the cell. As shown, a conduit has been inserted into said invention to employ anodes having a configuration other opening. It will be understood that any suitable type 50 than cylindrical, e.g., rectangular or triangular, and a dis of conduit means for withdrawing said anode products position within the cell other than vertical, e.g., horizontal. can be employed. A tubular thermocouple well 30 ex tends through said closure member 14 into said cathode in Theconnection anode assemblywith Example of FIG. X. 2 is described hereinafter compartment. A substantially cylindrical cathode 24, 55 In the flow sheet of FIG. 3, an organic compound to be here shown to be fabricated from a metallic mesh or fluorinated is introduced via conduit 90 into electrochem screen, is disposed in said cathode compartment around ical fluorination cell 91. Said cell 91 can be of any suit said diaphragm 26 and is maintained in position by being able type, such as those described in connection with the attached to said thermocouple well 30 (as by silver other drawings. In said cell said organic compound is flu soldering). Said thermocouple well 30 thus also serves orinated as described herein and cell effluent comprising as the means for supporting and for connecting said 60 fluorinated products and unreacted feed material is with cathode to a suitable source of direct current. A third drawn from the cell via conduit 92 and passed into prod opening 36 extends through said closure member 14 lict separation zone 93. Said product separation zone 93 into communication with said cathode compartment. can comprise any suitable means for effecting the desired Said third opening provides conduit means for removing separation between the products and the unreacted feed hydrogen produced at the cathode from the cell. It will material, e.g., fractional distillation, solvent extraction, be understood that any suitable type of conduit means adsorption means, etc. As discussed herein, the fluorinated can be inserted into said opening 36. A fourth opening products can comprise monofluorinated products, other 32 extends through said closure member 14 into com partially fluorinated products, and perfluorinated products. munication with said cathode compartment and com 70 As used herein and in the claims, unless otherwise speci prises conduit means for introducing electrolyte into the fied, the term "perfluorinated” refers to a material where cell. It will be understood that any suitable type of con in all the potential fluorinatable valence bonds have been duit means can be inserted in said opening 32. It will also fluorinated, e.g., hexafluoroethane, C2Fs. Said perfluori be understood to be within the scope of the invention, as nated products can be withdrawn from separation means when no diaphragm is employed, to provide the cell 75 93 via conduit 96 as one product of the process. Mono 3,511,760 13 14 fluorinated products can be withdrawn via conduit 94 as a The cell pressure was essentially atmospheric. The cell ter product of the process, or if desired recycled via conduit 97 minal voltage was in the range of 6 to 8 volts. The feed to conduit 90 for further fluorination in said cell 91. Simi stock was introduced into the pores of the anode at rates larly, the other partially fluorinated products can be with such that the breakout of the unreacted feedstock and/or drawn via conduit 95 as products of the process, or recy fluorinated feedstock from within the pores of the anode cled to cell 91 via conduits 98 and 90. Or, if desired, said into the main body of the electrolyte was essentially con partially fluorinated products and said perfluorinated prod fined to the top portion of the anode immediately adjacent ucts can be passed via conduits 100 and 101, respectively, the top seal 22, i.e., within the upper 0.25 inch of the into conduit 99, and then into burner and hydrogen anode, or less. The cell effluent was analyzed by conven fluoride recovery means 102. In said burner 102 said par tional means such as gas-liquid chromatography and mass tially fluorinated and said perfluorinated products are 0 spectrography. Other operating conditions and the results burned to recover hydrogen fluoride which can then be of the runs in terms of type and quality of products ob passed via conduits 103 and 104 to cell 91. Said burner tained are given in Table I below.

TABLE I.-ELECTROCHEMICAL FLUORINATION OF ETHANE Run number 1. 2 3 4. 5 6 Current density, malem.------100 00 100 166 233 300 Ethane feed rate, liters/hr.-----...... 2,85 7.88 1.60 7.95 7.92 8.0 Ethane feed rate, ml/min/cm.2 of anode 1. 1.58 4.38 0.89 4,42 440 4. 44 Ethane feel rate, ml. Emin.lcm.8 of anode - 80.6 223.4 45.4 225. 4. 224.4 226.4 Ethane conversion, mole percent------23.0 9.9 29,7 15.8 18.1 22 Distribution of products, mole percent Ethylfluoride------64.1 74, 9 46, 9 67.6 55.6 45.9 1,1-difluoroethane-- 9.6 7.2 9.8 8.1 11.1 12.4 1,2-difluoroethane-- 11, 5 7.9 11.2 10.1. 13.8 4.7 1,1,1-trifluoroethane-- 0.9 0, 6 16 0.8 1.4 1.9 1,1,2-trifluoroethane-. 4.8 2.9 7.8 4.3 7.0 10, 8 1,1,2,2-tetrafluoroethane- -- 1.1 0.9 3.4 1.3 2.3 3. 1,1,1,2-tetrafluoroethane------0.8 0.6 2.0 0.9 1.5 1.9 Pentafluoroethane.------1.3 1, 2 4.1. 1.7 2.5 2.7 Hexafluoroethane- 3.9 9 0. 2.9 2.9 3,3 C fluorides--- - 1. 1.7 2.1 1.8 1.3 2.6 C1 fluorides--- - - 0.9 0.2 1.0 0.5 0.6 0.7 Current efficiency tofluorinated products, 100, 0 100, 0 100,0 000 00, 0 100,0 percent------87. 90 87 94 90 94 G of fluorine introduced into prod cS: Per cm3 of anode 1 per hour------0.031 0.032 0.031 0.055 0.075 0.10 Perkwh.------45, 6 48.3 48.0 47.8 43.4 42.3 Gram moles products/kwh.------1.43 1.73 1.10 1.62 1.25 10 Geometric surface area. 2 Cross-sectional area.

and HF recovery means can comprise any suitable burner The data in the above Table I show that a normally for burning said fluorinated products, and any suitable gaseous hydrocarbon such as ethane can be readily flu means for recovering HF from the resulting combustion orinated in vapor phase and converted to fluorinated prod gases. Make-up hydrogen fluoride, together with any suit ucts with a high current efficiency. It should also be able conductivity additive, can be introduced into said cell 5) noted that upwards of 85 to 90 percent of the products in 91 via conduit 104. Although not shown in the drawing, each of the runs were partially fluorinated products. The it will be understood that unreacted feed materials can be production of significant amounts of 1,2-difluoroethane, a withdrawn from said product separation zone 93 and re product difficult to prepare by any other known process, is cycled to cell 91 for fluorination. noteworthy. Said, 1,2-difluoroethane is a valuable charge FIG. 4 is described hereinafter in connection with Ex 55 stock for the production of vinyl fluoride by dehydrohalo ample XI. FIGS. 5 and 6 are discussed hereinafter in con genation, or the production of 1,2-difluoroethylene by de nection with Example XII. hydrogenation. Attention is also invited to the exception The following examples will serve to further illustrate ally high yields of ethyl fluoride. Said ethyl fluoride is a the invention. good charge stock for the production of 1,2- and 1,1-di EXAMPLE I 60 fluoroethane, either by recycle or by charging to an addi A series of runs was carried out for the electrochemical tional fluorination cell. Attention is also invited to the fluorination of ethane. The fluorination was carried out in small amounts of cleavage products, e.g., C fluorides, a cell essentially like that illustrated in FIG. 1. The porous even at the high conversions of feedstock. anode was formed of the above-described Stackpole 139 65 porous carbon, had a side wall thickness of 0.635 cen EXAMPLE II timeter, and had an outside vertical surface area of 30 Square centimeters. The bottom and top surfaces were Another series of runs was made in which ethylene was coated with a resistant cement to restrict the cxposed electrochemically fluorinated. These runs were carried geometric surface to the vertical portion only. The cath 70 out in essentially the same manner, in essentially the ode was formed of a nickel screen (8 mesh). The electro same apparatus, and using the same type of electrolyte lyte employed was essentially anhydrous liquid hydrogen as employed in Example I. The runs were carried out at fluoride containing potassium fluoride as conductivity ad Substantially atmospheric pressure, a temperature in the ditive in the molar ratio of KF•2HF. Said runs were car range of 70 to 90° C., and cmploying a cell terminal ried out at a temperature within the range of 72 to 95° C. 75 voltage of 7 to 9 volts. Other operating conditions and 3,511,760 15 16 the results of the runs in terms of type and quantity of Again, it should be noted that the products obtained are products obtained are set forth in Table II below. predominantly partially fluorinated products. TABLE II.-ELECTROCHEMICAL FLUORINATION OF ETHYLENE Run number 1. 2 3 4. 5 Current density malem.------100 100 86 36 100 Ethylene feed rate litersfhr------4.13 8.39 2,06 7.01 2.1 Ethylene feed rate ml/min.icm2 of anode ------2,29 4.66 4 3.89 117 Ethylene feed rate ml.fmin.cm, of anode ------a------116.8 237.7 58,1 198, 4 59. Ethylene conversion mole perc 12, 5 7.5 34.5 12.9 22, 6 Cell effluent rate moles/hr- 0, 176 0.369 0.082 0.308 0,0897 Distribution of products mol Vinyl fiuoride------6.5 10, 2 4,7 0.5 6. Ethyl fuoride--- - 2,3 3, 6 6 3.3 2, 1 ill-difluoroethane. 0.5 0. 0, 6 0,7 0.8 1,2-difluoroethane.------22.5 26.6 20.7 19.9 22.6 1,1,2-trifluoroethane.----- 19.5 18, 2 17.0 7.4 17. 1,12,2-tetrafluoroethane-- 0.6 8, 6 9,8 9, 9.5 1,1,1,2-tetrafluoroethale-- 4.9 3.8 4.3 4, 6 3.9 Pentafluoroethane.------1.7 7.7 3.0 10.9 10. Hexafluoroethane. - 8. 6.0 18. 13.0 4.8 C4 fluorides.--. - 1. 3,9 9.8 0.3 12, 9 C1 fluorides------1.1 0. 0.4 0.3 0. Current efficiency to fluorinated prod 000 100.0 - 100.0 00.0 100,0 lucts percent------95 99.6 8) 100 89 G of fluorine introduced into prod - CS Per CIn of anode 1 per hour...----. 0.048. 0,051 0,065 0.082 0.043 Perkwh------... . 63.2 68.0 46.4 59,3 50.0 Gram moles of products/kwh....------... O 1.23 0.674 0.957 0,786 Geometric surface area. Cross-sectional area. The data in the above Table II show that an unsatu- EXAMPLE IV rated hydrocarbon such as ethylene can be converted to 30 Another series of runs was carried out in which iso fluorinated products in the electrochemical fluorination butane was electrochemically fluorinated in accordance process of the invention with a high current efficiency. with the process of the invention. These runs were car Upwards of 70 percent of the products obtained are ried out in essentially the same manner, in essentially the partially fluorinated products. The exceptionally high same apparatus, and employing the same type of electro yield of 1,2-difluoroethane, in the order of twice as much 35 lyte as in Example I. Said runs were made at substan as obtained from ethane in Example I, should be noted. tially atmospheric pressure, a cell temperature of 70 to The low yield of ethyl fluoride, as compared with the 90° C., and a cell terminal voltage of about 6.8 volts. results obtained in Example I, should also be noted. The The results of said runs in terms of the type and quantity small amounts of cleavage products, e.g., C. fluorides, of products obtained are shown in Table IV below. even at the high conversions of feedstock should also be 40 TABLE IV.-ELECTROCHEMICAL FLUORINATION OF noted. ISOBUTANE EXAMPLE II Runnumber

Anothnote Seriesies O.of runs Was carrieds out in whiwhich meth- 45 Current density, malem.------66 002 1003 ane was electrochemically fluorinated in accordance with EEE E. rate, E. - - - - - a dea 5.3 5.26 4.14 Sobutane feed rate, ml/min.lcm. anode 2 2.85 2.92 2,30 inthe essentially process of the the same invention. manner, These employing runs were essentially carried outthe ESSEESEE:RS:spbutane Conyersion, percent.------, 7 , 8, 2 is9,8 same apparatus, and employingk the same type of electro- Distribution2-fluoromethylpropane.--- of products, area percent:1 8.4 7.5 7.4 lyte as inO the runs of Example I. Said runs were carriedd 50 1-fluoromethylpropane.---difluoromethylpropane 65.75.8 59,77 57.67.4 out at substantially atmospheric pressure, a temperature SEE i; 1.3 i of from 74 to 76.O C., and a cell terminal voltage of trifluoromethylpropane-loronethylpropane .3 2.3o 2.79. about 6.8 volts. The results of said runs in terms of the 100.0 100.0 100.0 type and quantity of products obtained, together with See footnote on Table III. other operating conditions, are set forth in Table III 55 Geometric surface area, i. below. Cross-sectional area. TABLE III.-ELECTROCHEMICAL FLUORINATION OF METHANE Ruin number 2 3. 4. 5 Current density, malem.------. 00 167 100 167 Methane conversion, percent- 25.78 34.58 12.36 9.35 23.2 Methane feed rate, liters/hr.------. 4.3 4.35 8.79 8,74 8.7 Methane food rate, milmin.fcin.2 of anode------2.39 2.4 4.88 4.86 4.84 . Methane feed rate, ml/min.icm.2 of Distributionanode ------of products, area percent: 21,9. 122.9 248.9 247.9 246.8

CFH3- 66.28 5.59 68,20 6,78 53,22 6,07 2334 14, 19. 8,03 22,25 6, 6 2.12 6,71 8.77 . .2.80 1.04 12.9 0.89 1.43 1,73 00.00 99.99 99.99 i00, 01 - 100.00 fluoride.1 The cellefluent contained trace amounts of Nethane (or CO2), vinylfluoride, and ethyl 3 The area percent values represent the relationship of the area of the individual peaks for each individual product to the total area under the chromatogram obtained when the cell effluent was analyzed by gas-liquid chromatography. Such values have been found to usually correlate well proportionally with actual weight percent values. 3 Geometric surface area. Cross-sectional area. 3,511,760 17 18 The data in the above table show that a branched chain organic compound such as isobutane can be readily and TABLE VI conveniently fluorinated in the process of the invention. Electrochemical fluorination of 1,1,2-trifluoroethane Again, it should also be noted that the products obtained Current density, ma/cm.” ------100 are predominantly partially fluorinated products. Atten 5 1,1,2-trifluoroethane feed rate, liters/hr. ------3.36 tion is also invited to the large yield of 1-fluoromethyl 1,1,2-trifluoroethane feed rate, ml/min./cm. propane which was obtained. anode' ------1.87 EXAMPLE V 1,1,2-trifluoroethane feed rate, ml/min./cm. Another series of runs was carried out in which dichlo anode ------'s new - - pam - v new 95.4 romethane (methylene chloride) and trichloromethane 10 1,1,2-trifluoroethane conversion, mole percent --- 23.5 (chloroform) were fluorinated in accordance with the Distribution of products, mole percent: invention. These runs were carried out in essentially the same manner, in essentially the same apparatus, and em 1,1,2,2-tetrafluoroethane ------48.1 ploying the same type of electrolyte as used in Example I. 1,1,1,2-tetrafluoroethane ------21.2 Said runs were carried out at substantially atmospheric 5 Pentafluoroethane ------16.1 pressure, a cell temperaturer of 70 to 90° C., and a cell Hexafluoroethane ------13.1 terminal voltage of about 6.8 volts. The results of said C4 fluorides ------1.1 runs in terms of the type and quantity of products ob C1 fluorides ------0.4 tained are shown in Table V below. 20 100.0

TABLE WELECTROCEIEMICAL FLUORINATION OF COROFORMAND METEYLENE CHLORIDE Methylene Chloroform chloride Run number 1 2 3 42 52 Current density, malem.------66 133 66 Feed rate, litershir------1.75 1.75 1.9 100 100 Feed rate, milmin.icm. anodo 3- 0.97 0,97 1,06 45.7 2.5 Feed rate, ml/min.icm. anode 5 49.5 49.5 54.1 3.17 1.39 Conversion, percent------31 84 29 1617 70.9 Distribution of products, mole percent: 5 33 CCl3F------95.4 71.2 97.0 20.5 22.6 1.0 2.0 Trace 24.5 20, 2 ... 3 17.3 1.5 34.5 37,0 Trace 6.8 Trace 20.5 20.2 Trace 0.4 Trace Trace Trace 2.3 2.3 .5 . Trace Trace Current efficiency to fluorinated 100,0 100.0 100.0 00,0 100,0 products, percent------63 99.9 ------Gramsproducts: of fluorine introduced into Per cm2 of anode 3 per hour. 0.05 0.054 ...

PorkWh.------33. 59, 5 - Gram moles of products per kwh 76 2.43

-- efficiencyElectrolyte to fuorinated contained products. a few percent of water and CO2 was produced. This reduced the 2 Product analyses in these runs reported in area percent. See footnote 2 in Table III. 8 Approximate.Geometric surface area. Cross-sectional area.

The results set forth in the above Table V show that Additional fluorine introduced into products: the electrochemical process of the invention utilizing Grams per cm. of anode per hour ------0.031 chloroform (CCl3H) as the feedstock is capable of pro Grams per kwh. ------51.7 ducing trichlorofluoromethane, known commercially as 55 Gram moles of product per kwh. ------1.96 Freon 11, with a very high degree of selectivity. These Geometric surface area. results were surprising and unexpected in view of the Cross-sectional area. results obtained with the adjacent homologous material, methylene chloride (CCl2.H.). Utilizing methylene chlo The data given in the above Table VI also demonstrate ride as a feed resulted in a mixture of products, similarly that partially fluorinated organic compounds can be fur as is obtained with other feedstocks. 60 ther fluorinated in accordance with the invention. The In many instances, the trichlorofluoromethane product small amount of cleavage products, e.g., C fluorides, obtained in Runs 1 and 3 could be utilized without fur should be noted. ther purification. EXAMPLE VII EXAMPLE VI 65 Another run was carried out in which an even more In a qualitative run it was found that dimethyl ether highly fluorinated material, 1,1,2-trifluoroethane, was could be readily and conveniently fluorinated in accord fluorinated in accordance with the invention. This run ance with the invention. This run was carried out in es was carried out in essentially the same manner, using the sentially the same apparatus, in essentially the same same type of electrolyte as in Example I, a cell pressure 70 manner, and using the same electrolyte as in Example I. of essentially atmospheric, a cell temperature of from 70 Operating conditions were: feed rate, 5.7 liters per hour; to 90 C., and a cell terminal voltage of about 6.0 volts. temperature, 77° C.; cell pressure, substantially atmos The cell employed was essentially the same as in Example pheric; terminal voltage, 7; and current density, 100 milli I. The results of the run in terms of the type and quantity amps per square centimeter. No quantitative product data of products obtained are set forth in Table VI below. 75 were obtained in this run. However, gas-liquid chroma 3,511,760 19 20 tography analysis of the cell effluent showed the presence lector 48. Anode inner vent 56 extends from the upper in of the following products: ner surface of anode 40 and into communication with CHFOCH---- Monofluoromethylmethyl ether. said annular space 54. Said inner vent 56 provides a col CHFOCH---- Difluoromethylmethyl ether. lection zone for unreacted feedstock and fluorinated prod CHFOCH2F--. Bis-monofluoromethyl ether. 5 ucts exiting from the pores of the anode. Exit vent 58, in CHFOCHF-l. Monofluoromethyldifluoromethyl ether. communication with said annular space 54 and said inner . CFOCH3-----. Trifluoromethylmethyl ether. vent 56, is provided in the upper portion of said anode CFOCHF---- Trifluoromethylmonofluoromethyl ether. support and current collector 48 for withdrawing fluori CHFOCHF--. Bis-difluoromethyl ether. nated feedstock as anode products. Said anode products CFOCHF---- Trifluoromethylidifluoromethyl ether. 0. can thus be collected separately from the cathode prod CFOCFa-...--. Bis-trifluoromethyl ether. ucts if so desired. Cap 60 is provided for closing said exit vent as indicated by the dotted ines. EXAMPLE VIII In one series of runs the porous carbon anode 40 was In another qualitative run it was found that cyclopro made of National Carbon Company Grade 45 carbon pane could be readily and conveniently fluorinated in ac 15 (NC-45) having a pore volume of about 0.5 cc. per cordance with the invention. This run was carried out in gram with pore diameters ranging from 10 to 100 mi essentially the same apparatus, in essentially the same crons. The average pore diameter was about 58 microns. manner, and using essentially the same electrolyte as in The anode assembly was postiioned in a hydrogen fluo Example I. Operating conditions were: feed rate, 11.3 ride electrolyte, essentially like that described in the other liters per hour; temperature, 75° C.; cell pressure, sub 20 examples, and immersed to the point indicated by the stantially atmospheric; terminal voltage, 6.3 volts; and electrolyte level line in FIG. 2. With cap 60 in place, current density, 167 milliamps per square centimeter of ethylene feed was started flowing into the anode through anode geometric surface. No quantitative product data feed tube 42 at a rate of 10 liters per hour. The only place were obtained in this run. However, gas-liquid chroma bubbles formed was in the top portion of the anode im tography analysis of the cell effluent showed the presence mediately adjacent seal 50, i.e., within the upper 0.25 of the following products: monofluorocyclopropane inch of the anode. This demonstrates that the ethylene (major product); 1,3-difluoropropane; 1,2,3-trifluoropro had entered the pores of the carbon anode near the bot pane; 1,2-difluorocyclopropane; and minor amounts of tom thereof and had flowed vertically through the inner others. connecting pores of the anode without escaping there EXAMPLE X 30 from except at the top as described. The flow rate of ethylene was gradually increased to 60 liters per hour. At In another qualitative run it was found that ethyl chlo 60 liters per hour there was some breakout of feed at ride could be readily and conveniently fluorinated in ac points lower than the upper 0.25 inch of the anode but cordance with the invention. This run was carried out in still well within the upper portion of the anode. When essentially the same apparatus, in essentially the same 35 the increased flow rate had reached 90 liters per hour, manner, and using essentially the same electrolyte as in some bubble formation (breakout) was noted toward Example I. Operating conditions were: feed rate, 6.3 the bottom portion of the anode. However, it was ob liters per hour; cell temperature, 76° C.; cell pressure, served that substantially all of the ethylene continued substantially atmospheric; terminal voltage, 7.6 volts; and to flow up through the anode and exit therefrom in the current density, 100 milliamps per square centimeter of 40 top portion of the anode. When cap 60 was removed anode geometric surface. No quantitative product data there was no breakout from the surface of the anode, were obtained in this run. However, gas-liquid chroma even at the 90 liter per hour flow rate. tography analysis of the cell effluent showed the presence In another series of runs the porous carbon anode was of the following products: 1-chloro-2-fluoroethane; 1 fabricated from the above-described Stackpole 139 car chloro-1-fluoroethane; 1 - chloro-2,2-difluoroethane; 1 bon having a pore volume of about 0.2 to 0.3 cc. per chloro-1,2-difluoroethane; and others. gram with the pore diameters ranging from 0.1 to 10 microns. These runs were made with cap 60 removed. EXAMPLE X Flow of ethylene was started at 2 liters per hour. No Two series of runs were carried out to demonstrate bubble formation outside the upper 0.25 inch portion of entry of the feedstock into the pores of a porous anode 50 the anode was observed until the flow rate had reached and the flow of said feedstock within said pores in accord 40 liters per hour. This run shows that the less permeable ance with the method of the invention. Stackpole 139 carbon will not permit as high a flow rate In these runs an anode assembly essentially like that il of gas through its pores as will the more permeable lustrated in FIG. 2 was employed. Said anode assembly NC-45 carbon. was employed in a cell arrangement substantially like Another series of runs was made using the Stackpole that illustrated in FIG. 1 except that the cell container 139 carbon anode with the cap 60 in place closing exit was provided with a window for observation of the an 58. At flow rates of 2 liters per hour essentially all of ode. Said anode assembly comprised a porous carbon the breakout or bubble formation on the outer surface cylinder 40 having a side wall thickness of about 0.635 of the anode was within the upper 0.25 inch of the anode. centimeter and an outside vertical surface area of 30 60 At flow rates of 10 liters per hour there was some break square centimeters. The carbon cylinder had an outside out (bubble formation) outside the upper 0.25 inch por diameter of 1 inch and a height of 1.5 inches. A feed tion of the anode, but substantially all of the breakout tube 42 extended through a metal plug 44 attached to was still in the upper 0.25 inch portion of the anode. At the end of said feed tube 42. Said metal plug 44 was flow rates of 40 liters per hour the proportion of break sized to have a press fit with the lower inner circumfer 65 out outside the upper 0.25 inch portion of the anode in ence of said carbon cylinder, as illustrated. In assembly creased, but the major portion of the gas was still exit of the anode, said feed tube and metal plug are first in ing from the upper portion of the anode. These runs show serted into the carbon cylinder. Said carbon cylinder is that even with the less permeable Stackpole 139 carbon, then threaded onto the reduced diameter portion 46 of the feed enters the anode near the bottom and flows up the anode support and current collector 48, by means of 70 through the connecting pores and escapes from the upper the threads shown. The upper end of the carbon cylinder portion of the anode. fits against gasket or seal material 50. A Teflon tape seal material 52 coats the lower portion of said metal current EXAMPLE X collector 48. An annular space 54 is provided around said Another series of runs was carried out for the electro feed tube 42 within said anode support and current col 75 chemical fluorination of ethane. The fluorination was 8,511,760 21 22 carried out employing an anode assembly and cell ar Comparing the above Runs 1 and 2 in Table VII rangement essentially like that shown schematically in shows that said runs are an excellent check upon each FIG. 4. The porous anode 60 was formed of the above other, clearly within the limits of experimental error. described Stackpole 139 porous carbon, had a side wall In both runs fluorination of the ethane took place within thickness of 0.635 centimeter, and had an outside vertical the pores of the anode. Run 1 from Table I has been surface area of 30 square centimeters. The bottom sur included in the above Table VII for comparison purposes. face was coated with a resistant cement to restrict the Comparing said Run 1-Table I with Run 2 shows that exposed geometric surface to the vertical nortion only. results of the two runs agree within the limits of experi The cathode 61 was formed of a cylinder of 20 x 20 mental error, thus showing that in said Run 1-Table I mesh mild steel screen. The electrolyte employed was fluorination also took place within the pores of the car essentially anhydrous liquid hydrogen fluoride containing bon anode. potassium fluoride as conductivity additive in the molar EXAMPLE XII ratio of KF•2HF. Said runs were carried out at a tem In these runs, a horizontal anode 72 as shown sche perature within the range of 82 to 84 C. The cell pres matically in FIGS. 5 and 6 was employed. This anode sure was essentially atmospheric. The cell terminal volt 5 was 3 inches in length, had a triangular cross section, each age was in the range of 6.3 to 6.4 volts. The porous side surface was 1% inches wide, and two surfaces and anode assembly comprised the porous carbon cylinder the ends and part of the third side were insulated with a re 60 which was threaded onto the lower portion of anode sistant cement 74. This left 30 cm. of uninsulated surface support and current collector 62 by means of the threads on the anode. This uninsulated surface was turned upward shown. Passageway 64 provided means for introduction 20 in the electrolyte bath to face an iron wire gauze cathode of the feedstock to the small space 66 provided at the suspended above it about 1% cm. as shown in FIGS. 5 bottom of the anode. The top of carbon cylinder 60 was and 6. The electrolyte was the KF•2HF fused salt. In the sealed by means of gasket 68. Plastic tape 63 (Teflon) run the following operating parameters were held con was provided to protect the anode support 62. stant: (1) current level: 6 amperes (current density, 200 In Run No. 1 said anode assembly was placed in the 25 ma./cm2); (2) nominal space velocity: 0.58 hr. (com electrolyte with a small portion 70 (about A6 to /8 puted on the basis of no penetration of electrolyte in inch) of the anode exposed above the level of the elec pores of carbon); (3) cell temperature: 93-95 C.; (4) trolyte as shown in the drawing. The ethane feedstock feed: 1,2-dichloroethane; (5) feed rate: 0.22 g-moles/ was introduced into the bottom of the anode via feed hr.; and (6) anode material: NC-60 porous carbon. The passageway 64. It then passed vertically within the inner 30 only variable in these runs was depth of the anode sur connecting pores of the carbon anode and the fluorinated face below the surface of the electrolyte. This was achieved products escaped therefrom into the vapor space in the by moving the cathode-anode assembly up and down in cell above the electrolyte without bubbling through or the electrolyte bath. The feed inlet and products outlet passing out the confines of the anode below the electro were each connected to conduits (not shown) which ex lyte level. The absence of bubble formation of breakout 35 tended outside the cell. By this arrangement the feedstock of feed from the surface of the anode below the level of was introduced into the pores of the anode and removed the electrolyte was confirmed by visual observations. The therefrom without contacting the main body of the elec cell operated smoothly at a current density of 100 trolyte. Results obtained in these runs are summarized in ma./cm. under these conditions. Table VIII below. In Run No. 2 the cell arrangement was the same ex 40 cept that the anode assembly was lowered into the electro TABLE WIE lyte until the entire carbon anode was immersed in the Depth of immersion electrolyte and the level of the electrolyte was at Products (mole point A shown in the drawing. This arrangement caused percent) 9 6 6 6 2 C2Cl2F4--. 32.7 25.2 24, 9 25.6 27.7 the fluorinated products to bubble out into the electro CCEIF3. 16, 4 16.6 16.8 16,8 16.6 ... lyte within about the upper 0.25 inch portion of the 45 C2Cl2.H2F2- 17.3 20.4 20, 2 9.5 19.4 C2Cl23F 23, 1 25.3 25.5 24.7 24.2 anode as in the above-described Examples I-X. This By-products. - - 0.5 12, 5 2, 6 3.4 12. ... bubble formation or breakout within the upper 0.25 inch onversion.------14.5 4.9 15.4 15.3 15. portion of the anode was observed visually. The cell operated smoothly at 100 ma/cm. under these condi tions. 50 The by-products were essentially all trichloroethanes Other operating conditions and the results of said runs and monochloroethanes. Cleavage products and dimers in terms of type and quantity of products obtained are and higher condensed products totaled less than 2% of given in Table VII below. the products in each run. In all runs the number of moles TABLE VII.-ELECTRoCHEMICAL FLUORINATION of effluent recovered was the same as the number of moles OF ETHANE 5 5 of 1,2-dichloroethane feedstock (within experimental er Composition, mole percent ror). This shows that all the feedstock and all the fluori Run 1, nated products must have remained within the pores of - - Run 1 Run 2 Table the anode during the reaction and were withdrawn through Current density, ma?cm.------100 100 100 the products outlet shown in FIG. 6. Ethane feed rate, liters/hr. 3, 1 3. 2.85 60 Ethane feed rate, ml/minform.2 (geometric These results demonstrate that a horizontal electrode area)------1,72 72 1.58 can be employed under the conditions of the invention Ethane feed rate, ml/min.fcm,2 (cross With respect to maintaining the fluorination reaction Sectional area)------87.7 87.7 80.6 within the porous structure of the carbon anode. Compound:Conversion, percent------7. 9 17.6 23 Ethyl fluoride.---- 65.9 64.3 64. EXAMPLE XIII 1,1-difluoroethane-- 6.8 7.2 9.6 1.2-difluoroethane 7. 9 8.0 1.5 A series of runs was carried out for the electrochemical 1,1,1-trifluoroethane. 0.8 0, 8 0.9 1,1,2-trifluoroethane------5.5 5.9 4.8 fluorination of 1,1-difluoroethane. The fluorination was 1,1,2,2-tetrafluoroethane.------2.1 2, 1 l. 1 carried out employing an anode assembly and cell ar 1,1,1,2-tetrafluoroethane- 1.7 7 0.8 Pentafluoroethane- 2.3 2.5 1.3 rangement essentially like that shown schematically in Hexafluoroethane- 4.9 5.2 3.9 70 FIG. 4, and described above in connection with Example C fluorides------.9 2.0 1.1 C1 fluorides.-- - 0. 0.2 0.9 XI, except that porous anode 60 was formed of the above Vinyl fluoride------0. 0. ------described National Carbon Company Grade 60 (NC-60) 100.0 100.0 100.0 porous carbon. The runs were carried out at a temperature Current efficiency, percent------77 77 8 within the range of 82 to 84 C. The cell pressure was es Sentially atmospheric. The cell terminal voltage was 7.0 3,511,760 23 24 volts. Run No. 1 and Run No. 2 were each carried out in closure. Such modifications are within the spirit and Scope the manner described in Example XI. of the invention. In Run No. 1, the absence of bubble formation or We claim: breakout of feed from the surface of the anode below 1. A process for the electrochemical fluorination of a the level of the electrolyte was confirmed by visual ob fluorinatable organic compound feedstock, which process servation. The cell operated smoothly at a current density comprises: passing an electric current through a current of 200 ma./cm. under these conditions. conducting essentially anhydrous liquid hydrogen fluoride In Run No. 2, as in Run No. 2 in Example XI, the electrolyte contained in an electrolysis cell provided with bubble formation or breakout into the electrolyte oc a cathode and a porous anode; passing said feedstock curred within about the upper 0.25 inch portion of the O into the pores of said anode at a flow rate sufficient to anode. This was observed visually. The cell operated establish a pressure balance within said pores between the smoothly at 200 ma./cm. under these conditions. feedstock entering said pores from one direction and elec Other operating conditions and the results of said runs trolyte attempting to enter said pores from another and in terms of type and quantity obtained are given in Table opposing direction and, within said pores, at least par IX below. 15 tially fluorinating at least a portion of said feedstock; TABLE IX.-ELECTROCII EMICAL FLUORINATION OF passing fluorinated product and any remaining unfluori - 1,1-DFLUOROETHANE nated feedstock from within the pores of said anode; and Composition, mole recovering fluorinated product from an effluent stream percent from said cell. 20 2. A process according to claim 1 wherein said pressure Run Run 2 balance is such as to permit up to about 50 percent of the Current density, malem.------200 200 1,1-difluoroethane feed rate, litersihr.------6. 6. pores of said anode to be invaded by electrolyte. 1,1-difluoroethane feed rate, ml/min.icm.9 geo 3. A process according to claim 1 wherein said flow metric area of anode------3,39 3,39 ll-difluoroethale feed rate, milmillem, cross rate of said feedstock is sufficient to supply the minimum sectional area of allode.--...- 72 12 25 amount of feedstock sufficient to furnish enough hydro Civisit, talk it's it.----- ti. 2.5 listribution of lyroducts, mole increat; gen values to prevent evolution of free fluorine but in 1,1,1-trifluoroellalic------23.2 24, () sullicient to cause breakout of said feedstock and/or fluo 1,2-trifluoroll ...... 42.) 1.5 1,1,2,2-tetritiu'out-liii). i.) ...), rinated feedstock from within said porcs into said clec 1,12-tetrafluoro(that 10, 3,8 pollifluoroethal)--- . 9.7 trolyte from a region other than within the top portion of hixafluoroethano.... 1.2 ... 1 30 said anode. C; it turkls------Tiructs Trace 4. A process according to claim 1 whercin: said anode C fluorides------'00 Trace Current officiellcy to fluorinated producis.-----. 95.5 9. is porous carbon; and said feedstock is passed into the pores of said anode at a rate within the range of from 0.5 to 10 milliiiters per minute per square centimeter of Comparing the above Runs 1 and 2 in Table IX shows anode geometric surface area. that said runs arc good chccks upon cach othcr, clearly 5. A process according to claim 4 wherein said anode within the limits of experimental error. The data show has a pore volume within the range of from about 0.2 that in both runs fluorination of the 1,1-difluoroethane to about 0.5 cc. per gram with the pores ranging from took place within the pores of the anode. 0.1 to 60 microns in diameter. As additional examples further illustrating the inven 40 6. A process according to claim 1 wherein said anode tion, when an ester such as ethyl acetate is fluorinated in is porous carbon; and said feedstock is passed into the accordance with the invention, the products which are ob pores of said anode, and therein into contact with a tained include ethyl monofluoroacetate, ethyl diffuoro fluorinating species produced by said electrolysis, at a acetate; ethyltrifluoroacetate; and 1 - fluoroethylimono flow rate such that the inlet pressure of said feedstock fluoroacetate. When the feedstock is a mercaptain such as into said pores is less than the sum of (a) the hydrostatic ethyl mercaptain, the products which are obtained include pressure of said electrolyte at the level of entry of said . 2-fluoroethyl mercaptan; 2,2-difluoroethyl mercaptan; and feedstock into said pores and (b) the exit pressure of 2,2,2-trifluoroethyl mercaptan. When a feedstock such as any unreacted feedstock and fluorinated products from n-propanol is fluorinated in accordance with the invention, said pores into said electrolyte. the products obtained include 2-fluoropropanol; 2,3-di 50 7. A process according to claim 6 wherein said flow fluoropropanol; and 3,3,3-trifluoropropanol. When an aro rate is within the range of from 3 to 600 milliliters per matic compound such as toluene is fluorinated in accord minute per square centimeter of anode cross-sectional ance with the invention, the products obtained include area, benzyl fluoride; benzylidene fluoride; benzylidyne fluoride; 8. A process according to claim 7 wherein the residence 4-fluorotoluene; 2,4-difluorotoluene; and 1-fluoromethyl-3- 55 fluorobenzene. When a nitrile such as acetonitrile is fluori time of said feedstock and reaction products obtained nated the products include 1,1,1-trifluoroethane; 1,1,1,2- therefrom within the pores of said anode is within the tetrafluoroethane; 1,1,1,2,2 - pentafluoroethane; and tri range of from 0.2 to 2 minutes. fluoroacetonitrile. When the fecdstock is nitromethane, the 9. A process according to claim 7 wherein the pores products include: methane; carbon monoxide; nitrogen; 60 of said anode have a permeability within the range of carbon tetrafluoride; carbon dioxide; methyl fluoride; from 0.5 to 75 darcys and an average pore diameter with methylene fluoride; and fluoroform. in the range of from about 20 to about 75 microns. Herein and in the claims, unless otherwise specified, 10. A process according to claim 1 wherein said pres for convenience the volumetric feed rates have been ex sure balance is such that essentially no unreacted feed pressed in terms of gaseous volume calculated at standard 65 stock and/or fluorinated product leaves said pores to form conditions, even though the feedstock may be introduced bubbles which escape from said anode into said electro into the anode in liquid state. lyte. Porous anodes which can be employed in the practice 11. A process according to claim 10 wherein said flow of this invention are disclosed and claimed in copending rate is within the range of from 3 to 600 milliliters per application Ser. No. 680,123, filed of even date herewith, 70 minute per Square centimeter of anode cross-sectional in the name of W. V. Childs. aca While certain embodiments of the invention have been 12. A process according to claim 10 wherein said described for illustrative purposes, the invention obviously porous anode is porous carbon having a permeability is not limited thereto. Various other modifications will be within the range of from 0.5 to 75 darcys and an average apparent to those skilled in the art in view of this dis- 75 pore diameter within the range of from 1 to 150 microns. 3,511,760 25 26 13. A process according to claim 12 wherein said stock are passed from within said pores of said anode porous carbon anode has a permeability within the range directly into a collection zone which is at least partially of from about 2 to about 30 darcys and an average pore within the confines of said anode. diameter within the range of from about 20 to about 75 19. A process according to claim 12 wherein said microns. effluent stream from said cell comprises nonfluorinated 14. A process according to claim 12 wherein: said feedstock and partially fluorinated feedstock, said effluent feedstock is selected from the group consisting of par stream is passed to a product separation Zone, non tially halogenated organic compounds containing from fluorinated feedstock is withdrawn from said separation 1 to 6 carbon atoms per molecule, alkanes containing zone and at least a portion thereof is recycled to said cell from 1 to 6 carbon atoms per molecule, and alkenes con as feedstock, and said partially fluorinated feedstock is taining from 1 to 6 carbon atoms per molecule; said 0. withdrawn from said separation zone as product of the electrolyte contains a conductivity additive selected from process. w the group consisting of ammonium fluoride and the alkali 20. A process according to claim 12 wherein said metal fluorides, said additive being present in a molar effluent stream from said cell comprises nonfluorinated ratio of additive to hydrogen fluoride within the range of 5 feedstock, partially fluorinated feedstock, and perfluo from 1:4.5 to i:1; and said electric current is passed rinated feedstock; said cell effluent is passed to a product through said cell at a cell voltage within the range of separation zone; at least a portion of said partially from 4 to 20 volts and in an amount which is sufficient fluorinated feedstock is recycled from said product sepa to provide a current density within the range of from ration zone to said cell; at least a portion of said perfluo 30 to 1000 milliamps per square centimeter of anode 20 rinated feedstock is passed to a combustion and hydrogen geometric surface. fluoride recovery zone; and at least a portion of the 15. A process according to claim 14 wherein said feed recovered hydrogen fluoride is passed from said com stock consists essentially of ethylene and said fluorinated bustion and recovery zone to said cell to replenish hydro product includes 1,2-difluoroethane. gen fluoride consumed in the process. 16. A process according to claim 14 wherein said feed 25 stock consists essentially of ethane and said fluorinated References Cited product includes ethyl fluoride. 17. A process according to claim 12 wherein said fluo UNITED STATES PATENTS rinated product and any remaining unfluorinated feed 2,519,983 8/1950 Simons ------204-59 stock are passed from within said pores of said anode 30 FOREIGN PATENTS directly into a space above said electrolyte within said 740,723 11/1955 Great Britain. cell. - - 741,399 11/1955 Great Britain. 18. A process according to claim 12 wherein said fluo rinated product and any remaining unfluorinated feed HOWARDS. WILLIAMS, Primary Examiner