US3617453A

US3617453A - Temperature control in electrochemical conversion process

Info

Publication number: US3617453A
Application number: US858734A
Authority: US
Inventors: William V Childs
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1969-09-17
Filing date: 1969-09-17
Publication date: 1971-11-02
Anticipated expiration: 1988-11-02
Also published as: US3798144A

Abstract

Temperature control in an electrochemical conversion process is effected by maintaining a layer of feedstock on the surface of the electrolyte in an electrolytic cell provided with a porous electrode. A portion of said feedstock layer enters the pores of said porous electrode and is at least partially converted therein. A cell effluent stream is withdrawn through a reflux condenser, is partially condensed, condensate is returned as reflux to cool said cell, and conversion products are recovered from the uncondensed portion of said cell effluent stream.

Description

United States Patent inventor William V. Childs Austin, Tex. Appl. No. 858,734 Filed Sept. 17, 1969 Patented Nov. 2, i971 Assignee Phillips Petroleum Company TEMPERATURE CONTROL IN ELECTROCHEMICAL CONVERSION PROCESS 8 Claims, 1 Drawing Fig.

US. Cl 204/59, 204/72 int. Cl 801k 3/00 Field of Search 204/59, 72-80 [56] References Cited UNITED STATES PATENTS 2,5 l9,983 8/l950 Simons 204/59 3,5l 1,760 5/1970 Fox et al. 204/59 Primary Examiner-John H. Mack Assistant Examiner-Neil A. Kaplan Attorney-Young and Quigg TO PRODUCT SEPARATION T ANODE l l l l l l l l l l l l l L ll- I8 H l .5 l l l PATENTEU NUVZ IS?! TO PRODUCT SEPARATION CATHODE fius INVENTOR.

w. v. CHILDS A T TORNE Y5 TEMPERATURE CONTROL IN ELECTROCHEMICAL CONVERSION PROCESS This invention relates to an electrochemical conversion process.

Electrochemical conversion processes for converting a wide variety of feedstocks to desirable products are well known in the an. These processes include processes described as anode processes, e.g., processes wherein the desired reaction is carried out at or in the region of the anode, and also processes described as cathode processes, e.g., processes wherein the desired reaction is carried out at or in the region of the cathode. In many electrochemical conversion processes it is often desirable to maintain the electrolyte temperature at a desired value or at least within a narrow range of temperature. This sometimes becomes quite difficult due to PR losses within the electrolyte, coupled with the unavoidable heat of reaction. it is known to cool electrolytic cells by circulating various coolants in coils or tubes disposed within the cell. However, the most convenient coolant, water, frequently reacts with the electrolyte when leakage of the coolant occurs. In many cells there is also the danger of contaminating the products of the process with the coolant or with products of the reaction between the coolant and the electrolyte. Leakage of cooling water into the electrolyte is not an uncommon occurrence in view of the thin-walled cooling tubes employed and the corrosiveness of some cooling waters and some electrolytes.

The present invention provides an electrochemical conversion process comprising a novel method of feeding a porous electrode and wherein a solution is provided for the problem of maintaining the cell temperature within desired limits. Broadly speaking, in the practice of the invention a liquid layer comprising the feedstock to the cell is maintained on the surface of the electrolyte in said cell. A portion of said liquid layer passes into the pores of a porous electrode in the cell and within said pores is at least partially converted. A vaporous cell effluent stream comprising converted products and unconverted feedstock is withdrawn through a reflux condenser. Condensate from said condenser is returned to the cell to cool the electrolyte therein. Conversion products are recovered from the noncondensed portion of said cell effluent stream. In one presently preferred embodiment, a portion of the feedstock is also introduced into the bottom portion of said porous electrode.

An object of this invention is to provide an improved electrochemical conversion process. Another object of this invention is to provide a method for feeding a porous electrode in an electrochemical conversion process. Another object of the invention is to provide a method for removing heat from and maintaining the cell temperature in an electrochemical conversion process within desired limits. Still another object of this invention is to provide an improved electrochemical fluorination process. Another object of the invention is to provide improved apparatus which is useful in electrochemical conversion processes. Other aspects, objects and advantages of the invention will be apparent to those skilled in the art on studying this disclosure.

Thus, according to the invention, there is provided a process for the electrochemical conversion of an organic compound feedstock, which process comprises: passing an electric current through a current-conducting electrolyte contained in an electrolytic cell provided with a porous electrode and another electrode; introducing said feedstock into said cell and maintaining a liquid layer comprising same on the surface of said electrolyte and in contact with said porous electrode, a portion of said liquid layer passing into the pores of said porous electrode; operating said porous electrode at a temperature above the temperature of said electrolyte; in said pores, at least partially converting at least a portion of said feedstock therein; passing converted feedstock and unconverted feedstock from within the pores of said porous electrode; withdrawing a vaporous cell effluent stream comprising converted products and unconverted feedstock from said cell; passing said cell effluent stream through a condensing zone;

returning a stream comprising unconverted feedstock from said condensing zone to said cell; and recovering converted product from the uncondensed portion of said cell effluent stream.

Further according to the invention, there is provided apparatus comprising, in combination: a vessel for containing a body of a first liquid having a body of a second liquid, essentially insoluble in said first liquid, disposed as a layer on the surface of said first liquid; a phase splitter means disposed in said container, extending through said layer of second liquid and into said first liquid, for selectively removing said second liquid from the surface of said first liquid; and means for causing said second liquid to selectively flow into said phase splitter means and be removed from said cell.

Further according to the invention, there is provided a method of removing a layer of a first liquid from a body of a second liquid, said liquids being substantially insoluble in each other, which method comprises: causing said first liquid to selectively flow through the pores of and into a porous collection cup immersed therein; and then flowing said first liquid from said cup through a conduit connected thereto.

A number of advantages are realized or obtained in the practice of the invention. One advantage is that the design and construction of porous electrodes is simplified. Another advantage is that the introduction of the feedstock into the pores of a porous electrode is simplified. For example, in a cell provided with a plurality of porous electrodes, all of the feedstock for all of said porous electrodes can be introduced into the cell at one point. Another advantage of the invention is that the cell can be cooled without danger of contaminating the electrolyte by a coolant liquid.

The invention is applicable to any electrochemical conversion process wherein it is desired to remove heat of reaction from the system and wherein the feedstock has a significant vapor pressure at cell and/or anode operating conditions. The invention is particularly applicable to those processes and systems wherein close temperature control within a narrow range is desirable. In the practice of the invention the temperature of the electrolyte in the cell is maintained below the boiling point of the feedstock to the cell. If the normal boiling point of the feedstock is too low, the pressure in the cell can be increased as desired. lf the normal boiling point of the feedstock is too high, the pressure in the cell can be lowered as desired. Thus, the invention is applicable to processes utilizing a wide variety of feedstocks.

The invention is particularly applicable to electrochemical conversion processes in which porous electrodes can be employed. Some examples of such processes are electrochemical halogenation, electrochemical cyanation, and cathodic conversions such as the reduction of alcohols to hydrocarbons, the reduction of organic ozonolysis products, or the reduction of organic acids to alcohols. One electrochemical conversion process in which the invention is particularly valuable is the electrochemical fluorination of fluorinatable materials in the presence of an essentially anhydrous liquid hydrogen fluoridecontaining electrolyte. Thus, for purposes of convenience, and not by way of limitation, the invention will be further described in terms of being employed in the electrochemical fluorination of fluorinatable materials when using said hydrogen fluoride-containing electrolyte.

Various processes for carrying out electrochemical fluorination reactions are known. In one presently preferred process a current-conducting, essentially anhydrous, liquid hydrogen fluoride electrolyte is electrolyzed in an electrolysis cell provided with a cathode and a porous anode (preferably porous carbon), a fluorinatable feedstock is introduced into the pores of said anode and at least a portion of said feedstock is at least partially fluorinated within the pores of said anode, and fluorinated products are recovered from the cell.

Very few organic compounds are resistant to fluorination. Consequently, a wide variety of feed materials, both normally liquid and normally gaseous compounds, can be used as feedstocks in said process. Generally speaking, desirable organic starting materials which can be used are those containing from two to 12, preferably two to 10, carbon atoms per molecule. Some general types of organic starting materials which can be used include, among others, the following: alkanes, alkenes, alkynes, amines, ethers, esters, mercaptans, nitriles, alcohols, aromatic compounds, and partially halogenated compounds of both the aliphatic and aromatic series. It will be understood that the above-named types of compounds can be either straight chain, branched chain, or cyclic compounds.

One presently, more preferred class of starting materials for use in the practice of the invention includes the fluorinatable, partially halogenated compounds having a boiling point higher than at least the major portion of the fluorinated products obtained therefrom. In said halogen-containing feedstocks the halogen can be any of the halogens, chlorine, bromine, iodine, or fluorine. Partially chlorinated hydrocarbons have been found particularly useful. Examples of said compounds include, among others, the following: mono, di, tri, and tetrachloroethanes; monofluoro, mono, di, tri, and tetrachloroethanes; difluoro, mono, di, and trichloroethane; trifluoro, monochloro, and dichloroethanes; mono, di, tri, and tetrabromoethanes; mono, di, tri, and tetraiodoethanes; etc. Thus, applicable compounds include: methyl chloride; methyl fluoride; chloroform; methylene diiodide; bromoform; chlorofluoromethane; bromochloromethane; [,2- dichloroethane; 1,1-diiodoethane; l-bromo-2-fluoroethane; l,l ,Z-trichIoroethane; l, l -dichloro-2,2-difluoroethane; 1,2- dichloropropane; l-bromo-3-iodopropane; l-chloro-3- fluoropropene; l, l -dichloro-2,3-difluoropropane; l, l l ,2- tetrafluoropropane; l,l-dichlorobutane; 2,3-dibromobutane; l, l l-trichloro-3-iodobutane; l,4-difluorobutene-2; l,2,3- trichlorobutane; and the like, and mixtures thereof.

The hydrogen fluoride electrolyte can contain small amounts of water, such as up to about 5 weight percent. However, it is preferred that said electrolyte be essentially anhydrous, e.g., contain not more than about 0.1 weight percent water. Commercial anhydrous liquid hydrogen fluoride containing up to about I percent by weight of water can be used. Thus, as used herein and in the claims, unless otherwise specified, the term essentiallyanhydrous liquid hydrogen fluoride includes liquid hydrogen fluoride which can contain water not exceeding up to about 1 percent by weight. As the electrolysis reaction proceeds, any water contained in the hydrogen fluoride electrolyte is slowly decomposed and said electrolyte concomitantly approaches the anhydrous state. Pure anhydrous liquid hydrogen fluoride is nonconductive. To provide adequate conductivity in the electrolyte, and to reduce the hydrogen fluoride vapor pressure at cell operating conditions, an inorganic additive can be incorporated in the electrolyte. Presently preferred additives for this purpose are the alkali metal fluorides and ammonium fluoride. Said additives can be utilized in any suitable molar ratio of additive to hydrogen fluoride within the range of from 1:4.5 to lzl, preferably 1:4 to l:2.

Generally speaking, the fluorination process can be carried out at temperatures within the range of from -80 to 500 C. at which the vapor pressure of the electrolyte is not excessive, e.g., less than 250 mm. Hg. It is preferred to operate at temperatures such that the vapor pressure of the electrolyte is less than about 50 mm. Hg. A presently preferred range of temperature is from about 60 to about 120C.

Pressures substantially above or below atmospheric can be employed if desired. depending upon the vapor pressure of the electrolyte and the vapor pressure of the feedstock as discussed above. Generally speaking, the process is conveniently carried out at substantially atmospheric pressure.

Current densities within the range of 30 to 1,000, or more, preferably 50 to 500, milliamps per square centimeter of anode geometric surface can be used. The voltage which is normally employed will vary depending upon the particular cell configuration employed and the current density desired. Under normal operating conditions, however, the cell voltage or potential will be less than that required to evolve or generate free or elemental fluorine. Voltages in the range of 4 to 12 volts are typical. Generally speaking, the maximum normal voltage will not exceed 20 volts per unitcell. The term anode geometric surface" refers to the outer geometric surface area of the porous element of the anode which is exposed to the electrolyte and does not include the pore surfaces of said porous element.

Feed rates which can be employed will preferably be within the range of from 0.5 to 10 ml. per minute per square centimeter of anode geometric surface area. Since the anode can have a wide variety of geometrical shapes, which will affect the geometrical surface area, a sometimes more useful way of expressing the feed rate is in terms of anode cross-sectional area (taken perpendicular to the direction of flow). When at least a portion of the feedstock is being introduced into the pores of the anode at the lower end portion thereof, as described further hereinafter, the feed rate therefor will preferably be such that the feedstock is passed into the pores of the anode, and into contact with the fluorinating species therein, at a flow rate such that the inlet pressure of said feedstock into said pores is essentially less than the sum of (a) the pressure of the electrolyte at the level of entry of the feedstock into said pores and (b) the exit pressure of any unreacted feedstock and fluorinated products from said pores into the electrolyte. Said exit pressure is defined as the pressure required to form a bubble on the outer surface of the anode and break said bubble away from said surface. Said exit pressure is independent of electrolyte pressure. Under these preferred flow rate conditions, there is established a pressure balance between the feedstock entering the pores of the anode from one direction and electrolyte attempting to enter the pores from another and opposing direction. Essentially all of the feedstock travels within the porous anode via the pores therein until it exits from the anode at a point above the surface of the electrolyte. Broadly speaking, the upper limit on the flow rate will be that at which breakout" of feedstock and/or fluorinated product begins along the immersed portion of the anode. "Breakout" is defined as the formation of bubbles of feedstock and/or fluorinated product on the outer immersed surface of the anode with subsequent detachment of said bubbles wherein they pass into the main body of the electrolyte. Broadly speaking, the lower limit of the feed rate wiil be determined by the requirement to supply the minimum amount of feedstock sufficient to prevent evolution of free fluorine. As a practical guide to those skilled in the art, the feed rates can be within the range of from 3 to 600, preferably l2 to 240, cc. per minute per square centimeter of cross-sectional area (taken perpendicular to the direction of flow). Herein and in the claims, unless otherwise specified, for convenience the volu metric feed rates have been expressed in terms of gaseous volume calculated at standard conditions, even though the feedstock may be introduced into the porous anode in liquid state.

Referring now to the drawing, the invention will be more fully explained. in the drawing there is illustrated an electrolytic cell, denoted generally by the reference numeral 10, comprising a cell body ll having an anode 12 disposed therein. As here illustrated, said anode comprises a cylinder of porous carbon. Preferably, said anode is vertically disposed as illustrated. A current collector 14, formed of copper or other suitable conducting material, is provided in intimate contact with the interior of said porous carbon cylinder. The intimate contact between said current collector and said cylinder of porous carbon can be provided by threads, a tight wedge fit, or other suitable means. As illustrated, said current collector comprises a tubular conduit having a passageway 29 therein and extending into said cylinder of porous carbon to a point near the bottom thereof. Said current collector is connected by means of lead 16 to the anode bus of the current supply. it will be noted that the upper end portion of said anode 12 extends above the electrolyte level 18. A circular cathode 20, which can be a screen formed of a suitable-metal such as a stainless steel, surrounds said anode l2 and is connected to the cathode bus of the current supply by a suitable lead wire 22. Any suitable source of current and connections thereto can be employed in the practice of the invention. Thermocouple means 23 is provided for determining the temperature of the electrolyte. A feedstock inlet 24 is provided in the upper portion, preferably the top, of said cell. A feedstock conduit 26 is connected to said feedstock inlet. A valve 28 is disposed in said feedstock conduit. Said valve 28 can be any suitable type of valve. As here illustrated, said valve comprises a motor valve. A liquid level control means 30 is mounted on the wall of said cell body 11 and is operatively connected in conventional manner to said valve 28 for controlling the introduction of feedstock into the cell responsive to said liquid level controller 30. Any suitable type of liquid level controller can be employed. One suitable type is a Dynatrol detector type C L-lO-Houston, Texas. A reflux condenser means 32 is operatively connected to the upper portion of said cell body 11, preferably the top, and is in communication with the vapor space within said cell.

Conduits

34 and 36 are provided for the supply of a suitable coolant to said reflux condenser 32.

A phase-splitter means comprising a tubular conduit 38 having a passageway 41 therein, formed of a suitable metal or other conducting material, and a porous cup 40 mounted on and closing the lower end of said tubular conduit, is disposed in said cell body 11. Preferably, said cup 40 is mounted on said tubular conduit 38 in such a manner as to leave an enclosed space at the lower end of said tubular conduit. Preferably, said tubular conduit 38 of the phase splitter extends through the top or lid of the cell body 11. However, if desired, it is within the scope of the invention for said tubular conduit 38 to be curved and extend through a sidewall of cell body 11. Said tubular conduit 38 is connected by means of a suitable lead wire 42 to the anode bus of the current supply. A withdrawal conduit 44 is connected to the passageway 41 formed within said tubular conduit 38. Conduit 46, connected to said withdrawal conduit 44, extends into trap 48 as illustrated. Conduit 50, having vacuum pump means 52 disposed therein, is connected to the top of said trap 48. Returning to said anode, a conduit 27 is connected to the passageway 29 formed within the tubular current collector 14. Said conduit 27 is also connected at its other end to feedstock header conduit 25. An inlet 54 is connected to the op of cell body 11 for introducing gas pressure into the vapor space within said cell body.

In the operation of the apparatus illustrated in the drawing, for example, for the electrochemical fluorination of ethylene dichloride (1,2-dichloroethane) having a boiling point of about 83.5 C. and when using a KF'ZHF electrolyte, the temperature of said electrolyte can be maintained at about 80 C, and the temperature of the anode can be maintained at about 100 C. The temperature of the electrolyte can be controlled by the amount of reflux returned to the cell from reflux condenser 32. In some instances, it is desirable to maintain the temperature of the electrolyte slightly below, e.g., within the range of about 2 to about 60, preferably about 3 to about 2'0: below the boiling point of the liquid layer maintained oi top of the electrolyte. However, in other instances, it will be desirable to maintain the temperature of the electrolyte essentially at the boiling point of said liquid layer. The temperature of the anode can be controlled by controlling the amount of reaction taking place within the pores of said anode. This can be accomplished by balancing or correlating the feed flow rate and the current density applied to the anode. For a given feed flow rate to the anode, an increase in current density will result in a higher temperature within the pores of the anode, and vice versa. Generally speaking, it is desirable to maintain the temperature within the pores of the anode within the range of about 5 to about 20", preferably about 7 to about C., above the electrolyte temperature. The temperature within the pores of anode 12 can be determined by means of thermocouple( s) 29 embedded therein.

In one embodiment of the invention, the fresh feedstock is introduced to the cell exclusively through feed inlet 24 and a layer of feedstock is established on the surface of the electrolyte. The depth of said layer will depend upon the particular feedstock, the type of reaction being carried out, the size of the cell, the size and number of anodes in the cell, etc. Generally speaking, it will be desirable to maintain the depth of said layer within the range of about 0.1 to 2 inches, preferably about 0.5 to 1 inch. After the layer of feedstock has been established on the surface of the electrolyte, the current is turned on. The feedstock enters into the pores of the anode wherein it diffuses through the pores of the anode, is vaporized, contacts the fluorinating species, and at least a portion of said feedstock is at least partially fluorinated. Fluorinated product and any unfluorinated feedstock are passed from the pores of the anode above the level of the electrolyte and the supernatant layer thereon and into the vapor space in the upper porn'on of the cell. A vaporous cell efi'luent stream is withdrawn through reflux condenser 32. Said condenser is operated at a temperature and a pressure such that hydrogen fluoride and at least a portion of the unfluorinated feedstock will be condensed. The noncondensed portion of said vaporous cell effluent stream is passed through conduit 35 to a product separation zone wherein separation of the fluorinated products is effected in conventional manner.

In another preferred embodiment of the invention, the feeding of the anode from the supernatant layer of feedstock is supplemented by introducing fresh feedstock into the lower portion of the anode. In this embodiment of the invention, at least a portion of the fresh feedstock is introduced via conduit 27 and passed through passageway 29 into space 31 in the lower portion of the anode. In this embodiment of the invention, it is sometimes preferred to introduce all the fresh feedstock via space 31. From said space 31 the vaporized feedstock enters the pores of the anode, travels upward through the pores of the anode, and exits from the anode above the level of the electrolyte and supernatant liquid layer thereon, and into the vapor space in the upper portion of the cell. During passage of said feedstock through said pores at least a portion of the feedstock is at least partially fluorinated. A vaporous cell effluent stream is withdrawn through reflux condenser 32 and treated in the manner described above. When operating with this dual feeding system, the ratio of the feed introduced through space 31 to the feed introduced into the pores of the anode from layer 19 will usually be within the range of 0.5 to 0.95, preferably within the range of from 0.5 to 0.75 An important advantage of said dual feeding system is that if the feed to the lower portion of the anode is inadvertently interrupted, the supernatant layer on the surface of the electrolyte comprises a reservoir of feedstock. This will prevent, or at least reduce, production of elemental fluorine such as would occur if feedstock flow were suddenly stopped.

in the practice of the invention there will sometimes be a buildup of concentration of higher boiling fluorinated products in layer 19 which is maintained on the surface of the electrolyte. When the concentration of said higher boiling fluorinated products in layer 19 reaches a desired or limiting value, e.g., about 50 percent, it is desirable to remove a portion of said layer. I have discovered that this can be accomplished efficiently by utilizing the difference in contact angle of the electrolyte and the contact angle of the liquid in layer 19.

For example, the electrolyte KF'ZHF does not wet porous carbon, i.e., the contact angle of said electrolyte with the porous carbon is greater than Thus, the electrolyte KF'ZHF resists flow into the pores of the porous carbon. The contact angle for 1,2-dichloroethane and its fluorinated products is less than the contact angle for said electrolyte. These materials will thus preferentially or selectively flow into and through the pores of the porous carbon cup 40.

Referring to the drawing, this preferential or selective flow of layer 19 into and through the pores of porous cup 40 into collection zone 43 can be caused to take place by the application of gas pressure through inlet 54. Any suitable inert gas,

such as nitrogen, can be employed for applying gas pressure. The application of said gas pressure will cause the layer 19 to flow through the pores of porous cup 40 and pass upwardly through passageway 41 and into conduit 44 for disposal as desired. When all of the liquid in layer 19 has been forced out, the gas pressure will purge the system and leave the electrolyte behind essentially undisturbed. Said layer 19 can also be caused to flow through the pores of porous cup 40 by the application of vacuum. Said vacuum can be applied to trap 48 by means of pump 52 disposed in conduit 50 connected to the top of trap 48. Thus, by opening the valve in conduit 46 and closing the valve in conduit 44, layer 19 can be caused to flow through the pores of cup 40, up through passageway 41, and into tray 48.

1 have also discovered that the efficiency of the above method of separating layer 19 from the underlying layer of electrolyte can be increased by applying a positive voltage to the phase splitter device. Said voltage can be applied by connecting lead wire 42 to the anode bus of the system. Current flow will be established because cup 40 extends into the electrolyte which is in contact with cathode 20. It will generally be desirable to apply from 3 to 8 volts of direct current to the phase splitter at a current density level within the range of from about 1 to about 300 milliamps per square centimeter of geometric surface area.

The above-described method of separating two phases can be applied to any system in which the contact angle of one phase (either phase) is greater than 90, and the contact angle of the other phase is sufficiently different from, preferably less than, the contact angle of the first-mentioned phase. Generally speaking, it is desirable that the difference in said contact angles be at least 10. However, by the application of electric current as described above, the difference in contact angle can be increased and the initial difference in contact angle of the two phases is not unduly restrictive. While said phase splitter and its operation have been described as employing porous carbon for the porous cup 40, the invention is not limited to the use of porous carbon. Other suitable porous materials, such as porous Teflon, can be employed in the practice of the invention.

The following examples will serve to further illustrate the invention.

EXAMPLE I A run was carried out for the electrochemical fluorination of ethylene dichloride (1,2-dichloroethane) in an electrolytic cell embodying the essential elements of the apparatus illustrated in the drawing. The porous anode comprised a cylinder of porous carbon (National Carbon Company -Grade NC45) having an external diameter of about l% inches and a length of about 6 inches. Said anode was immersed in the KF-ZHF electrolyte to a depth of about 4 inches. The current collector 14 was about one-half inch in outer diameter and extended to about one-quarter to about one-half inch from the bottom of the porous carbon cylinder 12. The feed rate of ethylene dichloride from supernatant layer 19 into the pores of the anode was about 17.2 milliliters per hour. The level of layer 19 was controlled with a liquid level controller operatively connected to valve 28 to maintain the layer on the surface of the electrolyte about l-inch thick on the surface of the electrolyte. The voltage applied to the cell was about 7.9 volts at a current level of 23 amperes. The current density was about 200 milliamps per cm. of anode geometric surface area. A vaporous cell efiluent stream was withdrawn through reflux condenser 32. The electrolyte temperature was maintained at about 82 C. by means of reflux returned from reflux condenser 32. The anode temperature, i.e., the temperature within the pores of the porous carbon cylinder was in the range of about 95 to about 105 C. During the run the noncondensed portion of the vaporous cell effluent stream withdrawn through reflux condenser 32 was passed via conduit 35 to a GLC analyzer. A typical analysis in terms of the type and quantity of the products obtained are given in table 1 below.

EXAMPLE n A second run for the electrochemical fluorination of ethylene dichloride (1,2-dichloroethane) is carried out employing essentially the same apparatus as in the run of example I. In this run all the fresh ethylene dichloride feedstock is introduced into the pores of the anode via inlet conduit 27 and space 31 at the lower end portion of said anode at a rate of about 20 milliliters per hour. Additionally, said fresh ethylene dichloride feedstock is supplemented with ethylene dichloride feed from supernatant layer 19 at a rate of about 20 milliliters per hour. The thickness of said layer 19 on the surface of the electrolyte is maintained at about 1 inch by regulating the amount of reflux returned from reflux condenser 32. All other operating conditions are essentially the same as in example 1. A typical analysis in terms of type and quantity of products is given in table 1 below.

TABLE I Electrochemical Fluorination of l,2-dichloroethane The results of the above runs show that when operating in accordance with the method of example I the product distribution shifts toward the production of the more highly fluorinated products. When operating in accordance with the method example ll the product distribution shifts toward the production of the less or intermediate fluorinated products. Thus, in accordance with the invention, greater flexibility in the fluorination of organic materials is provided by adjusting the ratio of the amount of feedstock introduced into the pores of the anode at the lower portion thereof to the amount of feedstock introduced into the pores of the anode from the supernatant layer maintained on the surface of the electrolyte.

While certain embodiments of the invention have been described for illustrative purposes, the invention is not limited thereto. Various other modifications of the invention will be apparent to those skilled in. the art in view of this disclosure. Such modifications are within the spirit and scope of the disclosure.

1 claim:

1. A process for the electrochemical conversion of an organic compound feedstock, which process comprises: passing an electric current through a current-conducting electrolyte contained in an electrolytic cell provided with a porous electrode and another electrode; introducing said feedstock into said cell and maintaining a liquid layer comprising same on the surface of said electrolyte and in contact with said porous electrode, said liquid layer and said electrolyte being substantially insoluble in each other, a portion of said liquid layer passing into the pores of said porous electrode; operating said porous electrode at a temperature above the temperature of said electrolyte; in said pores. at least partially converting at least a portion of said feedstock therein; passing converted feedstock and unconverted feedstock from within the pores of said porous electrode; withdrawing a vaporous cell effluent stream comprising converted products and unconverted feedstock from said cell; passing said cell effluent stream through a condensing zone; returning a stream comprising unconverted feedstock from said condensing zone to said cell; and recovering converted product from the uncondensed portion of said cell effluent stream.

2. A process according to claim 1 wherein at least a portion of said feedstock is introduced into the pores of said porous electrode at the lower end portion thereof, is at least partially converted within the pores of said porous electrode, and converted product and unconverted feedstock are withdrawn from the pores of said porous electrode at the upper end portion thereof above the level of said liquid layer on the surface of said electrolyte.

3. A process according to claim 1 wherein: said process comprises an electrochemical fluorination process; said feedstock is a fluorinatablc feedstock; said porous electrode is a porous anode; and said electrolyte is essentially anhydrous hydrogen fluoride.

4. A process according to claim 3 wherein: said anode comprises porous carbon and an upper surface thereof extends above the level of said liquid layer on the surface of said electrolyte; said fluorinated feedstock and any remaining unfluorinated feedstock are passed from within the pores of said anode at said upper surface thereof, above the level of said liquid layer, and into a vapor space above said liquid layer; and said cell effluent stream is withdrawn from said vapor space.

5. A process according to claim 3 wherein: said anode comprises porous carbon, is vertically disposed in said cell, and the upper end thereof extends above the level of said liquid layer on the surface of said electrolyte; said fluorinated feedstock and any remaining unfluorinated feedstock are passed from within the pores of said anode at the upper end portion thereof, above the level of said liquid layer, and into a vapor space above said liquid layer; and said cell effluent stream is withdrawn from said vapor space.

6. A process according to claim 3 wherein: said porous anode is vertically disposed in said cell; at least a portion of said feedstock is introduced into the pores of said porous anode at the lower end portion thereof; is at least partially fluorinated to fluorinated product within the pores of said porous anode, and fluorinated product and any remaining unfluorinated feedstock are withdrawn from the pores of said porous anode at the upper end portion thereof above the level of said liquid layer on the surface of said electrolyte.

7. A process according to claim 6 wherein said anode comprises porous carbon and the upper end thereof extends above the level of said liquid layer on the surface of said electrolyte.

8. A process according to claim 7 wherein said feedstock is ethylene dichloride.

Claims

2. A process according to claim 1 wherein at least a portion of said feedstock is introduced into the pores of said porous electrode at the lower end portion thereof, is at least partially converted within the pores of said porous electrode, and converted product and unconverted feedstock are withdrawn from the pores of said porous electrode at the upper end portion thereof above the level of said liquid layer on the surface of said electrolyte. 3. A process according to claim 1 wherein: said process comprises an electrochemical fluorination process; said feedstock is a fluorinatable feedstock; said porous electrode is a porous anode; and said electrolyte is essentially anhydrous hydrogen fluoride.
4. A process according to claim 3 wherein: said anode comprises porous carbon and an upper surface thereof extends above the level of said liquid layer on the surface of said electrolyte; said fluorinated feedstock and any remaining unfluorinated feedstock are passed from within the pores of said anode at said upper surface thereof, above the level of said liquid layer, and into a vapor space above said liquid layer; and said cell effluent stream is withdrawn from said vapor space.
5. A process according to claim 3 wherein: said anode comprises porous carbon, is vertically disposed in said cell, and the upper end thereof extends above the level of said liquid layer on the surface of said electrolyte; said fluorinated feedstock and any remaining unfluorinated feedstock are passed from within the pores of said anode at the upper end portion thereof, above the level of said liquid layer, and into a vapor space above said liquid layer; and said cell effluent stream is withdrawn from said vapor space.
6. A process according to claim 3 wherein: said porous anode is vertically disposed in said cell; at least a portion of said feedstock is introduced into the pores of said porous anode at the lower end portion thereof; is at least partially fluorinated to fluorinated product within the pores of said porous anode, and fluorinated product and any remaining unfluorinated feedstock are withdrawn from the pores of said porous anode at the upper end portion thereof above the level of said liquid layer on the surface of said electrolyte.
7. A process according to claim 6 wherein said anode comprises porous carbon and the upper end thereof extends above the level of said liquid layer on the surface of said electrolyte.
8. A process according to claim 7 wherein said feedstock is ethylene dichloride.