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Publication numberUS3660254 A
Publication typeGrant
Publication dateMay 2, 1972
Filing dateJun 8, 1970
Priority dateJun 8, 1970
Publication numberUS 3660254 A, US 3660254A, US-A-3660254, US3660254 A, US3660254A
InventorsDunn Robert O
Original AssigneePhillips Petroleum Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Recovery of products from electrochemical fluorination
US 3660254 A
Abstract
Fluorinated products are recovered from an effluent stream from an electrolytic cell in an electrochemical fluorination process by employing a combination of steps comprising cooling said effluent stream to a temperature near its dew point but insufficient to cause any significant condensation thereof, compressing said cooled effluent stream, chilling said compressed effluent stream to a temperature sufficient to condense at least the major portion of the components thereof other than hydrogen, and recovering fluorinated products from said chilled stream. In a preferred embodiment the initial cooling of said effluent stream is effected by directly contacting same with a liquid stream comprising the feedstock to the electrolytic cell.
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United States Patent Dunn Primary Examiner-John H. Mack Assistant ExaminerNeil A. Kaplan Allorney--Y0ung and Quigg [72] Inventor: Robert O. Dunn, Bartlesville, Okla.

[73] Assignee: Phillips Petroleum Company [57] ABSTRACT [22) Filed: June 8, 1970 Fluorinated products are recovered from an effluent stream A I 44 041 from an electrolytic cell in an electrochemical fluorination Pp process by employing a combination of steps comprising cooling said effluent stream to a temperature near its dew point [52] U.S. Cl ..204/59, 204/275 but insufficient to cause any si nificant condensation thereof,

2 l --B01k3/00 compressing said cooled effluent stream, chilling said com- Fleld ofseal'ch pressed effluent tream to a temperature ufficient to condense at least the major portion of the components thereof [56] References Cited other than hydrogen, and recovering fluorinated products UNITED STATES PATENTS from said chilled stream. In a preferred embodiment the initial cooling of said effluent stream is effected by directly contact- 2,425,745 8/1947 Leonard et al ..260/683.41 i same ith a li uid stream comprising the feedstock to the 3,221,070 11/1965 0kamura.. ..260/653.3 electrolytic cell 3,511,760 5/1970 Fox et a1. 204/59 14 Claims, 1 Drawing Figure 54 5s 58 T0 CATHODE BUS 24 T 43 44 46 4a 2 o ANODE BUS 9 66L I I8 38 L 30 72 E 0. Lil (I) MFAKE-UP E g I ll so 3 9| 5 .0 X 5 a, g 28 f 29 27 Q 9 D 1 Wt 4 O Q 1 2.5. I42 5 74 E 5 5 5 z z 1 84 j j 1- i F n 5 5 r5 i 95 through said electrolyte between said anode and an oppositely charged element, e.'g., either another electrode immersed in said electrolyte or the cell body which can serve as said other element or electrode. In one such process a material to .be fluorinated is dissolved in the electrolyte and at least a portion of said material is converted into conversion products at the anode. In a variation of this process, the feedstock to be converted is bubbled into the electrolyte through a porous anode, such as a porous carbon anode, and said material is fluorinated in the electrolyte.

Recently it has been discovered that the reaction in an electrochemicalfluorination process can be carried out within the confines, e.g., within the pores, of the porous anode itself. This type of operation isof particular utility with many feedstocks because it provides or makes'possible a simple one-step route, at relatively high conversions, to produce partially fluorinated products whichhad previously been diflicult to obtain. This process also allows operation at high conversions without substantial formation of cleavage products which are generally produced by the-older methods when operating at high con versions. The feedstock to be fluorinated can be introduced into the pores of the porous anode at a point near its bottom and the fluorinated mixture removed from said pores at the top of the anode, generally above the electrolyte level. Passage of the feedstock into the bulk of the electrolyte is thus avoided.

One problem which is common to all of the above-described electrochemical fluorination processes is'the recovery of the fluorinated'productsfrom the cell effluent stream. In many instances when an electrolyte comprising a current-conducting hydrogen fluoride is employed, said cellefiluent will contain hydrogen which is produced as a cathode product, some hydrogen fluoride' whi'ch vaporizes'from the electrolyte, various fluorinated products produced from the feedstock, and

unreacted feedstock. Generally'speaking, in most instances saidiluorinated products will include low boiling compounds comprisingfluorinatedproducts which are lower boiling than the feedstock, the desired fluorinated product or products, and a small amount of a fluorinated high boiling by-product. Efficient separation of the hydrogen and hydrogen fluoride from the cell efiluent without loss of the low boiling fluorinated products is particularly troublesome.

The present invention provides a solution for the abovedescribed problems. Broadly speaking, the present invention provides a combination of steps wherein acell'effluent stream is cooled to atemperature near its dew point but insufficient to cause any significant condensation of the components thereof. Said-cooled efiluent stream is then compressed, and then chilled by refrigeration to a temperature sufficient to condense at least themajor portion of the components thereof other than hydrogen. Any hydrogen and hydrogen fluoride contained in the-chilled'stream are then separated therefrom. The fluorinated products are then recovered from the chilled stream.

An object of this invention is to provide an improved electrochemical fluorination process. Another object of this invention is to provide a method for recovering fluorinated products from a cell effluent stream in an electrochemical fluorination processwith minimum loss of fluorinated product and high purity of the recovered products. Other aspects, objects, and advantages of the invention will be apparent to those skilled in the art in view of this disclosure.

Thus, according to the invention, there is provided in a process for the fluorination of a fluorinatable organic compound feedstock wherein, an electric current is passed through a current-conducting, essentially anhydrous, liquid hydrogen fluoride electrolyte contained in an electrolysis cell provided with a cathode and an anode, said feedstock is passed into said cell and into contact with said anode and at least partially fluorinated, and fluorinated product is recovered from an effluent stream withdrawn from said cell, the improvement comprising the steps of: (a) passing said effluent stream to a cooling zone and therein cooling said stream to a temperature near its dew point but insufficient to cause any significant condensation thereof; (b) compressing said cooled effluent stream; (c) chilling said compressed effluent stream to a temperature sufficient to condense at least the major portion of the components thereof other than hydrogen; and (d) recovering fluorinated products from said chilled stream.

A number of advantages are realized or obtained in the practice of the invention. The invention provides a method for maximum recovery of fluorinated products of high purity from a cell effluent stream. The invention also provides for max imum recovery of hydrogen fluoride electrolyte in those processes wherein the cell effluent stream contains hydrogen fluoride electrolyte. The cooling efiected in the abovedescribed step (a) can be carried out by indirect heat exchange or by direct heat exchange. In a preferred embodiment of the invention, said cooling is effected by directly contacting the cell efiluent stream with a quenching liquid which comprises the feedstock to the electrochemical fluorination cell. The quench liquid is thus completely compatible with the celleffluent stream and can be returned to the cell as a portion of the feedstock thereto. Another major advantage of using direct heat exchange in said step (a) cooling is that the use of an expensive large surface area heat exchanger fabricated from expensive stainless steel is avoided. Still another advantage is that any liquid, e.g., such as liquid HF, which may have been entrained in the cell effluent stream will be washed out and removed by the quench liquid prior to compression step (b).

Very few organic compounds are resistant to fluorination. Consequently, a wide variety of feed materials, both normally liquidand normally gaseous compounds, can be used as'feedstocks in said process. Organic compounds which are normally gaseous or which can be introduced in gaseous state into the pores of a porous anode under the conditions employed in the electrolysis cell, and which are capable of reacting to form fluorinated products, are presently preferred as starting materials. Generally speaking, desirable organic starting materials which can be used are those containing from two to eight, preferably two to six, carbon atoms per molecule. However, reactants which contain less than two or more than six or eight carbon atoms can also be used. 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 group of presently preferred starting materials comprises the normally gaseous organic compounds, and particularly the saturated and unsaturated hydrocarbons, containing from two to four carbon atoms per molecule. Normally liquid feedstocks which can be vaporized under cell operating conditions are also preferred starting materials. Some examples of these are m thane, ethane, propane, butane, isobutane, ethylene, propylene, butane-2, acetylene, propyne, butyne-l, butadiene, and the like, and mixtures thereof.

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. Preferably, the halogen is one other than 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 trichloroethanes; trifluoro-, mono-, and dichloroethanes; mono-, di-, tri-, and tetrabromoethanes; mono-, di-, tri-, and tetraiodoethanes; etc. Thus, applicable compounds include: methyl chloride; methyl fluoride; chlorofonn; methylene diiodide; bromoform; chlorofluoromethane; bromochloromethane; 1,2-

dichloroethane; 1,1-diiodoethane; 1-bromo-2-fluoroethane; 1,1,2-trichloroethane; l,1-dichloro-2,2-difluoroethane; 1,2- dichloropropane; l-bromo-3-iodopropane; 1-chloro-3- fluoropropene; 1,l-dichloro-2,3-difluoropropane; l l ,1 ,2- tetrafluoropropane; l,l-dichlorobutane; 2,3-dibromobutane; l,1,1-trichloro-3-iodobutane; 1,4-difluorobutene-2; 1,2,3- trichlorobutane; and the like, andmixtures thereof.

The invention is applicable to any electrochemical fluorination process employing an electrolyte comprising essentially anhydrous hydrogen fluoride. The invention is particularly applicable to electrochemical fluorination processes in which porous anodes are employed. In one presently preferred process, a current-conducting, essentially anhydrous, liquid hydrogen fluoride 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 a cell eflluent stream.

Briefly, said preferred electrochemical fluorination process comprises passing the feedstock to be fluorinated into the pores of a nonwetting porous anode, e.g., porous carbon, disposed in a current-conducting, essentially anhydrous, hydrogen fluoride electrolyte such as KF-ZHF. Said feedstock contacts the fluorinating species within the pores of the anode and is therein at least partially fluorinated. Generally speaking, said fluorination can be carried out at temperatures within the range of from 80 to 500 C. (-1 12 to 932 F.) at which the vapor pressure of the electrolyte is not excessive. A preferred temperature range is from about 60 C. to about 120 C. (140 to 248 F.). Pressures substantially above or below atmospheric can be employed if desired. Generally speaking, the process is conveniently carried out at substantially atmospheric pressures. The feedstock to be fluorinated is preferably introduced into the pores of the anode at a rate such that there is established a pressure balance within the pores of the anode between the feedstock entering the pores and electrolyte attempting to enter said pores from another and opposing direction. Said feedstock flow rate can be within the range of from 3 to 600 milliliters per minute per square centimeter of anode cross-sectional area, taken perpendicular to the direction of flow and expressed in terms of gaseous volume calculated at standard conditions. Current densities employed can be within the range of 30 to 1,000, preferably 50 to 500, milliamps per square centimeter of anode geometric surface area. Typical cell voltages employed can range from 4 to 12 volts. Converted and unconverted products are withdrawn from the pores of the anode and the products recovered from a cell efiluent stream.

Further details of said preferred electrochemical fluorination process can be found in U. S. Pat. No. 3,511,760, issued to H. M. Fox and F. N. Ruehlen.

The drawing is a diagrammatic flow sheet illustrating one presently preferred embodiment of the invention wherein a feedstock, e.g., l,2-dichloroethane, is fluorinated and the products obtained are separated in accordance with the invention.

Referring now to the drawing, the invention will be more fully explained. By way of example, and not by way of limitation, the invention will be described with particular reference to using l,2 dichloroethane as the fresh feedstock to the electrolytic cell. Thus, the typical operating conditions given herein in connection with using said feedstock and separating the products therefrom are not to be construed as limiting on the invention. In said drawing there is illustrated an electrolytic cell, denoted generally by the reference numeral 10, comprising a cell body 12 having an anode 14 disposed therein. As here illustrated diagrammatically, said anode in its simplest form comprises a cylinder of porous carbon having a cavity 16 formed in the bottom thereof. Any suitable anode can be employed in said cell. Examples of other suitable anodes can be found in U. 8. Pat. No. 3,51 1,762, issued to W. V. Childs. A current collector 18, usually comprising a rod or hollow conduit of a metal such as copper, is provided in intimate contact with the upper portion of said anode l4 and is connected to the anode bus of the current supply. Preferably, the upper end of anode 14 extends above the electrolyte level 20. However, it is within the scope of the invention for the top of said anode to be below said electrolyte level. A circular cathode 22, which can be a screen formed of a suitable metal, such as carbon steel or stainless steel, surrounds said anode 14 and is connected to the cathode bus of the current supply by a suitable lead wire 24. Any suitable source of current and connections thereto can be employed.

In the operation of the system illustrated, a feedstock such as 1,2-dichloroethane is introduced into the cavity portion 16 of said anode via conduits 26, 28, and 29, travels upward through the pores of said anode, and exits from the upper end of the anode above electrolyte level 20. During passage through said anode, at least a portion of the feedstock is electrochemically fluorinated. Fluorinated products together with remaining unconverted feedstock, hydrogen, and possibly some electrolyte vapors, are withdrawn from the space above the electrolyte within cell 12 via conduit 30. During the introduction of said feedstock an electric current in an amount sufiicient to supply the desired operating current density at the anode is passed between the anode and the cathode.

Preferably, the cell eflluent stream in conduit 30 is cooled in quench zone 32 with a stream of liquid comprising the cell feedstock from conduit 26. Said quench zone 32 can comprise any suitable means for obtaining eflicient contact between a liquid stream and a vapor stream. For example, said quench zone 32 can comprise a tower filled with Raschig rings or other suitable contacting material, a bubble cap tower, etc. Initially, at least, quenching liquid is introduced from conduit 26 into conduit 34, passed through the cooler 36, and then introduced into quench zone 32 by means of conduit 38. in quench zone 32, said cell effluent stream is preferably cooled to a temperature which is near its dew point but which is insufficient to cause any significant condensation of the components thereof. As will be understood by those skilled in the art, said dew point will vary with the composition of said effluent stream and the pressure in said quench zone. Thus, the temperature to which said effluent stream is cooled can vary widely. When 1,2-dichloroethane is the charge stock to the electrochemical fluorination cell, said dew point will usually be in the order of about F. to about F. at essentially atmospheric pressure. Generally speaking, it is desirable to cool said effluent stream as nearly as practical to its dew point without causing said condensation of the components thereof. In most instances, said efiluent stream will be cooled to a temperature which is within 3 to 10 F. above said dew point. Condensation is preferably avoided so as to avoid passing liquid into the compressor in the subsequent compression step. It is, however, an advantage of my invention that any material which may be condensed within quench zone 32 will be absorbed by the quench liquid and thus only vapor will pass to compressor 44. Said cell effluent stream will preferably be cooled to a temperature which is not greater than about F. At temperatures above about 165 F. gaseous streams containing vaporous HF become excessively corrosive to carbon steel equipment. Said cooling or quenching can be carried out by continuously circulating the quenching liquid through quenching zone 32 via conduits 34, cooler 36, and conduit 38, and supplying only sufficient make-up quench liquid from conduit 26 as is necessary. Any buildup of quenching liquid can be withdrawn from the circulating stream via conduit 40 and returned to the cell as a portion of the feedstock thereto via conduit 42. It is generally desirable to bleed" a small portion of the quench liquid through conduit 40 and replace same with fresh feedstock via conduit 27, thus preventing buildup of any components which may be absorbed in the circulating quench liquid. However, it is within the scope of the invention to continuously circulate all or a portion of the fresh feed to the cell through said quench zone 32 by means of the manifolding arrangement shown in the drawing.

Quench zone 32 can be conveniently operated at a temperature of about 120 F. and a pressure of about psia. A vaporous stream is withdrawn from said quench zone via conduit 43, compressed in compressor 44 to a pressure of about 30 psia at a temperature of about 210 F. Said compressed effluent stream is passed via conduit 46 into chiller 48 wherein its temperature is decreased to about F. at a pressure of about 27 psia, and is then passed via conduit 50 into first phase separation zone 52 wherein it separates into a gaseous phase and two liquid phases. A gaseous stream comprising hydrogen is withdrawn from first separation zone 52 via conduit 54, compressed in compressor 56 to a pressure of about 85 psia at a temperature of about 155 F., then introduced into chiller 58 where it is chilled by means of refrigeration to a temperature of about l00 F. at a pressure of about 80 psia, and then introduced into second phase separation zone 60. A stream comprising hydrogen is vented from the system via conduit 62. A stream comprising liquid HF is withdrawn from second separation zone 60 via conduit 64 and passed to said first separation zone 52. Liquid HF is withdrawn from first separation zone 52 via conduit 66 and recycled to the electrochemical fluorination cell. Make-up HF can be introduced to the system via conduit 11.

A second liquid stream comprising fiuorinated products is withdrawn from first phase separation zone 52 via conduit 68 and introduced into stripping zone 70 wherein any remaining HF contained in the liquid stream can be stripped therefrom and returned via conduit 72 to conduit 46. Vapors for stripping said second liquid stream can be generated by means of the reboiler arrangement shown on the lower portion of stripper tower 70. Said stripping tower 70 can conveniently be operated at a pressure of about 45 psia, a top tower temperature of about 100 F., and a bottom tower temperature of about 166 F.

Said now stripped second liquid stream comprising fiuorinated products and unreacted feedstock is withdrawn from stripper zone 70 via conduit 74 and passed to a first distillation zone comprising a first fractionation column 76 and a second fractionation column 78. Said first fractionation column can conveniently be operated at a pressure of about 130 psia, a top tower temperature of about 145 F., and a bottom tower temperature of about 256 F. An overhead stream comprising chloropentafluoroethane is withdrawn from first fractionation column 76 via conduit 80 and introduced into said second fractionation column 78. Said second fractionation column 78 can conveniently be operated at a pressure of about 235 psia, a top tower temperature of about 123 F and a bottom tower temperature of about 199 F. An overhead stream comprising said chloropentafluoroethane is removed overhead from column 78 via conduit 82 as one of the products of the process. A bottoms stream comprising 1- chloro-l,l,2,2-tetrafluoroethane is removed from said second fractionation column 78 via conduit 84 and passed into conduit 42 for recycle to cell 12 as a portion of the feedstock thereto.

A bottoms stream comprising other fiuorinated materials and unreacted 1,2-dichloroethane feedstock is withdrawn from first fractionation column 76 via conduit 86 and passed to a second distillation zone comprising a third fractionation column 88 and a fourth fractionation column 90. Said third fractionation column 88 can conveniently be operated at a pressure of about 70 psia, a top tower temperature of about 126 F., and a bottom tower temperature of about 235 F. An overhead stream comprising 1,2-dichlorotetrafluoroetltane is recovered from said third fractionation column 88 via conduit 91 as another product of the process. A bottoms stream comprising said other fiuorinated materials and said unreacted 1,2-dichloroethane feedstock is passed from third fractionstion column 88 via conduit 92 into said fourth fractionation column 90. Said fourth fractionation column can conveniently be operated at a pressure of about 30 psia, a top tower temperature of about 136 F., and a bottom tower temperature of about 205 F. An overhead stream comprising 1,2-dichloro- 1,2,2-trifluoroethane is recovered from said fourth fractionation column via conduit 93 and introduced into said conduit 42 for recycle to said cell 12 as a portion of the feedstock thereto.

A bottoms stream comprising said other fiuorinated materials and said unreacted 1,2-dichloroethane feedstock is passed from said fourth fractionation column 90 to a third distillation zone comprising a fifth fractionation column 94 and a sixth fractionation column 95. Said fifth fractionation column can conveniently be operated at a pressure of about 60 psia, a top tower temperature of about 134 F., and a bottom tower temperature of about 180 F. An overhead stream comprising l,l,2-tricltloro-l,2,2-trifluoroethane is recovered from said fifth fractionation column via conduit 96 as another product of the process. A bottoms stream comprising said other fiuorinated materials and said unreacted 1,2-dichloroethane is passed from said fifth fractionation column 94 via conduit 97 into said sixth fractionation column 95. Said sixth fractionation column can conveniently be operated at a pressure of about 20 psia, a top tower temperature of about 192 F., and a bottom tower temperature of about 260 F. An overhead stream comprising 1,2-dichloro-l-monofluoroethane and said unreacted 1,2-dichloroethane feedstock is recovered from said sixth fractionation column via conduit 98 and introduced into said conduit 42 for recycle to said cell 12 as a portion of the feedstock thereto. A bottoms stream comprising a small amount of higher boiling heavy materials is withdrawn from sixth fractionation column via conduit 99 and removed from the system.

The following calculated example will serve to further illustrate the invention. The conditions set forth for the operation of the electrochemical fluorinau'on cell are based on numerous laboratory and pilot plant runs carried out for the electrochemical fluorination of 1,2-dichloroethane, and on laboratory distillations of the cell effluent.

7 EXAMPLE In this illustrative embodiment a run is carried out for the electrochemical fluorination of 1,2-dichloroethane in a system embodying the essential features of the system illustrated in the drawing and using an electrolyte in cell which has an approximate composition of KF'ZHF. Porous carbon cylinders embodying the essential features of anode 14 illustrated diagrammatically in the drawing are employed as anodes. Fresh 1,2-dichloroethane feedstock is introduced via conduits 26 and 28 into the pores of anode l4. Recycle feedstock is sup plied by conduit 42. The conversion in electrolytic cell 110 is carried out at an electrolyte temperature of about 210 F., employing a current density of about 250 amperes per square foot of anode geometric surface area, and a voltage of about 9.5 volts, D.C.' The pressure in cell 10, conduit 30, and quench zone 32 is substantially atmospheric; A cell eflluent stream is withdrawn via conduit 30 and processed essentially as described above in connection with the drawing for the recovery of products therefrom and the return of the recycle stream to the cell via conduit 42. Table 1 below sets forth the principal components in said cell eflluent stream and said recycle streams, and a calculated material balance for the system.

TABLE I.STREAM NUMBER, MOLS 1' 1 1 1t 1100 It Component 28 42 20 3O 54 02 01; (is 74 72 X 82 740 CCIF1CC1F: 1.63 1. 63 16.4.5 1.44 0. 0!! 111.154 0.08 0.83 0.8

- 14. G 14. 05 14. 71 0. 40 0. 0] l4 7 0. 3K CC1FT-CI1ZCL 4. J 4. 0 5. 4 0. 0x 7) 4 0. 0s CHCIF-CHCIF. 0.8 0.8 0.8 0. 0H l X 0. 07 14.7 14.7 14.7 0. 00 M 7 0. 0X .24. 3 42. 3 24.3 0. 05 .44. i u. u" O. 07 0. 07 0.72 0. 32 0. l5 0. 57 0. Hi 0. 57 ll. I50 0. 07 0.60 0.60 0. 68 0. 11 0. 0. 0.111; 0.01; 0.111 0.01 0, 00 0.35 0. 0. 66 0. 03 u. m; 0. 0 I 0. 06 0. 06 O. 66 0. 02 0. m; 0. 02 9. 00 9. 00 10.00 0 11 10.00 0.14 1.96 1.96 1.96. 1.1m. CllCl2CHzCl 0.98 0.98 0. 08 0. 08 HF 15.8 56 0.13 15 67 3.50 ll; 66.63 66 64 66.63 0.25

Total 18. 0 83. 00 101. 00 183. 43 75. 00 67. 03 15. 67 106. 64 100. 73 5. U1 2. 01 J. 51 1. 50

Component 86 92 93 80 0G 07 00 H8 11 38 27 40 CClF1-CClF-; 15.51 0.80 CHClF*(ClF 14.7 14.65 CClF-. C1I-1Cl. 5.4 5.4 CHClF CllClF. 9.8 9.8 CHClF-CHaCL 14.7 14.7 Cl-hCHCIIQCl 24.3 24.3

Total 9s. 72 15. 71 R3. 01 2s. 59 59.42 1. 50 57112 Tr 66. 76 1. 070. 0 1. 0 1. 0

Fresh feedstock. A M, V 7W" From the data set forth above, it will be seen that the invenfrom said first phase separation zone for recycle to said tion provides an efiicient method for the separation and cell; recovery of products from a cell effluent stream in the elecg. a gaseous stream comprising hydrogen is vented from said trochemical fluorination of organic compounds. 35 first phase separation zone; and

While certain embodiments of the invention have been h. said fluorinated products recovered in step (d) are described for illustrative purposes, the invention is not limited recovered f a Second li id stream comprising same thereto. Various other modifications or embodiments of the hi h i i hd f id fi t phase a ti zone, invention will be apparent to those skilled in the art in view of 6 A process according t l i 5 wh i this disclosure. Such modifications or embodiments are stream hydrogen in step com. the spirit and scope Ofthe disclosurepressed, then chilled, and then passed to a second phase I Claim! separation zone; 1. In a process for the fluorination of a fluorinatable organic ja stream mmprising hydrogen is Vented from said second compound feedstock wherein, an electric current is passed phase separation zone; and through a current-conducting, essentially anhydrous, liquid k. a stream comprising liquid hydrogen fluoride is returned hydrogen fluoride electrolyte contained in an electrolysis cell from said second phase separation zone to said first phase provided with a cathode and an anode, said feedstock is separation zone. passed into said cell and into contact with said anode and at 7. A process according to claim 5 wherein: said second least partially fluorinated, and fluorinated product is liquid stream of step (h) is passed to a stripper zone; hydrogen recovered from an effluent stream withdrawn from said cell, fluoride vapors are stripped from said second liquid stream; the improvement comprising the steps of: and said fluorinated products are recovered from said stripped a. passing said effluent stream to a cooling zone and therein second liquid stream.

cooling said stream to a temperature near its dew point 8. A process according to claim 6 wherein: but insufficient to cause any significant condensation 1. said second liquid stream from step (h) is passed to a thereof; stripper zone; b. compressing said cooled efiluent stream; m. hydrogen fluoride vapors are stripped from said second c. chilling said compressed effluent stream to a temperature liquid stream and returned to said compressed cooled efsuflicient to condense at least the major portion of the fluent stream of step b); and components thereof other than hydrogen; and n. said fluorinated products are recovered from said d. recovering fluorinated products from said chilled stream. t i d second li uid t am. 2. A process according to claim 1 wherein said efiluent 9. Aprocess according to claimZwherein: stream is cooled in step (a) by directly contacting same with a said feedstock to said cell comprises 1,2-dichloroethane; liquid stream comprising said feedstock. and

3. A process according to claim 2 wherein said efiluent said fluorinated products recovered in step (d) include at stream is cooled to a temperature not greater than about 165 least one of 1,1,2-trichloro-1,2,2-trifluoroethane; 1,2- dichlorotetrafluoroethane; and monochloropen- 4'. A process according to claim 2 wherein said compressed tafluoroethane. stream is chilled in step (c) to a temperature sufficient to con- 10. A process according to claim 7 wherein: dense hydrogen fluoride and higher boiling materials consaid feedstock to said cell comprises 1,2-dichloroethane; tained therein. and

5. Aprocess according to claim4wherein: said fluorinated products recovered from said stripped e. said Chilled efiluent stream from step (C) 15 passed to a second liquid include at least one of l,l,2-trich]oro-l,2,2-

first phase separation zone; trifluoroethane; 1,2-dichlorotetrafluoroethane; and

f. a liquid stream comprising hydrogen fluoride is withdrawn rnonochloropentafluoroethane.

1 l. A process according to claim 8 wherein:

said feedstock to said cell comprises LZ-dichlorocthane: and said fluorinated products recovered in step (n) include at least one of 1,1 ,Z-trichloro-l ,2,2-trifluoroethane: l,2-dichlorotetrafluoroethane; and monochloropentw fluoroethane. v 12. A process according to claim 7 wherein: said feedstock to said cell comprises l,2-dichloroethane;

said stripped second liquid stream is passed to a first distillation zone comprising a first fractionation column and a second fractionation column;

an overhead stream comprising monochloropentafluoroethane is passed from said first fractionation column to said second fractionation column;

an overhead stream comprising said monochloropentafluoroethane is removed overhead from said second fractionation column as a product of the process; and

a bottoms stream comprising l-chloro-1,l,2,2- tetrafluoroethane is recovered from said second fractionation column and recycled to said cell as a portion of said feedstock.

13. A process according to claim 12 wherein:

a bottoms stream comprising other fluorinated materials and unreacted l,2-dichloroethane is passed from said first fractionation column to a second distillation zone comrising a third fractionation column and a fourth fractionation column;

an overhead stream comprising l ,2 dichlorotetrafluoroethane is recovered from said third fractionation column as another product of the process;

a bottoms stream comprising said other fluorinated materials and said unreacted 1,2-dichloroethane is passed from said third fractionation column to said fourth fractionation column; and

an overhead stream comprising l,2-dichlorol ,2,2- trifluoroethane is recovered from said fourth fractionation column and recycled to said cell as a portion of said feedstock.

14. A process according to claim 13 wherein:

a bottoms stream comprising said other fluorinated materials and said unreacted 1,2-dichloroethane is passed from said fourth fractionation column to a third distillation zone comprising a fifth fractionation column and a sixth fractionation column;

an overhead stream comprising 1, l ,2-trichloro-1,2,2-

trifluoroethane is recovered from said fifth fractionation column as another product of the process;

a bottoms stream comprising said other fluorinated materials and said unreacted 1,2-dichloroethane is passed from said fifth fractionation column to said sixth fractionation column; and

an overhead stream comprising 1,2-dichloro-lmonofluoroethane and said unreacted 1 ,2- dichloroethane is recovered from said sixth fractionation column and recycled to said cell as a portion of said feedstock.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2425745 *Jun 10, 1944Aug 19, 1947Phillips Petroleum CoRecovery of hydrogen fluoride from gases
US3221070 *Sep 12, 1963Nov 30, 1965Thiokol Chemical CorpIsolation of tetrafluoroethylene and hexafluoropropene from the pyrolyzates of chlorodifluoromethane
US3511760 *Nov 2, 1967May 12, 1970Phillips Petroleum CoElectrochemical fluorination of organic compounds
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3950235 *Nov 15, 1974Apr 13, 1976Hoechst AktiengesellschaftHydrogen fluoride, perfluoro-olefins
US3957596 *May 21, 1975May 18, 1976Ontario Research FoundationElectrofluorination of a hydrocarbon with hydrogen fluoride
US4025567 *Nov 20, 1974May 24, 1977Phillips Petroleum CompanyPurification of fluorinated ethers
US7695595 *Apr 25, 2006Apr 13, 2010Solvay S.A.Process for the production of a purified hydrofluoroalkane, purified hydrofluoroalkane, use of the hydrofluoroalkane and method for the analysis of a hydrofluoroalkane
Classifications
U.S. Classification205/460
International ClassificationC25B3/00, C25B3/08
Cooperative ClassificationC25B3/08
European ClassificationC25B3/08