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Патент USA US3033779

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May 8, 1962
F. OLSTOWSKI ET AL
3,033,767
PREPARATION OF FLUOROCARBONS
Filed sept. 2, 1958
Owó0f
700
800
900
E/ecff-o/y/e Tempera/arg, ‘C
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Unite
States
atent
” ice
3,933,767
Patented May 8, 1962
2
l
be obtained with the anode of loosely confined carbon par
3,933,767
PREPARA’HÜN 0F FLUÜRÜCONS
ticles, low electrolyte temperatures and high anode current
densities must be used. Even with a low temperature the
amount of fluorocarbon obtained which have a higher
Franciszek (blstowski, Freeport, and .lohn I. Newport El,
Lake Jackson, Tex., assignors to The Dow Chemical
Company, Midland, Mich., a corporation of Delaware
Filed Sept. 2, 1958, Ser. No. 753,438
15 Claims. (Cl. MA1-«62)
ñuorocarbons generally may be more cheaply produced by
This invention relates to a process for the preparation
confined carbon particles than by iluorination of chlori
molecular weight than hexafluoroethane is not great. A1
though hexatluoroethane and higher molecular weight
electrolysis of a metal fluoride with an anode of loosely
of iiuorocarbons, and more particularly, to the electroly 10 nated or unsaturated hydrocarbons, a process is greatly
desired whereby hexañuoroethane and higher molecular
sis of non-volatile molten metal iiuorides to prepare these
iluorocarbons could be produced in larger amounts and
compounds.
more economically, especially fluorocarbons, such as octa
This application is a continuation-in-part of patent ap
fluoropropane and higher.
plication Serial No. 663,966, tiled June 6, 1957, now
It is, therefore, among the objects of this invention to
abandoned.
provide an improved process for the preparation of fluoro
Presently, the preparation of ilumine-containing com
carbons by the electrolysis of non-volatile molten metal
pounds has been mainly limited to fluorination of chlo
ñuorides. A further object is to provide an improvement
rinated or unsaturated hydrocarbons by the use of iluori
in the electrolysis of used metal iluorides so that relatively
mating agents, such as hydrogen fluoride, or fluori
high portion of the fluorocarbon anode product is hexa
nating of saturated hydrocarbons by elemental iluorine.
iiuoroethane and higher molecular weight iluorocarbons.
These processes involve handling hazardous materials
Another object is to provide a process for the electrolytic
which are expensive and require special equipment. Cer
production of metals from iluorides.
tain metal ñuorides are cheap raw materials and a process
The above and other objects are attained according to
whereby tluorocarbons could be prepared by electrolysis
of these fused metal ñuorides would considerably reduce 25 the invention by passing an electric current through a
molten electrolyte at a temperature of at least 600° C.
the production cost of these compounds.
between a porous carbon anode having a permeability in
In the electrolysis of molten metal tluorides a trouble
some phenomenon known as “anode effect” occurs which
Without any obvious external reason causes the voltage to
the range of 1 to 40 and an insoluble cathode.
The
molten electrolyte consists essentially of at least metal flu
increase suddenly and the amperage to decrease. Al 30 oride which is stable and non-volatile at the electrolysis
temperature and is non-wetting in respect to the anode
though this phenomenon may occur under many condi
selected from the group consisting of alkali metal ñuo
tions, it is most often encountered when the electrolyte
rides, alkaline metal earth ñuorides, and earth metal fluo
is at a high temperature and the cell operating at a high
rides. Upon the electrolysis, an anode product contain
anode current density. During the anode effect, the an
ing a series of homologous ñuorocarbons including both
ode seems to be entirely surrounded by gas Íilm and the
saturated and unsaturated is obtained. The anode prod
current is carried from the anode to the electrolyte
uct is gaseous at the electrolysis temperature and will come
through the gas ñlm mainly by a large number of shifting
arcs. Once the gas lilm is established it tends to perpetu
oit as the anode gas, but may contain higher molecular
ate itself, since the arcing generates localized heating
weight compounds, such as perlluorobenzene, perñuoro
which causes the gas to expand. Voltages which under 40 toluene, and perliuoronaphthalene, as well as aliphatic
fluorocarbons which are oils at room temperature.
normal operations are around 4 to 6 volts may increase up
The invention may be more easily understood when the
to over 60 volts during this period, and the cell can not be
detailed discussion is considered in conjunction with :the
operated under these conditions. It is necessary to vig
orously agitate the electrolyte to remove the gas iilm,
raise the anodes from the melt, or reverse the current to
overcome this effect. Sometimes the anode effect is ac
drawings, in which:
`FIIGURE 1 diagrammatically illustrates an electrolytic
has been speculated that some carbon halides are formed.
cell in which the invention can be carried out, and
FIGURE 2 shows the effect of temperature of the elec
trolyte on the composition of the anode product Obtained
Kroll in “Metal lndustry,” August 1953, pages 141-143,
from the electrolysis.
companied by a loss in weight of the carbon anode and it
reported that in an aluminum cell the anode gas during 50
the anode elîect contained a small amount of carbon
tetrailuoride. Thus, even though a small amount of fluo
l
The electrolytic cell diagrammatically shown in FIG
URE 1 comprises a metaltank 1 having a cover plate 2,
an electrical non-conducting cylindrical liner 3, and _an
anode assembly indicated generally as 4. The cover plate
rocarbons may be formed during the anode etlect, it is
is fastened to tank 1 by means of a multiplicity of screws
totally impractical to operate an electrolytic cell under
anode effect conditions to prepare ilumine-containing 55 5 but other means, such as clamps, may be used. >The’
anode assembly comprises a cylindrical graphite or carbon
compounds.
In United States Letters Patent No. 785,961, a process
for the preparation of carbon tetrañuoride by electrolysis
anode holder 6 having a passageway 7 in the center of
the holder extending along the longitudinal axis. At the
lower end of holder 6 a hollow-cup porous anode Si is
of sodium or potassium fluoride at 1000° C. and at a
voltage of 8 volts is described. An anode comprised of 60 attached to the holder. At the other end of the holder,
a pipe line 9 is attached so that the pipeline communi
soft carbonaceous material surrounding a hard carbon or
cates with the passageway 7. A lead 11 is electrically
graphite rod is used. In the method described only carbon
attached to the outer surface of tank 1 and another lead
tetrafluoride may be produced. In a copending patent
12 is attached to holder 6 through which the current
application of instant inventors, patent application Serial
No. 750,270, i’iled July 22, 1958, a process is described 65 to the cell is supplied. The anode assembly is inserted
into tank 1 with holder 6 passing through an opening
whereby hexañuoroethane and higher molecular weight
in cover plate 2‘ in which an electrical non-conducting
ñuorocarbons may be produced by using an anode of
seal `13: forms a gas tight seal between the holder yand
carbonaceous material in particulate form loosely con
the cover plates. The hollow-cup porous anode 8 is
fined. However, the current efficiencies and power etli
ciencies of a cell using a carbonaceous material in partic 70 immersed in the molten iluoride placed in the tank and
indicated by number 14 in the drawing. A metal 15 inert
ulate form could be materially improved. Also, while
other ñuorocarbons other than carbon tetrafluoride may
to the lluoride electrolyte and having a melting. point
3,033,767
3
>below the electrolysis temperature, such as lead, is placed
‘inthe cell lwhich »settles to the bottom of the tank con
tacting the tank and thus acts as a molten cathode. The
inert metal to act as a cathode is generally used when
'the metal Vdeposited at the cathode is lighter than Vthe
electrolyte. This simpliûes the Vcell construction, since
-no arrangement is necessary to remove `the metal deposited
'fromïthe surface of the electrolyte. In the operation of
the cell, the cover plate is tightened down to form a
:gas :tight seal andthe cell is placedin a furnace and
'heateduntil the electrolyte has attained the desired tem
perature. The current isthen passed through the elec
trolyte. The iluorocarbons formed during the electrolysis
‘pass >from fthe surface of the porous anode 8 into the
>opening ofthe anode and then discharge through passage
way 7 and pipeline 9. The anode product obtained from
be used as main constituent of the electrolyte but may
be tolerated in small amounts up rto- around 5 percent.
Although only one of the alkali metal fluorides, alkaline
earth metal ñuorides, or earth metal liuorides may be
used as the electrolyte, a mixture of these metal ñuorides
is often used to increase the conductivity or lower the
melting point of the bath. For this purpose, lithium fluo
ride is most ‘commonly added to the other metal ñuorides,
but other mixtures and combinations may also be used.
When other 'lluorides are added to-either increase the
conductivity or lower the melting point or" a particular
metal :iluoride bath, the ñuorides of metals which are
higher in the electromotive series or more electronegative
than the metal to be extracted at the cathode from the
.particular bath are preferred. By using iluorides of metals
-the cell is then further processed by known methods to
more electronegative, these metals will not deposit out
`at the cathode with the desired metal except at excep
separate the particular fluorocarbons obtained.
tionally high cathode current densities. Thus, the cathode
`
The composition of the anode gas or the amounts of
product is not contaminated under normal operating con
`the diñerent ñuorocarbons obtained as an anode product 20 ditions. Also in continuous operation of the cell, the
is a?ected by the temperature and somewhat by the anode
metal fluoride added to the electrolyte is not depleted by
`current: density. FIGURE 2 illustrates the eiîect of
the electrolysis and only the lluoride of the particular metal
temperature upon the composition of the fluorocarbon
being deposited at the cathode has tobe added continu
»product obtained 'in the electrolysis of a lithium fluoride
ously. For example, when lithium iluoride is added to
sodium ñuoride mixture as a function of the temperature
a magnesium ñuoride bath, the lithium is more electro
.of-the electrolyte. The details of the tests and data on
negative than magnesium and thus will not deposit out
which the figure is based are set forth in Example HI
at the cathode. Once >the lithium iluoride is added to
below. 4In `FIGURE .2, theabscissa represents the tem
the bath it will not be depleted bythe electrolysis and
perature ofthe electrolyte at which the electrolysis was
only magnesium -ñuoride has to be added for continuous
effected and the ordinate represents a composition of the 30 operation.
ñuorocarbon product obtained atthe anode in mole per
Illustrative examples of the mixtures that may be used
cent. To obtain the plot shown in FIGUREAZ, relatively
with the metal which will be preferentially deposited at
low anode currentdensities in the range of l to 5 amperes
the cathode are shown in the table below.
per square inch were used.
`
>In FIGURE. 2 it will be noted'that the amount of 35
hexatiuoroethane.increased’frorn approximately 35 mole
- ercent at 700° C. as the temperature of the electrolysis
Bath composition:
Metal preferentially
deposited at the
cathode
NaR‘LiF ______________________________ __ Na
increased to av point of .around 66' mole percent at 900° C.
It then decreased as the temperature was increased. _At
MgFg-LÍF _____________________________ __ Mg
41000u C., the ñuorocarbonzproduct obtained contained
BaF2~LiF ______________________________ __ Li
AlF3-LiF _____________________________ __ Al
only >around 45 percent hexafluoroethane. The amount of
octafluoropropane decreased with increase in temperature
AlF3~NaF ____ _.`. ________________________ __ Al
of the electrolysis. At 700° C. the Vproduct obtained con
AlF3-NaF~LiF _________________________ _.. Al
AlFZ-CaFZ‘MgFz _______________________ __ Al
MgF2~LiF-NaF ________________________ __ Na
tained approximately 14 percent octañuoropropane which
decreased to approximately l2 percent at 800° C. and 45
then down toabout3 percent at 900° C.
Ata relativelylow anode current density, the'ternpera~
MgFz-NaF
MgFg‘LiF'CaFz
____________________________
________________________ __
..._ Na
MgF2-CaF2 _____________________________ __ Mg
ture has considerable effect upon the `composition of the
AlFg‘LlF‘M'gFZ ________________________ ..._
ñuorocarbon product obtained as shown in FIGURE 2.
`Y'Fa'Lil-i _______________________________ __ Y
However at Vhigh, anode current densities, such as l2 50
Similar procedure of electrolysis may be employed
amperes per square inch and above, the composition of
regardless of the metal iiuoride or fluorides used as elec
the fluorocarbon product obtained does not dilïer greatly
trolyte. However, the optimumY conditions for particular
for temperatures in the range of 700° to 900° C. This
electrolytes used may vary to a certain degree. The tem
is> especially true’for the Vhigher molecular weight fluoro`
carbons. At ahigh anode current density, a lluorocarbon 55 perature of the bath must be at least at the melting point
product containing'about 12 mole percent octatluoro
propane and over `2 mole percent of octaiiuorobutenemay
be obtained at temperatures as high as 900° C.
VWhile the. amounts of carbon tetrafluoride, hexafluoro
of the bath so that the electrolyte is in a molten state.
The maximum emperature that may be used is either
limited by the cell structure, the stability and volatility
of the particular electrolyte employed, or the fluorocar
-bon desired. Since at a lower temperature the construc
ethane, and the higher molecular Weight fluorocarbons 60 tion of the cell is simpliñed and also a greater amount of
will vary somewhat with the particular metal lluoride or
the higher molecular Weight fluorocarbons is obtained,
iluorides employed, vsimilar results as those shown in
a temperature in the range of 700° to l000° C. is pre
FIGURE i?.V are obtained with the other metal fluoride
ferred for all the electrolytes, except for a LiF~NaF-AlF3
or fluorides. Alkali metal `iiuorides, alkaline earth metal
65 bath where the preferred temperature is in the range of
ñuorides, .and earth metal ñuorides which do not wet the
650° C. to 800° C. When Áit is desirable to obtain the
anode-'and are non-volatile and stable at the electrolysis
maximum amount of octofluoropropane, a temperature
temperature and mixtures thereof may be used as the elec
in the range of`650° C. to 850° C. is used.
trolyte in the production of these fluorocarbons. illus
While anode current densities from 4below l and up to
trative examples of'these metal ñuorides are magnesium 70 100 amperes per square inch may be used with certain
fluoride, aluminum fluoride, Vsodium fluoride, barium fluo
porous anodes, anode current densities in the range of
ride, strontium fluoride, calcium fluoride, lithium ñuoride,
l to 40 amperes per square inch are generally employed,
cesium fluoride, and a yttriu-rniluoride. An example of
preferably in the range of 2 to 15 amperes per square
a non-volatile,'stable metal ñuoride which wets .the anode
inch especially if it is desired to obtain higher molecular
is potassium 'ñu'oride Thus, potassium fluoride cannot 75 weight ñuorocarbon than carbon tetratluoride.
The
3,033,767
5
were obtained which had a molecular weight of around
410. The porous anode had a weight loss of 13.7 grams
and 3.4 grams of aluminum were produced. The above
run was repeated with an electrolyte comprising 62 weight
cathode current density is generally in the range of 1 to
30 amperes per square inch. To obtain these current
densities, a voltage up to 20 volts may be employed, but
a voltage in the range of 4 to 10 volts is preferred.
Porous carbon anodes generally used in the elec
percent aluminum fluoride and 38 weight percent sodium
trolysis of the metal fluorides and in the preparation of
fluoride. Approximately the same results as above were
the iluorocarbons are those having a permeability of at
least l and not greater than 40, preferably in the range
of 4 to 20. While anodes having a permeability greater
obtained.
than l may be used in special cases, no beneñcial ad
vantage is obtained. The maximum anode current densi
In a manner similar to above, íluorocarbons are ob
10
ty which may be used without encountering anode elîect
is proportional to the permeability, increasing with an
increase in permeability. With the permeabilities gener
ally used, normally all practical anode current densities
may be used without encountering the objectionable
phenomenon. In special cases, however, where relatively
low current densities are to lbe employed, an anode hav
ing a permeability as low as 0.2 may be used, if desired.
tained by the electrolysis of LiF, NaF, MgF2, NaF-Li‘?l,
BaF-LiF, SrFz-LiF, NaF-LiF-AlF3, etc.
Example 1I
To show the eiîect of a porous anode on anode
effect, an electrolysis similar to that in Example I was
carried out at a current density of 4 amperes per square
inch at a voltage of 5.45 volts for about 3 hours. The
cell operated smoothly and the anode gas contained ap
proximately 16 percent of carbon tetrañuoride, 70 weight
percent of perlluoroethane and higher gaseous fluoro
Likewise, an anode having a permeability greater than 40 20 carbons, and 14 weight percent of oil and tar.
may also be used, but the amount of the higher molecu
The porous anode was replaced first with an ordinary
lar weight ñuorocarbons obtained decreases.
graphite anode and then with an ordinary carbon anode
Permeability, as used herein, is expressed as the
and the cell again operated as above. 'With both of
amount of air passing through the porous carbon anode
in cubic feet per minute per square foot per one inch 25 these anodes the cell immediately went into anode effect
and very little current passed through the cell even at high
thickness at a pressure differential of 2 inches of water.
voltages.
When the ordinary anodes were replaced with
The term “carbon anode,” as used herein, means anodes
the porous anode, the cell again operated smoothly pro
made by combining ñne carbon particles with a binder
and sintering to form a cohered mass and includes anodes
ducing lluorocarbons.
made from amorphous carbon, such as petroleum coke, 30
coal, carbon black, etc. and allotropic carbon, such as
Example III
To illustrate the eiîect of electrolysis temperature upon
the fluorocarbon composition in the anode Product, a
graphite. The term “porous,” as used herein, means gas
permeable.
The shape of the anode is immaterial. A hollow-cup
type anode as shown in FIGURE 1 may be preferred
where high molecular weight iluorocarbons are obtained.
These compounds may `be readily drawn into the hollow
anode and easily removed from the system. When a solid
porous anode is used, it may be necessary in some cases
series of runs was made where an electrolyte consisting
essentially of 48 percent lithium iluoride and 52 weight
percent sodium fluoride was subjected to electrolysis at
relatively low anode current density at different tem
peratures.
An electrolytic cell similar to that shown in FIGURE
to use a hood or shield to enclose the anode to entrap 40 l was used except that a diíiîerent type of a porous car
the anode gases as they are formed and released. Other
types and shapes of porous anode assemblies which are
bon anode assembly was used. The porous carbon anode
assembly consisted of a cylindrical graphite lead which
apparent to those skilled in the art may be used.
was enlarged at the lower end and the passageway along
Various known electrolytic cell construction and vari
the longitudinal axis of this lead was also enlarged at the.
ous known types of cathodes may be used. The particu 45 lower end. A cylindrical porous carbon plug 1 inch in
lar cathode adopted will depend upon the metal being
diameter was inserted into the enlarged passageway leav
deposited.
The term “earth metals,” as used herein, means the
ing % inch of the plug extending below the graphite
lead. Thus the area of the porous carbon anode exposed
to the electrolyte was approximately 3.5 square inches.
the third group of the periodic system.
50
The porous carbon plug had a permeability of 4 as per
The following examples further illustrate the inven
manufacturer’s speciiìcation.
tion but are not to be construed as limiting it thereto.
`In the operation of the cell, lead which was to act as
elements aluminum, scandium, yttrium, and lanthanum of
Example I
a molten cathode and 1000 grams of a mixture contain
An electrolytic cell similar to the one shown in the at
tached drawing and equipped with a porous graphite
anode was used in the electrolysis of an aluminum iluo
ing 48 weight percent lithium fluoride and the remainder
sodium fluoride were placed in the cell inside of an alu
mina liner which had an inside diameter of 3 inches and
was 5 inches high. The cell was then placed in a fur
ride-lithium fluoride electrolyte. The permeability of the
nace and heated to the predetermined temperature. When
porous anode as rated by the manufacturer was 4. How
ever, in testing the anode -by a method similar to that 60 the electrolyte reached the desired temperature, the por
ous carbon anode assembly was inserted into the cell so
used by the manufacturer, an air rate of 3.7 cubic feet
that the porous plug was immersed in the electrolyte and
per minute per square foot per inch at a dilîerential pres
the cover plate tightened down to form a gas tight seal.
sure of one inch of water was obtained. The cell was
placed in a furnace and the electrolyte was maintained
Current was applied to the cell and it was operated for
l hour while the electrolyte was maintained at the de
at 900° C. A voltage of 4.6 volts was used and an aver
sired temperature. The anode gas formed by the elec
age anode current density of 2 amperes per square inch
trolysis was forced up the passageway of the carbon
was obtained. Molten aluminum in the bottom of the
holder holding the porous anode and was collected in a
cell served as the cathode.
The >anode gases were passed through >an oil trap and 70 500 milliliter glass gas bomb by displacing the air in
the bomb. The gaseous product in the bomb was an
collected in a glass sampling bomb. The gases were
alyzed by infra-red to determine the composition of the
analyzed by infra-red and found to contain 2.2 grams
fluorocarbon product obtained.
of carbon tetrañuoride, 8.4 grams of C2126 and 1.6 grams
The pertinent data and results obtained which are
of higher gaseous ñuorocarbons having the formula,
CnFzMg. In the oil trap, 2.25 grams of liuorocarbon oil 75 plotted in FIGURE 2 are shown in the table below.
agossfrsv
7
‘.8
Small amounts of oily tars were obtained but were not
The pertinent data~and results‘obtained are'shown in
analyzed.
the table below.
Electrelyte
Cell
Cell
ature,
density
amps.
tial,
° C.
amps/in.2
temperi
Elec-
Fluorocarbon analysis based
Anode
current current, poten-
’ trolyte
on total tlncrocarbons, mole
temperature,
percent
° C.
volts
>Fluoroearbon analysis based
anode
Cell
Cell
current current, potendensity amps. tial,
amps/in.2
700
1.25
5
5.5
44.6
35
.15,1
____
____
2.9
10
6.8
34.1
47.9
11.8
1.0
____
900
1,7000
2.9
4.9
l0
20
3.1
4.5
34.8
55
(i5
45
____
-___
_--____
_...
____
GF4 .CiFi CsFs CaFe CiFs
'700
800
900
In a manner similar to that described above the cell
was operated atrrelatively high anode current densities at
different temperatures.V
The pertinent data and results obtained are shown in
the table below. Small amounts of oily tars were also
obtained butwere not analyzed.
Electrolyte
Cell
Cell
700
13. 5
40
13. 3
36. 2 V43. 5
14. 5
2. 2
.3. 6
12. 1
40
l0
36. 4
5l
11.8
1.0
____
900
14. 3
40
9
38.1
47
11.9
1. 2
2. 1
To show .the eiiect upon the composition of the ñuoro
carbon product obtained with a porous carbon anode
made by combining line carbon particles with a binder
and cindering the mixture to form a porous solid mass
as used in this invention as compared to the composition
obtained with an anode made of carbonaceous material in
particulate form loosely confined, a series of runs was
60
50
82.2
v31
50
‘17
-___
-___
___-
____
.___
____
___.
____
.....
What is claimed is:
1. A process for thepreparation of'iluorocarbons which
comprises passing an electric current through a molten
electrolyte at a temperature of from 600° C. to l000° C.
between a cohered porous carbon anode having a perme
ability in the'range of l to 40 and an insoluble cathode
at an anode current density in the range of from l to 1‘00
amperes per square inch to `obtain an anode product
’
800
85
75
96
siderably greater voltage is required.
GF4 CzFß CaFg CaFd C4F3
.
7
20
35
cent obtained with a porous carbon'anode. Also va con
on total lluorocarbons, mol@l
percent
1
3
45
From the results obtained above, it can be seen that
J with an anode of loosely Yconfined petroleum coke the
amount of ñuorocarbons of higher molecular than hexa
iiuoroethane which can only be obtained at temperatures
below 800° C. is'considerably less than the 15 mole per
Fluoroearbon analysis based
Anode
temper- current current, potenature,
_ densi ty amps.
tial,
'° C.
amps/in.3
volts
percent
volts
GF4 CzFe CsFg CsFo ClFg
800
on total ñuorocarbons, mole
30
containing iluorocarbons, said molten electrolyte consist
ing essentially of at least one metal ñuoride which is non
wetting in respect to the anode and stable and non-volatile
at electrolysis temperature selected from the group con~
sisting of alkali metal fluorides, alkaline earth metal iluo
rides, and earth metal ñuorides, and recovering the fluoro
carbons from the `anode product.
2. A process according to claim'l wherein the temperature isin the range of 700° to 1000° C. and at an
anode current density of from 1 to 40 amperes per square
inch.
,
made with an anode made of loosely conüned particles
3. A process according to claim '2 wherein the molten
of petroleum coke.
'
electrolyte is an alkali metal ñuoride which is stable and
A cell «similar to that shown in FIGURE 1 was Vused
non-volatile at the operating temperature and is non
except .that a solid '% inch graphite rod was used in
wetting in respect to the anode.
stead of the carbon holder with a passageway shown in
4. A process according to claim 2 wherein the molten
the drawing. Also, the cover plate had anadditional open 45 electrolyte is a mixture of alkali metal iiuorides `which are
ing from >that shown Vinthe drawing through which a pipe
stable and non~volatile at the electrolysis temperature
was Vextendeda short way into the tank. The anode
and are non-wetting in respect to the anode.
gas formed in the cell was Withdrawn through this pipe.
5. A process according to claim 2 wherein Vthe molten
Lead which was to act as a molten cathode and 1000
electrolyte consists essentially of at least one alkali metal
grams `of a mixture or" lithium fluoride and sodium ñuoride 50 fluoride and one alkaline earth iluoride which are stable
similar to that used above was placed inside of the 3 inch
and non-volatile at the electrolysis temperature and are
in diameter alumina liner. The cell was then placed
non-wetting in Yrespect to the anode.
in a furnace and heated until the lithium ñuoride and
6. A process according to claim 2 wherein the molten
sodium l'luoride mixture was molten. The 3A inch graphite
electrolyte consists essentially of at least one alkali metal
rod was thenextended into the cell until it almost touched 55 fluoride and one earth metal Viluoridewhich are stable and
the ‘surface of the electrolyte. Petroleum coke in par
non-volatile at the electrolysis temperature andnon-wet
ticulate form passing through a 'Vs inch mesh screen
ting in'respect to the anode.
and being retained on'a 40 mesh standard screen was then
7. A process for the preparation of iluorocarbons, which
comprises passing an electric lcurrent through a molten
placed on top ofthe electrolyte to form a bed 2 inches
thick Within the alumina liner and surrounding the 3A 60 electrolyte consisting essentially of sodium fluoride and
lithium fluoride between a cohered porous carbon anode
inch graphite rod. Since the petroleum coke’was con
having a permeability in the range Vof 4 to 20 and an'
insoluble cathode `at a temperature in the range of 700°
to 1000D C. and at an anode current density in the range
The cover plate was bolted down and the cell was then
65 of from l to 40 amperes vper square inch to obtain an
further heated until the predetermined temperature was
anode product containing iiuorocarbons, and recovering
reached. Current was passed through the cell and the
the tluorocarbons from the anode product.
.
anode yproduct obtained within the cell collected in a
8. A process for the preparation of iiuorocarbons which
siderably lighter than the molten metal iluorides, it’lloated
upon the surface of the electrolyte.
bomb and analyzed -by intra-red from which the compo
sion Vof the iluorocarbon product was determined.
To determine the “anode current density,” the anode
comprises passingan electric current .througha molten
electrolyte consisting essentially of sodium ñuoride and
lithium _fluoride at a temperature in the range of 650°
to 850° C. betweena cohered porous carbon anode hav
upon which the petroleum coke iloated. Thus the total
ing a permeability in the range of 4 to 20 ‘and an in
cell `current in amperes was divided by the area of the
solublecathode at an anode current'density in the'range
electrolyte subjected -to- the petroleum coke.
75 of 2 `to 15 amperes per square vinch to «obtain ¿anode
area was considered to be equal to the area of electrolyte
La
3,033,767
9
10
product containing ñuorocarbcns, and recovering the
fluoride and lithium fluoride between a cohered porous
carbon anode having a permeability in the range of 4 to
ñuorocarbons from the anode product.
9. A process for the preparation of ñuorocarbons, which
20 and an insoluble cathode at a temperature in the range
of 700° to 1000° C. and at an anode current density in
the range of from 1 to 40 amperes per square inch to
comprises passing an electric current through a molten
electrolyte consisting essentially of magnesium fluoride
obtain an anode product containing ñuorocarbons, and
recovering the fluorocarbons from the anode product.
14. A process for the preparation of ñuorocarbons
an insoluble cathode at a temperature in the range of
which comprises passing an electric current through a
700° to 1000° C. and at an anode current density in the
range of from 1 to 40 amperes per square inch to obtain 10 molten electrolyte consisting essentially of aluminum
ñuoride and lithium fluoride at a temperature in the range
an anode product containing iiuorocarbons, and recovering
of 650° C. to 850° C. between a cohered porous carbon
the tluorocarbons from the anode product.
anode having a permeability in the range of 4 to 20 and
10. A process for the preparation of ñuorocarbons
an insoluble cathode at an anode current density in the
which comprises passing an electric current through a
and lithium fluoride between a cohered porous carbon
anode having a permeability in the range of 4 to 20 and
molten electrolyte consisting essentially of magnesium
15 range of 2 to 15 amperes per square inch to obtain anode
fluoride and lithium ñuoride at a temperature in the range
of 65 0° to 850° C. between a cohered porous carbon anode
having a permeability in the range of 4 to 20 and an
insoluble cathode at an anode current density in the range
of 2 to 15 amperes per square inch to obtain anode prod 20
uct containing tluorocarbons, and recovering the fluorocar
product containing iluorocarbons, and recovering the fluo
rocarbons from the anode product.
15. A process for the preparation of hexañuoroethane
and higher molecular weight ñuorocarbons which com
prises passing an electric current through a molten elec
trolyte at a temperature in the range of 650° to 850° C.
bons from the anode product.
11. A process for the preparation of ñuorocarbons,
which comprises passing an electric current through a
between a cohered porous carbon anode having a perme
ability in the range of 4 to 20 and an insoluble cathode
at an anode current density in the range of 2 to 15 am
molten electrolyte consisting essentially of magnesium 25 peres per square inch to obtain an anode product con
ñuoride, calcium ñuoride and lithium fluoride between a
cohered porous carbon anode having a permeability in
taining hexañuoroethane and higher molecular weight
íluorocarbons, said molten electrolyte consisting essen
tially of at least one lmetal fluoride which is non-wetting
the range of 4 to 20 and an insoluble cathode at a tem
perature in the range of 700° to 1000° C. and at an anode
with respect to the anode, stable, and non-volatile at the
current density of from 1 to 40 amperes per square inch 30 electrolysis temperature selected from the group consist
to obtain an anode product containing ñuorocarbons, and
ing of alkali metal fluorides, alkaline earth metal ñuorides,
recovering the fluorocarbons from the anode product.
and earth metal fluorides, and recovering the fluorocar
12. A process for the preparation of ñuorocarbons
bons from the anode product.
which comprises passing an electric current through a
molten electrolyte consisting essentially of magnesium 35
References Cited in the file of this patent
ñuoride, calcium fluoride, and lithium fluoride at ‘a tem
UNITED STATES PATENTS
perature in the range of 650° to 850° C. between a co
hered porous carbon anode having a permeability in the
range of 4 to 20 and an insoluble cathode at an anode
current density in the range of 2 to 15 amperes per square 40
inch to obtain anode product containing ñuorocarbons,
and recovering the iiuorocarbons from the anode product.
13. A process for the preparation of ñuorocarbons,
which comprises passing an electric current through a
molten electrolyte consisting essentially of aluminum 45
785,961
2,592,144
2,684,940
2,693,445
2,841,544
Lyons et al ___________ __ Mar. 28,
Howell et al ____________ __ Apr. 8,
Rudge et al ____________ -_ July 27,
Howell et al ___________ __ Nov. 2,
Radimer ______________ __ July l,
1905
1952
1954
1954
1958
FOREIGN PATENTS
896,641
Germany ____________ __ Mar. 15, 1954
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