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Патент USA US2406794

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Sept- 3, 1946.
Q
A. F. BENNING arm.
' 2,406,794
PROCESS OF SEPARATING PYROLYSIS PRODUCTS OF CHLORODIFLUOROMETHANE
_ Filed Feb. 14, 1945
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Josap D. Park
BY
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ATTORAEY
2,406,794
'- ‘Patented Sept. 3, 1946
UNITED STATE s . PATENT OFFICE‘,
2,406,794
PROCESS) OF SEPARATING PYROLYSIS
KlégDUCTS OF CHLQRODIFLUOROMETH
Anthony/F. Benning, Woodstown, and Frederick
B.\,Downing, Carneys Point, N. J., and Joseph
D. Park, Wilmington, DeIJassignors to Kinetic
Chemicals, Inc., Wilmington, Del., a corporation
of Delaware
Application February 14, 1945, Serial No. 577,871
7 Claims.
(01. 202---51)
/
1
‘ products, to'anhydrous fractional distillation un- .
This invention relates to a process, particularly
der pressures of from about 50 to about 150
pounds per square inch absolute and at temper
atures adjusted to distill oil’ HCl and 02F; simul
' for separating valuable components from the re
action mixture obtained in. the pyrolysis of
CHClFa.
'
In the copending application of Downing, Ben-? 5 taneously in a molar ratio of about 2 to 1 while retaining the rest of the mixture in the still.
ning and McHarness filed February 11, 1943, as
The mixture, remaining in the still, may then be
Serial No. 475,526, there is disclosed and claimed
subjected to a further anhydrous fractional dis
a process of pyrolyzing CHClFa to produce a re
tillation under pressures of from about 45 to
- action mixture comprising mainly HCl, (IE4 and
CHCIF: with small proportions of HF and ‘higher 10 about 150 pounds per square inch absolute and
at temmratures adjusted to distill 'o? CI-IClF:
boiling products. The separation of the valuable
components of such mixture has been attended ' from the rest of the mixture. The mixture of
C2F4 and HCl may be scrubbed with water to '
with considerable di?lculty. The usual proce
obtain substantially pure CzFl and and a sub
dure has been to wash the reaction mixture with
water to remove the acidic components, drying 15 stantially pure aqueous solution of HCl. Alterna
tively, if desired, the mixture of C2F4 and HCl
and condensing the washed products and then
may be subjected to a catalytic addition process
subjecting to fractional distillation to re
to cause them to react to produce C2HC1F4 as
move the cm. During the pyrolysis, only about
more i'ully described in the copending application
25% of the CHClF2 is converted to CaF4 so that
the reaction mixture containsorganic products 20 of Benning, Downing and Plunkett ?led February
18, 1943, as Serial No. 476,332.
. ‘
which comprise about 25 to about 30 mole per
We have found that, by such process, we are
cent of C2F4, about 69 to about'74 mole per cent
able to effectively separate the reactionmixture
of CHClFz and‘ about 1 to about 6 mole per cent
into its valuable components in an easy and eco- ,
of high boiling side reaction products, admixed
with HCl in a proportion corresponding substan 25 nomical manner and to largely overcome the ob
jections of the _ method previously ‘employed.
tially to the CHClFz converted toCzFi. This re
When the 02E; is distilled in the presence of about
quires .the use of large size equipment to wash,
2 mole proportions of HCl, there is little or no
dry‘ and condense the large amounts of CHClFz
tendency for the C2F4 to polymerize, even in the
in the reaction mixture. Also, substantial
- amounts of valuable CHClFz are lost by solution 30 presence of substantial amounts of oxygen. Only
relatively small amounts of material are sub
in the wash water. This procedure further in
jected ‘to the washing, drying and condensing
volves the loss of valuable HCl in the form of an
steps, whereby large economies are effected in the
aqueous solution contaminated with HF and
process and in the apparatus employed. Further
CHClFz. Furthermore, when it is attempted to
more. the HCl is recovered in a commercially
fractionally distill the 02E; from the washed and
dried reaction mixture, there is a tendency for 35 valuable and usable form. There is also substan
tially complete recovery of unreacted CHClFz
the C2F4 to polymerize, which polymerization is
since none is lost by solution in the scrubbing
further catalyzed by~oxygen unavoidably pres
water. It will thus be apparent that by our proc
ent during the distillation.
'It is an object of the present invention to pro- - ess, we are able to e?ectively recover the valuable
vide a process for recoveringthe valuable com 40 components oi the reaction mixture in a simple
and easy manner and to effect large economies
ponents from a reaction mixture obtained by py
in the process and in the apparatus. '
rolyzing CHClFz. Another object is to provide a
In order to more clearly illustrate our inven
process for separating C2F4 from the reaction
mixture obtained by pyrolyzing CHC1F2 and par 45 tion and the best modes of carrying the same into
ticularly without substantial polymerization of _ .
C2F4. A further object is to provide a process for
recovering HCl in a usable form from the reaction
mixture obtained by pyrolyzing CHClFz.
objects are to advance the art.
Other '
Still other ob
jects will appear hereinafter. '\
The above and other objects may be accom
plished in accordance with our invention which
comprises subjecting a reaction mixture, com
prising mainly HCl, C2F4 and CHClFa and, small
proportions 'of HF and higher boiling organic.
e?ect, our invention will be described in more de
tail with reference to the accompanying drawing
which illustrates one form of apparatus, shown
somewhat diagrammatically, which may be em
ployed for carrying out our invention.
50
The apparatus shown in Fig. 1 of the drawing
comprises a pyrolysis tube H), a cooler l2, 9. com
pressor ll, a precondenser 16, a re?ux column
l8 and a dephlegmator 20, all connected ‘in series
by suitable conduits. A still pot 22 is connected
to the‘ bottom of the re?ux column [8. There is.
2,406,794
also provided a re?ux column 24.‘ a dephlegma
tor 26‘and a still pct 28 connected by suitable
The HF‘ and higher boiling organic products
will pass to the still pct 28. The residue in the
' conduits. A conduit‘ leads from the still pot 22
still pct 28 will preferably be allowed to build
to the re?ux column 24. The dephlegmator 26
up until the pot is about half full and the residue
is connected to the pyrolysis tube Ill through a 5 drawn o?' therefrom as necessary to maintain
suitable conduit and valve 30. The still pot 28
the pot about half full. If all of the still residue
is also provided with an outlet tube for withdraw
ing still residues therefrom.
were removed from the pot, the still would tend
to operate erratically. By maintaining the pot
In operation, the CHCIF: is passed through the
about half full of residue, smoother and better
pyrolysis tube HI and pyrolyzed to produce CzF4 10 still performance is obtained. The residue from
and other products. The reaction mixture passes
the still pct 28 may be discarded, if desired.
from the pyrolysis tube through the cooler i 2
Frequently, it will be desirable to treat such resi
where it is cooled to about room temperature.
due further as by washing with water to remove
The reaction products then pass to the compres
the HF and then subjecting the high boilers to
sor l4 wherein they are compressed to form 15 fractional distillation.
about 50 to about 150 pounds per square inch
The apparatus and the operation thereof, as
absolute and forced through the precondenser
above described, illustrates one type of apparatus
16 where it is further cooled to about —-20° C.
for a continuous process. Other types of appa
and then into the re?ux column l8. The mixture
ratus may be substituted therefor. Also, the
entering the re?ux column I8 is partially liquid
20' process may be operated batchwise in suitable
and partially gaseous.
apparatus therefor. Furthermore. pressures,
The re?ux column 18 and the dephlegmator 2B
higher
and lower than those disclosed, may be
are operated at temperatures, corresponding to
‘employed with suitable adjustment of the tem
the pressure employed, to distill off the C2F4 and
peratures in accordance with the principles of
the HCl simultaneously in va ratio of about 2 25
our invention. Therefore, our invention is not
moles of HCl to each mole of C2F4, the temper
to be limited to the speci?c embodiments dis
ature and pressure relationship in the dephleg
closed, but we intend to cover our invention broad
mator being equivalent to the boiling point of
1y as in the appended claims.
such mixture. With pressures of from about 90
We claim:
_ to about 100 pounds per square inch absolute, the 30
l. The process of separating valuable compo
dephlegmator temperature will be from about /
nents from a reaction mixture comprising mainly
-45° C. to about —50° C. We have found these
HCl, C2F4 and CHClFz and small proportions of
last temperatures and pressures to be the most
HF
and higher boiling organic products, of, the
practical, but higher or lower pressures may be
character of that obtained by pyrolyzing CHClFz,
used with the temperatures adjusted accord 35 the
steps which comprise subjecting the reaction
ingly.
mixture
to anhydrous fractional distillation under
The C2F4 and HCl will pass off from the de
pressures of from about 50 to about 150 pounds
phlegmator substantially uncontaminated with
per square inch absolute and at temperatures ad
other components of the reaction mixture and the
justed to distill off HCl and C2F4 simultaneously
other components of the reaction mixture will 40
in
a molar ratio of about 2 to 1 while retainingv
pass to and be collected in the still pct 22. The
the rest of the mixture in the still.
mixture of CzF4 and HCl may be passed to a
2. The process of separating valuable compo
scrubber, not shown, where the HCl will be re
- nents from a reaction mixture comprising mainly
moved by scrubbing with water to obtain sub
HCl, C2F4 and CHClFz and small proportions :of
stantially ‘pure 'C2F4 and a substantially pure
HF and higher boiling Organic products, of the
aqueous solution of HCl.
character of that obtained by pyrolyzing CHClFz,
The residue in the still pot 22 may be dis—
the
steps which comprise subjecting the reaction
carded. However, for economical operation, it
mixture to anhydrous fractional distillation under
will be preferred to force this still residue, by
pressures of from about 50 to about 150 pounds
autogenous pressure, into the re?ux column 24.
There will be a slight pressure drop so that the 50 per square inch absolute and at temperatures ad
justed to distill oil HCl and C2F4 simultaneously
re?ux column 24 will normally operate at slight
in a molar ratio of about 2 to 1 while retaining
ly lower pressures than the re?ux column I8,
the rest of the mixture in the still, and then sub
e. g. at from about 45 to about 150 pounds per
jecting the mixture in the still to further anhy
square inch absolute. If desired, a. compressor
or other means can be included to increase the 50 drous fractional distillation under pressures of
from about 45 to about 150 pounds per square
pressure in the re?ux column 24, but this will
inch absolute and at temperatures adjusted to
generally be unnecessary. Preferably, the pres
distill off the CHClF-z from the rest of the mix
sure in the reflux column 24 and dephlegma
ture.
tor 26 will be from about 45 to about 70 pounds 60 3. The process of separating valuable compo
per square inch absolute. At these pressures, the
nents from a reaction mixture comprising mainly
temperature in the re?ux column will be about
HCl,
C2F4 and CHClFz and small proportions of
5° C. to about 15° C. and the operating temper
HF and higher boiling organic products, of the
ature of the dephlegmator will be from about
character of that obtained by 'pyrolyzing
-5° C. to about 0° C. The re?ux column 24 and
pehlegmator 26 will be operated at a tempera 65 CHC1F2, the steps which comprise subjecting the '
reaction mixture to anhydrous fractional distil
ture equal to the boiling point of CHClFz, where
lation under pressures of from about 50 to about
by substantially pure CHClFz, contaminated with
150 pounds per square inch absolute and at tem
a slight amount of HF (less than 0.1 mole per
peratures adjusted to distill off HCl and C2F4
cent) , will be removed from the dephlegmator 26. 70 simultaneously in a molar ratio of about 2 to 1
The CHClFz may be recovered, but preferably will
while retainingthe rest of‘ ‘the mixture-in the
be recycled into the pyrolysis tube III as shown.
still, and then washing the mixture of HCl and
If desired, the HF, in the CHClFz, may be re
CzFa. with an aqueous medium to remove the
moved by passage through a cartridge of calcium
HCl from the CaF4.
chloride or by other suitable means.
75 4. The process of separating valuable compo
2,406,794
6. The process of separating valuable compo
nents from a reaction mixture comprising mainly
HCl, C2F4 ,and CHCIF: and small proportions
of HF and higher boiling organic products, of
the character of that obtained by~ pyrolyzing
nents from a reaction mixture comprising mainly
CHClFz, the steps whichcomprise subjecting the
the steps which comprise subjecting the reaction
‘mixture-to anhydrous fractional distillation un
reaction mixture to anhydrous fractional distilla
tion under pressures of from about 50 to about
150 pounds per square inch absolute and at tem
peratures adjusted to distill off HCl and C2F4
HCl, 0E4 and CHCIF: and small proportions of
HF and higher boiling organic products, of the
character of that obtained by pyrolyzing CHClFa,
der pressures of from about 90 to about 100
pounds per square inch absolute'and at tempera
tures of from about -45° C. to about -50° C., to
simultaneously in a molar ratio of about 2 to 10 distill off 1101 and C2F4 simultaneously in a molar
l while~ retaining the rest of the mixture in the
ratio of about 2 to 1 while retaining the rest of
still, and then washing the mixture of HCl and
the mixture in the still.
C2F4 with a small amount of water to obtain a
'7. The process of separating valuable compo
commercial aqueous solution of HCl and sub
nents from a, reaction mixture comprising mainly
stantially'pure C2F4.
,
5. The process of separating valuable compo
nents from a reaction mixture comprising mainly
HCI, 02F‘ and CHClFz and small proportions of
15 HCl, C2F4 and CHClF: and small proportions of
HF and higher boiling products,of the character
of that obtained by pyrolyzing CHClFz, the steps
which comprise subjecting the reaction mixture
HF and higher boiling organic products, of the
to anhydrous fractional distillation under pres
character of that obtained by pyrolyzing CHClFa, 20 sures of from about 90 to about 100 pounds per
the steps which comprise subjecting the reac
square inch absolute and at temperatures of from
tion mixture to anhydrous fractional distillation
about ~45° C. to about —50° C., to distill oil HCl
- under pressures of from about 50 to about 150
and CzF4 simultaneously in a molar ratio of about
pounds'per-squareinch absolute and at tem
2 to 1 while retaining the rest of the mixture in
peratures adjusted to. distill off HCl and C2F4 25 the still, and then subjecting the mixture in the
simultaneously in a molar ratio of about 2 to 1
still to further anhydrous fractional distillation
while retaining the rest of the mixture in the
under pressures of from about 60 to about '70
still, and then subjecting the mixture in the still
pounds per square inch absolute and at tempera- '
to further anhydrous fractional distillation under
of from about 0° C. to about —-_5° C. to distillv
pressures of from about 45 to about 150 pounds 30 tures
o?
the
CHC1F2 from the rest of the mixture.
_r square inch ‘absolute and at temperatures
. ‘
ANTHONY F‘.v BENNING.
adjusted to distill off the CHClFa from the rest
FREDERICK B. DOWNING.
recycling
the
distilled
of the mixture, and
JOSEPH D. PARK.
.
-
CHCIF: to the pyrolysis operation.
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