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Патент USA US2108829

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Feb. 22, 1938. '
I
J. -slxT ET AL
PROCESS OF PRODUCING KETENE
Filed Sept. 6, 1934
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2,108,829
nasal resa-,1938
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2,108,829
UNlTED STATES PATENT OFFICE
2,108,829
PltooEss or rnonnomo KETENE
Johann Sixt and lMartin Mugdan, Munich, (llor-`
many, assignors to Consortium für Elektro
chemischc Industrie. G. m. b. H., Munich, Ger
many, a corporation oi' Germany
Appllooaop september s, 1934, serial No. 'Masas
~
In Germany September 16. 1933
9 claims. (ci. zoo-12s)
,This invention relates to a process of producing ketene from acetic acid. _
~
the ketene to recombine with the excess acetic
'
acid and thereby disappear. It was never thought
In the processes disclosed in Meingast 8i”
Mugdan Patents No. 1,570,514 of Jan. 19, 1926,
5 No. 1,636,701 of July 26, 1927, and No. 1,946,707
of Feb. 13,- 1934 and other patents, acetic anhydride is obtained by heating acetic acid vapor to
possible to obtain ketene as a ilnal product, hence
no measures have ever been taken with a view to
its isolation or further elaboration. The applica- 5
tion of such measures, herein described, is essen
-‘ tial for the present process. We have also found
temperatures of 40G-800° C., in the presence of
catalysts. The reaction takes place “according to
lo the equation: '
that the partial recombination of the ketene with
water to form acetic acid in the spaces behind the
.
’
_
ddl
H g
a
t
ng o
th
_
u
e vapors sma
m
quant
f
es o nitrogen
~
ZCHÑOOH‘@
o) 2O+H2O
_ containing bases such as ammonia, pyridine, di
y It has been ~assumed that the primary product methylamine or trimethylamine.
'
0f this' Splitting up is not anhydride.,but ketene.
15 which is generated according to equation:
The invention is illustrated by the following ex
amples taken in connection with the accompany- 15
cnooooH=CHico+Hio
and only then forms `anhydride with -acetic acid
beyond the heating zone, according to the follow20 ing formula:
apparatus for carrying4` out the process.
Example I
,
'
__
CH2CO+¢H3COOH(CHQCO) 20
We have found that the ,ketene primarily
formed according to-this assumption can be pre'25 vented to a great, in fact to a predominant degree,
from combining with acetic acid and water to
form anhydride 0r acetic vafßldiëmd can be iSOlated.
by Acarrying out the process of splitting up the
acetic acid under leSS than atmospheric pressure,
30 at between 400-900° C. and by subjectinge the
vaporous product of the splitting, which is under
vacuum, to condensation by cooling under `such
conditions as to allow the ketene insufficient time
to combine with the acetic acid or the water.
thi
bo
In '
sem diment of the invention, which is
illustrated
in Fig. 1, we employed an electrically
20
_heated copper tube 1 measuring 25 mm. in diam
eter and 1000 mm. in length, iìlled with pea size
“Carborundum” pieces coated with sodium meta- 25
phosphate. One end of the tube was connected
to an acetic acid evaporator 2 while the other end
was connected to a narrow tube 3 >adapted to carry
oil’ the dissociation products. The tube emptied
into a Liebig cooler 4 to which a cooled receiver 30
or condenser 5 was joined. 'I'his was followed by
a second condenser 6 cooled by means of cooling
brine of minus 50° C. From condenser 6 the gases
were'passed into two vessels 1 and 8 filled with
.
35 'I‘his can be done, for example. by preventing the ' acetic acid, the vessel 8 being cooled to minus 60° 35
\ condensation from taking place in spaces which C. and containing an addition of acetone in order ‘
l are too large, or by passing the split vapors to prevent freezing up. These two latter vessels
through a cooled liquid such as water _which dissolves the ketene not at all or only to a small ex-
40 tent. or by using from the very beginning dilute
acetic acid for the ketene formation. 'I'he ketene
into» anhydride. A vacuum pump 9 located at
the end ofthe apparatus-maintained the system 40
under an absolute pressure of about 15_ mm. In
gas .thus separated under low pressure from the
one hour 1055 grams of acetic acid vapor were sup- ‘
acetic anhydride, acetic acid and water is then
isolated by cooling to aflow temperature or by
plied to the tube I at a contact temperature of
650° C. (measured at the end the contact layer).
45 absorption, or it is obtained on the pressure side
of the vacuum pump. 'I'he ketene gas can also
be transformed into anhydride or other com-A
pounds by permitting it to
react' upon water-free
'
`acetic acid.
50
served to `determine the ketene by transformation
It has already been proposed to eil'ect the splitting up of acetic acid under reduced pressure but
ketene has never been obtained by-that method.
It would seem that the split vapors have always
been condensed in apparatus of very large sur55 face or under such other conditions as to allow
0f the total anhydride formed, namely 18.5 45 '
grams, 75% was found in receivers 5 and 6 and
25% was found inthe two acetic acid receivers
1 and 8, as anhydride. This latter portion corre
decomposition were negligible.
Í’
E
` l H _
_ ramp e
105 grams oi' acetic acid vapor, containing 0.2%
pyridine vapor, were passed-through the appara
tus described. in Example I, at 650° C. OI the 55
2,108,829
2
total anhydride produced (47.85 grams), 83% was
up. Of the anhydride a quantity of 21% was
found in the condensates of the two coolers I3
found in receivers 5 and 6 and 17% was found in
and I4, and 79%l had formed from ketene in the
8 as transformation product of
the free ketene. Losses by decomposition were
dripping tower I5. The loss in acetyl amounted
to 5.5% of the acetic acid used for the splitting
practically nil.
processes.
extent that, instead of the Liebig cooler I and re
ceiver 5, we used a vessel containing 100 grams of
1,946,707, particularly the use of phosphorus,
` receivers 1 and
Example III'
The apparatus of Example I was modified to the
10 water cooled to 0° C., through which the hot split
vapor products were passed. 105 grams of con
cent1-ated acetic acid produced, in one hour at
/
We furthermore found that in carryingÀ out
this process the utilization of the gaseous cata
lysts described in the above mentioned Patent
10
phosphoric acid and volatile esters of phosphoric
acid, offers considerable advantages as thereby
- 650° C. contact temperature, a total of 19.0 grams
of anhydride, of which 11% was found in receiv
15 ers 5 and 6, and 89% (as transformation product
of the free ketene) was found in receivers land 3.
disturbances through scattering
or spraying "
which may otherwise occur at high gas velocities,
are avoided.
15
Example VII
The apparatus of ExampleVI was employed
but the carbon tube I0 was empty. At an in
terior temperature of 700 to 740° ., 400 grams 20
The operation was the same as in Example III of acetic acid vapor were passed through the
20 except that 1% pyridine was added to the water ‘ reaction tube in one hour. Four parts per mil.
as a preliminary measure. An aggregate quantity triethylester of phosphoric acid were added to the
of 55.5 grams anhydride was produced of which acetic acid vapor, as catalyst. At the end of the
31.6% were obtained in receivers 5 and 6, and appara?is an absolute pressure of 35 mm. mer
cury was maintained. 0f the total quantity of f
68.4% in receivers 1 and 8.
Erllmple 1V
Example V
The operation was performed according to Ex
ample III except that the ketene discharged from
receivers 5 and 6.„was not allowed to react upon
30 acetic acid, but was separated out by means of
two low-cooled receivers arranged one behind the
other like vessels 1 and 8 of Fig. l and each filled
with 100 cubic centimeters of acetone to dissolve
anhydride formed, which was 200 grams, 41%
was found in the absorption tower as transfor
mation product of ketene` gas, and 59% was
found in the cooler condensates.
30
Example VIII
The operation was carried out according to
Example VII except that 3 parts pyridine per mil.
were added to the acetic acid-triethylphosphate
out the ketene. With an average of 105 grams of
concentrated acetic acid per -hour there were
formed 20 molecules of anhydride plus _ketene to
every 100 moleculesof acetic acid vapor, of which
mixture and 300 grams of the mixture were sup
plied to the heaterin lan hour. 0f the aggregate
quantity of 220 grams of anhydride formed, 75%
4.4 molecules were found in receivers 5 and 6 as
anhydride and 15.6 molecules in receivers 1 and 3
40 as pure ketene. ` There were no acetyl losses.
It is also possible to condense the ketene with
46
out solvents if thetemperature is maintained suf
iiciently low, as, for example, less than -100°.
Example VI
In this embodiment of the invention, which is
illustrated in Fig. 2, we employed a vertical tube
I0 composed of carbon, measuring 50 mm. in di
ameter and 800 mm. in height, stopped at the
50 lower end by a carbon stopper. This vessel was
mounted in an iron container II closely sur
rounding the carbon tube and heated electrically.
From the flanged cover of container II a copper
tube is led nearly to the bottom of .the carbon
tube. The carbon tube I0 was ñlled to a height
of 100 mm. with an equimolecular mixture of
sodium metaphosphate and lithium metaphos
phate. Two cooled receivers I3 and Il were at
tached to the iron container II, receiver I3 be
60 ing cooled with water and receiver Il being
cooled with brine at minus 20° C.
The gases were
then carried up through a dripping tower I5
which was filled with _Raschig rings, and sprayed
with concentrated acetic acid. The gases passed
thenthrough a water filled bottle I6 which re-v
tained traces of acetic acid; a vacuum pump I1
was attached to this bottle, whereby an absolute
pressure of 30 to 60 mm. of mercury was main
was obtained by absorption of the ketene gas in
the dripping tower, and only 25% condensed out `
of the split vapor products by the cooler. The\ 40
loss amounted to only 4% of the acetic acid em
ployed for the splitting process.
Example' IX
The operation was performed according to 45
Example VII except that, instead of triethyïphos
phate, 0.5 part per mil. of phosphorus vapor Vwas
added to the acetic acid vapor. Of the total
anhydride obtained, 27% was found in the ketene
absorption.
'
'
Example X
The operation was performed according to Ex
ample VIII except that, instead of ethyl phos
phate and pyridine, 1 part per mil. phosphoric
acid and 1 part per mil. ammonia were added
to the acetic acid vapor. Of the total anhydride
obtained, 40% was the result of absorption of
ketene.
It was further found that in this process the 00
operation can be carried on with very good re
sults substantially above 800° C. The ketene
yield increases without increasing _the decom-'
position to any substantial extent. The explana
tion of this may possibly be found in the short 65
sojourn of the diluted vapors in the hot space
and at the hot wall of the reaction chamber.
Example XI
An empty heated carbon tube, as in Example
VI, without a catalyst charge, was used as the 70
tained. The glacial acetic acid was passed reaction vessel. Also the other disposition was
70
through the melted catalyst heated to 730° C. - the same as in Example VI. The interior of
with 0.3% pyridine vapor with a speed of about the tube was maintained at a maximum tem
600 grams per hour. Altogether 296 grams of perature of 830° C., 600 grams of acetic acid
anhydride were obtained from 330 grams of vapor containing 3 parts triethylphosphate per 75
acetic acid which were exposed >to the splitting
2,108,829
mil. were supplied to the carbon tube in an hour,
«while an absolute pressure of 35 mm.V mercury
was maintained at the end of the apparatus. An
aggregate quantity of 475» grams of anhydride
was formed. Of this, 17% was in the cooled
condensates and 83% in the liquid iiowing from
taining catalyst and under at least a partial
vacuum, to form ketene as a primary dissociation
product, and subjecting at least a part of the
ketene to treatment for preventing its recombina
tion into acetic acid and acetic anhydride.-
4
the ketene absorption tower sprayed with acetic"l 3. A catalytic process for the production of
acid. 'I'he decomposition loss amounted to only ketene, which comprises heating acetic acid va
about 3% of the acetic acid used for the splitting
10 process.
at a temperature between 400° C. and 900° C. to 10
form ketene as a primary dissociation product,
and separating water, acetic acid and acetic an
hydride from the ketene before it has had time to
Example XII
The operation was performed according to Ex
ample XI except that instead of the triethyl
15 phosphate 0.5 part phosphorus per mil. was sup
recombine into acetic` acid and acetic anhydride.
plied to the acetic acid vapor. At a maximum
temperature of 870° C. in the interior of the re
action space, from 800 grams of acetic acid vapor
which were supplied in one hour, 375 grams of
20 anhydride were obtained, 74% of which was pro
duced through absorption ofthe ketene and 26%
of which was found in the condensates.
'I'he de
composition was small.
'
pors containing a non-metallic, acetic anhydride
' forming catalyst under at least a partial vacuum
'4. A process for producing ketene, which com
prises heating acetic acid vapors under at least
a partial vacuum at a temperature greater than
500° C. but less than 900° C. in the presence of
an‘acetic anhydride-forming catalyst, to form
ketene as the primary dissociation product, and 20
separating water, acetic acid and acetic anhy
dride from the ketene.
5. A catalytic process for the production of
' Example XIII
'I‘he operation was performed'according to
Example XI except that, in addition to the
`triethylphosphate, 3 parts pyridine vapor per
ketene, which comprises subjecting aceticl acid
vapors containing an acetic anhydride-forming
catalyst which is gaseous at the reaction tempera
ture, to heating at a temperature between
mil. were added -to the acetic acid vapor. At a 400° C.-900° C.; conducting the heating at least
30 maximum temperature of 890° C. in the interior ' under a partial vacuum whereby a mixture con
of the carbon tube, and with 1160 grams of acetic ' taining ketene, water, acetic acid and acetic an
acid introduced in one hour, there was formed
altogether _1120 grams of anhydride. 'I'he pro
hydride is formed, separating at least a part of
the ketene, and reducing the recombination of
portion of anhydride from absorbed ketene » ,the ketene during separation by carrying out the
amounted to 89.5% of the total...0nly 5% of separation in the presence of a nitrogen-con`-`
taining'base.
the acetic acid employed was lost by decomposi
tion.
'
6. A catalytic process for the production _of
Example XIV
ketene by the thermal dissociatiön of acetic acid,-
'I‘he operation was carried out according to
40 Example XIII except that ammonia was em
ployed‘as the baise addition instead of pyridine.
The aggregate output in anhydride amounted to
88% of the weight of acetic acid used.
The por
tion of K the anhydride obtained from ketene
45 amounted to 83%.y The `decomposition loss was
-
Small.
In carrying out our invention we may also em
_ ploy various other steps or expedients which
have proven advantageous for the production of
50 anhydride, as, for example, ‘preheating the acetic
which comprises subjecting acetic acid to heat
ing at a temperature between about 400° C. and
900° C. in the presence of_ a phosphorus-contain
40
ing catalyst iand under at least a partial vacuum,
to formI ketene as a` primary dissociation product,
and subjecting at least a part of the ketene to
treatmentv in the presence of a nitrogen-_contain
ing base for preventing its recombination into 45
acetic acid and acetic anhydride.
7. A catalytic processv for producing ketene,
which comprises subjecting acetic acid vapors to
heating under a partial vacuum at a temperature
between400° C. and 900° C. in the presence of a
acid vapor, utilization of other or special cata-_
non-metallic, acetic anhydride-forming catalyst 50
lysts, construction materials and apparatus.
to
form a mixture containing ketene, water, acetic
rli'he term “vacuum” as used ln the claims is
acid and acetic anhydride, and separating the
intended to indicate a_ pressure substantially be
55 low atmospheric pressure, and such asis obtained _ water, acetic acid and acetic anhydride com
ponents from the ketene by condensation of said 55
through the use of a vacuum pump or other suit
components in the presence of nitrogen-contain
ing compounds.
l
.
'I'he invention claimed is:
8. A process for producing ketene, which com-`
1. A catalytic process for~ the production of
60 ketene, which comprises subjecting acetic acid l prisesheating acetic acid vapors under at least
vapors containing an acetic anhydride-forming a. partial vacuum at a temperature greater than
400° C. but less than 900° C. in the presence of an
catalyst which is gaseous at the reaction temper
ature, to heating at a temperature between acetic anhydride-forming catalyst, to form_-- a
500° C..-900° C., conducting the heating at least mixture containing ketene. and subjecting the
mixture to a separation treatment which includes
65 under a partial vacuum whereby a mixture con
able pressure reducing arrangement. '
taining ketene, water, acetic acid and acetic an
hydride is formed and immediately separating at
least a part oi' the ketene from the other com
ponents.
70
.
cooling to substantially below 0° C.
'
-
9. A catalytic process for the production of
ketene, which comprises heating~acetic acid va
pors containing a volatile ester of phosphoric,
2. A catalytic process for the production of - acid, under at least a partial vacuum a a tem
perature between 400° C. and 900° C., _ o form
ketene by the thermal dissociation of acetic acid
in the presence of a phosphorus-containing cat
ketene as a primary dissociation product and im 70
mediately
water, acetic acid and acetic
alyst, which'comprises subjecting acetic acid to `anhydride separating
from the ketene.
heating at a temperature between about 400° C.
JOHANN SIXT.
and 900° C. in the presence of a phosphorus-con
MARTIN MUGDAN.
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