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Патент USA US2405470

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Patented Aug. 6, 17946
’ 2,405,470
STATES PTENT , OFFICE»
2,405,470
MANUFACTURE OF ACETIC ANHYDRIDE
Karl Heinrich Walter Tuerck, Banstead, and Hans
Joachim Lichtenstein, Epsom Downs, England,
assignors to The Distillers Company Limited,
Edinburgh, Scotland, a British company
N 0 Drawing. Application October 29, 1942, Serial
No. 463,820. In Great Britain July 28, 1941
5 Claims.
(Cl. 260-546)
1
This invention is for improvements in or re
2
Example I.—100 g. of paraldehyde containing
0.1 g. vanadic acid and (as a depolymerising agent
lating to the reduction of the peracid content of
oxidation reaction products.
When oxidizing acetaldehyde in order to obtain
acetic anhydride in good yields, the conditions of
for the paraldehyde) 0.14 g. parataluene-sul
phonic acid are oxidized at 33° C. by introducing
reaction are usually such as to cause the forma
ture being vigorously stirred.
tion of considerable amounts of peracetic acid in
the reaction mixture resulting in a spontaneous
rise in temperature during the working-up oper
oxygen under 10 lbs. pressure, the reaction mix
After 40 minutes the amount of acetic anhy
dride present is 40% by weight and the amount of
peracetic acid is 9% by weight. The oxygen pres
This rise in temperature is the cause of 10 sure is then released and air is admitted to the
reaction vessel. The stirring is continued for a
further 10 minutes, the temperature being raised
occur in plants where acetaldehyde is oxidised to
to and maintained at 40° C. The mixture then
acetic acid.
contains acetic anhydride, in a yield of 36.5% by
It has been proposed to use manganese acetate
ations.
the explosions which, as is well-known, frequently
or mixtures containing manganese acetate as
weight and 2.07% by weight of peracetic acid.
catalysts for this oxidation reaction in order to
avoid the formation of dangerous concentrations
of peracetic acid, but where manganese acetate is
in Example I except that instead of heating at
40° C, with air, nitrogen was introduced and the
really active in keeping the concentration of the .
peracetic acid low, it does not favour the forma
tion of acetic anhydride.
According to the present invention there is pro
vided a process for the manufacture. of acetic
Example II.--The reaction was carried out as
temperature was raised to 45° C.
After 2: min»
20 utes it was found that the content of percom
pounds had fallen to less than 0.8% by weight.
In a reaction carried out by way of compari
son the oxidation was carried out at 40° C., the
yield in acetic anhydride being only 29.6% by
anhydride which comprises oxidising acetalde
hyde in the liquid phase with molecular oxygen 25 weight, and the concentration of the. peracid
at a temperature below 40° C. to produce a reac
tion mixture containing more than 3% by weight
being 5.4% by weight.
‘
W’hen oxygen was used instead of air during
of percompounds, thereafter raising the temper
the decomposition of the peracid, the ?nal con
centration of the peracid was 2.8%.
ature of the reaction mixture to a value of 40° to
50° C., contacting said reaction mixture with an 30 The decomposition of the peracid in this proc
ess proceeds quickly in the region of its higher
atmosphere in which the partial pressure of oxy
gen is considerably less than the partial pressure
concentrations, and slows down to reach a ?nal
value, which depends on the oxygen concentra
of said molecular oxygen during the oxidation
and maintaining the reaction mixture under those
tion; we break off the treatment as soon as this
conditions ‘for a period of time su?lcient to reduce . ?nal value is reached or approached.
The reaction products are, after reduction of
the content of percompounds therein to a value
the peracid content thereof as above described,
below 3% by weight, of the reaction mixture which
either worked up in the usual ways or their
is no longer dangerous.
peracid content can be further reduced by means
The striking features of this process are the
smooth reduction of the peracid, which may be 40 of the addition of manganese salts or suitable
chemical reducing agents. When applied to the
present in an amount up to about 10% by weight
production of acetic anhydride the amount of
in the product obtained in the oxidation under
manganese salt added should preferably not be
pressure, and the remarkable yield of acetic an
hydride obtained, despite the fact that quick cool
greater than is su?icient to neutralise the cat
ing of the reaction mixture after the oxidation 45 alysts.
It is also possible to operate the process of this
has been considered an essential condition for
invention so as to reduce the amount of percom
the manufacture of acetic anhydride by processes
pounds in the reaction mixture simultaneously
hitherto proposed such for example as those de-A
scribed in prior U. S. Patent 2,177,494 and. Brit
with the oxidation process. For this purpose, a
ish Patents Nos. 446,259 and 443,151.
50 portion of the reaction mixture is withdrawn,
Heating for a period of from 5-30 minutes has
either continuously or periodically, from the oxi
been found to be su?icient.
dation vessel and heated in an atmosphere poor
The following examples illustrate the process of
in oxygen to a temperature up to about 45° C.
for a short period, to reduce the contents of per
the present invention as applied to the production
of acetic anhydride from paraldehyde.
55 compounds therein, and then return to the oxi
2,405,470
3
dation vessel. By this means the content of per
compounds in the oxidation vessel can be main
tained at a low value without the yield of acetic
oxygen at a temperature below 40° C. to produce
a reaction mixture containing acetic anhydride,
acetic acid, water and more than 3% by weight
anhydride being seriously affected.
compounds are formed as a result of an oxida
of percompounds, thereafter, and prior to the
working up of the reaction mixture, treating the
reaction mixture to reduce its content of per
compounds by raising the temperature of the re
tion of acetaldehyde and is not limited to the
action mixture to a value of 40° to 50° C., con
It will be appreciated that the present inven
tion is applicable to any process in which per
production of acetic anhydride from paraldetacting said reaction mixture with an atmosphere
hyde. The invention is, of course, applicable to‘ 10 of air and maintaining the reaction mixture un
the oxidation of acetaldehyde to acetic anhy
der those conditions for a period of time su?i
dride.
What we claim is:
‘
V
V
-
cient to reduce the content of percompounds
.therein'to a value below 3% by weight.
1. In a process for the manufacture ofacetic
74. In a process for the manufacture of acetic
anhydride by the oxidation ‘of acetaldehyde‘in
the liquid phase by meansof molecularoxygen,
the steps consisting in eifecting'the oxidation at
anhydride by the oxidation of acetaldehyde in
the liquid phase by means of molecular oxygen‘,
a'temperature below 40° C. to produce a reaction
mixture containing acetic anhydride, acetic acid;
water and more than 3% by weight of percom
pounds, thereafter, andprior to the working up of
the reaction mixture, treating the reaction mix
ture to reduce its content of percompounds by
raising the temperature of the reaction mixture
‘ the steps consisting in effecting the oxidation at
a temperature below 40° C. to produce a reaction
mixture containing acetic anhydride and more
than 3% by weight of percompounds, thereafter,
and prior to the recovery of the acetic anhydride
from the reaction mixture, treating the reaction
mixture to reduce its content of percompounds
by raising the temperature of the reaction mix
to a‘value of 40° to 50° C., contacting said reac 25 ture to a value of 40° to 50° 0., contacting said
reaction mixture with an atmosphere of nitrogen
tion mixture with an atmosphere poor in oxygen
and maintaining the reaction mixture under
and maintaining the reaction mixture under
those conditions for a period of time su?icient
those conditions for a period of time su?icient
to reduce the content of percompounds therein
to reduce the content of percompounds therein
to a value below 3% by weight.
30 to a value below 3% by weight.
5. In a continuous process for the manufacture
2. In a process for the manufacture of acetic
of acetic anhydride by the oxidation of acetalde
anhydride by the oxidation of acetaldehyde in
hyde in the liquid phase by means of molecular
the'liquid phase by means of molecular oxygen
oxygen, the steps consisting in effecting the
under superatmospheric pressure, the steps con
sisting in effecting the oxidation at a temperature 35 oxidation in a reactor at a temperature below
below 40° C. to produce a reaction mixture con
taining acetic anhydride, acetic acid, water and
40° C. to produce a reaction mixture containing
acetic anhydride, acetic acid, water and more
than 3% by weight of percompounds, continu
ally withdrawing a portion of the reaction mix
more than 3% by weight of percompounds, there
after, and prior to the working up of the reac
tion mixture, treating the reaction mixture to re ‘in ture from said} reactor, raising the temperature
of said portion of the reaction mixture to a
duce its content of percompounds by raising the
value of 40° to 50° C. whilst contacting it with
temperature of the reaction mixture to a value of
an atmosphere poor in oxygen for a sufficient
40° to 50° 0., contacting said reaction mixture
period of time to reduce its content of percom
with an atmosphere poor in oxygen and main
pounds to a value below 3% by weight, returning
taining the reaction mixture under those condi
said treated portion of the reaction mixture to
tions for a period of time suil‘icient to reduce the
the reactor, continually withdrawing a second
content of percompounds therein to a value be
portion of the reaction mixture from said reactor
low 3% by weight.
and treating said second portion for the recovery
3. In a process for the manufacture of acetic
of acetic anhydride therefrom.
'
anhydride by the oxidation of acetaldehyde in the
KARL HEINRICH WALTER TUERCK.
liquid phase by means of molecular oxygen, the
HANS JOACHIM LICH'I‘ENSTEIN.
steps consisting in effecting the oxidation with
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