Patented Mar. 30, 1926. 1,578.

454
UNITED STATES PATENT of FICE.
EYE.J.ABs.AL AND GEORGE s. shAw, of SEAwINIGAN FALLs, Quebec,
CANADA, ASSIGNORS, BYMESNEASSIGNMENTs, TO CANADIAN ELECTRo pronources
COMPANY, LIMITED, OF MONTREAL, CANADA. -
MANUFACTURE OF ACETIC ANHYDRIDE DACA3,
AND ACETALDEHYDE PBox ETHYLDEN
NoDrawing. Application aled January 26, 1920. Serial No. 354,225.
To all whom it may concern A comparison of the results obtained ac
Be it known that we, MELVILLE, J, MAR cording to this invention with results ob s
SHALL and GEORGE. S. SHAw, both subjects tained by the use of other catalysts is shown
of the King of Great Britain, and residents in the following table:-
of the town of Shawinigan Falls, in the
Province of Quebec and Dominion of Can - Ratio
ada, have invented certain new and useful
Improvements in the Manufacture of Acetic Catalyst
anhydride
to
acid
Anhydride and Acetaldehyde from Ethyl
O idene Diacetate, of which the following is
produced
Antonium persulphate--------------------.......... 5
a full, clear, and exact description.
This invention relates to improvements
Sulphuric acid---...----ser--------------------------
Phosphoric acid...................................
3.
9, 1
in the manufacture of acetic anhydride and
acetaldehyde from ethylidene diacetate, and
5 the object of the invention is to provide for The following example illustrates the proc
ess;-
an increased production of anhydride. 1000gms, of ethylidene diacetate is heated
A further object is to avoid the formation to ebulition at atmospheric pressure in a 70
of tar and the consequent production of vessel fitted with a rectifying column ter
acetic acid. minating in a condenser and the heating
20 In the production of acetic anhydride
from ethylidene diacetate according to the is continued during the reaction, preferably
equation; to such extent as will maintain the reaction 75
liquid in gentle ebullition. Concentrated
CHCH(OOCCH)-(CHCO)0--CHCHO phosphoric acid is then added, 12 drops at
25 by previously known methods, a serious loss a time, at intervals of 15 minutes to 30
of efficiency occurs, owing to the forma minutes, till 4 gms, in all have been added.
It is found that this rate is sufficient to
tion of considerable quantities of acetic acid keep the aldehyde coming off at a fairly
as the result of a secondary reaction. constant rate.
It has already been proposed to hasten
80 decomposition of the ethylidene diacetate
the This aldehyde on being condensed
amounts
by the use of catalysts, such as sulphuric of about 5% to about 250 gms. with a content
acid, sodium bisulphate, potassium bisul rated from the acetic acid, which can be sepa s
phate, mercuric sulphate, ammonium persul tillation. In most aldehyde by fractional dis
hate and the like. The use of these agents acid passing over with cases, however, the acetic
as the disadvantage that there is consider Small in amount. the aldehyde is quite
able secondary reaction producing a large Starting with nearly pure ethylidene diac
amount of acetic acid relatively to the anhy etate 740 gms. of a liquid of the following O
dride. w
composition is eventually left in the decom
According to this invention, the formation position
O
of anhydride is increased and the forma vessel: . Percent,
tion of acetic acid decreased as compared Acetic anhydride ----------------- 75. 0
with previously known results, by heating Acetic acid------------------------ 8.0
the ethylidene diacetate to ebullition and Ethylidene diacetate---------------- 17.0
45 adding thereto at suitable intervals a small
amount of phosphoric acid to serve as a 00, 0
catalyst. The catalyst should be added only
in very small amounts, since if an excess of Thus fully 87.4% of the total ethylidene OO
catalyst is present tar formation and the diacetate present has been decomposed.
50 production of largely increased amounts of This acetic acid and anhydride are then
acetic acid are unavoidable. The catalyst distilled from the vessel through a rectify
should therefore be added only in amounts ing column and condensed till only ethyli s
and at intervals sufficient to maintain the dene diacetate remains behind, or the unde
reaction at reasonable velocity. composed ethylidene diacetate may be puri
 1,578,454
fied byfordistillation and added material may be at the temperature of the
batch decomposition. Moreto ethylidene
a further boiling point of ethylidene diacetate at the
diacetate is then added to the kettle and commencement of the process, the tempera
the ture
process repeated. .. .. of the liquid may drop very materially
5 The condensate of acetic acid and acetic after the addition of the catalyst, and may 70
anhydride containing some ethylidene diace remainofatethylidenea temperature below the boiling
tate, is subjected to a further fractional dis point
material still has the
diacetate, although the
appearance of boiling.
tillation in a second still fitted with a very This appearance of ebullition is due to the
efficient rectifying column. In this, Way, a
0. mixture of acetic acid and acetic anhydride escape of a mixture, chiefly of acetaldehyde 75
is obtained practically free from ethylidene. and acetic anhydride, which, under the con
ditions of the reaction, come off at a tem
diacetate. O
perature below the boiling temperature of
This mixture normally contains 80% to ethylidene
90% acetic anhydride, which is better than diacetate.
15 the ordinary commercial material. For this Having thus described our invention, 80.
reason it is not necessary to separate any what we claim is:-
of the acetic acid from the anhydride by 1. A process for the manufacture of acetic
fractional distillation. t anhydride and acetaldehyde from ethylidene
While it has been stated in the foregoing diacetate in which phosphoric acid is added
20 example that concentrated phosphoric acid to the diacetate as a catalyst to facilitate 85
is used and the process carried on at atmos decomposition of the diacetate by heat.
pheric pressure, it will be understood that 2. A process according to claim 1 in
these conditions pertain solely to the par which the ethylidene diacetate is maintained
ticular example given and that the invention in ebullition and the produced acetaldehyde
is not limited thereto, as the process may continuously distilled off through a rectify 90
be carried on under any pressure practicable ing column, the temperature of which is
either sub-atmospheric or super-atmospheric adjusted to permit the passing off of alde
and with dilute acid. hyde only.
While for all practical purposes, the 3. A process for the manufacture of acetic
30 addition of phosphoric acid up to 15% of anhydride and acetaldehyde from ethylidene 95
the weight of the diacetate will be sufficient, diacetate, which includes adding phosphoric
it may nevertheless be found advisable acid to the ethylidene diacetate at intervals
under certain circumstances to add further of time until most of the diacetate is decom
acid, and therefore this invention contem posed and maintaining a temperature suffi 00
plates the addition of acid up to approxi cient to keep the reaction liquor in ebullition.
mately 5.0% of the weight of the diacetate. 4. A process according to claim 3, in
While the superior results of this process which the proportion of each addition of
are due largely to the use of phosphoric acid, catalyst to the diacetate is approximately
they are .03% by weight.
40 which thealso
aciddue partly to the manner in
is introduced. 5. A process for the manufacture of acetic 05
In the foregoing specification, certain anhydride and acetaldehyde from ethylidene
amounts of acid have been referred to and diacetate, in which the diacetate is heated
it will be understood that these amounts to ebullition with up to 5.0% of its weight
are free acid or acid available for the re of phosphoric acid added in small amounts 10
45 action of the invention. If the process is during the course of the decomposition.
carried out in a vessel of iron, aluminum, 6. A process for the manufacture of acetic
copper or any other ordinary metal, the anhydride and acetaldehyde from ethylidene
metal is slowly dissolved and precipitates diacetate, in which the diacetate is heated
50
a portion of the phosphoric acid as an in to ebullition with up to 1.0% of its weight
soluble phosphate. Therefore when appa of phosphoric acid for the duration of active
ratus is used which is attacked by the acid, decomposition, and the heating continued
it will be necesary to add an excess of acid with additions of phosphoric acid until most
over the requirements of the process. of the diacetate has been decomposed.
Apparatus of glass or earthenware is not 7. A process for the manufacture of acetic
55 destroyed, but is not satisfactory from a anhydride and acetaldehyde from ethlidene 20
commercial point of view and the process diacetate, in which the diacetate is heated
will therefore preferably be carried out in to ebullition with phosphoric acid under a
metal apparatus protected by suitable rectifying column and acetaldehyde re
60
enamel. . . covered at the outlet of the column during
The ethylidene diacetate as found in com the decomposition of the diacetate, the re.
merce is not a pure article but may contain sidual liquor being subsequently distilled
up to 25% of acetic acid. The presence of off until only ethylidene diacetate remains
the acid is not in any way detrimental to and the distillate freed from entrained
65
the reaction previously described. ethylidene diacetate by fractioning. 30
In carrying out the process, although the 8. A method of producing acetic anhy
 1,578,454. s

dride and acetaldehyde, which comprises total amount of acid added being not move
adding phosphoric acid to ethylidene diace- than 5% of the weight of ethylidene diace- 0
tate, heating the mixture and continuously... tate. .
separating the produced acetaldehyde. In witnes whereof, we have hereunto set
9. A method of producing acetic anhy- our hands.
dride and acetaldehyde, which includes the
step of gradually adding phosphoric acid MELVILLE J. MARSHALL.
to ethylidene diacetate while heating, the GEORGE. S. SHAW.