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Патент USA US2411567

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2,411,567
Patented Nov. 26, 11946
um'reo smug
'
PATENT
.
_' 2,411,567
oi'rica
MANUFACTURE or cannoxrmo ACID
ANHYDRIDES
James Wotherspoon Fisher, Spondon, near Derby,
England, assignor' to British Celanese Limited,
London, England, a company oi’ Great Britain .
_ Nu Drawing. Application July 13, 1944, Serial No.‘
' 544,823. In Great Britain August 23, 1943
9 Claims.
1
(01. 260-413)
'_ '
Y
Y ,
a2
.
boxylic acid; moreover the constant boiling" mix- .
ture which ‘it forms with acetic acid should con
tain a substantial proportion; for example at
‘ This invention relates to the manufacture of ,
anhydrides of carboxylic acids.
_ In one method of making anhydrides ‘of car- .
least 10% and preferably 20% or more, of acetic
acid. Examples of suitable azeotroping agents
are toluene, ethyl benzene and tetrachlorethyl
boxylic acids, which is useful in a great number
of instances, the carboxylic acid is caused to re
act with acetic anhydride, wherebythe carboxylic
acid is dehydrated to its anhydride and the
acetic anhydride is hydrated to acetic acid. The
usual method of carrying out this reaction is to
enee
In preparing carboxylic acid anhydrides by the
process of the invention a mixture of the car
10 boxylic acid, the azeotroping agent, and acetic
anhydride may be heated to boiling in a reaction
vessel under a fractionating column which is
maintained at- a temperature such that the con
anhydride is made by passing acetic anhydride
, pass acetic anhydride vapour through the car
boxylic acid at a temperature above the boiling
point of acetic anhydride. For example stearic
vapour through molten stearic acid.
_
stant boiling mixture of the azeotroping agent‘
and acetic acid isv distilled oil’ while any acetic‘
V
The reaction may be represented for a mono
anhydride or carboxylic acid vapour that may
_ carboxylic acid by the equation, ,
also be present is condensed and returned to the
reaction vessel. Heating may be continued un
til no more acetic acid is evolved, as indicated by
B being any suitable organic‘radicle, Thus in‘ 20 a rise in the temperature at the top of the frac
2R.COOH+ (CH3.CO) 20+
.
'
.
‘
_
(3.00) 20+2CH3.COOH
tionating column. above the boiling point of the
theory one molecular proportion of acetic anhy
dride should convert two molecular proportions
constant boiling mixture. The remainder of the _
azeotroping agent may then be removed, pref
[of the carboxylic acid into the corresponding an- ,
erably
by distillation under reduced‘ pressure,
hydride. vIn practice this is very far from being _
leaving the carboxylic acid anhydride in the reac
so, and it. is found necessary to pass through the 25
' carboxylic acid an amount of acetic anhydride ‘
many times greater than the theoretical quantity
' . if good yields of the anhydride are to be obtained.
‘tion vessel. The acetic acid and azeotroping
agent may subsequently be separated, for ex
ample by extracting the acetic acid with water,
and the azeotroping agent dried and re-used.
'As an example, when making stearicanhydride
The new process i‘s‘of particular value in the
the amount of acetic anhydride necessary for a 30
manufacture of the anhydrides of saturated acids
‘ substantially complete conversion of the stearic
acid may be as high as ?fty times the theoretical
quantity. This is a serious drawback, for even
if this acetic anhydride is for the most part re
' covered, its vapourisation requires the expendi
ture of a large amount of heat.
' ‘containing six or more carbon atoms in. the acid
' molecule, including both straight chain com
pounds such for example as stearic acid, palmiticv
35 acid, and lauricacid, and branched chain com- ‘
.
According to the present invention carboxylic}
acids are converted into their anhydrides by
heating themwith liquid acetic anhydride in the
presence of an organic liquid which does not en
ter chemically into reaction with the carboxylic
acid or its anhydride or ‘with the acetic anhy
_ dride, and which forms with acetic acid a con.
stant boiling mixture of minimum boiling point,
I
and as the reaction proceeds removing the acetic 45
acid produced thereby from the reaction zone by
distilling it oil as a constant boiling mixture.
pounds such for example as 2-ethylhexoic acid.
It may however also be used to make the anhy
drides of a great number of other carboxylic
‘ acids, including the anhydrides 'oiother'homo
logues of acetic acid, e. g. propionic and n-bu
tyric anhydridesyanhydrides of aliphatic dibasic
‘acids, e. g. succinic anhydride and ethyl‘suc
cinic anhydride, and aromatic acid anhydrides,
e. g. benzoic anhydride.
'
The invention is illustratedby the following I
examples;
-,
name, 1
By this means it is possible to secure very good
.1360 parts by weight of commercial stearic'
yields of the carboxylic acid anhydrides using
much less- acetic anhydride than has previously 50 acid were dissolved in 1730 parts of toluene (which
been required, for example less than 11.5 times
-
the theoretical quantity.
‘
4
~
had been dried by distilling oil water as its con
stant-boiling mixture'with toluene) in a reaction
vessel ?tted with a fracti'onating ‘column, and
The organic liquid (hereinafter referred to as
302 parts 01' 95% acetic anhydride was added‘ to
the azeotroping agent) which is used to assist
the reaction is preferably a solvent tor the car 55 the solution. The mixture was heated under at
1
.
v
3
,g -
-
mospheric pressure to
v120° C. At this temperature
a temperature
reaction takes
of about";
place,
and stearic anhydride and acetic acid are formed.
The constant boiling mixture of'acetic acid and‘
»
-
v
4
s
3. Process for the manufacture of the anhy
dride ofa saturated fattynacid containing at least
6 carbon atoms in the acid molecule, which com
prises heating the fatty‘ acid with'liquid acetic
toluene, boiling at about 105° C., was allowed to
distil on, any vapourised acetic anhydride being
condensed and returned to‘ the reaction ‘vessel.
Towards the end of the reaction the temperature .
of the liquid in the reaction vessel began to rise,
until when the reaction‘ was substantially com-=1. 10
plete (as indicated by a rise in the temperature _ ‘
at the top of ‘the fractionating column to the‘
boiling point of toluene) it had reached 160° C._
anhydride in the presence of an organic solvent
for the fatty acid which'does not enter chemi
cally into reactionwith the fatty acid or its an
hydride and which forms with acetic acid a con
stant boiling mixture of minimum boiling point
containing at‘ least 20% of acetic acid, and re- '
moving the acetic acid produced from the reac
tion zone as the reaction proceeds by distilling it
off as a constant boiling mixture with the or
ganic solvent.
At this point the fractionating colunm was cut
. out and, while the temperature of the liquid was. 15 ‘ 4. Process forv the manufacture of stearic an
held at 160° 0., the pressure was steadily reduced -, hydride, which comprises heating stearic acid
until substantially all the remaining toluene had ' _with liquid. acetic anhydride in the presence of
been removed, a small current of alrbeing passed
an organic solvent for stearic acid which does not
through the liquid meanwhile. When all the ' enter' chemically into reaction with stearic acid, '
toluene had been removed, there remained in the 20 stearic anhydride or acetic‘ anhydride and which
reaction vessel stearic anhydride of purity above
forms with acetic acid a'constant boiling mixture
90%.
'
of ‘minimum boiling .point, and removing the
The distillate,- comprising toluene and aceticv
‘acetic acid producedgby the reaction from the re
action zone as the reaction proceeds by distilling
acid, was extracted with apsmall quantity of wa
ter to remove the acetic acid; the toluene was 25 it off as a constant boiling mixture with the or
dried by distilling oi! the ?rst 2-3% of its bulk,
ganic solvent.
and was then available for re-use.
.
'
I
5. Process for the manufacture of ethyl-hexoic
The anhydrides of lauric acid and palmitic
anhydride, which comprises heating ethyl¢hexoic
acids- are made in a similar way, employing the- I
same molecular proportions of the reactants.
Example 2 ’
acid with liquid acetic anhydride in the presence
30 of an'organic solvent for ethyl-hexoic acid which
does not enter chemically into reaction with
ethyl-hexoic acid, ethyl-hexoic anhydride or ace-1
tic anhydride and which forms with acetic acid
' dissolved in 3700 parts of toluene, and 600 parts
a constant boiling mixture of minimum boiling
_ of acetic anhydride were added to the solution. 36 point. and removing the acetic acid produced by
1000 parts by weight of 2-ethylhexoic acid were
The mixture was heated under a fractionating .,
column, as described in Example 1, until ‘the
temperature of the liquid reached 150° C.
thereaction from the reaction zone as thereac
tion proceeds by distilling it off as a constant
The : boiling mixture. with the organic solvent.
reaction was .then substantially-complete. The
6. Process for the manufacture of lauric an
fractionating column was now out out and the 40 hydride, which comprises heating lauric acid with
temperature of the liquid allowed to fall to ‘125°
liquid acetic anhydride in the presence of anor
C., and maintained at. this level while the re
ganic solvent for lauric acid which does not enter
maining toluene was distilled off under increas- ’
chemically into reaction with lauric acid, lauric
, ingly low pressure.
When substantially all the ‘
anhydride or acetic anhydride and which forms
toluene had been removed, the residue contained 45 with acetic acid-a‘constant boiling mixture of
85-90% of 2'-ethy1hexoic anhydride.’
minimum boiling point, and removing the acetic
Having'described my invention, what I- desire
acid produced by the reaction from the reaction
to secure by Letters Patent is:
'
'
zone asthe reaction proceeds by distilling it oil‘
1. Process for the manufacture of the anhy
as a constant boiling‘ mixture ‘with the organic
_ dride of a carboxylic acid, which comprises heat 50 solvent.
’
‘ ing a carboxylic acid with liquid acetic anhydride
I '7. Process for. the manufacture of stearic an- -
in the presence of an organic liquid which does
not enter chemically into reaction with’ the car
hydride which comprises heating to boiling a
mixture of stearic acid, acetic anhydride and to]
uene, and removing the acetic acid produced by
- boxylic acid or its anhydride or the ‘acetic an‘
hydride and which forms with acetic acid a con
55
stant boiling mixture of minimum boiling point,
» and removing the ‘acetic acid produced by the
ing mixture with the toluene.v
reaction from‘ the reaction zone-as vthe reaction
proceedsby distilling. it off as a constant boiling
mixture.
.
.
60
which does'not enter chemically into reaction
anhydride and ‘which forms with acetic acid a
70
the reaction from the reaction zone as the reac
tion proceeds by distilling it off‘ as a constant ,
‘ boiling mixture.
constant boiling mixture with the toluene.
9. Process for the manufacture of lauric an
hydride which comprises heating to boiling a mix-~
ture of lauric acid, acetic anhydride and toluene,
and removing the acetic acid produced by the re
' with the fatty acid or its anhydride or the acetic
id produced by
mixture of ethyl-hexoic acid, acetic anhydride
and toluene, and removing'the acetic acid pro
duced by the reaction from the reaction zone as
the reaction‘proceeds by‘ distilling it off as a
anhydride in the. presence of an‘organic liquid 65
point, and removing the acetic
‘
8. Process for the manufacture of‘ethyl-hexoic
anhydride which comprises heating to boiling a
2. Process for the manufacture of ‘the anhy
dride ‘of a‘ saturated fatty acid containing at
least six carbon atoms in the acid molecule, which
comprises heating the fatty acid with liquid acetic
constant boiling mixture of minimum boiling
the reaction from the reaction zone as the_reac
tion proceeds by distilling it oil! as a constant boil
action from the reaction zone as the reaction
proceeds by distilling it of! as a constant boiling
mixture with the toluene.
'
-
JAMES WO'I'HERSPOON FISHER.
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