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Патент USA US2406561

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2,406,561
Patented Aug. 27, 1946
UNITED STATES PATENT OFFICE
' 2,406,561
AZEOTROPIC DISTILLATION OF METHANOL
FROM ADMIXTURE WITH ACRYLIC ESTERS
Chessie E. Rehberg, Philadelphia, Pa., assignor to
United States of America as represented by .
~ Claude R. Wickard, Secretary of Agriculture,
and his successors in oiiice
No Drawing. Application December 27,‘ 1943.
Serial No. 515,799
‘
2 Claims. (0]. 202-42) ’
(Granted under the act of March 3, 1883, as
amended April 30, 1928; 370 0. G. 757.) '
'
2
1
This application is made under the act oi’ March
3, 1883, as amended by the act of April 30, 1928,
and the invention herein described, it patented.
5° C., preferably even 15° C. or more, below the
boiling point of the acrylic ester, but not below
about 40° C.
-
.
Hexanes, mixtures of hexanes, and petroleum
may be manufactured and used by or for the
Government of the United States of America 5 fractions are examples oi’ hydrocarbons which
for governmental purposes without the payment
may be used- The Optimum hydrocarbon is one ‘
boiling as high as possible and yet distilling far
to me of any royalty thereon.
This invention relates to amethod for removing
enough below the acrylic ester'to allow it to be
alcohols from mixtures containing acrylic esters.‘
readily Sepemted from the acrylat? The Pal‘?
The lower alkyl acrylates form azeotropic mix- 10 tieulal' boiling range selected with depend on the
tures with several of the lower alkanols and
distillation equipmentwhich is to be used. the
hence these acrylates and alcohols cannot be sepemciency 0f the equipment, and the composition
arated from each other by simple distillation.
of the mixture being dihthled
It is often desirable, however, to be able to e?ect
liydmc?rbqns 0f the type described do not form
Also, they are
13°91’ solvents $01’ the lower elkenols. 80 that
when the alkanol-hydrocarbon azeotrope-is dis
tilled and condensed the distillate separates into
such a separation, as for example, in the prepara- 15 azeotl‘opes with acrylic esters
tion of a higher acrylic ester from a lower one by
alcoholysis. Thus, in the‘ production of ethyl,
butyl’ decyly or other acrylic ‘esters by the a1_
coholysis of methyl acrylate, methanol is formed
an upper layer which is mostly hydrocarbon and
and its continuous removal is desirable in order to 20 9' lower layer which is mostly alkanol This.
increase the rate of reaction and the completeseparation is even m°re marked when 8' small
ness of the conversion to the higher acrylate.
amount of Water is'added to the distillate, The
But Since methanol forms a binary azeotmpe with
addition of 1 percent by volume of water is eilec-~
methyl acrylate, the methanol‘ cannot be dis-
tive-
‘
tilled out of the reaction mixture without the 25 The separation of the azeoh'opic distillate may
simultaneous removal of methyl acrylate. A simhe °°nveniently carried out continuously during
ilar difficulty is encountered in the alcoholysis of
the distillation- For this purpose the distillate is
ethyl acrylate, since ethanol and ethyl acrylate
c0ndensed,.the hydrocarbon layer is ‘continuously
also form a binary azeotrope. Furthermore, in
drawn o? and returned to the stm while the all
the production of ethyl, Drew] and isopmpyl 30 cohol layer is continuously or, intermittently
acryiates ‘from methyl acrylate, numerous azeodrawn on from the sepammr
tropes are encountered, among them being meth- '
anol binary azeotrones with methyl. ethyl’. propyl
' and isopropyl acrylates, ethanol binaries with
methyl and ethyl acrylates, propanol binary with 35
methyl acrylate and isopropanol binary with
methyl acrylate. Methanol also distills azeotropically with methyl methacrylate. Accordingly,
My invention is
' examples:
illustrated by the following
'
~
_ EXAMPLE I
.
'
'
2 1110188 (92 g.) of ethanol, 6 moles (516 8-)
of methyl acrylate, 15's. of hydroquinone. 1 0001' Sulfuric acid and 200 cciof a petroleum hy
an object of this invention is to provide a method
drocel'hon fraction having a boiling range of 58°
' for the separation of the lower alkanols‘, particu» 40
61° C- Were re?uxed in a ?ask equipped With
‘
larly methanol, from' ‘admixture with acrylic
e 3 ft- fractichating column. The column had a
esters particularly methyl acrylate,
total-condensation, partial take-oil head from
I have found that the lower alkanolsv can be
which condensate could be either returned to the
effectively separated from the lower acrylic esters 45 column or sent into a continuous Separate!‘
as azeotropes with aliphatic hydrocarbons of suitWhere ‘the upper, or hydrocarbon layer, could be
able boiling range.
The. hydrocarbons used
continuously drawn O? and returned to the frac
should have a boiling point low enough to allow
tionetms column heel‘ its top- The column was
separation from the acrylic ester by distillation I Operated under total re?ux until the temperature
but not so low as to decrease the reaction tem-' 50 0f the vapcrat the still-head dropped to about
perature and rate of reaction unduly. "The lower
48° C. The rate of 'take-o? was then adjusted
boiling hydrocarbons should also be avoided be- .
so that the methanol was removed in‘the azeo
cause the percentage of alkanol in the azeotrope
iormed is less as the boiling point decreases.
trope as rapidly as it was produced in the reac
tion. This was achieved by keeping the tem
In general, the hydrocarbons should boil at least 55 perature of they vapor at the still-head at 45° to
3.
I
2,400,001
‘
.
‘
v
4
.
[50° 0., the take-oil being closed when the tem
perature exceeded 50° C.‘ Methanol slowly col
troplcally the lower alcohol as it is produced.v
Further; the lower aikanols can be removed from
‘ lected in the lower layer of the condensate in
mixtures containing one or more lower alkyl
the separator and was removed, either continu
acrylic esters‘ irrespective of whether or not the
‘ ously or intermittently. This methanol layer 5 mibiéture arose from the alcoholysis of an acrylic
es
r.
,
; contained a considerable amount of the hydro
Table‘ Ishows the approximate boiling points
carbon and it was found that much more com
‘ plete separation could be achievedlby adding a I‘ of the alkanol azeotropes formed with a petro
leum hydrocarbon fraction boiling substantially
small amount of water either 'to the condensate
in the separator or to the methanol layer after 10 within the range 58° to 61° C.‘ It should be un
derstood that ,a hydrocarbon compound or mix
its withdrawal.
.
.
e
'
ture of compounds of other suitable boiling range
might also be used and that the azeotrope formed
‘ the reaction having proceeded virtually to com- ,
by this material would have a different boiling
- pletion. The hydrocarbon was then distilledv out 15 point and different composition from that formed
by the material boiling from 68° to 61° C.
of the reaction mixture, leaving essentially a mix
After several hours of re?uxing, the produc
1'tion of methanol ceased or became very slow,;_
- l ture of methyl and ethyl acrylatesl By frac-'
.tional distillation of this mixture, an almost
TABLE I
1 quantitative yield of ethyl-acrylate was obtained.
EXAMPLE 11
‘ Ethyl acrylate was prepared by proceeding as
in Example I, except that the hydrocarbon was
omitted from the vreaction mixture,‘ and instead
2°
Boiling point of azeotropes of alkanols and pe
vtroleum fraction of boiling range 58° to 61° C’.
Alcohol _
B. P. of azeo
trope, °C.
‘ of ‘removingthe methanol as its azeotrope with
‘ the hydrocarbon, it was removed as its azeotrope
with methyl acrylate (B. P. of azeotrope, 62° 0.).
.I'I'he methanol-methyl acrylate azeotrope thus
‘obtained contained about 50 to 55 percent of‘
Having thus described my invention, I claim:
1. In the process of preparing higher acrylic
;methanol which was removed by adding about 30
' esters by the alcoholysis of methyl acrylate, the
' lone volume of the hydrocarbon (B. P. 58° to
61‘‘ C.) to three volumes of the azeotrope and , step which comprises ‘removing the methanol
formed in the alcoholysis reaction by distilling
‘distilling as in Example I. (In this way. the
"methanol-hydrocarbon azeotrope was distilled
it as an azeotrope with an aliphatic hydrocarbon
oil. the distillate was separated into two layers, 35 having a boiling point at least 5° 0. below the
1 the hydrocarbon layer was returned to the still
boiling point of methyl acrylate but not less than
and the process continued until all methanol had
about 40° C.
‘been removed from the methyl acrylate.
2. In the process of preparing‘higher acrylic A large number 01' higher esters of ‘acrylic 4 esters by the alcoholysis oi methyl acrylate, the
. acid can‘be made from methyl acrylate and the
step which ‘comprises removing the methanol
appropriate alcohol by the procedures described.
formed in the alcoholysis reaction by distilling
Also, ethyl, propyl or butyl acrylate may be used
it as, an azectrope with a petroleum fraction hav
ing a boiling point at least 5° C. below the boil
finstead‘of methyl acrylate and higher meth
acrylates can be made from methyl, ethyl, propyl 45 ing point of methyl acrylate but not less than
about 40°C.
hol, using a hydrocarbon liquid to remove ‘am
. _CHESSIE E. REHBERG.
' ,or butyl methacrylate and an appropriate alco
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