Patented Aug. 27, 1940
,
‘
2,212,810
UNITED STATES PATENT OFFICE
2,212,810
AZEOTROPIC DISTILLATION
Edmund Field, Wilmington, Del., assignor to E.
I. du Pont de Nemours & Company, Wilming
ton, Del.,‘ a corporation 01’ Delaware
No Drawing. Application February 6, 1940,
Serial No. 317,531
20 Claims. (Cl. 202-42)
This invention relates to a method for sepa
instance, should a mixture contain methyl ace
rating substances which either boil closely to- ' tate, in addition to benzene and cyclohexane,
gether or form binaries such that separation can
processing with acetone according to this inven
not be achieved by simple fractional distillation.
More particularly, this invention relates to the
separation of cyclohexane from benzene.
,
It is an object of thisinvention to providea
hexane-acetone mixture boiling at 53.5", whose
such as benzene (B. P. 80.1° C.) (which cannot
proximity of boiling temperatures may make sepa
ration di?lcult. Under such conditions, the
methyl acetate is preferably distilled from the‘
mixture before the addition of the acetone to 10
avoid, thereby, the presence of the methyl ace
tate-acetone azeotrope. In certain cases involv
ing constituents, part of which are water soluble,
water extraction may be substituted for distilla
tion. None of these priliminary treatments are 15
necessary, however, in the following illustrative
case, the technique of which I have successfully
employed in conjunction with a process for the
simultaneous manufacture of acetone and cyclo
be distilled ordinarly from cyclohexane, B. P.
80.8“ C.) by adding acetone to the mixture and
distilling. Acetone, I have found, forms a binary
propanol and benzene described in copending. ap
plication of E. P. Bartlett, Serial No. 265,932.
method for separating closely boiling substances
or substances which form azeotropes where sepa
ration by fractional distillation is di?icult or im
practical. It is a further object of this invention
to provide a method for separating cyclohexane
from benzene. Other objects and advantages of
the invention will be apparent from the follow
1 ing
speci?cation.
‘
'
O
According to the present invention, cyclohexane
can be removed from a mixture containing cyclo
hexane and substances of similar boiling point,
2
tion permits of two azeotropes, a methyl acetate
acetone mixture» boiling at 56.1° C. and a cyclo
hexane by exchange of hydrogen between iso 20
azeotrope with cyclohexane (67.3% acetone by
As a process of this type involves an equilibrium,
weight) which boils at a lower temperature
25 (531° C.) than either acetone or any benzene
cyclohexane mixture. Thus, I have found that a
weight ratio of acetone to cyclohexane of at least
2.0:1 is preferable when distilling under a pres
the product is a mixture of isopropanol, acetone,
30
sure of one atmosphere.
If it is desired subsequently to recover benzene
and cyclohexane each in the pure form, the distil
lation is continued.
The excess acetone distills
following the acetone-cyclohexane azeotrope, but
at a higher temperature, and finally benzene in
35 the pure form is obtained. The acetone-cyclo
hexane binary is then processed with water.
Preferably this involves water washing of the
binary which is carried out by conducting the
binary to the bottom of a baffled tower down which
40 water is flowing.
The counter-current flow of
water and binary e?ects solution of acetone in the
water and release of the cyclohexane which rises
to the topof the tower and is removed by de
cantation. The acetone dissolved in the water
45
may be recovered for further use by distillation
from its mixture with water. The cyclohexane
may be obtained chemically pure by removing
the traces of residual water by distillation or by
50 the use of common drying agents.
-
The process as above described may be applied
benzene and cyclohexane.
Such a mixture con
25
tains constituents for forming at least three differ
ent azeotropic mixtures, benzene-isopropanol
(B. P. 71.9“) , cyclohexane-isopropanol (B. P.
68.6“) , both of which are revealed in the litera
ture, and acetone-cyclohexane (B. P. 53.1“). 30
From such a mixture cyclohexane can be removed
quantitatively as its azeotrope with acetone. The
acetone-cyclohexane mixture is then separated
into its constituents by countercurrent water ex
traction such as previously outlined, or by some 35
other convenient, well known device. Acetone is
recovered from the water solvent by simple disti1_
lation. The cyclohexane is dried either by a suit
able drying agent or by a process of distillation
which takes advantage of the convenient cyclo
40
hexane-water pseudo-azeotrope.
Following the removal of cyclohexane, the re
sidual mixture of acetone, isopropanol and ben
zene is tapped to remove acetone, and the uncon 45
verted benzene and isopropanol are returned to
the hydrogenation unit for reprocessing.
While I have illustrated my invention by cer
tain applications, I do not limit my claims to such
speci?c cases, for there are many possible prob 50
lems of separation where solutions may employ
to any mixture of compounds containing cyclo
hexane, provided the boiling temperatures of the
as a basic principle the recovery of cyclohexane
from mixtures by means of its azeotrope with ace
additional constituents or any azeotropic mix
tone. Thus, for example, although not speci?cally
mentioned previously, the recovery of acetone 55
from mixtures of substances having similar boil
55 ture between such constituents or between such
constituents and acetone are su?iciently remote
from the boiling temperature of the cyclohexane
acetone binary. Even should the boiling tempera:
turesbe close, it will generally be found possible
60 to vary‘ the process to avoid this di?iculty. For
ing temperatures may also be accomplished ac
cording to the present invention. In other words,
although the speci?cation has been directed pri
marily to the removal of cyclohexane, the reverse 60
2
2,212,810
is also true. Acetone may be removed from mix
tures by the use of cyclohexane, thereby employ
ing the binary or azeotrope of acetone and cyclo
hexane.
I claim:
-
1. A method for the removal of cyclohexane
from admixture with other substances which com
prises treating the cyclohexane-containing mix
ture with acetone and distilling oil" the resultant
10
cyclohexane-acetone azeotrope.
2. A method for the removal of cyclohexane
from admixture with other substances which
comprises treating the cyclohexane-containing
mixture with acetone and distilling off the re
15 sultant cyclohexane-acetone azeotrope and there
after removing the cyclohexane by treating the
resultant distillate'with water.
3. A method for the removal of cyclohexane
from admixture with other substances which
20
comprises treating the cyclohexane-containing
mixtures with acetone in the ratio of at least 2.0
parts 'of acetone per part of cyclohexane and
thereafter distilling off the resultant cyclohexane
acetone azeotrope.
25
4. A method for the removal of cyclohexane
from admixture with other substances which
comprises treating the cyclohexane-containing
mixtures with acetone in the ratio of at least 2.0
parts of acetone per part of cyclohexane and
30 thereafter distilling off the resultant cyclohexane
acetone azeotrope and thereafter removing the
cyclohexane by treating the resultant distillate
with water.
5. A method for the removal of cyclohexane
' from admixture with other substances which
comprises treating the cyclohexane-containing
mixtures with acetone in the ratio of 2 parts of
acetone per part of cyclohexane and thereafter
distilling o? the resultant cyclohexane-acetone
40
binary.
6. A method for the removal of cyclohexane
from admixture with other substances which
comprises treating the cyclohexane-containing
mixtures with acetone in the ratio of 2 parts of
45 acetone per part of cyclohexane and thereafter
distilling oi? the resultant cyclohexane-acetone
binary and thereafter removing the cyclohexane
by treating the resultant distillate with water.
'7. A process for the removal of cyclohexane
50 from a mixture containing benzene and cyclo
hexane which comprises treating the cyclohexane
containing mixture with acetone and distilling off
the resultant cyclohexane-acetone azeotrope.
8. A process for the removal of cyclohexane
from a mixture containing benzene and cyclo
hexane which comprises‘ treating the cyclo
hexane-containing mixture with acetone and dis
tilling off the resultant cyclohexane-acetone
azeotrope and thereafter removing the cyclo
60 hexane by treating the resultant distillate with
water.
9. A process for the removal of cyclohexane
from a mixture containing benzene and cyclo
hexane which comprises treating the cyclo
65 hexane-containing mixtures with acetone in the
ratio of at least 2.0 parts of acetone per part of
cyclohexane and thereafter distilling-01f the re
sultant cyclohexane-acetone azeotrope.
10. A process for the removal of cyclohexane
70 from a mixture containing benzene and cyclo
after removing the cyclohexane by treating the
resultant distillate with water.
11. A process for the removal of cyclohexane
from a mixture containing benzene and cyclo
hexane which comprises treating the cyclo
hexane-containing mixtures with acetone in the
ratio of 2 parts of acetone per part of cyclohexane
and thereafter distilling oil‘ the resultant cyclo
hexane-acetone binary.
12. A process for the removal of cyclohexane 10
from a mixture containing benzene and cyclo
hexane which comprises treating the cyclo
hexane-containing mixtures with acetone in the
ratio of 2 parts of acetone per part of cyclohexane
and thereafter distilling off the resultant cyclo 15
hexane-acetone binary and thereafter removing
the cyclohexane by treating the resultant dis
tillate with water.
‘1'3. A process for the removal of cyclohexane
from a mixture containing cyclohexane, benzene,
isopropanol and acetone which comprises effect
ing an acetone-cyclohexane ratio at least equal
to the ratio there between in the acetone-cyclo
hexane azeotrope and then distilling oif the re
25
sultant acetone-cyclohexane azeotrope.
14. A process for the removal of cyclohexane
from a mixture containing cyclohexane, benzene,
isopropanol, and acetone which comprises effect
ing an acetone-cyclohexane ratio of at least 2.0
to 1 and then distilling oil’ the resultant acetone
cyclohexane azeotrope.
'
15. A process for the removal of cyclohexane
from a mixture containing cyclohexane, benzene,
isopropanol and acetone which comprises effect
ing an acetone-cyclohexane ratio of 2 to 1 and 35
then distilling oil’ the resultant acetone- cyclo
hexane azeotrope.
16. A process for the removal of cyclohexane
from a mixture containing cyclohexane, benzene,
isopropanol and acetone which comprises e?ect 40
ing an acetone-cyclohexane ratio above the ratio
therebetween in the acetone-cyclohexane azeo
trope and then distilling off the resultant ace
tone-cyclohexane azeotrope and thereafter re
moving the cyclohexane by treating the resultant 45
distillate with water.
’
17. A process for the removal of cyclohexane
from a mixture containing cyclohexane, benzene,
isopropanol and acetone which comprises effect
ing an acetone-cyclohexane ratio of at least 2.0 50
to 1 and then distilling oil’ the resultant acetone
cyclohexane azeotrope and thereafter removing
the cyclohexane by treating the resultant dis
tillate with water.
18. A process for the removal of cyclohexane 55
from a mixture containing cyclohexane, benzene,
isopropanol and acetone which comprises effect
ing an acetone-cyclohexane ratio of 2 to 1 and
then distilling of! the resultant acetone-cyclo
60
hexane azeotrope and thereafter removing the
cyclohexane by treating the resultant distillate
with water.
_
19. A method of removing a substance selected
from the group consisting of acetone and cyclo 65
hexane from admixture with other substances
which comprises treating the mixture with the
other substance from the group and distilling off‘
the resultant cyclohexane-acetone azeotrope.
20. A method for the removal of acetone from 70
admixture with other substances which comprises
hexane which comprises treating the cyclo
hexane-containing mixtures with acetone in the
treating the acetone-containing mixture with
ratio of at least 2.0 parts of acetone per part of
cyclohexane and thereafter distilling off the re
hexane-acetone azeotrope.
75 sultant cyclohexane- acetone azeotrope and there
cyclohexane and distilling off the resultant cyclo
EDMUND FIELD.
75