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Патент USA US2408923

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Patented Oct. 8, 1946
2,408,922
' 1
UNITED STATES PATENT OFFICE
2,408,922
SEPARATION OF'DIOLEFINS BY AZEO
TROPIC DISTILLATION
Theodore W. Evans, Oakland, Rupert 0. Morris,
Berkeley, and Edward C. Shokal, Oakland,
Calif., assignors to Shell Development Com
pany, San Francisco, Calif., a corporation of
Delaware
No Drawing. Application April 30, 1942,
Serial No. 441,246
8 Claims. (Cl. 202-42)
1
2
This invention relates to the separation of a
component of a ?uid mixture and particularly
to the separation of a component of a mixture
whose components possess little difference in
vapor pressure so that practical separation by
ordinary fractional distillation is very di?icult,
if not impossible. The invention more especially
pertains to a practical and economical method
dominating in piperylene and mono-ole?ns boil
ing close thereto. It is to the treatment of these
last-mentioned relatively narrow boiling frac
tions that the process of the present invention is
most particularly directed.
An object of the present invention, therefore,
is to provide an e?icient and easily executed proc
ess for effecting the separation of isoprene and
piperylene from relatively narrow boiling hydro
for effecting the separation of acyclic diole?ns
of at least ?ve carbon atoms from mixtures there
of with compounds of a lesser degree of unsatu
ration and/or saturated compounds having the
same number of carbon atoms.
10 carbon fractions wherein they are contained.
The process of the invention, whereby the fore
going. and other objects are accomplished, com
prises fractionally distilling a mixture containingr
an acyclic diole?n of at least ?ve carbon atoms
The pyrolysis or cracking of petroleum or pe
troleum fractions such as naphtha, kerosene, 15 and one or a plurality of mono-ole?ns and/or
one or a plurality of saturated hydrocarbons hav
stove oil, gasoline and the like, gives rise to many
ing a like number of carbon atoms in the presence
valuable compounds useful in a variety of indus
of a compound which has a preferential solvent
tries. Piperylene (pentadiene-l,3) and isoprene
power for the acyclic diole?n and which is capa
(2-methyl-butadiene-1,3) are examples of such
valuable compounds. In addition to many other 20 ble of forming constant boiling azeotropes with
each of the components of the mixture, includ
uses, both of these products of the pyrolysis of
ing the acyclic diole?n, the azeotrope of the di
petroleum are applicable to the preparation of
ole?n and the azeotrope-forming compound being
resins and other polymerization products.
higher boiling than the other azeotropes. Ac
separation of isoprene or piperylene from hydro 25 cording to a preferred mode of executing the
process, the components of the mixture other
carbon mixtures resulting from the pyrolysis of
than the diole?n or, more accurately, the major
petroleum or petroleum fractions by ordinary
portions thereof, are distilled off in the form of
fractional distillation, it is relatively easy to frac
their azeotropes with the azeotrope-forming com
tionally distill such mixtures to obtain a fraction
consisting of or predominating in hydrocarbons 30 pound which has been added in a quantity only
su?icient to form these azeotropes, the acyclic
having ?ve carbon atoms and to thereby mate
diole?n being thereby concentrated in the dis
rially increase the concentration of these acyclic
tillation kettle. In a second and more preferred
diole?ns. The following is a list of most of the
method of executing the process of the invention,
hydrocarbons of ?ve carbon atoms, all of which
may be present in such a fraction, together with 35 the azeotrope-forming compound is added in a
quantity greater than is required to form azeo
their boiling points:
tropes with the said other components of the
. °C.'
While it is practically impossible to e?ect the
3-"nethyl-butene-1 ____________________ __ 20.1
Pentene-l ____________________________ __ 30.1
2-methyl-butene-l ____________________ __ 30.05
mixture, whereby increased advantage is taken
of the preferential solvent power of the azeo
40 trope-forming compound for the diole?n and
36.4
more complete concentration thereof attained.
By means of the process of the invention, a hy
2-methyl-butene-2 ____________________ __ 38.4
drocarbon mixture containing less than 12 ~weight
2-methyl-butadiene-l,3 (isoprene) ______ __ 34.07
Pentene-2 ____________________________ __
Cyclopentadiene
______________________ __ 41.0
Pentadiene-1,3 (piperylene) ____________ __ 42.5
per cent of diole?n was concentrated in a single
45 treatment to over 70 weight per cent, whereas
Pentane ______________________________ __ 36
by ordinary fractional distillation of a mixture .
Cyclopentane _________________________ __ 44
much richer in original diene (34.3 mol per cent)
the best concentration which could be achieved
The applicability of ordinary fractional distil
was 52.6 mol per cent.
lation to the separation of isoprene and piperyl 50 As indicated, the process of the invention is
ene from among the reaction products obtained
most preferably applied to preliminarily fraction
by the pyrolysis of petroleum does not end with
ated materials, that is, to relatively narrow boil
the isolation of a fraction consisting of or pre
ing mixtures containing either isoprene or pi
dominating in hydrocarbons of ?ve carbon atoms
perylene to the substantial exclusion of the other.
as it is also economically practicable to fraction 55 However, the process is not to be construed as so
ally distill this fraction to obtain two relatively
limited. It may, for example, be applied to a
narrow boiling cuts or fractions, one consisting
mixture comprising all of the above listed ?ve
chie?y of isoprene and mono-ole?ns having boil
carbon atom hydrocarbons, rather than to iso
ing temperatures in the close vicinity of the boil
prene or piperylene fractions separated from such
ing temperature of this diole?n, the other pre 60 mixtures in' which event the separation is between
2,408,922
3
,
4
the acylic diole?ns on the one hand, the mono
ole?ns and paraffins on the other. It may be
amounts may be used. The amount of amine
added to the mixture to be treated shouid not,
here parenthetically noted that where the treated
hydrocarbon mixture has been obtained by the
pyrolysis of petroleum it will consist in the main
of unsaturated compounds, para?ins being pres
however, be less than the amount required to
form azeotropes with all of the components of
tropic distillation which constitutes the present
The azeotropic distillation constituting the
the. mixture other than the diole?n, as this prac—
tice greatly reduces the efficiency of the process.
When a quantity of amine is used which is not
ent only to a minor extent.
The presence of cyclopentadiene in a fraction
sui?cient to. form the azeotrope with the diole
subjected to treatment according to the present
?n, but which is suf?cient to form the azeotropes
process is not detrimental to the e?icient con 10 with the other components of the mixture, by
fractionally distilling off the azeotropes of the
centration or separation of the acyclic diole?n or
other components, a high concentration of di
diole?ns contained therein, but since this com
pound is easily removed, prior separation there
ole?n in the distillation kettle is achieved. While
of is recommended. Cyclopentadiene polymerizes
this method of executing the process of the in
to dicyclopentadiene in the presence of other ?ve
vention is convenient, superior results are at
carbon hydrocarbons upon the application of mild
tained by using an amount of amine adequate
heat, and since the dimeric material has a boil
to form the azeotrope with the diole?n as well as
ing point greatly in excess of that of any hydro
the other azeotropes. Isopropylamine has a pref
carbon of ?ve carbon atoms, the other compo
erential solvent power for acyclic cliole?ns of at
nents of the mixture are easily distilled off over- ‘
least ?ve carbon atoms present in mixtures with
head. If it is desired to later employ the cyclo
mono-ole?ns and/or. paraf?ns of similar vapor
pentadiene as such, care should be exercised to
pressures which is naturally exerted the more
apply only moderate temperatures in heating the
strongly the greater the concentration of the
mixture under treatment, as excessive heat, par
amine in the treated mixture. Even an excess
ticularly if prolonged for any appreciable period, 25 of amine over that, required to form, azeotropes
results in the formation of more complex poly
with all of the hydrocarbons of the treated mix
mers, such as tetra- and penta-cyclopentadiene
ture is without harmful effect.
which are a great deal more di?icult to depoly
When the mixture distilled comprises the most
merize Without excessive decomposition. It has
preferred quantity of amine, that is, not less
been found that the formation of these higher
than the amount required to form azeotropes with
polymers can be prevented and conversely that
all of the components of the mixture, the quan
the formation of the easily clepolymerized dimer
tity of diole?n leaving the still with the azeotropes
can be selectively accomplished in the presence
of the other components. is materially less than
of other hydrocarbons of ?ve carbon atoms if
when the treated mixture contains a lesser amount
the temperature applied to the treated mixture . of amine; hence, for the same result, towers of
is not permitted to substantially exceed 100° C.
fewer plates may be used which is distinctly ad
At this temperature, a conversion of 95% of the
vantageous. The distillation as executed with the
monomer to the dimer has been achieved without
preferred amount of amine is preferably carried
the aid of a catalyst.
,
to completion, the recovered fractions becoming
Returning now more speci?cally to the azeo 40 progressively richer in diole?n.
process, a compound which has been found par
present invention may be conducted at superat
ticularly adapted to the formation of constant
mospheric or subatmospheric pressures, but op
boiling azeotropic mixtures of the required char
eration at atmospheric pressure is preferred, It
acter with hydrocarbons of at least ?ve carbon 45 must be noted that varying the pressure may
atoms is isopropylamine. By azeotropic mixtures
change the ratio of the compounds in the azeo
of the required character is meant azeotrcpic
tropic mixtures, as well as the distillation tem
mixtures, the boiling ranges of which enable
peratures of these mixtures.
more e?icient and complete concentration of
The following example is introduced to illus
acyclic diole?ns of at least ?ve carbon atoms as 50 trate a mode of‘ executing the invention and the
contained in mixtures with mono-ole?ns and/or
results thereby attained. The invention is not
para?in hydrocarbons of similar vapor pressures
to be considered as limited either to the speci?c
than is practicable by ordinary fractional distil
fraction treated or the particular aliphatic amine
lation. The azeotropic mixtures which isopro
employed, or to the conditions of operation dis
pylamine forms with hydrocarbons of at least
closed.
?ve carbon atoms are minimum boiling. In other
Example
Words, isopropylamine in effect causes a lower
An isoprene fraction (boiling range 30° C.-38°
ing of the eifective distillation temperatures of
C.) was fractionated from a mixture resulting
the constituents of a mixture of hydrocarbons
of at least ?ve carbon atoms. The drop in dis 60 from the pyrolysis of second out straight run
gasoline. The fraction analyzed 42.5 mol per cent
tillation temperature, however, is not uniform for
(41.6 Weight per cent) dienes, 97.0 mol per cent
the different components, isopropylamine lower
total unsaturates. About 230 grams of the sepa
ing the distillation temperatures of ?ve-carbon
rated isoprene fraction was charged to a distil
acyclic diole?ns to a lesser extent than it lowers
the distillation temperatures of ?ve-carbon mono 65 lation unit together with approximately 460
grams of isopropylamine. The distillation unit
ole?ns and para?ins. Therefore, the azeotropes
included
a, helix-packed tower of 15 to 18 theo
of the mono-ole?ns and/or paraf‘rlns of the mix
retical plates, an automatic re?ux controller, and
ture boil before the azeotropes of the acyclic di
a condenser. The mixture was then subjected
ole?ns and thus an economical, efficient and ready
method for the separation or concentration of 70 to distillation at atmospheric pressure and at a
the latter is provided.
re?ux‘ ratio of 10‘ to 1, the overhead condensate
In general it is preferable to employ the iso
being collected in a. plurality of containers to de
propylamine in a quantity su?‘icient to form azeo
termine the diole?nic content of each of the frac
tropes with each and everyv hydrocarbon present
tions or cuts. thus obtained. In all, seven cuts
in the mixture treated’, but greater or lesser 75 were taken, the, most concentrated containing
2,408,922
5
Wt.
Cut
No.
Wu,
g.
Boiling
range, ° C.
per cent
hydrocarbon
Wt
jecting the resulting mixture to fractional distil
lation to attain a residue the hydrocarbon con
tent of which predominates in isoprene.
4:. A process for separating piperylene from
mixures thereof with compounds of the class con_
sisting of mono-ole?ns and parai?ns having va
por pressures close to that of piperylene which
Solvent free
er ce'nt hydrocarbon,
advent wt. per cent
“
dicncs
78
80
26. 5 to 28. 2
28. 2 to 29. 5
50. 7
49. 0
49.3
51
20.9
28.0
109
82
84
86
96
29. 5 to 29. 5
29. 5 to 29. 8
29. 8 to 30
30 to 30. 5
30. 5 to 31. 2
35. 3
42. 5
37. 5
31. 4
15.6
64. 7
57. 5
62. 5
68. 6
_84. 4
43. 2
39. 3
50. 2
62. 4
72. 4
6
of the mixture other than the isoprene, and sub
72.4 weight per cent diene. The complete data
covering the run are given in the following table:
Analysis of cuts
comprises adding isopropylamine to the mixture
in an amount only sufficient to form constant
boiling azeotropes with the components of the
mixture other than the piperylene, and subject
ing the resulting mixture to fractional distilla
tion to attain a residue the hydrocarbon content
of which predominates in piperylene.
The separation of the isopropylamine from the
various fractions obtained as above may
fected, by means of cooling, addition of
or by treatment of the azeotropic mixtures
other convenient manner known to those
in the art.
be ef
water,
in any
skilled 20
Although by the procedure of the example, the
diole?n is merely concentrated, it will be under
stood that any one or more of the fractions ob
tained may be resubjected to distillation accord
ing to the process of the invention until actual
separation is achieved. When the treated mix
ture comprises both isoprene and piperylene, their
separate fractionation from the fraction or frac
tions wherein they are obtained together may be
effected either in the presence or absence of the
aZeotrope-forming agent, but preferably the iso
propylamine is ?rst removed.
'
The invention claimed is:
1. A process for separating isoprene from mix
tures thereof with one or more compounds from
the class consisting of mono-ole?ns and paraf
?ns having vapor pressures close to that of iso
prene which comprises adding isopropylamine to
the mixture in a quantity adequate to form con
stant boiling azeotropes with each of the com
ponents thereof, subjecting the resulting mixture
to fractional distillation to distill off an azeo
tropic fraction the hydrocarbon content of which
5. A process for separating an acyclic diole?n
of five carbon atoms from mixtures thereof with
one or more compounds from the class consisting
of mono-ole?ns and paraffms having vapor pres
sures close to that of the acyclic diole?n which
comprises adding isopropylamine to the mixture
in an amount adequate to form constant boiling
azeotropes with each of the components thereof,
subjecting the resulting mixture to fractional
distillation to distill off an azeotropic fraction
the hydrocarbon content of which is made up
principally of the components of the original
mixture other than the acyclic diole?n, and con
tinuing the distillation at a higher still head tem
perature to obtain an azeotropic fraction the hy
drocarbon content of which predominates in the
~ acyclic diole?n.
6. A process for separating an acyclic diole?n
of ?ve carbon atoms from mixtures thereof with
one or more compounds from the class consisting
of mono-ole?ns and para?ins, the vapor pres
sures of which are close to that of the acyclic di
ole?n, which comprises adding'isopropylamine to
the mixture in an amount only su?icient to form
constant boiling azeotropes with the components
of the mixture other than the acyclic diole?n,
and subjecting the resulting mixture to frac
tional distillation to attain a residue the hydro
carbon content of which predominates in the
is made up principally of the components of the , acyclic diole?n.
7. A process for concentrating acyclic diole?ns
original mixture other than the isoprene, con
of ?ve carbon atoms as contained in mixtures
tinuing the distillation at a higher still head tem
with one or more compounds from the class con
perature to obtain an azeotropic fraction the hy
sisting of mono-ole?ns and paraffins, the vapor
drocarbon content of which predominates in iso
prene, and separating the isoprene from said last 50 pressures of which closely approach the vapor
mentioned fraction.
2. A process for separating piperylene from
mixtures thereof with one or more compounds
from the class consisting of mono-ole?ns and
paraflins having vapor pressures close to that
of piperylene which comprises adding isopropyl
amine to the mixture in a quantity adequate to
form constant boiling azeotropes with each of the
components thereof, subjecting the resulting mix
ture to fractional distillation to distill off an azeo
tropic fraction the hydrocarbon content of which
is made up principally of the components of the
original mixture other than the piperylene, con
tinuing the distillation at a higher still head tem
perature to obtain an azeotropic fraction the
hydrocarbon content of which predominates in
pressures of the acyclic diole?ns which comprises
adding isopropylamine to the mixture in an
amount at least sufficient to form minimum-boil
ing azeotropic mixtures with each of the com
. ponents thereof and subjecting the resulting
mixture to fractional distillation to obtain a plu
rality of overhead fractions progressively richer
in the acyclic diole?ns.
8. A process for concentrating acyclic diole?ns
of ?ve carbon atoms as contained in mixtures
60 with one or more compounds from the class con
sisting of mono-ole?ns and para?ins the vapor
pressures of which closely approach the vapor
pressures of the acyclic diole?ns which comprises
adding isopropylamine to the mixture in an
amount only suf?cient to form minimum boiling
azeotropes with the components thereof other
piperylene, and separating the piperylene from
than the acyclic diole?ns and subjecting the re
said last mentioned fraction.
sulting mixture to fractional distillation to obtain
3. A process for separating isoprene from mix
tures thereof with one or more compounds from 70 a residue the hydrocarbon content of which pre
dominates in the acyclic diole?ns.
the class consisting of mono-ole?ns and paraf?ns
having vapor pressures close to that of isoprene
THEODORE W. EVANS.
which comprises adding isopropylamine to the
RUPERT C. MORRIS.
mixture in an amount only sufficient to form
EDWARD C. SHOKAL.
75
constant boiling azeotropes with the components
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