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Патент USA US2411588

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Patented Nov. 26, 1946
2,411,588
our-r131)v STATES PAT-ENTEROFFICE
John W. Packie, Green Village, ‘and William S.
Craft, Elizabeth,iN. J., assignors to Standard
Oil Development Company, a corporation of
Delaware I
>
Application December 16,1944, Serial No. 568,498
10 Claims. (Cl. 260—681.5)_
This invention relates to improvements in the
separation and concentration of diole?ns from
mixtures. of saturated and unsaturated hydro
carbons containing diole?ns and relates par
ticularly to‘ the separation and concentration of
~ 2
produce butadiene substantially free of these
acetylenes.
_
An object of this invention. is to selectively
separate the less soluble ole?ns from an- am
moniacal cuprous salt solution containing ole
butadiene by the use of a cuprous salt solution;
?ns and diole?ns. Another object of this in
Organic products, obtained on crackingpe
vention is to separate diole?ns without a sub-~
troleum, brown coal, brown coal tar, synthetic
stantial loss of ammonia from the solution. A
para?ins and the like in the presence or absence
further object of this invention is to obtain a
of additional gas or vapors such as steam, hy 10 diole?n product low in acetylene content. These
drogen,v nitrogen, carbon dioxide and the like,v
and other objects of the invention will be clearly
frequently contain both ole?ns and diole?ns
understood upon reading the following descrip
that are» gaseous at ordinary temperatures and
tion with reference to the accompanying draw
pressures. It is. very dii?cult to separate. the ' ing showing a flow sheet of the process.
I
gaseous product into its component parts even by 15
refrigeration as theaboiling points of the said
ole?ns and diole?ns lie very close, for example,
in the case of .butene-I and butadiene, the
boiling points of which are —6.24° Ci. andv —4.5°
C. A, method used extensively at present in the
separation and concentration of the ole?n or di-~
ole?n is one in which a solvent is used to extract
the desired ole?n or diole?n which is there
after separated from the. solvent. A- solvent
used extensively is an aqueous solution of am
moniacal cuprous salt. One‘ of the di?iculties
encountered in using the ammoniacal cuprous
Referring to the drawing, hydrocarbon ‘feed
vapors consisting of ole?ns and diole?ins plus I
some other minor impurities enter extractor 2
through line I. This tower contains either,
bubble plates or packed sections and operates at
about 0 pounds per square inch gauge and 30° F.
Ammoniacal cuprous acetate solvent enters the
top of extractor 2 through line 3v and ?ows down‘
the tower countercurrently to the hydrocarbon
vapors rising in the tower. The unabsorbed hy
drocarbon vapors leave the‘ top of extractori.l
through line 4'. In this tower most of the buta
diene and: essentially all of the acetylenes con
tained in the feed are dissolved in the solvent.
ole?n generallycontain‘s a small fraction of other
soluble ingredients. When butadiene is ab 30 However, about 5 tov 20% of the ole?ns are also
dissolved in the solvent and must be selectively
sorbed by ammoniacal cuprous. acetate, the solu
removed. The solvent ?ows from extractor 2
tion contains not only the diole?n but alsoa
through stripper l5 wherein it is contacted coun
salt in that the solution of either the diole?n or ~
small fraction of the ole?n and acetylenes.
A complication encountered is the: di?iculty of
tercurrently‘with recycled butadiene vapors. in‘
troduced into the bottom of stripper l5 through
preparing. a butadiene product. sufficiently free 35 line 5. In the. stripper most of the undesired
from acetylenes‘ to meet speci?cations. Since
hydrocarbons. (principally ole?ns) are stripped
the copper solutionused as the solvent has a
from the‘ solvent thereby leaving in solution es
high dissolving power for acetylenes, methyl
sentially pure butadiene, and some dissolved
acetylene, ethyl acetylene. and vinyl acetylene
acetylenes. The solvent leaves thefbottom of
are undesirably removed along with the. diole?ns. 40 stripper l5 through line 6 and is heated to 60—90°
For example in the case of a hydrocarbon, gas
containing butadiene and 0.1% of any of the
acetylenes designated, a copper solution. brought
to equilibrium therewith-at 80° F. and 25p. s. i. a.
total pressure. contains» 0.023 mols of dissolved
acetylenes per liter of solution or about 0.1% by
weight. Whenthe rich. solution is heated to re
lease the butad-iene, a large. proportion, ot-these
F. and introduced into the top of desorber 1
above the top plate. This desorber- contains
either bubble plates or a combination of plates
and packed‘ sections and is maintained at a pres
sure of 5 to 25 pounds persquare inch gage, and
a temperature of (SO-90° F. Under‘ these
moderate conditions , very little desorption of
acetylenes occurs and from the top section of
the desorber tower ‘l, essentially pure low acet
butadiene’ productvv tormeet the speci?cation of 50 ylene-content butadiene vapor is withdrawn
1000 P. P. M., it is accordingly necessary for the
through line L6 as product. The partially de'
acetylenes released in the hot zone tov be sub
sorbed solvent passes down through desorber 'l
sequently reabsorbed. Since. these impurities
and is collected on pan 8. The solvent is with.
tend to .ta?ect or impair the reaction} qualities
drawn through line 9 by pump I2 and heatedto
acetylenes. are released also. For the ?nal
of’ the butadiene“ product, it is very desirable to
150-1809 F. in heat exchanger l0 and heater II,
2,411,588
3
4
tion having thus been set forth and a speci?c
illustration of the same given, what is claimed as
new and useful and desired to be secured by
Letters Patent is:
1. In the extraction of butadiene from mix
and is returned to the tower below pan 8. Essen
tially all the diole?n'remaining in solution is
rejected at this point together with consider
able amounts of ammonia, water, and acetylene.
These vapors pass up through the tower con
tures of saturated and unsaturated, hydrocarbons
tacting the descending cooler solvent, and most
with ammoniacal cuprous salt solution, the im
of the ammonia and water vapor and a portion
provements which comprise passing the mixture
of the vaporized acetylenes are reabsorbed. The
.of saturated and unsaturated hydrocarbons in
unabsorbed vapors comprising butadiene and a
large amount of acetylene are removed through 10 countercurrent flow to an aqueous solution of
ammoniacal cuprous salt at a temperature of
line 5 and recycled to the stripper [5. Lean sol- '
about 30° F. and a pressure of 0 pounds per square
vent leaving the bottom of desorber ‘I is cooled
inch, stripping the aqueous solution of am
and recycled to absorber 2 through line 3.
moniacal
cuprous salt by passing the said aqueous
The extraction of butadiene from a dilute buta
solution of ammoniacal cuprous salt in counter
diene feed using ammoniacal cuprous acetate sol—
current flow to a mixture of butadiene and acetyl
vent involves the following three steps:
ene, heating the stripped ammoniacal cuprous
1. Absorption-In this step, the desired buta
diene is dissolved in the solvent along with a small
salt solution to a temperature between 60—90° F.
to release substantially pure butadiene as an over
amount of undesired hydrocarbons. This step
may be carried out with the hydrocarbon phase 20 head product, further heating the ammoniacal
cuprous salt solution to a temperature ranging
in either the liquid or vapor state.
from
150—l80° F. and recovering butadiene high
2. Stripping.—ln this step, the undesired hy
in acetylene as a sidestream, and using said side
drocarbons of lower solubility than the desired
stream as the stripping medium in said stripping
product are removed from the solvent, leaving
essentially pure butadiene in the solvent. The 25 step.
2. In the extraction of butadienes from hydro
stripping may be carried out with the hydrocar
carbon mixtures containing both saturated and
bon phase in either the liquid or vapor state.
unsaturated hydrocarbons, the improvements
3. Desorption-In this step, the pure butadiene
which comprise passing a mixture of saturated
is recovered from the solvent by vaporization
30 and unsaturated hydrocarbons in countercurrent
therefrom.
?ow to an aqueous solution of, an ammoniacal
The conditions of operation given in the above
cuprous acetate, maintained at a temperature of
description are not to be construed as limiting but
about 30° F., stripping the aqueous solution of
as being merely representative. For example, the
the ammoniacal cuprous acetate by passing it in
temperatures and pressures given may be varied
35 countercurrent flow to a ,gas containing buta
diene, heating the thus stripped aqueous solution
The essential feature of this invention is the
of ammoniacal cuprous acetate to a temperature
two-stage desorption of butadiene from the rich
ranging from Bil-430° F. 'to release substantially
solution with the withdrawal, as product, of the
pure
butadiene as anoverhead product, further
low acetylene-content butadiene vapor from the
initial ?ash and the recycle of the high acetylene 40 heating the ammoniacal cuprous acetate solution
to a temperature ranging from 150-180° F. to
content butadiene vapor from the‘ second flash
expel substantially all of the remainder of the
back to the stripper. This type of operation per
butadiene and using the butadiene recovered in
mits consistently meeting the acetylene speci?ca~
the second step as the stripping medium in the
tion on the product butadiene with a minimum
stripping step.
number of trays in the desorber' tower.
3. In the extraction of. diole?ns from a mixture
The following tabulation illustrates the mag
of saturated and unsaturated hydrocarbons, the
nitude of the acetylene contents of the pertinent
improvements which comprise passing a mixture
streams when operating with a feed containing
of saturated and unsaturated hydrocarbons in
about 1000 P. P. M. of acetylenes.
countercurrent flow to, an aqueous solution of
First stage low temperature desorption
ammoniacal cuprous acetate solution to absorb
widely-
,
‘
v
the unsaturated hydrocarbons therein, stripping
Temperature _______________________ __°F__
80
Pressure ______________________ __p. s. i. g__
12
the thus enriched ammoniacal cuprous acetate
solution with a diole?n-cuntaining gas, heating
(product) ___________________ __P. P. M__ 500
‘ the stripped ammoniacal cuprous acetate solution
to a temperature ranging from (SO-90° F. and at a
Acetylene content of desorbed vapor
Second stage high temperature desorption
pressure ranging from 5-25 pounds per square
inch to release substantially pure diole?ns as the
Temperature of solution introduced to
second stage ___________________ __°F__
80
»
'
°F__
165
Desorption pressure _________ __p. s. i. g__
12
Acetylene content of vapor from reboilei'
(based on hydrocarbon) ____ __P. P. ML. 10, 000
Acetylene content of recycle vapor to
, 65
stripper __________________ __P. P. M__ 1, 500
Acetylene content of lean solution
Mols per liter__
desired product, further heating the ammoniacal
cuprous acetate solution to a temperature rang
Temperature of solution from reboiler
. 013
This invention has particular application in the
extraction of butadiene from a dilute butadiene
feed using ammoniacal cuprous acetate ‘solvent.
ing from 150—180° F. to release the remainder of
the diole?ns as an impure'product containing
acetylene and using these impure diole?n-s as the
stripping gas in said stripping step.
4. A method for preparing substantially pure
butadiene comprising contacting ‘a hydrocarbon
gas containing butadiene, acetylenes, paraf?ns
and ole?ns with an aqueous solution of am
moniacal cuprous acetate solution to absorb the
unsaturated hydrocarbons, stripping the ole?ns
and any physically absorbed para?ins from said
cuprous acetate solution by contacting it with a
However, with modi?cation, it might be appli
gas rich in butadiene, releasing pure butadiene
cable to other extraction systems, using different
from the stripped solution by heating the said so
solvents.
The nature and objects of the present inven 75 lution to a temperature of 60-90” F., releasing the
2,411,588
.
5
_
6
~
remainder of the butadiene and an appreciable
amount of the acetylene-from the solution by
nent B having vapor'pressures in the presence of
a selectivesolvent which contains a component C
heating it to a temperature between 150 and 180° '
increasing in the order named, comprising the
steps of absorbing component A, butadiene and
F. and using the acetylene-containing butadiene
as the stripping medium in said stripping step.
'5. A process for separating butadiene from gas‘
.mixtures comprising a major portion of buta
diene, ole?ns and a minor portion of acetylenes
comprising the steps of absorbing‘butadiene,ole
?ns and‘ acetylenes in ammoniacalcuprous vace
tate solution, stripping absorbed ole?ns from said
component B in said selective solvent containing
component C having a vapor pressure lower than
vthe vapor pressures of component A, butadiene
and component’ B to produce an enriched sol
‘ vent, stripping component B from said enriched
solvent by contacting it with a mixture of com-‘
ponent A and butadiene, heating said stripped
solution by contacting it with a mixture of buta
solvent under conditions to produce a ?rst over
diene and acetylenes, heating said stripped sol
head‘vapor rich in butadiene and leave a ?rst
vent under conditions to release a portion of the
bottoms product comprising said solvent con
butadiene in substantially pure form as a ?rst 15 taining dissolved components A and C and the re
overhead product and leave a bottom product
mainder of the butadiene, further. heating the
comprising said solvent containing dissolved acet
solvent under conditions to produce a second
ylenes, ammonia and the remainder of thebuta
overhead product comprising an appreciable
diene, further heating the solvent under condi
amount of component A, a portion of component
tions to produce a second overhead product com
C and the remainder of thebutadiene, contact
prising an appreciable amount of the acetylenes,
ing the mixture of 7 components A and C and
a portion of the ammonia and the remainder of
' butadiene with said solvent from said ?rst heat
the butadiene, contacting the overhead mixture
ing step to reabsorb component C, removing a
of butadiene, acetylenes and ammonia with the
side stream mixture comprising component A and
solvent from said ?rst heating step to reabsorb 25 butadiene not reabsorbed in the solution from
ammonia, removing as a side stream mixture the
said ?rst heating step and using said'mixture of
vapors, comprising butadiene and acetylenes not
component A and butadiene as the stripping
reabsorbed in the solution from the ?rst heat
medium in said stripping step.
‘
1
>
ing step and using the sidestream'mixture ‘as
> the stripping medium in said stripping step.
6. A process for separating butadiene from gas
9. A process for separating a gaseous mixture
comprising butadiene and components A and B,
component A, butadiene and component B hav
ing vapor pressures in the presence ofa selective
solvent increasing in the order named, compris
mixtures comprising butadiene, ole?ns and acet
ylenes, comprising the steps of absorbing the
butadiene, acetylenes, and ole?ns in a selective
ing the steps of absorbing components A and B
solvent, stripping the absorbed ole?ns from said 35 and butadiene in said selective solvent to produce ,
selective solvent by contacting it with a mixture of
an enriched solvent, stripping component B from
butadiene and acetylenes, heating the stripped
said enriched solvent by contacting it‘ with a
solvent under conditions to release a portion of
‘mixture of butadiene and component A, heat
the butadiene in substantially pure form, then
ing the stripped solvent under conditions to re
heating said solvent under conditions to release
the remainder of the butadiene and appreciable
acetylenes and using the mixture of butadiene
and acetylenes thus obtained as the stripping
medium in said stripping step.
7. In a process for separating butadiene from
gas mixtures comprising butadiene, saturated and
unsaturated hydrocarbons the steps which com
lease a ‘portion of the butadiene in ‘substantially
pure form, and then heating said solvent under
conditions to release the remainder of the buta
diene and an appreciable amount of component
A and using the mixture of butadiene and com
ponent A thus obtained as the stripping medium
in said stripping step.
10. A process for separating a diole?n from gas
prise absorbing the butadiene and unsaturated '
mixtures comprising the diole?n, ole?ns, and
hydrocarbons in a selective solvent, stripping the
acetylenes, comprising the steps of absorbing the
selective solvent by passing the selective solvent 50 diole?n, acetylenes, and ole?ns in a selective
in countercurrent ?ow to a mixture of butadiene
solvent, stripping the absorbed ole?ns from said
and acetylenes, heating the thus stripped solvent
selective solvent by contacting it with a mixture
' to release substantially pure butadiene as an over
of the diole?n and acetylenes, heating the stripped
head product, further heating the solvent to a
solvent under conditions to release a portion of
higher temperature to release further amounts
the diole?n in substantially pure form, then heat
of butadiene high in acetylene as a side stream,
ing said solvent under conditions to release the
and using said side stream as the stripping medi
remainder of the diole?n and appreciable acety
um in said stripping step.
lenes and using the mixture of diole?n and acety-é
8. A process for separating a gaseous mixture
lenes thus obtained as the stripping medium in
comprising 'major amounts of butadiene and a 60 said stripping step.
>
component B and minor amounts of a com
ponent A, component A, butadiene and compo
'
JOHN W. PACKIE.
WILLIAM S. CRAFT.
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