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Патент USA US2410496

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Nov. 5, 1946‘
Q
R. A. GRAFF
2,410,496
SEPARATION AND RECOVERY OF \UNSATURATED GASES
Filed April 20, 1943
R
ATTORNEYS ‘
Patented Nov. 5, 1946
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2,410,496
UNITED sTA'rEsjPATENr orrica ~
2,410,498 ,
,
SEPARATION AND RECOVERY OF
UNSATURATED GASES
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Robert A, Grail’, Louisville, Ky., asslgnor to The
Girdler Corporation, Louisville, Ky., a corpora
tion of Delaware
I ' Application April 20,
1943, Serial No. 483,720
4 Claims. (erase-ears)
1
This invention ‘relates to the separation and ,
recovery of unsaturated gases from the general
point quite different from that of"butadiene, said
medium‘ being av liquid hydrocarbon which prefer
type of aqueous copper-bearing ammoniacal: solu
ably has‘?ve or more carbon atoms.
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tions which have been heretofore proposed and
The preferred examples of such va stripping
used for the selective separationof unsaturated 5 agent are light hydrocarbon oils composed es
gases from gaseous mixtures.
Such solutions usually contain dissolved salts
of organic acids, such as formic, acetic, lactic,
-etc., and basic, nitrogen compounds soluble in
aqueous solutions, suchas ammonia and amines. 10
The amines may be alkanol amines or polyamines,
and the copper compound may be cuprcus chlo
ride. Such compoundshave a selective action on
sentially of octane, heptane or hexane, or‘mix- ~
tures thereof, having a boiling point in the gen
eral vicinity ‘of 100° F. Various other‘ stripping
agents may be used, such as suitable alcohols,
ketones, aldehydes, phenols, or: related com
pounds, or other liquids such as carbon tetra
chloride.
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.,
,_
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The invention permits the regeneration of'the
unsaturated hydrocarbons, and may therefore be ' unsaturated hydrocarbon bearing copper solution
used for the separation of the unsaturated from 15 without the application. of heat, and further per
the saturated hydrocarbons, particularly those
mits the recovery of the dissolved hydrocarbon
hydrocarbons which are in gaseous or vapor form.
More speci?cally, the present process relates to
the recovery of 1,3-butadiene, from-the hydro
_ carbon products resulting from cracking or re
forming operations.
'
'
It has been common practice to recovervdis
solved unsaturated" hydrocarbons, and partic
ularly 1,3-butadiene, from copper bearing am
in the lique?ed condition, whereas the vapor .
; phase is the condition of the product when the
_ conventional methods of -_reactivating\ copper
20 bearing solvents are used.
By means of the present process a very much
smaller amount of heat exchange equipment is
required, polymerization of the unsaturated hy
drocarbon is kept at a minimum, noextensive
‘ moniacal solutions by boiling at atmospheric pres 25‘ ammonia recovery equipment‘ is required, and no
sure, or at reduced pressures. This boiling entails ~ compressors are required for the recovery of un
heating the copper bearing solutions containing _ saturated hydrocarbon in lique?ed condition if
the dissolved unsaturated hydrocarbons to an
the hydrocarbon be of a type which is in gaseous
" elevated temperature. During this heating step, ' form at atmospheric temperature and pressure.
a considerable portion of the ammonia may be 80 The butadiene may be removed by blowing the
driven off,‘ thereby weakening the solvent and
enriched stripping agent containing the unsat
requiring separation of the ammonia from the bu
_ urated hydrocarbon with a stripping gas such as
tadiene and the return of the __ammonia to the
steam-or ammonia.‘ Ifammonia is used, it may
solution. The heating also results‘in a certain
be then separated from the unsaturated hydro
amount of the butadiene being lost by polymer 35 carbon gases by water washing, and if ‘steam is ‘
ization, and it requires a large amount of heat
used, it may be separated from the unsaturated
exchange equipment for the heating and cooling
hydrocarbon by fractional condensation. I
of the liquids and vapors. The large amount of
The following is a speci?c example of ap
heat required for driving off the absorbed un
plicant’s process as employed for separating bu- ,7
saturated hydrocarbons necessitates an equally 40 tacllene from gaseous hydrocarbonmixtures and
I large amount of cooling. In such a process, am
removing the butadiene from the solvent by the
monia is the nitrogen compound commonly em
ployed, and it is not practical to use amines, as
use of hexane.
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A gaseous hydrocarbon mixture containing 11
they readily oxidize with heat.
butane, butene-l, butene-2, isobutylene and 25
In, carrying out the present process the bu 45 mol. per cent 1:3 butadieneis contacted at 40° vF.
tadiene is removed from the copper bearing solu
tion by the action of a stripping agent which
is non-soluble or only slightly soluble in the solu
tion, which is miscible with but does not react
_ in a packed tower with a cuprous-cupric ammo
nium acetate solvent containing an excess of am
monia, and this solution, which will contain ap
" proximately 16 vols/vol. of substantially pure.
with the butadiene, which has low viscosity, which 50 butadiene, is passed“ into a second contacting
does not dissolve or react with ammonia, amines
or other constituents of the copper bearing solu
tion, and which may be easily separated from
tower where the rich solvent is introduced at the‘ 1
top and ?ows down to the bottom of the tower
countercurrently contacting hexane, which is in
the hydrocarbons for reuse in the process. The
troduced at the bottom of the tower and with
medium is preferably one which has a boiling 55 drawn at the top. The regenerated copper bear
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3",
2,410,496
ing solvent is drawn of! at the bottomof the tower _ and the ‘hexane phase, which now contains sub
' stantially all of the 1:3 butadiene formerly held -
r by the‘rich ‘solvent, flows to a continuous trace
.tionating still, operating under pressure, where
the butadiene product is taken overhead and con
densed, and the bottoms from the fractionating
22' for applying pressure to the diaphragm of a
valve 23 in the line i9.
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The pump l8 and line I! deliver the rich solu
tion to a second column or desorber 20, in which
the butadlene is washed out of the copper solu
tion by the stripping agent in liquid form. This
stripping agent will hereinafter be referred to as
still are cooled. through heat exchange and re
"hexane,” but this term is here used only to
simplify the description, and without limitation
- turned to the extraction process. . The condensed
- butadiene now recovered as a liquid product may 10 to the particular stripping agent employed.
As previously noted, the. stripping agent and the
be used in any of the conventional processes for
copper containing solvent are immiscible, so that
the production of elastomerss
‘
they tend to" form separate layers. The liquid
In the accompanying drawing there is shown
level between the two layers in the desorber col
diagrammatically the apparatus units which may
be used in a commercial process for separating 15 umn 20 is maintained near the upper part of the
column. and this is likewise effected by a suit
_ butadiene from mixtures containing saturated
able form of liquid level controller 24 applying
hydrocarbons, and the flow lines of the various '
pressure on the diaphragm of a valve 26 in the
liquids and gases employed.
line H which leads'from the bottom of the de
To simplify a description of‘ the process as car
ried out in this apparatus, reference will be made 20 sorber 20, and which line includes a suitable cir
tobutadiene asthe unsaturated gas to be ob- '
talned, and butane the saturated gas with which
culating pump 26.‘ The rate of circulation may
be varied through comparatively wide limits by
regulation of the speed of either or both of the
pumps 18 and 26. By circulating a large amount
limitations on the scope of the invention.
25 of the copper solution, very little refrigeration is
required.- Refrigerating the copper solution to
The mixture of butane and‘butadiene, together
about 25°‘ F. before delivering to the top of the
‘ with other saturated and unsaturated hydrocar
it was mixed. It is to be understood thatthese'are
given-as examples,- and not to indicate speci?c
' bonspin liquid form, under pressure, and at at
mospheric temperature, is delivered through the
line 10 to a heat exchanger H, where the pres
sure is reduced, the liquid converted'to gaseous
absorber column l5 would result in a somewhat
more complete removal of the butadiene from the
30 butane, but delivering the solution to the col
form, and the amount of heat absorbed is only
about equal‘ to the heat of vaporization‘of the
umn at a temperature of about 35° F., or even
up to 50° F., is more economical in many respects.
The liquid hexane or other stripping agent '
tionfwhich maybe a reagent containing cuprous
ating column 30. In this column the hexane
cooled by the vaporizing mixture of butane and
butadiene in the heat exchanger H, and is de
livered from the heat exchanger through the line
II at a lower, temperature, ‘for instance about
from the top of the column 30 through the line
containing the dissolved butadiene is taken from
mixture. The mixture in gaseous form is then
delivered through the line I! at a low temper 35 the top of the column 20 through the line 21,
and is delivered by a pump 28 through a heat
ature, for instance about 30° F., and at about
exchanger 29 to the lower portion of a fraction
. atmospheric pressure. The copper bearing solu
is heated to such a temperature as will cause the
copper, an organic acid, excess ammonia and
to volatilize under about '75 pounds
‘water, is circulated in_ a closed cycle. It is de 40 butadiene
pressure,
and
the gaseous butadiene passes oi! '
livered' at a temperature of 50° F. or'higher, is
3|.
.
.
, In order to provide the required heat, the hex
an'e'may be continuously withdrawn from the
bottom of the column 30 through a line 32 by a
pump 83, heated in a heater 3., and returned to
the column 30 at a point somewhat above the
bottom, at the required temperature. Thus the
permitting the down?ow'of liquid and the up?ow
heating is effected by circulating a portion of
of gases or vapors in intimate contact with each
the hexane through the heater 84, and the
other. The copper containing solution’ is deliv
amount-of heat delivered to the column 30 may
ered through the line ll to the upper part of the
be controlled by the temperature or volume of
column II, and the gaseous mixture containing
the steam or other heating medium used in the
. the butadiene is delivered through the line l2
heater 34, or by controlling the speed of the pump
55
to the base of the column. During the up?ow
33, or by both.
—
of the vapors and the downflow of the solvent; the
The
heated
hexane
or other stripping agent,
butadiene is selectively absorbed by the copper
which
is
substantially
free from butadiene, is
solution. The rich solution is withdrawn from
withdrawn from the ‘bottom of the column If!
‘the bottom of the tower through the line l6, and 60 through the line 35, and delivered through the
the butane and other gases which‘ are not ab
heat exchanger 29 and a cooler 36. A portion
sorbed pass off from the top of the columnv
of the heat of the-stripped hexane is, thus trans
through the line ll. So far as concerns the gen
ferred'to the‘ enriched hexane delivered to the
eral principles of operation of the packed column,
column 30 through the line 21, and the residual
this‘ process step and the apparatus employed 65 heat of the liquid hexane leaving the heat ex
need not di?er essentially from that heretofore
changer 29 through the line-31 is removed by
commonly employed.
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,
.the cooler It, so that cold liquid hexane is deliv
The rich solvent withdrawn through the line It
ered to the lower portion of thecolumn 20. The
rate of withdrawal from the column 30 may be
is ‘delivered by a- pump l8 through the line l9,
and the rate at which it iswithdrawnmay be 70 such that a fairly constant liquid level is main
tained in the column 30 near the lower end there- ‘
so controlled as to maintain a’ liquid level at the
of, and this may be effected by a liquid level con
bottom of the column at. approximately the point
troller 38 acting on the diaphragm of a valve 39
II. The ‘control may be obtained by the use of
in the line 35._ No pump. is required for the re
conventional flow control apparatus diagram
matically illustrated as a liquidlevel controller ' turn of the stripping agent from the column 30
_A packed column or absorber i5 is provided. in
which the packing may be of any common type
2,410,496
to the desorber 20. as the former is maintained '
at a higher pressure than the latter.
diene will'reedily separate from the condensed
steam.
Having thus described my invention, what I
The butadiene separated from the liquid hex
ane and leaving the column 30 through the line
claim as new and desire to secure by Letters ‘.
31 is cooled to such a temperature that it will
liquefy under the pressure employed in the col
umn 80, which temperature might be in the
Patent is:
I 1. The process for separating butadiene from a
solution of cuprous-cupric ammonium acetate
neighborhood of 100° R, if the pressure in the
containing an excess of ammonia which includes
column 30 is about 75 pounds. This cooling may - extracting said butadiene from said solution in
be effected by any suitable form of condenser 40 10 an absorber by the action of a liquid hydrocarbon _
in the line 3| which delivers to ‘a small tank
stripping agent immiscible with said solution and
4|. From the bottom of this tank the liquid
having a boiling point substantially above that
“ butadiene
‘may
be
continuously
withdrawn
of butadiene, thereafter separating said stripping
through a line 46, by a pump 41, and is prefer
agent from the butadiene in a desorber by blowing
ably divided into two parts by the lines 48 and 15 therethrough a gaseous medium immiscible with
49, the relative proportions of the-parts being
the stripping agent and the butadienaseparating
varied at will. Through the line 48 the buta
diene product is delivered from the system in
liquid form to any suitable point of storage or
use. If it contains any traces of ammonia picked
up in the column I5, such traces may be re
said medium from the butadiene and returning a
part of the butadiene in liquid form to‘the top
of the desorber to re?ux vapors of said ‘liquid
‘ hydrocarbon.
2. The process of separating butadiene from a
moved by water washing. The flow through the
solution containing a dissolved .cuprous com
line 48 is controlled by a valve 50, the diaphragm
of which is actuated by a liquid level controller
5|, so as to maintain a substantially constant
liquid level in the tank 4!.
vaqueous solutions which includes extracting the
The butadiene delivered through the line 49
tion, non-reactive with said butadiene and has a
pound and a basic nitrogen compound soluble in ' ‘ '
butadiene from said solution by the action oil a
stripping agentwhich is immiscible with said solu
passes to the upper portion of the column 30 to
act as a re?ux, and its ?ow is controlled by a
boiling point substantially higher than that of
butadiene, thereafter driving off the butadiene
valve 52, the diaphragm of which is actuated by 30 from the stripping agent in a desorber, blowing
an ori?ce type ?ow controller 53 in the line 49.
It will be understood that various other types
of apparatus parts and other details may be varied
through a wide range for carrying out my im
proved process.
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a gaseous medium therethrough, cooling the buta
dienep vapors to condense them to liquid form
under said pressure, and returning a part oi’ the
liquid butadiene to the top of the desorber to '
85 re?ux vapors of said stripping agent.
In the process as above described, the column
30 is operated under a superatmospheric pres
sure, for instance about 75 pounds gauge pres
3. The process of separating butadiene from a
solution of cuprous-cupric ammonium acetate
containing an excess of ammonia which includes
extracting said butadiene from said solution in an
may be operated at atmospheric pressure, but in 40 absorber by the action of- a liquid hydrocarbon
sure.
This is not essential, as the column 30
that event the butadiene, which leaves the top
stripping agent having a boiling point substantially above that of butadiene, thereafter driv
of the column as a vapor, must be compressed
if it is to be delivered from the system in liquid
form.
‘ ing off the butadiene from said stripping agent
,
in a desorber by blowing ammonia up through
said desorber, and water washing the ammonia
from the butadiene leaving the top of the de
In the process as above described, the butadiene
is removed from the hexane by the action of heat,
but at a temperature below that at which the
sorber.
I
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butadiene is liable to polymerize. ‘It is not essen
tial that heat» be employed, as ammonia may be
4. The process of separating butadiene from
a solution of cuprous-cupric ammonium acetate
delivered to the bottom of the column 30 in place 50 containing an excess of ammonia which includes
extracting said butadiene from said solution in
of heat, and the mixture of ammonia and buta
an absorber by the action of a liquid hydrocarbon
diene delivered by line 3| may be readily sepa
stripping agent having a boiling point substan
rated by water washing; as ammonia is very~
i
soluble in water, whereas butadiene is substan
tially insoluble.
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If the stripping agent be a hydrocarbon liquid
of relatively high boiling point (345° R), such for
tially above that of butadiene, thereafter driving
" off the butadiene from said stripping agent in a
‘desorber by blowing ammonia up through said
desorber, water washing the ammonia from the
butadiene leaving the'top of the desorber and re
instance as a C10 hydrocarbon, the butadiene in
turning a part of the separated liquid butadiene
solution may be driven o? in vapor form by 60 to the top of the desorber to re?ux vapors of said
blowing steam through the column 30. In this
stripping agent.
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_ case, upon cooling the outgoing vapors, the buta
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‘ ROBERT A. GRAFF.
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