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Патент USA US2408948

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Oct. 8, 1946.
H. S. NUTTING ETAL
2,408,947
>AZEOTROPIC DISTILLATION OF ALIPHATIC HYDROCARBONS HAVING THE FORMULAS
Guan AND «nml-.9.V FROM Q'IYDROCARBON MIXTURES COMPRISING SAME
'
Flled July 29, 1939
Umweg/¿méd 0,7 '605
ATTORNEYS
¿nach
Patented Oct. 8, 1946
UNITED STATES PATENT OFFICE
2,408,947
AZEOTRGPIC DISTILLATION OF ALIPHATIC
HYDRÜCARBÜNS HAVING THE FORMULAS
CNH2N ÀND CNHzN-z FROM HYDROCARBÜN
MIX'EURES COMPRÍSING SAME
Howard S. Nutting and Lee H. Horsley, Mid
land, Mich., assignors to The Dow Chemical
Company, Midland, Mich., a corporation of
Michigan
Application July 29, 1939, Serial No. 287,218
22 Claims. (Cl. 202--42)
l
2
This invention concerns an improved .method
mixture, but obviously such complete separation
of separating unsaturated aliphatic hydrocarbons
would be difficult and expensive due to the knum
ber of diiierent operations and the variety of
having the formulas Cul-ign and CnHzn-z, particu
larly dioleñnes and acetylenes containing from
3 to 6 carbon atoms in the molecule, from hydro
carbon mixtures comprising the same.
ln the industrial cracking of hydrocarbon ma
terials such as petroleum fractions, coal tar dis
tillate, etc., complex mixtures of gaseous or low
boiling liquid hydrocarbons which comprise par
afi’ins, ole?lnes, dioleñnes and acetylenes are pro
duced in large quantities and the separation o1"
such mixtures to recover the individual hydro
equipment required.
An object of this invention is to provide a rela
tively simple and inexpensive method whereby a
crude gaseous or low boiling hydrocarbon mix
ture comprising an oleñne and a dioleñne and/or
an acetylene may be separated into its com
ponents by a single type oi operation, viz. distil
lation. The primary object is to provide an im
proved method of distilling any low boiling hy
drocarbon mixture containing at least two dif
ferent kinds of unsaturated hydrocarbons of very
carbons in even technically pure form constitutes
a serious problem. For instance, when an organic 15 nearly the same boiling point, e. g. a mixture of
two or more of the compounds butylene-l, buta
product such as kerosene or other petroleum frac
diene-1.3 and ethyl-acetylene, to recover the in
tions, cyclohexane or other cycloparaiiin, cyclo
dividual unsaturated hydrocarbons in relatively
hexene, ethylene, etc. is pyrolized gaseous or low
pure form. Other objects will be apparent from
boiling mixtures comprising butadiene-1.3 and
one or more of the isomeric butylenes, e. g. buty 20 the following description of the invention.
We have discovered that whereas an oleñne and
lene-l, butylene-Z, or isobutylene is fractionally
a diolefine having the same number of carbon
obtained. Other hydrocarbons such as ethylene,
atoms in the molecule usually boil at very close to
propylene, ethane, propane, butanes, etc. may
the same temperature and cannot satisfactorily
be and usually are present in the mixture. It is
be separated from one another by ordinary rec
true that such mixture of saturated and unsatu
tincation at atmospheric or increased pressure,
rated hydrocarbons may be separated by distilla
such separation may readily be accomplished by
tion into fractions consisting for the most part of
carrying the distillation out in the presence of
hydrocarbons containing the same number of
ammonia. The ammonia forms an azeotropic
carbon atoms to the molecule, but each such frac
tion usually consists of a mixture of saturated 30 mixture with the oleñne and another-azeotropic
mixture with the dioleñne. The azeotrope of
and unsaturated hydrocarbons which can be sep
each hydrocarbon with ammonia boils at a tem
arated from one another only with diñioulty, or
perature below that of the ammonia or the corre
not at all, by further rectiiication. For instance,
such distillation of the crude pyrolysis mixture
sponding hydrocarbon alone, but the aZeotropes
may be carried out to obtain a fraction consisting 35 have boiling points and heats of vaporization
sufficiently divergent from one another to permit
-ior the most part of a mixture of butane,
separation by distillation at atmospheric or su
peratmospherio pressure. The difference between
very eiiicíent rectification it is possible to obtain at
the distilling temperatures of the two azeotropes
least partial separation of the two compounds bu
tane and ethyl-acetylene from the mixture. 40 becomes slightly greater as the pressure on the
listilling system is increased. However, the
However, the butylene and butadiene distill to
latent heats of vaporization of the two azeotropes
gether and cannot satisfactorily be separated
butylene, butadiene, and ethyl-acetylene, and by
from one another by ordinary rectification re
gardless of how carefully or efficiently the opera
tion is carried out. A number oi' methods for
separating certain unsaturated hydrocarbons
diverge considerably with increasing pressures.
In all instances, the azeotrope of ammonia with
an oleñne (or with a para?in hydrocarbon) varies
only slightly in composition as the pressure is
increased, but the ammonia content of the aZeo
trope of ammonia with a dioleñne increases
such as butylene and butadiene from one another
are known, but these involve operations other
markedly as the pressure on the distilling sys
than distillation, e. g. extraction with a selective
solvent, reaction of one or more of the hydrocar 50 tem is raised. By carrying such distillation with
ammonia out at a pressure suñicient to avoid
bons in the mixture with an added chemical re
necessity for refrigeration in order to liquefy the
agent such as sulphuric acid or cuprous chloride,
distilling vapors, e. g. at a pressure of 150 pounds
etc. By suitable combinations of such known
per square inch gage or more, separation of the
methods it may be possible to separate all of the
individual hydrocarbons from a crude pyrolysis 55 azeotropes is rendered most practical.
2,408,947
3
4
We have discovered another fact which is of
interest in this connection. The ease of separat
ing an oleiine from a mixture thereof with a di
in cracked-oil gas. In the rectification scheme
indicated by the flow sheet it will be noted that
not only are the diolelines and acetylenes each
separated in fairly pure form, but also each ole
oleñne having the Same number of carbon atoms,
which is brought about by distilling such hydro
íine of the crude gas mixture is recovered in a
form substantially free of other unsaturated com
carbon mixture under pressure with ammonia, is
apparently due not only to the divergence be
tween the distilling temperatures of the azeo
pounds.
In recovering from cracked-oil gas the oleñnes,
tropic mixtures formed, but also to the divergence
dioleflnes and acetylenic hydrocarbons contained
between the heats of vaporization of the two azeo 10 therein, as indicated in the drawing, we first liq
tropes. To illustrate this point, it may be men
uefy the crude gas and then fractíonally distill
tioned that the azeotropio mixtures of ammonia
the liquefied material, preferably while maintain
with butylene and with butadiene which are
ing it at superatmospheric pressure. Methods for
formed at a pressure of 175 pounds per square
carrying out this distillation, which is accom
inch gage, have, at said presurse, boiling points of 15 plished in the absence of ammonia, are well
approximately 30° and 33° C., respectively. Al
known, and this initial distillation step is not
though two substances having so nearly the same
claimed per se, but only in combination with the
boiling temperature are usually difñcultly sepa
other distillation operations that go to make up
rable or non-separable from one another by dis
our complete process. By this initial distillation
tillation, these two azeotropes may be separated‘l 20 without ammonia there is obtained a low boiling
without difficulty. This apparently is because the
fraction containing methane, ethane, and ethyl
lower boiling azeotrope requires far less heat for
ene; a second fraction consisting largely of pro
Vaporization than does the higher boiling azeo
pane, propylene, propadiene and methyl-acet
trope, so that within the distilling column a large
ylene; a third fraction consisting largely of
amount of heat liows rapidly from the azeotrope 25 butano, butylene, butadiene and ethyl-acetylene;
of ammonia and butadiene (i. e. the higher boil
a fourth fraction of pentane, amylenes, penta
ing azeotrope), during its condensation, to the
dienes (largely isoprene) and pentynes; and a
lower boiling azeotrope of ammonia and butylene,
fifth fraction consisting for the most part of hex
thereby maintaining the latter azeotrope largely
ane, hexenes, hexadienes and hexynes. Higher
in vaporized condition and giving rise to much 30 boiling material may, for the purpose of the pres
sharper fractionation than would be expected in
ent invention, be discarded.
View of the proximity of the boiling points of the
Any one of the fractions 2-5 thus obtained
two azeotropes.
is then introduced along with liquid ammonia
We have also found that certain unsaturated
into a still and is fractionally distilled in the pres
hydrocarbons which may be separated from one 35 ence of the ammonia. This distillation may be
another by ordinary distillation in the absence of
carried out in continuous or batch-wise manner,
ammonia, may not be separated readily during
but continuous distillation is preferred. During
distillation with ammonia. An example of this
this distillation with ammonia there may be ob
type is the mixture of butadiene and methyl
tained as a distillate a mixture of ammonia, the
acetylene. These two compounds have different 40 paraffin hydrocarbon, and the oleñne, e. g. a mix
boiling points and are separable by fractional dis
ture of ammonia, butane and butylene, desig
tillation. However, ammonia forms with buta
nated in the drawing as sub-fraction “tAf’ and as
diene and methyl-acetylene two azeotropes which
a residue fraction a mixture of ammonia, the
are difficult to separate by distillation; hence, the
dioleñne, and the acetylenic hydrocarbon, e. g, a
presence of ammonia interferes with the separa- l
mixture of ammonia, butadiene and ethyl-acet
tion of these hydrocarbons. In general, we find
ylene, designated as sub-fraction “B.”
that the presence of ammonia facilitates the sep
Each fraction is treated to separate the am
aration of an oleiine from a dioleiine or an acet
rnoniaJ from the hydrocarbons therein and the
ylene containing the same number of carbon
ammonia is returned to the distillation. This
atoms in its molecule, but that ammonia inter- »
feres with the separation by distillation of a di
olefine from an acetylene having one less carbon
atom than the dioleiine per molecule.
We have further found that any hydrocarbon
mixture containing lower unsaturated aliphatic
hydrocarbons which tend to distill together may,
regardless of the number or identity of the hy
drocarbons present, be rectified to recover each
ferred procedure being dependent upon the par
ticular hydrocarbons present. The parailin hy
drocarbons containing 5 or more carbon atoms
55
per molecule are practically insoluble in liquid
ammonia; hence, when a fraction of distillate
contains a large proportion of such hydrocarbons,
mechanical separation of the ammonia from the
hydrocarbons is usually possible. On the other
60
hand, the unsaturated hydrocarbons containing
individual unsaturated hydrocarbon in a form
substantially free of other unsaturated hydrocar
bons, by carrying the rectiiication out in succes
sive stages, ammonia being present in certain
stages of the rectiñcation, but absent in others.
More particularly, we have found that the diole
fines and the acetylenes having from 3 t0 6 car
bon atoms in the molecule which are present in
the hydrocarbon mixture may, by rectification as
just described, be isolated as individual com
pounds of good purity, i. e. as individual com
pounds of greater than 80 per cent and usually
greater than 95 per cent purity.
The accompanying drawing is a flow sheet
showing one series of operations which may be
employed in separating as relatively pure com
pounds the dioleñnes and acetylenes often found
treatment of a fraction to remove the ammonia
may be effected in any of several ways, the pre
5 carbon atoms to the molecule are, at room
temperature or above, soluble in ammonia, and
those containing 6 carbon atoms are somewhat
less soluble; so that when a fraction contains
these hydrocarbons it may be necessary to cool to
room temperature or below in order to effect
satisfactory mechanical Separation of the am
monia from the hydrocarbons. The hydrocar
bons containing 3 or 4 carbon atoms to the mole
cule are very soluble in liquid ammonia at room
temperature and cooling to below 10° C., prefer
ably below 0° C., is usually required in order to
break the solutions of these hydrocarbons in am
monia and mechanically separate the latter. The
small proportion of ammonia remaining with the
'2,408,947
5
hydrocarbons after such separation may be re
moved by washing with water or otherwise; how
ever, removal of the residual ammonia is usually
not necessary in order to carry out the successive
steps of the process.
6
mixture and which, when dissolved in that com
ponent,wil1 change its density suii'iciently to cause
separation.
The general procedure described above may be
modiñed without departure from the invention.
For instance, instead of initially distilling a liq
uefied cracked-oil gas in the absence of ammonia
The mixture of dioleñnic and acetylenic hydro
carbons, e. g. butadiene and ethyl-acetylene, thus
to obtain individual hydrocarbon fractions, each
obtained is then distilled in the absence of am
of which consists for the most part of a mixture
monia, preferably at a pressure sufñcient to per
mit condensation of the distillate Without need 10 of hydrocarbons having the same number of car
bon atoms per molecule, the initial distillation of
for refrigeration, to obtain the individual hydro
the crude hydrocarbon mixture may, if desired, be
carbons in substantially pure form.
carried out in the presence of ammonia. Such
By such successive distillations (in the pres
initial distillation in the presence of ammonia
ence of ammonia and then in its absence) of any
one of the fractions 2-5 of the hereinbefore men 15 changes, of course, the composition of each of the
carbons in suc-h fraction are recovered in a form
substantially free of other unsaturated com
individual fractions obtained. For instance, such
distillation of liqueñed cracked-oil gas with am
monia usually results in the amylenes and bu
yl-acetylene each as an at least technically pure
tion comprising an oleñne, a dioleñne and an
tioned initial distillation, the unsaturated hydro
tadiene being recovered in one fraction and the
pounds. Thus from the initial fraction contain
ing the hydrocarbons having 4 carbon atoms to 20 pentadienes and pentynes being recovered in an
other fraction. However, the various fractions of
the molecule, butylene may be recovered in ad
distillate obtained by such initial distillation in
mixture with butane, but in a form practically
the presence of ammonia may then each be re
free of other unsaturated hydrocarbons, and bu
distilled in the absence of ammonia to further
tadiene and ethyl-acetylene may each be recov
ered in purified form, i. e. in a form of greater 25 separate the hydrocarbons contained therein.
For instance, the hydrocarbon fraction compris
than 90 per cent purity. These same operations,
ing amylenes and butadiene obtained in such
when applied to the fraction of the initial dis
initial distillation with ammonia may be redis
tillation which contains propane, propylene, pro
tilled in the absence of ammonia to separate the
padiene and methyl-acetylene, result in the re
covery of propane and propylene as one ñnal frac 30 amylene and butadiene from one another.
Any of the distillations of a hydrocarbon frac
tion and in the recovery of propadiene and meth
acetylene in the presence of ammonia may be
carried out in Ways other than those hereinbe
ing 5 carbon atoms to the molecule, a fraction 35 fore described. For instance, the mixture of bu
tane, butylene, butadiene, and ethyl acetylene
of pentane and pentene is obtained and the pen
hereinbefore mentioned may be distilled in the
tadiene and pentyne in the starting material are
presence of just sufficient ammonia to distill off
separated from one another. Isoprene of greater
the butane and butylene in azeotropic admixture
than 80 percent purity (the impurities apparently
being one or more isomers of isoprene) has been 40 with the ammonia. The distillation may then be
continued in the absence of ammonia and the bu
recovered in the process. The fraction of the
tadiene and ethyl acetylene thereby be separated
initial distillation which consists for the most
from one another. As alternative procedure, dis
part of hydrocarbons containing 6 carbon atoms
tillation of the hydrocarbon fraction comprising
to the molecule may likewise, by such successive
an oleñne, a dioleñne and an acetylene may be
distillations with and without ammonia, be sep
carried to completion in the presence of ammo
arated into a fraction consisting of hexane and
nia to obtain a first fraction of ammonia and
hexene, and into other fractions consisting of
the oleñne and a second fraction of ammonia, the
hexadiene and hexyne, respectively.
dioleñne and the acetylene. The second frac
It has hereinbefore been mentioned that in
tion may then be treated to remove the ammonia
any of the steps involving distillation with ammo
and be redistilled in the absence of ammonia to
nia, each fraction of distillate containing ammo
separate the diole?lne and acetylene from one
nia and one or more hydrocarbons is, when suñi
another.
ciently cooled, a mixture (rather than a solution)
Although cracked-oil gas, because oi its com
of ammonia and the hydrocarbons. The hydro
plexity, was chosen as the starting material in
carbons containing less than 5 carbon atoms to
the foregoing general description, the invention
the molecule are of lower density than liquid am
is
not restricted to the treatment of cracked-oil
monia; hence, on cooling a solution of such hy
gas. Instead, it may be applied in separating
drocarbons and ammonia sufficiently to cause
any diole?ine or acetylene containing between 3
separation of the ammonia, the latter forms a
and 6 carbon atoms, inclusive, from any aliphatic
lower layer. The hydrocarbons having more than
hydrocarbon mixture regardless of the source of
5 carbon atoms to the molecule are of greater
the latter. For instance, the relatively simple
density than ammonia; hence on cooling suñî
mixture of butane, butylene, butadiene and ethyl
ciently to break a solution of these hydrocar
acetylene produced by the pyrolysis of butano
bons and ammonia, the ammonia separates as
may be treated in accordance with the invention
the upper layer. On the other hand, the hydro
to separate the unsaturated hydrocarbons from
carbons containing 5 carbon atoms to the mole
one another.
cule have practically the same density as that
The following examples illustrate certain ways
of liquid ammonia. Accordingly, when a solu
in which the principle of the invention `nas been
tion of these hydrocarbons and ammonia is cooled
applied, but are not to be construed as limiting
sufliciently to break the solution, little, if any,
the invention.
of the ammonia separates as a distinct layer; in
stead a heterogeneous liquid mixture results.
EXAMPLE' 1
This mixture is readily broken by adding just a
The
purpose
of
this
example is to summarize in
trace of Water or any other substance which is
schematic form our findings as to the various
soluble in only one of the components of the
compound. Similarly from the fraction of the
initial distillation consisting of hydrocarbons hav
2,408,947
7
8
fractions -of distillate that are obtainable by dis
Add more ammonia .to the residue and continue
distillation to obtain:
tilling a mixture -of paraiïin hydrocarbons, ole
ñnes, dioleñnes and acetylenes containing from
3 to 6 carbon atoms to the molecule under vari
ous conditions. In the distillation schemes indí 5
cated in the following table, the starting material
Fractions
Identity
is in each instance a hydrocarbon mixture .con
taining parañin hydrocarbons from propane ‘to
hexane, olefìnes from propylene to hexene, diole
ñnes from propadiene to hexadienes, and acet 10
0%
ylenic hydrocarbons from methyl-acetylene .to
Amylenes-i-Nlîa
{Pentanes?-NHH
Pentadienes
Pentyncs
hexynes. Each distillation is carried out under
Add ammonia and continue distillation to ob
pressure in the presence or in .the absence of am
tain:
monia as indicated. The table gives the various
fractions of distillate that are obtainable, de 15
Fractions
pending upon Whether or not ammonia is pres
ent during .the distillation.
N o.
Identity
TABLE I
D‘st‘uat‘f‘äc‘t‘gägut NH3'
9 {Hexanes-I-NH;
Hexenes-i-NH;
Hexadlenes
Distillati@ with NH3, fractions
l0
ll
No,
Identity
No.
1 {Propane
Identity
l Propane and NH3
Propylenc
2 {Propylenc
and NH3
Butancs and NH3
2
3
Methyl-acetylene
Butylenes
Butadiene
4
5
Ethyl-acetylene
Pentanes
Amylenes
Pentadienes
Hexane
Hexene
Hexadienc
7
6
Hexyne
8 {Hexadienes
NH:
Hexynes andand
N H3
3
4
5
6
Pentyncs
Butyle'nes and NH3
Butadiene and NH3
Pentanes and NH3
Amylenes and NH3
Methyl-acetylene and NH3
Ethyl-acetylene and NH3
Pentadienes and NH3
Pentyncs and N H3
Hexanes and NH3
Hexenes and N H3
Hexynes
EXAMPLE 3
415 pounds of liquid ammonia and 1025 pounds
of a, liqueñed cracked-oil gas fraction, containing
502 pounds of butylene (mostly butylene-1), 502
pounds of butadiene-1.3, and 2l pounds of acety
lenes (mostly ethyl-acetylene), were introduced
30 in steady flow separately but simultaneously into
a continuous still which was operated at a pres
sure of between 150 and 200 pounds per square
inch gage and at a still-head temperature of about
30° C. to distill oif the azeotrope of ammonia and
The distillate Was cooled during op
eration t0 obtain partial separation of the am
monia from .the hydrocarbons therein, and the
ammonia so-separated Was returned continuously
to the distillation. Butadiene was withdrawn
continuously from the lower end of the distilling
column. During (the distillation there was col
35 butylene.
EXAMPLE 2
The following Table II shows the fractions of
distillate that are obtainable by starting Ithe dis
tillation of a liqueñed hydrocarbon mixture
(similar to that employed in Example 1) in the
presence of suñicient ammonia Ito form azeotropes
lected 715 pounds of distillate (containing about
with the propane and propylene and, after this
454 pounds of butylene, 238 pounds of ammonia,
initial charge of ammonia is removed by distilla
and 22 pounds of butadiene) ; and there was with
tion, periodically adding more ammonia as indi 45 drawn from the bottom of the still 465 pounds of
cated. The distilling scheme indicated in the
material containing 446 pounds of butadiene, 9
table has resulted in the separation of dioleñnes
pounds of acetylenic hydrocarbon (largely ethyl
and acetylenes. Butadiene of greater than 99 per
acetylene), 5 pounds of butylene and 5 pounds
cent purity has been separated from such mix
of ammonia. The distillate was washed with
tures in this manner.
50 Water .to remove the ammonia, thus leaving butyl
ene of approximately 95 per cent purity, i. e. con
TABLE II
taining only 5 per cent of butadiene. The higher
boiling material withdrawn from the bottom of
Alternate distillation without and with NH3
'the
distilling column was likewise treated to re
Starting in the presence of ammonia dîstill off:
55 move ammonia, leaving butadiene of 97 per cent
purity, i. e. containing only 1.9 per cent of acet
Fractions
ylenic hydrocarbon and 1.1 per cent of butylene.
At the close of the distillation, the distilling col
No
Identity
umn was cooled to condense and drain out its in
60 ventory of refluxing material. This reflux inven
tory, which amounted to 146 pounds and consist
Propylene-I-NHa
2
Methyl-acetylene
ed of approximately 103 pounds of ammonia, 27
pounds of butadiene, 15 pounds of butylene, and
1 pound of acetylenic hydrocarbon, is retained
Add NH3 to .the still residue and Acontinue the
65 in the still column during continuous operation.
distillation in the presence of NH3 to obtain:
EXAMPLE 4
{Propane-l-NHa
Fractions
No.
Identity
3 {lâButanes-l-NHa
utylenes+NH3
4
5
Butadiene
Ethyl-acetylene
Cracked-oil gas was liquefied and distilled at
superatmospheric pressure to separate a fraction
70 consisting for the most part of hydrocarbons
having 5 carbon atoms to the molecule. Approx
imately 1750 grams of this hydrocarbon fraction
and 1100 grams of liquid ammonia were charged
into a still and the mixture was fractionally dis-'
75 tilled at superatmospheric pressure. During the
2,408,947
TABLE IV
distillation, 2500 grams of additional ammonia
was added in small portions and compressed
nitrogen was fed into the distilling system to
build up pressure and thereby facilitate con
densation of the distillate. The nitrogen was fed
into the condenser for the distillate. The pres
~
~
Other unsat
Frììçgion Volzlême, Pentîdgienes» Pentynesd mated hydro_
‘
sure during the distillation varied from 1GO
‘
'
carbons
l
44
44. 4
27 . 8
27. 8
2
3
4
5
6
7
57
59
25
48
45
ll
6l
85. 5
88
88
73
73
13
6. l
(i
4
6
5. 5
26
8. 4
pounds to 440 pounds per square inch gage and
6
8
the distilling temperature, i. e. the temperature
21
at the head of the distilling column, varied from 10
2l. 5
29° to 59° C., this temperature varying with the
pressure. The distillation at superatmospheric
The pentadiene-LS in the above fractions 3, 4,
pressure was continued until a fraction rich in
and 5 was found to be isoprene.
pentadienes was obtained. The remaining vola
Although the invention, as hereinbefore point
tile material was then distilled at atmospheric 15
ed out, is particularly applicable in separating
pressure without attempt at fractionation. The
from one another oleñnes, dioleñnes and acety
fractions obtained are described in the follow
lenes containing from 3 to 6 carbon atoms in the
ing table which gives the per cent by volume of
molecule, it may also be employed in separat
ammonia in each fraction of distillate and also
the identity of the hydrocarbons present and the 20 ing higher unsaturated hydrocarbons, e. g. ole
i‘lnes, dioleñnes, and acetylenes containing 7 or 8
molal per cent of each kind of hydrocarbon based
carbon atoms per molecule, from their mixtures.
on the total hydrocarbons in the fraction. The
At any given distilling pressure, the hydrocarbon
procedure in analyzing fraction 1, i. e. the lowest
content of the azeotropes of ammonia With hy
boiling fraction, was to wash it with water to 25 drocarbons of an aliphatic series, e. g. the oleiine
remove the ammonia, redistill it in the absence
series or the dioleiine series, becomes lower as
of ammonia to remove and identify the butadiene
hydrocarbons of increasing boiling point are em
therein, and then to treat the mixture of higher
ployed. Accordingly, a smaller proportion of am
boiling hydrocarbons chemically in known man
monia is required in separating unsaturated hy
ner, first to remove the 1.3-diolefines, e. g. 1.3
30 drocarbons having from 3 to 6 carbon atoms from
one another in accordance with the invention
pentadienes, then to remove the monoalkyl
than is required in eiîecting a similar separation
acetylenes, i. e. pentynes. The hydrocarbons re
of the higher unsaturated hydrocarbons.
maining after these treatments Were scrubbed
This application is a continuation in part of
successively with aqueous sulphuric acid solu
tions of 63 per cent and 87 per cent by Weight 35 our co-pending application Serial No. 199,600,
filed April 2, 1938.
concentrations, respectively, to remove by ab
Although the following claims indicate that the
sorption the other unsaturated hydrocarbons
separation of unsaturated hydrocarbons by dis
present. The hydrocarbons absorbed in the acid
tillation in the presence of ammonia in accord
consist of oleñnes, 1.2- or 1.4-dioleñnes and di 40 ance With the invention involves the formation of
alkyl acetylenes. In the table, they are termed
one or more azeotropes of ammonia With the hy
“other unsaturated hydrocarbons.” The sub
drocarbons, it will be understood that the frac
stances not absorbed in any of these treatments
tions obtained during such distillation 'do not
consisted of parafûns and air. They are referred
necessarily have the compositions of such azeo
to in the table as “inerts” The other fractions 45 tropes.
Other modes of applying the principle of the
of distillate Were similarly Washed with Water
invention may be employed instead of those ex
to remove the ammonia and an aliquot portion
plained, change being made as regards the meth
of the remaining hydrocarbons Was analyzed as
just described, except that the step of distilling 50 od herein disclosed, provided the step or steps
stated by any of the following claims or the equiv
oir butadiene (which not not present to appre
alent of such stated step or steps be employed.
ciable extent) Was, of course, omitted. It‘may
We therefore particularly point out and dis
be mentioned that fraction 9 in the table is the
tinctly claim as our invention:
material that was distilled at atmospheric pres
1. In a method of separating an unsaturated
sure without fractionaton.
TABLE III
Hydrocarbons, inolel per cent of total
-
Fraction
No.
Volume
NH3 content
’
cc. ’
peäâìägy
Bum:
Penn?
1
2
3
4
5
2, 000
l, 700
400
300
300
79. 3
69. 4
80
80
80
6
200
9()
7
300
90
0
15
2
70. 0
13. 0
8
9
300
350
90
0
0
0
24
54
54
25
22. 0
2l. 0
........ _
________ .._
diene-l.3
dienes-LS
Pentmes'l
27. 5
0
0
0
0
0
0. 5
2. 5
2. 6
4. 5
2. 7
0. 9
1. 3
7. 9
0
0
8
Fraction 9 was then fractionally distilled at at
mospheric pressure in the absence of ammonia
to obtain the following fractions, each of which
75
was analyzed as in the initial distillation:
3 v
Other unsat
äggêâgbïäg
Inerts
60. 5
88. 8
73. 7
73. 6
81. 8
9. 3
9. 8
22. 5
15. 9
13. 9
78. 0
11. 0
aliphatic hydrocarbon containing more than 2
and less than 7 carbon atoms in the molecule and
having the empirical formula CnI-Izn-z from a
mixture of hydrocarbons comprising the same
2,408,947
l1
12
and a more saturated hydrocarbon having the
same number of carbon atoms in the molecule,
the steps which consist in forming a mixture oi
presence of ammonia until a substantial pro
ammonia with the hydrocarbons to be separated
portion of the olenne is separated in a form rela
tively free of the acetylene and dioleñne, and
from one another and fractionally distilling the
resultant mixture at a pressure not substantially
lower than atmospheric pressure, whereby a rela
carrying the other distillation out at a pressure
not substantially lower than atmospheric pres
sure in the absence of ammonia, whereby the
acetylene, dioleiine, and oleñne are at least par
tively low boiling azeotrope of ammonia and said
tially separated from one another.
6. In a method of separating the components
more saturated hydrocarbon is formed, the irac
tional distillation in the presence ol ammonia 10 of a mixture of hydrocarbons comprising an
being continued until a substantial proportion ol’
acetylene, a dioleñne, and a more saturated hy
drocarbon, each having more than 2 and less than
the more saturated hydrocarbon has been sep
'7 carbon atoms per molecule and all having the
arated from the hydrocarbon of formula CnHzn-a
same number of carbon atoms in the molecule,
2. In a method of separating a dioleíine which
contains more than 2 and less than 7 carbon 15 the steps which consist in fractionally distilling
the liqueiied mixture at superatrnospheric pres
atoms in the molecule from a hydrocarbon mix
sure in the presence of added ammonia, whereby
ture comprising the same and a more saturated
a relatively low boiling azeotrope of ammonia and
oleñne having the same number of carbon atoms
the more saturated hydrocarbon is formed, con
in the molecule, the steps which consist in add
tinuing this distillation in the presence of am
ing ammonia to the hydrocarbon mixture and »
monia until a substantial proportion of the more
fractionally distilling at superatmospheric pres
saturated hydrocarbon is separated in a form re1
sure, whereby a relatively low boiling azeotrope
atively free of the acetylene and dioleñne and
of ammonia and said more saturated oleñne is
thereafter continuing the distillation in the sub
formed, the fractional distillation in the presence
stantial absence of ammonia to separate the di
of ammonia being continued until a substantial
oleñne from the acetylene hydrocarbon.
proportion of the more saturated oleñne has been
7. In a method of separating the components
separated from the dioleíine.
of a mixture of hydrocarbons comprising an
3. In a method wherein a hydrocarbon mixture
acetylene, a dioleñne, and a more saturated hy
comprising an acetylene, a dioleñne, and a more
drocarbon, each having 4 carbon atoms in the
saturated hydrocarbon, each having more than 2
molecule, the steps of fractionally distilling the
and less than 7 carbon atoms per molecule and
liquefied mixture at superatmospheric pressure
all having the same number of carbon atoms in
in the presence of added ammonia, whereby a
the molecule, is fractionally distilled to obtain a
relatively low boiling azeotrope of ammonia and
primary fraction and the primary fraction is re
distilled, the steps of carrying- one oi said distil 35 the more saturated hydrocarbon is formed, con
tinuing this distillation in the presence of ammo
lations out in the presence of added ammonia
nia until a substantial proportion of the more sat
at a pressure not substantially lower than atmos
urated hydrocarbon is separated in a form rela
pheric pressure, whereby a relatively low boiling
tively free of the acetylene and dioleñne, and
azeotrope of ammonia and the more saturated
hydrocarbon is formed and continuing this dis
tillation in the presence of ammonia until a sub
stantial proportion of the more saturated hydro
carbon is separated in a form relatively free of
the acetylene and dioleñne, and carrying the
other distillation out at a pressure not substan
tially lower than atmospheric pressure in the
absence of ammonia, whereby said hydrocarbons
thereafter continuing the distillation in the sub
stantial absence of ammonia to separate the di
oleñne from the acetylene hydrocarbon.
8. In a method of separating a diole?lne which
contains more than 2 and less than 7 carbon
atoms per molecule from a hydrocarbon mixture
containing the same and a more saturated oleñne
having the same number of carbon atoms in the
molecule, the steps of fractionally distilling the
containing more than 2 and less than 7 carbon
liquefied
mixture at superatmospheric pressure
atoms and having the same number of carbon
in the presence of added ammonia, whereby a
atoms in the molecule are separated from one 50 relatively low boiling azeotrope of ammonia and
another.
the more saturated oleiine is formed and con
4. In a method of separating butadiene from a
tinuing this distillation in the presence of am
hydrocarbon mixture containing the same and a
monia until a substantial proportion of the more
more saturated oleñne having the same number 55 saturated olefìne is separated in a form relatively
of carbon atoms in the molecule, the step of frac
free of the dioleñne, while separating ammonia
tionally distilling the hydrocarbon mixture at
fromv the distillate and returning the separated
superatmospheric pressure in the presence of
ammonia to the distillation.
added ammonia, whereby a relatively low boiling
azeotrope of ammonia and the more saturated
oleñne is formed and continuing the distillation in
the presence of ammonia until a substantial pro
portion of the more saturated oleñne is separated
from the butadiene.
5. In a method wherein a liquefied hydrocar
bon mixture comprising an acetylene, a dioleñne,
and an oleñne, each having 4 carbon atoms in
the molecule, is fractionally distilled to obtain a
primary fraction and the latter is redistilled,
the steps which consist in carrying one of said
distillations out at a pressure not substantially
lower than atmospheric pressure in the presence
of added ammonia, whereby a relatively low boil
ing azeotrope of ammonia and the oleñne is
formed, and ,continuing this distillation in the
_
9. The method which comprises separating
from cracked oil gas a liquefied mixture com
prising hydrocarbons having more than 2 and
less than 7 carbon atoms in the molecule, frac
tionally distilling the liquefied mixture to obtain
a fraction consisting substantially of hydrocar
bons having the same number of carbon atoms
in the molecule and comprising an acetylene, a
dioleñne, and an oleñne, fractionally distilling
such mixture at superatmospheric pressure in the
presence of added ammonia, whereby a relatively
low boiling azeotrope of ammonia and the olefine
is formed and continuing this distillation in the
presence of ammonia until a substantial propor
tion of the oleñne is separated in a form relatively
free of the acetylene and dioleñne, and continu
ing the distillation in the substantial absence of
l2,408,947
13
ammonia to separate the diolefine from the
acetylene.
'
.10. In a method of separating butadiene-1.3
from a mixture thereof with a butylene, the steps
of adding ammonia to the liquefied hydrocarbon
mixture and fractionally distilling at a pressure
not substantially lower than atmospheric pres
sure, whereby a relatively low boiling azeotrope
of ammonia and the butylene is formed and con
tinuing the distillation until a s-ubstantial pro
portion of the butylene is separated from the
butadiene.
11. In a method of separating butadiene-1.3
from a mixture thereof with butylene-1, the steps
of adding ammonia to the liquefied hydrocarbon
14
other the unsaturated components of a mixture
of hydrocarbons comprising an acetylene hav
ing 4 carbon atoms in the molecule, -butadiene
1.3, and a butylene, the steps of fractionally dis
tilling the liquefied mixture at a pressure between
about 100 and about 440 pounds per square inch
in the presence of added ammonia -and an inert
gas, whereby a relatively low boiling azeotrope
of ammoniaand the butylene is formed, con
tinuing this distillation in the presence of am
monia until a substantial proportion of the butyl
ene is separated in a form relatively free of the
acetylene hydrocarbon and the butadiene-L3,
and thereafter continuing the distillation in the
substantial absence of ammonia to separate the
butadiene-1.3 from the acetylene.
mixture and fractionally distilling at a pressure
16. In a method of separating butadiene-1.3
not substantially lower than atmospheric pres
lfrom
a hydrocarbon mixture comprising the same
sure, whereby a relatively low boiling azeotrope
and a butylene, the step of fractionally distil
of ammonia and the butylene-1 is formed and
continuing the distillation in the presence of am 20 ling the liquefied mixture at a pressure between
about 100 and about 440 pounds per square inch
monia until a substantial proportion of the butyl- Y
in the presence of added ammonia and an inert
ene-1 has been distilled together with ammonia,
gas, whereby a relatively low boiling azeotrope
leaving a residue consisting substantially of buta
diene-1.3.
12. In a method of separating an acetylene
which contains more than 2 and less than '7 car
bon atoms in the molecule from a hydrocarbon
mixture thereof with an olefme containing the
same number of carbon atoms in the molecule,
of ammonia and the butylene is formed, and con
tinuing this distillation in the presence of am
monia until the ammonia and butylene have
been distilled from the butadiene, whereby the
latter is obtained in a form relatively free of
the butylene and ammonia.
17. In a method of separating butadiene-1.3
the step of distilling the hydrocarbon mixture at 30
from
a mixture thereof with isobutylene, the
super-atmospheric pressure in the presence of
steps of fractionally distilling the liquefied hy
added ammonia, whereby a relatively low boil
drocarbon mixture in the presence of added am
monia, whereby a relatively low boiling azeo
ing azeotrope of ammonia and the oleñne is
formed and continuing the distillation in the
presence of ammonia until a substantial pro
portion of the oleiine is separated from the
trope of ammonia and isobutylene is formed,
and continuing the distillation in the presence
of ammonia until a substantial proportion of the
acetylene.
of hydrocarbons comprising an acetylene having
4 carbon atoms in the molecule, butadiene-1.3,
isobutylene has been separated from the bu
tadiene.
18. In a method of separating butadiene-1.3
from a mixture thereof with isobutylene, the
the substantial absence of ammonia to separate
the butadiene-1.3 from the acetylene,
of hydrocarbons comprising butadiene-1.3 and
isobutylene, the steps of fractionally distilling
13. In a method for separating from one an
other the unsaturated components of a mixture
steps of forming from the hydrocarbon mixture
and a butylene, the steps of fractionally distilling
and ammonia a liquefied mixture of ammonia
the liqueiied mixture at a pressure between about
and the hydrocarbons and distilling at a pressure
100 and about 440 pounds per square inch in the
presence of added ammonia, whereby a relatively 45 of at least 100 pounds per square inch a mixture
of ammonia and isobutylene which comprises
low boiling azeotrope of ammonia and the butyl
an azeotrope of said compounds to leave the
ene is formed, continuing this distillation in the
butadiene in relatively pure form as residue from
presence of ammonia until a substantial propor
the distillation.
tion of the butylene is separated in a form rela
19. In a method for separating from one an
tively iree of the acetylene and the butadiene 50
other the unsaturated components of a mixture
1.3, and thereafter continuing the distillation in
the liquefied mixture at a pressure between about
100 and about 440 pounds per square inch in the
presence of added ammonia and an inert gas,
CuHzn-z and containing more than 2 and less
whereby a relatively low boiling azeotrope of
than 7 carbon atoms in the molecule from a
ammonia and isobutylene is formed, and con
mixture of hydrocarbons comprising the same
tinuing the distillation in the presence of am
and a more saturated hydrocarbon having the
same number of carbon atoms in the molecule, 60 monia until a substantial proportion of the iso
butylene is separated from the butadiene-1.3.
the steps which consist in forming a mixture
20. A process for concentrating dioleñns con
of ammonia with the hydrocarbons to be sep
tained in a, mixture thereof with mono-oleñns
arated from one another and fractionally dis
possessing vapor pressures of the same magni
tilling the resultant mixture at a pressure be
tween about 160 and about 440 pounds per square 65 tude, which comprises distilling said mixture in
inch while introducing an inert gas into- the dis
the presence of liquid ammonia to produce a
tilling system to create at least part of the pres'
vapor fraction containing the major portion of
sure on said system, whereby a relatively low boil
said mono-olei'lns, and a residue containing the
14. In a method of sep-arating an aliphatic
hydrocarbon having the empirical formula
ing azeotrope of ammonia and the more saturated
hydrocarbon is formed, and continuing the dis
70
major portion of said dioleñns.
»
tillation in the presence of ammonia until a sub
21. In a method of separating butadiene from
a mixture thereof with a butylene, the steps of
stantial proportion of the more saturated hydro
carbon is separated from the unsaturated hydro
carbon of empirical formula CnHzn-z.
superatmospherie pressure in the presence of
added ammonia, whereby an azeotrope of am
15. In a method for separating from one an
fractionally distilling the liquefied mixture at
15
2,408,947
monia, and the butylene is formed and distilled,
and continuing .the distillation in the presence
of Vammonia until a substantial portion of the
butylene is separated in a form relatively `free
of the butadiene, while separating ammonia from
the distillate and returning Vthe separated am
monia to the distillation.
22. In a method of separating isoprene from a
hydrocarbon mixture comprising the same and
an amylene. the steps of Vfractionally distilling
16
the liqueñed hydrocarbon mixture in the presence
of added ammonia, whereby an azeotrope or
-ammonia and the amylene is formed and dis
tilled, and continuing the distillation in the pres
ence of ammonia, until a substantial portion of
the amylene has been separated from the iso
prene.
HOWARD S. NU‘I'I‘ING.
.LEE H. HORSLEY.
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