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Патент USA US2406695

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Aug. 27, 1946.
' G. R. LAKE
SEPAÈATION OF HYDROCARBONS BY DISTILLATIQN
Filed April 25, 1941
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1 2,406,695
2,405,695
Patented Aug. 27, 1946
>UNITED i STATES PATENTg OFFICE@
2,406,695
SEPARATION OF HYDROCARBONS BY
DISTILLATION
George R. Lake, Long Beach, Calif., assigner to
Union Oil Company of California, Los Angeles,
Calif., a corporation of California
Application April 25, 1941, Serial No. 390,264
4 Claims.
( Cl. 202-39.5)
2
This invention relates to the preparation of
ing at a lower temperature with one or more of
pure hydrocarbons from petroleum, these pure
the components so as to permit separation from
the other component. For this purpose, many
azeotrope formers, some of which will be referred
to hereafter, have been used. While the process
hydrocarbons being contained in a fraction of
petroleum hydrocarbons whose components have
small differences in boiling points, which renders
them inseparable by ordinary fractional distilla
of azeotropic distillation to separate different
tion.
An object of the present invention is to further
the progress in preparing pure compounds from
a heterogeneous petroleum mixture, using in this
hydrocarbons of substantially the same> boiling
point has its advantages over other methods- for
effecting the separation of these components,
l()
particular case a method which involves fewer
steps than a chemical method, and which yields a
purer product than that produced by careful
fractional distillation and/or extraction with se
lective solvents.
Y
_
Another object of the invention is to prepare
from a given fraction of petroleum, such as gaso
line, kerosene, or a narrow boiling range hydro
.carbon fraction prepared from such materials,
these fractions consisting of a mixture of paraf
such as extraction with selective solvents, the
process has the disadvantage of frequently re
quiring large and efficient fractionating columns
due to the fact that in many cases the difference
in boiling point between the mixture of azeotrope
former and the component associated therewith
on one hand and the component remaining un
distilled which may or may not be associated with
aromatic hydrocarbons, a fraction that is essen
azeotrope former on ther other hand, is small.
For example, in the case of separating toluene
from parañîn and/or other non-aromatic hydro
carbons having substantially the same boiling
point as the toluene employing methanol as the
tially paraiiinic or iso-parañînic or naphthenic
azeotrope former, the azeotrope of methanol and
or oleñnic or aromatic.
parañin and/ or other non-aromatic hydrocarbons
is distilled at a temperature ofabout 143° F.’while
the azeotrope of methanol and toluene is distilled
at a temperature of about 148° YF. Hence, while
the small difference in the distillation tempera
ñnic, iso-paraiiinic, naphthenic, oleñnic and
'
A particular object of my invention is to sep
arate aromatic hydrocarbons from non-aromatic
hydrocarbons having the same boiling point or
range, particularly from gasoline fractions con
taining relatively small quantities of the aromatic
tures ofthe two azeotropes permits the separa
hydrocarbons desired to be recovered from the 30 tion of the toluene from the non-aromatic hy
gasoline.
1
.
drocarbons, whereas without the azeotrope former
A particular object of my invention is to sep
such separation would be practically impossible
arate a component or class of components from
by fractional distillation, yet this small differ
a hydrocarbon mixture, the components of which
presence of an added substance, hereinafter re
ferred to as an azeotrope former which is adapted
to form an azeotrope or lower boiling mixture
with one of the components or class of compo
ence in distillation temperatures requires eili
cient fractionation equipment in order to effect
the desired separation. Also, in some cases, it
is impossible to separate one class of components
from another class of components from a rela
tively wide boiling range hydrocarbon fraction
due to the overlap in distillation temperatures
nentsand also effecting the distillation in the
of the azeotrope consisting of the azeotrope
Yhave substantially the same boiling point or boil- .;
ing point range, by fractional distillation in the
presence of a second added substance, hereinafter
former and the heavier components of one class
referred to as a vapor pressure depressant which
of components and the lighter components of
is adapted to lower the vapor pressure of the
the other class of components. My invention
other component or class of components. In 45 relates to an improvement in the foregoing proc
other words, it is an object of my invention to
ess whereby I effect an increase in the difference
increase the difference between the vapor pres
between the aforesaid distillation temperatures,
sures of the components desired to be separated
thereby facilitating the separation of dilïerent
by fractional distillation.
components or different classes of components.:V
I have discovered that in the aforesaid process
of azeotropic distillation, the presence 0f a cer
tain substance, i. e. a vapor pressure depressant
,
It is known to separate specific hydrocarbons
or hydrocarbon fractions from a mixture of dif
Vferent classes of hydrocarbons by a fractional
ldistillation process known as azeotropic distilla
' which has an aflinity for the higher boiling com
tion wherein a substance is added to the mixture
ponent or higher boiling azeotrope ordinarily re
to be distilled which will form an azeotrope boil .55 maining as still bottoms during the aforesaid
2,406,695
3
tion of the component remaining undistilled. At
when separating heptanes, octanes, nonanes, de
canes and/or naphthene hydrocarbons having
similar carbon atoms from toluene, xylenes and
substantially aifected. For example, in the af ore
used in substantially anhydrous form in order to
azeotropic distillation has the effect of depress
ing the vapor pressure or retarding the distilla
ethyl benzene. -Some of the azeotrope formers
the same time, the distillation temperature of the
`azeotrope formed with one of the components Ul mentioned herein .are more eflicient when used
in the‘presence of water while others must be
which is first distilled from the mix-ture is not
mentioned
obtain the best results. For exampley methyl
ethyl ketone may contain from 0 to 25% by vol
case of separating toluene from
paraffin and/or other non-aromatic hydrocar
bons employing an azeotrope former, the presence
ume of water to be operative.
As vapor pressure depressants which I have
found are phenolic compounds such as cresylic
of a vapor pressure depressant during the dis
tillation does not appreciably affect the distilla
acid, phenol, Xylenol and resorcinol.
In general, when choosing azeotrope formers
tion temperature at which the azeotrope con
sisting of azeotrope former and the parailin
and/or other non-aromatic hydrocarbons is dis
tilled; however, the vapor pressure depressant
materially retards the distillation of the higherboiling azeotrope of the azeotrope former and
toluene so that it Will require a somewhat higher
still temperature, depending of course, upon the
particular `substance employed as the vapor
pressure depressant in order to distill it, than
whenk the distillation is eiîected in the absence of
the vapor pressure depressant. This is particu
and vapor pressure depressants for eiîecting the
distillation, it is preferable to employ an azeo
trope former having substantially the same boil
ing point as the stock, and preferably boiling
not more than about 100° E'. below or about 40° F.
above the boiling point of the stock. When
choosingV a vapor pressure depressant, it is pref
erable to choose one boiling substantially above
the boiling point of the stock, preferably boiling
greater than about 100° F; above that of> the
stock.
Moreover, when choosing azeotrope
larly true in the case where the azeotrope former
formers and vapor pressure depressants for ef
fecting the distillation it is, of course, necessary
only forms an azeotrope with the non-aromatic
hydrocarbons and does not form an azeotrope
with the undistilled aromatic hydrocarbons. In
toselect pairs which arenot chemically reactive
with each other because if they did react the
this manner, the difference in distillation tern
reaction products would not necessarily be either
peratures of the paranin or non-aromatic hydro
carbons associated> with azeotrope former and
the toluene,_ whether associated with azeotrope
former or not, is increased considerably so that
it is possible to effect a sharper and more enicient
separation of the toluene fromv the paraliin
azeotrope formers or vapor pressure depressants.
In carrying out they process, the distillation of
the mixture of hydrocarbon fraction, azeotrope
former and vapor pressure depressant is con
tinued until all of one of the components has been
distilled from the mixture,
and/or other non-aromatic hydrocarbons. It is
possible that the presence of the vapor pressure
depressant will require a higher still tempera
ture to remove the azeotrope of paraffin and/or
other' non-aromatic hydrocarbons than without
40
its presence, yet the still temperature required to
distill the azeotrope of toluene and azeotrope
former is increased to a greater extent or pro
portion than without its presence so that the
net' difference inv distillation temperatures of the 45
foregoing azeotropes is greater than when the
distillation is effected in the absence of the vapor
pressure depressant.
Y
While the invention is adapted for the separa
tion of hydrocarbons of characteristics different
lfrom each other, I have found that this process
is particularly useful for producing toluene hav
ing a very high degree of purity from gasoline
fractions produced from straight run or syn
thetic gasolines such as lthose produced by crack 55
ing, polymerizing orv reforming. The production
of substantially pure toluene is highly important
>particularly when it is to be used in the manu
facture of explosives by nitrating the toluene
since small amounts of impurities seriously im
pair the ni-tration process.
.
As azeotrope formers which I have found use
full are aliphatic ketones such as methyl ethyl
ketone, acetone and cyclic aliphatic ketones
such as cyclohexanone.
Of'the above mentioned azeotrope formers, I
have found' methyl ethyl ketone and acetone,
particularly eñicient azeotrope formers for sepa
rating a hydrocarbon fraction having a boiling
range between 20G-300° li'. into hydrocarbon
components of different chemical characteristics
and are particularly useful for separating'paraf
ñn and/or naphthene hydrocarbons having 7 to
10 carbon atoms from aromatic hydrocarbons
having 9 or less carbon atoms, as for example,
60
This component
which` is Vaporized is condensed together with the
azeotrope former. In order to separate the azeo
trope former from the oil condensate, it is merely
necessary to cool and/or mix the-condensate mix
ture with water which dissolves in the azeotrope
former and allows the hydrocarbons to separate
from the azeotropeformer. By allowing this mix
ture to settle, two distinct layers are formed, an
upper layer consisting of the hydrocarbon and a
lower layer of diluted azeotrope former. «When
the azeotrope former isA used in the presence of
water in the distillation operation, the‘condensate
will ordinarily stratify into the two above-men
tioned layers. However, it may be desirable to
add additional water to the condensate' in order
to insure complete separation of the azeotrope
former from the hydrocarbon. The azeotrope
former may berecovered from the water by sim
ple distillation. If desired, the azeotrope former
may be returned to the still withI additional feed
stock, it being apparent that when the azeotrope
former is used in the presence 0f water and a
separate layer forms when the overhead is con
densed that the separated layer of Water and
azeotrope former may be returned directly to the
still. When all of the component has* been dis
tilled, the still temperature is raised and the other
component is distilled from the vapor pressure
65 depressant whether alone or associated with azeo
trope former.
When separating one class of hydrocarbons
from another class of hydrocarbons in an oil frac
tion having a Wide boiling range, it is preferable
to first fractionate the wideA boiling range stock
into a plurality of fractions, each having a nar
row boiling range. Each of' these fractions may
then be separately subjected to azeotropic distilla
tion in the presence of a vapor pressure depres
sant in order to- effect the separation into the
2,406,695
'5
.
variòus> classes of components,N These separated
6
By adding a vapor pressure depressant to the-
components'may then be blended in any desired
above mixture, this will tend to shift the distilla
proportion. ' For example, suppose it were desired
tion range of the aromatic hydrocarbons so that
to separate parañin hydrocarbons from aromatic
hydrocarbons in a petroleum fraction composed
of these components and having a wide boiling
range of, Vfor example, 200`to`400° F.; this stock
'may be fractionally distilled to produce ten frac
tions, each having a'`- boiling range difference of
about twenty degrees. Each fraction may then be 10
instead of the aromatic fraction having a distilla
subjected to azeotropic distillation in the presence
of vapor pressure depressantl to separate paraffin
hydrocarbons from aromatic hydrocarbons. The
-various paraii‘in hydrocarbons may then be blend
tion range of 200° to 500° F., it will now- have a
higher distillation range of, for example, SOO-600°
F.- so that the fraction now distilling between
100-300° F. will be substantially paraflinic, that
distilling between 300°-400° F. will be a mixture
of parafûnic and aromatic fractions while the
fraction remaining in the still which distills above
» 400° F. in the presence of the vapor pressure de
pressant will be substantially aromatic. Thus,
by effecting the distillation and separately col
ed to produce a hydrocarbon fraction having the 15 lecting the above fractions and removing azeo
same boiling range as the original stock andcom
posed ¿of substantially paraffin hydrocarbons.
This may be done with the'various aromatic hy
trope former and vapor pressure depressant, we
will now have the three oil fractions named above,
i. e. one paraliinic boiling between 20D-400° F.,
drocarbons. I have found that by carrying out
one aromatic boiling between 3D0-500° F. and one
the process in this manner that a sharper separa 20 a mixture of the two. Since the aromatic hydro
tion of components may be obtained from stocks
carbons boiling between 3D0-500° F. and the
having wide boiling ranges than if these stocks
’were subjected directly to the distillation without
prior separation into narrow .boiling range frac
tions.
The foregoing procedure of separating a wide
paraflinic hydrocarbons boiling'between 20G-400°r
boiling range fraction into narrow outs and sub
jecting each fraction to separate azeotropic dis
tillation in the presence of a vapor pressure de
F. have been separately recovered, the mixed frac
tion will be composed of aromatic hydrocarbons
boiling in the lower boiling range- of the stock,
i. e. 20G-300° F. and parafûn hydrocarbons boil
ing in the higher range 0f the stock, i. e. 40o-500°
F. After removing the azeotrope former by mix
ing with water and stratifying, the aromatic hy
pressant and then blending the components of
like characteristics is particularly useful in the
drocarbons may be readily separated from the
production of high viscosity index lubricating oils.
In order to produce high quality lubricating oils
from naphthene base crude oils, it is generally
vnecessary to subject the lubricating oil fractions
to extraction with solvents capable of effecting
Since there is a Wide diiïerenoe in boiling points
a separation of relatively non-paraiñnic from
relatively parañinic oil fractions. However, due
to the wide boiling range of the lubricating oil
paraflinic hydrocarbons by fractional distillation.
between these aromatic and paraiñnic hydrocar
bons, separation is readily accomplished. By
blending all' of the aromatic hydrocarbons thus
separated, we will have an aromatic hydrocarbon
fraction having the same boiling range as the
original stock. The same can be done with the
various paraflinic fractions. This same procedure
fractions, it has been impossible to accomplish 40 can be used to treat lubricating oil stocks in order
this by azeotropic distillation of the entire lubri
to recover the more paraflinic oil fractions which
give high quality lubricants.
'
cating oil fraction. However, by carrying out the
jazeotropic distillation in the presence of a vapor
The foregoing process is also applicable to the
pressure depressant, the lubricating oil stock may
separation of wax from oils containing the same.
be separated into fewer fractions, each having a 45 This is possible due to the fact that »the wax com
ponents 'are pure paraffin hydrocarbons while the
wide boiling range and thereby reducing the num
oil fractions are not pure parañìn hydrocarbons.
ber of azeotropic distillations necessary to effect
.
- s
Thus, the wax components will form an aZeo
While the foregoing separation of a wide boil
trope with azeotrope formers having a lower boil
ing range oil fraction into narrow cuts before 50 _ing point than the fluid oil components in the
lubricating oil stock. The boiling point of the lat
>azeotropic distillation of each cut in the presence
>ter is depressed by the presence of the vapor pres
of a vapor pressure depressant is preferred, I may
sure depressant. When a lubricating stock is
eñîect the separation of a wide boiling oil fraction
Vcomposed of wax, relatively paraflinic and rela- f
into its different components such as aromatic
>the desired separation.
and paraf’rlnic components, by the following pro 55 tively non-paraflinic oil fraction, azeotropic dis
tillation in the presence of the vapor pressure de
cedure, When the azeotrope former is added to
pressant ywill first cause the distillation of the
such an oil fraction, an azeotrope is formed with
waxy constituents and then the non-waxy rela
one class of components thus lowering their boil
tively more paraflinic fractions which may be sep
ing point. The boiling point range ofthe azeo
trope, however, ranges below and within the lower 60 arately collected. This wax separating procedure
may be carried out on either narrow boiling frac
_portion of the boiling range of the other class of
tions as described above or on a wide boiling frac
components in the hydrocarbon mixture. For
tion which may be separated intoits component
:examplalet us consider a hydrocarbon fraction
boiling between 200 and 500° F. and composed of
classes as also described above.
'
paramn and aromatic hydrocarbons. By adding 65 Other objects, featuresand advantages of my
invention will be apparent to those skilled in the
an azeotrope former only to this mixture, an azeo
art from the followingdescription of the invention
trope is formed with the paraiiin hydrocarbons
as taken from the drawing which represents a
distilling between 100° and 400° F. Thus, the
hydrocarbon material distilling from 100° F, to
diagrammatic arrangement of apparatus -for car
200° F. will be substantially paraffìnic and the 70 rying out my invention.
'
_
>hydrocarbon fraction distilling between 200°
In the drawing, the hydrocarbon feed to be
resolved into components of similar characteris
and ¿100° F. will be a mixture of parafñnic and
aromatic hydrocarbons, while the fraction re
tics, as for example, a hydrocarbon fraction pro
maining in the still which distills above 400° F.
duced from catalytically treated or reformed gas
vwill be substantially aromatic.
oline having a boiling range of about 220 to 235° F.
2,406,695
8
pumped by pump 55 through line 5Sv into frac-vtionating column 51 in which the aromatic hy
and; consisting of substantially 45%I toluene,~ 6%
o‘leñns and the» remainder parafiins andv naph
trolledv by valve I2 and pumped by pump i4 into
line l5. Azeotrope former, such as methyl ethyl
drocarbon, i. e. toluene, is distilled by steam heat
in coil 58 and is removed via line 59, condensed
in 60 and passed through line 5l into storage
ketone, containing about 10% water, is taken
from tank i6 via line I1 controlled by valve I8
umn consisting of cresylic acid are withdrawn via
thenes, is taken from tank l0 via line il con
tank 62.
The bottoms in the fractionating col
line $3 controlled by valve 64 and pumped by
pump 55 through line 60 into storage tank 2l.
In the foregoing, while- not disclosed, a portion
of the condensate obtained» by condensing the
and is pumped by pump l0 through line 20 into
line l5. Vapor pressure depressant, such as
cresylic acid, is taken from tank 2l via line 22
controlled by valve 23 and is pumped by pump 24
through line 25, Valve 20 and line 2l into line l5.
This mixture in line l5 consisting of the hydro
carbonv feed, azeotrope former and vapor pressure
depressant in the ratio of approximately one part
by volume of hydrocarbons,l one part of methyl
ethyl ketone and- water and ñve parts of cresylic
overhead from each fractionating column such as
23, 41 and 51 may be recycled tothe top of the
column to act as reflux and control the frac
tionation.
The foregoing description is not to be taken as
limiting my invention but4 only as illustrative as
many variations may be made by those skilled in
the art without departing from the scope of the
acid, is then passed into fractionating column 23
Where the mixture is subjected to fractionation,
heat being supplied by closed steam coil 2S. If 20 following claims.
l'. claim:
desired, the vapor pressure depressant may be in
1. A process for the treatment of a narrow
troduced directly into the fractionating column
boiling range complex hydrocarbon fraction to
via» line 2l’ controlled by valve EES’ and throughV
separate at least one component from other com
either valve 25a or 2Gb depending upon whether
it is desired to introduce it into the top or bottom 25 ponents contained therein which ordinarily distill
from the hydrocarbon fraction in the same tem
of the column. In some cases, it may be desired
perature range as said component distills there
to introduce the vapor pressure depressant into
from. which comprises fractionally distilling said
theA top of the column so as to act as reflux there
complexy hydrocarbon fraction in the presence of
a suiilcient amount of an aliphatic ketone having
a boiling point within 100° F. below and 40° F.
above the average boiling point of said complex
hydrocarbon fraction to vaporize at least one
in. In the fractionating column, the distillation
is controlled so'as to distilloverhead an azeotrope
consisting or the paraffin, olefin and naphthene
hydrocarbons and the methyl ethyl ketone and
water. In the example herein- given, this is ac
complished at an overhead temperature of ap
component of» said complex hydrocarbon fraction
proximately 160° F. If desired, the azeotropic dis 35 together with said. aliphatic ketone and in the
presence of a phenolic compound having a boiling
tillation may be carried out either at atmospheric
point
of at least 100° F. above the average boiling
orl superatmospheric pressure or under a vacuum.
point of saidr complex hydrocarbon fraction
The above overhead mixture is removed from the
adapted to remain in the residue together with
fractionating column via line 30, condensed in
at least one component of said complex hydro
condenser 3l and passed via line 32 into the bot
40
carbon fraction, thereby leaving at least one com
ponent of said complex hydrocarbon fraction in
such as broken tile 33a, for effecting intimate
the residue together with said phenolic compound
countercurrent contact with` water which is in
substantially completely separated from at least
troduced into the washer from tank 34 Via line 35
one component of said complex hydrocarbon frac
45
controlled by valve- 35 and pumped by pump 3l
tion.
Y
through line 38 into `the washer. The contact of
2. A process for the treatment of a narrow
the condensate of methyl ethyl ketone, water and
boiling range complex hydrocarbon fraction con
hydrocarbons introduced into the Washer with
taining relatively aromatic and relatively non
the Water causes the condensate to separate into
aromatic hydrocarbons to separate the relatively
two phases, i. e. an upper phase consisting of the
aromatic hydrocarbons from the relatively non
paraffin, olefin and> naphthene hydrocarbons and
aromatic hydrocarbons contained therein which
a lower phase consisting of methyl Vethyl ketone
ordinarily distill from said complex hydrocarbon
and water. The upper phase is withdrawn via
fraction in the same temperature range as the
line 39» and is passed through cooler ‘40 and line
relatively aromatic hydrocarbons distill there
4l to storage tank 42. The washing operation' is « from which comprises distilling said complex hy
preferably carried out at an elevated temperature
drocarbon fraction in the presence of a suiiicient
of approximately 300° F. under superatmospheric
amount .of an aliphatic ketone having a boiling
pressure.
point within 100o 1i'. below and 40° El. above the
The lower phase is withdrawn via line 43~ con
average boiling point of said complex hydrocar
trolled by Valve 44 and is pumped by pump 45 60 bon fraction to vaporize the relatively non-aro
through line 40 into fractionating column 41
matic hydrocarbons together with said aliphatic
where the methyl ethyl ketone containing the
ketone and in the presence of a suñicient amount
desired amount of water, i. e. about 10%, is re
of a phenolic compound having a boiling point
Y moved as an azeotrope aided by heat in steam
of at least 100° F. above the average boiling point
coil 48, as an overhead ‘vapor via line 49, con
of said complex hydrocarbon fraction adapted to
densed in condenser 50 and returned via line 5l
remain in the residue together with said relative
to= storage tank l5. The undistilled Water sub
ly aromatic hydrocarbons, thereby leavingk said
stantially free from methyl ethyl ketone is re
relatively aromatic hydrocarbons in the residue
moved Via line 49 controlled by valve 50 and is
torn of Washer 33 provided with packing material,
pumped by pump 5l through line 52 to storage ”
substantially completely separated from the hy
tank 34.
The bottoms in the fractionating column 28
consisting of aromatic hydrocarbons and vapor
hydrocarbons.
drocarbons other than said relatively aromatic
3. A process for separating toluene from paraf
iin and other non-aromatic hydrocarbons having
moved via line 53 controlled- by valve 54 and 75 similar boiling points which comprises addingv an
pressure depressant, i. e. cresylic acid, are re
2,406,695
`
t
9
10
‘
4. A process for separating toluene from paraf
ñn and other non-aromatic hydrocarbons having
similar boiling points which comprises adding
methyl ethyl ketone adapted to form an azeotrope
boiling point‘of said hydrocarbons and adding Ul with the parañin and other non-aromatic hydro
carbons and adding also cresylic acid adapted to
also a phenolic compound adapted to depress the
aliphatic ketone adapted to form an azeotrope
with the parafûn and other non-aromatic hydro
carbons, said aliphatic ketone having av boiling
point Within 100° F. vbelow and 40° F. above the
vapor pressure of the toluene„said phenolic com
pound having a boiling point of at least 100° F.
above the boiling point of said hydrocarbons and
fractionally distilling the mixture to vaporize an
azeotrope of said aliphatic ketone and non-aro
` matic hydrocarbons from said toluene and phe
nolic compound.
depress the vapor pressure of the toluene, and
fractionally distilling the mixture to vaporize an
-azeotrope of said methyl ethyl ketone and non
aromatic hydrocarbons from said toluene and
cresylic acid.
lGrEORG‘rE R. LAKE.
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