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Патент USA US2405300

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Aug. 6, 1946.
Filed Jan. '7, 1944
Patented Aug. 6, 1946
Vuru'rrsl) `sfm'nt s PATENT oFFicE
‘ nEcovEaY or xYLENEs '
Richard B. Greenburg, Melrose ark, Pa., assign
or to Allied Chemical & Dye Corporation, New
York, N. Y., a corporation of New York
Application January "l, 1944, Serial No. 517,335
>«t Claims. (Cl. 2055-42)
This invention relates to a process~for recover
ing xylene hydrocarbons from mixtures contain
ing them together with other hydrocarbons. In
this specification and the appended claims thev
term “xylene” is used in its comprehensive mean
ing as referring to aromatic compounds of the
benzene series boiling in the range of temper
atures at which the several xylenes boil. The
. term as thus used includes the three xylenes,
matic hydrocarbons including oleiins and par
affins or naphthenes,
By fractional distillation of these oils contain
ing xylene, fractions of increased xylene con
tent may be obtained. These xylene fractions,
however, will still contain large amounts of the
other constituents of the oil having boiling points
in the neighborhood of the boiling point of xy
lene or forming mixtures of constant boiling
points in the range of temperatures at which Xy
ortho-, meta- and para-xylene, and ethyl ben 10 lene distills from the oil. > Accordingly, recovery
Numerous hydrocarbon oils are known which
contain xylenes in varying proportions. For ex
of xylene of a relatively high purity from these
sources presents a diillcult problem of great in
dustrial importance.
ample, gasoline fractions obtained by the distil
The fact that the oils containing xylene have
lation of certain types of petroleum frequently
generally a relatively low content of xylene makes
contain substantial proportions of xylene, al
it particularly diiilcult to recover by fractional
.though mainly consisting of other hydrocarbons. ' distillation or selective solvent extraction or a
Oils of petroleum origin having a considerable
combination of both of these procedures a xylene
content of aromatics, including xylene, may be
product of a high degree of purity. For example,
treated by well known selective solvent processes 20 drip oils may contain about 5% ortho-xylene.
to produce fractions rich in aromatics; for exam
ple extraction of suitable fractions of such pe
troleum oils with sulfur dioxide may yield frac
tions of increased xylene content. In such cases
Distillation of a drip oil with efficient rectifica
tion of the vapors may b_e employed to recover
xylene is accompanied by non-aromatic oils which
may be largely paraflinic, naphthenic or oleiinic
. a fraction containing more than about 80% to
a fraction in which the ortho-xylene is concen
trated. However, even with efficient rectification
85% ortho-xylene can rarely be obtained. Ole
in character. A considerable portion of these
fins together with paraflins and usually some
non-aromatic oils cannot be separated from the
naphthenes and traces of meta- and para-xylene,
xylene by direct fractional distillation because 30 make up the remaining 15% to 20% of the ortho
of the closeness of their boiling points to that
xylene fraction.` The non-aromatic hydrocar
of xylene or because they form constant boiling
bons individually may have boiling points rang
mixtures with xylene. Also synthetic hydrocar
ing from considerably below' to above the boiling
bon liquid and gas mixtures produced by various
point of ortho-xylene, e. g. their boiling points
catalytic processes may contain xylene which is
may range from 100° to 155° C., whereas ortho
accompanied by similar difilcultly separable con 35 xylene boils at about 144° C. Nevertheless, these
non-aromatics cannot be 'separated from the
While ordinarily xylene may be separated by
ortho-xylene by fractional distillation of their
direct fractional distillation from light oils pro-`
mixtures, e. g. drip cils and cracked petroleum
duced by the gasification of coal, in some cases the
oils, under practical conditions.l Apparently in
xylene is accompanied by diflicultly separable
the mixture the various hydrocarbons form azeo
non-aromatic oils of the- same general character
tropes with each other and this prevents their
as described, owing to carbonization conditions,
separation by fractional distillation. Such hy
type of coal used or other special circumstances.
drocarbons, those which cannot be separated by
'This is particularly true of drip oils and oil frac
fractional distillation or are difilcultly separable
tions recovered therefrom containing ortho-xy 45 by fractional distillation under practicable con
lene and like-boiling, non-aromatic hydrocarbons,
ditions for distilling oils, are >referred to as
e. g. naphthenes, parafii’ns and oleiins.
“like-boiling” hydrocarbons. Chemical treatment
By "drip oil” I refer to those condensates from
of oils containing ortho-xylene and like-boiling
carburetted water gas such as the condensates
hydrocarbons may be used to recover pure ortho-50
formed in the gas distributing lines or holders or
xylene therefrom, but such known methods are
the light oil which may be condensed in cooling
cumbersome and expensive.
the carburetted water gas lafter removal of tar.
It is, therefore, an object of this invention to
A common characteristic of drip oils is that in
provide a process for azeotropically distilling the
addition to aromatic hydrocarbons, they contain 55 xylene-containing oil in the presence of an azeo
a substantial proportion of like-boiling, non-aro
;ropic agent which is particularly eiTectiv-e for
separating from the xylene klike-boiling, non
aromatic compounds contained ln the oil to ob
tain a commercially pure xylene product.
It is a further object of the invention to pro
vide a process for the separation of xylene from
fractions of petroleum oil or drip oil containing
xylene and a mixture of other hydrocarbons ~of
over. the ethylene diamine being then separated
_` from the xylene in any desired manner. for ex-'
ample, by washing the mixture with dilute hy
drochloric acid followed by a water wash of the
xylene to remove the acid and dehydration of the
washed xylene.I
The ratio of ethylene diamine substantially
free of water to the xylene fraction which may
similar boiling range.
be employed in carrying out this invention de
I have discovered that ethylene diamine forms 10 pends upon the amount and nature of the hydro
azeotropes with the xylenes and also with the
carbon impurities in the xylene fraction, the
non-xylene hydrocarbon constituents present in
purity desired in the xylene residue from the dis
the oil and distilling therefrom in the range of
tillation, the proportion of xylene in the original
temperatures at which the xylene distills from
xylene fraction which is to be recovered in the
the oil. The xylene azeotropes, however, boil at
residue, the procedure used for distillation of the
a substantially highertemperature than the non
ethylene diamine-xylene mixture, and the equip
`xylene ethylene diamine azeotropes, permitting
employed. The quantity of ethylene di~
separation of the xylene. It is significant to
used in the distillation of hydrocarbons
note that the spread between the boiling point
a given quantity of xylene fraction should
of the xylene-ethylene diamine azeotropes and 20 from
be in excess oi' that which will form azeotroplc
the point at which the non-xylene-ethylene di
mixtures with the non-xylene hydrocarbons which
amine azeotropes begin to distill over is greater
in the case of the ethylene diamine than in the
case of many of the numerous other azeotropic
agents tested in the extensive development work
which led up to the present invention.
The presence of substantial amounts of water
are to be vaporized and taken over into the dis
tillate. By returning most or all of the ethylene
diamine collected from the distillate to the still,
for example, as 'reñux liquid, the total amount
of ethylene diamine necessary to eil‘ect the sep
aration of the non-xylene constituents and the
in the complex mixture constituted of xylene,
xylene will be materially- reduced. If desired,
hydrocarbons of parafilnic character distilling at
fresh ethylene diamine may be introduced‘into
temperatures close to that of xylene, other close 30 the xylene fraction being distilled during the
boiling hydrocarbons which may be of naph
course of the distillation; also, the ethylene di
thenic or oleflnic character, and ethylene diamine,
amine separated from the -distillate may be re
should lbe avoided. Even the presence of 1% of
turned continuously or periodically to the still or
water is objectionable in that it involves some
rectification column while the distillation of the
loss of xylene. Accordingly, the preferred em 35 xylene fraction is progressing. ,
bodiment of the invention involves the use of sub
Regulation of the temperature in the rectliica
stantially anhydrous ethylene diamine as azeo
tion of the vapors to meet the aforesaid condi
tropic agent, e. g. the water present being limited
tions is accomplished by maintaining an adequate
to no more than 5% by weight of the ethylene
quantity of the ethylene diamine substantially
diamine. More water may be present at a sacri 40 free of water in the still or rectification column
fice in the eiliciency of the process but in no event
or both during the distillation of the iwlene frac
should it exceed 10% by weight of the ethylene
tion to selectively carry over through the rectifi
diamine. The expression “ethylene diamine sub
stantially free of water” is> used in this specifica
tion- and appended claims to define an anhydrous
ethylene diamine or an ethylene diamine con
taining up to but no more than 10% water.
In carrying out the distillation of the hydro
carbon mixture containing xylene, close boiling
cation treatment the vapors of the non aromatic
hydrocarbons to be removed from the xylene.
Some of the xylene may also be carried over, but
as long as the temperature of 114° C. in the recti
ñcation zone is not exceeded, the undistilled resi
due will be enriched in xylene, and by continuing
the distillation under the aforesaid conditions
non-aromatic hydrocarbons, and ethylene di 50 separation of the non-aromatic hydrocarbons of
amine to produce relatively pure xylene, the dis
similar boiling range to that of xylene from the
tillation is conducted with rectiiication of the
xylene will be accomplished`
evolved vapors While maintaining at a point in
As the distillation proceeds temperature read
the rectiñcation of the vapors a temperature not
ings are taken of the temperature at the top of
above 114° C. By supplying to the distillation 55 the rectification column and, by supplying addi
adequate amounts of ethylene diamine, this con
tional azeotropic agent when required to prevent
trol temperature may be maintained and the dis
this temperature from rising above 114° C. an
tillation continued until the unvaporized residue
adequate amount of ethylene diamine substan
contains at least 95 parts by weight of xylene for
tially free of water will be present during the sep
every 5 parts by weight of non-aromatic hydro 60 aration of the non-aromatic hydrocarbons from
car-bons of similar boiling range to that of xylene.'
the xylene fraction. It is not necessary that this
If the control temperature should tend to rise
point of control temperature be at the top of the
above 114° C., this is an indication that the
column, although this is a satisfactory point for amount of ethylene diamine is inadequate and
determining this temperature in the equipment
more of this material should be introduced. The
used for fractionating the vapors and condensing
closer to 114° C. the control temperature is main
vthe fractionated vapors for effective use of the
tained the purer the xylene product. By operat
rectification column. One skilled in the distilla
ing in accordance with these conditions I have
tion art will recognize suitable points for main
found it possible to produce from'xylene fractions
taining this control temperature in any specific
boiling Within the range 125° to 150° C. substan 70 apparatus according to well known distillation
tially 100% pure xylene; i. e., to eifect complete
separation from xylene of the hydrocarbons of
The distillation preferably is carried out at
similar boiling range to that of xylene by con
atmospheric pressure; it may, however, be carried
tinuing the distillation until only xylene and
out under vacuum or under superatmosphericfI
ethylene diamine are left in the still or distill 75 pressure. If carried out under vacuum or super
. 2,405,300
atmospheric pressure the »control temperature is
modified accordingly so that it corresponds tothe
boiling point of the xylene-ethylene diamine azeo
‘ lexceeded at a point in the rectification of the
distilled vapors.
The residue of the azeotropic distillation may
be purified further as desired to remove any
ethylene diamine which it contains and to remove
any other impurities present. When the distil
lation is carried to the point at which all of the
ethylene diamine hasl been distilled out of the
residue and the xylene constitutes substantially
trope under the changed pressure. The tempera
tures as given in this specification and the ap
. pended claims are corrected temperatures for 1
atmosphere pressure (760 mm. of mercury).
In practicing this invention in the treatment
of an oil such as has been described above, con
99% or more of the total hydrocarbon content of
taining xylene and other hydrocarbons, particu 10 the residue, the residue may be given a conven
larly when the xylene concentration of the oil is
tional treatment, for example, treatment with
low or the oil is one containing materials of wide
sulfuric acid and redistillation, to obtain a‘prod
boiling range, it is preferred to iirst fractionally
uct which is suitable for marketing as a nitration
` distill the oil to recover therefrom an enriched
grade xylene of particularly high purity.
xylene -fraction which contains in addition to 15
Instead of withdrawing the xylene residue from
xylene other hydrocarbons which distill at the
the still, the distillation may be continued „and
- same temperature as
the xylene distilled over and separately collected
xylene fractions having an end boiling point
from the distillate containing the hydrocarbons
above the boiling point of xylene (e. g. a boiling
from which the xylene residue previously had
point up to 150° C.) may be azeotropically dis
been separated by azeotropic distillation. If
tilled in the manner hereinafter described, I pre
ethylene diamine is present during the distilla
fer the xylene fraction recovered in the prelim
tion and collection of the xylene, the ethylene di
inary distillation step be one having a maximum
amine may be distilled out in the form of an
azeotrope of xylene. The xylene may be sepa
boiling point of ortho-xylene, i. e. 145° C. Fur 25 rated in any suitable manner from this azeotrope,
ther, it is preferred that the xylene fraction re
for example, by treatment with HCl of 10% con
covered by the preliminary distillation of the
centration which will remove the ethylene di
crude xylene oil be so cut as to exclude therefrom
amine from the xylene.
boiling point substantially corresponding to the
the forerunnings which do not contain substan
tial proportions of xylene, for example, to exclude
The following example is illustrative of the use
of my invention for the recovery of xylene from
oils containing it together with like-boiling, non
any materials distilling below 125° C. and pref
erably below 135° C.
A xylene fraction such as may be obtained by
aromatic hydrocarbons:
the preliminary distillation hereinabove de
process of this example is, diagrammatically illus
An apparatus suitable for carrying out the
scribed, e. g. a fraction boiling Within the range 35 trated in the accompanying~ drawing. It com
125° to 150° C., preferably 135° to 145° C., and
prises a still l with heater 2 and rectification col
which may contain parafiins, naphthenes or ole
umn 3 of conventional design. A condenser 4 is
ñns, is subjected to a second distillation and recti
provided to which the vapors from the top of the
fication of the vapors in the presence of ethylene
column pass and in which they» are cooled and
diamine substantially free of water. When the 40 condensed. A pipe 5 returns a portion of the con
hydrocarbon mixture is subjected to fractional
densate from the condenser to the top of the rec
distillation with rectification of the vapors under
tiñcation column to serve as reilux in the column.
conditions such that a temperature not exceeding
lA second pipe 6 is provided for drawing 01T a por
114° C. is maintained at a point inthe rectifica
tion of the> condensate as product. Pipes 1 and 8
tion of the vapors, the azeotropes of non-aromatic
are provided for introduction of liquids into still
hydrocarbons and ethylene diamine may be dis
I and a pipe 9 for withdrawal of residue from
tilled oiî from the mixture to leave a residue con
this still.
taining at least 95 parts by weight of xylene to
every 5 parts by weight of like-boiling non-aro
By fractional distillation of an aromatic petro
leum oil a cut was taken distilling over at 127° to
matic hydrocarbons originally present in the 50 150° C. in which the xylene of the petroleum oil
xylene fraction and not separable therefrom by
was concentrated. This xylene fraction con
tained 58% by volume xylene. To every 100 vol
umes of the xylene cut introduced into still I,
100 volumes of an ethylene diamine substantially
After the distillation has been carried to the
point where the residue contains xylene of a de 65 free from water (95% ethylene diamine and 5%
Water) was added and the mixture distilled with
sired purity with respect to non-aromatic hydro
rectification of the vapors in a conventional rec
carbons of similar boiling 'range to xylene, the
tiñcation'column 3 supplied with reflux obtained
distillation may be stopped and the residue with
by returning to the column through pipe 5 a part
drawn from the still, This residue ordinarily
ofthe condensate from the vapors leaving the top
will contain xylene and other hydrocarbons in the
of the column. Another part of this condensate
proportion of 95 or more parts xylene to 5 or less
direct fractional distillation in the absence of the
azeotropic agent.
parts of the total hydrocarbons other than xylene.
By suitably limiting the top boiling point of the
xylene fraction which is azeotropically distilled 65
a residue of the azeotropic distillation may be
produced of desired purity of ' its yhydrocarbon
content greater than 95 parts xylene to 5 parts
non-aromatic hydrocarbons. A residue contain
ing the xylene substantially free of non-aromatic
' hydrocarbons may be obtained by distilling a
was drawn olli as overhead distillate through
pipe 6.
" Distillation started with the vapors at the top
of the column at a temperature of 103.6° C. This
temperature rose during the distillation to 114° C.
' and the last fraction distilled over at that tem
xylene. The
perature contained 95% by volume
hydrochloric acid
~ residue was washed with 10%
solution to remove ethylene diamine and the oil
separated from the solution was found to contain
xylene fraction having a top boiling point not
98% by volume xylene.
higher than 145° C. in the presence of ethylene
It is, of course, obvious preliminary distilla
diamine in amount such that a temperature of
tion of a crude xylene oil to obtain a xylene
substantially 11B-114° C. is reached but is not 75
fraction suitable for recovery oi' xylene therefrom
by the areotropic distillation need not be carried
out in immediate conjunction with the azeo
tropic distillation. 'The >xylene fraction may be
produced in one plant, transported to and treated
later in another plant to azeotropically distill it.
Nor is my invention limited to any particular
procedure for the production of the xylene irac
ethylene diamine substantially free from water
while maintaining at a point in the rectincation
oi' the vapors a temperature not above 114° C. by
maintaining the presence of -said ethylene di
amine at said point, whereby said non-aromatic
hydrocarbons are removed as azeotropic distillate
with ethylene diamine, and continuing the saidv
distillation until the unvaporized residue of the
contains at least 95 parts by weight
ethylene diamine substantially free of water any 10 ’distillation
of xylene to each 5 parts by weight of non
oil containing xylene together with non-aromatic
aromatic hydrocarbons which distill from said
hydrocarbons which, when the oil is distilled, va
fraction in theabsence of ethylene diamine in
porize therefrom in the same temperature range
the same temperature range as the xylene.
tion. My invention contemplates distilling vwith
_ as the xylene, and, therefore, are not separable
3. A process for the recovery of substantially .
from the xylene by direct fractional distillation. 15 pure
xylene from a complex hydrocarbon fraction
boiling within the range of 135°' to 145° C. con
claims, the term “xylene fraction” refers to all
taining xylene and at least 15% of non-aromatic
such xylene-containing oils, yWhether produced
hydrocarbons which distill from said fraction in
by fractional distillation of xylene-containing
the same temperature range as the xylene dis
materials or by any other means. As has been 20 tills therefrom, which comprises distilling said
pointed out above, these xylene fractions in gen
fraction and rectifying the vapors evolved there
eral contain substantial quantities (15% or more)
from in the prœence of ethylene diamine sub
o_f non-aromatic hydrocarbons which it is par
stantially free from water while maintaining at
ticularly difficult, and in many cases impossible,
a point in the rectincation of the vapors a tem
to separate from the xylene by any practicable 25 perature
not above .114° C. by maintaining the
method of fractional distillation or solvent ex-‘
presence of said ethylene diamine at said point
traction. The process of my invention is particu
and continuing the said distillation until sub
larly valuable as a means for recovering relatively
all of the non-aromatic hydrocarbons
pure xylene from such fractions.
As used in this specincation and the appended
I claim:
present in said fraction are removed as an azeo
tropìc mixture with ethylene diamine, leaving a
residue of the distillation containing the xylene
complex hydrocarbon fraction having a top
substantially free of non-aromatic hydrocarbons.
boiling point no higher than 150° C. containing
4. A process for the recovery of substantially
xylene and non-aromatic hydrocarbons which
pure xylene from a complex hydrocarbon frac~
distill from said fraction in the ‘same tempera 35 tion having a top boiling point not higher than
ture range as the xylene distills therefrom, which
145° C. containing xylene and non-aromatic
comprises azeotropically distillìng said fraction
hydrocarbons including parañinic hydrocarbons
1. A process for the recovery of xylene from a
and rectifying the vapors evolved therefrom in
the presence of ethylene diamine substantially
and which may also include naphthenicand
' oleñnic hydrocarbons, said non-aromatic hydro
free from water, thereby removing said non 40 carbons normally distilling from said fraction at
aromatlc hydrocarbons as azeotropic distillate
about the same temperature at which the xylene
with ethylene diamine, and maintaining the pres
distills therefrom, which process comprises dis~
ence of ethylene diamine during said distillation
tilling said fraction and rectifying the vapors
.until the residue of distillation contains at least
evolved therefrom in the presence of ethylene
95 parts by weight of xylene to every 5 parts by
diamine substantially free from water present in
weight of non-aromatic hydrocarbons which
amount such that a temperature of substantially
distill in the absence of ethylene diamine in the
113-114° C. is reached but is not exceeded at a
same temperature range as the xylene.
2. A process for recovering xylene from a
xylene fraction boiling within the range of 125°
to 150° C. containing xylene and non-aromatic
hydrocarbons which distill from the xylene frac
tion in the same temperature range as the xylene
distills therefrom, which process comprises, dis
tilling said xylene fraction and rectifying the
vapors evolved therefrom in the presence of
point in the rectification zone, and continuing
the distillation in the presence of ethylene di
amine until substantially all of the non-aromatic
hydrocarbons in said fraction are removed as
azeotropic distillate with the ethylene diamine,
leaving a residue containing the xylene substan
tially free of non-aromatic hydrocarbons.
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