enema Dec. 19, 1933
~
1,940,065
UNITED STATES PATENT, OFFICE ’
1M...“
snraaa'rion AND runmca'non or
clinic, mam rm xrumn
Hangspannagel, Leverkuacn-on-the-Bhine.
and
Eduard Tschunknr, Cologne-Mulheim, Ger
many, asslgnors to I. G. Farbenindustrle Aktien
gelellachalt, Frankfort-on-the-llain, Germany,
a corporation of Germany
No Drawing.
v
Application December 12, 1928,
Serial No. 325,849,‘.and 'in- Germany December
15, 1927
2
‘(01. 200-108)
The present invention relates to the separation
and puri?cation of ortho, meta, and para-xylene
from crude xylene, technically pure xylenetorg
solvent naphtha containing xylene.
chamber, down to a temperature of about -60
to about -100° 0., whereby the meta xylene sep
aratesin crystalline form and can be separated.
Sho'uld‘the separating crystalline magma be too
No simple physical methods have so far‘ been thick, it will be advantageous to carry out the 60
known for the separation of ortho, meta and crystallization either in two stages at di?erent
para xylenes from crude xylene, technically pure temperatures or with the addition of an indiffer
xylene or solvent naphtha containing xylene.
ent, easily volatilesolvent, for example, benzine,
For the manufacture of pure xylenes it was
necessary to haverecourse to cumbersome chem
ical methods of separation, such as for example,
sulfonation of the techinically pure xylene, sep
aration of the sulfonic acids or of the salts there-1
alcohol, ether, acetone.
'
The meta and para’ xylenes obtained by the
above described crystallization by means of low
temperature cooling are not yet completely pure
after the ?rst separation and are puri?ed by re
of by crystallization and subsequent hydrolysis crystallization at a correspondingly low temper
15 of the pure sulfonic acids thus obtained for pro: ;ature, that means. the para xylene having a
ducing the corresponding xylenes therefrompit melting'point of +15? C. is cooled down to about 7o
follows that the application of so many ope'ra- - +2‘-’*~C.._and'the meta xylene to about -60 to
tions is very troublesome and costly.
- l.
-'70," v(23., ‘whereby the pure xylenes crystallize
In accordance with the present invention the ‘and "can ‘be separated from the mother liquor,
20 three isomeric xylenes can be separated in a com for'example, by ?ltration.
75
paratively cheap and simple manner fromcrude
If desired, the meta and para xylene may be
re-crystallized with the addition of a suitable
vent naphtha containing xylene and‘puri?ed by indi?erent, easily volatile solvent, such as for ex
xylene, technically pure xylene or also from sol
fractionating carefully the primary materials, re
25 peatedly if necessary, in an e?‘lcient distillation"
ample, toluene, benzine, methanol, ethanol,
acetone, ether and the like. In this case the 80
(rectificatiom-apparatus of any suitable origin temperatures required for the crystallization are
and construction, so that with the ?rst runnings lower, for example, for the'para xylene about
are distilled off any aliphatic hydrocarbons, ethyl —30° to about —60° C., and ‘for the meta xylene '
benzene and the like, boiling below para and about —90° to about ---l00"v C. The mother
meta xylene, and with the last running primarily liquors resulting from the re-crystallization are,
the ortho xylene, this being ascertained by test after‘removal of the solvent, returned for fur
ing the individual fractions with regard to boil
ther treatment to the distillation on their ?rst
ing point, speci?c gravity and freezing point. crystallization ‘depending on their respective
Generally we work up the mixtures into three
35 fractions; the ?rst boiling below 136° C., the
composition.
‘
_
The third fraction‘ boiling above 140° C. con
second boiling from 1362140? 0., and the third sists essentially of ortho xylene containing, for
boiling above 140° C.
example, about 80-90% ortho xylene. For more
The pure second fraction, thus obtained, con complete puri?cation, it is recrystallized at cor
sists essentially, after it has been fractionated respondingly low temperatures, for example, at
40 repeatedly, if necessary, of a mixture of varying about —30 to —50° 0., with the addition of an 95
quantities of meta and para xylene and is almost indifferent, easily volatile solvent if desired, such
completely free from ortho xylene (for example, as, for example, toluene, benzine, methanol, eth
it contains 20-30% of para xylene and about anol, acetone, ether and the like. The solvent
60-70% of meta xylene). The mixture of meta is advantageously recovered by fractional dis
45 and para xylene is then thoroughly cooled down tillation.
100
to a temperature within the range from about
The separation of the xylenes can also be ef
—-30° as the upper limit to about —60° as the fected successfully by ?rst freezing out and re
lower limit, whereby almost all the para iwlene moving the para xylene from the technically
can be obtained in well formed crystals which are 'pure xylene of commerce (which, besides meta
50 separated from the meta xylene (mother liquor), xylene as the main constituent, contains about 105
for example, by ?ltration.
15% of para and about thesame- quantity of
The thoroughly cooled mother liquor obtained ortho xylene) on cooling down- the mixture to
from the separation of the para xylene which is an appropriate low temperature oifv about —30 to
,rich in meta xylene is cooled further, advanta .—60° C. The mother liquor, essentially consist‘
55 geously in a second low temperature cooling ing of ortho and meta xylene, is then subjected 110
2
1,940,065
‘to a low temperature cooling process, whereby
the mixtures of ortho and. meta xylene crystallizes
at about ~60 to —,100° C. From the. mixture,
ortho and meta xylene are separated‘ by cooling
down to about ~L60 to —90° 0., whereby the ortho
xylene crystallizes out. Subsequently, the mother
The mother liquor is then reintroduced into
mixture.
Example 3.—250 kg. of technically pure xylene, 85
the cooling vessel and cooled down to about —80
to about —100‘? C., and after about 3 hours the
content‘of the vessel is centrifuged; about 95 kg.
of 80-90% meta xylene are thus obtained. A 80
meta xylene of about 97% is obtained by cooling
liquor is cooled down to about —100° 0., whereby down the product of a content of 80-90% to
the meta xylene crystallizes out. The tempera about —60 to —'l0° C. and separating the crystals
tures required depend on the composition of the from the mother liquor.
'
10
'
Moreover, the process can also be carried .out containing about 15% para xylene, 15% ortho
by freezing out and separating the para xylene xylene and 60% meta xylene, are introduced into
from the technically pure xylene on cooling down the cooling vessel mentioned in Example 1 and
the mixture to an appropriate low temperature cooled down to —40 to -60° C. After about 4
of about —30 to —60° C., as above described, then hours the crystals of para xylene are separated by 90
separating the mother liquor which has been ob centrifuging the content of the vessel. The
tained from the freezing operation and con-. mother liquor consisting essentially of ortho and
tains meta and ortho xylene by fractional dis meta xylene is cooled down to a low temperature
tillation into meta xylene and ortho xylene, and of —60 to -100° 0., whereby a mixture of ortho
and meta xylene separates. The mixture of 95
20 purifying the products thus obtained by re
crystallization at a correspondingly low temper ortho and meta xylene is then cooled down to —40
ature; with the addition of an appropriate in to —60° 0., whereby the ortho xylene separates
different solvent if desired, as above described.
possessing a melting point of 28° C. By cooling
The freezing out, crystallization and removal down the mother liquor, for example, to —60°
25 of the crystals of the xylenes can be carried out C., the meta xylene of the melting point —45° C. 100
technically in the customary double walled stit
is separated.
ring vessel and filters, or in insulated stirring
The xylenes thus obtained are not completely
vessels and ?lters provided with cooling worms pure and are puri?ed by recrystallization.
for low temperature cooling.
In the claims, the term “a mixture containing
The temperatures applied during the crystal the three isomeric xylenes” comprises crude 105
30
lization process at low temperatures are varied xylene, technically pure xylene and solvent
within wide limits depending on the composition naphtha containing xylene.
of the individual distillation fractions.
We claim:
‘
The invention is illustrated by the following ex
1. In a process of separating and purifying
isomeric xylenes from crude xylene, the step 110
35 amples, without being limited thereto:
Example 1.-250 kgs. of the ?nal runnings of which consists in cooling to a temperature be
a xylene fractionation, boiling above 140° C., are tween —-30 and —60° C. a mixture of xylenes con
cooled to —40° C. with stirring in a cooling ves sisting essentially of para-xylene and meta-xylene
sél provided with a cooling jacket and cooling with substantially no ortho-xylene, the mixture
40 worms. The ortho xylene crystallizes out in the containing more para-xylene than is necessary 115
course of about 1 to 2 hours, whereupon the con to form a eutectic with all of the meta-xylene
tents of the vessel are put on a ?lter provided present, whereby a substantial crystallization of
with a suitable cooling apparatus. The crystal said para-xylene results, and separating the re
line mass is thoroughly ?ltered oil‘.
sulting crystals.
The yield amounts to 120 kg. of ortho xylene of
2. The process of separating para-xylene from 120
45
the freezing point —-29° C.
'
crude xylene, which comprises obtaining from
Example 2.--250 kgs. of fractionated xylene the crude xylene by fractional distillation the
containing about 20% of para xylene and about fraction boiling between 136° to 140° C., said
60-70% meta xylene are cooled to —30 to —60° fraction containing more para-xylene than is
50 C. in the cooling vessel mentioned in Example 1. necessary to form a eutectic with all of the meta- 125
After about 4 hours the content of the vessel is xylene present therein, cooling said fraction to
?ltered on the cooled ?lter; about 60 kg. of 85 a temperature within the range from about —30
95% para xylene are thus obtained. In order to about —60° C., whereby a substantial crystal
to obtain a para xylene of higher percentage the lization of said para-xylene results, and separat
' 13G
55 product obtained on ?ltration is washed with ing the resulting crystals.
cooled alcohol whereby, after distilling of! the
alcohol mixed with it, a 98% para xylene is ob
tained.
HANS SPANNAGEL.
EDUARD TSCHUNKUR.
[L.S.]
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140
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