Note: Descriptions are shown in the official language in which they were submitted.
l~g~lS
l~he presellt invention relates to a method o$ separating a
diolefin from a mixture of hydroearbons eontaining the diolefin
and other hydrocarbons by an extraetive distillation.
More particularly, the invention is directed to the
separation of a diolefin, such as butadiene or isoprene, from a
mixture thereof with other hydroearbons by an extractive distil-
lation wherein the solvent employed comprises N-methyl-morpho-
line-3-one.
It is known to utilize heterocyclic compounds as extractive
solvents in the separation of hydrocarbons from hydrocarbon-
aeeous mixtures by operations oE extraetive distillation, gas-
liquid scrubbing or liquid-liquid scrubbing.
When evaluating such compounds to the end of an industrial
exploitation of same, numerous aspects must be considered, among
which selectivity, conveyance power, stability, ease of synthe-
sis, toxicity, vapor pressure, specific gravity, boiling point
temperature, melting point temperature and others.
It has been found that N-methyl-morpholine-3-one is a com-
pound whieh satisEactorily fulfils, in general, all o these
requirements and thus it can be used with advantage as an
extraetiv~ solvent.
~ he present invention thereEore provicles a me~hod oE
separating a diolefin from a mixture thereoE with other hydro-
earbons by an extractive distillation, which eomprises Eeecling
a stream of the mixture of hydrocarbons to a Eirst extractive
distillation column, feeding a stream of solvent comprised of
N-methyl-morpholine-3-one to the Lirs~ extractive distillation
column, withdrawing the other hytirocarbons and a minor quantity
of the diolefin from the head of the first extractive distilla-
tion column, recovering the solvent and the balance of theclioleEin Erom the first extractive distillation column as bot-
2 - ~.
1()91~l5
tom product, feeding the bottom product Erom the irst
extractive distillation column to a second extractive distilla-
tion column, recovering the dioleEin in the bottom product of
the first extractive distillation column from the second
extractive distillation column as head product, withdrawing
the solvent in the bottom product of the first extractive
distillation column from the second extractive distillation
column as bottom product, and recycling the bottom product from
the second extractive distillation column to the first
extractive distillation column.
The N-methyl-morpholine-3-one can be used either alone or
in a mixture with up to 20 ~ by weight of water or other
organic solvents, such as ethylene glycol.
The method of the invention is particularly useful for the
separation oE butadiene from a mixture of C4 hydrocarbons, or
of isoprene Erom a mixture of C5 hydrocarbons.
The following non-restrictive examples illustrate the
invention.
~XAMl~L~ 1
.
2Q With reference to the diagram of FIGURE 1, the extractive
distillation column 9 is Eed with a stream which is composed
by (line 1):
Isoprene282.0 mols/hour
Isopentane 13.2
l-pentene 39.7
2-methyl-1-butene 67.3
nor. pentane 120.]
2-uentene-trans 29.4 " "
2-pentene-iso 18.1 " "
2-methyl-2-butene 11.3 " "
1,3-cyclopentadiene1.7 " "
,!lt-.~';
Isopropenylacetylene 0.1 " "
The workin~ conditions are as follows:
Head pressure 1.1 absolute atmospheres
L/D O.g
No. of plates 65 .-
E3
~ - 3~ -
~as~6l~
The same column is fed through the line 2 with 500 kgs/hr
of a mixture composed by N-methyl-morpholine-3-one/water in the
proportion of 94 to 6 by weight.
From the head (line 3) a stream is dumped which is com-
posed by :
Isoprene 5.6 mols/hr
Isopentane 13.2 " "
l-pentene 39.7
2-methyl-1-butene 67-3
nor.pentane 12001
2-pentene-trans 29.4 " "
2-pentene-cis 11.1 " ~'
2-methyl-2-bu-tene 11.0
The stream coming from the bottom of column 9 (line 4) is
sent to the second extractive distillation column 10~ along with
a stream of 60 kgs/hr (line 5) o-f the above indicated solvent.
The col-~n 10 is operated under the following conditions:
Head pressure 1~1 abs~ atmospheres
L/D 0.9
No. o~ plates 75
From the head (line 6) is discharged a stream oE high-purity
~soprene~ which is particularly composed by .
lsoprene 270.8 mols/hr
2-methyl-2-butene 0.3
While from a lateral draw in vapor phase (line 7) the more
polar hydrocarbons (1~3-cyclopentadien~ and isopropenyl acetylene)
are discharged, from the bottom (line 8) the solvent is dumped,
which is exempt from hydrocarbons and is thus adapted to be re-
cycled in the abovementioned extractive distillation columns 9 and
10.
EXAMPLE 2
With reference to the diagram according to FIGURE 1~ the
4.
109~
extractive distillation column 9 is fed with a 1 kg/hr stream
composed by (line 1) :
C~ saturated hydrocarbons 20% by weight
C4 olefinic hydrocarbons 45% " "
1~3-butadiene 35% " "
Acetylene compound (such as
vinylacetylene)1~000 ppm " "
The working conditions are as follows :
Head pressure 4 abs. atmospheres
L/D o.9
No. of plates 70
To the same column, through the line 2~ are sent 10 kg/hr
oE a mixture composed by N-methyl-l-morpholine-3-one and water
in the propor-tion of 93/7 by weight.
From the head (line 3) a stream is discharged, oE o.65 kg/hr
which substantially contains saturated and oleEinic hydrocarbons.
The stream coming from the bottom of the column 9 (line 4)
is sent to the second extraction column 10~ together with a stream
of 2 kg/hr (line 5) of the abovementioned solvent .
The separa-tion in the column 10 is carried out under the
Eollowing conditions :
Head pressure 1.2 abs. atmospheres
L/D 0.9
No. oE plates 80
From the head is discharged (line 6) a stream oE about 0.34
kg/hr oE 1~3-butadiene with a high degree of purity and which con-
tains~ more particularly~ about 20 ppm (parts per million) of
acetylene compounds.
From a lateral draw in vapor phase (line 7) are discharged
the acetylene hydrocarbons together with a negligible quantity of
butadiene, whereas from the bottom is discharged (line 8) the
solvent~ which is hydrocarbon-free, and which is adapted to be
5.
l61~5
reused in the extraction columns 9 and 10 aforementioned.
EXAMPLE
With reference to the diagram according to FIGURE 2~ the
extractive distillation column 8 is Eed with a reformed ~asoline
stream composed by (line 1) :
Benzene 1050 kg/hr
Toluene 2.00
Xylenes 3.50 1l "
Nonaromatics 3.oo
The operative conditions are as follows :
Head pressure 1.1 abs. atmospheres
L/D 0.7
No. o plates 55
The same column is Eed through the line 2 with 30 ~g/hr
of a mixture of N-methyl-morpholine-3-one and monoethylene glycol
in the proportion of 95/5 parts by weight.
From the head (line 3) is discharged a stream of 3.05
kg/hr which substantially contains all the nonaromatic hydroçarbons
Eed to the same column 8.
The bottom product is sent (line 4) to a stripping column
(9) which is operated under the following conditions :
Head pressure 0.2 abs. atmosphere
L/D 0.2
No. oE plates 25
From the head (line 5) there is obtained a stream of aromatic
hydrocarbons having a preselected quantity of saturated compounds
whereas from the bottom the solvent is recovered~ which is required
for the operation oE the column (8) .
The stripping of the stream discharged from the bottom of
the column 8 can also carried out in two stages, as indicated by
the diagram according to FIGURE 3
6.
s
In such a case~ the same bottom product (line 4) is sent
to a first stripping column (9) which is operated under the
following conditions :
Head pressure 1.1 atmospheres
L/D 0.2
No. of plates 25
From the head (line 5) is obtained a stream having a speci-
fied contents of saturated compounds and which is composed by :
Benzene 1.49 kg/hr
Toluene 1.99 " "
Xylenes 0.47 " "
From the bottom (line 6) is discharged a stream which is
sent to a second stripping column (10) which is operated under
the following conditions :
Pressure 0.2 abs. atmosphere
L/D 0.1
No. of plates 15
While from the head (line 7) is discharged a stream of
xy~enes according to a preselected specification (3.03 kg/hr)~
Erom the bottom is recovered the solvent which is required for
the operation oE the column (8).
EXAMPLE~
~ ith reference to the diagram according to FIGURE 4~ the
c~tractive clistillation column (9) is fecl with a stream (line l)
of 100 kg/hr oE a C8 cut having the Eollowing composition :
C8 saturated and
oleEinic hydrocarbons 3.5%
o-xylene 17.0%
m-xylene and p-xylene43.1%
ethylbenzene 8.6%
styrene 27.8%
7.
109~
The operative conditions are as follows :
Head pressure 140 mmHg (absolute)
L/D 5
No. o~ plates 80
The same column is fed through the line 2 with 1,300
kg/hr of a mixture composed by N-methyl-morpholine-3-one and
water in the ratio of 96/4 by weight.
From the head (line 3) is discharged water and a stream of
organic refined mixture composed by :
C8 saturated and
ole~inic hydrocarbons 3.5 kg/hr
o-xylene 16.9
m-xylene and p-xylene 43.1 1~ "
ethylbenzene 8.6 " "
styrene o.3 ll ll
This stream is sent to a demixer (11) to separated water
(17) from the refined mixture (16).
From the tail is discharged a stream (line 4) which is sent
to the e~traction column (lO) together with a stream of 150 kg/hr
of the solvent aforesaid. The separation in the latter column is
carried out under the following conditions :
Head pressure 160 mmHg (abs)
L/0 2~5
No. o-~ plates 60
From the head (line 6~ a stream is removed which comprises
o-~ylene and styrene which is recyc.led to the column (9)~ whereas
~roln the bottom is discharged a stream (7) which is fed to the
stripping column (12).
Such stripping column is operated under the f:ollowing con-
0 ditiolls :Head pressure 190 mmHg (abs)
No. of plates 30
~g~61~
From the head is discharged a stream which is sent to the
demixer 13: from the line ~ is obtained styrene having a purity
of more than 99.8%.
From the tail of the same column the solvent is discharged,
which, upon having been admixed at 15 with tempered water from
17 and 18, is recycled.
EXAMPLE 5
With reference to -the diagram according to FIGURE 5, the
gas-liquid scrubbing column (9) is fed with a s-tream o l kg/hr
composed by :
C4 saturated hydrocarbons about 20~ by wt.
C4 olefinic hydrocarbons about 45% by wt.
The operative conditions are as follows :
Head pressure 5 abs atmospheres
No. of plates 40
The same column is fed through the line 2 with about 8.5
kg/hr of a mixture composed by N-methyl-morphol.ine-3-one and
water in the proportion of 94/6 by weight.
From the head (line 3) is discharged a gas stream of o.65
kg/hr which substantially contain saturated and olefinic hydro-
carbons~ whereas the bot-tom stream (line 4) is sent to the strip-
ping column (10).
The operation o~ the latter column is characterized b~ :
Head pressure 5.5 abs. atmospheres
No. o~ plates 45
From the head (line 5) is discharged a gas stream of C4 ole-
~l~s and 1~3-butadiene which is recycled to the column (9)~ where-
as ~rom the bottom is discharged a stream (6) which is fed to the
second stripping column (ll)o The la-tter column is operated under
30the following conditions :
Head pressure 1~1 abs. atmospheres
No. of plates 30
10~6~LS
The gaseous stream discharged from the head is sent to
the compressor (12~. From the line (8), upon condensation~ are
drawn about 0.35 kg/hr o~ 1~3-butadiene according to specification
containing saturated and olefinic compounds ( purity more than
99.5% by wt.), whereas through the line (7) fractions of the afore-
mentioned stream are recycled to the column (10).
From the tail of (ll) the solvent is recovered, which is re-
used in the column (9).
EXAMPLE 6
With reference to the diagram according to FIGURE 6~ the
charge which is used (line l) is a gasoline having the following
composition :
benzene 15% by wt.
toluene 25% " ~'
xylenes 25% " "
saturated 35~ " ll
This charge is fed to the liquid-liquid extraction column
(14) having 60 plates~ at the rate of flow of 5 kg/hr. Through
the line t13) are sent 13 kg/hr of a mixture of N-methyl-morpholine-
-3-one and water in the ratio of 95/5 by weight~ the entire column
being maintained at 40C-45C (head pressure about 2 atmospheres
absolute).
From khe head of the column (line 3) i~ discharged a stream
which ls ess~ntially composed by the saturated compounds which were
present in the original charge.
The extract emerging Erom the bottom is Eed to the head of
the column 15 (head pressure about 1.2 atmosphere absolute)0 No.
o~ plates = 30).
The head pressure of the column 15 (line 5) is condensed in
two consecutive stages at (17) and (18). The stream (6) condensed
above 120C is remixed to the charge whereas the stream (7) is re-
10.
lS
cycled to the base of the liquid-liquid extractor.
The stream as discharged from the bot-tom of the column
(15) (line 8) is sent to the column (16)~ (head pressure = 1.2
abs. atm., 30 plates)~
From the head is discharged a stream which is demixed at
(9): from the line 10 is drawn a stream of about 3.05 kg/hr of
aromatics having a specified contents of saturated compounds,
whereas from the bottom of the demixer is drawn an aqueous stream
which is par~.ly re-fluxed to the same column (16, 1.5 kg/hr) and
partly is recycled to the column 14 ( 0.7 kg/hr)~ The solvent
discharged from the bottom of (10) is re-used in the same liquid-
liquid extractor.
EX~MPLE 7
With reference to the symbolic diagram of FIGURE 7~ the
charge which is used (line l) is a reforming gasoline having the
following composition :
benzene 4% by weight
toluene 15% " "
xylenes 20% " "
saturated 61% " "
This charge is sent -to a first liquid-liquid extraction
column (12) which has 40 plates~ at a rate of Plow of 100 kg/hr.
Through thè line (S) are sent about 250 kg/hr of N-methyl-morpho-
line-3-one~ whereas through the line (10) are sent to the same
column 40 kg/hr oP pen-tane~ the extractor being maintained at 25C
(head pressure = 3 atmospheres abso:lute).
The stream discharged from the head (line 2) is sent to the
distillation column (13) whereas from the hea~ thereof (line 8)
the pentane is recovered which is required for the operation of
the extractor~ from the bottom (line 9) is discharged a stream of
about 61~3 kg/hr composed essen-tially by the saturated hydrocarbons
which were contained in the original charge (l).
lOg~61S
The bottom stream o the extractor (12) is sent to the
second liquid-liquid extractor (14) together with about 220 kg/hr
of pentane (line 11): this column is consti~uted by 20 plates and
operates constantly at 25C and 2.0 atmospheres absclute.
The stream discharged from the head (line 4) is sent to the
distillation column (15- whereas from the head thereof (line 6)
is recovered the pentane which is necessary for operating the
extractor~ from the bottom (line 7) is discharged a stream of about
38,7 kg/hr of a mixture of benzene~ toluene and xylene having a
specified percentage o~ saturated compounds.
From the bottom of the second extractor is recovered the
solvent which is used at 12.
EXAMPLE 8
With reference to the diagram according -to FIGURE 8, the
liquid-liquid extraction column (12) is fed with a stream equal to
that already disclosed in Example 1.
The same column (formed by 50 plates and working at a pressure
of 1.2 atmosphere absolute) is fed~ through the line 7~ also with
150 kg/hr of a mixture composed by N-methyl-morpholine-3-one and
water in the proportion of 95/5 by weightO
From the head (line 2) a stream is discharged which~ upon
stripping of the solvent contained therein (an operation which i9 not
shown in the drawing)~ is composed by :
isoprene 8,4
isopentan~ 13,2
l-pentene 39.7
2-methyl-1-butene 67-3
nor.pentane 120.1
2-pentene-trans 29~4
. 2-pentene-cis 18.1
2-methyl-2-bu-tene 10.8
The stream discharged from the bottom (line 3) is fed -to the
lQ~ S
stripping column (13) (head pressure about 1.5 atm.abs.~ 30
plates).
From the he~d (line 4) is discharged a stream of olefins
and isoprene, which is recycled to the extrac~or~ whereas from
the bottom is discharged a stream (5) which is -fed to the second
stripping column (14) (head pressure about 1.2 atm.abs.~ 20 plates~
L/D = 0.2).
From the line (6) is recovered isoprene having a speci~ied
contents o~ olefins and sa-turated compounds, which is sent to the
extractive distillation column (ll) for removing the polar hy~ro-
carbons~ whereas from the line (7) is recovered the solvent which
is necessary to operate the column (12)~
The column (12) is operated under the following conditions :
Head pressure 1.1 abs. atm~
L/D 0.9
No. of plates 75
From the head (line 8) is discharged a stream of highly pure
lsoprene~ which~ more particularly~ is composed by :
isoprene 268.o mols/hr
2-methyl-2-butene o 5 l~ ~t
While Erom the lateral draw in vapor phase (line 9) are
dischargecI-the most polar hydrocarbons ( 1~3-cyclopentadiene and
iso-propyl-acetylene), from the bottom is discharged (line 10) the
001vont~ which is exempt from hydrocarbons and thus adapted to be
r~-used in -the same column 11,
~X~IPLE 9
With reference to the diagram according to FIGURE 5 a the
gas-liquid scrubbing column (9) is fed with a stream constituted
by :
nor.butane 89.5 mols/hr
isobutane 2204 " "
13.
L6i5
l-butene 285 o2 mols/hr
2-butene-trans 117.6 " "
2~butene-cis 91.0 " "
1~3-butadiene 6.8 " "
The working conditions are as ~ollows :
head pressure 5 atm.abs.
No. of plates 40
The same column is fed~ through the line 2, with 1,200
kg/hr of a mixture constituted by N-methyl-morpholine-3-one and
water in the proportion oE 93/7 by weight.
The bottom stream (line 4) is sent to the first stripping
column (10)~ whereas from the head is discharged a gas stream
composed by :
nor.butane 87.7 mols/hr
isobutane 22.4 " ~
l-butene 5.7 " "
The operation of the column (10) is characterized by :
head pressure S.S atm.abs.
No. of plates ~0
From the head is discharged a gaseous s-tream of olefin~s
and saturated C4 which is recycled to the column (9)~ whereas frcm
the bottom is discharged a stream (6) which is ~ed to -the second
stripping column (11).
The latter column is operatecl under the ~`ollowing conditions:
head pressure 1.1 abs~atm.
No. o~ plates 30
The gaseous stream is sent to the compressor (12); from the
line (8), upon condensation, a stream is drawn which is composed
by :
nor.butene 1.8 mols/hr
l-butene 279-5 "
2-butene-trans 117.6 " "
14.
~1615
2-butene-cis 91~0 mols/hr
1~3-butadiene 6.8
A portion of the abovementioned stream sent to the com-
pressor is recycled through the line (7) to the column (10).
From the tail (11) the solvent is recovered which is re-
used in the column (9).
