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Патент USA US2355392

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Patented Aug. `8, 1944
raocEss Foa TREATMENT or
» Èeorge G. OberfellfBal-tlesvillc, Okla., assigner to ,
Phillips Petroleum Company, a corporation of
Application August 12, 1940, Serial No. 352,306
6 Claims. (cl. 26o-681.5)
Y '
i ._
This invention relates to a process for the
depolymerization to yield the original dioleflns
separation and concentration of dioleflnic hydro- rather than cracking toform lower hydrocarbons,
carbons such as butadiene and the like from mix
hydrogen, aromatica-etc.
tures containing other hydrocarbons. More par
Dioleñns, such as butadiene and isoprene,
ticularly it refers to the separation of diolefins
undergo two distinct types of polymerization;
by a process in which said dioleiins are succes
one leads to the lformation of dimers of a' cyclic
1 sively converted to polymers of- relatively low
nature and the other to the formation of more or
molecular weight, separated in polymer form by
less rubbery polymers of .high molecular weight
distillation or other suitable methods, and finally
and open branched or unbranched chain struc
10 ture. 'I‘he formation of the higher polymers is
generally favored by low temperatures, such as
An object of this invention is to separate di
i 20o-300° F. or lower, and by polymerization
~ oleiins from mixtures containing other hydrocar
bons such as parailins and monoleflns.
catalysts, such as oxygen, peroxides and other
- recovered as monomeric dioleilns by a depolymer
ization treatment.
«active oxygen’ containing compounds, alkali
Another object of this invention is to produce 15 metals, acids, and metal halides. In general
diolefins in concentrated' form suitable for use
in chemical conversion processes.
Ithese are either catalysts or chemicals which re
x act with the diolefln to form addition complexes.
,Another object of this invention is to freeof
I propose to carry out the polymerization of
diolefins hydrocarbon mixtures such as are pro
dioleiins under conditions which favor the forma- `
duced by cracking operations.
20 tion of dimers `rather than the higher polymers.
The manufacture of butadiene, isoprene, and
To accomplish this, I have found thatI can
similar Íconjugated dioleñns from petroleum hy
drocarbons by cracking, dehydrogenation, and
` similar methods is handicapped by the fact that
operate in the temperature range 30G-900° F.'
The -rate of reaction of course increases with
the temperature.
Elevated pressures are gener- `
the desired dioleiin generally is obtained in a 25 ally advantageous and I have found that pres
very dilute form. in admixture with other hydro
sures 'within the range of atmospheric to around
carbons. For example, the four-carbon-atom
500 pounds perl square inch gauge are particu
fraction of gases from vapor phase oil cracking
larly effective. Higher pressures, however, may '
stills will usually containless than 15 to 20 per
be employed where desirable, limited only by the
cent of butadiene. Pyrolysis of butane gas under 30 'degree of polymerization of the dioleiin. Solid
conventional conditions likewise gives very low
contact catalysts such as fuller’s earth, bauxite,
percentages of butadiene. As a rule, a similar
activated alumina, and silica gel favor the forma
fraction from other cracking processes will con
tion of the dimer in both liquid and vapor phase.
tain much smaller percentages of butadiene.
It is also frequently advantageous to use inhibi
In commercial processes utilizing dioleflns lit is
_very advantageous, if not economically impera
tivel to have said diolefins in concentrated form. I
For example, in the conversion of butadiene to
synthetic rubber by copolymerization with un
' saturated nitriles and other costly organic de
rivatives, it is generally uneconomical to start
with a butadiene product of less than 90-95 per
cent purity. For other processes and conditions,
tors which repress the formation of the higher
polymers, particularly in the lower part of the
temperature range specified above.
While I may apply my invention directly to
hydrocarbon fractions of comparatively wide
boiling range, I -prefer to separate fractions of
rather narrow distillation range containing the
desired diolefln and then subject the said frac--l
it may be economical to use lower concentrations
tions to the polymerization treatment.v For ex
ample, I may separate a fraction boiling from 15°
of butadiene, but generally higher concentrations
to 30° F. containing butadiene and `a fraction '
than can be Produced directly are desired. _
boiling from 85° to 105° F. containing isoprene
I have conceived the idea of producing a con
centrate of diolefin from a hydrocarbon mixture
for treatment by my process.
containing said dloleñn in a _dilute form by poly-A
merizing the dioleiln under conditions favoring
the formation of low polymers, preferably the
dimer, then separating the polymers from the un
polymerized hydi'ocarbe'tms> by - suitable means.
such as fractional distillation, and then treating
Since the dimers which I form in my- 'poly-f
merization step boil at much higher temperatures
than the original dioleflns, the separation of poly
mer may be readily accomplished by- ordinary
distillation. For example, the dimer of butadiene
boils above 320°> F. while butadiene boils at about
23° F. However, I do not limit myself to that
the low vpolymers under conditions which favor uA method of separation. The separation ofthe-
vent extraction, fractional precipitation> at low
temperatures or other convenient methods. The
depolymerization step is best carried out under
conditions of relatively high temperature, low
pressure, and relatively short heating times.
Pressures of atmospheric down to a very few
millimeters of mercury, absolute, are advanta
-geous and I prefer the range 3 to 100 mm. Tem
` peratures of 900°_to 1300° F. are preferred, but
coil 46. heated-by furnace 41. Lower and higher
boiling fractions are withdrawn from the frac
polymer may be accomplished‘ for example by sol
tionatingsystem 4|,.through pipes 42 and 44,
respectively. Products from the polymerization
coil 45 after suitable cooling are fractionated in
fractionator 49 anda normally liquid polymer is
withdrawn through expansion valve 80 and pipe
. 5I to depolymerization coil 52 heated ins furnace
53. Unpolymerized lig'ht hydrocarbons are with
drawn from fractionator 49 by means of pipe 50
considerably higher- temperatures may be used
providing the heating time is made suiliciently
short to limit ordinary thermal decomposition.
and may be either discharged, or fractionated
and partially recycled to the polymerization coil
46. The products from the depolymerization coil
52 are pumped through pipe 54 by means of pump
compressor 55 to fractionating system 5B, from
In general, shorter heating times are desirable at
v the higher temperatures. It is advantageous in
many cases to limit the‘extent of conversion per
pass in this manner and to separate and recycle
which a C4 fraction rich in butadiene is removed
through pipe 58. A more volatile fraction which
may be produced by partial cracking is with
'drawn from pipe 51. A normally liquid fraction
the unconfverted,l polymer in order to obtain
higher yields of the monomeric dioleñn.
As an alternative vto the use of very low pres:
sures I may dilute the polymers with an inert
is withdrawn through pipe 59- and may be re
cycled as a whole or fractionated to eliminate
gas such as nitrogen, or with steam. The main
object is yto maintain a low partial pressure of
very heavy materials and the lighter fraction re
dimer, and consequently of the monomeric diole‘
iin, in the reactor.
The flow diagrams show only the essential ap
paratus. In actual operation many modifications
The use of catalysts such as silver, copper,
may be advantageous. For example, heat ex
platinum, iron preferably in the form of the'
change between the products and the raw feed'
reduced oxides, and oxides of calcium and mage
of each of the furnaces may be applied. Greater
nesium -in the depolymerization step may also be
flexibility in operation and control may be' ef
advantageous. The optimum conditions of tem 30 fected by inserting accumulators between stages
perature and ñow rate foriany given catalyst
of the process. Some of the fractionating sys
may be determined by simple experiment;
tem shown as single columns would actually com
The voperation of the proce s is illustrated by
prise two or possibly three columns with the usual
the flow diagrams >of Figures 1 and 2. In Figure
auxiliary and control equipment.l Suitable cata
l a raw petroleum or natural gas fraction such 35 lysts may be used in polymerization coils I8 and
'as a Cz-I-Ca fraction enters through pipe I0 to
46 and depolymerization coils 24 -and 52. Other
suitable equipment and modifications will be obvi
is cracked to a suitably limited degree. The
ous to those skilled in the art.
products leaving vthe, cracking coil are suitably
Although the flow diagrams indicate continu
cooled and then passed intofractionating system 44.0 ous processes, my invention may obviously be
I3 which may consist of one or, preferably, two
applied as abatch process as well. The following
or three fractionating columns. A C4 fraction
examples include two methods of ’practicing my
’ vis removed from fractionating system I3, through
pipe I6 and circulated at high pressure by means
Example 1.-An ethane-propane mixture is
of pump Il through polymerization coil I8 heated 45 cracked at one atmosphere pressure and 1450° F.
by means of furnace I9. The partially polymer
temperature deeply enough to form 5 per cent of
ized product is removed through pipe 20 and
C4 and heavier hydrocarbons. A C4 fraction is
expansion Valve 3I to fractionating system 2| in
separated having `the following composition.
cracking coil II heated by furnace I2 where it
which the normally liquid hydrocarbons contain
ing diolefin dimers are separated' and removed
through line _23 and expansion .valve 32 to a de
so Butßnes‘, . PAT-‘fm
polymerizing coil 24. The normally gaseous hy»- `
’drocarbons’ are withdrawn from fractionating
system 2| through pipe 22 and may be wholly or
in part recycled to_ polymerization coil I8 or they
may be completely discharged. The oily polymer
is depolymerized in coil 24 heated by furnace 25
and _maintained at a suitably low pressure by
Per cent
»Butadiene, FAHR
-rsobucyœna 04H»
Normal butenes, CiHs ____________________ __ 10
fl‘his C4 fractionfis digesteu at 390° F. and 500
poundsv per square _inch gauge pressure long
pump-compressor 25. 'I-‘he products are treated.
enough` to convert 50 per cent of the total into
60 normally liquid hydrocarbons. The latter are
' in the fractionating system 21 consisting of _one
separated by fractional distillation and are then
or more columns. A Ci fraction rich in buta
diene is removed from pipe 29, a fraction com»> » depolymerized bypassing through an empty tube
Drising any lighter products formed by -cracking
at 1 atmosphere pressure and 1022° F. at such a
is discharged through pipe' 23 and a normally
liquid residue is withdrawn through valve 33 and
Dipe 3l and recycled through the depolymeriza
irate that 20 percent per pass is converted into
vgaseous products. The said’gaseous products are
tion coil.
l In Figure 2, is shown a similar apparatus suit
separated and a C4 fraction is cut therefrom
which is found to be concentrated butadiene.
c Liquids boiling at 2o to 450° r'.v are recycled to
able to apply the process of >this invention to the 70 the depolylnerization furnace.
Example 2.-A C4 fraction of the vapors pro->
concentration of butadiene from such products as
vapor phasev cracking gases'. 'I'hese gases enter
duced in a vapor phase oil cracking process are
fractionating system 4I "through pipe 4I. A C4
digestedvat 390° F._ and 500 pounds per square
fraction vis withdrawn through pipe 43 by means
inch gauge pressure suiliciently to convert 15 to
of Pump 45 and passed through polymerizatiçml
20’per‘l cent of the total into normally liquid hy
drocarbons. These polymeric liquid hydrocar
merizationy step to conditions of elevated tempera
bons are separated by fractionation and are then - . ture andv in the’~
presence ofbsuiilcient steam to
passed at atmospheric pressure through a tube
?lled with bauxite at 93011'. at such a rate that
20 per cent per pass is converted into gaseous
products. The said gaseous products are sepa
rated and a C4 fraction rich in butadiene is cut
therefrom while thenormaiiy liquid hydrocar
bons arerecycled to the cracking> furnace.
While the foregoing examples serve to illustrate
two possible adaptations oi' my process they are
not 'to be construed as limitations thereupon.
since many other modincations within the scope
of my invention will be obvioús to those skilled
in the
I claim :>
maintain low partial pressure of the dimer which » .
promote depolymerization ofthe dimer _to the
monomeric diolefin, fracticnating the eilluefnt of
the depolymsrization step to _separate the dioiefin
from the dimer, and recycling the dimer to the'
depolymerization sten»
4. The process for the separation of butadiene
from a mixture of C4 hydrocarbons which' com-`
Prises subjecting the mixturein a polymerization
step to conditions of elevated temperaturewith
in the range of 300° l'. to 900° F. and superat
mospheric pressure, _within fthe range or atmos
pheric pressure' to about 500 pounds per square
l. The process for the separation of a low
boiling open chain' dioleiin from a mixture of
hydrocarbons having vboiling points substantially
the same asV the boiling points of said diolenn
which comprises subjecting the hydrocarbon mix- '
V ture in a polymerization step to conditions of ele
vated temperaturel and superatmospheric pres
sure which promote dimerization of said diol'eiin
to the dimer thereof as the rincipal reaction
occurring, separating the resisting dimer from
the eiliuent of the .polymerization step. and sub
iecting the dimer in a depolyinerization- step to '
conditions of'eievated temperatures and in the
Ípresence of sumcient steam to maintain low par- '
tial pressure of said dimer electing conversion of
said dimer to the monomeric low~boiling open
inch which result in dimerization of butadiene in
the presence of other Ci hydrocarbons to -the
dimer thereof asthe principal reaction occurring.
separating the dimer from the eilluent of the
polymer-nation step. subiectins the dimer, urs de- ‘
polymerization step to conditions of elevated tem
ventures in the range o! 900° l". to 1300° F. and
in the presence of suiiicient steam maintain low
partiall pressure of the dimer which result in de
polyr'nerization of dimer to monomeric butadiene,fractionating the eiiluent of the depolymeris'ation
step in a fractionation step to form a fraction
containing the monomeric butadiene and atrae#
tion containing the dimer eiliuent oi the depoly
merization step. and recycling the dimer from
the fractionation step to the depolymerisation
" .
' chain dioleiin.
5. The process which comprisesrubiecting the
2. The processor claim i in which butadiene
dimer of `butadiene to a temperature within the
lathe low-boiling open chain dioleñn.- ' ~
35 range of about 4900’ Il'. to about 1300“ IIL-in ad
3. The process for the separatign'of a low
mixture with suiiicient steam to maintain the
boiling open chain diole?n from a mixture of hy
partial pressure of said dimer within the range
drocarbons- having boilingpoints within about
of 3 to 100 mm. eifecting depolymerisation of
15° F. of the boiling 'point of the dioiedn which
said dimer- as the principal reaction oi' the proc
comprises polymerizing the diolenn in the pres 40 ess.
ence of said hydrocarbons in a polymerization
8. The process which comprises subjecting the>
step under conditions of elevated temperature
dimer of butadiene to a temperature within the
and superatmospheric' pressure which- promote \
as the principal reaction dimerization of the di
y oleiin to the dimer thereof having a boiling point
appreciably greater than that of the diolefin.
ranae of about 900' l". to about i300’ Ein ad
mixture with suiiicient steam to maintain the par
to 100mm. and in the presence of a magnesium
fractionating the eilluent oi' the. polymerization ‘ oxide depolymerisation catalyst electing depoly- '
step to separate the dimer therefrom.> depoly
merisation of said dimer as the principal reaction .
o( the m
eiiluent of the; polymerization _step in a depoly-`
anoressia. gamma..
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