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Патент USA US2412936

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Dec. 17, 1946.
Filed June 13, 1944
Patented Dec. 17, 1946
. 2,412,936
Harold J. Hepp, Bartlelvllle, 0kla., asslgnor to
Phillips Petroleum Company, a corporation of
Application June 13, 1044, Serial No. 540.010
6 Claims.
(Cl. 260-668)
This invention relates to a process for the pro
dehydrogenation in which the production of cyclo
duction of cyclopentene by catalytic dehydrogena
pentadiene is suppressed. ,
tion of cyclopentane in the presence of hydrogen.
In one of its more speci?c aspects, the invention
Other-objects and advantages of the invention,
some of which are referred to hereinafter, will be
relates to a process in’ which cyclopentane to
obvious to those skilled in the art to which the 1
gether with hydrogen is ‘catalytically dehydro
genated in the vapor phase to produce cyclo
invention pertains.
I have discovered that cyclopentane may be
catalytically dehydrogenated in a single step or
cyclopentene is useful as an intermediate mate- '
stage to produce greatly increased yields of cyclo
rial for the synthesis of a. wide variety of organic 10 pentene when the dehydrogenation is carried ‘out
chemicals, such as cyclopentanol and cyclopente
in the presence of hydrogen. While the hydrogen
none, which are useful as industrial solvents, and
that is added to the cyclopentane that is charged ‘
which may be converted to other valuable com
suppresses somewhat the extent of dehydrogena
' pounds. Cyclopentane, but not cyclopentene, oc
tion of the cyclopentane, the yield of cyclopentene
curs naturally in many petroleum fractions.
15 from the cyclopentane that is dehydrogenated is
vIt has been found that cyclopentene may be
greatly increased. In addition to this favorable
readily dehydrogenated catalytically to cyclo
Such processes are described, for
effect on cyclopentene production, the presence of
. hydrogen greatly reduces the amount of carbo
example, in the following U. S. patents: Grosse,
naceous deposit formed on the catalyst. Loss of
No. 2,157,202; Grosse and Mavity, No. 2,157,203; 20 valuable products is also substantially reduced
and catalyst regeneration is greatly facilitated.
and Morrell, No. 2,157,939. I have found that
cyclopentane may be readily dehydrogenated in
The dehydrogenation process of my invention is ‘
the presence of a, number of dehydrogenation cat
practiced by passing cyclopentane mixed with hy
alysts, such as chromic oxide-alumina and mag
nesia-alumina, to produce cyclopentadiene. How
ever, the unsaturated hydrocarbon product of such
processes generally comprises a mixture of cyclo
pentadiene and cyclopentene in at least a, 1 to 1
ratio. (Cf. Frey, Industrial and Engineering
- drogen, which may be fresh added hydrogen or >
25 recycle hydrogen containing cyclopentadiene, in
vapor phase at a total pressure within the-range
of approximately 1 to approximately 10 atmos
pheres over an active dehydrogenation catalyst at
a dehydrogenation temperature and a suitable
Chemistry, 1934, vol. 26, page 198.) Attempts to 30 space velocity to produce the desired extent of
conduct the dehydrogenation of cyclopentene to
conversion. The conversion should be between
yield cyclopentene without the production of sub-f
approximately 20 and approximately 50 per cent,
stantial amounts of cyclo-pentadiene have hereto
preferably about 30 per cent, per pass. Conver
fore not been successful.
sion temperatures in the dehydrogenation range
of approximately 1000° to approximately 1300° F.,
depending upon the catalyst and the other pre
vailing reaction conditions, are contemplated. In
A catalytic process for the production of cyclo
pentene from cyclopentane by ?rst dehydrogenat
ing cyclopentane to cyclopentadiene, then hydro
genating the cyclopentadiene to cyclopentene, is’
general, the more active the catalyst, the lower
the required conversion temperature. It is desir
C. Ray, Serial No. 493,688, ?led July 6, 1943. This 40 able to employ a highly active dehydrogenation
catalyst in order to avoid cracking and other un
method, while satisfactory in many respects, has
side reactions.
the disadvantage that two separate stages, op
Hydrogen should be added or be present in the
erated under different reaction conditions, are re
cyclopentane charge stock in such quantity that
the feed to‘ the catalyst bed comprises not more
It is an object of the present invention to pro
than approximately 90, and not less than ap
vide a process for the production of cyclopentene
proximately 10 mol per centof cyclopentene, and
' disclosed in the copending application of Gardner
from’cyclopentane by dehydrogenation in which
the yield of cyclopentene is greater than has here
tofore been obtained.
It is a further object of the invention to provide
a one-stage process for the ‘production of cyclo
pentene by the catalytic dehydrogenation of cy
clopentane without the formation of large pro
portions of cyclopentadiene, that is, by catalytic
preferably not more than 80 nor less than 25 mol
per cent, respectively. When such conditions are
maintained, a greatly increased yield of cyclo
pentene is obtained in the dehydrogenation and
the proportion of cyclopentadiene in the result
ing product is substantially lower than that ob
tefined without the presence of hydrogen. The
effect of the hydrogen appears to be more than a
simple mass-action effect of hydrogen in sup
pressing the conversion of cyclopentane to cyclo
pentadiene since greater proportions of cyclo
pentene are produced than can be accounted for
on the basis of the hydrogen that is added. The
hydrogen that is added to the cyclopentane charge
is dehydrogenated. The e?luent mixture is then
‘ cooled to about 200° F. or lower, and passes into
?ash tank 3 under a pressure of about 25 pounds
per square inch or higher. From ?ash tank 3
a portion of the hydrogen is removed from the
system through conduit I, and the remainder of
the hydrogen is recycied through conduit 5 to
in the practice of my invention is preferably that
charge conduit l of the reaction zone 2. The
produced in the dehydrogenation process itself.
amount of hydrogen which is removed is ap
The effluent mixture from the catalyst bed is
that formed in the dehydrogenation
separated by suitable conventional means, as by 10 proximately
reaction or that amount which it is necessary‘
condensation and fractionation, into hydrogen,
to remove from the cycle at this point to main
cyclopentadiene, cyclopentene and cyclopentane
tain the hydrogen content of the charge _to the
catalytic reaction zone constant. The hydrogen
through conduit 4 is preferably passed
and part but not all of the hydrogen, is recycled 15 removed
means, not shown, where any cyclic
with fresh charge to the catalyst.
hydrocarbons containing five carbons in the ring
A very convenient means of facilitating the
are recovered, as by liquid extraction or by other
separation of cyclopentadiene and cyclopentene,
suitable means, and are subsequently returned
the boiling points of which differ by only a few
the process. Dlcyclopentadiene from the
degrees, is first to dimerize the cyclopentadiene to 20. to
process may be employed as a liquid for absorb
dicyclopentadiene, the boiling point of which is
ing such cyclic hydrocarbons, if desired.
much higher than that of any of the other ma
The liquid kettle product from ?ash tank 3,
terials involved‘ in the process. A preferred
comprising principally cyclopentene, cyclopenta
method of operation according to this modi?ca
diene and unconverted cyclopentene, is passed to
tion of the invention comprises ?ashing the hy
fractionator 6 wherein it is separated into a light
drogen from the cooled ei?uent mixture leaving
overhead fraction and a heavier kettle product.
the catalyst in a ?ash tank, then separating the
The kettle product, comprising chie?y unreacted
fractions. The unchanged cyclopentane, along
with part or, preferably, all of the cyclopentadiene
remaining hydrocarbon mixture by fractionation
cyclopentane and some dicyclopentadiene, is re
through conduit 1 to the reaction zone.
prising chie?y cyclopentene and cyclopentadiene 30
into light and heavy fractions, the former com
The overhead product from fractionator 6,
comprising chie?y cyclopentene. and cyclopenta
and the latter comprising chie?y unconverted
cyclopentane. The light fraction is then passed
diene, is conducted through conduit 8 to dimeriz
ing zone 9 in which the cyclopentadiene is poly
to a dimerizing zone wherein the cyclopentadiene
is polymerized to dicyclopentadiene by maintain
ing suitable conditions of temperature, pressure,
merized to dicyclopentadiene. The polymeriza
tion is effected thermally, merely by maintain
and contact time. Suitable temperatures are
within the range of 200° to 350° F. at super
atmospheric pressures and a time of contact with
ing the material at a temperature within the
range of approximately 200° to approximately
in the range of approximately 1/2 to approx‘
mately \15 hours. The mixture is then passed
350° F. at a superatmospheric pressure for a
to a second fractionation means for the separa
through conduit‘ l0 into fractionator II, where
in it is separated into a cyclopentene fraction
period of approximately 1/2 to 15 hours or longer.
From dimerizing zone 9, the- mixture is passed
tion of the cyclopentene from the dicyclopenta
diene. The cyclopentene overhead fraction is
that is discharged through conduit [2 and a di
removed as a product of the process and the
dicyclopentadiene may, together with the uncon
cyclopentadiene fraction, which is the kettle
product. The cyclopentene fraction is removed
as a product of the process. The dicyclopenta
diene fraction is passed through conduit l3 into
verted cyclopentane and part of the hydrogen, be
recycled to the catalyst bed.
In some cases it
may be desircbie to subject the dicyclopentacliene
to heating at a temmrature within the rangecf
approximately 350° to approximately 450° F. and
preferably at atmospheric, subatmospheric or a
low superatmospheric pressure, for a sufficient
period of time to effect depolymerlzaticn, before
recycling it to the catalyst.
In another method of operation, wherein the
depolymerization zone ‘iii. In this zone the di~
cyciemntadiene is thermally depolymerized at a
temperature within the range of approximately
350° to approximately 450° F. and a low pressure,
preferably about atmospheric or subatmospheric.
to cyclopentadiene. The cyclopentadiene is “hen
“recycled from zone id through conduit 15
inlet to reaction zone 2. Alternatively, the o
cyclopentadiene is not recycled to the catalyst
with the unconverted cyclopentene and hydrogen,
a further yield of cyclopentene may be produced
by half-hydrcgenating the cyclopentadiene in ac
cordance with the method disclosed in the co
pending application of Gardner C. Ray referred
to hereinabove
In the accompanying drawing, which is e. di=
agrammatic ?ow sheet of a preferred embodiment
of the process of the invention, fresh cyclopen
tane in the vapor state, together and in admin
may be recycled directly to the dehydrogenation
step through conduits i6 and i5.
Cyclopentane vapor together with added L. ~~
drogen was passed under controlled condi
of pressure, temperature and ?ow rate thr
a bed of 1%; inch pellets of a chromic o
alumina catalyst disposed in a catalyst tube.
65 catalyst tube was a vertically supported, 22-inch
length of quartz tubing having an internal di
ture with vaporized recycle cyclopentene, cyclo
ameter of 17 mm. that was provided with a
pentadiene and hydrogen, preheated to a suit
coaxial internal quartz thermocouple well. The
top'and bottom sections of the tube were packet;
with 0 to 14-mesh quartz chips; the central
section, approximately 3.75 inches in length, was
packed with the chromic oxide-alumina catalyst.
able temperature, is conducted through charge
conduit or line i into reaction zone 2. The mix
ture is contacted in the reaction zone with a
suitable active conventional dehydrogenation
catalyst under such conditions of temperature
The catalyst tube was heated in an 18-inch
electric tube furnace. The cyclopentane vapors
and pressure and period of contact that about
20 to 50 per cent of the cyclopentane entering 75 passed downwardly through the tube.
_ 2,412,936
At the beginning of the run, the catalyst was
heated to the operating temperature in a stream
clopentane to unsaturated cyclic hydrocarbons
containing a ?ve-carbon-atom ring, the major
portion of which-is cyclopentene.
2. A process for the production of cyclopentene
by the catalytic dehydrogenation of cyclopen
tane which comprises‘ passing a mixture of cy
clopentane and hydrogen containing at least
approximately 25 and less than approximately 80
of nitrogen and was then ?ushed with hydrogen.
During the run the total e?luent mixture was
collected for analysis. At the end of the run,
the catalyst was revivi?ed by a stream of air.
The water and carbon dioxide formed were
weighed and were used for computing the amount
of hydrocarbon material deposited on the cat
mol per cent cyclopentane into contact with a
10 chromium oxide dehydrogenation catalyst at a
For comparison, a run was also made under
temperature within the range of approximately
1000” to approximately 1300° F. for a suillcient
contact period to‘v convert at least 20 per cent of
substantially identical conditions in which no
hydrogen was charged with the. cyclopentane va
the cyclopentane to unsaturated cyclic hydrocar
The operating conditions that were maintained
and the results obtained were as follows:
bons containing a ?ve-carbon-atom ring, the '
major portion of which is cyclopentene.
3. A process for the production of cyclopentane
Hydrogen added, gas vol. percent__.._
Average temperature, '’ F ______ __
Cycle length, min ______________ ..
No. of cycles ___________________ __
1, 048
Space velocity (voL/vol. eat./hr.).___
E?luent analysis, percent by weight
0 3
9 '
Cyclopen tane ____ ._
Deposit on catalyst _____________________ _ _
tane which comprises passing a mixture of cy
20 clopentane and hydrogen containing at least ap
Pressure, atmospheres __________ __
l. 4
by the catalytic‘ dehydrogenation of cyclopen
4. 8
8. 3
8. 3
ll. 9
9. l
70. 4
9. 7
7i. 6
2. 8
100. 0
100. 0
cyclopentane conversion, percent ___________ __
29. 6
28. 4
Weight ratio, eyclopentene/cyclopentadiene_._
_ 1.31
From the above results it will be noted that
less material ‘is deposited on the catalyst when
hydrogen is charged with the cyclopentane and
that, although the conversion of cyclopentane is
proximately 25 and less than approximately 80
mol per cent cyclopentane into contact with a
dehydrogenation catalyst at a temperature
within the range of approximately 1000“ to ap
proximately 1300° F. for a sufficient contact pe
_ riod to convert at least 20 per cent of the cyclo
pentane touns'aturated cyclic hydrocarbons con
taining a ?ve-carbon-atom ring comprising cy
clopentene, cyclopentadiene, and dicyclopenta
diene, the major portion of which is cyclopen
tene, removing hydrogen in an amount equiva
lent approximately to that formed in the dehy
drogenation, separating cyclopentane from .the
resulting products, and recycling the unconverti
ed. cyclopentane, cyclopentadiene and any dicy
clopentadiene and the remaining hydrogen to
gether with additional fresh cyclopentane to the
dehydrogenation catalyst. ,
somewhat smaller, the amount of cyclopentene
4. A process as de?ned in claim 3 and flir
formed is greater and the formation of cyclopen 40 ther characterized in that the cyclopentene is
tadiene is suppressed.
separated from the cyclopentadiene in the prod
Although a chromium oxide catalyst is speci»
uct by subjecting the product to thermal treat
fled in the above example, it is to be understood
ment to dimerize the eyclopentadiene contained
that the. invention is not limited thereto. Chro
therein without substantial polymerization of the
mium oxide catalysts in general are preferred
,cyclopentene and thereafter separating the cy
catalysts but other conventional dehydrogena»
clopentene from the dicyclopentadiene by frac- x,
tion catalysts, particularly highly active catalysts,
may be used. Such alternative dehydrogenation
catalysts include bauxite, alumina and other '
metal oxides, alone or supported on catalyst car- .
riers, and with or without promoters. The con
version temperature which it will be desirable to
maintain will be dependent upon the ,nature of
the catalyst but will, in general, be within the
range of approximately NOW’ to approximately .
1300° F.
Inasmuch as the foregoing description‘ com
prises preferred embodiments of the invention it
is to be understood that the invention is not lim
ited thereto and that modifications and varia 60
tions may be made therein without departing
substantially from the invention, the scope of
which is to be limited only by the appended
I claim:
1. A process for the production of cyclopentene
by the catalytic dehydrogenation'of cyclopen
tane which comprises passing a. mixture of cy
clopentane and hydrogen containing at least
approximately 25 and less than approximately 80
mol per cent of cyclopentane into contact with
a dehydrogenation catalyst at a temperature
tional distillation.
5. A process as de?ned in claim 3 and fur
ther characterized in that the cyclopentene is
separated from the cyclopentadiene in the prod
_uct by subjecting the product to thermal treat
ment to dimerize the cyclopentadiene contained
therein without substantial polymerization of the
cyclopentene, thereafter separating cyclopentene
from the dicyclopentadiene by fractional distil
lation, thermally depolymerizing the separated
dicyclopentadiene, and recycling the recovered
cyclopentadiene together-with the recovered un
converted cyclopentane and hydrogen together
with additional fresh cyclopentane to the dehy
drogenation catalyst.
6. A process for the production of cyclopentene
by the catalytic dehydrogenation of cyclopenf
‘tane which comprises passing a. mixture oi.’ cy-'
clopentane and hydrogen containing at least ap
proximately 25 and less than approximately 80
mol per cent cyclopentane into contact with a
dehydrogenation catalyst at conversion condi
tions of temperature and‘ pressure for a sufficient
contact period to convert at least 20 per cent of
the cyclopentane to unsaturated-cyclic hydrocar~
bons containing a ?ve-carbon-atom ring, the.
within the range 01’ approximately 1000° to ap
major portion or which is’cyclopentene.
proximately'1300° F. for a su?icient contact pe;
dad to convert at least 20 per cent or the cy-' 75
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