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Patented Sept. 24, 1946
Carlos L. Gutzel‘t, Terre Haute, Ind., asslgnor to
Shell Development Company, vSan Francisco,
Calii?, a corporation'ol Delaware
No Drawing. Application September is, 1944,
Serial No. 554,124
4 Claims.
(Cl. 252-2304” '
4. n2
This application is a continuation-in-part of
co-pending application, Serial Number 516,971,
?led January 4, 1944.
This invention relates to a new and improved
iron oxide catalysts for dehydrogenation and
more particularly for the production of diole?ns
by the catalytic dehydrogenation of- the corre
sponding mono-ole?ns at high temperatures in
the presence of steam.
Primary objects of the invention are to pro
mixture of isomeric ole?ns. For example, buta
diene may be produced from either butene-l or
butene-2 or a mixture of the two, and isoprene
may be produced from methyl ethyl ethylene,
‘trimethyl ethylene, or isopropyl ethylene, or a
mixture of these ole?ns.
In order to facilitate the recovery of the di
ole?n and unconverted mono-olefin from ‘the
product, and for various other practical reasons,
10 it is usually desirable that the feed consist es
sentially of the desired‘ole?n or ole?ns. This
vide an improved process and improved catalysts
is, however, not essential and in some cases it
for the production of diole?ns, and particularly
may be more advantageousto use ole?n fractions
butadiene, by catalytic dehydrogenation a?ord
comprising appreciable amounts of relatively in
ing excellent conversions per pass and excellent
selectivity (i. e. conversion e?iciency) while al 15 ert diluents. Thus, for example, in the produc
tion of butadiene, a so-called butane-butylene
lowing the dehydrogenation to be effected sub
fraction containing, for instance, 50% butane
stantially continuously and at ‘ordinary or mod
may be used. The para?in hydrocarbons are
erate pressures.
substantially unaffected in the process of the in- v
According to the process of the invention, suit
able mono-ole?ns are converted in good yields 20 vention and may be considered as inert diluents.
In this respect the process of the invention dif
and'more or less selectively to the corresponding
fers fundamentally from most of the known de
diole?ns by catalytic dehydrogenation at tem
hydrogenation processes which are much more
peratures above about 580° C. in the presence of
suited for the dehydrogenation ofparaf?ns than
at least 2 mols of steam per mol of ole?n with
alkalized iron oxide or cobalt oxide catalysts pro 25 for the dehydrogenation of ole?ns and are‘ totally
incapable of selectively dehydrogenating ole?ns
vided with at least 1 mol per cent of chromium
oxide (calculated as CraOa) .
The process of the vinvention is particularly
advantageous for the production of butadiene
in the presence of para?ins.
I 1
The dehydrogenation of ole?ns to the corr -
sponding diole?ns di?ers from most other dehy
processes in requiring a low partial
from butene-l and/or butene-v2. It is, however, 30 drogenation
in the reaction zone. Thus,
also applicable and advantageous for the pro
in all known processes for the production of di
duction of other diole?ns, and particularly con
ole?ns by dehydrogenation, it is necessary either
jugated diole?ns, such as piperylene, isoprene,
to carry out the dehydrogenation under a sub
the various hexadienes, etc. from the correspond
vacuum or to employ large quantities of
ing mono-ole?ns. Thus, the process may gen 35
a diluent. Operation under a vacuum is very
erally be applied for the production of diole?ns
costly. The vuse of inert diluents to decrease the
from the corresponding mono-ole?ns having at
pressure of the reactants usually makes
least four non-quaternary carbon atoms in a
the e?lcient separation and recovery of the diole
straight chain. The process of the invention
involves the treatment of the ole?ns in the va 40 ?n from the product very di?icult and is a serious
disadvantage. Steam is an ideal diluent but, un
por phase at temperatures above about 580° C.
fortunatelyjmany of the most active dehydro
In order to produce the corresponding diole?ns
genation catalysts are not suited for use in the
more or less selectively, the ole?n treated is
presence of steam. Also, most of the known cat
therefore one which may be heated to tempera
tures above about 580° C. without substantial 45 alysts are not sufficiently selective in their ac
tion and, if steam is used as a diluent, they cat
decomposition. Since the tendency for the vari
alyze the oxidation of thepreactants by the steam,
ous ole?ns to undergo thermal cracking increases
with theirmolecular weights, preferred ole?ns
thus giving low yields.
The above-described ole?ns are dehydrogen
4 to about 6 non-quaternary carbon atoms in a 50 ated, according to the process of the invention,
to be treated are the lower ole?ns having from
straight chain. The ole?n to be dehydrogenated
may be a single hydrocarbon or, if desired, a
mixture of ole?ns may be dehydrogenated to
in the presence of a substantial mol excess of
steam with catalysts which are designed to selec
tively dehydrogenate ole?ns in the presence of
steam over long periods of time with relatively
produce a mixture of diole?ns. Also, in some
cases a single diole?n may be produced froma 55 infrequent regeneration without losing activity.
In the process of the invention the use of steam
oxide per se for the described dehydrogenation is
is not merely permissible, it is essential. Thus,
that, although the ultimate life of the catalyst
is suitable, the catalyst declines in activity during
use and must be periodically regenerated. Thus,
in the present process the ole?n to be dehydro
genated is contacted with the catalyst in the
presence of at least two and preferably at least
seven mol proportions of steam. In, the de
hydrogenation of butylene to butadiene, for ex
ample, the best results have been obtained when
the maximum process period is in the order of
50 to» 80 hours. It has been found, however, that
if the iron oxide is combined with chromium
‘oxide these disadvantages are avoided, and high
using between about '7 and 30 mols of steam per
ly active and selective catalysts result. Thus,
mol of butylene. The use of such amounts of 10 by providing the alkalized iron oxide catalyst
steam allows the process to be carried out at at
with a suitable amount of chromium oxide the
mospheric pressure or, if desired, even at moder
dehydrogenation may be carried out under con
ately superatmospheric pressures.
ditions chosen to produce maximum conversions
The catalysts used in the process of the inven
and yields of diolefins and the process may be
tion are special iron oxide or cobalt oxide cata
carried out in an essentially continuous opera
lysts which are highly active and retain their
tion. Chromium oxide (CrzOz) per so, when used
activity with little or no regeneration over long
under the described conditions. is somewhat less
periods of use in the presence of steam. Under
.e?ective than iron oxide AFezOs) per se. When
the described conditions they dehydrogenate ole
iron oxide is provided with suitable amounts of
?ns selectively in the presence of para?ins and 20 chromium oxide, however, the selective dehydro
catalyze .to a minimum extent the oxidation of
genatin'g activity under the described conditions
the reactants by the steam. Cobalt oxide is
is greater than that of either constituent alone.
somewhat more active than iron oxide and may be
The more important advantage of the present
substituted for part or all of the iron oxide. How
catalysts is, however, that whereas both iron oxide _
ever, in view of the relatively high cost of cobalt 25 per se and chromium oxide per se require fre
oxide, its practical application is probably limited
to use in minor concentrations. In the following
description the catalysts are referred to as iron
oxide catalysts with the understanding that the
iron om'de may be substituted in part by its equiv
alent, cobalt oxide.
Iron oxide has long been recognized to possess
quent periodic regeneration, the present iron oxide
catalysts provided with chromium oxide can be
used essentially continuously, i. e. regeneration,
if it is necessary at all. is required only after long
30 periods of operation.
For the purposes of the present speci?cation
an operation in which the conversion and con
" version e?iciency remain with no appreciable drop
taining iron oxide have been developed for special . for a, period of continuous operation of at least
purposes and some of them are used commercially. 35
10 hours under a ?xed set ofconditions is con
certain catalytic properties. Many catalysts con;
As will be apparent from the comprehensive and
detailed compilation of the catalysts mentioned
sidered to be an essentially oontinous operation.
hydrogenation are, ?rstly, their pronounced tend- -
and ?ve mol per cent of chromium oxide (CrzOa)
Iron oxide (FezOa) and chromium oxide (Cr203)
in the literature and patents relating to dehy
constitute a unique combination since these two
drogenation in Berkman, Morrell and Eglo?,
“Catalysis,” pages 888-906, (1940), iron oidde is 40 oxides form solid solutions in all proportions.
Also, as pointed out above, chromium oxide itself
recommended for use in dehydrogenation cata
exerts a; catalytic action which is comparable to
lysts only in a very'few special cases. This is
that of iron oxide per se. Probably because of
due, firstly, to certain undesirable properties of
these facts, the concentration of chromium oxide
iron oxide catalysts for most dehydrogenations
is not extremely critical. Even small amounts of
and, secondly, due to the availability of other more
chromium oxide are quite e?ective. Thus, for
desirable catalysts for the usual dehydrogenation
example, catalysts consisting essentially of alka
processes. The more objectionable properties of
lized iron oxide and containing only one, three
the hitherto-known iron oxide catalysts in de
ency to produce large amounts of carbon and, 50 have been prepared and have given excellent con
versions of butylenes to butadiene over periods
secondly, their relatively short life. The first of
of over 100 hours of continuous operation without
these objectionable properties is partly due to
any noticeable decline in activity or selectivity.
the fact that under the reducing conditions usual
However, very satisfactory catalysts have also
ly prevailing in dehydrogenation the iron oxide
tends to be converted at least in part to a lower 55 been prepared containing 30 mol %, 50 mol % and
70 mol % of chromium oxide (the remainder be
oxide or metallic iron which catalyzes decompo
ing the alkalized iron oxide, calculated as F8203).
sition to carbon. The second of these objection
The iron oxide (F6203) and chromium oxide
able properties, it is found, is due in pant to the
(CrzOz) may form a solid solution; however, they
tendency of the iron oxide to react or combine
with the carrier or support material used to pro 60 cannot react under oxidizing conditions to form
vide a large catalyst surface.
It has now been
the chromite. Since the process of the invention
is carried out in the presence of a large excess
found that certain dehydrogenation reactions
of steam, reaction to form the chromite is largely
such, in particular, as the dehydrogenation of
prevented. During long periods of use under se
ole?ns to the corresponding diole?ns may be much
more effectively and economically accomplished 65 vere conditions, and particularly if the catalyst is
accidentally subjected to strongly reducing con
using iron oxide catalysts provided that the iron
oxide is promoted with an alkali and is used in
the absence of substantial amounts of carriers or
other materials which tend to react therewith, and
ditions (as by failure of the steam ?ow), some
reaction to form the chromite may, however, take
place. This is undesirable since tests have indi
provided that the dehydrogenation is carried out 70 cated the chromite to be much less e?icient than
the mixed oxides (or solid solution) and since re
action to form the chromite reduces the concen
tration of free iron oxide. Danger of loss of
Alkalized iron oxide per se is a fairly active
activity due to this cause is largely avoided by
catalyst but is very sensitive to the reaction con
ditions. Another disadvantage of alkalized iron 75 using a molecular excess of iron oxide (calcu
in the presence of a large excess of steam at tem
peratures above about 580° C.
- 5
lated as FezOa) with respect to the chromium
oxide (calculated as CraOa) .
The best experimental evidence indicates that
te of oxidation of ‘the iron oxide during
the‘ action and perhaps also ‘the state of hydra-.
. tion are extremely critical;
The exact states of
oxidation and hydration. are dimcultwto'deter
mine and are not known. It is- known, however,
that whatever these states may be they are es
tablished and maintained by the described reac
rtjon conditions. Since the state of the iron oxide
Y The catalyst may be prepared by a variety of
methods. The iron oxide and chromium oxide
. can be combined, for example, by mixing or oo
grinding the powders, by thermally decomposing
a mixture of the nitrates, by co-precipitatins the
hydrous oxides, by mixing the hydrous gels or
sols, by calcination of a mixture‘of iron oxide
powder and a decomposable chromium compound,
or in general by any method providing an inti
contact between the components and pref
10 mate
erably a?ordlng an essentially homogeneous
mass. One particularly suitable method, for
is established by the reaction conditions and since
example, is to thoroughly mix as by .co-grinding
furthermore the crystal types of the iron oxides
or ball milling a mixture of powdered iron oxide
can quickly comejtos equilibrium through the
powdered chromium-oxide, form a paste of
medium of solid solutions, suitable catalysts may
the mixture with a solution containing the de
be prepared starting with various iron oxides
sired amount. of potassium salt, extrude or-pellet
from various sources. Various commercial iron
and dry. In most cases and, in particular when
oxides such as the iron oxide pigments, the iron
oxide produced as a by-product in the produc
the iron oxide and chromium oxide are combined
tion of alumina (Luxmass) may beuaused. Suit 20 by co-precipitation and similar methods, the cat
alysts have. a fairly large available surface, for
ableiron oxides may be also prepared, for in
instance above about 30 square meters per gram.
stance, by the thermal decomposition of iron com
In most dehydrogenation catalysts this is desir
pounds such as ferric nitrate, ferric oxalate, ferric
able. In the present catalysts, however, a large ‘
ammonium oxalate, etc., by precipitation from so
lutions of iron salts such as ferric nitrate, ferric 25 available surface is undesirable since catalysts
having a large available surface are insufficiently
sulfate, etc. followed by dehydration.
selective in their action in catalytic dehydro
'It is essential that theiron oxide be alkalized‘
genation at elevated temperatures in the presence
by the incorporation of a suitable alkali. All of
of steam. In such cases, therefore, where the
any of the oxides,v hydroxides and salts of the 30 catalysts produced, for example, by co-precipi
tation show relatively poor activity-or selectivity
alkali or alkaline earth metals may be used. The
the common alkalis appear to be suitable.
halides may be used but are less preferred. Par
ticularly suitable alkalis are the compounds, for
example, the hydroxide,.nitrate, sulfate and car
- they may be materially improved by subjecting
them to a fairly drastic calcination in air for av
time to decrease their available surface to below
bonate of potassium. These various materials 35 about 30 square meters per gram. The calcina
tion may be effected at temperatures between
are probably converted at least in part into the
about ‘700° C. and 1000° C. and-preferably be
corresponding ‘oxides or hydroxides during the
preparation and/or use of the catalyst.
The concentration of alkali, calculated as the
tween about 800" C. and 950° C. A suitable treat
ment, for example, may be a calcination at a
oxide, shouldbe at least 0.2% by weight of the 40 temperature of about 900° C. for about 5 to 10
catalyst and is preferably somewhat higher, for
The catalysts may be in any of the conven
instance between about 0.5% and 5%. During
tional forms such as powder, pills, spheres, sad
extended use of the catalyst the alkali used, par
dles, extrudates, or irregular fragments of a shape
ticularly if it is potassium, may be partly lost from
the catalyst by volatilization and this may cause 45 and size adapted for the reaction system to be
used. These catalysts, it is found, are unusually.
a decline in the activity of the catalyst. If this
‘sensitive to changes in the particle size., Thus,
happens the activity of the catalyst may be re
their e?ectiveness increases markedly with de
stored by simply adding additional alkali, for in
crease in the size of the catalyst particles. For
stance by impregnation or by adding a small
amount of potassium carbonate with the steam. 50 this reason, }it is desirable touse the catalysts
in the smallest size consistent with an allowable
The inclusion of additional agents in the cata
pressure drop through the converter. For exam
lysts is not precluded;- however, the major active
ple, in the production of butadiene from butylene
constituent should be the described alkalized iron
markedly improved results are obtained merely
oxide-chromium oxide and any other components
which tend to react with the iron oxide under 55 by decreasing the particle size of the catalyst par
ticles from lag-inch pellets (average volume of
the process conditions, for instance to formv 9.
about 0.113 cc.) to %-inch pellets (average vol
spinel, if present at all are present in minor mol
ume of about 0.038 cc.).
amounts with respect to the iron oxide. For this
The above-described catalysts are exception
reason such materials as alumina, magnesia and
the like, if present at all, are present in minor 60 ally rugged and may be heated to temperatures
up to about 900° C. to 1000" C. in the presence
concentrations and these and similar materials
of steam without loss of ef?ciency. They are
cannot be used as supports or carriers. Totally
adapted for use at high tempera
inert materials (with respect to the iron oxide),
tures in the presence of steam, and as pointed
may, if desired, be used as supports, carriers,
diluents or strengthening agents and may be pres 65 out above, steam isessential for their use. If
during use they become relatively ine?icient due
ent in any concentration. Since, however, the
to lack of su?icient steam, they may be restored
activity of the catalyst is proportional to the con
to essentially their original activity by simply
centration of the major active agent, i. e. the
steaming them for a few hours, preferably at a
alkalized iron oxide-chromium oxide, such dil
temperature between about 600° C. and 800° C.
uents or extenders, if used at all, are preferably
rllhe described catalysts are not only exceptionally
used in theirminimum effective concentrations.
suited for the selective dehydrogenation of ole
In the present description and ‘in the claims the
fins to diole?ns under the described conditions
expression “consisting essentially of” is not meant
but can be used for a few other reactions for
to exclude such totally inert materials which do
not affect the catalytic properties of the catalyst. 75 which these conditions are favorable. Thus, for
example, the catalysts are also particularly suit
able ‘for the dehydrogenation of. alkyl aromatics,
for instance, the dehydrogenation oi’ ethyl ben
The hydrous oxides of iron and chromium were
coprecipitated from mixed solutions of iron sul
fate and chromium nitrate with ammonium hy
z'ene to styrene.
droxide. The coprecipitated hydrous oxide mix
In the production of diole?ns, according to the 5 ture was washed, then mixed with the required
processiof the invention, the contact time of the
amounts of copper sulfate and potassium nitrate,
and ?nally dried at 100° C.-120° C. The resulting
ole?n with the catalyst affording the optimum
results depends upon the particular ole?n or mix
mass was broken up and screened to 6-14 mesh.
ture of ole?ns being dehydrogenated, and the
Prior to use the catalyst was heated at ‘750° C. for
particular conditions chosen and may best be 10 6 hours and then ?nally pretreated for one hour
determined for any given case by starting with
at about 600° C. with steam and hydrogen. This
a very short contact time and then gradually
pretreatment is not essential but shortens the
increasing the contact time until the desired con
period during which the catalyst comes to equi
version and conversion e?iciency are obtained.
librium during use.
Conversion is herein de?ned as the per cent of 15
This catalyst was used for the production of
the reactant applied which undergoes reaction
butadiene from a typical normal butylene frac
and is converted into a different product. Yield
tion consisting essentially of butene-l and bu
is de?ned as the per cent of the reactant applied
tene-2. The butylene was vaporized and pre
which is converted to the desired product. Con
heated, and passed in admixture with steam
version e?lciency is de?ned as the per cent of 20 through a stationary bed of the catalyst. The
the material converted or reacted which is con
dehydrogenation conditions were as follows:
verted to the desired product; ‘in this case, diole
Temperature ____ _. About 610“ C.
?ns having the same number of carbon atoms as
Butylene,G.H.S.V_ About 500 _
the parent material. In general, the conversion
and conversion e?iciency are interdependent, the 25 Steam, G.H.S.V___. About 7000
Pressure (at exit)- About 1 atmosphere absolute
conversion efficiency becoming lower as the con
version is increased. The optimum conversion
The operation was carried out continuously.
and conversion e?lciency for any given operation,
The conversion of butylene to butadiene increased
therefore, depend upon the particular economic
during the ?rst eight hours to about 25%-26%
factors. In the production of butadiene by the 30 and then remained substantially constant. The
present process, by way of example, conversions
conversion e?iciency increased during the ?rst
of about 30% are considered at present to be quite
eight hours to about 72%-74% and then re
mained substantially constant.
Example II
' suitable. Suitable contact times for the dehydro
genation of butylenes to butadiene, by way of
example, are of the order of 0.02 to 0.5 seconds.
The process of the invention allows excellent
conversions to diole?ns to be obtained quite selec
A quantity of powdered iron oxide (pigment
grade) was mixed with 5% by weight of techni
cal powdered chromium oxide for 10 minutes in
tively over a considerable range of suitable space
velocities. Suitable space velocities are, for ex
a Clear?eld mixer. A solution of potassium car
ample, between about 300 and 3000 volumes of 40 bonate and tannic acid equivalent to 4% by
gaseous reactant (N. T. P.) per volume of catalyst
weight potassium and 0.3% by weight of tannic
per hour. This is referred to as gaseous hourly
acid was added to form a paste containing about
space velocity (G. H. S. V.) .
27% to 35% water. The paste was mixed for an,
As pointed out above, the process of the inven
additional 20 minutes and then extruded and cut
tion is carried out at temperatures above about
into approximately {5-inch pellets. The pellets
. 580° C. at any desired pressure. In general, tem
were placed in metal trays to a depth of about 2
peratures between about 580° C. and 750° C. are
inches and dried for 8 hours at about 150°’ C.
suitable. In the production of butadiene, for
175°~C. The pellets were then calcined at 900° C
for 12 hours.
example, the best results have been obtained at
temperatures between about 590° C. and 690° C. 50 ’ This catalyst was used for the continuous de
Although either subatmospheric pressure or su
hydrogenation of butylene to butadiene under
the following conditions:
peratmospheric pressure can be used, it is most
advantageous for various practical reasons to
operate the process at substantially atmospheric
pressure, for instance, the slight pressure neces
sary to ?ow the reactant vapors and steam
Temperature __________________ __ About 620° C.
Butylene, G. H. S. V___' __________ __ About 300
55 Steam, G. H. S. V ________________ __ About 3600
Pressure (at exit) .. About 1 atmosphere absolute
through the catalyst zone under the prescribed
After .an initial induction period the conversion
and conversion e?lciency remained substantially
If desired, the process may be carried out in a
so-called dust catalyst, ?uidized catalyst, or mov 60 constant. After 415 hours of continuous opera
tion the conversion of butylene to butadiene was
ing bed system. Excellent results may, however,
be obtained by simply passing the preheated re
actant vapors and preheated steam through a
reaction chamber ?lled with the catalyst and
maintained at the desired temperature and pres
The steam in the product may be con
about 22.4% and the conversion e?lciency was
about '7'7.2%~ with no indication of catalyst ex
I claim as my invention?
1. A catalyst particularly adapted for e?ecting
densed and separated from the converted and
dehydrogenation at temperatures above about
unconverted material. The unconverted mate
580° C. in the presence of steam consisting essen
rial may be separated from the product in con
tially of a major mol amount of iron oxide, a
ventional manners and recycled.
70 minor mol amount of an alkaline compound of
potassium and a minor mol amount; of at least
Example I
one mol per cent of chromium oxide, the mixture
A catalyst designated 1322~C92, having the
having been calcined at a temperature between
composition 70 mols F6203, 30 mols CrzOs, 1 mol
about 800° C. and about 950° C. in an atmosphere
011804, 0.5 mol KNOB, was prepared as follows: 75 under which no appreciable formation of iron
chromite takes place and for a su?lcient length
of time to decrease the available surface of the
catalyst to below 30 square meters per gram.
2. A method for the production of a dehy
drogenation catalyst which comprises intimately
' mixing powdered iron oxide with a minor mol
amount of powdered chromium oxide (CI‘zOa),
forming the mixture into an extrudable paste
with an aqueous solution of a potassium salt,
in the presence of steam consisting essentially
of a major mol amount of iron oxide, a' minor
mol amount of an alkaline compound of potas
sium and a minor mol amount of at least one
mol per cent of chromium oxide, the mixture
having been calcined prior to use at a tempera
ture of about 900° C. in an atmosphere under
which no appreciable formation of iron‘ chromite
takes place and for a time between about 5 and
about 10 hours suf?cient to decrease the available
surface of the catalyst to below 30 square meters
and calcining them at a temperature between
per gram.
about 800° C. and about 950° C. in an atmosphere
4. A catalyst as de?ned in claim 1 in which
under which no appreciable formation of iron
chromium oxide (CrzOa) is about 5 mol per cent
chromite takes place and for a time su?icient to
decrease the available surface of the catalyst to 15 with respect to the iron oxide and the potassium,
calculated as K20, is in mol excess with respect
below 30 square meters per gram.
extruding the paste, drying the extruded pellets
3. A catalyst particularly adapted for effecting
dehydrogenation at temperatures above ‘580° C. >
to the chromium oxide.
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