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2,403,671
Patented July 9, 1946
. UNITED STATES PAT EN TjoFFlcE. 1
‘
r 2,403,671
ISOMERIZATION OF OLEFINIC
HYDROCARBONS,
‘
Maryan P. Matusizak, Bartlesville, Okla., assignor
to Phillips Petroleum'Company, a corporation
of Delaware
,7 No Drawing}; Application May 4, 1942,‘
‘
SeriaiNo. 441,705
9 Claims.
(Cl. 260,—683.2)
eryfis the discoverythat with this‘use ‘oia'rela
This invention relates tothe i'somerization of
organic compounds, more'particularly to isomerii
zation by catalytic shifting of at least one double
bond or ole?nic linkage in an aliphatic radical
tively, low isomerization temperature, the isomeri
zation occurs'without signi?cant change 'in‘the
carbon skeleton of the organic compQu'nd. .Isom‘—
erization of unsaturatedorganic ‘compounds’ in
accordance with the present inventiomis accom
having a chain of at least three carbon atoms,‘ and
more particularly to the isomerization' of vunsatu
rated hydrocarbons having one or more‘ shiftable
double,
bonds.
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p
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a
_
plished by catalysts comprising f‘black” chromium
oxide. The blackchromium oxide appears black
’
Although isomerization of unsaturated/organic
to the eye when viewed en masse orin ‘the’ term of
compounds by shifting of the} double bond can 10 granules. When ?nely divided, as in the form. of '
be obtained to some extent by known means, such
means generally either have given yields farfrom
the equilibrium values or have caused lac-com
panying changes'more drastic than a ‘simple shift
ing of the double bond.‘ For'example, a'number
of catalysts have been proposed for promoting the
isomerization of the normal butenes to isobuty
'
a line powder,_it may appearblack to dark green,
the green being much darker than ,the. bright
green that is characteristic of chromic oxide,for
chromiumcs'es‘quioxide. This black chromium 0X:
lene, whereby the ,four ’ carbon straight-chain
ide appears to vary somewhat in composition, but
appearsjto. approach or average the ‘composition
of 0102, so that some justi?cation may be said to
existv for calling it chromium dioxide" This cataé
structure of the normal butenes is destroyed.’ At
lytic'material should be distinguished from catar
times, such drastic changes in carbon-skeletal 20 lysts containing no, black chromium oxide, or
structure are undesired, as whenit is desired for ,
example to convert one of the normal‘butenes to
another normal butene. Similarly,‘ although non
catalytic isomerization of the normal butenes
without conversion to isobutylene is known, it
seems to start at such a hightemperature, be
tween 600 and 650° 0., that it isaccompan'iediby
extensive decomposition to lower-boiling products
(Hurd and Goldsby,‘J. Am. Chem. Soc,, 56,‘ 1,813
(1934)).
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chromium dioxide, and comprising, green or true
chromic oxide, Ci‘zOs. Catalysts comprising black
chromium oxide in accordance’ with the, present
invention possess the ability to. shift the’double
bond in a temperature rangeinwhich the rate
of isomerization is fast enough to, be‘ practical
without producing carbon-skeletal changes, "de
hydrogenation, decomposition, or polymerization,
and, therefore, they have an advantageous select
30 tivity for isomerization by simple shifting of the
It is an object of this invention to effect isome
erization of an unsaturated organic compound
double bond.
without change in the carbon skeleton thereof. ’
perature below the temperature range in which
the catalyst produces extensive dehydrogenation
Another object of this invention is to provide
e?'ective catalysts for such iso'merization.
_
Another object of this invention is to isomerize
an unsaturated hydrocarbon having atilea'st one
double bond and having at least four carbon
atoms linked together in a chain, by a simple shift
of the double bond.
,
A speci?c object of the invention is to convert
butene-l into butene-Z,
.
Another speci?c object is to convert butene-.-2
into
butene-l.
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I
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Another specific object is to convert noncon
jugated diole?ns into the'corresponding conju
gated dioleiins.
.
\_
_~
_
"
. The isomerization is best conducted atatem
of_ para?ins such as isobutaneor normal butane.
This dehydrogenation temperature range is
usually above about 400° 0., whichfmay be taken
as the approximate upper limit- of ;the tempera,
ture range for the visomerizationof role?nsvthe
40 most stable of the unsaturated organic’ com
.pounds which may be isomerized by means of the
present invention. In this connection, it may be
mentioned that the temperature range, for the
catalytic dehydrogenation of ole?ns to the co-r
4-5 responding diole?ns generally» is about 100°‘ C.
above .the temperature range for the dehydro
genation of the corresponding para?ins to a the
ole?ns; so that, in so far as any particular ole?n
is concerned, the temperaturerange for its isom
50 erization in accordance with this invention ‘is gen
and/or the appended claims.
'
erally separated from the temperature range for
The present invention is partly based ‘upon my
its dehydrogenation by about 100° C. Because of
discovery that certain hereinafter-described cat
Other objects and advantages of the invention '
will be apparent'from the following description
alysts'suitable for the dehydrogenation of hydro
this fact, complications from dehydrogenation of
the ole?n to be isomerized are substantially
carbons, as of paraf?ns to ole?ns, or o’f'ole?n's to
diole'?ns, or the like, possess the ability to isom 55 avoided. On occasion, a slight amount of inciden
erize ole?ns, diole?ns, and} other unsaturated or
ganic compounds by simple shifting of double
bonds at temperatures below the temperature
tal dehydrogenation may be tolerable, andqthe
temperature then permissibly may be so chosen,
if desired, as to be in the temperature interval be
tween the usual isomerization range and the usual
said dehydrogenation. ‘Linked with this discov- _ 60 dehydrogenation range. Generally, . however,
ranges in which these catalysts are used to effect
2,403,671
3
4
.
temperatures above about 450° C. should be avoid
ed, as the optimum isomerization, temperature is
as ammonia, without disruption of the original
positions comprising black chromium oxide, the
in the catalyst-a nonvolatile alkalizing compound,
as by treating the dried catalytic granules with
crystals. They may or may not comprise cata
lytically inferior or inert carriers or supports.
usually at least 100° C. below this value.
Usually a granular form of catalyst, such as 4
The lower limit of the temperature range for
isomerization depends upon the particular com UK to 40 mesh, is preferred, especially for vapor
phase isomerization. Usually also, a neutral or
position of the catalyst, and upon the organic
slightly alkaline composition is to be preferred to
compound being isomerized. For especially ac
an acidic composition, as traces of acids appear to
tive catalyst compositions and for relatively easily
promote carbon-skeletal changes. For this rea
isomerized compounds, it may be as low as room
temperature. However, for most catalyst com 10 son, it is sometimes advantageous to incorporate
lower temperature limit for isomerization is
usually about 100° C. The optimum temperature
a dilute solution, of a strength usually below about
5 per cent by weight, of‘an alkali-metal or alka
is usually in the range of about 150 to 350° C., but
in particular instances it may be somewhat above 15 line-earth hydroxide, carbonate, or other salt,
preferably of a volatile acid or of a metallate
or below this range. The exact optimum tem
forming acid such as aluminic, boric, chromic,
perature range for isomerization of any particu
molybdic, tungstic, or the like. However, overal
lar organic compound with the catalysts of this
kalizing should be avoided, as it decreases the
invention may be readily found by trial.
catalytic activity.
'
So faras is known at present, all catalysts com
Black chromium oxide in anyproportions acts
prising black chromium oxide that are useful in
the art of catalytic dehydrogenation of hydrocar
as an effective isomerization catalysts in accord
bons are suitable for use in the present isomeriza
tion process. Many modes of preparation of such
ance with this invention. However, it is generally
preferred that the catalyst composition contain
25 at least about 5 weight per cent, and it may con
tain on up to 100 per cent, of black chromium
tions, as for example in U. S. Patents 1,905,383,
catalysts .have been shown in different publica
oxide.
2,098,959, 2,270,887, 2,274,988, and many others,
Many modes of contacting the organic com
and for the sake of simplicity need not be re
pound to be isomerized with the catalyst may be
peated herein in detail, For the same reason,
many improved modes of catalyst preparation 30 practiced within the scope of this invention, in
cluding those in which the contact material is
that have been described need not be repeated
here, especially since the present invention does
?xed in position, which is usually preferable be
not depend upon any particular method of prepa
cause of its simplicity, and those in which it is
moved With or against the liquid and/or vapor.
ration. In general, however, the preparation of
such catalysts involves the nonspontaneous ther 35 The contacting may be batchwise, but in com
mercial practice it is preferably continuous.
mal decomposition of one or more chromium com
Liquid-phase isomerization is frequently advan
pounds, such as: chromic salts, preferably of
tageous, providing not, only excellent contacting
monobasic acids, hydrous chromium oxides
of the reactant with the catalyst but also aiding
and/or hydroxides, and various chromates or
in maintenance of catalytic activity by washing
polychromates of volatile nitrogen bases, prefer
away incidental traces of high-boiling materials
ably ammonia; also double or mixed chromates
such as may be represented by the general formula
that otherwise might occlude catalytic spots. Ob
viously, the properties of the organic compound
(NHQ 2M(CI‘O4)2, in which M is a divalent metal,
particularly such as cadmium, chromium, or cop
per.
must be considered, at least to some extent, for
11.5 it is impossible to have liquid-phase contacting
Many nonchromium compounds may also be
present in these catalysts, to impart to the cat
alysts desirable properties or characteristics.
Among such are the di?icultly reducible metal
oxides such as for example, alumina, thoria, urania,
magnesia, zirconia, silica, beryllia, vanadia, ti
tania, zinc oxide, and others. Of these oxides,
at temperatures above the critical temperature of
the compound. Similarly, the properties of the
catalyst, such as its particle size and its catalytic
activity, have some in?uence upon the choice of
operating conditions. The pressure in liquid
phase contacting must be suf?cient to maintain
the liquid phase. In vapor-phase contacting, the
those of the tetravalent metals that can exist as
pressure may vary widely, within vapor-pressure
gels, such as those of uranium, vanadium, and
limitations, from highly superatmospheric pres
‘sures to highly subatmospheric pressures, though
the metals of the left-hand column of group IV, :1
especially thorium, titanium, and zirconium, are
usually a pressure between about 1 and 5 atmos
exceptionally advantageous. One or more of
these oxides may be incorporated in the catalyst
pheres is preferred as being most easily obtain
able.
Suitable times of contact of the isomerization
mixture with the catalyst depend upon the par
in any desired proportions. Usually equimolecu
lar proportions are fully satisfactory. A preferred
manner of incorporation is by coprecipitation of
mixed gels containing chromium oxide and the
other metal oxide, especially with ammonium hy
droxide as the precipitating agent. An alterna
tive manner is intimate mixing of the highly hy
drous oxides, preferably soon after ‘formation by
precipitation, as from dilute aqueous solution, for
example in the manner described in U. S. Patent
2,098,959.
'
The catalysts may be in any form desired, such
as powder, pellets, 0r granules. Especially suit
able are gel-type granules, and crystallomorphous
granules such as those obtained by nonspontane
ous thermal decomposition of a crystalline salt of
chromic acid and a volatile nitrogen base ‘Such
ticular catalyst composition, the temperature,
and the particular compound or compounds in
volved. In vapor-phase isomerization, the time
of contact may vary also with the pressure. It
LA may vary from a fraction of a second in some
instances to many minutes or even an hour or more
in others. These interrelationships of catalyst,
temperature, compound, and contact time, will
be well understood by those skilled in the art.
The organic compound to be isomerized may be
treated undiluted, but dilution is sometimes ad
vantageous, especially for isomerization of high.
boiling compounds in the vapor phase. Dilution
may be effected if desired with an inert or carrier
" gas, such as nitrogen, methane, or the like. Usu
‘2,403,671
6
isomers by suitable means such as in a fractional
faliyialittle free molecular hydrogen admixed with
‘the compound being isomerized is advantageous,
though preferably it should not exceed about 1 or
‘distillation column that is not packed with the
isomerization catalyst, and the lower-boiling iso
2 mol per cent in order to avoid undesired exten
mer may be returned to the feed stream to the
catalyst-packed column. Instead of being so
separated'in another column, the mixture may
sive hydrogenation. 7. Such added gases may be
Tsubsequently removed from the product by known .
be advantageously separated in an auxiliary lower
-means,'as by condensation of the product and
'sectionzof the isomerizing column that is packed
with nonisomerizing packing’ or that has other
fractionating devices performing the function of
"separation of the gas. Pretreatment vof the cata
lyst with hydrogen at an elevated temperature,
. such as a temperature-of about 250° C. ‘or higher,
'or even within the dehydrogenation range, is also
fractionating plates, whereby the higher-boiling
isomer works its way downward'and is eventually
j/beneflcial. ' The mechanism producing the bene
‘withdrawn in substantially pure 'form from the
?cial effect of hydrogen is not completely under¢
‘stood, but it probably involves conditioning of
bottom of the column, whereas the lower-boiling
V the catalyst by adsorption of the hyrogen. 'It 15 isomer passes upwardly to the catalyst-packed
wilI-be understood that the present process is notv ' section of the column. In this way, for example,
l-ole?ns, such as butene-l, pentene-l, hexene-l,
,alprocess for hydrogenation of unsaturated com;
and the like, may be isomerized substantially
pQundsJarid that, if desired, hydrogen may be
'om-itted, especially when the catalyst has been" ‘quantitatively to the corresponding 2>-olelins.
‘pretreated with this/gas immediately before being 20 As is well known, the number of possible iso
‘used for the isomerization.
‘
mers of. an organic compound increases with in
j
A mode of contacting that is advantageous in
crease‘in the number of carbon atoms it contains.
“conducting many isomerizations of the type to
>_Hence isomerization of some compounds in‘ac
cordance with‘ this invention maybe used, with
"which this invention is applicable comprises the- 7
“use of a fractional-distillation column in which‘ 25 'the aid of certain modi?cations,‘ to produce iso
mers of boiling points intermediate those of vthe
the column packing comprises an isomerization
lowest-boiling isomer and the highest-boiling iso
catalyst. In one manner of operating, the
mer.' Thus, in the "isomerization of compounds
'higheréboiling isomer is passed as a liquid to the
of a su?icient number of'carbon atoms per mole
‘kettle’ or to a point in the lower section of the‘
column. This liquid is heated and vaporized, and 30. cule to permit the existence of ‘more than two
isomers, as for example in the case of the normal
‘the vapor becomes isomerized, in its upward pas
' or unbranch'ed hexenes, part or all‘of the isomer
sage through the catalytic packing, to the lower
ization mixture at one or more points along the
boiling isomer. Thus the packing simultaneously
isomerizing column may be withdrawn and sepa
"acts to e?ect isomerization of liquids and va
pors contacting it, and ‘promotes recti?cation in 35 rated, as by fractional distillation, to yield the in
termediate-boiling isomer, such as hexene-S, as a
the known manner of column packings by offer
product of the process. Any of the other iso
'ing effective surface for liquid-vapor contact.
mers may then be returned to the isomerizing col
>The resulting isomerized material is generally .a
umn for conversion into whichever isomer or iso
-mixture of both isomers approaching closely in
: composition the equilibrium mixture at the tem-_ 40 ‘mers are desired. Suitable [modi?cations of this
character are believed to be within the ability
perature in the upper part of the catalytic packj.
‘of. those ‘skilled in the art, in the light of 'the
"ing. This 'mixture may be withdrawn .as such,
and may be separated into the two isomers in any“ ' teachings of the presentfdisclosure.
desired‘ manner, as in a fractional-distillation
- column that is'not packed with the isomerization "
catalyst, andthe higher-‘boiling isomer may be re-.
turned to the feed stream to the catalyst-packed
<co1umn.‘ Instead of being so separated in an
:other column, the mixture may be advan
tageously separated in an auxiliary upper'sectio‘n
-
In thesevarious ways of contacting in catalyst~
vpacked columns, a temperature gradient exists
along the column, the bottom being at a higher
temperature than the top. This ‘gradient is es
tablished as in conventional fractional distilla
tion, as by in?ux or application of heat at the
bottom of the column and/or by withdrawal of
_of the isomerizing column that is packed with”
heat at the‘ top by means well-known in the art
.some inert or nonisomerizing packing or that is
‘of fractional distillation. Pressure maintained
provided with bubble-trays or plates or similar’
.fractionating devices, such as are 'Wéll-knOWn in
in the column will be dependent on the vapor
pressure of the organic compounds at the tem
peratures involved. Although this method of op
- the art of fractional distillation, whereby the low-_ - J
.er-boiling isomer may be withdrawn from the
' crating may appear to be super?cially similar to
. top of thecolumn substantially pure, and the‘
conventional distillation in packed columns, the
higher-boiling isomer is returned through. re?ux
ing to=the catalyst-packed section of the column.
use of a contact material simultaneously as col
,umn packing and. as isomerization catalyst is be
In this way, for example, 2-ole?ns, such as bu 60 lieved to be broadly novel for effecting isomeriza
tion. and separation of resulting‘ isomers of any
, tone-2, pentene-2, hexene-Z, and the like, may be
" compounds isomerizable bycontact with isomer
isomerized substantially quantitatively tosthe cor
. responding l-ole?ns.
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In another way of practicing such‘ contacting,
the column is operated in reverse, that is, the
lower-boiling isomer is fed into the top of the
catalyst-packed column. By contact with the
catalyst it becomes partly isomerized, and the re
sulting mixture, which is partly in the liquid con
dition,v ?ows downward through the catalyst
~-_packing and eventually reaches the end of the
catalyst-packed section as'a mixture of approxi
mately the equilibrium composition for the‘ tem
ization catalysts at temperatures below the criti
cal temperature of the compounds involved. , The.
selection of a suitable isomerization catalyst for
use as column packing is believed to be within the
ability of those skilled in’ the art of isomerizing
organic compounds, when the teachings herein
‘ are‘ considered together with the knownproper
> ties, especially the vapor pressure at various tem-
peratures and the critical temperatures of the
isomers involved.‘
'
The following examples are limited, ‘for the ‘
sake of simplicity and to facilitate‘com'parisons,
perature at that point. This mixture'may‘ be
.withdrawn and may be separated finto'th'e two 75 ~to’isomeri'zatioh'of the normal butenes, and illus
8
ZOther unsaturated compoundslas described‘ here.
spending to the ..equilibrium mixturev at the ,reac
tion temperature, giving an e?luent containing
in ‘may be isomerized undervsimilarconditions.
from about 10 tov 20 per cent butene-l, depending
.trate’ the general principles- of any v‘invention.
y
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.1
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upon the temperature.
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Although this invention in its broadest ‘aspects
is applicable to many unsaturated organiclcom
pounds in general, it has-been found'most useful
- -Butene-1 at atmospheric pressure'was passed
through a bed of 20 to 40 mesh chromium'oxide
gel that had been previouslytreated with nitro
.for- the :isomerization of unsaturated hydrocar
bonawhich present few or no complications such
as those presented by constituent elementasuch
as halogenstsulfur, oxygen, and the likethat may
in speci?cinstances cause-formation of trouble
some amounts-of catalyst poisons or undesired
'byeproducts. Because of this (fact, and in the
gen-diluted hydrogen while the temperature was
‘slowly increased from about room temperature to
about 500° C. and that had been cooled atv250°
C. while in pure'hydrogen. ' A different portion
of the same catalyshwhen tested for the dehy
drogenation of‘ isobutane at atmospheric pres
sure-and- at a space velocity of 2000 volumesper
volume per hour, had shown- itself'to be of at
interest of; simplicity-the; discussion herein is
leastme'dium dehydrogenation .activity by con
mated-hydrocarbons,» a few of’ which-namely cer
verting l7gper cent of the isobutane to isobutyl
tain simple ole?ns, have been already mentioned
devoted primarilyto the isomerization'iofy-unsat
speci?cally,- 'Many other and less-simple-role?ns
enefor a period of 18 hours inthe temperature
range ‘of .451 to 550° C. During the (present .20 and unsaturated hydrocarbons with more- than
one double bond may also be isomerized ‘in ac
isomerization run, the catalyst temperature was
cordance with this invention. ~ The following two
249- to 262° »C., and the space velocity was varied
generalizationscwhich are based on extensive ex
in steps as shown in the following tabulation.
:Thisjtabulation gives‘ the content of butene-Z
perimental ‘work, maybe used as guiding prin
in’ the effluent as determined by a'method simi
lar ‘to the dew-pressure method of Hachmuth
.ciples for any particular application to such less
(Ind. Eng. Chem” 24, 82 (1932)), as modi?ed by
Savellizet al. (Ind. Eng. Chem., anal.‘ed., 13,
373 (1941) ) , for analysis of two-component mix
First, at vmost isomerization temperatures, ‘as
herein given, the tendency for shifting of a double
bond from a terminal position, inwardly along
tures.
the carbon chain is greater than the reverse
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,simpleunsaturated hydrocarbons.
1
Sample
Space
Time min.
velocity,
'
vol./vo1./hr.
' VP
“cell
0. 0
83. 8
82. 2
78. 0
' 200
400
closer-it vis to an end of the carbon chain. In
butane 2
(Butene-l feed) ._ ____________ __
105 ____________ __
100
line with this principle,>1,5-hexadiene is readily
isomerized by the process of this invention to
ZA-hexadiene; in this isomerization, 1,4-hexa
‘ At thelowest space velocity this catalyst ef
fected practically equilibrium conversion of the‘
butene-l to butene-Z, and at higher space veloci
ties it continued to eifect excellent conversion.
No isobutylene was formed, and no dehydrogena
tion occurred. The catalystwas not revivi?ed 45
between samples and was still very active when
,
,
the run was stopped.
I
tendency. That is, the position of the double
bond'may be said to decrease in. stability the
" t
150 ____________ __
190 ____________ _ _
;
.40
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Example II
diene and 1,3-hexadiene are usually formed as
intermediate or by-product isomers, and'if de
sired can be. isolated. Similarly, allylbenzene is
very readily isomerized to propenylbenzene in
accordance with this invention,v as in a frac
tional-distillation column packed with a catalyst
comprising black chromium oxide ~and operated
in the afore-described reverse way. Allyl toluene
and various other allyl compounds are 'likewis
isomerizable to propenyl'compounds.v
‘
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Second,‘ the shifting of a double bond inwardly
along the carbon chain is greatlyfacilitated if
After the run of Example I, the catalyst was 50 the inward double-bond carbon is unattached
to hydrogen, that is, if it is carrying a side chain.
revivi?ed at 250° C. with 10 per cent oxygen in
In line with this principle, 2,5-dimethyl-1,5
nitrogen; a temperature rise of I70" 0. was ob
hexadiene is isomerized to 2,5-diinethyl-2A
served, caused by combustion of adsorbed mate
hexadiene by the process of this invention with
rial. This revivi?cation was followed by treat
ement with hydrogen at 250° 0., and the catalyst
greater ease than-is 1,5-‘hexadiene to 2,4-hexa
was then used at 262° C. for isomerizing butene- 1,
,which' was passed at atmospheric pressure
through the catalyst bed at a space velocity. of
to
diene, and 2-methyl-l,5-hexadiene is is'omeriz'e'd
2~methyl-2,4-hexadiene
with intermediate
ease.v More concretely, the ease of isomeriza
tion of these three initial diole?ns may be said
1000 volumes per volume per hour. A sample of
to be approximately as follows, LS-hexadienetZ
the e?iuent taken 15 minutes after the start‘ of
methyl-1,5¢hexadiene:'2,5 - dimethyl - 1,5 - hexa
the run had a butene-2 content of 80.0 per cent,
diene=1 : 10 :20. Similarly, isopentene (Z-me'thyl
showing that the catalyst e?ected excellent isom
l-butene) is readily isomerized to trimethylethyl
erization after revivi?cation, even at a relatively
ene,
apparently somewhat more easily than is iso
vhigh space velocity. At lower space velocities,
propyle'thylene
to trimethylethylene, indicating
the conversion to butene-2 approached or reached 65
that the tendency to shift past a carbon devoid
equilibrium conversion at the temperature, of the
of hydrogen is greater than the tendency to shift
catalyst bed.
inwardly along the chain; ‘however, either or both
Example III
initial ole?ns can be ‘used for the production
Butene-2, passed over a catalyst comprising
of trimethylethylene in accordance with the pres
black chromium oxide, at about atmospheric pres
ent invention.
sure, at temperatures in the range of about 200
to 350° C., and at space velocities of about 50 to
tene and Z-methyl-l-heptene are very vreadily
- 1000 volumes per volume of catalyst per hour, is
_.isomerized partly to butene-l, the. extent of
isomerization beingv substantially that. corre-v
Similarly still, Z-methyl-l-pen
isomerized to 2-methyl-2-pentene and Z-methyl
Z-heptene, respectively.
_
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' These foregoing two generalizations should not
be construed as indicating that the isomerizatlon
2,403,671
.9
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,goes in one direction only, for the isomerization
is reversible, and the equilibrium mixture at any
particular temperature can be Obtained from
either isomer. Thus, decrease in temperature
shifts the equilibrium in favor of one isomer, such
as, for example, butane-2, while increase in tem
perature shifts the equilibrium in favor of the
other isomer, such as, for example, butene-l.
The generalizations are helpful, however, as indi
cating roughly the probable proportions in which. 10
the isomers exist in the equilibrium mixture, as
10
.
allyl benzene, the carbon atom in the benzene
ring to which the allyl group is attached may be
considered to be a part of a chain containing
at least four carbon atoms.
Since the'invention may be practiced otherwise
:than as speci?cally described, and since many
variations and modi?cations ofit will be obvious
to those skilled in the art, this invention should
not be restricted otherwise than as speci?ed in
the appended claims.
~
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I claim:
1. A process for effecting catalytic shifting of
will be understood by those skilled in the. art.
an ole?nic linkage in an unsaturated hydrocar
Another generalization of the same type indi
cates that there is a considerable tendency for the ' bon containing said ole?nic linkage in an ali
double bond to shift into a side chain if this side 15 vphatic radical having a chain of at least three
chain is a methyl group centrally located in the , .carbon atoms without changing the carbon skele
ton thereof which comprises introducing said hy
molecule. Thus, there is a considerable tendency
" drocarbon into a fractional distillation column,
for the 3-methyl-2-pentene to isomerize to 2
at least a ‘portion of said column being packed
ethyl-l-butene. The opposite isomerization, of
course, also occurs to a greater or less extent, 20 with a solid granular isomerization catalyst com
prising black chromium oxide having an average
depending upon the temperatures involved.
composition corresponding to the empirical for
Isomerization of this particular type is especially
mula CI'Oz, said catalyst being so constituted and
well promoted by catalysts that comprise thoria
arranged as to effect said shifting of said ole?nic
in addition to black chromium oxide. Because _
“linkage simultaneously with liquid-vapor contact
of this effect, which manifests itself as an accel
eration or promotion of attainment of the equi 25 ing and consequent separation of the isomers by
recti?cation, and carrying out simultaneous frac
libria of the isomerizations to which this inven
tional distillation and said shifting of said ole?nic
tion is applicable, thoria is a preferred ingredient
linkage in said column while maintaining such
of the catalysts. Although widely varying pro
conditions of temperature and pressure; that said
portions of thoria and black chromium oxide may
shifting of said ole?nic linkage and said sep
be used, catalysts containing equal molecular pro~
‘ aration take place.
portions seem to be exceptionally suitable, espe
2. A process for effecting catalytic shifting of ’ ‘
cially when prepared by coprecipitation and dried
an ole?nic linkage in an unsaturated hydrocarbon
to give a gel-type catalyst. Urania also is ex
ceptionally advantageous in admixture with black
chromium oxide, sometimes appearing to be even
more so than thoria,
_
,
~
It may be observed that a number of the exem
containing said ole?nic linkage in an aliphatic
35 radical having a chain of at least three carbon
atoms without changing the carbon skeleton
thereof, which comprises intimately contacting
said hydrocarbonwith a catalyst containing as
plifying isomerizations mentioned in the fore
going discussion relate to the production of con 40 its active isomerizing constituent black chromium
oxide having an average composition correspond
jugated diole?ns from nonconjugated diole?ns.
ing to the empirical formula CrOz, at a tempera
Additional examples of this type are the follow
ture in the range of about 150 to 350° 0., for 'a
ing: 3-methyl-1,5-hexadiene to 4-methyl-1,3
period of time su?icient to effect shifting of‘said ‘
hexadiene; 1,5-heptadiene to 2,4-heptadiene; 3
methyl-1,5-heptadiene to 5-methyl-2,4-heptadi 45 ole?nic linkage to a substantial extent.
.3. A process according to claim 2 in which the
ene; and 2,6-octadiene to 3,5-octadiene. Still
hydrocarbon is butene-l and is thereby convert
other applications will be obvious to those skilled
in the art.
These isomerizations are substantially free
' ed to butene-2.
4. A process according to claim 2 in which the
from carbon-skeletal changes, unless the temper‘ 50 hydrocarbon is butene-2 and is thereby converted
to butene-l.
ature is excessively high. Decreasing the ?tem
' 5. A process according to claim 2 in which the
perature and compensatingly decreasing the space
hydrocarbon is an aliphaticnon-conjugated di
velocity may be resorted to if a tendency to car
bon-skeletal changes manifests itself. However, “ ole?n having at least four carbon atoms and is
thereby converted to the corresponding diole?n.
in isomerization of ole?ns with catalysts consist
6. A process according to claim 2 in’ which said
ing of black chromium oxide, experimental in
black chromium oxide is prepared by non-spon
.vestigation has shown that such tendency appears
taneous thermal decomposition of a crystalline
to be absent even at temperatures well within,
salt of chromic acid and a volatile nitrogen base
the dehydrogenation range, such as 500° C.
without disruption of the original crystals.
The use of catalysts comprising black chromi
_7. A process according to claim 2 in which the
um oxide in accordance with this invention in 60
catalyst is a black chromium oxide gel having an
volves treatment of organic compounds to pro
average composition corresponding to the em
mote the shifting of one or more ole?nic or dou
ble bonds or linkages contained in an unsatu
pirical formula CrOz.
.
'
rated aliphatic radical having a carbon chain of
_ 8. A process according to claim 2 in which the
catalyst also comprises zirconia associated there
at least three carbon atoms. In further explana
tion, it may be statedthat the organic compound
9. Aprocess according to claim 2 in which the
itself may not necessarily be entirelyaliphatic,
catalyst comprises as the active isomerizing con
but that in general the double bond to be shifted
is contained in the aliphatic portion thereof. The
stituent thereof from 5 to 100 per cent of black
aliphatic radical may be a part of a carbon chain 70 chromium oxide having an average composition
corresponding to the empirical formula CrOz. w
of four or more carbon atoms that may include
with.
a portion of a cyclic nucleus. For example, in
V
~
.
"
MARYAN P. MATUSZAK.
I
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