Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR THE SELECTIVE ISOMERIZATION OF ALPHA-OLEFINS IN THE
PRESENCE OF VINYLIDENE OLEFINS
RELATIONSHIP TO PRIOR APPLICATIONS
s (Not Applicable)
STATEMENT REGARDING FEDERALLY FUNDED RESEARCH
(Not Applicable)
FIELD OF THE INVENTION
The invention generally relates to a process for isomerizing alpha-olefins to
1o internal olefins without significant concurrent isomerization of vinylidene
olefins also
present in the reaction mixture.
BACKGROUND OF THE INVENTION
In the catalytic isomerization of olefins, it is common that isomerization of
a
vinylidene olefin to a trisubstituted olefin (Reaction 1 below) proceeds more
readily
15 than isomerization of an alpha-olefin to an internal olefin (Reaction 2
below) when
both are present in the same reaction mixture.
R H2 R
CH --=r \C CH3
R/ 2 R/
REACTION 1 - ISOMER(ZATION OF A VINYLIDENE
CH2~H-CH2-R -= CH3- CH=CH-R
REACTION 2 - ISOMERI7~ITfON OF AN ALPHA-OLEFIN
In Reactions 1 and 2, R and R' are rnonovalent groups such as straight or
branched
alkyl groups or aryl groups typically in the range of about 1-30 carbon atoms.
Some
2s of the hydrogen atoms in the R and R' groups may optionally be substituted
with
groups that do not interfere in the isomerization reaction.
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Accordingly, when both vinylidenes and alpha-olefins are present, it has been
difficult to selectively isomerize alpha-olefins to internal olefins without
also
isomerizing the vinylidene olefins. The present invention addresses this
problem and
provides a catalytic process for accomplishing the selective isomerization of
alpha-
s olefins to internal olefins in the presence of vinylidene olefins without
substantial
isomerization of the vinylidenes.
BRIEF DESCRIPTION OF THE INVENTION
This invention relates to a process for the conversion of olefins. More
specifically it relates to the isomerization of alpha olefins to internal
olefins wherein
1o vinyiidene olefins are also present in the alpha olefin feed or reaction
mixture. (t has
been found that the alpha olefins may be catalytical(y isomerized to internal
olefins
without significant concurrent isomerization of vinylidene olefins to
trisubstituted
olefins.
The selective isomerization process utilizes a metal-based homogeneous or
i5 heterogeneous catalyst. The catalysts used in the process are ruthenium
trihalides
including ruthenium trihalide hydrates. The preferred catalysts are ruthenium
trichloride and ruthenium tribromide including the various hydrated forms of
either.
Investigators Jochem U. Koehler and Hans L. Krauss (Journal of Molecular
Catalysis, 1997, Volume 123, Number 1, Pages 49-64) have reported the use of
2o RuCl3~3H20 as an active olefin isomerization catalyst. However, there is no
disclosure what-so-ever in the reference regarding selective isomerization of
alpha
olefins in the presence of vinylidene olefins.
The ruthenium trihalide (RuX3) catalysts of this invention may be employed in
homogeneous form, dissolved in neat liquid olefin or a mixture of olefin and a
solvent.
2s Alcohols are effective solvents for the RuX3 compounds of this invention.
The
selective alpha-olefin isomerization process of this invention using RuX3
compounds
may be conducted at temperatures in the range of about 50°C to about
250°C. The
isomerization process is typically conducted in an inert atmosphere e.g.,
under
nitrogen or in the presence of other gases such as hydrogen at any manageable
3o pressure.
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DETAILED DESCRIPTION OF THE INVENTION
For the sake of clarity, the term "comprising" as used in this application is
defined as "specifying the presence of stated features, integers, steps, or
components
as recited, but not precluding the presence or addition of one or more other
steps,
components, or groups thereof'. Comprising is different from "consisting of
which
does preclude the presence or addition of one or more other steps, components,
or
groups thereof.
The alpha olefins to be converted to internal olefin are C4 to C3o straight or
branched-chain monoolefinically unsaturated hydrocarbons in which the olefinic
unsaturation occurs at the 1- or alpha-position of the carbon chain. Typically
these
compounds have the following formula
RZ
I
R'-CHZ CHZ (CHZ)m C=CHZ
~5 where R' and R2 are the same or different and are hydrogen or alkyl, i.e.,
C, to C3o
linear or branched alkyl, preferably C, to C2o linear or branched alkyl, most
preferably
C, to C6 linear or branched alkyl, e.g. methyl, ethyl and the like, and m is
an integer
from 0 to 26. Particularly preferred are compounds where R' is alkyl and RZ is
hydrogen.
2o Such alpha-olefins are commercially available and can be made by the
thermal cracking of paraffinic hydrocarbons, by conversion of the
corresponding
alcohol to an olefin or by the we(I-known Zieg(er ethylene chain growth and
displacement from trialkylaluminum compounds. Individual olefins may be used
as
well as mixtures of such olefins. Examples of such olefins are 1-hexene, 1-
heptene,
25 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-
octadecene, 1-eicocene, and the like. The more preferred normal-alpha-olefins
are
those containing about 6-30 carbon atoms. The most preferred normal-alpha-
olefins
are those containing about 10-30 carbon atoms. Some internal alpha olefins may
also be present in the reaction mixture at the start of the reaction.
Obviously, the
so amount of internal olefin present in the reaction mixture will increase at
the conversion
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of alpha olefins _to internal olefins proceeds in accord with the process of
this
invention.
After conversion the internal olefins are useful, e.g., when oligomerized, as
oils.
Depending on their viscosity, different applications for such oils are known,
e.g., as
lubricants. These materials are generally mixtures of different percentages of
dimer,
trimer, tetramer, pentamer and higher oligomers which oligomers are produced
.in
different proportions in an oiigomerization process. In order to increase the
viscosity,
processes are used which either produce more of the higher oligomers or,
alternatively, some of the lower oligomers are removed typically by
distillation. Most
low viscosity dimer and trimer products are obtained as by-products of the
production
of higher viscosity synthetic oils. Due to 'the increasing use of dimers in
applications
such as low temperature lubricants and drilling fluids, methods for their
preferential
production from the isomerized alpha olefins are of interest.
Vinylidenes or vinylidene olefins may be represented by the formula
R3
~C CH2
R4
and "trisubstituted olefins" may be represented by the formula
R
C\ H
wherein R3, R4, and R5 represent hydrocarbon groups. Reaction 1 above shows
the
isomerization of a vinylidene olefin to a trisubstituted olefin. Typically,
the
isomerization of a vinylidene olefin to a trisubstituted olefin occurs with
greater facility
than the internal isomerization of an alpha olefin to an internal olefin when
both are
present. Upon oligomerization of such an isomerization mixture, the
oligomerization
products of trisubstituted species will be present together with the
oligomerization
products of internal olefins in the oligomer oils produced. In commercial
production, it
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may be difficult to obtain an oligomer product mix which, when fractionated,
will
produce the relative amounts of each viscosity product which correspond to
market
demand. Thus, the ability to selectively isomerize only the alpha olefin may
offer a
significant commercial advantage.
5 In this application, Applicants disclose a process which selectively
isomerizes
alpha olefins to internal olefins in a reaction mixture which also contains
vinylidene
olefins and without substantial isomerization of the vinylidene olefins to
trisubstituted
olefins. For the purpose of this invention, without substantial isomerization
of the
vinylidene is intended to denote that the conversion achieved in the desired
reaction
1o is at least five times as great as the conversion of vinylidene olefins to
trisubstituted
olefins. For example in a feed containing both alpha olefins and vinylidene
olefins
where 5 % (mole or weight %) of the vinylidene olefins were converted to
trisubstituted olefins by the method of this invention, a conversion of alpha
olefins to
internal olefins exceeding 25 % (mole or weight %) would be considered to have
met
T5 the condition without substantial isomerization of the vinylidene olefin to
trisubstituted
olefin.
The process utilizes a metal-based homogeneous or heterogeneous catalyst.
The catalysts used in the process are ruthenium trihalides including ruthenium
trihalide hydrates. The preferred catalysts are ruthenium trichloride and
ruthenium
2o tribromide including the various hydrated forms of either. The ruthenium
trihalide
(RuX3) catalysts of this invention are preferably employed in homogeneous
form,
dissolved in neat liquid olefin or a mixture of olefin and a solvent. Alcohols
are
effective solvents far the RuX3 compounds of this invention.
The selective alpha-olefin isomerization process of this invention using RuX3
25 compounds may be conducted at temperatures in the range of about
50°C to about
250°C, but preferably in the range of about 100°C to about
200°C. The isomerization
process is typically conducted in an inert atmosphere e.g., under nitrogen or
in the
presence of other gases such as hydrogen. The process is typically conducted
at
atmospheric pressure (about 1.0 bars) but may be conducted at any manageable
3o pressure typically in the range of about 0.1 to about 25 bars, and
preferably in the
range of about 0.5 bars to about 5.0 bars.
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Example
To a glass reaction vessel was added 100 ml of an olefin mixture containing
alpha, internal, vinylidene, and trisubstituted olefins of even carbon numbers
from 18
through 30. To this was added 0.5 m( of a 0.0024 molar solution of ruthenium
trichloride hydrate in hexanol, corresponding to a charge of about 1.2 ppm Ru
in the
reaction solution. The solution was vigorously stirred at room temperature and
a
small sample of the liquid was removed for analysis and designated as the
"Before
Reaction Sample". The reaction vessel was then immersed in an oil bath which
had
been pre-heated to 170°C. The reaction vessel was maintained at
170°C while.a flow
of hydrogen gas at atmospheric pressure was sparged through the reaction
solution
at 0.1 SCFH. Afterward, another liquid sample was removed (4Hour Reaction
Sample) from the vessel. The two samples were analyzed by NMR to determine the
types of olefins present. The results obtained are as shown in Table 1 below.
Table 1
Olefin Mole % Olefin Type Mole % Olefin Type
Type in in
Before Reaction Sample4-Hour Reaction Sample
Alpha 30.5 2.7
Internal 11.5 36.6
Vinylidene 55.3 55.2
Trisubstituted2.8 5.5
These results clearly indicate that isomerization of alpha-olefins to internal
olefins predominated over isomerization of vinylidene olefins to
trisubstituted species.
Comparative Example
The data for the following comparative example was taken from US Patent No.
4,724,274. Table 2 below shows the feed composition prior to isomerization and
the
product mixture after isomerization. The feed was passed over a fixed bed
catalyst
consisting of 0.3 weight percent palladium deposited on gamma alumina. Sulfur
(in
the form of dimethyl sulfide) was added to the feed so as to be present at a
level of 6
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PPM. The reaction was conducted in the presence of hydrogen at a pressure of
25
bars and a temperature of 80° C.
Table
Species Weight % in Feed Weight
Present Before IsomerizationAfter Isomerization
1-pentene 25 ~0
(alpha olefin)
internal olefins~0 ~0
2-methyl-1 butene40 7.2
(vinylidene olefin)
2-methyl-2-butene~0 32.7
(trisubstituted)
pentane 35
60
isopentane ~0 0.1
From this comparative example it is observed that 82 % of the vinylidene
olefin
present in the feed was converted to trisubstituted olefin while none of the
alpha olefin
present in the feed was converted to internal olefin. In fact, the alpha
olefin was
destroyed (hydrogenated to pentane). These results are in stark contrast to
the
working example of this invention where alpha olefin was selectively
isomerized to
internal olefin without substantial isomerization of the vinylidene olefin to
trisubstitued
olefin.
