Process for separating alpha and internal olefins

A feedstock containing alpha olefins and internal olefins is converted into a first product having an enhanced internal olefin content over that of the feedstock and into a second product having an enhanced alpha olefin content over that of the feedstock by: PA1 (a) contacting the feedstock with an anthracene at a temperature ranging from 150.degree. to 275.degree. C. to form an olefin adduct with anthracene, PA1 (b) separating the adduct from the product of step (a) to leave a first product enriched in internal olefin, PA1 (c) heating the separated adduct at a temperature of from 250.degree.-400.degree. C. to produce anthracene and an olefin product enriched in alpha olefin, and PA1 (d) separating anthracene from the product of step (c) to produce a second product enriched in alpha olefin. Linear olefins are preferred feedstocks.

Field of the Invention 
This invention relates to a process for separating alpha olefins and 
internal olefins from a mixture comprising alpha olefins and internal 
olefins. 
Background of the Invention 
Many industrial processes produce olefins that are mixtures of alpha 
olefins and internal olefins. Due to the similarities in properties of 
alpha and internal olefins of the same molecular weight it is not an easy 
matter to separate the two. Olefins are frequently used as intermediates 
for the production of oil additives and detergents. The alpha and internal 
olefins can each be used to prepare end products having very different 
properties although the olefins utilized have the same molecular weight. 
Alpha olefins are particularly valued, although the internal olefins have 
particular specialized uses such as gasoline additives. A process that 
would separate a mixed linear olefin feedstock into component alpha and 
internal olefins would be of considerable value. 
Copending application Ser. No. 07/263,225, filed Oct. 27, 1988 discloses 
the use of an isomerization catalyst coupled with an anthracene to convert 
an internal olefin feedstock or a mixed alpha and internal olefin 
feedstock to a product having an enhanced alpha olefin content. 
U.S. Pat. No. 3,052,737, issued Sept. 4, 1962, discloses reacting 
anthracene with vinylcyclohexene to produce an adduct which is then 
hydrogenated to convert the cyclohexene ring to a cyclohexane ring, 
followed by pyrolysis to produce vinylcyclohexane and anthracene. This 
reference does not suggest that anthracene would be useful in separating 
alpha and internal linear olefins. 
Summary of the Invention 
This invention relates to a process for converting a feedstock comprising 
alpha olefins and internal olefins into a first product wherein the 
internal olefin content is enriched or enhanced over that of the feedstock 
and a second product wherein the alpha olefin content is enriched or 
enhanced over that of the feedstock which process comprises: 
(a) contacting said feedstock with an anthracene at a temperature ranging 
of from about 150.degree. to about 275.degree. C. to form an olefin adduct 
with anthracene, 
(b) separating said adduct from the product of step (a) to leave said first 
product enriched in internal olefin, 
(c) heating said separated adduct at a temperature of from between about 
250.degree. to about 400.degree. C. to produce anthracene and an olefin 
product enriched in alpha olefin, and 
(d) separating anthracene from the product of step (c) to produce said 
second product enriched in alpha olefin. Linear olefins are a preferred 
feedstock. 
Detailed Description of the Invention 
The feedstock olefins preferably used in the process of the instant 
invention are those olefins that are produced by commercial processes such 
as the oligomerization of ethylene, followed by isomerization and 
disproportionation. These feedstocks are typically substantially linear 
olefins. Small amounts of branched olefins may be present in such feeds 
and do not detract from the process of the instant invention. These 
branched olefins will tend to be separated in the same fashion as the 
linear olefins, the degree of separation being determined by the degree 
and location of the branching. Typically the feed olefins will have a 
carbon number ranging from about 6 to about 22, more preferably from about 
8 to about 18. The physical properties of the olefins determine the 
suitable carbon numbers to be utilized. At the reaction temperature the 
olefins to be separated should be in the liquid or gaseous state rather 
than in the solid state. Olefins with carbon numbers greater than 18 and 
lower than 6 can be utilized in the instant process but from a 
commercially practical point of view feedstocks with carbon number ranging 
from about 6 to about 18 will be most frequently used. 
Anthracene is utilized in the instant process to form the adduct primarily 
with the alpha olefin in the feedstock. As used herein "anthracene" refers 
to C.sub.14 H.sub.10 (molecular weight 178.15) as well as substituted 
anthracenes possessing similar adducting properties as the unsubstituted 
anthracene including but no limited to anthracene bearing one, two or more 
simple substituents, including but not limited to, lower alkyl, e.g., 
methyl, ethyl, butyl; halo, e.g., chloro, bromo, fluoro; nitro; sulfato; 
sulfonyloxy; carboxyl; carbo -lower-alkoxy, e.g., carbomethoxy, 
carbethoxy; amino; mono- and di-lower-alkylamino, e.g., methylamino, 
dimethylamino, methylethylamino; amido; hydroxy; cyano; lower-alkoxy, 
e.g., methoxy, ethoxy; lower-alkyanoyloxy, e.g., acteoxy; monocyclic 
aryls, e.g., phenyl, xylyl, toluyl, benzyl, etc. The particular 
substituents utilized should be inert under the reaction conditions and 
relatively small, such that they do not provide so much steric hinderance 
that the Diels-Alder reaction is inhibited. For example, 
9-phenylanthracene is useful, whereas 9,10-phenylanthracene inhibits the 
Diels-Alder reaction. Suitable substituted anthracenes can be determined 
by routine experimentation. 
The process of the instant invention is basically a three step process 
wherein (a) anthracene is reacted with the olefin to form an adduct, (b) 
the adduct is separated from the reaction mixture and (c) the adduct is 
pyrolized to release the olefin and regenerate the anthracene. 
The Diels-Alder adduct forming reaction is carried out in a conventional 
fashion. It may be carried out continuously in a stirred tank reactor 
wherein olefin and anthracene are added continuously to a stirred tank and 
a reaction product is continuous withdrawn from the stirred tank. 
Alternatively, the reaction may be carried out in a batch reactor, wherein 
the olefin and the anthracene are charged to an autoclave which is then 
heated to reaction temperature to complete the reaction. The reaction is 
typically carried out over a range of temperatures from about 150.degree. 
to about 275.degree. C., preferably from about 200.degree. to about 
250.degree. C., and most preferably from about 210.degree. to about 
240.degree. C. Pressures are not critical and typically run from about 
atomspheric to about 100 atmospheres. The reaction can be carried out in 
the gas phase or liquid phase or mixed gas-liquid phase, depending on the 
volatility of the feed olefins. 
Stoichiometric proportions or an excess of either olefin or anthracene can 
be used in forming the adducts but an excess of olefin is preferred. 
Advantageous ratios of about 1 to 2 moles of the olefin to the anthracene 
are preferred. 
An inert solvent can be utilized to dissolve the feed olefins or the 
anthracene or both in the reactor. Preferred solvents are the hydrocarbon 
solvents which are liquid at reaction temperatures and in which the 
olefins, anthracence and olefin-anthracene adducts are soluble. 
Illustrative examples of useful solvents include the alkanes such as 
pentane, iso-pentane, hexane, heptane, octane, nonane, and the like; 
cycloalkanes such as cyclopentane, cyclohexane, and the like; and 
aromatics such as benzene, toluene, ethylbenzene, diethylbenzene, and the 
like. The amount of solvent to be employed can vary over a wide range 
without a deleterious effect on the reaction. 
After the anthracene-olefin adduct has been formed, it is separated from 
the reaction mixture. The olefin-anthracene adduct is separated from the 
reaction mixture by conventional means. For example, it may be separated 
by flash distillation of the olefin to leave the adduct. Preferably, it is 
separated by cooling the reaction mixture until the adduct crystallizes 
out, followed by filtration or centrifugation to remove the unreacted 
olefin. In most cases the unreacted anthracene will separate out with the 
adduct. 
After the adduct has been separated from the reaction mixture there is left 
a first product that is enriched in internal olefins over that of the 
feedstock olefins. This first reaction product may be subjected to one or 
more additional reactions with anthracene followed by separation of the 
adduct to further enhance the internal olefin content of the first 
product. 
The final step of the instant process is to heat or pyrolyze the recovered 
olefin-anthracene adduct at a temperature of from about 250.degree. to 
about 400.degree. C. preferably from about 300.degree. to about 
350.degree. C. This pyrolysis frees the olefin from the anthracene. The 
anthracene is then separated from the resulting mixture to produce a 
second product enriched in alpha olefin content over that of the olefin 
feedstock. This separation is carried out by conventional means, e.g., 
flash distillation, filtration, centrifugation, etc. This second reaction 
product may be subjected to one or more additional reactions with 
anthracene followed by separation of the adduct and pyrolysis of the 
olefin-anthracene adduct to produce a product having an even more enhanced 
alpha olefin content. 
The ranges and limitations provided in the instant specification and claims 
are those which are believed to particularly point out and distinctly 
claim the instant invention. It is, however, understood that other ranges 
and limitations that perform substantially the same function in 
substantially the same manner to obtain the same or substantially the same 
result are intended to be within the scope of the instant invention as 
defined by the instant specification and claims. 
The present invention will now be illustrated by means of the following 
illustrative embodiments and examples which are provided for illustration 
and are not to be construed as limiting the invention.

Examples 
The following example illustrates the process the instant invention. 
A 100 ml. Parr autoclave was charged with 0.054 moles of anthracene 
(unsubstituted) and purged three times with argon and sealed. The 
autoclave was placed in a dry box and 0.212 moles of decene feed which had 
been nitrogen purged was added to the autoclave along with 20 ml. of dry, 
nitrogen purged toluene. The autoclave was sealed, removed from the dry 
box, placed in a heating bath and heated to 220.degree.-230.degree. C. for 
24 hours. The autoclave was stirred at 600 rpm during heating. The 
autoclave was then cooled to 20.degree. C. The precipitated anthracene and 
dodecene-anthracene adduct was filtered out of the reaction product. The 
solid anthracene and dodecene-anthracene adduct were pyrolyzed in a 
nitrogen flow-pot heated to 300.degree.-350.degree. C. for 0.5 hours. 
After pyrolysis, the reaction product was filtered to separate the 
anthracene from a dodecene oil product. This product was analyzed by gas 
chromatography and ozonolysis. The results are shown in Table 1. 
Additional experiments were carried out using various substituted 
anthracenes. The results of these experiments are shown in Table 1. 
TABLE 1 
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Anthracene Used Temp. of Adduct 
RXN 
Decene Composition of Feeds 
for Diels-Alder Formation 
Time 
and Products of Adduct Pyrolysis 
Example 
Adduct Formation 
.degree.C. 
Hrs 
1-Decene 
2-Decene 
3-Decene 
4-Decene 
5-Decene 
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(N-decene feed) 
-- -- 53.2 19.6 12.4 10.4 4.4 
1 Anthracene 220-230 24 84.8 8.3 4.0 2.3 0.8 
2 9,10-dichloroanthracene 
220-230 24 77.0 14.8 4.7 2.7 0.8 
3 9,10-dimethylanthracene 
220-230 24 93.8 5.1 0.7 0.3 0.1 
4 9,10-diphenylanthracene 
220-230 24 No Reaction 
5 9-methylanthracene 
220-230 24 88.1 7.7 2.5 1.2 0.5 
6 9-phenylanthracene 
220-230 24 69.3 15.8 7.6 5.6 1.7 
7 2-t-butylanthracene 
220-230 24 85.0 8.1 3.7 2.4 0.8 
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