Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By double-bond-shift isomerization
Reexamination Certificate
2000-01-07
2002-06-18
Dang, Thuan D. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By double-bond-shift isomerization
C585S664000, C585S670000
Reexamination Certificate
active
06407302
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the isomerization of olefins and more particularly concerns the isomerization of a mixture of vinyl and vinylidene olefins.
BACKGROUND OF THE INVENTION
Mixtures of linear terminal mono-olefins, commonly referred to as linear alpha-olefins, are made commercially by ethylene chain growth of aluminum alkyls followed by displacement. Such products are mainly vinyl -olefins having the structure:
R
1
—CH
2
—CH
2
—CH
2
—CH═CH
2
Formula 1
wherein R
1
is an aliphatic hydrocarbon group. These olefins are referred to as “vinyl olefins”. In addition, a substantial portion of the alpha-olefins can be in the form of “vinylidene olefins” which have the structure:
wherein R
2
and R
3
are aliphatic hydrocarbon groups which may be the same or different.
For many applications, it is highly desirable to use linear internal olefins. Linear internal olefins can be made from alpha-olefins by isomerizing the olefinic double bond from a terminal to an internal position. Such linear internal olefins can be represented by Formulas 3, 4, 5, or 6,
R
1
—CH
2
—CH
2
—CH═CH—CH
3
Formula 3
R
1
—CH
2
—CH═CH—CH
2
—CH
3
Formula 4
R
1
—CH═CH—CH
2
—CH
2
—CH
3
Formula 5
R
1
in Formulas 3, 4 and 5 is as defined for Formula 1, and R
2
and R
3
in Formula 6 are as defined for Formula 2. Olefins having the structures of Formulas-3, 4 and 5 are known as “di-substituted” internal olefins. Olefins having the structure of Formula 6 are known as “tri-substituted” internal olefins. In Formulas 3 and 4, the olefinic double bond is at the second numbered and third numbered carbon atoms, respectively. In Formula 5, the olefinic double bond is at the fourth numbered carbon atom. Internal olefins in which the olefinic double bond is at the fourth or higher (for example, fifth or sixth) numbered carbon atom are called “deep” internal olefins.
Peters, U.S. Pat. No. 4,587,374 discloses that when this is done with the use of alumina or silica/alumina as an isomerization catalyst, a major portion of the olefin groups of the vinylidene olefins are isomerized to the adjacent carbon-carbon bond, thereby forming “tri-substituted” internal olefins. Brennan et. al., U.S. Pat. No. 3,864,424, discloses that, while the use of alumina or a combination of alumina and a strong acid as an isomerization catalyst is capable of isomerizing an olefinic double bond involving a tertiary carbon atom to one involving secondary carbon atoms, the use of a partially dehydrated weakly acidic alumina catalyst effects isomerization of an olefinic double bond involving a tertiary carbon atom to form trisubstituted ethylenes without any appreciable further isomerization to 1,2-disubstituted olefins and without the formation of dimers with other double bonded molecules. In addition, Myers, U.S. Pat. No. 4,225,419, discloses that alumina catalysts are effective in the skeletal isomerization of olefins to more highly branched olefins.
Thus far, there has been no disclosure of a method for the isomerization of alpha olefins to form a product having the desirable features of comprisi di- and tri-substituted internal olefins, and having a greater degree of branching, a kinematic viscosity less than 4 Cst measured at 40° C. and a pour point below −25° C., and comprising at least 20 weight percent of “deep” internal olefins, that is, internal olefins in which the olefinic double bond does not involve a second or third numbered carbon atom.
OBJECTS OF THE INVENTION
It is therefore a general object of the present invention to provide an improved process for the isomerization of a mixture of vinyl and vinylidene olefins that affords a product having the aforesaid desirable features.
More particularly, it is an object of the present invention to provide an aforesaid process in which a mixture of vinyl and vinylidene olefins is isomerized to form a mixture comprising both di- and tri-substituted internal olefins, having a greater degree of branching and at least 20 weight percent of deep internal olefins.
It is another object of the present invention to provide an improved aforesaid isomerization process that produces an isomerization product having a viscosity less than 4 cSt measured at 40° C. and a pour point below −25°.
Other objects and advantages of the present invention will become apparent upon reading the following detailed description and appended claims.
SUMMARY OF THE INVENTION
These objects are achieved by the isomerization method of the present invention, comprising: contacting a linear alpha-olefin mixture comprising vinyl and vinylidene olefins containing from 10 to 35 carbon atoms in the gas or liquid phase with a bed of porous solid acid catalyst particles comprising gamma alumina having a specific surface area of at least 100 square meters per gram, a pore volume of at least 0.4 cubic centimeter per gram, an average pore diameter of at least 30 Angstroms, a sodium content of less than 0.01 weight percent and an ammonia chemisorption of at least 0.1 millimole per gram, at a reaction temperature in the range of from about 200° C. to about 400° C., a reaction pressure in the range of from about 15 to about 500 pounds per square inch absolute and a weight hourly space velocity of from about 0.5 to about 20 pounds of the olefin mixture per pound of catalyst particles per hour, wherein the reaction temperature, pressure and weight hourly space velocity are selected so as to form a product mixture comprising at least 70 weight percent of di- and tri-substituted internal olefins, of which product mixture at least 20 weight percent are tri-substituted internal olefins, at least 20 weight percent are di-substituted internal olefins having a double bond at the fourth or higher numbered carbon atom position and less than 50 weight percent are di-substituted internal olefins having a double bond at the second or third numbered carbon atom position, and which has a kinematic viscosity less than 4 cSt measured at 40° C. and a pour point below −25° C.
The present invention is also the product of the aforesaid process, a mixture having the composition of the aforesaid product and a drilling fluid at least a portion of whose base oil comprises at least a portion of such product or mixture.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The feedstock employed in the method of the present invention comprises a mixture-of alpha olefins comprising vinyl and vinylidene olefins of Formulas 1 and 2 and having from 10 to 35 carbon atoms. The alpha olefin mixture preferably comprises, and more preferably consists essentially of, olefins containing from 16 to 18 carbon atoms. Although such a mixture is obtainable from a variety of sources, one suitable commercial source is the Ziegler process of triethyl aluminum-ethylene chain growth followed by displacement. Typically, the resultant olefin mixture contains from about 50 to about 95 weight percent of vinyl olefins of Formula 1 and from about 5 to about 50 weight percent of vinylidene olefins of Formula 2. Preferably, olefin mixtures for use as feedstocks for the method of the present invention contain from about 60 to about 90 weight percent of vinyl olefins of Formula 1 and from about 10 to about 40 weight percent of vinylidene olefins of Formula 2.
In Formulas 1, 3, 4 and 5 hereinabove, R
1
can contain from 5 to 30 carbon atoms, preferably from 11 to 13 carbon atoms. Examples of these vinyl olefins are 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and the like. In a highly preferred embodiment, the vinyl olefins in the mixtures consist essentially of 1-hexadecene and 1-octadecene. In Formulas 2 and 6, R
2
and R
3
each contain from 1 to 29 carbon atoms and their sum is in the range of from 5 to 30, preferably from 11 to 13, carbon atoms.
In addition, the initial olefin mixture prior to isomerization in the method of this invention may contain internal olefins. Generally, the amount of internal olefin in the initial mixture is quite low. Typically, amounts
Cox William L.
Twu Fred Chun-Chien
BP Corporation North America Inc.
Dang Thuan D.
Henes James R.
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