Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By addition of entire unsaturated molecules – e.g.,...
Reexamination Certificate
1999-09-16
2001-08-28
Knode, Marian C. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By addition of entire unsaturated molecules, e.g.,...
C585S510000, C585S511000, C585S526000, C585S520000, C585S521000
Reexamination Certificate
active
06281401
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the field of hydrocarbon upgrading processes. In another aspect, the invention relates to the oligomerization of olefins.
It is known in the art to oligomerize olefins in the presence of an acidic catalyst to diesel fuel range hydrocarbons. As gasoline fuel specifications become more stringent concerning sulfur content, aromatic content and Reid vapor pressure (“RVP”; defined as the vapor pressure of a hydrocarbon at 100° F. (37.8° C.) in pounds per square inch absolute and measured using ASTM test method D-323), the demand for diesel fuel could significantly increase. Therefore, development of a process for oligomerizing olefins to diesel fuel range hydrocarbons wherein the quality of the diesel fuel produced is enhanced, would be a significant contribution to the art and to the economy.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for oligomerizing olefins to diesel fuel range hydrocarbons.
It is yet another object of the present invention to provide a process for oligomerizing olefins wherein the weight % of C
11
+ hydrocarbons contained in the oligomers having at least 9 carbon atoms per molecule in the reactor effluent is enhanced.
It is still another object of the present invention to provide a process for oligomerizing olefins wherein the cetane number of the oligomers having at least 9 carbon atoms per molecule in the reactor effluent is enhanced.
In accordance with the present invention, a method has been found for oligomerizing olefins comprising the steps of:
(a) introducing a heavy hydrocarbon stream comprising at least one heavy olefin having at least 5 carbon atoms per molecule into a reaction zone containing an oligomerization catalyst and operating under reaction conditions for oligomerizing olefins;
(b) introducing a light olefin stream comprising at least one light olefin having less than 5 carbon atoms per molecule at a rate of introduction into the reaction zone as a co-feed with the heavy hydrocarbon stream;
(c) withdrawing from the reaction zone a reactor effluent comprising oligomers having at least 9 carbon atoms per molecule;
(d) identifying a baseline weight % of C
11
+ hydrocarbons contained in the oligomers, based on the total weight of the oligomers, when there is no step (b); and
(e) controlling the rate of introduction of the light olefin stream in step (b) such that the weight % of C
11
+ hydrocarbons contained in the oligomers, based on the total weight of the oligomers, of the reactor effluent of step (c) exceeds the baseline weight % of C
11
+ hydrocarbons contained in the oligomers identified in step (d).
Other objects and advantages will become apparent from the detailed description and the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
The catalyst useful in the present invention can be any oligomerization catalyst suitable for oligomerizing olefins to diesel fuel range hydrocarbons. Preferably, the oligomerization catalyst is an acid catalyst. More preferably, the oligomerization catalyst comprises an acid catalyst selected from the group consisting of perfluoropolyalkyl sulfonic acid, perfluoroalkyl sulfonic acid, polyfluoroalkyl sulfonic acid and compounds defined by the formulas:
C
n
X
y
F
(2n+1−y)
SO
3
H;
C
n
X
y
F
(2n−y)
(SO
3
H)
2
and combinations of any two or more thereof,
wherein:
X is selected from the group consisting of hydrogen, chlorine, bromine, iodine and combinations of any two or more thereof;
n ranges from 1 to and including 20;
y ranges from 0 to and including 39; and
the alkyl groups of the perfluoropolyalkyl sulfonic acid, perfluoroalkyl sulfonic acid and polyfluoroalkyl sulfonic acid can contain in the range of from 1 to 8 carbon atoms.
The presently most preferred oligomerization catalyst comprises an acid catalyst selected from the group consisting of perfluorooctane sulfonic acid, perfluoropolyalkyl sulfonic acid and combinations thereof.
The process of this invention involves a method for oligomerizing olefins. A heavy hydrocarbon stream comprising, consisting essentially of, or consisting of at least one heavy olefin having at least 5 carbon atoms per molecule is introduced or charged to a reaction zone containing an oligomerization catalyst operated under reaction conditions for oligomerizing olefins.
Preferably, the heavy hydrocarbon stream comprises at least one heavy olefin having in the range of from 5 to 6 carbon atoms per molecule. In addition, the heavy hydrocarbon stream can be obtained by fractionation of a gasoline stream, including, but not limited to, fluidized catalytic cracker gasoline, to at least partially remove the C
5
/C
6
olefin material for use as the heavy hydrocarbon stream in the present invention. This provides the benefits of reduced olefin content in the gasoline stream, reduced RVP of the gasoline stream (due to the removal of the high RVP C
5
olefins) and increased diesel fuel production from the C
5
/C
6
olefin material, which are all expected to be the future regulatory trend.
It has been discovered that the introduction of a light olefin stream as a co-feed, comprising at least one light olefin having less than 5 carbon atoms per molecule, to the reaction zone along with the heavy hydrocarbon stream unexpectedly results in an increased weight % of C
11
+ hydrocarbons in the produced oligomers having at least 9 carbon atoms per molecule as compared to the weight % of C
11
+ hydrocarbons in the produced oligomers having at least 9 carbon atoms per molecule when the light olefin stream is not co-fed. The light olefin stream is preferably a hydrocarbon compound selected from the group consisting of propylene, butylene, isobutylene and combinations of any two or more thereof.
The reactor effluent from the inventive process comprises oligomers having at least 9 carbon atoms per molecule. A baseline weight % of C
11
+ hydrocarbons in the oligomers having at least 9 carbon atoms per molecule (“oligomers”) of the reactor effluent is identified representing the baseline weight % of C
11
+ hydrocarbons contained in the oligomers of the reactor effluent when there is no introduction of the light olefin stream co-feed. The identified baseline weight % of C
11
+ hydrocarbons contained in the oligomers of the reactor effluent is generally less than about 40 weight %; more particularly less than about 35 weight %; and most particularly less than 30 weight %, based on the total weight of the oligomers.
The light olefin stream co-feed can be controllably introduced to the reaction zone resulting in a mole ratio of the light olefin stream co-feed to the heavy hydrocarbon stream. The mole ratio of the light olefin stream co-feed to the heavy hydrocarbon stream can be any ratio that can enhance the weight % of C
11
+ hydrocarbons contained in the oligomers of the reactor effluent over the identified baseline weight % of C
11
+ hydrocarbons contained in the oligomers of the reactor effluent when there is no introduction of the light olefin stream co-feed. The weight % of C
11
+ hydrocarbons contained in the oligomers of the reactor effluent when there is a controlled introduction of the light olefin stream co-feed is preferably greater than about 40 weight %; more preferably greater than about 50 weight %; and most preferably greater than 60 weight %. The mole ratio of the light olefin stream co-feed to the heavy hydrocarbon stream can be in the range of from about 0.01:1 to about 4:1; preferably from about 0.5:1 to about 3:1; and most preferably from 1:1 to 2:1.
This increase in weight % of C
11
+ hydrocarbons contained in the oligomers results in an increased cetane number for the C
9
+ material following hydrogenation, as demonstrated in the Examples.
The oligomerization reaction can take place in any reactor system known to those skilled in the art to be suitable for use in oligomerizing an olefin in the presence of an oligomerization catalyst. Typical reactor systems useful in the present inven
Anderson Jeffrey R.
Dang Thuan D
Knode Marian C.
Phillips Petroleum Company
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