Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By addition of entire unsaturated molecules – e.g.,...
Reexamination Certificate
1999-12-29
2002-04-30
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By addition of entire unsaturated molecules, e.g.,...
C585S504000, C585S950000, C134S022140, C134S022190
Reexamination Certificate
active
06380451
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to olefin preparation. This invention relates more specifically to a method of cleaning co-product polymer and catalyst residues from an oligomerization reactor, such as a trimerization reactor.
Olefins, particularly alpha-olefins, also referred to herein as 1-olefins, have many uses. In addition to their uses as specific chemicals, alpha-olefins are used in polymerization processes, either as monomers or co-monomers, to prepare polyolefins. Unfortunately, during the production of higher alpha-olefins, residue can be deposited on reactor walls and other surfaces of the reactor. This residue can build up on the interior walls, other portions of the reactor, inhibit heat transfer, and cause the reactor to overheat.
The problem of polymer co-product build-up and its effect on the heat transfer efficiency of a reactor is discussed in U.S. Pat. No. 5,689,028, the entirety of which is herein incorporated by reference.
A “hot wash” method has been devised, employing the process medium used at a higher temperature than the normal reaction temperature, to remove polymer residue from the reactor wall. The hot wash method has considerably alleviated the problem of heat transfer efficiency in olefin reactors, but the heat transfer efficiency of the reactor surfaces still goes down, or decreases, as the reactor is used over a period of time.
An alcohol, referred to here as a “catalyst kill agent,” previously has been added to the catalyst charge in the effluent of an olefin oligomerization reactor. See, for example, U.S. Pat. No. 5,689,028 discloses adding 2-ethylhexanol to the reactor effluent of a trimerization reactor to deactivate the catalyst system; U.S. Pat. No. 5,859,303, Example 1, discloses that addition of an alcohol deactivates the catalyst system; U.S. Pat. No. 5,750,816 teaches the addition of alcohols, phenols, carboxylic acids, primary or secondary amines, or ammonia, for example 1-hexanol (Example 13), to the effluent of the ethylene trimerization reactor. The '816 patent teaches generally that this step “maintain[s] the dispersed state of principally the catalyst components in the reaction dispersion, . . . in the process line from the outlet of the oligomerization reactor to the inlet of the distillation tower”; U.S. Pat. No. 5,750,816, col. 12, lines 20-23 and 49-67; U.S. Pat. No. 5,750,817 discloses the use of ethanol to terminate an ethylene trimerization reaction.
SUMMARY OF THE INVENTION
The inventors have discovered that catalyst residue, as well as polymer residue, can build up on the walls of an oligomerization reactor. This problem particularly has been noticed in connection with the use of catalyst systems including or made from aluminum alkyls. Catalyst residue can have a substantial effect on the heat transfer efficiency of the reactor walls. While the catalyst residue can build up more slowly than polymer residue, over time this catalyst residue can substantially reduce the heat transfer efficiency of the reactor, even if the problem of polymer build-up has been adequately addressed. None of the patents identified above disclose or suggest that catalyst residue can build up in an oligomerization reactor. None of these patents is believed to teach how to prevent or eliminate such a build-up.
Accordingly, one object of the invention is to provide a method for removing residue from the wall of an olefin reactor.
Another object of the invention is to improve the heat transfer efficiency of a reactor that has developed a residue or build up of catalyst systems.
An additional object of the invention is to remove a substantial proportion, if not all, of the residues from the walls of an olefin reactor.
One or more of the preceding objects, or one or more other objects which will become plain upon consideration. of the present specification, are satisfied in whole or in part by the invention described here.
One aspect of the invention is a method for cleaning a reactor in which a higher olefin has been made, using a catalyst system. The reactor has an interior surface on which a catalyst residue has been deposited. The method is carried out by contacting the interior surface of the reactor with an alcohol. The contacting step is accomplished under conditions effective to remove at least a substantial amount of the catalyst residue from the interior surface of the reactor.
Another aspect of the invention is a method for making a higher olefin. An olefin is reacted in a reactor, in the presence of a catalyst system. The reaction forms a higher olefin reaction product, but also can generate a co-product residue of the catalyst system to deposit on the interior surface of the reactor. The interior surface of the reactor then is contacted with an alcohol. This alcohol-contacting step is carried out under conditions effective to remove at least a substantial amount of the catalyst residue from the interior surface of the reactor.
One significant advantage of the invention is that the heat transfer efficiency of the reactor wall ordinarily would diminish with time and use, even if the polymer build-up were addressed. When the present invention is carried out, the catalyst residue deposit on the reactor wall is at least partially removed, resulting in an increase in the heat transfer efficiency of the reactor wall. In some instances, the heat transfer efficiency of the cleaned reactor wall can be as great as, or even slightly greater than, that of an unused reactor wall. This is a significant, previously unappreciated advantage of practicing the present invention.
DETAILED DESCRIPTION OF THE INVENTION
While the invention will be described in connection with one or more embodiments, it will be understood that the invention is not limited to those embodiments. On the contrary, the invention includes all alternatives, modifications, and equivalents as may be included within the spirit and scope of the appended claims. The mention of or statement of a preference for certain embodiments does not indicate an intent to exclude other embodiments that are not mentioned or stated to be preferred.
The reaction contemplated here broadly relates to oligomerization of ethylene and other lower olefins to produce higher olefins. In this context, “lower” and “higher” are relative; a lower alpha-olefin is converted to a higher olefin, or higher alpha-olefin, having a greater number of carbon atoms. The reaction is carried out in the presence of one or more catalyst systems under conditions encouraging the reaction to proceed.
The present invention will be exemplified in the context of a trimerization reaction, although it is contemplated that the invention can find use in other oligomerization reactions. “Trimerization,” as used in this disclosure, is defined as any combination of any two, three, or more olefins reducing the number of olefin, i.e., carbon-carbon double bonds by two. For example, the three olefin bonds in the combination of three ethylene units can be reduced by two, to one olefin bond, in 1-hexene. In another example, the four olefin bonds in the combination of two 1,3-butadiene units, can be reduced by two, to two olefin bonds in 1,5-cyclooctadiene.
As used here, the term “trimerization” is intended to include dimerization of diolefins, as well as “co-trimerization,” each as further discussed below. The reactants, catalysts, equipment, and reaction conditions useful in the present process and the reaction products and co-products formed as a result of the trimerization reaction are further described below. Additionally, while the term “trimerization”, as defied above, is used throughout this disclosure, this invention also encompasses oligomerization reactions and processes.
Reactants
The reactants applicable for use in the trimerization process of this invention include olefinic compounds which can self-react, i.e., trimerize, to give useful products. For example, the self-reaction of ethylene can give 1-hexene, and the self-reaction of 1,3-butadiene can give 1,5-cyclooctadiene.
The reactants appl
Ewert Warren M.
Knudsen Ronald D.
Kreischer Bruce E.
Griffin Walter D.
Phillips Petroleum Company
Sun Hsiang-ning
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