Chemistry of hydrocarbon compounds – Purification – separation – or recovery – By plural serial diverse separations
Reexamination Certificate
2000-09-27
2001-12-11
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Purification, separation, or recovery
By plural serial diverse separations
C585S259000, C585S261000, C585S258000, C585S510000, C208S142000, C208S143000, C208S144000, C208S263000
Reexamination Certificate
active
06329561
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the removal of oxygenated impurities from hydrocarbons such as isooctane and diisobutylene. More particularly, the present invention provides a process for producing diisobutylene and/or isooctane, which is substantially free of oxygenated contaminants, which contaminants if not removed interfere with the successful use of the hydrocarbons as internal combustion engine fuels.
2. Prior Art
The present invention is especially adapted for the production of high purity isooctane and/or diisobutylene from C
4
hydrocarbon streams comprising substantial quantities of unsaturated butenes. A C
4
stream containing unsaturated hydrocarbons can be obtained by cracking an appropriate saturated hydrocarbon stream or alternatively by dehydration of tertiary butyl alcohol which is co-produced in the Oxirane process. Technology is known for the dimerization of isobutylene from either source in high selectivity to produce diisobutylene and the subsequent hydrogenation of the diisobutylene to form isooctane. Illustrative of references demonstrating this particular art is Evans U.S. Pat. No. 5,877,372.
A disadvantage of prior procedures is that the diisobutylene and isooctane thus obtained contain small but significant amounts of oxygenated impurities. For example, the hydrocarbons may contain oxygenated impurities ranging from about 0.1 wt % to as much as 5 wt % of the isooctane or diisobutylene. Normally such oxygenated impurities are ethers, alcohols, acids, ketones and the like materials. The presence of oxygenated impurities in the diisobutylene or isooctane is undesirable in that these contaminants substantially decrease the utility of the diisobutylene or isooctane in internal engine combustion fuels such as gasoline blends.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the invention, diisobutylene is treated in order to convert oxygenated impurities contained therein to hydrocarbon and alcohol which are readily separated.
In accordance with another embodiment the present invention, a process is provided whereby diisobutylene is converted to isooctane and contained oxygenated impurities are converted to hydrocarbon and water in either a one-step or two-step procedure. In one practice of this embodiment, a one-step process, diisobutylene which is obtained by the dimerization of isobutylene and which contains oxygenated impurities, is hydrogenated in order to convert the diisobutylene to isooctane. As a feature of the hydrogenation, the conditions are adjusted so that during the hydrogenation conversion of the oxygenated impurities also takes place thus providing an end product of satisfactory purity. In another practice, a two-step process, isooctane is is obtained by the hydrogenation of diisobutylene at relatively mild conditions such that the oxygenated impurities are essentially unchanged and the isooctane thus formed is treated in a separate reaction step in order to convert the oxygenated impurities contained therein to hydrocarbon and water; hydrogen may or may not be employed.
DETAILED DESCRIPTION
Various methods are known in the prior art for the dimerization of isobutylene and for the production of isooctane. Reference can be made to U.S. Pat. No. 5,877,372 which illustrates a particularly favorable method for the production of isooctane wherein isobutylene is selectively oligomerized to mainly diisobutylene and the product diisobutylene is hydrogenated to isooctane. The disclosure of this patent is hereby incorporated herein in its entirety by reference. There are a great number of additional references which also illustrate the production of isooctane from a C
4
hydrocarbon stream by various procedures. Reference can be made to U.S. Patents such as U.S. Pat. Nos. 5,811,608, 5,847,252, 5,895,830, and the like. The disclosures of these references is hereby incorporated by reference it being understood that the dimerization of isobutylene and production of isooctane from C
4
hydrocarbon streams is by now a well known and well established art.
The diisobutylene produced by conventional procedures contains a small but contaminating amount of oxygenated materials, illustratively ethers, alcohols, ketones and like. An illustrative range of these impurities is 0.1 to 5 wt % based on diisobutylene. The presence of such impurities is sufficient to adversely effect the utility of the diisobutylene itself and, if carried through to product isooctane significantly lowers the value of the isooctane in a gasoline pool. It is extremely advantageous to provide a procedure whereby such oxygenated materials can conveniently be converted to non-deleterious materials. It should be noted, that due to the closeness in the boiling points of the oxygenated impurities and the various hydrocarbon materials, distillation is not a convenient method by which a separation can be accomplished.
In accordance with the present invention, in one particular embodiment, diisobutylene containing the oxygenated impurities is reacted at elevated temperature and pressure to convert the oxygenated impurities, eg. ethers, to hydrocarbon and alcohol which are readily separable. Diisobutylene substantially free of oxygenated impurities is readily obtained which has utility itself as a fuel component. In another embodiment, the impurities-containing diisobutylene is treated in one or two steps to produce isooctane free of the impurities. In the first embodiment of the invention described above, a diisobutylene stream containing the oxygenated impurities is subjected to a treatment whereby the oxygenated impurities are converted to hydrocarbon and alcohol or water. This treatment can be described as a high temperature ether cracking step whereby diisobutylene containing the oxygenates is heated to a temperature in the range of 50 to about 400° C. while in contact with suitable catalyst such as a nickel on silica catalyst. Although hydrogen can be used in this high temperature cracking, it is not necessary in order to accomplish the impurities conversion. The purified diisobutylene can be hydrogenated in conventional fashion to isooctane if desired.
Alternatively, in further embodiments of the invention, the diisobutylene containing oxygenated materials can be treated under conditions such that both hydrogenation of diisobutylene to isooctane takes place and also the ethers and other oxygenated materials contained therein are converted to hydrocarbon and water or alcohol. This hydrogenation can be carried out conveniently in either one or two steps. In a one step procedure the hydrogenation is carried out under conditions of sufficient severity to not only hydrogenate the diisobutylene but also to convert the oxygenated materials to hydrocarbon and water. Such a procedure is, however, less advantageous since side reactions tend to occur under the more severe conditions of hydrogenation. An alternative procedure is to stage the hydrogenation such that the great bulk is carried out under modest conditions whereby diisobutylene is selectively converted to isooctane and thereafter the conditions are made more severe for a relatively short period of time in order to accomplish the oxygenate conversions. These procedures will be illustrated in the following Examples.
REFERENCES:
patent: 4197185 (1980-04-01), Le Page et al.
patent: 5811608 (1998-09-01), Stine et al.
patent: 5847252 (1998-12-01), Stine et al.
patent: 5877372 (1999-03-01), Evans et al.
patent: 5895830 (1999-04-01), Stine et al.
Kahn Andrew P.
Kaminsky Mark P.
Webber Kenneth M.
Equistar Chemicals LP
Griffin Walter D.
Long William C.
Nguyen Tam M.
LandOfFree
Impurities removal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Impurities removal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Impurities removal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2584632