Chemistry of hydrocarbon compounds – Saturated compound synthesis – By alkyl transfer – e.g. – disproportionation – etc.
Reexamination Certificate
1998-12-30
2001-07-24
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Saturated compound synthesis
By alkyl transfer, e.g., disproportionation, etc.
C585S700000
Reexamination Certificate
active
06265630
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to processes for the disproportionation of pentane to alkanes containing fewer carbon atoms per molecule and alkanes containing more atoms per molecule in the presence of a catalyst composition. In one of its aspects the invention relates to the production of isobutane and isohexanes from a pentane-containing feedstock. In another of its aspects the invention relates to the use of a catalyst combining hydrofluoric acid (HF) with titanium tetrafluoride (TiF
4
) in the catalytic disproportionation of pentane. In another of its aspects the invention relates to the use of a sulfone diluent in combination with a disproportionation catalyst. In yet another of its aspects the invention also relates to a process for increasing the conversion of a pentane feedstock to desirable isobutanes and isohexanes.
It is known that generally Bronsted acids and Lewis acids can be used with a sulfone diluent as an effective catalyst combination for disproportionation of hydrocarbons, particularly with the use of hydrogen as a co-feed to the process. The present invention, however, provides within certain ranges of operating conditions the specific combination of hydrofluoric acid (a Bronsted acid), titanium tetrafluoride (a Lewis acid) and sulfolane (a sulfone diluent) that provides an unexpectedly effective catalyst for the disproportionation of pentane without the use of hydrogen as a co-feed to the process.
SUMMARY OF THE INVENTION
It is an object of this invention to at least partially convert pentane to alkanes having a fewer number of atoms per molecule, particularly isobutane, and to alkanes having a greater number of atoms per molecule, particularly isohexanes.
Another object of this invention is to employ a catalyst composition in the conversion of pentane by disproportionation to give an improved yield of isobutane and isohexane.
A further object of this invention is to provide the parameters within which the inventive catalyst composition can be most effectively employed to maximize conversion of pentane more specifically to isobutane or to isohexane.
In accordance with this invention a catalyst composition that is a mixture of two catalyst components, (1) hydrofluoric acid (HF) and (2) titanium tetrafluoride (TiF
4
), and (3) a sulfone diluent, preferably sulfolane, is employed at effective disproportionation conditions to convert pentane to alkanes having a fewer number of atoms per molecule, particularly isobutane, and to alkanes having a greater number of atoms per molecule, particularly isohexanes.
Other objects and advantages of the invention will become apparent from the detailed description and the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
The feed to the process of this invention can be any hydrocarbon-containing mixture that contains at least one pentane, either n-pentane or isopentane, preferably isopentane (2-methylbutane or [neopentane], or mixtures thereof. Generally, the feed contains more than about 50 weight-% pentane, preferably about 60-99.99 weight-% pentane. The feed can contain other hydrocarbons that do not interfere with the process of this invention, i.e. minor amounts of other alkanes, such as n-butane, isobutane, n-hexane and the like, alkenes (monoolefins). Other unsaturated compounds are to be substantially absent from the feed so that side reactions olefin oligomerization, and/or excessive ASO be avoided.
The catalyst composition useful in the process of this invention employs TiF
4
in combination with HF with a sulfone diluent present in an amount sufficient to enhance the effectiveness of the catalyst composition in the disproportionation of pentanes. The ratio of the total catalyst composition-TiF
4
, HF and the sulfone diluent- to the hydrocarbon feed on a weight/weight basis is in the range above about 2:1, preferably above about 3:1, and most preferably from about 2:1 to about 5:1.
Any sulfone that can be effectively combined in solution with HF and TiF
4
can be useful in the process of this invention. The sulfones preferred for employment in accordance with this invention include, but are not limited to, 3-methylsulfolane, 2,4-dimethylsulfolane and tetramethylenesulfone (sulfolane). Of these, sulfolane is currently most preferred.
Generally, to be effective, diluents are present in compositions in relatively large amounts. In the process of the present invention, however, the effective quantity of sulfone present in the catalyst composition ranges in an amount up to a ratio of sulfone:acid (HF and TiF
4
) of about 1:10 (volume/volume) for efficient conversions, particularly in the lower portion of the reaction temperature range.
The catalyst compounds, hydrofluoric acid and titanium tetrafluoride, can be employed in combination in a wide range of weight ratios in catalyst compositions suitable for use in the disproportionation of alkanes. When used, in accordance with this invention, in further combination with a sulfone diluent, the effective weight ratio of HF:sulfone is in a range of at least 9:1, preferably from about 9:1 to about 20:1, more preferably from about 9:1 to about 15:1.
TiF
4
is present in the catalytic composition in an amount in the range of about 1.5 mole % to about 10 mole %, preferably from about 3 mole % to about 8 mole %.
The disproportionation reaction temperatures suitable for the process of this invention are generally in the range of about 100° F. (38° C.) to about 190° F. (88° C.), preferably from about 110° F. (43° C.) to about 180° F. (82° C.). The reaction pressure can range from atmospheric to about 1000 psig, preferably from about 100 psig to about 500 psig. The reaction can be carried out as a batch process, as in a stirred autoclave, or as a continuous process. Whether the reaction is performed batchwise or on a continuous basis, the amounts (weight) of the catalyst components and the diluent used is determined by the weight of the hydrocarbon that is to be processed.
The product of the disproportionation reaction contains a variety of substances: HF, TiF
4
, sulfone diluent, propane, butanes, pentanes, hexanes, heptanes and higher alkanes. These various product components are separated from each other by any suitable means such as fractional distillation, either at an elevated pressure or, after depressurization, at atmospheric conditions. Generally the product is separated to obtain the specific product stream desired and to make the catalyst composition components and unconverted pentane available for recycle.
REFERENCES:
patent: 3679771 (1972-07-01), Hutson, Jr. et al.
patent: 4064189 (1977-12-01), Siskin et al.
patent: 4069268 (1978-01-01), Siskin et al.
patent: 4120912 (1978-10-01), Hulme
patent: 4472268 (1984-09-01), Olah
patent: 5449843 (1995-09-01), Achord et al.
patent: 5489727 (1996-02-01), Randolph et al.
patent: 2650309 (1977-05-01), None
Johnson Marvin M.
Randolph Bruce B.
Griffin Walter D.
Phillips Petroleum Company
Richmond, Hitchcock, Fish & Dollar
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