Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By ring formation from nonring moiety – e.g. – aromatization,...
Reexamination Certificate
2000-08-07
2001-05-22
Griffin, Steven P. (Department: 1754)
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
By ring formation from nonring moiety, e.g., aromatization,...
C585S651000, C502S063000, C502S064000, C502S071000, C502S077000, C502S080000
Reexamination Certificate
active
06235955
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a composition useful for converting a hydrocarbon to a C
6
to C
8
aromatic hydrocarbon and an olefin, to a process for producing the composition, and to a process for using the composition for converting a hydrocarbon to a C
6
to C
8
aromatic hydrocarbon and an olefin.
BACKGROUND OF THE INVENTION
It is well known to those skilled in the art that aromatic hydrocarbons and olefins are each a class of very important industrial chemicals which find a variety of uses in petrochemical industry. It is also well known to those skilled in the art that catalytically cracking gasoline-range hydrocarbons produces lower olefins such as, for example, propylene; and aromatic hydrocarbons such as, for example, benzene, toluene, and xylenes (hereinafter collectively referred to as BTX) in the presence of catalysts which contain a zeolite. The product of this catalytic cracking process contains a multitude of hydrocarbons including unconverted C
5
+alkanes; lower alkanes such as methane, ethane, and propane; lower alkenes such as ethylene and propylene; C
6
-C
8
aromatic hydrocarbons; and C
9
+aromatic compounds which contain 9 or more carbons per molecule. Recent efforts to convert gasoline to more valuable petrochemical products have therefore focused on improving the conversion of gasoline to olefins and aromatic hydrocarbons by catalytic cracking in the presence of zeolite catalysts. For example, a gallium-promoted zeolite ZSM-5 has been used in the so-called Cyclar Process to convert a hydrocarbon to BTX.
Olefins and aromatic hydrocarbons can be useful feedstocks for producing various organic compounds and polymers. However, the weight ratio of less useful C
1
-C
3
paraffins produced by the conversion process is generally too high. Additionally, a zeolite catalyst is generally deactivated in a rather short period, especially in a high sulfur and/or high polyaromatic environment, because of depositions of carbonaceous material, generally coke, on the surface of the catalyst. Moreover, the BTX purity in the product is generally not desirably high. Therefore, development of a catalyst and a process for converting hydrocarbons to the more valuable olefins and BTX and for reducing coke deposition would be a significant contribution to the art and to the economy.
SUMMARY OF THE INVENTION
An object of this invention is to provide a catalyst composition which can be used to convert a hydrocarbon to a C
6
to C
8
aromatic hydrocarbon and an olefin. Also an object of this invention is to provide a process for producing the catalyst composition. Another object of this invention is to provide a process which can employ the catalyst composition to convert a hydrocarbon to an olefin and a C
6
to C
8
aromatic hydrocarbon. An advantage of the catalyst composition is that it enhances the ratio of produced olefins to BTX. Another advantage of the catalyst composition is that it suppresses the deposition of coke during a hydrotreating process. A further advantage of the invention is that the production of less useful lower alkanes (C
1
-C
3
alkanes) is substantially suppressed. Other objects and advantages will becomes more apparent as this invention is more fully disclosed hereinbelow.
According to a first embodiment of the present invention, a composition which can be used as a catalyst for converting a hydrocarbon or a hydrocarbon mixture to an olefin and a C
6
to C
8
aromatic hydrocarbon is provided. The composition comprises a silylated zeolite-containing catalyst which comprises, consists essentially of, or consists of zeolite, a binder such as clay or silica, and optionally at least one metal or element selected from the group consisting of Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IIIB, Group IVB, Group VIB, of the Periodic Table of the Elements, CRC Handbook of Chemistry and Elements, 67th edition, 1986-1987 (CRC Press, Boca Raton, Fla.), and combinations of two or more thereof.
According to a second embodiment of the present invention, a process which can be used for producing a catalyst composition is provided. The process comprises the steps: (1) optionally contacting a zeolite with steam whereby a steamed zeolite is formed; (2) optionally contacting a zeolite or the steamed zeolite with an acid in an amount and under a condition effective to produce an acid-leached zeolite; (3) combining a zeolite, which can also be the steamed zeolite or the acid-leached zeolite, with a clay or silica and a promoter under a condition sufficient to bind the clay or silica to the zeolite to produce a clay-bound or silica-bound zeolite; (4) heat-treating the clay-bound or silica-bound zeolite to produce a modified zeolite; and (5) contacting the modified zeolite with a silylating agent wherein the promoter is selected from the group consisting of Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IIIB, Group IVB, Group VIB, of the Periodic Table of the Elements, CRC Handbook of Chemistry and Elements, 67th edition, 1986-1987 (CRC Press, Boca Raton, Fla.), and combinations of two or more thereof.
According to a third embodiment of the present invention, a process which can be used for converting a hydrocarbon or a hydrocarbon mixture to an olefin and a C
6
to C
8
aromatic hydrocarbon is provided which comprises, consists essentially of, or consists of, contacting a fluid which comprises a hydrocarbon or a hydrocarbon mixture with a catalyst composition, which can be the same as disclosed above in the first embodiment of the invention, under a condition effective to convert a hydrocarbon to an olefin and an aromatic hydrocarbon containing 6 to 8 carbon atoms per molecule wherein the weight ratio of the olefin to aromatic compound is enhanced.
DETAILED DESCRIPTION OF THE INVENTION
The catalyst composition of the first embodiment of the present invention can comprise, consist essentially of, or consist of a zeolite and a clay or silica. According to the present invention the weight ratio of clay or silica to zeolite can be any ratio that can enhance the production of an olefin from a hydrocarbon and can be in the range of from about 1:20 to about 20:1, preferably about 1:10 to about 10:1, and most preferably about 1:7 to about 5:1. The composition can also comprise, consist essentially of, or consist of, a zeolite, a clay or silica, and a promoter selected from the group consisting of Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Group IIB, Group IIIB, Group IVB, Group VIB, of the Periodic Table of the Elements, and combinations of two or more thereof.
The term “promoter” refers to a compound, a metal, or an element that, when incorporated in a zeolite, can suppress coke formation, or enhance olefin production, or both, in a hydrocarbon conversion process. The term “metal or element” used herein also includes a compound of the metal or element. For the interest of simplicity, any references to “metal” in the application, unless otherwise indicated, will include the elements listed above and a compound of any of the elements.
The term “substantial” or “substantially” signifies that which is more than trivial. The term “silylated catalyst” refers to a catalyst composition which can contain a zeolite having incorporated or impregnated thereon a promoter, binder, silica, or combinations of two or more thereof.
The weight ratio of each promoter to zeolite can be any ratio as long as the ratio can suppress the coke formation during a hydrocarbon conversion process. Generally, the ratio can be in the range of from about 0.01:1 to about 1:1, preferably about 0.03:1 to about 1:1, and most preferably 0.04:1 to 0.5:1. The composition can also comprise, consist essentially of, or consist of a zeolite, a clay or silica, a promoter, and optionally a second binder. The weight of the binder generally can be in the range of from about 1 to about 50, preferably about 5 to about 40, and most preferably 5 to 35 grams per 100 grams of the composition.
Any binders known to one skilled in the art for use with a
Drake Charles A.
Yao Jianhua
Griffin Steven P.
Nguyen Cam N.
Phillips Petroleum Company
Richmond, Hitchcock, Fish & Dollar
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