Processes employing hydrocarbon conversion catalyst

Details Processes employing hydrocarbon conversion catalyst Processes employing hydrocarbon conversion catalyst

2000-10-18

2004-08-31

Griffin, Walter D. (Department: 1764)

Chemistry of hydrocarbon compounds

Aromatic compound synthesis

By ring formation from nonring moiety, e.g., aromatization,...

C585S418000, C585S648000, C585S651000, C208S134000, C208S135000

Reexamination Certificate

active

06784332

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 (hydrocarbon conversion process).
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, 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 suppresses the deposition of coke during a hydrocarbon conversion process. 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 zeolite, optionally a binder, and 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 promoter, and optionally a binder under a condition sufficient to incorporate the promoter into the zeolite to produce a modified zeolite; and (4) heat-treating the modified zeolite to produce a promoted zeolite wherein the promoter is a 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 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 at least one saturated hydrocarbon 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.
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, a promoter, and optionally a binder. According to the present invention the weight ratio of binder to zeolite can be any ratio 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 promoter is a 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, 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 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.
Any binders known to one skilled in the art for use with a zeolite are suitable for use herein. Examples of suitable binders include, but are not limited to, a clay such as kaolinite, halloysite, vermiculite, chlorite, attapulgite, smectite, nontmorillonite (bentonite), illite, saconite, sepiolite, and palygorskite; aluminas such as for example &agr;-alumina and &ggr;-alumina; silicas; alumina-silica; aluminum phosphate; aluminum chlorohydrate; and combinations of two or more thereof. Because these binders are well known to one skilled in the art, description of which is omitted herein. The presently preferred binder, if employed, is silica because it is readily available.
The composition can further be characterized by having the following physical characteristics: a surface area as determined by the BET method using nitrogen in the range of from about 300 to about 600, preferably 350 to 500 m
2
/g; a pore volume in the range of from about 0.4 to about 0.8, preferably about 0.5 to about 0.75, and most preferably 0.6 to 0.75 ml/g; an average pore diameter in the range of from about 70 to about 300, preferably about 100 to about 250, and most preferably 125 to 200 Å; and a porosity of more than about 50%.
According to the present invention, any compound containing a metal or element selected from the group consisting of Group IA, Group IIA, Group IIIA, Group IVA, Group VA, Gro

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