Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By ring formation from nonring moiety – e.g. – aromatization,...
Reexamination Certificate
1996-08-12
2003-07-15
Norton, Nadine (Department: 1764)
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
By ring formation from nonring moiety, e.g., aromatization,...
C585S418000, C585S488000, C585S489000, C208S136000, C208S137000, C208S138000
Reexamination Certificate
active
06593503
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a catalyst composition useful for converting a hydrocarbon to a C
6
to C
8
aromatic hydrocarbon, 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.
BACKGROUND OF THE INVENTION
It is well known to those skilled in the art that aromatic hydrocarbons are 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 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, C
5
+ alkenes, C
5
+ cycloalkanes, or combinations of two or more thereof; lower alkanes such as methane, ethane, and propane; lower alkenes such as ethylene and propylene; and C
9
+ aromatic hydrocarbons. Recent efforts to convert gasoline to more valuable petrochemical products have therefore focused on improving the conversion of gasoline to more valuable aromatic hydrocarbons 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. The aromatic hydrocarbons can be useful feedstocks for producing various organic compounds and polymers. However, heavier, less useful aromatic compounds having 9 or more carbon atoms per molecule are also produced by the conversion process. Furthermore, a zeolite catalyst is generally deactivated in a rather short period because of depositions of carbonaceous material, generally coke, on the surface of the catalyst. Therefore, development of a catalyst and a process for converting non-aromatic hydrocarbons to the more valuable BTX in which the process and catalyst reduce the depositions of the carbonaceous material 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. 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 a C
6
to C
8
aromatic hydrocarbon. An advantage of the catalyst composition is that it enhances the production of BTX. 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 a C
6
to C
8
aromatic hydrocarbon is provided. The composition is an aluminosilicate which comprises, a silica, an alumina, and a metal selected from the group consisting of nickel, palladium, molybdenum, gallium, platinum and combinations of any two or more thereof wherein the weight ratio of elemental aluminum to elemental silicon is in the range of from about 0.002:1 to about 0.6:1 and the weight ratio of the metal to silicon is in the range of from about 0.0005:1 to about 0.1:1.
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) contacting a zeolite, which comprises or consists essentially of silicon and aluminum, with an acid in an amount and under a condition effective to reduce the aluminum content of the zeolite to produce an aluminum-reduced zeolite; (2) contacting said aluminum-reduced zeolite with a metal compound whose metal is selected from the group consisting of nickel, palladium, molybdenum, gallium, platinum, and combinations of any two or more thereof under a condition effective to impregnate the metal compound or the metal onto the aluminum-reduced zeolite to produce a metal-impregnated, alumina-reduced zeolite; and optionally (3) treating the metal-impregnated aluminum-reduced zeolite with a reducing agent under a condition effective to lower the oxidation state of the metal in the metal-impregnated, aluminum-reduced zeolite.
According to a third embodiment of the present invention, a process which can be used for converting a hydrocarbon or a hydrocarbon mixture to a C
6
to C
8
aromatic hydrocarbon for reducing the deposition of carbonaceous material on the surface of a catalyst 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 is the same as disclosed above in the first embodiment of the invention under a condition effective to convert a hydrocarbon to 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 is an aluminosilicate which can comprise, consist essentially of, or consist of a coke-reducing amount of a metal selected from the group consisting of nickel, palladium, molybdenum, gallium, platinum, and combinations of any two or more thereof.
According to the present invention, the term “coke” refers to a semi-pure carbon generally deposited on the surface of a metal wall or a catalyst. The weight ratio of aluminum to silicon can be any ratio that is effective to convert an aliphatic hydrocarbon to an aromatic hydrocarbon. Generally, the weight ratio of element aluminum to element silicon can be in the range of from about 0.002:1 to about 0.6:1, preferably about 0.005:1 to about 0.5:1, and most preferably 0.006:1 to 0.4:1. The weight ratio of the metal to element silicon can be in the range of from about 0.0001:1 to about 0.1:1, preferably about 0.0005:1 to about 0.05:1, more preferably about 0.001:1 to about 0.04:1, and most preferably 0.002:1 to 0.03:1.
Alternatively, the weight of element aluminum in the invention composition can be in the range of from about 0.1 to about 10, preferably about 0.2 to about 8, and most preferably 0.5 to 5 grams per 100 grams of the composition. The weight of element silicon in the invention composition can be in the range of from about 20 to about 50, preferably about 25 to about 45, and most preferably 30 to 40 grams per 100 grams of the composition. The weight of the metal can be in the range of from about 0.001 to about 10, preferably about 0.01 to about 5, and most preferably 0.1 to 2 grams per 100 grams of the composition. The composition can also be characterized by having the following physical characteristics: a micropore surface area, as determined by the BET method using nitrogen, in the range of from about 250 to about 600, preferably 300 to 500 m
2
/g; a micropore pore volume in the range of from about 0.01 to about 0.8, preferably about 0.01 to about 0.75 ml/g; an average micropore pore diameter in the range of from about 10 to about 300, preferably about 10 to about 250 Å; and a porosity of more than about 30%. Detailed physical property analyses are disclosed hereinbelow in the Examples section.
The aluminosilicate or zeolite component of the composition of the present invention can be prepared by combining any alumina and any silica in the element weight ratios disclosed above under any conditions sufficient to effect the formation of a zeolite according to any methods well known to one skilled in the art. However, it is presently preferred that the composition of the present invention be produced by the process disclosed in the second embodiment of the invention. In the first step of the second embodiment of the invention, a zeolite is contacted with an acid under a condition sufficient to effect the formation of an aluminum-reduced zeolite.
Any commercially available zeolites can be employed as a starting m
Drake Charles A.
Melton Ralph J.
Wu An-hsiang
Norton Nadine
Phillips Petroleum Company
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