Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Phosphorus or compound containing same
Reexamination Certificate
2000-01-20
2003-01-21
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Phosphorus or compound containing same
C502S204000, C502S207000, C502S210000, C502S211000, C502S213000, C502S214000, C502S206000, C502S240000, C502S254000, C502S258000, C502S219000, C502S220000, C502S221000, C502S222000, C502S223000
Reexamination Certificate
active
06509289
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a catalyst composition useful for converting a C
9
+ aromatic compound to a C
6
to C
8
aromatic hydrocarbon, a process for producing the composition, and a process for using the composition in a hydrodealkylation process.
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. Recent efforts to convert gasoline to more valuable petrochemical products have therefore focused on the aromatization of gasoline to aromatic hydrocarbons by catalytic cracking in the presence of a catalyst. The aromatic hydrocarbons produced by the aromatization process include C
6
to C
8
hydrocarbons such as benzene, toluene and xylenes (hereinafter collectively referred to as BTX) which can be useful feedstocks for producing various organic compounds and polymers. However, heavier, less useful aromatic compounds are also produced during the aromatization process. It is, therefore, highly desirable to convert these compounds to the more useful BTX.
Though a metal oxide-promoted alumina such as Cr/Al
2
O
3
has been used as catalyst in a hydrodealkylation process, the conversion of a C
9
+ aromatic compound and the selectivity to BTX are generally not as high as one skilled in the art would desire. It is also well known to one skilled in the art that alumina is an acidic metal oxide containing acid sites. One of the possible reasons for such low conversion and low selectivity is probably due to the acidity of an alumina-based catalyst.
However, a catalyst used in the hydrodealkylation of these heavier aromatic compounds is generally deactivated in a rather short period because of depositions of carbonaceous material such as, for example, coke on the surface of the catalyst. Generally, the more active the catalyst is, the more rapid deposition of coke on the catalyst is observed.
Accordingly, there is an ever-increasing need to develop a catalyst and a process for converting these heavier and less useful aromatic compounds to the more valuable BTX hydrocarbons (hereinafter referred to as hydrodealkylation process) and, in the meantime, for suppressing the coke formation. Such development would also 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 C
9
+ aromatic compound 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 C
9
+ aromatic compounds to C
6
to C
8
aromatic compounds. An advantage of the catalyst composition is that it suppresses coke deposits thereon and exhibits high hydrodealkylation activity, satisfactory yield of xylenes and BTX, and good stability. 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 C
9
+ aromatic compound to a C
6
to C
8
aromatic hydrocarbon is provided. The composition is a metal oxide-promoted alumina having incorporated therein an acid site modifier wherein the metal of the metal oxide is selected from the group consisting of chromium, cobalt, molybdenum, nickel, rhodium, palladium, platinum, tungsten, and combinations of any two or more thereof.
According to a second embodiment of the invention, a process for producing a composition which can be used as catalyst in a hydrodealkylation process is provided. The process comprises, consists essentially of, or consists of (1) contacting an alumina, which can be optionally calcined before being contacted, with an acid site modifier precursor under a condition sufficient to incorporate the acid site modifier into the alumina to form an acid site-modified alumina wherein the precursor is selected from the group consisting of silicon-containing compounds, sulfur-containing compounds, boron containing compounds, magnesium-containing compounds, tin-containing compounds, titanium-containing compounds, zirconium-containing compounds, germanium-containing compounds, indium-containing compounds, lanthanum-containing compounds, cesium-containing compounds, and combinations of any two or more thereof; (2) contacting the acid site-modified alumina with a phosphorus-containing compound, contemporaneously with a metal compound whose metal is selected from the group consisting of chromium, cobalt, molybdenum, nickel, rhodium, palladium, platinum, tungsten, and combinations of any two or more thereof whereby a modified alumina is formed; and (3) either calcining the modified alumina or contacting the modified alumina with steam under a condition sufficient to effect the conversion of the metal compound to its corresponding metal oxide wherein the acid site modifier precursor, phosphorus-containing compound, and the metal compound are each present in an amount that is sufficient to convert each of them to corresponding oxide form. The process can also comprise, consist essentially of, or consist of, (1) contacting an alumina with both a phosphorus-containing compound and a metal compound, simultaneously, under a condition sufficient to incorporate the metal compound into the metal alumina to form a modified alumina wherein the alumina can be optionally calcined before being contacted; and the metal of the metal compound is selected from the group consisting of chromium, cobalt, molybdenum, nickel, rhodium, palladium, platinum, tungsten, and combinations of any two or more thereof; and (2) contacting the modified alumina with steam under a condition sufficient to effect the conversion of the metal compound to its corresponding metal oxide wherein the amount of the metal compound or phosphorus-containing compound is the amount that is sufficient to convert the metal compound or phosphorus compound to its oxide form.
According to a third embodiment of the present invention, a process which can be used for converting a C
9
+ aromatic compound to a C
6
to C
8
aromatic compound is provided which comprises, consists essentially of, or consists of, contacting a fluid which comprises a C
9
+ aromatic compound, optionally in the presence of an inert fluid such as a hydrogen-containing fluid, 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 C
9
+ aromatic compound to an aromatic hydrocarbon containing 6 to 8 carbon atoms per molecule.
According to a fourth embodiment of the invention a process which can be used for improving the yield of BTX or xylenes, or both, in a hydrodealkylation of a C
9
+ aromatic compound is provided. The process comprises, consists essentially of, or consists of contacting an alumina-containing catalyst composition with a steam. The catalyst composition can be the same as that disclosed in the first embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
According to the first embodiment of the invention, a composition which can be used as catalyst in a hydrodealkylation process for converting a C
9
+ aromatic compound to a C
6
to C
8
aromatic hydrocarbon is provided. The composition can comprise, consist essentially of, or consist of, a metal oxide-promoted alumina having incorporated therein, or impregnated thereon, an acid site modifier selected from the group consisting of silicon oxides, phosphorus oxides, sulfur oxides, boron oxides, magnesium oxides, tin oxides, titanium oxides, zirconium oxides, molybdenum oxides, germanium oxides, indium oxides, lanthanum oxides, cesium oxides, and combinations of any two or more thereof wherein the acid site modifier is present in the composition in a BTX selectivity-improving amount to improve the selectivity to BTX
Drake Charles A.
Wu An-hsiang
Bell Mark L.
Hailey Patricia L.
Phillips Petroleum Company
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