Chemistry of hydrocarbon compounds – Adding hydrogen to unsaturated bond of hydrocarbon – i.e.,... – Hydrocarbon is aromatic
Reexamination Certificate
2001-10-02
2002-10-08
Silverman, Stanley S. (Department: 1754)
Chemistry of hydrocarbon compounds
Adding hydrogen to unsaturated bond of hydrocarbon, i.e.,...
Hydrocarbon is aromatic
C585S260000, C585S261000, C585S266000
Reexamination Certificate
active
06462244
ABSTRACT:
BACKGROUND OF INVENTION
The field to which this invention pertains is hydrogenation catalysts, and more particularly, sulfur tolerant, aromatic hydrogenation catalysts and a process for their use.
DESCRIPTION OF THE RELATED ART
There is today a significant need in the petroleum industry for non-aromatic solvents, including liquid hydrocarbons which boil in the range of about 200 to 1100° F. Such products include, for example, aviation turbine fuel, diesel fuel, solvents, white oil, lube oil and the like. Products in this boiling range are conventionally produced by the hydrotreating and/or hydrocracking of various refinery feed streams, boiling in and above the desired product range. While hydrotreating and hydrocracking operations generally affect substantial partial hydrogenation of polynuclear aromatics, the resulting products still contain a relatively high percentage of monoaromatic hydrocarbons and a substantial amount of sulfur. Further hydrogenation of these products is desired in many cases to produce acceptable solvent products and to meet specifications for jet fuels and other such final products.
Other conventional hydrogenation applications include the hydrogenation of benzene to cyclohexane. One process for the production of cyclohexane comprises contacting a mixture of benzene, cyclohexane and hydrogen under hydrogenation conditions in the presence of a Group VI and Group VIII metal hydrogenation catalyst, such as is disclosed in U.S. Pat. No. 3,622,645. See also U.S. Pat. No. 3,869,521 which discloses a transition metal catalyst useful for the conversion of benzene to cyclohexane.
The hydrogenation of unsaturated hydrocarbons, particularly aromatic hydrocarbons, to corresponding saturated hydrocarbons using platinum and/or palladium catalysts is disclosed in U.S. Pat. No. 3,637,484. In this patent, platinum and/or palladium are deposited selectively by cationic exchange upon a silica/alumina co-gel or copolymer, which in turn is dispersed in a large pore alumina gel matrix.
U.S. Pat. No. 3,674,888 discloses a process for selectively hydrogenating unsaturated hydrocarbons in their liquid phase utilizing palladium on an alumina catalyst. The catalyst is the product resulting from contacting alumina agglomerates of a specific surface area with steam, admixing the agglomerate with a palladium compound and calcining the resulting mixture.
A significant problem that can occur with platinum and/or palladium catalysts is that they can be poisoned by sulfur compounds that may be present in the feed stream. A platinum and palladium catalyst for the selective hydrogenation of aromatics and olefins with some tolerance for sulfur and nitrogen is disclosed in U.S. Pat. Nos. 4,049,576 and 3,943,053. These patents teach a catalyst containing from 0.2 to 1 percent by weight of each of platinum and palladium impregnated on an inert carrier, preferably a high surface area, gamma alumina.
Another high surface area gamma alumina-based catalyst useful for the hydrogenation of unsaturated hydrocarbons is disclosed by U.S. Pat. No. 3,674,888. Other high surface area catalysts, preferably using a gamma alumina carrier, are disclosed in U.S. Pat. No. 4,713,363. See also U.S. Pat. No. 4,952,549.
In addition to alumina-based carriers, silica-alumina carriers onto which noble metals, such as platinum or palladium, are impregnated for the hydrogenation of petroleum feed streams are disclosed, for example, in U.S. Pat. No. 3,637,484. A catalyst with sulfur tolerance for the hydrogenation of aromatics, wherein the carrier comprises a surface-modified alumina/silica support, onto which noble metals have been impregnated, is disclosed in WO 98/35754. See also U.S. Pat. Nos. 3,461,181, 3,859,370 and 4,251,392.
Other catalyst containing palladium and/or platinum secured on inert alumina and/or silica carriers are disclosed in U.S. Pat. Nos. 2,911,357, 3,173,857, 3,271,327, 3,280,041, 3,549,720, 3,759,823 and 3,703,461, GB 1,501,346 and WO 98/35,754.
While some of these catalysts are useful for hydrogenating various unsaturated feed streams, there is still a need for improved hydrogenation catalysts.
In addition, prior art noble metal catalysts are still susceptible to poisoning from sulfur and/or nitrogen present in conventional feed streams. Thus, improved catalysts which have a tolerance for sulfur are also needed.
It is therefore an object of the invention to provide a novel hydrogenation catalyst.
It is another object of the invention to provide an improved hydrogenation catalyst for the conversion of aromatics in a feed stream, where the catalyst has high activity.
It is another object of the invention to provide an improved hydrogenation catalyst for the conversion of benzene to cyclohexane, where the catalyst has high activity and selectivity.
It is another object of the invention to provide an improved hydrogenation catalyst with a tolerance for low to medium levels of sulfur in a feed stream.
It is another object of the invention to provide an improved hydrogenation catalyst containing platinum and palladium on a transition alumina carrier.
It is another object of the invention to provide an improved hydrogenation catalyst for the removal of aromatics from a feed stream, where the catalyst comprises one or more noble metals, preferably platinum and palladium, placed on a predominantly theta alumina carrier.
These and other objects of the invention are obtained by the product and process of the present invention.
SUMMARY OF THE INVENTION
The invention is directed to an improved hydrogenation catalyst for the hydrogenation of aromatics and other unsaturated compounds in a hydrocarbon feed stream, which boils in the range from about 200 to about 1100° F., and which may contain up to about 150 ppmw of total sulfur. The catalyst of this invention includes from about 100 ppm to about 5 percent by weight of each of platinum and palladium, preferably from about 0.1 to about 1.0 percent platinum and from about 0.2 to about 2.0 percent palladium. The preferred molar ratio of platinum to palladium in the catalyst is from about 1 to 4 to about 1 to 7. The carrier for the catalyst is an inert alumina carrier, wherein the alumina preferably comprises at least about 50 percent theta (or delta) alumina, with the remaining portion of the carrier being preferably alpha alumina, preferably from about 1 to about 40 percent. Minor amounts of other transition aluminas may also be present.
The invention is also directed to a process for the hydrogenation of feed streams containing aromatic or other unsaturated hydrocarbons and less than about 150 ppmw of sulfur in contaminants by use of the above-described catalyst.
The invention is also directed to a process for the production of the above-referenced hydrogenation catalyst.
DETAILED DESCRIPTION OF THE INVENTION
The catalyst of the invention is preferably a bimetallic, Group VIII catalyst, wherein the Group VIII elements are preferably platinum and palladium, which are impregnated on an inert catalyst support or carrier. While other noble metals may be used for the catalyst, it has been discovered that superior hydrogenation catalysts are produced when platinum and palladium are utilized.
The catalyst support or carrier for the platinum and palladium is preferably a medium to low surface area alumina carrier, more preferably a predominantly theta (or delta) alumina carrier. Preferably the surface area of the carrier is from about 30 to about 150 m
2
/g, more preferably 30-110 m
2
/g, most preferably from about 60 to about 100 m
2
/g. Theta (or delta) alumina comprises at least about 50 percent of the carrier, preferably at least about 60 percent. In order to maintain a relatively low surface area of less than about 150 m
2
/g for the catalyst, up to about 40 percent of the carrier may also constitute an alpha alumina. Any combination of theta (or delta) alumina carrier and alpha alumina carrier which produces a carrier with a surface area within the preferred range is within the scope of the invention. Minor amounts of other transition aluminas may also be pr
Faris William M.
Hopkins P. Donald
Huang Dinah C.
Jerus Paul
Cox Scott R.
Nguyen Cam N.
Sũd-Chemie Inc.
Silverman Stanley S.
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