Mineral oils: processes and products – Refining – Sulfur removal
Reexamination Certificate
1999-11-05
2001-10-02
Yildirim, Bekir L. (Department: 1764)
Mineral oils: processes and products
Refining
Sulfur removal
C208S143000, C585S269000
Reexamination Certificate
active
06296759
ABSTRACT:
BACKGOUND
The present invention is directed to a process for hydrogenation, hydroisomerization and/or hydrodesulfurization of a sulfur contaminant containing feedstock, and to a catalyst suitable for such a process.
When hydrogenation catalysts are used in the hydrogenation of petroleum distillates and derivatives thereof, often a problem presents itself in that the feed comprises sulfur and/or sulfur components, which adversely affect the life-time of the catalyst. In such processes conventional hydrogenation catalysts are usually applied, for instance supported nickel or platinum catalysts. To reduce this problem of deactivation, much attention has been paid to the removal of at least part of the sulfur and sulfur compounds from the gaseous or liquid feed prior, to the hydrogenation.
In general sulfur impurities are present in feeds as mercaptans or thiophenes, more in particular thiophene, dithiophene, benzothiophene, dibenzothiophene, as well as substitution products thereof, which sulfur impurities can be hydrogenated to H
2
S using a sulfidized Co—Mo catalyst. This method is also known as hydrodesulfurization (HDS).
The H
2
S produced therein is generally present in the gaseous phase. After separation from the liquid product stream the H
2
S is usually adsorbed from the gaseous phase and processed into elemental sulfur.
The product stream obtained from the HDS process still contains some sulfur. Typical sulfur levels of these product streams from HDS-units range from 0.1 to 500 ppm.
When nickel is used as a catalyst in the subsequent hydrogenation step, the major part of the sulfur is taken up by the nickel. As a result, the nickel catalyst will be deactivated in the course of time.
Similar problems to those described above may occur in hydroisomerization processes catalyzed by a metal catalyst on a support. In these processes, the carbon chain of a paraffin is converted into a different carbon chain having the same carbon to hydrogen ratio.
While the deterioration of nickel catalysts caused by sulfur poisoning is in practice an irreversible process, noble metal catalysts retain part of their activity in the presence of sulfur contaminants. The sensitivity of noble metals to sulfur is related to the properties of the support and the metal(s) used.
In U.S. Pat. No. 3,943,053 it has been proposed to use a catalyst of an alloy of platinum and palladium in a weight ratio of approximately 1:3 on a chlorinated alumina support for the hydrogenation of aromatics and olefins present in hydrocarbon fractions containing sulfur and nitrogen compounds. This catalyst was reported to decrease the amount of aromatics in an effluent by 66% compared to catalysts of the single metals.
The French patent application 2 569 995 describes the use of a catalyst based on vermiculite having a molar ratio of silica:alumina of at least 12:1 and a high specific surface area. The catalyst further comprises at least one metal or compound thereof chosen from Group VIII of the Periodic Table. The most preferred catalyst described in said French patent application comprises at least one oxide of a metal chosen from Group VIII of the Periodic Table in combination with at least one oxide of a metal chosen from Group VI of the Periodic Table on said vermiculite support.
The European patent application 0 669 162 discloses a catalyst for a process for reducing the aromatic content of a hydrocarbon stream. Said catalyst comprises a specific silica-alumina carrier on which one or more metals of Group VIII of the Periodic Table are deposited.
A comparable catalyst is disclosed in EP-A 582 347.
A disadvantage of this catalyst is that the specific silica-alumina carrier is obtained from a solution of an aluminum alcoholate and/or carboxylate and a silicon alcoholate and/or varboxlyate. The use of these organic starting materials for preparing the carrier is environmentally unattractive. Furthermore, the preparation of the carrier involves the extrusion of a viscous paste, which is an additional process step.
Other catalysts of platinum and palladium are disclosed in U.S. Pat. No. 5,308,914 and international patent application WO-A-94/19429. In the first document the disclosed catalyst is supported on a zeolite Y support and in the latter on a zeolite beta support.
Although the catalysts of platinum and palladium on zeolite supports appear to be more active than those on e.g. alumina, they have some disadvantages. It was found that hydrogenation, hydroisormerization and/or hydrodesulfurization using a catalyst based on platinum, palladium or a comination thereof on a zeolite support tends to become more difficult when the used feedstock is heavier. Furthermore, some of these zeolites are expensive materials, thus rendering the use of catalysts on these zeolite supports economically less attractive.
In view of the above, there is a need for an improved process for hydrogenation, hydroisomerization and/or hydrodesulfurization of sulfur containing feedstocks.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a process for hydrogenation, hydroisomerization and/or hydrodesulfurization of a sulfur contaminant containing feedstock, wherein a catalyst is used which has a low sulfur sensitivity.
Another object of the invention is to provide a process for hydrogenation, hydroisomerization and/or hydrodesulfurization of a sulfur contaminant containing feedstock, wherein a catalyst is used which comprises a support consisting of beads having high mechanic strength, which beads are prepared in an environmentally attractive manner.
It is a further object of the invention to provide a process for hydrogenation, hydroiacmrization and/or hydrodesulfurization of a sulfur contaminant containing feedstock, wherein a catalyst is used which has a high hydrogenation, hydroisomerization and/or hydrodesulfurization activity.
Still another object of the invention is to provide a process for hydrogenation, hydroisomerization and/or hydrodesulfuritation of a sulfur contaminant containing feedstock, wherein both light and heavy feedstocks may be hydrogenated, hydroisomerized and/or hydrodesulfurized.
Yet another object of the invention is to provide a process for hydrogenation, hydroisomerization and/or hydrodesulfurization of a sulfur contaminant containing feedstock, which process combines the above objects in an optimal manner, i.e. wherein a catalyst having a well-balanced, fine-tuned profile of all the above desired qualities and characteristics is used.
The present invention is based on the surprising discovery, that the use of a non-crystalline, acidic silica-alumina support, which support is obtained by sol-gel techniques, greatly improves the above-mentioned characteristics of catalysts based on platinum, palladium or combinations thereof, and having a degree of dispersion of at least 0.3, in a process for hydrogenation, hydroisomerization and/or hydrodesulfuriation.
DETAILED DESCRIPTION OF THE INVENTION
The present invention accordingly is directed to a process for hydrogenation, hydroisomarization and/or hydrodesulfurization of a sulfur contaminant containing hydrocarbon feedstock, wherein the feedstock is contacted in the presence of hydrogen gas with a catalyst having a dispersion degree of at least 0.3, at temperatures in the range of from 50 to 350° C., which catalyst comprises platinum, palladium or a combination thereof on a non-crystalline, acidic silica-alunna support, which support is obtained by sol-gel techniques, comprising the dropwise addition of an aqueous sol of inorganic salts of aluminum and silicon through an oil-phase to an alkaline water phase, and wherein the ratio of Si to Al is from 1:10 to 200:1.
An important and surprising advantage of the process of the invention resides therein that the support of the used catalyst consists of beads which have a much higher mechanical strength than the conventional extrudate supports. At the same time, the activity of the noble metal of a catalyst which is used in a process according to the invention is about equal or higher compared to that o
Berben Pieter Hildegardus
Reesink Bernard Hendrik
Vaarkamp Marinus
Engelhard Corporation
Miller Stephen I.
Yildirim Bekir L.
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