Mineral oils: processes and products – Refining – Sulfur removal
Reexamination Certificate
2000-10-13
2002-11-19
Norton, Nadine G. (Department: 1764)
Mineral oils: processes and products
Refining
Sulfur removal
C208S20800M, C208S247000
Reexamination Certificate
active
06482314
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the removal of sulfur from fluid streams of cracked-gasolines and diesel fuels. In another aspect this invention relates to sorbent compositions suitable for use in the desulfurization of fluid streams of cracked-gasolines and diesel fuel. A further aspect of this invention relates to a process for the production of sulfur sorbents for use in the removal of sulfur bodies from fluid streams of cracked gasolines and diesel fuels.
BACKGROUND OF THE INVENTION
The need for cleaner burning fuels has resulted in a continuing world wide effort to reduce sulfur levels in gasoline and diesel fuels. The reducing of gasoline and diesel sulfur is considered to be a means for improving air quality because of the negative impact the fuel sulfur has on the performance of automotive catalytic converters. The presence of oxides of sulfur in automotive engine exhaust inhibits and may irreversibly poison noble metal catalysts in the converter. Emissions from an inefficient or poisoned converter contain levels of non-combusted, non-methane hydrocarbon and oxides of nitrogen and carbon monoxide. Such emissions are catalyzed by sunlight to form ground level ozone, more commonly referred to as smog.
Most of the sulfur in gasoline comes from the thermally processed gasolines. Thermally processed gasolines such, as for example, thermally cracked gasoline, visbreaker gasoline, coker gasoline and catalytically cracked gasoline (hereinafter collectively called “cracked-gasoline”) contains in part olefins, aromatics, and sulfur-containing compounds.
Since most gasolines, such as for example automobile gasolines, racing gasolines, aviation gasoline and boat gasolines contain a blend of at least in part cracked-gasoline, reduction of sulfur in cracked-gasoline will inherently serve to reduce the sulfur levels in such gasolines.
The public discussion about gasoline sulfur has not centered on whether or not sulfur levels should be reduced. A consensus has emerged that lower sulfur gasoline reduces automotive emissions and improves air quality. Thus the real debate has focused on the required level of reduction, the geographical areas in need of lower sulfur gasoline and the time frame for implementation.
As the concern over the impact of automotive air pollution continues, it is clear that further efforts to reduce the sulfur levels in automotive fuels will be required. While the current gasoline products contain about 330 part per million with continued efforts by the Environmental Protection Agency to secure reduced levels, it has been estimated that gasoline will have to have less than 50 part per million of sulfur by the year 2010. (See Rock, K. L., Putman H. M., Improvements in FCC Gasoline Desulfurization via Catalytic Distillation” presented at the 1998 National Petroleum Refiners Association Annual Meeting (AM-98-37)).
In view of the ever increasing need to be able to produce a low sulfur content automotive fuel, a variety of processes have been proposed for achieving industry compliance with the Federal mandates.
One such process which has been proposed for the removal of sulfur from gasoline is called hydrodesulfurization. While hydrodesulfurization of gasoline can remove sulfur-containing compounds, it can result in the saturation of most, if not all, of the olefins contained in the gasoline. This saturation of olefins greatly affects the octane number (both the research and motor octane number) by lowering it. These olefins are saturated due to, in part, the hydrodesulfurization conditions required to remove thiophenic compounds (such as, for example, thiophene, benzothiophene, alkyl thiophenes, alkylbenzothiphenes and alkyl dibenzothiophenes), which are some of the most difficult sulfur-containing compounds to removed. Additionally, the hydrodesulfurization conditions required to remove thiophenic compounds can also saturate aromatics.
In addition to the need for removal of sulfur from cracked-gasolines, there is also presented to the petroleum industry a need to reduce the sulfur content of diesel fuels. In removing sulfur from diesel by hydrodesulfurization, the cetane is improved but there is a large cost in hydrogen consumption. This hydrogen is consumed by both hydrodesulfurization and aromatic hydrogenation reactions.
Thus there is a need for a process wherein desulfurization without hydrogenation of aromatics is achieved so as to provide a more economical process for the treatment of diesel fuels.
As a result of the lack of success in providing successful and economically feasible process for the reduction of sulfur levels in both cracked-gasolines and diesel fuels, it is apparent that there is still needed a better process for the desulfurization of both cracked-gasolines and diesel fuels which has minimal affect of octane while achieving high levels of sulfur removal.
It is thus an object of the present invention to provide a novel sorbent system for the removal of sulfur from fluid streams of cracked-gasolines and diesel fuels.
Another object of this invention is to provide a process for the production of novel sorbents which are useful in the desulfurization of such fluid streams.
Another object of this invention is to provide a process for the removal of sulfur-containing compounds from cracked-gasolines and diesel fuels which minimize saturation of olefins and aromatics therein.
A still further object of this invention is to provide a desulfurized cracked-gasoline that contains less than about 100 parts per million of sulfur based on the weight of the desulfurized cracked-gasoline and which contains essentially the same amount of olefins and aromatics as were in the cracked-gasoline from which it is made.
Other aspects, objects and the several advantages of this invention will be apparent from the following description of the invention and the appended claims.
SUMMARY OF THE INVENTION
The present invention is based upon our discovery that through the utilization of cobalt in a substantially reduced valence state, preferably zero, in a sorbent composition there is achieved a novel sorbent composition which permits the ready removal of sulfur from streams of cracked-gasolines or diesel fuels with a minimal effect on the octane rating of the treated stream.
Accordingly, in one aspect of the present invention there is provided a novel sorbent suitable for the desulfurization of cracked-gasolines or diesel fuels which is comprised of zinc oxide, silica, alumina and cobalt wherein the valence of the cobalt is substantially reduced and such reduced valence cobalt is present in an amount to permit the removal of sulfur from cracked-gasolines or diesel fuels.
In accordance with another aspect of the present invention, there is provided a process for the preparation of a novel sorbent composition which comprises admixing zinc oxide, silica and alumina so as to form a wet mix, dough, paste or slurry thereof, particulating the wet mix, dough, paste or slurry thereof so as to form a particulate granule, extrudate, tablet, sphere, pellet or microsphere thereof; drying the resulting particulate; calcining the dried particulate; impregnating the resulting solid particulate with a cobalt or a cobalt-containing compound; drying the resulting impregnated solid particulate composition, calcining the dried particulate composition and reducing the calcined product with a suitable reducing agent, such as hydrogen, so as to produce a sorbent composition having a substantial zero valence cobalt content in an amount which is sufficient to permit the removal with same of sulfur from a cracked-gasoline or diesel fuel stream.
In accordance with a further aspect of the present invention, there is provided a process for the desulfurization of a cracked-gasoline or diesel fuel stream which comprises desulfurizing in a desulfurization zone a cracked-gasoline or diesel fuel with a solid-reduced cobalt metal-containing sorbent, separating the desulfurized cracked-gasoline or diesel fuel from the sulfurized sorbent, regenerating at least a portion of the sulfurized-solid
Jolly Lynda S.
Norton Nadine G.
Phillips Petroleum Company
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