Mineral oils: processes and products – Refining – Sulfur removal
Reexamination Certificate
2000-06-26
2003-09-23
Norton, Nadine G. (Department: 1764)
Mineral oils: processes and products
Refining
Sulfur removal
C208S213000, C208S217000, C208S21600R, C208S089000, C208S058000, C208S059000
Reexamination Certificate
active
06623628
ABSTRACT:
The present invention relates to hydrotreatment of hydrocarbon fractions, for example middle distillates, to produce hydrocarbon fractions with a low sulphur, nitrogen and aromatic compound content particularly for use in the field of internal combustion engine fuels. These hydrocarbon fractions include jet fuel, diesel fuel, kerosine and gas oils. More particularly, the invention relates to the production of a fuel for a compression ignition engine. In this field, the invention relates to a process for transforming a middle distillate and more particularly a gas oil cut to produce a dearomatised and desulphurised fuel with a high cetane number.
Currently, gas oil cuts, whether derived from straight run distillation of a crude or from a catalytic cracking process, still contain non-negligible quantities of aromatic compounds, nitrogen-containing compounds and sulphur-containing compounds. The current legislation of the majority of industrialised countries requires that the fuel for use in engines must contain a quantity of sulphur of less than about 500 parts per million by weight (ppm). In the vast majority of these countries, there are no current regulations imposing a maximum content for aromatic compounds and for nitrogen. However, a few countries or states, like Sweden and California, are envisaging limiting the aromatics content to a value of less than 20% by volume or even less than 10% by volume, and some experts even believe that this content could be limited to 5% by volume. In Sweden in particular, some classes of diesel fuel already have to comply with very strict specifications. Thus in that country, class II diesel fuel must not contain more than 50 ppm of sulphur and more than 10% by volume of aromatic compounds, and class I diesel must not contain more than 10 ppm of sulphur and 5% by volume of aromatic compounds. In Sweden at the moment, class III diesel fuel must contain less than 500 ppm of sulphur and less than 25% by volume of aromatic compounds. Similar limits are also in force for the sale of that type of fuel in California.
Meanwhile, motorists in a number of countries have been pressing for legislation obliging refiners to produce and sell a fuel with a cetane number of a minimum value. Current French legislation requires a minimum cetane number of 49, but in the near future this minimum value will be at least 50 (as is already the case for class I fuel in Sweden), probably at least 55, and most probably 55 to 65.
A number of specialists seriously envisage the future possibility of having a standard imposed on the nitrogen content of less than about 200 ppm, for example, and quite possibly less than 100 ppm. A low nitrogen content can result in better stability of the products and will be of general interest both to the vendor and to the manufacturer.
Thus it is necessary to develop a reliable and effective process for producing a product with improved characteristics both as regards the cetane number and as regards the aromatic compound, sulphur and nitrogen contents from conventional straight run gas oil cuts or from catalytically cracked gas oil cuts (LCO cut) or from another conversion process (coking, visbreaking, residue hydroconversion, etc.). It is particularly important, and this constitutes one of the advantages of the process of the present invention, to produce a minimum of gaseous hydrocarbon compounds so as to obtain an effluent which is directly and integrally useable as a very high quality fuel cut. Further, the process of the present invention can allow production over a long period and without the need for regenerating the catalysts used, which has the advantage of being stable over time. Further, in one implementation of the invention a further advantage resides in the hydrogen recycle. In this implementation, only a fraction of the hydrogen-containing gas is sent to a drying-desulphurising zone before being recycled, enabling the size of the dryer-desulphuriser to be reduced along with the quantity of material required to carry out this operation. In a further variation of the invention, the unit start-up is facilitated when using a furnace to adjust the temperature of the feed entering the second reactor.
U.S. Pat. No. 5,114,562 describes a process for hydrotreating a middle distillate in at least two consecutive steps to produce desulphurised and dearomatised hydrocarbon cuts, comprising a first hydrodesulphurisation step from which the effluent is sent to a hydrogen stripping zone to eliminate the hydrogen sulphide it contains, then the desulphurised liquid fraction obtained is sent to a second, hydrogenation, zone comprising at least two reactors operating in series in which the aromatic compounds are hydrogenated. In this disclosure, the hydrogen used in the stripping zone is makeup hydrogen which has to be added to the process, and after condensation by cooling, the hydrocarbon compounds entrained during stripping are re-introduced into the first hydrodesulphurisation step. The gas separated from the hydrocarbon compounds in the condensation step is treated by washing with an amine solution to eliminate the hydrogen sulphide it contains and is then sent to the second, hydrogenation, zone, then the effluent leaving the hydrogenation zone is separated into a desired liquid fraction and a gaseous fraction which is sent as a mixture with fresh feed to the inlet to the first hydrodesulphurisation step. This mode of operating has a number of disadvantages. Thus the hydrocarbons entrained at the head of the stripper, which are light compounds and which are recycled to the hydrodesulphurisation step, vaporise in this step and thus cause a reduction in the partial pressure of the hydrogen which is not favourable to good hydrodesulphurisation. A further disadvantage is the necessity of having a recycling pump which increases the cost of the equipment and the running costs.
U.S. Pat. No. 5,110,444 describes a process comprising hydrotreatment of a middle distillate in at least three distinct steps. The effluent from the first hydrodesulphurisation step is sent to a hydrogen stripping zone to eliminate the hydrogen sulphide it contains, then the desulphurised liquid fraction obtained is sent to a first hydrogenation zone the effluent from which is sent to a second stripping zone which is distinct from the stripping zone following the hydrodesulphurisation zone. Finally, the liquid portion from the second stripping zone is sent to a second hydrogenation zone. The light hydrocarbons entrained overhead from the first hydrogen stripper are recycled to the hydrodesulphurisation step which is deleterious to the efficiency of this step since in vaporising, these compounds reduce the partial pressure of the hydrogen. Further, this recycling involves the obligatory use of a recycling compressor which increases the equipment costs and the running costs.
The present invention presents a solution which can largely overcome the disadvantages of prior art processes. However, the disclosure of the prior art and in particular that of the documents cited in the text of the present invention form an integral part of the knowledge of the skilled person and all of the features must be considered to be included in the present description.
In its broadest scope, the present invention thus concerns a process for hydrotreating a hydrocarbon fraction such as a middle distillate, and in particular for transforming a gas oil cut to produce a high cetane number, dearomatised and desulphurised fuel in at least two successive steps. It also concerns the fuel obtained by said process. In the present description, the term “middle distillate” designates hydrocarbon fractions boiling in the range about 130° C. to about 385° C., normally in the range about 140° C. to about 375° C. and usually in the range about 150° C. to about 370° C., determined using the appropriate ASTM method. The process of the present invention is also of application in the treatment of hydrocarbon fractions with a boiling point in the naphtha range. This process can be used to produce hydrocarbon
Bronner Charles
Carpot Laurence
Heinrich Gérald
Plain Cécile
Millen White Zelano & Branigan P.C.
Norton Nadine G.
LandOfFree
PROCESS FOR HYDROTREATING A MIDDLE DISTILLATE IN TWO... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with PROCESS FOR HYDROTREATING A MIDDLE DISTILLATE IN TWO..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and PROCESS FOR HYDROTREATING A MIDDLE DISTILLATE IN TWO... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3067599