Mineral oils: processes and products – Refining – Sulfur removal
Reexamination Certificate
1998-06-09
2001-01-09
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Refining
Sulfur removal
C208S213000, C208S060000, C208S058000, C208S086000, C208S089000
Reexamination Certificate
active
06171477
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the refining and conversion of the heavy fractions of hydrocarbon distillates containing, inter alia, sulphur impurities. It relates more particularly to a process which allows the conversion, at low pressure, at least in part, of a hydrocarbon charge, for example, a vacuum distillate obtained by direct distillation of a crude petroleum, into good quality petrol and diesel light fractions and into a heavier product which may be used as a charge for catalytic cracking in a conventional catalytic cracking plant in a fluidised bed and/or in a catalytic cracking plant in a fluidised bed comprising a double regeneration system and optionally a cooling system for the catalyst at the regeneration stage. The present invention also relates in one of these aspects to a process for the production of petrol and/or diesel comprising at least one catalytic cracking step in a fluidised bed.
SUMMARY OF THE INVENTION
One of the objects of the present invention is to produce, from a certain particular fraction of hydrocarbons which will be defined in the rest of the description, by partial conversion of said fractions, lighter fractions which are easy to exploit, such as motor fuels: petrol and diesel.
Within the scope of the present invention, the conversion of the charge to lighter fractions is usually between 20 and 75% and most often between 25 and 60% and even limited to about 50%.
The charges which are treated within the scope of the present invention are vacuum distillates of direct distillation, vacuum distillates originating from a conversion process such as, for example, those derived from coking, a hydroconversion in a fixed bed such as those originating from the HYVAHL® processes for the treatment of heavies, developed by the applicant, or processes for the hydrotreatment of heavies in a boiling bed such as those originating from the H-OIL® processes, oils deasphalted with solvent, for example, oils deasphalted with propane, butane or pentane which originate from the deasphalting of a vacuum residuum of direct distillation or of vacuum residua originating from the HYVAHL® or H-OIL® processes. The charges may also be formed by mixing these various fractions in any proportions, particularly deasphalted oil and vacuum distillate. They may also contain light cycle oil (LCO) of various origins, high cycle oil (HCO) of various origins and also diesel cuts originating from catalytic cracking generally having a distillation interval from about 150° C. to about 370° C. They may also contain aromatic extracts obtained within the context of the production of lubricating oils.
The object of the present invention is to obtain a product with a low sulphur content particularly under conditions of relatively low pressure so as to limit the cost of the investment required. This process makes it possible to obtain a petrol type motor fuel containing less than 10 ppm by mass of sulphur, thus complying with the most stringent specifications in terms of sulphur content for this type of fuel, and this from a charge containing more than 3% by mass of sulphur. Another particularly important aspect is that a diesel type motor fuel is obtained having a sulphur content of less than 500 ppm and a residuum whose initial boiling point is, for example, about 370° C., which may be passed as a charge or part of a charge to a conventional catalytic cracking step or to a reactor for the catalytic cracking of residuum, such as a double regeneration reactor, and preferably to a conventional catalytic cracking reactor.
In its broadest form, the present invention is defined as a process for the conversion of a hydrocarbon fraction having a sulphur content of at least 0.5%, often at least 1% and very often at least 2% by weight and an initial boiling point of at least 360° C., often at least 370° C. and most often at least 380° C., and a final boiling point of at least 500° C., often at least 550° C., and which may even be higher than 600° C. or even 700° C., characterised in that it comprises the following steps:
a) the hydrocarbon charge is treated in a treatment section in the presence of hydrogen, said section comprising at least one reactor containing at least one hydrodesulphurisation catalyst in a fixed bed under conditions that make it possible to obtain a liquid effluent with a reduced sulphur content;
b) at least part, and often all, of the hydrodesulphurised liquid effluent originating from step a) is passed to a treatment section in the presence of hydrogen, said section comprising at least one three-phase reactor containing at least one hydrotreatment catalyst in a boiling bed operating with an ascending stream of liquid and gas, said reactor containing at least one means of withdrawing the catalyst from said reactor situated near the bottom of the reactor and at least one means of making up fresh catalyst in said reactor situated near the top of said reactor;
c) at least a part, and often all, of the product obtained in step b) is passed to a distillation zone from which are recovered a gas fraction, a petrol type motor fuel fraction, a diesel type motor fuel fraction and a liquid fraction which is heavier than the diesel type fraction.
According to one variant, the heavier liquid fraction of hydroconverted charge originating from step c) is passed to a catalytic cracking section [stage d)] in which it is treated under conditions that make it possible to produce a gas fraction, a petrol fraction, a diesel fraction and a slurry fraction.
The gas fraction obtained in steps c) or d) usually contains mainly saturated and unsaturated hydrocarbons having 1 to 4 carbon atoms in their molecules (methane, ethane, propane, butanes, ethylene, propylene, butylenes). The petrol type fraction obtained in step c) is passed, for example, at least in part and preferably wholly to the fuel pool. The diesel type fraction obtained in step c) is passed, for example, at least in part and preferably wholly to the fuel pool. According to another embodiment of the invention, at least a part of the diesel type fraction obtained in step c) is returned to step a). The slurry fraction obtained in step d) is passed most often at least in part or even wholly to the heavy fuel pool of the refinery, generally after separation of the fine particles which it contains in suspension. In another embodiment of the invention, this slurry fraction is returned at least in part and even wholly to the entrance of the catalytic cracking unit of step d).
The conditions of step a) for treating the charge in the presence of hydrogen are usually as follows: In the desulphurisation zone, at least one fixed bed of conventional hydrodesulphurisation catalyst is used, and preferably at least one of the catalysts described by the applicant, in particular, at least one of those described in the patents EP-B-113297 and EP-B-113284. Operations are usually carried out at an absolute pressure of 2 to 35 MPa, often 5 to 20 MPa and most often 6 to 10 MPa at a temperature of about 300 to about 500° C. and often about 350° C. to about 450° C. The VVH and the hydrogen partial pressure are important factors which are chosen as a function of the characteristics of the charge to be treated and of the conversion required. Most often, the VVH is situated in a range from about 0.1 to about 5 and preferably about 0.5 to about 2. The amount of hydrogen mixed with the charge is usually about 100 to about 5000 normal cubic meters (Nm
3
) per cubic meter (m
3
) of liquid charge and most often about 200 to about 1000 Nm
3
/m
3
and preferably about 300 to about 500 Nm
3
/m
3
. It is useful to operate in the presence of hydrogen sulphide and the partial pressure of the hydrogen sulphide is usually about 0.002 times to about 0.1 times and preferably about 0.005 times to about 0.05 times the total pressure. In the hydrodesulphurisation zone, the ideal catalyst must have a considerable hydrogenating capacity so as to bring about thorough refining of the products and to obtain a substantial lowering of the sulphur co
Billon Alain
Duplan Jean-Luc
Kressmann St{acute over (e)}phane
Morel Fr{acute over (e)}d{acute over (e)}ric
Griffin Walter D.
Institut Francais du Pe'trole
Millen White Zelano & Branigan
Nguyen Tam M.
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