Mineral oils: processes and products – Chemical conversion of hydrocarbons – With preliminary treatment of feed
Reexamination Certificate
1998-10-14
2001-03-27
Myers, Helane (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
With preliminary treatment of feed
C208S058000, C208S210000
Reexamination Certificate
active
06207041
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to refining and converting heavy fractions of hydrocarbon distillates containing sulphur-containing impurities, inter alia. More particularly, it relates to a process for converting at least a portion of a hydrocarbon feed, for example a vacuum distillate obtained by straight-run distillation of a crude oil into good quality light gasoline and diesel fractions and into a heavier product which can be used as a feed for catalytic cracking in a conventional fluidised bed catalytic cracking unit and/or in a fluidised bed catalytic cracking unit comprising a double regeneration system and possibly a system for cooling the catalyst at the regeneration stage. In one aspect, the present invention also relates to a process for the production of gasoline and/or diesel comprising at least one fluidised bed catalytic cracking step.
BACKGROUND OF THE INVENTION
The prior art, in particular U.S. Pat. Nos. 4,344,840 and 4,457,829, describes processes for treating heavy hydrocarbon cuts comprising a first treatment step carried out in the presence of hydrogen in a reactor containing an ebullated bed of catalyst followed by a second step of fixed bed hydrotreatment. The descriptions illustrate the case of fixed bed treatment in the second step of a light gas fraction of the product from the first step.
One of the aims of the present invention is to produce, from certain particular hydrocarbon fractions which will be defined in the following description, by means of partial conversion of those fractions, lighter fractions which can easily be upgraded such as middle distillates (engine fuels: gasoline and diesel) and base oils.
Within the context of the present invention, the degree of conversion of the feed into lighter fractions is normally in the range 10% to 75%, or even 100% when the unconverted heavy fraction is recycled, and is usually in the range 25% to 60%, or even limited to 50%.
The feeds treated in the present invention are straight run vacuum distillates, vacuum distillates from a conversion process such as those from coking, from fixed bed hydroconversion such as those from HYVAHL® processes for treating heavy fractions developed by the Applicant, or from ebullating bed heavy fraction hydrotreatment processes such as those from H-OIL® processes, or from solvent deasphalted oils, for example propane, butane or pentane deasphalted oils originating from deasphalting a straight run vacuum residue or vacuum residues from HYVAHL® or H-OIL® processes. The feeds can also be formed by mixing those various fractions in any proportions, in particular deasphalted oil and vacuum distillate. They can also contain light cycle oil (LCO) of various origins, high cycle oil (HCO) of various origins and diesels from catalytic cracking generally having a distillation range of about 150° C. to about 370° C. They can also contain aromatic extracts and paraffins obtained from the manufacture of lubricating oils.
The aim of the present invention is to produce good quality products in particular with a low sulphur content under relatively low pressure conditions, to limit the necessary investment costs. This process can produce a gasoline type engine fuel containing less than 100 ppm by weight of sulphur thus satisfying the most severe specifications as regards sulphur content for this type of fuel, and this can be achieved using a feed which may contain more than 3% by weight of sulphur. Similarly, and this is particularly important, a diesel type engine fuel is obtained with a sulphur content much lower than 500 ppm and a residue with an initial boiling point which is, for example, about 370° C. which can be sent as a feed or part of a feed to a conventional catalytic cracking step or to a residue catalytic cracking reactor such as a double regeneration reactor, preferably to a conventional catalytic cracking reactor.
We have now discovered, and this constitutes one of the aims of the present invention, that it is possible in the second step to treat either the whole of the product from the first ebullating bed conversion step, or the liquid fraction from that step, recovering the gas fraction converted in that first step, under favourable conditions leading to good stability of the ensemble of the system and improved selectivity for middle distillate.
In its broadest aspect, the present invention is defined as a process for converting a hydrocarbon fraction with a sulphur content of at least 0.3%, normally at least 1% and usually at least 2% by weight and with an initial boiling point of at least 300° C., normally at least 340° C. and usually at least 360° C., and an end point of at least 400° C., normally at least 450° C. and which may reach 600° C. or even 700° C., characterized in that it comprises the following steps:
a) treating the hydrocarbon feed in a treatment section in the presence of hydrogen, said section comprising at least one three-phase reactor, containing at least one ebullating bed of hydroconversion catalyst the mineral support of which is at least partially amorphous, functioning in riser mode for liquid and for gas, said reactor comprising at least one means (5) located near the bottom of the reactor for extracting catalyst from said reactor and at least one means (4) located near the top of said reactor for adding fresh catalyst to said reactor;
b) sending at least a portion, normally all, of the effluent from step a) to a section for treatment in the presence of hydrogen, said section comprising at least one reactor containing at least one fixed bed of hydrotreatment catalyst the mineral support of which is at least partially amorphous, under conditions for producing an effluent with a reduced sulphur content and a higher middle distillates content.
Normally, the treatment section of step a) comprises one to three reactors in series and the treatment section of step b) also comprises one to three reactors in series.
In a preferred implementation of the invention, at least a portion, normally all, of the effluent obtained from step b) is sent to a distillation zone [step c)] from which a gas fraction, a gasoline type engine fuel fraction, a diesel type engine fuel fraction and a liquid fraction which is heavier than the diesel type fraction are recovered.
In a variation, the heavier liquid fraction of the hydroconverted feed from step c) is sent to a catalytic cracking section ]step d)] in which it is treated under conditions for producing a gas fraction, a gasoline fraction, a diesel fraction and a slurry fraction.
In a further variation, at least a portion of the heavier fraction of the hydroconverted feed from step c) is sent either to ebullated bed hydroconversion step a), or to fixed bed hydrotreatment step b), or to each of these steps. It is also possible to recycle all of that fraction.
The gas fraction obtained in steps c) or d) normally principally comprises saturated and unsaturated hydrocarbons containing 1 to 4 carbon atoms per molecule (for example methane, ethane, propane, butane, ethylene, propylene, butylenes). At least a portion, preferably all, of the gasoline type fraction obtained in step c) is sent to the gasoline pool, for example. At least a portion, preferably all, of the diesel type fraction obtained in step c) is sent to the gasoline pool. At least a portion, preferably all, of the slurry fraction obtained from step d) is usually sent to the heavy fuel pool of the refinery, generally after separating out fine particles which it contains in suspension. In a further implementation of the invention, at least a portion, preferably all, of this slurry fraction is returned to the inlet to catalytic cracking step d). In a still further implementation of the invention, at least a portion of this slurry fraction is sent either to step a), or to step b), or to each of these steps, generally after separating out the fine particles it contains in suspension.
One particular implementation of the present invention comprises an intermediate step a
1
) between step a) and step b) in which the produ
Bigeard Pierre-Henri
Duee Didier
Duplan Jean-Luc
Kressmann Stephane
Morel Frederic
Institut Francais du Pe'trole
Millen White Zelano and Branigan
Myers Helane
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