Mineral oils: processes and products – Chemical conversion of hydrocarbons – Plural serial stages of chemical conversion
Reexamination Certificate
2001-01-11
2003-09-16
Norton, Nadine G. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Plural serial stages of chemical conversion
C208S058000, C208S061000, C208S100000, C208S210000, C208S209000, C208S212000
Reexamination Certificate
active
06620311
ABSTRACT:
The present invention relates to refining and converting hydrocarbon fractions, in particular hydrocarbon distillates also comprising sulphur-containing impurities. More particularly, it relates to a process for converting at least a portion of a hydrocarbon feed, for example a vacuum distillate obtained from straight run distillation of a crude oil into very good quality light gasoline and gas oil fractions and to 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 optionally a system for cooling the catalyst in the regeneration step. The catalytic cracking unit integrated into the process of the present invention can produce a gasoline with a very low sulphur content that can be mixed with the light gasoline fraction to form a mixed gasoline with a sulphur content that complies with regulations envisaged for 2005.
One aim of the present invention is to use certain particular hydrocarbon fractions that will be described below, to produce readily upgradeable lighter fractions such as middle distillates (engine fuel: gasoline and gas oil) by partial conversion of said fractions. One advantage of the present invention is to be able to improve the diesel to gasoline ratio in the refinery and thus to better respond to market requirements in many countries where diesel consumption is increasing more rapidly than gasoline consumption.
Within the context of the present invention, conversion of the feed to lighter fractions is normally in the range 20% to 100% if the unconverted heavy fraction is recycled, normally in the range 30% to 100%, and usually in the range 30% to 95%.
Feeds which can be treated by the process of the present invention are vacuum distillates, usually termed VD, such as straight run vacuum distillates, vacuum distillates from conversion processes such as those from coking, from fixed bed hydroconversion such as those from HYVAHL® processes for treating heavy hydrocarbons developed by the Applicant, or heavy hydrocarbon hydrotreatment processes carried out in an ebullated bed such as those from H-OIL® processes, or solvent deasphalted oils, for example using propane, butane or pentane deasphalted oils originating from deasphalting straight run vacuum residues or vacuum residues from H-OIL® or HYVAHL® processes. The feeds can also be formed by mixing those various fractions in any proportions, in particular deasphalted oil (DAO) and vacuum distillate. They can also contain a light cycle oil (LCO) of various origins, a heavy cycle oil (HCO) of various origins, and also gas oil cuts from catalytic cracking or coking generally with a distillation range of about 150° C. to about 370° C. They can also contain aromatic extracts obtained from manufacturing lubricating oils.
The aim of the present invention is to produce excellent quality products particularly with a very low sulphur content under relatively low-pressure conditions, to limit the cost of plant. This process can produce a gasoline type engine fuel containing less than 50 ppm (parts per million) by weight of sulphur thus satisfying the most strict regulations envisaged for 2005 governing sulphur content for this type of fuel, from a feed which may contain more than 3% by weight of sulphur. Similarly, and this is of particular importance, a diesel type engine fuel is obtained with a sulphur content of less than 50 ppm, therefore satisfying the most severe specifications envisaged for 2005 regarding the sulphur content in that type of fuel.
The prior art includes descriptions, in particular in U.S. Pat. Nos. 4,344,840 and 4,457,829, of processes for treating heavy hydrocarbon feeds comprising a first treatment step carried out in the presence of hydrogen in a reactor containing an ebullated catalyst bed followed by a second fixed bed hydrotreatment step. Those descriptions illustrate the case of fixed bed treatment, in the second step, of a light gas fraction from the product from the first step. The Applicant's recent French patent FR-A-2 769 635 describes a process for converting hydrocarbon cuts containing sulphur, comprising an ebullated bed treatment step carried out in the presence of hydrogen and a second step in which either all of the product from the first ebullated bed conversion step, or the liquid fraction from this step is treated, recovering the converted gas fraction in this first step. In this way, it is possible to carry out a treatment in the second step under favourable conditions leading to good stability of the system as a whole and to an improved selectivity for middle distillates compared with that obtained in the previous processes.
When Applicant is referred to it is the Applicant in the context of French practice which in the United States corresponds to the Assignee, namely Institut Francais du Petrole.
However, in view of the results obtained in that process as described in Example 2 of that patent application, it can be seen that the sulphur content of the gas oil fraction is more than 200 ppm and will therefore not satisfy 2005 regulations. Further, the conversion remains limited to about 65% by weight and it can be seen that the production of gas oil with respect to the feed remains less than 50% by weight while the motor cetane number is relatively low.
The aim of the present invention is to propose a process for increasing the production of middle distillates (in particular gas oil) in particular with a sulphur content that will satisfy specifications in 2005, while retaining the advantage of being able to operate at a moderate pressure with a high to very high conversion.
In its broadest sense, the present invention is defined as a process for converting a hydrocarbon fraction with a sulphur content of at least 0.05% by weight, normally at least 0.3%, usually at least 1% by weight and even exceeding 2% by weight, and 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., usually at least 450° C., and which can be more than 600° C. or even 700° C., characterized in that it comprises the following steps.
a) treating the hydrocarbon feed (step a) in a converting section for treatment carried out in the presence of hydrogen, said section comprising at least one three-phase reactor, containing at least one hydroconversion catalyst, wherein the mineral support is at least partially amorphous, in an ebullated bed, operating in liquid and gas riser mode, said reactor comprising at least one means (
17
) for withdrawing catalyst from said reactor located close to the reactor bottom and at least one means (
16
) for supplying fresh catalyst to said reactor located close to the top of said reactor;
b) sending (step b) at least a portion, usually all, of the effluent EF
0
from step a) to a separation section (
2
) operating at a pressure and temperature substantially identical to the pressure and temperature of the treatment section of step a), said separation section (
2
) producing, normally overhead, a fraction F
1
normally containing at least a portion of the gas, gasoline and atmospheric gas oil contained in effluent EF
0
, and normally from the bottom, a fraction F
2
normally principally containing compounds with higher boiling points than those of the atmospheric gas oil and a small proportion of compounds with boiling points lower than those of the atmospheric gas oil;
c) sending at least a portion, usually all, of the fraction F
1
from step b) to a treatment section (step c), said treatment being carried out in the presence of hydrogen, said section comprising at least one reactor containing at least one fixed bed hydrodesulphurisation catalyst wherein the mineral support is at least partially amorphous, under conditions enabling an effluent EF
1
with a reduced sulphur content to be obtained;
d) after expansion, sending at least a portion, usually all, of the fraction F
2
from step b) to a catalytic cracking section (st
Colyar James
Kressmann Stephane
Morel Frederic
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
Norton Nadine G.
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