U.S. patent application number 13/997330 was filed with the patent office on 2013-12-05 for method for converting hydrocarbon feedstock comprising a shale oil by hydroconversion in an ebullating bed, fractionation by atmospheric distillation and hydrocracking.
This patent application is currently assigned to AXENS. The applicant listed for this patent is Christophe Halais, Helene Leroy, Frederic Morel, Cecille Plain. Invention is credited to Christophe Halais, Helene Leroy, Frederic Morel, Cecille Plain.
Application Number | 20130319908 13/997330 |
Document ID | / |
Family ID | 45581917 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130319908 |
Kind Code |
A1 |
Halais; Christophe ; et
al. |
December 5, 2013 |
METHOD FOR CONVERTING HYDROCARBON FEEDSTOCK COMPRISING A SHALE OIL
BY HYDROCONVERSION IN AN EBULLATING BED, FRACTIONATION BY
ATMOSPHERIC DISTILLATION AND HYDROCRACKING
Abstract
Method and plant for converting hydrocarbon feedstock comprising
a shale oil, comprising a step of hydroconverting in an ebullating
bed, a fractionation into a light fraction, a naphtha fraction, a
gas-oil fraction and a fraction heavier than gas-oil, the naphtha
and gas oil fraction being hydrotreated, the fraction heavier than
gas oil being hydrocracked, the products of the hydrocracking being
sent to the step for hydrotreating. The method aims to maximize the
yield of fuel bases.
Inventors: |
Halais; Christophe; (Lons,
FR) ; Leroy; Helene; (Saint Vigor D'ymonville,
FR) ; Morel; Frederic; (Chatou, FR) ; Plain;
Cecille; (Sant Germain en Laye, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Halais; Christophe
Leroy; Helene
Morel; Frederic
Plain; Cecille |
Lons
Saint Vigor D'ymonville
Chatou
Sant Germain en Laye |
|
FR
FR
FR
FR |
|
|
Assignee: |
AXENS
Rueil Malmaison
FR
TOTAL RAFFINAGE MARKETING
Puteaux
FR
|
Family ID: |
45581917 |
Appl. No.: |
13/997330 |
Filed: |
December 16, 2011 |
PCT Filed: |
December 16, 2011 |
PCT NO: |
PCT/FR11/53021 |
371 Date: |
August 21, 2013 |
Current U.S.
Class: |
208/14 ; 208/59;
422/140 |
Current CPC
Class: |
C10G 35/04 20130101;
C10G 2300/1077 20130101; C10G 65/00 20130101; C10G 2300/1018
20130101; C10G 1/00 20130101; C10G 1/002 20130101; C10G 45/06
20130101; C10G 2300/301 20130101; C10G 45/02 20130101; C10G 47/26
20130101; C10G 2400/06 20130101; C10G 2300/1014 20130101; C10G
65/12 20130101; C10G 2400/04 20130101; C10G 65/14 20130101; C10G
2400/02 20130101; C10G 47/12 20130101; C10G 65/10 20130101; C10G
45/08 20130101; C10G 2300/4081 20130101; C10G 2300/1074 20130101;
Y02P 30/20 20151101; C10G 2300/202 20130101 |
Class at
Publication: |
208/14 ; 208/59;
422/140 |
International
Class: |
C10G 65/10 20060101
C10G065/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 2010 |
FR |
1061246 |
Claims
1. Method for converting a shale oil or a mixture of shale oils
having a nitrogen content of at least 0.1%, comprising: a) the
feedstock is conveyed into a section for hydroconverting in the
presence of hydrogen, said section comprising at least one
ebullating bed reactor operating in gas and liquid upflow mode and
containing at least one supported hydroconversion catalyst, b) the
effluent obtained in step a) is conveyed at least partly into a
fractionating zone, from which, by atmospheric distillation, a
gaseous fraction, a naphtha fraction, a gas-oil fraction and a
fraction heavier than gas-oil are recovered, c) said naphtha
fraction is treated at least partly in a first section for
hydrotreating in the presence of hydrogen, said section comprising
at least one fixed bed reactor containing at least one
hydrotreating catalyst, d) said gas-oil fraction is treated at
least partly in a second section for hydrotreating in the presence
of hydrogen, said section comprising at least one fixed bed reactor
containing at least one hydrotreating catalyst, and e) the fraction
heavier than the gas-oil fraction is treated at least partly in a
hydrocracking section in the presence of hydrogen.
2. Method according to claim 1, wherein the hydrocracking effluents
obtained at the end of step e) are fractionated into a second
gaseous fraction, a second naphtha fraction, a second gas-oil
fraction, and a second fraction which is heavier than gas-oil.
3. Method according to claim 2, wherein the second naphtha fraction
is treated, at least partly, in the hydrotreating section of step
c).
4. Method according to claim 2, wherein the second gas oil fraction
is treated, at least partly, in the hydrotreating section of step
d).
5. Method according to claim 2, wherein the second fraction heavier
than gas oil is treated, at least partly, in the hydroconverting
section of step a).
6. Method according to claim 1, wherein the hydrocracking effluents
obtained at the end of step e) are separated into a gas oil
fraction and a fraction which is lighter than gas oil and a
fraction which is heavier than gas-oil.
7. Method according to claim 6, wherein the second fraction heavier
than gas oil is treated, at least partly, in the hydroconverting
section of step a).
8. Method according to claim 6, wherein the gas oil fraction and
the fraction which is lighter than gas oil is conveyed, at least
partly, in a fractionating zone of step b).
9. Method according to claim 2, wherein the second fraction heavier
than gas oil is treated, at least partly, in the hydrocracking
section of step e).
10. Method according to claim 1, wherein the effluent obtained in
step a) is fractionated by atmospheric distillation into a gaseous
fraction having a boiling point of less than 50.degree. C., a
naphtha fraction boiling at between about 50.degree. C. and
150.degree. C., a gas-oil fraction boiling at between about
150.degree. C. and 370.degree. C., and a fraction which is heavier
than the gas-oil fraction and which boils at above 340.degree.
C.
11. Method according to claim 1, wherein the fixed bed
hydrotreating sections in steps c) and/or d) comprise, upstream of
the catalytic hydrotreating beds, at least one specific guard bed
for arsenic compounds and silicon compounds.
12. Method according to claim 1, wherein hydroconverting step a)
operates at a temperature of between 300.degree. C. and 550.degree.
C., at a total pressure of between 2 and 35 MPa, at a mass hourly
velocity ((t of feedstock/h)/t of catalyst) of between 0.2 and 1.5
h.sup.-1 and at a hydrogen/feedstock ratio of between 50 and 5000
Nm.sup.3/m.sup.3.
13. Method according to claim 1, wherein step c) of hydrotreating
the naphtha fraction operates at a temperature of between
280.degree. C. and 380.degree. C., at a total pressure of between 4
and 15 MPa, at a mass hourly velocity ((t of feedstock/h)/t of
catalyst) of between 0.1 h.sup.-1 and 5 h.sup.-1, and at a
hydrogen/feedstock ratio of between 100 and 5000
Nm.sup.3/m.sup.3.
14. Method according to claim 1, wherein step d) of hydrotreating
the gas-oil fraction operates at a temperature of between
320.degree. C. and 450.degree. C., at a total pressure of between 7
and 20 MPa, at a mass hourly velocity ((t of feedstock/h)/t of
catalyst) of between 0.1 and 1 h.sup.-1, and at a
hydrogen/feedstock ratio of between 100 and 5000
Nm.sup.3/m.sup.3.
15. Method according to claim 1, wherein step e) of hydrocracking
the fraction heavier than gas-oil operates at a temperature of
between 350.degree. C. and 450.degree. C., at a total pressure of
between 10 and 20 MPa, at a mass hourly velocity ((t of
feedstock/h)/t of catalyst) of between 0.3 and 7 h.sup.-1, and at a
hydrogen/feedstock ratio of between 100 and 5000
Nm.sup.3/m.sup.3.
16. Method according to claim 1, wherein the catalysts in
hydroconverting step a), hydrotreating steps c) and d),
hydrocracking step e) are independently selected from the group of
catalysts comprising a group VIII metal selected from the group
consisting of Ni and/or Co, optionally a group VIB metal selected
from the group consisting of Mo and/or W, on an amorphous support
selected from the group consisting of alumina, silica,
silica-aluminas, magnesia, clays and their mixtures, or on a
support comprising at least partly a zeolite material.
17. Method according to claim 1, wherein the shale oil or the
mixture of shale oils is supplemented with a hydrocarbon feedstock
selected from the group consisting of oils derived from coal, oils
obtained from heavy tars and bituminous sands, vacuum distillates,
and residues of direct distillation, vacuum distillates and
unconverted residues obtained from a residue conversion process,
oils deasphalted with solvents, light cycle oils, heavy cycle oils,
gas-oil cuts originating from catalytic cracking and having
generally a distillation range from approximately 150.degree. C. to
approximately 650.degree. C., aromatic extracts obtained in the
manufacture of lubricating oils, pyrolysis oils of ligneous
residues such as wood residues, crudes obtained from biomass
("biocrudes"), vegetable oils and animal fats or mixtures of such
feedstocks.
18. Synthetic crude obtained by a method according to claim 1.
19. Plant for treating a shale oil, comprising: a section for
hydroconverting in the presence of hydrogen, comprising an
ebullating bed reactor operating in gas and liquid upflow mode and
containing at least one supported hydroconverting catalyst, a zone
for fractionation by atmospheric distillation, a first section for
hydrotreating in the presence of hydrogen, comprising a fixed bed
reactor containing at least one hydrotreating catalyst, a second
section for hydrotreating in the presence of hydrogen, comprising
at least one fixed bed reactor containing at least one
hydrotreating catalyst, a section for hydrocracking in the presence
of hydrogen, these elements being arranged for the implementation
of the method according to claim 1.
Description
[0001] The invention relates to a method for converting hydrocarbon
feedstocks comprising a shale oil into lighter products which can
be utilized as fuels and/or raw materials for petrochemistry. The
invention relates more particularly to a method for converting
hydrocarbon feedstocks comprising a shale oil that comprises a step
of hydroconverting the feedstock in an ebullating bed, followed by
a step of fractionating by atmospheric distillation to give a light
fraction, naphtha fraction and gas-oil fraction and to give a
fraction heavier than the gas-oil fraction, a dedicated
hydrotreating for each of the naphtha and gas-oil fractions, and a
hydrocracking of the fraction heavier than the gas-oil fraction.
This method enables shale oils to be converted into
very-high-quality fuel bases, and is aimed more particularly at an
excellent yield.
[0002] In view of high barrel price volatility and a reduction in
discoveries of conventional petroleum fields, petroleum groups are
turning towards non-conventional sources. Next to petroleum-bearing
sands and deep offshore, bituminous shales, although relatively
poorly known, are becoming ever more coveted.
[0003] Bituminous shales are sedimentary rocks which contain an
insoluble organic substance called kerogen. By heat treatment in
situ or ex situ ("retorting") in the absence of air at temperatures
of between 400 and 500.degree. C., these shales liberate an oil,
shale oil, with a general appearance like that of crude
petroleum.
[0004] Although of a different composition from crude petroleum,
shale oils may constitute a substitute for the latter and also a
source of chemical intermediates.
[0005] Shale oils cannot be directly substituted into the
applications of crude petroleum. Indeed, although these oils
resemble petroleum in certain respects (for example, in a similar
H/C ratio), they differ in their chemical nature and in a much
greater level of metallic and/or non-metallic impurities, thereby
making the converting of this non-conventional resource much more
complex than that of petroleum. Shale oils have, in particular,
levels of oxygen and of nitrogen that are much higher than those in
petroleum. They may also contain higher concentrations of olefins,
of sulphur or of metal compounds (especially compounds containing
arsenic).
[0006] Shale oils obtained by pyrolysis of kerogen contain a large
number of olefinic compounds resulting from cracking, and this
translates into additional hydrogen demand at the refining stage.
For instance, the bromine index, which enables calculation of the
concentration by weight of olefinic hydrocarbons (by addition of
bromine to the ethylenic double bond), is generally greater than 30
g/100 g of feedstock for shale oils, whereas it is between 1 and 5
g/100 g of feedstock for residues of petroleum. The olefinic
compounds resulting from cracking are essentially composed of
monoolefins and diolefins. The unsaturations present in the olefins
are a potential source of instability by polymerization and/or
oxidation.
[0007] The oxygen content is generally higher than in heavy crudes,
and may be as much as 8% by weight of the feedstock. The oxygen
compounds are often phenols or carboxylic acids. Consequently,
shale oils may have a marked acidity.
[0008] The sulphur content varies between 0.1% and 6.5% by weight,
necessitating stringent desulphurizing treatments in order to meet
the specifications for fuel bases. The sulphur compounds are in the
form of thiophenes, sulphides or disulphides. Moreover, the sulphur
distribution profile within a shale oil may be different from that
obtained in a conventional petroleum.
[0009] The most distinctive feature of the shale oils,
nevertheless, is their high nitrogen content, which makes them
unsuitable as a conventional feedstock for the refinery. Petroleum
generally contains around 0.2% by weight of nitrogen, whereas crude
shale oils contain generally of the order of 1% to approximately 3%
by weight or more of nitrogen. Moreover, the nitrogen compounds
present in petroleum are generally concentrated in relatively high
boiling ranges, whereas the nitrogen of the compounds present in
crude shale oils is generally distributed throughout all of the
boiling ranges of the material. The nitrogen compounds in petroleum
are primarily non-basic compounds, whereas, generally, around half
of the nitrogen compounds present in crude shale oils are basic.
These basic nitrogen compounds are particularly undesirable in
refinery feedstocks, since these compounds often act as catalyst
poisons. Furthermore, the stability of the products is a problem
which is common to numerous products derived from shale oil. Such
instability, including photosensitivity, appears to result
essentially from the presence of nitrogen compounds. Consequently,
crude shale oils must generally be subjected to a stringent
refining treatment (high total pressure) in order to obtain a
synthetic crude petroleum or fuel base products which meet the
specifications in force.
[0010] It is also known that shale oils may contain numerous metal
compounds in traces, generally present in the form of
organometallic complexes. The metal compounds include the
conventional contaminants such as nickel, vanadium, calcium,
sodium, lead or iron, but also metal compounds of arsenic. Indeed,
shale oils may contain an amount of arsenic of more than 20 ppm,
whereas the amount of arsenic in crude petroleum is generally in
the ppb (parts per billion) range. All of these metal compounds are
catalyst poisons. More particularly, they irreversibly poison the
hydrotreating catalysts and hydrogenating catalysts by gradually
being deposited on the active surface. The conventional metal
compounds and part of the arsenic are found primarily in heavy
cuts, and are removed by deposition on the catalyst. On the other
hand, when the products containing arsenic are capable of
generating volatile compounds, these compounds may be found partly
in the lighter cuts and may, as a result, poison the catalysts in
subsequent converting processes, during refining or in
petrochemistry.
[0011] Furthermore, shale oils generally contain sandy sediments
originating from bituminous shale fields from which the shale oils
are extracted. These sandy sediments may give rise to clogging
problems, especially in fixed bed reactors.
[0012] Lastly, shale oils contain waxes, which give them a pour
point higher than the ambient temperature, thereby preventing their
transport in oil pipelines.
[0013] In view of appreciable resources, and in view of their
evaluation as being a promising source of petroleum, there exists a
genuine need for converting shale oils into lighter products which
can be utilized as fuels and/or raw materials for petrochemistry.
Methods for converting shale oils are known. Conventionally,
conversion is practised alternatively by coking, by
hydrovisbreaking (thermal cracking in the presence of hydrogen) or
by hydroconverting (catalytic hydrogenation). Liquid/liquid
extraction processes are also known.
[0014] Thus, patent document FR 2197968 describes a process for the
filtration and hydrogenation of shale oils or of bituminous sand
oils containing particles, comprising the steps that consist in (a)
continuously passing said oil into the bottom of a reactor in a
mixture with hydrogen, (b) intermittently sending catalyst into the
top of the reactor and removing catalyst and entrained particles
from the bottom of the reactor to effect a catalyst transfer
through the reactor, (c) measuring the pressure drop between the
bottom of the reactor and the top of the reactor, and (d) adjusting
the catalyst flow rate to correct the pressure drop to a
preselected pressure which corresponds to a desired rate of
filtration in the reactor. The process described in FR 2197968 is
especially silent on the use of independent sections for the
hydrotreatment of naphtha and gas oil fractions.
[0015] Patent document U.S. Pat. No. 6,153,087 describes a process
for converting heavy feedstocks comprising an ebullated-bed
conversion and a hydrocracking operation. The process is applied to
various heavy feedstocks having an initial boiling point of at
least 300.degree. C. The application to shale oils is neither
mentioned nor suggested. The use of independent sections for the
hydrotreatment of naphtha and gas oil fractions is not
envisaged.
OBJECT OF THE INVENTION
[0016] The particular feature of shale oils in having a certain
number of metallic and/or non-metallic impurities makes it much
more complex to convert this non-conventional resource than
petroleum. The challenge for the industrial development of methods
for converting shale oils is therefore the need to develop methods
which are suited to the feedstock, allowing the yield of
high-quality fuel bases to be maximized. The conventional refining
treatments known from petroleum must therefore be adapted to the
specific composition of the shale oils.
[0017] The present invention aims to improve the known methods for
converting hydrocarbon feedstocks comprising a shale oil by
increasing, especially, the yield of fuel bases for a combination
of steps having a specific linkage, and a treatment appropriate to
each fraction obtained from the shale oils. Likewise, an object of
the present invention is to obtain high-quality products having
more particularly a low sulphur, nitrogen and arsenic content,
preferably meeting the specifications. Another objective is to
provide a method which is simple, i.e. having as few steps as
necessary, while remaining effective, allowing capital investment
costs to be limited.
[0018] In its broadest form, and according to a first aspect, the
present invention is defined as a method for converting hydrocarbon
feedstock comprising at least one shale oil having a nitrogen
content of at least 0.1%, often at least 1% and very often at least
2% by weight, characterized in that it comprises the following
steps:
[0019] a) The feedstock is conveyed into a section for
hydroconverting in the presence of hydrogen, said section
comprising at least one ebullating bed reactor operating in gas and
liquid upflow mode and containing at least one supported
hydroconverting catalyst,
[0020] b) The effluent obtained in step a) is conveyed at least
partly, and often entirely, into a fractionating zone, from which,
by atmospheric distillation, a gaseous fraction, a naphtha
fraction, a gas-oil fraction and a fraction heavier than gas-oil
are recovered,
[0021] c) Said naphtha fraction is treated at least partly, and
often entirely, in a first section for hydrotreating in the
presence of hydrogen, said first section comprising at least one
first fixed bed reactor containing at least one first hydrotreating
catalyst,
[0022] d) Said gas-oil fraction is treated at least partly, and
often entirely, in a second section for hydrotreating in the
presence of hydrogen, said second section comprising at least one
second fixed bed reactor containing at least one second
hydrotreating catalyst,
[0023] e) The fraction heavier than the gas-oil fraction is
treated, at least partly and often entirely, in a section for
hydrocracking in the presence of hydrogen.
[0024] The hydroconversion section in step a) typically comprises
from one to three, and preferably two, reactors in series, and the
first and second hydroconversion sections in steps c) and d)
comprises independently from each other from one to three reactors
in series.
[0025] The research work carried out by the applicants into the
conversion of shale oils has led to the finding that an improvement
to the existing methods, in terms of yield of fuel bases and in
terms of product purity, is possible through a combination of
various steps linked in a specific way. Each fraction obtained by
the method according to the invention is subsequently conveyed to a
treating section.
[0026] In a first time, the hydrocarbon feedstock comprising the
shale oil is subjected to a hydroconversion in an ebullating bed.
The technology of the ebullating bed, relative to the technology of
the fixed bed, enables the treatment of feedstocks which are
heavily contaminated with metals, heteroatoms and sediments, such
as the shale oils, while exhibiting conversion rates which are
generally greater than 50%. Indeed, in this first step, the shale
oil is converted into molecules which enable the generation of
future fuel bases. The majority of the metallic compounds, of the
sediments and of the heterocyclic compounds is removed. The
effluent emerging from the ebullating bed therefore contains the
most resistant nitrogen and sulphur compounds, and possibly
volatile arsenic compounds which are present in lighter
components.
[0027] The effluent obtained in the hydroconverting step is
subsequently fractionated by atmospheric distillation, producing
various fractions, for which a treatment specific to each fraction
is carried out subsequently. The atmospheric distillation enables
the preparation, in a single step, of the various fractions desired
(naphtha, gas-oil), thereby facilitating downstream hydrotreating
adapted to each fraction and, consequently, the direct production
of gas-oil or naphtha fuel base products which meet the various
specifications. Fractionation after hydrotreating is therefore not
necessary.
[0028] Owing to the high level of reduction in contaminants in the
ebullating bed, the light fractions (naphtha and gas-oil) contain
fewer contaminants and can therefore be treated in a fixed bed
section, which generally has improved hydrogenation kinetics in
relation to the ebullating bed. Similarly, the operating conditions
can be milder because of the limited contaminants content.
Providing a treatment for each fraction permits better operability
in accordance with the desired products. Depending on the operating
conditions selected (more or less stringent), it is possible to
obtain either a fraction which can be conveyed to a fuels pool or a
finished product which meets the specifications (sulphur content,
smoke point, cetane, aromatics content, etc.) in force.
[0029] Upstream of the catalytic hydrotreating beds, the fixed bed
hydrotreating sections preferably comprise specific guard beds for
any arsenic compounds and silicon compounds contained within the
diesel and/or naphtha fractions. The arsenic compounds, which have
escaped the ebullating bed (because they are generally relatively
volatile), are trapped in the guard beds, thus preventing poisoning
of the downstream catalysts, and enabling production of highly
arsenic-depleted fuel bases.
[0030] The atmospheric distillation also enables the concentration
of the most resistant nitrogen compounds in the fraction which is
heavier than the gas-oil fraction, which during step e) is
hydrocracked. This step of hydrocracking permits to upgrade the
fraction heavier than gas oil while producing products lighter and
permits consequently to minimize the upgrading problems and
economic outlets of this fraction.
DETAILED DESCRIPTION
[0031] The Hydrocarbon Feedstock
[0032] The hydrocarbon feedstock comprises at least one shale oil
or a mixture of shale oils. The term "shale oil" is used here in
its broadest sense and is intended to include any shale oil or a
shale oil fraction which contains nitrogenous impurities. This
includes crude shale oil, whether obtained by pyrolysis, by solvent
extraction or by other means, or shale oil which has been filtered
to remove the solids, or which has been treated by one or more
solvents, chemical products, or other treatments, and which
contains nitrogenous impurities. The term "shale oil" also
comprises the shale oil fractions obtained by distillation or by
another fractionating technique.
[0033] The shale oils used in the present invention generally have
a Conradson carbon content of at least 0.1% by weight and generally
at least 5% by weight, an asphaltenes content (IP143 standard/with
C7) of at least 1%, often at least 2% by weight. Their sulphur
content is generally at least 0.1%, often at least 1% and very
often at least 2%, and even up to 4% or even 7% by weight. The
amount of metals they contain is generally at least 5 ppm by
weight, often at least 50 ppm by weight, and typically at least 100
ppm by weight or at least 200 ppm by weight. Their nitrogen content
is generally at least 0.5%, often at least 1% and very often at
least 2% by weight. Their arsenic content is generally greater than
1 ppm by weight, and up to 50 ppm by weight.
[0034] The method according to the present invention is intended
for converting shale oils. Nevertheless, the feedstock may further
comprise, in addition to the shale oil, other, synthetic liquid
hydrocarbons, more particularly those which contain a substantial
amount of cyclic organic nitrogen compounds. This includes oils
derived from coal, oils obtained on the basis of heavy tars,
bituminous sands, pyrolysis oils from ligneous residues such as
wood residues, crudes obtained from biomass ("biocrudes"),
vegetable oils and animal fats.
[0035] Other hydrocarbon feedstocks may also supplement the shale
oil or the mixture of shale oils. The feedstocks are selected from
the group consisting of oils derived from coal, oil derived from
heavy tars and bituminous sands, vacuum distillates and direct
distillation residues, vacuum distillates and unconverted residues
obtained from conversion processes, such as, for example, those
originating from distillation to the point of coke (coking),
products obtained from fixed-bed hydroconversion of heavy
fractions, products obtained from ebullating-bed processes for
hydroconversion of heavy fractions, and oils deasphalted using
solvents (for example, oils deasphalted with propane, with butane
and with pentane, originating from the deasphalting of vacuum
residues from direct distillation or of vacuum residues obtained
from hydroconversion processes). The feedstocks may further
comprise light cycle oil (LCO) of various origins, heavy cycle oil
(HCO) of various origins, and also gas-oil cuts which originate
from catalytic cracking and have in general a distillation range
from about 150.degree. C. to about 650.degree. C. The feedstocks
may also comprise aromatic extracts obtained in the manufacture of
lubricating oils. The feedstocks may also be prepared and used in a
mixture, in any proportions.
[0036] Hydrocarbons added to shale oil or to the mixture of shale
oils may represent from 20% to 60% by weight of the total feedstock
(shale oil or mixture of shale oils+added hydrocarbons), or from
10% to 90% by weight.
[0037] Hydroconversion
[0038] The feedstock containing the shale oil is first of all
subjected to a hydroconverting step in an ebullating-bed [step a)].
By hydroconverting is meant reactions of hydrogenation,
hydrotreating, hydrodesulphurization, hydrodenitrogenation,
hydrodemetallation and hydrocracking.
[0039] The operation of the ebullating-bed catalytic reactor,
including the recycling of the liquids from the reactor to the top
through the agitated catalyst bed, is generally well known.
Ebullating bed technologies use supported catalysts, generally in
the form of extrudates having a diameter of generally of the order
of 1 mm or less than 1 mm, for example greater than or equal to 0.7
mm. The catalysts remain inside the reactors and are not evacuated
with the products. The catalytic activity can be held constant by
virtue of on-line replacement (addition and withdrawal) of the
catalyst. There is therefore no need to shut down the unit in order
to change the spent catalyst, or to increase the reaction
temperatures along the cycle in order to compensate for
deactivation. Moreover, working with constant operating conditions
enables consistent product qualities and consistent yields to be
obtained throughout the cycle of the catalyst. Since the catalyst
is held in agitation by substantial recycling of liquid, the head
loss over the reactor remains low and constant, and the heat of
reaction is rapidly averaged over the catalyst bed, which is
therefore almost isothermal and does not require cooling via the
injection of quenches. Implementing the hydroconversion in an
ebullating bed obviates the problems of catalyst contamination that
are associated with the deposits of impurities that are present
naturally in shale oils.
[0040] The conditions in step a) of treating the feedstock in the
presence of hydrogen are customarily conventional conditions for
ebullating-bed hydroconversion of a liquid hydrocarbon fraction. It
is customary to operate under a total pressure of 2 to 35 MPa,
preferably of 10 to 20 MPa, at a temperature of 300.degree. C. to
550.degree. C. and often of 400.degree. C. to 450.degree. C. The
hourly space velocity (HSV) and the hydrogen partial pressure are
important factors, which are selected according to the
characteristics of the product to be treated and to the desired
conversion. The HSV is usually situated within a range from 0.2
h.sup.-1 to 1.5 h.sup.-1 and preferably from 0.4 h.sup.-1 to 1
h.sup.-1. The amount of hydrogen mixed with the feedstock is
customarily from 50 to 5000 normal cubic metres (Nm.sup.3) per
cubic metre (m.sup.3) of liquid feedstock, and usually from 100 to
1000 Nm.sup.3/m.sup.3, and preferably from 300 to 500
Nm.sup.3/m.sup.3.
[0041] This hydroconverting step a) may usually be implemented
under the conditions of the T-STAR.RTM. process, as described for
example in the article Heavy Oil Hydroprocessing, published by the
AlChE, Mar. 19-23, 1995, Houston, Tex., paper number 42d. It may
also be implemented under the conditions of the H-OIL.RTM. process,
as described for example in the article published by NPRA, Annual
Meeting, Mar. 16-18, 1997, J. J. Colyar and L. I. Wilson under the
title The H-Oil.RTM. Process, A Worldwide Leader In Vacuum Residue
Hydroprocessing.
[0042] The hydrogen required for the hydroconversion (and for the
subsequent hydrotreating operations) may come from the steam
reforming of hydrocarbons (methane) or else from the gas obtained
from oil shales during the production of shale oils.
[0043] The catalyst in step a) is preferably a conventional
granular hydroconversion catalyst, comprising, on an amorphous
support, at least one metal or metal compound having a
hydrodehydrogenating function. Generally speaking, a catalyst is
used whose pore distribution is suitable for the treatment of
feedstocks containing metals.
[0044] The hydrodehydrogenating function may be provided by at
least one group VIII metal selected from the group consisting of
nickel and/or cobalt, optionally in combination with at least one
group VIB metal selected from the group consisting of molybdenum
and/or tungsten. It is possible, for example, to use a catalyst
comprising from 0.5% to 10% by weight of nickel and preferably from
1% to 5% by weight of nickel (expressed as nickel oxide, NiO) and
from 1% to 30% by weight of molybdenum, preferably from 5% to 20%
by weight of molybdenum (expressed as molybdenum oxide, MoO.sub.3),
on an amorphous inorganic support. The total amount of oxides of
metals from groups VIB and VIII is often from 5% to 40% by weight
and generally from 7% to 30% by weight. The weight ratio expressed
as metal oxide between group VI metal (or metals) and group VIII
metal (or metals) is generally from 20 to 1 and usually from 10 to
2.
[0045] The support of the catalyst will be selected, for example,
from the group consisting of alumina, silica, silica-aluminas,
magnesia, clays and mixtures of at least two of these minerals.
This support may also include other compounds, for example oxides
selected from the group consisting of boron oxide, zirconia,
titanium oxide and phosphoric anhydride. It is usual to use an
alumina support, and very often an alumina support doped with
phosphorus and optionally with boron. In this case, the
concentration of phosphoric anhydride, P.sub.2O.sub.5, is
customarily less than about 20% by weight and usually less than
about 10% by weight, and at least 0.001% by weight. The
concentration of boron trioxide, B.sub.2O.sub.3, is customarily
from approximately 0% to approximately 10% by weight. The alumina
used is customarily a .gamma. (gamma) or .eta. (eta) alumina. This
catalyst is usually in the form of an extrudate. The catalyst in
step a) is preferably based on nickel and molybdenum, doped with
phosphorus and supported on alumina. Use may be made, for example,
of an HTS 458 catalyst sold by Axens.
[0046] Prior to the injection of the feedstock, the catalysts used
in the method according to the present invention may undergo a
sulphurizing treatment to convert at least partly the metallic
species into sulphides before they are contacted with the feedstock
to be treated. This activation treatment by sulphurization is well
known to the skilled person and may be carried out by any method
already described in the literature, either in situ, i.e. within
the reactor, or ex situ.
[0047] The spent catalyst is partly replaced with fresh catalyst by
withdrawal at the bottom of the reactor and introduction at the top
of the reactor of fresh or new catalyst at regular intervals, for
example by individual or quasi-continuous addition. It is possible,
for example, to introduce fresh catalyst every day. The level of
replacement of the spent catalyst by fresh catalyst may be, for
example, from approximately 0.05 kg to approximately 10 kg per
m.sup.3 of feedstock. This withdrawal and this replacement are
carried out using devices which allow the continuous operation of
this hydroconverting step. The unit customarily comprises a
recirculation pump for maintaining the catalyst in an ebullating
bed by continuous recycling of at least part of the liquid
withdrawn at the top of the reactor and reinjected at the bottom of
the reactor. It is also possible to convey the spent catalyst
withdrawn from the reactor into a regenerating zone, in which the
carbon and sulphur it contains are removed, and then to return this
regenerated catalyst to the hydroconverting reactor of step a).
[0048] The operating conditions coupled with the catalytic activity
allow feedstock conversion rates of possibly from 50% to 95%,
preferably from 70% to 95%, to be obtained. The aforementioned
degree of conversion is defined as the mass fraction of the
feedstock at the start of the reaction section minus the mass
fraction of the heavy fraction having a boiling point of more than
343.degree. C. at the end of the reaction section, this figure
being divided by the mass fraction of the feedstock at the start of
the reaction section.
[0049] The technology of the ebullating bed allows treatment of
feedstocks which are highly contaminated with metals, sediments and
heteroatoms, without facing head loss problems or clogging
problems, which are known when a fixed bed is used. The metals,
such as nickel, vanadium, iron and arsenic, are largely removed
from the feedstock by deposition on the catalysts during the
reaction. The remaining (volatile) arsenic will be removed in the
hydrotreating steps by specific guard beds. The sediments present
in the shale oils are also removed via the replacement of the
catalyst in the ebullating bed without disrupting the
hydroconversion reactions. These steps also enable the removal, by
hydrodenitrogenation, of the major part of the nitrogen, leaving
only the most resistant nitrogen compounds.
[0050] The hydroconversion of step a) makes it possible to obtain
an effluent having a nitrogen content that is greatly reduced
relative to that of the feedstock, of the order of 3 times to 10
times less than in the feedstock.
[0051] Fractionation by Atmospheric Distillation
[0052] The effluent obtained in the hydroconverting step a) is
conveyed at least partly, and preferably in its entirety, into a
fractionating zone, from which a gaseous fraction, a naphtha
fraction, a gas-oil fraction and a fraction heavier than the
gas-oil fraction are recovered by atmospheric distillation.
[0053] The effluent obtained in step a) is preferably fractionated
by atmospheric distillation into a gaseous fraction having a
boiling point of less than 50.degree. C., a naphtha fraction
boiling at between about 50.degree. C. and 150.degree. C., a
gas-oil fraction boiling at between about 150.degree. C. and
370.degree. C., and a fraction which is heavier than the gas-oil
fraction and which boils generally at above 340.degree. C.,
preferably at above 370.degree. C.
[0054] The naphtha and diesel fractions are subsequently conveyed
separately into hydrotreating sections. The fraction heavier than
the gas oil fraction is conveyed into the hydrocracking section of
step e).
[0055] The gaseous fraction contains gases (H.sub.2, H.sub.2S,
NH.sub.3, H.sub.2O, CO.sub.2, CO, C.sub.1-C.sub.4 hydrocarbons,
etc.). It may advantageously undergo a purifying treatment for
recovery of the hydrogen and its recycling into the hydroconverting
section in step a) or into the hydrotreating sections in steps c)
and d). Following purifying treatments, the C.sub.3 and C.sub.4
hydrocarbons may be used to form LPG (liquefied petroleum gas)
products. The uncondensable gases (C.sub.1-C.sub.2) are generally
used as internal fuel for the heating ovens of the hydroconversion
and/or hydrotreating and/or hydrocracking reactors.
[0056] Hydrocracking
[0057] The process according to the invention comprises a
hydrocracking step [step e)], in which at least one portion,
preferably all, of the fraction heavier than gas oil obtained in
step b), is sent into a hydrocracking section in the presence of
hydrogen, in which said fraction heavier than gas oil is treated
conventionally under conditions well known to those skilled in the
art, in order to produce a second gaseous fraction, a second
naphtha fraction, a second gas oil fraction and a second fraction
heavier than gas oil, referred to as "unconverted oil". The second
naphtha fraction will be for example treated, at least partly, and
often in its entirety, into the section for hydrotreating of step
c). The second gas oil fraction will be, for example, at least
partly, often entirely, sent to fuel pools and/or recycled at least
partly, or even in its entirety, to the hydrotreating step d) The
second fraction heavier than gas oil will be, for example, at least
partly, or even in its entirety, sent to the heavy fuel oil pool
and/or recycled at least partly, or even in its entirety, to the
hydrocracking step e) and/or to the hydroconverting step a).
[0058] The hydrocracking effluents, obtained at the end of step e),
may also be separated into a gas oil and lighter than gas oil
fraction, and a second fraction heavier than gas oil. This gas oil
and lighter than gas oil fraction is a mixture of a second gaseous
fraction, a second naphtha fraction and a second gas oil
fraction.
[0059] The gas oil and lighter than gas oil fraction may be sent,
at least partly, and often in its entirety, to a fractionation zone
of step b).
[0060] A brief description of hydrocracking can be found for
example in ULLMANS ENCYCLOPEDIA OF INDUSTRIAL CHEMISTRY, VOLUME
A18, 1991, page 71. A conventional catalyst or an assembly of
conventional catalysts positioned on different fixed beds is
customarily used. The catalysts used comprise combinations of
metals supported on aluminas or zeolites. Examples of catalysts
used within the context of the industrial operation of a
hydrocracker include the catalysts Ni--Mo on alumina, Ni--Mo on
zeolite, Ni--Mo and Ni--W on silica-alumina, Co--Mo on alumina and
Co--Mo on zeolite. These catalysts may also contain, as a function
of the desired properties, other metals chosen from transition
metals and rare earth metals, in trace amounts or in relatively
large proportions (from less than 1% by weight to 30% by weight
relative to the total charge of metals) in metallic form or in
oxide form.
[0061] The hydrocracking is carried out in a vertical reactor,
generally in downflow mode. The feedstock is preheated in the
presence of hydrogen before being introduced into the top of the
reactor. A hydrogen makeup is introduced between each catalyst bed
(quench gas) in order to reduce the temperature. This quench gas is
then intimately mixed with the feedstock, usually in devices known
as "quench boxes".
[0062] The choice of the catalyst and of the operating conditions
varies according to the products desired as a function of the
feedstock treated. Hydrocracking units are usually operated at
temperatures between 320.degree. C. and 450.degree. C., preferably
between 350.degree. C. and 400.degree. C., with weight hourly space
velocities between 0.3 and 7 h.sup.-1, with a hydrogen/feedstock
ratio between 300 and 1000 Nm.sup.3 of hydrogen/m.sup.3 of
feedstock. Two types of hydrocracker are distinguished, as a
function of their operating pressure: (1) MHC or mild hydrocracking
units, which have operating pressures customarily between 8 and 15
MPa, more generally between 10 and 12 MPa, and (2) DHC or
distillate hydrocracking units, which have operating pressures
customarily between 12 and 20 MPa, more generally between 15 and 20
MPa.
[0063] Step e) of hydrocracking the fraction heavier than gas oil
is carried out at a temperature between 350.degree. C. and
450.degree. C., preferably between 370.degree. C. and 425.degree.
C., at a total pressure between 10 and 20 MPa, preferably between
15 and 18 MPa, at a weight hourly space velocity between 0.3 and 7
h.sup.-1, preferably between 0.5 and 1.5 h.sup.-1, and at a
hydrogen/feedstock ratio between 100 and 5000 Nm.sup.3/m.sup.3,
preferably between 1000 and 2000 Nm.sup.3/m.sup.3.
[0064] The use of an MHC unit, within the context of the invention,
will produce effluents that are around 10% to 20% converted,
sufficient for forming a synthetic crude oil, after mixing with the
various naphtha and gas oil cuts resulting from the process. This
synthetic crude will then be able to be sent to a conventional
refinery. Alternatively, the use of a DHC unit, within the context
of the invention, will produce effluents that are 80% to 90%
converted, which should make it possible to direct the products
more towards commercialization as bases for the manufacture of
fuels.
[0065] Hydrotreating of the Naphtha Fraction and of the Gas-Oil
Fraction
[0066] The naphtha and gas-oil fractions are subsequently subjected
separately to fixed-bed hydrotreating [steps c) and d)].
Hydrotreating refers to reactions of hydrodesulphurization,
hydrodenitrogenation and hydrodemetallation. The objective,
depending on the operating conditions, which are selected so as to
be more or less stringent, is to bring the various cuts up to the
specifications (sulphur content, smoke point, cetane, aromatics
content, etc.) or to produce a synthetic crude petroleum. Treating
the naphtha fraction in one hydrotreating section and the gas-oil
fraction in another hydrotreating section allows improved
operability in terms of the operating conditions, so as to be able
to bring each cut up to the required specifications with a maximum
yield and in a single step per cut. In this way, fractionation
after hydrotreating is unnecessary. The difference between the two
hydrotreating sections is based more on differences in operating
conditions than on the selection of the catalyst.
[0067] The fixed-bed hydrotreating sections preferably comprise,
upstream of the catalytic hydrotreating beds, specific guard beds
for the arsenic compounds (arsenic-containing compounds) and
silicon compounds that are optionally present in the naphtha and/or
diesel fractions. The arsenic-containing compounds which have
escaped the ebullating bed (being generally relatively volatile)
are trapped in the guard beds, thereby preventing the poisoning of
downstream catalysts and enabling highly arsenic-depleted fuel
bases to be obtained.
[0068] The guard beds which allow removal of arsenic and silicon
from naphtha or gas-oil cuts are known to the skilled person. They
comprise, for example, an absorbent material comprising nickel
deposited on an appropriate support (silica, magnesia or alumina)
as described in FR2617497, or else an absorbent material comprising
copper on a support, as described in FR2762004. Mention may also be
made of the guard beds sold by Axens: ACT 979, ACT 989, ACT 961,
ACT 981.
[0069] The operating conditions in each hydrotreating section are
adapted to the feedstock to be treated. The operating conditions
for hydrotreating the naphtha fraction are generally gentler than
those for the gas-oil fraction.
[0070] In the naphtha fraction hydrotreating step [step c)] it is
customary to operate under an absolute pressure of 4 to 15 MPa,
often of 10 to 13 MPa. The temperature during this step c) is
customarily from 280.degree. C. to 380.degree. C., often from
300.degree. C. to 350.degree. C. This temperature is customarily
adjusted in accordance with the desired level of
hydrodesulphurization. The hourly space velocity (HSV) is usually
situated within a range from 0.1 h.sup.-1 to 5 h.sup.-1, and
preferably from 0.5 h.sup.-1 to 1 h.sup.-1. The amount of hydrogen
mixed with the feedstock is customarily from 100 to 5000 normal
cubic metres (Nm.sup.3) per cubic metre (m.sup.3) of liquid
feedstock, and usually from 200 to 1000 Nm.sup.3/m.sup.3, and
preferably from 300 to 500 Nm.sup.3/m.sup.3. It is useful to
operate in the presence of hydrogen sulphide (for the sulphurizing
of the catalyst), and the hydrogen sulphide partial pressure is
customarily from 0.002 times to 0.1 times, and preferably from
0.005 times to 0.05 times, the total pressure.
[0071] In the gas-oil fraction hydrotreating step [step d)] it is
customary to operate under an absolute pressure of 7 to 20 MPa,
often of 10 to 15 MPa. The temperature during this step d) is
customarily from 320.degree. C. to 450.degree. C., often from
340.degree. C. to 400.degree. C. This temperature is customarily
adjusted depending on the desired level of hydrodesulphurization.
The mass hourly velocity ((t of feedstock/h)/t of catalyst) is
comprised between 0.1 and 1 h.sup.-1. The hourly space velocity
(HSV) is usually situated within a range from 0.2 h.sup.-1 to 1
h.sup.-1, and preferably from 0.3 h.sup.-1 to 0.8 h.sup.-1. The
amount of hydrogen mixed into the feedstock is customarily from 100
to 5000 normal cubic metres (Nm.sup.3) per cubic metre (m.sup.3) of
liquid feedstock, and usually from 200 to 1000 Nm.sup.3/m.sup.3,
and preferably from 300 to 500 Nm.sup.3/m.sup.3. It is useful to
operate in the presence of hydrogen sulphide, and the hydrogen
sulphide partial pressure is customarily from 0.002 times to 0.1
times, and preferably from 0.005 times to 0.05 times, the total
pressure.
[0072] In the hydrotreating sections, the ideal catalyst must have
a high hydrogenating power, so as to produce thorough refining of
the products, and to obtain a substantial lowering of the sulphur
content and nitrogen content. In the preferred embodiment, the
hydrotreating sections operate at relatively low temperature, which
promotes thorough hydrogenation and a limitation on the coking of
the catalyst. The use of a single catalyst or of two or more
different catalysts, simultaneously or successively, in the
hydrotreating sections would not depart from the scope of the
present invention. The hydrotreating in steps c) and d) is
customarily carried out industrially in one or more reactors with
liquid downflow.
[0073] In the two hydrotreating sections [steps c) and d)], the
same type of catalyst is used; the catalysts in each section may be
identical or different. At least one fixed bed of conventional
hydrotreating catalyst is used, comprising, on an amorphous
support, at least one metal or metal compound having a
hydrodehydrogenating function.
[0074] The hydrodehydrogenating function may be provided by at
least one group VIII metal selected from the group consisting of
nickel and/or cobalt, optionally in combination with at least one
group VIB metal selected from the group consisting of molybdenum
and/or tungsten. It is possible, for example, to use a catalyst
comprising from 0.5% to 10% by weight of nickel and preferably from
1% to 5% by weight of nickel (expressed as nickel oxide, NiO) and
from 1% to 30% by weight of molybdenum, preferably from 5% to 20%
by weight of molybdenum (expressed as molybdenum oxide, MoO.sub.3),
on an amorphous inorganic support. The total amount of oxides of
metals from groups VI and VIII is often from about 5% to about 40%
by weight, and generally from about 7% to 30% by weight, and the
weight ratio expressed in terms of metal oxide between metal (or
metals) from group VIB to metal (or metals) from group VIII is in
general from about 20 to about 1, and usually from about 10 to
about 2.
[0075] The support is for example selected from the group
consisting of alumina, silica, silica-aluminas, magnesia, clays and
mixtures of at least two of these minerals. This support may also
include other compounds, for example oxides selected from the group
consisting of boron oxide, zirconia, titanium oxide and phosphoric
anhydride. It is usual to use an alumina support, and very often an
alumina support doped with phosphorus and optionally with boron. In
this case, the concentration of phosphoric anhydride,
P.sub.2O.sub.5, is customarily less than about 20% by weight and
usually less than about 10% by weight and at least 0.001% by
weight. The concentration of boron trioxide, B.sub.2O.sub.3, is
customarily from approximately 0% to approximately 10% by weight.
The alumina used is customarily a .gamma. (gamma) or .eta. (eta)
alumina. This catalyst is usually in the form of beads or
extrudates.
[0076] Prior to the injection of the feedstock, the catalysts used
in the method according to the present invention are preferably
subjected to a sulphurizing treatment enabling to convert at least
partly the metallic species into sulphides before they are
contacted with the feedstock to be treated. This activation
treatment by sulphurization is well known to the skilled person and
may be carried out by any method already described in the
literature, either in situ, i.e. within the reactor, or ex
situ.
[0077] The hydrotreating in step c) of the naphtha cut produces a
cut containing not more than 1 ppm by weight of nitrogen,
preferably not more than 0.5 ppm of nitrogen, and not more than 5
ppm by weight of sulphur, preferably not more than 0.5 ppm of
sulphur.
[0078] The hydrotreating in step d) of the gas-oil cut produces a
cut containing not more than 100 ppm of nitrogen, preferably not
more than 20 ppm of nitrogen, and not more than 50 ppm of sulphur,
preferably not more than 10 ppm of sulphur.
[0079] According to a penultimate aspect, the invention relates to
the preparation of a synthetic crude by a method according to one
of its preceding aspects.
[0080] According to a last aspect, the invention relates to a plant
intended for treating a shale oil, employing a method according to
one of its preceding aspects.
[0081] Such a plant comprises:
[0082] a section for hydroconverting in the presence of hydrogen,
comprising an ebullating bed reactor operating in gas and liquid
upflow mode and containing at least one supported hydroconverting
catalyst,
[0083] a zone for fractionation by atmospheric distillation,
[0084] a first section for hydrotreating in the presence of
hydrogen, comprising a fixed bed reactor containing at least one
hydrotreating catalyst,
[0085] a second section for hydrotreating in the presence of
hydrogen, comprising at least one fixed bed reactor containing at
least one hydrotreating catalyst,
[0086] a section for hydrocracking in the presence of hydrogen.
[0087] These elements are arranged for the implementation of the
method according to the invention.
[0088] Accordingly, for example:
[0089] the section for hydroconverting is connected to the zone for
fractionation in order to feed this zone for fractionation with
effluents issued from the section for hydroconverting,
[0090] a first duct (line) connects the zone for fractionation to
the first section for hydrotreating, a second duct (line)
connecting the zone for fractionation to the second section for
hydrotreating, and a third duct (line) connects the zone for
fractionation to the section for hydrocracking.
[0091] The plant may further comprise one or several recycle ducts
for conveying different fractions to the section for
hydroconverting, to the section for hydrocracking or to any of the
first and second sections for hydrotreating.
[0092] FIG. 1 represents diagrammatically the method according to
the present invention. FIG. 2 represents diagrammatically a variant
of the method in which the separation of several cuts is performed
in the same distillation unit.
[0093] According to FIG. 1, the feedstock comprising the shale oil
(1) to be treated enters by the line (2) into the ebullating-bed
hydroconverting section (3), in the presence of hydrogen (4), the
hydrogen (4) being introduced by a line (5). The effluent from the
ebullating bed hydroconverting section (3) is conveyed by the line
(6) into an atmospheric distillation column (7), at the end of
which a gaseous fraction (8), a naphtha fraction (9), a gas-oil
fraction (10) and a fraction (11) heavier than the gas-oil fraction
are recovered. The gaseous fraction (8), as well as a second
gaseous fraction (26) containing hydrogen, may be purified (not
shown) for recycling the hydrogen and reinjecting it (i) into the
ebullating bed hydroconverting section (3) via the line (2) and/or
(5), and/or (ii) into a hydrotreating sections (12) via a line (18)
and/or (14), and/or (iii) into a hydrotreating sections (13) via a
line (19) and/or (15), and/or (iv) into a hydrocracking sections
(20) via a line (21) and/or (22). The naphtha fraction (9) is
conveyed into the fixed bed hydrotreating section (12), at the end
of which a naphtha fraction (16) depleted in impurities is
recovered. The gas-oil fraction (10) is conveyed into the fixed bed
hydrotreating section (13), at the end of which a gas-oil fraction
(17) depleted in impurities is recovered. The two hydrotreating
sections (12) and (13) are fed by hydrogen via the lines (14) and
(15). The fraction (11) heavier than the gas-oil fraction is sent
to the hydrocracking section (20) via the line (21). The
hydrocracking effluents (23) are sent via a line (24) to a
separation section (25) at the outlet of which the second gaseous
fraction (26), a second naphtha fraction (27), a second gas oil
fraction (28), and a second fraction heavier than gas oil (29) are
recovered. The second naphtha fraction (27) may be sent, completely
or partly, to the hydrotreatment section (12) via a line (30). The
second gas oil fraction (28) is preferably sent to the gas oil pool
or may be sent, completely or partly, to the hydrotreatment section
(13) via a line (31). The second fraction heavier than gas oil (29)
may be (i) drawn off, and/or (ii) sent back, completely or partly,
to the hydrocracking section (20) via a line (32), and/or (iii)
sent back, completely or partly, to the ebullated-bed
hydroconversion section (3) via a line (33).
[0094] In FIG. 2, the hydroconverting, separating and hydrotreating
steps (and reference symbols) are identical to those of FIG. 1
until the hydrocracking step, which present some differences.
[0095] The feedstock comprising the shale oil (1) to be treated
enters by the line (2) into the ebullating-bed hydroconverting
section (3), in the presence of hydrogen (4), the hydrogen (4)
being introduced by a line (5). The effluent from the ebullating
bed hydroconverting section (3) is conveyed by the line (6) into an
atmospheric distillation column (7), at the end of which a gaseous
fraction (8), a naphtha fraction (9), a gas-oil fraction (10) and a
fraction (11) heavier than the gas-oil fraction are recovered. The
gaseous fraction (8) containing hydrogen, may be purified (not
shown) for recycling the hydrogen and reinjecting it (i) into the
ebullating bed hydroconverting section (3) via the line (2) and/or
(5), and/or (ii) into a hydrotreating sections (12) via a line (18)
and/or (14), and/or (iii) into a hydrotreating sections (13) via a
line (19) and/or (15), and/or (iv) into a hydrocracking sections
(20) via a line (21) and/or (22). The naphtha fraction (9) is
conveyed into the fixed bed hydrotreating section (12), at the end
of which a naphtha fraction (16) depleted in impurities is
recovered. The gas-oil fraction (10) is conveyed into the fixed bed
hydrotreating section (13), at the end of which a gas-oil fraction
(17) depleted in impurities is recovered. The two hydrotreating
sections (12) and (13) are fed by hydrogen via the lines (14) and
(15). The fraction (11) heavier than the gas-oil fraction is sent
to the hydrocracking section (20) via the line (21). The
hydrocracking effluents (23) are sent via a line (24) to a
separation section (34) at the outlet of which, at the top, a
mixture (35) comprising a second gaseous fraction, a second naphtha
fraction and a second gas oil fraction (28) is recovered, and, at
the bottom, a second fraction heavier than gas oil (29) is
recovered. The mixture (35) is sent via a line (36) to the
distillation column (7). The second fraction heavier than gas oil
(29) may be (i) drawn off, and/or (ii) sent back, completely or
partly, to the hydrocracking section (20) via a line (32), and/or
(iii) sent back, completely or partly, to the ebullated-bed
hydroconversion section (3) via a line (33).
EXAMPLE
[0096] A shale oil is treated that has the characteristics set out
in Table 1.
TABLE-US-00001 TABLE 1 Characteristics of the shale oil feedstock
Density 15/4 -- 0.945 Hydrogen % by weight 10.9 Sulphur % by weight
1.9 Nitrogen % by weight 0.8 Oxygen % by weight 1.8 Asphaltenes %
by weight 1.8 Conradson carbon % by weight 3.6 Metals ppm 236
[0097] The shale oil is treated in an ebullating bed reactor
containing the commercial catalyst HOC 458 from Axens. The
operating conditions are as follows: [0098] Temperature in the
reactor: 435.degree. C. [0099] Pressure: 195 bar (19.5 MPa) [0100]
Hydrogen/feedstock ratio: 600 Nm.sup.3/m.sup.3 [0101] Overall HSV:
0.3 h.sup.-1
[0102] The liquid products obtained from the reactor are
fractionated by atmospheric distillation to give a naphtha fraction
(C5.sup.+-150.degree. C.), a gas-oil fraction (150-370.degree. C.)
and a residual fraction 370.degree. C.sup.+, which forms the
fraction heavier than gas oil
[0103] The naphtha fraction is subjected to fixed bed hydrotreating
using an NiMo-on-alumina catalyst. The operating conditions are as
follows: [0104] Temperature in the reactor: 320.degree. C. [0105]
Pressure: 50 bar (5 MPa) [0106] Hydrogen/feedstock ratio: 400
Nm.sup.3/m.sup.3 [0107] Overall HSV: 1 h.sup.-1
[0108] The gas-oil fraction is subjected to fixed bed hydrotreating
using an NiMo-on-alumina catalyst. The operating conditions are as
follows: [0109] Temperature in the reactor: 350.degree. C. [0110]
Pressure: 120 bar (12 MPa) [0111] Hydrogen/feedstock ratio: 400
Nm.sup.3/m.sup.3 [0112] Overall HSV: 0.6 h.sup.-1
[0113] The fraction heavier than gas oil is then subjected to a
hydrocracking operation using catalysts containing NiMo on alumina,
NiW on silica alumina and NiMo on zeolite. This preheated feedstock
in the presence of hydrogen is introduced into the top of a
vertical reactor containing 5 catalyst beds. The operating pressure
is 16 MPa absolute, the temperature is 380.degree. C., the
hydrogen/feedstock ratio is 1200 Nm.sup.3/m.sup.3, and the HSV is
0.6 h.sup.-1. A hydrogen makeup is introduced between each catalyst
bed (quench gas) in order to reduce the temperature. This quench
gas is intimately mixed with the feedstock in devices known as
"quench boxes".
[0114] The hydrocracked hydrocarbons are drawn off at the bottom of
the reactor and are cooled. They are sent to a fractionation unit,
from which are isolated, as overhead, the gases, at least one
naphtha cut, at least one gas oil cut, and at least one cut heavier
than gas oil, as bottoms.
[0115] Table 2 gives the properties of the various feedstocks in
each step and also the yields obtained in the various units, and
the overall yield. Hence it is observed that, starting from 100% by
weight of shale oil, 93.9% by weight of products (LPG, naphtha,
middle distillates) are obtained conforming to the commercial Euro
V specifications.
TABLE-US-00002 TABLE 2 Refinery unit H-Oil.sub.DC Hydrocracker
Feedstock C5+ Shale oil Bottoms Bottoms Product ex H-Oil.sub.RC ex
H-Oil.sub.DC Product yield relative to % by weight 16.0 shale oil
feedstock Properties of the products density (d15/4) -- 0.852
sulphur % by weight 0.05 Total nitrogen % by weight 0.25 Yield
relative to each unit LPG % by weight 2.2 2.5 Naphtha % by weight
27.1 23.5 Middle distillate % by weight 50.7 61.0 Bottoms % by
weight 16.0 15.0 % by weight Yield relative to shale oil % by
weight LPG % by weight 2.2 0.4 Naphtha % by weight 27.1 3.8 Middle
distillate % by weight 50.7 9.8 Bottoms % by weight 16.0 2.4 Total
(LPG + naphtha + 80.0 13.9 middle distillate)/shale oil feedstock
Total (LPG + naphtha + 93.9 middle distillate)/shale oil
feedstock
* * * * *