U.S. patent application number 15/101004 was filed with the patent office on 2017-02-02 for process for selective cascade deasphalting.
This patent application is currently assigned to IFP Energies nouvelles. The applicant listed for this patent is IFP ENERGIES NOUVELLES. Invention is credited to Jerome MAJCHER, Isabelle MERDRIGNAC.
Application Number | 20170029719 15/101004 |
Document ID | / |
Family ID | 50482948 |
Filed Date | 2017-02-02 |
United States Patent
Application |
20170029719 |
Kind Code |
A1 |
MERDRIGNAC; Isabelle ; et
al. |
February 2, 2017 |
PROCESS FOR SELECTIVE CASCADE DEASPHALTING
Abstract
The invention describes a process for the deasphalting of a
heavy feedstock by liquid/liquid extraction, said process
comprising at least two stages of deasphalting in series carried
out on the feedstock to be treated making it possible to separate
at least one fraction of asphalt, at least one fraction of heavy
deasphalted oil, referred to as heavy DAO and at least one fraction
of light deasphalted oil, referred to as light DAO, at least one of
said stages of deasphalting being carried out by means of a mixture
of at least one polar solvent and at least one apolar solvent, said
stages of deasphalting being implemented under the subcritical
conditions of the mixture of solvents used.
Inventors: |
MERDRIGNAC; Isabelle;
(Chaponnay, FR) ; MAJCHER; Jerome; (Lyon,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
IFP ENERGIES NOUVELLES |
Rueil-Malmaison |
|
FR |
|
|
Assignee: |
IFP Energies nouvelles
RUEIL-MALMAISON CEDEX
FR
|
Family ID: |
50482948 |
Appl. No.: |
15/101004 |
Filed: |
November 27, 2014 |
PCT Filed: |
November 27, 2014 |
PCT NO: |
PCT/EP2014/075850 |
371 Date: |
June 2, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 21/12 20130101;
C10G 2300/206 20130101; C10G 53/06 20130101; C10G 2300/1077
20130101; C10G 21/14 20130101; C10G 2300/201 20130101; C10G 21/02
20130101; C10G 21/003 20130101 |
International
Class: |
C10G 53/06 20060101
C10G053/06; C10G 21/02 20060101 C10G021/02; C10G 21/14 20060101
C10G021/14; C10G 21/00 20060101 C10G021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 2013 |
FR |
1362028 |
Claims
1. Process for the deasphalting of a heavy feedstock by
liquid/liquid extraction, said process comprising at least two
stages of deasphalting in series carried out on the feedstock to be
treated, making it possible to separate at least one fraction of
asphalt, at least one fraction of heavy deasphalted oil, referred
to as heavy DAO and at least one fraction of light deasphalted oil,
referred to as light DAO, at least one of said stages of
deasphalting being carried out by means of a mixture of at least
one polar solvent and at least one apolar solvent, the proportions
of said polar solvent and said apolar solvent in the mixture of
solvents being adjusted according to the properties of the
feedstock treated and according to the desired yield of asphalt
and/or the quality of the deasphalted oil, said stages of
deasphalting being implemented under the subcritical conditions of
the mixture of solvents used.
2. Process according to claim 1 comprising at least: a) a first
stage of deasphalting comprising bringing the feedstock into
contact with a mixture of at least one polar solvent and at least
one apolar solvent, the proportions of said polar solvent and said
apolar solvent being adjusted so as to obtain at least one fraction
of asphalt phase and one fraction of complete deasphalted oil phase
referred to as complete DAO; and b) a second stage of deasphalting
comprising bringing at least a part of the deasphalted oil phase
originating from stage a) into contact with either an apolar
solvent, or a mixture of at least one polar solvent and at least
one apolar solvent, the proportions of said polar solvent and said
apolar solvent in the mixture being adjusted so as to obtain at
least one fraction of light deasphalted oil and one fraction of
heavy deasphalted oil, said stages of deasphalting being
implemented under the subcritical conditions of the apolar solvent
or of the mixture of solvents used.
3. Process according to claim 2, in which the deasphalted oil phase
originating from stage a) is previously subjected to at least one
stage of separation in which the deasphalted oil is separated from
the mixture of solvents or at least one stage of separation in
which the complete deasphalted oil referred to as complete DAO is
separated only from the apolar solvent.
4. Process according to claim 2, in which the deasphalted oil phase
originating from stage a) is previously subjected to at least two
successive stages of separation in which the polar and apolar
solvents are separated individually.
5. Process according to claim 3 in which the deasphalted oil
separated from the solvents is sent into at least one stripping
column before being sent into the second stage of deasphalting.
6. Process according to claim 1 comprising at least: a) a first
stage of deasphalting comprising bringing the feedstock into
contact with either an apolar solvent, or a mixture of at least one
polar solvent and at least one apolar solvent, the proportions of
said polar solvent and said apolar solvent in the mixture being
adjusted so as to obtain at least one fraction of light deasphalted
oil phase and an effluent comprising an oil phase and an asphalt
phase; and b) a second stage of deasphalting comprising bringing at
least a part of the effluent originating from stage a) into contact
with a mixture of at least one polar solvent and at least one
apolar solvent, the proportions of said polar solvent and said
apolar solvent being adjusted so as to obtain at least one fraction
of asphalt phase and one fraction of heavy deasphalted oil phase,
said stages of deasphalting being implemented under the subcritical
conditions of the apolar solvent or of the mixture of solvents
used.
7. Process according to claim 6, in which the effluent originating
from stage a) is previously subjected to at least one stage of
separation in which the effluent is separated from the apolar
solvent or from the mixture of solvents or at least one stage of
separation in which said effluent is separated only from the apolar
solvent contained in the mixture of solvents.
8. Process according to claim 6, in which the effluent originating
from stage a) is previously subjected to at least two stages of
separation in which the polar and apolar solvents are individually
separated.
9. Process according to claim 7 in which the effluent separated
from the solvents is sent into at least one stripping column before
being sent into the second stage of deasphalting.
10. Process according to claim 1 in which the proportion of polar
solvent in the mixture of polar solvent and apolar solvent in at
least one of the stages of deasphalting is comprised between 0.1
and 99.9% volume.
11. Process according to claim 1 in which the polar solvent used is
selected from the pure aromatic or naphthene-aromatic solvents, the
polar solvents comprising hetero-elements, or a mixture thereof or
cuts rich in aromatics such as cuts originating from FCC (Fluid
Catalytic Cracking) or originating from the petrochemical units of
refineries, cuts derived from coal, biomass or biomass/coal
mixture.
12. Process according to claim 1 in which the apolar solvent used
comprises a solvent made up of saturated hydrocarbon(s) comprising
a carbon number greater than or equal to 2, preferably comprised
between 2 and 9.
13. Process according to claim 1 in which the feedstock is selected
from the feedstocks of petroleum origin of crude oil type,
atmospheric residue, vacuum residue type originating from so-called
conventional crude, heavy crude or extra heavy crude, a residual
fraction originating from any pre-treatment or conversion process
such as hydrocracking, hydrotreatment, thermal cracking,
hydroconversion of one of these crudes or of one of these
atmospheric residues or one of these vacuum residues, a residual
fraction originating from the direct liquefaction of
ligno-cellulosic biomass alone or in a mixture with coal and/or a
fraction of residual petroleum.
14. Process according to claim 3 in which, when the recycled
solvents are in a mixture, the apolar/polar proportion is verified
on-line and readjusted as needed via makeup tanks individually
containing the polar and apolar solvents.
15. Process according to claim 3 in which, when the solvents are
separated individually, said solvents are individually recycled
into said respective makeup tanks.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the field of the treatment
of crude oil. More particularly, the present invention relates to a
novel process for the selective deasphalting in series of a heavy
feedstock, in particular of crude oil residues, by liquid/liquid
extraction.
PRIOR ART
[0002] Crude oil residues are characterized by a continuum of
molecular structures of increasing polarity and molecular weights
that can generally be grouped together in four families: [0003] The
family of saturated hydrocarbons comprising hydrocarbons of
saturated and unsaturated character without an aromatic ring and
having the least polar nature of the four families, [0004] The
family of aromatic hydrocarbons essentially comprising aromatic
and/or heteroatomic and/or polyaromatic rings that are generally
sulphur-containing and/or nitrogen-containing. This family has a
more polar nature than that of the family of the saturated
hydrocarbons. [0005] The family of resins essentially comprising
heteroatomic aromatic rings that are generally sulphur-containing
and/or nitrogen-containing and/or metal-containing with metals such
as nickel and vanadium. This family also comprises polyaromatic
and/or heteroatomic polyaromatic rings. This family has an even
more polar nature than that of the family of aromatic hydrocarbons.
[0006] The family of asphaltenes comprising the most polar
molecular structures of the continuum, which are of the
heteroatomic polyaromatic type. The asphaltenes are predominantly
compounds rich in sulphur-containing, and/or nitrogen-containing
and/or oxygen-containing impurities with which metals such as
nickel and vanadium are complexed.
[0007] Resins are contained in the petroleum fractions the boiling
point of which is generally greater than 300.degree. C., whereas
the asphaltenes are mainly concentrated in the fractions with high
boiling points generally greater than 500.degree. C.
[0008] Among the existing processes, the crude oil residues can be
subjected to a deasphalting pre-treatment well known to a person
skilled in the art. The principle of deasphalting is based on
separation, by precipitation, of a petroleum residue into two
phases: i) a phase referred to as "deasphalted oil", also called
"oil matrix" or "oil phase" or DAO (De-Asphalted Oil) which can be
upcycled by means of various refining processes; and ii) a phase
referred to as "asphalt" or sometimes "pitch" containing the
refractory molecular structures described above. The asphalt, due
to its mediocre quality and its variable state which can pass from
a solid, then to a pasty and finally to a liquid phase depending on
the temperature conditions, is a product detrimental to refining
systems, that should be minimized. In fact, the performances of the
processes for the upcycling and conversion of the heavy feedstocks
come up against limitations which are mainly governed by the
presence of these so-called refractory molecular structures
contained in the asphalt.
[0009] This deasphalting, called conventional deasphalting in the
remainder of the text, is generally implemented using a solvent of
paraffinic type.
[0010] The U.S. Pat. No. 7,857,964 describes the impact of the
nature of the paraffinic solvent used in a deasphalting process on
the performance of the hydrotreatment of the residues.
[0011] The U.S. Pat. No. 4,305,812 and U.S. Pat. No. 4,455,216
describe deasphalting in the form of counter-current extraction in
a column with several solvents of increasing polarity injected at
different heights of the column.
[0012] The patent US 2008/149534 deals with a process for cascade
deasphalting, in particular in two stages. A first paraffinic
solvent with 5 or 7 carbon atoms (C5 or C7) is used in order to
extract the asphalt. The deasphalted oil DAO collected is then
treated with another paraffinic solvent containing less carbon (C3
or C4) in order to separate a fraction comprising the resins from
the oil matrix. However this process has the drawback of producing
low yields of deasphalted oil DAO linked to the use of a paraffinic
solvent.
[0013] The solutions proposed in the prior art are all based on
conventional deasphalting which, due to its principle, has
limitations in terms of yield and flexibility with regard to the
upcycling envisaged for the petroleum residues. The use of solvents
or of a mixture of solvents of paraffinic type in conventional
deasphalting imposes a limitation on the yield of deasphalted oil
DAO, said yield increasing with the molecular weight of the solvent
(up to C6/C7 solvent) then levelling off at a threshold specific to
each feedstock and each solvent.
[0014] The present invention makes it possible to push back the
limitations described previously. It makes it possible to improve
the flexibility of separation as well as the yield of upcyclable
products. The implementation of such a process comprises at least
two stages of deasphalting in series and makes it possible to
increase the selectivity of the separation of the feedstock. It
makes it possible to obtain a more varied range of fractions of
molecular structures. At least one of the stages of deasphalting
according to the invention is carried out by means of a mixture of
at least one polar solvent and at least one apolar solvent, the
proportions of said polar solvent and said apolar solvent being
adjusted according to the properties of the feedstock, according to
the objective of each stage of deasphalting, according to the
desired yield of asphalt and/or according to the quality of the
desired DAO fractions, said stages of deasphalting being carried
out under the subcritical conditions of the mixture of
solvents.
[0015] An object of the process according to the invention is to
allow greater flexibility in the treatment of feedstocks by
accessing a range of separation selectivity previously inaccessible
with conventional deasphalting. The process according to the
invention allows more selective adjustment of the properties of the
upcyclable fractions of the feedstock of residues during its
upcycling while maximizing the final yield of all of the different
separated fractions of deasphalted oils DAO of the process.
DESCRIPTION OF THE FIGURES
[0016] FIG. 1 represents a diagram of deasphalting according to the
invention.
[0017] FIG. 2 represents a diagram of deasphalting incorporating
two separators and recycling of the solvents individually into
their respective tanks.
DETAILED DESCRIPTION OF THE INVENTION
[0018] In the remainder of the text and in the above, the
expression "mixture of solvents according to the invention" is
understood to mean a mixture of at least one polar solvent and at
least one apolar solvent according to the invention.
[0019] The process according to the invention comprises at least
two stages of deasphalting in series carried out on the feedstock
to be treated, making it possible to separate at least one fraction
of asphalt, at least one fraction of heavy deasphalted oil,
referred to as heavy DAO and at least one fraction of light
deasphalted oil, referred to as light DAO, at least one of said
stages of deasphalting being carried out by means of a mixture of
solvents, said stages of deasphalting being implemented under the
subcritical conditions of the mixture of solvents used.
[0020] The selection of the solvents as well as the proportions of
said polar solvent and said apolar solvent in the mixture of
solvents are adjusted, on the one hand, according to the properties
of the feedstock to be treated and according to the yield of
asphalt and/or the quality of the desired deasphalted fractions of
heavy DAO and light DAO, and, on the other hand, according to the
specifications of the subsequent upcycling processes envisaged for
each of the fractions such as hydrocracking, hydrotreatment,
hydroconversion, catalytic cracking, thermal cracking etc. This
results in a substantial gain in terms of separation performances,
the yields and the quality of the separated fractions being
improved and/or optimized depending on the objective of the system
in which the process according to the invention is included.
[0021] The process according to the invention, due to specific
deasphalting conditions, allows greater flexibility in the
treatment of the feedstocks depending on their nature, but also
depending on the envisaged upcycling system downstream of said
treatment. The deasphalting conditions according to the invention
make it possible to overcome the limitations of the yield of
deasphalted oil DAO, as imposed in conventional deasphalting by the
use of paraffinic solvents. The process according to the invention,
due to specific deasphalting conditions, makes it possible to go
further in maintaining the solubilization in the oil matrix of all
or part of the polar structures of the heavy resins and asphaltenes
which are the main constituents of the asphalt phase in the case of
conventional deasphalting. The invention thus makes it possible to
select which type of polar structures remain solubilized in the DAO
oil matrix. The asphalt extracted during the deasphalting according
to the invention corresponds to the final asphalt that is
essentially composed of the most refractory polyaromatic and/or
heteroatomic molecular structures in the conversion and refining
processes. This results in an improved total yield of deasphalted
oil.
[0022] The invention thus makes it possible to obtain at least
three fractions: a fraction of asphalt, a fraction of heavy
deasphalted oil referred to as heavy DAO and a fraction of light
deasphalted oil referred to as light DAO with greater flexibility
than in the case of conventional deasphalting in terms of
optimization of yield and/or quality of each of the fractions
obtained.
[0023] According to the invention, the feedstock used is selected
from the feedstocks of petroleum origin of the crude oil type, or a
residual fraction originating from crude oils such as an
atmospheric residue or a vacuum residue originating from so-called
conventional crude (API degree >20.degree.), heavy crude (API
degree comprised between 10 and 20.degree.) or extra heavy crude
(API degree <10.degree.). Said feedstock can also be a residual
fraction originating from any pre-treatment or conversion stage,
such as for example, hydrocracking, hydrotreatment, thermal
cracking, hydroconversion of one of these crudes or one of these
atmospheric residues or one of these vacuum residues. Said
feedstock can also be a residual fraction originating from the
direct liquefaction of coal (atmospheric or vacuum residue) with or
without hydrogen, with or without catalyst, irrespective of the
process used or also a residual fraction originating from the
direct liquefaction of ligno-cellulosic biomass alone or in a
mixture with coal and/or a fraction of residual petroleum, with or
without hydrogen, with or without catalyst, irrespective of the
process used.
[0024] The boiling point of the feedstock according to the process
of the invention is generally greater than 300.degree. C.,
preferably greater than 400.degree. C., more preferably greater
than 450.degree. C.
[0025] The feedstock can be of different geographic and geochemical
origins (type I, II, IIS or III), and also of different degrees of
maturity and biodegradation.
[0026] The feedstock according to the process of the invention can
have a sulphur content greater than 0.5% m/m (percentage expressed
as mass of sulphur relative to the mass of feedstock), preferably
greater than 1% m/m, more preferably greater than 2% m/m, even more
preferably greater than 4% m/m; a metals content greater than 20
ppm (parts per million expressed as mass of metals relative to the
mass of feedstock), preferably greater than 70 ppm, preferably
greater than 100 ppm, more preferably greater than 200 ppm; a C7
asphaltenes content greater than 1% m/m (percentage expressed as
mass of C7 asphaltenes relative to the mass of feedstock, measured
according to the NF T60-115 method), preferably greater than 3%
m/m, preferably greater than 8% m/m, more preferably greater than
14% m/m; a Conradson carbon content (also called CCR) greater than
5% m/m (percentage expressed as mass of CCR relative to the mass of
feedstock), preferably greater than 7% m/m, preferably greater than
14% m/m, more preferably greater than 20% m/m. Advantageously, the
level of C7 asphaltenes is comprised between 1 and 40% and
preferably between 2 and 30% by weight.
[0027] The stages of deasphalting of the process according to the
invention can be carried out in an extraction column or extractor,
preferably in a mixer-settler. Preferably, the mixture of solvents
according to the invention is introduced into an extraction column
or a mixer-settler, at two different levels. Preferably, the
mixture of solvents according to the invention is introduced into
an extraction column or a mixer-settler, at a single introduction
level.
[0028] According to the invention, the liquid/liquid extraction of
the stages of deasphalting is implemented under the subcritical
conditions for said mixture of solvents, i.e. at a temperature less
than the critical temperature of the mixture of solvents. When a
single solvent, preferably an apolar solvent, is utilized, the
stage of deasphalting is implemented under the subcritical
conditions for said solvent, i.e. at a temperature less than the
critical temperature of said solvent. The extraction temperature is
advantageously comprised between 50 and 350.degree. C., preferably
between 90 and 320.degree. C., more preferably between 100 and
310.degree. C., even more preferably between 120 and 310.degree.
C., even more preferably between 150 and 310.degree. C. and the
pressure is advantageously comprised between 0.1 and 6 MPa,
preferably between 2 and 6 MPa.
[0029] The ratio of the volume of the mixture of solvents according
to the invention (volume of polar solvent+volume of apolar solvent)
to the mass of feedstock is generally comprised between 1/1 and
10/1, preferably between 2/1 to 8/1 expressed as litres per
kilogram.
[0030] The mixture of solvents used in at least one of the stages
of selective deasphalting according to the invention is a mixture
of at least one polar solvent and at least one apolar solvent.
[0031] Advantageously, the proportion of polar solvent in the
mixture of polar solvent and apolar solvent is comprised between
0.1 and 99.9%, preferably between 0.1 and 95%, preferably between 1
and 95%, more preferably between 1 and 90%, even more preferably
between 1 and 85%, and very preferably between 1 and 80%
volume.
[0032] Advantageously according to the process of the invention,
the boiling point of the polar solvent in the mixture of solvents
according to the invention is above the boiling point of the apolar
solvent.
[0033] The polar solvent used in the process according to the
invention can be selected from the pure aromatic or
naphthene-aromatic solvents, polar solvents comprising
hetero-elements, or mixtures thereof. The aromatic solvent is
advantageously selected from the monoaromatic hydrocarbons,
preferably benzene, toluene or the xylenes alone or in a mixture;
the diaromatics or polyaromatics; the naphthenic
hydrocarbons-aromatic hydrocarbons such as tetralin or indane; the
heteroatomic aromatic hydrocarbons (oxygen-containing,
nitrogen-containing, sulphur-containing) or any other family of
compounds having a more polar nature than the saturated
hydrocarbons such as for example dimethylsulphoxide (DMSO),
di-methyl formamide (DMF), tetrahydrofuran (THF). The polar solvent
used in the process according to the invention can be a cut rich in
aromatics. The cuts rich in aromatics according to the invention
can be for example cuts originating from FCC (Fluid Catalytic
Cracking) such as heavy gasoline or LCO (LCO (light cycle oil)) or
originating from the petrochemical units of refineries. The cuts
derived from coal, biomass or biomass/coal mixture optionally with
a residual petroleum feedstock following thermochemical conversion
with or without hydrogen, with or without catalyst may also be
mentioned. Preferably, the polar solvent used is a monoaromatic
hydrocarbon, pure or in a mixture with an aromatic hydrocarbon.
[0034] The apolar solvent used in the process according to the
invention is preferably a solvent made up of saturated
hydrocarbon(s) comprising a number of carbon atoms greater than or
equal to 2, preferably comprised between 2 and 9. These solvents
are used pure or in a mixture (for example: a mixture of alkanes
and/or cycloalkanes or light petroleum cuts of the naphtha
type).
[0035] Combined with the temperature and pressure conditions of the
extraction according to the invention, the selection of the nature
of the solvents, the selection of the combination of apolar/polar
solvents in at least one of the stages of deasphalting makes it
possible to access a minimum of two key points of adjustment in
series which can be adjusted and which make it possible to access a
range of selectivity previously inaccessible with conventional
deasphalting. In the case of the present invention, the
optimization of the two key points of adjustment makes it possible
to separate the feedstock into three fractions: a fraction of
asphalt referred to as final, enriched with impurities and
compounds resistant to upcycling, a heavy deasphalted oil phase
referred to as heavy DAO enriched with structures of the least
polar resins and asphaltenes that are not refractory, and a light
deasphalted oil phase referred to as light DAO depleted of resins
and asphaltenes, and generally of impurities (metals,
heteroatoms).
[0036] According to the process of the invention, the nature of the
solvent and/or the proportion and/or the intrinsic polarity of the
polar solvent in the mixture of solvents can be adjusted according
to whether the asphalt is to be extracted during the first stage of
deasphalting or during the second stage of deasphalting.
[0037] In a first embodiment, the process according to the
invention is implemented in a configuration referred to as having
decreasing polarity, i.e. the polarity of the mixture of solvents
used during the first stage of deasphalting is higher than that of
the solvent or mixture of solvents used during the second stage of
deasphalting. This configuration makes it possible to extract,
during the first stage of deasphalting, a fraction of asphalt phase
referred to as final and a fraction of complete deasphalted oil
referred to as complete DAO; the two fractions referred to as heavy
deasphalted oil and light deasphalted oil being extracted from the
complete deasphalted oil referred to as complete DAO during the
second stage of deasphalting.
[0038] In a second embodiment, the process according to the
invention is implemented in a configuration referred to as having
increasing polarity, i.e. the polarity of the solvent or mixture of
solvents used during the first stage of deasphalting is lower than
that of the mixture of solvents used during the second stage of
deasphalting. In such a configuration, during the first stage a
fraction of deasphalted oil referred to as light and an effluent
comprising an oil phase and an asphalt phase are extracted; said
effluent being subjected to a second stage of deasphalting in order
to extract a fraction of asphalt phase and a fraction of heavy
deasphalted oil phase referred to as heavy DAO.
First Embodiment
[0039] According to this embodiment, the process according to the
invention comprises at least: [0040] a) a first stage of
deasphalting comprising bringing the feedstock into contact with a
mixture of at least one polar solvent and at least one apolar
solvent, the proportions of said polar solvent and said apolar
solvent being adjusted so as to obtain at least one fraction of
asphalt phase and one fraction of complete deasphalted oil phase
referred to as complete DAO and [0041] b) a second stage of
deasphalting comprising bringing at least a part of the complete
deasphalted oil phase referred to as complete DAO originating from
stage a) into contact with either an apolar solvent or a mixture of
at least one polar solvent and at least one apolar solvent, the
proportions of said polar solvent and said apolar solvent in the
mixture being adjusted so as to obtain at least one fraction of
light deasphalted oil and one fraction of heavy deasphalted oil,
the stages of deasphalting a) and b) are implemented under the
subcritical conditions of the apolar solvent or mixture of solvents
used.
[0042] For a given feedstock, the higher the proportion and/or
intrinsic polarity of the polar solvent in the mixture of solvents,
the higher the yield of deasphalted oil, a part of the polar
structures of the feedstock remaining solubilized and/or dispersed
in the deasphalted oil DAO phase. Reducing the proportion of polar
solvent in the mixture has the effect of increasing the quantity of
asphaltenic phase collected.
[0043] The first stage of deasphalting thus makes it possible to
extract selectively and in an optimal manner suited to each
feedstock, a fraction of asphalt referred to as final, enriched
with impurities and compounds resistant to upcycling, whilst
leaving solubilized in the complete DAO oil matrix, all or part of
the polar structures of the least polar heavy resins and
asphaltenes which, for their part, are not resistant with respect
to the downstream upcycling stages. Thus, depending on the
proportion of apolar/polar solvent, the yield of deasphalted oil
DAO can be significantly improved and the yield of asphalt
therefore minimized. The asphalt yield can range from 0.1 to 50%
and more particularly from 0.1 to 25%. This is a point of interest
knowing that the upcycling of the asphalt (detrimental fraction)
always constitutes a real limitation to systems including this type
of process.
[0044] The complete deasphalted oil referred to as complete DAO
originating from stage a) with, at least in part, the mixture of
solvents according to the invention during the first stage of
extraction, is preferably subjected to at least one stage of
separation in which the complete deasphalted oil referred to as
complete DAO is separated from the mixture of solvents according to
the invention or at least one stage of separation in which the
complete deasphalted oil referred to as complete DAO is separated
from the apolar solvent only.
[0045] In a variant of the process, the complete deasphalted oil
referred to as complete DAO originating from stage a) with, at
least in part, the mixture of solvents according to the invention
is subjected to two successive stages of separation making it
possible to separate the solvents individually in each stage. Thus,
for example, in a first stage of separation the apolar solvent is
separated from the mixture of complete deasphalted oil referred to
as complete DAO and polar solvent; and in a second stage of
separation the polar solvent is separated from the complete
deasphalted oil referred to as complete DAO.
[0046] The stages of separation are carried out under the
supercritical or subcritical conditions.
[0047] At the end of the stage of separation, the complete
deasphalted oil DAO separated from the mixture of solvents
according to the invention is advantageously sent into at least one
stripping column before being sent to the second stage of
deasphalting.
[0048] The mixture of polar and apolar solvents or the individually
separated solvents are advantageously recycled. In a variant of the
process, only the apolar solvent is recycled into its respective
makeup tank. When the recycled solvents are in a mixture, the
apolar/polar proportion is verified on-line and readjusted as
needed via makeup tanks individually containing the polar and
apolar solvents. When the solvents are separated individually, said
solvents are individually recycled into said respective makeup
tanks.
[0049] The separated asphalt phase from the first stage of
deasphalting is preferably in the liquid state and is generally
diluted at least in part with a portion of the mixture of solvents
according to the invention, the quantity of which can range up to
200%, preferably between 30 and 80% of the volume of asphalt drawn
off. The asphalt extracted with, at least in part, the mixture of
polar and apolar solvents at the end of the stage of extraction can
be mixed with at least one fluxing agent so as to be drawn off more
easily. The fluxing agent used can be any solvent or mixture of
solvents that can solubilize or disperse the asphalt. The fluxing
agent can be a polar solvent selected from the monoaromatic
hydrocarbons, preferably benzene, toluene or xylene; the
diaromatics or polyaromatics; the naphthene-hydrocarbons-aromatic
hydrocarbons such as tetralin or indane; the heteroatomic aromatic
hydrocarbons; the polar solvents with a molecular weight
corresponding to boiling points comprised for example between
200.degree. C. and 600.degree. C. such as a LCO (light cycle oil
from FCC), a HCO (heavy cycle oil from FCC), FCC slurry, HCGO
(heavy coker gas-oil), or an aromatic extract or an extra-aromatic
cut extracted from an oil chain, the VGO cuts originating from a
conversion of residual fractions and/or of coal and/or of biomass.
The ratio of volume of fluxing agent to the mass of the asphalt is
determined so that the mixture can be easily drawn off.
[0050] The second stage of deasphalting can be implemented on at
least a part, preferably the whole of the complete deasphalted oil
referred to as complete DAO originating from the first stage of
deasphalting in the presence of a mixture of at least one polar
solvent and at least one apolar solvent under the subcritical
conditions for the mixture of solvents used. The second stage of
deasphalting can also be implemented on at least a part, preferably
the whole of the complete deasphalted oil referred to as complete
DAO originating from the first stage of deasphalting in the
presence of an apolar solvent under the subcritical conditions for
the solvent used. The polarity of said solvent or mixture of
solvents is preferably lower than that of the mixture of solvents
used in the first stage of deasphalting. This extraction is carried
out so as to obtain a precipitated heavy deasphalted oil phase
referred to as heavy DAO, predominantly comprising the family of
the least polar resins and asphaltenes and a light deasphalted oil
phase referred to as light DAO depleted of resins and asphaltenes,
and generally of impurities (metals, heteroatoms). The light
deasphalted oil phase referred to as light DAO predominantly
comprises the family of the saturated hydrocarbons and the family
of the aromatic hydrocarbons.
[0051] According to the invention, the separation selectivity and
therefore the composition of the fractions of heavy deasphalted oil
referred to as heavy DAO and light deasphalted oil referred to as
light DAO can be modified by adjusting the polarity of the mixture
of solvents by means of the nature and proportion of the
apolar/polar solvents in the mixture or the nature of the apolar
solvent.
Second Embodiment
[0052] In a second embodiment, the process according to the
invention comprises at least: [0053] a) a first stage of
deasphalting comprising bringing the feedstock into contact with
either an apolar solvent, or a mixture of at least one polar
solvent and at least one apolar solvent, the proportions of said
polar solvent and said apolar solvent in the mixture being adjusted
so as to obtain at least one fraction of light deasphalted oil
phase and an effluent comprising an oil phase and an asphalt phase;
and [0054] b) a second stage of deasphalting comprising bringing at
least a part of the effluent originating from stage a) into contact
with a mixture of at least one polar solvent and at least one
apolar solvent, the proportions of said polar solvent and said
apolar solvent being adjusted so as to obtain at least one fraction
of asphalt phase and a fraction of heavy deasphalted oil phase,
said stages of deasphalting being implemented under the subcritical
conditions of the apolar solvent or of the mixture of solvents
used.
[0055] In the present embodiment, the order of extraction of the
categories of products is reversed: the polarity of the solvent or
of the mixture of solvents used in the first stage of deasphalting
is lower than that of the mixture of solvents used in the second
stage of deasphalting.
[0056] The first stage of deasphalting thus makes it possible to
selectively extract from the feedstock a fraction of light
deasphalted oil referred to as light DAO and an effluent comprising
an oil phase and an asphalt phase. The first stage of deasphalting
can be implemented both on an apolar solvent and on a mixture of
solvents according to the invention. The nature, the proportion
and/or the polarity of the polar solvent in the mixture of solvents
is adapted, under the subcritical conditions of the solvent or of
the mixture of solvents used, so as to extract a fraction of light
deasphalted oil predominantly comprising the family of the
saturated hydrocarbons and the family of the aromatic
hydrocarbons.
[0057] The effluent comprising a heavy deasphalted oil phase
referred to as heavy DAO and an extracted asphalt phase from the
first stage of deasphalting can contain, at least in part, the
apolar solvent or the mixture of solvents according to the
invention. Advantageously according to the invention, said effluent
is subjected to at least one stage of separation in which it is
separated from the apolar solvent or from the mixture of solvents
according to the invention or at least one stage of separation in
which said effluent is separated only from the apolar solvent
contained in the mixture of solvents.
[0058] In a variant of the process according to the invention, said
effluent can be subjected to at least two successive stages of
separation making it possible to separate the solvents individually
in each stage of separation (as described in the first embodiment
of the invention).
[0059] The stages of separation are carried out under supercritical
or subcritical conditions.
[0060] At the end of the stage of separation, the effluent
comprising the heavy deasphalted oil phase referred to as heavy DAO
and the asphalt phase separated from the solvent or from the
mixture of solvents according to the invention can be sent into at
least one stripping column before being sent to the second stage of
deasphalting.
[0061] The mixture of polar and apolar solvents or the individually
separated solvents are advantageously recycled. In a variant of the
process, only the apolar solvent is recycled into its respective
makeup tank. When the recycled solvents are in a mixture, the
proportion of the apolar and polar solvents is verified on-line and
readjusted as needed via makeup tanks containing said polar and
apolar solvents individually. When the solvents are separated
individually, said solvents are individually recycled into said
respective makeup tanks.
[0062] The second stage of deasphalting is implemented on at least
a part, preferably the whole of the effluent comprising a heavy
deasphalted oil phase referred to as heavy DAO and an asphalt phase
originating from the first stage of deasphalting in the presence of
a mixture of at least one polar solvent and at least one apolar
solvent under the subcritical conditions for the mixture of
solvents used. The polarity of said mixture of solvents is
preferably higher than that of the solvent or of the mixture of
solvents used in the first stage of deasphalting. This extraction
is carried out so as to selectively extract from the effluent, a
fraction of asphalt referred to as final, enriched with impurities
and compounds resistant to upcycling, whilst leaving solubilized in
the heavy deasphalted oil matrix referred to as heavy DAO, all or
part of the polar structures of the least polar resins and
asphaltenes remaining generally contained in the fraction of
asphalt in the case of conventional deasphalting.
[0063] The process according to the invention has the advantage of
allowing a significant improvement in the total yield of light and
heavy deasphalted oils referred to as light DAO and heavy DAO over
an entire range previously unexplored by conventional deasphalting.
For a given feedstock for which the total yield of light and heavy
deasphalted oils obtained levels off at 75% (extraction with normal
heptane in conventional deasphalting), the deasphalting implemented
in the invention makes it possible, under specific conditions, to
cover the range of 75-99.9% of total yield of light and heavy
deasphalted oils referred to as light DAO and heavy DAO, by
adjustment of the proportion of polar solvent and apolar
solvent.
[0064] The process according to the invention, due to its
separation selectivity and its flexibility, makes it possible to
obtain a fraction of asphalt with a yield of asphalt much lower
than that which can be obtained by a conventional deasphalting
process in the case of a given feedstock. Said yield of asphalt is
advantageously comprised between 1 and 50%, preferably between 1
and 25%, more preferably between 1 and 20%.
[0065] The present invention has the advantage: i) of an
improvement in the properties of the feedstocks treated allowing
easier and more efficient upcycling whilst ii) limiting the yield
of asphalt in a controlled manner.
[0066] Thanks to two key points of adjustment, the process
according to the invention has the advantage of improved
flexibility with respect to: [0067] the nature of the feedstock:
the invention is suited to the treatment of a wider range of
feedstock, [0068] the upcycling of the products: depending on the
upcycling route of the products sought, the invention makes it
possible to orient the selectivity of the separation towards
obtaining fractions of heavy deasphalted oil referred to as heavy
DAO and light deasphalted oil referred to as light DAO optimized in
terms of yield and/or chemical composition.
[0069] The fraction of light deasphalted oil referred to as light
DAO can for example be upcycled as feedstock for hydrocracking, FCC
(in order to increase the upcycling of gasoline for example) or for
any other refining treatment process. The fraction of heavy
deasphalted oil referred to as heavy DAO can for example be
upcycled as feedstock for hydrotreatment, hydroconversion or any
other refining treatment process, but also recycled in certain
refining processes.
DESCRIPTION OF THE FIGURES
[0070] According to an embodiment of the invention described in
FIG. 1, the feedstock (1) heated beforehand using furnaces and/or
exchangers (not shown) is introduced into an extractor (13) such as
an extraction column, preferably a mixer-settler. The mixture of
polar solvent (3) and apolar solvent (2) is produced upstream in a
mixer (10) fed by two makeup tanks each filled separately with
polar solvent (tank 4) and apolar solvent (tank 5). The mixture of
solvents is for example introduced into the extractor (13) at two
different levels. At least a part of the mixture of solvents is
sent via the conduit 11 in a mixture with the introduced feedstock
into the extractor (13) via the conduit 1. At least one other part
of the mixture of solvents is sent via the conduit (12) directly
into the extractor (13) in which the extraction is carried out
under conditions according to the invention defined above.
[0071] According to FIG. 1, the asphalt (16) also containing, at
least in part, the mixture of solvents according to the invention,
is drawn off from the extractor (13) in the form of a liquid
mixture or in the form of a dispersed solid using a fluxing agent
sent via the conduit 14. The mixture of asphalt, solvent according
to the invention and fluxing agent can then be sent to an
additional stage of separation that is not shown. The separated
solvents or part of the solvents or fluxing agent can be reused in
the process of the invention.
[0072] At the end of the first stage of extraction, the complete
deasphalted oil referred to as extracted complete DAO, in a mixture
with, at least in part, the mixture of solvents according to the
invention is sent via the conduit 15 to the separator (17) in which
the complete deasphalted oil is separated from the mixture of
solvents or only from the apolar solvent contained in the mixture
of solvents (22). The process can comprise a second separator (see
FIG. 2) in the case where the solvents are separated individually.
The mixture of solvents or the solvents taken individually are
advantageously separated in the separator under supercritical or
subcritical conditions. The complete deasphalted oil is then
preferably sent into a stripping column (19) via the conduit (18),
before being recovered via the conduit (20). The solvent
originating from the stripping column is sent to the line (23) via
the conduit (21).
[0073] The solvent originating from the separator (17) and the
stripping column (21) is advantageously recycled internally in the
process via the line (23) to the extractor (13). The composition of
the mixture of polar and apolar solvents is preferably verified
on-line by a density meter or a refractometer (24). The proportions
of polar solvent and apolar solvent are, as needed, readjusted with
a makeup of polar solvent and apolar solvent respectively conveyed
from the makeup tanks (4) and (5) via the conduits (6) and (7). The
mixture readjusted in this way is advantageously homogenized in a
static-type mixer (25) before being sent into the mixer (10). When
the solvents are separated individually, each solvent is recycled
into its original tank.
[0074] The complete deasphalted oil recovered via the conduit (20)
is then sent to a second extractor (37) utilized under conditions
according to the invention and making it possible to separate a
fraction of light deasphalted oil referred to as light DAO (38) and
a fraction of heavy deasphalted oil referred to as heavy DAO (39).
The mixture of polar solvent (27) and apolar solvent (26) is
produced upstream in a mixer (34) fed by two makeup tanks each
filled separately with polar solvent (tank 28) and apolar solvent
(tank 29). The polar and apolar solvents can be different from
those used in the first extractor. In the case where the polar and
apolar solvents used in the two extractors are identical, the
mixture of solvents used in the second extractor can be fed by the
two makeup tanks (4) and (5). Otherwise, the mixture of solvents
used in the second extractor is fed by the two makeup tanks (28)
and (29). In another case in point, only the apolar solvent (26)
can be utilized.
[0075] The fraction of light deasphalted oil referred to as light
DAO (38) extracted in a mixture with, at least in part, the apolar
solvent or the mixture of solvents according to the invention is
sent to a separator (40) in which the light deasphalted oil
referred to as light DAO (41) is separated, in part or not, from
the solvent according to the invention (45). The process can
comprise a second separator in the case where the solvents are
separated individually as described above in the case of the
mixture of solvents. The mixture of solvents or the solvents taken
individually are advantageously separated in the separator under
supercritical or subcritical conditions. The light deasphalted oil
referred to as light DAO (41) is then preferably sent into a
stripping column (42), before being recovered via the conduit (43).
The solvent originating from the stripping column is sent to the
line (46) via the conduit (44).
[0076] The fraction of extracted heavy deasphalted oil referred to
as heavy DAO (39) in a mixture with, at least in part, the apolar
solvent or the mixture of solvents according to the invention is
sent to a separator (49) in which the heavy deasphalted oil
referred to as heavy DAO (50) is separated from the apolar solvent
or from the solvent according to the invention or only from the
apolar solvent contained in the mixture of solvents (53). The
mixture of solvents or the solvents taken individually are
advantageously separated in the separator under supercritical or
subcritical conditions. The heavy deasphalted oil referred to as
heavy DAO (50) is then preferably sent into a stripping column
(51), before being recovered via the conduit (52). The solvent
originating from the stripping column is sent to the line (46) via
the conduit (54).
[0077] The solvents originating from the separators (40, 49), of
the stripping columns (42, 51) are advantageously recycled
internally in the process via the line (46) to the extractor (37).
In the case of a mixture of solvents, the composition of the
mixture of polar and apolar solvents is preferably verified on-line
by a density meter or a refractometer (47). The proportions of
polar solvent and apolar solvent are, as needed, readjusted with a
makeup of polar solvent and apolar solvent conveyed from the makeup
tanks (28) and (29) or from the makeup tanks (4) and (5) according
to whether the solvents used in the second extractor are identical
to or different from those used in the first extractor. The mixture
readjusted in this way is advantageously homogenized in a
static-type mixer (48) before being sent to the mixer (34). When
the solvents are separated individually, each solvent is recycled
into its original tank.
[0078] FIG. 2 shows a diagram of the process according to the
invention incorporating two separators (17) and (20) making it
possible to separate the solvents individually and recycle them
individually into their respective tanks. Thus according to FIG. 2,
the feedstock (1) heated beforehand using furnaces and/or
exchangers (not shown) is introduced into an extractor (13) such as
an extraction column, preferably a mixer-settler. The mixture of
polar solvent (3) and apolar solvent (2) is produced upstream in a
mixer (10) fed by two makeup tanks, each filled separately with
polar solvent (tank 4) and apolar solvent (tank 5). The mixture of
solvents is for example introduced into the extractor (13) at two
different levels. At least a part of the mixture of solvents is
sent via the conduit (11) in a mixture with the introduced
feedstock into the extractor (13) via the conduit (1). At least one
other part of the mixture of solvents is sent via the conduit 12
directly into the extractor (13) in which the extraction is carried
out under conditions according to the invention defined above.
[0079] The asphalt (16) also containing, at least in part, the
mixture of solvents according to the invention is drawn off from
the extractor (13) in the form of a liquid mixture or in the form
of a dispersed solid using a fluxing agent sent via the conduit
(14). The asphalt (16) can be subjected to the same treatment as
that described for FIG. 1.
[0080] At the end of the first stage of extraction, the extracted
complete deasphalted oil referred to as complete DAO in a mixture
with, at least in part, the mixture of solvents according to the
invention is sent via the conduit (15) to the separator (17) in
which the complete deasphalted oil referred to as complete DAO is
preferably separated from the apolar solvent (19). The apolar
solvent is advantageously recycled into the tank (5). The complete
deasphalted oil referred to as complete DAO, in a mixture with the
polar solvent, is then sent via the conduit (18) to the second
separator (20) in which the complete deasphalted oil referred to as
complete DAO is separated from the polar solvent (21) sent to the
line (26). The solvents are advantageously separated in the
separators under supercritical or subcritical conditions. The
complete deasphalted oil referred to as complete DAO is then
preferably sent into a stripping column (23) via the conduit (22),
before being recovered via the conduit (24). The solvent
originating from the stripping column is sent to the line (26) via
the conduit (25). The polar solvent originating from the separator
(20) and the stripping column (23) is recycled into the tank (4)
via the line (26).
[0081] The complete deasphalted oil referred to as complete DAO
recovered via the conduit (24) is then sent to a second extractor
(38). The separated fractions of deasphalted oil are subjected to
the same treatment as that described above in FIG. 1.
EXAMPLES
[0082] The feedstock selected for the examples is a vacuum residue
originating from Athabasca in northern Canada. Its chemical
characteristics are given in Table 1.
Example 1
Not According to the Invention
[0083] Example 1 corresponds to the implementation of conventional
two-stage deasphalting as described in the patent US 2008149534.
The selected feedstock has been subjected to a first deasphalting
with the paraffinic solvent normal heptane, then the collected
deasphalted oil C7 DAO has been subjected to a second deasphalting
with normal propane in order to obtain the heavy DAO and light DAO
fractions. The properties as well as the extraction yields of each
of the fractions are summarized in Table 1.
[0084] The yield of C7 DAO is 75% for a C7 asphaltenes content
(measured according to the standard NFT60-115) of 14%. This shows
that a part of the resins has also been extracted with the C7
asphaltenes in order to constitute the asphalt.
TABLE-US-00001 TABLE 1 Properties of the feedstock as well as
yields and properties of the fractions originating from the
conventional two-stage deasphalting carried out with the solvents
nC7 for the first stage then nC3 for the second stage. Initial
Athabasca 1st stage 2nd stage Residue Asphalt DAO heavy DAO light
DAO 480.degree. C.+ nC7 nC7 nC3 nC3 Extraction (% of 100 25 75 41
34 yield feedstock) Analyses d4, 15 -- 1.044 1.11 1.021 1.059 0.974
Sulphur % m/m 5.72 7.90 5.00 6.22 3.50 Nitrogen ppm 6200 7944 5625
8927 1581 Ni ppm 115 306 52 93 2 V ppm 317 823 150 268 5 CCR % m/m
20.5 45 12.4 20.5 2.5
[0085] In this example, the yields as well as the qualities of the
various DAOs are fixed by the nature of the paraffinic solvent used
in each of the two stages.
Example 2
According to the Invention
[0086] The feedstock selected is subjected to the selective
two-stage deasphalting according to the invention. The first stage
of extraction is carried out with the combination of solvent nC3
(propane)/toluene (36/65; v/v) at a temperature of 130.degree. C.,
the solvent/feedstock ratio is 5/1 (v/m). This first stage has made
it possible to selectively extract 50% of the C7 asphaltenes from
the fraction of asphalt, whilst minimizing the asphalt yield
thereof (10% m/m) (see Table 2). The first stage makes it possible
to upcycle 90% of the residue (deasphalted oil DAO yield of 90%).
The most polar structures in the feedstock are concentrated in the
fraction of asphalt.
[0087] The fraction of deasphalted oil DAO originating from the
first stage of deasphalting is then separated from the solvent
according to the invention before being subjected to the second
stage of extraction. Cases No. 1 and No. 2 illustrate the
flexibility of the process according to the quality or the
envisaged yield of the separated fractions depending on the
specifications required for the units situated downstream.
Case No. 1: Obtaining a Good-Quality Fraction of Light Deasphalted
Oil
[0088] The second stage of extraction is carried out on the
fraction of deasphalted oil DAO originating from the first stage of
deasphalting with the same solvents as in the first stage of
Example 2, propane (nC3) and toluene. In this case No. 1, the
proportions of propane (nC3) and toluene are adjusted in order to
meet the objective of obtaining a fraction of good-quality light
deasphalted oil referred to as light DAO. The operation is carried
out with a mixture of solvents nC3/toluene (99.5/0.5; v/v), a
temperature of 120.degree. C. and a solvent/DAO ratio of 5/1 (v/m).
A fraction of heavy deasphalted oil referred to as heavy DAO and a
fraction of light deasphalted oil referred to as light DAO are
obtained, with respective yields of 54% and 36% (yields calculated
with respect to the initial feedstock residue). All of the results
are summarized in Table 2.
TABLE-US-00002 TABLE 2 Yield and properties of the fractions
originating from the selective two-stage deasphalting carried out
in the case of obtaining a light DAO fraction of good quality.
Initial 1st stage 2nd stage Athabasca Asphalt DAO heavy DAO light
DAO residue nC3/toluene nC3/toluene nC3/toluene nC3/toluene
480.degree. C.+ (35/65; v/v) (35/65; v/v) (99.5/0.5; v/v)
(99.5/0.5; v/v) Extraction (% of 100 10 90 54 36 yield feedstock)
Analyses d4, 15 -- 1.044 na 1.029 1.064 0.976 Sulphur % m/m 5.72
9.32 5.32 6.49 3.56 Nitrogen ppm 6200 8900 5900 8431 2103 Ni ppm
115 511 71 116 3 V ppm 317 1460 190 313 6 CCR % m/m 20.5 >50
16.3 25.4 2.6 *na: not analyzable.
[0089] It is noted that the qualities of the fraction of light
deasphalted oil obtained in Example 1, are very close to those
obtained in the light deasphalted oil according to the invention,
with the yield of light deasphalted oil according to the invention
being identical.
[0090] The fraction of heavy deasphalted oil referred to as heavy
DAO obtained according to the invention is enriched with the least
polar resins and asphaltenes. This fraction has a marked aromatic
nature and a higher concentration of impurities (metals,
heteroatoms) than the fraction of light deasphalted oil referred to
as light DAO. If the properties of this fraction are compared to
those of the heavy deasphalted oil of Example 1, it is noted that
they are richer in heavy structures but can be upcycled, unlike
Example 1 where these structures remain non-upcycled as they are
contained in the fraction of asphalt. The yield of heavy
deasphalted oil referred to as heavy DAO produced that can be
upcycled is clearly improved (54% as against 41% in the case of the
conventional SDA of Example 1).
Case No. 2: Obtaining the Fraction of Light Deasphalted Oil
Referred to as Light DAO with a Better Yield
[0091] The second stage of extraction is carried out on the DAO
originating from the first stage of deasphalting with the same
solvents as in the first stage of Example 2, propane (nC3) and
toluene. In this case No. 2, the proportions of propane (nC3) and
toluene are adjusted in order to meet the objective of obtaining a
light deasphalted oil referred to as light DAO with a high yield.
The extraction conditions of the first stage of the process remain
unchanged. The operation is carried out with a mixture of solvents
nC3/toluene (72/28 (v/v)). The temperature is 125.degree. C. and
the solvent/DAO ratio is 5/1 (v/m).
[0092] The results shown in Table 3 show that the fraction of light
deasphalted oil referred to as light DAO is obtained with a yield
of 60% instead of 36% in case No. 1. On the other hand, this
deasphalted oil now contains a part of the least polar resins.
Consequently, the yield of the heavy deasphalted oil referred to as
heavy DAO is reduced from 54 to 30% (compared with case No. 1) and
it concentrates a majority of the least polar asphaltenes and the
most polar resins. This heavy deasphalted oil can be recycled and
is sought depending on the objective of the system in which the
invention is incorporated.
[0093] The advantage of using a combination of apolar/polar solvent
is being able to adjust and optimize as desired and without
limitation the yield (unlike conventional deasphalting), the
yield/quality relationship of the extracted fractions originating
from the stages of deasphalting for a given feedstock and for an
objective of a given system. There is no longer any restriction
imposed by the nature of the solvents as in the case of
conventional deasphalting, which is what gives the process all its
flexibility.
TABLE-US-00003 TABLE 3 Yield and properties of the fractions
originating from the selective two-stage deasphalting carried out
in the case of obtaining a fraction of light deasphalted oil
referred to as light DAO, with a better yield. Initial 1st stage
2nd stage Athabasca Asphalt DAO heavy DAO light DAO residue
nC3/toluene nC3/toluene nC3/toluene nC3/toluene 480.degree. C.+
(35/65; v/v) (35/65; v/v) (72/28; v/v) (72/28; v/v) Extraction (%
of 100 10 90 30 60 yield feedstock) Analyses d4, 15 -- 1.044 na
1.029 1.105 0.991 Sulphur % m/m 5.72 9.32 5.32 8.00 3.98 Nitrogen
ppm 6200 8900 5900 7496 5102 Ni ppm 115 511 71 151 31 V ppm 317
1460 190 324 123 CCR % m/m 20.5 >50 16.3 33.9 7.5 *na: not
analyzable.
* * * * *