U.S. patent application number 12/248163 was filed with the patent office on 2009-04-23 for process for the conversion of heavy charges such as heavy crude oils and distillation residues.
This patent application is currently assigned to ENI S.P. A.. Invention is credited to Sebastiano Correra, Alberto Delbianco, Mario MARCHIONNA, Romolo Montanari, Nicoletta Panariti, Sergio Rosi.
Application Number | 20090101540 12/248163 |
Document ID | / |
Family ID | 11448011 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090101540 |
Kind Code |
A1 |
MARCHIONNA; Mario ; et
al. |
April 23, 2009 |
PROCESS FOR THE CONVERSION OF HEAVY CHARGES SUCH AS HEAVY CRUDE
OILS AND DISTILLATION RESIDUES
Abstract
Process for the conversion of heavy charges such as heavy crude
oils, tars from oil sands and distillation residues, by the
combined use of the following three process units: hydroconversion
with catalysts in slurry phase (HT), distillation or flash (D),
deasphalting (SDA), characterized in that the three units operate
on mixed streams consisting of fresh charge and recycled streams,
by the use of the following steps: sending at least one fraction of
the heavy charge to a deasphalting section (SDA) in the presence of
hydrocarbon solvents obtaining two streams, one consisting of
deasphalted oil (DAO), the other of asphalts; mixing the asphalt
with a suitable hydrogenation catalyst and optionally with the
remaining fraction of heavy charge not sent to the deasphalting
section and sending the mixture obtained to a hydro-treatment
reactor (HT) into which hydrogen or a mixture of hydrogen and
H.sub.2S is charged; sending the stream containing the
hydro-treatment reaction product and the catalyst in dispersed
phase to one or more distillation or flash steps (D) whereby the
most volatile fractions are separated, among which the gases
produced in the hydro-treatment reaction; recycling at least 60% by
weight, preferably at least 80%, more preferably at least 95%, of
the distillation residue (tar) or liquid leaving the flash unit,
containing the catalyst in dispersed phase, rich in metallic
sulfides produced by demetallation of the charge and possibly coke,
to the deasphalting zone.
Inventors: |
MARCHIONNA; Mario; (Milan,
IT) ; Delbianco; Alberto; (Robecco Sul Naviglio
(Milan), IT) ; Panariti; Nicoletta; (Lecco, IT)
; Montanari; Romolo; (San Donato Milanese (Milan),
IT) ; Rosi; Sergio; (San Donato Milanese (Milan),
IT) ; Correra; Sebastiano; (San Donato Milanese
(Milan), IT) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
ENI S.P. A.
Rome
IT
SNAMPROGETTI S.p.A.
San Donato Milanese-Milan
IT
ENITECNOLOGIE S.p.A.
San Donato Milanese
IT
|
Family ID: |
11448011 |
Appl. No.: |
12/248163 |
Filed: |
October 9, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11404746 |
Apr 17, 2006 |
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12248163 |
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10188785 |
Jul 5, 2002 |
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11404746 |
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Current U.S.
Class: |
208/13 ; 208/56;
208/58 |
Current CPC
Class: |
C10G 2300/205 20130101;
C10G 67/0454 20130101; C10G 2300/1077 20130101; Y02P 30/20
20151101; C10G 67/00 20130101; C10G 2300/4081 20130101; C10G
2300/1033 20130101; C10G 2300/44 20130101; C10G 2300/206 20130101;
C10G 2300/207 20130101; C10G 2300/107 20130101 |
Class at
Publication: |
208/13 ; 208/56;
208/58 |
International
Class: |
C10G 49/18 20060101
C10G049/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 6, 2001 |
IT |
MI2001A 001438 |
Claims
1. A process for the conversion of heavy charges selected from
heavy crude oils, distillation residues, "heavy oils coming from
catalytic treatment, "thermal tars", tars from oil sands, various
kinds of coals and other high-boiling charges of a hydrocarbon
origin known as "black oils", by the combined use of the following
three process units: hydroconversion with catalysts in slurry phase
(HT), distillation or flash (D), deasphalting (SDA), characterized
in that the three units operate on mixed streams consisting of
fresh charge and recycled streams, with the use of the following
steps: sending at least one fraction of the heavy charge to a
deasphalting section (SDA) in the presence of hydrocarbon solvents
obtaining two streams, one consisting of deasphalted oil (DAO), the
other of asphalts; mixing the asphalt with a suitable hydrogenation
catalyst with the remaining fraction of heavy charge not sent to
the deasphalting section and sending the mixture obtained to a
hydro-treatment reactor (HT) into which hydrogen or a mixture of
hydrogen and H.sub.2S is charged; sending the stream containing the
hydro-treatment reaction product and the catalyst in dispersed
phase to one or more distillation or flash steps (D) whereby the
most volatile fractions are separated, among which the gases
produced in the hydro-treatment reaction; recycling at least 60% by
weight of the distillation residue (tar) or liquid leaving the
flash unit, containing the catalyst in dispersed phase, rich in
metallic sulfides produced by demetallation of the charge and
possibly coke, to the deasphalting zone.
2. The process according to claim 1, wherein at least 80% by weight
of the distillation residue or liquid leaving the flash unit is
recycled to the deasphalting zone.
3. The process according to claim 2, wherein at least 95% by weight
of the distillation residue or liquid leaving the flash unit is
recycled to the deasphalting zone.
4. The process according to claim 1, wherein at least part of the
remaining part of distillation residue (tar) or liquid leaving the
flash unit, not recycled to the deasphalting zone, is recycled to
the hydro-treatment section.
5. The process according to claim 1, wherein the recycling ratio
between the streams containing asphaltenes, or fresh charge, tar
and asphalts, must be such that: (.upsilon..sub.mix/RT)
(.delta..sub.asph-.delta..sub.mix).sup.2<k wherein:
.delta..sub.asph is the highest value among the solubility
parameters of the two C.sub.7 asphaltenes of the mixture (highest
value) .upsilon..sub.mix is the molar average of the molar volumes
of the maltene components .delta..sub.mix is the volumetric average
of the solubility parameters of the maltene components k is a
constant whose value ranges from 0.2 to 0.5; R is the gas constant
with a value of 1.987 cal/mol K; and T is the temperature with
units of K.
6. The process according to claim 1, wherein the distillation step
is carried out at a reduced pressure ranging from 0.001 to 0.5
MPa.
7. The process according to claim 6, wherein the distillation step
is carried out at a reduced pressure ranging from 0.05 to 0.3
MPa.
8. The process according to claim 1, wherein the hydro-treatment
step is carried out at a temperature ranging from 370 to
450.degree. C. and a pressure ranging from 30 to 300 Atm.
9. The process according to claim 8, wherein the hydro-treatment
step is carried out at a temperature ranging from 380 to
440.degree. C. and a pressure ranging from 100 to 200 Atm.
10. The process according to claim 1, wherein the deasphalting step
is carried out at temperatures ranging from 40 to 200.degree. C.
and a pressure ranging from 1 to 70 Atm.
11. The process according to claim 1, wherein the deasphalting
solvent is a light paraffin with from 3 to 6 carbon atoms.
12. The process according to claim 1, wherein the deasphalting step
is carried out by means of extraction with a solvent operating in
supercritical phase.
13. The process according to claim 1, wherein the stream consisting
of deasphalted oil (DAO) is fractionated by conventional
distillation.
14. The process according to claim 1, wherein the stream consisting
of deasphalted oil (DAO) is mixed with the products separated in
the flash step after being condensed.
15. The process according to claim 1, wherein the hydrogenation
catalyst is an easily decomposable precursor or a preformed
compound based on one or more transition metals.
16. The process according to claim 15, wherein the transition metal
is molybdenum.
17. The process according to claim 1, wherein the concentration of
catalyst in the hydroconversion reactor, defined on the basis of
the concentration of the metal or metals present, ranges from 350
to 10000 ppm.
18. The process according to claim 17, wherein the concentration of
catalyst in the hydroconversion reactor ranges from 1000 to 8000
ppm.
19. The process according to claim 18, wherein the concentration of
catalyst in the hydroconversion reactor ranges from 1500 to 5000
ppm.
Description
[0001] The present application is a continuation application of
U.S. Ser. No. 11/404,746, pending, which is a Continuation
application of U.S. Ser. No. 10/188,785, abandoned, which claims
priority to MI 2001A001438, filed on Jul. 6, 2001.
[0002] The present invention relates to a process for the
conversion of heavy charges, among, which heavy crude oils, tars
from oil sands and distillation residues, by the use of three
process units: hydroconversion of the charge using catalysts in
dispersed phase, distillation and deasphalting, suitably connected
and fed with mixed streams consisting of fresh charge and
conversion products.
[0003] The conversion of heavy crude oils, tars from oil sands and
oil residues in liquid products can be substantially effected in
two ways: one exclusively thermal, the other by means hydrogenating
treatment.
[0004] Current studies are mainly directed towards hydrogenating
treatment, as thermal processes have problems linked to the
disposal of the by-products, in particular coke (even obtained in
quantities higher than 30% by weight with respect to the charge)
and to the poor quality of the conversion products.
[0005] Hydrogenating processes consist in treating the charge in
the presence of hydrogen and suitable catalysts.
[0006] Hydroconversion technologies currently on the market use
fixed bed or ebullated bed reactors and catalysts generally
consisting of one or more transition metals (Mo, W, Ni, Co, etc.)
supported on silica/alumina (or equivalent material).
[0007] Fixed bed technologies have considerable problems in
treating particularly heavy charges containing high percentages of
heteroatoms, metals and asphaltenes, as this pollutants cause a
rapid deactivation of the catalyst.
[0008] Ebullated bed technologies have been developed and
commercialized for treating these charges, which provide
interesting performances, but are complex and costly.
[0009] Hydro-treatment technologies operating with catalysts in
dispersed phase can provide an attractive solution to the drawbacks
met in the use of fixed or ebullated bed technologies. Slurry
processes, in fact, combine the advantage of a wide flexibility of
the charge with high performances in terms of conversion and
upgrading, and are therefore, in principle, simpler from a
technological point of view.
[0010] Slurry technologies are characterized by the presence of
particles of catalyst having very small average dimensions and
effectively dispersed in the medium: for this reason hydrogenation
processes are easier and more immediate in all points of the
reactor. The formation of coke is considerably reduced and the
upgrading of the charge is high.
[0011] The catalyst can be charged as powder with sufficiently
reduced dimensions (U.S. Pat. No. 4,303,634) or as oil-soluble
precursor (U.S. Pat. No. 5,288,681). In this latter case, the
active form of the catalyst (generally the metal sulfide) is formed
in-situ by thermal decomposition of the compound used, during the
reaction itself or after suitable pretreatment (U.S. Pat. No.
4,470,295).
[0012] The metallic constituents of the dispersed catalysts are
generally one or more transition metals (preferably Mo, W, Ni, Co
or Ru). Molybdenum and tungsten have much more satisfactory
performances than nickel, cobalt or ruthenium and even more than
vanadium and iron (N. Panariti et al., Appl. Catal. A: January
2000, 204, 203).
[0013] Although the use of dispersed catalysts solves most of the
problems mentioned for the technologies described above, there are
disadvantages, however, mainly associated with the life cycle of
the catalyst itself and with the quality of the products
obtained.
[0014] The procedure for the use of these catalysts (type of
precursors, concentration, etc.) is in fact extremely important
from an economic point of view and also with respect to
environmental impact.
[0015] The catalyst can be used at a low concentration (a few
hundreds of ppm) in a "once-through" configuration, but in this
case the upgrading of the reaction products is generally
insufficient (N. Panariti et al., Appl. Catal. A: January 2000,
204, 203 and 215). When operating with extremely active catalysts
(for example molybdenum) and with higher concentrations of catalyst
(thousands of ppm of metal), the quality of the product obtained
becomes much better, but the catalyst must be recycled.
[0016] The catalyst leaving the reactor can be recovered by
separation from the product obtained from hydro-treatment
(preferably from the bottom of the distillation column, downstream
of the reactor) using conventional methods such as, for example,
decanting, centrifugation or filtration (U.S. Pat. No. 3,240,718;
U.S. Pat. No. 4,762,812). Part of the catalyst can be recycled to
the hydrogenation process without further treatment. However, the
catalyst recovered using known hydro-treatment processes, normally
has a reduced activity with respect to fresh catalyst and a
suitable regeneration step must therefore be effected to restore
the catalytic activity and recycle at least part of the catalyst to
the hydro-treatment reactor. These recovery procedures of the
catalyst, furthermore, are costly and extremely complex from a
technological point of view.
[0017] With respect to the chemical description of conversion
processes, it is convenient to introduce the stability concept
which, for a crude oil or oil residue, expresses their tendency to
precipitate the asphaltene component due to a change in the
operating conditions or chemical composition of the oil and/or
asphaltenes (incompatibility) following dilution with hydrocarbon
cuts or chemical re-arrangement induced by cracking processes,
hydrogenations, etc.
[0018] Hydrocarbons which can be precipitated by a crude oil or oil
residue by treatment with n-heptane under standard conditions
established by regulation IP-143, are conventionally defined as
asphaltenes.
[0019] From a qualitative point of view, it can be affirmed that
incompatibility phenomena arise when products with very different
characteristics are mixed with each other, with respect to the
nature of the maltene, or non-asphaltene component, as in the case
of the mixing of paraffinic crude oils with aromatic crude oils or
the dilution of oil residues with cutter stocks of a paraffinic
nature (a typical case is the flushing of tar from visbreaking with
scarcely aromatic gas oils).
[0020] In conversion processes of oil residues, tars from oil sands
and heavy crude oils to distillates, the maximum conversion level
is limited by the stability of the residue produced. These
processes, in fact, modify the chemical nature of oil and
asphaltenes causing a progressive decrease in the stability with an
increase in the degree of severity. Over a certain limit, the
asphaltenes present in the charge can cause a phase separation (or
precipitate) and therefore activate coke formation processes.
[0021] From a physico-chemical point of view, the phase separation
phenomenon can be explained by the fact that as the conversion
reactions proceed, the asphaltene phase becomes more and more
aromatic due to dealkylation and condensation reactions.
[0022] Consequently, over a certain limit, the asphaltenes are no
longer soluble in the maltene phase also because, in the meantime,
the latter has become more "paraffinic".
[0023] The stability loss control of a heavy charge during a
thermal and/or catalytic conversion process is therefore
fundamental for obtaining the maximum conversion degree without
running into problems relating to the formation of coke and
fouling.
[0024] In once-through processes, the optimum operating conditions
(mainly reaction temperature and residence time) are simply
determined on the basis of the stability data of the reactor
effluent by means of direct measurements on the non-converted
residue (P value, Hot Filtration Test, Spot Test, etc.).
[0025] All these processes allow more or less high conversion
levels to be reached depending on the charge and type of technology
used, generating however a non-converted residue at the stability
limit, which we will call tar, which, depending on the specific
cases, can vary from 30 to 85% of the initial charge. This product
is used for producing fuel oil, tars or it can be used as charge in
gasification processes.
[0026] In order to increase the overall conversion degree of
residue cracking processes, schemes have been proposed which
comprise the recycling of more or less significant quantities of
tar to the cracking unit. In the case of hydro-conversion processes
with catalysts dispersed in slurry phase, the recycling of the tar
also allows recovery of the catalyst, and for this reason, the same
applicants have described in patent application IT-95A001095, a
process which enables recycling of the recovered catalyst to the
hydro-treatment reactor without the need for a further regeneration
step, at the same time obtaining a high-quality product without the
production of residue ("zero residue refinery").
[0027] This process comprises the following steps: [0028] mixing
the heavy crude oil or distillation residue with a suitable
hydrogenation catalyst and sending the mixture obtained to a
hydro-treatment reactor into which hydrogen or a mixture of
hydrogen and H.sub.2S is charged; [0029] sending the stream
containing the hydro-treatment reaction product and the catalyst in
dispersed phase to a distillation zone in which the most volatile
fractions are separated; [0030] sending the high-boiling fraction
obtained in the distillation step to a deasphalting step, and the
consequent production of two streams, one consisting of deasphalted
oil (DAO), the other consisting of asphalt, catalyst in dispersed
phase and possibly coke and enriched with metals coming from the
initial charge; [0031] recycling at least 60%, preferably at least
80%, of the stream consisting of asphalt, catalyst in dispersed
phase and possibly coke, rich in metals, to the hydro-treatment
zone.
[0032] It has now been found that in the case of the upgrading of
heavy crude oils or tars from oil sands to complex hydrocarbon
mixtures to be used as raw material for further conversion
processes to distillates, it may be convenient to use different
process configurations with respect to that described above,
whereby the following advantages are obtained: [0033] maximization
of conversion yields to distillable products (deriving from both
atmospheric and vacuum distillation), and to deasphalted oil (DAO),
which in most cases may exceed 95%; [0034] maximization of the
upgrading degree of the charge, i.e. of the removal of the poisons
present (metals, sulfur, nitrogen, carbonaceous residue),
minimizing the production of coke; [0035] maximum flexibility in
treating charges differing in the nature of the hydrocarbon
component (density) and level of pollutants present; [0036]
possibility of completely recycling the hydrogenation catalyst
without the need for regeneration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 shows an embodiment of the invention including
deasphalting;
[0038] FIG. 2 shows variation of the k parameter in relation to the
composition of a mixture.
DETAILED DESCRIPTION OF THE INVENTION
[0039] The process, object of the present invention, for the
conversion of heavy charges by means of the combined use of the
following three process units: hydroconversion with catalysts in
slurry phase (HT), distillation or flash (D), deasphalting (SDA),
is characterized in that the three units operate on mixed streams
consisting of fresh charge and recycled streams, using the
following steps: [0040] sending at least one fraction of the heavy
charge to a deasphalting section (SDA) in the presence of solvents
obtaining two streams, one consisting of deasphalted oil (DAO), the
other of asphalts; [0041] mixing the asphalt with a suitable
hydrogenation catalyst and optionally with the remaining fraction
of heavy charge not sent to the deasphalting section and sending
the mixture obtained to a hydro-treatment reactor (HT) into which
hydrogen or a mixture of hydrogen and H.sub.2S is charged; [0042]
sending the stream containing the hydro-treatment reaction product
and the catalyst in dispersed phase to one or more distillation or
flash steps (D) whereby the most volatile fractions are separated,
among which the gases produced in the hydro-treatment reaction;
[0043] recycling at least 60% by weight, preferably at least 80%,
more preferably at least 95%, of the distillation residue (tar) or
liquid leaving the flash unit, containing the catalyst in dispersed
phase, rich in metallic sulfides produced by demetallation of the
charge and possibly coke, to the deasphalting zone.
[0044] The heavy charges treated can be of different kinds: they
can be selected from heavy crude oils, distillation residues, heavy
oils coming from catalytic treatment, for example heavy cycle oils
from catalytic cracking treatment, thermal tars (coming for example
from visbreaking or similar thermal processes), tars from oil
sands, various kinds of coals and any other high-boiling charge of
a hydrocarbon origin generally known in the art as "black
oils".
[0045] The possible remaining part of the distillation residue
(tar) or liquid leaving the flash unit, not recycled to the
deasphalting zone, can be either totally or partially recycled, to
the hydro-treatment section.
[0046] The catalysts can be selected from those obtained from
easily decomposable oil-soluble precursors (metallic naphthenates,
metallic derivatives of phosphonic acids, metalcarbonyls, etc.) or
from preformed compounds based on one or more transition metals
such as Ni, Co, Ru, W and Mo: the latter is preferred due to its
high catalytic activity.
[0047] The concentration of catalyst, defined on the basis of the
concentration of metal or metals present in the hydroconversion
reactor, ranges from 350 to 10000 ppm, preferably from 1000 to 8000
ppm, more preferably from 1500 to 5000 ppm.
[0048] The hydro-treatment step is preferably carried out at a
temperature ranging from 370 to 480.degree. C., preferably from 380
to 440.degree. C., and at a pressure ranging from 3 to 30 MPa,
preferably from 10 to 20 MPa.
[0049] The hydrogen is fed to the reactor, which can operate either
under down-flow or, preferably up-flow conditions. The gas can be
fed to different sections of the reactor.
[0050] The distillation step is preferably carried out at reduced
pressure, at a pressure ranging from 0.001 to 0.5 MPa, preferably
from 0.05 to 0.3 MPa.
[0051] The hydro-treatment step can consist of one or more reactors
operating within the range of conditions indicated above. Part of
the distillates produced in the first reactor can be recycled to
the subsequent reactors.
[0052] The deasphalting step, effected by an extraction with a
solvent, which may or may not be hydrocarbon, (for example with
paraffins having from 3 to 6 carbon atoms), is generally carried
out at temperatures ranging from 40 to 200.degree. C. and at a
pressure ranging from 0.1 to 7 MPa. It can also consist of one or
more sections operating with the same solvent or with different
solvents; the solvent can be recovered under supercritical
conditions thus allowing further fractionation between asphalt and
resins.
[0053] The stream consisting of deasphalted oil (DAO) can be used
as such as synthetic crude oil (syncrude), optionally mixed with
the distillates, or it can be used as charge for fluid bed
Catalytic Cracking treatment or Hydrocracking.
[0054] Depending on the characteristics of the crude oil (metal
content, content of sulfur and nitrogen, carbonaceous residue), it
is possible to advantageously modulate: [0055] the ratio between
the heavy residue to be sent to the hydro-treatment section (fresh
charge) and that to be sent for deasphalting; said ratio can vary
from 0 to 100, preferably from 0.1 to 10, more preferably from 1 to
5; [0056] the recycling ratio between fresh charge and tar to be
sent to the deasphalting section; said ratio preferably varies from
0.1 to 100, more preferably from 0.1 to 10; [0057] the recycling
ratio between fresh charge and asphalts to be sent to the
hydro-treatment section; said ratio can vary in relation to the
variation in the previous ratios; [0058] the recycling ratio
between tar and asphalts to be sent to the hydro-treatment section;
said ratio can vary in relation to the variation in the previous
ratios.
[0059] This flexibility is particularly useful for better
exploiting the complementary characteristics of the deasphalting
units (reasonable HDN and dearomatization) and hydrogenation units
(high HDM and HDS).
[0060] Depending on the type of crude oil, the stability of the
streams in question and quality of the product to be obtained (also
in relation to the particular downstream treatment), the fractions
of fresh charge to be fed to the deasphalting and hydro-treatment
sections can be modulated in the best possible way.
[0061] Furthermore, to achieve the best possible running of these
processes, it is advisable to guarantee compatibility of the
streams to be mixed, or that the flows of [0062] fresh charge and
tar [0063] fresh charge and asphalt (possibly containing resins or
an aliquot thereof) [0064] tar and asphalt (possibly containing
resins or an aliquot thereof) having different physico-chemical
characteristics, are mixed in such ratios as to avoid precipitation
of asphaltenes in all process phases.
[0065] The process, object of the present invention, can be further
improved, as far as the compatibility of the streams to be mixed is
concerned, by controlling that the recycling between the streams
containing asphaltenes, or fresh charge, tar and asphalt, has such
a ratio that:
(.nu..sub.mix/RT)(.delta..sub.asph-.delta..sub.mix).sup.2<k
wherein: [0066] .nu..sub.mix is the molar volume of the maltene
component (i.e. non-asphaltene) of the mixture (cm.sup.3/mole);
[0067] .nu..sub.mix is the solubility parameter of the maltene
component of the mixture (cal/cm.sup.3).sup.1/2; [0068]
.delta..sub.asph is the solubility parameter of the asphaltenes of
the mixture (the highest value among the values of the two
components of the mixture is considered)(cal/cm.sup.3).sup.1/2;
[0069] R=Gas Constant (1.987 cal/mol.degree. K.); [0070] T:
temperature expressed in Kelvin degrees.
[0071] The asphaltenes used as reference for determining the
properties indicated above are the insoluble n-heptane fraction
(C.sub.7 asphaltenes).
[0072] The values indicated in the formula are calculated as
follows: [0073] .delta..sub.mix=molar average of the molar volumes
of the maltene components [0074] .delta..sub.mix=volumetric average
of the solubility parameters of the maltene components [0075]
k=constant whose value ranges from 0.2 to 0.5.
[0076] The application described is particularly suitable when the
heavy fractions of complex hydrocarbon mixtures produced by the
process must be used as charge for catalytic cracking plants, both
Hydrocracking (HC) and fluid bed Catalytic Cracking (FCC).
[0077] The combined action of a catalytic hydrogenation unit (HT)
with an extractive process (SDA), in fact, allows deasphalted oils
to be produced with a reduced content of contaminants (metals,
sulfur, nitrogen, carbonaceous residue), which can therefore be
more easily treated in catalytic cracking processes.
[0078] Furthermore, the investment cost of the whole complex can
also be minimized as, with respect to the scheme described in
patent application IT-95A001095, for the same charge unit treated,
the dimensions of the deasphalting section are increased whereas
those of the hydro-treatment section (and downstream distillation
column) are reduced; as the deasphalting unit involves lower
investment costs than the hydro-treatment unit, there is a
consequent saving on the investment cost of the whole complex.
[0079] A preferred embodiment of the present invention is now
provided with the help of FIG. 1 enclosed, which however should not
be considered as limiting the scope of the invention itself.
[0080] The heavy charge (1), or at least a part thereof (1a), is
sent to the deasphalting unit (SDA), an operation which is effected
by means of extraction with solvent.
[0081] Two streams are obtained from the deasphalting unit (SDA):
one (2) consisting of deasphalted oil (DAO), the other consisting
of asphalts and resins (3); the latter can be further separated
into the two groups of compounds of which it is formed, and the
fraction of resins (4) can be divided between DAO and asphalt.
[0082] The stream consisting of asphalt and resins (or a fraction
of these) is mixed with fresh make-up catalyst (5) necessary for
reintegrating that used up with the flushing stream (14), with the
part of heavy charge (1b) not fed to the deasphalting section and
optionally with the stream (15) (which will be described further on
in the text) coming from the bottom of the distillation column (D)
to form a stream (6) which is fed to the hydro-treatment reactor
(HT) into which hydrogen (or a mixture of hydrogen and H.sub.2S)
(7), is charged. A stream (8) containing the hydrogenation product
and catalyst in dispersed phase, leaves the reactor and is
fractionated in a distillation column (D) from which the lighter
fractions (9) and distillable products (10), (11) and (12) are
separated from the distillation residue containing the dispersed
catalyst and coke. This stream, called tar, (13), is completely or
for the most part, except for a flushing (14), recycled to the
deasphalting reactor (SDA). A part of this (15) can be optionally
sent to the hydro-treatment unit (HT).
[0083] Some examples are provided below for a better illustration
of the invention without limiting its scope.
EXAMPLE 1
[0084] Following the scheme represented in FIG. 1, the following
experiment was carried out.
Deasphalting Step
[0085] Charge: 300 g vacuum residue from Ural crude oil (Table
1)
[0086] Deasphalting agent: 2000 cc of liquid propane (extraction
repeated 3 times)
[0087] Temperature: 80.degree. C.
[0088] Pressure: 35 bars
TABLE-US-00001 TABLE 1 Characteristics of Ural vacuum residue
500.degree. C..sub.+ API gravity 10.8 Sulfur (w %) 2.6 Nitrogen (w
%) 0.7 CCR (w %) 18.9 Ni + V (ppm) 80 + 262
Hydro-Treatment Step
[0089] Reactor: 3000 cc, steel, suitably shaped and equipped with
magnetic stirring
[0090] Catalyst: 3000 ppm of Mo/charge added using molybdenum
naphthenate as precursor
[0091] Temperature: 410.degree. C.
[0092] Pressure: 16 MPa of hydrogen
[0093] Residence time: 4 h
Flash Step
[0094] Effected by means of a laboratory apparatus for liquid
evaporation (T=120.degree. C.)
Experimental Results
[0095] 10 consecutive deasphalting tests were effected using, for
each test, a charge consisting of Ural vacuum residue (fresh
charge) and atmospheric residue obtained from the hydro-treatment
reaction of C.sub.3 asphaltenes of the previous step in order to
allow the complete recycling of the catalyst added during the first
test. At every step, the autoclave was fed with a quantity of
charge consisting of Ural vacuum residue (fresh charge) and C.sub.3
asphaltenes deriving from the deasphalting, which was such as to
bring the total charge mass (fresh charge+recycled C.sub.3
asphaltenes) to the initial value of 300 g.
[0096] The ratio between quantity of fresh charge and quantity of
recycled charge reached under these operating conditions was
1:1.
[0097] The data relating to the out-going streams after the last
recycling (weight % with respect to the charge) are as follows:
[0098] Gas: 7%
[0099] Naphtha (C.sub.5-170.degree. C.): 8%
[0100] Atmospheric gas oil (AGO 170-350.degree. C.):17% [0101]
Deasphalted oil (VGO+DAO): 68%
[0102] The asphaltene stream recovered at the end of the test
contains all the catalyst initially fed, sulfides of the metals Ni
and V produced during the 10 recycles from the hydro-treatment and
a quantity of coke in the order of about 1% by weight with respect
to the total quantity of Ural residue fed. In the example
indicated, there was no need to effect any flushing of the recycled
stream. Table 2 provides the characterization of the product
obtained.
TABLE-US-00002 TABLE 2 characteristics of test reaction products
according to Example 1. Sulfur Nitrogen RCC Ni + V w % (ppm) Sp.
Gr. (w %) (ppm) Naphtha C.sub.5-170.degree. C. 0.06 450 0.768 -- --
AGO 170-350.degree. C. 0.52 2100 0.870 -- -- VGO + DAO 1.45 2500
0.938 3 1
EXAMPLE 2
[0103] An experiment was conducted, similar to the one described in
experiment 1, effecting the hydro-treatment step, however, at
420.degree. C.
[0104] The ratio between quantity of fresh charge and quantity of
recycled product reached under these operating conditions was
1:1.5.
[0105] The data relating to the out-going streams after the last
recycling (weight % with respect to the charge) are as follows:
[0106] Gas: 9%
[0107] Naphtha (C.sub.5-170.degree. C.): 11%
[0108] Atmospheric gas oil (AGO 170-350.degree. C.):24%
[0109] Deasphalted oil (VGO+DAO): 56%
[0110] In the example indicated, there was no need to effect any
flushing of the recycled stream.
[0111] Table 3 provides the characterization of the product
obtained.
TABLE-US-00003 TABLE 3 characteristics of test reaction products
according to Example 2. Sulfur Nitrogen RCC Ni + V w % (ppm) Sp.
Gr. (w %) (ppm) Naphtha C.sub.5-170.degree. C. 0.05 300 0.759 -- --
AGO 170-350.degree. C. 0.51 2950 0.864 -- -- VGO + DAO 1.45 2200
0.922 2.5 1
EXAMPLE 3
[0112] The following example shows the use of the relation
(.nu..sub.mix/RT)(.delta..sub.asph-.delta..sub.mix).sub.2<k
indicated in the present invention to evaluate the compatibility
limits of the various streams to be subjected to
hydro-treatment.
[0113] The streams used in Examples 1 and 2 were characterized to
determine the properties used in the above relation.
[0114] Starting from the properties indicated in Table 4 and using
the above relation, the parameter k values were calculated in all
the possible mixture situations of the two streams: from 0% of the
first component and 100% of the second component up to the reverse
situation, i.e. 100% of the first component and 0% of the second
component. The temperature to which reference was made for
determining the properties is 140.degree. C.
[0115] The values obtained are indicated in the graph of FIG.
2.
TABLE-US-00004 TABLE 4 Properties of the streams used in Examples 1
and 2 PROPERTIES CHARGE (RV) RECYCLE .delta. mix
(cal/cm.sup.3).sup.1/2 8.9 9.15 .delta. asph.
(cal/cm.sup.3).sup.1/2 9.2 9.4 .nu. mix (cm.sup.3/mole) 1300 750
Density @ 15.degree. C. (g/cm.sup.3) 0.912 1.11 k 0.28329
0.11350
[0116] It can be noted from the graph that the two separate streams
are stable (k.ltoreq.0.5), whereas the vacuum residue charge
immediately becomes unstable (k values<0.5) with small additions
of recycled stream. For recycled stream additions higher than 25%,
the mixture becomes stable again (k values.ltoreq.0.5).
* * * * *