OA12971A - Process for the conversion of heavy charges such as heavy crude oils and distillation residues. - Google Patents

Description

1 012971

PROCESS FOR THE CONVERSION OF HEAVY CHARGES SUCH AS HEAVY CRUDE OILS AND DISTILLATION RESIDUES.

The présent invention relates to a process for theconversion 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 usingcatalysts in dispersed phase, distillation and deasphalt-ing, suitably connected and fed with mixed streams consist-ing of fresh charge and conversion products.

The conversion of heavy crude oils, tars from oilsands and oil residues in liquid products can be substan-tially effected in two ways: one exclusively thermal, theother by means of hydrogenating treatment.

Current studies are mainly directed towards hydrogen-ating treatment, as thermal processes hâve problems linkedto the disposai of the by-products, in particular coke(even obtained in quantifies higher than 30% by weight withrespect to the charge) and to the poor quality of the con-version products. 2 012971

Hydrogenating processes consist in treating the chargein the presence of hydrogen and suitable catalysts.

Hydroconversion technologies currently on the market use fixed bed or ebullated bed reactors and catalysts gen- erally consisting of one or more transition metals (Mo, W,Ni, Co, etc.) supported on silica/alumina (or équivalentmaterial).

Fixed bed technologies hâve considérable problems intreating particularly heavy charges containing high per-centages of heteroatoms, metals and asphaltenes, as thispollutants cause a rapid deactivation of the catalyst.

Ebullated bed technologies hâve been developed and commercialized for treating these charges, which provideinteresting performances, but are complex and costly.

Hydro-treatment technologies operating with catalystsin 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 advan-tage of a wide flexibility of the charge with high perform-ances in terms of conversion and upgrading, and are there-fore, in principle, simpler from a technological point of view.

Slurry technologies are characterized by the presenceof particles of catalyst having very small average dimen-sions and effectively dispersed in the medium: for this 3 012971 reason hydrogénation processes are easier and more immédi-ate in ail points of the reactor. The formation of coke isconsiderably reduced and the upgrading of the charge is high.

The catalyst can be charged as powder with suffi- ciently reduced dimensions (U.S. 4,303,634) or as oil-soluble precursor (U.S. 5,288,681). In this latter case,the active form of the catalyst (generally the métal sul-fide) is formed in-situ by thermal décomposition of thecompound used, during the reaction itself or after suitable pretreatment (U.S. 4,470,295).

The metallic constituents of the dispersed catalystsare generally one or more transition metals (preferably Mo,W, Ni, Co or Ru) . Molybdenum and tungsten hâve much moresatisfactory performances than nickel, cobalt or ruthéniumand even more than vanadium and iron (N. Panariti et al.,

Appl. Catal. A: Jan. 2000, 204, 203).

Although the use of dispersed catalysts solves most ofthe problème mentioned for the technologies describedabove, there are -disadvantages, however, mainly associatedwith the life cycle of the catalyst itself and with thequality of the products obtained.

The procedure for the use of these catalysts (type ofprecursors, concentration, etc.) is in fact extremely im-portant from an économie point of view and also with re- 4 012971 spect to environmental impact.

The catalyst can be used at a low concentration (a. few hundreds of ppm) in a "once-through" configuration, but inthis case the upgrading of the reaction products is gener-ally insufficient (N. Panariti et al., Appl. Catal. A: Jan.2000, 204, 203 and 215). When operating with extremely ac-tive catalysts (for example molybdenum) and with higherconcentrations of catalyst (thousands of ppm of métal), the quality of the product obtained becomes much better, but the catalyst must be recycled.

The catalyst leaving the reactor can be recovered by séparation from the product obtained from hydro-treatment (preferably from the bottom of the distillation column,downstream of the reactor) using conventional methods suchas, for example, decanting, centrifugation or filtration(U.S. 3,240,718; U.S. 4,762,812). Part of the catalyst canbe recycled to the hydrogénation process without furthertreatment. However, the catalyst recovered using known hy-dro-treatment processes, normally has a reduced activitywith respect to fresh catalyst and a suitable régénérationstep must therefore be effected to restore the catalyticactivity and recycle at least part of the catalyst to thehydro-treatment reactor. These recovery procedures of thecatalyst, furthermore, are costly and extremely complexfrom a technological point of view. 5 012971

With respect to the Chemical description of conversionprocesses, it is convenient to introduce the stability con-cept which, for a crude oil or oil residue, expresses their tendency to precipitate the asphaltene component due to achange in the operating conditions or Chemical compositionof the oil and/or asphaltenes (incompatibility) followingdilution with hydrocarbon cuts or Chemical re-arrangementinduced by cracking processes, hydrogénations, etc.

Hydrocarbons which can be precipitated by a crude oil or oil residue by treatment with n-heptane under standardconditions established by régulation IP-143, are conven-tionally defined as asphaltenes.

From a qualitative point of view, it can be affirmedthat 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 par- affinic 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 visbreakingwith scarcely aromatic gas oils).

In conversion processes of oil residues, tars from oilsands and heavy crude oils to distillâtes, the maximum con-version level is limited by the stability of the residueproduced. These processes, in fact, modify the Chemical na- 6 012971 ture of oil and asphaltenes causing a progressive decreasein the stability with an increase in the degree of sever-ity. Over a certain limit, the asphaltenes présent in thecharge can cause a phase séparation (or precipitate) andtherefore activate coke formation processes.

From a physico-chemical point of view, the phase sépa-ration phenomenon can be explained by the fact that as theconversion reactions proceed, the asphaltene phase becomes more ànd more aromatic due to dealkylation and condensation reactions.

Consequently, over a certain limit, the asphaltenesare no longer soluble in the maltene phase also because, in the meantime, the latter has become more "paraffinie".

The stability loss control of a heavy charge during athermal and/or catalytic conversion process is thereforefundamental for obtaining the maximum conversion degreewithout running into problems relating to the formation ofcoke and fouling.

In once-through prôcesses, the optimum opérâting con-ditions (mainly reaction température and résidence time)are simply determined on the basis of the stability data ofthe reactor effluent by means of direct measurements on thenon-converted residue (P value, Hot Filtration Test, Spot

Test, etc.).

Ail these processes allow more or less high conversion 7 012971 levels to be reached depending on the charge and type oftechnology used, generating however a non-converted residueat the stability limit, which we will call tar, which, de-pending on the spécifie cases, can vary from 30 to 85% ofthe initial charge. This product is used for producing fueloil, tars or it can be used as charge in gasification proc-esses.

In order to increase the overall conversion degree of residue cracking processes, schemes hâve been proposedwhich comprise the recycling of more or less significantquantifies of tar to the cracking unit. In the case of hy-dro-conversion processes with catalysts dispersed in slurryphase, the recycling of the tar also allows recovery of thecatalyst, and for this reason, the same applicants hâve de-scribed in patent application IT-95A001095, a process whichenables recycling of the recovered catalyst to the hydro-treatment reactor without the need for a further régénéra-tion step, at the same time obtaining a high-quality prod-uct without the production of residue ("zéro residue refin-ery").

This process comprises the following steps: • mixing the heavy crude oil or distillation residuewith a suitable hydrogénation catalyst and sending themixture obtained to a hydro-treatment reactor intowhich hydrogen or a mixture of hydrogen and H2S is 8 012971 charged; • sending the stream containing the hydro-treatment re-action product and the catalyst in dispersed phase to a distillation zone in which the most volatile frac-tions are separated; • sending the high-boiling fraction obtained in the dis-tillation step to a deasphalting step, and the consé-quent production of two streams, one consisting of deasphalted oil (DAO), the other consisting of as-phalt, catalyst in dispersed phase and possibly coke and enriched with metals coming from the initial charge ; • recycling at least 60%, preferably at least 80%, ofthe stream consisting of asphalt, catalyst in dis-persed phase and possibly coke, rich in metals, to thehydro-treatment zone.

It has now been found that in the case of the upgrad-ing of heavy crude oils or tars from oil sands to complexhydrocarbon mixtures to be used as raw material for furtherconversion processes to distillâtes, it may be convenientto use different process configurations with respect tothat described above, whereby the following advantages are obtained: • maximization of conversion yields to distillable prod-ucts (deriving from both atmospheric and vacuum dis- 9 012971 tillation), and to deasphalted oil (DAO), which in most cases may exceed 95%; • maximization of the upgrading degree of the charge,i.e. of the removal of the poisons présent (metals,sulfur, nitrogen, carbonaceous residue) minimizing the production of côke; • maximum flexibility in treating charges differing inthe nature of the hydrocarbon component (density) andlevel of pollutants présent; • possibility of completely recycling the hydrogénationcatalyst without the need for régénération.

The process, object of the présent invention, for theconversion of heavy charges by means of the combined use ofthe following three process units: hydroconversion withcatalysts in slurry phase (HT), distillation or flash (D),deasphalting (SDA) , is characterized in that the threeunits operate on mixed streams consisting of fresh chargeand recycled streams, using the following steps: • sending at least one fraction of the heavy charge to adeasphalting section (SDA) in the presence of solventsobtaining two streams, one consisting of deasphaltedoil (DAO), the other of asphalts; • mixing the asphalt with a suitable hydrogénation cata-lyst and optionally with the remaining fraction ofheavy charge not sent to the deasphalting section and 10 012971 sending the mixture obtained to a hydro-treatment re- actor (HT) into which hydrogen or a mixture of hydro- gen and H2S is charged; • sending the stream containing the hydro-treatment re-action product and the catalyst in dispersed phase to one or more distillation or flash steps (D) wherebythe most volatile fractions are separated, among whichthe gases produced in the hydro-treatment reaction; • recycling at least 60% by weight, preferably at least 80%, more preferably at least 95%, of the distillationresidue (tar) or liquid leaving the flash unit, con-taining the catalyst in dispersed phase, rich in me-tallic sulfides produced by demetallation of thecharge and possibly coke, to the deasphalting zone.

The heavy charges treated can be of different kinds: they can be selected from heavy crude oils, distillationresidues, heavy oils coming from catalytic treatment, forexample heavy cycle oils from catalytic cracking treatment,thermal tars (coming for example from visbreaking or simi-lar thermal processes), tars from oil sands, various kindsof coals and any other high-boiling charge of a hydrocarbonorigin generally known in the art as "black oils" .

The possible remaining part of the distillation resi-due (tar) or liquid leaving the flash unit, not recycled tothe deasphalting zone, can be either totally or partially 11 012971 recycled, to the hydro-treatment section.

The catalysts can be selected from those obtained fromeasily decomposable oil-soluble precursors (metallic naph- thenates, metallic dérivatives ôf phosphonic acids, metal-carbonyls, 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.

The concentration of catalyst, defined on the basis ofthe concentration of métal or metals présent in the hydro-conversion reactor, ranges from 350 to 10000 ppm, prefera-bly from 1000 to 8000 ppm, more preferably from 1500 to 5000 ppm.

The hydro-treatment step is preferably carried out ata température ranging from 370 to 480°C, preferably from380 to 440°C, and at a pressure ranging from' 3 to 30 MPa, preferably from 10 to 20 MPa.

The hydrogen is fed to the reactor, which can operateeither under down-flow or, preferably up-flow conditions.The gas can be fed to different sections of the reactor.

The distillation step is preferably carried out at re-duced pressure, at a pressure ranging from 0.001 to 0.5MPa, preferably from 0.05 to 0.3 MPa.

The hydro-treatment step can consist of one or morereactors operating within the range of conditions indicatedabove. Part of the distillâtes produced in the first reac- 12 012971 tor can be recycled to the subséquent reactors.

The deasphalting step, effected by an extraction witha solvent, which may or may not be hydrocarbon, (for exam-ple with paraffins having from 3 to 6 carbon atoms) , isgenerally carried out at températures ranging from 40 to 200°C and at a pressure ranging from 0.1 to 7 MPa. It can also consist of one or more sections operating with the saroe solvent or with different solvents; the solvent can be recovered under supercritical conditions thus allowing fùr-ther fractionation between asphalt and resins.

The stream consisting of deasphalted oil (DAO) can beused as such as synthetic crude oil (syncrude), optionallymixed with the distillâtes, or it can be used as charge forfluid bed Catalytic Cracking treatment or Hydrocracking.

Depending on the characteristics of the crude oil(métal content, content of sulfur and nitrogen, carbona-ceous residue),. it is possible to advantageously modulate: • the ratio between the heavy residue to be sent to thehydro-treatment section (fresh charge) and that to besent for deasphalting; said ratio can vary from 0 to100, preferably from 0.1 to 10, more preferably from 1 to 5 ; • the recycling ratio between fresh charge and tar to besent to the deasphalting section; said ratio prefera-bly varies from 0.1 to 100, more preferably from 0.1 13 012971 to 10; • the recycling ratio between fresh charge and asphaltsto be sent to the hydro-treatment section; said ratiocan vâry in relation to the variation in the previous ratios ; • the recycling ratio between tar and asphalts to besent to the hydro-treatment section; said ratio canvary in relation to the variation in the previous ra-tios.

This flexibility is particularly useful for better ex-ploiting the complementary characteristics of thedeasphalting units (reasonable HDN and dearomatization) andhydrogénation units (high HDM and HDS).

Depending on the type of crude oil, the stabili'ty ofthe streams in question and quality of the product to beobtained (also in relation to the particular downstreamtreatment) , the fractions of fresh charge to be fed to thedeasphalting and hydro-treatment sections can be modulatedin the best possible way.

Furthermore, to achieve the best possible running ofthese processes, it is advisable to guarantee compatibilityof the streams to be mixed, or that the flows of • fresh charge and tar • fresh charge and asphalt (possibly containing resinsor an aliquot thereof) 14 012971 • tar and asphalt (possibly containing resins or an ali- quot thereof) having different physico-chemical characteristics, aremixed in such ratios as to avoid précipitation of asphalte- nes in ail process phases.

The process, object of the présent invention, can be further improved, as far as the compatibility of thestreams to be mixed is concerned, by controlling that therecycling between the streams containing asphaltenes, orfresh charge, tar and asphalt, has such a ratio that: (vmix/RT) (Ôasph-Ô mix) < k wherein:

Vmix is the molar volume of the maltene component (i.e. non-asphaltene) of the mixture (cm3/mole);

Smix is the solubility parameter of the maltene component ofthe mixture (cal/cm3)1^2 ; ôasph is the solubility parameter of the asphaltenes of themixture (the highest value among the values of the twocomponents of the mixture is considered) (cal/cm3)1/2; R = Gas Constant (1.987 cal/mol°K); T: température expressed in Kelvin degrees.

The asphaltenes used as reference for determining the properties indicated above are the insoluble n-heptanefraction (C7 asphaltenes) .

The values indicated in the formula are calculated as 15 012971 follows: vmix = molar average of the molar volumes of the maltenecomportent s ôTOix = volumétrie average of the solubility parameters ofthe maltene components k = constant whose value ranges from 0.2 to 0.5.

The application described is particularly suitablewhen the heavy fractions of complex hydrocarbon mixturesproduced by the process must be used as charge for cata-lytic cracking plants, both Hydrocracking (HC) and fluidbed Catalytic Cracking (FCC).

The combined action of a catalytic hydrogénation unit(HT) with an extractive process (SDA), in fact, allowsdeasphalted oils to be produced with a reduced content ofcontaminants (metals, sulfur, nitrogen, carbonaceous resi-due) , which can therefore be more easily treated in cata-lytic cracking processes.

Furthermore, the investment cost of the whole complexcan also be minimized as, with respect to the scheme de-scribed in patent application IT-95A001095, for the samecharge unit treated, the dimensions of the deasphaltingsection are increased whereas those of the hydro-treatmentsection (and downstream distillation column) are reduced;as the deasphalting unit involves lower investment coststhan the hydro-treatment unit, there is a conséquent saving 16 012971 on the investment cost of the whole complex. A preferred embodiment of the présent invention is nowprovided with the help of figure 1 enclosed, which however should not be considered as limiting the scope of the in-vention itself.

The heavy charge (1), or at least a part thereof (la),is sent to the deasphalting unit (SDA), an operation whichis effected by means of extraction with solvent.

Two streams are obtained from the deasphalting unit(SDA) : one (2) consisting of deasphalted oil (DAO) , theother consisting of asphalts and resins (3); the latter canbe 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.

The stream consisting of asphalt and resins (or afraction of these) is mixed with fresh make-up catalyst (5)necessary for reintegrating that used up with the flushingstream (14), with the part of heavy charge (lb) not fed tothe deasphalting section and optionally with the stream(15) (which will be described further on in the text) Corn-ing from the bottom of the distillation column (D) to forma stream (6) which is fed to the hydro-treatment reactor(HT) into which hydrogen (or a mixture of hydrogen and H2S)(7), is charged. A stream (8) containing the hydrogénationproduct and catalyst in dispersed phase, leaves the reactor 17 012971 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, ex- cept for a flushing (14), recycled to the deasphalting re-actor (SDA). A part of this (15) can be optionally sent tothe hydro-treatment unit (HT).

Some examples are provided below for a better illus-tration of the invention without limiting its scope. EXAMPLE 1

Following the scheme represented in figure 1, the fol-lowing experiment was carried out.

Deasphalting step • Charge: 300 g vacuum residue from Ural crude oil (Table1) • Deasphalting agent: 2000 cc of liquid propane (extractionrepeated 3 times)

• Température: 80°C • Pressure: 35 bars

Table 1 : Characteristics of Ural vacuum residue 500°C+ API gravity 10.8 Sulfur (w%) 2.6 Nitrogen (w%) 0.7 CCR (w%) 18.9 Ni + V (ppm) 80 + 262 18 012971

Hydro-treatment step • Reactor: 3000 cc, Steel, suitably shaped and equippedwith magnetic stirring • Catalyst: 3000 ppm of Mo/charge added using molybdenum naphthenate as precursor

• Température: 410°C • Pressure: 16 MPa of hydrogen • Résidence time: 4 h

Flash step • Effected by means of a laboratory apparatus for liquidévaporation (T = 120°C)

Experimental results 10 consecutive deasphalting tests were effected using,for each test, a charge consisting of Ural vacuum residue(fresh charge) and atmospheric residue obtained from thehydro-treatment reaction of C3 asphaltenes of the previousstep in order to allow the complété recycling of the cata-lyst added during the first test. At every step, the auto-clave was fed with a quantity of charge consisting of Uralvacuum residue (fresh charge) and C3 asphaltenes derivingfrom the deasphalting, which was such as to bring the total charge mass (fresh charge + recycled C3 asphaltenes) to theinitial value of 300 g.

The ratio between quantity of fresh charge and quan-tity of recycled charge reached under these operating con- 19 012971 ditions was 1:1.

The data relating to the out-going streams after the last recycling (weight % with respect to the charge) are as follows: • Gas: 7% • Naphtha (C5-170°C): 8% • Atmospheric gas oil (AGO 170-350°C):17% • Deasphalted oil (VGO + DAO): 68%

The asphaltene stream recovered at the end of the testcontains ail the catalyst initially fed, sulfides of themetals Ni and V produced during the 10 recycles from thehydro-treatment and a quantity of coke in the order ofabout 1% by weight with respect to the total quantity ofUral residue fed. In the example indicated, there was noneed to effect any flushing of the recycled stream.

Table 2 provides the characterization of the product ob- tained.

Table 2 : characteristics of test reaction products accord-ing to Example 1.

Sulfur w% Nitrogen (ppm) Sp.Gr. RCC (w%) Ni+V (ppm) Naphtha C5-170°C 0.06 450 0.768 - - AGO 170-350°C 0.52 2100 0.870 - - VGO+DAO 1.45 2 5 0Ό 0.938 3 1 20 012971 EXAMPLE 2-

An experiment was conducted, simila.r to the one de-scribed in experiment 1, effecting the hydro-treatment step, however, at 420°C.

The ratio between quantity of fresh charge and quan-tity of recycled product reached under these operating conditions was 1:1.5.

The data relating to the out-going streams after thelast recycling (weight % with respect to the charge) are as follows: • Gas: 9% • Naphtha (C5-170°C): 11% • Atmospheric gas oil (AGO 170-350°C) :24% • Deasphalted oil (VGO + DAO): 56%

In the example indicated, there was no need to effectany flushing of the recycled stream.

Table 3 provides the characterization of the product ob- tained.

Table 3 : characteristics of test reaction products accord-ing to Example 2.

Sulfur w% Nitrogen (ppm) Sp.Gr. RCC (w%) Ni+V (ppm) Naphtha C5-170°C 0.05 300 0.759 - - AGO 170-350°C 0.51 1950 0.864 - - VGO+DAO 1.45 2200 0.922 2.5 1 21 012971 EXAMPLE 3

The following example shows the use of the relation (vmix/RT) (Sasph-S mix) < k indicated in the présent invention to evaluate the compati-bility limits of the various streams to be subjected to hy- dro-treatment.

The streams used in Examples 1 and 2 were character-ized to détermine the properties used in the above rela-tion.

Starting from the properties indicated in Table 4 andusing the above relation, the. parameter k values were cal-culated in ail the possible mixture situations of the two streams: from 0% of the first component and 100% of thesecond component up to the reverse situation, i.e. 100% ofthe first component and 0% of the second component. Thetempérature to which referençe was made for determining theproperties is 140°C.

The values obtained are indicated in the graph of figure 2.Table 4 : Properties of the streams used in Examples 1 and 2 PROPERTIES CHARGE (RV) RECYCLE δ mix (cal/cm3)1/2 8.9 9.15 δ asph. (cal/cm3)1/2 9.2 9.4 v mix (cm3/mole) 1300 750 Density@15°C (g/cm3) 0.912 1.11 k 0.28329 0.11350 22 012971

It can be noted from the graph that the two separate streams are stable (k < 0.5), whereas the vacuum residuecharge 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 < 0.5) .

Claims (15)

1. 23 012971 CLAIMS

   1. A process for the conversion of heavy charges selectedfrom 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 followingthree process units: hydroconversion with catalysts inslurry phase (HT), distillation or flash (D) ,deasphalting (SDA), characterized in that the threeunits operate on mixed streams consisting of freshcharge and recycled streams, with the use of the fol-lowing steps: • sending at least one fraction of the heavy chargeto a deasphalting section (SDA) in the presence of hy-drocarbon solvents obtaining two streams, one consist-ing of deasphalted oil (DAO), the other of asphalts; • mixing the asphalt with a suitable hydrogénationcatalyst and with the remaining fraction of heavycharge not sent to the deasphalting section and send-ing the mixture obtained to a hydro-treatment reactor(HT) into which hydrogen or a mixture of hydrogen andH2S is charged; • sending the stream containing the hydro-treatmentreaction product and the catalyst in dispersed phase 24 012971 to one or more distillation or flash steps (D) wherebythe most volatile fractions are separated, among which the gases produced in the hydro-treatment reaction; • recycling at least 50% by weight of the distilla-tion residue (tar) or liquid leaving the flash unit,containing the catalyst in dispersed phase, rich in metallic sulfides produced by demetallation of thecharge and possibly coke, to the deasphalting zone. The process according to claim 1, wherein at least 80%by weight of the distillation residue or liquid leav-ing the flash unit is recycled to the deasphalting zone. The process according to claim 2, wherein at least 95%by weight of the distillation residue or liquid leav-ing the flash unit is recycled to the deasphalting zone. The process according to claim 1, wherein at leastpart of the remaining part of distillation residue(tar) or liquid leaving the flash unit, not recycledto the deasphalting zone, is recycled to the hydro- treatment section. The process according to one of the daims from 1 to4, wherein the recycling ratio between the streamscontaining asphaltenes, or fresh charge, tar and as-phalts, must be such that: 25 012971 (Vmix/RT) (ÔaSph~S τπίχ! < k wherein: 8asph is the highest value among the solubility parame-ters of the two C7 asphaltenes of the mixture (highest 5 value) vmix is the molar average of the molar volumes of themaltene components Ômix is the volumétrie average of the solubility parame-ters of the maltene components 10 k is a constant whose value ranges from 0.2 to 0.5.
2. 6. The process according to claim 1, wherein the distil-lation step is carried out at a reduced pressure rang-ing from 0.001 to 0.5 MPa.
3. 7. The process according to claim 6, wherein the distil- 15 lation step is carried out at a reduced pressure rang- ing from 0.05 to 0.3 MPa.
4. 8. The process according to claim 1, wherein the hydro-treatment step is carried out at a température rangingfrom 370 to 450°C and a pressure ranging from 30 to 20 300 Atm.
5. 9. The process according to claim 8, wherein the hydro- treatment step is carried out at a température rangingfrom 380 to 440°C and a pressure ranging from 100 to 200 Atm.
6. 10. The process according to claim 1, wherein the 26 012971 deasphalting step is carried out at températures rang- ing from 40 to 200°C and a pressure ranging from 1 to 70 Atm.
7. 11. The process according to claim 1, wherein thedeasphalting solvent is a light paraffin with from 3 to 6 carbon atoms.
8. 12. The process according to claim 1, wherein thedeasphalting step is carried out by means of extrac-tion with a solvent operating in supercritical phase.
9. 13. The process according to claim 1, wherein the streamconsisting of deasphalted oil (DAO) is fractionated by conventional distillation.
10. 14. The process according to claim 1, wherein the stream consisting of deasphalted oil (DAO) is mixed with theProducts separated in the flash step after being con- densed.
11. 15. The process according to claim 1, wherein the hydro-génation catalyst is an easily decomposable precursoror a preformed compound based on one or more transi-tion metals.
12. 16. The process according to claim 15, wherein the transi-tion métal is molybdenum.
13. 17. The process according to claim 1, wherein the concen-tration of catalyst in the hydroconversion reactor, defined on the basis of the concentration of the métal 27 012971 or metals présent, ranges from 350 to 10000 ppm.
14. 18. The process according to claim 17, wherein the concen-tration of catalyst in the hydroconversion reactorranges from 1000 to 8000 ppm.
15. 19. The process according to claim 18, wherein the concen- tration of catalyst in the hydroconversion reactor ranges from 1500 to 5000 ppm.