Process for deasphalting a heavy hydrocarbon feedstock

A process for deasphalting a heavy hydrocarbon feedstock, comprising two stages of precipitation from the feedstock of an asphaltene fraction alone or, alternatively, of a resin fraction along with the asphaltene fraction, by means of a heavy solvent and a light solvent, respectively, is disclosed. In accordance with the process, the heavy solvent and the light solvent both contain, in different proportions, at least one hydrocarbon having 3 carbon atoms and at least one hydrocarbon having at least 5 carbon atoms, the proportion of the hydrocarbon having 3 carbon atoms being higher in the light solvent than in the heavy solvent.

The present invention relates to a process for deasphalting a heavy 
hydrocarbon feedstock. 
A heavy hydrocarbon feedstock within the meaning of the invention is a 
feedstock having a density above about 930 kg/m.sup.3 and composed 
substantially of hydrocarbons but containing also other chemical compounds 
which have, in addition to carbon and hydrogen atoms, heteroatoms such as 
oxygen, nitrogen or sulfur, and metals such as vanadium or nickel. 
This feedstock may consist in particular of a crude petroleum or of a heavy 
oil having said density. 
The feedstock may also come from the fractionation or treatment of crude 
petroleum, of a heavy oil, of oil shales or even of coal. Thus it may be 
the residuum from vacuum distillation or the residuum from atmospheric 
distillation of the starting products cited above or, for example, of the 
products obtained by the thermal treatment of these starting products or 
of their distillation residua. 
The trend in recent years has been to seek to upgrade the high-density 
hydrocarbonaceous products more and more, which was not the case before. 
The need to upgrade heavy products has become more pressing since it is 
anticipated that the demand for light products such as motor fuels will be 
increasing at a relatively faster pace than the demand for heavier 
products, such as the fuel oils. 
The heaviest portion of heavy hydrocarbon feedstocks consists of a mixture 
of an oil phase and an asphaltic phase. One way of obtaining light 
products from the oil phase is to subject the latter to catalytic 
cracking. However, the catalytic cracking feedstock should not be too 
contaminated with metals and should not have too high a Conradson residue. 
It should be noted that the Conradson residue, which is indicative of the 
tendency of a product to coke, is determined in conformity with French 
standard AFNOR NFT 60-116. 
As has been pointed out above, heavy hydrocarbon feedstocks contain 
compounds which have, in addition to hydrogen and carbon atoms, 
heteroatoms such as oxygen, nitrogen or sulfur as well as metals. Some of 
these compounds, and particularly those containing metals, are present 
especially in the asphaltic phase. 
Two groups are customarily distinguished among the compounds which make up 
the asphaltic phase: the resins and the asphaltenes. Both the asphaltenes 
and the resins have polycyclic aromatic structures. Apart from aromatic 
rings, thiophene and pyridine rings are present. However, the resins have 
less-condensed structures than the asphaltenes and lower molecular 
weights. 
The name "asphaltenes" is generally applied to compounds which are 
precipitated by the addition to the charge stock of a saturated aliphatic 
hydrocarbon having from 5 to 7 carbon atoms, such as pentane, hexane or 
heptane. Under standard AFNOR NFT 60-115, the asphaltene content of a 
product thus is determined by precipitation with normal heptane at 
boiling. 
The resins precipitate at the same time as the asphaltenes when a 
hydrocarbon with a lower boiling point, for example, propane, is used. In 
fact, this is a conventional differentiation, and it is obvious that when 
a given solvent is employed at a given temperature to treat a feedstock, 
precipitation of asphaltene-type compounds can be obtained if the solvent 
and the temperature are appropriate. If the feedstock freed from the 
asphaltenes is then treated with the same solvent at a higher temperature, 
precipitation of the resins is obtained. 
In the well-known deasphalting process, the oil phase and the asphaltic 
phase are separated by the operation which consists in extracting the oil 
phase from the residuum with a solvent. The solvent may be selected from 
the group comprising saturated or unsaturated aliphatic hydrocarbons 
having from 2 to 8 carbon atoms, alone or in admixture; mixtures of 
hydrocarbons known as distillates, with molecular weights close to those 
of hydrocarbons having from 2 to 8 carbon atoms; and mixtures of all of 
the hydrocarbons cited above. 
Deasphalting can be carried out in a single stage, in which case an oil 
phase and an asphaltic phase are obtained, the latter containing both the 
asphaltenes and the resins. It can also be carried out in two stages, 
using two different solvents and/or different operating conditions in the 
two stages. (See U.S. Pat. Nos. 3,830,732 and 2,940,920, for example.) In 
the two-stage process, the oil phase, the resins and the asphaltenes are 
obtained separately. 
U.S. Pat. No. 3,830,732 thus describes a process using two solvents, 
propane and pentane, which requires two completely separate solvent 
recovery units, and hence a substantial investment. 
In the single-solvent process (see U.S. Pat. No. 2,940,920, for example), 
it is necessary, and difficult, to adjust the operating conditions of the 
two stages very precisely in order to obtain products with the desired 
qualities. With this process, it is even impossible at times to obtain 
both an oil phase that is suitable for use as a catalytic cracking feed 
and a very hard pitch that can be ground and used as a solid fuel. 
The present invention utilizes a two-stage deasphalting process which uses 
in the two stages solvents between which there is both little difference 
in physical and chemical properties, which makes it possible to employ, at 
least in one embodiment, a single solvent stripping installation, yet 
sufficient difference in volatility and separability for obtaining both a 
"clean" oil phase of a quality perfectly suitable for use as catalytic 
cracking feed, without additional hydrogen treatment, and an asphaltene 
fraction that is sufficiently solid at ambient temperature to be ground 
and used as a solid fuel. 
The asphaltene fraction therefore does not require an additional 
expenditure for a flux to be used in the liquid state. 
The present invention thus seeks to prepare, particularly from a heavy 
hydrocarbon feedstock, a product that is suitable for use as catalytic 
cracking feed. 
To this end, the invention has as a preferred embodiment a process for the 
deasphalting of a heavy feedstock which yields a deasphalted oil phase 
with a Conradson carbon value of 10 or less; a resin fraction; and an 
asphaltene fraction with a softening point of 150.degree. C. or higher, 
said process comprising two stages of precipitation from the feedstock 
both of the asphaltene fraction alone and of the resin fraction, 
optionally along with the asphaltene fraction, with a heavy solvent and a 
light solvent, respectively, said process being characterized in that both 
the heavy solvent and the light solvent contain, in different proportions, 
at least one hydrocarbon having 3 carbon atoms and at least one 
hydrocarbon having at least 5 carbon atoms, the proportion of the 
hydrocarbon having 3 carbon atoms being higher in the light solvent than 
in the heavy solvent. 
In view of the fact that the separation between the oil phase, the resins 
and the asphaltenes cannot be defined precisely from the chemical 
standpoint, in this object of the invention and hereafter in the present 
specification, 
1. "oil phase" is intended to mean a phase from which has been eliminated 
practically the entire asphaltic phase, that is, the phase which is 
precipitated by the addition of a light solvent, as defined in the object 
of the invention, this oil phase having a Conradson residue of 10 or less 
(as determined in conformity with standard AFNOR NFT 60-116), and 
2. "resin fraction" and "asphaltene fraction" are intended to mean the 
lightest fraction and the heaviest fraction, respectively, of the 
asphaltic phase, the boundary between these two fractions, within the 
meaning of the invention, being defined by the fact that the asphaltene 
fraction should have a softening point of 150.degree. C. or higher (as 
determined in conformity with standard AFNOR NTF 66-008). 
In the process of the invention, two solvents are used, a light solvent and 
a heavy solvent, which contain the same chemical compounds but in 
different proportions, which explains their different functions: The heavy 
solvent is capable of causing the asphaltene fraction to precipitate but 
solubilizes the resin fraction and, a fortiori, the oil phase, while the 
light solvent is capable of causing the precipitation of the resin 
fraction, and hence of the asphaltene fraction, of course, but solubilizes 
the oil fraction. 
The two solvents contain at least one hydrocarbon having 3 carbon atoms 
(propane and/or propylene) and at least one saturated aliphatic or 
olefinic hydrocarbon having at least 5 carbon atoms (including, in 
particular, pentane, pentene, hexane, hexene, heptane, heptene). 
The process is thus characterized by a search for selectivity, which leads 
to the combination of two solvents containing little or no hydrocarbon 
having 4 carbon atoms, for variation of the selectivity according to the 
stage involved. 
The solvents may consist of a single hydrocarbon or of a mixture of 
hydrocarbons; thus, the heavy solvent may consist of a mixture of pentane 
and hexane, for example. 
It should be noted that when a hydrocarbon, for example, pentane, is cited 
within this object and hereafter in the present specification, it may be 
either a well-defined hydrocarbon, such as normal pentane or, 
alternatively, as will be practically always the case industrially, a 
mixture of isomers of that hydrocarbon, such as, in the case of pentane, 
mainly normal pentane and isopentane. 
The light solvent contains a larger proportion of hydrocarbon having 3 
carbon atoms than the heavy solvent. 
In general, the heavy solvent will preferably contain from 5 to 40 percent 
by volume of a hydrocarbon having 3 carbon atoms and from 60 to 95 volume 
percent of at least one hydrocarbon having at least 5 carbon atoms. The 
light solvent will preferably contain from 20 to 80 volume percent of a 
hydrocarbon having 3 carbon atoms and from 20 to 80 volume percent of at 
least one hydrocarbon having at least 5 carbon atoms. 
The process in accordance with the invention may be carried out in two 
different ways: 
In the first mode of carrying out the process of the invention, the first 
stage is the stage of separation of the asphaltene fraction by means of 
the heavy solvent. 
At the end of this stage, there are recovered the asphaltene fraction 
containing some solvent, which is later removed, on the one hand and, in 
solution in the heavy solvent, the resin fraction and the oil phase on the 
other hand. 
The resin fraction is then precipitated with a light solvent. 
To obtain this light solvent in one particular embodiment, there is added 
to the mixture of heavy solvent, resin fraction and oil phase, in a second 
stage which is the stage of resin separation, a third solvent that is 
lighter than the light solvent, the latter thus resulting from the 
combination of heavy solvent and said third solvent. At the end of this 
stage, there are recovered the resin fraction containing some solvent, 
which is later removed, on the one hand and the oil phase in solution in 
the light solvent on the other hand. 
This solution is then subjected to a treatment that makes it possible to 
obtain said third solvent, which is recycled to the second stage, and a 
solution of the oil phase in the heavy solvent, from which it is separated 
conventionally, the heavy solvent being recycled to the first stage. 
The treatment of the solution of the oil phase in the light solvent may 
consist, in particular, of heating said solution to vaporize 
preferentially the hydrocarbon having 3 carbon atoms. 
Instead of being heated, said solution may be vacuum flashed. 
In the first stage of this first mode of carrying out the process of the 
invention, the heavy solvent will preferably contain from 10 to 40 percent 
by volume of a hydrocarbon having 3 carbon atoms and from 60 to 90 volume 
percent of at least one hydrocarbon having at least 5 carbon atoms, and, 
better yet, from 15 to 35 volume percent of a hydrocarbon having 3 carbon 
atoms and from 65 to 85 volume percent of at least one hydrocarbon having 
at least 5 carbon atoms. 
In the second stage of this first mode of carrying out the process of the 
invention, the light solvent will preferably contain from 20 to 80 percent 
by volume of a hydrocarbon having 3 carbon atoms and from 20 to 80 volume 
percent of at least one hydrocarbon having at least 5 carbon atoms, and, 
better yet, from 25 to 75 volume percent of a hydrocarbon having 3 carbon 
atoms and from 25 to 75 volume percent of at least one hydrocarbon having 
at least 5 carbon atoms. 
In the second mode of carrying out the process of the invention, the first 
stage is a stage of simultaneous precipitation of the resin and asphaltene 
fractions with the light solvent obtained by combining in this stage the 
heavy solvent and a third solvent that is lighter than the light solvent 
desired. At the end of this first stage, there are obtained a mixture of 
the resin and asphaltene fractions on the one hand and, on the other hand, 
the oil phase in solution in the light solvent, from which it is later 
separated. 
In a second stage, heavy solvent which solubilizes the resin fraction is 
added to the mixture of the resin and asphaltene fractions. At the end of 
this second stage there are obtained the asphaltene fraction containing 
some solvent, which is later removed, and the resin fraction in solution 
in the heavy solvent, from which it is later separated. 
In the first stage of this second mode of carrying out the process of the 
invention, the light solvent will preferably contain from 20 to 80 percent 
by volume of a hydrocarbon having 3 carbon atoms and from 20 to 80 volume 
percent of at least one hydrocarbon having at least 5 carbon atoms, and, 
better yet, from 30 to 70 volume percent of at least one hydrocarbon 
having 3 carbon atoms and from 30 to 70 volume percent of at least one 
hydrocarbon having at least 5 carbon atoms. 
In the second stage of this second mode of carrying out the process of the 
invention, the heavy solvent will preferably contain from 5 to 30 percent 
by volume of a hydrocarbon having 3 carbon atoms and from 70 to 95 volume 
percent of at least one hydrocarbon having at least 5 carbon atoms, and, 
better yet, from 10 to 25 volume percent of a hydrocarbon having 3 carbon 
atoms and from 75 to 90 volume percent of at least one hydrocarbon having 
at least 5 carbon atoms. 
The operating conditions in the deasphalting stages may be as follows: 
Pressure ranging from 20.multidot.10.sub.5 to 1.107 pascals abs. 
Temperature ranging from 100.degree. to 300.degree. C. 
Mass ratio of solvent to fraction to be deasphalted ranging from 1 to 10. 
These conditions will vary, of course, depending on the nature of the 
feedstock and on the nature of the solvents employed.

With reference to FIG. 1, which shows a unit for implementing the first 
mode of carrying out the process of the invention, the heavy hydrocarbon 
feedstock to be deasphalted is introduced by way of line 1 into the upper 
part of a first extraction tower 2. A heavy solvent, whose source will be 
explained further on, is further introduced into the bottom of tower 2 
through a line 3. 
The same heavy solvent may also be added to the feedstock in line 1 through 
a line which is not shown. 
The heavy solvent in line 3 and the operating conditions of tower 2 are 
selected so that only the asphaltene fraction of the feedstock 1, whose 
softening point is 150.degree. C. or higher, precipitates in said tower. 
The pressure in the interior of tower 2 may range from 20.multidot.10.sup.5 
to 1.multidot.10.sup.7 pascals abs and the temperature from 100.degree. to 
200.degree. C., and the mass ratio of heavy solvent to feedstock may range 
from 1 to 10; however, these values be regarded as limits. 
For example, in the case of a C.sub.3 -20/C.sub.5 -80 heavy solvent, that 
is, one containing 20 volume percent propane and 80 volume percent 
pentane, the pressure may be about 40.multidot.10.sup.5 pascals abs, the 
temperatures at the bottom and at the top of tower 2 being about 
100.degree. C. and 140.degree. C., respectively, and the mass ratio of 
heavy solvent to feedstock being about 2/1. 
The asphaltene fraction containing some heavy solvent is recovered at the 
bottom of tower 2 through line 4. 
At the top of tower 2, through line 5, the feedstock which has been freed 
from the asphaltene fraction is recovered in solution in the major portion 
of the heavy solvent introduced into tower 2 
After passing into at least one heater 6, the fraction recovered by way of 
line 4 is piped to a flash tower 7 which, in the case of a C.sub.3 
-20/C.sub.5 -80 heavy solvent, is operated at a temperature of about 
300.degree. C. and a pressure of about 5.multidot.10.sup.5 pascals abs. 
Heavy solvent is recovered at the top of tower 7 through line 8 and, after 
passing through a cooler 9, conducted to a vessel 10. 
The vessel 10 is used to store heavy solvent. In the case of a C.sub.3 
-20/C.sub.5 -80 heavy solvent, the temperature in vessel 10 is about 
60.degree. C. and the pressure about 5.multidot.10.sup.5 pascals abs. 
The asphaltene fraction is recovered at the bottom of tower 7 by way of 
line 11 and conveyed to a tower 12 which, in the case of a C.sub.3 
-20/C.sub.5 -80 heavy solvent, is operated at a temperature of about 
300.degree. C. and a pressure of about 0.5.multidot.105 pascals abs. 
The asphaltene fraction that has been freed from heavy solvent is collected 
at the bottom of tower 12 through line 13. This fraction may be used as a 
solid fuel after grinding. 
At the top of tower 12, solvent is withdrawn by way of line 19 and piped to 
a condenser 14. 
At the outlet of condenser 14, water (the source of which will be explained 
further on) is withdrawn through line 15 and discharged, and, in the case 
of a C.sub.3 -20/C.sub.5 -80 heavy solvent, the hydrocarbon or 
hydrocarbons having at least 5 carbon atoms is or are recovered through 
line 16 and conducted to vessel 10, and the hydrocarbon having 3 carbon 
atoms is recovered through line 17 and, after passing through a compressor 
18, flows through line 8, and hence to vessel 10. 
The mixture of heavy solvent and feedstock freed from the asphaltene 
fraction, recovered by way of line 5, is conveyed to a second extraction 
tower 20. Through line 21, a third solvent is introduced into tower 20 so 
that in the latter the extraction is carried out by means of a light 
solvent which results from the combination of the heavy solvent and of the 
third solvent, and wherein the proportion of the hydrocarbon having 3 
carbon atoms is higher than that of the heavy solvent. 
In the case of a C.sub.3 -20/C.sub.5 -80 heavy solvent, the third solvent 
may thus be a C.sub.3 -40/C.sub.5 -60 solvent, that is, one containing 40 
volume percent propane and 60 volume percent pentane, the light solvent 
then being a C.sub.3 -30/C.sub.5 -70 solvent containing 30 volume percent 
propane and 70 volume percent pentane. 
The operating conditions in the interior of tower 20 are such that the 
resin fraction precipitates. 
The pressure in the interior of tower 20 may range from 
20.multidot.10.sup.5 to 1.multidot.10.sup.7 pascals abs and the 
temperature from 100.degree. to 300.degree. C., the mass ratio of light 
solvent to charge stock of tower 2 ranging from 1 to 10; however, these 
values should not be regarded as limits. 
For example, in the case of a C.sub.3 -30/C.sub.5 -70 light solvent, the 
pressure may be about 40.multidot.10.sup.5 pascals abs, and the 
temperatures at the bottom and top of tower 20 about 110.degree. C. and 
150.degree. C., respectively, the volume ratio of light solvent to charge 
stock of tower 2 being about 4/1. 
At the top of tower 20, a mixture of deasphalted oil phase and light 
solvent is recovered through line 22. 
At the bottom of tower 20, the resin fraction containing some light solvent 
is recovered through line 28. 
After passing through a heater 23, the mixture of deasphalted oil phase and 
light solvent recovered through line 22 is piped to a flash tower 24 
which, in the case of a C.sub.3 -30/C.sub.5 -70 light solvent, is operated 
at a pressure of about 25.multidot.10.sup.5 pascals abs and a temperature 
of about 150.degree. C. As a result of the passage through heater 23, a 
portion of the solvent is vaporized, the hydrocarbon having 3 carbon atoms 
being preferentially vaporized. Consequently, a third solvent enriched in 
hydrocarbon having 3 carbon atoms is recovered at the top of tower 24 
through line 25. In the case of a C.sub.3 -30/C.sub.5 -70 light solvent, a 
third, C.sub.3 -40/C.sub.5 -60 solvent is so obtained. 
If necessary, plates may be installed in the interior of this tower to 
improve separation. 
After passing through a cooler 26, the third solvent recovered through line 
25 is conveyed to a storage vessel 27. In the case of a C.sub.3 
-40/C.sub.5 -60 third solvent, the temperature in the interior of vessel 
27 will be about 110.degree. C., and the pressure about 25 bars. 
The third solvent is then recycled to tower 20 through line 21. 
At the bottom of tower 24, a mixture of deasphalted oil and heavy solvent 
is recovered by way of line 29 and, after passing through a relief valve 
30, where its pressure and temperature are reduced (in the case of a 
C.sub.3 -20/C.sub.5 -80 heavy solvent to about 5.multidot.10.sup.5 pascals 
abs and 100.degree. C., respectively), and passing through a heater 31, 
piped to a flash tower 32 which, in the case of a C.sub.3 -20/C.sub.5 -80 
heavy solvent, is operated at a pressure of about 5.multidot.10.sup.5 
pascals abs and a temperature of about 130.degree. C. 
The major portion of the heavy solvent is recovered at the top of tower 32 
by way of line 33 and, after passing through a cooler 34, piped to vessel 
10. 
Vessel 10 is connected through a line 35 to line 3 and the heavy solvent 
can therefore be recycled to tower 2. 
The deasphalted oil phase which still contains some solvent is withdrawn at 
the bottom of tower 32 through a line 36 and, after passing through a 
heater 37, conducted to a steam stripping tower 38, into which steam is 
introduced through a line 39. 
In the case of a C.sub.3 -20/C.sub.5 -80 heavy solvent, this tower is 
operated at a pressure of about 1.5.multidot.10.sup.5 pascals abs and a 
temperature of about 250.degree. C. 
The deasphalted oil is recovered at the bottom of tower 38 through line 41 
and water and solvent are withdrawn at the top of that tower through line 
40 and piped to condenser 14. 
After passing through a heater 50, the resin fraction containing some light 
solvent which has been recovered through line 28 from the bottom of tower 
20 is conducted to a flash tower 51 which, in the case of a C.sub.3 
-30/C.sub.5 -70 light solvent, is operated at a pressure of about 
5.multidot.10.sup.5 pascals abs and a temperature of about 280.degree. C. 
Some light solvent is recovered at the top of tower 1 through a line 52 and 
piped to line 8. 
The resin fraction which still contains some solvent collected from the 
bottom of tower 51 through a line 53 is conducted to a steam stripping 
tower 54, into which steam is introduced through a line 55. 
The resin fraction recovered at the bottom of tower 54 through line 57 may 
be used as a fuel-oil base, or incorporated into bitumens, or serve as an 
excellent visbreaker feed. 
Water and solvent are withdrawn from the top of tower 54 through a line 56 
and piped to condenser 14. 
It should be noted that when heavy solvent is introduced into vessel 10 
through line 33, light solvent coming from lines 52 and 56 is also 
introduced. All of this is recycled as heavy solvent. The amount of light 
solvent actually is very low in relation to the heavy solvent, and all 
that need to be done to obtain a heavy solvent of the proper composition 
is to add a little hydrocarbon having at least 5 carbon atoms to vessel 
10. 
In the units shown in FIG. 1, as well as in FIGS. 2 and 3 which will now be 
described, solvent make-up (not shown) is of course provided to compensate 
for solvent losses. 
With reference to FIG. 2, which shows a unit for implementing the second 
mode of carrying out the process of the invention, the heavy hydrocarbon 
feedstock to be deasphalted is introduced by way of line 101 into the 
upper part of a first extraction tower 102. A light solvent, whose source 
will be explained further on, is further introduced into the bottom of 
tower 102 through a line 103. The resin and asphaltene fractions 
precipitate. 
The light solvent may be a C.sub.3 -60/C.sub.5 -40 solvent, for example, 
containing 60 volume percent propane and 40 volume percent pentane. 
The pressure in the interior of tower 102 may range from 
20.multidot.10.sup.5 to 1.multidot.10.sup.7 pascals abs and the 
temperature from 100.degree. to 300.degree. C., and the mass ratio of 
light solvent to feedstock may range from 1 to 10; however, these values 
should not be regarded as limits. 
For example, in the case of a C.sub.3 -60/C.sub.5 -40 light solvent, the 
pressure may be about 40.multidot.10.sup.5 pascals abs, the temperatures 
at the bottom and top of tower 102 being 100.degree. C. and 130.degree. 
C., respectively, and the mass ratio of light solvent to feedstock of 
tower 102 being about 2/1. 
From the bottom of tower 102, through line 105, all of the asphaltic phase 
containing the asphaltene and resin fractions and some light solvent is 
withdrawn. To this mixture there is added, through line 106, a solvent 
whose source will be explained further on. This solvent contains little 
hydrocarbon having 3 carbon atoms. After passing through a heater 108, 
this new mixture is piped through line 107 to a second extraction tower 
109, where the extraction is effected in the presence of a heavy solvent, 
owing to the mixture of solvents from lines 105 and 106. 
The solvent and the operating conditions of tower 109 are selected so that 
only the asphaltene fraction from line 105, whose softening point is 
150.degree. C. or higher, precipitates in that tower. 
When the light solvent is a C.sub.3 -60/C.sub.5 -40 solvent, the heavy 
solvent may be a C.sub.3 -20/C.sub.5 -80 solvent, the solvent in line 106 
being a C.sub.3 -10/C.sub.5 -90 solvent 
The pressure in the interior of tower 109 may range from 
20.multidot.10.sup.5 to 1.multidot.10.sup.5 pascals abs and the 
temperature from 100.degree. to 200.degree. C., and the mass ratio of 
heavy solvent to feedstock of tower 102 may range from 1 to 10; however, 
these values should not be regarded as limits. 
For example, in the case of a C.sub.3 -20/C.sub.5 -80 heavy solvent, the 
pressure may be about 40.multidot.10.sup.5 pascals abs, the temperatures 
at the bottom and top of tower 109 being 100.degree. C. and 140.degree. 
C., respectively, and the mass ratio of heavy solvent to feedstock of 
tower 102 being about 2/1. 
From the bottom of tower 109, through line 110, the asphaltene fraction 
containing some heavy solvent is withdrawn. 
The treatment of this fraction is the same as that of the unit of FIG. 1. 
For the sake of simplicity, it will not be described. This part of the 
unit that is identical with that of FIG. 1 is shown in the same manner, 
the reference numerals of the equipment items being primed. 
From the top of tower 109, through line 111, a mixture of resin fraction 
and heavy solvent is withdrawn. 
After passing through a heater 112, the mixture of resin fraction and heavy 
solvent withdrawn through line 111 is piped to a flash tower 113 which, in 
the case of a C.sub.3 -20/C.sub.5 -80 heavy solvent, is operated at a 
pressure of about 25.multidot. 10.sup.5 pascals abs and a temperature of 
about 150.degree. C. As a result of the passage through heater 112, a 
portion of the solvent is vaporized, the hydrocarbon having 3 carbon atoms 
being preferentially vaporized. Consequently, C.sub.3 -60/C.sub.5 -40 
light solvent is recovered at the top of tower 113 through line 114 and, 
after passing through a cooler 115, recycled to line 103 to replenish the 
light solvent flowing in line 105. 
The installation of plates in the interior of tower 113 will permit 
separation to be improved, if need be. 
From the bottom of tower 113, through line 116, a mixture of resins and of 
a solvent that is heavier than the heavy solvent is withdrawn and, after 
being passed through a relief valve 117, where its pressure and 
temperature are reduced (in the case of C.sub.3 -10/C.sub.5 -90 solvent to 
about 5.multidot.10.sup.5 pascals abs and 120.degree. C., respectively), 
and through a heater 118, piped to a flash tower 119 which, in the case of 
a C.sub.3 -10/C.sub.5 -90 solvent, is operated at a pressure of about 
5.multidot.10.sup.5 pascals abs and a temperature of about 140.degree. C. 
The major portion of the solvent is recovered at the top of tower 119 by 
way of line 120 and, after passing through a cooler 121, piped to a vessel 
122. 
Vessel 122 is connected through a line 123 to line 106, and the solvent can 
therefore be recycled. 
The resin phase which still contains some solvent is withdrawn at the 
bottom of tower 119 through a line 124 and, after passing through a heater 
125, conducted to a steam stripping tower 126, into which steam is 
introduced through a line 127. 
In the case of a C.sub.3 -10/C.sub.5 -90 solvent, this tower is operated at 
a pressure of about 1.5.multidot.10.sup.5 pascals abs and a temperature of 
about 280.degree. C. 
The resins are recovered at the bottom of tower 126 through a line 128, and 
water and solvent are are withdrawn at the top of that tower through a 
line 129 and piped to condenser 14'. 
A mixture of deasphalted oil and light solvent is recovered from the top of 
tower 102 through line 130 and, after passing through a heater 131, 
conducted to a flash tower 132 which, in the case of a C.sub.3 -60/C.sub.5 
-40 light solvent, is operated at a pressure of about 25.multidot.10.sup.5 
pascals abs and a temperature of about 140.degree. C. 
The major portion of the light solvent is recovered from the top of tower 
132 through line 133 and recycled to line 103 by way of line 114 and 
cooler 115. 
The deasphalted oil which still contains some solvent is recovered from the 
bottom of tower 132 through line 134 and, after passing through heater 
135, conducted to a steam stripping tower 136, into which steam is 
introduced through a line 137. 
In the case of a C.sub.3 -60/C.sub.5 -40 light solvent, that tower is 
operated at a pressure of about 1.5.multidot.10.sup.5 pascals abs and a 
temperature of about 250.degree. C. 
The deasphalted oil is recovered at the bottom of tower 136 through line 
138, and water and solvent are withdrawn at the top of that tower through 
line 139 and piped to condenser 14'. 
FIG. 3 illustrates an alternative to FIG. 1 in which the separation of the 
light solvent from the deasphalted oil is effected in such a way that the 
light solvent contains still more hydrocarbon having 3 carbon atoms. The 
separation of the resins from the oil is improved and makes it possible to 
obtain a deasphalted oil that is still "cleaner", that is, has an even 
lower Conradson residue. 
To describe this figure, a C.sub.3 -20/C.sub.5 -80 heavy solvent and a 
C.sub.3 -35/C.sub.6 -65 light solvent will be taken as an example; 
however, this example of a pair of solvents should not, of course, be 
construed as limitative. 
Only the portion of FIG. 3 which differs from FIG. 1 will be described, and 
only the equipment items holding different products than or differing 
themselves from the equipment items of FIG. 1 are renumbered, with the 
other elements retaining the same reference numerals. 
The mixture of C.sub.3 -20/C.sub.5 -80 heavy solvent and feedstock 
containing no longer any asphaltenes which has been recovered through line 
5 is piped to a second extraction tower 200. A third, C.sub.3 -50/C.sub.5 
-50 solvent is fed to that tower by way of a line 210, the extraction 
being actually effected with a C.sub.3 -35/C.sub.5 -65 light solvent. The 
pressure inside the tower may be about 40.multidot.10.sup.5 pascals abs, 
the temperature at the bottom and top of tower 200 being about 115.degree. 
C. and 145.degree. C., respectively, and the mass ratio of light solvent 
to feedstock of tower 2 being about 4/1. 
The mixture of deasphalted oil phase and C.sub.3 -35/C.sub.5 -65 light 
solvent is recovered at the top of tower 200 through a line 220. 
The resin fraction containing some solvent is withdrawn from the bottom of 
tower 200 through line 28 and treated in the same manner as in FIG. 1. 
After passing through a heater 230, the mixture of deasphalted oil phase 
and C.sub.3 -35/C.sub.5 -65 light solvent is piped to a flash tower 240 
which, in the case of the C.sub.3 -35/C.sub.5 -65 light solvent, is 
operated at a pressure of 25.multidot.10.sup.5 pascals abs and a 
temperature of 145.degree. C. 
Tower 240 is provided with three take-off points. As a result of the 
partial vaporization of the hydrocarbon having 3 carbon atoms, there are 
recovered: 
From the bottom of the tower, through a line 290, a mixture of deasphalted 
oil and C.sub.3 -20/C.sub.5 -80 solvent which, after passing through a 
relief valve 300, where its pressure and temperature are reduced to 
5.multidot.10.sup.5 pascals abs and 95.degree. C., respectively, and 
through a heater 310, is piped to a flash tower 320 operated at a pressure 
of 5.multidot.10.sup.5 pascals abs and a temperature of about 120.degree. 
C.; 
through a side take-off 500, a C.sub.3 -30/C.sub.5 -70 solvent, one portion 
of which is piped to line 33 while the other portion is recycled to tower 
240 through a line 510 after passing through a cooler 520; and 
from the top of tower 240, through line 250, a C.sub.3 -50/C.sub.5 -50 
solvent which, after passing through a cooler 260, is piped to a storage 
vessel 270, this solvent then being recycled to tower 200 through line 
210. 
Tower 320 is provided with three take-off points: 
From the top of this tower, there is recovered, through a line 528, C.sub.3 
-50/C.sub.5 -50 solvent, which is recycled to line 250; 
through a side take-off 530, there is recovered a C.sub.3 -15/C.sub.5 -85 
solvent, one portion of which is piped to line 33 while the other portion 
is recycled to tower 320 through a line 550 after passing through a cooler 
540; and 
from the bottom of tower 320, the deasphalted oil phase containing some 
solvent is recovered through a line 360. 
As in the case of FIG. 1, for removal of the solvent from the oil phase in 
line 360, that phase, after passing through a heater 370, is piped to a 
steam stripping tower 380, into which steam is introduced through a line 
390. 
The deasphalted oil is recovered at the bottom of tower 380 through a line 
410, and water and solvent are withdrawn at the top of that tower through 
a line 400 and piper to condenser 14. 
The combination of the solvents from lines 500 and 530 makes it possible to 
obtain a C.sub.3 -20/C.sub.5 -80 heavy solvent, which is recycled from 
vessel 10 through line 3. 
As is apparent from this description of FIG. 3, the two side take-offs of 
towers 240 and 320 permit the light solvent to be enriched in hydrocarbon 
having 3 carbon atoms. 
As the examples which follow will show, the process in accordance with the 
invention is particularly useful for the simultaneous preparation of a 
deasphalted oil suitable for use as catalytic cracking feedstock with a 
Conradson residue of 10 or less, and preferably of 9 or less, and, better 
still, of 8 or less, and of an asphaltene fraction having a softening 
point of 150.degree. C. or higher, and preferably of 160.degree. C. or 
higher, and, better still, of 170.degree. C. or higher. 
These examples are intended to illustrate the invention in a nonlimitative 
manner. 
References throughout to French standards designated by AFNOR NFT are to 
standardized test procedures similar to U.S. ASTM tests. 
EXAMPLE 1 
This example relates to the treatment of a hydrocarbon feedstock consisting 
of the vacuum-distillation residuum of the atmospheric-distillation 
residuum of a crude petroleum originating in Safaniya. 
The characteristics of this feedstock are as follows: 
______________________________________ 
Density at 15.degree. C.: 
1,035 kg/m.sup.3 
(determined in conformity with standard 
AFNOR NFT 60-101) 
Viscosity at 100.degree. C.: 
0.56 .multidot. 10.sup.-2 m.sup.2 /s 
(determined in conformity with standard 
AFNOR NFT 60-100) 
Conradson residue: 23 wt. % 
(determined in conformity with standard 
AFNOR NFT 60-116) 
Asphaltene content: 16 wt. % 
(determined in conformity with standard 
AFNOR NFT 60-115) 
Sulfur content: 5.5 wt. % 
(determined by x-ray fluorescence) 
Nickel content: 43 ppm 
(determined by x-ray fluorescence) 
Vanadium content: 138 ppm 
(determined by x-ray fluorescence) 
______________________________________ 
This feedstock is treated in a unit for carrying out the process of the 
invention of the type shown in FIG. 1. 
In that unit, C.sub.3 -C.sub.5 solvents are used which have the 
compositions given in Table 1 which follows. 
TABLE 1 
______________________________________ 
Composition in percent by volume 
Heavy Light Third 
solvent solvent solvent 
______________________________________ 
Propane 20 30 40 
Butanes 0.8 0.9 1 
n-Pentane 63 55 47 
Isopentane 
16 14 12 
Hexanes 0.2 0.1 Traces 
______________________________________ 
The operating conditions are given in Table 2 below. 
TABLE 2 
______________________________________ 
Tower Tower 
2 20 
______________________________________ 
Pressure (in 10.sup.5 pascals abs) 
40 40 
Temperature at the top (.degree.C.) 
140 155 
Temperature at the bottom (.degree.C.) 
110 120 
Mass ratio 2/1 4/1 
of solvent to feedstock line 1 
______________________________________ 
The final balance obtained after separation of the solvent from the various 
products is given in Table 3 which follows. 
TABLE 3 
______________________________________ 
Feedstock 2,500 
Line 1 
(tons/day) 
Resins produced 550 
Line 57 
(tons/day) 
Deasphalted oil produced 
1,100 
Line 41 
(tons/day) 
Asphaltenes produced 
850 
Line 13 
(tons/day) 
______________________________________ 
The characteristics of the products obtained are given in Table 4 below. 
TABLE 4 
______________________________________ 
Product Characteristics 
______________________________________ 
Deasphalted oil 
Density (kg/m.sup.3) 960 
Viscosity at 100.degree. C. (10.sup.-6 m.sup.2 /s) 
80 
Conradson residue (wt. %) 
5.8 
Nickel (ppm) 4 
Vanadium (ppm) 10 
Asphaltenes (wt. %) Traces 
Resins Density (kg/cm.sup.3) 
1,042 
Viscosity at 100.degree. C. (10.sup.-6 m.sup.2 /s) 
3,200 
Conradson residue (wt. %) 
20 
Softening point (.degree.C.) 
50 
Asphaltenes 
Density (kg/m.sup.3) 1,147 
Softening point (.degree.C.) 
169 
Conradson residue (wt. %) 
47 
______________________________________ 
It is readily apparent from this table that the process of the invention is 
advantageous inasmuch as it yields very hard asphaltenes and an oil 
suitable for use as a catalytic cracking feedstock since it has a 
Conradson residue of less than 8. 
EXAMPLE 2 
This example relates to the treatment of a hydrocarbon feedstock consisting 
of the effluent from the vis-breaking of a residuum from vacuum 
distillation of a Safaniya crude petroleum. 
The characteristics of this feedstock are as follows: 
______________________________________ 
Density at 15.degree. C.: 
1,060 kg/m.sup.3 
(determined in conformity with standard 
AFNOR NFT 60-101) 
Viscosity at 100.degree. C.: 
0.17 .multidot. 10.sup.-2 m.sup.2 /s 
(determined in conformity with standard 
AFNOR NFT 60-100) 
Conradson residue: 27 wt. % 
(determined in conformity with standard 
AFNOR NFT 60-116) 
Asphaltene content: 22 wt. % 
(determined in conformity with standard 
AFNOR NFT 60-115) 
Sulfur content: 6.2 wt. % 
(determined by x-ray fluorescence) 
Nickel content: 53 ppm 
(determined by x-ray fluorescence) 
Vanadium: 175 ppm 
(determined by x-ray fluorescence) 
______________________________________ 
This feedstock is treated in a unit for carrying out the process of the 
invention of the type shown in FIG. 1. 
In that unit, C.sub.3 -C.sub.5 solvents are used whose compositions are the 
same as those of the solvents of Example 1. 
The operating conditions are given in Table 5 below. 
TABLE 5 
______________________________________ 
Tower Tower 
2 20 
______________________________________ 
Pressure (in 10.sup.5 pascals abs) 
40 40 
Temperature at top (.degree.C.) 
138 148 
Temperature at bottom (.degree.C.) 
108 118 
Mass ratio 1.2/1 2.5/1 
of solvent to feedstock line 1 
______________________________________ 
The final balance obtained after separation of the solvent from the various 
products is given in Table 6 below. 
TABLE 6 
______________________________________ 
Feedstock 2,500 
Line 1 
(tons/day) 
Resins produced 350 
Line 57 
(tons/day) 
Deasphalted oil produced 
1,250 
Line 41 
(tons/day) 
Asphaltenes produced 
900 
Line 13 
(tons/day) 
______________________________________ 
The characteristics of the products obtained are given in Table 7 which 
follows. 
TABLE 7 
______________________________________ 
Product Characteristics 
______________________________________ 
Deasphalted oil 
Density (kg/m.sup.3) 972 
Viscosity at 100.degree. C. (10.sup.-6 m.sup.2 /s) 
30 
Conradson residue (wt. %) 
6.3 
Nickel (ppm) 3 
Vanadium (ppm) 8 
Asphaltenes (wt. %) Traces 
Resins Density (kg/m.sup.3) 1,112 
Viscosity at 200.degree. C. (10.sup.-6 m.sup.2 /s) 
106 
Conradson residue (wt. %) 
42 
Softening point (.degree.C.) 
97 
Asphaltenes 
Density (kg/m.sup.3) 1,190 
Softening point (.degree.C.) 
178 
Conradson residue (wt. %) 
51 
______________________________________ 
It is readily apparent from this table that the process of the invention is 
advantageous inasmuch as it yields very hard asphaltenes and an oil 
suitable for use as a catalytic cracking feedstock since it has a 
Conradson residue of less than 8. 
EXAMPLE 3 
This example relates to the treatment of a hydrocarbon feedstock consisting 
of the residuum from vacuum distillation of the residuum from atmospheric 
distillation of a crude petroleum orginating in Iraq. 
The characteristics of this feedstock are as follows: 
______________________________________ 
Density at 15.degree. C.: 
1,016 kg/m.sup.3 
(determined in conformity with standard 
AFNOR NFT 60-101) 
Viscosity at 100.degree. C.: 
900 10.sup.-6 m.sup.2 /s 
(determined in conformity with standard 
AFNOR NFT 60-100) 
Conradson residue: 17 wt. % 
(determined in conformity with standard 
AFNOR NFT 60-116) 
Asphaltene content: 6 wt. % 
(determined in conformity with standard 
AFNOR NFT 60-115) 
Sulfur content: 4.9 wt. % 
(determined by x-ray fluorescence) 
Nickel content: 43 ppm 
(determined by x-ray fluorescence) 
Vanadium content: 102 ppm 
(determined by x-ray fluorescence) 
______________________________________ 
This feedstock is treated in a unit for carrying out the process of the 
invention of the type shown in FIG. 1. 
In that unit, C.sub.3 -C.sub.5 solvents are used which have the 
compositions given in Table 8 below. 
TABLE 8 
______________________________________ 
Composition in percent by volume 
Heavy Light Third 
solvent solvent solvent 
______________________________________ 
Propane 30 50 70 
Butane 1 1.5 2 
n-Hexane 55 38 21 
Isohexane 14 10.5 7 
______________________________________ 
The operating conditions are given in Table 9 below. 
TABLE 9 
______________________________________ 
Tower Tower 
2 20 
______________________________________ 
Pressure (in 10.sup.5 pascals abs) 
40 40 
Temperature at top (.degree.C.) 
150 160 
Temperature at bottom (.degree.C.) 
120 130 
Mass ratio 2/1 4/1 
of solvent to feedstock line 1 
______________________________________ 
The final balance obtained after separation of the solvent from the various 
products is given in Table 10 below. 
TABLE 10 
______________________________________ 
Feedstock 2,500 
Line 1 
(tons/day) 
Resins produced 650 
Line 57 
(tons/day) 
Deasphalted oil produced 
1,450 
Line 41 
(tons/day) 
Asphaltenes produced 
400 
Line 13 
(tons/day) 
______________________________________ 
The characteristics of the products obtained are given in Table 11 which 
follows. 
TABLE 11 
______________________________________ 
Product Characteristics 
______________________________________ 
Deasphalted oil 
Density (kg/m.sup.3) 955 
Viscosity at 100.degree. C. (10.sup.-6 m.sup.2 /s) 
75 
Conradson residue (wt. %) 
6.1 
Nickel (ppm) 2 
Vanadium (ppm) 4 
Asphaltenes (wt. %) Traces 
Resins Density (kg/m.sup.3) 1,080 
Viscosity at 100.degree. C. (10.sup.-6 m.sup.2 /s) 
Not 
deter- 
mined 
Conradson residue (wt. %) 
27 
Softening point (.degree.C.) 
100 
Asphaltenes 
Density (kg/m.sup.3) 1,174 
Softening point (.degree.C.) 
200 
Conradson residue (wt. %) 
41 
______________________________________ 
It is readily apparent from this table that the process of the invention is 
advantageous inasmuch as it yields very hard asphaltenes and an oil 
suitable for use as a catalytic cracking feedstock since it has a 
Conradson residue of less than 8. 
EXAMPLE 4 
This example relates to the treatment of a hydrocarbon feedstock consisting 
of the residuum from vacuum distillation of the residuum from atmospheric 
distillation of a crude petroleum originating in Safaniya. 
The characteristics of this feedstock are as follows: 
______________________________________ 
Density at 15.degree. C.: 
1,035 kg/m.sup.3 
(determined in conformity with standard 
AFNOR NFT 60-101) 
Viscosity at 100.degree. C.: 
5,600 10.sup.-6 m.sup.2 /s 
(determined in conformity with standard 
AFNOR NFT 60-100) 
Conradson residue: 23 wt. % 
(determined in conformity with standard 
AFNOR NFT 60-116) 
Asphaltene content: 16 wt. % 
(determined in conformity with standard 
AFNOR NFT 60-115) 
Sulfur content: 5.5 wt. % 
(determined by x-ray fluorescence) 
Nickel content: 43 ppm 
(determined by x-ray fluorescence) 
Vanadium content: 138 ppm 
(determined by x-ray fluorescence) 
______________________________________ 
This feedstock is treated in a unit for carrying out the process of the 
invention of the type shown in FIG. 2. 
In that unit, C.sub.3 -C.sub.5 solvents are used which have the 
compositions given in Table 12 below. 
TABLE 12 
______________________________________ 
Composition in percent by volume 
Light Heavy 
solvent solvent 
______________________________________ 
Propane 60 20 
Butanes 0.8 0.8 
n-Pentane 31 63 
Isopentane 8 16 
Hexanes 0.2 0.2 
______________________________________ 
The operative conditions are given in Table 13 below. 
TABLE 13 
______________________________________ 
Tower Tower 
102 109 
______________________________________ 
Pressure (in 10.sup.5 pascals abs) 
40 40 
Temperature at top (.degree.C.) 
130 140 
Temperature at bottom (.degree.C.) 
100 110 
Mass ratio 2/1 1.8/1 
of solvent to feedstock line 101 
______________________________________ 
The final balance obtained after separation of the solvent from the various 
products is given in Table 14 below. 
TABLE 14 
______________________________________ 
Feedstock 2,500 
Line 101 
(tons/day) 
Resins produced 700 
Line 128 
(tons/day) 
Deasphalted oil produced 
1,000 
Line 138 
(tons/day) 
Asphaltenes produced 
800 
Line 13' 
(tons/day) 
______________________________________ 
The characteristics of the products obtained are given in Table 15 which 
follows. 
TABLE 15 
______________________________________ 
Product Characteristics 
______________________________________ 
Deasphalted oil 
Density (kg/m.sup.3) 955 
Viscosity at 100.degree. C. (10.sup.-6 m.sup.2 /s) 
70 
Conradson residue (wt. %) 
5 
Nickel (ppm) 2 
Vanadium (ppm) 5 
Asphaltenes (wt. %) Traces 
Resins Density (kg/m.sup.3) 1,040 
Viscosity at 100.degree. C. (10.sup.-6 m.sup.2 /s) 
2,500 
Conradson residue (wt. %) 
20 
Softening point (.degree.C.) 
45 
Asphaltenes 
Density (kg/m.sup.3) 1,150 
Softening point (.degree.C.) 
175 
Conradson residue (wt. %) 
48 
______________________________________ 
It is readily apparent from this table that the process of the invention is 
advantageous inasmuch as it yields very hard asphaltenes and an oil 
suitable for use as a catalytic cracking feedstock since it has a 
Conradson residue of less than 8.