US3159571A

US3159571A - Residual oil refining process

Info

Publication number: US3159571A
Application number: US154277A
Authority: US
Inventors: Gerrit H Reman; Groothuis Hendrik
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1960-11-28
Filing date: 1961-11-22
Publication date: 1964-12-01
Anticipated expiration: 1981-12-01

Description

Dec. 1, 1964 H. REMAN ETAL 3,159,571

RESIDUAL OIL. REFINING PROCESS Filed Nov. 22, 1961 2 Sheets-Sheet 1 OIL STR IPPER DEASPHALTED PRECiPITANT CHARGE on. FEED l ASPHALTENE STRPPER ASPHALTENES INVENTORS=' GERRIT H REMAN HENDRIK GROOTHUIS THEIR AGENT G. H. REMAN ETAL RESIDUAL OIL REFINING PROCESS Filed Nov. 22, 1961 2 Sheets-Sheet 2 -CHARGE OIL FEED n. STRIPPER l7 -30 CYCLONE,

PRECIPITANT K PRECIPITANT 21 2 CYCLONE PREClPlTANT- DEASPHALTED on. as

ASPHALTEN x3 32 ASPHALTIC B|TUMEN- F| -u'x on IINVENTORS:

GERRIT H. REMAN HENDRIK GROOTHUIS THEIR AGEN 3,159,571 RESIDUAL OIL REFININ G PROCESS Gerrit H. Reman and Hendrik Groothuis, Amsterdam, Netherlands, assignors to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed Nov. 22, 1961, Ser. No. 154,277

Claims priority, application Netherlands Nov. 28, 1960 8 Claims. (61. 208251) The invention relates to a process for the removal of asphaltenes and ash-forming constituents from residual petroleum fractions, by precipitating them with a precipitant and separating the precipitated constituents from the the metal to form a compound with a'lower melting point.

As aresult, the protective film is attacked, after which corrosion proceeds more rapidly.- A similar corrosion phenomenon occurs in gas turbines, where the use of this kind of residual oils may within a short time cause serious damage to turbine blades andother metallic parts; in

United States a Patent addition, the deposition of the ash components will greatly reduce the efficiency of the turbine. 7

It has already been proposed to remove ash-forming constituents from residual oils. For example, vanadiumcontaining material maybe removed from resdiual petroleum fractions by addition of C -C paraffins and separating the oil-insoluble phase so formed. Removal according to this route is possible because the metallic compounds are preseut'in the oil mainly in the form of porphyrin-like structures in a peptized condition. Upon addition of the paraifins the above-mentioned second phase is formed, which contains the metallic compound as well as other high-molecular-weight components, the

asphaltenes.

In this connection it is observed that the individual C 0; paraiiins do not show the same results with respect to e the nature and the quantity of the second phase formed. Thus, propane and butane form an oily phase.

for instance for analytical purposes, application on a commercial scale gives rise to premature clogging of the filter, so that a technically and economically warranted process is notfeasible.

It is an object of this invention to improve the quality of residual oils. It is a particular object of the invention to provide a process for the eificient reduction in ash content -and asphaltenes of residual oils. It' is a particular object of the invention to provide a process having the above objectives without resorting to the disadvantageous means described hereinbefore. Other objects will become apparent during the following discussion of the invention.

Now in accordance with the present invention, it has been found that a very simple separation of the precipitated solid particles is possible by passing the oil-containing mixture through one or more hydrocyclones (including multi-cyclones) under carefully controlled conditions.

The figures illustrate suitable arrangements of apparatus for conducting the process of the invention.

The invention therefore relates to a process for the removal of asphaltenes and ash-forming constituents from residual petroleum fractions by precipitating them with-a precipitant and separating the precipitated constituents from the oil. It is characterized in that the complete or partial separation of the precipitated components from the oil is efiected by passing the oil-containing mixture through one or more hydrocyclones and/ or multi-cyclones.

It has also been found that separation of the asphaltenes can be considerably facilitated by keeping the oil containing the freshly precipitated constituents in motion for some time. This might be explained by assuming agglomeration of elementary asphaltene particles to take place, leading to formation of larger units. Keeping the oil'in motion main- 1y aims at improving the contact between the elementary asphaltene particles, which promotes'fon'nation of larger units.

To separate the asphaltenes and ash-forming constitu ents the oil mixture is forced through one or more hydrocyclones.

A hydrocyclone is here understood to be a vessel bounded by a closed and internally smooth surface of revolution,

which near one end is provided with a tangential inlet or with a number of correspondingly directed tangential inlets, as well as with a central discharge aperture at this end, called below also overflow aperture, while a second discharge aperture is at the other end. If the latter end On the one'hand, this isan advantage, because this phase-for instance in a continuous counter-current-process may drain from the installationias a liquid stream. -On the other hand, however, it is a drawback, because the yield 7 I of deasphalted oil' is relatively low, while there'are few application of the process appears to lead to almost insurmountable difiiculties. These ditliculties arise in the separation of the precipitated mat r l, Which,unlike the but consists of very fine, solid asphaltene particles, which according to some investigators have a size corresponding phase precipitated with propane and butane, is not" oily,

tapers, the discharge aperture is located in the apex of the preferably between 1 and 3 cm. When such cyclones are used, a satisfactory efficiency of separation can be realized for the oil mixture to be separated at moderate feed pressures, which as a rule lie between 3 and 10 atmospheres (preferably 47) gauge.

Preferably -95 percent by volume of the quantity of oil mixture fed inis discharged from the hydrocyclone (cyclones) via the overflow aperture, such that the asphaltene content of the oil discharged (after removal of pentane, etc.) is less than 1 percent by Weight and preferably less than 0.5 percent by weight. For this purpose 3 hydrocyclones are applied in which the diameters of inlet,

with a molecular weight of less than 90,000,'which points to a particle diameterof 6 5 A. or less. -'(Pfeifier, The

Properties of Asphaltic Bitumen" (1950), pp. 367.)

Though these particles' can be'separated' byv filtration,

overflow aperture and apex aperture are in the ratio of 1.5/3/1 to 2.5/3/2. Goodresults are obtained with hydrocycloneswhose cylindrical part has a diameter of y 10 mm, the inlet, overflow aperture and apex aperture diameters being 2mm., 3. mm. and 1.5 mm., respectively. 5

A particularly surprising feature is that in spite of the extremely high shear stresses that may occur in hydrocyclones with a diameter of between 0.5 and 4 cm., hardly, if any, disintegration of the agglomerated units to elementary asphaltene patricles occurs. Seeing that hardly any disintegration takes place, itis on the other hand surprising that these agglomerates, under the infiuence of the great centrifugal forces, should not be thrown as a sticky mass against the wall of the cyclone, which would lead to the narrow apex aperture becoming blocked. For, the asphaltene particles precipitated with pentane, etc., although being dry and hard per se, occur as sticky particles in the oil-pentane medium. The stickiness of the particles is probably also responsible for the rapid clogging of filters, as referred to above.

To increase the throughput, various hydrocyclones of the above type can be connected in parallel, which can be very suitably realized by applying what are called multi-cyclones, which are understood to be constructive units containing a large number of hydrocyclones and as a rule provided with one inlet and two discharge lines.

The efficiency of separation can be increased by applying hydrocyclones connected in series. These cyclones can be used both for the separation of asphaltene particles entrained by the oil phase via the overflow aperture and for further concentration of the asphaltene suspension draining from the apex aperture.

The asphaltene suspension is preferably concentrated after dilution with precipitant. Via the overflow aperture an oil-containing pentane solution is thereby for instance obtained, which increases the yield of deasphaltenized oil. However, the oil-containing pentane solution can also be returned to the process and-together with or instead of pure pentanebe applied as precipitant for the asphaltenes in the base oil.

Starting from a residual petroleum fraction one can in this way on the one hand prepare an oil which is entirely or substantially asphaltene-free and on the other hand obtain pure or substantially pure, i.e. oil-free, asphaltenes, which may contain the ash-forming constituents. The oilfree asphaltenes may then be obtained in the form of a powder.

As precipitants suitable for precipitating asphaltenes and ash-forming constituents can be considered hydrocarbons with 4-9 (preferably 5-7) carbon atoms in the molecule, and having a surface tension with respect to air of less than 24 dynes per cm. (at 25 C.). As examples may be mentioned alkanes (including cycloalkanes) such as n-pentane, isopentane, n-hexane and n-heptane, as well as methylcyclohexane and dimethylcyclopentane and mixtures thereof. For reasons of economy use is preferably made of paraflins, as are obtained in the form of technical mixtures, for instance in the straight run distillation of crude oil, and which are therefore available in large quantities in nearly every refinery. In particular, pentane-containing fractions are applied, because the components of these fractions have relatively low boiling points, so that they can be very simply and completely removed from the deasphaltenized oil and from the asphaltene concentrate by evaporation. It may beadded that the presence in these fractions of unsaturated compounds, such as alkenes, does not interfere.

To precipitate asphal-tenes and ash-forming constituents,

3 to 6 parts by volume and preferably 4 to 5 parts by volume of precipitant per part by volume of oil are as a rule used.

Precipitation can be carried out either batchwise or continuously. The continuous procedure, however, is the preferred one. The residual oil which, to reduce its viscosity, is preferably first mixed with. precipitant, is for this purpose introduced continuously either into a line under turbulent flow conditions or fed into a mixing vessel, where the oil mixtureis stirred. The average.

residence time in both cases is preferably 0.5 to 10 (preferably 15) minutes in the presence of precipitant.

If no precipitant was added before, a quantity of precipitant is added but even if the oil stream introduced into the line or the mixing vessel did already contain precipitant, a further quantity thereof may be added, if required. Subsequently the mixture with agglomerated asphaltene particles is forced through one or more hydrocyclones and/or multi-cyclones, the oil phase obtained from the overflow aperture and the asphaltene suspension obtained from the apex aperture being separately collected and freed from precipitant, if desired, by evaporation or otherwise. The recovered precipitant can be returned to the process.

Precipitation is as a rule carried out at a slightly elevated temperature, because this will reduce the viscosity of the mixture somewhat and promote agglomeration of precipitated particles. Temperatures of between 30 and and 70 C. (preferably 35-65 C.) are applied both for precipitation and during hydrocy-clone separation.

The precipitant may be supplemented by, or replaced with, aliphatic polar compounds containing 39 carbon atoms per molecule including alcohols, dialkyl ethers, aliphatic ketones, and aliphatic esters. Species of these include isopropyl alcohol, diethyl ether, ethyl tertiary butyl ether, ethyl isoamyl ether, acetone, and ethyl acetate. Mixture of C -C alkanes with 1 or more of the above aliphatic polar compounds (preferably an alkane: polar compound ratio between about 3 to 1 and about 1 to 1 results in faster and/ or better agglomeration of the precipitated asphaltenes and consequently in improved separation of the hydrocyclone and/ or in a higher amount of solid material precipitated.

As base materials can be considered residual petroleum fractions obtained by straight run distillation of crude oils containing asphaltenes and/or ash-forming constituents, as well as residues obtained in thermal or catalytic cracking processes. In those cases where the crude oil contains only a small percentage of volatile constituents the crude oil can be used as base material almost per se, i.e., after distilling off only the most volatile components. In general, however, fractions with an initial boiling point of 340-360 C. (ASTM) will be applied. One can also start from fractions with higher initial boiling points, for instance 390 C. at 30 mm. mercury pressure. An advantage of the latter base material is that the quantity of material to be passed through the cyclone is considerably smaller.

In general it is advisable to filter the base oil before precipitation of the asphaltenes, for the residual oils obtained in the refinery as a rule contain a small quantity of solid impurities, which might cause the narrow inlet and the apertures of the hydrocyclones to become blocked. To facilitate filtration the viscosity of the base oil is reduced by addition of a certain quantity of precipitant or another diluent, such that little, if any, precipitation of asphaltenes takes place yet.

The invention is further elucidated by the apparatus illustrated in FIGURES 1 and 2, which are not considered to be limiting features of the invention, but explain processes (with several alternatives) by which the invention may be effected. FIGURE 1 represents a one-stage process and FIGURE 2 is an embodiment of a two-stage process producing'asphaltenes in powder form.

Lines for heat exchangers, pumps and control valves are not shown in the figures.

In FIGURE 1 a charge oil from a source 1 is diluted with aprecipitant from a source 2 either by in-line mixing or by 'intermixing of thetwo streams in a time tank 3, preferably fitted with an agitation device (not shown). The diluted oil feed is held in the time tank (or in a mixing line) for a time and at a temperature suitable to cause precipitation of at least about by' weight of the asphaltenes originally present in the charge oil feed. The mixture comprising precipitant, precipitated asphaltenes and oil dissolved in the precipitant are then transmitted by means of line 4 to the cyclone 5, which is usually a multicyclone Le. a bank containing a substantial number of cyclone units in parallel; The asphaltenes leave the cyclone(s) by means of the apex aperture line 6 which enters a stripping column 7 wherein any residual precepitant is flashed otl andreturned by means of line 8 to the precipitant source 2, whereas the asphaltenes free from precipitant are. drawn off via line 13.

In one alternative aspect of the invention, the cyclone is operated in such a way that the asphaltene slurry comprises precipitated asphaltenes and a separate precipitant phase containing part of the oily constituents of the charge oil feed. Hence, before entering the asphaltene stripper, a settling tank (not shown) may be utilized to separate a majority of the oil-precipitant solution from the precipitated asphaltenes before sending the latter to the asphaltene stripper 7. The oil precipitant solution may then be either returned to the precipitant source 2 or may be subjected to a stripping operation to remove the precipitant from the oil. It is then possible, of course, to recombine any part of the. asphaltenes with any part of the oil from the latter source or from the main oil source to obtain desired products of either a residual fuel or asphalt character.

The principal body of the precipitant leaves the overflow section of the cyclone by means of overflow line 9. Usually the oil solution if then conducted to the oil stripper 10 wherein the precipitant is flashed oif and returned by means of line '11 to the principal precipitant source 2 whereas the deasphaltenized oil is drawn ofl-via line 14. However, in many instances it is possible to utilize this oil-precipitant solution without stripping for the purpose of precipiating asphaltenes from further portions of the charge oil feed. Consequently, any part of the oil-precipitant solution leaving the overflow line 9 may be returned to admixture with charge oil feed by means of line 12. V I V A special embodiment of the process according to the invention is represented in FIGURE 2 which relates to the continuous and simultaneous preparationof asphaltene-free or substantially asphaltene-free oils and of pure I For this purpose aresidual petroleum fraction from a source or substantially pure- -ie. oil-freeasphaltenes.

is mixed tor some time in a line 17 with precipitant from a source 16, after which the mixture is'passed through a first cyclone 18. Via the overflow line 19 of this hydrocyclone a product is discharged consisting of a solution of substantially deasphaltenized oil in precipitant. The flow discharged via the apex aperture of the cyclone 18 into line is a product consisting of a suspension of ,solid asphaltene particles .in precipitant together with -'a relatively small quantity of oil. The asphaltene concentrated drained via line 25 is subsequently mixed in line 26 with pure or substantially pure precipitant supplied via line 24 and then passed through a second cyclone 27. It should be added that the precipitant with which the asphaltene concentrate from the first hydrocyclone 18 is mixed originates from the recovery system 21for instance a distillation column-for the deasphaltenized oil discharged via overflow line 19 from the first hydrocyclone 18 and/ or from the recovery system 29 for the underflow 28 of the second hydrocyclone 27 to be mentioned hereinafter. Via overflow line 16 of the second hydrocyclone 27 a product is obtained consisting of a solution of a relatively small quantity of substantially deasphaltenized oil in precipitant. This solution is. admixed with the base oil to efl'ect precipitation and separation of asphaltenes and ash-forming constituentsin the first hydrocyclone 18. Via apex aperture line 28 of the second hydrocyclone 27 a suspension is drained ofi of solid asphaltene particles in precipitant. discharged" via the overflow line 19 of the first hydrocyclone 18 is passed to a recovery System21 in which on the one hand substantially deasphaltenized oil (via line 22) and on the other hand pure or substantially pure precipitant (via line 23) is obtained. The product drained The product 6 via the apex aperture 28 of the second hydrocyclone 27 is passed to a recovery system 29 where on the one hand pure or substantially pure asphaltenes (via line 31) and on the other hand pure or substantially pure precipitant (via line 30) is obtained, which, as observed above, is returned to the process.

The pure asphaltenes obtained via line 31 may e.g. be admixed with an appropriate flux oil supplied via line 32, in order to produce a synthetic asphaltic-bitumen which is discharged via line 33.

In all cases where in the above procedure a hydrocyclone is mentioned, also a multicyclone can be applied. The (largest) inside diameter of the cyclones according to the present invention may vary within wide limits. In general preference is given to a diameter between 0.5 and 4 em, but cyclones with larger diameters e.g. up to 10 cm. may also be used.

As observed above the precipitant may be supplemented by aliphatic polar compounds containing 3-9 carbon atoms per molecule. By applying these mixtures the precipitating power towards asphaltenes and similar constituents of the residual oil can be influenced. For example, when mixtures of pentane and isopropyl alcohol are used instead of pentane, the amount of precipitate increases with an increasing concentration of isopropyl alcohol in the mixture (the ratio of precipitant to residual -oil being kept constant), while also the properties of the units, thus improving the separation of the asphaltenes and ash-forming constituents in the hydrocyclone(s).

7 Example I Q A fraction obtained as a residue of a straight run distillation of a Venezuelan crude oil, said residue having an initial boiling point of 350 C. (ASTM), a vanadium content of 520 p.p.m. and a sodium content of 61 p.p.m.

was usedin the following test. The viscosity of the oil was 30,000 cs. at 100 F.

16.8 litres of this residual fraction were mixed with stirring with 82 litres of n-pentane in a pressure vessel, after'which stirring was continued at a temperature of 35 C. for another 10 minutes. The oil-pentane mixture with precipitated asphaltenes and ash-forming constituents was then forcedthrough a hydrocyclone at a nitrogen pressure of 4 atm. gauge.

The dimensions of the cyclone were:

Mm. Diameter of cylindrical part 10 Height of cylindrical part 6 Height of conical part 55 Diameter of inlet 2 'Diameter of overflow aperture 3' Diameter of apex aperture 1.5 Length of vortexfinder 4 ents, respectively. The viscosity of the deasphaltenized oil was 8500 cs. at F. The vanadium content of the oil had dropped to 200 p.p.m. (vs. 520 initial) and A fraction with an'initial boiling point of 350 C. I

(ASTM), a vanadium content of 52 p.p.m.- and a sodium content also of 52 p.p.m., obtained. by straight run distillation of a Middle East crude oil, was used as base material. The viscosity of the base oil was 1618 cs. at 100 F.

Under continuous flow conditions 20 liters/hour of this residual fraction and 130 liters/hour of n-pe-ntane were pumped simultaneously into a tank. with a useful capacity of 25 liters. The oil-pentane mixture with precipitated asphaltenes and ash-forming constituents, which under the prevailing conditions had an average residence time in the tank of 10 minutes, was pumped continuously through the same cyclone as described in Example I at a pressure of 4 atm. gauge at a rate corresponding with the rate at which the oil-pentane mixture was fed into the tank.

Via the overflow aperture 130 liters/hour of oil-pentane mixture and via the apex aperture liters/hour of pentane-containing asphaltene concentrate were obtained. After evaporation of the pentane, deasphaltenized oil and an asphaltene concentrate remained behind, containing 0.3 and 28% W. of precipitated constituents, respectively. The viscosity of the deasphaltenized oil was 833 cs. at 100 F. The vanadium content of the oil had dropped to 23 p.p.m. and the sodium content to 2.4 p.p.m.

Example III The asphaltene concentrate obtained according to Example II was once more passed through a hydrocyclone to be further concentrated For this purpose a hydrocyclone was used of the same dimensions as applied in the preceding examples.

19.9 liters of the asphaltene concentrate were for this purpose first diluted with 69 liters of n-pentane and then forced through the hydrocyclone at a pressure of 4 atm. gauge. Via the overflow aperture 70.4 liters of pentaneoil mixture and via the apex aperture 18.5 liters of pentane-containing asphaltene concentrate were separated. After evaporation of the pentane 1.96 liters of oil and 1.44 liters of asphaltene concentrate with an asphaltene content of 66% w. were obtained.

Example IV The same residual fraction as mentioned in Example II was used as base material for the simultaneous production of deasphaltenized oil and asphaltenes containing ash-forming constituents, in the apparatus illustrated in FIGURE 2.

Under continuous flow conditions 1000 kg. per hour of the above residual fraction-heated to 100 C.were supplied via line 15 and mixed with 5000 kg. per hour of a precipitantheated to 52 C.consisting of a solution of a relatively small quantity of deasphaltenized oil in n-pentane, discharged via overflow line 16 of multicyclone 27. The mixture thus obtained which now had a temperature of 60 C., was passed under turbulent flow conditions via line 17 into a multicyclone 18, which consisted of 10 cyclones in parallel. Each of these cyclones had the following dimensions:

Diameter of cylindrical part Diameter of inlet 7 Diameter of overflow aperture 8.5 Diameter of apex aperture 4 The length of line 17 was such that the residence time of the mixture in it was one minute, which was sufiicient to effect precipitation of the asphaltenes present in the to a distilling column 21. At the bottom of this column 950 kg. per hour of deasphaltenized oil with an asphaltene content of 0.5% w. was recovered via line 22. The

vanadium content of the deasphaltenized oil had dropped to 23 p.p.m. and the sodium content to 2.4 p.p.m. The pentane discharged via line 23 at the top of the distilling column at a rate of 4607 kg. per hour was returned to the process via line 24 at a temperature of 20 C. and mixed in line 26 with the asphaltene concentrate (60 C.), which drained via line 25 from the apex aperture of cyclone 18 at a rate of 442 kg. per hour. The mixture of pentane and asphaltene concentrate, which had a temperature of 23 C., was passed under turbulent flow conditions through line 26 into multicyclone 27 which, like the .first multi-cyclone 18, consisted of 10 cyclones in parallel,

each of the same dimensions as the first. Via the overflow line 16 of this cyclone 27 5000 kg. per hour of pentane with an oil content of 1.2% w. was discharged, whichafter being heated to 52 C.was applied as precipitant for the base oil fed via line 15. Via line 28 asphaltene concentrate was discharged at a rate of 442 kg. per hour to recovery system 29, where via line 30 pentane was discharged at a rate of 400 kg. per hour, to be mixed, together with the pentane recovered via line 23 from the distilling column 21, via line 24 with the asphaltene concentrate from apex aperture line 25 of cyclone 18, via line 31 asphaltenes in powder form, with an oil content of 10% w., were recovered in a quantity of 50 kg. per hour.

Example V The same residual fraction as mentioned in Example II was used as a base material for the simultaneous production of deasphaltenized oil and asphaltenes containing ash-forming constituents in the apparatus illustrated in FIGURE 2 and under the same conditions as described in Example IV, with the exception that the 5000 kg. per hour of oil-containing precipitant discharged via line 16 of multicyclone 27 were kept at 20 C. instead of 52 C. and the 1000 kg. per hour of residual oil, supplied via line 15, were heated to only C. instead of C., thus yielding a mixture of the precipitant and the residual oil in line 17 having a temperature of only 29 C. At

this temperature precipitation and/or agglomeration of the asphaltenes during the one-minute residence time in line 17 were not suflicient to effect efl'lcient separation in multicyclone 18. The deasphaltenized oil discharged via line 22 from the bottom of distilling column 21 still contained 3.0% w. of asphaltenes, while via the underflow of multicyclone 27 and recovery system 29 only 22 kg. per hour of asphaltenes, with an oil content of 10% w.,' were recovered.

Under the same conditions as mentioned above it appeared that the separation of asphaltenes and ash-forming constituents could be favourably influenced by replacing part of the pentane by isopropyl alcohol. With the same amount .of precipitant as above, but which now consisted of pentane and isopropyl alcohol in a 70 to 30 weight ratio, a deasphaltenized oil containing only 1.7% w. of asphaltenes was obtained via line 22, While via recovery system 2? asphaltenes in powder form, with an oil content of 10% w., were recovered in a quantity of 51 kg. per hour.

Example VI part of residual oil.

CONTINUOUS DEASPI-IALTIZING OF KUWAIT LONG RESIDUE' It will be seen by the data contained in the table above that asphaltene particles permitting separation by means of hydrocyclone are formed more rapidly at the relatively higher temperatures.

Recapitulating some of the advantages gained by use of the present invention, the process enables the economic separation of asphaltenes from oily constituents of petroleum residues and at the same time the substantial reduction in ash constituents such as vanadium and sodium, concentrating these in the asphaltenes. The oil so produced has substantially improved properties insofar as its eventual utility is concerned relative to reduced ash content and, thereby, reduced corrosion characteristics. Moreover, due to the reduction in these particular ash constituents, it has been found that catalytic treatment of oils so obtained is more efiicient in that catalyst decline is at a substantially lower rate than when treating the full range petroleum residue. This is especially noticeable in hydrogenation procedures, including hydrodesulphurization.

The asphaltenes isolated by the process of the invention are highly desirable constituents in asphalt compositions and may be combined with a number of oils known in the art such as aromatic extracts or heavy distillates to obtain asphalt compositions having blown asphalt characteristics. Consequently it will be seen that utilization of such asphaltenes reduces or eliminates the necessity for blowing such compositions in order to obtain the properties of blown asphalts.

We claim as our invention:

1. The process for the fractionation of an ash-containing asphaltenic residual petroleum oil teed whichcomprises diluting said oil with 3-6 volumes of a precipitant consisting essentially of at least one C alk-ane per volume of said oil, holding the diluted oil mixture .for a period of 05-10 minutes at a temperature of 30-70 (1., whereby asphaltenes are precipitated, and passing the mixture through at least one hydrocyclone at a pressure of 3-10 atmospheres whereby an alkane solution of oil having a reduced ash content and containing less than about 2% by weight of asphaltenes is separated from an alkane slurry of asphaltenes, said asphaltenes having a substantially greater ash content than that of the feed.

2. The process for the fractionation of ash-containing asphaltenic' residual petroleum oil feed which comprises diluting said feed with 4.5-5.5 volumes of a precipitant consisting essentially of at least one C alkane per volume of feed, holding the diluted feed for a period of 1-5 minutes at a temperature of 35-65 C., whereby asphaltenes are precipitated and passing the mixtures so treated through at least one hydrocycloneat a pressure of 4-7 atmospheres whereby an alhane solution of oil having a reduced ash content and containing less than about 2% by weight of :asphaltcnes is separated from an alkane slurry of asphaltenes, said asphaltenes having a substantially greater ash content than that of the feed.

3. A process according to claim 2, wherein the diameters of the inlet, overflow aperture and apex aperture are in the ratio from 1.5/3/1 to 2.5/3/2.

4. A process according to claim 2 wherein the diluent comprises n-pentane.

5. A process according to claim 4 wherein the pentane is normal pentane.

6. The process for the fractionation of an ash containing asphaltenic residual petroleum oil feed which comprises diluting said oil with 3-6 volumes of a precipitant consisting essentially of at least one liquid of the group consisting of C alkanes, C alcohols, C dialkyl ethers, C aliphatic ketones, C aliphatic esters and mixtures thereof per volume of said oil, holding the diluted oil mixture for a period of 0.5-10 minutes at a temperature of Bil-70 0, whereby asphaltenes are precipitated, and passing the mixture through at least one hydrocyclone at a pressure of 3-10 atmospheres whereby a solution of oil in said liquid, said oil having a reduced ash content and containing less than about 2% by weight of asphaltenes is separated from a slurry of asphaltenes in said liquid, said asphaltenes having a substantially greater ash content than that of the feed.

7. A process for the simultaneous production of deasphaltenized oil and asphaltenes which contain ash-forming constituents by precipitating asphaltenes and dasht'orming constituents from a residual petroleum oil fraction by diluting said fraction with 3-6 volumes of a precipitant consisting essentially of at least one liquid of the group consisting of C5 7 alkanes, C alcohols, C dialkyl ethers, C aliphatic ketones, C aliphatic esters and mixtures thereof per volume of said oil, holding the diluted oil fraction for a period of 05-10 minutes at a temperature of 30-70 C., the diluted 'oil fraction through a first hydrocyclone yielding an overflow product consisting of a solution of precipitant and substantially deasphaltenized oil and an underflow product consisting of a suspension of solid asphaltene particles in precipitant underflow of the second hydrocyclone, passing the mixture of the underflow product of the first hydrocyclone and substantially pure precipitant through a second hydrocyclone yielding an overflow product consisting of precipitant and a relatively small quantity of substantially dea-sphaltenized oil and an underflow product consisting essentially of a suspension of solid asphaltene particles in precipitant, using the overflow product of the second hydrocyclone for the precipitation and separation of asphaltenes in the first hydrocyclone, passing the overflow product of the first hydrocyclone to a recovery system to yield substantially deasphaltenized oil and substantially pure precipitant and passing the underflow product of the second hydrocyclone to a second recovery system to yield substantially pure asphaltenes and substantially pure precipitant.

8. The proces of claim 7 wherein multicyclones are employed instead of hydrocyclones.

References Qited in the file of this patent UNITED STATES PATENTS Bieber et a1. Apr. 26, 1960