JPH0149319B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves separating a fraction consisting essentially of asphaltenes from heavy hydrocarbon materials and then processing the separated fraction to subject it to cracking and visbreaking. , relates to a method of making additive liquid products with reduced metal content.

In the past, many methods have been proposed for extracting various fractions of bityumen-like materials. The most well-known method is called ``propane extraction,'' which uses propane as an extractant to separate asphalt-like materials from extracted hydrocarbons to produce deasphalted oil and asphaltene-containing residue. It is something.

Other extraction methods have been developed because it is desirable to obtain the maximum amount of oil possible from heavy hydrocarbon materials such as crude oil. U.S. Patent No. 2,940,920 states:
A method is described that is capable of cutting deeper into heavy hydrocarbon materials than can be achieved with propane extraction. The term "cutting" is well known to those skilled in the art, and refers to extracting heavy hydrocarbons to separate resin and oil from asphaltenes. This US patent describes the use of high temperature-pressure methods and the use of pentane as one of a group of suitable solvents to effect the separation. This method allows for a deeper cut into heavy hydrocarbon materials and produces an asphaltene-containing residue with a higher viscosity than that produced by propane extraction.

Typically, the asphaltene-containing residue also contains a substantial portion of the organometallic compounds present in the heavy hydrocarbon material. This residue has limited commercial use due to its high viscosity and metal content. The residue can be used as a soil conditioner, asphalt hardener, pigment in printing inks, sizing agent in paper, and solid granular insulation. The physical and chemical properties of the residue substantially limit its use as a liquid fuel, even when diluted with hydrocarbon cutlet feedstock.

The asphaltene-containing residue is converted by visbreaking or pyrolysis under controlled conditions into a lighter product with an acceptably low viscosity suitable for use as a liquid fuel. It is desirable to make it into a product. Various methods of visbreaking heavy hydrocarbon materials by pyrolysis are described in U.S. Pat.
It is described in the same No. 3234118 and the same No. 3349024.

Previous attempts to produce liquid products from asphaltenes have met with limited success. Attempts to visbreak or thermally decompose asphaltenes resulted in coking within the processing equipment. In the equipment used for this method,
At the high temperatures at which this equipment is operated, coking occurs when the feedstock is not maintained in turbulent conditions. The high viscosity of asphaltene prevents it from maintaining the turbulent flow conditions necessary to prevent coking. This results in low yields of the desired visbreaking product and short on-stream times until coking of the feedstock terminates the process. The coke must be manually removed from the equipment or burnt out by blasting with air.

In this invention, heavy hydrocarbon material is processed by the method described below to deeply cut into the oil of the heavy hydrocarbon material and then remove asphaltene-containing residues by visbreaking under controlled conditions. It has been found that the process can eliminate or substantially reduce coking within a visbreaking device while producing additional liquid product.

The method includes contacting a heavy hydrocarbon material with a first solvent in a first mixing zone to create a mixture for introduction into a first separation zone. The first separation zone separates the mixture into a fluid first light phase comprised of a first solvent, an oil and a resin, and an asphaltene comprising a majority of the organometallic compound present as well as some first solvent. The temperature and pressure are maintained at such a high temperature and pressure that it separates into a structured fluidic first heavy phase.
The first light phase is removed from the first separation zone and introduced into a second separation zone for additional fractionation or recovery as product.

A first heavy phase is then introduced into the visbreaking zone. In this zone, the asphaltene is heated under high pressure to a high temperature for pyrolysis. The pressure within the visbreaking zone is so high that no separate vapor phase is formed at the maximum temperature within this visbreaking zone. The product of the visbreaking zone is removed from this zone as one condensed phase and introduced into a third separation zone.

In the third separation zone, the product of the visbreaking zone is flash distilled in one or more stages. Preferably, the last stage is carried out under vacuum to separate at least a portion of the distillable liquid containing the first solvent as well as the gaseous product from the substantially non-distillable liquid product and the residue. After this, the residue is introduced into a fourth separation zone where it is brought into contact with a second solvent and kept at elevated temperature and pressure.

In a fourth separation zone, a fourth light phase is formed, the remainder consisting of a liquid product consisting of a substantially non-distillable product, a distillable product and a second solvent, residual asphaltenes, organometallic compounds, coke,
A fourth heavy phase is separated, which constitutes a residue made up of catalyst fines (if any) as well as other heavy carbon materials. A fourth light phase is removed from the fourth separation zone and introduced into the fifth separation zone.

The fifth separation zone is for separating the fourth light phase into a fifth light phase composed of the second solvent and a fifth heavy phase composed of the liquid product of the visbreaking process. Maintain appropriate temperature and pressure conditions. The second solvent is circulated in this manner and the visbreaking liquid product is recovered for use as a liquid fuel with reduced metal content.

The drawing illustrates the method of the invention. A feedstock consisting of a heavy hydrocarbon material comprised of asphaltenes and one or both of a resin and an oil is introduced via conduit 10 into a mixing zone 12 . A first solvent is introduced into mixing chamber 12 via conduit 14 and contacts and mixes with the feedstock to form a mixture. The volume ratio of solvent to feedstock in the mixture (measured at ambient temperature conditions) is from about 2:1 to about
In the range of 20:1, preferably from about 8:1 to about 12:1
Sufficient first solvent is introduced into the mixing zone 12 so that the first solvent is within the range of . It should be appreciated that larger amounts of the first solvent may be used, but such use is not particularly advantageous.

In this specification, the term "first solvent" refers to paraffin hydrocarbons containing from 4 to 9 carbon atoms, such as pentane, hexane, heptane, octane, and nonane, and cyclopentane, cyclohexane, and its methyl Like derivatives, carbon atoms
less than 10 cycloparaffinic hydrocarbons and monoolefinic hydrocarbons containing from 4 to 8 carbon atoms, such as butenes, pentenes, hexenes, heptenes and octenes, and at least a portion of the heavy hydrocarbon feedstock material. can be dissolved,
A fluid composed of at least one material selected from the group consisting of any other known fluid that can then be separated from the dissolved feedstock.

The mixture is then conveyed via conduit 16 to first separation zone 18 . The first separation zone separates the mixture into a first
A liquid first light phase consisting of a solvent, an oil and a resin, and a fluid first heavy phase consisting of an asphaltene, an organometallic compound and some of the first solvent. Temperature and pressure are maintained. As previously stated, a substantial portion of the organometallic compounds present in heavy hydrocarbon materials are related to asphaltenes.

More specifically, the first separation zone 18 is approximately
150〓 to approximately the critical temperature of the first solvent, and at least equal to the vapor pressure of the first solvent at a temperature below the critical temperature of the first solvent; The pressure level is maintained at least equal to the critical pressure of the first solvent when it is at a temperature equal to or above its critical temperature. The temperature level ranges from about 50° below the critical temperature of the first solvent to about 50° below the critical temperature of the first solvent.
Preferably kept within the range of 50〓 high places. Preferably, the pressure level is maintained at or above the critical pressure of the first solvent.

Alternatively, the heavy hydrocarbon material as well as the first solvent may be introduced directly into the first separation zone 18 in the previously mentioned ratios without prior mixing, but the phase They can be introduced at different locations and then separated as described above.

The first light phase is transferred from the first separation zone 18 to the conduit 20.
It is taken out and collected through the . In one embodiment, the separated first light phase is transferred from the first separation zone to conduit 20.
into the second separation zone 22 via. Second
The separation zone 22 operates at a temperature level higher than that of the first separation zone 18 and converts the first light phase into a fluid second light phase comprised of oil, resin, and some first solvent. It is kept at such high pressure that it separates. The temperature level of the second separation zone 22 is preferably maintained within a range of about 5 to about 100 degrees above the temperature of the first separation zone 18, but about 5 to about 50 degrees above the critical temperature of the solvent. It is most preferable to keep it at

The pressure level in the second separation zone 22 is such that the pressure level in the second separation zone 22 is
is maintained at a temperature below the critical temperature of the first solvent, the vapor pressure of the first solvent is maintained at least equal to the vapor pressure of the first solvent, and the zone 22 is equal to or greater than the critical temperature of the first solvent. When maintained at temperature, it is maintained at least equal to the critical pressure of the first solvent. The pressure level in the second separation zone 22 is
The pressure level maintained in the first separation zone 18 can be approximately the same.

A second light phase is transferred from the second separation zone 22 to the conduit 26.
is withdrawn via the feedstock and circulated in this manner into contact with another fresh feedstock. The second heavy phase can be introduced into a separate stripping zone (not shown) and at least a portion of the first solvent that may be contained therein can be removed by stripping. Preferably, the stripping area comprises a stream stripping vessel. The first solvent thus recovered by stripping can be recycled in this manner. A second heavy phase is removed from the second separation zone 22 via conduit 24 and the first heavy phase contained therein is removed from the second separation zone 22 via conduit 24.
After releasing the solvent, it is recovered for advantageous use, for example, as a liquid fuel or as a feedstock for a hydroprocessing process.

The first heavy phase is transferred from the first separation zone 18 to the conduit 28.
and introduced into the visbreaking section 30. In the visbreaking zone 30, the first heavy phase is heated to a temperature above 850° C. while maintaining high pressure to convert the asphaltenes into smaller molecular weight fragments. The temperature level is preferably maintained above 900°, most preferably above 950°, in order to effect efficient decomposition of asphaltene. The pressure level is such that both the pressure of the first heavy phase entering the visbreaking zone 30 and the pressure level of the product exiting the zone 30 are equal to or lower than any discrete vapor pressure level at any operating temperature level within the zone 30. The pressure is controlled to be above the minimum pressure level necessary to prevent phase formation. Such control of pressure levels prevents the formation of excessive amounts of coke and gas within the visbreaking zone 30 by substantially limiting the degree of degradation of the products in the visbreaking zone. be done. This control effect is due to the fact that the first heavy phase passes through the visbreaking zone 30 at a temperature below the decomposition temperature of asphaltenes as well as a temperature above the decomposition temperature of asphaltenes.
is monitored by measuring the pressure drop of the heavy phase. The pressure drop in these two different conditions remains substantially the same when only one condensed phase is present in zone 30. At temperatures above the asphaltene decomposition temperature, the increase in pressure drop in zone 30 indicates that a separate vapor phase is forming and that excess coke formation is also likely occurring.

In the visbreaking zone 30, the first heavy phase is
If a condensed hydrocarbon gas is generated, a visbreaking product consisting of this gas, a distillable liquid product, and a substantially non-distillable liquid product containing organometallic compounds is formed. converted.
The visbreaking product then passes from the visbreaking zone 30 to the third separation zone 34 via conduit 32.

In the third separation zone 34, the visbreaking product is flash distilled to render at least a portion of the gaseous and distillable liquid product (including the first solvent), if any, substantially non-distillable. separate from the liquid product. The separated part is the third
via a conduit 36 from a separation section 34 of the
It will be collected. The separated first solvent can be recycled to the first separation zone 18.

In another embodiment of the invention, the first heavy phase passing through conduit 28 is treated (not shown) and circulated to mixing zone 12 so that at least a portion of the first solvent, if present, is Separate. Removal of the first solvent from the first heavy phase significantly increases the viscosity of the remaining asphaltenes and organometallic compounds within the first heavy phase. To facilitate the decomposition of the asphaltenes in the first heavy phase in the visbreaking zone 30, a diluent is added to the asphaltenes and the organometallic compound to reduce the viscosity of the mixture before entering the zone 30. Diluent is introduced into the mixture in conduit 28 via conduit 56 in an amount sufficient to reduce the viscosity of the mixture to a level such that it can flow easily.

The diluent used in practicing this invention is about
It is a stream of petroleum by-products with a strong aromatic character, with boiling points ranging from 400° to about 1000°. The diluent can be comprised of catalytic cracking recycle feedstocks, such as light catalytic cracking recycle oils, heavy catalytic cracking recycle oils, or catalytic cracking slurry oils, pyrolyzed petroleum feedstocks, and lube oil aromatic extracts. Diluent is about 400〓 to about 800〓
It is preferable to have a boiling point in the range of 〓, approximately 400〓
Most preferably, it has a boiling point in the range of from about 650° to about 650°.

The diluent imparts fluidity to the mixture of asphaltenes and organometallic compounds, allowing the mixture to be heated to the high temperatures necessary to decompose the asphaltenes without producing too much coke, gas, or lighter molecular weight fragments. make it easier. Generally, the diluent is not thermally degraded during the visbreaking process because it is itself a product of the previous high temperature catalytic cracking conversion process. The catalytic cracking slurry oil typically contains finely divided catalysts within the visbreaking zone 30 that act to improve cracking rates and reduce side reactions that tend to result in coke and gaseous product formations. This makes it a particularly satisfactory diluent. Finely divided catalysts also tend to adsorb any metal values and other contaminants that may be released from asphaltenes and organometallic compounds during the visbreaking process.

Visbreaking product and diluent are removed from the visbreaking zone 30 and introduced via conduit 32 into a third separation zone 34. The gaseous distillable liquid product and diluent are separated from the substantially non-distillable liquid product and organometallic compounds and removed via conduit 36. A portion of the diluent in conduit 36 is circulated through conduit 38;
Fresh feedstock to the visbreaking zone 30 can be contacted.

In yet another embodiment of the invention, the amount of first solvent present in the first heavy phase is so small that it no longer has the necessary fluidity to treat the asphaltenes within the visbreaking zone 30. , the diluent can be added to the first heavy phase without prior separation of the first solvent. The first heavy phase and diluent mixture is processed as previously described, and in the third separation zone 34 the first solvent is recovered along with the diluent.

Regardless of the operation in the braking zone 30, the third heavy phase is transferred from the third separation zone 34 to the conduit 4.
0 and is contacted with a second solvent introduced via conduit 42 into a fourth separation zone 44 .

The second solvent is introduced in an amount sufficient to provide a ratio of the second solvent to the third heavy phase in the range of about 2:1 to about 10:1. It should be appreciated that even higher amounts of the second solvent may be used, but such use is not particularly advantageous.

Although the second solvent is mentioned, the second solvent can be the same as the first solvent or can consist of any other fluid suitable for use as the first solvent. .

In the fourth separation zone 44, the third heavy phase and the second
a fourth light phase consisting of the substantially non-distillable liquid product of the visbreaking operation and a second solvent substantially free of organometallic compounds; and residual asphaltenes, organometallic compounds. A fourth heavy phase is separated, comprising a residue made up of compounds, coke, finely divided catalyst (if any), and other heavy carbonaceous materials.

More specifically, the fourth separation area 44 is
a temperature level ranging from about 150°C to a value above the critical temperature of the second solvent, and at least equal to the vapor pressure of the second solvent at a temperature below the critical temperature of the second solvent; The second solvent is maintained at a pressure level at least equal to the critical pressure of the second solvent at a temperature equal to or higher than its critical temperature. Preferably, the temperature level is maintained within a range of about 50° below the critical temperature of the second solvent to about 50° above the critical temperature of the second solvent. Preferably, the pressure level is kept above the critical pressure of the second solvent.

A fourth heavy phase is transferred from the fourth separation zone 44 to the conduit 50.
It is taken out and collected via the The fourth heavy phase can be used as a solid feed to a gasifier or otherwise treated before disposal.

A fourth light phase is transferred from the fourth separation zone 44 to the conduit 46.
and introduced into the fifth separation section 48. In the fifth separation zone, the fourth light phase is separated from the second
and a fifth heavy phase consisting of the liquid product of the visbreaking operation and some of the second solvent. dripping The temperature level in the fifth separation zone 48 is maintained at a higher level than the temperature level in the fourth separation zone 44. The pressure level in the fifth separation zone 48 is maintained at least equal to the vapor pressure of the second solvent when the zone 48 is maintained below the critical temperature of the second solvent;
is maintained at a temperature equal to or greater than the critical temperature of the second solvent, at least equal to the critical pressure of the second solvent. More specifically, the temperature level of the fifth separation zone 48 is preferably maintained above the critical temperature of the second solvent, and is about 5° to 50° above the critical temperature of the second solvent.
It is best to keep it high.

The separated fifth light phase is removed from the fifth separation zone 48 via conduit 52 and circulated in this manner.

A fifth heavy phase is transferred from the fifth separation zone 48 to the conduit 54.
and recovered for use as a liquid fuel whose potency generally corresponds to No. 6 fuel oil.

The fourth and fifth heavy phases can be introduced into separate stripping zones (not shown) to remove at least a portion of the second solvent that may be contained within each heavy phase. . Preferably, the stripping area comprises a steam stripping vessel. At this time, the second solvent can be circulated in this manner.

In another embodiment of the invention, the fifth separation zone 4
8 comprises a flash zone, flash-distilling the fourth light phase to a sufficiently low pressure to produce at least one stream consisting of the liquid product of the visbreaking operation as well as another stream consisting of the second solvent. 1
form two streams. After this, the liquid product is collected and the solvent is recycled as previously described.

To illustrate the method of the invention, and without intending to limit it, the following example is provided.

Example 1 18% asphaltene, 30% resin and
Extracted crude oil, consisting of 52% oil (softening point approximately 110
〓) is mixed with a first solvent composed of n-pentane in a solvent to feed volume ratio (measured at 60 〓) of about 10:1 and introduced into the first separation zone 18. . The first separation zone is maintained at a temperature level of about 370° and a pressure level of about 650 psig. The feed mixture contains a first light phase, asphaltenes and some n
- a first heavy phase consisting of pentane.

The n-pentane is separated from the first heavy phase by flash distillation, and the remainder of the first heavy phase is made up of a catalytic cracking slurry oil in a diluent to feed ratio of about 3:1. and a diluent to form a mixture, which is introduced into the visbreaking zone 30. The mixture is heated in the visbreaking zone 30 to a temperature of about 950 psi while maintaining a pressure level of about 500 psig to prevent the formation of a separate vapor phase within the visbreaking zone 30. The product of the visbreaking zone is introduced into a third separation zone comprised of a flashing zone to separate the distillable liquid product from the substantially non-distillable liquid product as well as the organometallic compounds. The nondistillable liquid product and the organometallic compound are then contacted with a second solvent comprised of n-hexane at a solvent to feed ratio of approximately 8:1 to form a mixture. , this mixture is introduced into the fourth separation zone 44.

The fourth separation zone is maintained at a temperature level of about 450°C and a pressure level of about 650 psig to separate the mixture therein into a fourth light phase and a fourth heavy phase comprising the organometallic compound-containing residue. Separate into After this,
The fourth light phase is introduced into a fifth separation zone 48 comprising a flash zone where the pressure level on the fourth light phase is reduced to approximately atmospheric pressure to evaporate the second solvent and form a liquid product. form a flow. This liquid product has a reduced metal content and its quality corresponds to No. 6 fuel oil.

EXAMPLE The exemplary extracted crude oil is mixed with a first solvent comprised of cyclohexane in a 20:1 solvent to feed volume ratio and introduced into the first separation zone 18. The first separation zone is maintained at a temperature level of about 500° and a pressure level of about 650 psig. The feed mixture is separated into a first light phase and a first heavy phase composed of asphaltenes and some pentane.

The first heavy phase is then mixed with a diluent comprised of catalytic cracking slurry oil at a diluent to feed ratio of approximately 3:1, and the resulting mixture is introduced into the visbreaking zone 30. do. Visbreaking area 30
Approximately 500 psig to prevent the formation of a separate vapor phase within the
The mixture is heated in the visbreaking zone 30 to a temperature of approximately 950°C while maintaining a pressure level of .
The product of the visbreaking zone 30 is then introduced into a third separation zone comprised of a flashing zone to separate the distillable liquid product and the organometallic compound. contacting the non-distillable liquid product and the organometallic compound with a second solvent comprising benzene in a solvent to feed ratio of about 7:1 and introducing the resulting mixture into a fourth separation zone 44; do.

The fourth separation zone is maintained at a temperature level of about 545㎓ and a pressure level of about 750 psig to maintain the mixture in the fourth separation zone.
into a light phase and a fourth heavy phase constituting a residue containing an organometallic compound. A fourth light phase is then introduced into the fifth separation zone. This area is maintained at a temperature level of approximately 575㎓ and a pressure level of approximately 725 psig. Fourth
a fifth light phase in which the light phase is composed of a second solvent;
The liquid product of the visbreaking operation is separated into a fifth heavy phase consisting of some second solvent. The fifth heavy phase is then steam stripped to separate the remaining second solvent from the liquid product. This liquid product has a reduced metal content and is comparable in quality to No. 6 fuel oil.

The examples described above illustrate the means by which the present invention can be used to increase the yield of useful liquid products recovered from heavy hydrocarbon materials.

As used herein, the term "heavy hydrocarbon material" refers to igneous bitumen, natural bitumen, or one or more fractions or components thereof.
Igneous bityumen is heavy or low API gravity crude oil, extracted crude oil (steam or vacuum refined),
Contains hard and soft wood pitch, coal tar residue, decomposed tar, tall oil, etc. Natural bitumens include gilsonite, urtiumite, albite, and natural asphalts, such as trinidan asphalt.

As used herein, the term "liquid phase product" refers to a product that has a characteristic tendency to flow under process conditions.

Although this invention has been described with reference to embodiments that are currently considered preferred, it goes without saying that those skilled in the art will be able to make various modifications within the scope of this invention.

[Brief explanation of drawings]

The drawing is a schematic representation of the method of the invention.

Claims (1)

[Scope of Claims] 1. Heavy hydrocarbon materials composed of oils, resins, asphaltenes, and organometallic compounds, paraffin hydrocarbons containing 4 to 9 carbon atoms, and cycloparaffin hydrocarbons containing less than 10 carbon atoms. hydrogen,
and at least one selected from the group consisting of monoolefin hydrocarbons containing 4 to 8 carbon atoms.
a first solvent composed of different materials at high temperature levels ranging from 150 °C to a temperature above the critical temperature of the first solvent as well as at a temperature below the critical temperature of the first solvent. a first separation zone maintained at a pressure level at least equal to the vapor pressure of the first solvent and at least equal to the critical pressure of the first solvent at a temperature equal to or greater than the critical temperature of the first solvent; and introducing the heavy hydrocarbon material and the first solvent into a first light phase comprising the first solvent and a first light phase comprising asphaltenes, an organometallic compound, and some first solvent. 1
A first solvent is recovered from the first light phase in a second separation zone, and a light catalytic cracking circulating oil and a heavy phase catalytic cracking are added to the first heavy phase. The catalytic cracking recycle feedstock such as recycle oil or catalytic cracking slurry oil, pyrolyzed petroleum feedstock, and a diluent comprised of lube oil aromatic extract are added to
〓 into a visbreaking zone maintained at a high temperature and pressure level above, such that a separate vapor phase is not formed at the temperature level within the visbreaking zone, and the asphaltenes in the heavy phase are decomposed, producing a distillable and substantially non-distillable liquid visbreaking product comprising an organometallic compound;
separating at least a portion of the distillable liquid product from the remainder, and separating at least a portion of the distillable liquid product from the remainder from the third separation zone and from 4 to 9 carbon atoms.
cycloparaffin hydrocarbons containing less than 10 carbon atoms, and monoolefin hydrocarbons containing 4 to 8 carbon atoms. and a second solvent at an elevated temperature level within the range of 150°C to a temperature above the critical temperature of the second solvent and a vapor pressure of the second solvent at a temperature below the critical temperature of the second solvent. said mixture by introducing it into a fourth separation zone maintained at a pressure level at least equal to and at least equal to the critical pressure of the second solvent at a temperature equal to or greater than the critical temperature of said second solvent. a non-distillable liquid product substantially free of organometallic compounds, a distillable liquid product if present, and a second
A step of separating into a fourth light phase composed of a solvent and a fourth heavy phase composed of a residue containing an organic compound and some second solvent, and recovering the fourth light phase. A method of separating a fraction consisting of. 2. The method according to claim 1, wherein the fourth light phase is heated to a temperature level higher than the temperature level of the third separation zone, and the fourth light phase is composed of a second solvent. and a fifth heavy phase consisting of a substantially non-distillable liquid product and a remaining distillable liquid product produced in the visbreaking zone. A method comprising the step of introducing into a fifth separation zone maintained at an elevated pressure level and recovering said fifth heavy phase. 3. In the method set forth in claim 2, the fifth separation zone is maintained at a temperature level within a range from 5㎓ to 100㎓ higher than the temperature level in the fourth separation zone. and maintaining the fifth separation zone at a higher temperature level than the fourth separation zone. 4. A method as claimed in claim 2, wherein the fifth separation zone is maintained at a temperature level above the critical temperature of the second solvent. 5. The method of claim 1, wherein the first separation zone is maintained at a temperature level above the critical temperature of the first solvent. 6. In the method of claim 1, the fourth light phase is flash distilled to produce at least one stream consisting of a second solvent and the visbreaking reduced metal content. forming another stream comprised of a substantially non-distillable liquid product from the zone and recovering said substantially non-distillable liquid product. 7. The method of claim 1, comprising the step of recovering the second solvent from the fourth light phase in a fifth separation zone.