US3291727A - Solvent separation of monocyclic aromatic, dicyclic aromatic and non-aromatic hydrocarbons - Google Patents

Description

Dec. 13, 1966 R. A. WOODLE ETAI. 3,291,727

SOLVENT SEPARATION OF MNOCYCLC AROMATIC, DICYCLIC ND NON-AROMATIC HYDROCAFBONS Filed May 22, l94

AROMATIC A United States Patent O 3,291,727 SOLVENT SEPARATlON OF MONOCYCLIC ARO- MATIC, DICYCLIC AROMATIC AND NON-ARO- MATIC HYDRCARBONS Robert A. Woodle, Nederland, Tex., and Howard H. Gross, Pleasantville, NY., assguors to Texaco Inc., New York, N.Y., a corporation of Delaware Filed May 22, 1964, Ser. No. 369,513 12 Claims. (Cl. 208-316) This invention relates to a hydrocarbon treating process and more particularly to a process of treating a hydrocarbon oil containing dicyclic aromatic hydrocarbons, monocyclic aromatic hydrocarbons, and nonaromatic hydrocarbons. In accordance with the process of this invention, a hydrocarbon oil comprising dicyclic, monocyclic, and nonaromatic hydrocarbons is separated into three fractions, a first fraction rich in dicyclic aromatic hydrocarbons, a second fraction rich in monocyclic hydrocarbons, and a third fraction rich in nonaromatic hydrocarbons. The hydrocarbon oil feed is contacted with furfural at selective conditions in a first contacting zone effecting separation of a fraction rich in dicyclic aromatic hydrocarbons and a raffinate comprising monocyclic and nonaromatic hydrocarbons. The raffinate is treated in a second contacting zone with furfural at conditions effecting extraction of the monocyclic aromatics from the nonaromatic hydrocarbons. Highly selective conditions are maintained in the first contacting zone in order to effect separation of dicyclic hydrocarbons and monocyclic hydrocarbons. Advantageously, conditions of high selectivity are effected by employing a backwash comprising nonaromatic hydrocarbons boiling outside the range of the charge oil and preferably below 400 F. Additionally highly selective conditions are achieved by employing furfural solvent containing dissolved water, relatively low contacting temperatures, and relatively high solvent dosages.

Gas oils from some aromatic crude sources and gas oils from thermal and catalytic cracking contain substantial quantities of aromatic hydrocarbons, including monocyclic aromatic hydrocarbons, dicyclic aromatic hydrocarbons, and nonaromatic hydrocarbons. The dicyclic aromatic hydrocarbons, for example, naphthalene and alkyl naphthalenes, provide an excellent source of naphthalene and naphthalene precursors, that is alkyl naphthalenes which may be converted to naphthalene by dealkylation, Naphthalene precursors include alkyl naphthalenes, tetralin, or decalin derivatives and generally any hydrocarbon structure containing the basic naphthalene dicyclic ring. Similarly, the monocyclic aromatic `fraction provides a desirable source of benzene and alkyl benzenes which may be dealkylated to benzene. Nonaromatic hydrocarbons of the gas oil boiling range are preferred for use as burner fuels, diesel fuels and jet fuels because of their clean combustion characteristics, high cetane number and high luminometer number.

It is an object of this invention to provide a means of separating dicyclic aromatic hydrocarbons, monocyclic aromatic hydrocarbons and nonaromatic hydrocarbons as separate product fractions from mixtures of monocyclic, dicyclic and nonaromatic hydrocarbons. How this and other objectives are attained will be apparent from the following description, examples and claims.

Dicyclic aromatic hydrocarbons are highly soluble in furfural, monocyclic aromatic hydrocarbons are soluble to a lesser degree and nonaromatic hydrocarbons are still less soluble in furfural. Because of this differing solubility, it is possible to separate dicyclics, monocyclics and nonaromatics by extraction with furfural. However, in order to separate fractions of high purity, highly selective conditions must be employed particularly to effect the separation between dicyclics and monocyclics. In accordance 3,291,727 Patented Dec. 13, 1966 ice with this invention, extraction is effected at conditions of extremely high selectivity to separate dicyclics from monocyclics and the raffinate containing remaining monocyclic aromatics and non-aromatic hydrocarbons is reextracted to effect separation of the monocyclics and nonaromatic hydrocarbons.

High selectivity is achieved by employing relatively low extract-mix outlet temperatures within the range of about 60 to 175 F. and preferably within the range of about 100 to 125 F. A temperature gradient is usually maintained in the extraction tower. The maximum temperature in the extraction tower may be about 50 F. higher than the extract-mix outlet temperature although the former is not critical and may vary over a broad range with little effect on yield or quality. In addition, high selectivity is achieved by including dissolved water in the furfural solvent in an amount within the range of about 1.0 to 7.0 percent and preferably within the range of about 2.0 to 6.0 percent. It is also desirable to use extract recycle.

Since monocyclic and dicyclic aromatic hydrocarbons Y in high concentration are both completely miscible with furfural, they may not be separated in pure form from each other or from mixtures with nonaromatics by extraction with furfural alone. In order to effect separation of a primary extract consisting of substantially only aromatics and having a high concentration of dicyclic aromatics in our rst extraction stage, we employ solvent dosage within the range of about to 250 percent and prefreably within the range of 150 to 225 percent together with a backwash with a hydrocarbon boiling wholly outside the boiling range of the gas oil feed. This backwash not only displaces gas oil boiling range nonaromatics from the extract into the rafnite but also increases the selectivity of furfural as between the monocyclic and dicyclic aromatics so that monocyclics are carried into the raffinate. Since the hydrocarbon backwash boils outside the range of the gas oil feed, it may be removed from the extract and raffinate by distillation. Desirably a paraflinic hydrocarbon boiling below about 400 F. is employed as backwash. The backwash is introduced into the lower portion of the contacting zone whereby monocyclic aromatic hydrocarbons and nonaromatic hydrocarbons are displaced from the extract-mix thereby increasing the concentration of dicyclic aromatics in the extract. This low boiling parafiinic hydrocarbon is separated from the aromatic extract when the furfural solvent is stripped from the extract. The low boiling paraffinic hydrocarbon also facilitates separation of furfural from the extract by azeotroping with the furfural. A backwash rate within the range of 20 to 70 volume percent of the oil charge and preferably within the range of 30 to 60 volume percent is empl-oyed.

Ralinate is stripped and is then reextracted with furfural at conditions effecting separation between aromatic and nonaromatic hydrocarbons. When a light hydrocarbon backwash is employed in the primary extraction, the backwash is separated with the furfural in stripping the raffinate. The stripped raffinate is contacted at a temperature Within the range of to 175 F. and preferably within the range 4of 120 to 170 F. with furfural either dry or containing up to about 6.0 percent water at a solvent dosage within the range of about 75 to 200 percent and preferably within the range of about 100 to 175 percent. Advantageously, the extract-mix from the reextraction step may be cooled separating a fraction of intermediate aromaticity and increasing the mononuclear aromatic concentration in the extract-mix. This intermediate oil is recycled to the primary extraction tower with the oil charge. The remaining extractmix is stripped separating the monocyclic aromatics in increased concentration.

The accompanying drawing diagrammatically illustrates the process of this invention. Although the drawing illustrates one arrangementof apparatus in which the process of this invention may be practiced, it is not intended to limit the invention to theparticular material or apparatus described.

Charge oil, for example, a catalytically cracked gas oil containing about 20 to 30 percent dicyclic amomatics, 20 to 30 percent monocyclic aromatics and 40 to 60 percent nonaromatic hydrocarbons and boiling within the range of about 400 to 600 F. is charged through line 1 to primary extraction tower 2. Extraction tower 2 may be a rotating disc contactor, a packed column, or a device for countercurrent contacting such as a centrifugal countercurrent contactor or a box counterflow contactor. Oil rising through tower 2 is countercurrently contacted with furfural introduced at the top through line 3. A light paraiin backwash, for

example, a raihnate fraction from the extraction of catalytic reformate boiling within the range of about 250 to 400 F. and preferably within the range of about 300 to 350 F. is introduced into the bottom of tower 2 through line 5. A side stream is withdrawn from tower 2 from trap tray 6 through line 7, cooled in cooler 8 `and returned to the bottom of tower 2 through line 9 to control extract-mix outlet temperature. A recycle stream of stripped extract may also be passed through lines land. 9 to increase the selectivity of extraction in tower 2.

Extract-mix comprising furfural, dissolved dinuclear aromatic hydrocarbons, and a small amount of dissolved hydrocarbon backwash is withdrawn from line and passed to primary extract stripper 16. Primary extract stripper 16 is a distillation facility wherein furfural and dissolved backwash are stripped from the extract in one or more distillation towers. Stripping may be assisted by the introduction of steam through line 17 or the azeotroping effect of the backwash by hydrocarbons may be used as described in the copending application Serial Number 190,592 led April 27, 1962, now Patent No. 3,239,456. Stripped extract comprising dicyclic aromatic hydrocarbons is withdrawn through line 18 as a first product fraction of the separating process. Vapors comprising furfural, hydrocarbon backwash, and steam are withdrawn from stripper 16 through line 19.

Ranate from the top of primary extraction tower 2 is withdrawn through line 25 and passed to primary rainate stripper 26. Primary railinate stripper 26 is one or more distillation towers employed to separate furfural and the hydrocarbon backwash from the rafnate hydrocarbons by stripping optionally with steam introduced through line Z7. Stripped vapors comprising furfural, hydrocarbon backwash and steam are discharged through line 28, and combined with the vapors in line 19 from primary extract stripper 16. The combined vapors are condensed in cooler 30 and the resulting condensate is passed through line 31 into decanter 32. Line 31 may comprise a barometric leg discharging under the liquid level so that stripping and condensation of vapors may be eiected under vacuum and the resulting condensate discharged into decanter 32 with other streams at about atmospheric pressure. Condensate in line 31 comprises three phases, Aa light oil phase containing dissolved furfural and water, an intermediate water phase containing dissolved furfural and oil and a heavy furfural phase containing dissolved water and oil. Decanter 32 is provided with weirs 36 and 37. The heavier furfural phase :accumulates behind Weir 36 and is withdrawn from drum 35 through line 38. Oil and water phases overflow Weir 36 and water collects between wcirs 36 and 37. Water phase is withdrawn through line 39. Oil phase overows Weir 37 and collects in the end compartment of decanter 32. Oil is withdrawn through line 5 for return as backwash to primary extraction tower 2.

Furfural in line 38 is saturated with water and oil and contains about 6 weight percent water at condensate temperatures of about 100 F. This stream may be passed directly to tower 2 by way of line 3. lt it is desired to reduce the water content of the furfural, at least a portion of the material in line 28 is passed through line 40 into furfural drying tower 41. Tower 41 is a distillation column in which water is removed as an azeotropic distillate with a small :amount of furfural. Dry furfural is withdrawn through line 42 to supply all or a part of the furfural in line 3. The water content of the furfural in line 3 then may be varied from zero to saturation by varying the proportion of furfural passed to the drying tower. Distillate from tower 41 is passed through line 43, cooler 44 and line 45 into the liquid in decanter 32 wherein the resulting phases are separated.

Water phase in line 39 from decanter 32 is distilled to recover dissolved furfural in distillation tower 50. Azeotrope vapors are discharged through line 51, and combined with the vapors in line 43 for recovery. Water substantially free of furfural is discharged through line 52.

Stripped raiinate comprising monocyclic aromatic hydrocarbons and nonaromatic hydrocarbons is withdrawn through line 55 and passed to secondary extraction tower 56. Secondary extraction tower 56 is a countercurrent contacting apparatus, and like primary extraction tower 2, may be for example, a rotating disc contactor, a packed column or other contacting apparatus. In secondary extraction tower 56, the primary rainate is contacted with furfural introduced through line S7 effecting extraction of monocyclic aromatics Extract-mix is withdrawn through line 58. A temperature gradient is maintained in tower 56 by withdrawing a side stream from trap tray 60 through line 61, cooling the stream in cooler 62 and returning the cooled stream to tower 56 through line 63. Rainate comprising nonar-omatic hydrocarbons and a small amount of dissolved furfural is withdrawn through line 65 to secondary raffinate stripper 66. Furfural vapors are withdrawn through line 67 and the stripped nonaromatic product is withdrawn through line 68.

Extract-mix in line S8 is cooled in exchanger 70 eiecting separation of an intermediate oil phase from remaining extract-mix. The cooled mixture passed through line 71 which discharges below the interphase level 72 in decanter 73. Decanter 73 comprises a drum wherein the oil and remaining extract-mix phases separate. This oil phase is withdrawn through line 74 for recycle to the primary extraction tower with the oil feed in line 1. The remaining cooled extract-mix of increased aromaticity is withdrawn through line and passed to secondary extract stripper 81. Secondary extract stripper 81 is a distillation tower employed to strip furfural from the extract. Furfural vapors are withdrawn through line 82 and combined with vapors in line 67, condensed in cooler 83 and condensed furfural is passed through line 84 to accumulator 85. Stripped extract comprising monocyclic aromatics is withdrawn as product through line 90.

By employing separate furfural condensation and recovery facilities, the furfural from the primary extraction system and secondary extraction may be separated with separately controlled moisture content and light hydrocarbon dilution of the solvent in the secondary extraction system avoided. However, common facilities may be employed where economic considerations require minimizing investment. Although furfural recovery in the secondary extraction system of the ligure does not use steam stripping, steam maybe used in the manner employed in the primary extraction system.

Example I A light gas oil from catalytic cracking is treated in accordance with the process of this invention to separate a fraction rich is dicyclic aromatics suitable as feed stock for the manufacture of naphthalene, a fraction rich in monocyclic aromatics useful as a feed stock in the manufacture of benzene and a paraiinic raflinate useful as a jet fuel of high luminometer number. The cracked gas oil is characterized by the following tests:

Refractive index at 70 C. 1.4830

The cracked gas-oil charge stock is contacted with furfural containing 2.0 percent water at a dosage of 201 percent in a rotating disc contactor. The oil charge is introduced into the contacter at an intermediate point and a light hydrocarbon backwash at a dosage of 50 percent of the and volume percent extract. Upon stripping of the raflinate the following tests are obtained:

Refractive index at 70 C. 1.4150 Hydrocarbon analysis, vol. percent:

Mononuclear aromatics 1.0 Dinuclear aromatics None Nonaromatics 99.0 Cetane number (ASTM designation:

D-613) 63.5 Luminometer number (ASTM designation:

The secondary extract upon stripping is found to have the following tests:

Hydrocarbon analysis, vol. percent:

Mononuclear aromatics 49.4 Dinuclear aromatics 20.8 Nonaromatics 30.8 Ratio mono/dinuclear aromatics 2.37

A summary of the yields basis the catalytic gas oil feed is shown in Table I, following:

YIELDS BASIS CATALYTICALLY CRACKED GAS OIL FEED Primary Secondary Secondary Extract Extract Reainate Charge Oil (D inuclear (Mononuclear (Nonaromatic Aromatic Aromatic Fraction) Fraction) Fraction) Dinuclear aromatics- 34. 5 31. 3 3. 2 0. 0 Mononuclear aromatics. 13. 7 5. 6 7. 6 0. 5 Nonarornatics K 51.8 0.0 5.0 46.8

Total 100.0 36.9 15.8 47.3

Ratio, mono/dinuelear aromatics 0. 397 0. 179 2.37

charge 1s introduced at the bottom of the rotatlng d1sc Example 2 contactor. The vhydrocarbon'backwash comprises a raffinate from the solvent extraction of a catalytic reformate and has a boiling range of 300 to`350 F. by true boiling point distillation, contains 96.5 volume percent nonaroinatic hydrocarbons, and has an API gravity of 58.6. Rainate is withdrawn at 170 F. and extract-mix at 120 F., the temperature differential being maintained by withdrawing, cooling and reintroducing a portion of the extract-mix into thelower section of the rotating disc contractor. The' yield of primary extract is 36.9 volume percent. The primary extract has the following tests:

Refractive index at 70 C. 1.5612 Gravity API 12.3

Hydrocarbon analysis, vol. percent:

`Dinuclear aromatics 84.8 Mononuclear aromatics 15.2 Nonaromatics None Ratio mono/dinuclear aromatics 0.179

The primary rainate, after stripping of solvent and hydrocarbon backwash, has the followin-g tests:

Refractive index at 70 C 1.4374

The secondary raffinate is reextracted with furfural containing 1.5 percent water at a dosage of 125 percent. Rainate is withdrawn at 170 F. and extract-mix at 120 F. No light hydrocarbon backwash is used. Yields in the secondary extraction are 75 volume percent raflinate A comparison is made of the method 'of this invention of solvent extraction at selective conditions followed by reextraction of the raffinate with an alternative processing sequence wherein an oil is subjected to an initial extraction under less selective conditions to separate aromatics from nonaromatics and the primary extract is reextracted under selective conditions to separate monocyclic and dicyclic aromatics. In each case, a 450 to 540 F. cut of light catalytically cracked gas oil containing 53.6 weight percent aromatics is used. When employing primary extraction at the highly selective conditions of this invention, a yield of 41.4 weight percent of primary extract is obtained containing 84.8 weight percent dicyclic and 15.2 weight percent monocyclic aromatics. The primary extract contains 77.2 percent of the aromatics and 94.7 weight percent of the dicyclic aromatic hydrocarbons contained in the feed stock. The primary raffinate is produced in a yield of 58.6 weight percent and contains 21.2 weight percent aromatics. The gravity of the primary rafnate is 40.7, the cetane number 52.0 and the pour point 20 F. This primary raffinate is -reextracted separating a nonaromatic fraction containing 1.0 weight percent monocyclic aromatics and no dicyclic aromatics and a'second extract product fraction containing 46.1 weight percent monocyclic aromatics and 19.5 weight percent dicyclic aromatics.

In a comparison test the same feed stock is extracted with furfural under nonselective conditions and the extract is then reextracted with furfural employing a light hydrocarbon backwash under selective conditions to separate a dicyclic aromatic fraction. The primary raffinate contains 15.6 weight percent monocyclic aromatics and no dicyclic aromatics. The secondary rainate from the reextraction step contains 43.6 weight percent monocyclic and 18.1 weight percent dicyclic aromatics. A fraction containing 100.0 percent aromatics is obtained in a yield of 37.5 weight percent with a recovery of 70.0 percent of the total aromatics and 90.3 percent of the dicyclic aromatics contained in the feed. The primary and secondary raiiinates are combined giving a total yield basis charge of 62.5 percent. The total aromatic content of the mixed rafinates is 25.8 percent, the gravity 40.1 API, the cetane number 53.2, and the pour point 30 F The foregoing comparison shows that the use of an initial highly selective extraction step followed by reextraction of the raiiinate produces a higher yield of dinuclear aromatic fraction containing a higher portion of the dinuclear aromatics present in the charge as compared with the reverse sequence of employing an initial solvent extraction step to separate all aromatics and then reextracting the primary extract to separate a dinuclear aromatic rich fraction.

We claim:

1. A method of treating a hydrocarbon oit boiling within the range of about 400 to 600 F. and comprising dicyclic aromatic hydrocarbons, monocyclic aromatic hydrocarbons, and nonaromatic hydrocarbons effecting separation of a rst product fraction rich in said dicyclic aromatic hydrocarbons, a second product fraction rich in said monocyclic hydrocarbons and a third product fraction 4rich in said nonaromatic hydrocarbons which comprises:

contacting said hydrocarbon oil, a solvent comprising furfural and a backwash comprising nonaromatic hydrocarbons boiling below 400 F. in a first zone effecting separation of a first extract-mix comprising said r'irst product fraction, furfural and a minor amount of said nonaromatic hydrocarbons boiling below 400 F. and a first rainate comprising monocyclic aromatic hydrocarbons, nonaromatic hydrocarbons boiling within the range of about 400 to 600 F., and nonaromatic hydrocarbons boiling below 400 F.,

separating said first product fraction from said first extract-mix, p

separating said iirst rafinate into a raiiinate fraction boiling below 400 F. and a rainate fraction boiling above 400 F.,

contacting at least a part of said rainate fraction boiling above 400 F. with a solvent comprising furfural at conditions effecting extraction of aromatic hydrocarbons to the substantial exclusion of nonaromatic hydrocarbons in a second contacting zone eecting separation of a second extract-mix comprising said second product fraction and a second raffinate comprising said third product fraction,

separating said second product fraction from said second extract-mix, and

separating said third product fraction from said second raiiinate.

2. The process of claim 1 wherein said second extractmix is cooled effecting the separation of an intermediate fraction comprising said dicyclic aromatic hydrocarbons, said monocyclic aromatic hydrocarbons and said nonaromatic hydrocarbons boiling above 400 F., and said intermediate fraction is recycled to said first contacting zone.

3. A method of treating a hydrocarbon oil boiling within the range of about 400 to 600 F. and comprising dicyclic aromatic hydrocarbons, monocyclic aromatic hy.

drocarbons and nonaromatic hydrocarbons effecting 'sep-` aration of a first product fraction rich in said dicyclic aromatic hydrocarbons, a second product fraction rich in said monocyclic hydrocarbons and a third product fraction rich in said nonaromatic hydrocarbons which comprises:

contacting said hydrocarbon oil, a solvent comprising furfural and a backwash comprising nonaromatic hydrocarbons boiling below 400 F. in a first zone effecting separation of a first extract-mix comprising said iirst product fraction, furfural and a minor amount of said nonaromatic hydrocarbons boiling below 400 F. and a first raffinate comprising monocyclic aromatic hydrocarbons, nonaromatic hydrocarbons boiling within the range of about 400 to 600 F., and nonaromatic hydrocarbons boiling below 400 F., separating saidrst product fractions from said first extract-mix, j y separating said first raiiinate into a rainate fraction boiling below 400 F., and a raffinate fraction boiling vabove 400 F., contacting said raffinate fraction boiling above 400 F. with a solvent comprising furfural at conditions effecting extraction of aromatic hydrocarbons to the substantial exclusion of nonaromatic hydrocarbons in a second contacting zone effecting separation of a second extract-mix comprising said second product fraction and a second raffinate comprising said third product fraction, separating said second product fraction from said second extract-mix, and

separating said third product fraction from said second raiinate.

4. The process of claim 3 wherein said hydrocarbon oil boils within the range of about 420 to 540 F.

5. 'Ihe process of claim 3 wherein said hydrocarbon oil is a cracked gas oil.

6. The process of claim 3 wherein the solvent in said first contacting zone contains within the range of about 1.0 to 7.0 percent Water.

7. The process of claim 3 wherein the solvent in said second contacting zone contains within the range of about 2.0 to 6.0 percent water.

8. The process of claim 3 wherein the to hydrocarbon oil in said first zone is about to 250 percent.

9. The process of claim 3 wherein the ratio of V"said solvent to said first raffinate in said second contacting zone is Within -the range of about 75 to 200 percent.

ratio of solventv within the range of 10. The process of claim 3 wherein said first'extract-"f mix is separated from said first contacting zone at a temperature within the range of about 60 to 13.5 F.

11. The process of claim 3V wherein said second extractmix is separated from said contacting zone at a temperature within the range Iof about tov 175 F.

12. The process of claim 3 wherein said backwash is applied ata dosage within the range of 20 to 70 volume percent of said hydrocarbon oil.

References Cited by the Examiner UNTED STATES PATENTS 2,216,932 10/ 1940 'Atkins 208`316 3,205,167 9/ 1965 Demeester 208-327 DELBERT E. GANTZ, Primary Examiner". HERBERT LEVINEa Assistant Examiner.

Claims (1)

1. A METHOD OF TREATING A HYDROCARBON OIL BOILING WITHIN THE RANGE OF ABOUT 400 TO 600*F. AND COMPRISING DICYCLIC AROMATIC HYDROCARBONS, MONOCYCLIC AROMATIC HYDROCARBONS, AND NON-AROMATIC HYDROCARBONS EFFECTING SEPARTION OF A FIRST PRODUCT FRACTION RICH IN SAID DICYCLIC AROMATIC HYDROCARBONS, A SECOND PRODUCT FRACTION RICH IN SAID MONOCYCLIC HYDROCARBONS AND A THIRD PRODUCT FRACTION RICH IN SAID NONAROMATIC HYDROCARBONS WHICH COMPRISES: CONTACTING SAID HYDROCARBON OIL, A SOLVENT COMPRISING FURFURAL AND A BACKWASH COMPRISING NONAROMATIC HYDROCARBONS BOILING BELOW 400*F, IN A FIRST ZONE EFFECTING SEPARATION OF A FIRST EXTRACT-MIX COMPRISING SAID FIRST PRODUCT FRACTION, FURFURAL AND A MINOR AMOUNT OF SAID NONAROMATIC HYDROCARBONS BOILING BELOW 400*F. AND A FIRST RAFFINATE COMPRISING MONOCYCLIC AROMATIC HYDROCARBONS, NONAROMATIC HYDROCARBONS BOILING WITHIN THE RANGE OF ABOUT 400 TO 600*F., AND NONAROMATIC HYDROCARBONS BOILING BELOW 400*F., SEPARATING SAID FIRST PRODUCT FRACTION FROM SAID FIRST EXTRACT-MIX, SEPARATING SAID FIRST RAFFINATE INTO A RAFFINATE FRACTION BOILING BELOW 400*F. AND A RAFFINATE FRACTION BOILING ABOVE 400*F., CONTACTING AT LEAST A PART OF SAID RAFFINATE FRACTION BOILING ABOVE 400*F. WITH A SOLVENT COMPRISING FURFURAL AT CONDITIONS EFFECTING EXTRACTION OF AROMATIC HYDROCARBONS TO THE SUBSTANTIAL EXCLUSION OF NONAROMATIC HYDROCARBONS IN A SECOND CONTACTING ZONE EFFECTING SEPARATION OF A SECOND EXTRACT-MIX COMPRISING SAID SECOND PRODUCT FRACTION AND A SECOND RAFFINATE COMPRISING SAID THIRD PRODUCT FRACTION, SEPARATING SAID SECOND PRODUCT FRACTION FROM SAID SEC OND EXTRACT-MIX, AND SEPARATING SAID THIRD PRODUCT FRACTION FROM SAID SECOND RAFFINATE.

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