US2151592A - Hydrocarbon oil treatment - Google Patents

Description

S. W. FERRS HYDROCARBON OIL TREATMENT Makch 2l, 1939.

`lFiled July 18, 1955 2 Sheets-Sheet l ZSLQE Mah 2l, T939. 5 Wv FERR@ I vHYDROCARBON OIL TREATMENT Filed July 18, 1935 2 Sheets-Sheet 2 HUHHHI ITN Seymour IVE/:Ferris Patented Mar. 21, 1939 HYDROCARBON OIL TREATMENT Seymour W. Ferris, Aidan, Pa., assignor to The Atlantic Refining Company, Philadelphia, Pa., a. corporation of Pennsylvania Application July 18, 1935, Serial No. 31,966

7 Claims.

An object of this invention is the extractionof components 'of hydrocarbon oils, especially 10 naphthenic and color-imparting bodies, in such a manner. that the extracted components will comprise a minor portion of the oil undergoing treatment, and the separation of such extracted components from the rened oil will be relative- 1y rapid and complete. A

A further object of this invention isvthe extraction of components of hydrocarbon oils with the minimum quantity of a selective solvent which will eii'ect the desired extraction at telm= peratures such that the application of heat land/or refrigerati-on will be substantially reduced.

Heretofore, it has'benf found that certain selective solvents., as for `einixnple, nitrobenzene, phenol, aniline,f,urfural and others, may be employed toA eect a separation of hydrocarbon oils, such as petroleum, or distillates or residuum thereof, into fractlonsof vsubstantially the same boiling range butoiydifferent chemical com-f 30 position Jand*v of different .physical properties.

The differencein physical properties'of the lfracvtions-.so produced, fi. e., `the degree of paramnicity l or naphthenicity. of .said fractions, maybe ex-A pressed by-the relationship ofviscosityfto grav-z ityfor .any particular oil. nThe viscosity-gravity constant, as developed by -.and Coats, referred toinfIndustrial and1= Engineering'fChemistry, vol. 20,` page'641-(192'8) willkbe used herein.. to indicate the* degreef'of parafflnicity :of naph- In the solvent extraction of certain-lubricating '45 oil stocks, particularly highly. viscousl and relaremove a relatively small fraction, i. e., of the order of 5% 4to 10%, as extract,fconcentitingsj' therein as much of the `'napli.'thenicgjhydrocar,

bons and color-bodies as is possible. When'this is effected, fr example, my means of a solvent having great solvent power, fsucl'f-as-initroben-Vv zene or phenol, the quantity of solint employed is relatively small and the rate of settling 'and tively expensive stock such as, for* fexamplegf Pennsylvania cylinder stock., vit is, 7desirable .,Vtoz

separation of the railinate and extract phases is undesirably slow.

In the case of extraction with a relatively large volume of solvent, for example, 150% to 300% by volume of the stock, the extract phase is present in considerably larger volume than is the raffinate phase and constitutes the continuous phase, therefore the ralinate phase or disperse phase is, in all probability, distributed in droplets and settles throughv the relatively non-vis- 10 cous extract phase. In the case .of extraction with a small volume of solvent, Afor example, the extraction of a Pennsylvania cylinder stock with 20% to '10% by volume of solvent, there is considerably more -of therailinate phase presen 15 thanv the vextract phase; therefore, the extract phase is probablyl distributed as droplets and must settle throughlth'e'viscous rafiinate phase.

In this instancejsettling is much more diicult and lengthy than' in the former" case., 20 I therefore propose to enhance the settling rates in the extraction of stocks such .as may be obtained fromv Pennsylvania crude oil, as well as oil stocks derived from crudes other than -Pennsylvania, by artificially increasing the pro- 25 portion of extract phase in the mixture resulting from the contacting oi' the oil stock with sollvent to such a degree lthat the extract phase will alwaysconstitutefthe continuous 'phase of the system.l This ,I accomplishwitricuggemploy- 30 ingr additionalhsolye'nt jand 'without "substantially changing thevaiious otherjconditions'of ythe extractionnprocess. Forexamplel in'a'continuous Iva rate 'corresponding to the' rate of charger to ythe mixing vessel and b oth phases 'would be rem'o'vedfrom the system. However; in accordance with my invention; a portion of the extract phase withdrawn from the settling vessel, for

example, from a few percent up to as much as or 90%, is returned to the mixing vessel iin/dis` preferably `agitated with the stock and `solfvents.V normally charged thereto. In this man- 50 ner," without employing additionalquantities of solvent land ,without substantially changing the ycjomposition `equilibrium -between the rafnate and extract phases, the volume percentage of extract in the mixture passing from the mix- 55 ing vessel to the settling vessel is suitably increased and the settling rate and completeness oi separation is markedly enhanced.

The enect of increasing the volume ratio of extract phase above that which is normally encountered iii extractions involving the use of From the data given in Tables I and II, it will be seen that, in general, when the volume ratio of extract phase to railinate phase is of the order oi 0.4 or greater, the rate oiseparation of the phases and the settling into layers is much greater than in the instances where such ratio is less than about 0.4. In practice this ratio will vary, depending upon the character of the solvent 'and stock, the quantity oi' solvent employed and the temperature oi separation.

Referring now to Fig. 1 of the accompanying drawings, which illustrates graphically the rela-- tionship between ysettling time of the phases and the volume percent of solvent employed when a Pennsylvania residuum is extracted with nitrobenzene and settled at 82 F., it will be noted that for treatments with from about 40% to about Table I Percent Settling solvent Ratio. extract to Settling time am solvent bzgg k011 teem' raillnate (seconds) F. Pmnniunia mlduum (da- N itr o b e n- 52 l 82 0. 315 (normal) 1000 colori ud) une. s2 0. 33' v 1000 s. um. alc r.1sa" gg ggg 1% Gran] llt-25.0 i 82 0:40 1w V. G. constant-0.814 82 o' 50 170 s2 1.00 190 60 82 0. 357 (normal) 1200 B2 0.37 1200 82 0.39 150 82 0.41 150 B2 0.50 f 170 82 1.00 190 Penminnia mldmm (lm- 50 82 0. 304 (normal) Above 10, 000 maud) (11% A ve B. Unis. 210 FJIH Grav. F.-2c.8 s2 2'0" v. ummm-osos 82 4-00 t y,

MM dal 50 82 0. 356 (normal) 700 S. U. VIL/210 F.1d 82 0. 50 200 afm/elo' r.m- 82 1' 0 20 constant-0.88 f

Gui/Onondldiiiau f t0 es 0.34 (normal) 000 s. U. vla/zio 1ra-.iwf gg g3g?,

. 'j/w' "'32" as 1.00 loo 150 82 2.13 (normal) l5 s2 1.00 15 s2 0.50 lo Table I! gmk so] t oelrveeililtt gemme Ratio' extract to giggling ven m e baateolkon weg ralnate (seconds) auf om: mmm l F s. U. vu. 10 1an-11s" clamorosa leiser so 's2 0.28 n r s1 zooo Grav. GOAL-20.4 n y 82 1.00( .o m 4.0 V. G. constant-0.863

Gulf Cout distillata Phenol 50 90 0.49 (normal) 1200 s. U. vll. no' am" 9 1-00 130 Grsv./ F.20,7 V. G. constant-0.876

.Pennsylvania rniduum f 'l duoloriud) Nitrobenzene gg gg 3% (normal) 13052)) norma l v'j iflltww g gg g-g mfml lg lll'm V. G. constant-0.814 70 82 0 55 normal) 150 77 82 0.05 normal) 160 150 82 1.89 normal) 150 y300 82 4.10 (normal 150 900 82 8.20 normal) 140 :lol

56% by volume of solvent based on the stock, the settling time was of the order of 1000V seconds, but with about 56% or more of solvent, the settling time was of the order of about 150 seconds. In other words, when employing less than about 56% by volume of solvent, under these particular conditions, the ratio of extractphase to rafllnate phase is such that the viscous rafilnate constitutes the continuous phase through which the relatively non-viscous extract or disperse phase must settle, with the resultant slow rate of stratiiication. On the other hand, when 56% to 60% or more of solvent is employed, the relationship of the phases appears to be reversed, i. e., the non-viscous extract constitutes the continuous phase, and the viscous railinate the disperse phase. When this relationship exists, settling and stratification oi' the extract and raffinate phases into layers occurs relatively rapidly.

The shift in phase relationships as correlated with the rate of settling and formation of extract and raiiinate layers is further illustrated in tially complete after about 700 seconds and the ratio of the volume of extract layer to ralnate layer was 0.356. This relationship ofv extract to rafllnate as correlated with settling time is represented by the upper end of the curve of Fig. 2, Y

and it will be seen that the settling rate is of the order of '700 seconds. Under the conditions y of this separation, with an extract-rainate ratio of 0.356, the light colored, viscous rafnate constituted the continuous phase throughout which was dispersed the dark colored, relativelynon-A viscous extract phase. This condition is clearly shown by the photomicrograph Fig. 3, taken during the settling step.

After separating the resultant extract and rafflnate layers, the extract and raiflnate were admixed in varying proportions so that the ratio of extract to raffinate was successively increased above the value 0.356, while the temperature and composition equilibrium was maintained unchanged. The settling time for the various mixtures was determined and it will be seen from the curve of Fig. 2 that when the volume ratio of extract to raflinate phases was of the order of about 0.47 or greater, the rate of settling was markedly increased, i. e., to the order of about 200 seconds. The photomicrograph Fig. 4, taken during the settling step in which the ratio of extract phase to raffinate phase was 1.0, shows thatl the phase relationship has been reversed. In this case the dark colored, relatively non-Viscous extract constitutes the continuous phase, while the light colored, viscous raillnate constitutes the disperse phase, and settling of the rafiinate through the extract is'relatively rapid. In both instances the composition of the extract and railinate phases is identical, since at constant temperature the equilibrium between the two phases is undisturbed even though the ratio of extract phase to raffinate phase in one case is 0.356 and in the second, 1.0. Thus, it appears that in the solvent extraction of oils, employing relatively small quantities of solvent, it becomes necessary to adjustthe ratio of extract to railinate, and therefore the phase relationship. in such a manner that rapid and complete settling of the phases maybe accomplished.

For purposes of illustration, reference is made to Fig. 5 of the accompanying drawings which shows diagrammatically, one form of apparatus suitable for carrying on my process:

In the drawings, a series of alternate mixing vessels 6, II and I6 and settling vessels 8, I4 and I9 are disposed in step-like arrangement, the mixing vessels being provided with paddle stirrers 1, I2 and I1 respectively, or other suitable mixing devices, means for introducing thereinto oil and solvent, and means for passing the mixture therefrom into the respective settling vessels. The settling vessels are provided with heating and/or cooling coils 9', 9" and 9" and means for passing undissolved oil (rafiinate) to succeeding stages, and solvent containing dissolved oil (extract) to the mixing vessel of the stage from which it was withdrawn and/or' to the mixing vessels of the preceding stages. 'Ihe system is` equipped with low pressure pumps, feed lines and heat exchangers so arranged as to maintain a regulated countercurrent iiow of oil and solvent through the extraction stages, the heat exchangers 4, 24, 30, 33, 39, 42 and 49 controlling the temperature of the oil and solvent streams, and indirectly the temperatures in the mixing and settling vessels.

In the operation of my process, I may choose, for example, to extract a Pennsylvania lubricating oil distillate having a Saybolt Universal viscosity of 143 seconds at 210 F., an A. P. I. gravity of 26.5, a..viscositygravity constant of 0.810, and an O. D. color of 2929, employing nitrobenzene as the selective solvent.

In order to commence the operation of the extraction system, 100 barrels per hour, for example, of the above mentioned oil stock, supplied from a storage vessel not shown, is drawn through valve-controlled pipe I by means of pump 2, and is passed through pipe 3 and heat exchanger 4 wherein it is brought to the. desired temperature, for example, 70 F. The oil is then passed by means of pipe 5 into mixing vessel 6. The selective solvent, i. e., nitrobenzene, is conducted, at a rate of, for example, 150 barrels per hour, from a storage vessel not shown, through valve-controlled pipe 2|, and is passed by means of pump 22 through pipe 23 and heat exchanger 24 wherein it is brought to the desired `temperature, for example, '70 F. The solvent is then passed through pipe 25 into mixing vessel I6.

-After sulcient oil stock and solvent have been supplied to the system, a countercurrent flow willmay be carried on with a relatively small volume 'I'he rate of char'ge of oil `stock is,

of solvent. however, maintained constantjat about 100 barrels per hour.

The oil stock is charged to the mixing vessel 6, and a portion of the partially spentv solvent (extract) from the bottom of settling Vessel I4, which flows through valve-controlled pipe 35, is forced by pump 36 through pipe 31 and valvecontrolled pipe 4I to heat .exchanger 42, wherein the temperature of the extract is adjusted to about 70 F. This extract is passed from heat exchanger 42 through pipe 43 into `mixing vessel 6, wherein it is contacted with the oil stock by agitation with stirrer 1. The oil-solvent mixture is withdrawn from vessel 6 by means of pipe 9 and is passed into settling vessel 8 wherein set- 'tlingand separation of the raflinate and extract phases is effected at a temperature of about 70 F., the rainnate comprising the upper layer and the extract the lower layer. The lower or extract layer is withdrawn from the bottom of settling vessel 8 by means of valve-controlled pipe 44 and a portion of such extract is forced from the system by pump 45, through pipe 4B and valvecontrolled pipe 41, and the extract may thereafter be separated into oil and solvent fractions by distillation. The remaining portion of extract, for example, 100 barrels per hour or 100% based on the volume of oil stock charged, is passed from pipe 46 through pipe 48, heat exchanger 49 and valve-controlled pipe 50 into mixing vessel 6. This operation occurs simultaneously with the normal mixing step and constitutes the recirculation of extract to the same stage of the system from which it was withdrawn, and such operation makes possible the employment of small quantities of solvent while still maintaining a rapid settling rate.

The undissolved oil layer or raffinate, containing a small quantity of solvent, occupies the upper lportion of settling vessel 8, and is passed therefrom by means of pipe I into the mixing vessel II of the 2nd stage. Vessel II is simultaneously supplied with a portion of the partially spent solvent k(extract) from the lower section of settling vessel I9, which extract flows through valve-controlled pipe 26 and is forced by pump 21 through pipe 28 and valve-controlled pipe 32 into heat exchanger 33, wherein the temperature of the extract is adjusted to about 70 F., and thence thro-ugh pipe 34 into said vmixing vessel II.

The oil and solvent are herein thoroughly contacted by means of stirrer I2 and the oil-solvent mixture is passed by means of pipe I3 into settling vessel I4f wherein settling Vand separation of the extract and raffinate phases is effectedy at a temperature of about 70 F., the ralnate comprising the upper layer and the extract the lower layer. This lower or extract layer is withdrawn from the bottom of settling lmixing vessel as above described. v,The remaining portion, for example, 60 barrels per hour or 60% based on the volume of the oil stock charged, is passed from pipe 31 through pipe 38, heat exchanger 39 and valve-controled pipe 40 into mixing vessel II. This step of recirculating occurs simultaneously with the normal mixing step, and, as above pointed out, permits of a rapid rate of settling and formation of extract and raffinate layers, particularly when relatively `small quantities of solvent are employed.

The undissolved oil layer or raffinate, containing a small quantity of solvent, occupies the upper portion of settling vessel I4, and is passed therefrom by means of pipe I5 into mixing vessel IB of the 3rd stage. neously supplied with fresh solvent which is introduced thereinto from a storage vessel not shown. Such solvent is drawn through valvecontrolled pipes 2| and is forced by pump 22 through pipe 23, the temperature being adjusted in heat exchanger 24 to about 70 F. and thence passed by means of pipe into mixing vessel I6. The oil and solvent are herein thoroughly contacted by means of stirrer I1 and the oil-solvent Vessel I6 is simultamixture is passed through pipe I8 into settling vessel I9 wherein settling and separation of the extract and raffinate phases is eiected at a temperature of about 70 F., the raffinate comprising the upper layer and the extract the lower layer. This lower or extract layer is withdrawn from the bottom of settling vessel I9 by means of valve-controlled pipe 26 and a portion thereof is pumped to the 2nd stage mixing vessel II as hereinbefore described. The remaining portion, for example, 60 barrels per hour or 60% based on the volume of the oil stock charged, is passed from pipe 28 through pipe 29, heat exchanger 30 and valve-controlled pipe 3I into mixing vessel I6. Here again the step of recirculating occurs simultaneously with the normal mixing step and permits of relatively rapid settling and formation of extract and rafnate layers.Y The undissolved oil layer or raflinate, containing a small quantity of solvent, is withdrawn from the upper portion of settling vessel I9 by means of valvecontrolled pipe 20. The residual solvent may be removed from the rafinate by distillation, preferably under reduced pressure.

In accordance with the above described operation of the extraction system, employing recirculation `of extract to each stage, there was produced a railinate oil amounting to 94.3% of the stock charged, such rafnate having a Saybolt Universal viscosity of 127 seconds at 210 F., an A. P. I. gravity of 27.1 at 60 F., a viscositygravity constant of 0.806 and an O. D. color of 1700. The extract oil, amounting to 5.7% of the stock charged, had a Saybolt Universal viscosity of 360 seconds at 210 F., an A. P. I. gravity of 14.0 at 60 F. and a viscosity-gravity constant of 0.895. l

While, in the example given above, I have shown a 3-stage countercurrent system, I do not intend to limit myself thereto, but may employ any system of one or more stages, all of the stages being operated at the same or different temperatures. Furthermore, while I have shown recirculation ofextract to each of the stages of the system, I have found that in some instances it is necessary or desirable to recirculate extract to vonly one of the stages, usually the 1st stage, in

order to eect a rapid settling and formation of f-extraot and reafinite layers. It will be seen that in a multi-stage, extraction system, the ratio of' solvent or extract to rainnate in the last stage is greatest, and, in general, becomes progressively less in the successive preceding stages, so that in the 1st or possibly the 1st and 2nd stages the ratio of extract to rafiinate may be so low that satisfactory settling cannot be obtained. In such instances, the application of recirculation to the 1st and/or 2nd stages becomes absolutelynecessary in order that the system may function successfully. In all cases, regardless of ,theyy number of stages employed and the particular` stages lto which recirculation is applied, ,it is to' be noted that for any given stage the composition equilibrium between extract and raffinate phases is substantially unchanged by the addition or recirculation of extract, since the extractrrecirculated was in equilibrium with the raffinate during settling;

The following example will serve as a further illustration of the results which may be obtained in accordance with my invention.

A Pennsylvania residuurn having a Saybolt Universal viscosity of 162 seconds at 210 F., an A. P. I. gravity of 25 at 60 F., a viscosity-gravity constant of 0.818 and an O. D. color of 8220 was -from each stage was recirculated to each respectivevstage at the rate of about 400 barrels per hour. The raffinate oil obtained from lthe system,

after removal therefrom of- Atraces of solvent, amounted to about 94% by volume of the stock charged. This "oil had al Saybolt Universal Yviseesity of 147`seconds`at 210 F., and an A. P. I. gravity of 26.5 .at 60 F., a viscosity-gravity constant of 0.808 and an O. D. color of 4215. 4The extract oil, afterremoval of solvent, amounted to about 6% by volume of the stock charged and had a Saybolt Universal viscosity of 610 seconds at 210., an A. P. I. gravity of 12.8 at 60 F., a

viscosity-gravity constant color of 33,243.

My invention is particularly adapted tothe extraction of hydrocarbon oils, especially oils derived from Pennsylvania crudes, when it is necessary to use relatively small quantities of solvent. In the solvent treatment of Pennsylvania lubricating stocks, one of the-primary requirements is the .production of high yields of rafnate of the desired quality, since such lubricating stocks are relatively expensive. In order to obtain. high yields of raillnate oil when employing selective solvents of high selectivity and solvent power, it becomes necessary to use small quantities of`\ solvent to prevent too great an extraction of deof 0.902 and an O. D.

' sirable oil components along with the undesirable components which are to be'extracted. Since the use of relatively small quantities of solvent, i. e., of the order of 20% to 70% of the volume of the stock, involves certain dilculties with respect to settling of the extract from the raiiinate phase.. which dilculties at times render the extraction inoperable, it becomes necessary to resort tothe yrecirculation of extract to efiect the settling at reasonably rapid rates. `For example, a Pennsylvania lubricating stock, when extracted in the N normal manner with 40% `by volume of nitrobenzene, could notlbe satisfactorily settled within a practical and reasonable time. However, by articially increasing the ratio'of extract phase to raiinate phase, in accordance with my invention, the settling rate was markedly increased and the extraction was completed successfully to give a yield of'over 90% of railinate oil ol." desired quality On the other hand, when the same lubricating stock was extracted with 100% by volume of nitrobenzene, no separation difflculties were encountered, but there resulted a yield of only 84% of rafllnate oil which was of' a higher qualityv than that desired.

In the extraction of wax-bearing hydrocarbon oils, the' waxy'A hydrocarbons usually remain in the more paraflinic or rafllnate layer. ,Such layer lmay be separated into solidl and liquid -hydrocarbons by an'of the well-known dewaxing processes, such as by cold settling, centrifuging or lter pressing. In many instances it may be advantageous to dewax the oil prior to subjecting same to extraction. Howeverit is vto be understood that in accordance with my invention, dewaxing may be eiected either prior: or subsequent to extraction. Furthermore, the oil stocks employed may be 'sublected to any desired rening treatment, for example, acld treatment,

prior to extraction, or the oil fractions resulting frommy extraction process may be further refined in the conventional manner with acid and/or clay or other treatment. v

My process is practically independent of the particular nature or source ofthe crude oil fractions to be extracted. However, my process is especially adapted to thetreatment of viscous hydrocarbon oils, whether they be distillate oils,

or residuums ,and particularly when noamalaw settling periods of the order of 5,000 to 10,000 seconds or greater are encountered. `Herein, while I have lshown the use of vselective solvents such as nitrobenzene, dichloro ethyll ether and phenol, I vdo not intend to limit myself thereto but contemplate' as within the scope of my invention any one or more of the conventional selective solvents, including, for example, any

one or mixture of those mentioned by Ferris,V

Birkhimer and Henderson in their article in Industrial and Engineering Chemistry, vol. 23, p. 753 etc. (1931).

Herein, and in the appended claims, when oil is specifically referred to as being viscous, it is to be understood that the oil is of substantial viscosity, i. e., of the order of 50 seconds Saybolt Universal at 100 F., or more.

l. In 'a process for extracting a viscous hydrocarbon oil with a selective solvent in an extraction system `comprising a mixing zone and a settling zone to form a ra'lnate phase containing the more paraftlnic constituents of the oil and an extract phase containing the more naphthenic constituents thereof, wherein the quantity of selective solvent employed is of the order of from 20%-,to '70% by volume of the viscous hydrocarbon oil being treated and causes the raffinate phase to form the continuous phase and the `extract phase to form the disperse phase,

the step of reversing the phase relationship be-` tween ralnate and extract phases to enhance the rate of separation of one from the other in said settling zone, which comprises intimately commingling the admixture of railinate and exditional quantity of extract phase as will cause a reversal of said phase relationship, said added extract phase having substantially the same composition` as the extract phase being separated in said settling zone;

tially thesame composition as the extract phase ents of the oil and an extract phase containing 1 the more naphthenic constituents thereof,

wherein the quantity of nitrobenzene employed is of the order oi"v from 20% to 70% by volume of the viscous hydrocarbon oil being treated and causes the raflinate phase to form the continuous phase and the extract phase to' form the disperse phase, the step of reversing the phase relationship between raffinate and extract phases to enhance the rate of separation of one from vthe -other in saidsettling zone, which comprises intimately commingling the admixture of railinate and extract phases in said mixing zone with such additional quantity of extract phase.

as will lcause a reversal of said phase relationship, said added extract phase having substanbeing separated in said settling zone.

45 tract phases in said mixing zone with such adt' 3. The process as recited in claim 1, wherein the selective solvent employed is nitrobenzene.

4. In a process for extracting a viscous hydrocarbon oil with a selective solvent in an extraction system comprising a mixing zone and a settling zone to form a ralnate phase containing the more paraillnic constituents of th oil and an extract phase containing the more naphthenic costituents thereof, wherein the volume ratio of the extract phase to the rafinate phase is less than substantially 0.4, said extract phase comprising the disperse phase and said raffinate phase comprising the continuous phase, the step of increasing the volume ratio of extract phase to raffinate phase to a. value greater than substantially 0.4 to cause reversal of the phase relationship between the extract and the raflinate phases and to enhance the rate of separation of one from the other in said settling zone, which comprises intimately commingling the admixture of extract and railinate phase in said mixing zone with such additional quantity of extract phase as will increase said ratio to a value greater than substantially 0.4, said added extract phase having substantially the same composition as the-extract phase being separated in said settling zone.

5. The process as received in claim 4, wherein the quantity of selective solvent employed in extracting the viscous hydrocarbon oil is oi the order from to 70% by volume of the viscous hydrocarbon oil being treated.

6. The process as recited in claim 4 wherein the selective solvent employed is nitrobenzene.

7. In a process for extracting a viscous hydrocarbon oil of Pennsylvania type with nitrobenzene in an extractiva system comprising a mixing zone and a settling zone to form a rafnate phase containing the more parafiinic constituents of the oil and an extract phase containing the more naphthenic constituents thereof, wherein the volume ratio of the extract phase to the raflinate phase is less than substantially 0.4, said extract phase comprising the disperse phase and said railinate phase comprising the continuous phase, the step of increasing the volume ratio of extract phase to raiinate phase to a value greater than substantially 0.4 to cause reversal of the phase relationship between the extract and the raffinate phases and to enhance the rate of separation of one from the other in said settling zone, which comprises intimately commingling the admixture of extract and railinate phases in said mixing Zone with such additional quantity of extract phase as will increase said ratio to a value greater than substantially 0.4, said added extract phase having substantlally the same composition as the extract phase being separated in said settling zone.

SEYMOUR W. FERRIS.

CLFJRTIFIGATE- OF CORRECTION Patent No. 2,151, 592.

SEYMOUR W FERRIS March 21, 1959.

It ishereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page l, first column, line 59, for of" second occurrence, read or; line 52, for "my" read by; page 5, .first column, line 29, for "8200 F." read 82 F.; page LL, first column, line YO, for "pipes" read pipe; page il, second column, line 149, for "reaffinite" `read raffinate; page 5, first column, line 2l, for "2100" read 210o F'.; line 66, for "an" read any; page 6, first column, line 9, claim li, for "costituents" read constituents; line 2l, same claim, for "phase" read phases;

line 28, claim 5, for "received" read recited; and second column, line l, same claim, before "from" insert of; line 7, claim 7, for

"extractive" read extraction; and that the said Letters Patent should be rend with'this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd dey of' May, A. D. 1959.-.

Henry Van Arsdale (Seal) Acting Commissioner of vPatents..

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