US2054052A

US2054052A - Solvent refining of hydrocarbon oil

Info

Publication number: US2054052A
Application number: US9005A
Authority: US
Inventors: Francis X Govers
Original assignee: INDIAN REFINING CO
Current assignee: INDIAN REFINING CO
Priority date: 1935-03-02
Filing date: 1935-03-02
Publication date: 1936-09-08
Anticipated expiration: 1953-09-08

Description

Sept. 8, 1936. F. x. GovERs SOLVENT REFINING OF' HYDROCARBON OIL Filed March 2, 1955 .SSR

h ERM@ bw Patented Sept. 8, 1936 PATENT ol-Fics 2,054,052 SOLVENT REFlNlNgIgF HYDBOCABBON;

Francis X. Govers, Vincennes, Ind., signor to Indian Refining ompany, a corporation of Maine Application March 193s, semi No. 9,005 1a claim.. (ci. iss-17) This invention relates to the treatment of hydrocarbon oil, and particularly to a method ot treating mineral oil with selective solvents. Y

The invention broadly contemplates a process 5 for `solvent rening mineral oil for the production of lubricating oil oi' high viscosity index, low

pour testf, and other desired properties and char-` acteristics.

'I'he invention comprises extractively treating `l mineral oil stock with a selective solvent, such as furfural, for example, wherein the oil is separated into an extract phase containing low viscosity index constituents of the oil, and a railinate phase comprising high vviscosity index constitul ents of the oil. 'I'he two resulting phases are separately cooled, to eifect alteration of mutual solubility of component parts, and centrifuged or settled to remove the component parts not retained in solution. 'I'he matter thus removed from each phase is returned, all or in part, to the zone ofextraction wherein it is brought into contact with fresh oil undergoing treatment.

In the treatment of wax-bearing oil, the railinate phase, containing substantially all of the parain constituents of the oil, is dewaxed, as

will be more fully described, by means oi.' selective dewaxing solvents to produce therefrom a lubricating oil of low pour test and high viscosity index. In the solvent treatment of mineral lubricating oil stock with furfural, solvent action increases with elevated temperatures, and the selectivity increases with lower temperatures; thus, at 250 F. the total solvent power of the furfural is far greater than at 80 F. but the selectivity is greater at 80 F. than at 250 F. Economy, based alone on the amount of solvent used, predicates the use of high temperature, and economy based on percentage yields of high viscosity index oils 40 predicates the use of low temperatures.

I have discovered that furfural is quite selective, even at high temperatures, when saturation points for any particular constituent or component part of the mineral oil stock are not ex- I have discovered that by the proper use of limited amounts of furfural at high temperatures, extraction refining can be practiced economically in such a way as to eiect maximum 50 action of solvent rening with minimum loss of desirable constituents while at the same time increasing the susceptibility of the ralnate phase to the refining action of certain solvents for still further improvement in color, viscosity 55 index, sulphur, and Conradsen carbon.

I have discovered that the oils separated from the cooled extract phase are more susceptible to solvent rening than-the original stock.

I have discovered that the raiilnate phase, when cooled and separated from the Aretained 5 extract phase, is highly susceptible to the solvent retlning action of ketones, such as methyl ethyl ketone and methyl isobutyl ketone. K

:I have discovered that this process, when practiced in the order o1' the steps herein disclosed, 10 will, from any given wax-bearing lubricating stock, give higher percentage yields of low pour test oils of any given viscosity index with resultant lighter specic gravity, lower Conradsen carbon, lower sulphur, and better color, without 15 treatment with mineral acid, than any solvent` process heretofore described.

I have discovered that the process, when practiced in the order of the steps as herein disclosed, is particularly. advantageous in the treatment of 20 either heavy distillates, or residual oils.

I have discovered that the ramnate can be dewaxed by means of a selective solvent comprising in part the selective washing or rening sol- .ventused inl the last step of extraction, and that 25 the iinal result is increased yields of low pour test, high viscosity index oils of very low Conradsen carbon and sulphur.

Accordingly, the invention comprises a process for treating wax-bearing lubricating oil stock 30 in which the oil is extracted with a solvent comprising furfural at temperatures of around 170250 F., and the mixture separated into extract and raffinate phases respectively. The extract phase will contain low viscosity index undesirable constituents, blended with a certain amount of desirable relatively higher viscosity index constituents. 'I'he rainate phase will comprise the relatively higher viscosity index constituents of the oil containing some of the ex- 40 tract phase retained or suspended therein.

The two pl'ases are separated from each other. The raffinate phase is cooled and subjected to centrifuging or settling to separate these retained extract phase bodies. The extract phase is cooled, to release from solution, and subjected to centrifuging or settling to separate part of the desirable relatively higher viscosity index constituents. The separated bodies are then returned, all or in part, to the extraction zone where they are brought in contact with fresh charge.

When oil is extracted with furfural at elevated temperatures, as for example around 17o-250 F., the resulting ramnate phase contains an appreci- -able amount oi' extract phase material retained therein, and likewise the extract phase also retalus a substantial amount of relatively higher viscosity index oil which, at the high temperature prevailing, is soluble in the solvent. Accordingly, by cooling the raiilnate phase down to a temperature below 170 F., or in the range of 13D-150 F., depending upon the pour test oi' the oil. and upon centrifuging the thus cooled rafllnate phase, a substantial portion of the retained extract phase material may be separated from the ralilnate phase. Similarly, in the case of the extract phase, upon cooling for example to about 110 F. and standing at this temperature, a substantial quantity of oil separatcsfrom solution.

The extract phase material, separated from the raillnate phase in the foregoing centrifuging step, comprises furfural containing oil dissolved thereinl. 'I'his material may be returned to the extraction zone or be mixed with fresh charge entering the extraction zone.

It is of advantage also to return the oil separated from the cooling of the extract phase to the extraction zone. This oil is of a relatively parafiinic natureand its addition to the fresh charge has a tendency to increase the selectivity of the extraction solvent or to facilitate the separation of the oil into extract and rainate phases, respectively rich in low viscosity index and high viscosity index constituents of the oil.

Consequently, by returning the extract phase material separated from the raffinate phase, and the oil separated from the extract phase, to the extraction zone, advantage is taken of the furfural retained therein since it is thus used in the further extraction of fresh oil. It also enables the obtaining of higher ultimate yields of high viscosity index oil since the oil constituents contained in the separated material are subjected io further separating action.

The railinate phase, after centrifuging, will still retain some extract phase material, and this and other undesirable constituents are removed by subjecting the raffinate phase to a washing treatment with a solvent adapted to Y effect their removal. Such a solvent may comprise, for example, a. ketone such as methyl ethyl ketone, methyl isobutyl ketone or homologs.

When the oil undergoing treatment comprises a wax-bearing oil, the subsequent dewaxing operation is effected by means of a selective solvent mixture comprising, for example, a mixture of an anti-solvent liquid of the character of an aliphatic ketone, such as acetone or methyl ethyl ketone, and a good oil solvent such as benzol or toluol. The wax anti-solvent liquid component ofthe dewaxing solvent mixture advantageously comprises a solvent which is also suitable by itself as a washing solvent capable of dissolving from the raflinate phase any extract phase material remaining therein.

I have found that methyl ethyl ketone, for example, is a suitable solvent for this purpose. Thus, in carrying out the process of my invention, as applied to a wax-bearing oil, the resulting rafilnate phase, after cooling and -centrifuging to remove extract phase material, is then subjected to washing with methyl ethyl ketone.

In this washing step, the methyl ethyl ketone dissolves any remaining extract phase material retained in the cold railinate phase, and which' may comprise furfural as well as low viscosity index oil. Other impurities in the oil, insoluble' or sparingly in the furfural, as for example sulphur compounds and other bodies which tend to form color or to produce residual carbon, will also be removed by the washing solvent.

In washing the raillnate with the wash solvent, there results a separation into two phases. One phase will comprise the solution of wash solvent liquor, furfural, color forming matter and undesirable constituents dissolved from the raffinate phase, while the other phase will comprise the puried ramnate phase in a suspended nely divided condition. These two phases can be separated by filtration. The lter cake, comprising the washed raffinate phase will, in the case of the above wax-bearing oil, contain wax constituents and, therefore, the retained wash solvent, namely, methyl ethyl ketone, is left mixed with the washed raffinate phase to serve as a component of the subsequent dewaxing solvent mixture.

Accordingly, an additional quantity of methyl ethyl ketone, together with sulcient benzol or toluol, is added to the washed rafilnate to produce a solvent mixture which has selective action as between oil and Wax at temperatures of the order of F. and below. This mixture is then chilled to precipitate the Wax and the precipitated wax constituents removed therefrom by ltering, centrifuging, settling or other mechanical means. After removal of the solvent from the dewaxed oil, the oilis nished up, for example, by contacting with solid adsorbent material to produce a finished lubricating oil product of superior characteristics.

In order to more clearly describe the invention, reference will now be made to the accompanying ow diagram which illustrates the practice of the process of my invention as applied to the treatment of wax-bearing oil such as a waxbearing lubricating distillate derived from Mid- Continent crude.

The wax-bearing oil to be treated is conducted from a storage tank l and delivered by a pump through a pipe 2 to the lower portion of the separator 3.

The separator 3 comprises a vertical, cylindrical vessel provided with agitation means 4, as shown. The separator and agitating means are advantageously of the type described in my copending application Ser. No. `1,331, led January 11, 1935.

The oil may be heated to suitable temperature prior to introduction to the separator 3 in which case it is passed through a heater 5. Where it is not necessary to thus heat the oil, it may be by-passed around the heater 5, as indicated in the flow diagram.

The furiural is conducted from a tank 6 through pipe 1 to the upper portion of the separator 3. As in the case of the entering oil charge, the furfural may be heated by passage through a heater 8 prior to introduction to separator 3. The amount of heating to which the solvent and oil is subjected will depend upon the particular temperature condition which it is desired to maintain within the separator 3 and it is contemplated that all of the heat may be supplied either by heating the oil or by heating the furfural alone.

The furfural being heavier than the oil flows through the separator 3 countercurrently to a rising body of oil. Intimate contact between the oil and solvent is brought about by rotation of the agitating means 4. As a result of the contact between oil and solvent within the separator, the mixture separates into extract and ramnate phases respectively. The extract phase i The resulting chilled extract phase is then conducted to a settling chamber II wherein, upon standing at the above temperature, paraillnic oil separates from the mixtureand is drawn off to a tank I2. It is to'be understood that instead of settling, the cooled extract phase may, of course, be subjected to centrifuging if desired.

'I'he remaining extract phase from which the paraillnic oil has been separated is then drawn to a tank I3 wherein it may be stored for such further treatment as may be desired.

The raillnate phase formed in the separator 3, and which rises to the upper portion of the separator, is withdrawnv therefrom through pipe I4 to cooler I5 wherein it is cooled to a suitable temperature above the solidifying point of the waxbearing raflinate'oil. This temperature will depend upon the proportion of wax present as well as upon the viscosity of the oil.

The cold raflinate phase is then delivered to a centrifuge or other separating means, such as a settling chamber I 6, wherein the extract phase material retained therein is separated. The thus separated extract phase material is conducted to a tank I1 for return to the separator 3, as will be subsequently described.

The centrifuged raffinate phase is then mixed in a mixer I3 with about equal volume of methyl ethyl ketone drawn from a tank I8. This mixing is carried out advantageously at a temperature just sufficient to complete solution of the railnate phase in the methyl ethyl ketone.

From the mixer I9, it is passed through a chiller wherein it is chilled to a temperature of around 30 F. At this temperature, the parafnic constituents or the oil, including parain wax, will be converted to a substantially solid form.

This cold mixture is then conducted to a filter 2l wherein the liquid is separated from the solid matter. The liquid or filtrate will comprise methyl ethyl ketone containing in solution extract material dissolved from the railinate phase, as well as other undesired impurities freely soluble in methyl ethyl ketone but sparingly soluble in furfural, including sulphur compounds, colorforming, as well as residual carbon-forming bodies.

The separated liquid or filtrate is withdrawn from the illter 2l and conducted to a still 22. The methyl ethyl ketone is vaporized from this liquid, and the resulting vapors cooled and condensed in a cooler 23, and from there returned to the tank I8, previously mentioned.

The residual liquid remaining in the still 22, comprising furfural and oil, is withdrawn to tank 24. From this tank, it is returned to the separator 3 directly, or else ilrst mixed with fresh charge, as will be subsequently described.

The filter cake comprising parafilnic bodies of the oil, including wax, remaining in the filter 2|, is withdrawn through a pipe to a mixer 26. Prior to introduction to the mixer, this paraillnic oil is mixed with an additional quantity of methyl ethyl ketone, from the tank I8, and also with benzol drawn from a tank 21. The methyl ethyl ketone and benzol are added in the proportions of about 40% ketone to 60% benzol, and mixed with the oil in the proportion of 3 to 4 parts of solvent mixture to 1 part of oil.

From the mixer 26 the oil and solvent is conducted to a chiller 28 wherein it is chilled to a temperature of around 10 F. in order to precipitate the wax from the solution.-

The chilled mixture is then conducted to a illter 23 wherein the precipitated wax is separated The lter cake is removed and -4 as a illter cake. the solvent recovered from the wax. The dewaxed ltrate is then delivered to a still 30 for removal of the solvent which latter may be returned for use in dewaxlng further oil.

The dewaxed oil, free from solvent, is conducted to a contact vessel .3I where it is advantageously contacted with adsorbent clay in the presence of steam at temperatures of around 40G-500 F. The contacted oil is then delivered to lter 32 for removal of the solid adsorbent material therefrom. The resulting illtrate, comprising finished lubricating oil of low sulphur and low carbon residue content and high viscosity index, coupled with low pour test, is delivered to a tank 33. f A

`The separated oil of paraillnic nature accumulating in tank I2, together with the extract phase material accumulating in tank IT and the mixture of furfural and oil in tank 24, is drawn off to a pipe 34. This combined material is then delivered by a pump 35 to the pipe 2, previously referred to, and wherein it is mixed with fresh oil entering the lower portion of the separator 3. Instead of combining this material in this way, those portions accumulating in tanks I'I andA 24 may be returned directly to the upper portion of the separator 3.

The nature and amount of oil which is separated from the rafnate and extract phases in the foregoing operation may be illustrated by reference to the following data obtained in the solvent refining of a wax bearing distillate having the following characteristics:

Gravity A. P. I 25.4 Viscosity Saybolt universal at 130 F 143 Viscosity Saybolt universal at 210 F 50 Carbon residue .16% Viscosity index. '7l

there resulted a separation of a lower layer ofmaterial comprising about 2% oil and 98% furfural. This lowerlayer was removed, and the oil and solvent separated. The oil thus obtained from this lower layer amounted to about .07% of the total railnate oil. The solvent was also removed from the upper layer comprising raiiinate oil, and the following is a tabulation of the tests on this raflinate oil of the upper layer and of the separated oil in the lower layer:

Raiinate oil Separated oil Gravity A. P. I Viscosity Saybolt universal'at 100 F.. Viscosity Saybolt universal at 210 F. Carbon residue Viscosity index 97 olor 90V" cell Similarly, when the extract phase was cooled to 130 F. there resulted a separation of oil comprising about 1.65% of the extract phase. The tests on this oil, after the solvent had been removed, were as follows:

Gravity A. P. I 24.9 Viscosity Saybolt universal at l100 F 331 Viscosity Saybolt universal at 210 F 51 Viscosity index 67.5

It will be observed fromthe foregoing that the cycle oil thus separated from the extract phase is very similar in character to the original wax distillate prior to extraction and thus contains a substantial portion of valuable oil.

The process of this invention is not restricted to any specific solvent or mixture of solvents, but it is contemplated that other solvents or mixed solvents, possessing the desired selective action as between constituents of the oil of differing viscosity index or between solid or liquid constituents of the oil, may be used. While the process of my invention is particularly adapted to extraction with solvent of the character of furfural, at elevated temperatures, the process is nevertheless applicable to operations in which the oil is extracted with other solvents, such as nitrobenzene, aniline etc., since, as I have already indicated, centrifuging of the resulting extract and radin-ate phases permits therefrom separation of material retained in each phasey methyl ethyl ketone, as many undesired impurities and constituents are thus rendered soluble in the wash solvent without affecting its selective action on the high viscosity index constituents.

Also, as regards the dewaxing step, solvents other than methyl ethyl ketone and benzol may be employed. For example, it has been found that methyl isobutyl ketone may be substituted for methyl ethyl ketone since this solvent not only possesses anti-solvent properties of wax, but is also adapted as a wash solvent for removal from the raffinate phase and remaining extract phase material retained therein. Either one of these solvents may be employed in conjunction with benzol or toluol, or a mixture of benzol and toluol, to provide a selective dewaxing solvent mixture.

The process of this invention is not limited to any particular type of hydrocarbon oil or petroleum fraction. It is adapted to the treatment of either distillate or residual fractions of petroleum, and while the invention has been described as to the separation of wax from waxbearing lubricating oil stocks, it is contemplated that it may also be employed for the separation of oil from petrolatum or other waxy concentrates.

Moreover, it is contemplated that, as regards the specic manner in which the invention is practiced, temperatures and proportions of solvent may vary from those mentioned above. In the case of dewaxed oils, or relatively less viscous oils, lower extraction temperatures may be employed. The extraction of the oil with the selective solvent may be carried out in either a continuous or stage countercurrent operation.

Extraction by the batch method of operation may also be employed.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, but only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In the process of rening mineral lubricating oil with a selective solvent to produce therefrom a lubricating oil of high viscosity index, the method which comprises extracting the oil with a selective solvent to remove low viscosity index constituents as an extract phase and produce a rainate phase comprising high viscosity index oiland retaining some extract phase, removing the raffinate phase, centrifuging the raffinate phase to remove retained extract phase material, and washing the centrifuged raninate phase with a -liquid having the solvent characteristics of methyl ethyl ketone to remove remaining retained material.

2. In the process of refining mineral lubricating oil with a selective solvent to produce therefrom a lubricating oil of high viscosity index, the method which comprises extracting the oil with a selective solvent to remove low viscosity index constituents as an extract phase and produce a rafnate phase comprising high viscosity index oil and retaining some extract phase, removing the raffinate phase, centrifuging the ranate phase to remove retained extract phase material, washing the centrifuged rainate phase with a liquid having the solvent characteristics of methyl ethyl ketone to remove remaining retained material, removing the wash solvent containing dissolved matter, separating the solvent from the dissolved material and returning the said material to the extraction zone.

3. In the process of refining mineral lubricating oil with a selective solvent to produce therefrom a lubricating oil of high viscosity index, the method which comprises extracting the oil with a solvent comprising furfural, in an extraction zone at a temperature of around 200 F., forming an extract phase comprising 10W viscosity index constituents of the oil dissolved in the solvent, and a raffinate phase comprising high viscosity index constituents of the oil and retaining some extract phase, separating the two phases, cooling the rainate phase to a temperature below the extraction temperature, centrifuging the cooled ranate phase to separate retained extract phase material, and washing the centrifuged rafhnate phase with a liquid having the solvent charac,- teristics of methyl ethyl ketone to remove remaining retained material.

4. In the process of refining mineral lubricating oil with a selective solvent to produce therefrom a lubricating oil of high viscosity index, the method which comprises extracting the oil with a solvent comprising furfural, in an extraction zone at a temperature of around G-250 F., forming an extract phase comprising low viscosity index constituents of the oil dissolved in the solvent, and a raffinate phase comprising high viscosity index constituents of the oil and retaining some extract phase, separating the two phases, cooling the rainate phase to a temperature below the extraction temperature, centrifuging the cooled raffinate phase to separate retained extract phase material, returning the separated material to the extraction zone, washing the centrifuged rafnate phase with a liquid having the solvent characteristics of methyl ethyl ketone to remove remaining retained material, removing the Wash solvent and dissolved material, separating the solvent from the dissolved material, and returning said'dissolved material to the extraction zone.

5. In the process of reiining wax-bearing mineral lubricating oil with a selective solvent to produce therefrom a lubricating oil of high viscosity index, the method which comprises extracting the oil with furfural at a temperature substantially n above atmospheric temperature to remove low viscosity index constituents as an extract phase and produce a raiiinate phase comprising high viscosity index constituents and retaining some extract phase, removing the raihnate phase, cooling the raflinate phase to a temperature below the extraction temperature to separate retained extract phase material, removing the thus separated material, washing the remaining raflnate phase with a solvent having the solvent characteristics of methyl ethyl ketone to remove remaining retained material, and dewaxing the washed ramnate phase.

6. In the process of refining wax-bearing mineral lubricating oil with a selective solvent to produce therefrom a lubricating oil of high viscosity'index and low pour test, the method which comprises extracting the oil with a. solvent comprising furfural, at a temperature of 150-250 F., while at such temperature forming an extract phase comprising dissolved oil of low viscosity index and retaining some oil of intermediate character as regards viscosity index, and a railnate phase comprising high viscosity index constituents of the oil and retaining some of the extract phase, separating the two phases, cooling the rahnate phase to a temperature just above that at which it solidies, centrifuging the cooled rafnate phase to remove retained extractfphase material, washing the centrifuged raffinate phase V with a solvent having the solvent characteristics or methyl ethyl ketone to remove remaining retained extract phase material, removing the wash solvent and dissolved bodies, and dewaxing the washed raiiinate phase.

7. in the process of refining wax-bearing min-r` eral lubricating oil with a selective solvent to produce therefrom a lubricating oil of high viscosity index and low pour test, the method which comprises extracting the oil with a solvent having at a temperature of 150 F. and above the essential selective action of furfural as between constituents of the oil of differing viscosity indices, forming an extract phase containing low viscosity index constituents dissolved in the solvent, and a ramnate phase comprising high viscosity index constituents including wax and retaining some extract phase, removing the rafflnate phase, centrifuging the rafnate phase to remove retained extract phase material, washing the centrifuged raffinate phase with a liquid having the solvent characteristics of methyl ethyl ketone to remove remaining retained material, and dewaxing the washed rafnate phase inthe presence of a chilled solvent mixture having selective action as between solid and high viscosity index hydrocarbons and having as a component part of such a chilled solvent mixture the wash solvent liquid retained by the raffinate phase.v

8. In the process of refining wax-bearing mineral lubricating oil with a selective solvent to produce therefrom a lubricating oil of high viscosity index and low pour test, the method which comprises extracting the oil with a solvent comprlsingurfural in an extraction zone at a temperature around 200 F., forming an extract phase containing low viscosity index constituents dissolved in the solvent, and a raiiinate phase comprising high viscosity index constituents including wax and retaining some extract phase, removing the railinate phase, cooling the raftinate phase to a temperature below the extraction temperature, centrifuging the cooled railinate phase to remove retained material, washing the centrifuged rainate phase with a liquid having the solvent characteristics of methyl ethyl ketone, to remove remaining retained material, returning the retained material separated from the raffinate phase during the centrifuging and washing steps to the extraction zone, and dewaxing the washed raihnate phase in the presence of a chilled solvent mixture having selective action as between solid and high viscosity index hydrocarbons and having as a component part of such a chilled solvent mixture the wash solvent liquid retained by the railnate phase.

9. In the process of rening mineral lubricating oil with a selective solvent to produce therefrom a lubricating oil oi high viscosity index and low pour test, the method which comprises extracting the oil in anextraction zone at a temperature substantially above atmospheric with a solvent having at a temperature of 150 F. and above the essential selective action of furfural as between constituents of the oil of differing viscosity indices, forming an extract phase containing low viscosity index constituents dissolved in the solvent and retaining some oil of intermediate character as regards viscosity index constituents of the oil and a raiiinate phase comprising high viscosity index constituents and retaining some of the extract phase, separating the two phases, separately cooling the two phases to separateretained material, removing the thus separated material, washing the rafiinate phase Y with a solvent having the solvent characteristics Y of methyl ethyl ketone to remove remaining retained material and returning the retained materials separated from each phase to the extraction zone.

i0. In the process of reiining wax bearing mineral lubricating oil with a, selective solvent to produce therefrom'a, lubricating oil of high viscosity index and-low pour test, the method which comprises extracting the oil in an extraction zone at a temperature above atmospheric with a solvent having at a temperature of 150 F. and above the essential selective action of furfural as between constituents of the oil of differing `viscosity indices, forming an extract phase containing low viscosity index constituents dissolved in the solvent and retaining some oil of intermediate character as regards viscosity index, and a raiiinate phase comprising high viscosity index constituents of the oil and retaining some of the extract phase, separating the two phases, separately cooling the two phases to separate retained material, removing the thus separated material, washing the raflinate phase with a solvent having the solvent characteristics of methyl ethyl ketone to remove remaining retained material and returning the retained materials separated from each phase to the extraction zone, and dewaxing the railinate phase in the presence of a chilled solvent mixture having selective action between solid and high viscosity index hydrocarbons and having as a. component part of such chilled solvent mixture the wash solvent liquid retained by the washed raffinate phase.

eral lubricating oil with a selective solvent to` produce therefrom a lubricating oil of high viscosity index and low pour test, the method'which comprises extracting the oil in an extraction zone with a solvent comprising furfural, at a temperature in the range of 15G-250 F., whiie at such temperature forming an extract phase comprising dissolved oil oi low viscosity index and retaining some oil of intermediate character as regards viscosity index, and a ramnate phase comprising high viscosity index constituents of the oil and retaining some o the extract phase, separating the two phases, separately cooling the two phases to a temperature substantially below the extraction temperature, centrituging the cooled raiilnate phase to remove retained extract phase material, settling the cooled extract phase to remove retained relatively high viscosity index oil, washing the centrifuged raillnate phase with a solvent having the solvent characteristics of methyl ethyl ketone adapted to remove remaining retained extract phase material, returning the bodies separated from the two phases to the extraction zone, and dewaxing the washed rafilnate phase.

12. In the process of reilning wax bearing mineral lubricating oil with a selective solvent to produce therefrom a lubricating oil of high viscosity index and low pour test, the method which comprises extracting the oil with a solvent comprising iurfural, at a temperature in the range of 15G-250 F., while at such temperature forming an extract phase comprising dissolved oil of low viscosity index and retaining some oil oi intermediate character as regards viscosity index, and a raffinate phase comprising high viscosity index constituents of the oil and retaining some of the extract phase, separating thev two phases,

40 cooling the raillnate phase to a temperature substantially below the extraction temperature, centrifuging the cooled rafnate phase to remove retained extract -phase material, washing' the centrifuged rafnate phase with a liquid having the solvent characteristics of methyl ethyl ketone to remove remaininglimpurities, and dewaxing the washed rafnate phase in the4 presence of a chilled solvent mixture having selective action as` between solid and high viscosity index hydrocarbons and having as a component part of such charged solvent mixture the wash solvent liquid retained by the high viscosity index constituents.

13, In the process of refining wax-bearing mineral lubricating oil with a selective solvent to produce therefrom a lubricating oil of high viscosity index and low pour test, the method which comprises extracting the oil with a solvent comprising furfural, at a temperature in the range of 15G-250 F., while at such temperature forming an extract phase comprising dissolved oil of low viscosity index and retaining some cil of intermediatev character as regards viscosity index, and a rainate phase comprising high viscosity index constituents of the oil and retaining some of the extract phase, separating the two phases, cooling the raffinate phase to a temperature substantially below the extraction temperature, lcentrifuging the cooled raiinate phase to remove retained extract phase material, washing the centrifuged ralnate phase with methyl ethyl ketone to remove remaining impurities, mixing with the washed rafnate phase further methyl ethyl ketone together with a modifying solvent of the character of benzol, in proportions such that the solvent mixture has selective action as between solid and liquid hydrocarbons at temperatures of the order of 0 F., chilling the resulting mixture to precipitate the wax and separating the thus precipitated wax and removing the solvent liquids from the dewaxed oil.

FRANCIS X. GOVERS.