US2218516A

US2218516A - Method for producing lubricating oil

Info

Publication number: US2218516A
Application number: US486724A
Authority: US
Inventors: Ulric B Bray
Original assignee: Union Oil Company of California
Current assignee: Union Oil Company of California
Priority date: 1930-10-06
Filing date: 1930-10-06
Publication date: 1940-10-22
Anticipated expiration: 1957-10-22

Description

Oct. 22, 1940. u, B.A BRAY l METHOD FOR PRODUGING LUBRICATING OIL Filed Oct. 6, 1950 2 Sheets-Sheet l Wild mw U. B. BRAY 2,218,516

METHOD FOR PRODUCING LUBRICATING OIL Filed oct. e, 195o 2 sheets-sheet 2 Oct. 2.2, 1940.

Patented oa. 22, 1940 PATENT OFFICE METHOD FOR PROlIIJEING LUBRICATING Ulric B. Bray, Palos Verdes Estates, Calif., as-

signor to Union Oil Company of California, Los Angeles, Calif., a corporation of lCalifornia.

Application October 6, 1930, Serial No. 486,724 y claims.

sion of Serial No. 466189l claiming dewaxing4 with butane with or without heating of the waxbearing oil with butane to effect solution prior to chilling; Patent No. 1,944,491, claiming separation of asphalt and wax from oils containing them; Patent No. 1,949,989, ,claiming separation of asphalt from oils by treatment with liquefied normally gaseous hydrocarbon with or Without washing of precipitated asphalt with fresh solvent; Patent No. 2,006,098,` claiming chemical treatment of oilsdissolved in a liquefied normally gaseous hlydrocarbon solvent; Patent No. 2,031,204,r claiming deasphalting and/or dewaxing with a liquefied volatile solvent and with a heavier solvent material; and Patent No. 2,081,731, claiming distillation of oils to remove light fractions, substantial deasphalting of the residue, andthe subsequent distillation of the partially deasphalted residue to produce a lubricating oil distillate.

It has been discovered that superior lubricating oils and asphalts can be obtained from 4crude oil by causing separation of the lubricatingoil from the asphalt at temperatures below that at which deleterious changes are induced in the oil.

It has been found that if oil containing asphalt is heated in the presence of the asphalt, the latter catalyzes certain reactions in the oil which .result in the destruction of those characteristics of e the lubricating oils which are most desirable.

It has been found advisable to cause the sepaf ration of asphalt from the oil by means of volatile solvents which are capable of dissolving the oil and any Wax and which do not dissolve the asphalt. Such solvents are light petroleum fractions, such as casinghead gasoline and naphtha and also petroleum fractions normally vaporous at ordinary temperatures and pressures. Other solvents which may be used are alcohol, ether, mixtures of alcohol and ether,acetone, etc. I prefer to use as my volatile solvent a petroleum fraction obtained by the rectiflcation'of natural gasoline. The fractions are composed in the main of propane and isobutane. A typical analysis of such a fraction is l6.72% ethane, 72.2% propane and 19.91%-isobutane and 1.17% normal butane. It will be understood, however, that these merely illustrate the type of fraction used and the composition may vary. This fraction will hereinafter be referred to as propane for purposes of simplicity. A

In order to cause the extraction with this liquid lo fraction, the solution is maintained at a pressure suicient to maintain the propane liquid at ordinary temperatures. The fraction above described is liquid at ordinary temperatures at about lbs. The extraction of the oil from the asphalt at such pressures results in an asphalt substantially free of oiland a solution of oil in the liquid petroleum fraction. This solution contains substantially all the wax present in the crude oil.

It has also been4 found that oil containing asphalt and impurities such as Vwax may be first -freed from the asphalt by a primary extraction with a light solvent such as the solvent described above and that the impurities such as wax may then be removed at a suitable temperature by the aid of a heavier solvent such as naphtha in4 which the wax is substantially insoluble at the lowl temperature employed. By heavier solvent I mean one of higher boiling point than the light solvent previously described.

Advantage is taken of the high volatility of the light solvent to cause a cooling of the oil upon a release of pressure to produce the separation of the contained Wax. A further advantage in cooling the oil in this manner is to bring the oil to a proper temperature for acid treatment. By acid treatment I intend to include treatment with acid followed by the step of neutralization and/or clay treatment.

If a large proportion of the propane is removed from the solution after the asphalt has been separated, the remaining solution becomes too viscous and not of sufficiently low specic gravity to permit satisfactory behavior in the dewaxing operation which is conveniently accomplished in a centrifuge. Dlmculties are also encountered in chemically treating oils oi' high viscosity.` My invention avoids these diiiiculties by mixing the oil with naphtha before dewaxing to reduce the vis- 4cosity and place the oil in proper Condition f01 50 dewaxing. 'I'he reduced viscosity is also advantageous in chemical treatment of the oil. If naphtha is expanded at very low pressure into the oil prior to dewaxing, it may also have a cooling effect similar to that caused by the expansion of 55 ethylene, trichlorethylene or the like, or mixtures of benzol with acetone or other ketones, or mixtures of benzol and butanol or other alcohols.

In addition to the power which thenaphtha has of reducing' the-viscosity of the asphalt-free oil, it also is used as an extracting medium for wax or other material whose presence is deleterious in a finished, high grade lubricating oil. The naphtha 'if used in sufficient quantities acts as a solvent for the oil during the removal of the wax or other impurities in a manner similar to the action of the propane solution during the removal of the asphalt. By regulating the quantity substantially oil free wax may be precipitated. In comparing their volatility and specific gravity, the propane is considered to be the light solvent and the naphtha is the heavier solvent. An advantage in using both light and heavy solvents resides in the fact that th'e dewaxing may take place in the presence of the heavier solvent after the lighter, more volatile 'solvent has been evaporated with a consequent decrease in the temperature of the wax containing oil. A y

It is therefore an object of'my invention to produce lubricating oil from oil containing aspurities such as wax from the asphalt free oil by means of a heavier solvent under reduced pressure. e

It is furthermore ,an object of my invention to produce lubricating oil from oil containing asphalt and wax by mixing this oil with a solvent in which the lubricating oil fractions and wax are soluble, but in which the asphalt is insoluble, and subsequently separating the wax from the lubricating oil fractions in the presence of naphtha. .Y

It is a further object of this invention to mix the naphtha with the oil either in the presence of substantially all the propane used to precipitate the asphalt, or in the presence of only a portion of said propane, or the naphtha may be added after substantially all the `propane has been separated from the oil and wax.

It is a further object of this invention to produce lubricating oil from oil containing asphalt and wax by precipitating the asphalt with a sol- ,vent for the oil and wax and to chemically treat the oil either before or after removal of the Wax from the oil, and either before or after the addition of naphtha to the oil and wax.

Another object of this invention is to produce lubricating oil from oil containing asphalt and wax by mixing a volatile solvent therewith under pressure to precipitate the asphalt and dissolve the lubricating oil fractions and wax, separate the precipitated wax under pressure, and taking advantage of the highly volatile characteristics of the solvent by releasing the pressure and allowing the solvent to vaporize and consequently cool the oil and wax, lthereby precipitating the latter, and to separate the wax from the oil in the presence of naphtha.

Another object of the invention is to produce lubricating oil in the manner described above and to make further use of the volatility of the solvent by partially releasing the pressure on the oil, solvent and wax subsequent to the removal of` the precipitated asphalt under pressure, whereby the oil, wax and the solvent which remain in the liquid form are suiciently cooled to be at the desired temperature for chemical treatment, and after chemical treatment, making use of the volatility of the remaining solvent byfurther releasing the pressure andprecipitating the wax due to the consequent cooling.

The process will be more adequately understood by reference to the drawings which show preferred schematic arrangements of the apparatus to carry out the process described herein.

Fig. 1 is a schematic arrangement of apparatus in which the oil is first made asphalt free and thenis dewaxed in the presence of naphtha and chemically treated in the substantial absence of solvent.

l Fig. 2 is a schematic arrangement of apparatus in which the oil is first made asphalt free and then is dewaxed in the presence of naphtha and chemically treated in the presence of substantial quantities of solvent.

Referring more particularly to Fig.. l, topped residuum obtained by distilling crude oil at a temperature preferably not over 60G-625 F. to remove all fractions up to and including all or a portion of the light lubricating oil, is taken from tank I and is passed through line 2 to pump 3 and to T 4 where it meets a propane solution of lubricating oil coming through line I5. 'Ihe propane and residuum pass through the turbulence or mixing coil 5 and then into decanter 6;

The asphalt in the'residuum is precipitated by the propane and settles to the bottom of decanter 6 in the form of a. slurry which is passed through pump 'I and line I Il where it is mixed with propane from storage 8 via pump 9 and line I0. 'I'he mixture then is passed into mixing coil II and into decanter I2. lDecanters 6 and I2 and propane storage 8 are maintained at the same pressure by means of equilibrium lines I6 controlled by valves I1. The pressures in 6, I2 and 8 are sufficient to maintain the solvent in liquid state at ordinary temperatures. For"the solvent given above, this is about 125 lbs. per square inch.

The clear overflow from decanter I2, consisting of liquid propane in which is dissolved a small amount of lubricating oil, is passed through line I3, pump I4 to line I5 to T 4 where it is mixed with the incoming topped residuum and passes through turbulence coil 5 into decanter 6, as described above. 'I'he asphalt slurry from decanter I2 is'drawn off through the pressure release valve IB and ashed through coil I8 in furnace 20. Sucient heatis supplied to cause vaporization of the propane and to melt the asphalt. The heated mixture of asphalt and propane is now sent into evaporator 2| where superheated steam is introduced via 22 in order to complete the evaporation of the propane and to reduce the asphalt to satisfactory iiash and fire speciilcations. The overhead from evapo- IThe overflow from decanter 6, consisting of a.

more concentrated solution of lubricating oil and propane is passed through pump 35 and line 34 through pressure reduction valve 36 where it meets naphtha from tank 31 passing through pump 38 and valve'39. In the operation of cooling chamber 4|, if a very large portion of the propane is evaporated, the remaining solution would be too viscous and not of sufliciently low specific gravity to permit satisfactory behavior in the dewaxng operation. Therefore, a suitable quantity of naphtha is added in line 48 to the incoming propane solution. The addition of the naphtha also reduces the loss of propane in the centrifuging operationif the centrifuge is not gas tight in construction.

It is desired to release the pressure upon the propane solution so that propane will evaporate from the solution and thereby suiliciently lower the temperature of the remaining solution to permit asatisfactory dewaxing operation. The propane solution passing through pressure reductionl valve 36 goes through line 48 into cooling chamber 4| which is in effect a rectifying column held at a predetermined pressure corresponding to the desired 'dewaxing temperature. As the propane evaporates the temperature of the remaining solution falls to that in which the vapor pressure will correspond to that being maintained in the cooling chamber by propane compressor 43. The

propane vapors pass out through line 42 to compressor 43. The conditions in rectifying column 4| are maintained by the prooer manipulation of valve 36 and by controlling the suction of compressor 43 so that only the solvent is removed and the lubricating oil and naphtha are retained as bottoms. By reducing the pressure to substantially atmospheric a temperature of 40 F. can be obtained. Substantially al1 the propane may be removed from the solution in rectifying column 4| or only the necessary quantity may be allowed .to vaporize therefrom in order to provide for sufficient cooling to dewax the oil. If desired, the vapors rising in the column 4| may be washed by the addition of naphtha into the top thereof. 'I'he compressed vapors leaving compressor 43 pass through line 32 to condenser 33 where the vapors are liquefied and passed into liquid propane storage 8.

The cooled mixture from the bottom vof rectifying column 4| is carried through line 44 to -pump 45 from which it is sent to centrifuge- 46. The centrifuge, is operated by motor 41 which is positioned outside a gas tight insulated chamber 48 which contains centrifuge 46. Wax is discharged from the centrifuge through line 49. The discharged wax may be worked up in any suitable manner for the recovery of propane, naphtha and oil. The dewaxed'oil is discharged through line 58 and is passed into heater 5|. The heater 5| may consist of any convenient equipment which will impart heat to the cold oil passing through line 58, such as a heated coil set in a furnace or heat exchanger. As shown it is a steam heater, steam entering at 52 and leaving at 53. The dewaxed oil solution leaving heater 5| may be sent by either of two courses.

If it is desired to acid and alkali treat the de- Waxed lubricating oil stock while in naphtha solution, the oil is lpassed through valve 54 to evaporator 55. In yevaporator 55 practically all of the remaining propane is removed from the solution, passed through mist extractor 55', through line 56 to propane compressor 38, where it is compressed and sent through line 3| and line 32 to condenser 33 where it is liqueed and passed into propane storage 8. The column 55 is operated to keep the naphtha in the oil by the proper manipulation of valve 54 and by controlling the suction of propane compressor 38. This is merely a simple rectifying step. Rectifying plates may be provided to assist in this operation as will be understood by those skilled in the art.

The naphtha solution from the bottom of evaporator 55 passes through pump 58, line 51 to dewaxed naphtha solutionstorage 59. From 59 the dewaxed naphtha solution passes through valve 6|, pump 62, via line 88 to agitator 63 Where itis treated with sulfuric acid from tank 64, pumped by 65 through valve 66 in line 61. The acid treated oil is decanted from the sludge through the valves 1| and lines 184 and run into agitator 13 through line 12. The acid sludge is withdrawn through line 68 controlled by valve 69. In 13 it 1s rst treated with water passing from 18 via pump 19 and valve 88 through line 11. `lIhe water is withdrawn through 8|` controlled by valve 82. The oil is then treated with caustic soda passing from 14 via pump 15 and valved line 16 to line 11. 'I'he spent caustic is withdrawn through 8|. The alkali treated .oil is then washed with water as previously described. The treated naphtha solution is carried from agitator 13 by line 83. The treated naphtha solution passes through line 83, pump 84, line 85, valve 86 to heat interchanger 81. y

If it is not desired to perform the acid and alkali treatment in the presence of the naphtha, the oil leaving heater 5| is passed through valve 54' to heat interchanger 81, valves 54 and 86 being closed and valve 54' open. Oil leaving 81, Where its temperature is raised somewhat. is sent through line 88 to coil 89 in furnace 28 wh'ere its temperature is raised still further before being introduced into evaporator 9| Athrough line 98. Steam is introduced via 92 in evaporator 9| to aid in the flashing of the naphtha and residual propane and to reduce the remaining oil to satisfactory flash and fire specifications. `The oil remaining in the bottoml of evaporator 9| vis drawn of! through line 93 and sent tov dewaxed oil storage 95 via pump 94. If the oil has not been chemically treated in naphtha solution, it may now be treated free from naphtha.

The treated naphtha solution travels from heat interchanger 81 in the same path described above in order to be freed of naphtha and residual propane.

The overhead from evaporator 9| is passed through 96 and, heat. exchanger 81 into line 91 and is further condensed in condenser 98 from which it passes into separator 99. 'Ihe naphtha condensate is sent by pump |82 through line |83 to naphtha storage 31. Any uncondensed propane in separator 99 passes through line |88 to propane compressor 38. The compressed propane passes through line 3| and 32 to condenser 33 where it liqu'ees and passes to propane storage 8. The condensed steam is withdrawn through IOI.

Referring more particularly to Fig. 2, this embodiment `relates to the aforesaid process in which a modification is made whereby the chemical treatment takes place in the presence of substantial quantities of the solvent which is in solution with the oil and wax.

The crude oil to be used as a source of lubricating oil is taken from a crude oil storage tank I and sent by pump 2 through coil 2 in furnace 3, whence it is.sent to evaporating column 4. The vapors passing through line 5 consist of gas oil, kerosene and gasoline vapors which go to dephlegmator 6 where they are fractionated into gasoline overhead and kerosene and gas oil bottoms. These may be rerun or handled in any conventional manner. The vapors passing through 1 are condensed in condenser 8 and the condensate, i. e., gasoline, is collected in 9. A

' part thereof may be returned by pump I0 through line I controlled by valve 9 to distributor I to act as a reflux. The dephlegmator bottoms are removed through by pump I2 and are cooled in I3. They consist of gas oil and kerosene. Part thereof is returned as a wash via line |4 and spray I5.

The bottoms from evaporator 4, consisting of fuel oil or refinery residuum, pass through the run-down line I6 to the hot residuum storage tank |1 which may serve as a surge tank in the continuous operation of the process. The hot residuum from tank .I1 is passed through pump I8 which sends the hot residuum through coil I9 in furnace 20 where the residuum is heated to about 625 F. Care is taken at this point not to overheat the residuumbecause of the danger of injuring the quality ofthe lubricating oil to be obtained as the nal product. The heated residuum passes to fractionating column 22.

Steam superheated in coil 2| is introduced in If desired, as many tanks as there are side streams A may be employed. The side stream distillates may be processed in any suitable manner to produce desirable products.

The overhead from column 22 is removed through line 29, cooled in condenser 30 and sent to receiver- 3I. Uncondensed vapors areremoved therefrom via 32 while condensed oil and water from the steam used in column` 22 are removed via

lines

33 and 34 respectively. The bottoms from column 22 are run through line 35 by pump 36 to heat exchanger 31 and line 38 to cooler 39 from which they are delivered toA the topped residuum tank 40. Theoperation of coil I9 and column 22 is so regulated as to produce the desired predetermined extent of topping necessary to give the proper viscosity oil in the later extraction of propane.

In the above description of the production of a topped residuum, the foregoing equipment and operations are intended merely to exemplify one of the many ways iny which a satisfactory topped residuum can be prdduced. Many other features of construction and' operation such as are known to those skilled in the art may be substituted for or included. in the above without departing from my invention. It will be understood that the topping operation here described is equally applicable to the process illustrated in Figi 1.

The 'topped residuum from tank 40 is passed by pump 4| through line 42 where it meets a propane solution of lubricating oil coming through line 54. The propane and residuum pass through the turbulence or mixing coil 43 and then into decanter 44. The asphalt in the residuum is precipitated by the propane and settles to the bottom of decanter 44. The pre. cipitated asphalt resembles a slurry and may be drawn off from the bottom of the decanter with suiiicient liquid propane to permit pumping.

The asphalt propane slurry is passedl through line 45, pump 46 and line 41 where it is mixed with fresh liquid propane from storage 48 sent via pump 49 and line 41. The mixture is then passed into mixing coil 50 and into decanter 5|. If it is desired to produce an asphalt containing still less oil or wax, the countercurrent washing with propane may be extended to as many steps as desired. Decanters 44 and 5| and storage 48 are maintained at the same pressure by means of equilibrium lines 55 controlled by valves 56. The pressures in 44, and 48 are suiiicient to maintain the solvent in liquid state at ordinary temperatures.

The clear overflow from decanter 5| consisting of liquid propane in which is dissolved asmall amount of oil is sent through line 52, pump 53 and line 54 to its connection with line 42 where it is mixed with the incoming topped residuum. 'Ihe mixed residuum and propane pass through mixing coil 43 and into decanter 44 as described above.

The clear overow from decanter 44, now conthe pressure is released to that corresponding tomatic pressure regulating valves. A tempera- .ture of about 40 F. is desirable in the followingl `valve 6|. The propane which has been vaporized in 58, in order to lower the temperature ot the remaining oilsolution, passes through line 68, valve 6| and line |86 to compressor |26 where the .propane vapors are compressed; liquefied'and sent to propane storage 48 after cooling in cooler |21. i.

The cooled propane solution in expansion chamber 59 is sent through. line 62 by pump 68 to turbulence or mixing coil 61 and thence to decanter 68. Suliuric acid is introduced from .tank 65 by means of 4pump 66 into line 64. 'Ihe acid treated oil solution is decanted `and the sludge isWithdrawn through line 68.` The oil is sent by line 18 and pump 12| into turbulence or mixing coil 11 and thence to decanter 18. Water l for use in washing the acid `treated oil is introduced in line 18 from'water storage 12 via pump 13, valve 14 and line 16. The washed oil is then decanted and is removed from decan-ter 18 via line 88 and pump 8| intoline 82. The Wash water is removed from decanter 18 through line 18.

Alkali froml alkali storage 83 is then admitted to line 82 'via' pump 84 and line 85. The oil and alkali flow through turbulencecoil 86 into decanter 81 from which the alkali sludge is removed via line 88. The decanted oil from 81 The treated oil solution leaving the treating group by means of line 8 5 is passedby pump 86 through a second expansion valve 81 where to the dewaxing temperature. This pressure will be substantially atmospheric and its correspond- `ing temperature will be about 35 F. In order -to obtain an voil of extremely lowcold testand to reduce the danger of loss oi propane in the centrifuging operation, practically all of the propane is now evaporated. In order to maintain suilicient fluidity and a proper specific gravity of the solution to be dewaxed by centrifuging, naphtha from tank 88 is added to the propane solution in line 85 via pump 88 and line |88. The mixture of oil, propane and naphtha passes into expansion chamber l8|. of the propane reduces the .temperature of the remaining material to a satisfactory dewaxing temperature. The chilled material then passes through line |81 to centrifuge |88 where the y wax is thrown out and carried away by line ||8. 'I'he centrifuge is driven by motor |88. The wax stream may then betreated in any desired manner for thevrecovery of `naphtha and propane. 'I'he dewaxed oil solution is lcarried away by line topump |'|2. From pump ||2 the oil 'Ihe evaporation` where the temperature is raised by heat exchange with the bottoms from evaporator I I6 and column 22 respectively, before being sent by lines ||4 and ||5 to evaporator ||6. Evaporator ||6 may consist of any suitable equipment, but is shown as a simple column heated by steam coil In this exhausting column, all of the naphtha and any remaining propane are removed so that the oil remaining has proper flash and fire points. ,The overhead from evaporator |6 passes through line '||1 to condenser ||8 and then to separator I8. The naphtha recovered in` 8 is sent through line |22 to naphtha storage 88V, andthe uncondensed propane is sent through line |28 to back pressure regulating valve |2| and thence through line |86 to the propane compressor |26 and liqueiler |21 to be returned to propane storage 48. 'I'he bottoms from evaporator ||6 are drawn oil through line |23 and are sent to heat exchanger ||3 where heat' is imparted to the incoming Anaphtha solution as indicated above. Leaving heat exchanger H3, the bottoms pass through 4 line |24 to tank |25 which is the acid treated dewaxed oil storage tank.

`It is to be understood that the above is merely illustrative of preferred embodiments ofthe invention of which many variations may be made by those skilled in the art without departing from the spirit thereof.

I claim:

l. A method of separating asphalt ,and wax from oil containing the same which comprises mixing said oil with asolvent, separating the asphalt from the solvent, oil and wax, adding naphtha, separating the solventfrom the naphtha, oil and wax at' reduced temperature, separating the wax from the oil and naphtha at reduced temperature and subsequently separating the naphtha from the oil.

2. A method of separating asphalt and wax from oil containing the samel which comprises mixing said oil with asolvent, separating said asphalt from the solvent, oil and wax, removing part of said solvent before the addition of naphtha, adding naphtha to said solventsolution, separating the remaining solvent from said solution, separating wax from the oil and naphtha and subsequently separating naphtha from the oil.

3. A method of separating asphalt and wax from oil containing 'the same which comprises mixing said oil with a volatile solvent under superatmospheric pressure sufficient to maintain said solvent liquid, separating said asphalt from the solvent, oil and wax under such pressure, releasing the pressure to partially evaporate the solvent and to cool the oil .and precipitate the wax, adding naphtha, separating wax from said oil, naphtha and remaining solvent, further' mixing said oil with a volatile solvent under superatmospheric pressure suiilcient to maintain saidsolvent liquid, separating said asphalt from the solvent, oil and wax under such pressure, adding naphtha, reducing the temperature and pressure, separating said solvent from the oil, wax

' and naphtha under reduced pressure, acid treating the oil and oil. u g

5. A process for the'production of lubricating Oil from an oil containing asphalt and wax which separating the naphtha from the and remaining propane from said acid treated oil.

comprises commingling said oil with liquid propane. separating the asphalt from the propane, oil and wax, adding a heavier solvent to said propane, oil and wax, cooling said oil, propane and heavier solvent suillciently to precipitate the wax, separating the precipitated wax from the oil, propane and heavier solvent and subsequently separating said propane and said heavier solvent from said dewaxed oil.

6. A process for the production of lubricating oil from an oil containing asphalt and wax which comprises commingling said oil with liquid propane, separating the asphalt from the propane, oil and wax, adding naphtha to said propane, oil and wax, vaporizing a portion of the liquid propane and cooling the oil suiliciently to precipitate the Wax, separating the wax from the oil, naphthaA and remaining propane, acid treating said oil in the presence of the naphtha and remaining propane and subsequently separating the naphtha '7. A process for the production of lubricating oil from oil containing wax which comprises mixing said oil with a volatile solvent under superatmospheric pressure suillcient to maintain said solvent liquid, adding a wax extracting solvent, releasing the pressure and vaporizing4 the volatile solvent to cool the oil and precipitate the wax, separating the wax from the oil and wax extracting solvent and subsequently separating the wax extracting solvent from the oil.

8. A process for the production of lubricating oil from oil containing wax which comprises mixing said oil with a volatile solvent under superatmospheric pressure sufllcient to maintain said solvent liquid, acid treating said oil and wax under said pressure in the presence of said volatile solvent, alkali treating said acid treated oil and wax under said pressure in the presence of said volatile solvent, adding naphtha under said pressure, releasing the pressure and vaporizing the volatile solventfrom the oil, wax and naphtha, separating the waxfrom the oil and naphtha ztiidlubsequently separating the naphtha from 9. A process for the production of lubricating oil from oil containing wax which comprises mixing said oil with a liqueiied normally gaseous hydrocarbon solvent under superatmospheric pressure suilicient to maintain said hydrocarbon solvent liquid, reducing the pressure partially and vaporizing a portion',of the solvent to cool the oil, acid treating said cooled oil in the presence of the remaining solvent, adding naphtha while maintaining the cooled oil solvent mixture under said reduced pressure. releasing the pressure and vaporizing the 'solvent to further cool theoil and precipitate the wax, separating the precipitated wax from the oil and naphtha and separating the naphtha from the oil. i

i0. A process for the production of lubricating oil from oil containing wax which comprises mixins said oil with a liquefied normally gaseous hydrocarbon solvent and under superatmospheric pressure sufficient to maintain said hydrocarbon solvent liquid, cooling the oil to a temperature insufiicient to precipitate substantial quantities of Wax by partially reducing the pressure to effect vaporization of a portion of the solvent, acid treating said cooled oil in the presence of the remaining solvent under said partially reduced pressure, adding naphtha under such pressure, releasing the pressure and vaporizing the 'solvent to further cool the oil and precipitate the wax, separating the precipitated wax from the oil and naphtha and subsequently separating the naphtha from the oil.

11. A. process for the production of lubricating oil from oil containing asphalt and wax which comprises mixing said oil with a liqueed normally gaseous hydrocarbon solvent under superatmospheric pressure sufficient to maintain said hydrocarbon solvent liquid to precipitate asphalt, separating the asphalt from the oil solvent solution, reducing the pressure partially and vaporizing a portion of the solvent to cool the oil, acid treating said cooled oil in the presence of the remaining solvent, adding naphtha under such pressure, releasing the pressure and vaporizing the solvent to further cool, the oil and precipitate the wax, separating the precipitated wa'x from the oil and naphtha and separating the naphtha from the oil.

12. A process for the production of lubricating oil from oil containing asphalt and wax which comprises mixing said oil with a liquefied normally gaseous hydrocarbon solvent under super.. atmospheric pressure suiicient to maintain said hydrocarbon solvent liquid to precipitate asphalt, separating the asphalt from the oil solvent solution, cooling the ,oil to a temperature insuiilcient to precipitate substantial quantities of wax by partially reducing the pressure to effect vaporization of a portion of the solvent, acid treating said cooled oil in the presence of the remaining solvent under said partially reduced pressure, adding naphtha under such pressure, releasing thepressure and vaporizing the solvent to further cool the oil and precipitate the wax, separating the precipitated wax vfrom the oil and naphtha and subsequently separating the naphtha from the oil. 13. The process of dewaxing hydrocarbon oils bearing a wax crystallization retarder in the form of coloring material, including the steps orf blending a diluent with the hydrocarbon oil, chilling the solution thus formed substantially to a temperature at which' the retarding eilect of the coloring material is overcome, removing such a portion of the coloring material that the wax crystallization retardation eiect of the remainder will not prevent substantially complete wax precipitation on further chilling, sub-chilling the solution to precipitate the wax and separating the wax from' the solution. 4

14. A process according to claim 7 in which the volatile solvent is a liqueiled normally gaseous hydrocarbon having a vapor pressure higher than that of butane and lower than that of ethane.

`15. A process according to claim 'l in which the volatile solvent consists chieily of liquid