US2041278A - Process for treating oils - Google Patents

Description

May 1.9, 1936. B. G. ALDRIDGE ET A1. 2,041,278

PROCESS 4FOR TREATING 'OILS Filed June l5, 1933 www WWN @@S@ .xbvh

INVENTORS lair' (7T /dr'z'qge g? Baszflopper ATTORNEY,

Patented May 19, 1936 vil 1 stares! raooass ron rann'rmo ons poration of California.

Application June 13, i933, serial No. 675,594

8 Claims.

The present invention relates to a method for separating, asphalt, or asphalt andwax from oil. More specifically it relates to a method for separating asphalt from oils containing asphalt or from oils containing both asphalt and wax where the asphalt is separated -in a plurality of stages and at dilerent temperature levels.

Processes are known to separate asphalt and wax from crude oils or topped crude oils containing the same by means of solvents to produce lubricating oil. 'In such processes, the asphalt and Wax are precipitated and separated in two stages of operation. In the iirst stage of the process, the asphalt and wax containing M oil is commingled with a liqueiied normally gaseous hydrocarbon solvent, such as liquid propane, under pressure suilcient to maintain the propane in a liquid state. This permits the asphaltn to precipitate from the solution of oil and propane and settle to the bottom of the decanter. The oil solvent solution is then separated from the precipitated asphalt .and is thenchilled by evaporating a portion of the propane under reduced pressure, This causes the wax to precipitate from solution. The wax is then sepa' rated and iinally the propane is removed from the remaining oil solvent solution to produce a lubricating oil which is substantially free from f asphalt and wax.

30 We prefer to carry out our invention by means of such hydrocarbons as are normally vaporous .at ordinary temperature and pressure. Such hydrocarbons include methane, ethane, propane, butane, isobutane and mixtures thereof. These volatile solvents may be obtained by liqueiaction of casinghead gasoline by the so-called stabilization method now conventional in the natural gasoline industry. They are the overhead -obtained. They are liquefied by compression and cooled in the conventional manner and are drawn oi into pressure chambers where they are maintained in alliquid state until used. typical analysis of such a fraction is 6.72% ethane, 72.20% propane, 19.91% isobutane and 1.17% normal butane. Such a fraction may be maintained in a liquid state at a pressure of 125 lbs. per sq. in., and a temperature of about 75 F. This composition is merely exemplary and as will be understood' by those skilled in the art, the composition may vary within wide limits. However, `it will be observed that the predominating` member in this mixture is propane.

In the foregoing process, We have observed thatvthe lubricating oil produced is an oil substantially free from wax due to its precipitation lthey contain wax.

by chilling and subsequent separation from the oil solvent solution. This oil is also a superior grade of lubricating oil due to the fact that it has a low Conradson carbon value. This is attributed to the fact that the chilling of the oil to precipitate wax also precipitates further quany titles of asphaltic material, such as heavy viscous oil fractions `which will not precipitate from the oil and solvent at the atmospheric temperatures of about 70 F. to 80 F. usually employed for 10 asphalt precipitation, except by chilling to such low temperatures as are necessitated in thedewaxing stage. In other words, chilling of the oil to precipitate wax will also effect precipitation of the heavy viscous oil fractions which, when separated from the oil, result in the production of lubricating oil of low Conradson carbon value. It isour belief that the presence of such heavy viscous oil fractions -are largely responsible for high Conradson carbon values of lubricating oil.

Where the treatment with solvents to separate asphalt is eected on asphaltic oils at atmospheric temperature, the heavy viscous oll fractions will not precipitate fromsolution and unless the solution is chilled, such fractions will not precipitate and, therefore, cannot be separated. t will be observed that substantially all asphaltic oils contain the heavy viscous oil fractions responsible for vhigh Conradson carbon values of lubricating oils, irrespective of whether All asphaltic oils contain more or less wax; some contain large quantities of wax, while others are substantially free but nevertheless contain a small quantity. In the further discussion of our invention, we have indicated such California asphaltic oils which are substantiallyfree from wax and such others as contain large quantities of wax. The present invention is related to the treatment of both 4o types of asphaltic oils.

The foregoing process relating to the treatment of oils containing asphalt and wax wherein the asphalt is separated in one stage at atmospheric temperatur'eand the Wax is separated in the sec- 4,5 ond stage ata low temperature, is subjected to the serious disadvantage of operation in that during the chilling operation to precipitate wax, the unseparated asphaltic material of the rst stage is also precipitated and will be admixed with the wax to form a dark, sticky waxy material which settles to the bottom of the chilling column and obstructs withdrawal of the solution of the oil, propane and precipitated material from the bottom thereof when it is desired to pass the mixture to a wax settler, centrifuge or other wax separating equipment. In order to permit withdrawalof the mixture, it is first necessary to free the withdrawal line and the bottom of the chilling column of this sticky material. Furthermore, the wax recovered, as stated above, comprises adark, sticky material which must be subjected to expensive treatment before it can be converted into comercial petrolatum.

' -By the present invention, we aim to avoid the difllculties attending the prior method of operation. We have discovered that if the oil containing asphalt is commingled with a proper amount of solvent, such as propane, at approximately atmospheric temperature, a substantially hard asphalt will precipitate and settle rapidly from solution. If the supernatant solution is then decanted and transferred to another decanter maintained at substantially thesame temperature ofthe first decanter and therein given suilicient settling time, further quantities of asphaltic material will settle to the bottom thereof. This asphaltic material will be somewhat softer. Then if the loil solvent solution is decanted and transferred to still another decanter maintained at a lower temperature further quantities of asphaltic material will precipitate and settle from solution. 'Ihis asphaltic material will `comprise a light asphalt. It is more like a heavy residuum or road oil but nevertheless is an asphalt in characteristics. This fraction may be termed a heavy viscous oil. It will be observed that by the term asphalt we intend to include such asphaltic and non-waxy stages or decanters operated at successively lower temperatures asistated aforesaid. If substantially the entire amount of asphalt contained in the -oil is precipitated in one stage at a low temperature, that is, at a temperature sufcient to precipitate the hard asphalt as well as the soft or pseudo asphalt, the process will be accompanied with the disadvantage that the asphalt settled at th bottom of the decanter will comprise a solid asphalt which cannot be satisfactorily removed from the decanter.. l

The temperatures to be maintained in the lower ltemperature asphalt precipitator or decanter will depend upon the composition of the oil entering the process. We prefer to recover the asphaltic material in any of these decanters as a fraction substantially free from wax. If the original oil is substantially free fromvwax, temperatures emplayed may be as low as desired. In such cases,

the temperature may be reduced to as low as F. or lower to precipitate the secondary asphalt.

However, if the original oil also contains wax, we prefer to chill the oil to temperatures not substantially below the cloud point of wax so that asphaltic fractions precipitating and settling at the bottom of the decanter will be substantially free of wax. The temperature of any asphalt precipitation, therefore, should not be substantially below 30 to 40 F. Lower temperatures may be employed at this stage if contamination of the asphalt with some wax is not disadvantageous to the uses to which the asphalt is to be placed. These temperatures will be suflicient to remove substantially all of the deleterious asphaltic material from the oil so that the second wax precipitation stage will not be materially impaired by the presence of the asphaltic materials in the oil. The wax recovered will also be free from asphaltic material so that it may be easily treated for the production of commercial petrolatum in accordance with methods now conventional and as known by those skilled in the art.

In order to precipitate wax from the substantially asphalt free solution of oil and propane or other volatile solvents employed, we prefer to chill the solution by vaporizing a portion of the solvent under reduced pressure. The reduction of temperature in the asphalt precipitators may likewise be accomplished by reduction of pressure and vaporization of solvent.

In a preferred employment of the invention, it is desirable that suflicient propane is present in the wax precipitating 'chiller so Vthat subsequent to the vaporization a sufficient quantity of propane will remain in the oil to provide for adequate settling of the precipitated wax from the solution of oil and propane. During wax settling, it is desirable to maintain a ratio of substantially or in excess of 4 volumes of propane to one volume of the oil. A volumetric ratio of 4 to 1 is adequate for good settling of the precipitated wax. If sufficient propane is not present during chilling, make up propane may be introduced so that the final volumetric ratio of propane to oil will not be substantially below 4 to l. The makeup propane may be introduced into the solution of oil and propane prior to any chilling by vaporization of propane or the makeup propane may be gradually introduced into the chilling column and at such rate as to maintain a constant ratio of 4 to 1 in the chilling column.

From the above discussion it will be perceived that it is one of the objects of our invention to asphalt in ya plurality of stages maintained at lower temperature levels. However, the temperature in any of the asphalt precipitating stages is not maintained below the temperature where wax will precipitate from solution and settle with the precipitated asphalt.

A further object of our invention resides in commingling ,an asphalt Iand wax containing oil wltha liquefied normally gaseous solvent under pressure sufficient to maintain the solvent in the liquid state and at an atmospheric temperature in the neighborhood of about 70 F. to 80 F. to thus precipitate asphalt from'solution, in separating the precipitated asphalt in a plurality of stagesy maintained at approximately the aforementioned atmospheric temperature, in then reducing the temperature of the oil solvent solution 'in a subsequent stage to approximately 35 F. to

45 F. by evaporating a portion of the solvent under reduced pressure to precipitate further quantities of asphalt from the solution of `oil'and solvent, in then separating the later precipitated asphalt in one or more stages maintained at the reduced temperature, in then chilling the oil and solvent to precipitate wax by evaporating a portion of the solvent under reduced pressure, in then separating the precipitated wax from the oil and in then separating the solventv from the oil.

Another object of our invention resides in settling the precipitated wax in the presence of a suicient quantity of solvent to give good settling;`this amount comprising not less than approximately 4 parts of solvent to one part of the oil. .Y It is another object of the invention to maintain a volumetric ratio of solvent to oil during chilling to precipitate asphalt and/or wax of not less than approximately 4 to 1, this being accomplished, when necessary, by the introduction of solvent into the chilling column during the evaporation of the solvent to obtain the chilling eiect.

Other objects and advantages of` our invention will be apparent from the following description of our invention taken from the drawing which refers to a schematic arrangement df apparatus for carrying out our invention.

Referring to the drawing, an asphalt and wax containing oil and preferably, a topped crude, is taken from tank l and is drawn into line 2 by pump@ where it meets a liquefied normally gas ecus hydrocarbon solvent such as liquid propane taken from storage tank t via line 5 and pump 6 which forces the liquid propane through valve 'i into line 2. The amount of propane introduced into line 2 will depend upon the character of the oil and the temperatures desired in the subsequent chilling columns. The mixture of liquid propane and oil containing asphalt and wax is passed through turbulence or mixing coil 8 into the rst chiller 9 where the temperature of the mixture is reduced to approximately atmospheric temperature, that is, approximately 80 F., by evaporating a portion of the liquid propane. The vaporized propane passes into line il) controlled by a back pressure controller il into line lila., to the suction of compressor i4 and is then sent into line i5 and then through cooler i6 where it ris liqueiied and is then passed through line il into propane storage tank Il. A pressure of approximately 175 lbs. per square inch is maintained in chiller 9. The amount of propane introduced into the oil will also depend upon whether it is desired to'remove the asphalt at the bottom of the decanters 23 and 46 as a slurry of asphalt and propane, i. e. as a mixture of substantially pure bitumen 'or' hard asphalt and propane or as a liquid fraction of asphalt conf taining propane and some oil. If it is desired to separate the asphalt invdecanters 23 Aor 46 as a liquid fraction, the volumetric ratio of propane to oil passing into these-decanters will be within a range of 0.66 to 1 depending upon the character of the oil and the degree to which it is topped, Higher volumetric ratios will precipitate the asphalt as a slurry of substantially pure bitumen and propane, particularly in the iirst decanter 23. In the chiller 9, the admixture of the propane with the oil will effect precipitation of the asphalt from solution but due to the turbulent action in the chiller by reason of the ebullition of the propane and due also to the fact that sufcient settling time is not provided inthe chiller, the precipitated asphalt is not permitted to separate or stratlfy from the solution of oil and propane.

The mixture of propane and oil containing wax heavy or hard asphalt to settle or stratii'y from solution. If the volumetric ratio of propane to oil entering the decanter 23 is suiicient to precipitate a substantially pure bitumen, this asphaltic fraction will settle rapidly to thebottom of the decanter. However, if the volumetric ratio is low, the material settling to the bottom of the decanter will comprise a liquid asphalt, that is, an asphalt containing a substantial amount of oil to render the substantially pure bitumens in the oil liquid. 4Of course, a certain amountof propane will also settle with the asphaltic iraction. The material settling at the bottom of the decanter 23 is withdrawn via line 24 controlled by valve 25 and is pumped by pump 26 into line 21 through heater 28 where it is heated to a sumciently high temperature to melt the asphalt and vaporizeresidual propane. The heated mixture is then passed through line 29 and flashed through pressure reduction valve 30 into evaporator 3l which operates at a lower pressure: Superheatedsteam is introduced into the evaporator through perforated pipe 32 to supply additional heat, and

propane from separator 36 is sent through line 3l controlledby valve 38 into line 39a to vacuum pump 39 which operates at approximately 29 inches of mercury and then passes to compressor l0 via line lilla which operates at approximately atmospheric to 30 lbs. per square inch. The partially compressed propane is then passed into line #lla to compressor il which operates at a pressure of approximately 30 to 60 lbs. per square inch and then into line Ma to compressor M which operates under a pressure of 60 to 200 lbs. per square inch. The propane under the high pressure is then sent into cooler i6 via line l5 where 'it is liqueed andY is passed into propane storage cipitated but unstratiiied or unsettled asphaltic material to settle from the solution of oil containing wax and propane.` The characteristics of the asphaltic material settling in the bottom of the decanter 46 will depend largely upon the volumetric ratio of propane to oil entering the decanter 23. If the volumetric ratio is suiiiciently high to separate asphalt as a substantially pure bitumen, a lighter asphalt will settle in decanter 46 due to the fact that substantially all of the pure bitumen will be removed from the solution entering the second decanter. However, if the volumetric ratio is low, that is, a substantially liquid asphalt is separated in decanter 23, a portion of the harder asphalt will remain in the oil solvent solution and will be decanted into the decanter 46. 'I'he asphaltic material settling in dectanter 46 will then have substantially the same characteristics as the asphaltic material removed from decanter 23. A

The asphaltic material settling in decanter 46 withdrawn from the bottom via line 41 controlled'by valve 48 and is pumped by pump 49 into tank 50. This asphaltic material may be depropanized in accordance with the method outlined for the depropanization and treatment of the asphaltic material removed from decanter 23. This asphaltic material may be treated separately or, if desired, may be run into line 24 and treated together with the material separated from decanter 23. II desired, the depropanizing system including heater 28 and evaporator 3| may be operated alternately, first with the material removed from decanter 23 and then with the material separated in decanter 46 or separate similar depropanizing systems may be provided. The

recovered asphalts may then be 'stored separately or may be oommingled in any desirable proportion to produce asphalt of desired characteristics.

The temperature maintained in decanters 23 and 46 will approximate that of chiller 9, i. e., approximately v80 F. However, we desire to maintain a higher pressure in these -decanters to prevent boiling of the mass and to give good settling. This pressure will comprise approximately 200 lbs. per sq. in. and is maintained by pump 22 and back pressure controller 52 situated on line t The overow from decanter 46 comprising a solution of propane, oil containing wax and unprecipitated light asphalt, malthas or heavy viscous oil fractions are withdrawn from the decanter and passed via line 5| and back pressure regulator 52 into a second chiller 55 where the temperature is dropped to approximately 20 F. to 70 F., i. e. to a temperature below that maintained in the previous chiller and decanters, by vaporization of propane in order to precipitate the light asphaltic material or heavy viscous oil fractions heretofore mentioned. The pressure to be maintained in chiller 55 will approximate from 50 to 150 lbs. per sq. in. and this pressure is controlled by back pressure controller 51 on lineq56. The vaporized propane issues from the chiller and passes via line 56 and controller 5l to the suction of compressor 4| via line 4|a where its pressure is raised to 30 to 60 lbs. per sq. in. and then into the high pressure compressor I4 via line |4a, cooler I6 via line I5 and into propane storage tank 4 via line |1. The temperature to be maintained lin chiller 55 will depend largely upon the character of the topped residuum enterin'g the process. If the residuum or topped crude is substantially free from wax, such as residuums obtained from such California crude oils as McKittrick, Poso Creek, Coalinga, Summerland and Sunset, the temperature may be reduced considerably, i. e. from 40 F. to 40 F. by reduction of the pressure in 55 to the proper low pressures and the precipitated material will thus be substantially free from wax. However, if the process` is carried` on residuums obtained from crude oils\` containing wax as Well a s yasphalt such as the California crude oils obtained from Montebello, Kettleman Hills, Santa Fe Springs, Elwood, Torrance and4 Santa Barbara, we prefer to reduce the temperature in the chiller 55 to a temperature not Isubstantially below the cloud point, i. e. the temperature at which wax will precipitate from solution, in order that the heavy viscous oil fractions or secondary asphalt will not be contaminated with wax. 'I'his temperature will approximate from' 30 F. to40 F. The chilled mixture is withdrawn from the bottom of the chiller via line 58 controlled by valve 59 and is pumped by' pump 60 into asphalt precipitator or decanter 6| where sufllcient settling time is provided for the precipitated secondary asphalt to settle from solution. If desired, a plurality of such settlers may be provided and operated alternately so that suillcient settling time can be provided and the process operated continuously.

'I'he asphaltic materials settling to the bottom of the decanter 6| (is withdrawn via62 controlled by valve 63 and is pumped'by pump 64 into tank 65. This asphaltic material may also be separately treated for removal of residual propane infaccordance with the method outlined for the treatment of the asphaltic material removed from decanter 23; or it may be run into line 24 and treated with the asphaltic material removed from decanter 23 and/or the material run in from decanter 46. If desired, this asphaltic material may be commingled with the material removed from decanter 46 Aand treated in admixture separate from the material removed from decanter 23. The character of this asphaltic material will depend largely upon the character of the material separated in the previous decanters. If a substantially pure bitumen is removed from decanter 23, this asphaltic material will approximate the characteristics of the material removed from decanter 46. However, if substantially liquid asphalts are separated from decanters 23 and 46, this asphaltic material will be more, like theasphalts separated previously. It is to be observed that the characteristics of the materials separated in the various decanters will depend .largely upon various factorssuch as the volumetric ratios of propane to oil and character of the residuum entering the process. The pressure to be maintained in decanter 6| will be slightly higher than that of the chilling column 55 or about 25 lbs. per sq. in. above that maintained in the chiller 55. This is for the reason that we desire to prevent substantial ebullition of the mass and to thus provide for good settling. The pressure in decanter 6| is maintained by pump 60 and back pressure controller 61 on line 66.

The solutionl of propane and oil containing wax but substantially free from asphalt and heavy viscous oil fractions is withdrawn from the decanter Via line 66 and controller 6l. If the original residuum was substantially free from Wax, the solution may be passed via line 66 and, valve 69 to acid treatment and neutralization which may be accomplished in the presence of the propane. Valves 1| and 13 on lines 10 and 12, respectively, will be closed.' However, if the original stock contains wax, we prefer to separate the wax prior to any chemical treatment. If desired, however, the oil may be chemically treated and then dewaxed. In our preferred embodiment, valves 69 on line 68 will be closed and valve 1| on line 10 will be opened and the solution cf oil and propane is passed via line and valve 1| into the low temperature chiller 15 by means of spray head 14. In chiller 15, suicient propane vaporizes to reduce the temperature of the remaining material to a suiliciently low temperature which causes wax to precipitate from solution. 'I'his is accomplished by maintaining a low pressure in the chiller by proper operation of the the chilling column 15 with oil and solvent to be dewaxed under sucient pressure to prevent substantial vaporization of propane and then gradually chill the mixture. This is accomplished by controlling the pressure in the chiller by proper operation of the prezsure controller '|1 on line 1B so that the pressure will be gradually reduced and thus the temperature will also be gradually lowered for` example, at the rate of 2 or 3 degrees F. per minute, by the vaporization of the propane. 'I'he vaporized propane from the chiller 15 passes via line 16 and pressure controller 11 to the suction of compressor 40 where its pressure is raised and is then sent to compresor 4| via line 4|a and then to compressor |4 va line 4a and into line |5, cooler "I5, line `I1 and propane storage tank 4. In order to provide for sufficient chilling time and to make the process continuous, if necessary, a plurality of chillers 15 may be employed, operated alternately. If the solution of oil and propane entering chiller 15 does not contain sufcient propane to effect the desired chilling effect, further quantities of liquid propane may be introduced via line 12 and valve 13 which is connected to line 10.

In the preferred operation, we desire to maintain a volumetric ratio of approximately more .than four parts of propane to one part of oil in the chiller '|5, that is,the oil and propane entering the chiller will have a volumetric ratio of four to one and as the propane is vaporized, further quantities of liquid propane are introduced to make up for that vaporized and to maintain the volumetric ratio of 4 to l. When the temperature in the chiller has been reduced to approximately 40 F., the mixture of propane and oil containing precipitated wax is withdrawnirom the bottom via line l0 and is pumped by pump '|9 through valve 00 into the vapor tight wax separator or settler 9|. ln batch operation, merely one of such settlers will suice but to make the process continuous, a plurality of such settlers may be provided and Aoperated alternately in order to provide for suiiicient settling periods. In order to prevent ebullition in the wax separator during the wax settling operation, pressure is imposed upon the solution of oil. yThis is accomplished by maintaining pressure within the separator by pump 19. As the ychilled mass in the wax separator remains in a non-ebullient state, the wax settles out and is collected by.

vanes 02, operated by pulley 03, connected to a suitable source of power not shown.

The wax free oil dissolved in propane is withdrawn from the. separator 0| and passed into line 05 to pump 86 which forces the solution into line 0l. The solution may then be sent via line 00, controlled by valve 89 to acid and alkali treatf ment, where such chemical treatment may be effected in the presence of the propane contained in `the oil. The treated oil may then be depropanized in accordance with the method hereinafter described. However, if it is desired to depropanize the solution of. oil and propane prior to any chemical treatment, valve 89 on line B9 is closed and valve 9| on line 90 is opened and the cold solution of oil and propane is passed through heat exchanger 92. and through heater 93 Where its temperature is raised to approximately 2509 F. and its pressure toapproximately 200 lbs. per square inch. The heated mixture is thenpassed to the lowermost section 94 of the three compartment evaporator 95 which is provided with baffles 96. 'Ihe vaporized propane passing countercurrent to the oil over baille plates 96 is withdrawn via line 91, controlled by valve 98, cooled in heat exchanger 92. and then introduced into line 99 which connects with line I5. The propane vaporized in the lowermost compartment 94 will be under sufficiently high pressure when passed into line |5 'that subsequent cooling will liquefy the propane vapors. This cooling is accomplished in cooler I6 and then the liquefied propane is passed via line I1 into propane storage tank 4. The bottoms in section 94 of evaporator.

propane is withdrawn via line ||0, controlled byvalve and passed into line ||2 to compressors 00, 4| and I4 to cooler I6 and then into propane storage tank 4. The oil at the bottom of section |05 freed from further quantities of propane but retaining `a small amount thereof is withdrawn from the bottom of the compartment via line |4 through valve 5 into the uppermost section ||6 of evaporator 95 in which the propane is vaporized by the aid of vacuum pump |20. A temperature of approximately 248 F. and a vacuum of Yapproximately 29 inches of mercury is maintained in section ||0 of evaporator 95. rIfhe vaporized propane is withdrawn from the upper chamber via line controlled by valve ||8 and is sent into line 39a to the suction of vacuum pump 99 and then to the succeeding compressors 40, 0| and |4 to cooler |6 and storage tank 4. The de-propanized oil is withdrawn from the bottom of the compartmerit'llb` via line |2| controlled by valve |22 and'is pumped by pump |23 to oil storage tank |24.

The wax slurry collecting at the bottom of` the Wax settler 9| is withdrawn via line |30 and is pumped by pump |9| through valve |32 to heater |33 where its temperature is raised to approximately 300 F. and its pressure to approximately 200 lbs. per square inch and is then introduced into the lowermost chamber |94V of -evaporator |35 wherel a portion of the propane intermediate section |40 of evaporator |35 'which l is maintained at a temperature oi approximately 290 F. and at atmospheric pressure.

This willl release further quantities of propane inches of mercury and at a temperature oi.' approximately 290 F. This will cause the wax to be substantially freed from propane. The vaporized propane is withdrawn via line |46 con- (trolled by valve |41 and passed into line 39a together with the propane vaporized in section ||6 of evaporator 95. The depropanized wax is withdrawn from' the bottom of chamber |45 via line |48 controlled by valve |49 and pumped by pump |50 into the wax storage tank ISI.

It is to be understood that the above is merely illustrative of preferred embodiments of our invention of which many variations may be. made by those skilled in the art without departing iled'normally gaseous hydrocarbon solvent contains a substantial proportion of propane.

3. A process for separating asphalt from oils containing the same which comprises mixing said oil with a liquefied normally gaseous hydrocarbon solvent under superatmospheric pressure to precipitate asphalt, separating relatively hard precipitated asphalt from the remaining relatively soft asphalt, oil' and solvent in one stage and separating the relatively soft precipitated asphalt from the oil and solvent in a second stage, said stages being maintained at substantially the same non-elevated and non-dewaxing temperatures and at substantially the same superatmospheric pressure.

4. A process for separating asphalt from oils containing the same which comprises mixing said oil with a liquefied normally gaseous hydrocarbon solvent to precipitate asphalt, separating relatively hard precipitated asphalt from the remaining relatively soft asphalt, oil and solvent in one stage, separating the relatively soft precipitated asphalt from the oil and solvent in a second stage, said stages being maintained at substantially the same non-elevated and nondewaxing temperatures, subsequently chilling the oil solvent solution to precipitate further quantities of asphaltic material, said chilling being insufiicient to precipitate substantial quantities of wax and separating said further quantities of asphaltic material from the oil solvent solution.

5. A process'for separating asphalt from oils containing the same which comprises mixing said oil with a liquefied normally gaseous hydrocarbon solvent to precipitate asphalt, separating the relatively hard precipitated asphalt from the remaining relatively soft asphalt, oil and solvent in one stage, separating the relatively soft precipitated asphalt from the oil and solvent in a second stage, said stages being maintained at substantially the same non-elevated and nondewaxing temperatures, subsequently chilling the oil solvent solution to precipitate further quantities of asphaltic material, said chilling being insufficient to precipitate substantial quantities of wax, separating said further quantities of asphaltic material from the oil solvent solution, chilling the oil solvent solution to a dewaxing temperature to precipitate .wax and separating said precipitated wax from the oil and solvent.

6. A process as in claim 5 in which said chilling to separate further quantities of asphaltic material is accomplished by vaporizing a portion of the said solvent.

J7. A process for separating asphalt from oils containing the same which comprises mixing said oil with a liquefied normally gaseous hydrocarbon solvent under superatmospheric pressure and at substantially atmospheric temperature to precipitate asphalt, separating said precipitated asphalt from the oil solvent solution in a plurality of stages maintained at substantially said. atmospheric temperature while under superatmospheric pressure, reducing the pressure on the oil solvent solution to vaporize a portion of the ,solvent and to chill the oil to precipitate further quantities of asphaltic material, said chilling temperature being insufficient to precipitate substantial quantities of wax and separating said further quantities of precipitated asphalt from the oil solvent solution.

8. A process for separating asphalt and wai:

-:from oils containing the same which comprises mixing said oil with liquid propane under pres sure sufficient to maintain the propane liquid and at substantially atmospheric temperature to precipitate asphalt from solution, separating said precipitated asphalt in a plurality of stages maintained at substantially saicl atmospheric temperature, reducing the pressure on the oil propane solution to vaporize a portion of the propane and to chill the oil to precipitate further quantities of asphaltic material but to retain the wax in solution, separating said further quantities of precipitated asphalt from the solution of oil, propane and wax, reducing the pressure on the solution to vaporize further quantities of propane and to chill the oil to a dewaxing temperature to precipitate wax and separating said precipitated wax from the oil and propane.

BLAIR G. ALDRIDGE.

BASIL HOPPER.

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