US1988713A - Fractionation of mineral oil - Google Patents

Description

U. B. BRAY 1,988,713

FRACTIONATION OF MINERAL OIL Filed Feb. 2s, 1952 2 sheets-sheet 1 Jan. 22, 1935.

u, B. BRAY 1,988,713

FRACTIONAT-ION OF MINERAL OIL Filed Feb. 23, 1932 2 Sheets-SheetvZ .En R tm. n mm Y um. m Qn Non. L.. .W O 8N SN www BN Y www mB n Y .c oww# .www SN Sww U low Il Y Q f www SN w. www lv* www www www n .3N 4 mmm u am D N: QT w3 EN S IY www www NbvN www u@ www Jan. 22, 1935 www@ Patented Jan. 22, 1935 UNITED STATES FRACTIONATION OF MINERAL OIL Ulric B. Bray, Los Angeles, Calif.. assigner to Umpn Oil Company of California, Los Angeles, Calif., a corporation of California.

Application February 23, 1932, Serial No. 594,606

13 Claims. (Cl. 196-13) This invention relates to a process for the fractionation of hydrocarbon mixtures. More specifically, it is concerned with a novel means of separating petroleum into lubricating oil fractions by the aid of solvents.

In general, crude petroleum consists of a mixture of hydrocarbons which vary physically and structurally over a wide range. Upon isolation at ordinary temperature and pressure the lightest members present in crude oil are gases; the intermediate members are liquids and the heaviest members present are substantially solids. Due to the progressive increase in boiling point with the increase in the molecular weight of the hydrocarbons present in crude oil fractional distillation aords one means of separating such a hydrocarbon mixture into its various components. Thus by ordinary distillation, crude oil may be separated into such products as light naphtha, gasoline, kerosene, gas oil and lubricating oil. Provided asphalt is present in the crude oil undergoing distillation this material is left in the still after the distillationis complete.

While ordinary distillation methods are satisfactory for the separation of the lightfractions, such as naphtha, gasoline, kerosene and gas oil from petroleum they possess certain objectionable features when employed to separate the heavier oil fractions present. The light fractions present in the crude oil distill oli without any difficulty but the heavier fractions, such asthe lubricating oils, are injured, more or less, by the high temperatures which must be maintained in the still to vaporize these components.

Among the properties which are exhibited by a superior lubricating oil are, a low viscosity temperature susceptibility, i. e., a minimum change in viscosity for a given change in temperature, a low oxidation value and a high degree of oiliness.

I have found that heavy oil distillates have a greater viscosity temperature susceptibility, i. e., their viscosity decreases more rapidly with increase of temperature, are more Asusceptible to oxidation and are less oily in character than oils produced from the same undistilled hydrocarbons by solvent fractionation. In distilling the heavy fractions overhead some change in molecular configuration appears to take place in the oil which is responsible for the deterioration irl 50 lubricating qualities. Just what the mechanism of this change may be is not thoroughly understood.

I have also found that crude oils which contain asphalt are more diicult to distill without impairing the lubricating qualities of the heavier hydrocarbons present than crude oils which do not contain asphalt. 'I'he presence of the asphalt in the crude oil during the distillation appears to catalyze those reactions which are responsible for the deterioration in the lubricating quality of `5 the heavier components.

In my application, Serial No. 466,189, led July '7, 1930, I have shown a novel method for the production of lubricating oil from oil containing asphalt wherein I am able to preserve the lubrieating qualities ofthe heavier oils present in the crude which are injured by ordinary distillation methods. The crude oil is distilled to remove the light constituents present, such as gasoline, kerosene, and gas oil and the light lubricating oil components. 'Ihe residue containing the asphalt and the heavier lubricating oil components is then extracted under pressure with liquid propane. 'I'he asphaltic material in the petroleum residue being insoluble in the liquid propane remains undissolved whereas the oils present form a solution withthe propane which is easily .separable from the undissolved asphalt by ordinary decantation methods. The oily constituents dissolved in the propane are recovered by allowing the propane to distill oil under reduced pressure. Oils prepared by this method have a low viscosity temperature susceptibility, i. e., their viscosity changes only moderately with increase o1' temperature, a low oxidation value as measured by the Sligh method of test and a high degree of oiliness which most overhead lubricants do not possess.

The asphalt which is obtained by the foregoing process is substantially free from oily hydrocarbons as these components are removed by the liquid propane. However, there are certain heavy hydrocarbons present which are substantially solid at ordinary temperature and which are insoluble in the propane but which can be recovered 40 therefrom by the use of solvents, such as liquid butane and liquid pentane.

Furthermore, by re-extracting the propane soluble portion of the oil with liquid ethane I am able to separate this fraction into an ethane soluble portion and an ethane insoluble portion. Thus it is apparent that the oil can be separated into fractions by first treating it with liquid ethane and thereafter successively subjecting the insoluble residue obtained to the solvent action of propane, butane and pentane, respectively.

By successively extracting oil under presssure with the light liquid hydrocarbon solvents in the order just mentioned, I am able to obtain oil fractions which progressively. increase in specic gravity and viscosity. The lightest oils present in the topped crude are soluble in the liquid ethane and the heaviest oils present are soluble in the liquid pentane. It is, of course, possible to obtain further fractions from the oil by employing still heavier hydrocarbon solvents but the yield in most instances is too low for consideration.

While propane is a valuable solvent for extracting lubricating oil fractions from petroleum residues I have found that superior oils may be produced from such residues by' extracting them with a light hydrocarbon solvent, such as ethane or a mixture of propane and ethane. I have discovered that lubricating oil fractions which have been produced from petroleum by extraction with ethane have a lower Conradson carbon value than oils which have been produced by extracting such oil with propane, butane, pentane or heavier hydrocarbon solvents. While the true value of the Conradson carbon test in judging lubricating oil is not well understood, yet it is thought to be in a certain degree a measure of carbon forming propensity of the oil. Pure ethane is an ideal solvent for the separation of lubricating oil having a low viscosity temperature susceptibility, a high flash point and a low Conradson value from petroleum residues. Its power to selectively separate the more valuable oil constituents from petroleum residues progressively decreases, however,

4when it is diluted with increasing amounts of the heavier hydrocarbons, such as propane, butane and pentane. Thus, when extracting petroleum residues for the production of superior lubricating oils it is desirable to use relatively pure ethane.

'I'hus it is apparent that the character of the extract obtained from the oil depends upon the composition of the hydrocarbon solvent employed. The lower the molecular weight of the solvent employed for the extraction the lower will be the Conradson carbon value, and the higher the flash for a given viscosity. Thus a solvent consisting substantially of ethane will yield oil fractions having a lower Conradson carbon value and a higher flash point than an oil fraction produced by a solvent consisting substantialy of liquid propane and having a higher molecular weight.

The light solvents which I propose to use in my process are obtained during the stabilization of natural gasoline. They are not pure hydrocarbons, i. e., they are not composed of individual hydrocarbons but consist of a mixture of hydrocarbon homologues in which one member preponderates in quantity. Thus when I speak of liquid ethane, I am referring to a light hydrocarbon liquid which is composed mainly of ethane and contains a small amount of hydrocarbons of higher molecular weight, such as propane and butane. When I refer to a hydrocarbon mixture consisting of propane and butane I mean a mixture in which these two hydrocarbons preponderate and which may contain small quantities of such hydrocarbons as ethane, pentane and hexane.

As an alternative method of carrying out my process I may first extract the oil with liquid pentane and thereafter successively re-extract the solvent soluble portion of the oil with butane, propane and then ethane to obtain oil fractions soluble in these respective solvents and fractions insoluble in these respective solvents.

In some instances I may find it desirable to obtain intermediate oil fractions between those oil fractions which are soluble in the pure hydrocarbon solvents. This is accomplished by using mixed solvents. For example, I may first extract the oil with liquid ethane, subject the ethane insoluble portion to a mixed solvent composed of ethane and propane, and then subject the residue insoluble in the mixed ethane-propane solvent to the solvent action of propane. By continuing the extraction in this manner upon the insoluble portion of the oil with successive solvents consisting of a mixture 'of .propane and butane, butane, a mixture of butane and pentane and pentane, I may obtain fractions from the oil which are soluble only in these respective solvents. Or the oil may first be extracted with pentane after which the solvent soluble portion may be successively subjected to the selective solvent action of a pentane butane mixture, propane, a propane ethane mixture and lastly ethane for the production of oil fractions soluble in these particular solvents.

The solvents which I have described so far to carry out my invention belong to the saturated paraffin series. I do not limit myself to the use of saturated hydrocarbon solvents, however, as hydrocarbon solvents belonging to the unsaturated series may also be employed successfully. Thus I may use hydrocarbon solvents belonging to the olefin series, such as ethylene, propylene, butylene and pentylene (amylene) in the same manner as I employ the solvents of the paraflin series to carry out my novel fractionation process.

While I have described the use of my novel method of fractionation in connection with topped crude oil, it may be employed for the separation of any mixture of hydrocarbons wherein there exists any selective solvent effect of the solvents described. Thus hydrogenated oil may be separated into fractions by my process by proceeding with the extraction according to the foregoing methods. Furthermore, my process is applicable to the fractionation of the oils present in coke oven tar, gas tar and heavy oil mixtures produced by destructive distillation or cracking operations.

It is, therefore, an object of my invention to fractionate hydrocarbon mixtures by the use of selective solvents.

It is a further object of my invention to successively extract a mixture of heavy hydrocarbons with light hydrocarbon solvents which are capable of selectively separating said heavy hydrocarbon mixture into fractions.

`It is a further object of my invention to successively extract topped petroleum with liquid ethane, liquid propane, liquid butane, liquid pentane and mixtures thereof, respectively.

It is still a further object of my invention to extract topped petroleum with liquid pentane, reextract the pentane soluble portion of the oil with butane, re-extract the butane soluble portion with propane, re-extract the propane soluble portion with ethane to separate said tapped petroleum into oil fractions.

It is another object of my invention to selectively separate oil by the use of hydrocarbon solvents of different molecular weights in a series of extraction by the different hydrocarbon solvents.

Figure 1 is a schematic arrangement of one form of apparatus which may be employed to carry out my process.

Figure 2 is another schematic arrangement of apparatus which may be employed to carry out my process.

Referring more particularly to Figure l, crude oil which has been distilled to remove the light constituents is withdrawn from tank 1 through line 2 and sent by means of line 4 into agitator 5 where it is mixed with liquid pentane coming from tank through valve 21, line 116, pump 22 and line 23.

The thoroughly mixed mass in agitator 5 passes by means of line 6 into settling chamber 7 where any undissolved asphalt present settles out and is removed through valve 8 and line 9.

The pentane solution of oil in settling chamber'7 is withdrawn through line 10 into pump 11 which forces it through line 12 into vaporizer 13 where by the aid of steam introduced through closed coil 24 the pentane present is vaporized and is removed through valve 14 and line 15 to compressor 16 which forces the pentane vapor through line 17 into condenser 18 where it is liquefied and passes by means of line 19 into pentane storage tank 20.

'I'he pentane free oil in vaporizer- 13 is Witndrawn through valve and passes by means of line 26 into pump 27 which forces it through line 28 into cooler 29 where the temperature of the oil is lowered to about 60-70 F. The cool oil passes from cooler 29 through line 30 into agitator 31 where it meets a stream of butane coming from tank 46 through line 47, valve 48, pump 49 and line 50. The thoroughly mixed oil and butane pass from agitator 31 through line 32 into settling chamber 33 where the heavy oil fractions which are insoluble in the butane settle out and are removed through valve 51, line 52 into storage tank 53. i

The butane solution of oil in settling chamber 33 is removed through line 34, valve 35 and line 36 into pump 37 which forces it through line 38 into vaporizer 39 where the butane present is vaporized by the aid of steam introduced into closed steam coil 54. 'Ihe butane vapors are removed from the vaporizer 39 through valve 40 and line 41 to compressor 42 which forces it through line 43 into condenser 44 where it is liquefied and passes by means of line 45 into butane storage tank 46.

The butane free oil in vaporizer 39 is removed through valve and line 56 to pump 57 which forces it through line 58 into cooler 59 where the temperature of the oil is lowered to about 60-70 F. The cooled oil passes from cooler 59 by means of line 60 into agitator 61 where it meets a stream of liquid propane coming from tank 78 through valve 79, line 80, pump 81 and line 82. 'I'he thoroughly mixed oil and propane pass from agitator 61 by means of line 62 into settling chamber 63 where the heavy oil fractions present, which are insoluble in the lquid propane, settle out and are removed via valve 64 and line 65 into storage tank 66. The propane solution of oil in settling chamber 63 is removed through valve 67 and line 68 into pump 69 which forces it through line 70 into vaporizer 71 where the propane is vaporized with the aid of steam introduced through closed steam coil 83. The propane vapor is withdrawn from vaporizer 71 through valve 72 and line 73 to compressor 74 which forces it through line 75 to condenser 76 where it is liqueed and passes by means of line 77 into propane storage tank 78.

The propane free oil in vaporizer 71 is removed through valve 84 and line 85 to pump 86 wh'ch forces it through line 87 into cooler 88 where the temperature of the oil is lowered to approximately 60-70 F. The cooled oil passes from cooler 88 through line 89 to agitator 90 where it meets a stream of liquid ethane coming from tank 107 through valve 108, line 109, pump 110 and line 111. The throughly mixed oil and ethane passes from agitator 90 through line 91 into settling chamber 92 where the ethane insoluble oil fraction settles out and is removed through valve 93, line 94 into storage tank 95.

The ethane solution of oil in settling chamber 92 lis removed through valve 96, and line 97 to pump 98 which forces it through line 99 into vaporizer 100 Where the ethane present is vaporized by aid of steam introduced through closed coil 112. The ethane vapors are removed from vaporizer 100 through valve 101 and line 102 to compressor 103 which forces it through line 104 to condenser 105 where it is liquefied and passes by means of line 106 ini-o ethane storage tank 107.

The ethane free oil in vaporizer 100 iswithdrawn through valve 113 and passes by means of line 114 into storage tank 115.

In some instances it may be found desirable to employ mixed solvents to fractionate the oil. For example, the raw oil in tank 1 of Figure 1 may be first treated with a mixture of pentane and butane in agitator 5 for the production of the solvent solution of extract in chamber 7. This -extract may then be freed Vfrom its solvent content and then treated with a mixture of butane and propane in agitator 31 for the production of a second extract and a solvent insoluble fraction. The solvent insoluble fraction may be removed by settling it out in settling chamber 33 and removing it to tank 53. The extract dissolved in the butane-ethane mixture may be freed from its solvent content in vaporizer 39 and then re-extracted in agitator 61 with an ethane-propane mixture to produce an oil fraction insoluble in the ethane-propane mixture and an oil fraction soluble in this solvent. The oil fraction insoluble in the ethane-propane mixture may be separated from the oilfraction soluble in the ethane-propane solvent by pumping the mixture into'settling chamber 63 where the heavier insoluble oil fraction settles to the bottom and is removed through valve 64 and line 65 to storage tank' 66. The oil fractions dissolved in the ethane-propane mixture may be recovered by passing the solvent solution of oil into vaporizer 71 where the ethane and propane are separated from the oil.

If desired the raw oil in tank 1 may be treated with relatively pure liquid hydrocarbon solvents and with mixed solvents. For example, the pentane extraction may be followed with an extraction with a mixed solvent composed of pentane and butane; the butane extraction may be followed with an extraction with butane and propane; and the propane extraction may be followed with an extraction with a mixed solvent composed of propane andv ethane. By using a combination of pure hydrocarbon solvents 'and mixed hydrocarbon solvents as has been explained immediately above, it is possible to increase the number of fractions into which the raw oil may be separated. The proportion of individual hydrocarbons blended together to form the mixe-:l

solvent will vary with the type of oil being fractionated and the particular type of fractions desired. Each oil to be fractionated must be treated with mixed solvents having compositions which will give the results desired. This can be found by experimentally treating the oil to determine what compositions give the best results.

Referring more particularly to Figure 2 heavy oil in tank 200 passes by means of line 201 to pump 202 which forces it through line 203 to agitator 204 where it meets a streaml of ethane coming from tank 219 through line 220, valve 221, pump 223 and line 224. The heavy oil and ethane are thoroughly mixed in agitator 204 after which the mixture passes through line 205 into settling chamber 206 where the undissolved residue settles out of the oil fraction dissolved in liquid ethane. The fraction of oil dissolved in liquid ethane is removed from settling chamber 206 through valve 207 and line 208 and is sent by means of pump 209 through line 210 into vaporizer 211 where the ethane is vaporized by aid of steam introduced through closed coil 225. The ethane vapor is removed from vaporizer 211 through line 212, valve 213 and line 214 into compressor 215 which forces it through line 216 to condenser 217 where it is liquefied and passes by means of line 218 into ethane storage tank 219. The ethane free oil in vaporizer 211 is removed through valve 226 and line 227 into storage tank 228.

The etha-ne insoluble portion of the heavyoil in settling chamber 206 is removed through valve 229 and pump 231 into line 233 Where it meets a stream of liquid propane coming from tank 253 through valve 254, line 255, pump 256 and line 257. The residue and propane then pass by means of line 233 into agitator 234 Where thorough mixing of the residue and propane takes place. The mixture in agitator 234 then passes into settling chamber 236 Where the undissolved portion settles out. The oil fraction dissolved in liquid propane is removed from settling chamber 236 through valve 237 and line 238 into pump 239 which forces it through line 240 into vaporizer 241 where the propane present is vaporized by the aid of steam introduced through closed coil 242. The vaporized propane passes from vaporizer 241 through line 246, valve 247 and line 248 into compressor 249 which forces it through line 250 into condenser 251 where it is liquefied and passes by means of line 252 into propane storage 253. The propane free oil in vaporizer 241 is removed through valve 244 and line 243 into storage tank 245.

The propane insoluble residue in settling chamber 236 is removed through valve 258, line 259 and passes through pump 260 into line 261 Where it meets a stream of liquid butane coming from tank 264 through valve 265, line 266, pump 267 and line 268. The butane and residue pass from line 261 into agitator 262, where they are thoroughly mixed. The mixture in agitator 262 then 'passes into settling chamber 263 Where the insoluble residue settles out of the oil dissolved in liquid butane. The butane solution of oil is removed from settling chamber 263 through valve 269 and line 270 into pump 271 which forces it through line 272 into vaporizer 273 Where the butane present is vaporized by aid of steam introduced into closed steam coil 281. The vaporized propane is removed from vaporizer 273 through line 274, valve 275 and line 276 into compressor 277 which forces it through line 278 into condenser 279 where it is liquefied and passes by means of line 280 into butane storage tank 264. The butane free oil in vaporizer 273 is removed through valve 282 and line 283 into storage tank 284.

The butane insoluble residue in settling chamber 263 is removed through valve 285 and forced by pump 286 into line 287 where it is mixed With liquid pentane coming from tank 304 through line 305, valve 206, pump 307 and line 308. The

pentane and residue pass from line 287 into agitator 288 Where they are thoroughly mixed. The mixture in agitator 288 passes by means of line 289 into settling chamber 290 where the insoluble asphalt settles out and is removed through Valve 291 and line 292. The oil fractions dissolved in liquid pentane are removed from settling chamber 290 through valve 293 and line 294 to pump 295 which forces it through line 296 into vaporizer 297 where the pentane is vaporized by aid of steam introduced through closed steam coil 309. The pentane vapor is removed from vaporizer 297 through line 298 and valve 299 to compressor 300 which forces it through line 301 to condenser 302 where it is liquefied and passes by means of line 303 to pentane storage tank 304.

The pentane free oil in vaporizer 297 is removed through valve 310 and passes by means of line 311 into storage tank 312.

Thus it is obvious from the foregoing descriptions that the successive extractions are made at different pressures. The extractions made upon the crude stock by the process described in Figure 1 are at successive increasing pressures, whereas the extractions made upon the crude stock in Figure 2 are at successive decreasing pressures.

The above is not to be taken as limiting, but as illustrative of the preferred method of carrying out my invention as many variations may be made by those skilled in the art.

I claim:

1. A process for the separation of hydrocarbon oil into fractions which comprises commingling said oil with a hydrocarbon solvent to form an extract fraction dissolved in said solvent and a fraction insoluble in said solvent, separating said fractions and then commingling o ne of said fractions with another hydrocarbon solvent of different molecular weight than said first mentioned solvent to form a fraction dis. solved in said second mentioned solvent and a fraction insoluble in said second mentioned solvent and separating said fractions.

2. A process as claimed in claim 1 in which the solvents comprise hydrocarbon mixtures.

3. A process for the separation of hydrocarbon oil into fractions which comprises commingling said oil with a light hydrocarbon solvent to form an extract fraction dissolved in said solvent and a fraction insoluble in said solvent, separating said fractions, commingling the extract fraction with a second hydrocarbon solvent having a lower molecular weight than said first solvent to form an extract fraction dissolved in said second solvent and a fraction insoluble in said second solvent and separating said fractions formed by the extraction with said second solvent.

4. A process for the separation of hydrocarbon oil into fractions which comprises commingling said oil with a hydrocarbon solvent of low molecular weight to form an extract fraction dissolved in said solvent and a fraction insoluble in said solvent, separating said fractions, commingling said insoluble fraction with a second hydrocarbon solvent having a higher molecular Weight than said first solvent to form an extract fraction dissolved in said second solvent and a fraction insoluble in said second solvent and separating said fractions formed by extraction with said second solvent.

5. A process for the separation of hydrocarbon oil into fractions which comprises commingling said oil with a liquefied normally gaseous hydrocarbon solvent to form a fraction dissolved in said solvent and a fraction insoluble in said solvent, separating said fractions and then commingling one of said fractions with another liquefied normally gaseous hydrocarbon solvent of different molecular weight than said first mentioned solvent to form a fraction dissolved in said second mentioned solvent and a fraction insoluble in said second mentioned solvent, separating said fractions and recovering the oil from said fractions.

6. A process for the separation of hydrocarbon oil into fractions which comprises commingling said oil with a liquefied normally gaseous hydrocarbon solvent to form an extract fr action dissolved in said solvent and a fraction insoluble in said solvent, separating said fractions, separating the solvent from said extract fraction, commingling said extract fraction with a second liquefied normally gaseous hydrocarbon solvent having a lower molecular weight than said first mentioned solvent, to form an extract fraction dissolved in said second solvent and a fraction insoluble in said second solvent, separating said fractions formed by extracting with second solvent and recovering the oil therefrom.

7. A process for the separation of hydrocarbon oil into fractions which comprises commingling said oil with a liqueed normally gaseous hydrocarbon to form an extract fraction dissolved in said solvent and a fraction insoluble in said solvent, separating said fractions, commingling saidl Aby extracting with said second solvent and recovering the oil therefrom.

8. A process for the separation of asphaltic oil intoA fractions which comprises vcommingling said oil with a hydrocarbon solvent to form a fraction dissolved in said solvent and an asphaltic fraction insoluble in said solvent, separating said fractions and then commingling one of said fractions with another hydrocarbon solvent having a molecular weight different from said rst mentioned solvent to form a fraction dissolved in said second mentioned solvent and an asphaltic fraction insoluble in said, second mentioned solvent, separating said fractions and recovering the oil from said fractions.

9. A process for the separation of asphaltic oil into fractions which comprises commingling said oil with a light liquid hydrocarbon solvent to form an' extract fraction dissolved in said solvent and an asphaltic fraction insoluble in said solvent, separating said fractions, separating the solvent from said extract fraction, commingling said extract fraction with a second liquid hydrocarbon solvent having a lower molecular weight than said first mentioned solvent, to form an extract fraction dissolved in said'second solvent and an asphaltic fraction insoluble in said second solvent, separating said fractions and recovering the oil from said fractions.

10. A process for the separation of asphaltic oil into fractions which comprises commingling said oil with a light liquid hydrocarbon solvent to form an extract fraction dissolved in said solvent and an asphaltic fraction insoluble in said solvent,l separating said fractions, separating the solvent from said extract fraction, commingling said extract fraction with a second liquid hydro carbon solventv having a lower molecular weight than said first mentioned solvent to form an extract fraction dissolvedin said second solvent and an asphaltic fraction insoluble in said second solvent, separating said fractions formed by extracting with said second solvent and recovering the oil therefrom. I

11. A process for the separation of asphaltic oil into fractions which comprises commingling said oil with a light liquid hydrocarbon solvent to form an extract fraction dissolved in said solvent and an asphaltic fraction insoluble in said solvent, separating said fractions, commingling said fraction insoluble in said solvent with a second liquid hydrocarbon solvent having a higher molecular Weight than said first mentioned solvent to form an extract fraction dissolved in said second solvent and an asphaltic fraction insoluble in said second solvent, separating said fractions and recovering the oil from said fractions. 12. A process for the separation of asphaltic oil into fractions which comprises commingling said cil with a light liquid hydrocarbon solvent to form an extract fraction dissolved in said sol-l vent and an asphaltic fraction insoluble in said solvent, separating said fractions, commingling said fraction insoluble in said solvent with a second liquid hydrocarbon solvent having a higher molecular weight than said4 rst mentioned solvent to form an extract fraction dissolved in said solvent and an asphaltic fraction insoluble in said second solvent, separating said fractions formed by extracting with said second solvent and recovering the oil therefrom.

13. A process for the recovery of valuable asphalt from an oily substance containing the same which comprises precipitating said asphalt in stages by adding to said oily subst-...nce first a liquefied normally gaseous methane hydrocarbon of higher molecular Weight than ethane, separating 'the portion of the asphalt thereby precipitated and then precipitating the remainder of the asphalt by the addition to the oily substance of a liquefied normally gaseous hydrocarbon ofA lower molecular Weight.

ULRIC B. BRAY.

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