US2006094A - Process for treating oil - Google Patents

Description

U. B. BRAY ET AL PROCESS FOR TREATING OIL Original Filed Aug. 4, 1931 June 25, 1935.

Patented June 25, 1935 UNITED STATES PATENT OFFICE PROCESS FOR TREATING OIL Original application August 4, 1931, Serial No.

Divided and this application June 12, 1934, Serial N0. 730,215

21 Claims.

This invention relates to a method and apparatus for treating petroleumto produce lubricating oil. This invention is a division of our copending application Serial No. 555,018, led August 4, 1931.

One of the distinctive characteristics of a lubricating oil is its viscosity. For many purposes lubricants are preferred which exhibit a minimum variation in viscosity with variations in temperature, i. e., have low Viscosity temperature susceptibility. It is generally known vthat the viscosity of lubricating oil produced from Western crude, such as California naphthene base crudes, that is, crude containing asphalt varies more with change in temperaturethan do lubricating oils produced from parain base crudes.

That is, if two such oils have the same viscosity at 100 F., the Western oil will have a much lower viscosity at 210 F. than will the parain base v oil. This change in viscosity with temperature kis. .sometimes called the temperature viscosity susceptibility of an oil. It is one of the characteristics of Western lubricating oils that they are distillates, that is, are vaporized from crude oil and condensed. Lubricating oils produced from parafn base oils, containing substantially no asphalt, are generally produced by rst distilling light oils overhead, including the kerosene and gas-oil and also taking overhead light lubricating oils called neutrals having a viscosity in the neighborhood of G-200 seconds, Saybolt universal at 100 F., leaving an undistilled residue termed bright stock. The oils of various viscosity are made by blending these neutrals and bright stock in any desired proportion to obtain the desired viscosity.

It has been observed by one of us that many oils containing asphalt and wax are mixtures of hydrocarbons analogous both to the hydrocarbons present in paraiin base oils and those present in asphalt base oils.- It has further'been observed by one of us that during the heating of an oil containing asphalt, the asphalt apparently induces certain chemical and perhaps certain physical reactions at relatively low temperatures which tend to destroy the inherent low viscosity temperature susceptibility of the lubricating oil fractions. This apparent catalytic phenomenon seems to explain the observed changes although We do not Wish to be understood as being bound by this theory. It has been observed that these temperatures at which the changes appear are below the vaporizing temperatures in batch distillation (vacuum or steam) of the lubricating oil fractions which have Sayl bolt universal viscosities above 400-500 secondsY at 100 F. It is safe to say that no oil contain-` ing asphalt can be topped to the point Where fractions above 400-500 seconds, Saybolt universal viscosity at 100 F. are vaporized without a degeneration of those characteristics of the parain hydrocarbons whichimpart to the oil a low temperature viscosity susceptibility. During the distillation of the heavy oils in the presence of 'asphalt some change in molecular structure or configuration takes place which is attended by a change of viscosity temperature characteristics. 'I'his behavior is thought to be due to pyrolytic reactions which are catalyzed by the presence of asphalt. The above discovery is made the subject matter of application Serial No. 466,189. l

In order to preserve the inherent characteristics of the lubricating oil components of crude oil containing asphalt which are impaired by distillation methods as previously described, we have, in accordance with the process of the above application, caused the separation of the oil and wax from the asphalt by a method wherein the lubrieating oil constituents present in the crude oil are separated from the asphalt present in such a manner that the oil retains those characteristics which it possessed in the original crude oil. As a means of attaining this end it has been found advisable to cause the separation of the asphalt from the oil by means of solvents which are capable of dissolving the oil and which do not dissolve the asphalt. Such solvents are light petroleum fractions, such as naphtha, casinghead gasoline and petroleum fractions normally vaporous at ordinary temperature and pressure. Other solvents which may be used are alcohol, ether, mixtures of alcohol and ether, acetone, etc. We prefer to use as our solvent a petroleum fraction obtained by the rectification of natural gasoline. For most purposes a fraction composed of 6.72% ethane, 72.2% propane, 19.91% isobutane and 1.17% normal butane is satisfactory and is an example of commercially obtainable propane. It will be understood, however, that these merely illustrate the type of fractions which may be used and that the composition may vary. This fraction will hereinafter be referred to as propane for purposes of simplicity.

In carrying out the extraction of the oil with this light liquid fraction the solution is maintained at a pressure suiiicient to maintain the propane. liquid at ordinary temperatures. The fraction described above is liquid at ordinary -temperatures at a pressure of about 125 pounds per square inch. The extraction of the oil from the petroleum at such pressures results in an asphalt substantially free of oil consisting chiefly of pure bitumen and a solutitm of oil and wax in the liquid petroleum fractions. The oil dissolved in the liquid propane contains substantially all of the lubricating oil components which are present in the crude oil and in substantially the same form as they exist in the original crude oil and also the major portion of the wax present in the crude oil.

We have discovered that many lubricating oils obtained by extraction with solvents, for instance, propane, from crude oil containing asphalt and wax are composed of oils which have a relatively high temperature viscosity susceptibility and oils which have a relatively low temperature viscosity susceptibility and that these oils may be separated into oils which exhibit a low temperature viscosity susceptibility resembling oils produced from non-asphalt containing crude and oils which exhibit a high temperature viscosity susceptibility corresponding to oils produced by distillation. For convenience, we will call the oils which exhibit a low temperature viscosity susceptibility paraiiinoid and those which exhibit a high temperature viscosity susceptibility and resemble the western lubricating oil distillates non-parafnoid. The propane extract which consists of such a mixture of paraiiinoid and non-paraflinoid oils may be separated into these respective oils by the use of solvent agents which will selectively dissolve out the non-parafiinoid components. We have found that certain solvents have a selective solvent action'for the non-paranoid oils. As solvent agents which will eect this separation we have found liquid sulphur dioxide, mixtures of acetone and benzol, aniline or methyl formate useful. Acetone alone, in addition to being an asphalt precipitant, also has in some measure the ability to split the oil in the above manner. The use of liquid sulphur dioxide has been found especially valuable as a solvent to separate the propane extract into oils which exhibit low temperature viscosity susceptibility and into oils which exhibit high temperature viscosity susceptibility.

As the propane extract from the crude oil consists of a mixture of Wax and oil normally solid at ordinary temperatures, it cannot be separated into its paraiiinoid and non-paraiiinoid components by the use of sulphur dioxide, without considerable diiiiculty, unless dissolved in a carrying medium. We have found it advantageous to carry out the extraction of the wax Oil mixture with sulphur dioxide in the presence of the liquid propane used ln separating the asphalt. The wax oil mixture is dissolved in liquid propane after which it is extracted with liquid sulphur dioxide to remove therefrom the non-paraflinoid components. The propane solution of parainoid oil is then chilled to precipitate the wax present after which the chilled mass is cold settled, centrifugal, or filtered to separate the wax from the propane solution of oil. By removing the sulphur dioxide soluble bodies from the propane solution of waxy oil prior to the dewaxing operation we are able to obtain a final product with a lower pour point, i. e. wax content, than could be obtained if the sulphur dioxide extraction operation Were performed subsequent to wax ,removal. The sulphur dioxide removes from-oil certain bodies present which are good wax solvents and which have a tendency to prevent precipitation of the wax during the dewaxing operation.

The propane solution of oil recovered from the dewaxing operation substantially free of asphalt and wax may be further purified by treatment with sulphuric acid. Such treatment removes from the paraiiin oil further impurities whichv were not removed from the oil by the treatment with liquid sulphur dioxide. Y

Generally stated, it is the object of our invention to isolate from crude oilthose oils having characteristics which impart to it the low temperature viscosity susceptibility typical of paraffin base oil.

More particularly, it is an object of our invention to isolate from asphalt containing oils those components which impart to the oil the reduced susceptibility to change in viscosity with temperature which is characteristic of oils obtained from non-asphalt containing oils; that is, to, separate the paraiiinoid from the non-parafnoid components of the asphalt containing crude oils.

It is a further object of our invention to separate asphalt from an oil containing asphalt, oil and wax by means of a solvent, to separate the wax and paraiiinoid oil from the non-paraflinoid oil by means of a second solvent used in the presence of the first solvent, to separate the wax from the parainoid oil and thereafter to treat the paraffinoid oil dissolved in said first solvent with sulphuric acid.

It is a further object of our invention to separate`oil and wax from an oil containing asphalt, oil and wax by the use of liquid propane; to separate the wax and paraiiinoid oil from the nonparaflinoid oil by the use of liquid sulphur dioxide in the presence of liquid propane to separate the wax from the parafiinoid oil and thereafter to treat the parainoid oil with sulphuric acid.

The drawing represents one form of apparatus which we may employ to carry out our process.

Referring more particularly to the drawing, the crude oil Which has been distilled to remove light oils such as gasoline and kerosene and is itself a residual oil containing lubricating fractions, asphalt and wax in tank l is withdrawn through valve 2 and sent by means of pump 3 through line t where it meets a stream of liquid propane coming from tank l0 through valve ll, line i2, pump H5 and line l2. The mixture of topped crude and liquid propane passes from line 4 to chiller 5 where a portion of the propane is allowed to Vaporize through valve 6 and passes by means of line 'l to pump 32 where it is compressed and sent to condenser 8 where it is liquefied and sent by means of line 9 to storage tank lll. The vaporization of the propane in chiller 5 causes the temperature of the mass therein to be lowered. The cool mass from chiller 5 passes by means of line I3 to agitator I4 where it is thoroughly mixed and sent by means of line I5 to decanter I6 where the asphalt is allowed to settle out.

The asphalt is withdrawn from decanter I6 through valve l'l and sent by means of pump I8 through line I9 toV heater 20 where the propane and moisture are vaporized. The heated mass passes from heater 20 through line 2i to separator 22 where the asphalt separates from the vapors and is withdrawn through valve 23 and line 24 in the storage tank 25. The vapors in separator'22 are withdrawn through line 26 into condenser 21 where the water vapor present is condensed. The condensed Water and propane vapor pass into separator 28 where the water separates and is withdrawn through valve 29 and line 30. Propane vapor passes from separator 28 through line.3|

to compressor ||3 thence to condenser l where it is liqueed and passes bymeans of line l to y storage tank I0.

' and sent by means of pump 39 through line 40 to the lower zone of extraction column 4|. Liquid sulphur dioxide from tank 42 is withdrawn through valve 43 and sent by means of pump 44 through line 45 to the upper zone of extraction column 4I. Due to the diilerence in specific gravity of the oil introduced through the lower zone of the extraction column and the liquid sulphur dioxide introduced into the upper zone of the extraction column, these two liquids tend to separate. As the liquid sulphur dioxide descends through the extraction c-olumn it dissolves certain components present in the oil.

The solution of liquid sulphur dioxide and oil is removed from the extraction column 4| through the valve 45 and sent by means of line 41 tov vaporizer |05 where the sulphur dioxide is vaporized by aid of steam introduced through closed coil |0| and passes through line |05 to com-I pressor |01 Where it is compressed and sent through line |08 to condenser |09 where it is liquefied and sent to storage tank 42. Sulphur dioxide free oil in vaporizer |05 is Withdrawn through valve |02 and sent through line |03 to tank |04.

The ascending column of oil in extraction column 4|, from which'the liquid sulphur dioxide soluble components have been removed, passes through valve 48 to line 49 to auxiliary separator 50 where any remaining liquid sulphur dioxide is settled out. A clear solution of oil is withdrawn from auxiliary separator 50 through line 52 where it may be mixed with a further quantity of liquid propane coming from storage tank I0 through valve 53, pump ||4 and line 54. The solution of oil and propane carrying a small quantity of sulphur dioxidepasses into chiller where a portion of propane is allowed to vaporize by opening valve 5|. The vaporized propane contaminated with sulphur dioxide, passes through line 52 to compressor where it is compressed and sent through line 88 to condenser 89'Where both the sulphur dioxide and the propane are condensed and pass by means of line ||0 to separator 90 Where these two materials separate due to their great difference in specific gravity. The liquid propane in separator is withdrawn through valve 9| and sent by means of pump 93 through line 96 to storage tank |0. The liquid sulphur dioxide in separator 90 is withdrawn through valve 92 and sent by means of pump 94 through line to storage tank 42. The vaporization of the propane in chiller 55 cools the remaining solution of oil present which passes out through valve 55 and line 51 to pump 58 which forces it through lter press 59 where the precipitated wax is removed through line 50.

The wax-free oil from filter press 59 passes through line 61 Where it meets a stream of sulphuric acid coming from tank 53 through valve 54, line 55 and pump 6B. The mixture of acid and oil passes from line 61 through agitator 58 where the mass is thoroughly agitated, after which it passes through line 59 to separator 10 where the sludge is allowed to settle out. The sludge in separator 10 is withdrawn through valve 15, line 15, to pump 11 which forces it through line 18 to heater 19 where the mass is heated sufliciently to vaporize the propane present. The heated mass passes from heater 19 through line 80 to separator 8| Where the sludge separates from the propane and is Withdrawn through valve 82 and sent through line 83 to storage 84.- The propane vapor is withdrawn from separator 8| through line 85 to compressor ||2 where it is compressed and sent by means of line 88 to condenser 89 where` it is liquefied and sent by means of line ||0 to separater 90 where it is separated from any` liquid sulphur dioxide and sent by means of valve 9|, pump 93, line 95 to storage tank |0. The liquid sulphur dioxide in separator 90 is withdrawn through valve 92 and sent by pump 94 to sulphur dioxide storage tank 42. Y

The acid treated oil in separator 10 dissolved in propane carrying varying amounts of sulphur dioxide, is withdrawn through line 1| and passed through clay tower 12 where any remaining sludge is separated out. The fraction of oil leaving clay tower 12 passes by means of line 13 to evaporator 14 Where the propane and sulphur dioxide present are vaporized by aid of steam introduced through closed` coil 91 and are sent by means of line 8E to compressor 81 where they are compressed and sent by means of line 88 to condenser 89 where they are liquefied and sent by means of line 0 to separator 90. Liquid propane in separator 90 is returned to storage tank I0 through valve 9|, pump 93, and line 96. The sulphur dioxide in separator 90 is returned to storage tank 42 through valve 92, pump 94 and line 95. The oil in evaporator 14 which is free from propane and sulphur dioxideis removed through valve 98 and sent by means of line 99 to rened oil tank |00.

As illustrative of the operation of our process for one type of oil and without intending to limit" our invention, Water free residual oil in tankll at a temperature of about 200 F. is mixed with liquid propane and cooled by allowing a portion of the propane to vaporize under reduced pressure until the temperature of the topped oil and propane is about F., after which it is thoroughly mixed in agitator |4. The thoroughly agitated mass is then passed into decanter IB where the propane solution of lubricating oil and Wax is separated from the undissolved asphalt. This oil dissolved in liquid propane vcontains a mixture of paranoid and non-parafnoid components. By subjecting this mixture to the selective solvent action of liquid sulphur dioxide in the presence of liquid propane, it is possible to resolve the mixture into a portion of `non-parafnoid nature soluble in liquid sulphur dioxide and a portion of a parainoid nature soluble in liquid propane. 'lhe Wax present in the mixture being more soluble 'in the liquid propane than in the liquid sulphur dioxide remains in solution inthe former. This mixture of paraflinoid oil ,Y and Wax dissolved in liquid propane is then with sulphuric acid to remove further undesirable bodies present, after which thesolution formed is settled-out and the propane removed by distillation from the refined oil.

The foregoing exemplary description is merely illustrative of a preferred mode of carrying out our invention and is not to be taken as limiting, as many variations may be made within the scope of the following claims by a person skilled in the art without departing from the spirit thereof.

We claim:

1. A process for the treatment of oil containing wax which comprises dissolving said oil in a liquefied normally gaseous hydrocarbon, extracting said oil dissolved in said` liquefied normally gaseous hydrocarbon with a selective solvent for non-paraflinoid oil to form a fraction dissolved in said liquefied normally gaseous hydrocarbon containing Wax and a fraction dissolved in said selective solvent, separating said fractions, chilling said wax containing fraction dissolved in said liquefied normally gaseous hydrocarbon to precipitate wax and removing the precipitated wax from the oil and liquefied normally gaseous hydrocarbon.

2. A process as claimed in claim 1 in which the liquefied normally gaseous hydrocarbon contains a major portion of hydrocarbons having less than four carbon atoms.

3. A process as claimed in claim 1 in which the liquefied normally gaseous hydrocarbon contains a major portion of propane.

`4. A process as claimed in claim 1 in which the dewaxed oil is treated with sulphuric acid.

5. A process as claimed in claim 1 in which the dewaxed oil is treated with sulphuric acid and clay.

6. A process for the treatment of oil containing wax which comprises dissolving said oil under superatmospheric pressure in a liquefied normally gaseous hydrocarbon diluent, extracting said oil dissolved in said diluent with a selective sol- Vent for non-paraffinoid fractions to form a fraction containing Wax dissolved in said diluent and a fraction dissolved in said selective solvent, separating said fractions, vaporizing a portion of the diluent under reduced pressure from the fraction dissolved in said diluent to chill the oil and precipitate wax, and separating the wax from said fraction and remaining diluent.

'7. A process as claimed in claim 6 in which the liqueed normally gaseous hydrocarbon contains a major portion of hydrocarbons having less than four carbonr atoms.

8. A process as claimed in claim 6 in which the liquefied normally gaseous hydrocarbon contains a major portion of propane.

9. A process as claimed in claim 1 in which the selective solvent is liquid sulphur dioxide.

10. A process as claimed in claim 1 in which the liquefied normally gaseous hydrocarbon is preponderantly propane and the selective solvent is liquid sulphur dioxide- 11. A process as claimed in claim 6 in which the selective solvent is liquid sulphur dioxide.

l2. A process for the treatment of oil containing asphalt and Wax which comprises commingling said oil with an asphalt precipitating solvent to precipitate asphalt and to dissolve the oil and wax, removing the precipitated asphalt from the solvent solution of oil and wax, extracting the oil and wax dissolved-in the asphaltprecipitating solvent with a-selective solvent for non-parainoid oil to form av fraction dissolved in the selective solvent and a fraction dissolve in the asphalt' precipitating solvent containing wax, chilling the oil and wax dissolved with asphalt precipitating solvent to precipitate wax and separating the wax from the oil dissolved in the asphalt precipitating solvent.

13. A process as claimed in lclaim 12 in which the asphalt precipitating solvent is a liquefied normally gaseous hydrocarbon. l

14. A process as claimed in claim 12 in which the asphalt precipitating solvent is a liquefied normally gaseous hydrocarbon containing a major portion o1 hydrocarbon of less than four carbon atoms.

15. A process as claimed in claim 12 in which the asphalt precipitating solvent is a liquefied normally gaseous hydrocarbon and the selective solvent is liquid sulphur dioxide.

16. A process for the treatment of oil containing asphalt and wax which comprises commingling said oil with a liquefied normally gaseous hydrocarbon to precipitate asphalt and to dissolve the oil and wax, removing the precipitated asphalt from the oil and wax dissolved in the liquefied normally gaseous hydrocarbon, extracting the oil and wax dissolved in the liquefied normally gaseous hydrocarbon with a selective solvent for non-paraflinoid oil to form a fraction dissolved in the selective solvent and a fraction dissolved in the liquefied normally gaseous hydrocarbon including wax, separating said fractions, vaporizing a portion of the liquefied normally gaseous hydrocarbon from the liquefied normally gaseous hydrocarbon solvent solution of oil and wax to chill the oil and precipitate Wax and. removing the precipitated wax from the oil dissolved in the remaining liquefied normally gaseous hydrocarbon.

17. A process as claimed in claim 16 in which the selective solvent is liquid sulphur dioxide.

18. A process as claimed in claim 16 in which the liquefied normally gaseous hydrocarbon contains a major portion of hydrocarbons of less than four carbon atoms.

19. A process as claimed in claim 16 in which the liquefied normally gaseous hydrocarbon contains a major portion of propane.

20. A process for producinglubricating oil from an oil containing asphalt and wax which comprises, commingling said oil with a liquefied normally gaseous hydrocarbon to dissolve the oil and wax and to precipitate the asphalt, removing the asphalt from the oil and wax dissolved in the liquefied normally gaseous hydrocarbon, extracting the oil and wax dissolved in the liquefied normally gaseous hydrocarbon with a selective solvent for non-paraflinoid oil to form a fraction dissolved in the selective solvent and a fraction dissolved in the liquefied normally gaseous hydrocarbon including wax, separating said fractionsand removing the wax from the wax containing fraction.

21. A process according to claim 20 in which the deasphaltized and dewaxed fraction is treated with sulphuric acid.

ULRIC B. BRAY. CLAUDE E. SWIFT.

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