Process for treating oil

Patented May 21, 1935

2,002,004

UNITED STATES PATENT OFFICE

2,002,004

PROCESS FOR TREATING ΟΪΕ

Earle W. Gard, Palos Verdes Estates, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California

No Drawing. Application August 7, 1933, Serial No. 684,123

Claims. (CI. 196—13)

This invention relates to a process for the production of lubricating oil. More specifically, it relates to a process for the production of lubricating oil by the use of solvents.

In the production of lubricating oils from asphaltic crudes, as for example crude oils in California, it has been proposed to distill the oil and remove the light fractions present, such as gasoline, kerosene and gas oil, and then to contact the residue containing the lubricating oil fractions and asphalt with a solvent capable of dissolving the lubricating oil fractions but in which the asphalt is insoluble. Solvents which have been proposed for the purpose of separating the asphalt from the lubricating oil fractions are naphtha, gasoline, casinghead gasoline and liquefied normally gaseous hydrocarbons, such as liquid ethane, liquid propane, liquid butane and mixtures thereof. Furthermore, it has been proposed to use such solvents as alcohol, alcohol and ether, acetone, acetone and ether and alcohol containing benzol for the separation of the lubricating oil fractions from the residue containing oil and asphalt.

For the separation of asphalt from an asphalt containing oil it has been found that those hydrocarbons which are normally gaseous at ordinary temperatures and pressures are capable of producing the most efficient separation of the asphaltic bodies and carbonaceous materials present in asphaltic residues. These normally gaseous hydrocarbons include compounds such as ethane, propane, butane or mixtures thereof.

In the production of lubricating oil from asphaltic residues produced by distilling asphalt base crude and removing the gasoline, kerosene and gas oil fractions it is customary to separate the asphalt from the oil by commingling the asphaltic residue with the liquefied normally gaseous hydrocarbons under sufficient pressure to maintain the hydrocarbons in the form of a liquid and then to separate the oil dissolved in the liquefied normally gaseous hydrocarbon from the insoluble asphalt. Where liquid propane is employed as the asphalt precipitant and for the lubricating oil solvent a pressure of about 125 pounds per square inch and a temperature of 70° F. insufficient to maintain this light hydrocarbon fraction in the form of a liquid. Undermost circumstances it has been found that three to five volumes of liquid propane to one volume of the asphaltic oil is the proper ratio of these two materials in order to effect satisfactory separation of the asphaltic material present.

Normally gaseous liquefied hydrocarbons, such as propane, are capable of removing substantially all of the asphaltic material present in petroleum residues. However, the separation is never complete and there still remains in the oil after treatment with these light hydrocarbons 5 a small quantity of asphalt, resins and gummy bodies. The concentration of these materials is vary low and is seldom detrimental to the finished product. However, where it is desired to remove the remaining traces of these undesirable 10 constituents, the oil may be further treated with such materials as acids, metallic halides, etc., in order to separate out these remaining impurities.

I have discovered that substantially all of these impurities may be concentrated in one fraction 15 of the oil and then by treating this fraction containing the concentrated impurities with suitable solvents I am able to purify this fraction sufficiently so that it may be employed as a lubricating oil in most cases without any other further treat- 20 ment. According to my process, lubricating oils are produced from asphaltic crudes by distilling the crude oil and removing the light materials present, such as gasoline, kerosene and gas oil. The residue remaining after the removal of the 25 light fractions is then treated with asphalt precipitating solvents, such as I have already described, for the separation of the asphalt, resinous and gummy materials. The oil from which the asphalt, resinous and gummy materials have been 30 removed is then distilled into appropriate overhead fractions and a residual oil fraction. Ίΐιβ residue contains substantially all of the impurities which were present in the oil after treatment with the solvent capable of removing substantially all 35 of the asphalt, resinous and gummy materials and is re-treated with one of the solvents which I have set forth above for the separation of the remaining impurities. If desired, the residue after re-treatment with the solvent to separate 40 the remaining impurities, may be treated with chemicals, such as acids or metallic halides for the separation of any remaining impurities. In carrying out my process the crude oil is distilled until all of the light fractions present, includ- ⁴⁵ing gas oil, have been recovered as overheads. The residue left after removing the light fractions is removed from the still, cooled and then mixed with a light liquid hydrocarbon, such as propane, under a pressure of about 125 pounds per square inch and at a temperature of about 70° F. Usually from three to five parts of liquid propane to one part of asphaltic residue will result in a mixture in which substantially all of the asphalt present is insoluble. However, I do not propose

2,002,004 to bind myself by these limits as I may use more or less of the light liquid hydrocarbon, according to the character of the residue undergoing treatment. After mixing the residue with a suitable quantity of the light liquid hydrocarbon, the mixture is passed into a settling zone in which the asphalt is allowed to settle out. The solution of oil fractions dissolved in the light liquid hydrocarbon is decanted away from the asphaltic residue and then given a further treatment if desired. However, in most instances, treatment at this point is not necessary. This solution of oil dissolved in the light liquid hydrocarbon is then distilled in order to separate the asphalt precipitating solvent from the oil fractions. The oil fractions remaining after the removal of the asphalt precipitating solvent is then distilled into any number of suitable over-head fractions desired. The distillation is usually carried to a point at which approximately 60 to 80% of the oil fractions have been recovered in the form of distillates. However, in some cases I may find it more desirable to recover more or less of the material in the form of a distillate. The distillates which are produced by distilling the solvent treated oil are substantially free from asphalt, resinous and gummy materials. These impurities accumulate or are concentrated in the still residue left after the removal of the distillates. The concentration of these undesirable impurities in the residue is sufficiently high to permit a further separation of these materials when the residue is contacted, commingled or dissolved in a further quantity of one of the asphalt precipitating solvents which I have described above. For example, by commingling the still residue with liquid propane in the proportion of one part of the still residue to three or five parts of liquid propane under about 125 pounds pressure and at about 70° F. substantially all of the impurities remaining in the residue precipitate. By passing this mixture of oil dissolved in liquid propane and precipitated impurities to a settling chamber the propane solution of oily fractions may be separated from the relatively heavy impurities present which have been precipitated by the solvent and which settle out upon standing. The propane solution of oily fractions is usually sufficiently free from impurities so that no further treatment is required. However, if the small quantity of asphaltic, resinous or gummy material left in the oil is considered detrimental, these materials can be removed by such further treatment as treatment with sulphuric acid, either in the presence or absence of normally gaseous liquefied hydrocarbons.

The ability of these light, normally gaseous, liquefied hydrocarbons to separate impurities, such as asphalt, from oil is a function of the molecular weight of the light hydrocarbon. A more complete separation of asphalt from oil is accomplished by the use of liquid ethane than by the use of the heavier hydrocarbons, such as propane, butane or pentane. However, in order to employ the extremely light hydrocarbons for the separation of the asphalt from the oil apparatus must be employed which will withstand very high pressures. As high pressure equipment is expensive an economic balance must be found which is governed by the asphalt precipitating power of a particular solvent and the pressure required to maintain this solvent in the form of a liquid. For most purposes it is not economically possible to employ solvents which have a higher vapor pressure than liquid propane, This material will not separate asphalt from oil as completely as liquid ethane, however, the precipitation obtained by the solvent is usually satisfactory for most purposes.

As a modification of my process, I may distill the crude oil to a residue, treat this residue with a hydrocarbon solvent, such as naphtha, gasoline, pentane or butane, for the separation of a major part of the asphalt, distill the oil from which the major portion of the asphalt has been removed into appropriate over-head cuts and a residue, and then re-treat the residual fraction with a further quantity of a light hydrocarbon solvent, such as propane or ethane or mixtures thereof, for the separation of the remaining asphalt in the still residue. By treating the oil according to this modification, the major portion of the asphalt is separated from the oil with solvents which do not require expensive high pressure equipment. The only high pressure equipment required is for the treatment of the still residue which remains after the distillation of the oil from which the major portion of the asphalt has been removed by the solvent treatment. As the quantity of the oil re-treated with the relatively light solvent, such as propane or ethane or mixtures thereof, is comparatively small in volume the expense of treatment is materially lessened.

It is, therefore, an object of this invention to ; commingle asphalt containing oils with an asphalt precipitating solvent to separate the oil from the precipitated asphalt, separate the oil into fractions containing substantially no impurities, such as asphalt, and a fraction contain- ; ing impurities and to re-treat the fraction containing the impurities for the separation of the oil from the impurities.

It is another object of this invention to treat asphaltic oil with a solvent capable of precipitating the major portion of the asphalt and dis. solving the oil to separate the oil and solvent from the precipitated asphalt, separate the oil by distillation into an over-head fraction relatively free from impurities and a residual fraction containing impurities and to re-treat this still residue with a further quantity of the solvent for the separation of the remaining impurities.

It is still another object of this invention to extract an asphaltic oil with liquid propane to separate the propane solution of oil from the precipitated asphalt to separate the propane from the oil and distill the oil into an over-head fraction and a residual fraction with liquid propane to separate substantially all of the impurities from said residual fraction and then to remove the propane from said residual fraction.

It is still a further object of my invention to extract an asphaltic oil with gasoline, naphtha or liquid propane for the separation of the major portion of the asphalt, distill the oil separated from the major portion of the asphalt into an over-head fraction substantially free from asphalt and a residual fraction containing the remaining asphalt and to re-extract this residual fraction containing the remaining asphalt with another solvent, such as propane or ethane, or mixtures thereof, for the separation of the remaining asphalt in said residual oil fraction and to give this residual oil fraction from which the remaining asphalt has been separated any further treatment, such as treatment with acid, alkali, clay, etc., to produce a finished oil.

In some cases the oil to be treated contains both asphalt and wax. In such case the major portion :

2.002.004 3 of the asphalt may be separated from the oil by the method described above and then the oil may be dewaxed. The oil which has been separated from the major portion of the asphalt and dewaxed may then be distilled and treated according to the methods which I have previously described for the separation of the remaining impurities.

The distillation of the oil from which a major portion of the asphalt, or asphalt and wax, has been removed may be distilled by the conventional use of fire and steam at ordinary atmospheric pressure. However, if desired, I may employ vacuum distillation in the production of the over-head fraction.

In some cases I find it desirable to treat the asphaltic oil with a solvent capable of precipitating the major portion of the asphalt at ordinary temperatures, to distill the oil from which the major portion of the asphalt has been precipitated for the production of over-head fraction substantially free from asphalt and a residue containing the remaining asphalt and to re-treat the residue containing the remaining asphalt at a relatively low temperature for the separation of the oil from the remaining asphalt. For example, an asphaltic oil produced by distilling a California asphalt base crude to a point at which the gasoline, kerosene and gas oil fractions are removed in the form of distillates is treated with liquid propane in the proportion of one part of the asphaltic oil residue to three to five parts of liquid propane at ordinary temperatures, i. e., 70° F. and under a pressure of approximately 125 pounds per square inch. The mixture of liquid propane and asphaltic oil is placed in a settling zone where the relatively heavy material is allowed to settle out. The propane solution of oil is decanted away from the precipitated asphalt and distilled to remove the propane. The oil recovered after the separation of the propane is then distilled until 60 to 80% of the material is recovered as an over-headfraction. The still residue comprising 20 tt> 40% of the stock charged to the still is re-mixed or re-extracted with a further portion of the liquid propane in the proportion of one part of the still residue to three to five parts of liquid propane, after which the temperature of the mass is lowered to —20 or —40° F. This, lowered temperature may be obtained by vaporizing a portion of the liquid propane under reduced pressure. By re-extracting the still residue with liquid propane at these low temperatures a further quantity of impurities separate from the solution. These impurities consist of materials, such as asphalt, resins and gums. By allowing the cooled mass to remain in a quiescent state these materials settle.due to their relatively high specific gravity. The propane solution of oily fractions is then decanted away from the precipitated impurities and may be further treated if desired with sulphuric acid, caustic soda and/or absorbent material, such as fuller’s earth, Death Valley clay or diatomaceous earth for the production of a finished oil.

It is, therefore, an object of this invention to commingle an asphaltic oil at ordinary temperature with an asphalt precipitating solvent for the separation of a major portion of the asphalt from the oil, to distill the oil from which the major portion of asphalt has been separated into an over-head fraction substantially free from impurities and a residual fraction containing the remaining impurities not removed by the initial extraction with the asphalt precipitating solvent, to re-extract the still residue containing the remaining asphalt and impurities with a further quantity of an asphalt precipitating solvent at a relatively low temperature for the separation of the remaining asphalt and impurities.

It is still another object of this invention to extract an asphaltic oil with liquid propane at a 5 temperature of about 70° F. and under sufficient pressure to maintain the propane in the liquid state, to separate the propane solution of oil from the precipitated asphalt and to separate the propane from the oil, to distill the propane ex- 10 tracted oil for the production of an over-head fraction and a still residue, to re-extract said still residue with a further quantity of liquid propane at a temperature of about —20 to —40° F. and under sufficient pressure to maintain the propane 15 in a liquid state at these respective temperatures, to separate the propane solution of oil recovered at these respective temperatures from the separated impurities and, if desired, to re-treat the oil recovered in the propane with chemicals, as 20 previously described for the production of a finished oil.

As a specific example, a crude oil similar to deep Santa Fe Springs having a gravity of 32° Be. is topped of its gasoline, kerosene, stove distillate, 25 light and heavy gas oil fractions and then the residue or long residuum is mixed with propane in the ratio of about 4 volumes of propane to 1 of oil. The mixture is chilled to 70° F. and the precipitated asphalt—about 25% of the long re- 30 siduum—is drawn off. The oil and propane solution is then chilled by evaporating the propane, to a temperature of —50° F. This temperature is sufficient to precipitate the wax. The wax is removed and the propane-oil solution is then 35 distilled to free it of the propane. The propanefree oil is then fed to a vacuum still and heated to a temperature of around 750° F. with or without steam, and 75% is taken off through the overhead vapor line. The bottoms—or 25%—are 40 then withdrawn. The bottoms are then mixed with propane in a ratio of 3 propane to 1 of oil and the heavy residue that is precipitated— 50% of the original stock—is withdrawn. The decantate is then freed of its propane. The pro- 45 pane-free oil will have a much lower carbon residue. This oil can then be acid treated or treated with liquid sulphur dioxide or other selective solvents to produce a finished oil.

The fraction recovered as an insoluble residue 50 by re-treating the distillation bottoms with liquid propane or other asphalt precipitating solvent is an excellent source of raw stock for the production of pale binder or colorless asphalt. By distilling out the light oily fractions from 55 this insoluble fraction a product is obtained which has properties similar to those of asphalt but which is more transparent or translucent and is useful for many purposes for which ordinary asphalt cannot be used because of its dark βθ color. For example, this light colored and transparent plastic material may be employed as a roof coating in conjunction with colored pigments or stone, or it may be employed as a binding material for aggregate in sidewalks or walk-ways.

Where a lighter color is desired, the crude plastic material is treated with such agents as sulphuric acid, caustic, clays, metallic halides, etc., either in the presence or absence of diluents such ₇₀as naphtha, gasoline, gas oil, or aromatic extracts produced by treating hydrocarbon mixtures with liquid sulphur dioxide. The treated material is. then distilled to remove the light constituents present. The melting point of the plastic mate- 75

2,002.004 rial can be increased to the point desired by the distillation. As the distillation continues, the melting point of the material in the still increases.

It is, therefore, another object of my invention to produce plastic material from asphaltic oil by treating said asphaltic oil with agents capable of separating the major portion of the asphaltic material from the oil, concentrating the remain10 ing asphaltic, gummy or plastic material remaining in the oil into an oil fraction and then recovering the gummy, plastic or asphaltic material concentrated in said fraction by agents capable of separating the plastic material concentrated 15 in the oil.

The above is merely illustrative of one mode of carrying out my invention, and is not to be taken as limiting, as many variations may be made by a man skilled in the art within the scope of the 20 following claims.