US2315131A - Method of treating mineral oils - Google Patents

Description

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Patented Mar. 30, 1943 METHOD OF TREATING MINERAL OILS Stanislaw Pilat and Marian Godlewicz, Lemberg,

Poland, assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application January 30, 1934, Serial No. 708,988

` In Poland February 6, 1933 (Cl. 19E- 13) 16 Claims.

This invention pertains to a method of separating mineral oils into fractions of different physical and/or chemical properties, and is particularly concerned with the vtreatment of relatively viscous mineral oils, petroleum residues, lubricating oil distillates, coal tar and coal tar oils, and other hydrocarbon mixtures, with gases under pressure, said pressure being insufcient for liquefaction of the gases in question.

While a number of extraction methods employing various liquids as selective solvents for extracting mineral oils are well known, we have discovered that the separation of oils into fractions may be accomplished Without making use of liquid solvents, but by regulating the degree of saturation of the oil with a gaseous substance. Considerable advantages are inherent in our method of treatment, one of which is that relatively loW pressures (far below liquefaction pressures of said gaseous substances) and ordinary or elevated temperatures (not exceeding 200 C.) may be employed in carrying out the process of our invention. No chemical changes are involved in separating mineral oils by the method of our invention, the treatment being of a physical and not chemical type.

Briefly, the invention consists of introducing into a mineral oil a gas under a superatmospheric pressure until a concentration is reached at which the oil separates into two phases of different specic gravities. Relative quantities and compositions of the oil portions in the phases are regulated by maintaining suitable treating temperatures and pressures, as well as by selecting or regulating the composition of the gaseous -treating agent; as gaseous treating agents may be used: methane, ethane, carbon dioxide, hydrogen, water-gas, dry natural gas, or any other substance or a mixture of substances, which is gaseous at the temperature and pressure employed and which is capable, on being introduced in the gaseous state under a superatmospheric pressure into Athe oil being treated, to cause the separation of the same into two phases of different properties.

The process can be modified by dissolving the oil to be treated in a suitable solvent which may be of the typel of known deasphaltizing agents, such as normally liquid or liquefied hydrocarbons, as propane, propylene, normal or isobutanes, butylenes, normal or iso-pentanes, hexanes, o1' their mixtures, light straight run naphthas, or other light aromatic-free fractions of a mineral oil; or said solvent may be chosen from a group of what are known as selective or naphthenic solvents, such as liquid SO2, furfural, nitrobenzene, Chlorex dichloroethyl ether), cresylic acid, phenol, aniline, and a large number of others, their mixtures, or solutions with diluents; We also found, that in practicing our invention auxiliary treating agents of the type of oil decolorizing agents, such as fullers earth, naphthalene, phenanthrene, dinitrobenzene, and the like, may be advantageously used either instead of or in conjunction with deasphaltizing agents and/or selective solvents described hereinbefore.

In carrying out our invention in practice we prefer to dissolve the mineral oil distillate or residue to be treated in a deasphaltizing agent or in a naphthenic solvent or in a mixture of both, although our process is applicable in treating undissolved mineral oils. The purpose of dissolving the oil in a solvent is to modify the fractionating eiect of the gaseous treating agent, because we found -that compositions of the fractions obtained by our method of treating an oil, after rst dissolving the oil in a solvent, are somewhat different from those obtained from undissolved oils; operating conditions, such as temperatures and pressures, under which a gaseous treating agent is introduced into the oils being separated into fractions, are also aected by the use of either deasphaltizing or other selective solvents in conjunction with our treatment.

In the preferred form of our invention a solvent is usually added to the oil in such quantity as substantially to saturate the oil without causing it to separate into two phases at the temperature used in our treatment. The dissolved oil is then contacted with a gaseous treating agent under pressure, which is lower than the lliquefaction pressure of the 'agent at the corresponding temperature, to cause this agent to dissolve in the oil solution and saturate this solution with accompanying separation of a second heavier phase. The' light and heavy phases produced in this manner may be separated by settling or in some other manner, without changing or the two methods may alternate in a series of consecutive treatments.

It may be desirable in a series of consecutive treatments not only to vary the treating conditions, like pressures and temperatures, -or the gaseous treating agent, but also to modify the quantity or the composition of the solvent in which the oil is dissolved, by adding, for example, more `of the solvent already present in the solution, or by adding a new liquid diluent or other solvent; for instance, liquid Soz-benzol solution, Chlorex dichloroethyl ether) alone or ln solution with benzol, or furfural-benzol solution may be used in conjunction with our invention. This may be conveniently Veffected by introducing a suitable modifying solvent from the source 4 by means of the pump 20.

We found it possible to separate by our method mineral oils into fractions of different chemical characteristics, as indicated, for example, by the temperature-viscosity relationships of diierent fractions, as well as of diierent boiling rangesthe manner of separation being dependent on the solvent and/or gaseous treating agent used.

In order to illustrate some of the applications of our invention, the following examples are set forth, without intending, however, to limit this invention to any specific features of these examples.

Eample I.-A topped Urycz crude was deasphaltized by dissolving it in about 5-10 volumes of a liquid propane-butane fraction. After the precipitated asphalt was separated, the propanebutane-oil solution was saturated with a dry natural gas under a pressure of about 40 atmospheres at a room temperature. A second heavy dark-colored phase was formed and removed. The light phase was further saturated with the same gas and at the same temperature, but under a pressure of about 100 atmospheres, whereby a new heavy phase was caused to separate, leaving in the secondary light phase a highly deasphaltized oil.

Example II.-A topped crude having specic gravity .9565 at C. and Engler viscosity of 3.03 at 100 C. was dissolved in 10 volumes of a liquid propane-butane fraction. After the separation of precipitated asphaltic substances, a natural gas consisting substantially of methane and ethane (from Daszawa) under a pressure of about 150 atmospheres was introduced into the deasphaltized solution, which was maintained at room temperature. Under these conditions a heavy liquid layer containing 17.08% of the original topped crude sample separated out. The oil separated from the lighter phase had specific gravity .9325, a good color and a viscosity index of 37 (609 sec. Say. at 100 F., 58.6 sec. at 210 F.) a duplicate run produced the corresponding oil having a viscosity index of 4l. For comparison, a vacuum distillate from the same crude and having specific gravity .9377 had a viscosity index of 21 (532 sec. Say. at 100 F., 54.9 sec. at 210 F).

Eample III.-A sample of the same topped crude as was used in the Example II was dissolved in 3 volumes of a liquid propane-butane fraction; this was accompanied by precipitation of asphalt, which was removed. The propanebutane-oil phase was saturated with a dry natural gas, consisting substantially of CI-I4 and CHaCHs, under a pressure of 75 atmospheres at a room temperature; at this pressure a second phase containing about 33% of original oil, which consisted mainly of heavier and darker-colored components of the oil, separated out. The phases were separated and the lighter one was then saturated with the same gas under a pressure of 100 atmospheres at the same room temperature; new phases were formed and separated. Altogether the process-Was repeated four times with 4the following results:

Fractionation of Urycz topped crude at room temperature At pressure Specific Percent o'il precipitated atmosgravity Vlisncgty phares at 15 C.

Example IV.-A heavy cylinder oil distillate of the following characteristics:

Specic gravity at l5 C .9599 Viscosity Say. at 100 F sec-- 10,400 Viscosity Say. at 210 F sec 222 Viscosity index 42 was dissolved in 3 voliunes of a propane-butane fraction and then saturated with a dry natural gas at room temperature under a pressure of 60 atmospheres. The precipitated layer contained 48% of the original oil. After removing this layer, the lighter phase was subjected to a treatment with the same natural gas under 75 atmospheres, which resulted in the precipitation of 39% of oil; the precipitated oil had a viscosity index of 51 (205 sec. Say. at 210 FJ. A further treatment under a pressure of 100 atmospheres produced an oil with viscosity index of 74 (8l/2% of the original oil) Depending upon the required properties of oll fractions, the pressure changes in the consecutive stages of our process may be quite small; in many cases a. difference of five atmospheres at a substantially constant temperature of the oil produces distinctly different oil fractions; generally, the greater is the change in pressure, the greater is the yield ofthe heavier phase. On the other hand, a lowering of the treating oil temperature by 10 C., while maintaining a substantially constant gas pressure, may be suicient in some cases to effect the separation of a gas-saturated oilr solution into two phases.

We are aware of the German patent to Metan No. 362,458 disclosing the deasphaltizing eiect of dissolving an oil in liquefied normally gaseous hydrocarbons. However, our invention, as described, is directed to the method of fractionating mineral oils by saturating them with gaseous substances incapable of being liqueed under the treating conditions of our process, so that our process may be operated at temperatures, which are beyond the critical temperature of the particular gaseous treating agent which may be used in the process.

We claim as our invention:

l. In a process of separating a hydrocarbon oil into fractions having diferent properties, the steps of v'subjecting the oil to the precipitating action of a quantity of a gaseous hydrocarbon treating agent consisting substantially of at least one of the hydrocarbons having less than three carbon atoms per molecule, said precipitating action being exerted under a superatmospheric pressure below the condensation pressure of said gaseous treating agent at the treating temperature, 'said quantity being-sufficient to cause the of said gaseous formation of two liquid oil-containing phases of different specific gravities, and separating one phase from another.

2; Theprocessof claim 1 in which the gaseous treating agent is natural gas.

3. The process of claiml in which the treating temperature is above the critical temperature of the gaseous treating agent.

4. In a process'of separating a hydrocarbon oil into fractions having different properties, the steps of dissolving the 'oil in a liquid diluent for s aid oil, subjecting the resulting solution to the precipitatingV action of a quantity of a gaseous hydrocarbon treating agent consisting substantially of at least one of the hydrocarbons having less'than three carbon atoms per molecule, said precipitating action being exerted under a superatmospheric pressure below` the condensation pressure of said gaseous treating agent at the treating temperature, said quantity being sufficient to cause the formation of two liquid oilcontaining phases of different specific gravities,

and separating one phase from another.

5. In a process of separating a hydrocarbon oil into fractions having different properties the steps of dissolving the oil in a liquid hydrocarbon diluent having more than two carbon atoms per molecule, introducing into the resulting solution a quantity of a gaseous hydrocarbon treating agent consisting substantially of at least one of the hydrocarbons having less than three .carbon atoms per molecule under a superatmospheric pressure below Ythe condensation pressure of said gaseous treating agent at the treating tempera# ture, said quantity being sufficient to cause the formation of two liquid oil-containing phases of different specific gravities, and separating one phase from another.

. 6. In a process of separating a hydrocarbon oil into fractions having different properties the steps of dissolving the oil in a liquid naphthenic solvent,V introducing into the resulting solution a quantity of; a gaseous hydrocarbon treating agent` consisting substantially of at least one of the hydrocarbons having -less than three carbon atoms per molecule under a superatmospheric pressure below the condensation pressure of said gaseous treating agent at the treatingtemperature, said quantity being sufficient to cause the formation of two liquid oil-containing phases of different specific gravities, and separating one phase from another.

v'7. .In a process r.of separating a hydrocarbon oil into fractions having different properties, the steps of subjecting the oil to the precipitating action of a quantity of a gaseous hydrocarbon treating agent -consisting substantially of at least one of the hydrocarbons having less than threevcarbon atoms per molecule, said precipitating action being exerted under a superatmosphericpressure below the condensation pressure treating agent at the treating temperature, said quantity being sufcient Vto cause the formation of two liquid oil-containing phases of different specific gravities, separating one phase from another, subjecting ythe separated liquid phase of lower specic gravity to the precipitating faction of another quantity of a gaseous hydrocarbon treating agent consisting substantially of at least one of the hydrocarbons having vless than three carbon atoms per molecule,r said precipitating action being exerted unfder a superatmospheric pressure below the condensation pressure of said gaseous treating agent 4 at4 the` treating temperature, said second quanti- Cil 'ty of the treating agent being sufficient to cause the formation of two liquid oil-containing phases of different specific gravities, and separating one phase fromanother.

8. vIn a process of separating a hydrocarbon oil into fractions having different properties, the stepsof subjecting the oil to the precipitating action-of a quantity of a gaseous hydrocarbon treating agent consisting substantially of at least one of the hydrocarbons having less than three carbon atoms per molecule, said precipitating action being exerted under superatmospheric pressure and at a temperature abovethe critical 'temperature of the gaseous treating agent, said quantity being sufficient to cause the formation of two liquid loil-containing phases of different specific gravities, and separating ane phasefrom another.

9. In a process of separating a hydrocarbon oil into fractions having different properties, the steps of subjecting the oil to the precipitating action of a quantity of a gaseous hydrocarbon treating agent consisting substantially of Aat least one of the hydrocarbons having less than three carbon atoms per molecule, said precipitating action being exerted under a pressure and at a temperature above the critical pressure and critical temperature, respectively, of the gaseous treating agent, said quantity being sufficient to cause the formation of two liquid oil-containing phases of different specific gravities, and separating said liquid phases one from the other.

10.V In a process of separating a hydrocarbon y oil into fractions having different properties, the

steps of subjecting the oil to the precipitating action of a quantity of a normally gaseous hy.- drocarbon treating agent, said precipitating action being exerted under a pressure and ata temperature above the critical pressure and crit'- ical temperature, respectively, of the gaseous treating agent, said quantity being suflicient to cause the-formation of two liquid oil-containing phases of different specific gravities, and separating said liquid phases one from the other.

l1. In a process of separating a, hydrocarbon oil into fractions having different properties, the steps of subjecting the oil to the precipitating action of a quantity of a gasiform light hydrocarbon treating agent, said precipitating action being exerted under a pressure and at a temperature above thev critical pressure and critical temperature, respectively, of the gasiform treatring agent, said quantity being suflicient to cause theformation of two liquid oil-containing phases of different specific gravities, and separating said liquid phases one from the other.

12. In a process of separating a hydrocarbon `oil into fractions having different properties, the

steps of subjecting the oil to the precipitating action of a quantity of a gaseous hydrocarbon treating agent consisting substantially of at least one of the hydrocarbons having less than three carbon atoms per molecule, said precipitating action being exerted at progressively varying pressures above the critical pressure of the gaseous treating agent and at a temperature above the critical temperature of the gaseous treating agent, said quantity being sufficient to cause the formation of two liquid oil-containing phases of different specific gravitiesv and separating said liquid phases one from the'other.

13. In a process of separating a hydrocarbon oil into fractions having different properties, the steps of subjecting the oil to the precipitating action of a quantity of a gaseous hydrocarbon treating agent consisting substantially of at least one of the hydrocarbons having less than three carbon atoms per molecule in the presence of a liquid naphthenic solvent, said precipitating action being exerted under a pressure and at a temperature above the critical pressure and critical temperature, respectively, of the gaseous treating agent, said quantity being suflicient to cause the formation of two liquid oil-containing phases of different specic gravities, and separating said liquid phases one from the other.

14. Process for separating hydrocarbon material into constituent parts which comprises extracting the hydrocarbon material with a normally liqueable gaseous hydrocarbon solvent at a temperature above the critical temperature of the liqueable hydrocarbon solvent and varying the density of the liqueable hydrocarbon solvent by a progressive change in pressure and by the addition to the liqueable hydrocarbon sol- 20 vent of a substance misclble therewith and capable of changing its density.

15. Process according to claim 14 in which the substance added to change the density is a nonhydrocarbon substance.

16. A process for separating a mineral oil containing a normally gaseous hydrocarbon and normally liquid hydrocarbons into constituent parts comprising the steps of Varying the density of the normally gaseous hydrocarbons and precipitating normally liquid hydrocarbons to form a liquid phase heavier than said material, by a change in pressure without the addition of heat at a temperature above the critical temperature of the normally gaseous hydrocarbon, and separating said heavier liquid phase from the unprecipitated portion of said hydrocarbon material.

STANISLAW PILAT. MARIAN GODLEWICZ.

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