US2107291A - Treatment of hydrocarbon oil - Google Patents

Description

reamed Feb. s, was

' UNITED STATES PATENT OFFICE No Drawlnl. Alll cliion April 19, 1935,

' Serial No. 17,262

20 Claims. (Cl- 196-13) The present invention relates to the art of.

mineral oil refining, and has particular reference to the separation of crude petroleum or petroleum products into fractions of different chemical com- 5 position while of approximately the same distillation range.

In accordance with my invention, crude petroleum or petroleum products, particularly oils of substantial viscosity, are separated into various 10 fractions by extraction with a mixture of solvents, and more particularly with selective solvents such as nitrobenzene, nitrotoluene, benzaldehyde, dichloro ethyl ether, pyridine, cresylic acid and furfural, to which has been added a 1.3 polyhydroxy cyclic compound such as, for example, resorcinol, pyrocatechin, pyrogaiiol, and the homologues thereof.

It is recognized in the art that mineral oils, such as petroleum, comprise essentially a mixture 20 of hydrocarbons of various groups or homologous series of compounds, such for example, as parailins of the general formula CnH2n+2, olefines of the general formula C1IH27l, hydroaromatics and polymethylenes of the same empirical for- 35 mula, and various other series of compounds of chain and/or ring structures in which the hydrogen to carbon ratio is less than in the foregoing series. A large number of individual compounds of each series and of differing boiling points are present in petroleum.

The various types of crude petroleum, which are generally classified into three groups, namely, pai'aflinic base, naphthenic or asphaltic base, and mixed base, contain the various series of hydro- 35 carbons mentioned heretofore in different proportions. For example, in the paraffinic base crude oils, such as those obtained from the oil fields of Pennsylvania, there is a relatively high proportion of hydrocarbons having a chain struc- 4 lure and a high hydrogen to carbon ratio, whereas in the naphthenic or asphaltic base crude oils, there is a relatively large proportion of hydrocarbons having ring structures and a low hydrogen to carbon ratio. Mixed base crude oils, such b as are obtained from the Mid-Continent oil fields,

contain hydrocarbons in proportions intermediate between these two extremes.

The paraflin base oils and their distillates are said to be more paraflinic than the mixed base oils and their distillates and these in turn are more paraflinic than the naphthene base oils and their distillates. Conversely the naphthene base oils are more naphthenic than the mixed base oils and these in turn more naphthenic than the paramn base oils. The usual criteria 0! the 116- gree'of paramnicity or naphthenicity of an oil are the viscosity-gravity constant and the viscosity index. The viscosity-gravity constant is a constant relating viscosity and specific gravity 5 and is described in an article entitled The viscosity-gravity constant of petroleum lubricating oils by J. B. Hill and H. B. Coates which will be found in vol. 20, page 641 et seq., of Industrial and Engineering Chemistry. Viscous oils resulting from the distillation of Pennsylvania type crudes have viscosity-gravity constants ranging from about .805 to about .828, and in most instances are below .820. Those resulting from the distillation of Mid-Continent crudes have visl6 cosity-gravity constants ranging from about .835

to about .855, whereas those from naphthenic crudes are generally higher than .860. The viscosity index is a coefllcient based on the change of viscosity with temperature, and is described by Dean and Davis in vol. 36, page 618 of Chemical and Metallurgical Engineering. The more paraflinic oils are characterized by low viscositygravity constants and high viscosity indices, whereas the more naphthenic oils are characterized by higher viscosity gravity constants and lower viscosity indices.

My invention is based upon the discovery that oils containing both the paraflinic series of hydrocarbons and the various naphthenic series may be fractionally extracted with a selective solvent in admixture with a polyhydroxy cyclic compound. The various series of hydrocarbons possess a differential solubility in such solvent mixture, the naphthenic hydrocarbons being as much more soluble therein than the paraflinic hydrocarbons. By means of extraction with such solvent mixture, it is therefore possible to efl'ect apartial separation of the naphthenic hydrocarbons from the paraflinic, and to obtain from an 40 oil containing both classes of hydrocarbons, an oil which is much more paraflinic than the original oil and one which is much more naphthenic. By my invention, for example, it is possible to produce an oil of the quality normally obtained from Appalachian crudes, from crudes of the mixed base type from the Mid-Continent area or from those of the naphthenic base type and, conversely, to obtain oils from mixed base crudes or paraflinic base crudes such as are normally obtained from the naphthenic oils of the Gulf Coast area. In general, from oils from any source there may be obtained by my process, oils which are respectively more parafiinic and more naph- 55 thenic than the oils normally obtainedfrom such source by distillation. I

It has been known heretofore to separate hydrocarbon oils into fractions by means of solvents such as sulfur dioxide, furfural, and others. Such separation is accomplished by agitating the oil with the solvent and bringing the mixture to such a temperature, below the temperature of complete miscibility of the oil and solvent, that the mixture separates into two layers, one of which is the undissolved and more paraflinic portion of the oil containing some dissolved solvent, and the other of which is solvent containing dissolved naphthenic constituents of the oil. These two layers are separated at this separation temperature" and the solvent may subsequently be removed from each. I have found it highly advantageous to eil'ect such separation by employing a mixture of a selective solvent and a polyhydroxy cyclic compound. In particular, the aromatic nitro solvents, for example, nitrobenzene, are highly selective but usually require a separation temperature below, for example, 60 F., due to their relatively low miscibility temperature with the hydrocarbon oils. The separation temperatures employed are, in general, about 45 F. below the miscibility temperature of the oil and solvent. By employing a suitable mixture of a selective solvent and a polyhydroxy cyclic compound, I am able to separate hydrocarbon oils into fractions at temperatures considerably above those which could be employed with the selective solvent alone. For example, 100 parts, by volume, of a dewaxed high viscosity oil from Barber's Hill (Texas) crude oil was mixed with 150 parts, by volume, of nitrobenzene, and the miscibility temperature was found to be 104 F. In general, this would indicate that the extraction should be carried out attemperatures not higher than about,60 F. When 100 parts of the same oil was admixed with 150 parts of a solvent composed of by weight of nitrobenzene and 5% by weight of resorclnol, the miscibilty temperature was found to be 138 F., indicating that an extraction could be carried out satisfactorily at a temperature of the order of 95 F. When parts of the same oil were mixed with parts of solvent composed of 90% by weight of nitrobenzene and 10% by weight of resorcinol, the miscibility temperature was found to be 192 R, which would permit of extraction at temperatures as high as about 150 F. It will be understood, of course, that the quality of the undissolved or more parafiinic oil fraction produced by means of the solvent mixture will frequently be somewhat lower than that of a similar fraction produced with nitrobenzene alone. In

general, greater yields are obtained and higher operating temperatures may be employed when a mixture of a selective solvent and a polyhydroxy cyclic compound is utilized. In any event, an economic balance must be struck between the yield and quality of the refined oil, and the cost of producing the same.

Furthermore, in accordance with my invention, I am able to separate hydrocarbon oils into fractions with my solvent mixture, which could not be economically treated with a selective solvent alone. For example, it is not practical to employ a solvent, such as nitrobenzene, in treating very asphaltic oil stocks such as those derived from some California crude oils, for the reason that the miscibility temperature of the oil and solvent is very low, excessive refrigeration is required, and in certain cases the nitrobenzene may crystallize before separation of fractions can be efiected. However, by adding to the selective solvent, e. g., nitrobenzene, a suitable quantity of a polyhydroxy cyclic compound, for example 5% or 10% of resorcinol, I am able to treat in a satisfactory manner, even the very 'asphalti California oils.

In accordance with my invention, I first mix the oil to be treated in a suitable proportion of a mixture of a selective solvent and a polyhydroxy cyclic compound at a temperature such that complete solution is eflected and a homogeneous liquid obtained. I then cool the solution to a temperature at which separation of the liquid into a two-layer system will take place. one layer will contain a relatively small amount of the solvent dissolved in the parafllnic portion of the oil while the other layer will contain the more naphthenic portion of the oil dissolved in the major quantity of the solvent. Or, I may agitate the mixture of solvent and oil at temperatures at which the liquids are only partially miscible, and thereby etl'ect solution of the naphthenic portion of the oil in the solvent. In either of the above procedures I may take advantage of the principles of countercurrent extraction.

After the extraction proper, I eiiect separation of the two layers which form, by any suitable procedure, as for example, by decantation. I then remove from each of the separated layers, the portion of solvent which each contains, by suitable procedure, such as by vacuum distillation, thereby to obtain two oils of similar distillation ranges but of different chemical composition and diiferent physical characteristics.

Before removing the solvent from the undissolved or more parafllnic layer, I may add a further quantity of the solvent mixture and repeat the extraction, thereby to remove additional naphthenic constituents from said layer. The extraction step may be repeated any desired number of times, each repetition producing an oil of higher paraihnicity as evidenced by its lower viscosity-gravity constant.

A countercurrent relationship in these successive extractions may be established in the conventional manner by employing the partially spent solvent containing dissolved naphthenic oil from the succeeding stages of the extraction system to extract additional quantities of oil in the preceding stages. In the event that the miscibility temperature of the oil with the selective solvent in the latter stages of the system is sufllciently high, the polyhydroxy cyclic compound may be introduced at any desired preceding stage, in order to lessen or eliminate the refrigeration required in the earlier stages.

Where substantial quantities of waxy hydrocarbons belonging to the true paraflln series (CnH2n+2) are present, such hydrocarbons remain in the undissolved or more parafllnic layer and may cause such layer to be solid or semisolid, after the removal of the solvent therefrom. In some cases, the extraction and separation of the layers may be effected at temperatures above the melting point of the waxy hydrocarbons, .so that substantial entrainment of oil n the molten or liquid war is avoided. Such layer may be separated into solid and liquid hydrocarbons by any of the well-known dewaxing processes such as by cold-settling, filtering, or by centrifuging. many instances it may be advantageous to dewax the oil prior to extraction. However, it is to be understood that in accordance with my invenaroma tioh, dewaxing may -be eifected eitherprior or subsequent to extraction. I

My invention will be further understood from the following specific examples:

I. 100 parts by volume of a residuum from a Gulf Coast crude oil having a viscosity of 518 seconds Saybolt universal at 210 F., a specific gravity of 0.9759 at 60 F., and a viscosity-gravity constant of 0.894, was mixed with 200 parts by volume of a solvent consisting of by weight of nitrobenzene and 10% -by weight of pyrocatechin, and heated to slightly above the temperature of complete miscibility, i. e., about 143 F. The homogeneous liquid which resulted was cooled, with agitation, to F. and allowed to settle, whereupon a two-layer system was formed. After separation, the layers were each freed of solvent by vacuum distillation. The resulting undissolved oil fraction comprising 35.0% of the stock had a viscosity of 208 seconds Saybolt universal at 210 F., a specific gravity of 0.9188, and a viscosity-gravity constant of 0.833. The initial Gulf Coast residuum had a miscibility temperature of 91 F; with nitrobenzene alone, and would have required extraction at temperatures below 46 F., to effect a satisfactory separation of oil fractions.

II. parts by volume of a Barber's I-Iill lubricating oil distillate having a viscosity of seconds Saybolt universal at 210 F., a specific gravity of 0.926 at 60 F., and a viscosity-gravity constant of 0.854, was mixed with 200 parts by Volume of a solvent consisting of 90% by weight of nitrobenzene and 10% by weight of pyrogallol, and heated to slightly above the temperature of complete miscibility, i. e., about 185 F. The homogeneous liquid which resulted was cooled, with agitation, to 158 F. and allowed to settle, whereupon a two-layer system formed. After separation, the layers were each freed of solvent by vacuum distillation. The resulting undissolved fraction comprising 47.7% of the stock had a viscosity of 94 seconds Saybolt universal at 210 F., a specific gravity of 0.9088, and a viscosity-gravity constant of 0.834. The initial lubricating oil distillate had a miscibility temperature of 110 F. with nitrobenzene alone, and

would have required extraction at temperatures below 66 F., to effect a satisfactory separation of oil fractions.

III. A Gulf Coast lubricating oil stock having a viscosity of 7'? seconds Saybolt universal at 210 F., a specific gravity of 0.923 at 60 F., and a viscosity-gravity constant of 0.857 was continuously extracted in a 3-stage countercurrent systern with 114% by volume of a solvent consisting of 90% by weight of nitrobenzene and 10% by weight of resorcinol, at a temperature of about 149 F., or-about 49 F. below the temperature of miscibility, i e., 198 F. The resulting undissolved oil fraction, after removal of solvent by vacuum distillation, comprised 70% of the oil stock charged to the extraction system. This refined oil fraction had a viscosity of 69 seconds Saybolt universal at 210 F., a specific gravity of 0.9024, and a viscosity-gravity constant of 0.833. The initial lubricating oil stock had a miscibility temperature of 104 F. with nitrobenzene alone, and would have required extraction at temperatures below 60 F., to eflect a satisiactory separation of the oil into fractions.

From the above examples, it will be noted that by extraction of an oil with a solvent mixture comprising a selective solvent, such as nitrobenzene and a polyhydroxy cyclic compound,

there may be obtained oil fractions which are respectively more parafiinic and more naphthenic than the original oil. By repetition of the extraction process upon the undissolved fraction,

oils of even greater parafiinicity will result. The

quantity of polyhydroxy cyclic compound to be employed in conjunction with the selective solvent will vary, depending upon the character of the selective solvent, the temperature at which the extraction is to be carried out, and the quality of refined oil desired. In general, the quantity of polyhydroxy cyclic compound employed will be of the order of from about 5% to about 10% by weight of the selective solvent. However, more or less of the polyhydroxy compound may be employed, depending upon the temperature at which the extraction is. to be carried out.

While, in the above examples, I have shown the use of. a selective solvent such as nitrobenzene in admixture with various polyhydroxy cyclic compounds, I do not intend to limit myself thereto, but may employ various selective solvents in conjunction with the polyhydroxy cyclic com- P t Polylhydroxy bMlistci- Mis'cihil erccn eye it: comii.y my amp semen Solvent by weight pound percent temp increase by weight F. F.

100 110 90 Resorcinol 10 201 01 100 77 Do 90 Resorcinol 10 93 Benzaldehyde 100 103 Do '90 Resorcinol i0 201 98 BB dichloro ethyl ether 100 143 90 Resorcinol 10 221 78 100 225 90 Resorcinol i0 289 64 mo 103 9O Resoreinol 10 237 74 My process is practically independent of the particular nature or source of the crude oil or oil fraction to be extracted. There may be produced by my process oil products of desired characteristics from oil which by distillation will not produce such products. Moreover, it will be understood, that in accordance with my invention, an important aspect thereof is the increase of the miscibility temperature of the oil and naphthenic solvent by the presence of the polyhydroxy cyclic compound regardless of whatever, if any,.selective action such compound may have upon the oil.

When, in the appended claims, oil is referred to as being viscous, it is to be understood that the oil is of substantial viscosity, i. e., of the order of 50 seconds Saybolt universal at 100 F., or

more.

What I claim is:

1. In the art of refining mineral oils, the process which comprises separating a viscous oil containing paraffinic and naphthenic hydrocarbons into fractions respectively richer in paraflinic and naphthenic compounds by extracting said oil with a selective solvent for naphstantially increase the miscibility temperature oi said selective solvent with said oil, heating the mixture to such temperature as to effect solution, cooling the solution to form a two-layer system, and separating the upper layer from the lower layer.

3. In the art of refining mineral oils, the

process which comprises adding to a viscous 011 containing parafllnic and naphthenic hydrocarbons a selective solvent fornaphthenic hydrocarbons, said solvent containing a polyhydroxy cyclic compound in sufilcient quantity to substantially increase the miscibility temperature of said selective solvent with said oil, heating the mixture to such temperature as to effect solution, cooling the solution to form a two-layer system, removing the lower layer, and similarly re-treating the upper layer with said solvent mixture.

,' 4. In the art of refining mineral oils, the process which comprises bringing a viscous mineral oil containing paraflinic and naphthenic hydrocarbons into contact with a selective solvent for naphthenic hydrocarbons, said solvent containing a polyhydroxy cyclic compound in suiilcient quantity to substantially increase the miscibility temperature of said selective solvent with said oil, thereby to efiect solution of a portion richer in naphthenic hydrocarbons in the solvent mixture, separating the solution so formed from the remainder of the oil, and re-' moving the solvent from both portions of. the oil, thereby to obtain fractions of the oil respectively richer in parafilnic and naphthenic hydrocarbons.

5. The process for separating viscous mineral oils containing paraflinic and naphthenic hydrocarbons into fractions, which comprises bringing the oil into contact with a selective solvent for naphthenic hydrocarbons, said solvent containing a polyhydroxy cyclic compound in suflicient quantity to substantially increase the miscibility temperature of said selective solvent with said oil, thereby to effect solution of a portion of the oil richer in naphthenic hydrocarbons in the solvent mixture, separating the solution so formed from the remainder of the oil, and distilling the solvent from both of the portions of the oil, thereby to obtain fractions of the oil respectively richer in parafiinic and naphthenic hydrocarbons.

6. In the art of refining mineral oils, the process which comprises bringinga viscous mineral oil containing paraiiinic and naphthenic hydrocarbons into contact with a selective solvent for naphthenic hydrocarbons, said solvent containing a polyhydroxy cyclic compound in sufficient quantity to substantially increase the miscibility temperature of said selective solvent with said oil, ther'eby to effect solution of a portion richer in naphthenic hydrocarbonsrin the solvent mixture, separating the solution so formed from the remainder of the oil, and retreating the oil remaining with additional amounts of the solvent mixture.

7. The method for producing paramnic lubricating oil from mixed base crude; which comprises distilling the crude and bringing a portion thereof into contact with a selective solvent for naphthenic hydrocarbons, said solvent containing a polyhydroxy cyclic compound in sumcient quantity to substantially increase the miscibility temperature of said selective solvent with said oil, thereby partially dissolving the oil, separating the solution of oil so treated, and removing the solvent from the treated oil.

8. In the art of. refining mineral lubricating oil containing parailinic and naphthenic hydrocarbons, the step of fractionally extracting the oil with a selective solvent for naphthenic hydrocarbons, said solvent containing a polyhydroxy a cyclic compound in suilicient quantity to substantially increase the miscibility temperature of said selective solvent with said oil, to elect a separation of fractions respectively richer in parafllnicand naphthenic compounds. I

9. The process of treating a viscous fraction of a crude oil of one type containing parailinic and naphthenic hydrocarbons to procure a fraction having the quality of a corresponding fraction of a crude oil of difierent type having a greater content of. paraifinic hydrocarbons, which comprises extracting the viscous fraction with a selective solvent for naphthenic hydrocarbons,

said solvent containing a polyhydroxy cyclic compound in sufiicient quantity to substantially' increase the miscibility temperature of said selective solvent with said oil fraction, and separating the oil so treated into portions respectively richer in parafiinic and naphthenic hydrocarbons.

10. The process of treating a viscous fraction of a mixed base crude oil to procure a fraction having the quality of a corresponding traction of a parafiinic base crude, which comprises extracting the viscous fractionwith a selective solvent for naphthenic hydrocarbons, said solvent containing a polyhydroxy cyclic compound in sumcient quantity to substantially increase the miscibiiity temperature of said selective solvent with said oil fraction, and separating the oil so treated into portions respectively richer in paraillnic and naphthenic compounds.

11. In the art of. refining mineral oils, the process which comprises bringing a viscous hydrocarbon oil of a quality other than that of a Pennsylvania type viscous oil, and containing paraiilnic and naphthenic components into intimate contact with a selective solvent for naphthenic hydrocarbons, said solvent containing a polyhydroxy cyclic compound in sufficient quantity to substantially increase the miscibility temperature of said selective solvent with said oil, thereby to dissolve from the oil substantial amounts of its naphthenic components, thereafter removing the solvent mixture and oil dissolved therein from that portion of the oil which remains undissolved, thereby to produce an oil such as is normally obtained from Pennsylvania type crude by distillation.

12. In the art of refining mineral oils, the

process which comprises separating a viscous oil containing parafiinic and naphthenic hydrocarbons into fractions respectively richer in parafiinic and naphthenic compounds by extracting said oil with nitrobenzene containing a polyhydroxy cyclic compound.

13. In the art of refining mineral oils, the process which comprises bringing a-mineral oil containing paraflinic and naphthenic hydrocarbons into contact with nitrobenzene containing a polyhydroxy cyclic compound thereby to efiect solution of a portion richer in naphthenic hydrocarbons in the solvent, separating the solution so formed from the remainder of the oil, thereby to obtain fractions of the oil respectively richer in paraflinic and naphthenic hydrocarbone.

14. The process of treating a viscous fraction of a crude oil of one type containing paraflinic and naphthenic hydrocarbons to procure a fraction having the quality of a corresponding fraction of a crude oil of different type having a greater content of paraflinic hydrocarbons, which comprises extracting the viscous fraction with nitrobenzene containing a polyhydroxy cyclic compound, and separating the oil so treated into portions respectively richer in paraflinic and naphthenic hydrocarbons.

15. The method for producing a paraflinic lubricating oil from a mixed base crude oil, which comprises distilling the crude and bringing a portion thereof into contact with nitrobenzene containing a polyhydroxy cyclic compound, thereby partially dissolving the oil, separating the solution of the oil so treated, and removing the solvent from the treated oil.

16. In the process of decreasing the viscositygravity constant of a viscous mineral oil, the step of extracting the oil with a solvent mixture comprising an aromatic nitro compound and a polyhydroxy cyclic compound.

17. In the process of decreasing the viscositygravity constant of a viscous mineral oil, the step of extracting the oil with nitrobenzene containing resorcinol.

18. In the processof decreasing the viscositygravity constant of a viscous mineral oil, the step of extracting the oil with nitrobenzene containing pyrogallol.

19. In the process of decreasing the viscositygravity constant of a viscous mineral oil, the step of extracting the oil with nitrobenzene containing pyrocateqhin. Y

20. A method for increasing the miscibility temperature of a selective solvent with a hydrocarbon oil, which comprises adding to said solvent for naphthenic components a polyhydroxy cyclic compound completely soluble therein and capable of increasing to substantial extent the miscibility temperature of the solvent with the oil.

SEYMOUR W. FERRIS.