US2166140A - Dialkyl formamides as selective solvents for refining mineral oils - Google Patents

Description

Patented July 18, 19 39 I v I i UNIITED'STATES PATENT OFFICE I v a saiio I DIALKYL FORMAMIDES as SELECTIVE SOL- VENTS FOR REFINING MINERAL oms Virgil L. Hanslcy, Niagara Falls, N. Y., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application April 20, 1937,

Serial No. 137,928

15 Claims. (Cl. 196-43) This invention relates to the separation of mix- "dialiphatic as employed herein and in the claims tures of hydrocarbons by selective solvent extracwill be restricted to hydrocarbon radicals and tion and more particularly to thesolvent refining will include unsaturated and cyclic aliphatic hyof mineral oils. drocarbon radicals as well as the saturated and 5 It is now well known that a large proportion "open chain aliphatic hydrocarbon radicals. 5 of the mineral oils and gasolines of today are com- The hydrocarbon mixture or oil is mixed with plex mixtures. of parafllnic and non-parafllnic the formamide under such conditions that two I hydrocarbons. It is frequently desirable to sepalayers are formed; one of which comprises the rate the non-parafllnic hydrocarbons from the constituents which it is desired to extract from paraflinic hydrocarbons for various reasons. One the oil dissolved in the bulk of the liquid solvent, 10 o! the main reasons is that the paraflinid hydrowhile the other comprises the undissolved and carbons are in general more resistant to decomrelatively paraflinic oil in admixture with a relaposition through heat and oxidation than the tively small amount of the solvent. Preferably, non-paraflinic hydrocarbons. Accordingly, the my method comprises mixing the substituted oil containing the larger proportion of parafiinic formamide with the hydrocarbon mixture inap- 15 constituents or, in other words, the relatively proximately equal volumes and heating with agimore parafllnic oils are more stable than the less tation to a temperature at which the solvent and paraflinic oils and hence are more desirable as oil become substantially completely miscible. lubricants and for other purposes This solution is then cooled with agitation to a Various methods have been proposed for sepatemperature at least C. below the temperature 20 rating the non-parailinic from the parafllnic conof complete miscibility. The resulting mixture is stituents of oils. One of the more common and allowed to stand until it separates 'into two layers. oldest is by treatment with sulfuric acid which The two layers are separated by separately withremoves some of the non-parailinic compounds drawing each layer. The dialiphatic iormamide from the oils. More recently it has been proposed is recovered from each layer, preferably by disto separate the non-parafllnic hydrocarbons by tillation. The residue from the layer containing means of selective solvent extraction. the larger amount of solventconsists of a large An Object of the Present invention is to Provide proportion 01' non-parafllnic and undesirable conmethod Sep a mixture of Da afl stituents. The residue from the layer containing 8nd -pa fin c ydrocarbons into portions, the smaller amount of solvent consists primarily one of which is relatively more -paraiiinic than of the desirable paraflinic hydrocarbons. the original mixture and the other relatively less In the examples given below, the selective p Another Object is the Separation 0f moval oi non-paramnic constituents from a minrelatively nonparaflinic bodies from mineral lul 11 has been measured by following the brlcating oilsto produce lubricating oils of relachange i viscosity-gravity constant of the oil. 85 tively high paraflinic character. Afurther object This t t h s b d ib d by J 3, Hill is theproduction of lubricating oils with improved and Coates in I d t i l nd En i i viscosity-temperature curves from oils with poor Chemistry, V l me 20, page 641, et seq., in an viscosity-temperature curves. Still other objects article e t t Viscosity-Gravity Constant 0 will pp hereinafterof Petroleum Lubricating Qils. If a given crude 40 These Objects y be accomplished in accord petroleum be distilled into successive fractions ance with my invention which comprises P and the specific gravities and viscosities of the ing mixtures'of parafiinic and non-parafiinic hyseveral fractions determined, it will be found that drocarbons with an N-dialiphatic substituted they nf to the'general relationship: formamide boiling below about 250 C. to remove 752 I the non-parafilnic hydrocarbons by the selective i 10g (v 38) action of the formamide. The dialiphatic formamides of my invention may be represented by in which G is the specific gravity at F.,

the formula V" is Saybolt Universal viscosity at F., and

o R a is the viscosity-gravity constant. These con- 5 H K stants are lower for fractions of parafllnic crudes than are the constants iorfractions of the naphthenic crudes. The viscosity-gravity constant is, whereinR and R represent aliphatic hydrocarbon therefore, an index of the paraflinicity oi an oil, radicals. It will be understood that the term and a decrease in the value of this constant for a 55 given fraction of lubricating oil indicates an increase in parafiin hydrocarbon content.

Example 1 temperature solvent and oil were miscible. The

solution was cooled to 80 C., allowed to settle one-half hour, and the two layers withdrawn into separate containers. Dimethyl formamide was removed from both layers under reduced pressure. The top layer was found to contain 80% of the volume of the original oil and to have a viscosity-gravity constant of 0.848.

Example 2 V The lubricating oil distillate given in Example 1 was heated with agitation with twice its volume of dimethyl formamide to 100 (3., cooled to Example 3 The distillate used in Example 1 was heated with an equal volume of diethyl formamide to 100 C. with agitation, cooled to 70 C. and allowed to settle one-half hour. After separation of the two layers and removal of solvent from each, an oil recovery of 76% was obtained from the top layer, this oil having a viscosity-gravity constant of 0.858.

- Dialiphati c formamides may be used with advantage in conjunction .with other solvents which areknown to possess selective solvent action in petroleum refining but which frequently have disadvantages'of low separation temperatures and relatively poor yields of refined oil. Some of such other solvents are beta-beta'-dichloro-diethyl ether, nitrobenzene, cyclohexanol, methyl acetate, phenol, cresylic acids, cyclohexanone and aniline. Generally, the dialiphatic formamide should constitute from about or more of such solvent mixture and preferably about 50% thereof. Used in conjunction with such solvents, dimethyl formamide materially raises the separation temperatures, avoiding the necessity of refrigeration, and improves the yield of refined oils. The following examples will illustrate these points:

Example 4 A solvent was prepared by mixing one part of dimethyl formamide with one part of nitrobenzene. The lubricating oil distillate given in Example 1 was heated with an equal volume of this mixed solvent to 45 0., the temperature of complete miscibility. The solution was cooled to 20 C., settled one-half hour, and the separated layers treated as in the previous examples. From the top layer a yield of 70% of raflinate was obtained having a viscosity-gravity constant of 0.840. Nitrobenzene on the same stock under similar conditions required a separation temperature of 0 C. and yielded only 58% of raifinate of the same viscosity-gravity constant.

Example 5 A solvent was prepared by mixing equalparts Example 6 Equal volumes of dimethyl formamide and cyclohexanol were mixed for use as a solvent. The lubricating oil distillate described in Example 1 was treated with an. equal volume of the mixed solvent in the manner previously described, the temperature of complete miscibility being 75 C. Separation into two phases was accomplished at C. -The yield of raflinate from the top layer was 64% with a viscosity-gravity constant of 0.854. In attempting to use cyclohexanol alone on this stock, separation into two phases couldnot be accomplished even by chilling to While I have disclosed the use' of dimethyl and diethyl formamides, in the above examples, other dialiphatic formamldes with boiling points up to 250 C. may be employed in place thereof. Some of such other compounds which would be suitable are dipropyl formamide, diisopropyl formamide, dibutyl formamide, di-isobutyl formamide, methyl ethyl formamide, methyl propyl formamide, methyl isobutyl formamide, ethyl isopropyl formamide, ethyl butyl formamide, isopropyl isobutyl formamide, divinyl formamide, diallyl formamide, and similar compounds. However, the dialkyl forniamides are preferred and of these dimethyl formamide and diethyl formamide are the most satisfactory. Further, the dialiphatic formamides used for extraction need not be pure compounds but may be mixtures boiling between about 150 C. and

about 250 C.

The conditions of application of the solvent will vary with the nature of the oil. Highly naphthenic oils will, in general, require a lower temperature to effect separation than highly parafllnic oils. The temperatures employed will, in general, range from about 0 C. to about 200 C; At the higher temperatures, it may be necessary to employ pressure to prevent substantial vaporization of the solvent. The ratio of solvent to oil may be varied within rather wide limits and will depend largely upon the nature of the oil being treated, the amount of non-parafllnic constituents therein and the quality of the refined oil desired. In general, the ratio of solvent to oil will lie between 1 to 10 and 5 to 1 parts by volume.

The application of the 'dialiphatic formarnides as selective solvents is not confined to lubricating oil distillates. They may be employed to refine other hydrocarbon or mineral oil fractions such as cracked naphthas, gasoline, or kerosene fractions, whose boiling ranges are sufiiciently difierent from the solvent to permit separation of the solvent from the hydrocarbon mixture. Extraction treatment with the dialiphatic formamide may be applied to a raw distillate or to a par-.

it may be desirable to supplement the extraction with the usual acid, alkali, doctor, or clay treatment applied either before or after the solvent extraction.

From the above disclosure, it will appear that I have provided new and improved selective solvents ior refining petroleum oils and particularly for the production of high grade lubricating oil from mediocre crudes. The dialiphatic formamides possess high miscibility temperatures with 0115 thus permitting their utilization as extraction solvents over a wide temperature range. Further, the dialiphatic iormamides may be employed in combination with other selective solvents having lower miscibility and extraction temperatures to permit extraction at higher temperatures and with improved yields of refined oil.

While I have disclosed the preferred embodiments of my invention and the preferred modes of carrying the same into effect, it will be readily apparent to those skilled in the art that many variations and modifications may be made therein without departing from the spirit of my invention. Accordingly, the scope of my invention is to be limited solely by the appended claims con strued as broadly as is permissible in view of the prior art.

I claim:

1. The method of treating a normally liquid hydrocarbon mixture containing relatively paraflinic and relatively non-paraifinic compounds which comprises extracting the hydrocarbon mixture with an N-dialiphatic formamide boiling below 250 C. to separate the relatively nonparafiinic compounds from the relatively paraffinic compounds.

2. The method of treating a normally liquid hydrocarbon mixture containing relatively paraflinic and relatively non-paraflinic compounds which comprises mixing an N-dialiphatic formamide boiling below 250 C. with the hydrocarbon mixture, causing the resulting mixture to separate into two layers and separating the lay ers, whereby the relatively non-parailinic compounds are separated from the relatively paraffinic compounds.

3. The method of treating a normally liquid hydrocarbon mixture containing relatively parafiinic and relatively non-parafiinic compounds which comprises mixing with the hydrocarbon mixture an N-dialiphatic formamide boiling below 250 C., heating the resulting mixture to a temperature where the formamide becomes completely miscible with the hydrocarbon mixture, cooling the mixture to a temperature at least 20 C. below the temperature of complete miscibility and to where the mixture separates into two layers, separating thetwo layers, and removing the formamide from each layer, whereby the relatively non-paraffinic compounds are separated from the relatively paraflinic compounds.

4. The method of treating a normally liquid hydrocarbon mixture containing relatively paraffinic and relatively non-paraflinic compounds which comprises extracting the hydrocarbon mixture with N-dimethyliormamide to separate the relatively non-paraflinic compounds from the relatively parafiinic compounds.

5. The method of treating a normally liquid hydrocarbon mixture containing relatively paraifinic and relatively non-paraffinic compounds which comprises mixing N-dimethyl formamide with the hydrocarbon mixture, causing the resulting mixture to separate into two layers and separating the layers, whereby the relatively non-paramnic compounds are separated from the relatively paraffinic compounds.

6. The method of treating a normally liquid hydrocarbon mixture containing relatively par hydrocarbon mixture containing relatively paraflinic and relatively non-parafiinic compounds which comprises extracting the hydrocarbon mixture with a solvent mixture comprising an dialkyl formamide boiling below 250 C. and a selective solventhaving a substantially .lower separation temperature, to separate the relatively non-parafiinic compounds from therelatively parafiinic compounds.

8. The method of treating a normally liquid hydrocarbon mixture containing relatively parafiinic and relatively non-parafilnic compounds which comprises extracting the hydrocarbon mixture with a solvent mixture comprising an N-dialkyl formamide boiling below 250 C. and nitrobenzene, to separate the relatively nonparafiinic compounds from the relatively paraflinic compounds.

9. The method of treating a normally liquid hydrocarbon mixture containing relatively paraflinic and relatively non-paraflinic compounds which comprises extracting the hydrocarbon mixture with a solvent mixture comprising dimethyl formamide and a selective solvent having a substantially lower separation temperature, to separate the relatively non-paraflinic compounds from the relatively parafiinic compounds.

10. The method of treating a normally liquid hydrocarbon mixture containing relatively paraflinic and relatively non-parafiinic compounds which comprises extracting the hydrocarbon mixture with a solvent mixture comprising dimethyl formamide and beta-beta-dichlorodiet yl ether to separate the relatively non-para lo compounds from the relatively parafflnic compounds.

11. -The method of treating a normally liquid hydrocarbon mixture containing relatively paraflinic and relatively non-paraffinic compounds which comprises extracting the hydrocarbon mixture with a solvent mixture comprising dimethyl formamide and nitrobenzene, to separate the relatively non-parafiinic compounds from the relatively paraflinic compounds.

12. The method of treating a normally liquid hydrocarbon mixture containing relatively paraffinic and relatively non-paraffinic compounds which comprises mixing with the hydrocarbon mixture a solvent mixture comprising an N- dialkyl formamide boiling below 250 C. and a selective solvent having a substantially lower separation temperature, heating the resulting mixture to a temperature where the solvent mixture becomes completely miscible with the hydrocarbon mixture, cooling the mixture to a 13. The method of treating a normally liquid hydrocarbon mixture containing relatively paraflinic and relatively non-paraflinic compounds which comprises mixingwith the hydrocarbon mixture a solvent mixture comprising an N- dialkyl formamide boiling below 250 C. and cyclohexanol, heating the resulting mixture to a temperature where the solvent mixture becomes completely miscible with the hydrocarbon mixture; cooling the mixture to a temperature at least 20 0. below the temperature of complete miscibility and to where the mixture separates into two layers, separating the two layers and removing the solvent mixture from each layer, whereby thexelatively non-parafllnic compounds are separated from the relatively paraflinic compounds.

14. The method of treating a normally liquid hydrocarbon mixture containing relatively paraflinic and relatively non-paraflinic compounds which comprises mixing with the hydrocarbon the two layers and removing the solvent mixture from each layer, whereby the relatively nonparafllnic compounds are separated from the relatively paraflinic compounds.

15. The method of refining petroleum oil con-' taining relatively parafllnic and relatively nonparaflinic compounds which comprises extracting the oil with an N-dialkyl formamide boiling below 250 C. to remove the relatively non-paraflinic compounds from the oil.

VIRGIL L, HANSLEY.