US2286852A - Solvent extraction of petroleum - Google Patents

Description

June 16 1942. d 2,286,852

SOLVENT EXTRACTION 0F PETROLEUM Filed Sept. 16, 1938 RAFFINATE MfLV/N M. HOLM INVENTOR ATTORNEY Patented June 16, 1942 2,286,852 SOLVENT EXTRACTION or PETROLEUM Melvin M. Holm, San Francisco, Calif., assignor to Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware Application September 16, 1938, Serial No. 230,229

16 Claims.

This invention relates to refining hydrocarbon oil and more particularly to the extraction of mineral oil fractions, such as petroleum naphtha or mineral lubricating oils, by solvent treatment.

The invention contemplates the treatment and refinement of mineral oil with a selective solvent liquid to separate therefrom desired or undesired constituents. It contemplates particularly the treatment of lubricating oil to produce therefrom lubricating oil products of desired characteristics. It also contemplates the extraction of lower boiling petroleum fractions, such as petroleum naphtha, to effect a refinement thereof and/or to separate a fraction of a desired chemical type.

The drawing comprises a diagrammatic flow sheet of one method of effecting solvent extraction with the selective solvent of this invention.

The invention involves selective solvent extraction of mineral oil with a solvent comprising an amine containing more atoms of carbon than of nitrogen in its molecule and belonging to the group of such compounds which can be formed by the interaction of ethylene dichloride with ammonia followed by liberation of free amine by treatment with caustic. The term polyethylene amines is used herein to designate these types of' compounds.

The selective solvent of the process is, in general, either an open chain compound of the general formula NH2.C2H4(C2H4.NH).NH2, where a: is a whole number, or a ring compound having the general formula oH.NH)aozmuH:

where :L' is a whole number. The first group is exemplified by diethylene triamine (NH2.C2H4.NH.C2H4.NH2)

triethylene tetramine (NH2.C2H4.NI-I.C2H4.NH.C2H4.NI-Iz) and tetraethylene pentamine (NI-I2.C2H4.NH.C2H4.NH.C2H4.NH.C2H4.NH2)

Examples of the second group are diethylene diamine.

NH NH C2H and triethylene triamine NH Cg C1114 NHCiHiNH Thus this invention broadly embraces the use of a selective solvent comprising a polyethylene amine containing more carbon atoms than nitro-,

gen atoms and further characterized by the presence of the chemicalgroup Lubricating oils derived from mixed base crudes contain relatively paraffinic constituents as well as relatively non-paraffinic constituents including naphthenic, aromatic and unsaturated hydrocarbon bodies. The polyethylene amines above mentioned are particularly Well adapted to the treatment of mineral lubricating oil fractions to effect separation between the parafiinic and relatively non-parafinic constituents. Accordingly, the solvent liquids'of the invention are adapted to remove relatively non-parafiinic constituents from lubricating oil and produce therefrom lubricating oil products of more parafiinic character and having a higher viscosity index.

In the application of the invention to the treatment of mineral oil for the production of lubricating oil, one part of the oil is mixed with from about one-half to about three or more parts of the solvent liquid. This mixture is then subjected to agitation at a suitable temperature, as for example, about 32 F. to 300 F., and then separated into an extract phase'and a raffinate phase. The extract phase comprises the nonparaifinic constituents of the oil dissolved in the solvent liquid, while the raffinate phase comprises the relatively paraifinic constituents of the oil.

The two phases are separated from each other and the solvent removed therefrom by distillation or by washing with another suitable solvent liquid.

The extent to which the oil is soluble in the solvent depends upon the nature of the oil as well as the temperature of extraction and the ratio of solvent liquid to oil employed during extraction. The extraction temperature and the ratio of solvent to oil may be Varied for the purpose of efiecting the particular degree of extraction desired. Consequently, in some instances, it may be desired to employ temperatures either somewhat below or somewhat higher than those mentioned above, and likewise the ratio of solvent to oil may be either greater or less than that specified.

As a specific example, a lubricating oil comprising a heavy distillate from a California (Midway) crude and having the tests indicated below was extracted with triethylene tetramine. The oil was extracted with about 100% by volume of the solvent at a temperature of about F. The mixture was separated into extract and rafiinate phases and the raflinate phase, upon removal of the solvent liquid, comprised about 83% of the original charge.

The tests on the oil before extraction and on the resulting rafiinate and extract oils were as follows:

As previously pointed out, the invention also contemplates the separation of petroleum naphthas into fractions of difierent chemical type. One particular utility for this species of the invention comprises the production of low aniline point thinners, that is, fractions of high aromatic content, from petroleum naphthas. These low aniline point thinners are highly desirable for use in paint compositions and wherever petroleum fractions with high solvent power are sought. This aspect of the invention may also be utilized to extract undesired constituents, such as sulfur, from naphthas to give a raffinate of decreased sulfur content.

As a specific example of this species of the invention, a fraction of a dehydrogenated naphtha from a Kettleman fields crude, having a boiling range of 200 F. to 300 F. was extracted with 100 volume per cent of triethylene tetramine in a one stage batch treatment. The contacting and separation of the layers were ef fected at approximately 70 F. The rafiinate and extracted oil fractions were freed of associated solvent in an ordinary distillation system. Since the end boiling points of the respective oil fractions were much lower than the boiling point of the solvent, substantially complete vaporization of the rafiinate oil and the extract oil were effected without vaporization of the solvent. This mode of operation is highly advantageous because it is only necessary to vaporize one volume of oil in total raflinate and. extract for the several s g Rafiinate Extract Volume percent yield 100 83 17 Gravity, A. P. I 54. 4 56. 4 47. 7 Weight percent sulfur 0. 01 0. ll Aniline point 99 109 48 It will be observed that the raffinate obtained in the above example is of higher gravity and the extract has a lower aniline point than the original naphtha. Subsequent refining treatments may be given either the raffinate or extract fraction if further refinement is required for particular purposes. Among such additional treatments are sulfuric acid treatment, contact with adsorbent earths and the like. Similarly, the lubricating oil may be subjected to the foregoing extraction treatment with polyethylene amines either before or after dewaxing, and also either before or after treatment with other solvents or chemicals.

A second example of a method of treating pctroleum naphthas with polyethylene amine selective solvents to refine the same and/or prepare low aniline point thinners comprises a process wherein the normally liquid petroleum fraction is countercurrently contacted with the selective solvent at a temperature above the initial boiling point of the hydrocarbons being treated. Such a process is illustrated by the flow sheet of the drawing in which the petroleum stock to be treated passes from storage hrough valve controlled line H3, heat exchanger I I, line l2, heat exchanger l3, line I l, vaporizer i5, and line [6 to a single extraction tower ll. The liquid phase selective solvent comprising a polyethylene amine, such as triethylene tetramine together with its dissolved extract, flows from .the bottom of tower ll through line Hi to vaporizer IS. A portion only of the extract is flashed into vapor form and recirculated through line 28 to tower ll. Solvent is continuously removed from vaporizer l9 through line 21 and passed to still 22 for removal of the extracted hydrocarbons. The extract is separated from the solvent in fractionating column 23 and flows through line 24, heat exchanger I3, line 25, and condenser 25 to storage. The selective solvent is continuously removed from the still and recirculated to extraction tower I! through valve controlled line 21. The liquid level in Vaporizers l5, l9 and 22 is maintained above the conduit connections I4, l8, 2i and 21 to produce a liquid seal and prevent the flow of vapors through these conduits. Railinate vapors flow from the top of extraction tower [1, through line 28 to heat exchanger H where partial condensation occurs. As much of this partial condensate as is desired may be returned to the extraction tower through line 30, controlled by valve 3i. The remainder of the raffinate passes through condenser 29 to storage. Valve controlled conduit 32 provides means for supplying additional condensate to the reflux line when the desired reflux ratio is higher than that obtainable with the partial condensate alone.

In a single stage extraction process, such as that involved in the drawing, it is essential that the vapor phase hydrocarbons and the liquid phase selective solvent be intimately contacted. One eflicient means for effecting this result comprises the conventional bubble cap fractionating column in which the vapors thereby extracted rise upwardly through a series of bubble caps and are thereby intimately mixed with the downflowing selective solvent. Such an extraction tower is the preferred form but other types of towers may be utilized, for example, packed towers containing Raschig rings, broken quartz and the like.

The type of process illustrated in the drawing is particularly applicable to the separation of aromatic hydrocarbons from petroleum fractions and is effective to obtain a sharp separation of hydrocarbon fractions having a boiling range in the order of 100 F. or more and containing parafiinic hydrocarbons having a boiling point as much as from 20 F. to 60 F. above the boiling point of the aromatics being extracted. It will be observed that this process is characterized by its ability to separate components of a complex mixture, such as a petroleum naphtha containing and consisting essentially of aromatic, cyclic non-benzenoid, and paraflinic hydrocarbon compounds having overlapping boiling ranges by passing said hydrocarbons through an extraction zone at a temperature above the initial boiling point of the mixture but below the end boilin oint thereof whereby a vapor phase is formed, countercurrently extracting these vapor phase hydrocarbons with a polyethylene amine selective solvent maintained in liquid phase but at a temperature above the initial boiling point of the hydrocarbon mixture in the extraction zone and separating a vapor phase rafiinate and a liquid phase extract from the extraction zone.

'I'riethylene tetramine is a selective solvent which has marked stability at high temperatures. Tests have established that decomposition of this solvent was less than 0.1% in eight hours at 340 F, This property, together with the fact that polyethylene amine solvents are not corrosive and are not caustic in nature, renders these solvents particularly useful for selective solvent processes operated at elevated temperatures.

The various extractions disclosed hereinabove may be carried out in a continuous countercurrent type of operation or in an intermittent batch type of operation. In the continuous countercurrent type of operation, the ratio of oil to sol-- vent may be somewhat less than that used in the batch type of operation.

In some instances it may be of advantage to carry out the extraction in the presence of a modifying solvent liquid, such as aniline and xylidine or other solvents Which are selective in themselves, or with diluents, such as benzene, toluene, the carbitols and other non-selective solvents, or with anti-solvents for the oil, such as water, methyl alcohol, ethyl alcohol, glycerol and the like.

Although certain specific amounts of solvent, temperatures, conditions and sequences of operation and proportions of solvent to oil have been exemplified above in detail, it is to be understood that all such amounts, proportions, conditions and sequences are merely illustrative and are not to be considered as limiting. Numerous changes and modifications therein can be made, as will be apparent to those skilled in the art, according to the character both of the oils to be refined and the results sought to be accomplished, and all such changes and modifications as come within the scope of the appended claims are embraced by the invention.

I claim:

1. In the refining of petroleum oils, the method which comprises mixing the oil with a selective solvent comprising a polyethylene amine, said polyethylene amine molecule having more atoms of carbon than of nitrogen and being further characterized by the presence of the chemical group forming an extract phase containing a portion of said petroleum oil dissolved in the solvent and a raflinate phase comprising undissolved oil, and separating the two phases.

2. In the refining of petroleum oils, the method which comprises mixing the oil with a selective solvent comprising an amine having the general formula where :13 represents a whole number, forming an extract phase and a raflinate phase, and separating the two phases.

3. In the refining of petroleum oils, the method which comprises mixing the oil with a selective solvent comprising an amine having the general formula where x represents a Whole number, forming an extract phase and a raflinate phase, and separating the two phases.

4. In the refining of petroleum oils, the method which comprises mixing the oil with a selective solvent comprising triethylene tetramine, forming an extract phase and a rafiinate phase, and separating the two phases.

5. In the refining of mineral lubricating oil containing relatively parafiinic and relatively non-paraflinic constituents, to separate therefrom a parafiinic fraction of relatively high viscosity index, the method which comprises mixing the oil with a selective solvent comprising a polyethylene amine, said polyethylene amine molecule having more atoms of carbon than of nitrogen and being further characterized by the presence of the chemical group i r r r-r-r-rr- H H H H H forming an extract phase containing relatively non-parafiinic constituents of the oil dissolved in the solvent liquid and a rafiinate phase comprising the relatively parafiinic constituents of the oil, separating the two phases, and removing the solvent liquid therefrom.

6. In the refining of mineral lubricating oil containing relatively paraffinic and relatively non-parafiinic constituents, to separate therefrom a paraffinic fraction of relatively high viscosity index, the method which comprises mixing the oil with a selective solvent comprising an amine having the general formula Where n: represents a whole number, forming an extract phase containing relatively non-paraffinic constituents of the oil dissolved in the solvent liquid and a rafilnate phase comprising the relatively parafi'inic constituents of the oil, separating the two phases, and removing the solvent liquid therefrom.

7. In the refining of mineral lubricating oil containing relatively paraffinic and relatively non-parafiinic constituents, to separate therefrom a parafiinic fraction of relatively high viscosity index, the method which comprises mixing the oil with a selective solvent comprising an amine having the general formula where :1: represents a whole number, forming an extract phase containing relatively non-paraffinic constituents of the oil dissolved in the solvent liquid and a raffinate phase comprising the relatively paraflinic constituents of the oil, sep-. arating the two phases, and removing the solvent liquid therefrom.

8. In the refining of mineral lubricating oil containing relatively parafiinic and relatively non-paraifinic constituents, to separate therefrom a paraffinic fraction of relatively high viscosity index, the method which comprises mixing the oil with a selective solvent comprising triethylene tetramine, forming an extract phase containing relatively non-paraffinic constituents of the oil disolved in the solvent liquid and a raflinate phase comprising the relatively paraffinic constituents of the oil, separating the two phases, and removing the solvent liquid therefrom.

9. In the refining of a normally liquid low boiling petroleum oil containing parafiinic and aromatic constituents, to separate therefrom a relatively aromatic fraction of high solvent power, the method which comprises mixing the oil with a selective solvent comprising a polyethylene amine, said polyethylene amine molecule having more atoms of carbon than .of nitrogen and being further characterized by the presence of the chemical group forming an extract phase containing relatively,

aromatic constituents of the petroleum dissolved in the solvent liquid and a rafilnate phase comprising the relatively paraflinic constituents of the oil, separating the two phases, and removing the dissolved hydrocarbons from said extract.

10. In the refining of a normally liquid low boiling petroleum oil containing paraffinic and aromatic constituents, to separate therefrom a relatively aromatic fraction of high solvent power, the method which comprises mixing the oil with a selective solvent comprising an amine having the general formula where :t represents a whole number, forming an extract phase containing relatively aromatic constituents of the petroleum dissolved in the solvent liquid and a raflinate phase comprising the relatively paraffinic constituents of the .oil, separating the two phases, and removing the dissolved hydrocarbons from said extract.

12. In the refining of a normally liquid low boiling .petroleum .oil containing paraffinic and aromatic constituents, to separate therefrom a relatively aromatic fraction of high solvent power, the method which comprises mixing the oil with a selective solvent comprising triethylene tetramine, forming an extract phase containing relatively aromatic constituents of the petroleum dissolved in the solvent liquid and a raflinate phase comprising the relatively paraffinic constituents of the oil, separating the two phases, and removing the dissolved hydrocarbons from said extract.

13. A process of separating components of a complex mixture containing and consisting essentially of aromatic, cyclic non-benzenoid, and parafiinic hydrocarbon compounds having overlapping boiling ranges which comprises passing said hydrocarbons through an extraction zone at a temperature above the initial boiling point of the mixture whereby a vapor phase is formed, countercurrently extracting said vapor phase hydrocarbons with a selective solvent comprising a polyethylene amine having more atoms of carbon than of nitrogen maintained in a liquid phase but at a temperature above the initial boiling point of said hydrocarbon mixture, separating a vapor phase rafiinate comprising the more paraflinic portion of said original complex mixture,.separating from said extraction zone a liquid phase extract comprising the more aromatic portion of said complex mixture and separating the extracted hydrocarbons from said polyethylene amine.

14. A process as defined in claim 13 in which said polyethylene amine is triethylene tetramine.

15. A process as defined in claim 13 in which said polyethylene amine is an amine having the general formula NH2.C2H4. (C2H4.NH) 9:.NI'I2 where :1: represents a whole number.

16. A process as defined in claim 13 in which the polyethylene amine is an amine having a general formula where m represents a Whole number.

MELVIN M. HOLM.

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