US2247475A - Modified lubricating oil - Google Patents

Description

Patented July l, 1941,

MODIFIED LUBRICATIN G OIL Ulric B. Bray, Palos Verdos Estates, and Donald E.

Carr, Los Angeles, Calif., assignors to Union Oil Company of California, Los Angeles, Calii'., a corporation of California No Drawing. Application November 23, 1936, Serial No. 112,352

7 Claims.

This invention relates to lubricating oils and particularly to the improvement of .very heavily treated or highly refined mineral lubricating oils to correct them for apparently undesirable effects such as corrosion of modern type bearings,

ring-sticking and the like, due apparently to what may be termed overtreatment resulting in the removal of protective agents by "deep-cutting modern solvent treating processes.

More recently the use of various selective solvents' such as liquid sulfur dioxide-benzol mixture. phenol, dichlorethylether and thelike have been employed for the extraction of both Eastern or paraflinic type, and Western or asphaltic and naphthenic type oils. These extractions resulted in the removal of large quantities of carbon-forming, naphthenic, unsaturated, and other types of materials not strictlyparafiinic in nature which.

have been considered by many investigators to be less desirable in lubricating oils. However, it appears that not only have the undesirable materials been removed by such treating processes,

"distillate are extracted with liquid sulfur dioxide,

but also protective agents of some type have been removed which prevent or counteract the formation of corrosive compounds, ring-sticking compounds and the like.

stituents can be added to or returned to the final lubricating product and thereby overcome the corrosive, ring-sticking and other characteristics above mentioned. l'he preferred fractions of these extracts are the intermediate or heart out constituents; these may in general be considered as consisting largely of preferred stable aromatic materials associated with naphthenic constituents also removed by the action of the selective solvent. The heavier unstable aromatics, resinous and tarry materials and the like are objectionable and are removed as by some form of extraction or precipitation and discarded because they sludge too readily. The lighter materials preferably are also eliminated, as by means of some form of solvent extraction, because the tend to excessive ring sticking.

This invention therefore resides in the separation from the solvent extractsobtained from extracting lubricating oil stocks as above described, of lighter gravity extract constituents consisting chiefly .of stable aromatic fractions and naphthenes. and employing these in small percentages in the highly refined lubricating oils produced by said solvent treating processes, or

similar very highly paramnic oils exhibiting similar characteristics. More particularly the invention includes the use of intermediate or heart cut fractions of said solvent extracts from petroleum lubricating stocks, as represented by materials having a gravity in the order of 13 to 18 A. P. I. The invention further includes the modified miner-a1 oil products or blends so obtained.

As illustrative of this invention, oils such as a deasphalted and dewaxed S. A. E. 50 lubricating and the extract (after driving oil the sulfur dioxide) mixed with propane at atmospheric pressure, under which conditions a considerable pro,- portion of the extract goes into solution with the propane. Again, the same type of dewaxed S. A. E. 50 lubricating distillate may be extracted with phenol according to known procedures to yield anextract having a gravity ofabout 12 A. P. I. at F., the raffinate being highly parafiinic. For purposes of this extraction about 250 volume-percent of phenol are used at 125 F. and the extract is in turn extracted with8 volumes of propane at to F. After driving oil. the propane, this yields a propane-soluble phase amounting to about 60% of the phenol extract. In this fashion the heavy materials including petroleum resins and tarry bodies in general and unstable and highly aromatic materials are re- Jected and fighter portions of the extracts are obtained which have good lubricating properties in themselves. By acid-treating the propanesoluble fraction while still dissolved in the propane and employing about 25 lbs. of 98% sulfuric acid per barrel of oil at 80F., the propane being present to the extent of about 5 to 8 volumes, and then following with a treatment of 5% clay at somewhat elevated temperature, namely about 350 F., remaining unstable aromatic and kindred materials are removed whereby a valuable naphthenic and aromatic oil stable in character and of unusually high viscosity and flash point is obtained. Such oil has a viscosity gravity constant of .888 and an A. P. I. gravity of 16.2, as against the V. G. C. of .903 and an A. P. I. gravity of 13.7 for the propane-soluble portion without acid tr atm n d'as a ainst a ,V. G. C. or .918 and a gravity of 11.5 for the phenol extract itself before propane treatment. The temperatures given are merely indicative. For instance, the propane extraction of thephenol extract may be run at temperatures anywhere from around 70 to. 90 F. up to F., this treatment causing the propane to reject the heavy insoluble tar phase while taking a heavy lubricating material into solution. The temperature for the acid treatried on-according to any known or preferred procedure.

Similar treatments of liquid sulfur dioxide extract or of extract obtained with mixtures of liquid sulfur dioxide and benzene may be made. These extracts of course vary to some extent, but in each instance the heavy portions will be removed as by precipitation with propane or by acid treatment or both, and the lighter materials may also be removed when objectionable. It is always desirable to reject the heaviest portions of the extracts in some manner, of which the propane solution method is a convenient procedure; this readily eliminates the unstable aromatics. Where the light constituents are objectionable because of being present in amount to produce excessive ring sticking or for other reason, they may be eliminated as by another selective solvent extraction which recovers desirable constituents. Again, series treatments of lubricating stocks with the solvents mentioned may be relied upon to obtain the desired intermediateor heart cut extract. Here the first step will be comparatively light and will remove the heavy tarry and unstable highly aromatic materials.

The next cut will be deeper and may. recover the desirable intermediate fractions of the present invention." The next cut may then be still deeper so as to remove objectionable lighter materials such as naphthenes. Of course, it is to be understood .that in practice each of these three stages of extractions may consist of a plurality of steps. All of these 'heart cut fractions which have been freed from 'both the heavier and lighter constituents are in themselves good lubricating \materials as above indicated, and when blended with heavily refined or very highly parafiinic lubricating oils, as heretofore mentioned, impart to said oils the desirable characteristics sought by the present invention, that is, to overcome corrosiveness, ring sticking and the like. They also impart oiliness and improved film strength.

The intermediate extracts and in some instances mixed intermediate and light extracts, such as those having an A. P. I. gravity of about 13 to 18 and being free from tarry and resinous materials and unstable highly aromatic materials, are then added to the above mentioned highly refined lubricating raffinates in com-- paratively small quantities, in the order of to of the lubricating oil. This includes the portions of phenol extracts and liquid sulfur dioxide-extracts soluble in propane at temperatures around normal, for example from about 60 or 70 F. to 100 or 110 F., and also includes the lightly acid treated propane-soluble portions of said extracts as above described, The acid treatment is. used to eIiminate heavier constituents which may not be desired but which, however, were taken into solution in the propane. Not only the extracts obtained from lubricating fractions may be employed but extracts obtained from transformer oils and spray oils by liquid sulfur dioxide treatment, as effected by the well known'Edeleanu process, may be employed in like manner. Where series treatments are employed, the intermediate extracts will, in

general, be preferred, although the final extracts also sometimes have value when not too rich in ring-sticking constituents. Such extracts may be used without propane treatment or acid treatment. Other solvents than the phenol, liquid sulfur dioxide and benzol-sulfur dioxide above.

mentioned, may be employed such as dichlorethyl ether, furfural and others known for selective extraction, including nitrobenzene and chloraniline.

Any form of extract of the character described is within the scope of this invention regardless of the method of obtaining it. For example, the lubricating stock may be exhaustively vacuum distilled to leave a heavy resinous fraction. This heavy residue may then be solvent extracted to obtain a out having the desirable stable aromatic materials within the range above described. The heavy portions will be discarded and the lightest portions may be either retained or discarded according to their ring-sticking and other characteristics, as above described.

It is to be understood that in some instances after the heavier portions of the extract have been eliminated, the lighter materials may be retained so long as they do not produce ring but will produce excessive ring sticking in Diesel engines. For a general purpose .oil, only the heart out or intermediate fraction of the extracts will be returned to the heavily refined lubricating oils mentioned. By reason of having eliminated the heavy materials including the unstable highly aromatics, and by reason of having eliminated the lighter extract materials which tend to ring-sticking or other difficulties, the resultant blend of the highly refined or highly parafilnic oil and intermediate extract constituents will produce non-corrosive, non-sticking, non-sludging parafiinic-type lubricating oil of great desirability for all practical engine lubricating purposes, and for other purposes as well.

Suitable extract fractions sometimes may be obtained by making a single selective-solvent extraction, andthen treating the extract with sulfuric acid somewhat as aboveoutlined to remove the heavy, tarry, highly aromatic and reactive constituents and similar materials and yield a stable aromatic-type extract of the present invention.

The highly parafiinlc oils with which these such as Cabin Creek (Penn.) crude will yield'a lubricating Bright stock" of about .801V. G. C. and about V. I. with 27.5 A. P. I. gravity and about seconds Saybolt viscosity at 210 F. These oilsare not thoroughly satisfactory for such uses as airplane and Diesel engine lubricants, because they tend to corrosion of bearings and ring-sticking. It is to such oils as these that th herein described extracts are adapted in varying amounts such as 5% to 10% or more to overcome such objectionable characteristics. Such blends will have V. G. C .s of about .811 to .815 according to the amount of extract added to produce the desired modification.

istry, vol. 20, page 641 (1928).

The term viscosity index (V. I.) is defined by Dean and Davis in Chemical and Metallurgical Engineering, vol. 36, 1929, page 618. The viscosity index of a lubricating oil is an indication of its composition or type, i. e., whether it is a paraffin or naphthene base oil. Paraflin base oils are arbitrarily assigned a viscosity index of 100, and certain naphthene base oils from the Gulf Coast are assigned a viscosity index of and mixed base'oils lie between these-extremes. The term viscosity-gravity constant (V. G. C.) is defined by Hill and Coats in the Journal of Industrial and Engineering Chem- This constant represents the parafilnicity or naphthenicity of a given oil. A high value indicates a high degree of naphthenicity while low values indicate relatively greater paraflinicity. Lubricating oils from natural crudes range from .903 (for an extreme Gulf Coast type) to .807 for an extreme Pennsylvania type, or even beyond.

Somewhat, similar ends may be obtained by regulating the solvent extraction in the production of a lubricating oil with solvents. Thecomextract is returned to the oil, anopportunity however being afforded for removal of the heavy unstable constituents As a further modification, one of the above described extracts from which the heavy constituents have not yet been removed, maybe added to the highly refined lubricating oil which it is desired to modify, and the mixture thereof may be treated for the purpose of removing said heavier constituents of the extract. This may be by means of a clay treatment according to any well known procedure such as that employing percent of a filtering or bleaching clay at temperaturein the neighborhood of 350 F.

' Again, a product may be obtained by adding a quantity of the original dewaxed stock to the highly refined lubricating oil product and clay treating to remove the heavy constituents and other constituents removable by clay. The quantity of stock added will be that sufficient to introduce the necessary proportions ofsaid desired modifying constituents. This procedure may be followed where the remaining lighter constituents, which would normally occur in an extract and are not removable by the clay, do not possess objectionable ring-sticking or other characteristics. While these clay treating methods may sometimes be employed, they are not preferred. The preference rests with the use of extracts from which the heavy extractibles have been --eli'minated, and particularly the above mentioned heart out or intermediate extract fractions from which the lighter extractibles also have been removed.

Where lubricating type oils have been subiected to clay treatment to remove various constituents} a fraction akinto the "heart cut can under practical lubricating conditions.

, between about 13 and 18.

around 7 or 8% have been found highly efficient.

These added materials are in themselves good lubricants,'impart good film strength and oiliness.

characteristics, are resistant to carbon and varnish formation and have a stabilizing effect in general upon the oils, especially upon those low viscosity-gravity constant raflinates above referred to as highly refined or over-treated. purpose is to introduce only that portion of the described portions which will impart the desired characteristics. This statement applies also to those variations of the process where fractions containing objectionable heavy and other constituents are added and the blend clay treated to remove heavy, readily reactive and other undesired materials.

These blends havelhad their corrosive and varnish-forming or ring-sticking characteristics reduced to negligible amounts. Thus, said hi hly treated or highly parafiinic oils have been modified by'return of natural constituents in order to restore the non-corrosiveand non-ring-stiching characteristics which they would have home had theabove mentioned protective constituents not been removed by heavy refining. This renders such highly parafilnic oils thoroughly serviceable Where extracts are themselves solvent extracted for separation of intermediate from lighter constituents, such as rin -sticking materials, the same ype of selective solvent elsewhere mentioned may he used.

The extract fractions above mentioned as having lubricating characteristics in themselves when employed for the present purposes, contain large quantities of complex organic materials including sulfur compounds, nitrogen compounds, aromatics, unsaturates, and the like. Presumably some or all of these constituents have the desired effects. The heavy tarry and resinous constituents and unstable aromatic and unsaturated constituents as well as asphaltenes have been largely removed, thereby leaving only rela: tively stable materials together with naphthenic constituents carried along in thetreatment. The materials desired have an A. P. 1". gravity range They appear to be solvents or plasticizers for gums and varnishes which tend to form' in engine operation and cause ring sticking, and to overcome or inhibit formation of corrosive constituents. This theory is presumed to represent their function but applicants do not Wish to be bound thereto.

The addition of the fractions herein described to over-refined or heavily refined lubricating oils which tend to possess corrosive or ring-sticking characteristics, produces a stabilizing effect upon such highly treated oils of low V. GAL. and prevents or greatly reduces such corrosiveness and ring sticking. Also there is ,a tendency to resist formation of carbon and'variation at high operating, temperatures thereby especially adapting theseoils to extreme service coonditions as in the case of airplane engines and Diesel engines.

The.

These disclosures are to be taken as illustrative and not limiting of the generic invention, it being evident that other variations within the scope of the claims may be developed by those skilled in the art. Thus, fractions kindred to the described "heart cut," and having similar characteristics and performing like .functions, may be used even though their gravity be difierent, for example somewhat lighter in specific gravity.

We claim:

1. Highly refined parafilnlc type lubricating oil of low viscosity gravity constant and otherwise havln'g tendencies to develop corrosive and ring sticking characteristics, containing added minor proportions of non-parafilnic selective-solventextract fractions from petroleum lubricating stocks which fractions are substantially entirely stable aromatic and naphthenic materials and are free from tarry, unstable, highly reactive and highly aromatic fractions obtainable from said fractions having lubricating properties and being free fromthe lightest extract constituents and from the heaviest extract constituents including the more unstable and reactive constituents.

3. Mineral lubricating oil comprising heavily solvent-treated parafllnic lubricating oil, and added minor proportions of solvent extract fractions of lubricating, 011 stock added as such, which fractions are soluble in selective solvents 'for non-paraflinic fractions of the type represented by liquid sulphur dioxide, liquid sulphur dioxide-benzol mixtures, phenol and dichlorethyl ether, said fractions being free from the lightest constituents and also from-the heavy and more unstable and more reactive constituents of the lubricating oil stock relatively more soluble in said selective solvents.

. 4. An over-refined low V. G. C. highly paraffinic lubricating oil containing an added petroleum extract fraction added as such and obtained from a petroleum lubricating oil stock, said extract fraction being soluble in selective solvents for non-paraffinic materials of the petroleum inbricating oil stock and being of relatively high molecular weight and of aromatic character relatively less soluble in said selective solvents and free 'from heavy, tarry and highly aromatic and .reactive constituents relatively more soluble in said selective solvents, said extract fraction having a gravity in the order 13 to 18 A. P. I. and being present in quantity sufllcient to impart to the blend freedom from the characteristic of developing substantial corrosive and ring-sticking tendencies.

5. A method for producing lubricating oils comprising treating a petroleum lubricating stock for the removal of paraffin and asphalt therefrom, treating the dewaxed, deasphalted stock with a selective solvent and recovering from the stock a solvent extract containing heavy, aromatic, resinous, tarry, unsaturated and naphthenic constituents, separating said extract, removing the selective solvent from the extract, treating the extract with a precipitant to-eliminate'heavy, highly aromatic and reactive constituents and tarry and resinous materials'and to yield a relatively stable aromatic and naphthenic fraction, treating said fraction with a selectlve solvent for the separation of lighter naphthenic constituents and yielding a relatively stable naphthenic and aromatic type fraction, and blending with a dewaxed, deasphalted, highly refined paraifinic type lubricating oil a quantity in the order of several percent of said relatively stable aromatic-type extract fraction suflicient to impart non-corrosive and non-ring-sticking characteristics to said rafllnate.

6. A method according to claim 5 wherein the highly parafilnic raflinate is treated with said selective solvent to possess a viscosity-gravity-constant below about 0.810, and the stable aromatic fraction to be added to said rafiinate is treated to possess a viscosity-gravity constant of about 0.8800.9l0'and a gravity above about 13 A. P. I.

7. A mineral lubricating oil containing as major constituents highly refined solvent-treated parafilnic type mineral lubricating oil fractions and added stable non-parafflnic lubricating fractions added as such including non-reactive aromatic and naphthenic materials soluble in selective solvents for said non-paraffinic materials, the lubricating oil being free from reactive and unstable fractions which would be relatively more soluble in said selective solvents and being substantially free from the characteristic of de- 1 veloping corrosion and ring sticking tendencies.

ULRIC B. BRAY. DONALD E. CARR.