US2674568A - High viscosity index lubricating oil - Google Patents

Description

April 6, 1954 J. G. LILLARD HIGH VISCOSITY INDEX LUBRICATING on Filed July 26, 1950 m 7 v 6 E I I w v [I L j I I a 8 M E I5 I B M M w A III H m L H N u :0 3 M A I R Ii M 4 1-- H 4. N \I 6 M E II I I 5 I EM" mu 9 m 2 u I I l l I I I I I I I I I I I I I I I I I I IL 1|| 2 r IIL. u H u y In M m 2 5 5 4 4 T I II I N ll 7 L I 4 8 o 4 S .Il R A I- 0 P E e u M A 0 m T II T I I. s s W I H w J9 m v a 3 n 2 L 4 3 4 I 8 4 3 5 3 7 M 3 'l-Illl 2 6 3 3 8 2 n I n G L LOW VISCOSITY INDEX l VERY LOW VISCOSIT Y INDEX HIGH VISCOSITY INDEX LOW VISCOSITY INDEX IN VENTOR.

Patented Apr. 6, 1954 James G. Lillard, Baytowng Tc'x.; assignor, by-

mesne assignments, to StandardnOiI Develop--v ment Company,- Elizabeth N J of Delaware a corporation 5 Application July 26, 1950, Serial No. 176,003 1 Claim: (Cl. 196151) Thepresent invention may be described briefly as a high viscosity index lubricating oil composttioncontaining only components which will allow the composition to have a high: viscosity index. Thecomposition of the present invention consists of a mixture of 'paraffinic naphthenes and aromatic naphthenes boiling in the lubricatingoil boiling ranger thenes to aromatic mately -7':1.'

Paraffinic and-aromatic naphthenes employed in the lubricating oil of the present invention may 'be characterized by the following formula-:

M(n -l.4750),- 8*

in which M is theaverage: molecular weight and The ratio of paraffinic naphnaphthenes may be approxin is i the index of refraction at 20, F. of said:

naphthenes using the sodium D. line." The. nue meral *l.4750 is-obtained by plotting-"the reciprocal of th"e-molecular--weight of a: largenumben ofhydrocarbons of T different typessagainst the refractive index of these hydrocarbons to obtain Each type of :'hydro-I-- carbon will "follow along a separate-straight line 1 but all h'ydrocarbons of the same:=type..will:fol1ow:

a series of straight lines.

in the-same line.- to one anotheran'd These :linesware not parallel which they converge. forinfinite-'molecular welght occurs at arefractive" index of -1.4750

It has been observed that 'the various hydro carbonsin lubricating oil fractions have factors; as determined from which vary widely. Generally, th'at paraffins have values (F)" or factors determined from the foregoing equation substantially rule ":above 8 while the have high viscosity indexes while those fractions having'F factors or aviscosity indexes:

It has been found that lubricating oil may be: separated 'bysilica :gel percolation into. about 5- fractions-having: widely different viscosity index:

*fRihg Analysis of Hydrocarbon Mixtures, Report PRL'448,issued by'-the-Petro1eum Refining Laboratory; The, Pennsylvania: State College, State- Collcge,. Pa. June 7,1948.

may-be extended to a .point: corresponding to infinite molecular weight at: The point offl convergence when' using-the D line of: sodiumat a temperature of hydrocarbons of the foregoing equation,-

it has been found value above 8 havev low characteristics.- These various fractions each.

consist of a largenumber of compounds ofa certain type.' Silica gel percolation separates as a first fraction of lubricating oil a parafiinic- A naphth'ene fraction containing from 1 to 3 naphthene rings, aromatic-naphthenes containing con aromatic and '1 naphthenic ring;

the average 1 and condensed naphthenes-containing 2 or more naphthene rings, nap hthalenes containing 2 or more aromaticrings of which only 2 are condensedwand higher condensed aromatics containingy3 or more aromatic rings of which at least 3 are condensed-.-

The paraffinic naphthenes may be considered as parafiinicand naphthenic fractions, whereas the aromatic naphthenes may-be considered as single ring aromatic fractions whichhas a naphthenic ring attached-thereto, as described by Watson et al. in Patent 2,643,217, issued June 23, 1953, where identical compounds are described; Terminology of a-similar'naturg is described by Rossini in 'Refiner and Natural Gasoline Manufacturer,vol. 17, No.11, November, 1938.

When F factors or values for these various compound types'are obtained from lubricating oil, for example, by silica gel percolation thereof;

thecompounds areseparated'largely as shown in' the following table:

Table I Compound Type F W Paraffinic Naphthenes 4 to +6 Condensed Naphthenes 8 to 10. Aromatic Naphthenes 2 to 6. Naphthaleues a. 10 to 20. Higher Condensed Aromatic Greater than 40.

Inemploying the-F value to characterize. the various components in for a particular stock assuming a constant molecular weight for. the lubricating oil fraction forwhichthevalue is to be obtained. Sinc the vmolecular weights of the narrow fractions secured by silica gel percolation of the lubricating oil fraction have a max:- imum variation of'about 10 the F factor may have a maximum variation of about 10% due to the molecular .weight change.

The paraffinic-naphthenes and: aromaticnaphthenes forming the composition of the present invention may be blended together in. any'ratio to give the desired viscosity index. However, since both the a lubricating oil fraction it may be determined by paraffinic-naphthenes J and" the 'aromatic-naphthenes have high vis- 1 cosity indexes as compared to the low viscosity indexes of the other components of the lubricating oil, it will be desirable to utilize all of the aromatic-naphthenes with the paraflinic-naphthenes obtainable from a given lubricating oil fraction. It has been determined that the paraffinic-naphthenes and aromatic-naphthenes are present in lubricating oil fractions from the Panhandle field in Texas and from the Texas Coastal crudes in the approximate ratio of '7 parts by volume of paraflinic-naphthene to about 1 part by volume of aromatic-naphthene. While this is the preferred ratio, it will be understood that greater amounts of the parafiinic naphthenes may be used depending on the viscosity index of the particular aromatic-naphthene secured from a particular lubricating oil.

In order to illustrate the invention further, lubricating oil fractions obtained from Panhandle crude from the Panhandle field in Texas and from Texas Coastal crudes were subjected to contact with a column of silica gel. The lubricating oil fractions from the Panhandle crude were a dewaxed medium motor oil distillate and a finished Bright Stock. The dewaxed motor oil distillate on percolation through the column of silica gel gave the following results:

The data in the foregoing table show the percentage and the viscosity index of the various fractions. It will be noted that the paraffinicnaphthenes have a viscosity index of 124 whereas 1 the condensed naphthenes have a viscosity index of only 47. On the other hand, the aromaticnaphthenes have a viscosity index of 9'7. Both of these fractions, therefore, are suitable for blending together to form the composition of the present invention. It will be noted that the ratio of paraffinic naphthenes to aromatic naphthenes is 7 /2 :1; consequently it is desirable to blend the paraifinie naphthenes with the aromatic naphthenes in this ratio to obtain maximum yields.

The parafiinic-naphthenes in Table II contain 1 to 3 naphthene rings. The condensed naphthenes contain 3 or more rings, at least 2 of which are condensed, while the aromatic naphthenes contain on the average 1 naphthene ring and l aromatic ring.

A finished Bright Stock from Panhandle crude was also percolated through a silica gel column and was found to contain 60% by volume of parafimic-naphthene having a viscosity index of 109. The Bright Stock also contained 8% by volume of naphthenes having a viscosity index of 97. These fractions may also be blended to obtain a composition in accordance with the present invention.

A medium motor oil distillate from a Texas Coastal crude was also percolated through a silica gel column and was found to contain 57% by volume of paraffinic naphthenes and 7% by volume of aromatic naphthenes, the parafiinic:

naphthenes had a viscosity index of 102 while that of the aromatic naphthenes was somewhat lower. In thi particular instance, it will be noted that the ratio of paraifinc naphthenes to aromatic naphthenes is not quite 7 :1. It will be desirable, therefore, to blend the parafiinicnaphthene the aromatic-naphthenes in this particular ratio.

It has been mentioned that the composition of the present invention may be obtained by percolating a lubricating oil fraction through silica gel and blending the segregated fractions. The segregation of a lubricating oil fraction into components of varying viscosity index characteristics by means of silica gel may be carried out on a batch or continuous basis. The optimum ratio of hydrocarbon oil to silica gel for a batch operation is well known. a value of 1:10 by volume being typical. The silica gel i charged into a column whose ratio of diameter to length is governed by the degree of separation desired. For the type of separation described in this memorandum, a ratio of diameter to length of 1:300 is preferred.

The temperature at which the percolation is conducted may be a temperature in the range of about to about 150 F. A temperature of F. will give quite satisfactory results, if the viscosity of the oil is reduced by dilution with a light paraflinic solvent, such as normal heptane.

The invention will be further illustrated by reference to Fig. 1 in which a mode is described allowing the segregation of the high viscosity index fractions necessary to provide the composition of the present invention, and

Fig. 2 wherein the composition of a given lubricating oil is shown graphically with reference to the composition of the present invention.

The segregation of a lubricating oil fraction into fractions of varying viscosity index characteristics and recombination of certain fractions to obtain an oil of improved viscosity index is illustrated in Figure 1. Column I0 is filled with silica gel. The quantity of oil, which is optimum for the amount, of silica gel placed in column ID, is withdrawn from hydrocarbon charge tank II by means of pump l2 through line l3 and valve l4 and discharged into charge blending tank l5. After valve [4 is closed, paraffinic solvent is withdrawn from tank l6 by pump I? through line l8 and valve I9 until the desired ratio of paraffin solvent to oil for control of the viscosity of the mixture is obtained.-

Valve I9 is then closed and connected to controller 20 which keeps it in a closed position until activated by liquid level control 2|. It is not necessary that the oil and paraflinic solvent be mixed in a tank before charging them to the silica gel column; if it is more convenient, the two may be continuously pumped in the proper ratio into a line containing go directly from the incorporator into the silica gel column. After the hydrocarbon and paraffin solvent have been thoroughly mixed by mixer 22, valve 23 is opened and the charge passes from the charge blending tank through pump 24 into the silica gel column. Before valve 23 is opened, valves 24A and 26 are closed and outlet valve 25 is opened. As the mixture of hydrocarbon and paraflin solvent passes through the silica gel, it is separated into various fractions, depending upon the afiinity of the silica gel for the various compound types. The order of increasing affinity of silica gel for the vari ous compound types is: paraifinic naphthenes,

an incorporator and aiergoes finic solvent under" the-condition being de* scribed. The 'efllue'nt from the silica gel column In passes through line}? and valve 25 where it is pumped by'purnp'zs intofractionating column 29. This column causesa. separation between the hydrocarbon and theparaflinic solvent admixed with it. The paraffinic solvent is taken as overhead'through line 3fl-and pumped into the-*paraffinic solvent storage tank-I B. The hydrocarbon' is withdrawn as bottoms through line 3| and all; or a portion of it, passes through a refractive index incheating-recording device 32. The signal from the refractive indexindicator is transmitted through line 33 into recorder 34 which convertsdt"int'o"'an'F"value. The recorder' '34 is adjusted for the i molecular "weight of the lubricating oil being-percolated lar narrow lubricating oil fraction" recovered from column I will not varygreatly, the F value will not be effected substantially by any: slight variation thereof. If the F value is 8 or greater, a signal is transmitted through line 35 to valve 36 causing it to open and through line 40 to valve 4| causing it to close; the material is discharged through line 31 and pump 38 into tank 39 which contains the lower viscosity index fractions. If the F factor is less than 8, a signal is transmitted through line 40 to open valve 4| and through line 35 to close valve 36. Thus, material for which F is less than 8 is passed into tank 42 through line 43. This tank 42 contains the higher viscosity index components of the lubricating oil fraction. When the charge contained in the charge blending tank I is depleted, liquid level control 2| causes valve 20 to be opened and a paraiiinic solvent is pumped through the charge blending tank into the silica gel column HI. This solvent flushes remaining materials for which silica gel does not have a relatively strong affinity from column In into fractionator 29. When the paraifinic solvent no longer desorbs appreciable quantities of material from the silica gel in column Hi, the liquid level in column 29 decreases and causes liquid level control 44 to close valve 23, open valve 24A, close valve 25, and open valve 26. When the valves are positioned in this manner, a polar solvent such as benzene or alcohol is withdrawn from tank 45 and forced into silica gel column H] by pump 46 to cause the material remaining adsorbed on the silica gel to be desorbed and pass out of the column l0 through line 21 and valve 25 and be pumped into fractionator 41 which effects a separation between the polar solvent and the material which it has desorbed. When desorbing the silica gel in column In with a polar solvent, the output of the column l0 does not pass through a refractive index determining device because it has been found that all hydro carbons that have to be desorbed from silica gel by using a polar solvent have F factors considerably greater than or 15. Therefore, all of the material desorbed by the polar solvent will have undesirable lower viscosity index characteristics. When the silica gel in column III has been completely desorbed as indicated by liquid level indicator 43, all valves are closed and the silica gel is regenerated. This regeneration may be car ried out in the silica gel column H] by any one mamma -"naphthenes: naphthalenes, and highencondense'd aromatics;

in 'coliim'n' I0. Since the molecular weight of the-particu-' of several methods such as by blowing with steam The facilities "for "the' regeneration described since they are well known to the art. In-somecaees it may or hot-air. operation are not shown or be preferable todiscard the spentsilica gel and recharge thecolurnn with fresh silica gel. As a matter' of convenience, a second column may with the first columns'obe connected in parallel that another chargeof' hydrocarbon and paraffin solvent may be passed through this second column while *the first is being regenerated. operate more than one silica gel column withthe same auxiliary equip equipment for the segre gation of the hydrocarbon into the desired'vls Thus, it is possible to ment and the necessary cosity index components is simplified.

The action of column |0 control of its operation by referring to Fig. 2'wherein the various shaded bands indicate different volume per cent being taken at the right. The area 49 represents the parafiinic-naphthenes fraction, 50 represents the condensed naphthenes fraction, 5| represents the aromatic-naphthenes fraction, 52 represents the naphthalenes fraction, and the shaded area 53 represents the higher condensed aromatics fractions. The viscosity in dex characteristics of these various fractions is indicated within the rectangle representing each fraction. The line 54 indicates the separation usually obtained by phenol extraction, the material below the line being that extracted by the phenol. Increasing the severity of a conventional phenol treat causes the central portion 55 of the line 54 to move to the left, thus extracting more of the low viscosity index fraction 50 and also of the high viscosity index fraction 5| with the total effect being to increase the viscosity index of the material not taken up by the phenol. In the same manner decreasing the severity of the phenol treat causes the central portion 55 to move to the right which not only causes more of the high viscosity index fraction 5| to be included in the raflinate, but also includes more of the low viscosity index fractions 50'and 52, thus decreasing the total viscosity index of the material not taken up in the phenol. The present method of separation controlled by the characterization factor F does not allow these various fractions to be smeared into one another, and, thus, at all times allows a sharp separation of the high and low viscosity index components. The line 56 separating fractions 5| and 52 is the natural cut point for compounds adsorbed on silica gel between the desorbing powers of paraffinic and polar solvents, with the material to the left of this line being removed from silica gel by paraffinic solvents, and the material to the right of the line requiring polar solvents for elutriation.

From the foregoing description taken with the two figures, it will be seen that two components of the lubricating oil of the present invention may suitably be obtained by silica gel extraction. The lubricating oil may be separated into paraffinic-naphthenes and into aromatic-naphthenes by extraction with solvents but this may be a tedious, time-consuming operation.

In obtaining the paraflinic-naphthenes and aromatic-naphthenes for the lubricating composition of the present invention, it is desirable to in combination with' by means of the char acterization factor F may be-readily understood silica gel fractions from a'lubricating oil. The horizontal axis of the bar represents the volume per cent distribution of the hydrocarbon fraction, with zero volume per cent being taken in the left of the figure'and' extract untreated lubricating oil fractions. Otherwise, if a lubricating oil is subjected to a treatment with sulfuric acid such, for example, as practiced in the petroleum refinery, or to contact with clay, such as Super Filtrol or other types well known in the refining industry, there is danger that the aromatic-naphthenes may be lost either by chemical action or by physical adsorption. While it is desirable to work with the total or untreated lubricating oil fraction, it is within the purview and scope of my invention to work with solvent extracts or raffinates which contain paraffinic-naphthenes and aromaticnaphthenes for segregation thereof for use in the composition of my invention.

The nature and objects of the present invention having been fully described and illustrated, what I desire to claim as new and useful and to secure by Letters Patent is:

A lubricating oil composition consisting of a mixture of approximately 7 parts of a paraffinio and naphthenio fraction having from 1 to 3 naphthene rings and approximately 1 part of single ring aromatic fraction having an average of one naphthene ring and one aromatic ring boiling in the lubricating oil boiling range, said.

fractions being characterized by the formula M (n 1.4750 8 where M is the average molecular weight and n is the index of refraction at 20 F. for the sodium D line of said naphthenes, said fractions having viscosity in dexes of 102 to 124 and 97, respectively.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Refiner and Natural Gasoline Manufacturer, vol. 17, No. 11, Nov. 1938, pages 557-567 inclusive (Rossini).

Indust. and Engineering Chemistry, vol. 39, No. 12, Dec. 1947, pages 1585-1596, inclusive (Hirsch ler et al.)

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