US2091399A - Synthetic lubricating oils - Google Patents

Description

u'g 31, 1937. F. w. SULLIVAN. JR.. ET Al. 2,091,399

" SYNTHETIC LUBRICAT'ING OILS Original Filed March 15, 1929 2 Sheets-Sheet 2 Q Q Q am@ l Si ATTORNEY 30 60 70 80 l90 100 1.10 1Z0 .L30 .M0-'.160` .[60 .170*180 190 ZOO of straight-chain parailin hydrocarbons. g wax may suitably be parain wax which occurs in Patented Aug. '31, 1937 UNITED STATES;

PATENT OFFICE SYNTHETIC LUBRICATING OILS Frederick W. Sullivan, Jr., and Vanderveer Voorhees, Hammond, Ind., assignors to Standard Oil Company, Chicago, Ill., a corporation of Indianal Original application March 1 5, 1929, Serial No.

347,446. Divided and this application Noveml be'r 1, 1932, Serial No. 640,634

5 Claims.

This invention relates to hydrocarbon lubricat.

ing oils, and particularly to synthetic lubricating oils comprised mainly'of groups of straight chain hydrocarbons resulting from the action of alumi- 5 num chloride or other equivalentv polymerizing` yagent upon suitable straight chain hydrocarbon material, as hereinafter set forth. The invention is illustrated by the accompanying drawings,

ity-temperature curves of typical natural lubricant oils and oils prepared in accordance with the present' invention.

In accordance with this invention, we employ as the source of hydrocarbon material what may be termed a high boiling product consisting largely or entirely of normal parain hydrocarbons. For

example, we may use hydrocarbon waxes, which are now well understood to consist substantially 'I'his Pennsylvania and Mid-Continentfcrude petroleum or other waxy material, such as petrolatum, slop wax, ozokerlte wax or other hydrocarbon waxes. It must be understood, however, that-the term straight-chain hydrocarbon material is not limited to waxes, since it is obvious that in oils containing wax, there is undoubtedly present straight-chain material of similar character, but of smaller molecular weight so that they do not solidify as readily as the ordinary waxes.

' Thus,l it is well recognized that Pennsylvania oil, for example, gas oil, contains more normal paraiin hydrocarbon material than does a similar distillate derived from Mid-Continent crude 4o petroleum, while the latter likewise contains more straight-chain material than do similar oils derived from Coastal crudes. We may define our high boiling normal parain hydrocarbon material as one containing a larger amount or percentage or normal parailln hydrocarbons than does a similar representative Pennsylvania distillate oil, and containing substantial proportions of constituents having a boiling point under atr mospheric pressure conditions exceeding 600 F. In order to convert this normal hydrocarbon l material into lubricating oils, it is necessaryto induce a combination of molecules or polymerization. Because o! the well-known unreactive na- '55 ture of the paramn hydrocarbons it is mst necessary to convert these substances into a more active form. This may be done by subjecting the normal hydrocarbons to pyrolysis as will be hereinafter described.

In producing improved lubricating oils according to this invention, we rst crack the high-boiling normal parailin hydrocarbon material to pro'- duce a desired type of unsaturated hydrocarbons suitable for= the desired reaction with aluminum chloride. The cracking operation is preferably carried out under low pressure, substantially vapor phase conditions, suitably at atemperature' between 750 and 1l00 F.and at pressures below 100 lbs. Higher pressures may be employed, however. In general, it is preferred to determine the optimum conditions for cracking to secure'maximum yield of desired products from a given im'- tial material; asl variations of temperature and pressure may materially affect vthe ultimate yield.

'Ihe distillate from sucha cracking process may be redistilled to give a lfraction substantially free of waxy material. Thus, we iind'ordinarily that if the end v-point of such fraction'is carriedl much above 500 F. thelubricating oilsproduced therefrom have an undesirably high cold test. When a distillate of about 500 F. end-point is polymerized to a lubricating oil, this oil will contain noapparent wax. AOn reduction of the polymerlzed oil, both the light overhead and the high viscosity bottom will have a low cold test. If desired, the distillate from the cracking operation may be fractionated into several yportions which may be separately polymerized to products containing.

higher proportions of lighter or heavier lubricant products according to the nature of the cracked fraction employed.

In polymerizing'the cracked fraction we may suitably employ from 0.5 to 4% of anhydrous aluminum chloride, but excellent results may be secured with larger and occasionally with smaller proportions. We also prefer to conduct the polyymerization at va temperature between 100 and 250 F. a longer period of timey being required at lower temperatures and a higher yield of more viscous products being produced. During the polymerization the mixture is thoroughly agitated. Substantial yields are obtained in three or four hours at temperatures of 175 F. and higher, but it is preferred tovprolong the time of reaction to 15 to 20 hours, and at lower temperatures to as 1 long as hours, in order to obtain the maxim yield of lubricating oil.

After polymerization, it isl necessary to separatetar or aluminum chloride sludge from the 2 oil. Most of the tar settles on standing and can be drawn off, leaving a brown oil containing particles of suspended tar. In order to obtain oils of the best color and lowest Conradson car- 5 bon, it is desirable to remove the remaining suspended tar. This may suitably be done by ltering with a small quantity of adsorbent earth, such as clay fines, or by prolonged settling, for example, 48 hours at 10U-150 F. The oil may then be washed with an alkaline solution, as a 5 to 10% solution of caustic soda, if neutralization is required. The oil is then reduced by steam and iire or vacuum distillation to remove light oils and naphtha leaving a lubricating residue l5 which may be separated by distillation to yield lubricating oils of desired viscosity.

The invention will more readily be understood from the following detailed description of a specific example: I

A. wax product derived, such as slack wax or a sweat oil (for example 110-120 melt) from Mid- Continent oil, containing 85% of mineral wax, the remainder being oil, is vaporized and the vapors heated at atmospheric pressure to a temperature between 900 and 980 F. to bring about cracking. After cracking, the vapors are separated from tar and are fractionated and condensed to yield a distillate having an end-point of about 500 F. The tar is eliminated and the intermediate condensate is recycled and cracked 'with the feed. It is preferred to operate tol produce between 10 and 25% of distillate per pass. During this cracking operation, 28% of gas, 5% of tar and 67% of distillate by weight are produced.

To such distillate about 1 to 3% of anhydrous aluminum chloride is added and the charge is maintained at about 210 F. for about 18 hours with thorough stirring. At the end of this pe- 40 riod, the stirring is stopped and the tar, which amounts to about 7 to 10% of the initial charging stock is Vallowed to settle and is removed.

The remaining oil is reduced with steam; about 10% of light distillate, 80% of oil of 90 viscosity (210 F.), and about 10% of tar are produced. The heavy loil has the following inspection, after filtering through a small quantity of clay to secure the desired color:

Gravity, 32.5 A. P. I.; ilash, 500 F.; pour,

25 F.; viscosity at 210 F., 90 sec. Saybolt;

viscosity'at 100 F. 850 to 900 sec. Saybolt; viscosity index 107-112; Conradson carbon 0.13%; color 2 N. P. A.

0f course, it must be understood that other lubricating oilsI may be produced by a suitable control of the distillation. Thus, we may take on 10% of light distillate; 27.6% of oil of viscosity between and 105 sec. Saybolt at 100 F.; 3.3% of oil of viscosity between 250 and 275 sec.

60 Saybolt, at 100 F.; and leave a bottom consisting of 49% of oil of viscosity of 190 sec.'Saybolt at 210' F. The inspection ofthis bottom after clayingis as follows:

Gravity, 31 A. P.'I.; flash, 620 F.; pour 5 F.; viscosity at 21o? F. 19o sec. Saybolt; viscosity at 100 F., 3000 sec. Salbolt; Conradson carbon 0.33%; color, 4 N. P. A. The yields of the lubrieating oils thus obtained, based `on, the -wax charging stock, are 48.6% of viscosity oil and n 28% of 190 viscosity oil (viscosities at 210 FJ.

The aluminum chloride sludge may be reused on fresh oil to be polymer-ized to 'effect the deaired change in whole or in part. Thus the 1| cracked distillate treated may rst be subjected to .the action of sludge from previous treatment, and subsequently, to the action of fresh anhydrous aluminum chloride. 'The sludge resulting from the latter step may then -be used in treating fresh distillate.

The oils produced according to the present invention possess remarkable properties which distinguish them from all lubricating oilsY known to applicants. Thus, we can produce oils which have a substantially better viscosity-temperature gradient than Pennsylvania i lubricating oils, which possess very remarkable cold test properties and show a low Conradson carbon test. The viscosity temperature gradient is indicated by the viscosity index calculated by the method of Dean & Davis described in Chemical and Metallurgical Engineering, 1929, vol. 36, pg. 618.

As indicated above many of the new oils produced according to our invention possess a lower temperature co-efdcient of viscosity and a higher viscosity index than Pennsylvania lubricating oils. It will be understood that oils of various degrees of viscosity can be 'produced which will have a viscosity-temperature gradient less than that of a Pennsylvania oil of similar viscosity. For convenience, we will give the Saybolt viscosity of various oils at two arbitrary temperatures, viz. F. and 210 and will compare the viscosity change with a standard Pennsylvania lubricating oil of the same viscosity at the lower temperature. Thus, with wax derived from Mid-Continent crude petroleumcontaining about 15 or 25% of oil as starting material, the finished lubricating oil has a viscosity-temperature gradient substantially the same as that of Pennsylvania lubricating oil. With higher percentages of wax the lubricating oil has a lower temperature co-eflicient of viscosity than Pennsylvania as indicated by the specific example given above, while an even better gradient is obtained with more puried wax. With a parailin base oil which is richer in straight line hydrocarbon material than is Mid-Continent oil, the eiect of koil content of the vwax is not so marked.

It must be understood that our invention is not limited to oils having a viscosity-temperature gradient better than Pennsylvania oils, since it comprises many oils which have outstanding valuable properties, but which, nevertheless, may have a temperature co-eflicient of viscosity equal to or not quite so good as Pennsylvania oil; an oil may be made having a lower temperatureviscosity co-eiiicient than for example, a Mid- Continent lubricating oil and at thesame time a cold test lower than a Coastal lubricating oil of the -same viscosity at 100 F. with its normal wax content.

An important characteristic of our oils, both those superior to and somewhat inferior to Pennsylvania with respect to viscosity change with temperature is their low pour or solid points.

This characteristic of 'our oils may suitably beexpressed as follows: l

lSSS'LZl0BmViu-134- wheres is the solid point in degrees Fahrenheit,

and Vino is viscosity in seconds .Saybo'lt at100" F. The solid point, in the aboverormula, is 5 F. below the pour point, as determined by suit- `able methods.` The logarithm -in theequation isl to the base 10. In Fig. 1 ,thel equation S=37.2logioVioo-134 is plotted on semi-log coordinates, the abscis'sae representing the solid point in degrees lFahrenheit and the ordinates the logarithms of the viscosity in seconds Saybolt at 100 F. The points SI, S2, S3 and S4 indicate the positions on the graph of the correspondingly designated oils of the present invention in the table hereinafter set forth.

In addition to these characteristics, our lubricating oils possess very `low Conradson carbon tests, vvery good color and very high flash points. l Thus, oils produced from material containing 85% wax and upward as starting material have ysubstantially higher flash points than Pennsylvania lubricating oilsl of similar viscosity at a standard temperature.

In order to ascertain more definitely the nature of our products, we give the following examples of oilsof the first class, that is lubricating oils produced by the present process having viscosity temperature gradients better thanv standard Pennsylvania or parain base lubricating oil of similar viscosity. AThese lubricating. oils were produced substantially as described above, from the starting material indicated.

It may be noted that not only do these products show better temperature-viscosity characteristics than Pennsylvania lubricating oils, but they show high A. P. I. gravity and low cold test characteristics within the definitions set forth above. As a result of the high A. P. I. gravity (low specific gravity) these oils have abnormally low -viscosity gravity constants -as shown inthe table. The viscosity gravity constant is calculated from the following equation:

Viscosity gravity constant:

` 10G-1.0752 log (V-38) 10-log (V-38) in which G is the specic gravity at 60 F., and

V is the Saybolt viscosity at 100 F., and the logarithms are to the base 10.

As examples of lubricating oils which are not superior to Pennsylvania-oils with respect to temperature-viscosity gradient, but which are superior to Mid-Continent lubricating oils in that respect and which possess remarkable cold test Lubricating oil of present invention Stamlginng ma Initial stock Viscosity sec. Saybolt Viscos- Viscosity in Bec. Baybolt garantia con- At 210 At100 -v. I 210 F. 100 F. etant F F. V. I.

S4 857 wax from M. C. crude-- 190 2800 -10 31 0. 541 P2 190 3000 S1|95 a wax from M. C. crude.- 133 86 075 -35 34 0. 779 P1 86 860 104. 8

S2 Reiined petrolatum wa.x 118. 6 87 735 -30 34 0. 700 87 900 102.7

perature-viscosity relationships of typical nature 1n Fig. l2 of the drawings, curves of the temvproperties within the aforesaid definitions, we

give the following:

Standard Mid-Con- Lubricating oil ol our process nent lubricating ou Initial stock Viscosity sec. Saybolt Vis- Viscosity, sec. Saybol t I Ccm Gravcosity n te A nl? I gravity t at con- V. I. 210 F. 100 F. stmt 210 F. 100 Fl v. I.

F. 65 f om M. C. crude 91.8 77 8M 20 29.4 0.800 M177 930 74.1 70% fir-om M. C. crude-; 108.4 84 835 -36 30.8 0.788 M284 1120 73.6 75% wax from M.hC. crulceii.-. l0 83 840 -20 30.9 0.788 83 1100 72. 7

Paraiiin' va or asecr stillateog 250 end-point) 87.3 88 1083 -25 31.5 0.719 88 1220 74.4 Pari'llfn; Igvilpor lhse craciei dis een an f 1o%t-; 9&2 85` 92e -25 31.3 sa nso, 73.4

oils are shown, the abscissae'representing viscosities in seconds Saybolt at 210 F. and the ordinates representing viscosities in seconds Saybolt at 100 F. on a logarithmic scale. 'I'he curve designated C is typical of Coastal oils; that designated MC, of Mid-Continent oils; that designated P of Pennsylvania oils, and that designated S of oils of the present invention. The points Pl and P2 designate the positions on the graph of the correspondingly marked Pennsylvania oils in the table above, and those marked' Sl, S2, and SI of the correspondingly marked synthetic oils of the present invention in the table above.

These oils also have the specific gravity which characterize most of our oils. y

In Fig. 2, the points MI and M2 designate'the positions on-the graph of the Mid-Continent oils in the above table having the corresponding markings and the point M3 designates a typical- Mid-Continent oil of a viscosity of 152 sec. Saybolt at 210 F. and 3200 sec. Saybolt at 100 F. described by Gruse, Petroleum and its Products, published 1928, on pg. 267.

Although'the present invention has been described in connection with the details of' specitlc examples thereof, it must be understood that such details are not intended to be limitative of the invention, except insofar as set forth in the accompanying claims. For example, other means of activating normal paraflin hydrocarbons and wax may be employed besides cracking, and other l methods of polymerizing these materials into 1u- 5 bricating oils are contemplated. We have discovered that these materials 'may be converted said synthetic oil being characterized by having its component molecules consisting predominately of groups ofV atoms which groups vof atoms have substantially the same arrangement and weight as the polymerizable molecules in a fraction of cracked straight chain hydrocarbon wax, which fraction hasa boiling range lower than wax, said synthetic oil having a viscosity index between about 91.8 and about 133, a solid point between about 10 F. andl about -36 F., and

an A. P. I. gravity between about 29.4 and about 34 degrees.

2. A synthetic hydrocarbon lubricating oil derived -from straight chain hydrocarbon wax, said synthetic oil being characterized by having 'its component molecules consisting predominately of groups of atoms which groups of atoms have Y substantially the same arrangement and weight as the polymerizable molecules in a fraction of cracked straight chainl hydrocarbon wax,- which 35 fraction has a boiling range lower than Wax, said synthetic oil having a viscosity index between about 91.8 and about 133, a viscosity between about 95 and about 3,000 seconds Saybolt at 100 F. and an AQP. I. gravity between about 29.4

and about 34 degrees. y

` 3. A wax-'free synthetic hydrocarbon lubricating oil derived from straight chain hydrocarbon wax, said synthetic oil being characterized by having its component molecules lconsisting predominately of groups of atoms which groups of atoms have substantially the same arrangement and weight as the polymerizable molecules in a fraction of cracked straight chain hydroby a viscosity at 210 F.

carbon Wax, which fractionv has a. boiling range I lower than wax, said synthetic oil having a viscosity index between about 91.8 and about 133, an A. P: I. gravity between about 29.4 and about 34- degrees, a solid point between about 36 F. and the maximum value,

Where V is the viscosity in seconds Saybolt at 100 F. and the solid point is expressed in degrees Fahrenheit.

4. A substantially wax-free synthetic'hydrocarbon lubricating oil derived from parain'wax by converting the wax into normally liquid polymerizable compounds, of lower molecular weight than the Wax and of the nature of straight chain fragments of the wax, and thereafter treating with a polymerizing catalyst, thereby producing hydrocarbons of higher molecular weight, said lubricatingxoil being essentiallyl composed of molecules which are polymers of normally liquid compounds of the nature of straight chain fragments of the -paraffm wax, said oil being characterized further between about 83 and about Saybolt, a proportionately increasing viscosity at 100 F. 4of between about "840, and about 3,000 Saybolt and `a solid point" between about 36 F. and the maximum value indcated by the relation 37.2 log1oV1t-134 wherein V109 is the Saybolt viscosity at 100 F. and the solid point is expressed in degrees Fahrenheit.

5. A synthetic hydrocarbon lubricating oil derived lfrom straight chain hydrocarbon wax,

said synthetic oil being characterized by having its component molecules consisting predominately of groups of atoms which groups ofvatoms have substantially the same arrangement and weight as the polymeriza'ble molecules in a fraction of cracked straight chain hydrocarbon wax, which fraction has aboiling range lower than wax, said synthetic oil having a viscosity between about 835 and about 3,000 Saybolt at 100 F., a viscosity index between about 101 :and about 133and a viscosity gravity constant between about' 0.760 and about 0.541.

FREDERICK W.' SULLIVAN, JR. VANDERVEER VOORHEES.

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