US2065551A - Method of preparing lubricants - Google Patents

Description

"Dec. 29, 1936. L. c. BEARD. JR 2,065,551

METHOD OF PREPARING LUBRICANTFS Filed March 14, 19:54

CRACKING UNDER GASOLINE PRODUCING CONDITIONS NON CRncKmq DISTILLATION NON VISCOUSDISTILLATE REsIDUE Viscous DISTILLATE I S LVENT REFININQAS WITH- LmwbSO HI H V. LFRAcTioN Low VlfkacTmN DEXWAX Fmsmzo LUBRICANT INVENTOR Patented 'Dec. 29, 1936 PATENT OFFICE LIETHOD OF PREPARING LUBRICANTS Leslie C. Beard, Jr., Brooklyn, N. Y., assignor to Socony-Vacuum Oil Company, Incorporated, a corporation oi New York Application March .14,

4 Claims.

This invention has to do with the preparation of lubricating oils of good quality from sources not hitherto used, such as residues from the cracking of gas oils under heat and pressure, 5 and the like.

It has long been known that in the cracking under heat and pressure of gas oils and the like to produce gasoline, that some of the oil seems to react in the reverse direction. That is, when a charging stock containing initially no material heavier or lighter than gas oil is subjected to controlled conditions of heat and pressure for the production of gasoline/a considerable portion of the charge is converted into materials of heavier nature. It has been recognized that certain fractions of these heavier products had'the properties of lubricants at ordinary temperatures, and it has been proposed to separate these lubricant fractions and use them as such. Experience with these products, prepared by simple distillation from cracking residues and refined'by the current methods has been disappointing. The oils soprepared have a much greater tendency toward oxidation and sludging than ordinary oils of the same general characteristics, and of more 3 im rtancelose viscosity with increase of tempnefature much more rapidly than most of the re rapidly thinning normal oils. Additionally such oils have an abnormally high gravity for a given viscosity. All of these qualities have militated against the adoption and widespread use of such oils. Attempts have been made to cover or alter these properties by blending such products with other oils and by combining them with other materials, such as sulphur, for instance,

but without notable success.

I have found that by properly refining these oils, lubricants can be made which comparefavorably in all respects with normally produced lubricants now orithe market.

It has therefore been an object of this invention to prepare a lubricant of normal characteristics from sources now deemed incapable of yielding such an oil, to devise a process whereby that lubricant can be recovered. and refined, to develop methods whereby the cracking or gas oils can be caused to yieldgood lubricants as well as gasoline, and such other objects and advantages as may hereinafter appear.

To assist in the itnther discussion, reference is made to that property of lubricants known as viscosity index, and developed by Dean and Davis, Chemical and Metallurgical Engineering, vol. 36, page 618. In brief, viscosity index is a. measure of the tendency of a lubricant to become less viscous at high temperatures, as measured by the viscosities at 100 F. and 210 F. re- "*'spectively, as related to certain oils used as standards. The index so calculated for present day lubricants derived from Pennsylvania grade crude 1934, Serial No. 715,470

is approximately 100, that for most grades of Mid-Continent base lubricants rapge from to 80, and for some Texas Gulf Coastal ibase lubricants range from zeroto 20. The lower the viscosity index, the greater the rapidity with which the oil loses viscosity on heating. The scale is arbitrarily fixed.

A further criterion of value is that known as the viscosity-gravity constant. This was developed by Hill and Coates, Industrial and Engineering Chemistry, 1928, page 641, the equation being:

Viscosity-gravity constant= Specific gravity0.240.0221ogxo (Vis 210-35) .755

The viscosity-gravity constant of present day lubricants of Pennsylvania origin range from approximately .800 to .830, of Mid-Continent lubricants from .830 to .870, and of California and Gulf Coastal oils from .870 to .890. This classification is not entirely rigid; some oils otherwise having properties consistent withtheir source falling out of place in the above rough classification. I I

The process of my invention may be very briefly described as separating from a pressure tar, by

distillation, the fraction containing ingredients capable of being refined into acceptable lubricants, separating unacceptable ubricants from the distillate fraction by suitable methods, and finishing the remaining portion 'of the distillate fraction in'to commercially acceptable lubricants.

The essential features of my process may be noted by reference to the drawing attached to this specification, which shows in outline form the sequence of steps herein disclosed.

As an example of my process, I may cite the following:

A gas oil of normal characteristics, containing no lubricant fractions, but composed of fractions much less viscous than lubricants, was charged to a Cross cracking still, and subjected to the usual conditions of operation therein.

From this cracking process a tar was recovered, which had the following characteristics:

Gravity 12.8 A. P. I. Viscosity 19" Saybolt furol Initial boiling point 381 F. I

% over at 705 F.

still and distilled at an absolute pressure of 5 mm.

'mercury. The condensate fraction between 56% over and over, inclusive, was collected, and found to have the following properties:

Gravity 10.3 A. P. 1.

.Flash C. 0. C 445 F.

Fire C. O. C 520 F.

Pour point". 35 F.

Viscosity at F 1032" Saybolt universal Viscosity at F 343" Saybolt universal Viscosity at 210 F 65" Saybolt universal Viscosity index. Minus 12 Color Dark green Conradson carbon 1.56%

Sulphur 0.79%

I have found that by subjecting this oil to certain methods of refining, there may be isolated from it an acceptable lubricant. The refining methods capable of performing this operation are those methods broadly known as selective solvent refining methods.

The general aim of these selective solvent methods is to increase the viscosity index of the oil treated by separating from it ingredients of low resistance to loss of viscosity with rise in temperature. Among various agents proposed for this purpose there may be named nitrobenzine, benzonitrile, phenol, furfural, acrolein, and crotonaldehyde, dichloroethylether, (known as chlorex) mixtures of liquid sulphur dioxide and benzol, liquid sulphur dioxide, and similar solvents. These above named reagents act as selective solvents for; the ingredientsof low viscosity index originally present in the oil, and remove them as an extract. It is also possible to use liquid propane, either pure or mixed with small percentages of butane, etc. for this purpose, this reagent acting as a selective solvent for the ingredients of high viscosity index. Other processes ofthis type pro- .pose to use simultaneously two counter-current solvent streams, such as for instance cresol for the selective solution of ingredients of low viscosity index, and liquid propane for the selective solution of ingredients of high viscosity index, as in Tuttle, U. 8. Patent No. 1,912,349. The functional operation of all of these processes are somewhat similar, the actual details of operation are characteristic of each process, and of the stock being treated, and all are directed to the same end.

In the present example, I have treated the above mentioned vacuum distillate fraction of pressure tar with liquid sulphur dioxide, using four batch extractions a 16 F., and each time treating the oil with an amount of liquid sulphur dioxide equal in volume 'to 50% of the oil being treated. Frorti the distillate I recovered approximately 40% of a refined 011 having the following properties:

Viscositygravitycoristant. .875

With the exception of pour point, this is to all respects a good lubricant, capable oif comparison with the greater volume of lubricants on today's markets. To reduce the pour point, I dewaxed this oil, yielding a finished oil of the followin tests:

Viscosity gravity constant. .885

This oil, it may be noted, has an unusually good pour, a viscosity index of the same nature as Mid-Continent base lubricants, which is considerably better than Coastal lubricants, and a viscosity-gravity constant which is of acceptable nature. comparable quality with normal lubricants.

Former attempts to produce lubricants from pressure tar have not resulted in usable lubricant oils, for the reasons pointed out heretofore. The selective solvent treatment of lubricants as heretofore developed has beenem gaged in bettering the quality of oils already acceptable to a salable. degree as lubricants. I am not aware of any indication in the selective solvent treatment of lubricants that would point out that the treatment of a pressure tar fraction by those methods would result in the production of a good lubricant from an oil initially so low in viscosity index, so highly susceptible to oxidation and so high in carbon forming constituents. This is most forcibly pointed out by the unusual increase in viscosity index.

It has not been previously recognized, so far as I am aware, that the cracking of gas oil produces 'a substantial proportion of products of polymerization which are highly paraflinicfin nature and capable of being isolated and refined to produce lubricants of the same character as those which might be produced from the heavier fractions of the crude by processes which are at pains to avoid cracking.

My process enables me to recover from pressure still residues a lubricant having a viscosity index of about the same value as Mid-Continent oils, a-good viscosity-gravity constant, good re- In other respects it is definitely of r sistance to oxidation, and other qualities in every way comparable to'regular lubricants, and that in economic percentages. Inasmuch as the source of this oil was originally'a gas oil, I have been enabled to materially add to the amount of good lubricants recoverable from a given crude. Broadly, my process contemplaks the treatment of pressure tar by distillation under vacuum, and the refining of the distillate by fractional solution methods, followed by such other conventional operations of dewaxing, etc. as may be found necessary, audit is not intended that it be limited to the conditions which are herein set forth inv an exemplary manner only. but only to such limitations as may be found in the appended claims.

What is claimed is:

1. The method of synthesizing a lubricant oil of high viscosity index and resistant to oxidagas oil to produce gasoline, cycle gas oil and pressure tar, separating the pressure tar from the remaining products of the cracking operation, subjecting the pressure tar to a non-cracking distillation to produce a non-viscous distillate, a viscous distillate, and a residue, treating the viscous distillate with -a selective solvent capable of removing therefrom the portion highly susceptible to loss of viscosity upon rise of temperature, and finishing the remainder of the viscous distillate as a lubricant substantially equal in quality to current lubricants of Mid- Continent origin.

2. In the process of preparing a lubricant oil of high viscosity index and resistant to oxidation from the liquid residue of cracking, the steps which comprise subjecting the liquid residue to non-cracking distillation to produce a non-viscous distillate, a viscous distillate,and a residue, and treating the viscous distillate to remove from it ingredients highly susceptible to loss of viscosity upon rise of temperature, by extraction with liquid sulphur dioxide at low temperature, said treatment being continued until attainment of a raflinate oil having a viscosity index not less than when dewaxed.

3. In the process of preparing a lubricant oil of high viscosity index and resistant to oxidation from the liquid residue of cracking, the steps which comprise subjecting the liquid residue to non-cracking distillation to produce a non-viscous distillate, a viscous distillate, and a residue,

and treating the viscous distillate at low tem- 1 perature with liquid sulphur dioxide to remove from it ingredients highly susceptible to loss of viscosity upon rise of temperature, thereby to produce a final lubricant product substantially equal in quality to current lubricants oi Mid-Continent origin.

4. In the process of synthesizing from petroleum distillates initially containing substantially no fractions of high viscosity a lubricant oil substantially similar in resistance to loss of viscosity with rise in temperature, low carbon content, and resistance to oxidation to lubricant oils of like viscosity normally prepared directly from the viscous fractions of Mid-Continent crude oils, the steps which comprise subjecting the non-viscous petroleum distillate to cracking conditions of temperature and pressure capable of LESLIE C. BEARD, JR.

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