US2027770A - Process of treating lubricating oil stock - Google Patents

Description

Patented Jan. 14, 1936 UNITED STATES PROCESS OF TREATING LUBRICATING OIL STOCK John D. Fields, Los Angeles, Calif.

No Drawing. Application October 20, 1931, Serial No. 570,048

Claims. (Cl. 19634) The present invention relates to the production of high quality lubricating mineral oil, which will be entirely stable and will be free from tendency to thicken or form gum, during 5 use.

As is well known, lubricating mineral oil has heretofore been prepared from petroleum, after distilling off the lighter fractions, in several different manners. One method is to distill (some times steam distill or some times vacuum distill or some times distill with steam under vacuum) the desired fraction from the petroleum. In other cases the residue in the still after distilling off the lighter fraction is drawn off and either filtered or purified chemically or both. The lubricating distillate or the residue is commonly purified first by treating with sulphuric acid, one or more batches being added, followed by settling, then sometimes washing with water,,then washing with a dilute caustic alkali solution to neutralize acidity. Such purification does not remove all of the impurities present, as is proven by the fact that the oil even after such treatment frequently causes gumming of the bearings, and causes gumming or thickening when the oil is used in internal combustion engines as a lubricant.

On account of the viscosity of lubricating oils, and more particularly the heavy lubricating oils, it is difficult to completely treat the oils with any kind of a chemical, and for that reason there is considerable waste of acid and alkali in the purification of lubricating stock. In some of the methods of purifying lubricating oil, it is customary to add a thinning agent such as naphtha or gasoline, or even kerosene, for ex ample in the removal of amorphous wax (material similar to petrolatum) from the oil, by the Sharples process.

I have found that it is possible to economically purify the lubricating oil, and take out all of the gum-forming impurities, by treatment with metallic sodium. Instead of sodium other similar metals such as lithium, potassium, calcium, barium and strontium can be employed, this group being hereinafter referred to as alkali metal. The said metal is used in the metallic condition, and preferably at or below room temperature, and in any case at temperatures not exceeding 125 F.

The thinned lubricating oil can be passed as a continuous current through one or more tanks, the alkali metal being preferably stationary therein, and in a more or less comminuted condition, say in the form of small bars or rods in order to expose a considerable amount of surface to the action of the oil mixture under treatment. The thinned oil should be substantially free from water, and if the original stock contains water (as in the case of steam-distilled oil) it is advisable to thoroughly dehydrate the thinned oil before the same is brought into contact with the sodium, otherwise the water would react with the sodium and use up a large amount of sodium without any useful results being thereby secured. The thinned oil may also be subjected to filtration if the same contains any sub stantial amount of insoluble materials. The removal of both the water and insoluble matter, if present, can be accomplished by filtration and then passing the filtrate through a suitable centrifugal liquid separator, or in other well known manners.

ditions, and which was a highly viscous oil, was

first diluted with about twice its volume of a light petroleum naphtha, and the mixture well stirred. The mixture was found to contain asubstantial proportion of water and a small amount of insoluble solid material. This was filtered through a filter press, then passed through a centrifugal liquid separator to remove the suspended matter and water. The liquid was then passed through a tank containing metallic sodium, this being supported on grids above the bottom, the mixture of oil and naphtha entering at the bottom of said tank and flowing upwardly through the same, and remaining in the tank about two hours. The sodium was in the form of short bars about two inches long and a third of an inch square, in the form of a layer about a foot thick, so that in passing through the tank the oil mixture was brought into very intimate contact with the surfaces of the sodium. Some of the impurities in the oil were precipitated on the surface of the sodium, as a somewhat gummy coating. Some of the impurities in the oil were apparently coagulated into a gummy mass, a part of which settled into the bottom of the treating tank, and another part of which settled out in a settling tank following the treating tank. After a large amount of the oil had been treated, it was withdrawn from the settling tank, filtered and then run into a still in which the naphtha was distilled off, the latter portion of this distillation being conducted under a vacuum of about five pounds per square inch, in order to prevent any cracking of the oil, and the temperature was carried up to about 500 F., While some steam was bubbled through, during the last twenty minutes of the distillation.

The lubricating oil, after cooling, was found to be of a very light color, was found to be entirely stable when exposed to sun light for a substantial period, was found to be free from gumming tendency when used as a lubricant on shaft bearings and also when used as a lubricant in an automobile engine.

It was found that a portion of the impurities coagulated from the oil will deposit as a more or less gummy layer on the surfaces of the pieces of sodium. When this deposit gets thick it will slow down the action of the process, and for that reason it is advisable to provide means for renewing the surfaces of the sodium, from time to time by dissolving away the accumulated ma.- terial therefrom. This can be accomplished by discontinuing the flow of the oil and solvent mixture, drawing off the oil and solvent from the treating tank, and flowing through the treating tank a mixture of benzol and alcohol (for which purpose substantially dehydrated denatured alcohol can be employed) it being preferable to use from 5 to 10% of the said alcohol in the benzol, and to flow the mixture through the tank until the surface of the sodium is found to be bright and free from deposit. The benzol and alcohol mixture removes this deposit very rapidly, and care should be taken not to continue this treatment after the surface of the sodium has become bright, otherwise the sodium will react chemically with the alcohol, with a loss of sodium. For this purpose glass covered peep holes are provided in the treating tank opposite the layer of sodium, for watching this operation. The sodium in being cut up and put into the treating tank may frequently acquire a thin film of oxide on its surface, and preferably I give the sodium a very short Wash with the benzol-alcohol mixture, before introducing the solution of oil and thinning agent.

During the action practically none of the sodium is used up, and a given charge of sodium is capable of refining an immense amount of the lubricating oil solution.

The lubricating oil product is entirely stable, and is free from gumming tendency, as stated above. It is also free from substances producing a corrosive action on metal bearings. A further and highly important advantage is that the refining loss is extremely low, amounting to only a minor fraction of the refining loss which is encountered when refining a similar oil by the sulphuric acid and alkali method.

After the benzo-alcohol mixture has been used several times for revivifying or 'reactivating the metallic sodium (alkali metal), this solution can be run into a still and the benzol and alcohol distilled off for reuse, leaving a valuable residue, which can be used in making road oil or for other purposes, so that there are no waste products to be disposed of.

I have above spokenof distilling off the naptha from the lubricating oil after the treatment of the solution of lubricating oil, with alkali metal. This naptha having been treated with sodium in the process, is also highly refied during the process. If this recovered naphtha is mixed with more of the lubricating oil, for the next run of the process, there is no impurity therein to be coagulated or precipitated on the alkali metal whereby cleaning of the latter by the benzol-alcohol mixture does not have to be so frequent.

It is also possible, instead of using naptha, gasoline, kerosene, etc., as the solvent or thinning agent, to use a mixture of one or several of these mixed with a small fraction (say onefourth, more or less) of benzol, since such mixture will not act as a solvent to prevent precipitation of the gum-forming constituents of the oil and naptha, etc.

Where I have spoken of benzol, as a cleaning fluid for the alkali metal, I include also its homelogues, toluol, xylol, solvent naptha, etc., or mixtures thereof (benzol or its homologues, or single ring liquid aromatic hydrocarbon). Hydrogenated aromatic hydrocarbons, such as hexahydrobenzene, tetralin, etc., can be used in place of all or a part of the benzol. Ordinarily I prefer to use well dried (substantially anhydrous) 90% benzol, which as is well known contains a considerable proportion of toluol and other aromatic hydrocarbons.

I have referred to treating a specific lubricating oil distillate but various other lubricating oil cuts can be employed. In some cases the distillate may be of about 24 B., while in other cases various distillates of gravities between about 18 and 36 B., can be treated by the process, and it is understood that highly viscous oils will need more of the thinning agent, and less viscous oils need less thereof. With a light lubricating stock of 26 B., I may use an equal volume of gasoline, which will give a mixture of about 38 to 40 B., and of sufficiently low viscosity.

I claim l. A process of treating a lubricating petroleum oil stock which comprises thinning same with a light petroleum hydrocarbon solvent, in such proportions as to give a mixture of low viscosity, and thereafter flowing the mixture, in a substantially anhydrous condition, into intimate contact with a solid alkali metal in a comminuted state at not substantially above normal room temperature, until impurities therein have been coagulated, separating said oily materials and the coagulated impurities from each other, before chemical reaction of any substantial proportion of the alkali metal with hydrocarbon compounds is effected, and distilling said light petroleum hydrocarbon solvent, from the lubricating oil stock.

2. A process of treating a lubricating petroleum oil stock which comprises thinning same with a light petroleum hydrocarbon solvent, to produce an intimate admixture therewith, removing water' from said mixture, and thereafter treating the mixture, in a substantially anhydrous condition, with a solid alkali metal at not substantially above normal room temperature, until impurities therein have been coagulated, separating said oily materials and the coagulated impurities from each other, before chemical reaction of any substantial proportion of the alkali metal with hydrocarbon compounds is effected, and distilling said light petroleum hydrocarbon solvent, from the lubricating oil stock, and thereafter when the alkali metal has become coated, contacting same with a mixture which is mostly a benzol hydrocarbon with a minor fraction only of a lower alcohol, until said metal becomes bright.

3. A process of treating a lubricating petroleum oil stock which comprises thinning same with a light petroleum hydrocarbon solvent, to produce an intimate admixture therewith, removing material insoluble in said solvent, and thereafter treating the mixture, in a substantially anhydrous condition, with a solid alkali metal at not substantially above normal atmospheric temperature, until impurities therein have been coagulated, separating said oily materials and the coagulated impurities from each other, before chemical reaction of any substantial proportion of the alkali metal with hydrocarbon compounds is effected, and distilling said light petroleum hydrocarbon solvent, from the lubricating oil stock.

4. A process of treating a lubricating petroleum oil stock which comprises thinning same with a light petroleum hydrocarbon solvent, to produce an intimate low viscosity free-flowing admixture therewith, and thereafter treating the mixture, in a substantially anhydrous condition, with a solid alkali metal at not substantially above atmospheric temperature, until impurities the solvent in a condition suitable for reuse in the process.

5. A process of refining a lubricating distillate from petroleum oil, which comprises mixing said 1 lubricating distillate with a light readily-volatile petroleum hydrocarbon distillate, and thereafter treating the mixture, in a substantially anhydrous condition, with a solid alkali metal at not substantially above atmospheric temperature,.

until impurities therein have been coagulated, separating said oily materials and the coagulated impurities from each other, before chemical reaction of any substantial proportion of the alkali metal with hydrocarbon compounds is,

efiected, and distilling said light petroleum hydrocarbon solvent, from the lubricating oil.

JOHN D. FIELDS.