US2083247A - Lubricating oil - Google Patents

Description

vvul bll lluul zoo-52a Patented June 8, 1937 XS'DQ ($15 UNITED STATES PATENT OFFICE Kenneth Taylor, Chicago, Ill., and Bernard H. Shoemaker, Hammond, Ind., assignors to Standard Oil Company, Chicago,-lll., a corporation of Indiana No Drawing. Application February 23, 1933, Serial No. 658,150

1 Claim. (Cl. 196-13) This invention relates to a method of treating mineral lubricating oils and it pertains more particularly to the art of preparing lubricating oils stable to oxidation and sludging.

5 Petroleum is essentially a mixture of hydrocarbons comprising several groups or homologous series of compounds, such as the paraiiins, hydroaromatics, aromatics, polymethylenes, and various other series of compounds in which the hyviscosity index", as used herein, refers specifically to the index defined by Dean and Davis in Chemical and Metallurgical Engineering, vol. 36, 1929, page 618. The viscosity index of a labricating oil is an indication of its composition or type, i. e., whether it is a paraffin base or naphthene base oil. Paraflin base oils are arbitrarily assigned a viscosity index of 100, naphthene base oils are assigned a viscosity index of drogen to carbon ratio varies to a wide degree. 0, and mixed base oils lie between these extremes. 10

A large number of individual compounds of each For example, if an oil shows a viscosity index of series are present and have different boiling about 85 to 90, it is evident that the oil is prepoints, physical and chemical properties. In the dorninately paraflinic in nature. various types of crude petroleum commonly One of the common ways of increasing the known as paraflin base, naphthene or asphalt paraflinic content of a lubricating oil is to treat 15 base, and mixed base oils, these various series the oil with fuming sulfuric acid. The oil and of hydrocarbons are present in different proporacid are mixed and agitated in the proportion of tions. For example, in paramn base oils, such about one to two pounds of fuming acid for each as those from the Appalachian field, there is a gallon of oil. The mixture is then allowed to relatively high proportion of parafiinic hydrosettle and the acid layer, comprising sulfuric acid 20 carbons having a chain structure and a high hyand acid sludge, settles to the bottom and is drogen to carbon ratio, whereas in the California drawn off. The top layer comprises an oil which and Gulf Coastal oils there is a high proportion is high in parafiinic compounds. Also, lubricatof naphthenic hydrocarbons and hydrocarbons ing oil refined in this way contains a relatively with ring structures and low hydrogen to carbon large quantity of sulfonic compounds which must 25 ratio. The mixed base oils, such as those from be removed before the oil can be satisfactorily Oklahoma and the Mid-Continent area, are in used for most lubricating purposes, and this opgeneral intermediate between these extreme eration is often expensive and wasteful because typ of troublesome emulsions which are encountered.

In normal refining of crude petroleum, the The quality of the acid treated lubricating oil 30 fractions of varying distillation ranges which are can be fairly judged from two of its properties, successively obtained by distillation of the oils that is, the viscosity index and stability against partake of the general character of the crude; sludge formation. The sludge stability is deterfor example, lubricating oils derived from Apmined by bubbling air at the rate of 10 liters per palachian crudes will show parafiinic characterhour into a 250 cc. sample of oil at 340 F. Sam- 35 istics, whereas the lubricating oils derived from ples of 10 grams each are withdrawn at inter- Gulf Coastal oils show naphthenic characterisvals and tested to determine the amount of sludge tics. The distillates from the mixed base crudes, formed for each 10 grams of oil. When the such as those from the Mid-Continent area, will amount of sludge has increased to 10 mg., the

40 show characteristics common to both the naphnumber of hours of oxidation is noted and the 4 thenic and parafiinic oils. An important propsludge stability of the oil is then expressed in erty of paraflinic lubricating oils is their low vishours required to form 10 mg. of sludge per ten cosity temperature coefficient or rate of change grams of oil. The amount of sludge is deterof viscosity with temperature. This property mined by diluting the 10 gram sample of oil with makes them particularly suitable for certain luprecipitation naphtha, filtering off the precipita- 45 brication problemswhere high temperatures are tion naphtha insoluble residue, and then washencountered. At low temperatures also, these ing the filter repeatedly with precipitation naphoils retain their fluidity better, an important contha-the residue being sludge. sideration in cold weather operation of automo- Another method of increasing the paraflinic biles, for example. For this reason it is very hydrocarbon content of lubricating oils, as ex- 50 desirable to separate the mixed base oils into emplified by the viscosity index, is to extract the their paraffinic constituents and non-paraffinic oil, preferably a dewaxed oil, with an organic sol- .constituents. vent such as chlorinated ethers, sulfur dioxide,

The parafiinic characteristics of an oil may be chlorohydrins, mixtures of nitro-benzene and x sed by its viscos ty ndex. The expression acetone, sulfur dioxide, and benzene and the 55 like. These solvents have a preferential solubility for the naphthenic constituents of the oil and are capable of separating a mixed base oil into two major fractions. They are the paraffinic fraction of hydrocarbons and the naphthenic fraction of hydrocarbons. These extraction processes are usually carried out by mixing 2 to 5 parts of solvent with about 1 to 2 parts of oil and then heating and agitating the mixture until substantially complete miscibility is obtained. The mixture is then permitted to cool and stratify. The major portion of the solvent and naphthenic aromatic and aromatic-like compounds and hydrocarbons settle to the bottom and the paraffinic portion of the oil segregates into the top layer and is called the rafiinate. The lower layer comprising most of the solvent and naphthenic compounds, is then withdrawn from the raffinate.

. The rafiinate is then heated and treated with steam or an inert gas to remove the small amount of solvent dissolved therein. This treated rafflnate is clay-treated and may be given subsequent treatments with sulfuric acid in order to obtain good sludge and color stability. Alternatively, the extraction may be carried out in countercurrent manner by methods well known in the art, in which case it will usually be desirable to work at ordinary temperatures or below.

The object of our invention is provide a method separate from the highly paraflinic oil. The temperature at which this separation is effected is called the extraction temperature. In this particular example we use an extraction temperature of about 60 F. It should be understood, however, that the extraction temperature may vary with different oils and solvent, but generally the extraction temperature is at least 40 F. below the miscibility temperature. Also, the oil may be cooled step-wise, that is, two or more separations may be made at different temperatures.

The solvent containing aluminum chloride and extract, or bottom layer, is withdrawn from the bottom of the agitator, and then the rafflnate is stripped with an inert gas or steam to recover the solvents therefrom. Generally, the stripping is performed at a somewhat elevated temperature.

The raffinate or highly parafiinic fraction of the oil may then be clay treated in the ratio of about 300 to 1000 gallons per ton of clay in order to improve the color of the final product. Fullers earth, bentonite, Attapulgus clay or other suitable decolorizing clay may be used for this purpose.

The first example of the following table discloses the properties of the above oil when treated in the manner and under the conditions hereinabove set forth. The second example discloses the properties of the oil when extracted and treated under the same conditions but in the of extracting mineral oils so as to impart good absence of aluminum chloride.

Table I T 1 Y. M Clay Saybolt sludgling timel'lle C0 01 1e VISCOSl y OUIS Example alter extrac- (per 35??? 3 a tion cent) tori) 210F. F. 10 mg. 100mg.

1 13s 69 33a 87 1044 a 88.5 94 129 2 256 67 33s 89 1087 13 88.5 72 112 sludge and color stability thereto simultaneously with the step of solvent extraction. We have found that a small amount of metal halides such as aluminum chloride dissolved and/or colloidally suspended in the solvent will greatly improve the color and increase the sludge stability of the raflinate.

. We will describe our process by extracting a Mid-Continent mixed-base lubricating oil with a single organic solvent containing about 1% of aluminum chloride dissolved and/or suspended therein. In this particular example we will use a Mid-Continent lubricating oil distillate having a Saybolt viscosity of 114 at 210 F. and 2350 at 100 F. and a viscosity index of 56.5, sludging time of less than 10 hours for 10 mg. of sludge. However, it should be understood that our process is applicable to any distillate or bottom derived from mixed base oils or naphthenic oils. One volume of the oil is mixed in a suitable agitator with 1.5 volumes of beta-beta dichlorethyl ether containing about 1% of aluminum chloride. The mixture is then agitated and heated to a temperature somewhat above the miscibility temperature which is about F. In this particular example the mixture was heated to F. Generally the solvent or solvents are miscible with the oil within the range of 50 to 220 F. However, with some solvents the miscibility temperature may be lower than this.

After the oil and solvent containing aluminum chloride have been heated to the miscibility tem perature, the mixture is cooled to a temperature below the miscibility temperature where the solvent containing aluminum chloride and extract From Example 2 of the above table, which gives the results of the extraction in the absence of aluminum chloride, it will be noted that the true color of the rafiinate before claying was 256; after claying the true color was 13. The time required for 10 mg. of sludge to form under the excessive oxidizing conditions was 72 hrs. and the time required for 100 mg. of sludge to form was 112 hours. Example 1 discloses the properties of the oil when treated under exactly the same conditions but in the presence of 1% by Weight of aluminum chloride. It will be observed that the true color of the raffinate after this ex traction was 136; after claying the true color was 3-a great improvement over the color obtained in the absence of aluminum chloride. The time required for 10 mg. of sludge to form was 94 hrs. and the time required for 100 mg. of sludge to form was 129 hrs.

In view ofthe above table and explanation it is apparent that the presence of a small amount of aluminum chloride in the solvent greatly decreases the true color and adds increased sludge stability to the oil. It should be observed that there is no decrease in the yield or viscosity index of the oil in order to obtain this improved color and sludge stability. In fact, it will be noted that a slight increase in yield was obtained. If the above oil is treated with aluminum chloride per se, about 9%, the sludge stability is very low. In fact, it required only 31 hrs. to form 10 mg. of sludge.

The following table sets forth the properties of the refined oil obtained by the hereinbefore described process when one volume of distillate (114 Saybolt viscosity at 210 F., 2350 Saybolt viscosity at 100 F. and a viscosity index of 56.5) is extracted with one volume of the halogenated ether in the presence of 2% of aluminum chloride by weight at 160 F.

By comparing the properties of the oil set forth in Table II with, the properties of the oil in Example 2 of Table I it will be observed that the true color of the oil after claying are the same, but 1000 gals. of oil were treated per ton of clay in the case of the oil in Table II and only 333 gals. were treated per ton of clay in the case of the oil in Example 2 of Table I. It will be noted that the extraction with a solvent in the presence of a small amount of aluminum chloride provides a process of obtaining 1000 gals. of oil of 13 true color per ton of clay, whereas, in the absence of aluminum chloride only 333 gals. of oil of 13 true color were obtained per ton of clay.

The second example of the following table represents the results obtained when one volume of the above oil (Saybolt viscosity of 114 at 210 F., 2350 at 100 F. and a viscosity index of 56.5) is treated with 1% volumes of nitrobenzene containing 1% by weight of aluminum chloride. The treating temperature used in this example was 200 F. The first example of this table discloses the properties of the above oil when treat ed under the same conditions with the same VVUI \Ill solvents in the presence of metallic halides, we may use other organic selective solvents. Examples of solvents which may be used in combination with these metallic chlorides such as aluminum chloride, boron trichloride and zinc chloride are: methyl 2-chlorethyl ether, di(2- chlorethyl)ether, methyl chloropropyl ether, methyl 2-3 dichloropropyl ether, ethyl 2-3 dichloropropyl ether. ethyl 2-3 chloropropyl ether, 2-chlorethyl propyl ether, dichlorisopropyl ether, dichloropropyl ether, nitrobenzene, nitrotoluene, nitroxylene, ethyl chloracetate, ethyl dichloracetate, ethyl chlorpropionate, 2-chlorethyl acetate, methyl chloracetate, 2-chlorethyl propionate, sulfur dioxide, dioxane, pyridine. nitronaphthalene, or mixtures of the above. We have found that the alpha chlorinated aliphatic ethers and esters are more reactive than the beta or gamma halogenated compounds and that satisfactory results are not obtained with these alpha halogenated compounds.

Instead of using a single organic solvent in the presence of these metallic halides, we may use mixed solvents in combination with aluminum chloride, boron tri-chloride or zinc chloride. Examples of mixed solvents which may be used for extracting lubricating oils are:

Table IV Acetone and nitrobenzene Acetone and di(2-chlorethyl) ether Acetone and dichlorobenzene Acetone and cresol Methyl ethyl ketone and di(2-chlorethyl)ether Methyl propyl ketone and nitrobenzene Methyl propyl ketone and di(2-chlorethyl) ether Ethyl acetate and nitrobenzene Ethyl acetate and di 2-chlorethyl)ether Carbon dioxide and sulfur dioxide Propyl ether and nitrobenzene solvent but in the absence of aluminum chloride. Iso-propyl ether and nitrobenzene Table III Saybolt Sludging Clav True color meld viscosity t1ruehours treated True Viscosity Example igfi gg 53 (gals. per color index 210 F. 100 F. 10 mg. 100 mg.

From Example 2 of the above table it will be observed that the color and sludge stability of the oil treated in the presence of aluminum chloride is greatly improved. It is apparent that the presence of a small amount of aluminum chloride materially decreases the true color of the oil and adds increased sludge stability to the oil. Furthermore, it will be observed that these enhanced properties were obtained without the loss of yield or viscosity index. In fact, the viscosity index of the oil which was treated with nitrobenzene containing aluminum chloride dissolvent and/or dispersed therein was slightly better than the oil which was extracted with the same solvent but in the absence of aluminum chloride. White oils, or substantially colorless mineral oils can be prepared by our process by repeating the extraction of the oil several times with the solvent and metallic halide. The degree of refining will determine the number of extractions. Petroleum naphthas may likewise be refined by our process as'hereinbefore described.

Instead of using the hereinabove mentioned Iso-propyl ether and chlorinated aliphatic ethers Methyl acetate and nitrobenzene Methyl acetate and di(2-chlorethyl)ether Propyl acetate and nitrobenzene Ethyl propionate and nitrobenzene Ethyl propionate and di(2-chlorethy1) ether Methyl propionate and nitrobenzene Sulfur dioxide and benzene Sulfur dioxide and dimethyl ether Sulfur dioxide and diethyl ether The metallic halides which have proven most desirable for this process are substantially an- IIUL ployed in this specification and claim in a generic sense to include the compounds that have a low viscosity index, low A. P. I. gravity, and usually rapid sludge-forming characteristics, examples of which are the aromatic, aromatic-like, olefins, high molecular weight polymethylenes, nitrogen and sulfur compounds.

The term non-sludging and stable to oxidation and sludging is used in the specification and claim to cover an oil which has greater sludge stability than the parent oil. These terms are not intended to define oils that are absolutely stable against sludge formation under rigid oxidizing conditions for long periods of time.

In addition to or instead of extracting the lubricating oils in the presence of aluminum chloride, we may first treat the oil With aluminum chloride and then extract with a selective solvent. However, this procedure is usually more expensive for the reason that it requires additional operations after the extraction with the solvent. We have found that the process of extracting in the presence of aluminum chloride is very economical.

The oil treated by our process may be dewaxed before and/or after the extraction, but we prefer to dewax the oil before extraction. While we have described our invention with reference to specific materials and proportions of solvents, it should be understood that the scope of our invention is not limited thereto except insofar as set forth in the appended claim.

We claim:

The method of preparing a non-sludging lubricating oil having a low true color from a mineral oil containing naphthenic and paraflinic constituents, the steps comprising mixing one volume of said mineral oil with at least one volume of a selective solvent selected from the group consisting of di(2-chlorethyl)ether and nitrobenzene which has a small amount of aluminum chloride dissolved therein, heating said mixture to an elevated temperature to effect substantially complete solution, cooling said admixture to a temperature at which phase separation occurs, withdrawing the top layer and removing therefrom the dissolved solvent.

KENNETH TAYLOR. BERNARD H. SHOEMAKER.