US1976544A

US1976544A - Method of treating mineral lubricating oils

Info

Publication number: US1976544A
Application number: US609776A
Authority: US
Inventors: Sterling H Diggs; Jr James M Page
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1932-05-06
Filing date: 1932-05-06
Publication date: 1934-10-09
Anticipated expiration: 1951-10-09

Description

Patented Oct. 9, 1934 UNITED STATES PATENT OFFICE METHOD OF TREATING MINERAL LUBRICATING OILS No Drawing. Application May 6, 1932, SerialNo. 609,776

-- 5 Claims. (01. 196-13) This invention relates to a'method of treating mineral lubricating oils and it pertains more particularlyto the art of preparing lubricating oils stable to oxidation and sludging.

Petroleum is essentially'a mixture of hydrocarbons comprising several groups or homologous series of compounds, such as the paraflins, hydroaromatics, aromatics, polymethylenes, and various other series of compounds in which the hydrogen to carbon ratio is even lower than in the above classes. A large number of individual compounds of each series are present and have different boiling points, physical and chemical properties. In the'various types of crude petroleum commonly known as paraffin base, naphthene or asphalt base, and mixed base oils, these various series of hydrocarbons are present in different proportions. For example, in paraflln base oils such as those from the Appalachian field, there is a relatively high proportion of parafilnic hydrocarbons having a chain structure and a high hydrogen to carbon ratio, whereas in the-Gulf Coastal oils there is a high proportion of naphthenic hydrocarbons and hydrocarbons with ring structures and low hydrogen to carbon ratio.

. The mixed base oils, such as those from Oklahoma and the Mid-Continent area, are in general intermediate between these two extreme types.

In normal refining of crude petroleum, the fractions of varying distillation ranges which are successively obtained by distillation of the .oils partake of the general character of the crude; for example, lubricating oils derived from Appalachian crudes will show parafiinic characteristics, whereas the lubricating oils derived from Gulf Coastal oils show naphthenic characteristics. The distillates from the mixed base crudes, such as those from the Mid-Continent area, will show characteristics common to both the naphthenic and paraflinic oils. An important property of paraflinic lubricating oils is their low viscosity temperature coeflicient or rate of change of viscosity with temperature. Thisproperty makes them particularly suitable for certain lubrication problems where high temperatures are encountered. At low temperatures also, these oils retain their fluidity better, an important consideration in cold weather operation of automobiles, (for example. For this reason it is very base oil. Paraffin base oils are arbitrarily assigned a viscosity index of 100, naphthene base oils are assigned a viscosity index of 0, and mixed base oils lie between these extremes. @For example, if an oil shows a viscosity index ,of about 85 to 90, it is evident that the oil is predominately parafllnic in nature.

One of the common ways of increasing the parafllnic content of a lubricating oil is to treat the oil with fuming sulfuric acid. The oil and acid are mixed and agitated in the proportion of about one to two pounds of fuming acid for each gallon of oil. The mixture is then allowed to settle and the acid layer, comprising sulfuric acid and acid sludge es to the bottom and is drawn off. The top layer comprises an oil which is high in parafiinic compounds. Also, lubricating oil refined in this way contains a relatively large quantity of sulfonic compounds which must be removed before the oil can be satisfactorily used for most lubricating purposes, and this operation is often expensive and wasteful because of troublesome emulsions which are encountered. The quality of the acid treated lubricating oil can be fairly judged from two of its properties, that is, the viscosity index and stability against sludge formation. The sludge stability is determined by bubbling air at the rate of 10 litres per hour into a 250 cc. sample of oil at 340 F. Samples of 10 grams each are withdrawn at intervals and tested to determine the amount of sludge formed for each 10 grams of oil. When the amount of sludge has increased to 10 mg. the number of hours of oxidation is noted and the sludge stability of the oil is then expressed in hours for 10 mg. of sludge. The amount of sludge is determined by diluting the 10 gram sample of oil with hexane and then filtering off the hexane insoluble residue.

,The following table shows the sludge stability of a Mid-Continent lubricating oil distillate of 21.3 A. P. I. gravity, 101.9 Saybolt viscosity at 210 F., and a viscosity index of 54, when treated with different quantities of fuming sulfuric acid.

From the above table it will be observed that a 2.7 pound acid treat increased the viscosity index of the oil from 54 to 92, and the treated oil hada sludge stability of 125 hours. Also, it will be noted that the yield is only 35%. From the above data it is apparent that a. largequantity of oil is temperature.

lost when highly stable oils are prepared by acid treating.

Mixed base oils can be made more paraflinic, as indicated by the viscosity index, by extracting the naphthenic and naphthenic-like compounds, or sludge forming hydrocarbons, from the oil with organic solvents. The solvent extraction may be performed with single solvents or with mixed solvents, and the extraction may be performed in one or several stages. Oils prepared by solvent extraction have very high viscosity indices, but the oils produced in this way are not stable against sludge formation. We have found that a light sulfuric acid treatmentfollowing the step of solvent extraction will make the oils very resistant to oxidation. We have found that the oils prepared by organic solvent extraction are particularly unstable as to sludge formation, but a light acid treatment is also capable of making these oils very resistant to sludge formation.

We will describe our preferred process by extracting a Mid-Continent lubricating oil distillate with a. single organic solvent, di(2 chlorethyl) ether, and then follow this extraction with a light sulfuric acid treatment. We will use the same oil as described in connection with Table I, that is, a Mid-Continent lubricating oil distillate of 21.3 A. P. I. gravity, 101.9 seconds Saybolt viscosity at 210 F., and a viscosity index of 54. It should be understood that our process is applicable to any mixed base lubricating oil. The lubricating oil and di(2 chlorethyl) ether are mixed in the ratio of 3 volumes of solvent for each volume of oil, and the mixture is then agitated and heated to the miscibility temperature. Generally the solvent or solvents are miscible with the oil within the range of -210 F. In this particular example we used a miscibility temperature of 155 F.

After the oil and solvent have been heated to the miscibility temperature, the mixture is cooled to a temperature below the miscibility temperature where the solvent and extract separate from the highly paraflinic oil. The temperature at which this separation is effected is called the "extraction temperature." In this particular example we used an extraction temperature of about 65 F. It should'be understood that the extraction temperature may vary with different oils and solvents, but generally the extraction temperature is at least 40 1?. below the miscibility The uppermost layer of oil comprises the highly parafllnic oil, and this layer is referred to as the rafllna The solvent and extract are withdrawn from the bottom of the agitator, and then the raflinate isstripped withaninert gas. 7 Generally, the stripping is performed at a somewhat elevated temperature.

The rafllnate is then given a light sulfuric acid treatment. In this example, we used one-half pound of 93% sulfuric acid for each gallon of raiiinate. The oil and acid were mixed and agitated at about F. for a short time, the acid layer was allowed to settle and was'then drawn off. The acid treating may be performed at any suitable temperature, but generally a temperature within the range of 20 to 200 F. is satisfactory. Also, the quantity of acid may be varied in accordance with the quality of the oil desired, but generally from one-fourth to one pound of 80-98% sulfuric acid will give a very stable oil. It should be understood that the more highly concentrated acid may be used in smaller quantities.

Typical results illustrating the cooperation between solvent extraction and acid treating are given in the following table.

Example 1 shows the viscosity index, sludge stability and yield of the oil after solvent extraction, and Example 2 shows the viscosity index, sludge stability and yield of the oil after solvent extraction followed with alight acid treatment.

It will be observed from Example 1 in the above table that solvent extraction, per se, produced an oil of high viscosity index. Before extracting, the oil had a viscosity index of 54, but by solvent extraction this was raised to a viscosity index of 93. Notwithstanding the high viscosity index,

the sludge stability of the oil is relatively low.

By comparing the oil prepared by solvent extraction, as set forth in Example 1 of Table II, with the oil prepared by acid treatment, as set forth in Example 1 of Table I, it will be observed that both oils have the same sludge stability, but the oil prepared by solvent extraction has a much higher viscosity index, that is, the solvent extracted oil is more paraflinic than the acid treated oil. It will be observed from Example 2 of Table II, that a one-half pound 93% acid treat applied to the oil in Example 1 of Table II raises the sludge stability from 66 hours to hours for 10 mg. of sludge. Also, the yield of oil is 55%, whereas with acid treating per se, see Example 2, Table I, the yield is 35% fora 125 hour oil. So, by using a light acid treatment after solvent extraction we can obtain a 55% yield of 125 hour oil having a viscosity index of 94, whereas by acid treating alone, as shown in Example 2 of Table I, a 35% yield of 125 hour oil having a viscosity index of 92 was obtained. Also, the combination of solvent extraction and 93% acid treating gave an oil with properties that could not be obtained with 93% acid treating alone.

A lubricating oil distillate of 22.8 A. P. I. gravity and 101 sec. Saybolt viscosity at 210 F. was given three successive di(2 chlorethyl) ether extractions and the railinate was then given a light acid treatment. The volume of chlorinated ether used for each extraction was 66% of the volume of oil. The following table shows the results from this treatment.

It will be observed that the light acid treatment raised the sludge stability of the solvent extracted 011 from about 60 hours to 231 hours. Also, the yield of finished product was 55% whereas if fuming acid treatment alone had been used to produce a 231 hour oil, the yield would'have been much below 35%.

It is difllcult to explain why such a small amount of acid treatment following solvent extraction of an oil should be so effective in raising the sludge stability of the oil, and at the same time give a high yield of finished product. Possibly the solvents remove the naphthenic compounds that usually protect the sludge-forming compounds,-

thereby making the sludge-forming compounds of the oil more vulnerable to the action of acids.

As pointed out above in connection with acid treated oils, a large quantity of soluble sulfonic compounds remained dissolved in the acid treated oil, and it is necessary to remove these sulfonic compounds before the oil can be used for most lubricating purposes. Several processes have been used to remove the sulfonic compounds, the most common of which is to treat the oil with a soap solution. By using our process of solvent extraction followed with a light acid treatment, we overcome the difliculty of having sulfonic com pounds dissolved in the rafiinate. The solvents v remove, among other substances, those compounds which react with sulfuric acid and form sulfonic acids; consequently, when the oil is given a light acid treatment, the soluble sulfonic compounds are not formed to any appreciable extent and their removal constitutes no problem nor entails serious loss of oil.

As pointed out in the above process of chlorinated ether extraction, it is necessary to strip the raflinate of the solvent dissolved therein, but it is very difiicult to remove the last trace of solvent from the oil. If all of the halogenated compound is not removed, it will eventually decompose and produce chlorine compounds which are very corrosive. Also, if the oilis extracted with other organic compounds they will dissolve in the raflinate and it is frequently very diflicult or even impossible to remove the last trace. Frequently, the color of the oil is impaired when the oil is subjected to severe stripping. Also, if every trace of solvent is not removed from the oil, the oil frequently becomes discolored and deteriorated in other ways. This is particularly true of solvents such as furfural. We have found that by giving the oil a light acid treatment subsequent to the steps of solvent extraction and light stripping, the last traces of solvent that remain in the oil can be very satisfactorily removed and we thereby prevent corrosive and color forming compounds from remaining in the finished oil.

The railinate, or highly parafiinic oil, which is to be given a light acid treatment, may be obtained by extracting oil with any suitable selective solvent or mixture of solvents which will remove the constituents responsible for low viscosity index. Examples of some of the single solvents suitable for extracting oils are halogenated ethers, nitroaryl compounds, aryl amines, phenols, halogenated esters, and heterocyclic compounds. The following table gives examples of some of the above compounds which may be used for extraction.

Table IV Methyl 2-chlorethyl ether di(2-chlorethyl) ether Methyl chloropropyl ether Methyl 2-3 dichloropropyl ether Ethyl 2-3 dichloropropyl ether Ethyl chloropropyl ether Table IV-C'ontinued 2-chlorethyl propyl ether Dichlorisopropyl ether Dichlorpropyl ether Nitrobenzene Nitrotoluene Nitroxylene Aniline Phenol Cresols Cresylic acid Ethyl chloracetate Ethyl dichloracetate Ethyl chlorpropionate 2-chlorethyl acetate Methyl chloracetate 2-chlorethyl propionate Furfural Dioxane Pyridine Nitronaphthalene alpha dichlorohydrlns chlorohydrins Mixed solvents are also very effective for extracting mixed base lubricating oils, particularly the low boiling ketones, esters or ethers may be mixed with any of the solvents selected from the above Table IV. The following table gives examples of some of the mixed solvents that may be used for solvent extraction.

Table v Acetone and nitrobenzene Acetone and di(2-chlorethyl) ether Acetone and furfural Acetone and dioxane Acetone and paraldehyde Acetone and dichlorobenzene Acetone and ethylene dichloride Acetone and phenol Acetone and aniline Acetone and pyridine Acetone and cresol Diacetone alcohol and nitrobenzene Diacetone alcohol and di(2-chlorethyl) ether Methyl ethyl ketone and di(2-chlorethyl) ether Methyl ethyl ketone and pyridine. Methyl ethyl ketone and di(2-chlorethyl)ether Methyl ethyl ketone and phenol Methyl propyl ketone and nitrobenzene Methyl propyl ketone and di(2-chlorethyl) ether Methyl isopropyl ketone and furfural Ethyl acetate and nitrobenzene Ethyl acetate and di(2-chlorethyl) ether Ethyl acetate and furfural Ethyl acetate and nitrotoluene Ethyl acetate and paraldehyde Ethyl acetate and phenol Glycerine and phenol Glycerine and furfural Glycerine and aniline Glycol and aniline Glycol and phenol Glycol and furfural Propyl ether and nitrobenzene Isopropylether and nitrobenzene Isopropylether and chlorinated ethers Ethyl acetate and dioxane Ethyl acetate and ethylenedichloride Methyl acetate and nitrobenzene Methylacetate and di(2-chlorethyl) ether Methyl acetate and phenol Propyl acetate and nitrobenzene Propyl acetate and di(2-chlorethyl) ether Table V-Continued Propyl acetate and phenol Propyl acetate and furfural Propyl acetate and dichlorobenzene .Butyl acetate and phenol Butyl acetate and furfural Butyl acetate and paraldehyde Butyl acetate anddim-chlorethyl) ether Butyl acetate and nitrobenzene Ethyl propionate and nitrobenzene Ethyl propionate and di(2-chlorethyl) ether Ethyl propionate and phenol Methyl propionate and nitrobenzene When any of the solvents set forth in Table IV or V are used to extract mixed base mineral oils, the ratio of solvent to oil is preferably from one to 5 volumes of solvent for each volume of oil. The mixed solvents usually comprise from one to four volumes of ketone, alcohol, ester or ether 'for each volume of the other solvent. For example, one volume of acetone and about two volumes of nitrobenzene are mixed and used to extract one volume of oil. The process, temperatures used,

etc., as set forth in connection with the process I of using di(2-chlorethyl) ether as a solvent, may in general be successfully used with'the solventsgiven in Tables IV and V.

When a mixed base lubricating oil distillate is extracted with any of the above solvents, the

cating oil distillate of 21.6 A. P. I. gravity, 114 seconds Saybolt viscosity and a. viscosity index of 56.5 was extracted with different mixed solvents, and the following table shows the effect of such extraction upon the viscosity index yield and sludge stability of the oil. One volume of oil was extracted with the mixed solvents set forth in the examples of the following table.

Table VI i Rati 1 Percent Viscosity Exam- Components com compo yield W m index nents 1 Acetone and nitrobenune 1.5 0.521 87.5 2 do 66 3 1:2 98.0 3 Acetone and di(2- chlorethyl) ether.. 75. 6 2 1:1 87. 5 icettgneanggiagflxanad 70 2 1:1 82.5

ce ne'an ehyde 00.8 a 3:1 84 6 Acetone and dibe 76 2 1.8:0.2 8i 7 Acetone and ethylene dichloride.-- 64. 6 3 2:1 84. 5 8 Acetone and phenol- 79.6 1, 5i 0. 5:1 82 9 Ethyl acetate and nilrobenzene 70 1.5 0.6:1 88 10 Diacetone alcohol and nitrobenaena- 06 l. 5 0. 5:1 83. 6

viscosity index from 56.5 to a viscosity index of 81 or above. Notwithstanding the high viscosi index, or paramnieity of these oils, they are susceptible to sludge formation when used under oxidizing conditions. Most of the oils prepared .by the above extraction will produce 10 mg. of

sludge in about sixty hours. Also the yield of oil after the acid treatment will be of the order of 5 to 10% below the yield given in the above table with the solvents alone, but if acid treating- .from'the above data that a light acidtreatrnent following an organic solvent extraction gives a higher yield of finished product than could be obtained by acid treating alone. prepared by solvent extraction and combined light acid treating have a good color, and clay treating may be eliminated.

The term naphthenic hydrocarbons is employed in the specification and claims in a generic sense to include the compounds that have a low viscosity index and rapid sludge forming characteristics, examples of which are the aroe mati'c, aromatic-like, oleflnes, polymethylenes, nitrogen and sulfur compounds.

The method used for mixed solvent extraction followed with a light acid treatment may be the same as set forth hereinabove with single solvents. Also the oil may be extracted with a single solvent, then extracted with a mixed solvent, and then given a light acid treatment to raise the oxidation stability if desired. Also, if desired, the oils may be given a light acid treatment before the step of solvent extraction.

The theory set forth herein to'explain the unexpected results obtained by sulfuric acid treating combined with solvent extraction of lubricating oils is not to be considered as limitations upon the scope of our invention, and though the present invention has been described in connection with the details of specific examples, neither is it I intended that such examples shall be regarded as limitations upon the scope of the herein described invention except as set forth in the claims.

We claim:

1. The process for preparing a ;lubricating oil which is highly resistant to sludge formation from a mineral oil containing naphthenic and parafflnic hydrocarbons, which comprises extracting the oil with a solvent containing a halogenated ether and thereby separating the highly naphthenic compounds from the paraflinic compounds,

Also, the oils then treating the highly paraflinic fraction with a small quantity of strong sulfuric acid.

2. The process for preparing a lubricating oil which is highly resistant to sludge formation from a. mineral oil containing naphthenic and parafflnic hydrocarbons, which comprises extracting the oil with a solvent containing a halogenated ether and a ketone and thereby separating the naphthenic hydrocarbons from the paraflinic hydrocarbons, and then treating the paraflinic hydrocarbons with a small quantity of strong sulfuric acid.

. 3. The process for preparing a lubricating oil which is highly resistant to sludge formation from a mineral oil containing naphthenic and parafflnic hydrocarbons, which comprises extracting theoil with a mixture of acetone and di(2-chlorethyl) ether and thereby removing the naphthenic hydrocarbons from the parafllnic hydrocarbons, and then treating thehighly paraflinic hydrocarbons with a small quantity of sulfuric 1 acid.

4. The process for preparing a lubricating oil which is highly resistant to sludge formation from 1 a mineral oil containing sludge-forming and paraflinic hydrocarbons, which comprises heating and agitating the oil with an organic solvent containing acetone and nitrobenzene, cooling the mixture until the oil separates into a highly parafiinic fraction of hydrocarbons and a fraction of sludge-forming hydrocarbons, and then treating the highly paramnic fraction of oil with 98% sulfuric acid in the proportion of about one to one-half pounds of acid per gallon of oil.

STERLING H. DIGGS. JAMES M. PAGE, JR.