US2413311A - Lubricant and process for preparing same - Google Patents

Description

Patented Dec. 31, 1946 2,413,311 LUBRICANT AND PIOCESS FOR PREPARING Charles A. Cohen, Roselle Park, N.

J assignor to Standard 011 Development Company, a corporation of Delaware No Drawing. Application October 8, 1943, Serial No. 505,507

14 Claims. (01. 260-504) This invention relates to an improved heavy duty lubricant and the process of its production. More particularly it is concerned with mineral oils which are compounded with the neutralization products of a group of oil-soluble sulfonic acids derived from the sulfuric acid treatment of petroleum hydrocarbons, known technically as mahogany sulfonate." A principal object of this invention is the production of a certain type of purified mahogany sulfonate in a petroleum lubricating oil, in situ, using the lubricating oil as the source of the organic radicals contained in the mahogany sulfonate.

The use of mahogany sulfonates as additives to lubricating oils has been practiced by the oil industry for some time. When added in an amount of about 0.1% up to about 2 or 3% by weight of the oil, the composition exhibits improved lubricating properties especially in heavy duty service such as is encountered in Diesel engines, aircraft engines and the like. Oils containing mahogany sulfonates have a detergent action On those parts of the engine that they lubricate and are capable of being used under increased loads and temperatures without causing seizure of hearings, or sticking of piston rings by formation of varnish.

Oils compounded with these sulfonates also act as rust preventives in the engine during periods of quiescence.

The mahogany sulfonates used in this service have in the past been obtained as a by-product from the manufacture of white oils, from which they are usually isolated as a sodium salt containin varying amounts of inorganic salts, oil and other organic impurities. When the mahogany sulfonates are used as additives to lubricating oils it is generally preferred to use the salts of the alkaline earths such as magnesium, calcium and barium. The conversion of the sodium salt to the calcium salt for example, requires an additional series of chemical manipulations and purification steps and a further object of this invention is the production of the alkaline earth, or other metal salts of the mahogany acids without preliminary isolation and purification as an alkali salt.

This invention is a continuation-in-part of my copending application U. S. Serial No. 371,777

filed December 26, 1940, which has matured into Patent No. 2,388,677, dated November 11, 1945, and is an extension of the basic principles disclosed in said application.

According to the present invention, a lubricating oil base stock which may or may not have been previously acid treated, deasphalted, dewaxed or extracted with solvents such as ketones, nitrobenzene, phenol, cresol, chlorex, etc., or which may be a distillate, neutral or bright stock or a mixture of these, but is still reactive with sulfuric acid, is treated with about 0.5% up to about by volume of sulfuric acid strong enough to form mahogany acids having an average combining weight in excess of 400, This acid may vary in strength from 100% to fuming acid containing up to 25% S03, or the oil may be treated with S03 either in thesolid state or in the gaseous state, with or without gaseous diluent, within the range of temperature of 20 to 120 (3., 20 to C. being the usual range. and from subto super-atmospheric pressure. If acid of lower concentration than is used. the sulfonic acids formed are too low in' combining weight (i. e., 3'75 or even 350 or lower): whereas only those of 400 and'above'are suitable for this invention. The total quantity of acid-treating agent may be used either in a single application or may be split into a series of applications with intermediate batch or continuous settling of the sludge formed during the treating process. One may use either a single strength'of acid-treating agent for all of the applications or may us'e'a weaker acid for the early treats, or use sludge from the final treats for the first treats in a partial countercurrent system of treating, or use a true countercurrent method of treating. During this process of treating and settling, temperature may be maintained constant throughout the system or varied within the limits indicated. Instead of separating the sludge by settling, a centrifuge may be used either alone or in combination with a partial settler.

The oils which are preferred for acid treating in the practice of this invention may vary in viscosity from about 50 to 1000 seconds Saybolt at 100 F. and may be predominantly parafiinic, naphthenic or aromatic in character. When treating oils of high viscosity, a diluent may be added which may be hydrocarbon in character or other organic liquid which is not materially attacked during the process of acid treatment. When treating lighter oils, one may add varying percentages of extracts recovered from other oils, such extracts generally being predominantly aromatic in character, so as to enhance the yield of mahogany acids recoverable, either by a process of direct sulfonation. .or alkylation or both. :The oil should contain hydrocarbons which on reaction with 100% or stronger acid will yield sulfonic acids having an average combining weight of 400 or higher.

when a petroleum lubricating oil has been treated with sulfuric acid in the manner and under the conditions described above, two major products are formed. The lesser in importance consists of a lower sludge layer comprising asphaltic material, tar, unreacted sulfuric acid and a group of water-soluble sulfonio acids known as "green" or black acids. The other product consists of an upper oil layer which, when separated from the sludge by decantation or the like, is strongly acidic in nature due to dissolved sulfur dioxide and a group of oil-soluble sulfonic acids known as "mahogany acids, and is black to reddish brown in color and nearly opaque due to suspended and colloidally dispersed globules or particles of sulfuric acid and water-soluble sulfonic acids, sludge and tar. The latter group of acids, sludge and tar which remain suspended in th' acid oil after the major portion of the sludge has separated out by settling is known collectively as "pepper sludge."

If an acid oil prepared as above is neutralized while containing dissolvedsulfur dioxide and sulfonic acids, and also suspended pepper sludge, with an alkali or alkaline earth oxide, hydroxide or carbonate for example, the corresponding alkali or alkaline earth salts are formed, including normally water-soluble sulfates, sulfites, and water-soluble sulfonates, part of which remains peptized in the oil because of the presence of the dissolved mahogany sulfonate formed and is not readily removed by filtration. The neutralization products of the torial power and are largely responsible for the characteristic reddish brown color of ordinary commercial mahogany sulfonates. Once formed they are difiicult to remove. While the poorer color is objectionable, the chief objection to the inclusion of the sulfites and the neutralization products of the pepper sludge in the oil is their harmful effect on the lubricating oil and engine and their instability during use, especially at the higher temperatures encountered in modern engine operation.

One of the major objects of this invention is to prepare lubricating oils by the neutralization with a polyvalent metal, e. g. alkaline earth, of a sulfuric acid treated petroleum hydrocarbon containing the desired mahogany acids, which has been entirely freed of sulfur dioxide and "pepper sludge" prior to neutralization.

According to the present invention, a sulfuric acid-treated oil, after substantial removal sludge by settling or by centrifuging but before neutralization, is treated with a finely divided precipitant such as one selected from the group comprising filter aids of diatomaceous origin, materials of siliceous origin such as tripoli or finely ground silica, or activated carbon, the finely divided pepper sludge complex removed by settling and/or by filtration, the dissolved sulfur dioxide removed, as by air blowing, or inert gas blowing or by vacuum stripping, and the resulting oil containing only mahogany acid, is neutralized by a basic substance containing the desired polyvalent metal. This process yields as product a refined lubricating solution of the desired mahogany suifonate which is free of objectionable inorganic and organic impurities, is clear and pale in color and shows improved stability at high temperatures.

Materials of diatomaceous origin which are suitable for the practice of this invention a e epper sludge possess high tinc- 0f the ,sludge has a relatively commercially available as filter aids such as the J-M Celites and "Filter Cels" or "Dica1ites. Either the natural dried and ground earth may be used or it may be calcined with or without alkali or may be acid treated and calcined. Materials of siliceous origin such as tripoli or finely ground silica such as is used for polishing agents and commercially available as Snow Floss" or Super Floss are suitable as is finely ground carborundum. Another class of materials suitable for the practice of this invention is finely ground carbon which may be natural, acid treated, or an activated type. Other materials of like nature may be used but the above are the preferred types. Various finely ground clays, such as Attapulgus fines may on occasion he used under special circumstances but such materials as natural bentonite are not considered desirable.

The filter aid is added to the acid oil in an amount of from 1 to 40 lbs. per 1000 gallons of oil. The method of treating the oil with the above substances may be either by the direct addition of these materials to the oil in the form of a dry powder or by preliminary admixture with a portion of the clear oil to form a slurry which can then be pumped into the main body of the oil. The oil, after the addition of the filter aid, may be agitated for a period of from 5 minutes to onehalf hour. If, for example, filter aid has been used, the filter aid-pepper sludge complex is then removed either by settling, or filtering, or both.

It filtering alone is used, it may be done with conventional filter presses such as the plate and frame press or with a continuous rotary type of press. It is advantageous when using a filter press to precoat the press with filter-aid in the proportion of 5 to 10 lbs. of filter aid for every one-hundred square feet of filter press area. If settling is the means used for removing the filter aid-pepper sludgecomplex from the acid oil, it may be accomplished by running the acid oilfilter aid mixture into a settling drum at a rate designed to give the oil a settling time of from 5 minutes to one hour. A combination of settling and filtration may be used in that the oil after treatment is given a settling time sufficient to drop most of the filter aid-pepper sludge complex out and is then finished by filtering either wtih or without the addition of more filter aid. An alternate method of separating the filter aidpepper sludge complex from the oil is by means of a centrifuge such as a basket type or one capable of discharging a slurry continuously.

No attempt is made here to postulate a theoretical mechanism for the operation of this invention but the diversity of materials which are suitable for the practice of this invention and the rapidity with which agglutination or clumping of the pepper sludge particles takes place after the filter aid or tripoli, etc., has been added, without diminishing within the limits of experimental error the original mahogany acid content of the acid oil, has led to the assumption that the phenomenon represents a mutual coprecipitation of oppositely. charged colloidal particles. An unexpected result in the practice of this invention is that within certain limits, the less filter aid is used, the more rapidly does the filter aid-pepper sludge complex settle. This is thought to be due'to the fact that the pepper high density and when precipitated with the filter aid. the less the amount of filter aid used the higher the resultant density.

As will be apparent to those skilled in the acid-treating art, the precise conditions of acid strength, volume of acid applied to the oil, temperature of treating, time of contact and possible use of diluent used in the acid treatment of the lubricating oil will vary within the limits specified, depending on viscosity of the oil used. degree and method of preliminary refinement if applied before acid treatment, physical characteristics of the oil such as specific gravity, aniline point, viscosity index, etc., and chemical characteristics such as unsaturation, and various proportions, of parafilns, naphthenes and aromatics present. Moreover, the final concentration of mahogany soap and the characteristics of the oil obtained after treating are profoundly infiuenced by the exact method of treating. Therefore the exact conditions for acid treating any particular oil are best determined by experiment and such variations introduced as to make the best use of the equipment at hand. Most oils will, however, follow a general pattern of behavior when acid treated. It is found for example,-between the limits of temperature indicated, that for a given oil and acid strength, a particular quantity of acid will form nearly the same amount of mahogany soap. However, the distribution of the mahogany soap between the oil and sludge layers appears to be a function of the temperature used for treating. At low temperatures, such as C. or 30 C., the partition of the mahogany acid in the direction of. the sludge is favored, but as the temperature is raised,

the solubility of the mahogany acid in the oil phase is favored to the extent that it is possible to treat under conditions where only traces of mahogany acid remain in the sludge. With a rise in temperature of treating to about 70 C. or 80 C., the sludge concommittantly releases some oi1 which is normally held in solution by the mahogany acid contained in the sludge, so that in general somewhat higher yields of oil are likewise obtained when the oil is treated at higher temperature.

The following examples will illustrate the efiect of the acid treating temperature on the yields of refined oil and mahogany soap.

An oil having a 105 sec. Saybolt viscosity at 100 F. of Mid-Continent origin, which had been dewaxed to 0 F. pour point, was treated with a total of 21% by volume of free S03 fuming sulfuric acid in 3 substantially equal dumps at C. and in one case at 70 C. in another. The yields of products obtained are shown in the table below, expressed in volume or weight percent based on the original oil distillate.

Oil soluble sulfonate distribution Mahog. sul- I Sulfonatc in fonate in oil Total sulfonate Temp. of treat sludge, weight mahog. weight produced per cent on dist. per cent on The ,extent to which advantage can be taken of the higher oil and mahogany sulfonate yield obtained by high treating temperatures may be limited by the character of the distillate or oil treated. As noted above, when treating at higher 1 temperature, the sludge is de-oiled and may become too stiff to move through ordinary pipe lines or may have a tendency to coke on exposure to air. This is especially true of straight run distillates of high viscosity which contain much asphaltic material. The tendency to form a stiff sludge in the early treats given such an oil, can be prevented to a large extent by using somewhat lower temperature and weaker acid strengths. After acid treating, contacting with filter aid. or equivalent, and settling or filtering, the acid oil is entirely free of pepper sludge and contains the original amount of mahogany acids present along with a certain amount of dissolved sulfur dioxide.

The sulfur dioxide is then removed by airblowing, or by countercurrent air or inert gas stripping in a packed or bubble plate column, or the acid oil may be subjected to vacuum at ordinary or elevated temperatures by means well known to the art. The removal of the sulfur dioxide may be made an inherent feature of the filtration step in that the filtration may be run under vacuum such as is commonly done in the laboratory in a Buchner funnel or a combinaon hydrolysis or decomposition yields an oxide,

hydroxide or carbonate selected from the metal whose mahogany soap is desired. The base may be added either in the form of a dry powder, aqueous solution or suspension, or dissolved or dispersed in an alcohol, naphtha, or lubricating oil which may or may not be volatile at moderately elevated temperatures. I may use metallo-organic compounds which on hydrolysis or thermal decomposition will yield an oxide, hydroxide or carbonate capable of reacting with the mahogany acid present in the oil. Examples of materials which I may usefor neutralization are magnesium, calcium, strontium and barium oxides, hydroxides or carbonates or mixtures thereof in aqueous solution or suspension, or alcoholic solutions of certain of the above bases such as a methyl alcoholic solution of barium hydroxide, or these bases may be mixed or partially dissolved in high boiling alcohols such as oleyl or octadecyl alcohol, or one may use metallo-organic compounds such as calcium, magnesium or aluminum alcoholates. Basic compounds of Sn, Ni,

G0, etc., may also be used; The mixture of refined acid oil-and basic substance may be heated, e. g., to C. or higher to insure complete reaction. It is preferred to use an excess of basic substance, especially if of the insoluble type and then filter to remove unreacted neutralizing agent. For instance, the oil may be filtered through a bed of finely divided calcium oxide, -hydroxide, or -carbonate to convert all dissolved sulfonic acids into calcium sulfonates which remain dissolved, and to simultaneously insure that any trace of sulfur dioxide or sulfuric acid is converted into insoluble sulfite or sulfate and removed by the filtration, or adsorption.

After neutralization, the water or solvent may be removed by means of heat used with or without a gas stream or may be subjected to the 7 action of heat and vacuum. In the case where solvents have been used during the acid treatment especially with high viscosity oils, they maybe recovered after neutralization by stripping with steam or fire and steam, or by the use of vacuum. In those cases where the acid treatment has been carried to the extent where the mahogany acid concentration is relatively high, e. g., above 3% or 4% and perhaps as high as 10%, 15% or even 20%, or higher, a refined lubricating oil base stock (thesame as or different from the one treated) may be blended into the concentrate either before or after final neutralization or removal of the water or solvent, to make a finished blend having the desired concentration of about 0.1-3% of sulfonate.

These oils may, if desired, be further compounded with other additives such as oxidation inhibitors and the like. Lubricating oils made in accordance with this invention are generally pale in color and show good stability especially at high temperatures and hence possess valuable advantages over oils made by compounding an ordinary pre-formed commercial alkaline earth sulfonate with a separately refined oil.

The invention will be more clearly illustrated by the following examples:

Example 1 A 1000 gallon batch of an oil composed of a mixture of a straight run parafiinic distillate and a low pour coastal distillate having a viscosity of 105 seconds Saybolt at 100 F. was treated with 150 gallons of acid sludge obtained fromfurther treatment of the same oil with 20% fuming acid, at a temperature of 70' C. for 1 hour. The mixture was allowed to settle for 12 hours and the acid oil removed from the sludge by decantation. 910 gallons of oil was recovered and was given a second treat at 70 C. with 90 gallons of 20% S: fuming sulfuric acid and allowed to settle as before. After decantation from the sludge, 820 gallons of acid oil was recovered. This oil was agitated for 15 minutes at a temperature of 25 C. with pounds of Johns Manville Standard Filter-Gel, filter pressed through a plate and frame press and countercurrently air blown in a column packed with Raschig rings until free of sulfur dioxide.

Titration of a sample of the oil showed it to have an organic acidity of .154 Normal. 800 gallons of the oil was mixed in a heated agitator with an exact equivalent of 1.15 Normal methyl alcoholic solution of Ba(OH)2.8H2O. Heat was applied and the methyl alcohol and water slowly distilled from the oil-mahogany soap mixture. When a temperature of 120 C. was reached, a vacuum equal to 5 mm. of mercury was applied until no further loss of volatile material was observed.

A clear amber product was obtained which was neutral in reaction and which set to a gel on cooling. Analysis showed this product to contain about by weight of barium sulfonate. On dilution of this concentrate with a standard motor oil to a concentration of1.5% by weight of barium sulfonate, a clear, stable solution was obtained which gave excellent performance in the standard 36-hour Chevrolet engine test described in the 1942 edition of A. S. T. M. Standards on Petroleum Products and Lubricants, pages 28 to .42.

Example 2 An acid oil made from the same lubricating oil stock, and'treated in the same manner with acid as inExample 1, was neutralized with an aqueous slurry of calcium hydroxide. After neutralization and removal of the water by heating. a slight haze due to the presence of siliceous matter in the lime, was removed by filtration. A clear concentrate of calcium sulfonate of pale color was obtained, which when diluted to a 1.0% by weight of solution in a standard motor oil gaze an excellent performance in an engine The combining weight of the sulfonic acid is best determined by dissolving a sample of the sulfonic acid salt in 50% isopropyl alcohol, washing free of all oil by means of petroleum ether, and converting to the potassium salt by treating with an excess of potassium carbonate. 0n evaporation of a sample of the alcoholic solution of the potassium sulfonate, the product is obtained free of oil and inorganic salts. This purified sulfonate is ignited to potassium sulfate and the average combining weight of the sulfonic acid calculated from the following equation:

QRSOIK -----0 K1804 where R. is the organic group of the sulfonic acid.

It is not intended that this invention be limited to any of the particular materials recited merely for the sake of illustration nor to any theory as the mechanism as to the operation of the invention, but only by the appended claims in which it is intended to claim all modifications coming within the scope and. spirit of the invention.

I claim:

l. The process which comprises contacting a finely divided siliceous filter aid selected from the group consisting of diatomaceous' filter aids, tripoli, and finely ground silica, with an acidtreated oil containing pre-formed pepper sludge in dispersion, dissolved sulfur dioxide, and oilsoluble sulfonic acids having a combining weight of at least 400 to co-precipitate the pepper sludge with the filter aid, removing co-precipitated pepper sludge and filter aid from the oil, removing dissolved sulfur dioxide from the oil, and thereafter neutralizing the oil-soluble sulfonic acids with a basic compound of polyvalent metal to form soluble sulfonates of said metal in the acid-treated oil from which pepper sludge and sulfur dioxide have been removed.

2. Process according to claim 1, in which the finely divided filter aid is a siliceous material of diatomaceous origin.

3. Process according to claim 1, in which the dissolved sulfur dioxide is removed from the oil by air blowing after removal of the pepper sludge.

4. Process according to claim 1, in which the sulfur dioxide is removed from the oil under reduced pressure.

5. Process according to claim 1, in which the basic compound used for neutralizing the dissolved sulfonic acids in the oil is selected from the'group consisting of the oxides. hydroxides. and carbonates of the alkaline earths.

6. Process according to claim 1, in which the basic compound used for neutralizing the oilsoluble sulfonic acids in the oil is a basic compound of calcium.

7. Process according to claim 1, in which the basic compound used in neutralizing the oilsoluble sulfonic acids is a basic compound of barium.

aaasn 8. Process according to claim 1. in which said basic-compound of a polyvalent metal used for neutralizing the oil-soluble suli'onic acidsis barium hydroxide, and the barium hydroxide is dissolved in methyl alcohol.

9. Process according to claim 1, in which the co-precipitated filter aid and pepper sludge are settled in the acid-treated oil and are removed by decantation of the oil.

10. Process according to claim 1, in which the finely divided filter aid admixed with the acidtreated oil is a material of diatomaceous origin and is admixed in a proportion of 1 to 40 pounds per 1,000 gallons of the acid-treated oil to coprecipitate with the pepper sludge, and the coprecipitated filter aid and pepper sludge are removed from the acid-treated oil by filtration.

11. The method of finishing a lubricating oil residual oil freed from pepper sludge until said residual oil is free from sulfur dioxide. and

neutralizing oil-soluble sulionic acids dissolved in the residual oil, freed from p pper sludge and sulfur dioxide, by reaction with a polyvalent metal base.

12. The process which comprises treating with a sulfuric acid of at least 100% concentration a hydrocarbon lubricating oil which on reaction with such acid yields oil-soluble sulfonic acids having an average combining weight of at least 400; removing resultant acid sludge until the residual acid-treated oil contains not more than 1% of sludge by volumebut contains a small amount of colloidallydispersed pepper sludge, thereafter contacting the residual acid-treated oil with about 1 to 40'pounds diatomaceous filter aid per 1,000 gallons of oil to precipitate the pepper sludge, removing the precipitated pepper sludge and the filter aid co-precipitated therewith, air-blowing the residual acid-treated oil until free from sulfur dioxide, then treating the residual acid-treated oil, free from pepper sludge and from sulfur dioxide but still containing the oil-soluble sulfonic acids, with a substantially equivalent amount of neutralizing basic compound of calcium to form a solution of oil-soluble calcium sulfonates in the oil.

13. Process according to claim 1 in which the filter aid is tripoli.

14. Process according to claim 1 in which the filter aid is finely ground silica.

CHARLES A. COHEN.