Overbased sulfonates
I United States Patent 1 1 1111 3,878,116  
 Rueckert Apr. 15, 1975 [54] OVERBASED SULFONATES 3,155,616 11/1964 Voorhees 252/33 3,223,630 12/1965 Gragson 252/33 [751 Invenm Hans Rueckm, Nuys 3,262,880 7/1966 Voorhees 252/33 73 A I B 1 L A 1 3,318,809 5/1967 Bray 252/33 Ssgnee (zompany OS nge 3,488,722 1/1970 Allphin 252/33 3,595,790 7/1971 Norman et a1 252/33 [22] Filed: Sept. 9, 1970 3,658,703 4/1972 Gragson et al 252/33 (Under Rule 47) Primary ExaminerDe1bert E. Gantz [21] Appl. No.2 70,857 Assistant Examiner-1. Vaughn 52 us. c1 252/334; 252/33 [57] ABSTRACT v 51 Int. Cl. Cl0m 3/34; C10m 3/02 A lubricating Oil additive having an alkali value above [58] Field of Search 252/334, 18, 25, 33 400 is made y reacting an Oxide of a metal of Group II with methanol and carbon dioxide and emulsifying 5 References Ci with an oil so1ub1e sulfonate in a succession of stages, UNITED STATES PATENTS the resulting carbonate dispersion being stabilized by treating with water, then dehydrating after each stage. 2,881,206 4/1959 KJOHHZS et a1. 252/334 3,105,049 9/1963 Voorhees 252/33 8 Claims, 1 Drawing Figure PATENTEDAPR 1 5197s METf/A/VOL REC VCLE sou/Em L R YER PRE- C&#39;ARBO/VA T/0/V 26 OIL- S ULFOA/AT E SOLUT/O/V EMULSION STAGE I Gof /2 ME T HA/VOL STRIP WATER WATER TREAT DEH YDRA TE FILTER C&#39;OMPL EX WATER EMULS/O/V 5T4 GEE METHANOL STRIP WATER TREAT FILTER v METHAIVOL SOLUTION DEHYDRA TE J EMULSION smeslzz 37 f a ME T HA/VOL S T/?/ P WA TER TREA T DE H YDRA TE FILTER SOLVE/VT STRIP HIGH BASIC PRODUCT IN VE/V l/A/vs u. Run/(5m- 1 OVERBASED suLroNATps This invention relates to the manufacture of oil soluble sulfonates of high reserve alkalinity and to the process of making them. More particularly, it relates to dispersions in oil of the carbonates of metals of Group 11 of the Periodic System in which the carbonate particles are of colloidal dimensions, below 0.1 micron, leaving the oil transparent to visible light.  
  In recent years, it has been found very desirable to add to lubricating oils particularly oils used in internal combustion engines, marine service, and similar applications .where acids and corrosion are encountered basic substances which all neutralize acids as they arise in the operation of the machine before they reach a concentration sufficient to attack the machine parts or catalyze the formation of sludge in the oil. Colloidal carbonates of the alkaline earth metals, particularly calcium and barium, have been found ideally suited to the purpose, owing to their water insolubility. Because of their lower combining weight, calcium and magnesium offer certain advantages over barium. These carbonate dispersions are stabilized by oil soluble surface active agents such as the fatty acid soaps, the phosphonates, and especially the sulfonates of the alkaline earth metals in which the sulfonic acid portion of the molecule has a molecular weight above about 400 usually 450 to 600. These sulfonates are made by sulfonation of lubricating oil fractions from petroleum and by sulfonation of alkyl benzenes having the desired molecular weight, as is well known in the art. Benzene alkylates with straight chain alkyl groups are especially de&#39; sirable.  
  Numerous patents have been issued on processes of making these carbonate dispersions in oil. Because of the many requirements such dispersions must meet such as transparency, stability at elevated temperature, water resistance, storage stability, filterability, freedom from corrosive salts, and high ratio of excess metal above that in combination with the surface active agent many problems have been encountered in their manufacture. Perhaps the most successful methods involve making a complex between an alcohol, the oxide or hydroxide of an acid accepting metal and CO then dispersing the complex in a lubricating oil and removing the alcohol and unreacted solids. Such methods are described in U.S. Pat. Nos. 3,105,049; 3,155,616; 3,170,880; and 3,170,881, and in British Pat. No. 789,820 published Jan. 29, 1958. The role of water in the reaction is a much debated matter, but indications are that the presence of more than a trace of water in the carbonation stage results in a coarser particle and a less desirable product.  
  The complex of metal oxide, alcohol, and CO can be formed in solution in the absence of the oil and dispersant, then mixed with the oil and dispersant to form an emulsion from which the-alcohol is removed by distillation as in U.S. Pat. No. 3,105,049, or the oil, dispersant, alcohol, and oxide can be emulsified, then carbonated. In either case, difficulty is usually encountered when the product has an alkali value above about 250 mg. KOl-l per gram equivalent, owing to gelling of the complex on removal of alcohol usually methanol. In this case, gelling and caking on the coils or other heating surfaces may take place when the temperature reaches about 175F. Use of a hydrocarbon solvent such as xylene, toluene, or petroleum naphtha aids in preventing gel separation. Addition of water will break the gel and reverse the phases of the emulsion, making it oil continuous, but it is dangerous to introduce water before all free methanol has been removed which usually requires a temperature of 220-260F., inasmuch as water in the presence of alcohol causes a degradation of the dispersed carbonate to a cloudy or muddy product which is impossible to clarify and which usually cannot be filtered, even with large additions of filter aid such as diatomaceous earth.  
  One object of this invention is to produce an oil having a high titratable alkali value above 350 and preferably above 400. Another object of the invention is to produce an oil having a high metal ratio, i.e., the ratio of total metal to that combined with the dispersant, e.g., the metal sulfonate. The invention is illustrated by a drawing which is a flow diagram of the process.  
  1 have discovered that oils of high alkali value above 400, and even up to 600, can be made by conducting the process in a succession of stages, limiting the amount of metal oxide used in each stage to give not more than an increase of about 200 milligram KOH equivalents per gram, generally about l00200, except in the first stage which can be made to 250 or even 300 alkali value. In each stage, however, it has been found essential to remove the alcohol and treat the oil with water, then dehydrate, usually at 250 to 350F. to stabilize the carbonate dispersion, before it is subjected to further treatment with oxide, CO and anhydrous alcohol. Thus, when employing a lubricating oil containing about 40 percent neutral calcium sulfonate representing 1.6 percent calcium as metal, an initial treat with 16-18 percent calcium oxide, methanol, xylene solvent, and CO gives an oil which, after methanol stripping, water treating, and dehydration, has an alkali value of 250. When this oil is retreated with oxide, methanol, and CO using only about 8-10 percent of oxide, the final oil product has an alkali value of 400, and no gel trouble is encountered. From this, it appears that the treatment with water followed by dehydration has rendered the colloidal carbonate inert.  
 . Inasmuch as the hydrocarbon diluent employed to facilitate mixing and contact has a boiling point substantially above that of the alcohol, it can be largely left with the oil after the initial and intermediate stages of the process, even aiding in the dehydration by azeotroping water from the product. Removal of water from the carbonate dispersion in the intermediate stages is essential to prevent degradation to coarsely colloidal carbonate which imparts a cloudy appearance to&#39; the product, sometimes called mustard.&#34; Water appears to associate with the carbonate and evaporates from it with difficulty, even at 300400F. Presence of the hydrocarbon solventboiling at about 380F. is advantageous. Petroleum xylene boiling at about 2803l0F. is quite satisfactory. Petroleum naphtha known as varnish makers and painters naphtha (V.M.&amp;P.) can also be used. The amount employed is usually about 2 to 3 times the volume of the oil-dispersant solution. It can be recovered from the product oil by distillation and steamstripping and recycled in the process after separating water by settling and/or absorption in calcium chloride, silica gel, etc.  
  The sulfonate employed can be made by sulfonation of solvent refined lubricating oil, using oleum as in U.S. Pat. No. 2,689,221, or it can be made by sulfonation of a benzene alkylate, preferably the higher boiling fraction from alkylation of benzene with an olefin or a monochlor hydrocarbon of about -13 carbon atoms having a normal or straight chain structureQSuch an alkylate has the following characteristicsz- Gravity. API 28-32 Pour Point, F. 70 Flash, C.O.C. 420 Viscosity, cs. at 100F. 35-25 Molecular Weight 400 Distillation at 10 mm.  
 Initial. T. 412 571 444 50% 494 907: 534  
 When this alkylate was blended with a neutral oil such as 150 neutral in a ratio (volume) of 45 alkylate to 55 neutral, the blend sulfonated with oleum to yield a product, after neutralization with lime, having a calcium sulfonate soap content of about 40-45 percent by weight and a neutral calcium content of 1.55 percent determined by the quarternary ammonium sulfonate method (Q.A.S.). This method is described in Analytical Chemistry, Volume 26, Sept., 1954, pages 1,492-97; also in Technical Bulletin, Rohm and Haas Company, Feb., 1960, Assay of Hyamine Products&#34;. The Alkali Value (or Acid Value) is determined by ASTM Method D664-58 and is expressed in milligrams KOH equivalent per gram of sample. Ash (sulfated) is determined by ASTM Method D874-59T. By metal ratio&#34; is meant the ratio of total calcium to Q.A.S. calcium, i.e. that in combination with organic acid.  
  The following examples illustrate batchwise operations in stages, employing calcium sulfonate of about 900 molecular weight in lubricating oil containing about 1.6 percent calcium, equivalent to about 38 to 40 percent sulfonate.  
 EXAMPLE 1 222 cc, methanol was placed in a turbine mixer with 255 cc. xylene solvent and grams calcium oxide. CO was passed in until the temperature rose 20F. Then, 100 grams of calcium sulfonate-oil was added, diluted with 120 cc. xylene solvent. CO was continued until a drop in temperature showed the reaction was ended. Methanol was then evaporated by heating to a temperature of 260F. without encountering gel formation. The oil was then cooled to 200F. and treated with 50 cc. water, then dried by heating to 280 and filtered. The clear solution was stripped to 400F. and the resulting oil tested for alkali value. With phenolphthalein indicator, it tested 18, and with methyl orange, 240.  
  To 100 grams of the above oil was added 100 cc. xylene for dilution. This solution was added to a mixture of 222 cc. methanol, 255 cc. xylene, and 20 grams calcium oxide which had been carbonated to a temperature rise of 20F. The mixture of oil and metal oxide complex was then further carbonated until the temperature began to fall, indicating completion of the reaction. Methanol was then distilled off to a temperature of 230F. The oil was then again treated with 50 cc. water and dehydrated to 280F. After filtering and stripping solvent, the product oil titrated 425 basic.  
 EXAMPLE 2 In a three stage operation, 200 cc. anhydrous methanol and 300 cc. xylene were mixed in a turbine mixer with 18.6 gm. CaO. After initial carbonation with CO there was added grams calcium sulfonate-oil soluble type, having 1.58 percent combined calcium content. Carbonation gave a rise in temperature from 77 to F.  
  Methanol removal and water treating followed as in Example 1. The solvent-free oil tested 235 alkali value.  
  100 grams of this oil were treated as just described, using 16 grams calcium oxide this time. No gelling occurred on removal of methanol by distillation. The oil product, after water treatment and drying, tested 405 alkali value.  
  In a third stage, 100 grams of this oil were again treated as above, using 11 grams of calcium oxide in preparing the methanol-CO complex. The temperature rose during carbonation from.80 to 1 12F. No gel appeared during the removal of methanol. After water treating, dehydration, filtering, and stripping, the clear red brown oil product tested 510 alkali value. It was a viscous oil, but flowed readily at room temperature.  
 EXAMPLE 3 This example gives the results of four successive stages, beginning with a neutral sulfonate-lubricating oil of 1.6 percent calcium content.  
 STAGE I In the first stage, 27 grams of calcium oxide were partially complexed with 200 cc. methanol and 350 cc. xylene solvent, passing CO into the mixture. To the mixture were then added 150 grams of oil-sulfonate and carbonation was completed within 30 minutes. Methanol was then stripped off to a temperature of 260F. The product was then treated with 75 cc. of water, dehydrated, filtered, and stripped of solvent at 350F. Alkali value was 235.  
 STAGE II The above operation was repeated with 150 grams of the 235 A.V. oil. No gelling occurred on removal of methanol and the product tested 420 alkali value.  
 STAGE III The above operation was again repeated with 150 grams of the 420 A.V. oil but using only 15 grams of calcium oxide. No gelling was encountered. The product was a free flowing red-brown oil of 505 alkali value.  
 STAGE IV In this operation, 19 grams of calcium oxide were complexed with methanol and CO as before and grams of the 505 A.V. oil were used. To the mixture was added 200 cc. more xylene solvent to maintain fluidity. Methanol was removed from the fully carbonated reaction mixture by heating to 260F. without trouble from gel formation. After treating with 100 cc. water, dehydrating, filtering, and stripping to 400F., the heavy oil product tested 600 alkali value. Although quite viscous, it flowed readily at ambient temperature.  
 EXAMPLE 4 A 2 stage pilot plant batch operation was conducted as follows:  
  10 gallons of xylene solvent and 10 gallons of methanol 0.35 percent water content were mixed with 9.5 pounds CaO. CO was passed in at 66F. When the temperature reached 88&#34;, 53 pounds of calcium sulfonate-oil containing 1.55 percent calcium were added,  
  20 minutes at 155F. 35 minutes at 165F. 55 minutes at 285F. 65 minutes at 292F.  
 5 gallons over 5 gallons over 5 gallons over 4 gallons over Total lb gallons Considerable amounts of xylene solvent distilled over with the methanol in later fractions. The oil was treated with 1,300 cc. water at 180F. Seven gallons of xylene solvent were added as make-up. Water was distilled off to 290F., taking over 5 gallons xylene. The oil-solvent solution was filtered with standard diatomaceous earth, recovering l l 1 pounds of solution, clear. A test showed 54 percent solvent-free oil analyzing 245 alkali value with methyl orange indicator.  
  1n the second stage, 9 pounds of calcium oxide were used in the same mixture as above and carbonated for 19 minutes while the temperature rose from 70 to 90F. The oil solution (111 pounds) was added and CO continued for a total of 58 minutes, terminating the reaction at 135F. Seventeen gallons of methanolsolvent were distilled off to 290F. and 7 gallons of solvent were added to the oil as make-up. 1,300 cc. water was added at l90F., thoroughly mixed and dehydrated to 290F., taking over 9.5 gallons xylene with the excess water. The product oil-solvent solution filtered rapidly with diatomaceous earth filter aid giving a clear solution containing 59 percent oil free of solvent. Analysis showed a combined calcium (Q.A.S.) of 1.09 percent and alkali value of 400. When stripped with steam at 300F., the final product weighed 60.5 pounds and had the following analysis:  
 Alkali Value 395 Color Bright. clear red Q.A.S. 1.07%  
 Sediment 0.02%  
 Flash &#34;325F.  
 Water 0.35&#39;71 Referring to the drawing, a solution of metal sulfonate in oil, usually of 30 to 60 percent concentration Q.A.S. calcium of about 1.25 to 2 percent is prepared in 10. It is convenient to have this sulfonate solution diluted with hydrocarbon solvent in a ratio of about 1:1 by volume. Toluene, xylene, petroleum naphtha, etc. can be used for the purpose, a petroleum xylene boiling in the range of about 280-310F. being quite satisfactory. From 10, the solution flows to the first emulsion stage 11, where it is mixed with the desired amount of methanol-metal oxide-CO complex from precarbonator 12, introduced by line 13. This reagent complex is prepared by mixing, with good agitation, metal oxide,&#39;methanol, and C0 The methanol is substantially anhydrous but may contain from 0.1 to 0.5 percent water, which, in some cases, accelerates the formation of the complex. More water than this must be avoided as it has an adverse effect on the final metal carbonate dispersion. When recycling methanol in the process, it is also convenient to have solvent present in precarbonator 12, which, in the case of xy&#39; lene, may amount to to 25 percent by volume of the mixture.  
  I prefer to employcalcium oxide in the process, usually made by a light roast at 1,800-2,000F. and ground to about 250-300 mesh or finer. Barium oxide can also be used, as can MgO when in an active state. In the case of magnesium, the metal can be dissolved in methanol to give the methylate which can be added in methanol solution. Carbonation is rapid, the reaction being completed within about 5 to 10 minutes. The carbonation can be carried to completion or stopped part way, for example, when the temperature of carbonator 12 has risen about 20F. The ratio of lime to methanol is usually about 1:10 to 1:15 by weight.  
  The rate of transfer of carbonated complex to reactor 11 can be controlled by automatic flow controllers in a continuous plant operation. I prefer to control the rate to give an alkali value in Stage 1 of about 200-300, while the increase is less in later stages. The mixture in 11 is suitably 1 volume of lube oil-sulfonate, 2 volumes of methanol, and 3 volumes of hydrocarbon diluent. Additional CO is introduced by line 14 in case the complex from 12 is incompletely carbonated. The temperature of the emulsion may range from 1 10 to 150F. The mixture next flows to methanol stripper 15 where the methanol is removed by heat to 260 and vapors of methanol are withdrawn by line 16 leading to recycle line 17, condensation not shown. Some solvent vapors come over with the methanol, especially toward the end of the stripping operation when the temperature reaches about 260 to 280F. and recycles with the methanol without interfering with the reaction.  
  From stripper 15, the oil with solvent passes next to water treater 18 where it is mixed with sufficient water to convert it to a water-in-oil type emulsion. I believe the water serves to hydrate the carbonate, rendering the colloidal particles or micelles stable and resistant to coagulation. The dispersion now has lost its gelling tendency and behaves like a true lubricating oil. The amount of water required is about 1 to 4 mols per mol of metal oxide present. It should be mixed at a temperature below the boiling point, e.g., 200F., then heated to dehydrate. The resulting emulsion passes to dehydrator 19 where it is heated to drive out the water, for example, to 260-290F. The water and solvent vapors pass by line 20 to line 21, thence to water separator 22 where water settles out and is drawn off at 23, condensation not shown. Some methanol released from the complex in 18 will be found in the water at 23 and can be recovered if desired. Solvent passes to dryer 24 where any remaining dissolved or entrained water is removed, for example, with fused CaCl flakes, before returning by line 25 to carbonator 12. If desired, solvent can be passed into sulfonate in 10 by line 26.  
  The colloidal carbonate dispersion in 19 may be clarified in filter 27 before passing to emulsion stage 11 in 28. However, if the metal oxide employed in the process is sufficiently pure, for example, 98 percent or better, filtration can be omitted. The sulfonate-oil solution in 19 should contain an equal volume of hydrocarbon solvent, e.g., xylene. If needed, more solvent can be added at this stage by line not shown.  
  Into mixer&#39;28 is introduced a stream of methanollime complex from 12 by lines 29 and 30 at a rate sufficient to increase the base number of the oil by about to 200 mg. KOH per gram equivalent. in my continuous operation, this is conveniently accomplished by means of a flow controller on the feed line 30. Additional CO is introduced by line 31 as needed to complete the carbonation of metal oxide not fully carbonated in 12. Methanol is next distilled off in 32, the vapors passing into line 17 and condensed by condenser not shown, in a manner well known to the art. The temperature of stripper 32 is about the same as in l5.  
  After cooling to about 200F. or below, the oil is next treated with water in 33 as in 18, sufficient water being added to hydrate the metal carbonate introduced by line 30. The oil is next dehydrated in 34 by heating to the boiling temperature of the solvent, about 280F. in case of xylene and about 240F. in case of toluene. Optionally, the oil-solvent solution is then filtered in 35 and conductedto emulsion stage 36 wherein it is mixed with a further amount of the methanol-lime complex from 12 led by lines 29 and 37. The amount of metal complex should be sufficient to increase the base number of the oil by about 100-150 mg. KOl-lper gram equivalent. Carbon dioxide enters 36 by line 38 as required to complete the carbonation.  
  The emulsion from 36 then is stripped of methanol in 39, the methanol with some solvent passing to recycle line 17. The oil is next water treated again in 40, liberating combined methanol from the metal oxide complex and hydrating the carbonate. Excess water and a part of the hydrocarbon solvent is then removed in dehydrator 41, the vapors being condensed by condenser, not shown, and led by line 42 into recycle line 21. The solution is then filtered in 43 and stripped free of solvent by heating in still 44 where steam can be used to complete removal of solvent from the oil. Finished product oil flows from stage 44 by line 45 and may be again filtered hot if desired. By this three stage process, I have been able to make oils having a base number of 600. For base numbers of 400 to 500, I can operate with only two stages, removing the oil after dehydration stage 34 and filtering and stripping it in 43 and 44. Filtration of the oil in 43 is greatly facilitated by filtration between stages, thus reducing the amount of troublesome solids to be removed in the final clarification, particularly in cases where the metal oxide employed contains more than 23 percent of unreactive material such as silica, iron oxide, etc.  
  Having thus described my process, what I claim is: 1. The process of making a lubricating oil additive of high alkali value wherein an oil-soluble sulfonate of a metal of Group ll is mixed in a first stage with a complex formed from the oxide of said metal with anhydrous methanol and carbon dioxide, in the presence of a hydrocarbon solvent boiling above methanol, the amount of metal in said complex being sufficient to impart to said oil and alkali value of at least 250, distilling methanol from the mixture at a temperature of at least 220F., treating the methanol-free mixture with water in an amount equal to about 1 to 4 mols per mol of oxide present, thereby converting said complex to carbonate, inert to gelling, dehydrating the mixture by heating to at least 250F., cooling the dehydrated oil and colloidal inert carbonate and mixing it in a second stage with sufficient metal oxide-methanol-CO complex to impart to the oil an alkali value of at least 400, stripping methanol from said complex to at least 220F., treating with water in proportion of about 1 to 4 mols per mol of metal oxide added in said secondstage and thereafter dehydrating and filtering the product oil.  
  2. The additive of claim 1 wherein said Group II metal is calcium.  
  3. The additive of claim 1 wherein said Group &#39;11 metal is magnesium.  
  4. The additive of claim 1 wherein the said Group II metal is barium.  
  5. The method of making an overbased lubricating oil additive of high alkali value which comprises, in a first stage, emulsifying a lubricating oil solution of an oil soluble sulfonate with the oxide of a metal of Group II of the Periodic System, anhydrous methanol and hydrocarbon solvent while introducing carbon dioxide sufficient to convert said oxide to carbonate being sufficient to impart to said oil an alkali value of about 250300, removing the methanol by distillation at about 200-260F. and then hydrating the carbonate by treating with water in an amount equal to about 1 to 4 mols per mol of oxide present, thus rendering the carbonate inert, dehydrating the resulting dispersion to remove excess water, then repeating the treatment with oxide, methanol and water in a succession of stages until the alkali value of the oil has been increased to at least 400 mg. KOH per gram equivalent.  
  6. The method of claim 5 wherein the amount of oxide employed in the said first stage is sufficient to produce an oil with an alkali value of about 250 to 300 while, in later stages, the oxide is controlled to give an increase in alkali value of to 200 in each stage.  
  7. The method of claim 5 wherein the hydrocarbon solvent employed has a boiling point substantially above that of water and solvent is allowed to remain with the oil after removal of methanol, water treating and dehydration between stages.  
  8. The overbased lubricating oil additive prepared by the process of claim 5 wherein said additive has a base number of about 500 to 600 milligrams of KOH per gram equivalent.