Process for preparing highly basic magnesium sulfonates
BACKGROUND OF THE INVENTION 
     This invention relates to an improved process for the preparation of fluid, highly basic magnesium sulfonates useful as lubricants for internal combustion engines and as diesel fuel additives. 
     Highly basic magnesium sulfonates are known to be particularly effective additives for internal combustion engine lubricating oils and for diesel fuels. In this context, the term &#34;highly basic&#34; refers to sulfonates containing an amount of magnesium substantially in excess of that required to form a neutral sulfonate. Other terms which have been used to describe such sulfonates include overbased, superbasic and hyperbasic. 
     Many, many processes are known for preparing fluid, highly basic magnesium sulfonates. See, e.g., U.S. Pat. Nos. 3,492,230; 3,524,814; 3,609,076; 3,629,109; 3,865,737; and the numerous patents cited therein. While many of these prior art processes and patents claim to be suitable for commercial scale production of highly basic magnesium sulfonates, few highly basic magnesium sulfonates are available on the market. 
     Accordingly, there is still a need for improved, commercially viable processes for the preparation of commercial scale batches of fluid, highly basic magnesium sulfonates, especially processes which have a high utilization of magnesium and which produce sulfonates that have a high total base number (TBN), of about 385 or more, a low viscosity, an absence of haze and sediment, and good stability under engine use conditions. 
     SUMMARY OF THE INVENTION 
     This invention broadly relates to a process for treating a neutralized, fluid, oil-soluble, magnesium sulfonate with magnesium oxide and a unique combination and sequence of promoters and processing conditions to produce a fluid, highly basic magnesium sulfonate. The highly basic magnesium sulfonate produced by this process possesses an excellent combination of properties, including a high base number, a low viscosity, an absence of sediment and haze, and excellent engine stability; and it can be made economically, on a commercial scale. 
     In a preferred aspect of this invention, oil-soluble sulfonic acids are neutralized with a previously prepared overbased magnesium sulfonate, by admixing the sulfonic acid and the magnesium sulfonate and heating to neutralize. The neutralized magnesium sulfonates prepared in this manner may then be treated with magnesium oxide and the unique combination and sequence of promoters and processing conditions of the invention to produce a commercial quality, fluid, highly basic magnesium sulfonate. 
     In yet another preferred aspect of this invention, certain specific types of magnesium oxide are employed which aid in the production of high quality, fluid, highly basic magnesium sulfonates. 
     In a highly advantageous embodiment of the invention, an oil-soluble sulfonic acid is mixed with a previously prepared overbased magnesium sulfonate having a total base number (TBN) in excess of about 200, in the presence of a suitable volatile solvent. Preferably, a minor amount of a lower alkanol, such as methanol, is added to the mixture. This mixture is then heated to a temperature between about 180° F. and 260° F. or more, preferably between 200° F. and 220° F., to neutralize the sulfonic acid. After the neutralization has been completed, the solution is cooled, and a naphthenic acid, a lower alkanol, such as methanol, and magnesium oxide are added to the neutralized solution to form a second admixture. The magnesium oxide employed in this embodiment preferably has the following specific characteristics: a bulk density between about 13 and 20 lbs/ft 3 , an Iodine No. between about 35 and 60 meq/100 g, and a particle size of about 200 mesh or smaller. Preferably, a non-volatile diluent oil is added at this point in the process. 
     This second admixture is then carbonated, preferably with gaseous or liquid carbon dioxide, at a temperature below about 120° F., preferably between 100° F. and 120° F. Water and ammonia or an ammonium compound are added as promoters during the initial phase of carbonation. Substantially all of the water and the ammonia or ammonium compound must be added after carbonation has begun and before the addition of the first 25% of the carbon dioxide has been completed. Preferably, these carbonation promoters are added slowly during the addition of the first 15% to 20% of the carbon dioxide. After carbonation has been completed, the solution is heated to a temperature in excess of the boiling point of the water and the lower aklanol, advantageously to 250° F. or more, to remove those substances and to eliminate or minimize the haze in the final product. 
     After heating, the solution is cooled somewhat, to a temperature between about 180° F. and 220° F., at which temperature additional carbon dioxide is added for a short time, for from about 10 to 30 minutes. Next, the solution is heated to an elevated temperature, advantageously about 250° F. or more, and then it is cooled to a temperature below about 220° F. Preferably, additional volatile solvent is then added. Next, the solution is clarified, preferably by centrifugation and/or filtration, to remove suspended solids and sediment, after which the volatile solvents advantageously are removed, by heating the solution, preferably under a vacuum. 
     A fluid, highly basic magnesium sulfonate made in accordance with this invention has a high TBN of 385 (mg KOH/g) or more, preferably 400-500, a relatively low viscosity, an absence of haze and sediment, and good stability under engine use conditions and in compatability tests. Such magnesium sulfonates also normally consist of from 25 to 35% magnesium sulfonate and from about 9 to 10.5% magnesium. 
     The principal advantage of the process of the invention is its ability to economically produce a commercially acceptable, fluid, highly basic magnesium sulfonate on a commercial scale. Other advantages of the invention include its high level of magnesium utilization and the consistently high base number and satisfactory engine and compatability test and use performance levels attainable with the highly basic magnesium sulfonate product. Further advantages include the product&#39;s consistent clarity, bright appearance, low viscosity, stability, and the extent of sulfonation. 
     Additional features and advantages of the invention are described in and will become apparent from the Description of the Preferred Embodiments and the Examples which are set forth below. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The initial steps in the preferred embodiments of the process of this invention comprise the neutralization of an oil-soluble sulfonic acid or a mixture of such acids with a previously prepared magnesium sulfonate having a TBN in excess of about 200, in the presence of a suitable volatile solvent and a minor amount of a lower alkanol. 
     Suitable oil-soluble sulfonic acids (RS0 3  H) are well known in the art. They include both the mahogany or natural sulfonic acids and the synthetic sulfonic acids prepared from hydrocarbon feedstocks. The molecular weight of these oil-soluble sulfonic acids is preferably in the range of about 450 to 650, most preferably in the range of about 500 to 575. The hydrocarbon (R) portion of the oil-soluble sulfonic acids may be either an alkyl or an alkaryl hydrocarbon, with the alkyl groups being either straight or branch chains. The molecular weight of the hydrocarbon portion of the sulfonic acids employed in this process is advantageously in the range of about 385 to about 600. 
     The synthetic sulfonic acids are preferred for use in this process. These sulfonic acids may be prepared from alkyl or alkaryl hydrocarbons, or mixtures thereof, by any of the methods well known in the art. A particularly preferred synthetic sulfonic acid comprises a mixture of straight and branched chain sulfonated alkylates, with the branched chain alkylates having a molecular weight in the range of about 385 to about 450, preferably about 400 to about 450, and the straight chain alkylates having a molecular weight in the range of about 500 to about 600, preferably between about 500 and 575. These straight and branched chain alkylates may be sulfonated together, or they may be sulfonated separately and later combined. 
     The magnesium sulfonate used to neutralize the oil-soluble sulfonic acid may be any previously overbased magnesium sulfonate having a TBN in excess of about 200, advantageously between about 250 and 350, preferably between about 275 and 330. The other characteristics of this previously overbased magnesium sulfonate are not particularly critical since the primary reason for its use is to neutralize the oil-soluble sulfonic acid. Accordingly, the magnesium sulfonate may be made by any of the overbasing processes well known in the art, using the oil-soluble sulfonic acids well known in the art, as long as the TBN exceeds about 200. For example, the magnesium sulfonate may be made by the processes described in U.S. Pat. Nos. 3,609,076; 3,524,814; 3,629,109; and the like. The amount of magnesium sulfonate employed in the process should be sufficient to neutralize the oil-soluble sulfonic acid. Advantageously, sufficient magnesium sulfonate is employed to obtain a base number of between about 5 and 40, preferably between 5 and 10, for the neutralized product. 
     Suitable volatile solvents include hydrocarbon solvents having at least a part of their boiling point range between about 250° F. and 300° F. Preferably, the volatile solvent is either (a) an aliphatic hydrocarbon solvent having a boiling point range between about 250° F. and 300° F., preferably between about 260° F. and 285° F., or (b) a mixture of aliphatic and aromatic hydrocarbons, with the aliphatic hydrocarbon component having a boiling point range between about 140° F. and 190° F., and the aromatic hydrocarbon having a boiling point range between about 250° F. and 300° F., preferably between aout 265° F. and 285° F. Preferably, the volatile solvent comprises approximately 60 to 65 percent by weight of the total sulfonate neutralization mixture, although those skilled in the art will recognize that higher or lower concentrations of solvent may be employed. Advantageously, most, if not all, of the volatile solvent employed at this point in the process is the solvent used for the preparation of the oil-soluble sulfonic acid. 
     Suitable lower alkanols include methanol, ethanol, isopropanol, butanol, pentanol, hexanol, methoxy ethanol, ethoxy ethanol, butoxy ethanol, and the like. Methanol is the preferred alkanol, in large part for reasons of economy. Preferably, the concentration of lower alkanol employed in the sulfonic acid neutralization step is between about 0.5 and 1 percent by weight of the combined charge of the sulfonic acid and the volatile solvent. 
     The oil-soluble sulfonic acid, the overbased magnesium sulfonate, the lower alkanol and the volatile solvent may be admixed in any desired manner. Once suitably combined, the solution is heated to a temperature between about 180° F. and 260° F. or more, preferably between about 200° F. and 240° F., with agitation, to neutralize the sulfonic acid, volatilize off the lower alkanol, and to improve the stability of the final overbased magnesium sulfonate product. Any low boiling aliphatic solvent (boiling point below about 200° F.) present in the neutralization solution should also be vaporized off during this heating step, which may necessitate the use of a higher temperature or longer heating time than would otherwise be employed. 
     After the sulfonic acid has been neutralized, the neutralized sulfonate mixture is cooled to a temperature below about 140° F., preferably to between about 100° F. and 120° F. At this point, a non-volatile diluent oil, naphthenic acid, a lower alkanol, and magnesium oxide (preferably having certain specific characteristics) are added to the neutralized sulfonate to form a second admixture. 
     A wide variety of non-volatile diluent oils are suitable in the process of this invention. The principal requisites desired in the diluent oil are that it act as a solvent for the various materials employed in the process and that it has a flash point of 385°-400° F. or above. Advantageously, the diluent oil is a naphthenic lubricating oil. Preferably this naphthenic lubricating oil has a viscosity range of 100-600 SSU at 100° F. 
     The naphthenic acid is employed in this process as a promoter and as a stabilizing agent. If naphthenic acid is not employed, the final magnesium sulfonate product will tend to be noticeably hazy and to have an unacceptably low TBN of about 170-300 and a lighter than normal color. Advantageously, the naphthenic acid has an acid number between about 150 and 200 with non-saponifiables of about 25 to 30%. The naphthenic acid advantageously comprises from about 1 to 15 percent by weight of the final highly basic product, preferably from about 2 percent to 7 percent. 
     The magnesium oxide used in this process preferably has a bulk density between about 13 and 20 lbs/ft. 3 , an Iodine No. between about 35 and 60 meq/100 g, and passes through a 200 mesh screen. Most preferably the magnesium oxide has a bulk density of 13-17 lbs/ft 3 . The type of magnesium oxide used in this process appears to be quite important and magnesium oxides which do not have all of the above characteristics have a strong tendency to produce hazy, low TBN overbased sulfonates. For example, magnesium oxides having an Iodine Number number significantly in excess of 60 result in overbased magnesium sulfonates which generally are noticeably hazy and have TBN&#39;s of 300 or below. Of course, the amount of magnesium oxide employed in the process depends on the desired TBN of the final product and the amount of neutralized sulfonate employed. Since magnesium oxides very in their reactivity, the amount of magnesium oxide also depends on the utilization level of the specific batch being used. 
     Suitable lower alkanols include any of the lower alkanols noted above. Again, the preferred lower alkanol for the second admixture is methanol. Advantageously, the lower alkanol is added in an amount of from about 15 to 40% of the weight of the magnesium oxide employed in the process, preferably in an amount of from about 22 to 32% of the weight of the magnesium oxide. 
     The non-volatile diluent oil, the naphthenic acid and the lower alkanol may be added to the neutralized sulfonate in any order, but all should be added prior to the addition of the magnesium oxide. If this procedure is followed, the temperature of the second admixture will normally drop to about 50°-60° F. prior to the addition of the magnesium oxide. With magnesium oxide addition, the temperature of the stirred solution tends to increase and should advantageously be stabilized at between about 70° F. and 80° F. during the remainder of the magnesium oxide addition. 
     After all of the magnesium oxide has been added, the admixture is then carbonated, preferably with gaseous or liquid carbon dioxide. During the carbonation step, the temperature of the admixture should perferably be maintained between about 100° F. and 120° F. In large scale preparations, the preferred rate of carbon dioxide addition is about 20-22 lbs/min, and the total addition time normally is between about 11/2 and 21/2 hours, although the carbonation time is not a critical feature of the invention. Of course, the total amount of carbon dioxide added depends on the amount of overbasing magnesium oxide. In large scale preparations, approximately one mole of carbon dioxide should be used per reactive mole of magnesium oxide as amounts substantially in excess of one mole per mole tend to produce undesirable properties in the final product, such as haze, gel formation, etc. In small scale preparations, relatively large amounts of carbon dioxide (between about 1.0 and 1.3 moles per mole of magnesium oxide) may be employed. 
     Water and either ammonia or an ammonium compound, such as ammonium hydroxide, an ammonium salt, and the like, are added as promoters during the initial phase of the carbonation. Preferably, water and ammonia (added in the form of ammonium hydroxide) are used as the promoters. Substantially, all of the carbonation promoter (i.e., the water and ammonia) must be added after carbonation begins, during the addition of the first 25% of the amount of carbon dioxide added. The addition of a substantial amount of the carbonation promoters either before carbonation begins or after the initial 25% of the carbon dioxide has been added tends to produce severe processing and product quality problems. Preferably, all of the carbonation promoter is added slowly, after carbonation has begun and before the addition of the first 15% to 20% of the carbon dioxide has been completed. It should be noted that the promoter addition period truly appears to be dependent on the amount of carbon dioxide which has been added, not on the time over which the addition takes place. 
     The amount of water used as a promoter advantageously is about 35 to 75 percent of the weight of magnesium oxide. Preferably, the water is present in an amount of from about 44 to 60 percent of the weight of the magnesium oxide. Ammonia advantageously is added in an amount of from about 3 to 12 percent of the magnesium oxide, preferably from about 6.4 to 10.3 percent. When ammonium hydroxide is used as the source of ammonia, it advantageously is added in an amount of from about 10 to 35 percent of the magnesium oxide, preferably from about 19 to 27 percent. 
     After all of the carbon dioxide has been added, the carbonated solution is heated to a temperature in excess of the boiling point of the water and the lower alkanol to remove those substances from the solution, which tends to eliminate or minimize the haze in the final product. Advantageously, the carbonated solution is heated to a temperature of about 250° F. or more, preferably to a temperature between about 260° F. and 290° F. 
     After this heating step, the solution is cooled to a temperature between about 180° F. and 220° F., preferably between about 190° F. and 200° F., at which temperature additional carbon dioxide is added. This second carbon dioxide addition is advantageously made at a rate equivalent to the initial charge, for from about 10 to 30 minutes. Preferably this second carbon dioxide charge lasts about 15 minutes at the same rate of addition as the initial carbon dioxide charge. This step is used to help stabilize the sediment for easier removal during clarification. 
     After the second carbon dioxide addition, the solution is again heated to an elevated temperature to remove water. As before, the ultimate temperature attained during this heating step is about 250° F. or more, preferably between about 260° F. and 290° F. 
     The solution is next cooled to a temperature between about 100° F. and 220° F., preferably about 200° F. Additional volatile solvent is then added to form a solution having between about 60% and 80% solvent and diluent oil. Preferably this additional volatile solvent is a mixture of aromatic hydrocarbons having a boiling point range between about 250° F. and 300° F., most preferably between about 270° F. and 285° F. 
     After dilution, the solution is clarified, preferably by centrifugation and/or filtration, to remove suspended solids and sediment. The clarified solution is then advantageously heated to a temperature in excess of 300° F., preferably in excess of about 355° F., under vacuum, to remove the volatile solvents. Additional diluent oil and the like may be added, as needed, to meet specific customer specifications. 
     A typical highly basic magnesium sulfonate made in accordance with the preferred embodiments of this invention has the following general characteristics: 
     
         ______________________________________                                    
TBN, mg KOH/g        385 Min.-500                                         
Magnesium, wt. %     9-10.5 (preferably                                   
                     9.2-9.7)                                             
Sulfonate, wt. %     25-35 (preferably                                    
                     27-30)                                               
Sulfur, wt. %        1.8-2.2                                              
Viscosity, SSU at 210° F.                                          
                     700-1000                                             
Density, lbs/gal     9.2-9.5                                              
Flash, °F.    370 Min.                                             
Color, D-1500        5.5 Max.                                             
BS &amp; W, wt. %        0.05 Max.                                            
Water, wt. %         0.6 Max.                                             
Odor                 Bland                                                
Appearance           Bright &amp; Clear                                       
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     Fluid, highly basic magnesium sulfonates made in accordance with the invention have been tested under in use conditions and have been found to have satisfactory stability and compatability for commercial use. 
    
    
     EXAMPLE 1 
     To a one liter flask were added: 111 g of sulfonic acid A*; 185 g of sulfonic acid B*; 30 g of a previously overbased magnesium sulfonate having a TBN of 327; about 2 g of methanol; and 250 g of an aromatic solvent having a distillation range of 280°-290° F. Sulfonic acid A was prepared by sulfonating a straight chain alkylate having a molecular weight of about 550 under standard conditions in an aliphatic solvent having a distillation range of about 140°-190° F. Sulfonic acid B was prepared by sulfonating a branched chain alkylate having a molecular weight of about 425 under standard conditions in an aliphatic solvent having a distillation range of about 140°-190° F. This admixture was stirred and heated to about 220° F. to neutralize the sulfonic acids and to remove the aliphatic solvent and the methanol. After heating, the solution was cooled to 100°-120° F. and the following were added: 5 g of a naphthenic lubricating oil having a viscosity of about 200 SSU at 100° F.; 7 g of a naphthenic acid having an acid number of 155 and non-saponafiables of about 25-30%; and 10  g of methanol. 36 g of magnesium oxide were then added. This magnesium oxide had a bulk density of 15 lbs/ft 3 , an Iodine No. of 35 meq/100 g and a screen size of 200 mesh. 
    
     Carbonation with gaseous carbon dioxide was then begun at a temperature between 100° F. and 120° F. and a rate of about 0.5-1.5 g/min. A promoter solution consisting of 8 g of ammonium hydroxide (27-30% ammonia) and 20 g of water was added uniformly from the beginning of the carbonation, at a rate sufficient to complete the promoter addition by the time 20% of the necessary carbon dioxide had been added. After completion of the promoter addition, the carbon dioxide addition was allowed to continue for a total of about 2 hours, until the required amount of carbon dioxide had been added. Following carbonation, the solution was heated to 275° F. and then cooled to 190°-200° F. Additional CO 2  was added, for 15 minutes, at the same rate as that of the initial CO 2  addition. The solution was next heated to 260° F., and then cooled to 200° F. and diluted with additional volatile solvent. Next, the diluted solution was clarified by centrifugation and the volatile solvents were then removed by heating to 400° F. After cooling, the product was found to have a TBN (mg KOH/g) of 430 and a viscosity of 1000 SSU at 210° F. The product contained 31.45% by weight magnesium sulfonate (at an equivalent weight 612) and the product had a bright appearance, good color, and was free of haze and sediment. 
     EXAMPLE 2 
     An admixture was prepared from 296 parts (by weight) of a sulfonic acid (including solvent), 30 parts of a previously overbased magnesium sulfonate and about 2 parts methanol. The sulfonic acid had a molecular weight of 612 and was prepared from a mixture of straight and branched chain alkylates. The magnesium sulfonate again had a TBN of 327. This admixture was stirred and then heated to about 220° F. to neutralize the sulfonic acid. After cooling to 100°-120° F., the following were added: 5 parts of a naphthenic lubricating oil, 7 parts of a naphthenic acid, 10 parts of methanol and 36 parts of a magnesium oxide having the characteristics listed in Example 1. Carbonation was then begun and a promoter solution of 8.2 parts ammonium hydroxide and 20 parts water was added at a uniform rate concurrently with the addition of the first 20% of the carbon dioxide gas. Following carbonation, the solution was heated to 275° F. and then cooled to 190°-200° F. Additional CO 2  was added for about 15 minutes at the same rate as that of the initial CO 2  addition. The solution was then heated to about 260° F. and thereafter cooled to about 200° F. and diluted with additional volatile solvent. After dilution, the solution was clarified and the volatile solvents were then removed by heating to about 400° F. The final magnesium sulfonate product had a TBN of 430 and a viscosity of 1000 SSU at 210° F. The product contained 31.45% by weight magnesium sulfonate and 10.43% by weight magnesium. It had a color of 5.0 according to D-1500 and was bright and clear in appearance. 
     EXAMPLE 3 
     A highly basic magnesium sulfonate was prepared from the following components in accordance with the procedure of Example 1: 
     
         ______________________________________                                    
Material            Parts by Weight                                       
______________________________________                                    
Sulfonic acid (M.W. 524)                                                  
                    152                                                   
Magnesium sulfonate (TBN 327)                                             
                    30                                                    
Diluent oil         28                                                    
Naphthenic acid     10                                                    
Magnesium oxide     36                                                    
Methanol            13                                                    
Ammonium hydroxide  10                                                    
Water               20                                                    
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     The final product had a TBN of 413 and a viscosity of 800 SSU at 210° F., and it contained 10.16% magnesium and 31.90% magnesium sulfonate. It had a color of 4.5 and was bright and clear. 
     EXAMPLE 4 
     Another highly basic magnesium sulfonate was prepared from the following components in accordance with the general procedure described in Example 1: 
     
         ______________________________________                                    
Material            Parts by Weight                                       
______________________________________                                    
Sulfonic acid (612 M.W.)                                                  
                    1386                                                  
Magnesium sulfonate (TBN 287)                                             
                    220                                                   
Diluent oil         443                                                   
Naphthenic acid     95                                                    
Magnesium oxide     316                                                   
Methanol            110                                                   
Ammonium hydroxide  89                                                    
Water               222                                                   
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     Aromatic solvent having a distillation range of 260°-285° F. was used as a diluting solvent prior to clarification. The final product had a TBN of 423 and contained 34.2% magnesium sulfonate and 10.28% magnesium. It had a viscosity of 1200 SSU at 210° F., a color of 5.5 and was bright and clear. 
     EXAMPLE 5 
     The following materials were used in a 5 liter preparation in accordance with the general procedure described in Example 1: 
     
         ______________________________________                                    
Material            Parts by Weight                                       
______________________________________                                    
Sulfonic acid (612 M.W.)                                                  
                    1480                                                  
Magnesium sulfonate (TBN 327)                                             
                    150                                                   
Diluent oil         25                                                    
Naphthenic acid     35                                                    
Magnesium oxide     180                                                   
Methanol            50                                                    
Ammonium hydroxide  41.4                                                  
Water               100.8                                                 
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     The final product obtained from these materials had a TBN of 426, a viscosity of 1186 SSU at 210° F., and it contained 10.31% magnesium and 32.98% magnesium sulfonate. It also was bright and clear and had a color of 4.5. 
     EXAMPLE 6 
     The following materials were used in a 12 liter preparation: 
     
         ______________________________________                                    
Materials        Parts by Weight                                          
______________________________________                                    
Sulfonic acid    3552                                                     
Magnesium sulfonate                                                       
                 360                                                      
Diluent oil      60                                                       
Naphthenic acid  84                                                       
Magnesium oxide  432                                                      
Methanol         120                                                      
Ammonium hydroxide                                                        
                 138                                                      
Water            240                                                      
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     These materials were utilized in accordance with the general procedure of Example 1. The final product had a TBN of 412, and it contained 33.28% magnesium sulfonate and 10.01% magnesium. It had a color of 5.0 and was bright and clear in appearance. 
     EXAMPLE 7 
     The charge and conditions employed in Example 1 were followed except that the aromatic solvent was omitted. The alkylate was sulfonated with an aliphatic solvent having a distillation range of 260°-285° F. and additional aliphatic solvent of the same range was added to give the same charge as in Example 1. The product was bright in appearance, fluid and had a TBN of about 420. 
     EXAMPLE 8 
     Example 1 was repeated using a naphthenic acid having an acid number of 195 and saponifiables of about 25-30%. The product had essentially the same characteristics as the product of Example 1. 
     EXAMPLES 9-13 
     In these Examples the charge of Example 1 was modified as indicated, while the process conditions remained essentially unchanged. 
     The ammonium hydroxide was doubled to 16 g. Thickening occurred in the stripping procedure and the solution gelled. 
     10 
     The water was increased to 30 g. The final product had a noticeable haze and a TBN of only about 250-272. 
     11 
     The naphthenic acid was omitted. The product was much lighter in appearance and had noticeable haze. The TBN was about 270-300. 
     12 
     A different magnesium oxide was employed. It had a bulk density of about 15, an Iodine No. of 30 and passed a 200 mesh screen. The product had a TBN between 200 and 300 and was noticeably hazy. 
     13 
     Thirty-six grams of a magnesium oxide having an Iodine No. of 65, a bulk density of 20, and a particle size less than 200 mesh were employed along with the following components: 
     
         ______________________________________                                    
Materials        Parts by Weight                                          
______________________________________                                    
Sulfonic acid    296                                                      
Magnesium sulfonate                                                       
                 30                                                       
Diluent oil      5                                                        
Naphthenic acid  7                                                        
Methanol         10                                                       
Ammonium hydroxide                                                        
                 8.2                                                      
Water            20                                                       
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     The final product had a TBN of 275 and was slightly hazy. 
     EXAMPLES 14-18 
     In these Examples the charge of Example 1 was employed but the process conditions were altered as indicated. 
     14 
     The neutralization heating step was omitted. The product lacked stability in solubility tests and had a high sediment level. The TBN was between 250 and 300. 
     15 
     The ammonium hydroxide and water were added before the start of the carbonation. The solution thickened during carbonation with a tendency toward gel formation. If a product can be recovered, it typically has a TBN between 180 and 250 and is very hazy. 
     16 
     The ammonium hydroxide and water were added slowly to extend their addition period beyond the initial 25% of the carbonation. Thickening occurred during carbonation and subsequent heating resulted in gel formation. The product was very difficult to recover and was typified by a viscosity of 20-30,000 SSU at 210° F. 
     17 
     The carbonation temperature was kept to between 80° F. and 100° F. The solution did not darken during carbonation. Appearance was hazy and the TBN was between 200 and 300. Sediment was high and filtration poor. 
     18 
     The carbonation temperature was permitted to range between 80° and 140° F. The product had a slight haze. A hard to remove hazy sediment also has occurred under such temperature conditions. 
     Repeated attempts to utilize the preferred embodiments of the process for calcium overbasing have been unsuccessful. 
     Percentages used herein and in the following claims are weight percentages unless otherwise stated. 
     While particular embodiments of the invention have been described, it will be understood that the invention is not limited thereto, but includes such modifications and variations as come within the scope and spirit of the claims.