Continuous process for preparing overbased salts

A continuous method of preparing an overbased calcium sulfonate which comprises repeating the following steps until a desired TBN is obtained, said method comprising:

• (a) contacting Ca(OH.sub.2 and methanol with a normal calcium sulfonate hydrocarbon solution at a temperature ranging from about 60.degree. C. to about 100.degree. C. to solubilize at least a portion of the Ca(OH).sub.2 ;
• (b) filtering the sulfonate solution to separate and remove the non-solubilized Ca(OH).sub.2 from the solubilized Ca(OH).sub.2 contained in an obtained sulfonate filtrate;
• (c) treating said sulfonate filtrate with gaseous CO.sub.2 in a mole ratio of CO.sub.2 to sulfonate of about 1.0:1.0 to convert the solubilized CA(OH).sub.2 to solubilized CACO.sub.3 ;
• (d) blowing said solubilized CaCO.sub.3 with nitrogen to remove therefrom any excess CO.sub.2 and the aqueous phase generated therein to obtain an overbased sulfonate liquid;
• (e) adding more of said normal calcium sulfonate solution to said overbased sulfonate liquid and contacting said overbased sulfonate liquid with said non-solubilized Ca(CO).sub.2 and additional fresh Ca(OH).sub.2 to obtain an overbased sulfonate liquid product;
• (f) repeating steps (b) through (e) until the desired TBN ranging from about 200 to about 500 of the sulfonate liquid product is obtained, and removing an amount of sulfonate liquid product after step (d) equal to the additions of normal calcium sulfonate and Ca(OH).sub.2 in step (e);
• and
• (g) stripping the methanol and hydrocarbon solvent from the sulfonate liquid removed after step (d) to obtain the overbased calcium sulfonate product.