Continuous overbasing of petroleum sulfonate with water removal and methanol addition between reaction stages

A method for the continuous overbasing of petroleum sulfonate comprising:

• (1) contacting CO.sub.2 at reaction conditions with a reaction mixture of (a) neutral petroleum sulfonate, (b) solvent refined 100 neutral lube oil stock, (c) lime, (d) methanol, and (e) naphtha in a series of reaction vessels in which additional CO.sub.2 is contacted seriatim in each succeeding reaction vessel with the effluent from the preceding reaction vessel,
• (2) removing at least a portion of the effluent from each reaction vessel,
• (3) reducing the water content of said at least a portion of said effluent to produce a reaction mixture of sufficiently reduced water content to reduce inhibition of the succeeding reaction,
• (4) subsequently, supplementing the methanol content of said at least a portion of said effluent to provide a more reaction efficient amount of methanol in the succeeding reactor,
• (5) introducing said at least a portion of said effluent into the succeeding reactor, and
• (6) collecting overbased petroleum sulfonate reaction product from the last succeeding reactor.