Process for preparing overbased magnesium sulfonates

Abstract

A method of preparing overbased or superbased magnesium sulfonates by sulfonating an alkyl benzene with a material containing SO.sub.3, preferably oleum, and reacting the alkyl benzene sulfonate with magnesium oxide in the presence of a low viscosity diluent, such as No. 2 oil or LOPS (low odor paraffin solvent), together with water, alcohol, and CO.sub.2. The newness of the method lies in the steps of preferably positively utilizing oleum which contains a minor amount of sulfuric acid as a promoter and utilizing also a surfactant couple of a C.sub.12 -C.sub.18 fatty acid such as oleic acid and an ethanol amide such as a lauryl diethanol amide, which may be Witcamide 5138; where a ready made sulfonate is used, such as SA697 (Conoco), H.sub.2 SO.sub.4 is utilized. In certain instances the amide may be omitted with satisfactory results occurring by using the acid alone. Of particular interest is the preparation of a concentrated magnesium sulfonate wherein the water and alcohol are removed by distillation and a diluent such as LOPS or No. 2 oil is added to produce a slurry. An important feature of this process lies in the reduction in size of the magnesium oxide particles. CO.sub.2 is preferentially bubbled through the mixture after introduction of the magnesium oxide and at a temperature range of 30.degree.-80.degree. C. with stirring.