Chemical analysis of overbased calcium sulfonate detergents by coupling XPS, ToF-SIMS, XANES, and EFTEM

Different methods (EFTEM, XPS, XANES, and ToF-SIMS) are used to determine particles size and detailed chemical composition of overbased calcium alkyl benzene sulfonate (OCABS) micelles. Colloids are obtained by carbonation of calcium hydroxide in hydrocarbon phase used in lubricant in the presence of ABS surfactant. The reaction leads to well-defined nanoparticles. This paper describes the location in the nanoparticle of expected molecular species and the quantity of each species. The originality of this study is to show the presence of residual calcium hydroxide in overbased detergents. As calcium carbonate has a highly amorphous character despite a local order close to calcite one, calcium hydroxide is suspected to be present in the core even at the end of the reaction. Its quantity and location are determined by the complementarities of these surface analysis techniques.