Neutralization of Acidic Exhaust Gas Components by Overbased Additives in Marine Oils: Effects of the Acid Composition on the Neutralization Mechanism

Abstract

Using a combination of IR spectroscopy and small-angle X-ray scattering methods, the study investigates the initial steps of the neutralization of commercial additives, such as overbased calcium alkylbenzene sulfonate and calcium alkyl salicylate, by a number of model acids. The model acids included sulfuric acid, nitric acid (both simulating acidic products of marine fuel combustion), and acetic acid. For the sulfonate additive, it was shown that the amorphous CaCO3 core crystallizes, predominantly into vaterite, with a simultaneous slight increase in the size of the additive’s solid core. In the case of the salicylate additive, no CaCO3 crystallization was observed, and the solid core was slightly reduced in size. The paper proposes an explanation for these transformations, which rests on the difference in the strength of the acids that constitute the shell of the additive’s nanoparticles, and in the water solubility of the calcium salts produced.