Acid Neutralization of Overbased Detergents (Part 2)

Temperature and acid droplet size effects in acid neutralization of marine cylinder lubricants

“…This means the rate (-dr t /dt) of acid neutralization may be significantly increased when a droplet gets smaller than a certain value (CP on its r t -vs.-t curve), after which the curvature of acid droplet may affect the neutralization considerably. These results support the above analysis and agree with Hosonuma and Tamura's report [1] that small-size acid-droplet emulsions had a higher reactivity, and also explain Wu et al result [4] that the initial size of an acid droplet did not influence on the rate of acid neutralization since the droplet size might have not yet reduced to a level corresponding to its change point as we found in the present work. The neutralization of sulfuric acid by overbased detergents in a MCL may result in the growth of crystal calcium sulfate hydrates [10,11] or the shrinking of acid droplets while maintaining their structure, i.e., without crystal growth [10].…”

“…In 2000, Wu et al [4], our previous work, reported that initial acid droplet size did not affect the rate of reaction between nitric acid droplets and commercial MCLs by using a video-enhanced capillary microscopy. This seems to contradict with Hosonuma and Tamura's results that the smaller the size of acid emulsions, the higher the reactivity [1]. In the temperature range of 25-55°C, Wu et al [5] investigated the neutralization between sulfuric acid and model MCLs by using a static phase-transfer technique.…”

“…In order to obtain optimal formulations of MCL, early researchers made several efforts to explore temperature and acid droplet size effects on the rate of acid neutralization in MCL. In 1984, Hosonuma and Tamura [1] investigated the neutralization between sulfuric acid emulsions and overbased detergents in a diesel engine oil. Higher reactivity was observed with decreasing size of acid emulsions.…”

Acid Neutralization by Marine Cylinder Lubricants Inside a Heating Capillary: Strong/Weak-Stick Collision Mechanisms

“…Hosonuma and Tamura 10 suggested and Wu et al 14 directly visualized that the acid neutralizations occurred at the acid/oil interface of the acid droplets (at relatively large scale), whereas Lewis, 13 Roman, 12 and Hone et al 9 proposed that the reactions happen in the bulk at the solubilized acid droplets (at relatively small scale). Hosonuma and Tamura 10 suggested that the reaction products should be formed inside the acid droplets, and Hone et al's "base transfer channel" 9 agreed with this, but Papke 23 found, and Roman 12 proposed, that the reaction products were solubilized in the bulk, whereas Wu et al 14 found that the products were first formed at the acid/oil interface on the oil side and then solubilized into the bulk.…”

“…Two commonly used methods monitor the changes of (i) pH [7][8][9] and (ii) the pressure of carbon dioxide [10][11][12] during the process of neutralization. Changes in pH value and carbon dioxide pressure result from the reaction between acid samples and preformed base particles in MCLs.…”