[SY-O4] Symposium O-4

[SY-O4] Molecular simulation to better understand soot-detergent interactions in engine oils

Invited

^○Sophie LOEHLE¹, Elias Gebremedhn², Michael Mazarin¹, Stephan Steinman², Carine Michel² (1.Total M&S, France, 2.ENS Lyon, France)

In the engine, soot is formed as a result of incomplete combustion. Some of the formed soot is absorbed into the lubricating oil film present until a certain level is reached in which it precipitates. This lead not only to the increase of the lubricant’s viscosity but also it adsorbs on the metallic surface, thus increasing engine wear. Most automotive enhancement additives contain, among other additives, detergents which help control the agglomeration and deposition of soot particles and other corrosive contaminants. A typical detergent molecule features a head part with constituting polar functional groups and a long hydrocarbon tail group [1]. The common perception is that the detergents do the job as dispersants and/or through formation of protective coating on steel surfaces. However, little is known about the complex physicochemical and structural details of the soot-detergent interfaces, and it seems that such details are too difficult to capture using conventional experimental techniques alone. In this respect, molecular modeling can fill the gap by providing atomistic level understandings on soot-detergent interactions and interfacial structural features.Finding an atomistic representation of the soot is the crucial step in modeling soot-detergent interactions. First, we show how we developed reliable soot model using experimental data [2-4], we employed a deterministic structural elucidation method to automatically generate representative soot structures. Following, we show how we assessed physisorption energies between the soot models and some polar detergent-head groups using the latest semi-empirical PM7 method, and how the result can be used to complement experimental screening techniques.

References:
1- J.D. Burrington, J. K. Pudelski, J. P. Roski, Chapter 18: Challenges in detergents and dispersants - Practical Advances in Petroleum Processing 2007
2- Christine Esangbedo, Andre L. Boehman, Joseph M. Perez, Tribology International 2012, 47, 194
3- A. La Rocca, F. Bonatesta, M. W. Fay, F. Campanella, Tribology International 86 (2015) 77-84
4- I. Z. Jenei et al., Nanotechnology n°8, Vol 29 (2018)