Kiw Yu Min, Schaeffer Philippe, Adam Pierre, Thiébaut Benoît, Boyer Chantal, Papin Géraldine
University of Strasbourg, CNRS, Institut de chimie de Strasbourg, UMR 7177 F-67000 Strasbourg France
TOTAL Solaize Research Center BP22-69360 Cedex France.
RSC Adv. 2020 Oct 14;10(62):37962-37973. doi: 10.1039/d0ra07329f. eCollection 2020 Oct 12.
The tribological performances of engine oils have been shown to be enhanced by the synergistic interactions between Mo dithiocarbamates (Mo(DTC)) with other additives, and notably Zn dithiophosphates (Zn(DTP)). Being two key components in formulated lubricants, a detailed understanding of the mechanisms involved between these two types of additives is needed to develop engine oils with enhanced friction reduction performances, and improved fuel economy. In this context, we report here the investigation at the molecular level of the interactions between Mo and Zn complexes with DTC and DTP ligands using laboratory experiments. Our analytical approach comprised NMR spectroscopy (H, C, P) allowing direct investigation of both homoleptic and heteroleptic Mo and Zn complexes as well as a specifically-developed HPLC-MS method for the investigation of the different DTC species formed during lubricant ageing experiments. The results showed that ligand exchange reactions between Mo(DTP) and Zn(DTC) complexes strongly favor the migration of the DTC ligands from Zn to Mo, illustrating the higher affinity of Mo for DTC ligands. In the case of binary mixtures involving Mo(DTC) and Zn(DTP) - a combination of additives frequently used in formulated lubricants - the formation of mixed complexes (Mo(DTC)(DTP)) resulting from ligand exchange reactions could be directly evidenced for the first time by the analytical methods used. These species could account, at least to some extent, for the synergistic effect of Mo(DTC) and Zn(DTP) on the friction reducing properties of engine oils. However, they were formed in significantly lower proportions than those previously reported in the literature using indirect methods.
发动机油的摩擦学性能已被证明可通过钼二硫代氨基甲酸盐（Mo(DTC)）与其他添加剂（尤其是二烷基二硫代磷酸锌（Zn(DTP)））之间的协同相互作用得到增强。作为配方润滑剂中的两个关键成分，需要详细了解这两种添加剂之间的作用机制，以开发具有增强减摩性能和改善燃油经济性的发动机油。在此背景下，我们在此报告使用实验室实验对Mo和Zn配合物与DTC和DTP配体之间相互作用的分子水平研究。我们的分析方法包括核磁共振光谱（H、C、P），可直接研究同配和异配的Mo和Zn配合物，以及专门开发的高效液相色谱-质谱法，用于研究润滑剂老化实验过程中形成的不同DTC物种。结果表明，Mo(DTP)和Zn(DTC)配合物之间的配体交换反应强烈有利于DTC配体从Zn迁移到Mo，这说明Mo对DTC配体具有更高的亲和力。在涉及Mo(DTC)和Zn(DTP)的二元混合物（配方润滑剂中常用的添加剂组合）的情况下，通过所使用的分析方法首次直接证明了配体交换反应产生的混合配合物（Mo(DTC)(DTP)）的形成。这些物种至少在一定程度上可以解释Mo(DTC)和Zn(DTP)对发动机油减摩性能的协同作用。然而，它们的形成比例远低于先前文献中使用间接方法报道的比例。
