The Antioxidant Properties of Organomolybdenum Compounds in Engine Oils

摘要

A series of four organomolybdenum components are evaluated for antioxidant performance in a conventional Group I engine oil and a low phosphorus Group II engine oil using oxidation bench tests commonly used to evaluate engine oils. The results indicate that all molybdenum types are effective as antioxidants, but molybdenum responds more favorably in Group I engine oils containing conventional levels of ZDDP-derived phosphorus. Greater antioxidant differentiation between the different organomolybdenum compounds is observed in the Group I system. Factors such as organomolybdenum chemistry, the presence of sulfur in the molybdenum complex, and component purity are less important to overall antioxidant performance. A synergistic antioxidant interaction between molybdenum and alkylated diphenylamines is highly effective at controlling oxidation in the Sequence IIIF engine test. This study demonstrates that very low levels of molybdenum can be utilized as engine oil antioxidants provided the proper bases-tocks are selected and antioxidants synergistic with molybdenum are utilized.