Oxidation and thermal stability analysis of hexadecyl mercaptan added to engine oil

This research mainly involves the oxidation stability and thermal stability tests of commercially available 10W50 engine oil after adding organic sulfide, here hexadecyl mercaptan (C16H34S), as an additive. First, differential scanning calorimetry was applied to evaluate the oxidation induction time (OIT). Second, thermogravimetry was adopted for isothermal thermogravimetric analysis. Then kinematic viscosity was tested to calculate the viscosity index. According to the results, the sample with the optimal addition ratio was selected, and the crude oil was subjected to follow-up experiments. Thermogravimetry was utilized to perform kinematic heating thermogravimetric analysis with the thermokinetic model and to calculate the apparent activation energy. Based on the characteristic analysis of modified engine oil, it was found that hexadecyl mercaptan as a lubricant additive can effectively ameliorate its oxidation stability and obtain extended oxidation time. Among them, the sample added with 3.0 mass% additive was the optimal addition ratio and its OIT was extended to 33 min. Thermal stability was also significantly improved. E-a was increased by ca. 20 kJ mol(-1).