Lubricity enhanching bioadditive for low sulfur diesel fuel from Nyamplung-Oil (Calophyllum inophyllum L.) Glycerides

The problem of lubricating low-sulfur fossil diesel in diesel engines is a significant concern because desulfurization removes important polar compounds from fossil diesel. Removing these polar compounds reduces the lubricity of fossil diesel. Hence adding additives is required. Using conventional additives from fossil fuels has low biological degradability and is unsustainable. Replacing conventional additives with non-edible vegetable oil-based bio-additives is a promising option. This research focuses on synthesizing Nyamplung Oil-Glycerides (NOG) bio-additives through a glycerolysis reaction between Nyamplung Oil methyl ester (NOME) and glycerol. The fatty acids composition of Nyamplung oil was identified using a Gas Chromatography-Mass Spectrometer (GC-MS). The fraction of NOG was identified using Gas Chromatography (GC) with a derivation process using MSTFA reagent according to the ASTM D6584-17 method. The lubricating properties of fossil diesel, NOG, and a mixture of both (0.2; 0.4; 0.6; 0.8; and 1.0 % v/v) were evaluated using the High-Frequency Reciprocating Rig (HFRR) instrument with the standard procedure of ASTM D6079-18. The NOG has a wear scar diameter (WSD) of 214 µm, a coefficient of friction (CoF) of 0.051, and an average film thickness of 86%. Adding 1.0 % v/v NOG to fossil diesel demonstrated good lubricity compared to fossil diesel without NOG. It is due to the effect of the fatty acids composition of nyamplung oil, which contains 71.04% unsaturated fatty acids such as linoleic acid (35.88%) and oleic acid (34.87%). Furthermore, the effect of the composition of the glycerides also determines the lubricating properties. The results showed that the composition of NOG consists of 64.81% monoglycerides (MG), 30.39% diglycerides (DG), and 4.80% triglycerides (TG). Hydroxyl groups on MG improved the lubricating performance of low-sulfur diesel. Thus, NOG could potentially serve as a bio-additive for enhancing the lubricating properties of fossil diesel.