Bio-waste crude extracts as alternatives to synthetic antioxidants in petroleum lubricants

Abstract

The increasing environmental concerns and the need for enhanced lubricant stability in petroleum industry necessitate sustainable solutions. This paper reports the use of crude extracts from bio-wastes of lemongrass and pepper fruits, as eco-friendly antioxidants to improve thermal and oxidation stability in petroleum lubricants. The bio-wastes samples were collected from Buguruni market in Ilala district of Dar es Salaam, Tanzania. The samples were dried, ground into powder, methanol-extracted, and concentrated to yield crude extracts. The crude extracts were then analyzed via phytochemical tests, Fourier Transform Infrared (FTIR) and gas Chromatography Mass Spectrometry (GC-MS) to identify antioxidant compounds. The extracts were blended with petroleum base oils and tested for oxidation and thermal stability using a Seta oxidation stability bath and Thermogravimetric Analysis, respectively. Kinematic viscosity and volatility analyses were also conducted. The phytochemical, FTIR, and GC-MS analyses confirmed that the extracts were rich in radical scavengers. The oxidation tests showed that base oils added with crude extracts had an induction time of 400 min, compared to the 320 min for those without, demonstrating that the extracts suppress oxidation. Thermal stability tests indicated that the oils blended extracts exhibited higher temperatures at maximum weight loss (>250 °C) and had fewer insoluble residues, suggesting improved stability. Moreover, kinematic viscosity increased and volatility reduced, implying enhanced lubrication and high-temperature stability. Both lemongrass and pepper fruits extracts had similar antioxidant effectiveness, validating their potential in petroleum lubricants. This research underlines bio-waste's viability as an antioxidant source, contributing to a circular economy in the energy sector.