Biolubricant Production from Castor Oil Using Rice Husk Ash Catalyst

Petroleum-based lubricants pose environmental challenges due to poor biodegradability, toxicity, and reliance on fossil resources, driving the search for sustainable alternatives. This study investigates the production of biolubricants from castor oil using rice husk ash (RHA) as a heterogeneous catalyst. The RHA was synthesized through controlled calcination and acid activation and analyzed using SEM, BET, and XRF techniques. Transesterification reactions were conducted under varying conditions of temperature, reaction time, and methanol-to-oil ratio, and the resulting biolubricants were evaluated by physicochemical analysis. The activated RHA catalyst exhibited improved surface morphology, a significant increase in BET surface area (136.4 to 287.7 m²/g), and a silica-rich composition (70.27 wt.% SiO₂), confirming its suitability as an effective catalyst. Reaction conditions strongly influenced transesterification efficiency, with optimum parameters of 60 °C, 1.5 h, and a 6:1 methanol-to-oil ratio producing a biolubricant with desirable physicochemical properties. Catalyst reusability tests further demonstrated its stability and potential for repeated use. These findings establish RHA as a low-cost, sustainable, and efficient heterogeneous catalyst for castor oil-based biolubricant production. The study highlights the potential of agricultural waste valorization in advancing eco-friendly lubricant technologies.