Enhanced Room-Temperature Transesterification of Palm Oil Using a DES K2CO3–Glycerol Catalyst with Acetone as Co-Solvent

Abstract

Biodiesel production conventionally requires elevated temperatures (65–70 ℃), resulting in high energy consumption. This study investigates a low-energy alternative by employing a deep eutectic solvent (DES) catalyst based on K₂CO₃–glycerol for transesterification of palm cooking oil at room temperature (27-28 ^oC), assisted by acetone as a co-solvent to enhance phase miscibility. The effects of methanol concentration (25–35%), DES K₂CO₃–glycerol catalyst loading (4–6%), and reaction time (2 and 4 h) were examined. Biodiesel properties—including density, viscosity, acid value, total glycerol, methyl ester content, and yield—were evaluated with reference to SNI 7182-2015 and ASTM D6751 standards. Increasing catalyst loading, methanol concentration, and reaction time generally reduced density, viscosity, and total glycerol while increasing methyl ester content. The most favorable operating conditions were obtained at 6% catalyst, 35% methanol, and 4 h reaction time, producing biodiesel with a density of 0.866 g/cm³, viscosity of 3.73 cSt, total glycerol of 0.404%, and methyl ester content of 95.7004%. While density and viscosity met SNI and ASTM specifications, the acid value and total glycerol did not fully comply, indicating the need for further catalyst and purification optimization. This work demonstrates the potential of DES K₂CO₃–glycerol for room-temperature (27-28 ^oC) biodiesel synthesis and highlights key factors governing fuel quality in low-energy production routes.