Mono- and Co- solvency based transesterification of Caryota urens seed oil

This study aims to comprehensively evaluate the reaction parameters and fuel properties of biodiesel derived from underutilized waste Caryota urens seed oil (CUO) using mono- and co-solvency-based transesterification. The CUO was extracted through both solvent extraction at the laboratory scale and mechanical screw press for large-scale purposes, with a maximum oil content of 7.76 ± 1.52% (wt%) reported. Transesterification of CUO was carried out using methyl, ethyl, and methyl-ethyl-based reaction systems employing KOH as a base catalyst and ethanol as a co-solvent. The highest yields were achieved under optimized reaction conditions: molar ratio of 1:9, catalyst concentration of 0.75, 0.6, and 0.6 wt%, reaction temperatures of 60, 75, and 70 °C, reaction times of 135, 90, and 40 min, and methanol to ethanol ratio of 4.5/4.5. Notably, the addition of ethanol in an equivalent ratio to methanol altered the reaction kinetics and product distributions, encouraged reactions at higher temperatures without any loss of solvent loss, reduced the overall reaction time, enhanced the overall ester yield, and exhibited the most favourable fuel properties. In fact, fuel properties of both CUO ethyl and methyl-ethyl esters, evaluated as per ASTM D6751 standards, reported enhanced calorific value (40.14 and 39.67 MJ/kg), cetane number (69.29 and 68.27), kinematic viscosity (5.27 and 5.03 mm²/s), and reduced density (870.76 and 871.41 kg/m³) than compared to CUO methyl esters. The findings of this research indicate that CUO esters, regardless of their form, hold significant potential as a promising source of biodiesel fuel.