Kinetic studies on the extraction of oil from a new feedstock (Chukrasia tabularis L. seed) for biodiesel production using a heterogeneous catalyst.

Abstract

This study has identified a new feedstock Chukrasia tabularis L. (C. tabularis) seed for the production of biodiesel. Oil was extracted from the seeds with and without autoclave-assisted ultrasonic homogenization (AUH) pretreatment using different solvents. The solvent n-hexane with AUH pretreatment yielded a maximum oil yield of 32 wt%. The kinetics and thermodynamics of the extraction process were studied in a batch. The data showed that extraction followed first-order kinetics with a rate constant of 1.4 × 10-4min-1, activation energy of 63.604kJmol-1 and pre-exponential factors of 66.66 × 104s-1. The physiochemical properties of the oil were determined from which it was identified that C. tabularis oil has high free fatty acid (FFA) content, requiring a single-step esterification cum transesterification reaction to produce biodiesel economically. The modified aryl diazonium salt reduction process was used to synthesize a heterogeneous acid catalyst (HAC) from activated carbon precursor and was used to catalyze biodiesel reaction. Furthermore, HAC was characterized by different analytical techniques and it was found that it had an acid site density of 1.02mmolg-1 and a specific surface area of 602 m2g-1. The parameters affecting the biodiesel process were studied to obtain a maximum biodiesel conversion of 98.5% at 6 wt% catalyst loading, 15:1 methanol to oil molar ratio, 120min reaction time, 70 ºC reaction temperature, and 500rpm stirring rate. Reusability studies were performed which showed that HAC can be recycled up to five cycles with a conversion above 90% in the fifth cycle. Moreover, the fuel properties of biodiesel were determined using standard methods and were compared with ASTM D6751 and EN14241 standards.