The biodiesel production from the cotton thistle seed oil (Onopordum acanthium L.)

The seed oil of cotton thistle (Onopordum acanthium L.) was used for fatty acid methyl ester synthesis in a two-step process that includes the H2SO4-catalyzed esterification of free fatty acid from the oil and the KOH-catalyzed methanolysis of the esterified oil. The kinetics of the methanolysis reaction of the esterified oil could be described by both the irreversible pseudo-first order and pseudo-second order law, though the higher conformity was achieved by the latter kinetic model. The reaction rate constants and activation energies were calculated. The adequacy of the model was evaluated using the R2 values and the mean relative percentage deviation between the experimental and calculated values of the triacylglycerol conversion degree. The obtained biodiesel generally satisfied the EN 14214 standard limits. Therefore O. acanthium L. may be used as a low-cost and valuable raw material for the biodiesel synthesis.