Optimization of biodiesel production and purification for maximizing biodiesel yield from camelina oil

Abstract

Because of the depletion of the world’s petroleum reserves and the increasing environmental concerns, biodiesel, as a low-emission renewable fuel and one of the best substitutes for petro-diesel fuel, has attracted great public interest over the past decades. At present, camelina oil has been considered as a low-cost feedstock for biodiesel production because of its high oil content and environmental benefits.

In the present study, the optimization of biodiesel production and purification from camelina oil is studied extensively in order to maximize the biodiesel yield. The orthogonal array design is used to optimize the biodiesel production and four relevant process conditions for affecting biodiesel yield are investigated: methanol to oil ratio, catalyst concentration, reaction time and temperature. For the optimization study on biodiesel purification, five commonly used washing methods are also investigated: cold deionized water washing, hot deionized water washing, phosphoric acid washing, ultrasonic assisted washing, and magnesol washing.

The optimization study, based on traditional mechanical stirring process, reveals that the decreasing ranking of significant factors for biodiesel production is catalyst concentration > reaction time > reaction temperature > methanol to oil ratio. The maximum biodiesel yield is found at a molar ratio of methanol to oil of 8:1, a reaction time of 70 min, a reaction temperature of 50℃, and a catalyst concentration of 1 wt.%. After testing the fuel properties of the final product, the optimized biodiesel meets the relevant requirements of the biodiesel standards and thus can be used as a qualified fuel for diesel engines.

The optimization study, based on ultrasonic-assisted transesterification process, reveals that the maximal fatty acid methyl ester yield of the final biodiesel product is obtained under a methanol to oil molar ratio of 8:1, catalyst concentration of 1.25 wt.%, reaction time of 50 min and reaction temperature of 55 ℃. Compared with traditional mechanical stirring production process, ultrasonic-assisted transesterification process improves the biodiesel production since it could reduce the production cost and save energy.

For the optimization study on biodiesel purification, the fatty acid methyl ester yield of the final biodiesel product, energy consumption and economic costs of different washing methods are compared. The comparisons indicate that the ultrasonic assisted washing method is the best method for biodiesel purification, when energy consumption and operation costs are considered.

A preliminary kinetics study of transesterification reaction of camelina oil is carried out. After discussing four cases for overall reaction, a third-order reaction mechanism was proposed to fit the experimental data better because of the highest coefficient of determination. Based on the best-fit plot, the rate constants and activation energy are also determined.

To sum up, the present research focuses on the optimization of biodiesel production and purification from camelina oil, and provides insights into the optimal process conditions for maximizing the biodiesel yield. Further research works are finally recommended to be continued.