Production and optimisation of biodiesel using heterogeneous catalyst.
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In this work, it is required to investigate the production and optimisation of biodiesel using heterogeneous catalyst to determine whether the resulting biodiesel may be utilised in an existing diesel engine without modification. Castor oil and sunflower oils were chosen in the present study and conventional methods of biodiesel production, in the form of transesterification, were employed. The type of alcohol and catalyst chosen was methanol and calcium oxide, respectively, due to their relatively low cost and wide availability. The Box-Behnken Design was used to design the experiments and conduct statistical analysis in Minitab™ on each oil. The factors tested were temperature, catalyst loading, reaction time and alcohol/oil molar ratio. The experimental methodology followed was the conventional method which comprised the heating of oil and alcohol in the presence of a catalyst under continuous stirring, followed by separation using a separation funnel. However, due to the high acid value of castor oil, esterification was performed using sulphuric acid as a catalyst in the presence of methanol. The process of esterification meant that three types of oils were now considered in the design, viz, base castor oil, esterified castor oil and sunflower oil. The optimisation study conducted on castor oil esterification revealed that alcohol/oil molar ratio had the largest effect on the reduction of free fatty acids, resulting in a value of 0.715 % from a value of 12 % free fatty acids. Calcium oxide catalyst required calcination at 600℃ for 3 ℎ𝑟𝑠 for activation. Castor oil transesterification was conducted by first producing a large amount of esterified castor oil; at the optimal conditions; in the presence of calcium oxide and methanol where temperature proved to have the largest effect on the yield of biodiesel produced and a maximum yield of 97.2 % was achieved which was in accordance with the optimal conditions predicted by the regression full quadratic model. Similar to esterification, sunflower oil transesterification was largely affected by alcohol/oil molar ratio and an optimal yield of 98 % was achieved. The physical properties of the resulting fuels were tested, and biodiesel produced from sunflower oil is recommended, whereas biodiesel produced from castor oil does not meet ASTM D6751 fuel standards. The resulting fuels were blended with kerosene to form bio-jet fuel in fractions of 10 % and 20 %. The resulting blends are recommended for fuel testing to determine if further refinements are necessary according to ASTM standards. Biodiesel derived from sunflower oil could potentially reduce the strain on depleting fossil fuel reserves, lower overall greenhouse gas emissions, as well as promote job creation and further academic advancement within the alternative fuel environment.