An investigation into the synthesis of biodiesel from canola oil via heterogeneously catalyzed transesterification reaction.

Abstract

Biodiesel has gained a great deal of attention worldwide due to its reduced toxicity, biodegradability, and renewable characteristics. Biodiesel fuel seems to be a promising alternative to petroleum diesel as it is derived from renewable feedstocks. The more conventional production of biodiesel is synthesized in the presence of homogeneous catalysts. However, heterogeneous catalysts have recently gained tremendous importance because of the current climate e.g., increased competition, stringent pollution regulations, etc. Biodiesel is manufactured ideally through catalyzed transesterification reactions whereby the triglycerides (animal fats or vegetable oils) are reacted with an alcohol (with low molecular weight) to produce alkyl esters (biodiesel) and glycerol as a by-product. This study focused on the transesterification reaction of triglycerides to synthesize fatty acid ethyl esters in the presence of heterogeneous catalysts respectively. Canola oil was investigated in this study along with ethanol, and heterogeneous catalysts calcium oxide and magnesium oxide respectively. Canola oil had a free fatty acid content of 0.042 wt.% which was significantly lower than the recommended 0.5 wt.%, indicating no pretreatment step was necessary and only a single-step transesterification was required. The process variables taken into consideration included reaction temperature, catalyst loading, alcohol to oil molar ratio, and reaction time, and the response variable was the biodiesel yield attained. Box-Behnken design along with response surface methodology (RSM) was used to obtain the optimum process variable conditions which resulted in attaining a maximized biodiesel yield. Biodiesel produced in the presence of calcium oxide achieved an optimum yield of 93.80%, while biodiesel produced in the presence of magnesium oxide achieved an optimum yield of 96.90%. The biodiesel yields obtained at the optimum conditions were subjected to being blended with kerosene to produce bio-jet fuel. Both biodiesel and bio-jet fuel were subjected to property testing in accordance with ASTM standard fuel requirements. The biodiesel yields produced from canola only in the presence of both calcium oxide and magnesium oxide respectively met all ASTM standard requirements except for the kinematic viscosities which were higher than the stipulated limit, however, biodiesel produced with magnesium oxide was closer to the specified limit. Nevertheless, biodiesel produced from canola oil reacting with ethanol in the presence of the aforementioned heterogeneous catalysts respectively is not recommended to be used in a diesel engine without further modification. The jet fuel samples met all the ASTM standard requirements, except for the kinematic viscosity and acid value properties, thus these are not recommended for use in an engine without further modification.