Abstract
This work investigated the possibility of using response surface methodology based on a four factor five level central composite design to optimize biodiesel production from castor oil. The reaction variables were oil: ethanol ratio, lipozyme concentration, time and temperature. The properties of the biodiesel produced were assessed. The linear coefficient of lipozyme concentration (B), temperature (D), the quadratic coefficient of lipozyme concentration (B 2 ), time (C 2 ), temperature (D 2 ), the interaction of oil/ethanol ratio and lipozyme concentration (A*B), the interaction of lipozyme concentration and time (B*C) had significant effect on the biodiesel yield (p 0.05).The specific gravity was (0.91), refractive index (1.41 + 0.01), viscosity (14.1), cetane number (53.9), calorific value (38.0+ 0.10), flash point (150 o C), cloud point (7 o C) iodine value (101 + 0.53), acid value (0.57 + 0.01), and saponification value (180+0.25). Maximum yield was found to be 93.0% under the conditions of oil: ethanol ratio of (1:7.14), lipozyme concentration (40 U), time (165 min) and temperature 50 o C.The properties of the biodiesel produced were largely in conformity with ASTM D6751 standards. Keywords : Biodiesel, castor oil, optimization, transesterification_
Highlights
The rapid depletion of world's petroleum reserves and increased ecological concerns have prompted the demand of environment friendly renewable energy resources (Ashish et al, 2010)
Several parameters, such as the type of catalyst, alcohol/ oil molar ratio, temperature, purity of the reactants and free fatty acid content have a greater influence on the transesterification reaction (Giovanilton et al, 2011)
The decrease in biodiesel yield at higher oil ethanol ratio could be due to separation problem resulting from excessive ethanol, or in activation of the enzyme by ethanol (Molla and Nigus, 2014).The decrease in biodiesel yield at high lipozyme concentration and oil ethanol ratio could be that, in the presence of a high amount of lipase because the enzyme active site cannot be exposed to the substrates and many molecules of the enzyme aggregate together and results in low biodiesel yield (Liou et al, 1998)
Summary
The rapid depletion of world's petroleum reserves and increased ecological concerns have prompted the demand of environment friendly renewable energy resources (Ashish et al, 2010). The use of non-edible oils such as karanja, polanga, jatropha, and castor oil have attracted great attention as they do not pose threats to food security when used as feedstock in fuel industry (Koh and Mohd, 2011). Several parameters, such as the type of catalyst, alcohol/ oil molar ratio, temperature, purity of the reactants and free fatty acid content have a greater influence on the transesterification reaction (Giovanilton et al, 2011)
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