OPTIMIZATION OF OPERATIONAL VARIABLES ON THE ALKALI – CATALYZED TRANSESTERIFICATION OF SOYBEAN OIL USING RESPONSE SURFACE METHODOLOGY

ABSTRACT

The need for renewable sources of energy is pertinent because of the fast depleting rate of fossil fuels. In order to meet with the high demand of biodiesel, optimization of the production process is necessary. In this work, the optimization of operational variables for the alkali-catalyzed transesterification of soybean oil using Response Surface Methodology (RSM) of a statistical package Design-Expert software version 7.0 was studied. Central Composite Design of RSM was used to create a set of 20 experimental runs and develop the interactive relationship between the three variables (catalyst concentration, time and temperature of reaction). Methanol and potassium hydroxide were used as the alcohol and catalyst respectively for the transesterification process. The process variables ranges selected were as follows: Catalyst concentration (1 to 3%), Time (40 to 80 minutes) and Temperature (50 to 70℃). The yield, density and viscosity of the biodiesel determined were in-putted into the software as responses. The responses were analysed using Analysis of Variance (ANOVA) which showed that the model was significant (P ≤ 0.05). The highest yield of 89.17% of biodiesel with viscosity of 5.3 mm²/s and density of 0.879 g/cm³ was obtained at optimum conditions of Temperature (70 ℃), Time (80 minutes) and catalyst concentration (1 %). The viscosity and density of the biodiesel fell within the range of ASTM (American Society for Testing and Materials) standard for biodiesel.