Study of catalytic behavior of KOH as homogeneous and heterogeneous catalyst for biodiesel production

Increased industrialization and motorization are the major cause of environmental pollution and diminishing petroleum reserves. Biodiesel being renewable and environment friendly is one of the alternate sustainable energy sources having similar fuel properties as that of petroleum diesel. The objective of this study is to produce biodiesel from cheap raw material (waste cooking oil) and to get optimum reaction conditions for both homogeneous and heterogeneous catalytic transesterification. A comparison is also made to make the transesterification process techno-economically feasible. Potassium hydroxide (KOH) was selected as a homogeneous catalyst and KOH loaded on alumina as a heterogeneous catalyst. A yield of 96.8% fatty acid methyl ester (FAME) was obtained with heterogeneous catalyst at the optimum conditions of reaction temperature 70 °C, reaction time 2 h, catalyst concentration 5%, catalyst loading 15 wt%, and methanol to oil molar ratio 9:1, whereas 98.2% yield was obtained with homogeneous KOH catalyst at the optimum reaction conditions of reaction temperature 70 °C, reaction time 1 h, catalyst concentration 1%, and methanol to oil molar ratio 6:1. The fuel properties were also measured for biodiesel to observe its competitiveness with conventional diesel fuel. Reusability test of KOH loaded on alumina catalyst gave reasonable yield up to 3 cycles.