Comparison of Biodiesel Production between Homogeneous and Heterogeneous Base Catalysts

Abstract

Homogeneous base catalyst has wide acceptability in biodiesel production because of their fast reaction rates. However, postproduction costs incurred from aqueous quenching, wastewater and loss of catalysts led to the search for alternatives. Heterogeneous base catalyst is developed to cater these problems. The advantages of heterogeneous catalyst are their high basicity and non-toxicity. This work compared the production of biodiesel using two different kind of catalysts that is homogeneous catalyst (sodium hydroxide, NaOH and potassium hydroxide, KOH) and heterogeneous catalysts (calcium, oxide, CaO catalyst derived from chicken and ostrich eggshells). Transesterification of waste cooking oil (WCO) and methanol in the presence of heterogeneous base catalyst was conducted at an optimal reaction condition (calcination temperature for catalyst: 1000 °C; catalyst loading amount: 1.5 wt%; methanol/oil molar ratio: 10:1; reaction temperature: 65 °C; reaction time: 2 hours) with 97% biodiesel yield was obtained. While, the homogeneous base catalyst gave higher biodiesel yield of 98% at optimum operating condition (catalyst concentration: 0.75 wt%; methanol/oil molar ratio: 6:1; reaction temperature: 65 °C; reaction time: 1 hours). The slight difference in the biodiesel yield was due to the stronger basic strength in the homogeneous catalyst and were not statistically not different (p=0.05). However, despite these advances, the ultimate aim of producing biodiesel at affordable low cost and minimal-environmental-impact is yet to be realized.