Biodiesel fuels through a continuous flow process of chicken fat supercritical transesterification

Supercritical transesterification of chicken fat with methanol was investigated at various temperatures (350, 375, and 400 °C), pressures (100, 200, and 300 bar), methanol-to-chicken-fat molar ratios (from stoichiometric 3:1 to 12:1), and residence times (3-10 min). The best experimental results for the conversion of triglycerides and the decomposition of glycerol to fuel components were obtained under the following conditions: 400 °C, 300 bar, methanol-to-triglycerides molar ratio = 9:1, and residence time = 6 min. The thermal decomposition products of long-chain methyl esters and glycerol were identified in the biodiesel samples and their potential influence on fuel characteristics such as viscosity, cold flow, cetane number, and flash point is discussed. Because of the low excess of methanol used in this study in comparison with similar supercritical transesterification processes (methanol-to-feedstock molar ratios of 3-12 vs 40+), costs associated with the pumping, preheating, and recovery of the excess methanol will be greatly reduced in commercial applications. Use of low-cost feedstocks and a moderate excess of methanol, coupled with glycerol decomposition to valuable fuel components, certainly will increase the profitability of a much simplified method, in comparison with competitive technologies.