Fuel properties of biodiesel produced from Camellia oleifera Abel oil through supercritical-methanol transesterification

The fuel properties of the biodiesel produced from Camellia oleifera Abel oil through supercritical-methanol transesterification with no catalyst was investigated in this study. An emulsion of raw C. oleifera Abel oil dispersed in methanol was prepared prior to being poured into a supercritical-methanol reaction system to undergo the transesterification reaction. The fuel properties of the resulting biodiesel were analyzed and compared with those of a commercial biodiesel and with ASTM No. 2D diesel fuel. The experimental results show oleic acid (C18:1) and palmitic acid (16: 0) to be the two major components of the C. oleifera Abel oil biodiesel. It also contains significantly higher mono-unsaturated fatty acids and long carbon-chain fatty acids ranging from C20 to C22 than those found in the commercial biodiesel. However, relative to the commercial biodiesel, the C. oleifera Abel oil biodiesel has significantly fewer poly-unsaturated fatty acids with more than three double bonds, which implies that it also has a much higher degree of oxidative stability. In addition, the biodiesel produced from C. oleifera Abel oil was also found to have more favorable fuel properties than the commercial biodiesel produced from waste cooking oil, including a higher heat of combustion and flash point and lower levels of kinematic viscosity, water content, and carbon residue. Moreover, the former appears to have much lower peroxide and acid values, and thus a much higher degree of oxidative stability than the latter. (C) 2011 Elsevier Ltd. All rights reserved.