Biodiesel fuels from vegetable oils via catalytic and non-catalytic supercritical alcohol transesterifications and other methods: a survey
- A. Demirbas
- Energy Convers Manage
The effects of ethanol, methanol and their blends at different percentage mixtures on the properties and yields of biodiesel at varied trans-esterification times and temperatures using sodium hydroxide as a base catalyst have been investigated. At 70 o C, the optimum yields were: for ethanol 88.4%, 94.2%, 94.8%, and 95.2% and for methanol, 90.6%, 95.6%, 96.0%, and 96.4% at 1 hour, 2 hours, 3 hours and 4 hours respectively. The biodiesel yields increased as time of reaction progressed for both solvents but the yields obtained from methanol were generally higher than those from ethanol. A mixture of both solvents at 50% each produced the overall highest of biodiesel yield of 98.6% at 70 o C and in 4 hours compared to either solvent used alone at the same time and temperature. The properties such as densities, viscosities, flash points and pour points of the biodiesels tested were found to conform to ASTM standards. The average values were as follows: densities at 15 o C, were 0.8951, 0.8876 and 0.8832g/cm 3 ; viscosities (at 40 o C) were 4.7160cSt, 4.7380cSt and 4.5055cSt; flash points were 140.9 o C, 147.4 o C and 161.6 o C while for pour points they were -2.4375 o C, -1.6875 o C and -6 o C for ethyl, methyl and ethyl/methyl biodiesel respectively.