Preparation and characterization of bio-diesels from various bio-oils

Methyl, ethyl, 2-propyl and butyl esters were prepared from canola and lins eed oils through transesterification using KOH and/or sodium alkoxides as c atalysts. In addition, methyl and ethyl esters were prepared from rapeseed and sunflower oils using the same catalysts. Chemical composition of the es ters was determined by HPLC for the class of lipids and by GC for fatty aci d compositions. The bio-diesel esters were characterized for their physical and fuel properties including density, viscosity, iodine value, acid value , cloud point, pure point, gross heat of combustion and volatility. Methyl and ethyl esters prepared from a particular vegetable oil had similar visco sities, cloud points and pour points, whereas methyl, ethyl, 2-propyl and b utyl esters derived from a particular vegetable oil had similar gross heati ng values. However, their densities, which were 2-7% higher than those of d iesel fuels, statistically decreased in the order of methyl similar to 2-pr opyl > ethyl > butyl esters. Butyl esters showed reduced cloud. points (-6 degreesC to -10 degreesC) and pour points (-13 degreesC to -16 degreesC) si milar to those of summer diesel fuel having cloud and pour points of -8 deg reesC and -15 degreesC, respectively. The viscosities of bio-diesels (3.3-7 .6 x 10(-4) Pa s at 40 degreesC) were much less than those of pure oils (22 .4-45.1 x 10(-4) Pa s at 40 degreesC) and were twice those of summer and wi nter diesel fuels (3.50 and 1.72 x 10(-4) Pa s at 40 degreesC), and their g ross heat contents of approximately 40 MJ/kg were 11% less than those of di esel fuels (similar to 45 MJ/kg). For different esters from the same vegeta ble oil, methyl esters were the most volatile, and the volatility decreased as the alkyl group grew bulkier. However, the bio-diesels were considerabl y less volatile than the conventional diesel fuels. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.