''The Transesterification process is the reaction of a triglyceride (fat/oil) with an alcohol to form esters and glycerol. A triglyceride has a glycerine molecule as its base with three long chain fatty acids attached. The characteristics of the fat are determined by the nature of the fatty acids attached to the glycerine. The nature of the fatty acids can in turn affect the characteristics of the biodiesel. During the esterification process, the triglyceride is reacted with alcohol in the presence of a catalyst, usually a strong alkaline like sodium hydroxide. The alcohol reacts with the fatty acids to form the mono-alkyl ester, or biodiesel and crude glycerol. In most production methanol or ethanol is the alcohol used (methanol produces methyl esters, ethanol produces ethyl esters) and is base catalysed by either potassium or sodium hydroxide. Potassium hydroxide has been found to be more suitable for the ethyl ester biodiesel production, either base can be used for the methyl ester. A common product of the transesterification process is Rape Methyl Ester (RME) produced from raw rapeseed oil reacted with methanol. ''

http://www.esru.strath.ac.uk/EandE/Web_sites/02-03/biofuels/what_biodiesel.htm

''Renewable green diesel-type alkanes can be produced by hydrotreating jatropha oil and vegetable oils at standard hydrotreating conditions (i.e., 543−573 K) with Pt/H-ZSM-5 catalysts, which are active under the weight ratio of jatropha or vegetable oil/catalyst of 1. The carbon molar yield of straight chain C15−C18 alkanes was 80% for hydrotreating pure jatropha oil. However, under the jatropha oil/catalyst weight ratio of 10, being important from a practical point of view, the alkanes yield falls to only 2.3%. Under a high jatropha oil/catalyst ratio of 10, rhenium-modified Pt/H-ZSM-5 catalyst is found to be effective for raising the C15−C18 alkanes yield. The yield of C15−C18 alkanes is 67% at an optimun Re/Al molar ratio of 0.8. Investigation of catalyst natures indicates that metallic Pt and Re are independently present on the surface, but synergism of these two metals could play an important role in the hydrotreating reaction, even at a high ratio of jatropha oil/catalyst of 10. The reaction pathway involves hydrogenation of the C═C bonds of the jatropha oils followed by mainly hydrodeoxygenation with decarbonylation and decarboxylation to form C15−C18 straight chain alkane mixtures''

http://alfin2300.blogspot.com/2010/03/better-catalysts-better-biodiesel-from.html