Freedman et al. (1986)studied the transesterification kinetics of soybean oil. The S-shaped curves of the effects of time and temperature on ester formation for a 30:1 ratio of butanol and soybean oil (SBO), 1% H2SO4 and 77–117°C at 10°C intervals indicated that the reaction began at a slowrate, proceeded at a faster rate and then slowed again as the reaction neared completion. With acid or alkali catalysis, the forward reaction followed pseudo-first-order kinetics for butanol:SBO=30:1. However, with alkali catalysis the forward reaction followed consecutive, second-order kinetics for butanol:SBO=6:1.