Abstract: Biodiesel was prepared by catalytic methyl esterification under higher pressure and higher temperature from acidic soybean oil with high content of free fatty acids. Optimal conditions for methyl esterification were studied and verified by methyl esterification of acidic soybean oil, acidic rapeseed oil, and waste oil. The content of total fatty acid methyl esters and yield of biodiesel was 95% and 94%, respectively, under the conditions of mass ratio of methanol to oil 1:1.25, catalyst NaA/MgR 1% by weight to oil, pressure 3.0MPa, reaction temperature 188℃, reaction time 120 min. After refination the biodiesel products quality can meet ASTM 6751-03a specification. This technology can be used for industrialization.

Key words: high acidic oils, methyl esterification, biodiesel