The preparation conditions of biodiesel from Jatropha oil catalyzed by immobilized lipase(Novozym 435) were investigated in a solvent-free system.The results showed that the silica gel in the system could improve the reaction rate of transesterification and the conversion of the Jatropha oil,and the methanoJ couJd be added in one step,which simplified the process.The appropriate conditions for the transesterification were molar ratio of methanol to oil 3,enzyme mass fraction 7%based on oil mass,mass ratio o...