Production of biodiesel from Jatropha curcas L. oil

A two-step process consisting of pre-esterification and transesterification was developed to produce biodiesel from crude Jatropha curcas L. oil. The free fatty acids (FFAs) in the oil were converted to methyl esters in the pre-esterification step using sulfuric acid or solid acid prepared by calcining metatitanic acid as catalysts. The acid value of oil was reduced from the initial 14 mg-KOH/g-oil to below 1.0 mg-KOH/g-oil in 2 h under the conditions of 12 wt% methanol, 1 wt% H2SO4 in oil at 70 °C. The conversion of FFAs was higher than 97% at 90 °C in 2 h using 4 wt% solid acid and a molar ratio of methanol to FFAs of 20:1. Phospholipid compounds were eliminated during pre-esterification and a separate degumming operation was unnecessary. The yield of biodiesel by transesterification was higher than 98% in 20 min using 1.3% KOH as catalyst and a molar ratio of methanol to oil 6:1 at 64 °C.