Process for production of biodiesel

A three-stage transesterification reaction for preparing biodiesel comprising:

• (a) reacting a triglyceride feedstock, alcohol and catalyst in a high-shear reactor to form a first intermediate reacted mixture, wherein the high-shear reactor is a cavitation reactor operating at a shear rate of greater than 8,000 s−1, and wherein the ratio of the catalyst to the triglyceride feedstock is less than 1.9 by weight;
• (b) reacting the first intermediate reacted mixture in a low-shear reactor to form a second intermediate reacted mixture;
• (c) passing the second intermediate reacted mixture through a separation vessel to form a purified second intermediate reacted mixture;
• removing glycerol and unreacted alcohol from the second intermediate reacted mixture to form a purified second intermediate reacted mixture, the glycerol and unreacted alcohol removed from the second intermediate reacted mixture being recycled back to the high-shear reactor;
• (d) adding additional non-recycled alcohol and additional non-recycled catalyst to the purified second intermediate reacted mixture, wherein the ratio of the total catalyst to the triglyceride feedstock is less than 0.8 by weight;
• (e)) reacting the purified second intermediate reacted mixture in a second low-shear reactor to form a crude biodiesel reacted mixture;
• wherein the low-shear and the second low-shear reactor are operating at a shear rate of less than 1,000 s−1,
• (f) passing the crude biodiesel reacted mixture through a separation vessel to form a purified biodiesel product that product meets the triglyceride feedstock conversion level required by ASTM 6751.