Process intensification of catalytic liquid-liquid solid processes: Continuous biodiesel production using an immobilized lipase in a centrifugal contactor separator

- Centrifugal separator contactors have been used for L-L-S reactions.
- The concept was demonstrated for continuous biodiesel synthesis using an immobilized enzyme.
- Further improvements were possible in a cascade of a CSTR and CCCS.
- Average biodiesel yield at steady state conditions was 86%-mol for a 9 h run.

Biodiesel or fatty acid methyl ester (FAME) synthesis from sunflower oil and methanol using an immobilized lipase, an example of a liquid-liquid solid reaction, was studied in batch and various continuous reactor set-ups including the use of a centrifugal contactor separator (CCCS). The latter is an example of a highly intensified device, integrating liquid-liquid reactions and subsequent phase separations. An exploratory study in batch was performed to optimize enzyme and buffer concentrations. Close to quantitative biodiesel yields were obtained at 30 °C when using 20% (w/w) of enzyme after a batch time of about 250 min. Subsequent continuous biodiesel synthesis was performed in a stirred tank reactor (CSTR) and a CCCS device. In the latter case, the immobilized enzyme was present in the annular, outer zone of the device. Average biodiesel yields in the CSTR and CCCS were similar (72%-mol respectively) when using a weight hourly space velocity (WHSV) of 3.3 and 3.03 h−1, respectively, at 30 °C. Cascade experiments were performed in a CSTR followed by a CCCS with the immobilized enzyme present in both reactors. The cascade was run for 9 h without any operation issues and an average FAME yield of 85%-mol was obtained. The advantage of the use of the cascade compared to a single CSTR is an improved yield combined with an efficient separation of the biodiesel layer and the glycerol. The biodiesel yield was about constant during the run, indicating that enzyme deactivation was negligible. The performance of the various reactor configurations were modelled successfully using standard balances for continuous reactors in combination with a kinetic model derived from the batch experiments.