The advantage of biodiesel manufacturing by heterogeneous base catalyst

The manufacturing of biodiesel by heterogeneous catalysis has major economic benefits compared to the traditional homogeneous catalysis.

The main reason is the suppression of operations generating large amounts of waste water (except during feedstock pretreatment), namely the catalyst removal by acid/base neutralisations, washing of FAME and glycerol, as well as at methanol recovery by distillation of aqueous solutions.

There is no salt waste, and catalyst consumption drops dramatically.

In the homogeneous process the glycerol has maximum 85% purity after expensive separations, while the heterogeneous process delivers glycerol that is >98% pure, a valuable product.

In addition, the continuous operation is intrinsically more efficient than batchwise. Heterogeneous catalysis may be applied both to low and to high FFA oils. In the last case a preliminary esterification with methanol is necessary, which can be performed by employing solid acid catalyst, as e ion-exchange resins.

The small amounts of water  formed can be removed simply by adsorption. Higher FFA lipids, as animal fat and industrial greases, can be treated in a reactive distillation device.