Reactive extraction for biodiesel production

One of the advantages of biodiesel is the flexibility of the feedstock from which it can be produced. Consequently, it is available in almost all parts of the world. Conventionally biodiesel is produced from the reaction between vegetable oil and alcohol in the presence of a catalyst. In situ transesterification (IST) or reactive extraction is the reaction between the oil-bearing materials and alcohol with catalyst to yield biodiesel and glycerol. This method removes the process steps associated with oil extraction and can potentially reduce the cost of biodiesel production.

The energy required for recovering the excess alcohol from the products of IST makes the cost of production higher than conventional transesterification. In order to make IST cost effective, the high alcohol (methanol) requirement for the process must be reduced.

In this study, IST was carried out using a pre-soaking method. In this method the rapeseed is pre-treated with methanol. The results show higher yields of biodiesel using this method when compared to seed that had not been pre-soaked. The effects of catalyst concentration and soaking time have been investigated using Face Centred Central Composite experiment design. High yields of biodiesel (> 90%) were obtained with flaked-rapeseed at a slightly reduced methanol:oil molar ratio of 390:1 compared to the usual ratio of 475:1. This value represents an 18% reduction in alcohol requirement for IST. Despite this reduction more work needs to be done to further reduce the alcohol requirement.

Kinetics studies of IST for flaked and ground rapeseed are also being undertaken in order to study how the physical structure of the seed affects the rate of the reaction. It has been demonstrated for the first time that Fourier Transform Infra-Red (FTIR) spectrometry (mid-IR) can be used to monitor IST in real time.