Supercritical Fluid Technology for Sustainable Biofuel Production

The methyl esters of vegetable oil – or biodiesel – are very similar to conventional (fossil) diesel fuel, and can be used as a blend in any conventional diesel engine without any modification. The base-catalyzed or acid-catalyzed transesterification of the triglycerides in vegetable oil with a simple alcohol – such as methanol – to form glycerol and the fatty acid methyl esters (FAMEs) has been the preferred method for a long time. However, a relatively long reaction time is needed when using either an acidic (1-45 h) or basic (1-8 h) catalyst to form the esters. In addition, removal of both the catalyst and the saponified products (which are formed due to a side reaction of the triglycerides with the catalyst) after the reaction is needed to obtain purified biodiesel. This downstream-processing step, however, consumes a lot of process water.

To avoid the problems associated with the conventional production method, VITO investigated the production of biodiesel in high temperature pressurized methanol (HTPM) without using a homogeneous catalyst. In this process, pure biodiesel can be obtained without the need for elaborate downstream processing. The purpose of the first part of this presentation is to give an overview of the production of biodiesel using the HTPM process. The advantages and disadvantages are addressed. The paper also addresses our latest efforts, in which VITO – together with three industrial partners – has set up a consortium that is responsible for the international marketing, production and exploitation of the new biodiesel technology.

In the second part of the talk, the opportunities that supercritical fluids can offer to treat lignocellulosic feedstocks for bioethanol production will be addressed.