It all gels for corn catalysis

Most industrial catalysts are mineral-based, whether created in a laboratory or extracted from a mine. Neither method is regarded as sustainable.

But a team at the University of York's Clean Technology Centre has found a way to make highly effective catalysts out of one of the largest sources of biomass on the planet - corn starch.

Starch has been overlooked as a catalytic material because it has a low surface area and pore volume - both vital properties for catalysis, which is a surface-mediated process. However, it is relatively simple to give starch a large surface area, say researchers James Clark and Duncan MacQuarrie in a paper in the journal Chemical Communications.

Heating starch powder in water at 100 degrees - 130 degrees C causes it to swell, then collapse into a gel. Rather than drying this gel, the researchers hold it at 5 degrees C. This treatment transforms the substance into a porous gel network with surface areas greater than 100m2 per gram and pore volumes above 0.5cm3 per gram.

Moreover, the researchers say, these networks can be made functional by adding aminoalkyl or quaternary ammonium hydroxide to the network. This gives a material which can be used to catalyse organic reactions. For example, amino-functionalised expanded corn starch achieved 100 per cent conversion of benzaldehyde to ethyl cyanoacetate - an industrial process known as the Knoevenagel reaction - in just two hours.