(365a) Dissolution and Fractionation of Wood and Straw Using Ionic Liquids

Authors: 
Tavares Cardoso, M. A., Delft University of Technology
van Spronsen, J., Delft University of Technology
Witkamp, G., Delft University of Technology
de Jong, W., Delft University of Technology
van Ommen, J. R., Delft University of Technology
Marcotulio, G., Delft University of Technology


The decrease in the resources of fossil fuels together with the global warming alarms have led to an intensified search for alternative fuels to supply the modern society. Among them, the concept of biorefinery is becoming increasingly important since it presents the potential to be a real alternative for large scale production of fuels with a neutral carbon dioxide balance. In this biorefinery context, biomass resources such as wood and straw have not yet been properly valorised since these materials are mostly incinerated to produce heat. In addition, production of fuels from lignocellulosic biomass, especially wood, minimizes the competition with the food chain and presents higher yields when compared to first generation biofuels. The challenge now is to make this process attractive from an economical point-of-view. One of the major difficulties when dealing with these raw materials is related with the need of pre-treatments to dissociate the biomass structure. Lignocellulose consists mainly of cellulose (35 -50%), hemicellulose (20 -35%) and lignin (5-30%). These components are assembled in a complex three-dimensional structure remarkably resistant against chemicals and microbial attacks that makes them very difficult to hydrolyze, which is key for its future utilization. An effective dissociation of these components and their separation can lead to the production of several high value products prior to the production of fuels. This integrated approach increases the competitiveness of the biorefinery industry and can make it attractive even considering the actual oil prices (2009). As previously reported, ionic liquids offer a new and attractive route for the dissolution of lignocellulosic biomass. Besides the amount of biomass that can be dissolved in some ionic liquids (that can reach 8 % w/w), their complete recycling and significant environmental advantages make this class of compounds the best possible choice for a new pre-treatment to dissolve and fractionating the lignocellulosic biomass prior to biorefinery processing.

In this work, the complete dissolution of both wood and wheat straw in ionic liquids was followed by the fractionation of the several components that constitute the biomass and the analysis of each fraction was performed to close the mass balance. Two different ionic liquids, 1-ethyl-3-methylimidazolium chloride and 1-butyl-3-methylimidazolium chloride, and their mixtures were tested. The results were compared both in terms of yield and selectivity for the different constituents of both types of biomass. The obtained results show that this is a promising process for the pre-treatment of lignocellulosic biomass, regardless the type (wood or straw). Moreover, since the ionic liquids can be almost 100% recycled, this is a low cost, fast, simple and environmentally friendly pre-treatment that can increase significantly the competitiveness of modern biorefineries.