(180h) Computer-Aided Molecular Design of Ionic Liquids for the Pretreatment of Biomass Using the Signature Molecular Descriptor

Cellulose is an abundant, renewable resource available from plants that can be turned into ethanol and help replace fossil fuels. Potential feed stocks for cellulose include waste products like corn stover and sugar cane bagasse, or planting a specific crop of switchgrass for harvest. Currently, the cost of cellulosic ethanol is too high for practical consideration. Ionic liquids have been identified for a pretreatment step in the production of cellulosic ethanol as a way to reduce the cost. Dissolving cellulose in an ionic liquid disrupts the ordered crystalline structure to a more amorphous form.[1] The dissolved cellulose can be regenerated by adding water, and then more easily broken down into fermentable sugars by enzymatic hydrolysis. In addition, ionic liquids are preferred over traditional pretreatment solvents because of environmental and safety considerations.

Some important properties for developing more effective ionic liquids for cellulose pretreatment include melting point, viscosity, and cellulose solubility. One of the current challenges associated with designing innovative ionic liquids for cellulose pretreatment is accurately estimating physical properties to save time and resources. In fact, there are an estimated 1018 possible combinations of cation/anion pairs available to create ionic liquids.[2] Ideally, one would like to design new ionic liquids on a computer which are predicted to possess the desired properties before actually performing experiments in the lab. Applying this approach is much quicker, less expensive and allows for a more comprehensive search for the most suitable potential candidates. In this work, we use a computer-aided molecular design technique known as inverse design.[3] Quantitative structure-property relationships (QSPRs) using the Signature molecular descriptor were created to predict melting point, viscosity, and cellulose solubility. The inverse-QSPR algorithm was employed to develop new ionic liquids with predicted properties suitable for cellulose pretreatment. A focused database of ionic liquids was created to provide a starting point for the evaluation and testing of the new and/or non-intuitive pre-treatment candidates. Results on the synthesis and evaluation will be reported in the poster presentation.

1. R. P. Swatloski, S. K. Spear, J. D. Holbrey and R. D. Rogers, J. Am. Chem. Soc., 2002, 124, 4974-4975.

2. A. R. Katritzky, R. Jain, A. Lomaka, R. Petrukhin, M. Karelson, A. E. Visser and R. D. Rogers, J. Chem. Inf. Comput. Sci., 2002, 42, 225-231.

3. D. P. Visco, Jr., R. S. Pophale, M. D. Rintoul and J. L. Faulon, J. Mol. Graph. Model., 2002, 20, 429-438.