Ionic liquid solvent properties as predictors of lignocellulose pretreatment efficacy

• Published in: Green chemistry : an international journal and green chemistry resource : GC 2010-01, Vol.12 (11), p.1967-1975
• Main Authors: Doherty, Thomas V, Mora-Pale, Mauricio, Foley, Sage E, Linhardt, Robert J, Dordick, Jonathan S
• Format: Article
• Language: English
• Subjects: Anions
• ISSN: 1463-9262
• DOI: 10.1039/C0GC00206B

Effective pretreatment of lignocellulosic biomass is vital to its bioconversion to a usable liquid fuel. A growing body of work has focused on using room temperature ionic liquids (RTILs) to pretreat lignocellulose for subsequent fermentation. However, little is known about the physicochemical parameters of RTILs that promote effective pretreatment. In this work we examine the relationship between the Kamlet-Taft [small alpha], [small beta], and [small pi]* solvent polarity parameters of different RTILs ([Emim][OAc], [Bmim][OAc], and [Bmim][MeSO4]) and effective pretreatment of lignocellulosic biomass. We find the [small beta] parameter is an excellent predictor of pretreatment efficacy. Acetate containing RTILs ([small beta] 1.0) remove 32% of lignin from maple wood flour and significantly reduce cellulose crystallinity, resulting in 65% glucose yields after 12 h cellulase hydrolysis. Pretreatment in [Bmim][MeSO4] ([small beta] = 0.60) results in the removal of only 19% of the wood flour's lignin with no decrease in crystallinity, and no improvement in sugar yield over untreated wood flour. The addition of water and the dilution of the acetate anion with the methyl sulfate anion decrease the [small beta] value and subsequently have a negative impact on lignin extraction, cellulose crystallinity, and sugar yields.