Lignocellulose is the most abundant form of biomass, which offers great potential as naturally substantial and renewable carbon resource for a sustainable future. Lignocellulose is composed primarily of polysaccharides such as cellulose, hemicellulose; with lignin, a phenolic polymer, as the third major component. The annual production of lignocellulose is around 170 billion metric tons, however, within which no more than 5% has been utilized for chemicals and energy production, due to the complexity of lignocellulose and its notorious resistance to chemical transformation.
Ionic liquids (ILs) are a class of low temperature molten salts having near-zero vapor pressure, comprised of diverse designable cations and anions. Certain types of ILs were found to not only have special solubility for one or more components of lignocellulose, but also serve as excellent reaction media or even catalysts for catalytic transformation of lignocellulose. Therefore, ILs have offered scientists promising opportunities for processing lignocellulose to obtain renewable chemicals and fuels. A number of novel catalysts have emerged with excellent catalytic activities in the transformation of carbohydrates and lignin in recent years. In order to generate more efficient catalysts through rational design, theoretical methods and diverse physical characterization technologies, especially 2D NMR and FIR, have been developed and applied for in-depth study of the catalytic mechanisms.
In a review published in WIREs Energy and Environment, a discussion of how in the last five years, the transformation of carbohydrate and lignin in ILs has made significant progress in terms of development of new functionalized catalysts, application of nontraditional protocols, and a deeper understanding of fundamental reaction mechanisms involved in ILs-based catalytic systems is provided. However, there are still several critical issues to be addressed in the development of an economic biomass refinery in ILs media, which requires sustained effort of scientists and researchers to achieve a more sustainable society.
Kindly contributed by Yiwen Yang, Cheng Zhang, and Z. Conrad Zhang.