A new paper in the ACS journal Chemical Reviews examines recent work exploring the use of ionic liquids (IL) in the formation of 5-Hydroxymethylfurfural (HMF) from biomass. (Earlier post.) 5-HMF is a promising chemical intermediate for fuels and chemicals. (Earlier post.)
The strategy of direct use of the lignocellulosic biomass for the large-scale production of 5-HMF and its derivatives would be ideal. It could remove a major barrier for the development of a sustainable 5-HMF platform.
...This review summarizes current achievements in the synthesis of 5-HMF using ionic liquids as published in scientific periodicals up to the middle of July 2010. Moreover, it points out obstacles described in the studies presented and discusses perspectives in the application of ionic liquids to the conversion of biomass-derived carbohydrates.—Zakrzewska et al.
Among the perspectives offered by Zakrzewska et al. are:
5-HMF, together with its important derivatives, can be classified as novel biomass derived platform chemicals corresponding to those already established for fossil fuel based platform chemicals. The authors say that the 5-HMF building block is the only furan derivative that has been obtained so far from carbohydrates or raw biomass using ILs. to the best of their knowledge. They suggest the extension of green methods of synthesis to other furan derivatives be carefully designed and intensively explored, especially now that ionic liquids or supercritical fluids have been successfully applied in processes such as separation, enzymatic reactions, hydrogenation, oxidation,and others.
Ionic liquids, water, carbohydrates, a catalyst, etc. are capable of acting either as co- or antisolvent. This is why the vapor-liquid equilibria of ternary, quaternary, and multicomponent phases, partition coefficients, and separation factors must be determined for particular systems to develop optimal conditions for extraction of 5-HMF from the postreaction broth.
The direct conversion of raw biomass that must be investigated more extensively. Either various kinds of lignocellulosic biomass or scaling up the process should be investigated to make the formation of 5-HMF more feasible and industrially applicable, they suggest.
Comparison of the formation of 5-HMF in classical processes and by IL-mediated methods demonstrates that classical methodology can be a treasury of new ideas that should be explored in more sustainable media, including ILs. As an example, the employment of zeolite catalysts in IL-mediated processes can be given, similarly to what has already been shown in traditional processes.
Among several unresolved problems, the high cost of the production is the most troublesome. Nevertheless, a relatively small number of data already proves that ILs create a promising alternative in this field and open up a broad variety of new opportunities.—Zakrzewska et al.
Małgorzata E. Zakrzewska, Ewa Bogel-Łukasik, and Rafał Bogel-Łukasik (2010) Ionic Liquid-Mediated Formation of 5-Hydroxymethylfurfural—A Promising Biomass-Derived Building Block. Chem. Rev., Article ASAP doi: 10.1021/cr100171a