Sugars and sugar derivatives in ionic liquid media obtained from lignocellulosic biomass: Comparison of capillary electrophoresis and chromatographic analysis

• Wood sawdust (of pine, spruce, birch) was treated with ionic liquids (EmimCl or EmimOAc, respectively) for 0–880 h at 80–100 °C.
• Monosaccharides, 5-HMF and furfural were analyzed by means of chromatography respective capillary electrophoresis – GC, HPLC and CE.
• >100 h (or ≥150 °C) results into tar formation and degradation of all sugars.
• More 5-HMF was formed than furfural.
• Gal, Glc, Man and Xyl were the main monosaccharides observed.

Processing of woody lignocellulosic biomass, under heating in combination with ionic liquids (ILs) was studied in order to obtain simple (fermentable) sugars. Due to the new environmental challenges, finding greener ways to produce platform chemicals and/or bio-fuels has become a popular research area. Various industrial, pilot or laboratory scale technologies for the depolymerization or fractionation of lignocellulosic polysaccharides to monomers are known. One of the new, interesting, methods is to utilize ILs in biomass pre-treatment procedures with an aim to bypass other pre-treatment methods. Furthermore, in order even to initiate studies whether ILs can contribute to catalytic depolymerization, there has to be a robust way to analyze the IL-treated lignocellulosics. This is a major issue since woody samples that contain any salts such as ILs can indeed be quite challenging from the analytic point of view. The applied capillary electrophoresis was found to be an excellent analytical method providing substantial improvements compared to the earlier used chromatographic methods.In this work it was demonstrated that application of ILs, at elevated temperatures, contributes to hydrolysis and depolymerization of lignocellulose. The effect is time and temperature dependent: in harsh conditions sugars degrade but too low processing temperatures or short treatment times result in no meaningful effect. The formation of the degradation products of the monosaccharides is a good indicator of the harshness of the applied chemical conditions. Evidently, furfural and 5-(hydroxymethyl)furfural formed in rather short treatment times.

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