Developing energy efficient lignin biomass processing – towards understanding mediator behaviour in ionic liquids Article Swipe
YOU?
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· 2016
· Open Access
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· DOI: https://doi.org/10.1039/c5fd00226e
· OA: W2269066045
Environmental concerns have brought attention to the requirement for more efficient and renewable processes for chemicals production. Lignin is the second most abundant natural polymer, and might serve as a sustainable resource for manufacturing fuels and aromatic derivatives for the chemicals industry after being depolymerised. In this work, the mediator 2,2′-azino-bis(3-ethylbenthiazoline-6-sulfonic acid) diammonium salt (ABTS), commonly used with enzyme degradation systems, has been evaluated by means of cyclic voltammetry (CV) for enhancing the oxidation of the non-phenolic lignin model compound veratryl alcohol and three types of lignin (organosolv, Kraft and lignosulfonate) in the ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate, ([C<sub>2</sub>mim][C<sub>2</sub>SO<sub>4</sub>]). The presence of either veratryl alcohol or organosolv lignin increased the second oxidation peak of ABTS under select conditions, indicating the ABTS-mediated oxidation of these molecules at high potentials in [C<sub>2</sub>mim][C<sub>2</sub>SO<sub>4</sub>]. Furthermore, CV was applied as a quick and efficient way to explore the impact of water in the ABTS-mediated oxidation of both organosolv and lignosulfonate lignin. Higher catalytic efficiencies of ABTS were observed for lignosulfonate solutions either in sodium acetate buffer or when [C<sub>2</sub>mim][C<sub>2</sub>SO<sub>4</sub>] (15 v/v%) was present in the buffer solution, whilst there was no change found in the catalytic efficiency of ABTS in [C<sub>2</sub>mim][C<sub>2</sub>SO<sub>4</sub>]–lignosulfonate mixtures relative to ABTS alone. In contrast, organosolv showed an initial increase in oxidation, followed by a significant decrease on increasing the water content of a [C<sub>2</sub>mim][C<sub>2</sub>SO<sub>4</sub>] solution.
