The depolymerisation of lignin directly in the black liquor was studied, comparing two ionic liquids as extracting solvents (butylimidazolium hydrogen sulphate and triethylammonium hydrogen sulphate), under oxidising conditions.

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Oxidative depolymerization of lignin obtained from pine and willow can be achieved in a novel system encompassing the ionic liquid (IL) 1-butylimidazolium hydrogensulfate coupled with a vanadium based polyoxometalate (POM) under oxygen rich conditions. Along with an array of phenols and functionalized aromatics, vanillin and syringaldehyde were the main products extracted from the IL. The overall yield of aldehyde products were shown to be higher on lignin samples obtained with shorter pretreatment times, with vanillin being the exclusive aldehyde product obtained from pine. In the presence of molecular oxygen, the highest yield of aldehyde products was obtained when 5 wt % of the POM relative to the IL was employed and constituted the major product in the extracted oils. This system succeeds in exploiting the ability of ILs to depolymerize lignin and the remarkable properties of the POM to oxidize the lignin fragments into useful platform chemicals

We report a method to extract lignin from willow, using triethyl ammonium hydrogen sulphate [Et3NH][HSO4. This method is used to manufacture fibers with a range of compositions.. This extraction achieved an 18% yield of lignin as characterized by ATR-IR and elemental analysis indicated a high carbon yield. 1-Ethyl-3-methylimidazolium acetate [C2C1im][OAc] was then used as a solvent to manufacture lignin-cellulose fiber blends. The Young's modulus of a 75:25 lignin:cellulose fiber was found to be 3.0 ±0.5 GPa which increased to 5.9 ±0.6 GPa for a 25:75 lignin:cellulose blend. From a characterization of the surface morphology using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) it was observed that a rich lignin content in the fiber blend increased the surface roughness. FT-IR analysis confirmed the presence of aromatic groups of lignin from the presence of peaks located at ~1505 cm -1 and ~1607 cm -1 . The presence of lignin improves the thermal stability of the fiber blends by allowing them degrade over a wider temperature range. This is potentially useful for the utilisation of renewable lignocellulosic biomass derived fibers as carbon fiber precursors. Although the mechanical properties of the regenerated fibers were diminished by the addition of lignin, the blends prepared produced a solution suitablefor a stable fiber spinning process.