Efficient dissociation of poplar fibres using a γ-valerolactone/formic acid binary solvent system-Structural changes...

A binary organic solvent system comprising γ-valerolactone (GVL) and formic acid (FA) was developed to achieve green and efficient wood fibre dissociation by using biomass dissolution capability and enhanced acid-catalysed reaction ability of GVL. Without the need for raw material crushing or pretreatment, lignin was effectively separated from poplar wood using the GVL/FA system, with a removal rate of 84.16 %. Under optimal dissociation conditions (temperature 120 °C, reaction times 3 h, ratio GVL:FA = 1:3, solid-liquid ratio = 1:20), the retention rate of cellulose was 88.25 %, and the fibres were almost completely retained while being dissociated. Various techniques, including nuclear magnetic resonance spectroscopy (2D-HSQC,³¹P NMR),gel permeation chromatography (GPC) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) were applied to characterise the lignin structures. The results showed that β-ether bonds were effectively cleaved and condensation occurred at the C_α position. Furthermore, it was observed that numerous phenolic structures containing CO and CC bonds were generated on the side chains.Additionally, lignin was observed to migrate from the interior of the cell wall to the surface, causing the enrichment of lignin. It was significantly modified to add functional groups on the surface of fibres. The dissociated fibres were used for the preparation of functional materials and artificial boards.