Insight into the dissolution behaviour and rheological characterisation of lignin in 1-butyl-3-methylimidazole bisulphate-ethanol system.

Lignin dissolution and the fluid behaviour of reaction systems play important roles in the conversion rate of lignin. This study investigated the solubility of enzymatic hydrolysis lignin (EHL) in 1-butyl-3-methylimidazole bisulphate ethanol solutions ([BMIM]HSO₄/ethanol) and the dynamic shear rheological characterisation of EHL-[BMIM]HSO₄/ethanol. Different with [BMIM]HSO₄/water, [BMIM]HSO₄/ethanol exhibited excellent abilities to dissolve EHL at [BMIM]HSO₄% 20%–90%, with the maximum EHL solubility obtained at 40%–70%. The dynamic shear rheological characterisation strongly depended on temperatures, [BMIM]HSO₄% and EHL%, exhibited as pseudoplastic fluid at higher [BMIM]HSO₄% and EHL%, and Dilatant fluid at lower [BMIM]HSO₄% and EHL%. Adjusting an appropriate [BMIM]HSO₄% and EHL%, EHL-[BMIM]HSO₄/ethanol was Newtonian fluid with the viscosity stable. EHL was regenerated from EHL-[BMIM]HSO₄/ethanol without obvious changes in the chemical structure and thermal behaviour. This study provided ideas for the design of the [BMIM]HSO₄/ethanol system and the optimisation of conversion processes for the economic utilisation of lignin. [ABSTRACT FROM AUTHOR]