Effects of solubility properties of solvents and biomass on biomass pretreatment

• Hildebrand solubility parameter provides information to select a suitable solvent.
• The parameter of the mixture of EMIM-AC and organic solvent was investigated.
• The parameter of the mixture at different lignin contents was investigated.
• The parameter for biomasses is in the ranges of 25.14–26.11.

Hildebrand solubility parameters of biomasses and pretreatment solvents were examined by a method of intrinsic viscosity. This is to be used as basic information in selecting a suitable solvent for biomass pretreatment processes. The effects of mixing1-ethyl-3-methylimidazolium acetate (EMIM-AC) and different solvents, lignin content in a pretreatment solvent, and biomass type on the Hildebrand solubility parameter and thermodynamic properties were carried out and calculated in this work. The Hildebrand solubility parameters of the mixtures are according to those of organic solvents: δH[EMIM-AC/DMA] = 25.07 < δH[EMIM-AC/DMF] = 25.48 < δH[EMIM-AC/DMSO] = 26.10 < δH[EMIM-AC/Ethanolamine] = 26.95. The Hildebrand solubility parameters of biomass compositions (microcrystalline cellulose, xylan and alkali lignin) and biomasses (cassava pulp residue and rice straw) vary in the ranges of 25.14–26.13. The increases of lignin content in the pretreatment solvents lead to the Hildebrand solubility parameter becoming closer to that of lignin.