Effective Phase Separation of Biomass Pyrolysis Oils by Adding Aqueous Salt Solutions

Effective separation methods must be developed to generate fractions of similar polarity and to concentrate the undistillable compounds before bio-oils are to be a source of chemicals production. Phase separation is one effective pathway to realize initial separation of bio-oil. By adding a little salt (3 wt % of bio-oil) or aqueous salt solution (10 wt % of bio-oil) including LiCl, CaCl2, FeCl3, (NH4)SO4, K2CO3, and Fe(NO3)(3), the pyrolysis bio-oil of rice husk would quickly form two phases (40-80 wt % of the upper phase, 20-60 wt % of the bottom phase). On the basis of elemental analysis, C-13 NMR integrations and GC/MS analysis, it has been demonstrated that some major components in the bio-oil are concentrated in upper/bottom phases respectively. The upper layers exhibit high contents of water, acetic acid, and water-soluble compounds; low density, viscosity, and calorific values; and high distillable substances (up to 65%). The bottom layer consists of low water content, high lignin-pyrolysis compounds, and low distillable substances (< 10%), with high viscosity and calorific values. The physiochemical properties of two phases from the phase separation depend on the nature and dosage of salt added.