(414c) Removing Selective Structural Inorganics from Corn Stover By Type III Deep Eutectic Solvent

High ash biomass contains significant amount structural inorganics (monovalent, divalent and polyvalent metals) which affect the overall biomass quality as a biofuel. Deep Eutectic Solvent (DES) is such a unique solvent that can leach structural inorganics out of biomass during pretreatment and augment in effective mass transfer during downstream conversion. The purpose of this study is to pretreat raw biomass (e.g. Corn Stover High Ash Fraction, obtained from air classification technology) with Type-III DES, i.e. choline chloride and oxalic acid (1:1 molar ratio) and observe the material, chemical and morphological change. The DES, above their eutectic point, are mixed with the raw biomass and shaken for 0.5-6h at 25, 60, 90 and 120 °C in the oil bath. The treated biomasses are vacuum filtered with DI water and confirmed of no residual DES left by conductivity test. Finally, the biomasses are hydrothermally carbonized at three different temperatures (180 ºC, 220 ºC, 260 ºC), characterized through thermogravimetric analysis, scanning electron microscopy (SEM), SEM-energy dispersive x-ray (SEM-EDX) and induced coupled plasma-optical emission spectrometry (ICP-OES, and compared with untreated hydrochars of the same temperatures. It is hypothesized that the DES interacts with the polyvalent metals through softening the lignin-(hemi)-cellulose (LCC) complex as found in Van Soest fiber analysis method and aids in deashing (ash reduction). Overall, the pretreatment could notably improve the preprocessing step for higher biomass conversion process.

Keywords: pretreatment; deep eutectic solvent; hydrothermal carbonization; cellulose; hemicellulose; lignin;