Treatment and characterization of biomass of soybean and rice hulls using ionic liquids for the liberation of fermentable sugars

Abstract We investigated the changes in the physical structure of cellulose recovered from soybean and rice hulls treated with the ionic liquids 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) and 1-butyl-3-methylimidazolium acetate ([bmim][Ac]). The characterization was carried out by a combination of thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Regenerated cellulose from soybean hull showed loss of crystallinity and high structural disruption caused by both ionic liquid treatments as compared to the untreated material. In contrast, rice hull presented only a small structural disruption when treated with [bmim][Ac] and was practically unaffected by [bmim][Cl], showing that this biomass residue is recalcitrance towards physico-chemical treatments, possibly as a consequence of its high composition content in silica. These results suggest the use of soybean hull as a substrate to be treated with ionic liquids in the preparation of lignocellulosic hydrolysates to be used in second-generation ethanol production, whereas other methods should be considered to treat rice hull biomass.

摘要：本研究探究了经离子液体（ionic liquids）1-丁基-3-甲基咪唑氯盐([bmim][Cl])与1-丁基-3-甲基咪唑醋酸盐([bmim][Ac])处理后，从大豆壳和稻壳中回收的纤维素的物理结构变化。本研究采用热重分析（thermogravimetric analysis, TGA）、傅里叶变换红外光谱（Fourier transform infrared spectroscopy, FTIR）、X射线衍射（X-ray diffraction, XRD）以及扫描电子显微镜（scanning electron microscopy, SEM）相结合的方法完成表征。相较于未处理原料，经两种离子液体处理后的大豆壳再生纤维素均出现结晶度损失与严重结构破坏。与之相反，稻壳经[bmim][Ac]处理后仅出现轻微结构破坏，经[bmim][Cl]处理后几乎未受影响，表明该生物质残渣对物理化学处理具有抗降解性，这可能源于其较高的二氧化硅组分含量。上述结果表明，大豆壳可作为经离子液体处理的底物，用于制备木质纤维素水解液（lignocellulosic hydrolysates）以生产第二代乙醇；而稻壳生物质的处理则需考虑采用其他方法。