Investigation of organosolv and hot-compressed water pretreatments of rice straw

Abstract

Ethanol organosolv pretreatments followed by hot-compressed water pretreatments of rice straw have been investigated. The formation of monomeric and oligomeric sugar productions, degradation products, and soluble lignin in liquid fraction was analyzed. A solid to liquid ratio of 1:10 (w/w) was used for pretreatments. The organosolv pretreatment was carried out at the temperatures (170, 190, 210 °C) for (0, 30, and 60 min). Hot-compressed water pretreatment was performed at 220 °C for 15 min starting from dried solid residues recovered from organosolv pretreatments. The highest amount of dissolved lignin and xylan (oligosaccharides) in liquor was 64.6 mg/g and 0.07 % at 190 °C for 60 min, respectively. The production of sugar and dissolved lignin in liquor in hot-compressed water pretreatment was decreased with increase temperature and time, but degradation products increased. The crystallinity index of untreated and treated rice straws was calculated based on X-ray diffraction (XRD) data. The structural feature of untreated and treated rice straws was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM).