Abstract
The pretreatment and saccharification processes are both the bottlenecks of lignocellulose bioconversion. Pretreatment plays an important role in the saccharification efficiency. In this paper, ethanol-assisted FeCl3 pretreatment was developed to reduce lignocellulose resistance and to enhance the hydrolysis efficiency. The effect of various pretreatment conditions, such as the concentration of FeCl3 and ethanol, pretreatment temperature and time, on the chemical compositions and physical structures of lignocellulose were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier infrared spectrum (FTIR). The increase in the concentration of FeCl3 and ethanol could both boost the degradation of hemicellulose and delignification, respectively. The optimized conditions were obtained, i.e. the concentration of FeCl3 is 0.1 mol/L, the concentration of ethanol is 60 % (v/v), 120 °C and 60 min. The ratio of cellulose conversion at solid loading of 10 % after pretreatment under the optimized conditions reached 96.8 %. And we found that the solution of FeCl3 provided significantly acidic environment, which promoted the degradation of hemicellulose when the pH reached a certain degree (pH 2.5). The iron ions could be absorbed by the pyran ring of carbohydrate to form complex, which may trigger the degradation of carbohydrates and delignification. Our work suggested that the ethanol-assisted FeCl3 pretreatment was very competitive for biomass bioconversion.
