Effects and Mechanism of Metal Chloride Salts on Pretreatment and Enzymatic Digestibility of Corn Stover

The effects of three metal chlorides including FeCl3, CuCl2, and AlCl3 on corn stover biomass pretreatment and enzymatic hydrolysis were studied under lower severity conditions (reaction temperature of 150-160 degrees C, salt concentration of 0.075-0.125M, and reaction time of 10 min). The results were compared with dilute sulfuric acid pretreatment at the same conditions. The maximum monomeric xylose yields were observed to be 93 and 94 wt % when CuCl2 and FeCl3 were used in the pretreatment at 160 degrees C for 10 min at 0.125 M concentrations, which were higher than the sulfuric acid pretreatment yields at the same reaction conditions. However, monomeric xylose yield for corn stover pretreated with AlCl3 was observed to be 8 wt % at the same condition. This could be explained by isomerization of xylose to xylulose and subsequent dehydration into furfural. However, enzymatic digestibility yields for the three metal chloride pretreated samples at 160 degrees C were greater than 92 wt %. These yields were higher than sulfuric acid pretreated samples at the same reaction conditions. The overall formation of fermentation inhibitor products for samples pretreated with CuCl2 and FeCl3 was observed to be similar to the control samples (pretreated with sulfuric acid at the same conditions).