Corn stover pretreatment by inorganic salts and its effects on hemicellulose and cellulose degradation

Inorganic salts, NaCl, KCl, CaCl2, MgCl2, FeCl2, FeSO4, FeCl3, and Fe2(SO4)3, were studied as catalysts for the degradation of hemicellulose in corn stover. FeCl3 significantly increased the hemicellulose degradation in aqueous solutions heated between 140 and 200 °C with high xylose recovery and low cellulose removal, amounting to ∼90% and <10%, respectively. Hemicellulose removal increased 11-fold when the corn stover was pretreated with 0.1 M FeCl3 compared to pretreatment with hot water under otherwise the same conditions, which was also 6-fold greater than pretreatment with dilute sulfuric acid at the same pH. Optimum pretreatment conditions were found where the corn stover was pretreated with 0.1 M FeCl3 at 140 °C for 20 min. Under such conditions, 91% of hemicellulose was removed, and the recovery of monomeric and oligomeric xylose in liquid fraction achieved 89%, meanwhile, only 9% of cellulose was removed.