Enhanced Bio-oil Yield from Liquefaction of Cornstalk in Sub- and Supercritical Ethanol by Acid-Chlorite Pretreatment

Acid chlorite pretreatment was developed to enhance bio-oil yield and decrease the optimum reaction temperature of cornstalk liquefaction in a stainless steel reactor (0.5 L) at temperatures of 200-340 degrees C. The effects of liquefaction temperature and ethanol amount on the bio-oil yield from liquefaction of cornstalk before and after pretreatment were investigated. The results showed that the pretreatment could markedly enhance the bio-oil yield and decrease the optimum temperature. The highest bio-oil yield (31.4%) was obtained from the liquefaction at the reaction temperature of 260 degrees C from the 1.5 h pretreated cornstalk. Unpretreated and pretreated cornstalks differed in chemical components, in which the add chlorite pretreatment increased carbohydrate content and removed some amount of lignin. Scanning electron microscopy showed that the pretreated cornstalks had extensive anomalous porosity and lamellar structures. X-ray analysis showed that this pretreatment process was unable to break apart inter- and intrachain hydrogen bonding in cellulose fibrils. GC/MS analysis showed that the pretreatment had an important effect on the formation of various compounds in the bio-oil.