Liquefaction of fermentation residue of reed- and corn stover-pretreated with liquid hot water in the presence of ethanol with aluminum chloride as the catalyst

• Aluminum chloride significantly promotes liquefaction process of fermentation residues.
• Process conditions of liquefaction with aluminum chloride were optimized.
• The products and residues after liquefaction were identified in detail.

Bioethanol fermentation residues of reed- and corn stover-pretreated with liquid hot water were liquefied using aluminum chloride as the main catalyst in the presence of ethanol. Effects of various liquefaction conditions on the liquefied residue content were investigated. Compositions of the liquefaction products were analyzed after being separated into three fractions: water-insoluble fraction, chloroform extract, and remaining product after chloroform extraction. The major component of water-insoluble fraction was lignin. After chloroform extraction, the extracted fractions were mainly esters, phenols, hydrocarbons, and their derivatives, and the residues mainly contained some acids such as levulinic acid, acetic acid, propionic acid and formic acid. It was found that aluminum chloride promoted the liquefaction process significantly in the presence of ethanol, and breakdown of some linkage bonds in lignin of the fermentation residues, such as methoxy group, C–C and C–O, was occurred in the liquefaction process.