Mechanism of ketones formation from cellulose liquefaction in sub- and supercritical ethanol

Cornstalk cellulose was liquefied in sub- and supercritical ethanol using an autoclave at 320°C for 60 min. Effects of ethanol dosages on ketones formation from cellulose liquefaction were investigated. The yield of ketones was 1.25% in the absence of ethanol and then increased to 18.38% while adding 160 mL ethanol. Ethanol favored the formation of ketones from cellulose liquefaction. The liquid products at different ethanol dosages were analyzed by FT-IR and GC/MS. The results were shown as follows: Cellulose was converted to active cellulose which was transformed into aliphatic ketones such as 4-hydroxy-4-methyl-2-pentanone by dehydration, decomposition, ring-opening reactions, isomerization and aldol condensation. The alicyclic ketones (cyclopentenone) was formed by the cleavage of C-O-C and C-C bonds of the active cellulose under the effects of ethanol free radicals. Aromatic ketones (2-(formyloxy)-1-phenyl ethanone) were generated by cyclopentenone reaction with intermediates. Aromatic ketones were decomposed to carboxylic acids and small molecule ketones under ethanol free radicals. According to the above results, the reaction network of ketones formed from cellulose in sub- and supercritical ethanol was proposed.