PRETREATMENT OF FURFURAL RESIDUES WITH ALKALINE PEROXIDE TO IMPROVE CELLULOSE HYDROLYSIS. CHARACTERIZATION OF ISOLATED LIGNIN

Abstract

Furfural residues were pretreated with alkaline peroxide (AP) to remove lignin and then hydrolyzed to produce glucose. The maximum glucose yield – of 92.38% – was achieved when the pretreated sample with a lignin removal of 56.7% was hydrolyzed for 120 h at an enzyme loading of 25 FPU/(g cellulose), which was 48.3% higher than that attained from the raw materials. However, the glucose yield decreased when the removal of lignin exceeded 56.7%. The effect of enzyme loading on enzymatic hydrolysis was also investigated. In addition, three AP lignin fractions were successively isolated and comparatively characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, 13 C-nuclear magnetic resonance spectroscopy and thermal analysis. Depolymerization, including destruction of the aromatic skeleton in lignin, and repolymerization of AP lignin occurred during peroxide delignification; however, depolymerisation dominated the reaction, especially at high pretreatment severity. It was also found out that the AP treatment increased the thermal stability of the lignin fractions.