Study On Influence Of Fe₃O₄@C-SO₃H/Ethanol Combined Pretreatment On Enzymatic Hydrolysis Of Eucalyptus

Considering environmental pollution, food security and energy crisis, more and more researchers were focusing on the production of bioethanol from lignocellulosic biomass now, while the pretreatment of lignocellulose was regarded as a key step for its effective conversion. In this study, mesoporous carbon-based magnetic solid acid catalyst Fe3O4@C-SO3H was prepared and used to replace homogeneous acids in the combined pretreatment of Eucalyptus biomass at 140-180℃ with 50 vol% aqueous ethanol solvent. The pretreated materials were then subjected to enzymatic hydrolysis to produce glucose. The results demonstrated that both the increase of pretreatment temperature and the reduction of the size of Eucalyptus particles benefited the pretreatment of Eucalyptus in ethanol solvent. The addition of solid acid catalyst significantly reduced the temperature requirement for the pretreatment reaction, and gave higher tolerance for lignocellulosic biomass with larger particle size. Simultaneously, slight loss of cellulose part was observed under this combined ptreatment of solid acid and hot-pressed solvent. The material retained 90% of its original cellulose after Fe3O4@C-SO3H/ethanol combined pretreatment at 180℃. Pretreatment reaction with proper catalyst dosage, pretreatment temperature and particle size of biomass could amplify the catalysis performance of solid acids. Under the condition of 50 vol% aqueous ethanol solution, Fe3O4@C-SO3H dosage of 20%, solid-liquid ratio of 1 g:20 mL, temperature of 160℃, time of 60 min, high delignin ratio of 61.71% and dehemicellulose ratio of 52.53% were achieved for Eucalyptus with particle size of 60-200 mesh, respectively. This pretreated material was enzymatic hydrolyzed by cellulase and cellobiase at 50℃, which improved the hydrolysis yield of cellulose from 1.71%(untreated Eucalyptus) to 32.22% after 72 h, and finally provided high hydrolysis yield of 48.07% and glucose yield of 43.55% after 168 h. The hydrolysis yield of cellulose had a significantly positive correlation with the removal of lignin and hemicellulose in Eucalyptus, but was less affected by the crystallinity of cellulose part. The recovery of Fe3O4@C-SO3H catalyst was higher than 80% after pretreatment, while the recovered catalyst showed considerable activity and stability in the second cycle for the pretreatment of Eucalyptus.