Hemicelluloses extraction from Eucalyptus sp. sawdust by hydrothermal treatment

RANGEL, J.; HORNUS, M.; FELISSIA, F.; AREA, M.C.

Colonia del Sacramento

Congreso; 6th International Colloquium on Eucalyptus Pulp (6th ICEP); 2013

ICEP

The eucalyptus sawdust is the main waste of the primary processing of wood, being usually burned as it is. The objective of this work is to optimize the conditions of hydrothermal pretreatment of eucalyptus sawdust for hemicelluloses extraction. This treatment also removes water-soluble substances, obtaining a solid fraction consisting of cellulose and lignin, which follow other separation processes for their use. The sawdust was the waste of a sawmill and carpentry, which processes 12-50 years-old Eucalyptus rostrata, grandis, and saligina. A factorial design was initially applied to verify the influence of the time of treatment (30, 45 and 60 min), temperature (120, 150 and 180°C) and liquid / solid ratio (5, 10, 15). This last variable was not significant. A Central Composite Face-Centered Design was used for the optimization, varying time (20, 30 and 40 min) and temperature (170, 180 and 190°C). Treatments were performed in 200mL digesters in glycerin bath. The chemical characterization was performed according to LAP's National Renewable Energy Laboratory (NREL) standards. The best point obtained was validated with a change of scale using a 4.6 L digester. The temperature was the most influential factor on the autohydrolysis pretreatment of sawdust. The higher extraction of hemicelluloses (89% of initial hemicelluloses) was obtained at 190°C and 20 min, but when the intention was to minimize the generation of furfural by optimizing multiple responses, the best condition was found to be 180°C and 20 min. The response surface showed that similar results could be achieved at 170°C, extending the treatment time to 50 min.