Kinetic study of the extraction of hemicellulosic carbohydrates from sugarcane bagasse by hot water treatment

MARÍA EVANGELINA VALLEJOS; FERNANDO ESTEBAN FELISSIA; JULIA KRUYENISKI; MARÍA CRISTINA AREA

Industrial Crops and Products

ELSEVIER SCIENCE BV

Año: 2014

0926-6690

Sugarcane bagasse is a lignocellulosic agro-industrial waste, which is usually burned in the sugar andbio-ethanol mills to produce heat and electricity. This work presents the kinetic study of the carbohy-drates extracted from the mild hot water pretreatment of sugarcane bagasse, to explain the variation ofhemicellulosic carbohydrates during the treatment. This could allow the selection of optimum conditionsto obtain the desired products in spent liquors, as high concentration of xylans and low concentrationsof fermentation inhibitors. Sugarcane bagasse was hydrothermally treated under isothermal conditionsat 160, 170, and 180◦C, using a liquid to solid ratio of 14:1. Glucans, xylans, arabans, xylose, glucose,arabinose, acetic acid, formic acid, HMF and furfural were first identified in the spent liquor. A kineticmodel was applied, considering the direct extraction of xylose and oligomers from the solid, xylose pro-duction from the oligomers, and furfural generation from xylose. It was supposed that the reaction rateconstants have first-order kinetics. The fractionation by hydrothermal treatment has proven to be effec-tive for hemicelluloses removal. Most glucans were retained in the solid, and a partial delignification (at180◦C, 9.8% and 36.3% of the initial lignin at 20 and 240 min, respectively) was achieved. The maximumconcentration of xylans in spent liquors with the low furfural content (0.5% on oven dry bagasse) wasachieved at 180◦C and 20 min of treatment (17.6% on oven dry bagasse, about 74% of the initial amount).An activation energy of 128.8 kJ mol−1has been obtained for the fast hydrolysis of xylans from sugar canebagasse. The maximal concentration of xylans + xylose in liquors was obtained with a P-factor of 800.