Optimal conditions for hemicellulose extraction from wooden biomass in a semi-continuous system have been assessed in this work. This study would constitute the first stage for a profitable and green industrial process. Eucalyptus globulus was selected as raw material due to its low water consumption, high growth and its efficiency in lignocellulose production.
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Moreover its cultivation is very popular in southern Europe. Samples of 5.0 g of wood were fractioned using a pressurized hot water semi-continuous system, to produce sugars (pentoses and hexoses) and a solid residue enriched in lignin.
Five flow rates between 2.50 and 20.00 mL/min and four temperatures between 135.0 and 285.0 °C were tested in order to maximize the production of sugars, avoiding the formation of degradation products.
Optimum conditions for the extraction of hemicellulose were identified at 185.0 °C and 5.00 mL/min, leading to a pentoses yield of 67.409 wt%, with 0.702 wt% of degradation products. Almost all the pulp is extracted at 285.0 °C.
SEM images show very well the changes in the wood structure at different temperatures.
A kinetic model was developed, describing the extraction and hydrolysis of hemicellulose and cellulose with absolute average deviations around 10% for sugar extracted mass.