Changes in the chemical composition of black locust wood after hot-water pretreatment before bioethanol production
2016
Kačík František | Ďurkovič Jaroslav | Kačíková Danica | Zenková Eva
Bioethanol produced from various lignocellulosics, mainly wood, have the potential to be a valuable substitute for gasoline. The initial step in this process is a pretreatment to remove hemicelluloses, break down the lignin structure and make the cellulose accessible to hydrolysis for conversion to fuels.Hot-water pretreatment is one of the most promising technologies due to that no additional chemicals are required. In this paper, we present changes in the chemical composition of Robinia pseudoacacia wood as well as the amounts of carbohydrates in the solids after hot-water pretreatment at 180°C during 5, 10, 20, 30 and 50 minutes. Main wood components were determined by wet chemistry methods, whereas saccharides were analysed by high-performance liquid chromatography according to the National Renewable Energy Laboratory (NREL) analytical procedure.Hot-water pretreatment of black locust wood resulted in increased contents of both cellulose and extractives, and a decrease in the amounts of lignin, holocellulose and hemicelluloses. The amount of holocellulose decreased during pretreatment, especially at the beginning of the process because the content of hemicelluloses diminished rapidly. In the first stage of experiment (5 min), approximately 65% of hemicelluloses were released from black locust wood, and only 20% of hemicelluloses remained in the solid at the end of pretreatment (50 min). We have found that optimum time for black locust wood hot-water pretreatment at 180°C is 20 minutes.
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