Hydrolysis of Japanese beech by batch and semi-flow water under subcritical temperatures and pressures

Hydrolysis of lignocellulosic biomass by hot-compressed water is creating an opportunity to obtain saccharides from both hemicelluloses and cellulose for biofuel production as well as saccharides production. In this work, the hydrolysis of Japanese beech (Fagus crenata) by batch and semi-flow hot-compressed water was investigated. After the treatments, the monosaccharides, oligosaccharides and decomposition products in water-soluble portion were determined, while the structural variation as well as chemical composition of residue was analyzed. The results demonstrated that the production of total saccharides increased with the temperature for both batch and semi-flow hot-compressed water treatments. The maximum yield of total saccharides was achieved at 250 °C when treated by semi-flow hot-compressed water, which was higher than the corresponding maximum production of saccharides obtained at 190 °C when treated by batch hot-compressed water. The xylooligosaccharides which came from hemicelluloses were produced until the temperature was higher than 230 °C when treated by batch hot-compressed water, while they were produced until 270 °C when treated by semi-flow hot-compressed water. On the other hand, the cellooligosaccharides which came from cellulose began to produce from 170 °C when treated by batch hot-compressed water, while they were not produced below 210 °C when treated by semi-flow hot-compressed water. In conclusion, both batch and semi-flow hot-compressed water can be used to hydrolyze hemicelluloses though at different optimal temperature, while semi-flow hot-compressed water was better than batch hot-compressed water for hydrolysis of cellulose.