Decomposition behavior of cellulose in supercritical water, subcritical water, and their combined treatments

A comparative study on decomposition of cellulose between supercritical water (400°C, 40MPa) and subcritical water (280°C, 40MPa) treatments was made to elucidate the difference in their decomposition behavior. Consequently, the supercritical water treatment was found to be more suitable for obtaining high yields of hydrolyzed products. However, cellulose was found to be more liable to fragment under supercritical water treatment, resulting in a decrease in the yield of hydrolyzed products. On the contrary, cellulose was found to be liable to more dehydration in the subcritical water treatment. Based on these results, we have proposed the combined process of short supercritical water treatment followed by subcritical water treatment so as to inhibit fragmentation. Consequently, this combined treatment was able to effectively control the reaction condition, and to increase the yield of hydrolyzed products.