The Separation and Structure Change of Hemicellulose from Pretreated Wheat Straw by Steam explosion

Pretreatment of wheat straw on steam explosion has been attempted to achieve separation of hemicellulose. Different reaction conditions were explored for pretreatment by varying operating pressure (1.2, 1.4, 1.6, 1.75 and 2.0Mpa) and reaction time (2, 3, 3.5, 5 and 7min), and experiment to find out that pressure was the main factor leading to degree of separation of hemicellulose, the rate of which could achieve almost 90.90%.With further research of structure change of hemicellulose from steam explosed wheat straw, which obtained at 70% volume fraction ethanol by precipitation method. Based on the FT-IR, TGA, ¹H NMR studies, hemicelluloses were degraded very clear and thorough, collected and used in the form of polysaccharides from the steam blasting residual liquid. H_P become unstable structure under the high pressure and time condition of steam explosion, which contrary to H_L. Hemicelluloses from steam explosion pulp had a main structure composed of the (1-4) linked β-d-xylopyranosyl backbone with 4-O-methyl-α-d-glucuronic acid attached to O-2 of the xylose residues, but without arabinofuranosyl attached to O-2 or at both O-2 and O-3, which could be found in structure of HL due to degradation by steam explosion pretreatment.