ISOLATION OF HEMICELLULSOES FROM THE PRE-HYDROLYSIS OF KRAFT PULPING METHOD USING TWO ALTERNATIVE APPROACHES

摘要

Hemicelluloses are the raw materials for the production of various value-added products. In this work, the isolation of hemicelluloses from the prehydrolysis liquor (PHL) of the kraft-based dissolving pulp production process was evaluated in two alternative pathways. In one method, PHL was first acidified to a pH of 2 for removing lignin, and then hemicelluloses were isolated using ethanol with a ratio of 4:1 (v/v). It was found that the hemicelluloses and lignin contents of the isolated hemicelluloses samples were 86.25% and 0.44%, respectively, which confirmed the high selectivity of this method for isolating hemicelluloses. Additionally, xylose/xylan was the predominant sugar component (46.7%) of the hemicelluloses isolated. In another method, ethanol was directly applied to PHL for isolating hemicelluloses. Then, different ECF bleaching steps were applied on the isolated hemicelluloses to further purify the hemicelluloses isolated. It was evident that the hemicelluloses content was about 81% of the total solid, while the lignin content is about 5%. Furthermore, the hemicelluloses content, and the lignin content were reduced in each stage of the subsequent bleaching process.