Isolation and cationization of hemicelluloses from pre-hydrolysis liquor of kraft-based dissolving pulp production process

Hemicelluloses are the main organics dissolved in the pre-hydrolysis liquor (PHL) of the kraft-based dissolving pulp production process. In this study, two methods were employed to isolate the hemicelluloses from industrial PHL samples. The results showed that the hemicelluloses, precipitated in ethanol after an acidification step (Method 2), had a very high brightness (83% ISO) and low lignin content (0.44%) compared with the hemicelluloses obtained by the direct precipitation in ethanol without the acidification (Method 1), which had a brightness of 17.2% ISO and a lignin content of 5.67%. Furthermore, the hemicelluloses isolated via Method 2 were rendered cationic by using glycidyltrimethylammonium chloride (GTMAC), and the process parameters for the cationization reaction were studied, including the water content, reaction temperature and time, molar ratio of GTMAC/hemicelluloses, and the sodium hydroxide dosage. The optimized conditions for the cationic modification were 35% water content, 5% sodium hydroxide (both based on the mass of hemicelluloses), 1 (mol) GTMAC/hemicelluloses ratio, 65 °C, and 4 h reaction time. Finally, the cationic hemicelluloses were characterized and compared with unmodified hemicelluloses using the FT-IR and NMR analyses.