Esterification of Hemicelluloses from Poplar Chips in Homogenous Solution ofN, N- Dimethylformamide/Lithium Chloride

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Abstract
Hemicelluloses, extracted from the delignified poplar chips with 8.0% NaOH-1.0% Na2B4O7-10H2O, were esterified with various acyl chlorides in the homogeneous N,N-dimethylformamide/lithium chloride system. Comparative reactions were performed with different molar ratios of acyl chloride/anhydroxylose, different concentrations of triethylamine, various reaction times, and reaction temperatures between 45°C and 75°C. The degree of substitution was controlled between 0.32 and 1.51. Under optimum conditions (sample 8, molar ratio 3:1, TEA% 280), over 75% of the hydroxyl groups in native hemicelluloses were stearoylated. The preparations were characterized by FT-IR and GPC techniques as well as their solubilities in various organic solvents. The molecular weight measurements showed minimal degradation of the hemicelluloses during the rapid reactions at 45-75° C for 30-45 min.