Esterification of hemicelluloses from poplar chips in homogenous solution of N,N-dimethylformamide/lithium chloride

Hemicelluloses, extracted from the delignified poplar chips with 8.0% NaOH- 1.0% Na2B4O7. 10H(2)O, were esterified with various acyl chlorides in the h omogeneous N,N-dimethylformamide/lithium chloride system. Comparative react ions were performed with different molar ratios of acyl chloride/anhydroxyl ose, different concentrations of triethylamine, various reaction times, and reaction temperatures between 45 degrees C and 75 degrees C. The degree of substitution was controlled between 0.32 and 1.51. Under optimum condition s (sample 8, molar ratio 3.1, TEA% 280), over 75% of the hydroxyl groups in native hemicelluloses were stearoylated. The preparations were characteriz ed by FT-IR and GPC techniques as well as their solubilities in various org anic solvents. The molecular weight measurements showed minimal degradation of the hemicelluloses during the rapid reactions at 45-75 degrees C for 30 -45 min.