Acetylation of wheat straw hemicellulose B in a new non-aqueous swelling system

The acetylation of wheat straw hemicellulose B was carried out in a homogeneous N,Ndimethylformamide and lithium chloride system with acetic anhydride using 4dimethylaminopyridine as a catalyst. The degree of substitution of hemicellulose B acetates ranged between 0.59 and 1.25 as a function of experimental conditions. Under an optimum condition (85°C, 60 h), approximately 75% of the free hydroxyl groups in native hemicellulose B were acetylated. The molecular weight measurements (31,890¯ 34,090 g mol-1) showed a controllable degradation of hemicellulose B chains during the reactions at temperature 60¯85°C and duration of 2¯60 h. It was found that the thermal stability of the products was increased by chemical modification.