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 homogen eous N,N-dimethylformamide and lithium chloride system with acetic anhydrid e using 4-dimethylaminopyridine as a catalyst. The degree of substitution o f hemicellulose B acetates ranged between 0.59 and 1.25 as a function of ex perimental conditions. Under an optimum condition (85 degrees C, 60 h), app roximately 75% of the free hydroxyl groups in native hemicellulose B were a cetylated. The molecular weight measurements (31,890-34,090 g mol(-1)) show ed a controllable degradation of hemicellulose B chains during the reaction s at temperature 60-85 degrees C and duration of 2-60 h. It was found that the thermal stability of the products was increased by chemical modificatio n. (C) 2000 Elsevier Science Ltd. All rights reserved.