Acetylation of wheat straw using simplified procedure and ultrasonic irradiation

Abstract

An investigation of the acetylation of wheat straw with acetic anhydride using a simplified procedure and with or without ultrasonic irradiation was undertaken. The new procedure greatly shortened the reaction time and simplified the chemical recovery. Acetylation weight gains of 15.8% can be achieved in 1 h at 120°C without ultrasound assistance. At the same reaction conditions but with ultrasound assistance at 60°C for 5 min, a weight percent gain (WPG) value of 15.0% was obtained, indicating a slightly negative effect of ultrasonic irradiation on the rate of acetylation without solvents or catalysts. However, a positive sonication effect on the solubility of low molecular materials, mainly extractives, was found in all the cases of the reactions. The characterization of acetylated wheat straw was performed by FTIR, solid-state 13 C-NMR, and thermal studies, which provided evidence for acetylation. The thermal stability of acetylated straw was found to be higher than that of unmodified wheat straw.