Comparative study of cellulose isolated by totally chlorine-free method from wood and cereal straw

Highly purified cellulose preparations were obtained by pretreatment of dewaxed barley straw, oil palm frond fiber, poplar wood, maize stems, wheat straw, rice straw, and rye straw with 2.0% H2O2 at 45 degrees C and pH 11.6 for 16 h, and sequential purification with 80% acetic acid-70% nitric acid (10/1, v/v) at 120 degrees C for 15 min. The purified cellulose obtained was relatively free of bound hemicelluloses (2.3-3.2%) and lignin (0.4-0.6%) and had a yield of 35.5% from barley straw, 39.6% from oil palm frond fiber, 40.8% from poplar wood, 36.0% from maize stems, 34.1% from wheat straw, 23.40% from rice straw, and 35.8% from rye straw. The weight-average molecular weights of the purified cellulose ranged from 39,030 to 48,380 g/mol. The thermal stability of the purified cellulose was higher than that of the corresponding crude cellulose. In comparison, the isolated crude and purified cellulose samples were also studied by Fourier transform IR and cross-polarization/magic-angle spinning C-13-NMR spectroscopy. (c) 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 322-335, 2005.