Comparative studies of hemicelluloses solubilized during the treatments ofmaize stems with peroxymonosulfuric acid, peroxyformic acid, peracetic acid, and hydrogen peroxide Part 2. Spectroscopic and thermal characterizations

Ten hemicellulosic preparations, obtained by treatments of the water-extrac ted maize stems with peroxymonosulfuric acid, peroxyformic acid, peracetic acid, and 2 % hydrogen peroxide under the conditions given, respectively, w ere investigated by gel permeation chromatography and spectroscopic techniq ues such as Fourier transform infrared and carbon-13 nuclear magnetic reson ance. Under an optimum extracting condition (2% H2O2, 45 degrees C, 12 h, p H 11.5-12.0), the hemicelluloses obtained represented 63.3-64.7 % of the or iginal hemicelluloses and had high weight-average molar mass between 69060 and 54740 g mol(-1). The most obvious feature was found that the alkaline p eroxide treatment of the stems under the conditions used did not affect the overall structure of the hemicelluloses. The thermal stability of the hemi celluloses was found to increase slightly with increasing molar mass. All t he hemicellulosic preparations were. however. to varying degree thermally u nstable at temperature above 180 degrees C.