Investigation of biomass- and polymer-based carbon materials using C-13 high-resolution solid-state NMR

Carbon materials produced through the thermal decomposition of biomass (ric e hulls) and a polymer (polyvinyl chloride) were investigated by C-13 high- resolution solid-state NMR under two different magnetic fields (2.0 and 9.4 T). The details revealed by the high-field NMR spectra provide important i nformation about the chemical changes in the initial stages of pyrolysis: T hese are shown to be directly related to the original structure of the prec ursors and the results: complement well some conclusions existent in the li terature. From a heat treatment temperature of about 600 degreesC upwards, the general shape of the C-13 NMR spectra, attained with low applied magnet ic field, is very similar fur both chars, with a strong resonance line near 125 ppm from TMS (carbon nuclei in aromatic planes). The analysis of the e volution of the main parameters associated with this resonance line shows a behavior typical of heat-treated carbon materials, which is interpreted on the basis of the structural evolution of both chars. We show that the resu lts are well understood when a comparison is made with the features of the C-13 NMR spectrum of polycrystalline graphite. (C) 2001 Elsevier Science Lt d. All rights reserved.