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

Carbon materials produced through the thermal decomposition of biomass (rice hulls) and a polymer (polyvinyl chloride) were investigated by 13C 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 information about the chemical changes in the initial stages of pyrolysis: These are shown to be directly related to the original structure of the precursors and the results complement well some conclusions existent in the literature. From a heat treatment temperature of about 600°C upwards, the general shape of the 13C NMR spectra, attained with low applied magnetic field, is very similar for both chars, with a strong resonance line near 125 ppm from TMS (carbon nuclei in aromatic planes). The analysis of the evolution 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 results are well understood when a comparison is made with the features of the 13C NMR spectrum of polycrystalline graphite.