High temperature thermal degradation of cellulose in air studied using FTIR and 1H and 13C solid-state NMR

Solid-state NMR spectroscopy and Fourier transform IR (FTIR) spectroscopy have been used to study the degradation of cellulose in the form of transformer insulating paper and Whatman filter paper in air at temperatures from 200°C to 550°C for 1 h with and without 0.01 wt.% NaCl, ZnCl2 and CuCl2. The NMR studies included 1H wide line measurements of the spin-lattice relaxation time (T1) and spin-lattice relaxation time in the rotating frame (T1ρ), and 13C magic-angle spinning experiments. The 1H spectra and relaxation times indicated the presence of absorbed water and oxygen in the papers. On degradation, the 1H intensity and line width decreased, indicating the loss of hydrogen nuclei, and the 1H relaxation times decreased due to the formation of paramagnetic species. The 13C-NMR spectra and FTIR spectra indicated the formation of aromatic structures on degradation above 250°C, the conversion being essentially complete at 450°C. The presence of the salts had little or no effect on the rate or mechanism of degradation.