Effect of Cellulose Crystallinity on Solid/Liquid Phase Reactions Responsible for the Formation of Carbonaceous Residues during Pyrolysis

This study reports changes in solid phase composition when samples of Avicel cellulose (crystallinity: 60.5%) and ball-milled microcrystalline cellulose (crystallinity: 6.5%) were subjected to pyrolysis in a spoon reactor. Solid state chemistry evolution was examined by hydrolysis-ion exchange chromatography, scanning electron miscroscopy (SEM), Fourier transform infrared (FTIR), and 13C nuclear magnetic resonance (NMR). The liquid reaction intermediate was found to cause particle agglomeration at temperatures below 300 °C. At higher temperatures, the ball-milled cellulose melted completely but the more crystalline cellulose conserved its fibrous structure. The formation of CO and CC groups was accelerated by the presence of liquid intermediates derived from the amorphous cellulose. The content of cross-linked cellulose was quantified by the combined use of acid hydrolysis and 13C NMR. A new reaction mechanism to describe the changes in the solid residue composition at different reaction conditions is proposed.