Potential of Cellulose After Oxidative Torrefaction for Fuel Enhancement and Utilization: Properties and Pyrolysis Characteristics

This study explored the properties and pyrolysis characteristics of oxidatively torrefied cellulose to enhance biomass utilization and conversion. Cellulose was torrefied at 200–300 °C with oxygen concentrations of 0%–15%. The carbon content in cellulose could reach up to 53.06%, while the oxygen content decreased to 41.53% under the conditions of 300 °C and a 15% oxygen concentration. Meanwhile, its higher heating value (HHV) increased from 15.22 to 16.95 MJ/kg, improving the energy density and fuel quality. Both the carbon yield (CY) and energy yield (EY) of cellulose decreased noticeably with increasing oxygen concentrations at 300 °C, reaching minimum values of 46.33% and 51.05%, respectively, which were lower than the 64.5% and 71.85% observed under non-oxidative torrefaction. FTIR and XRD showed that higher temperatures and oxygen concentrations accelerated cellulose bond breaking and crystallinity disruption, enhancing thermochemical conversion. Oxidative torrefaction lowered the pyrolysis initiation temperature, with the most evident effect occurring at a 5% oxygen concentration of 300 °C. Increased oxygen concentrations altered pyrolysis products, with anhydrosugars rising then falling, and more furans, aromatics, and phenols produced. This study demonstrates that oxidative torrefaction effectively enhances the energy density of cellulose, showing promising potential for biomass utilization as a renewable fuel.