Pyrolysis of cellulose nanofibers: detailed assessment of process kinetics and thermodynamic parameters

Owing to their exceptional properties, such as high mechanical strength, low density, a large number of surface functional groups, excellent optical properties, and sustainability, cellulose nanofibers (CNFs) have piqued the scientific community's interest. This work aims to develop a comprehensive understanding of the pyrolysis behavior of CNFs by analyzing thermal degradation and evaluating the kinetic triplets, which are activation energy (E-alpha), preexponential factor (A), and reaction model. To better understand the effect of surface morphology and surface functionality, three distinct types of CNFs: ionic liquid hydrolyzed (ILCNF), high-speed mechanically sheared (MCNF), and TEMPO-mediated oxidized (TCNF) were studied here. As a result of the presence of carboxylate groups on the surface and a small diameter (average 3.5 nm), TCNF degraded the earliest (T-peak 286 degrees C) and left the most residue (23.2% for 2 degrees C/min). The average E-alpha and lnA for ILCNF, MCNF, and TCNF were 192.75, 192.68, 149.81 kJ/mol, and 34, 32.4, and 25.6, respectively. The master plots revealed that all CNFs adhere to the random scission model. The evaluated kinetics triplets were used to reconstruct the rate of reaction, which ultimately validated the estimated kinetic triplets via the superior regression coefficient ( R-2 0.964-0.993) for all CNFs at all heating rates. Further, the thermodynamics parameters were evaluated and analyzed to understand the nature of the pyrolysis process. The low potential barrier of 4.9 kJ/mol facilitated the production of pyrolysis products. This research can be used to create products for resource remediation and alternative energy by pyrolyzing waste CNFs.