Resolving the Kinetic Parameters of Cellulose Pyrolysis

Biomass pyrolysis is an emerging technology used to convert renewable resources into energy, biofuels and chemicals. The gaseous, liquid, and char products are alternatives to conventional resources and contribute less greenhouse gases to the environment. Thus, there has been great interest in research on the kinetic mechanisms governing biomass pyrolysis, much having been performed using thermal gravimetric analysis (TGA). Nonetheless, the actual kinetic parameters for biomass pyrolysis, such as activation energies, are still vigorously debated. Among the most contentious issues is heating rate effects and activation energy invariance as a function of the same. Our hypothesis is, in fact, the opposite; the kinetic parameters for cellulose pyrolysis are a function of heating rate. To test this hypothesis, cellulose pyrolysis data was collected from four TGA experiments run at heating rates of 1, 10, 50, and 150 K/min. Three methods were then utilized to extract kinetic parameters: (1) linear regression of single heating rates, (2) co-regression of multiple heating rates, and (3) application of an isoconversional kinetic analysis. The collective outcomes suggests that activation energy appears to depend on the heating rate since the activation energy for higher heating rates is significantly different from those of lower heating rates. Due to this finding, co-regression methods could not produce reliable or accurate results. Surprisingly, isoconversional methods produce parameters that are inconsistent with single heating rate analysis, and remains a yet unresolved issue.