Title
Continuous activation energy representation of the Arrhenius equation for the pyrolysis of cellulosic materials: Feed corn stover and cocoa shell biomass
Authors
ABHISHEK S. PATNAIK and JILLIAN L. GOLDFARB

Received January 22, 2015
Published Volume 50 Issue 2 February
Keywords Arrhenius equation, biomass pyrolysis, evolved compounds, activation energy

Abstract
Kinetics of lignocellulosic biomass pyrolysis – a pathway for conversion to renewable fuels/chemicals – is transient; discreet changes in reaction rate occur as biomass composition changes over time. There are regimes where activation energy computed via first order Arrhenius function yields a negative value due to a decreasing mass loss rate; this behavior is often neglected in the literature where analyses focus solely on the positive regimes. To probe this behavior feed corn stover and cocoa shells were pyrolyzed at 10K/min. The activation energies calculated for regimes with positive apparent activation energy for feed corn stover were between 15.3 to 63.2 kJ/mol and for cocoa shell from 39.9to 89.4 kJ/mol. The regimes with a positive slope (a “negative” activation energy) correlate with evolved concentration of CH4 and C2H2. Given the endothermic nature of pyrolysis, the process is not spontaneous, but the “negative” activation energies represent a decreased devolatilization rate corresponding to the transport of gases from the sample surface.