On the effects of CO2 atmosphere in the pyrolysis of Salicornia bigelovii

Abstract

This study focuses on understanding the effects of a CO$_2$ atmosphere on the pyrolysis of $\textit{Salicornia bigelovii}$ by performing a detailed kinetic analysis and investigating the pyrolysis products. In comparison to N$_2$ pyrolysis, CO$_2$ pyrolysis increased the amounts of acids, phenols, amines/amides and N-aromatics in the bio-oil. Biochar showed a 6.5% increase in carbon and a 5.8% decrease in oxygen due to the presence of CO$_2$ in the pyrolysis atmosphere. CO$_2$ also inhibited the volatilization of certain functional groups, such as phenols, tertiary alcohols and aromatics from the biochar, and the surface area of the biochar was 12 times larger than pyrolysis in N$_2$ atmosphere. Pyrolysis in CO$_2$ led to an increase in the average apparent activation energy from 146.5 kJ mol$^{−1}$ in N$_2$ to 163.4 kJ mol$^{−1}$. The kinetic equation was found to conform to a three dimensional diffusion mechanism. Finally, the pre-exponential factor was determined for each reaction.