Study of Cocoa Pod Husks Thermal Decomposition

Abstract

Thermal decomposition of cocoa pod husks under inert and oxidizing atmospheres was studied. Samples from Cotopaxi, Ecuador were used as raw material. Thermogravimetry based experiments were used to obtain decomposition data vs. temperature. A novel strategy to fit the TG and DTG curves was used giving good fit by considering, in the kinetic model, four biomass fractions following independent reactions. Analytical pyrolysis was used to determine the composition of volatile compounds obtained in slow (150–350, 350–500 °C) and flash pyrolysis (400 °C). The results indicate that in the slow pyrolysis experiments at low temperatures (150–350 °C), the highest area percentages correspond to ketones (7.5%), organic acids (12.5%) and phenolic derivatives (10%), while at increased temperatures (350–500 °C) the higher percentages are clearly focused on phenolic derivatives (12%) and aromatic compounds (10%). Comparing the results of flash pyrolysis at 400 °C (i.e., higher heating rate but lower final temperature), an increase in the yield of ketones and organic acids is observed compared to slow pyrolysis, but the percentage of phenols and aromatics decreases. The results obtained allow deducing the operating conditions to maximize the mass fraction of the different functional groups identified.