Red Sea seaweed (Sargassum spp.) pyrolysis and its devolatilization kinetics

Sargassumspp. of Red Sea originwas investigated using thermogravimetric analysis (TGA) to study the kinetics of pyrolysis. Dried Sargassumspp. sampleswere non-isothermally heated at 10, 15, 20 and 25 degrees C center dot min(-1) from40 to 900 degrees C in an inert atmosphere. The differential thermogravimetric analysis (DTG) showed three distinct zones of vaporization and degradation. In the active pyrolysis zone, amass loss of 65-70% was recorded in a temperature range of 480-950 K. Friedman, Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Starink methods were used to calculate the apparent activation energies (E-a) from 10% to 90% conversion. The calculated Eawas observed to exponentially increase with increasing conversion. The kinetic analysis indicates that the pyrolysis of Sargassum spp. can be kinetically described as five independent parallel reactions. These five independent reactions correspond to five pseudo-components (water, hemicellulose, cellulose, lignin/protein and biochar). The degradations of the pseudo-components were obtained by deconvoluting the peaks in the DTG curves. The apparent Ea values of the pseudo-components were calculated fromKissinger'smethod using the peak maximum temperature (T-m). T-m increased with the increasing heating rate. Cellulose degradation had the highest apparent Ea among the components. Cellulose and hemicellulose had the fastest degradation rate during the pyrolysis, whereas lignin and protein had the slowest rate, which implies that lignin and protein degradation was rate-limiting and most difficult to obtain. (C) 2016 Elsevier B. V. All rights reserved.