Thermogravimetric analysis and analytical pyrolysis of a variety of lignocellulosic sorghum

• The thermal decomposition of a variety of lignocellulosic sorghum was investigated.
• The kinetics indicated the occurrence of three reactions with different kinetics.
• Py-GC/MS tests were performed in a temperature range employed in fast pyrolysis.
• The temperature did not significantly affect the composition of the main components.
• The tests indicate a bio-oil of good quality compared with other types of sorghum.

Global economic growth and the deep concerns for human quality of life make it imperative to discover new technologies for generating renewable energy. Lignocellulosic biomass can be used as an alternative for energy production via thermochemical conversion processes such as pyrolysis. The constitution of each material causes it to display a particular characteristic when pyrolyzed, due to the proportion of its components. Hence, its characterization is very important to gain a better understanding of the pyrolysis process. This work involved the characterization and study of the thermal decomposition of a variety of lignocellulosic sorghum. Knowledge of the kinetics of pyrolysis was deepened by studying the decomposition of sorghum based on thermogravimetric analysis, using nitrogen as the purge gas at a flow rate of 30 mL/min. Analytical pyrolysis tests of this biomass were also performed in a temperature range normally employed in fast pyrolysis (823 and 923 K), using an inert helium atmosphere. The estimated values of activation energy ranged from 70.3 to 210 kJ mol−1 and the pre-exponential factors showed results varying from 7.0 × 104 mol−2 l2 s−1 to 5.0 × 1016 s−1. The experimental derivative weight loss curves revealed the predominant presence of two major peaks at all the heating rates, the first corresponding mainly to hemicellulose decomposition and the second to cellulose decomposition. The change in temperature did not significantly influence the percentage area of the main detected components: 2-methyl-1,3-butadiene, acetic acid, limonene, and hexadecane, indicating a bio-oil of good quality (high amount of non-oxygenated compounds) compared with other types of sorghum.

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