Thermo-catalytic pyrolysis of sawdust by a synthesized NiO/Al2O3 composite catalyst: investigation on its reaction mechanism, kinetics, and thermodynamics

The study reveals the effect of catalysts on the thermal degradation of sawdust where Ni-based catalysts were used (prepared by wetness impregnation method). The catalyst was prepared at 10% and 20% Ni loading onto the alumina-support by impregnating metallic precursor (Ni (NO3)(2).6H(2)O). The prepared catalyst was characterized using various analytical techniques and observed that it was a composite of NiO and Ni(II) aluminates having a particle size in the range of nano scale. Thermo-catalytic degradation analysis of the sawdust was evaluated by varying the catalyst loading (5%, 10%, 15%, and 20% by weight) at a single heating rate (20 K min(-1)) within 303-1173 K temperature. Based on the degradability of the catalyst, the effect of the heating rate was perceived. The Kissinger-Akahira-Sunose (KAS) method was followed to observe the degradation kinetics and thermodynamics at every 5% increase in the conversion beyond the evaporation zone. The use of a catalyst during thermal degradation displayed less variation in the activation energy within 65% conversion compared to the thermal. However, a significant variation in the activation energy was observed within 65-95% conversion. The positive value of Gibb's free energy confirmed the requirement of more energy during thermal compared to catalytic pyrolysis.