Thermo-catalytic decomposition of walnut shells waste over cobalt doped cerium oxide: Impact of catalyst on kinetic parameters and composition of bio-oil

This research work is aimed at investigating the pyrolysis of walnut shells mixed with cobalt doped cerium oxide and non-catalytic pyrolysis of walnut shells. The pyrolysis experiments were performed in a locally designed pyrolysis chamber. The oils from catalytic and non-catalytic pyrolysis were characterized with GC-MS. It was found that in case of catalytic pyrolysis, the bio-oil obtained has several short-chain compounds as compared to bio-oil obtained through non-catalytic pyrolysis. Thermogravimetric analysis was conducted to assess the kinetics of pyrolysis of biomass both with and without catalyst. The kinetic parameters were determined using Kissinger equation. The activation energy (Ea) values for the decomposition of hemicelluloses, cellulose, and lignin were found as 167.72, 181.35, and 191.22 kJ mol-1 for non-catalytic pyrolysis and 107.48, 121.79, and 137.57 kJ mol -1 for catalytic pyrolysis. Moreover, the optimum temperature of pyrolysis was effectively reduced to 410 degrees C employing a catalyst, as opposed to the maximum temperature of 430 degrees C in the case of non-catalytic pyrolysis. Keeping in view the reduction in activation energy and improvement in quality of oil from catalyzed reaction in presence of cobalt doped cerium oxide, it can be concluded that the findings of this study can contribute to the development of a process for sustainable utilization of walnut shells as energy source.