Catalytic Pyrolysis Using a Nickel-Functionalized Chemically Activated Biochar Catalyst: Insight into Process Kinetics, Products, and Mechanism

The present study highlighted the impact of biochar (BC)-based catalysts on catalytic pyrolysis of pine needle biomass. Thermogravimetric plots showed positive influence of catalysts by indicating reduction in the temperature requirement of the process. The same had also been stated through process kinetics by demonstrating reduction in the process’s activation energy (Ea). Ea had been reduced from 25.95 kJ/mol in noncatalytic pyrolysis to 20.79, 15.20, 10.52, 13.99, and 9.69 kJ/mol for BC, Ni/BC, Ni/BC-ZnCl2, Ni/BC-H3PO4, and Ni/BC-NaOH catalytic pyrolysis, respectively. Physicochemical characteristics of bio-oil indicated improvement in its high heating value and % deoxygenation achieved during the process. Catalyst incorporation in the process increased the production of phenols as well as aliphatic and aromatic hydrocarbons. The presence of surface acidic functionalities coupled with metallic sites in Ni/BC-ZnCl2, Ni/BC-H3PO4, and Ni/BC-NaOH increased the aromatics selectivity to 35.18, 36.47, and 35.64%, respectively. Similarly, aliphatics were also enhanced to 9.61, 10.12, and 11.68% using Ni/BC-ZnCl2, Ni/BC-H3PO4, and Ni/BC-NaOH, respectively. Also, chemically activated catalysts showed high stability toward deactivation. Thus, low-cost BC-based catalysts can be effectively employed in place of currently utilized high-cost catalysts in the catalytic pyrolysis process, which will help to make the process more integrated and closed-loop.