Enhanced CO₂ Methanation over Nickel‐Based Unsupported Catalyst Synthesized by Chemical Precipitation Method

This study investigated the catalytic CO 2 methanation using nickel oxide (NiO) nanoparticles and nickel oxalate (NiC 2 O 4 ) as catalysts. The NiC 2 O 4 precursor was synthesized through a chemical precipitation reaction between nickel (II) nitrate hexahydrate (Ni(NO 3 ) 2 .6H 2 O) and oxalic acid (H 2 C 2 O 4 .2H 2 O). Nickel oxide (NiO) nanoparticles were synthesized through thermal decomposition of NiC 2 O 4 precursor at 450 °C in air. The samples were characterized by XRD, FTIR, BET, SEM, and EDX. The XRD and FTIR analyses revealed that the NiO nanoparticles were well‐crystallized having size 17.30 nm. The BET analysis of the NiO sample revealed mesoporous NiO nanoparticles with a specific surface area (S BET ) of 29.08 m 2 /g and a narrow distribution of pore sizes. The catalytic performance of NiO and NiC 2 O 4 catalysts studied for the CO 2 methanation in tubular packed bed reactor at 150–550 °C and 1 atm. The reduced NiO nanoparticles exhibited more catalytic activity than the decomposed NiC 2 O 4 catalyst. At 380 °C, 1 atm, and gas hourly space velocity (GHSV) of 9000 mL g −1 h −1 , the reduced NiO nanoparticle catalyst showed high catalytic activity, with a maximum CO 2 conversion of 85.54 %, 99 % CH 4 selectivity, and 84.69 % CH 4 yield. Furthermore, the NiO nanoparticle catalyst demonstrated excellent stability after 12 h of streaming at 380 °C.