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

This study investigated the catalytic CO2 methanation using nickel oxide (NiO) nanoparticles and nickel oxalate (NiC2O4) as catalysts. The NiC2O4 precursor was synthesized through a chemical precipitation reaction between nickel (II) nitrate hexahydrate (Ni(NO3)(2).6H(2)O) and oxalic acid (H2C2O4.2H(2)O). Nickel oxide (NiO) nanoparticles were synthesized through thermal decomposition of NiC2O4 precursor at 450 degrees 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 NiC2O4 catalysts studied for the CO2 methanation in tubular packed bed reactor at 150-550 degrees C and 1 atm. The reduced NiO nanoparticles exhibited more catalytic activity than the decomposed NiC2O4 catalyst. At 380 degrees 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 CO2 conversion of 85.54 %, 99 % CH4 selectivity, and 84.69 % CH4 yield. Furthermore, the NiO nanoparticle catalyst demonstrated excellent stability after 12 h of streaming at 380 degrees C.