Engineering biochar-supported nickel catalysts for efficient CO2 methanation.

Carbon dioxide methanation is a promising approach to convert captured CO 2 into green natural gas. Developing high performance biochar-supported nickel catalysts promotes a circular economy and the application of sustainable catalysts. Western red cedar biochar was produced via pyrolysis at 400, 500, and 600 °C and loaded with nickel via incipient wetness impregnation. Methanation was done at 400, 500, and 600 °C with the highest methane yield of 59% achieved at 500 °C with 10 wt.% Ni loading. This is comparable to a γ-Al 2 O 3 supported catalyst prepared and tested similarly, which achieved a methane yield of 53%. Biochar-supported catalysts showed deactivation whereby methane yield decreased from 59% to 51% over 5 h, likely due to coking and/or the sintering of nickel. Various space velocities were tested, and results demonstrated that with a space velocity of 37.5 mL/g.min methane selectivity was 89% after 1 h on stream compared to methane selectivity of 42%, which was achieved at a space velocity of 112.5 mL/g.min. This shows that a much higher rate of deactivation is observed at higher space velocities. Increasing the nickel loading from 5 wt.% to 10 wt.% increased methane yield from 40% to 58% after 1 h on stream. The higher loading also showed significantly less deactivation. Future work focusing on the extent and impact of metal-support interactions and metal dispersion on catalytic performance and deactivation during CO 2 methanation is recommended. [Display omitted] • Biochar catalysts perform comparably to alumina catalysts for CO 2 methanation. • 58% CH 4 yield was reached at 10 wt.% Ni loading and 500 °C methanation temperature. • Deactivation was observed over 5 h likely due to sintering and/or coking. • Pyrolysis temperature from 400 to 600 °C did not significantly affect performance. • Methanation performed at 500 °C balanced thermodynamic and kinetic limitations. [ABSTRACT FROM AUTHOR]