methanation

Methanation is a chemical process that converts carbon monoxide (CO) or carbon dioxide (CO2) with hydrogen (H2) into methane (CH4) and water, typically on a solid transition-metal catalyst. The two main reactions are CO + 3 H2 → CH4 + H2O and CO2 + 4 H2 → CH4 + 2 H2O. The latter is known as the Sabatier reaction and is widely used for CO2 utilization.

Catalysts are usually transition metals supported on oxides or carbon. Nickel-based catalysts are common for CO methanation because of low cost and good activity; ruthenium-based catalysts are more active for CO2 methanation and can operate at lower temperatures. Other metals such as cobalt, iron, or palladium may be used, often with promoters and supports to improve stability and dispersion. Because the methanation reactions are exothermic, lower temperatures favor methane selectivity, while higher temperatures increase rate; many industrial processes operate at moderate temperatures and pressures to achieve a practical balance and to shift equilibrium toward CH4.

Applications include removal of CO or CO2 from synthesis gas, upgrading gas streams to pipeline-quality methane, and storing renewable energy in the form of methane in power-to-gas schemes by converting surplus hydrogen and captured CO2. Methanation is also a step in some CO2 utilization pathways and in synthetic natural gas production.

Biological methanation refers to methane production by methanogenic archaea using CO2 and H2 under anaerobic conditions, a cornerstone of biogas systems and certain fermentation processes.