Sabatier reaction

The Sabatier reaction or Sabatier process produces methane and water from a reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400 °C) and pressures (perhaps 3 MPa ^[1]) in the presence of a nickel catalyst. It was discovered by the French chemists Paul Sabatier and Jean-Baptiste Senderens in 1897. Optionally, ruthenium on alumina (aluminium oxide) makes a more efficient catalyst. It is described by the following exothermic reaction:^[2]

${\displaystyle {\ce {CO2{}+4H2->[{} \atop 400\ ^{\circ }{\ce {C}}][{\ce {pressure+catalyst}}]CH4{}+2H2O}}}$ ∆H = −165.0 kJ/mol

There is disagreement on whether the CO₂ methanation occurs by first associatively adsorbing an adatom hydrogen and forming oxygen intermediates before hydrogenation or dissociating and forming a carbonyl before being hydrogenated.^[3]

${\displaystyle {\ce {{CO}+ 3H2 -> {CH4}+ H2O}}}$ ∆H = −206 kJ/mol

CO methanation is believed to occur through a dissociative mechanism where the carbon oxygen bond is broken before hydrogenation with an associative mechanism only being observed at high H₂ concentrations.

Methanation reactions over different metal catalysts including Ni,^[4] Ru^[5] and Rh^[6] have been widely investigated for the production of CH₄ from syngas and other power to gas initiatives.^[3] Nickel is the most widely used catalyst owing to its high selectivity and low cost.^[2]