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Methanation is the conversion of COx to methane CH4 through hydrogenation. The methanation reactions of COx were first discovered by Sabatier and Senderens in 1902.

COx methanation have many practical application as a means of CO removal from process gases for gas separation purposes and is also being discussed as an alternative to PROX in fuel processors for mobile fuel cell applications

Methanation as a means of producing synthetic natural gas has been considered since the 1970's. More recently it has been considered as a way to store energy produced from solar or wind power. This would also allow it to serve as a potential carbon capture mechanism.

Chemical reactions
The following reactions describe the methanation of carbon monoxide and carbon dioxide respectively:
 * {CO} + 3H2 -> {CH4} + H2O
 * {CO2} + 4H2 -> {CH4} + 2 H2O

The methanation reactions are classified as exothermic.

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. CO methanation is believed to be methanated 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 reaction over different carried metal catalysts including Ni, Ru and Rh has been widely investigated for the production of CH4 from syngas and other power to gas intitiatives. Nickel is the most widely used catalyst due to its high selectivity and low cost.

Creation of Synthetic Natural Gas
Methanation is an important step in the creation of synthetic or substitute natural gas (SNG). Coal or wood undergo gasification which creates a producer gas that must undergo methanation in order to produce a usable gas that just needs to undergo a final purification step.

The first commercial synthetic gas plant opened in 1984 and is the Great Plains Synfuel plant in Beulah, North Dakota. It is still operational and produces 1500 MW worth of SNG using coal as the carbon source. In the years since it's opening other commercial facilities have been opened using other carbons sources such as wood chips.

Ammonia Synthesis
In ammonia production CO and CO2 are considered poisons to most commonly used catalysts. Methanation catalysts are added after several ammonia synthesis steps to prevent carbon oxide buildup as methane does not have similar adverse effects on ammonia synthesis rates.