Sabatier reaction

The Sabatier reaction or Sabatier process was discovered by the French chemist Paul Sabatier in the 1910s. It involves the reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400 °C) and pressures in the presence of a nickel catalyst to produce methane and water. Optionally, ruthenium on alumina (aluminium oxide) makes a more efficient catalyst. It is described by the following exothermic reaction:

It has been proposed in a renewable-energy-dominated energy system to use the excess electricity generated by wind, solar photovoltaic, hydro, marine current, etc. to make methane (natural gas) via water electrolysis and the subsequent application of the Sabatier reaction. In contrast to a direct usage of hydrogen for transport or energy storage applications, the methane can be injected into the existing gas network, which in many countries has one or two years of gas storage capacity. The methane can then be used on demand to generate electricity (and heat—combined heat and power) overcoming low points of renewable energy production. The process is electrolysis of water by electricity to create hydrogen (which can partly be used directly in fuel cells) and the addition of carbon dioxide CO₂ (Sabatier process) to create methane. The CO₂ can be extracted from the air or fossil fuel waste gases by the amine process, amongst many others. It is a low-CO₂ system, and has similar efficiencies of today's energy system. A 6 MW power-to-gas plant went into production in Germany in 2013, and powered a fleet of 1500 Audi A3s.

Oxygen generators on board the International Space Station produce oxygen from water using electrolysis; the hydrogen produced was previously discarded into space. As astronauts consume oxygen, carbon dioxide is produced, which must then be removed from the air and discarded as well. This approach required copious amounts of water to be regularly transported to the space station for oxygen generation in addition to that used for human consumption, hygiene, and other uses—a luxury that will not be available to future long-duration missions beyond low Earth orbit.

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