Methanation

The methanation is a chemical reaction in which carbon monoxide or carbon dioxide in methane is converted. The reaction of carbon dioxide to methane is also known as the Sabatier process . It was discovered in 1902 by Paul Sabatier and JB Sendersens. In addition to the chemical process, methanation is also possible biologically, see biological methanation .

reaction

Methanation of CO ₂ using electrolytically obtained hydrogen

In this reaction, carbon monoxide or carbon dioxide reacts with hydrogen at temperatures of 300 to 700 ° C to form methane and water. This reaction is exothermic, but must be accelerated by a catalyst . For this purpose mostly nickel catalysts are used , which are improved with various promoters and stabilizers such as aluminum oxide and zirconium dioxide , but the catalytic effect of ruthenium has also been investigated.

Reaction with carbon monoxide

${\displaystyle \mathrm {CO+3\ H_{2}\longrightarrow CH_{4}+H_{2}O} }$

Reaction with carbon dioxide

${\displaystyle \mathrm {CO_{2}+4\ H_{2}\longrightarrow CH_{4}+2\ H_{2}O} }$

Applications

Large-scale technology

At the present time (2011), methanation is not used for the large-scale production of methane, as this can be obtained more cheaply from natural gas . However, it plays a role in removing traces of carbon monoxide, which in some processes act as catalyst poisons. This is the case, for example, with ammonia synthesis in the Haber-Bosch process , in which the hydrogen used must be as low as possible in carbon monoxide. Methanation can be used to produce synthetic natural gas from gases with a high CO content .

Solar or wind energy methanation

→ Main article : "Methanation" in the article Power-to-Gas

A technical application of methanation, which is expected to become increasingly important, is the generation of wind or solar gas , where methane is obtained as synthetic natural gas after prior water electrolysis using renewable energies . From an energy point of view, however, methanation of hydrogen only makes sense if the currently still large-scale hydrogen production from fossil natural gas has been completely converted to electrolysis hydrogen from renewable energies, as otherwise hydrogen from fossil methane / natural gas and artificial methane from hydrogen would be produced at the same time. In 2010, German industry consumed more than 60 TWh of hydrogen.

Analytics

In the field of gas chromatography , methanation is used to be able to detect individual analytes with detectors that have advantages in the specific application, for example because they are more cost-effective or allow higher detection sensitivities than comparable detection methods that do not require chemical conversion of the analytes.

In practice, the analysis mixture is first separated into individual components on the chromatographic separation column and these are then reduced to methane in a methanation process. The reduction takes place in a heated capillary column filled with a catalyst, the output of which is directly linked to the detector. For example, carbon dioxide, carbon monoxide or formaldehyde can be determined as methane with a flame ionization detector , which is around 500 times more sensitive than a thermal conductivity detector , with which the substances could be detected even without reduction.

See also

• Methane slip

literature

• Entry on methanation. In: Römpp Online . Georg Thieme Verlag, accessed on June 16, 2014.
• Heinz Hiller et al .: Gas Production. In: Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim 2001, doi : 10.1002 / 14356007.a12_169.pub2 .
• Jens Sehested, Søren Dahl, Joachim Jacobsen, Jens R. Rostrup-Nielsen: Methanation of CO over Nickel: Mechanism and Kinetics at High H ₂ / CO Ratios. In: J. Phys. Chem. B. 2005, 109, 6, pp. 2432-2438, doi: 10.1021 / jp040239s .

Individual evidence

1. ↑ see: ASUE Working Group for Economical and Environmentally Friendly Energy Consumption eV (Ed.): Natural gas from green electricity. 2011, p. 11, accessed on March 3, 2012 (PDF; 3.0 MB).
2. ↑ Cf. Viktor Wesselak , Thomas Schabbach , Thomas Link, Joachim Fischer: Handbuch Regenerative Energietechnik. 3rd updated and expanded edition, Berlin / Heidelberg 2017, p. 763.
3. ^ J. William Weaver: Analytical methods for a textile laboratory. American Association of Textile Chemists and Colorists 1984, ISBN 0-9613350-0-9 , p. 338 ( limited preview in Google book search).