Water gas shift reaction

The water gas shift reaction , or WGS for short, or water gas shift reaction (historically also carbon oxide conversion ), is a process for reducing the carbon monoxide content in synthesis gas and for generating hydrogen . The reaction equation is also known as the conversion equilibrium.

${\displaystyle \mathrm {CO+H_{2}O\rightleftharpoons CO_{2}+H_{2}} \qquad \Delta H_{R\ 298}^{0}=-41{,}2\ \mathrm {kJ/mol} }$

The negative free enthalpy G (T) decreases with increasing temperature.

When water vapor is added , the CO reacts to form CO ₂ and H ₂ . The enthalpy of reaction of −41.2 kJ / mol is quite low. As the temperature rises, the chemical equilibrium shifts from the reaction products to the reaction educts. At approx. 700 ° C the negative free enthalpy increases to 0 kJ / mol.

At a higher temperature there is fast kinetics but an unfavorable chemical equilibrium . Iron (III) oxide catalysts accelerate the conversion at low temperatures of 250 to 450 ° C. In chemical reactors , the shift reaction is often carried out in two stages: in a high-temperature and low-temperature shift stage (in short: HT and LT shift). The CO content can be reduced to 0.6 to 1.5% by volume, depending on how the reactor is operated .

See also

• Steam reforming
• Water gas

literature

• J. Pasel, et al .: Test of a water-gas-shift reactor on a 3 kW _e- scale - design points for high- and low-temperature shift reaction. In: Journal of Power Sources 152 (2005) pp. 189-195, doi: 10.1016 / j.jpowsour.2004.12.051

Web links

• Video: Thermodynamic classification of the water gas shift reaction - exothermic, endothermic, exotropic, endotropic, exergonic or endergonic . Jakob Günter Lauth (SciFox) 2013, made available by the Technical Information Library (TIB), doi : 10.5446 / 15705 .