WasserGasShiftReaktionen

Wasser-Gas Shift, commonly known as the water-gas shift reaction (WGS), is a chemical process in which carbon monoxide reacts with water vapor to form carbon dioxide and hydrogen. The overall reaction is CO + H2O ⇌ CO2 + H2, and it is exothermic with a standard enthalpy change of about -41 kJ/mol. The reaction is a key step in adjusting the hydrogen-to-carbon monoxide ratio in synthesis gas (syngas) produced by steam reforming or coal gasification, enabling higher hydrogen yields for downstream processes such as ammonia synthesis, methanol production, or fuel-cell feedstock.

Industrial practice uses two main catalyst classes, often in separate stages. High-temperature shift (HTS) typically employs iron oxide and chromia-based catalysts at around 320–450°C to provide rapid conversion, while low-temperature shift (LTS) uses copper-based catalysts on alumina at roughly 200–250°C to push further conversion with higher selectivity. Many plants employ a two-stage configuration, with HTS first to achieve fast kinetics and broad conversion, followed by LTS to approach higher overall CO conversion at a lower temperature. Because the reaction is exothermic, increasing temperature shifts the equilibrium toward carbon monoxide and water, while decreasing temperature favors hydrogen production but slows reaction rates.

Process design considerations include maintaining sufficient water vapor, controlling residence time, and integrating CO2 removal or hydrogen purification stages (e.g., pressure swing adsorption) to obtain high-purity hydrogen. The Wasser-Gas Shift is widely used in modern gas processing and chemical industries to optimize hydrogen yield from syngas. The term is common in German-language literature as Wasser-Gas-Shift.