For the conversion of CO into CO₂ and H₂, most ammonia plants, use a combination of two shift conversion steps, a High Temperature and a Low Temperature step. The CO content is decreased from about 10-12% (dry gas base) to approximately 0.2-0.4% (dry gas base) (IPTS/EC, 2007 p.41).

An energy efficient option is to add the Selective Catalytic Oxidation (Selectoxo) process after the Low Temperature Shift converter. When compared to other oxidation processes, the Selectoxo provides improved energy efficiency as it significantly reduces the CO slip to about 0.03%, improves process flexibility, and increases the throughput when revamped. The plant throughput can be increased by 1.5-2.0% (Maxwell, 2004 p.156). To achieve the selective oxidation, a precious-metal catalyst is used at 40-135^oC. The CO₂ formed adds only slightly to the load on the downstream CO₂ absorption system (Ullmann’s, 2011 p.185).