Temperature Shift Conversion LTS

The copper oxide is reduced in situ with hydrogen and a carrier gas (usually nitrogen) to form the fine copper crystallites of about 10 6 cm on which the activity depends. 

The LTS catalyst is protected by a guard bed, formerly loaded with ZnO, but nowadays usually with LTS catalyst [621]. Changing the guard bed more frequently prolongs the service life of the main LTS catalyst bed. Without a guard bed the lifetime is normally 2-4 years, depending on gas quality. With an upstream guard bed, 

Compared to the HT shift reaction fewer publications exists on the reaction kinetics of LT shift reaction. Studies made before 1979 may be found in [602]. A rather simple power law (Eq. 85), for example [624] fitted well measurements between 200 and 250 °C, but the weak point is that the exponents are temperature dependent. An expression of the Langmuir -Hinshelwood-type, published in [625], includes additionally the influence of H2 and C02 concentration on the reaction rate. 

For comparison of the activity of commercial shift catalysts, sometimes the so-called Kw value is found in the literature. This term, introduced by K. Atwood is defined for shift reactions as follows [626]  

For the LT shift an oxidation reduction mechanism has been discussed which is similar to that proposed for the HT shift, but this concept is not unquestioned and the presently available experimental material provides no convincing evidence. 

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