Over-reduction of medium-temperature catalysts
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There is a concept of excessive reduction of the medium-temperature catalyst when changing positions; I would like all fellow sailors to discuss what excessive reduction of the medium-temperature catalyst means What are the hazards of excessive reduction of medium-temperature catalysts? How to avoid excessive reduction of the medium-temperature catalyst?
Excessive reduction should be the reduction of the active component Fe3O4 in the medium-temperature catalyst to elemental Fe. Excessive reduction significantly reduces the conversion activity of the catalyst, and it also promotes the reaction of H2 and N2 to form NH3.
A way to avoid excessive reduction is to ensure that the steam-to-gas ratio in the medium-temperature furnace is not lower than 0.35
When reducing highly variable catalysts, steam must be added simultaneously in order to prevent the already reduced catalyst from being over-reduced by hydrogen, resulting in the formation of metallic iron: Fe3O4 + 4H2 → 3Fe + 4H2O – 149.93 KJ/mol; Fe3O4 + 4CO → 3Fe + 4CO2 – 149.93 KJ/mol. Metallic iron can facilitate the exothermic reaction between CO and H2 to produce methane, which is harmful to both the catalyst and the converter. Additionally, metallic iron may cause CO to undergo disproportionation reactions, leading to carbon deposition on the surface of the catalyst. Therefore, once the catalyst reaches the reduction temperature, it is absolutely not permissible to introduce reducing dry gas containing CO and H2; an adequate amount of steam must be supplied instead