| A mobility of potassium in the iron catalyst for ammonia synthesis has been studied under various pressure conditions: ultrahigh vacuum, atmospheric pressure and 10 MPa. Under UHV the surface diffusion of potassium from iron catalyst on the iron foil has been studied with AES method. Diffusion of potassium atoms has been observed in the temperature range between 500° C and 600° C. A mathematical model for the surface diffusion was proposed and compared with the experimental results. At atmospheric pressure the diffusion of potassium from one layer of catalyst bed to another has not been observed at the temperature of 550° C. Under the same conditions the intergranular diffusion of potassium has been observed. The intergranular diffusion of potassium has also been observed during the activation of iron catalyst at 10 MPa and 400 - 650° C. |
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