Maximum temperature for heating high-varying catalysts with air
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The high-variability variant is heated with air; the catalyst’s maximum temperature is 149°C, after which steam is used for heating. Why can’t air be heated above 149°C? Because at this point, CAT is still in a passivated state.
The reason might be to completely displace the air remaining inside the catalyst; once the catalyst reaches its reduction temperature and gas is introduced, a reduction reaction takes place, and if there is still air in the catalyst, it will be oxidized again.
Agree with the comment above; I’m concerned that if the air temperature rises too much, the steam generated later won’t be able to completely displace the oxygen in the system, and the catalyst will oxidize again after sulfiding. Does the original poster use steam to raise the temperature? We use nitrogen for heating, with electric heaters providing the heat.
Medium-temperature catalysts contain graphite, which can burn easily at high temperatures, eventually destroying the catalyst.