Pre-sulfurization of hydrogenation catalysts
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According to the documentation, pre-sulfurization of hydrogenation catalysts: To prevent hydrogen reduction reactions in the catalyst, the temperature at the highest point of the catalyst bed should be below 150 when hydrogen is introduced into the system℃； Before hydrogen sulfide penetrates the catalyst bed, the temperature at the highest point of the bed should not exceed 230°C. Can someone explain to me how to understand this and why? Thanks
Upon leaving the factory, the catalyst exists in the oxidized state of metals such as nickel and molybdenum; it must be converted to a sulfided state in order to become active. If it is exposed to hydrogen, a reducing agent, at high temperatures, a reduction reaction occurs, preventing the catalyst from being sulfided and thus causing it to lose its activity.
Typically, the metals used for hydrogenation are in an oxidized state; above 230 degrees Celsius, in a hydrogen atmosphere and in the absence of hydrogen sulfide, these metals can be reduced to their elemental form, thereby losing their hydrogenation activity and affecting the efficiency of the catalyst.
Introducing hydrogen at high temperatures can cause hydrogen embrittlement, a form of hydrogen corrosion. Additionally, 230 degrees is the catalyst reduction point; that is, at temperatures higher than this, the catalyst is reduced in a pure hydrogen environment, causing it to lose its activity permanently
Hydrogenation catalysts can be pre-sulfurized either inside the reactor or outside it; in both cases, the oxidized forms of Ni and Mo are converted into their active sulfided forms. If the temperature is too high in a hydrogen atmosphere, the catalyst will be reduced back to its oxidized state, and oxidized catalysts have no activity.
Does the poster use dry vulcanization or wet vulcanization?
Before hydrogen sulfide penetrates the catalyst, if the temperature is above 230°C, the catalyst in its oxidized state will be reduced to metallic form by hydrogen, thereby reducing the catalyst’s activity and affecting its sulfurization process. It is generally necessary to avoid hydrogen embrittlement and catalyst reduction.
The 2nd floor is correct. If it is reduced first, it has a significant impact on the sulfidation effect