How to remove the catalyst when shutting down the hydrogen production unit for catalyst replacement
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Our unit is about to have its catalyst replaced, and we don’t know how to remove the current catalyst, as it catches fire when removed. Some say it needs to be oxidized first, but the hydrogenation catalyst is converted from an oxidized state to a sulfided state; is the pre-sulfidation reaction of hydrogenation catalysts a reversible reaction?
Cobalt-molybdenum catalysts in the sulfided state undergo intense oxidation when exposed to air at high temperatures; usually, the temperature must be reduced to around room temperature before they can be exposed to air. The presulfurization reaction of hydrogenation catalysts is a reversible reaction, but it is conditional; catalyst regeneration makes use of this condition.
The presulfurization of hydrogenation catalysts involves converting it from an oxidized state to a sulfided state; this presulfurization reaction is reversible. After the hydrogenation catalyst is removed, it reacts with oxygen, releasing heat, and if the temperature rises too high, ignition can occur. The removal of hydrogenation catalysts is carried out under the protection of inert gases to prevent contact with air; this process is usually handled by specialized companies, and dry ice is sprayed to lower the temperature whenever it rises
It can be directly added to deionized water for soaking and then removed; if concerned, the catalyst can be cooled by pouring water on it outside the container.
Proper packaging combined with nitrogen protection to keep the catalyst away from air ensures safety.