Is pre-sulfurization required before the hydrogenation reactor is put into use next time?

Generally, if passivation is not carried out when a hydrogenation reactor is shut down, pre-sulfurization is usually not required when it is restarted.

Hehe! We had this question too when we hadn’t started working! But the reply we received later was as Clauspolunit said!

During shutdown, the hydrogenation catalyst is not passivated; is there any sulfur accumulation in the catalyst bed after shutdown? Additionally, how is the catalyst protected?

Hydrogenation reactors generally do not have sulfur accumulation issues, and the catalyst does not require special protection during shutdown.

As long as there are no issues with heating the hydrogenation reactor, there is no need for further presulfurization

It is acceptable not to perform passivation on the hydrogenation reactor during shutdown; it is best to keep the reactor sealed, and nitrogen can be used for protection along with proper temperature monitoring to prevent the bed layer from overheating. If no overheating due to air ingress and spontaneous combustion occurs, pre-vulcanization is not required before restarting operation.

First, it is necessary to clarify the purpose of pre-sulfurization of hydrogenation catalysts: Pre-sulfurization is applied only to new catalysts or those that have been regenerated and returned to the factory, as in these cases the active components in the hydrogenation catalyst exist primarily in the form of cobalt oxide and molybdenum oxide. It is cobalt sulfide and molybdenum sulfide that actually carry out the hydrogenation catalytic function during normal operation of the plant. Therefore, after installing new catalysts, it is necessary to pre-sulfurize them by converting the oxidized metal forms into sulfided forms. Secondly, it is necessary to clarify the role of shutdown passivation: Shutdown passivation in hydrogenation reactors is carried out to prevent the spontaneous combustion of ferrous sulfide within the reactor after it is shut down, by using air to slowly oxidize the ferrous sulfide present in the catalyst beds and equipment of the hydrogenation system. Passivation of the hydrogenation reactor does not change the morphology of cobalt sulfide and molybdenum sulfide in the catalyst. In other words, when a hydrogenation reactor is restarted after being shut down for passivation, there is no need to carry out catalyst presulfidization. Finally, it should be noted that if only a portion or the entire hydrogenation catalyst is replaced during the shutdown for maintenance, it is necessary to carry out pre-sulfidization again.