4 replies to this topic

[Skyline]

Dear all,

Do you know the reaction occurs in hydrocracking catalyst activation (reduction) using butyl mercaptan? And I don't understand why they use mercaptan? I thought that sulphur is one of poison for catalyst, and also can cause corrosion to the material of the vessel (reactor). The catalyst is DHC-8 from UOP. Any litrature or explanation would be a great help for me.
Thank you very much before.

Best regards,


Skyline

[Zauberberg]

Sulfiding is common activity prior to unit startup so as to activate the catalyst. Read more at:

http://www.tricatgro.../sulfiding.html
http://www.criterion...mstonevail2.pdf

http://www.tricatgro...resentation.pdf

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[Root]

Sulfiding will not create corrosion problem initially but for fresh catalyst sulfiding will reduce the catalyst activity for desired selectivity. Because fresh catalyst is more reactive and have tendency for exothermic behaviors, Petrochemical and Refineries are doing sulfinding for slow down the reaction initially.

Toor

[Skyline]

Dear Toor and Zauberberg

Thank you very much for the explanation and also the literatures...It really helps me a lot...

Best regards,


Skyline

[iyer]

Skyline

Initially your catalyst is in oxidized form. An oxidized form is not reactive, ie. it does not convert Sulfur in feed to H2S or Nitrogen to ammonia. The first step is to replace the oxide sites with sulfide. This is the process of catalyst activation. Now where does the sulfur come from, well DMDS, Butyl mercaptan, DMS, TBPS etc are some sources. Now a low temperature (not too low about 180-200) decomposition complimented by a high sulfur content is what we desire in a sulfiding agent. DMDS is the best, but butyl mercaptan can also be used, It is more likely to take more time though and it depends on the source where it comes from. Corrosion is a problem, but if you do look at things, the reactor system is of high metallurgy and is H2S resistant. The frac section is of lower metallurgy and needs the stripper running before we start sulfiding, to remove H2S.
If you have any more doubts feel free to ask.