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• In continuation of my previous question regarding catalyst finalization for diesel hydrotreater, I would like to understand,

  After hydrotreater feed specification is finalized, containing considerable Sulphur(1.5%) Nitrogen(400 ppm) and total aromatics in feed (30%).

  if I choose, same volume of NiMo catalyst in Reactor 1 and same volume of CoMo catalyst in Reactor 2 for same feed, does both Reactor 1 and 2 outlet product  gets same specification in terms of Sulphur/Nitrogen/Aromatics at same operating conditions??

  If not why?

  What changes needs to be done in NiMo loaded reactor and CoMo loaded reactor w.r.t volume of Catalyst/ Pressure / Temperature to obtain same product specification? Kindly guide.

  Feb-2023

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Answers

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• Marcio Wagner da Silva, Petrobras, marciows@petrobras.com.br

  Once the CoMo is less active than NiMo catalysts, the first is applied to improve sulphur removal and olefins saturation while the NiMo catalyst is responsible for promoting nitrogen removal and aromatics saturation.

  Considering the hypothetic scenario mentioned is expected different compositions downstream of the reactors 1 and 2. The reactor containing NiMo catalysts tends to present lower contaminants concentration (Sulphur, Nitrogen, and aromatics) in the hydrotreated stream than the reactor filled with CoMo catalyst. As previously mentioned, the NiMo catalyst is chemically more active than CoMo and tends to present better performance for hard feedstock like the presented case.

  To achieve similar performance in both reactors would be necessary to raise the severity in the reactor 2 including higher temperature, pressure and catalyst mass for this reason a blend of catalysts is normally carried out in industrial scale aiming to achieve hydrotreating goals with acceptable capital and operating costs.

   

  Feb-2023