An ex situ presulfided MoNiP/γ-Al 2 O 3 catalyst was prepared, and its hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) performances were evaluated with dibenzothiophene and quinoline as the model compound, respectively. Results indicated that the ex situ presulfided catalyst presented a similar sulfur removal rate as the in situ presulfided catalyst but its hydrogenation activity and HDN efficiency were relatively lower. However, its hydrogenation activity increased with longer time on stream (TOS). In a pilot test with fluidized catalytic cracking (FCC) diesel oil as feed, close HDS and HDN efficiencies were acquired for both presulfided catalysts. Furthermore, along with the running period, the ex situ presulfided catalyst exhibited incremental HDN efficiency as well as hydrogenation activity. An active-phase study was performed by means of Brunauer−Emmett−Teller (BET), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). Results showed that the ex situ presulfided catalyst presented relatively weaker MoS 2 diffraction peaks and a lower stacking number and length of MoS 2 slabs than those of the in situ presulfided catalyst with short TOS but those could be significantly enhanced with long TOS. XPS data also indicated that the ex situ presulfided catalyst only became partially sulfurized during the ex situ presulfiding process but could be further sulfided with long TOS. The conclusion was made that it was the distinction lying in the MoS 2 active phase that caused the ex situ presulfided catalyst to have a lower hydrogenation activity with short TOS, and the distinction would be far more diminished with long TOS or in a real diesel oil system.
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Li et al. (2009) studied this question.
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