Investigation of carbonaceous compounds deposited on NiMo catalyst used for ultra-deep hydrodesulfurization of gas oil by means of temperature-programmed oxidation and Raman spectroscopy

Naoto Koizumi, Yoshihisa Urabe, Kazuhiro Inamura, Takashi Itoh, Muneyoshi Yamada

Research output: Contribution to journalConference articlepeer-review

28 Citations (Scopus)

Abstract

NiMo/Al2O3 catalyst used for ultra-deep HDS of several gas oils at various conditions was characterized by both temperature-programmed oxidation combined with mass spectroscopy (TPO-MS) and/or gas chromatography (TPO-GC), and Raman spectroscopy to make clear how the catalyst was deactivated. TPO-MS showed the presence of carbonaceous compounds containing H and N atoms on the used catalysts. TPO-GC showed that the combustive property of the carbonaceous compounds sensitively changes depending on the HDS reaction conditions and the position of the catalyst charged in the HDS reactor. A curve fitting analysis of TPO-GC profiles indicated that the carbonaceous compounds combusted below 680 K during TPO were observed on all the spent catalysts examined here whereas more refractory carbonaceous compound (combusted at around 690 K during TPO) was observed on the catalyst that had experienced severe HDS reaction conditions. More refractory carbonaceous compound was preferentially observed on the catalyst charged near the outlet of the HDS reactor. Raman spectra of the carbonaceous compounds indicated that the carbonaceous compounds combusted below 680 K during TPO has an amorphous-like structure whereas the refractory carbonaceous compound has a graphite-like one. Raman spectra also indicated that the graphite-like carbonaceous compound possesses a greater lateral size than the amorphous-like one, implying that the refractory carbonaceous compound can cover the catalyst surface more effectively. The carbonaceous compound having a graphite-like structure is one of main reasons for the catalyst deactivation. It is suggested that the precursor for this type of carbonaceous compound is not formed directly from the feed, but indirectly formed during the HDS of gas oil, because of its preferential deposition on the catalyst charged near the outlet of the HDS reactor.

Original languageEnglish
Pages (from-to)211-218
Number of pages8
JournalCatalysis Today
Volume106
Issue number1-4
DOIs
Publication statusPublished - 2005 Oct 15
EventInternational Conference on Gas-Fuel 05 International Conference on Gas-Fuel 05 -
Duration: 2005 Nov 142005 Nov 16

Keywords

  • Carbonaceous compound
  • Catalyst deactivation
  • Raman spectroscopy
  • TPO
  • Ultra-deep HDS

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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