Novel hydrodesulfurization catalysts derived from a rhodium carbonyl complex

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 2004-02, Vol.209 (1), p.155-162
• Main Authors: Lee, Jeayoung, Ishihara, Atsushi, Dumeignil, Franck, Miyazaki, Kou, Oomori, Yuji, Qian, Eika W, Kabe, Toshiaki
• Format: Article
• Language: English
• Subjects: Catalysis; Catalyst; Catalytic reactions; Chemistry; Dibenzothiophene; Exact sciences and technology; formula omitted; General and physical chemistry; Hydrodesulfurization; Rhodium carbonyl; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2003.08.020

Catalysts derived from alumina-supported rhodium carboxyl exhibited a higher DBT HDS activity than that of Ru carboxyl-based catalysts. Further, the specific activity calculated per rhodium was considerably higher than the one of a conventional Co-Mo catalyst. The high performances were explained by the formation of a great quantity of active sites (labile sulfur atoms). The first part of this work aimed at optimizing Rh based HDS catalysts by modification of the precursor nature as well as the selection of an adequate pre-activation method. Further, the combination of the Rh catalysts with Ru catalysts was also investigated. Although no obvious synergetic effect was observed, the combined Rh-Ru catalysts exhibited higher activities than the single metal-based ones. Among all the prepared catalysts, the RhCs/Al 2O 3 catalysts prepared from the rhodium carbonyl precursor with a ratio Rh/Cs=1–2 exhibited the most interesting catalytic performance. The effect of the Rh loading on the activity of these catalysts was studied. An increase in activity was observed when the Rh loading increased up to 0.5 wt.% but further Rh addition did not lead to any noticeable effect on the catalytic performance. Whilst the prepared catalysts exhibited a gross activity inferior to that of a classical CoMo system, their specific activity calculated per mole of metal was considerably higher than the one obtained for the latter conventional system. Furthermore, the conversion of the 4 wt.% Rh catalyst was about twice as high as the one of a 4 wt.% Ru catalyst. Therefore, in order to elucidate the interesting catalytic properties of such Rh based catalysts, 35 S radioactive tracer DBT HDS experiments were performed. We found that for 4 wt.% Rh, k RE, the H 2S release rate constant, was almost the same as the one obtained for the 4 wt.% Ru catalyst. However, S 0 was significantly higher on the Rh catalyst than on the Ru catalyst (+70%). This indicated that the high activity was due to the formation of a great quantity of active sites (labile sulfur atoms).