Edge dispersion of supported MoS2 and WS2 catalysts as evaluated by using Co(CO)3NO as a probe molecule

Autor: Akira Kato, Yasuaki Okamoto, Takashi Kubota, Takashi Fujikawa, Katsuaki Ishida, Kenji Sato, Yasuhiro Araki, Takeshi Ebihara, Usman
Rok vydání: 2005
Předmět:
Zdroj: Applied Catalysis A: General. 290:17-24
ISSN: 0926-860X
DOI: 10.1016/j.apcata.2005.05.031
Popis: SiO 2 - and Al 2 O 3 -supported MoS 2 and WS 2 catalysts were prepared to exploit the evaluation technique of the edge dispersion of MoS 2 and WS 2 particles. A chemical vapor deposition (CVD) technique using Co(CO) 3 NO as a probe molecule was used for the evaluation. Results were compared with those from conventional techniques such as NO adsorption and TEM. A proportional correlation was obtained between the amount of NO adsorption and the amount of Co atoms accommodated by the CVD technique on WS 2 /SiO 2 and WS 2 /Al 2 O 3 catalysts, demonstrating a selective location of the Co atoms on the edges of WS 2 particles, as previously established for MoS 2 catalysts. A comparison of the amounts of NO adsorption and Co accommodation on MoS 2 and WS 2 catalysts suggested a 70% higher density of sulfur vacancy on MoS 2 particles than on WS 2 particles regardless of the support. The Co atoms on the edges of MoS 2 and WS 2 particles showed the identical NO adsorption property. We propose that Co(CO) 3 NO can be used as a probe molecule to evaluate and directly compare the edge dispersions of MoS 2 and WS 2 catalysts. The dispersion of MoS 2 particles was about two times higher than that of WS 2 particles with the SiO 2 -supported catalysts. With the Al 2 O 3 -supported catalysts, MoS 2 and WS 2 particles were dispersed to a similar extent but much more highly dispersed than the counterparts in the SiO 2 -supported catalysts. The evaluation of the edge dispersion of MoS 2 and WS 2 particles by means of TEM may pose problems when SiO 2 - and Al 2 O 3 -supported catalysts are compared. The edges of unpromoted MoS 2 particles exhibited a significantly higher intrinsic activity for the HDS of thiophene than those of WS 2 particles.
Databáze: OpenAIRE
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