Influence of the Preparation Conditions of Oxidic NiMo/Al2O3 Catalysts on the Sulfidation Ability: A Quick-XAS and Raman Spectroscopic Study

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• 作者：Am茅lie Rochet ; Bertrand Baubet ; Virginie Moizan ; Elodie Devers ; Antoine Hugon ; Christophe Pichon ; Edmond Payen ; Val茅rie Briois
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：October 22, 2015
• 年：2015
• 卷：119
• 期：42
• 页码：23928-23942
• 全文大小：713K
• ISSN：1932-7455

文摘

The structure of oxidic precursors of supported NiMo hydrodesulfurization catalysts has been investigated in-depth by the combination of laser Raman spectroscopy and X-ray absorption spectroscopy measured at the Mo and Ni K edges at the different stages of the preparation. The oxidic catalysts were prepared by incipient wetness impregnation of 未-alumina with a solution obtained by dissolving MoO₃ in H₂O₂ and subsequently adding Ni(NO₃)₂路6H₂O in this as-prepared solution (8 wt % MoO₃; 2 wt % NiO). The formation of the 6-molybdoaluminate Anderson-type heteropolyanion (AlMo₆O₂₄H₆)^{3鈥?/sup> and of a mixture of oxo鈥揾ydroxo nickel species and bulk and/or surface NiAl-layered double hydroxide dispersed at the surface of the support has been identified after drying. Upon further thermal treatment at 723 K under dried air, calcined dehydrated catalyst is constituted of highly distorted isolated or partially condensed tetrahedral Mo units with terminal mono-oxo groups and of bulk and/or surface NiAl₂O₄-type and NiO-type species. After further exposure of the calcined catalyst to air moisture, a partial recovery of the Anderson-type molybdenum heteropolyanion and NiAl-layered double hydroxide species is evidenced by X-ray absorption spectroscopy. The nature and dispersion of active species formed after sulfidation under H₂S/H₂ of the different oxidic catalysts (dried-NiMo, dehydrated-calcined NiMo, and calcined-NiMo samples) are finally discussed in light of the structure of the parent oxidic precursors.}