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

Abstract

The structure of oxidic precursors of supported NiMo hydrodesulfurization catalysts has been investigated indepth by the combination of laser Raman spectroscopy and Xray 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 δ-alumina with a solution obtained by dissolving MoO 3 in H 2 O 2 and subsequently adding Ni(NO 3 ) 2 ·6H 2 O in this asprepared solution (8 wt % MoO 3 ; 2 wt % NiO). The formation of the 6-molybdoaluminate Anderson-type heteropolyanion (AlMo 6 O 24 H 6 ) 3− and of a mixture of oxo−hydroxo 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 NiAl 2 O 4 -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 H 2 S/H 2 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.

Correlation of Sol–Gel Alumina‐Supported Cobalt Catalyst Processing to Cobalt Speciation, Ethanol Steam Reforming Activity, and Stability

“…The presence of the aluminate‐like phase can be also related to the formation of surface hydrotalcite‐type phase during the impregnation stage . The hydrotalcite formation during impregnation of γ‐Al 2 O 3 with Ni or Co solutions was reported in literature .…”

“…The presence of the aluminate‐like phase can be also related to the formation of surface hydrotalcite‐type phase during the impregnation stage . The hydrotalcite formation during impregnation of γ‐Al 2 O 3 with Ni or Co solutions was reported in literature . In addition to be a support, the γ‐Al 2 O 3 acts as a source of aluminium for coprecipitation with Ni or Co ions leading to the hydrotalcite‐like phase formation .…”

In situ QXAS study of sulfidation/oxidative regeneration reactions of zinc molybdate (ZnMoO4) and ZnO–MoO3 materials

“…In recent works, multivariate analysis based on the so-called MCR-ALS method (Multivariate Curve Resolution with Alternating Least Squares) has been used in the qualitative and quantitative investigation of time-resolved evolving XAS data recorded during solid-state reactions. [1][2][3][4][5][6][7][8][9][10] The purpose of this chemometric approach is to extract the spectrum of each component whose sum constitutes the experimental spectrum and to determine the concentrations of each of these components in the mixture. 11 The set of normalized XAS experimental spectra, recorded upon H 2 The MCR-ALS minimization on the Quick-XAS data presented herein was carried out using the MCR-ALS GUI 2.0 developed by Roma Tauler and his group on the Matlab® platform.…”

In Situ Local Temperature Mapping in Microscopy Nano‐Reactors with Luminescence Thermometry

“…Here, X‐ray spectroscopy can play an important role. For instance, by combining X‐ray absorption spectroscopy with Raman spectroscopy, bulk studies of catalysts have been performed which can correlate short‐range order, valence state and local geometry of the metals to product formation and reaction intermediates . Although these results are insightful, detailed information on the single catalyst particle level is still lacking.…”

“…For instance, by combining X-ray absorption spectroscopy with Raman spectroscopy, bulk studies of catalysts have been performed which can correlate short-range order, valence state and local geometry of the metals to product formation and reaction intermediates. [18][19][20] Although these results are insightful, detailed information on the single catalyst particle level is still lacking. Especially hydrocarbon deposition or coke formation on the single particle level could reveal valuable information since it is believed that this is one of the main reasons for catalyst deactivation.…”