Quasiin situNiK-edge EXAFS investigation of the spent NiMo catalyst from ultra-deep hydrodesulfurization of gas oil in a commercial plant

Abstract

Ni species on the spent NiMo catalyst from ultra-deep hydrodesulfurization of gas oil in a commercial plant were studied by Ni K-edge EXAFS and TEM measurement without contact of the catalysts with air. The Ni-Mo coordination shell related to the Ni-Mo-S phase was observed in the spent catalyst by quasi in situ Ni K-edge EXAFS measurement with a newly constructed high-pressure chamber. The coordination number of this shell was almost identical to that obtained by in situ Ni K-edge EXAFS measurement of the fresh catalyst sulfided at 1.1 MPa. On the other hand, large agglomerates of Ni(3)S(2) were observed only in the spent catalyst by quasi in situ TEM/EDX measurement. MoS(2)-like slabs were sintered slightly on the spent catalyst, where they were destacked to form monolayer slabs. These results suggest that the Ni-Mo-S phase is preserved on the spent catalyst and Ni(3)S(2) agglomerates are formed by sintering of Ni(3)S(2) species originally present on the fresh catalyst.

Influence of H 2 O and H 2 S on the composition, activity, and stability of sulfided Mo, CoMo, and NiMo supported on MgAl 2 O 4 for hydrodeoxygenation of ethylene glycol

“…Co9S8 formation can be minimized by application of a chelating agent, such as citric acid, to the impregnation solution, which has been reported to stabilize Co and Mo precursors at the catalyst surface and facilitate a high degree of promotion of Co in the resulting MoS2 structure[56,90,96].The catalytic activity repeatability test (see section 3.3.1 andFigure 6) might thus be improved by altering the catalyst preparation procedure.For NiMo, the EXAFS results obtained at the Ni K-edge indicated the presence of a NiMoS phase.The Ni-S CN of 3.60 with bond length 2.22 Å is similar to the results obtained by Rochet et al[97] for a sulfided NiMo/Al2O3 catalyst, which was prepared with approximately the same metal loading per nm 2 available support surface area as for this work. The Ni K-edge XANES spectrum for the sulfided catalyst (see supplementary information,Figure S.4), showed similar features as the NiMoS XANES spectrum reported in literature[98]. Furthermore, a small bump at ≈ 8352 eV corresponded to the white line characteristics of NiAl2O4 indicating some interaction of Ni with the MgAl2O4 support.…”

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

“…Nevertheless the XANES spectra of catalysts are superimposable neither to the one of the Ni 3 S 2 reference nor to the spectra of NiS and NiS 2 reported in the literature. 63,64 Actually the shape of the XANES spectra of the sulfide catalysts is very similar to the one published by Hamabe et al 65 for a homemade sulfide NiMo/Al 2 O 3 catalyst (Ni/Mo = 0.2), which was identified as representative of the active NiMoS phase 66 by the analysis of RT EXAFS data in an extended k-range. It is nevertheless important to note that, as for the spectrum reported by Hamabe et al, the XANES spectra reported for the calcined sulfided catalysts (calc-sulf-NiMo and dehydrated-calcsulf-NiMo) display at 8353 eV a small bump that we ascribe as a reminiscence of the white line characteristic of the NiAl 2 O 4 -type species.…”

Intermediate Species Revealed during Sulfidation of Bimetallic Hydrotreating Catalyst: A Multivariate Analysis of Combined Time-Resolved Spectroscopies

“…It corresponds to a shell of 3.1 ± 0.8 sulfur atoms at 2.21 Å (Table S2), which could be consistent with the decoration of Ni at the edges of MoS 2 slabs. − Although no direct evidence of the formation of the mixed NiMoS species with a significant identification of a Ni–Mo contribution arises from the EXAFS fitting of the spectrum recorded at 400 °C, the comparison of its XANES spectrum is clearly different from the spectrum measured for monometallic nickel sulfidic NiS x species supported on δ-alumina prepared and sulfided in the same conditions that the sample studied herein (Figure S10). This strongly suggests that in addition to the expected formation of NiS x species, , even if no quantification can be done from the presented data, the active NiMoS phase is also formed upon sulfidation of the studied catalyst.…”