Research ArticleChemistry

Enhancing hydrogenation activity of Ni-Mo sulfide hydrodesulfurization catalysts

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Science Advances  08 May 2020:
Vol. 6, no. 19, eaax5331
DOI: 10.1126/sciadv.aax5331
  • Fig. 1 Electron micrographs.

    (A) SEM of NiMo-3 before leaching with enlarged view below showing MoS2 rods and compact NiSx particles in false color. (B) SEM of NiMo-3 after leaching showing only MoS2 rods. (C) SEM of NiMo-1 after leaching with enlarged view below showing corrugated surface of MoS2 rods. (D) MoO3 catalyst precursor used in hydrothermal synthesis. (E) Transmission electron micrograph of sulfided NiMo-3 after acid treatment. (F) SEM showing agglomerates of unidentified fine particles on NiMo-4 before leaching.

  • Fig. 2 Results of XAS at the Ni K-edge and structural model.

    (A) Top row: Magnitude (black) and imaginary part (gray) of the k3-weighted Fourier transform before leaching (left) and after leaching (right) with best fit (dashed line). Bottom row: k3-weighted EXAFS and best fit (dashed line) before (left) and after leaching (right). The distance between two vertical tick marks is 5 Å−3 (k-space) and 5 Å−4 (R-space). See fig. S4 for EXAFS of NiMo-1, NiMo-2, and NiMo-4. (B) Top: Normalized near-edge absorption (E0 = 8333 eV) of Ni-Mo sulfide catalysts, Ni3S2, and Ni metal. The inset shows an enlarged view of the pre-edge. Arrows highlight features discussed in the text. Bottom: Derivative of normalized absorption of Ni3S2, NiMo-3-p, and NiMo-3-L. Continuous and dotted lines correspond to parent and leached samples, respectively. (C) Proposed local environments of Ni derived from EXAFS results. Single Ni atom incorporated at the metal edge and neighboring Ni atoms incorporated at the sulfur edge of MoS2 shown from different perspectives [two-dimensional (2D) projections to scale, 3D representation schematic]. The numbers indicate the distance to the Ni absorber in Å (absorber denoted with asterisk).

  • Fig. 3 Ni distribution among active and inactive phases.

    (A) Representative SEM micrograph and (B) schematic representation of NiMo-3 before leaching, showing secondary rod-like MoS2 phase intermixed with crystalline NiSx. (C) Enlarged cross section of the corner of one rod-like particle before leaching. (D) Cross section after leaching. (E) Comparison of total amount of Ni present in the catalysts (“Ni total” determined via elemental analysis) with amount of available edge positions (“Metals at edge” determined via TEM) before and after leaching.

  • Fig. 4 DBT HDS network and measured selectivities.

    (A) Reaction network. (B) Selectivity for DDS and HYD of DBT on Ni-Mo sulfide catalysts before and after acid treatment as a function of temperature [trickle-bed reactor, 280° to 330°C, 5.0 MPa total pressure (H2), 1 weight % DBT in decalin, gas/liquid = 500 Nm3/Nm3, weight hourly space velocity = 1]. mol %, mole percent.

  • Fig. 5 Correlations between the reaction rates, IER, and the total CUS concentration.

    (A) IER as a function of total CUS concentration (normalized to total Mo content) as determined by NO chemisorption on parent (closed symbols) and leached catalysts (open symbols). Note that the factor 0.5 on the x axis results from assuming dinitrosyl adsorption at Ni-associated edge sites. (B) Initial DDS rate and (C) initial HYD rate normalized to surface area as a function of total CUS surface density in parent (closed symbols) and leached catalysts (open symbols).

  • Table 1 Initial DDS and HYD reaction rates and apparent energies of activation.

    CatalystInitial rates
    (mmol g−1 h−1 or mol molMo−1 hour−1)*
    (kJ mol−1)
    NiMo-1-p1.5 (0.36)0.58 (0.14)0.96 (0.22)152 ± 4177 ± 4140 ± 5
    NiMo-2-p1.4 (0.34)0.46 (0.12)0.89 (0.22)164 ± 5239 ± 12145 ± 6
    NiMo-3-p2.6 (0.49)1.0 (0.19)1.6 (0.30)153 ± 10176 ± 12142 ± 9
    NiMo-4-p6.9 (2.02)2.1 (0.63)4.7 (1.39)151 ± 4205 ± 9136 ± 4
    MoS2-p2.5 (0.39)0.46 (0.07)2.0 (0.32)
    NiMo-1-L2.3 (0.41)0.83 (0.15)1.5 (0.26)147 ± 5174 ± 8135 ± 5
    NiMo-2-L2.9 (0.53)1.1 (0.20)1.8 (0.33)157 ± 5220 ± 12138 ± 5
    NiMo-3-L4.5 (0.86)1.6 (0.30)2.9 (0.56)144 ± 3170 ± 5134 ± 3
    NiMo-4-L11.0 (2.23)3.7 (0.73)7.7 (1.50)156 ± 4214 ± 8139 ± 4
    MoS2-L2.4 (0.39)0.41 (0.07)2.0 (0.32)

    *Initial rates (± 5%) at 330°C; values outside and in the parentheses are normalized to the catalyst mass and to the total amount of Mo, respectively.

    †Temperature range: 280° to 330°C.

    Supplementary Materials

    • Supplementary Materials

      Enhancing hydrogenation activity of Ni-Mo sulfide hydrodesulfurization catalysts

      Manuel F. Wagenhofer, Hui Shi, Oliver Y. Gutiérrez, Andreas Jentys, Johannes A. Lercher

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      • Supplementary Methods
      • Figs. S1 to S8
      • Tables S1 to S6
      • References

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