Research ArticleChemistry

Self-supported hydrogenolysis of aromatic ethers to arenes

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Science Advances  22 Nov 2019:
Vol. 5, no. 11, eaax6839
DOI: 10.1126/sciadv.aax6839
  • Fig. 1 Strategies used for the transformation of aromatic ethers.

  • Fig. 2 Characterization of RuW/SiO2 catalyst.

    (A) XRD patterns of RuW/SiO2 [3.5 weight % (wt %) Ru, 20 wt % W] catalyst (red), W/SiO2 (20 wt % W) catalyst (pink), Ru/SiO2 (3.5 wt % Ru) catalyst (blue), and amorphous SiO2 (black). Standard pattern of RuW alloy from [International Centre For Diffraction Data Portable Document Format (ICDD PDF)] card (65-6705 for RuW) is shown at the bottom. (B) TEM image of RuW/SiO2 catalyst (inset: RuW alloy particle size distribution of RuW/SiO2 catalyst). (C) HRTEM image of RuW/SiO2 catalyst. (D) HRTEM EDS line scan profiles of W (black) and Ru (red) in the RuW/SiO2 catalyst recorded along the arrow shown in the HRTEM image (C), XPS spectra for Ru 3p region (E), and W 4f region (F). (G) Rietveld refinement of RuW/SiO2 catalyst (3.5 wt % Ru, 20 wt % W) using XRD pattern in (A) (inset: crystal structure of RuW alloy NPs). White circle marks (○) represent the observed intensities, and the red solid line is Rietveld-fit profile. The difference plot (blue) is shown at the bottom. The olive tick marks indicate the positions of the Bragg reflections as obtained in the Rietveld refinement. The RuW alloy parameters are as follows: space group Im-3m, a = b = c = 3.1609 Å. Rp = 7.60% and Rwp = 9.32%. (H) Fourier-transformed (FT) EXAFS k2-weighted χ(k) function spectra of RuW/SiO2 (3.5 wt % Ru, 20 wt % W) catalyst, references, and corresponding EXAFS R-space fitting curve for RuW/SiO2.

  • Fig. 3 Proposed mechanism for SSH reaction of anisole on RuW/SiO2 catalyst.

    The inset shows the calculated profiles in electron volts. DFT optimized geometries of the structures of the initial state (IS) of anisole, final state (FS) of products, intermediates (IM), and transition states (TS) of the key elementary steps are shown in the reaction cycle (side view). The reaction cycle corresponds to the energy profile of path I, which is shown by the green dashed lines in the inset. The red dashed lines present the energy profile of path II specifically shown in fig. S5A.

  • Fig. 4 Transformation of biomass-derived substrates to arenes.

    The general reaction scheme is shown at the top. The chemical structure colored with red is removed, and the chemical structure colored with green is the SSH product. Yields of products provided are at full conversion of substrates, as averages of three experiments conducted in parallel. Reaction conditions: Substrate (1.0 mmol), H2O (5.0 ml), 0.5 MPa Ar, 800 rpm. (A) Condition A1: RuW/SiO2 catalyst (100 mg, 3.5 wt % Ru, 20 wt % W), 195°C, 12 hours; condition A2: RuW/SiO2 catalyst (110 mg, 4.0 wt % Ru, 30 wt % W), 210°C, 20 hours. (B) Condition B1: RuW/SiO2 catalyst (90 mg, 3.5 wt % Ru, 20 wt % W), 180°C, 10 hours; condition B2: RuW/SiO2 catalyst (110 mg, 3.5 wt % Ru, 20 wt % W), 200°C, 16 hours. (C) Condition C1: RuW/SiO2 catalyst (130 mg, 4.0 wt % Ru, 30 wt % W), 230°C, 24 hours; condition C2: RuW/SiO2 catalyst (140 mg, 4.0 wt % Ru, 30 wt % W), 240°C, 24 hours. (D) Condition D1: RuW/SiO2 catalyst (110 mg, 3.5 wt % Ru, 20 wt % W), 210°C, 14 hours; condition D2: RuW/SiO2 catalyst (120 mg, 3.5 wt % Ru, 20 wt % W), 220°C, 18 hours.

  • Fig. 5 Transformation of kraft lignin to arenes over RuW/SiO2 catalysts.

    Reaction conditions: kraft lignin (0.5 g), RuW/SiO2 catalyst (0.2 g, 5.0 wt % Ru, 40 wt % W), water (7.0 ml), 0.5 MPa Ar, 280°C, 24 hours, 800 rpm.

  • Table 1 Results for the transformation of anisole over supported metal catalysts at different conditions.
    Embedded Image
    EntryCatalytic system*T
    (hours)
    Conversion
    (%)
    Selectivity (%)Yield of
    1 (%)
    CatalystGas123456
    1Ar4.50.00.00.00.00.00.00.00.0
    2Ru/SiO2Ar4.50.00.00.00.00.00.00.00.0
    3Pt/SiO2Ar4.50.00.00.00.00.00.00.00.0
    4Pd/SiO2Ar4.50.00.00.00.00.00.00.00.0
    5Ni/SiO2Ar4.50.00.00.00.00.00.00.00.0
    6RuW/SiO2Ar4.596.6>99.90.00.00.00.00.096.5
    7§RuW/SiO2Ar5.0100>99.90.00.00.00.00.0>99.9
    8PtW/SiO2Ar4.528.880.20.019.80.00.00.023.1
    9PdW/SiO2Ar4.520.573.70.017.09.30.00.015.1
    10NiW/SiO2Ar4.50.00.00.00.00.00.00.00.0
    11||Ru-W/SiO2Ar5.09.8>99.90.00.00.00.00.09.8
    12RuW/SiO2H24.596.578.821.20.00.00.00.076.0
    13PtW/SiO2H24.596.811.831.20.03.219.534.311.8
    14NiW/SiO2H24.525.631.818.20.09.115.525.48.1
    15PdW/SiO2H24.597.00.067.70.00.521.110.70.0
    16Ru/SiO2H21.095.90.042.00.00.04.653.40.0
    17W/SiO2Ar4.50.00.00.00.00.00.00.00.0
    18W/SiO2H24.50.00.00.00.00.00.00.00.0

    *Reaction results are the averages of three experiments conducted in parallel. Anisole (1.0 mmol), H2O (5.0 ml), 175°C, 0.5 MPa Ar, or 1.0 MPa H2, 800 rpm.

    †Ru/SiO2 (3.5 wt %), Pt/SiO2, Pd/SiO2, Ni/SiO2, 20 wt % W/SiO2 (the content of metal is based on SiO2 and determined by ICP); RuW/SiO2, PtW/SiO2, PdW/SiO2, NiW/SiO2 (3.5 wt % Ru, Pt, Pd, and Ni metals, 20 wt % W, the content of metal is based on SiO2 and determined by ICP).

    ‡Without catalyst, or only SiO2 was used.

    §Turnover number (TON) = 38; TON is expressed in mole of anisole converted per mole of ruthenium.

     ||Mechanical mixture of Ru/SiO2 (3.5 wt % Ru) and W/SiO2 (20 wt % W) catalysts is denoted as Ru-W/SiO2 catalyst.

    Supplementary Materials

    • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/11/eaax6839/DC1

      Fig. S1. Nitrogen adsorption-desorption isotherm and the pore size distribution of the SiO2 support.

      Fig. S2. The analyses of the liquid and gaseous product obtained from the transformation of anisole over the RuW/SiO2 catalyst.

      Fig. S3. EDS elemental mapping analysis of the RuW/SiO2 catalyst.

      Fig. S4. XANES and FT-EXAFS spectra of RuW/SiO2 catalyst.

      Fig. S5. Proposed path II mechanism for SSH reaction and DFT optimized geometries in the proposed mechanism.

      Fig. S6. Identification of formaldehyde and origination of the negatively charged hydrogen in hydrogenolysis.

      Fig. S7. Optimization of reaction conditions over RuW/SiO2 catalyst, recyclability and stability of RuW/SiO2 catalyst.

      Fig. S8. 2D HSQC NMR spectra of the kraft lignin before and after the transformation with RuW/SiO2 catalyst.

      Fig. S9. GC trace of liquid products generated from the transformation of the kraft lignin.

      Table S1. Results for the transformation of anisole in different solvent systems.

      Table S2. Structure parameters of the RuW/SiO2 catalyst extracted from the EXAFS fitting.

      Table S3. Results for the transformation of substrates over the RuW/SiO2 catalyst.

      Table S4. Elemental analysis of the kraft lignin sample.

      Reference (59)

    • Supplementary Materials

      This PDF file includes:

      • Fig. S1. Nitrogen adsorption-desorption isotherm and the pore size distribution of the SiO2 support.
      • Fig. S2. The analyses of the liquid and gaseous product obtained from the transformation of anisole over the RuW/SiO2 catalyst.
      • Fig. S3. EDS elemental mapping analysis of the RuW/SiO2 catalyst.
      • Fig. S4. XANES and FT-EXAFS spectra of RuW/SiO2 catalyst.
      • Fig. S5. Proposed path II mechanism for SSH reaction and DFT optimized geometries in the proposed mechanism.
      • Fig. S6. Identification of formaldehyde and origination of the negatively charged hydrogen in hydrogenolysis.
      • Fig. S7. Optimization of reaction conditions over RuW/SiO2 catalyst, recyclability and stability of RuW/SiO2 catalyst.
      • Fig. S8. 2D HSQC NMR spectra of the kraft lignin before and after the transformation with RuW/SiO2 catalyst.
      • Fig. S9. GC trace of liquid products generated from the transformation of the kraft lignin.
      • Table S1. Results for the transformation of anisole in different solvent systems.
      • Table S2. Structure parameters of the RuW/SiO2 catalyst extracted from the EXAFS fitting.
      • Table S3. Results for the transformation of substrates over the RuW/SiO2 catalyst.
      • Table S4. Elemental analysis of the kraft lignin sample.
      • Reference (59)

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