Research ArticlePHYSICAL SCIENCE

Direct carbon-carbon coupling of furanics with acetic acid over Brønsted zeolites

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Science Advances  16 Sep 2016:
Vol. 2, no. 9, e1601072
DOI: 10.1126/sciadv.1601072
  • Fig. 1 Direct acylation of MF with acetic acid over HZSM-5.

    (A) Schematic of 2-MF acylation with acetic acid over HZSM-5. (B) TPD experiment over HZSM-5 showing 2-acetyl-5-MF desorbing with 2-MF pulses from catalyst bed saturated with surface acyl species at 220°C.

  • Fig. 2 Reaction kinetics of MF acylation with acetic acid over HZSM-5.

    (A to C) Natural logarithm of acylation reaction rate versus concentration of acetic acid (A), concentration of 2-MF (B), and concentration of water (C) over CBV8014 with 0.0198 mmol of catalyst at a reaction temperature of 250°C and 30-min time on stream. The included table (D) shows conversion, product yields, and product selectivities observed upon passing 2-MF and acetic acid over HZSM-5 after 30-min time on stream with a constant 0.0198 mmol of Brønsted site catalysts. An acetic acid–to–2-MF mole ratio of 1:0.258 was used in this study, with a catalyst mass of 0.05 mg. *Embedded Image; †Embedded Image. (E) TOF of 2-MF acylation with acetic acid over HZSM-5 and Hβ as a function of time at 250°C and 0.05 mg of catalyst. (F) Apparent activation energy of acetic acid acylation over HZSM-5 estimated for a temperature range of 220° to 250°C. The molar feed rate of acetic acid (0.00437 mol/hour) and 2-MF (0.00113 mol/hour) with 0.0198 mmol of catalyst was used to obtain apparent activation energies.

  • Fig. 3 DFT calculations of acylation of 2-MF with acetic acid.

    All the values are reported in kilojoules per mole. The transition states are shown as the insets with C, O, H, Si, and Al atoms colored cyan, red, gray, black, and green, respectively. The results calculated using the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional (red) are also shown, for comparison with the PBE results (black). The reaction path is schematically shown at the bottom.

  • Fig. 4 Charge transfer and density of states calculated using the hybrid functional.

    (A) Charge transfer between the molecules (the desorbed acyl and 2-MF) and the zeolite framework in the transition state of the C–C coupling step. (B) The same charge transfer in the absence of the 2-MF molecule. Red and blue indicate charge accumulation (negative charge) and charge depletion (positive charge), respectively. The isosurface corresponds to a charge density of ±0.015 e Å−3. (C and D) Plane-averaged charge transfer (see the methods in the Supplementary Materials) of the same area as in (A) and (B). Electron depletion at the desorbed acyl (indicated by dashed circles) via the Bader charge analysis. (E) Projected density of states (PDOS) onto the desorbed acyl species (acylium ion) in (A) and (B).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/9/e1601072/DC1

    Supplementary Information

    fig. S1. IPA TPD profile of CBV8014 and CPC814C, showing the evolution of IPA, propylene, and ammonia as a function of temperature.

    fig. S2. Scanning electron microscopy image of CBV8014 to estimate the crystal size of the catalyst.

    fig. S3. X-ray diffraction data for CBV8014, showing that the sample is a crystalline zeolite with MFI framework type.

    fig. S4. Comparing TOF with increasing water cofeeding at a reaction temperature of 250°C.

    fig. S5. Comparing TOF with increasing partial pressure of 2-MF at a reaction temperature of 250°C.

    fig. S6. Comparing rate of acylation between CBV80114 and Na-exchanged CBV8014 to test internal diffusion limitations.

    fig. S7. Optimized structures from DFT calculations.

    fig. S8. DFT calculations of acyl formation from acetic acid in Hβ.

    fig. S9. Apparent activation energy of acetic acid ketonization over CBV8014 estimated for a temperature range of 270° to 310°C.

    fig. S10. Comparing the conversion of MF by using different catalyst amounts.

    fig. S11. Online gas chromatography–flame ionization detector spectrum for MF acylation with acetic acid at a conversion level of 15%.

    fig. S12. Gas chromatography–MS spectrum to identify compounds of MF acylation reaction with acetic acid.

    References (46, 47)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Information
    • fig. S1. IPA TPD profile of CBV8014 and CPC814C, showing the evolution of IPA, propylene, and ammonia as a function of temperature.
    • fig. S2. Scanning electron microscopy image of CBV8014 to estimate the crystal size of the catalyst.
    • fig. S3. X-ray diffraction data for CBV8014, showing that the sample is a crystalline zeolite with MFI framework type.
    • fig. S4. Comparing TOF with increasing water cofeeding at a reaction temperature of 250°C.
    • fig. S5. Comparing TOF with increasing partial pressure of 2-MF at a reaction temperature of 250°C.
    • fig. S6. Comparing rate of acylation between CBV80114 and Na-exchanged CBV8014 to test internal diffusion limitations.
    • fig. S7. Optimized structures from DFT calculations.
    • fig. S8. DFT calculations of acyl formation from acetic acid in Hβ.
    • fig. S9. Apparent activation energy of acetic acid ketonization over CBV8014 estimated for a temperature range of 270° to 310°C.
    • fig. S10. Comparing the conversion of MF by using different catalyst amounts.
    • fig. S11. Online gas chromatography–flame ionization detector spectrum for MF acylation with acetic acid at a conversion level of 15%.
    • fig. S12. Gas chromatography–MS spectrum to identify compounds of MF acylation reaction with acetic acid.
    • References (46, 47)

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