Solid base catalysed 5-HMF oxidation to 2,5-FDCA over Au/hydrotalcites: fact or fiction?

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Ardemani, Leandro ; Cibin, Giannantonio ; Dent, Andrew J. ; Isaacs, Mark A. ; Kyriakou, Georgios ; Lee, Adam F. ; Parlett, Christopher M. A. ; Parry, Stephen A. ; Wilson, Karen (2015)
  • Publisher: Royal Society of Chemistry
  • Related identifiers: doi: 10.1039/c5sc00854a
  • Subject: catalysts; gold; reaction intermediates

Nanoparticulate gold has emerged as a promising catalyst for diverse mild and efficient selective aerobic oxidations. However, the mechanism of such atom-economical transformations, and synergy with functional supports, remains poorly understood. Alkali-free Mg-Al hydrotalcites are excellent solid base catalysts for the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furan dicarboxylic acid (FDCA), but only in concert with high concentrations of metallic gold nanoparticles. In the absence of soluble base, competitive adsorption between strongly-bound HMF and reactively-formed oxidation intermediates site-blocks gold. Aqueous NaOH dramatically promotes solution phase HMF activation, liberating free gold sites able to activate the alcohol function within the metastable 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) reactive intermediate. Synergistic effects between moderate strength base sites within alkali-free hydrotalcites and high gold surface concentrations can afford highly selective and entirely heterogeneous catalysts for aqueous phase aldehyde and alcohol cascade oxidations pertinent to biomass transformation.
  • References (29)
    29 references, page 1 of 3

    2 wt% Au/HT catalyst. In the absence of diffusion limitations, 15 P. Ferrini and R. Rinaldi, Angew. Chem., Int. Ed., 2014, 53, and the presence of available reaction sites, the mass normal- 8634-8639.

    ized FDCA productivity should be independent of sub- 16 C. Chatterjee, F. Pong and A. Sen, Green Chem., 2015, 17, 40- strate : catalyst ratio, whereas Fig. 5 inset reveals that halving 71.

    the HMF : surface Au ratio imparts a seven-fold increase in 17 H. B. Zhao, J. E. Holladay, H. Brown and Z. C. Zhang, Science, FDCA productivity. Reactive gold sites for HMFCA oxidation 2007, 316, 1597-1600.

    only become available for HMF : surface Au ratios below a 18 M. Moliner, Y. Roman-Leshkov and M. E. Davis, Proc. Natl.

    critical threshold wherein it can effectively compete with Acad. Sci. U. S. A., 2010, 107, 6164-6168.

    adsorption of the parent HMF. 19 A. Osatiashtiani, A. F. Lee, D. R. Brown, J. A. Melero, In Conclusion, the combination of operando XAS and G. Morales and K. Wilson, Catal. Sci. Technol., 2014, 4, detailed kinetic mapping has elucidated the nature of the active 333-342.

    site and mechanism of Au catalysed 5-HMF aerobic selox to 20 A. A. Rosatella, S. P. Simeonov, R. F. M. Frade and 2,5-FDCA. A delicate balance is revealed between the rate of base C. A. M. Afonso, Green Chem., 2011, 13, 754-793.

    catalysed 5-HMF activation and the latter's self-poisoning of 21 W. Partenheimer and V. V. Grushin, Adv. Synth. Catal., 2001, requisite metallic gold sites for subsequent oxidation of reac- 343, 102-111.

    tively-formed HMFCA/FFCA intermediates. Hydrotalcite solid 22 T. Pasini, M. Piccinini, M. Blosi, R. Bonelli, S. Albonetti, base can only drive 5-HMF selox in concert with high concen- N. Dimitratos, J. A. Lopez-Sanchez, M. Sankar, Q. He, trations of surface gold, a discovery that has important impli- C. J. Kiely, G. J. Hutchings and F. Cavani, Green Chem., cations for gold catalysis and cascade oxidations. 2011, 13, 2091-2099.

    23 Z. Miao, Y. Zhang, X. Pan, T. Wu, B. Zhang, J. Li, T. Yi, Acknowledgements Z. Zhang and X. Yang, Catal. Sci. Technol., 2015, 5, 1314- 1322.

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