Selective hydrogenation of benzoic acid over Au supported on CeO2 and Ce0.62Zr0.38O2: Formation of benzyl alcohol

Noemie Perret, Xiaodong Wang, Juan J. Delgado, Ginesa Blanco, Xiaowei Chen, Carol M. Olmos, Serafin Bernal, Mark A. Keane

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Abstract

The gas-phase hydrogenation of benzoic acid was studied over Au supported on CeO2 and Ce0.62Zr0.38O2 (CZ). HAADF-STEM has established formation of nanoscale (mean = 1.5-2 nm) Au particles, which is consistent with CO adsorption measurements. Incorporation of Au facilitated partial support reduction during TPR to 573 K where the presence of Zr increased oxygen mobility, resulting in a greater degree of Ce4+ reduction (to Ce3+ in Au/CZ, as demonstrated by oxygen storage capacity and XPS measurements. Hydrogenation of an aqueous benzoic acid feed generated benzaldehyde and benzyl alcohol with a higher rate over Au/CZ that is attributed to the action of oxygen vacancies, which activate the carboxyl function for hydrogen attack. A parallel/consecutive kinetic model has been applied to quantify catalytic selectivity. A concerted (single step) conversion is proposed for Au/CeO2 that involves bridging interaction of the benzoate with Ce cations and Au nanoparticles with hydrogen addition. A stepwise conversion on Au/CZ is achieved via a Mars and van Krevelen mechanism with benzoic acid activation at an oxygen vacancy and reaction with surface hydrogen to generate benzaldehyde as a reactive intermediate that is converted to benzyl alcohol via nucleophilic C = O attack. Switching from an aqueous to ethanolic feed increased rate due to greater oxygen vacancy availability with higher selectivity to benzaldehyde and appreciable toluene formation over Au/CZ. (C) 2014 Elsevier Inc. All rights reserved.

Original languageEnglish
Pages (from-to)114-125
Number of pages12
JournalJournal of Catalysis
Volume317
DOIs
Publication statusPublished - Aug 2014

Keywords

  • Selective hydrogenation
  • Benzoic acid
  • Benzyl alcohol
  • CeO2
  • CeO2-ZrO2
  • Supported Au catalysts
  • AROMATIC CARBOXYLIC-ACIDS
  • CEO2-ZRO2 MIXED OXIDES
  • GAS-PHASE HYDROGENATION
  • TEMPERATURE-PROGRAMMED DESORPTION
  • CERIA-ZIRCONIA CATALYSTS
  • GOLD CATALYSTS
  • METAL-OXIDES
  • CORRESPONDING ALDEHYDES
  • STRUCTURAL-PROPERTIES
  • SULFATED ZIRCONIA

Cite this

Perret, N., Wang, X., Delgado, J. J., Blanco, G., Chen, X., Olmos, C. M., Bernal, S., & Keane, M. A. (2014). Selective hydrogenation of benzoic acid over Au supported on CeO2 and Ce0.62Zr0.38O2: Formation of benzyl alcohol. Journal of Catalysis, 317, 114-125. https://doi.org/10.1016/j.jcat.2014.06.010