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

Formation of benzyl alcohol

Noémie Perret, Xiaodong Wang, Juan Delgado, Ginesa Blanco, Xiaowei Chen, Carol Olmos, Serafin Bernal, Mark Keane

Research output: Contribution to journalArticle

24 Citations (Scopus)

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 Cdouble bond; length as m-dashO 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.
Original languageEnglish
Pages (from-to)114–125
Number of pages12
JournalJournal of Catalysis
Volume317
Early online date10 Jul 2014
DOIs
Publication statusPublished - Aug 2014

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Benzyl Alcohol
Benzoic Acid
Benzoic acid
benzoic acid
Oxygen vacancies
Hydrogenation
hydrogenation
Hydrogen
alcohols
Alcohols
oxygen
Oxygen
Benzoates
attack
Toluene
Carbon Monoxide
hydrogen
selectivity
Cations
X ray photoelectron spectroscopy

Keywords

  • selective hydrogenation
  • benzoic acid
  • benzyl alcohol
  • CEO2
  • CeO2–ZrO2
  • supported AU catalysts

Cite this

Selective hydrogenation of benzoic acid over Au supported on CeO2 and Ce0.62Zr0.38O2 : Formation of benzyl alcohol. / Perret, Noémie; Wang, Xiaodong; Delgado, Juan; Blanco, Ginesa; Chen, Xiaowei; Olmos, Carol; Bernal, Serafin; Keane, Mark.

In: Journal of Catalysis, Vol. 317, 08.2014, p. 114–125.

Research output: Contribution to journalArticle

Perret, N, Wang, X, Delgado, J, Blanco, G, Chen, X, Olmos, C, Bernal, S & Keane, M 2014, 'Selective hydrogenation of benzoic acid over Au supported on CeO2 and Ce0.62Zr0.38O2: Formation of benzyl alcohol', Journal of Catalysis, vol. 317, pp. 114–125. https://doi.org/10.1016/j.jcat.2014.06.010
Perret, Noémie ; Wang, Xiaodong ; Delgado, Juan ; Blanco, Ginesa ; Chen, Xiaowei ; Olmos, Carol ; Bernal, Serafin ; Keane, Mark. / Selective hydrogenation of benzoic acid over Au supported on CeO2 and Ce0.62Zr0.38O2 : Formation of benzyl alcohol. In: Journal of Catalysis. 2014 ; Vol. 317. pp. 114–125.
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AB - 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 Cdouble bond; length as m-dashO 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.

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