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

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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 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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