Hydrogenation of benzaldehyde via electrocatalysis and thermal catalysis on carbon-supported metals

Yang Song, Udishnu Sanyal, Dhananjai Pangotra, Jamie D. Holladay, Donald M. Camaioni, Oliver Y. Gutiérrez, Johannes A. Lercher

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118 Scopus citations

Abstract

Selective reduction of benzaldehyde to benzyl alcohol (model reaction for low-temperature stabilization of bio-oil) on C-supported Pt, Rh, Pd, and Ni in aqueous phase was conducted using either H2 (thermal catalytic hydrogenation, TCH) or hydrogen generated in situ electrocatalytically (electrocatalytic hydrogenation, ECH). In TCH, the intrinsic activity of the metals at room temperature and 1 bar H2 increased in the sequence Pt/C < Rh/C ≤ Pd/C, while Ni/C is inactive. At these conditions, the coverage of benzaldehyde is high while the coverage of adsorbed H is low and the reaction follows a Langmuir-Hinshelwood mechanism. All tested metals were active in ECH of benzaldehyde above the onset potentials of the H2 evolution reaction (HER). Thus, hydrogenation competes with HER. The relative rates of H reacting to H2 and H addition to benzaldehyde determines the selectivity to ECH and HER. Accordingly, the selectivity of the metals towards ECH increases in the order as follows: Ni/C < Pt/C < Rh/C < Pd/C. The latter having ECH selectivity around 99%. In ECH, the intrinsic activities of all tested metals were higher and the activation energies of benzaldehyde hydrogenation were lower than in TCH.

Original languageEnglish
Pages (from-to)68-75
Number of pages8
JournalJournal of Catalysis
Volume359
DOIs
StatePublished - Mar 2018

Keywords

  • Aqueous phase reactions
  • Benzaldehyde
  • Carbon-supported metals
  • Electrocatalysis
  • Hydrogenation

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