Selective CO methanation on isostructural Ru nanocatalysts: The role of support effects

Shilong Chen, Ali M. Abdel-Mageed, Cornelius Gauckler, Sine Ellemann Olesen, Ib Chorkendorff, R. Jürgen Behm*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Aiming at a more detailed understanding of support effects on the catalytic performance of supported Ru catalysts, here specifically in the selective methanation of CO, we have prepared and investigated a set of three isostructural Ru catalysts with different supports (TiO2, Al2O3, and ZrO2), but similar surface area, Ru loading, and Ru particle size. The activity was found to increase with increasing reducibility in the order Ru/Al2O3 ≤ Ru/ZrO2 < Ru/TiO2, which goes along with a significant increase of electron density on the Ru NPs, in the number of O-vacancies, and the amount of basic sites in the oxide supports, as probed by XPS and pyrrole titration. In situ FTIR spectra recorded during reaction indicate that the high activity on Ru/TiO2 is correlated with the highest COad/Ru-multicarbonyl coverage, while Ru/ZrO2 and Ru/Al2O3 exhibit significantly lower COad coverages, indicative of lower CO adsorption energies. Kinetic measurements using isotope labelled gas mixtures, H2/CO and D2/CO, show a small, but distinct inverse kinetic isotope effect (KIE), which is more pronounced on Ru/TiO2 (RH/RD = 0.76) than on Ru/ZrO2 and Ru/Al2O3 ((RH/RD = 0.91). These trends are explained by and discussed in terms of differences in electronic metal-support interactions (EMSIs), caused by the differences in O-vacancy formation (reducibility) of the support materials and consequently in charge transfer to the Ru nanoparticles. Such effects are considered to be of general importance for reactions taking place under strongly reductive conditions.
Original languageEnglish
JournalJournal of Catalysis
Volume373
Pages (from-to)103-115
Number of pages13
ISSN0021-9517
DOIs
Publication statusPublished - 2019

Keywords

  • Selective CO methanation
  • Support effect
  • Electronic metal-support interactions (EMSIs)
  • Kinetic isotope effect
  • Pyrrole titration
  • CO adsorption
  • Ru catalyst

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