Journal article
Evolution of intermetallic GaPd2/SiO2 catalyst and optimization for methanol synthesis at ambient pressure
National Centre for Nano Fabrication and Characterization, Technical University of Denmark1
Nanocharacterization, National Centre for Nano Fabrication and Characterization, Technical University of Denmark2
Electron matter interaction, Nanocharacterization, National Centre for Nano Fabrication and Characterization, Technical University of Denmark3
Department of Physics, Technical University of Denmark4
Universidade de São Paulo5
Neutrons and X-rays for Materials Physics, Department of Physics, Technical University of Denmark6
Karlsruhe Institute of Technology7
Surface Physics and Catalysis, Department of Physics, Technical University of Denmark8
Nanostructure and Functionality, Nanocharacterization, National Centre for Nano Fabrication and Characterization, Technical University of Denmark9
The CO2 hydrogenation to methanol is efficiently catalyzed at ambient pressure by nanodispersed intermetallic GaPd2/SiO2 catalysts prepared by incipient wetness impregnation. Here we optimize the catalyst in terms of metal content and reduction temperature in relation to its catalytic activity. We find that the intrinsic activity is higher for the GaPd2/SiO2 catalyst with a metal loading of 13 wt.% compared to catalysts with 23 wt.% and 7 wt.%, indicating that there is an optimum particle size for the reaction of around 8 nm.
The highest catalytic activity is measured on catalysts reduced at 550 °C. To unravel the formation of the active phase, we studied calcined GaPd2/SiO2 catalysts with 23 wt.% and 13 wt.% using a combination of in situ techniques: X-ray diffraction (XRD), X-ray absorption near edge fine structure (XANES) and extended X-ray absorption fine structure (EXAFS).
We find that the catalyst with higher metal content reduces to metallic Pd in a mixture of H2/Ar at room temperature, while the catalyst with lower metal content retains a mixture of PdO and Pd up to 140 °C. Both catalysts form the GaPd2 phase above 300 °C, albeit the fraction of crystalline intermediate Pd nanoparticles of the catalyst with higher metal loading reduces at higher temperature.
In the final state, the catalyst with higher metal loading contains a fraction of unalloyed metallic Pd, while the catalyst with lower metal loading is phase pure. We discuss the alloying mechanism leading to the catalyst active phase formation selecting three temperatures: 25 °C, 320 °C and 550 °C.
Language: | English |
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Publisher: | Taylor & Francis |
Year: | 2019 |
Pages: | 521-531 |
ISSN: | 18785514 and 14686996 |
Types: | Journal article |
DOI: | 10.1080/14686996.2019.1603886 |
ORCIDs: | Fiordaliso, Elisabetta M. , Chorkendorff, Ib and Damsgaard, Christian D. |
CO2 hydrogenation GaPd2 Intermetallics Methanol synthesis Optimization in situ EXAFS in situ XRD
102 Porous / Nanoporous / Nanostructured materials 205 Catalyst / Photocatalyst / Photosynthesis 50 Energy Materials Biotechnology Materials of engineering and construction. Mechanics of materials TA401-492 TP248.13-248.65 co2 hydrogenation gapd2 in situ exafs in situ xrd intermetallics methanol synthesis optimization