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Structure–Activity Studies on Highly Active Palladium Hydrogenation Catalysts by X-ray Absorption Spectroscopy

MPG-Autoren
http://pubman.mpdl.mpg.de/cone/persons/resource/persons22107

Shao,  Lidong
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons22288

Zhang,  Bing Sen
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons21743

Knop-Gericke,  Axel
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons22243

Willinger,  Marc Georg
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons22071

Schlögl,  Robert
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons22163

Teschner,  Detre
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

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Zitation

Bauer, M., Schoch, R., Shao, L., Zhang, B. S., Knop-Gericke, A., Willinger, M. G., et al. (2012). Structure–Activity Studies on Highly Active Palladium Hydrogenation Catalysts by X-ray Absorption Spectroscopy. Journal of Physical Chemistry C, 116(42), 22375-22385. doi:10.1021/jp306962v.


Zitierlink: http://hdl.handle.net/11858/00-001M-0000-0010-0D9C-0
Zusammenfassung
Functionalized carbon nanotubes were used to produce Pd-based hydrogenation catalysts. Pd/CNT with small (1–2 nm) Pd particles showed classical catalytic behavior in propyne hydrogenation, with high propene selectivity at moderate conversion levels and propane formation near full conversion. Pd/CNT with larger (15 nm) nanoparticles, however, was selective (88%) toward propene even at practically full propyne conversion. An additionally prepared Pd2Ga/CNT catalyst exhibited even higher propene selectivity at full conversion. All of these materials were studied in situ by X-ray absorption spectroscopy at the Pd K-edge. Pd2Ga/CNT was stable under all conditions examined without variation in XANES or in the derived EXAFS parameters. Both Pd/CNT samples formed β-hydride under hydrogen, as assessed from the calculated lattice expansion and the characteristic red shift of the XANES maxima. The minor spectroscopic difference between the monometallic catalysts observed at high propyne conversion suggests the decisive role of a Pd–C (subsurface C) contribution in the structure of larger Pd particles, being absent with ultrasmall nanoparticles. In general, all factors (intermetallic phase formation, subsurface C, etc.) that reduce the surface H coverage will give rise to enhanced partial hydrogenation selectivity of palladium when secondary alkene hydrogenation at late bed segments or diffusion issues in the pores are avoided.