The Roles of Subsurface Carbon and Hydrogen in Palladium-Catalyzed Alkyne Hydrogenation
Detre Teschner,1*
János Borsodi,1,2
Attila Wootsch,2
Zsolt Révay,2
Michael Hävecker,1
Axel Knop-Gericke,1
S. David Jackson,3
Robert Schlögl1
Alkynes can be selectively hydrogenated into alkenes on solid palladium catalysts. This process requires a strong modification of the near-surface region of palladium, in which carbon (from fragmented feed molecules) occupies interstitial lattice sites. In situ x-ray photoelectron spectroscopic measurements under reaction conditions indicated that much less carbon was dissolved in palladium during unselective, total hydrogenation. Additional studies of hydrogen content using in situ prompt gamma activation analysis, which allowed us to follow the hydrogen content of palladium during catalysis, indicated that unselective hydrogenation proceeds on hydrogen-saturated β-hydride, whereas selective hydrogenation was only possible after decoupling bulk properties from the surface events. Thus, the population of subsurface sites of palladium, by either hydrogen or carbon, governs the hydrogenation events on the surface.
1 Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.
2 Institute of Isotopes, Hungarian Academy of Sciences, Post Office Box 77, Budapest H-1525, Hungary.
3 WestCHEM, Department of Chemistry, University of Glasgow, Glasgow G128QQ, Scotland, UK.
* To whom correspondence should be addressed. E-mail: teschner{at}fhi-berlin.mpg.de
