Hävecker, M.

Knop-Gericke, A.

Schlögl, R.

Schnörch, P.

Teschner, D.

Vass, E.

Zafeiratos, S.

English

MPG.PuRe

14th International Workshop onNanoscale Spectroscopy and NanotechnologyRathen17-21 September 2006In situ XPS investigations in heterogeneous catalysisD. Teschner, S. Zafeiratos, M. Hävecker, E. Vass, P. Schnörch, A.Knop-Gericke, R. SchlöglFritz-Haber-Institut, Berlin, Department of Inorganic Chemistry2IntroductionLiterature carbon laydown selective hydrogenation“similar” catalysts different activity & selectivity(structure sensitivity?)Selectivity issue: what defines selectivity?[     ]+ H23Model of overlapping TDS peaksHydrogenation in the presence ofsubsurface H[Pd particles]  No hydrogenation withoutsubsurface H[Pd(111)]  Pentenes to pentaneDoyle AM, Shaikhutdinov SK, Jackson SD, Freund HJANGEWANDTE CHEMIE-INTERNATIONAL EDITION 42 (42): 5240-5243 2003 4Acetylene hydrogenation (TDS)Subsurface Hat low TadsTotal hydrogenation decreases strongly withoutsubsurface HKhan NA, Shaikhutdinov SK, Freund HJCATALYSIS LETTERS, 108 (3-4) 159-164, 2006  5Hydrogenation (TDS)alkynesub-surface Hsub-surface H6Summary1. Subsurface H : effective for alkene-to-alkane but also for alkyne-to-alkane transformation7Pulse experiments1-pentyne Adsorption 0.0E+002.0E-054.0E-056.0E-058.0E-051.0E-04Moles1 2 3 4 5 6 7Pulse Number1-pentyne 1-pentene trans-2-pentenecis-2-pentene pentane unknown• First pulse shows activity• 65% conversion– 38.5% 1-pentene– 6.5% trans-2-pentene– 3.5% cis-2-pentene– 6.5% pentane– 11.5% Unknown(After H2 pretreatment)                         1%Pd/Al2O3Hneeded/Pdtotal ratio: 13-to-1     Source of H? Spillover8Summary1. Subsurface H : effective for alkene-to-alkane but also for alkyne-to-alkane transformation2. Surface H : could be selective (spillover)9Hydrogenationp(C5)=10 Torr0500100015002000250030003500400045000 100 200 300 400p(H2), TorrTOF (1/h)020406080100Conversion (%)0204060801000 100 200 300 400p(H2), TorrSelectivity (%)Pentane1-Pentene2-pentenes1. 1-Pentyne hydrogenation over 1% Pd/Al2O3 in a closed loop-reactor, t=5 min. (after repeated runs at each condition)2. 1-Pentyne hydrogenation over 1% Pd/Al2O3 in continuous flowH2:C5 = 4:1 total hydrogenationH2:C5 = 3:1 selective hydrogenation10Summary1. Subsurface H : effective for alkene-to-alkane but also for alkyne-to-alkane transformation2. Surface H : could be selective (spillover)3. Different reaction orders in the different selectivity regimes & Abrupt changes between regimes11During TEOM experiment[     ]+ H2170 mins40 mins89.281.681.158.70.1trace1-pentyne10.617.116.240.1tracetrace1-pentenetrace0.20.7trace0.1trace2-pentenes0.31.12.01.299.8100n-pentane--74.942.83.6trace1-pentyne--22.454.70.5trace1-pentene--Quartz Wool, 303 K--Quartz Wool, 358 K1.90.7Al2O3, 100 % H22.30.2Pd Black, 5 % H284.511.3Pd Black, 100 % H2100tracePd/Al2O3, 100 % H2n-pentane2-pentenes12During TEOM experiment[     ]+ H2170 mins40 mins89.281.681.158.70.1trace1-pentyne10.617.116.240.1tracetrace1-pentenetrace0.20.7trace0.1trace2-pentenes0.31.12.01.299.8100n-pentane--74.942.83.6trace1-pentyne--22.454.70.5trace1-pentene--Quartz Wool, 303 K--Quartz Wool, 358 K1.90.7Al2O3, 100 % H22.30.2Pd Black, 5 % H284.511.3Pd Black, 100 % H2100tracePd/Al2O3, 100 % H2n-pentane2-pentenes13During TEOM experimentReaction with 100% H2 Reaction with 5% H2Up to x5 more carbon is retained in the selective hydrogenation regime0123456780 1 2 3AdsorbedRetained0 1 2 3AdsorbedRetainedMass change [micro g / mg catalyst]Time since introduction of 1-pentyne [hours]Pd Black14Summary1. Subsurface H : effective for alkene-to-alkane but also for alkyne-to-alkane transformation2. Surface H : could be selective (spillover)3. Different reaction orders in the different selectivity regimes & Abrupt changes between regimes4. C uptake is significantly more in the selective regime 15In situ XPS systemExperimental cellsupplied by gas lines (p0)X-rays enter the cell at 55° incidence through an SiNx window(thickness ~ 1000 Å)Analyzerinput lensFocal point of analyzerinput lensFirst differentialpumping stage (10-4p0) Second differentialpumping stage (10-6p0) Third differentialpumping stage (10-8p0) Hemisphercalelectronanalyzer(10-9p0)mass spectrometerand additional pumping16Reaction in the mbar p region (in-situ XPS)-~2~20~5SelectivityPentane [%]100~98~80~95SelectivityPentene [%]<1~2.5~5~ 10Conversion[%]Pd(111)Pd foil3% Pd/Al2O35% Pd/CNT+ H2Recation conditions: C5/H2 = 1:9, 1 mbar, 358 K17In-situ XPS: Pd 3d (hν: 720 eV)18In-situ XPS: Pd 3d depth profilingNot only adsorbate-induced surface core level shift !But on-top location!19In-situ XPS: C1s (Switching off experiments)1: reaction mix.2: C5 off3: H2 off4: C5 gas-phase20In-situ XPS: Pd 3d (Switching off experiments)1: reaction mix.2: C5 off3: H2 off4: reaction; high T523 K21In-situ XPS: Pd vs. C depth profiling100 200 300 400 500 600 700 8002025303540455055606570A  Palladium Inelastic Mean Free Path [Å]Carbon Content [%]Electron Kinetic Energy [eV] Experiment: 358 K Model: 358 K Model: 3.5 ML Experiment: C5 off Model: C5 off5.25 7.15 9.05 15.15202530354045505560657075100 200 300 400 500 600 700 800 22.3513.2510.25 Electron Kinetic Energy [eV]Carbon content [%]Carbon Inelastic Mean Free Path [Å] Epxeriment: 523K Model: 523K Model: 4.2 ML7.25B0.3 nm1.4 nm14 nm22HRTEM: lattice expansion5% Pd/CNT after reaction0.2025 nm   +4.2%   0.1944 nm    2 0 00.2027 nm   +4.3%   0.1944 nm    0 2 00.1421 nm   +3.4%   0.1374 nm    2 2 00.1434 nm   +4.4%   0.1374 nm   -2 2 0Pd nanoparticle (5nm x 6nm) with typicallattice dilatations, angular distortions arenegligiblebackground: rather disordered graphiticlayers of a CNT23Summary1. Subsurface H : effective for alkene-to-alkane but also for alkyne-to-alkane transformation2. Surface H : could be selective (spillover)3. Different reaction orders in the different selectivity regimes & Abrupt changes between regimes4. C uptake is considerably more in the selective regime 5. Pd-C surface phase forms in the early stage of selective pentyne hydrogenation & there is significant amount of subsurface Cbelow of it24Model (during the reaction)25Summary1. Subsurface H : effective for alkene-to-alkane but also for alkyne-to-alkane transformation2. Surface H : could be selective (spillover)3. Different reaction orders in the different selectivity regimes & Abrupt changes between regimes4. C uptake is considerably more in the selective regime 5. Pd-C surface phase forms during selective hydrogenation of pentyne & there is significant amount of subsurface C below of it6. Dynamic behaviour of Pd-C and subsurface C 26M. Hävecker, Surface Analysis, Dept. AC, Fritz-Haber-Institut (MPG), Berlin, GermanyOutlook: In situ XPS / XASThe future at BESSYInstallation of a beamline exclusively used for in situ spectroscopy in the soft X-ray rangeInstallation of infrastructure optimized for these kind of experiments on site (e.g. chemical lab, gas supply, gas analytics)ISISS:Innovative Station for In Situ Spectroscopy A project of BESSY and the Dep. Inorganic Chemistry, Fritz-Haber-Institut Later, further implementation of other in situ spectroscopy techniques: multi wavelength Raman, UV-Vis, fluorescence yield ?!Start of user operation of the beamline: 200727M. Hävecker, Surface Analysis, Dept. AC, Fritz-Haber-Institut (MPG), Berlin, GermanyOutlook: In situ XPS / XASThe future at BESSYISISS:Sketch of laboratory: dr. heinekamp, Berlin, Germany28M. Hävecker, Surface Analysis, Dept. AC, Fritz-Haber-Institut (MPG), Berlin, GermanyOutlook: In situ XPS / XASThe future at BESSY1,0E+091,0E+101,0E+110 200 400 600 800 1000 1200 1400Photon Energy / eVflux (phot./s/0.1A/0.1%BW)1200 l/mm, 80 μm1200 l/mm, 20 μm600 l/mm, 80 μm600 l/mm, 20 μm100030005000700090000 200 400 600 800 1000 1200 1400Photon Energy / eVResolution (E/dE)1200 l/mm, 80 μm1200 l/mm, 20 μm600 l/mm, 20 μm600 l/mm, 80 μm29M. Hävecker, Surface Analysis, Dept. AC, Fritz-Haber-Institut (MPG), Berlin, GermanyOutlook: In situ XPS / XASThe future at BESSY30M. Hävecker, Surface Analysis, Dept. AC, Fritz-Haber-Institut (MPG), Berlin, GermanyOutlook: In situ XPS / XASThe future at BESSY31M. Hävecker, Surface Analysis, Dept. AC, Fritz-Haber-Institut (MPG), Berlin, GermanyOutlook: In situ XPS / XASThe future at BESSY32Thanks to:• Detre Teschner, Elaine Vass, Michael Hävecker, EvgueniKleimenov,,Spiros Zafeiratos, Péter Schnörch, Hermann Sauer, Robert Schlögl  (FHI, Dept. AC)• Harald Gabasch, Bernd Klötzer, Werner Unterberger, KonradHayek (University Innsbruck, Dept. Physical Chemistry)• Balazs Aszalos-Kiss, Dima Zemlianov (Purdue University)• Mounir Chamam, Attila Wootsch (Institute of Isotops, Budapest) • Arran S. Canning, Jonathan J. Gamman, S. David Jackson (Glasgow University)• James McGregor, Lynn F. Gladden (Cambrigde University)• BESSY staff !!

In situ XPS investigations in heterogeneous catalysis

In situ XPS investigations in heterogeneous catalysis

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