FisMat2017 - Submission - View

Abstract's title: Developing of new setup at APE beamline for in situ/operando NEXAFS experiment on heterogeneous catalysts
Submitting author: Luca Braglia
Affiliation: University of Turin
Affiliation Address: Via Pietro Giuria 7, Torino, 10125
Country: Italy
Oral presentation/Poster (Author's request): Poster
Other authors and affiliations: Matteo Signorile (Department of Chemistry, NIS and INSTM Reference Centers, University of Turin, Turin, Italy), Ilya Pankin (Southern Federal University, Rostov-on-Don, Russia), S. Bordiga (Department of Chemistry, NIS and INSTM Reference Centers, University of Turin, Turin, Italy and inGAP Centre for Research Based Innovation, Dept. of Chemistry, University of Oslo, Oslo, Norway) ,Elena Groppo (Department of Chemistry, NIS and INSTM Reference Centers, University of Turin, Turin, Italy), Piero Torelli (dElettra—Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, Trieste I-34149, Italy), Carlo Lamberti (Southern Federal University, Rostov-on-Don, Russia and Department of Chemistry, CrisDi Interdepartmental Centre and INSRM reference University of Turin, via Pietro Giuria 7, 10125 Turin, Italy)

In this study are shown preliminary NEXAFS results performed on two classes of Ti zeolites: perfect and defective TS1 and ETS10. Ti-zeolites are interesting materials because of their key role in partial oxidation reactions, as well as under a fundamental point of view being regarded as single site catalysts. They are characterized by the isomorphous substitution of the framework Si4+ with Ti4+. Hence we collected NEXAFS spectra at Ti L2,3-edge and at O K-edge after the activation treatment and after the exposure to NH3. Soft X-rays have the advantage that with respect to XAS at the metals K-edges, L3 and L2 transitions are usually more intense (because formally electric-dipole allowed) and more reach in details. First-row transition-metal L-edges consist of 2p-3d transitions, which directly probe the unoccupied valence density of states. Hence, XAS on metal L-edges is very sensitive to metal-ligand interactions, and perfectly complementary to XAS at the metal K-edges. The short attenuation lengths of soft X-rays has prevented until a short time ago the application of NEXAFS in reaction condition, and in-situ observations of surface reactions were limited only under the presence of gases with pressures lower than 10-6 Torr. Recently, new experimental set-ups are being developing to go beyond this limitation, and a few examples of NEXAFS applied to heterogeneous catalysts in operando can be found in the literature. NEXAFS measurements in the soft x-ray range in reaction conditions require the use of a specially designed experimental set-up which are not commonly present at soft x-ray beamlines. This set-up has been recently developed and is now available at APE beamline at Elettra. The new device allows NEXAFS spectra to be collected in total electron yield (therefore with high surface sensitivity) while the sample in this particular cell can be treated with different gas feed up to 120°C.