Methane oxidation over Pd/Al2O3 under rich/lean cycling followed by operando XAFS and modulation excitation spectroscopy
Artikel i vetenskaplig tidskrift, 2017

Rich/lean cycling is used to study the total oxidation of methane over a Pd/Al2O3 catalyst at different oxi- dation states. Time-resolved energy-dispersive X-ray absorption fine structure is used in a modulation excitation approach to monitor the chemical state of the palladium nanoparticles during the cycling, and the resulting spectra are demodulated using phase sensitive detection. Cycling is performed using oxygen pulses with a concentration of 0.15, 0.25, and 1.5% over a constant flow of 0.1% methane. For the two lowest oxygen concentrations the methane conversion is generally low but increases at the switches between the rich and the lean periods, while for the highest oxygen concentration the conver- sion is highest during the lean periods. The oxidation state of Pd changes rapidly but to a limited extent for the two lowest oxygen concentrations, whereas for the high oxygen concentration the oxidation appears to proceed via a two-step process, where the first step is rapid and the second step is slower. EXAFS fitting of the demodulated spectra is used to quantify the Pd oxidation state, the first rapid oxida- tion step is assigned to surface oxidation, while the second step is assigned to bulk oxidation of Pd. A low methane conversion is observed when the Pd nanoparticles are covered with chemisorbed oxygen or sur- face oxide, the methane conversion is higher when the Pd nanoparticles are bulk oxidized.

Författare

Johan Nilsson

Kemi och kemiteknik, Tillämpad kemi, Teknisk ytkemi

Kompetenscentrum katalys (KCK)

Per-Anders Carlsson

Kompetenscentrum katalys (KCK)

Kemi och kemiteknik, Tillämpad kemi, Teknisk ytkemi

Natalia Mihaela Martin

Kompetenscentrum katalys (KCK)

Kemi och kemiteknik, Tillämpad kemi, Teknisk ytkemi

Emma Adams

Kompetenscentrum katalys (KCK)

Kemi och kemiteknik, Tillämpad kemi, Teknisk ytkemi

Giovanni Agostini

European Synchrotron Radiation Facility

Henrik Grönbeck

Kompetenscentrum katalys (KCK)

Chalmers, Fysik, Kemisk fysik

Magnus Skoglundh

Kompetenscentrum katalys (KCK)

Kemi och kemiteknik, Tillämpad kemi, Teknisk ytkemi

Journal of Catalysis

0021-9517 (ISSN) 1090-2694 (eISSN)

Vol. 356 237-245

Drivkrafter

Hållbar utveckling

Styrkeområden

Nanovetenskap och nanoteknik

Transport

Produktion

Materialvetenskap

Ämneskategorier

Fysikalisk kemi

Kemiska processer

DOI

10.1016/j.jcat.2017.10.018