Electron microscopic studies of natural gas oxidation catalyst – Effects of thermally accelerated aging on catalyst microstructure

Mari Honkanen*, Thomas W. Hansen, Hua Jiang, Marja Kärkkäinen, Mika Huuhtanen, Olli Heikkinen, Kauko Kallinen, Jouko Lahtinen, Riitta L. Keiski, Jakob B. Wagner, Minnamari Vippola

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

8 Citations (Scopus)

Abstract

Structural changes of PtPd nanoparticles in a natural gas oxidation catalyst were studied at elevated temperatures in air and low-oxygen conditions and in situ using environmental transmission electron microscopy (ETEM). The fresh catalyst shows <5 nm, PtPdOx particles on the γ-Al2O3 support. At 700 °C, the noble metal oxide decomposes and Pt gets trapped by PdO particles followed by formation of metallic Pd and Pt containing particles. At 1000 °C, the particles had a metallic Pd and Pt containing core surrounded by PdO particles. In addition, the presence of <10 nm sized particles was always observed. The activity measurements indicate the decrease in activity at the elevated temperatures. ETEM studies showed significant mobility of the noble metal particles above 850 °C. Above 1100 °C, PtPd particles were mobile and smaller particles were trapped by larger ones by a particle coalescence mechanism.

Original languageEnglish
Pages (from-to)19-29
Number of pages11
JournalJournal of Catalysis
Volume349
DOIs
Publication statusPublished - 1 May 2017
MoE publication typeA1 Journal article-refereed

Keywords

  • Environmental transmission electron microscope
  • Low-oxygen conditions
  • Natural gas oxidation
  • Palladium
  • Platinum
  • Sintering
  • Thermal aging

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