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Effect of support material Al2O3 vs ZrO2-TiO2 on the Ba availability for NSR catalyst: an in situ and operando IR study

by Sandra Palma Del Valle, Olivier Marie,  Hai P. Nguyen

in Applied Catalysis B: Environmental

http://dx.doi.org/10.1016/j.apcatb.2017.02.053

Highlights

• ZrO2-TiO2 presents a high superficial density of BaO anchoring sites compared to Al2O3.
• Medium sized isolated BaO clusters form over Al2O3.
• ZrO2-TiO2 stabilizes high density of small BaO particles.
• IR operando shows high Ba availability over ZrO2-TiO2 resulting in fast nitration.

Abstract

The evolution of Ba sites in two distinct NOx storage and reduction (NSR) catalysts that are based on alumina or zirconia-titania mixed oxide (ZrO2-TiO2 or ZT) during NOx adsorption/desorption was investigated by in situ and operando IR spectroscopy. Based on various evidences from the in situ study, medium sized Ba sites on alumina supported fresh catalysts are proposed to experience sintering under NOx adsorption to form bigger particles, while for ZT, initially possessing smaller sized Ba particles, the formation of a thin layer or very fine particles of Ba would proceed under the same condition. This evolution can also be affirmed by observations from the operando IR study showing that NOx adsorption on ZT supported catalyst is initially faster than on alumina supported catalyst (time on stream lower than 300 sec), but after long adsorption time (about 50 min) the two catalysts show similar storage capacity. This new mechanistic insight suggests that NOx ad/desorption rate, which is critical for optimizing NSR performance, needs to be controlled by support materials whose interaction with the Ba particles not only determines their initial size (fresh catalyst) but also their resistance towards sintering during the NOx adsorption

Keywords

  • NSR catalysis;
  • alumina;
  • zirconia;
  • titanium oxide;
  • Ba coverage;
  • adsorption kinetics;
  • operando spectroscopy

 

Source : Effect of support material Al2O3 vs ZrO2-TiO2 on the Ba availability for NSR catalyst: an in situ and operando IR study

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