Pt agglomeration and entombment in single channel zeolites

Pt/LTL

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

This paper presents a transmission electron microscopy study of the role of Pt agglomeration and channel blockage in the deactivation of Pt/K-zeolite L aromatization catalysts. A Z-contrast imaging study of Pt particle size distributions shows that there is an increase in the number of channel blockages by Pt with increasing catalyst reaction time. Modeling shows that when agglomeration proceeds so that there is a likelihood of two or more blockages per channel, significant quantities of Pt become entombed. This problem is exacerbated by long zeolite L channel lengths. Conversely, if the channels are too short, Pt seepage to the external surfaces becomes significant and the rate of coke production increases, again resulting in loss of accessible Pt. Ideally, the best Pt/KL catalysts have all of the Pt inside the channels in a finely dispersed state. It is argued that there exists an optimum 'length-loading' window for Pt/KL catalysts:0.25≤wl≤0.5where w is the percentage of Pt by weight in the zeolite, and l is the channel length (μm). The upper limit minimizes the deleterious effects of multiple channel blockages by ensuring that, on average, there is not enough Pt in the channels to form two or more blockages. The lower limit guards against Pt seepage to the exterior surfaces when channel lengths are too short.

Original languageEnglish (US)
Pages (from-to)271-292
Number of pages22
JournalMicroporous and Mesoporous Materials
Volume28
Issue number2
StatePublished - Apr 1999
Externally publishedYes

Fingerprint

Zeolites
agglomeration
zeolites
Agglomeration
Catalysts
Seepage
Aromatization
seepage
catalysts
Coke
Particle size analysis
Transmission electron microscopy
Imaging techniques
coke
particle size distribution
reaction time
deactivation

Keywords

  • Channel blockage
  • Length-loading criterion
  • LTL
  • Pt/LTL
  • Z-contrast

ASJC Scopus subject areas

  • Catalysis
  • Materials Science(all)

Cite this

Pt agglomeration and entombment in single channel zeolites : Pt/LTL. / Treacy, Michael.

In: Microporous and Mesoporous Materials, Vol. 28, No. 2, 04.1999, p. 271-292.

Research output: Contribution to journalArticle

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