The effect of the pore structure of medium-pore zeolites on the dehydroisomerization of n-butane: A comparison of Pt-FER, Pt-TON, and Pt-ZSM5

G. D. Pirngruber, O. P.E. Zinck-Stagno, K. Seshan, J. A. Lercher

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27 Scopus citations

Abstract

The dehydroisomerization of n-butane requires a bifunctional catalyst comprising a metal function for dehydrogenation of n-butane to n-butylenes and an acid function for isomerizing the n-butylenes to isobutylene. Several catalysts have been used for the skeletal isomerization of butylene, e.g., FER, TON, ZSM-23, SAPO-11, MeAPO, MCM22, etc. A study of the catalytic dehydroisomerization of n-butane over Pt-ZSM5, Pt-TON, and Pt-FER showed that Pt-ZSM5 had the highest yield and selectivity to isobutylene. Most of the by-products of Pt-ZSM5 were formed by oligomerization/cracking of butylene, while acid-catalyzed cracking and metal-catalyzed hydrogenolysis of n-butane were more pronounced with Pt-TON, particularly with Pt-FER. The skeletal isomerization of butylene and cracking of n-butane were acid catalyzed. However, as the rate of n-butane cracking strongly depended on the concentration of acid sites than the rate of butylene isomerization, low acid site concentrations were beneficial for dehydroisomerization catalysts. The dehydrogenation activity of the Pt-zeolites was not related to the metal dispersion. Pt-FER had the highest dispersion, but it also had the lowest dehydrogenation activity, which was ascribed to diffusional constraints in the narrow pores of the large ferrierite crystals.

Original languageEnglish
Pages (from-to)374-386
Number of pages13
JournalJournal of Catalysis
Volume190
Issue number2
DOIs
StatePublished - 10 Mar 2000
Externally publishedYes

Keywords

  • 10-membered-ring zeolites
  • Bifunctional catalysis
  • Dehydroisomerization of n-butane

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