Electron spectroscopy of sulfated zirconia, its activity in n-hexane conversion and possible reasons of its deactivation

G. Resofszki, M. Muhler, S. Sprenger, U. Wild, Z. Paál

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48 Citations (Scopus)

Abstract

Sulfated zirconia catalysts were prepared and characterized by X-ray photoelectron spectroscopy taken in the dried state (fresh) and after calcination at 900 K (calc.). A maximum activity was observed as a function of the calcination temperature. The Zr 3d region showed that any Zr hydroxide in the dried catalyst transformed into zirconium oxide upon calcination. The O 1s peak could be fitted by two components corresponding to ZrO2 and sulfate, respectively. Sulfur was present as sulfate. Both catalysts showed activity in n-hexane conversion (including isomerization) between 300 and 473 K. The activity of the calcined catalyst was much higher. The main products were isopentane and isobutane, along with 2-methyl- and 3-methylpentane. The activity was not stable and only a limited amount of n-hexane transformed before final deactivation. This observation pointed to a limited amount of active sites able to start the reaction. The activity could be fully regenerated by oxygen treatment. Thus, the "oxidative" start of the reaction [ A. Ghenciu, D. Farcasiu, Catal. Lett. 44 (1997) 29] may have also played a role apart from those on strong acid sites. Deactivation may have been due to a partial reduction of sulfate groups rather than to carbon accumulation, as shown also by the minor amounts of S4+ detected by XPS. Parallel isomerization and splitting of hexane into two C3 units may occur, followed by the formation of surface C9 units, the latter being intermediate of larger fragments.

Original languageEnglish
Pages (from-to)71-81
Number of pages11
JournalApplied Catalysis A: General
Volume240
Issue number1-2
DOIs
Publication statusPublished - Feb 10 2003

Keywords

  • Electron spectroscopy
  • N-Hexane
  • Sulfated zirconia

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

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