Cyclohexane conversion over H-zeolite supported platinum

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Abstract

The catalytic conversion of cyclohexane over H-ZSM-5 in hydrogen or nitrogen and in hydrogen atmosphere over a series of H-zeolites loaded with platinum was studied using a flow-through microreactor/GC on-line system at pressures of 13bar. The distribution of the products formed via hydrodecyclization was found to depend definitely on whether or not dimerization of primarily formed hexyl-carbenium ions is sterically hindered in the zeolitic pore system. Reaction routes are suggested which involve, as an essential step, the hydrogenation of intermediate carbenium ions, formed either primarily by reactant adsorption or cracking, by spill-over hydrogen activated on the metallic catalyst component. The basically different product distribution obtained by decyclization of cyclohexane in nitrogen atmosphere or over monofunctional H-ZSM-5 is attributed to disproportionation of primarily formed hexyl-carbenium ions and subsequent hydrogen transfer reactions which results in a broad spectrum of paraffins and aromatics in the effluent and in carbon-rich deposits on the catalyst surface causing fast catalyst deactivation. This process does not manifest itself in bifunctional catalysis due to the much faster hydrogenation and, hence, elimination of carbenium ions by hydrogenation.

Original languageEnglish
Pages (from-to)65-74
Number of pages10
JournalApplied Catalysis A: General
Volume229
Issue number1-2
DOIs
Publication statusPublished - Apr 10 2002

Keywords

  • Cracking
  • Cyclohexane
  • Hexanes
  • Isomerization
  • Pt/zeolite
  • Ring opening

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

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