Isobutane dehydrogenation in a DD3R zeolite membrane reactor

Johan van den Bergh*, Canan Gücüyener, Jorge Gascon, Freek Kapteijn

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

Dehydrogenation of isobutane has been studied in a DD3R zeolite membrane reactor (MR) at 712 and 762K, using pure isobutane at 101kPa as feed gas and N2 as sweep gas. Clear advantage of using the small-pore zeolite DD3R is that it offers an absolute separation of H2 from isobutane by a molecular sieving mechanism. Experiments in a conventional packed bed reactor served as benchmark. Cr2O3 on Al2O3 was used as catalyst. The DD3R membrane showed an excellent H2/isobutane permselectivity (>500 @ 773K) and a reasonable H2 permeance (∼4.5×10-8molm-2s-1Pa). At low residence times isobutene yields 50% above the equilibrium could be obtained. At 762K and 0.13kgfeedkgcat -1h-1, the isobutene yield in the membrane reactor (MR) is 0.41, where the equilibrium yield is ∼0.28. The increased performance is attributed to removal of H2 from the reaction zone by the membrane, up to 85% at the lowest space velocity. The removal of H2 mildly promotes coke formation, suppresses hydrogenolysis reactions and appears to slightly reduce the catalyst activity. The membrane permeation parameters and reaction rate constants have been estimated independently from membrane permeation and packed bed reactor (PBR) experiments, respectively. From these parameters the behaviour of the MR can be simulated well. Two important dimensionless parameters determine the MR performance primarily, the Damköhler (Da) and membrane Péclet number (Peδ). For a significant improvement of the MR performance as compared to a PBR Da≥10 and Peδ≤0.1. DaPeδ should be ≈1 to optimally utilize both catalyst and membrane. In the current MR unit both the hydrogen removal capacity and catalyst activity stand in the way of successful application. Using a more active catalyst and a more favourable area to volume ratio could greatly improve the MR performance. Operation at a higher feed pressure could be a possible solution. Since membranes with higher fluxes are already available, the limited catalyst activity and stability under relative low temperature and H2 lean conditions are the important limiting factors regarding application of MRs in dehydrogenation reactions.

Original languageEnglish (US)
Pages (from-to)368-377
Number of pages10
JournalChemical Engineering Journal
Volume166
Issue number1
DOIs
StatePublished - Jan 1 2011
Externally publishedYes

Keywords

  • Characteristic times
  • Chromia catalyst
  • Isobutane dehydrogenation
  • Membrane reactor
  • Zeolite DD3R
  • Zeolite membrane

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Chemistry(all)
  • Industrial and Manufacturing Engineering
  • Environmental Chemistry

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