Solution-processable exfoliated zeolite nanosheets purified by density gradient centrifugation

Kumar Varoon Agrawal, Berna Topuz, Zheyu Jiang, Kevin Nguenkam, Bahman Elyassi, Lorraine F. Francis, Michael Tsapatsis, Marta Navarro

Research output: Contribution to journalArticlepeer-review

73 Scopus citations


Highly crystalline exfoliated MFI-nanosheets can pave the way for large-scale deployment of sub-500-nm zeolite membranes due to their processing and packing advantages. Exfoliated MFI-nanosheets prepared by melt compounding contain a large amount of polymer and unexfoliated particles which are detrimental to the fabrication of ultrathin zeolite membranes. Complete removal of polystyrene from the nanosheet suspension in toluene is demonstrated by centrifugation of the suspension across chlorobenzene as confirmed by thermogravimetric analysis (TGA) data and transmission electron microscopy (TEM) images. Rate-zonal centrifugation in a nonlinear density gradient fractionated exfoliated MFI-nanosheets from unexfoliated particles. The purified nanosheets were highly crystalline as indicated by high-resolution TEM (HRTEM) and electron diffraction (ED). Coating of purified MFI-nanosheets on a smooth α-alumina support, fabricated by filtration of α-alumina suspension, led to a compact, b-oriented, 80-nm-thick film. A mild hydrothermal treatment of the film led to a 200-nm-thick membrane, which demonstrated molecular sieving properties.

Original languageEnglish (US)
Pages (from-to)3458-3467
Number of pages10
JournalAIChE Journal
Issue number9
StatePublished - Sep 2013


  • Density gradient centrifugation
  • Membrane support
  • Zeolite membrane
  • Zeolite nanosheets


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