Assessing nanoporous materials by interference microscopy: remarkable dependence of molecular transport on composition and microstructure in the silicoaluminophosphate zeotype STA-7

  • chair:

    Tzoulaki, D. / Heinke,  L. / Castro, M. / Cubillas, P. / Anderson, M. / Zhou, W. / Wright, P. / Kärger, J. (2010)
  • place:

    Journal of the American Chemical Society 132 (2010), 33, 11665–11670
  • Date: 2010

  • Tzoulaki, D. / Heinke, L. / Castro, M. / Cubillas, P. / Anderson, M. / Zhou, W. / Wright, P. / Kärger, J. (2010): „Assessing nanoporous materials by interference microscopy: remarkable dependence of molecular transport on composition and microstructure in the silicoaluminophosphate zeotype STA-7“. In: Journal of the American Chemical Society 132 (2010), 33, 11665–11670

Abstract

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The influence of the chemical composition and of the storage and activation protocol on the diffusion of methanol into strongly chemically zoned crystals of the silicoaluminophosphate zeotype STA-7 has been investigated by interference microscopy. Analysis of the evolution of transient intracrystalline concentration profiles reveals that just-calcined SAPO STA-7 crystals with lower Si content (Si/(Si + P) = 0.18) exhibit higher surface permeability and bulk diffusivity than those with higher Si content (S/(Si + P) = 0.37).

Remarkably, crystals with the higher Si content which were stored in the calcined form crack during activation along planes of weakness already present in the as-prepared crystals, creating fresh surfaces through regions of lower Si that are much more easily penetrated by the adsorbing methanol than are the original surfaces.