title: Assessing molecular transport properties of nanoporous materials by interference microscopy: remarkable effects of composition and microstructure on diffusion in the silicoaluminophosphate zeotype STA-7.
abstract: 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.
authors.affiliation: Technische Chemie II, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany. despina.tzoulaki@tum.de
authors.forename: Despina
authors.initials: D
authors.lastname: Tzoulaki
authors.forename: Lars
authors.initials: L
authors.lastname: Heinke
authors.forename: Maria
authors.initials: M
authors.lastname: Castro
authors.forename: Pablo
authors.initials: P
authors.lastname: Cubillas
authors.forename: Michael W
authors.initials: MW
authors.lastname: Anderson
authors.forename: Wuzong
authors.initials: W
authors.lastname: Zhou
authors.forename: Paul A
authors.initials: PA
authors.lastname: Wright
authors.forename: Jörg
authors.initials: J
authors.lastname: Kärger