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Diffusion and Reaction of Methylaluminoxane (MAO) within a Silica Membrane
Author(s) -
Hansen Eddy W.,
Bernauer Bohumil,
Blom Richard
Publication year - 2004
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200400023
Subject(s) - toluene , chemistry , diffusion , thermal diffusivity , membrane , analytical chemistry (journal) , permeation , thermodynamics , organic chemistry , biochemistry , physics
Summary: The self‐diffusion coefficient of MAO confined within a silica membrane is not experimentally accessible by traditional PFG NMR measurements, probably due to a susceptibility effect resulting in rather broad, unobservable resonance lines. A more indirect approach was therefore applied to probe the diffusivity of MAO within a silica membrane. MAO confined in a bulk toluene solution on one side of the membrane was free to diffuse through the membrane (saturated with toluene) and into a corresponding deuterated toluene solution on the other side of the membrane where its proton NMR signal intensity was monitored as a function of time. By introducing a relevant diffusion model, the diffusivities of both toluene and MAO were derived by model‐fitting. By refining the diffusion model, the formation of methane within the silica was explained, and its diffusivity estimated. The results suggest a significant reduction in diffusivities of both MAO and toluene within the silica as compared to the corresponding diffusivities in bulk solution.1 H NMR spectra as a function of time within the shift region δ = 2.0–2.5 ppm (toluene) acquired during the first 40 h of the diffusion process.