Diffusion in confinement: kinetic simulations of self- and collective diffusion behavior of adsorbed gases.

Diffusion in confinement: kinetic simulations of self- and collective diffusion behavior of adsorbed gasesw

Molecular understanding of diffusion in confinement.

We introduce a computational method to directly relate diffusivities to the microscopic behavior of the adsorbed molecules. We apply this method to gases in an MFI-type molecular sieve, the reference system in this field. Transitions in the number and nature of adsorption sites result in temporary local increases in the diffusion. This occurs at different loadings in each of the x, y, and z dir...

X-Nuclei NMR Self-Diffusion Studies in Mesoporous Silica Foam and Microporous MOF CuBTC

A standard X-observe NMR probe was equipped with a z-gradient coil to enable high-sensitivity pulsed field gradient NMR diffusion studies of Li⁺ and Cs⁺ cations of aqueous salt solutions in a high-porosity mesocellular silica foam (MCF) and of CO₂ adsorbed in metal-organic frameworks (MOF). The coil design and the necessary probe modifications, which yield pulsed field gradients of up to ±16.2T...

Molecular dynamics studies of straight-chain alkanes diffusion in SiO2 ceramic versus Bosanquet formula

Molecular Dynamics (MD) simulations were applied to calculate self-diffusion coefficients (Di ) and heats of adsorption for ethane, propane and n-butane. The simulations were done in temperature range of 300-525 K for various concentrations inside the pores of silicalite type zeolite. The calculated values of self-diffusion coefficients and heats of adsorption resulted from the current wo...

The Generalized Maxwell-Stefan Model Coupled with Vacancy Solution Theory of Adsorption for Diffusion in Zeolites

It seems using the Maxwell-Stefan (M-S) diffusion model in combination with the vacancy solution theory (VST) and the single-component adsorption data provides a superior, qualitative, and quantitative prediction of diffusion in zeolites. In the M-S formulation, thermodynamic factor (Г) is an essential parameter which must be estimated by an adsorption isotherm. Researchers usually utilize the ...