Recently, modified zeolite membranes rendered feasible methane oxidation in the aqueous phase at moderate temperatures.  Contributing to the efficiency of the conversion process is the diffusion of the methane substrate through the zeolite lattice to reactive centers in the catalyst framework. In the aqueous phase, methane transport rates are influenced by 1) the porosity of the zeolite matrix 2) non-bonding interactions between methane and the silicate surface and 3) competition between zeolite hydration and methane-driven dehydration of the catalyst surface. Here, we utilize computer simulation to resolve the relative contribution of these factors to effective methane transport rates in a prototypical zeolite framework. Namely, building from successful multiscale models of methane diffusion in zeolites, we developed a ’homogenized’ model of methane transport valid at micron and longer length scales that incorporates atomistic-scale kinetic information. The atomistic-scale data are obtained from extensive molecular dynamics simulations that yield local diffusion coefficients and potentials of mean force. With this model, we demonstrate that methane transport rates can be tuned through regulating water/zeolite surface interactions, for example by modulating silanol defect ratios or functionalization. We additionally discuss modifications to the homogenization method to account for defects in the largely periodic zeolite lattice.

Multiscale modeling of aqueous phase methane diffusion in zeolite frameworks

2019 Spring National Meeting

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