Multiscale Modeling of Methane Permeation in Hierarchical Zeolite Frameworks

Multiscale modeling of methane permeation in hierarchical zeolite frameworks Abstract Vast quantities of raw natural gas are released as a byproduct of shale oil extraction, which has ignited interest methane extraction and conversion to more useful liquid hydrocarbons. Methane processing has been explored in zeolites, which are inexpensive, porous, highly adsorbent, naturally-occurring minerals. Variants of these materials are already valued at $30 billion for petroleum refinement, but for methane conversion they are of limited utility, given poor kinetics and thermodynamics of reactions and mass transport. A critical step toward realizing the industrial potential of these zeolitic materials is an improved quantitative understanding of molecular-scale methane/zeolite interactions and bulk per11 meation properties, which can inform computer-guided materials optimization. So far, bulk kinetic and thermodynamic details as well as high-resolution electron microscopy data are widely available, yet those effects on methane transport are only indirectly known through permeation and adsorption trends. Efforts to explain methane transport in these materials have largely used molecular simulations in perfect (defect-free) zeolite crystals that have no higher order structure, which are difficult to translate to industrial-grade cata17 lysts that are thousand-fold larger, exhibit sophisticated micron-scale macro-structure and are microscopically imperfect. We propose two developments will enable the simulation of methane transport in realistic, hierarchically-structure zeolite films and membranes: 1) the lack of micron-scale gas transport simulations in zeolites with framework defects and heterogeneous, higher-order three-dimensional structure 2) molecular simulations of methane/zeolite surface interactions at common zeolite defects including grain bound23 aries and stack faults. Quantitative predictions of methane transport from our modeling could inform zeolite catalyst design and operation, while having a broader impact of new computational tools for probing a wide-range of industrial catalysts.