Predictive assessment of mass transfer resistances in nanoporous membranes.

摘要

Nanoporous materials are excellent candidates for materials to serve as the active layer of membranes. Their ordered and atomic scale porous networks are size and shape selective to different guest molecules, performing effective and low energy cost separations of mixtures. The realization of these nanoporous material membranes to large scale industrial usage requires a fundamental understanding of their performance under a wide range of operating conditions. This comprehensive theoretical framework is best based upon atomistic simulations so that a comprehension of the molecular behavior forms the basis of first principles predictions of the macroscopic properties of membranes.; Work has been performed by Drs. Skoulidas and Sholl and other talented researchers to use molecular simulations to model membrane performance. In these studies, however, they only included the mass transfer resistance inherent to the diffusion through the nanaporous material. They did not take into account additional mass transfer resistances at the gas-membrane interface and grain boundaries. This thesis has focused on using molecular simulations and models to study the impact that the gas-membrane interface and grain boundaries have on the reduction of the membrane permeance.; We show that these resistances are very important for membranes in the 102 nm regime for silicalite, a well known zeolite and studied zeolite. However, these resistances are negligible in the current experimental thickness regime of ∼1 mum. We then study the gas-membrane interface of carbon nanotubes and observe that the surface barriers are very important even in regimes near the current experimental regime.