(6ga) Separation and Catalysis Using Nanoporous Materials: A Computational Approach

Authors: 
Bai, P., University of Minnesota

Theory and molecular modeling have seen tremendous growth in recent years; capitalizing on theoretical and algorithmic developments and advancements in computer hardware, many previously intractable models for complex systems can now be solved numerically to sufficiently high levels of fidelity that their results can augment experiments. Applications of computational methods have begun to penetrate into all fields of sciences. In this poster presentation, I will highlight applications in the field of separation and catalysis using crystalline nanoporous materials, primarily zeolites, and show how molecular modeling can be used both to gain a microscopic understanding into phenomena difficult to probe experimentally and to predict accurate data at a scale beyond the reach of the traditional trial-and-error approach. First, I will describe the development of a new, transferable force field for all-silica zeolites, TraPPE-zeo, which is applicable to any type of sorbate molecule and framework structure. With the improved intermolecular potentials as well as better methodologies, it was then possible to study several complex systems involving articulated molecules and liquid mixtures, such as the multi-component adsorption of aqueous alcohol, polyol, glucose, and furfural solutions. These studies demonstrate the important effects of hydrogen-bonding, which render both the bulk and adsorbed phases highly non-ideal and are for certain molecules so strong that adsorption becomes entropically rather than enthalpically driven. In another application, the unusual adsorption and diffusion behaviors in a hybrid microporous/mesoporous zeolite are investigated [1], and our simulations allow us to unravel the distinct features exhibited by such hierarchical materials. More recently, using first-principles calculations, factors contributing to the reactivity and selectivity of zeolites as solid acid catalysts were carefully examined [2]. A better understanding achieved from this study on the different effects, including the chain lengths and architectures of reactant molecules and the different degrees of framework confinement of the reactant/product as well as transition states, affords the potential of rational catalyst design and optimization. Finally, such an effort is described, in which a large number of zeolites were screened with the purpose of finding better candidates for two energy-related applications, ethanol/water separation and hydrocarbon iso-dewaxing. Predictions from this work were subsequently verified by experiments and together this demonstrates the possibility of using theory and computation in a predictive mode to expedite the pace of materials discovery for complicated, realistic, and industrially relevant applications.

[1] “Understanding unique diffusion behavior in hierarchical zeolites,” to be presented at 2015 AIChE Annual Meeting, Symposium on ‘Diffusion, Transport and Dynamics in Adsorption Systems,’ Salt Lake City, UT.

[2] “Chain-length and framework effects in alkane cracking on solid acid catalysts,” to be presented at 2015 AIChE Annual Meeting, Symposium on ‘Catalysis with Microporous and Mesoporous Materials,’ Salt Lake City, UT.