Modeling Adsorption in Complex Porous Structures: Equilibrium, Hysteresis and Dynamics

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Peter A. Monson, University of Massachusetts - Amherst"Modeling Adsorption in Complex Porous Structures: Equilibrium, Hysteresis and Dynamics"This research will use molecular modeling to understand the behavior of fluids confined in porous materials with complex pore structures. The primary goal is to develop a more refined understanding of how the combined effects of molecular interactions and the structure of the porous material over several length scales yield particular kinds of adsorption behavior. This understanding is central to important applications such as separations and catalysis, as well as in porous materials characterization. A combination of dynamical as well as equilibrium modeling techniques is a central feature of this project. Two complementary areas of research are planned.In the first area the PI is concerned with coarse-grained lattice models of adsorption/desorption in complex pore structures. The goal of this work is to develop a framework for understanding the relationship between adsorption measurements and the porous material microstructure - particularly for states in the capillary condensation and hysteresis regime. The recent work has shown that coarse-grained lattice models provide important insights into hysteresis and the PI seeks to build on this in several ways. In the proposed work the PI will extend the range of materials that can be treated by this approach, including applications to a variety of mesoporous silica materials, and apply the approach to analysis of intrusion/extrusion hysteresis in mercury porosimetry.The second research area is concerned with the dynamics of adsorption and desorption. The PI's goal here is to use simulations that mimic dynamic uptake experiments to investigate the stability of states in the hysteresis region. The PI has used this approach to establish the significance of the hysteresis loops encountered in Monte Carlo simulations and to investigate the role of pore blocking in hysteresis. The proposed work deals with dynamical simulations of coarse-grained lattice models as well as application to mercury porosimetry. The PI also plans to extend these techniques to the study of wetting dynamics in confined geometries in the context of nanotechnology applications.Broader Impact: The research while fundamental is closely linked with application, especially in the context of porous materials characterization. Traditionally engineers and others using porous materials have had to view the porous material microstructure using rather imprecise quantities like the pore volume, surface area and pore size distribution. It is anticipated that the project could provide a foundation for a new approaches to the characterization of porous materials. There is substantial potential impact in applications of porous materials ranging from traditional areas such as catalysis and separations to emerging areas in nanotechnology.The research program has a strong educational component through the involvement of graduate students, postdoctoral scholars and undergraduates. The students regularly attend and present their work at major conferences. Research group meetings are designed in part to develop the ability of students to communicate their research achievements, and our graduate students participate in teaching undergraduate courses as an educational requirement of their degree program. The project features collaboration with industry (Quantachrome Corporation) as well as an international collaboration with researchers at the Technical University of Berlin, Germany.