Document Type

Open Access Thesis

Embargo Period

2-24-2016

Degree Program

Chemical Engineering

Degree Type

Master of Science (M.S.)

Year Degree Awarded

2016

Month Degree Awarded

May

Abstract

Porous materials have application in adsorption based processes due to their high internal surface area and tailorable pore size. They find uses in fields such as catalysis, separation, biotechnology, and microelectronics. Fluids confined in such materials exhibit interesting behavior in regards to the condensation and evaporation mechanisms. Understanding study the behavior of fluids confined in these porous materials is necessary for the efficient design of these materials. The adsorption/desorption isotherm provides valuable information about the effect of network features like pore connectivity and pore size distribution on fluid behavior during pore condensation and evaporation. Such insight can be useful in the characterization of these porous materials.

Three dimensionally ordered mesoporous (3DOm) carbon is a porous material that has recently emerged and is of interest. These porous structures are obtained from templating colloidal crystals formed from lysine-silica nanoparticles. The resulting structure consist of spherical pores connected to each other by windows. Due to the use of silica nanoparticles a range of tunable pore sizes can be obtained. These structures have high degree of order. They find applications in the synthesis of zeolites due to their highly controllable pore size. Hence a study of the adsorption properties of these structures is of importance.

Molecular modeling has proved effective in the study of porous materials. The development of the density functional theory (DFT) and the dynamic mean field theory (DMFT) has led to great advances in the study of the behavior of confined fluids. The DFT enables the study of the adsorption desorption hysteresis phenomena of confined fluids. The DMFT describes the density profile versus time for a step change in relative pressure on the isotherm. These theories have been applied in the past to two dimensional model pore networks to investigate the mechanisms of adsorption and desorption. In this research project we aim to apply the same to various model 3DOm carbon pore networks. Studying the density distributions in these networks can help understand the thermodynamics of fluid adsorption and desorption in these structures. The results could be useful in understanding the effect of pore structure features like pore size and windows on adsorption and desorption. Also the effect of disorder in the pore network as well as effect of variation in pore size on fluid behavior can be studied. Study of the dynamics of adsorption gives an insight into the nucleation mechanisms that govern the condensation of fluid in the pore. These results could prove useful in the characterization of these porous structures.

First Advisor

Peter A Monson

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