“Phase Transitions of Binary Gases in Porous Materials” Menachem Sahler Faculty Mentor: Dr. Peter Monson, Chemical Engineering Engineering the interaction between gases and adsorbent materials is normally done empirically since the dynamic process of molecular interactions is not well understood. However, through using quasi-realistic models to illustrate such molecular interactions, it is possible to get a better idea of what happens when a gas enters a pore. Although still quite complex, theoretically discretizing volume and artificially limiting interactions between non-adjacent molecules results in a dramatically simplified system and reality can be modeled with surprisingly low deviation. Through the study of statistical thermodynamics and molecular mechanics and programing, software can be written to quickly perform, otherwise unfeasible, iterative calculations needed to model the aforementioned molecular behavior. Some methods of modeling used are the Langmuir equation and its subsequent adaptations. In addition, the mean field theory will also be used to calculate the complexity of numerous interactions. The objective of modeling molecular interactions between gases and adsorbent materials is ultimately to develop a governing theory that can be better utilized by engineers in the field than empirical knowledge alone. One such utilization under serious consideration is the long term storage of carbon dioxide in coal mine tunnels. Methane, a valuable energy source, evolves in the pores of coal, however, is not released because of its molecular affinity for the porous surfaces containing it and therefore largely stays underground in a liquid phase within the coal's pores. It is known through laboratory testing that carbon dioxide has a significantly higher affinity to be adsorbed by coal than does methane. At some given temperature and pressure, when coal is exposed to carbon dioxide, the coal will become saturated and swollen with gas and at high enough concentration, a phase transition will occur from gas to liquid. By pumping carbon dioxide into coal mines, methane is displaced and can be harvested as a fuel source upon release. Thusly, detrimental greenhouse gases can be somewhat reduced while simultaneously acquiring an ideal hydrocarbon fuel. A dilemma arises with the observation that using pure carbon dioxide to saturate coal can cause the coal to swell to a point where it impedes permeation of the carbon dioxide itself. Albeit in preliminary stages, a solution being considered is the use of a binary gas to displace the methane. Under prime consideration is nitrogen which at some as-of-yet unknown concentration can be mixed with carbon dioxide prior to exposing to the coal mines. This study (the REU program) will hopefully aid in shedding light on the validity of this solution and help define the idyllic parameters for utilization in methane harvesting as well as other numerous applications.
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