Understanding Separation Mechanisms of Monoatomic Gases, Such as Kr and Xe, via DD3R Zeolite Membrane Using Molecular Dynamics

Abstract

Noble gas fission byproducts, such as Kr and Xe, are generated within nuclear power reactors are currently being discharged into the atmosphere. This practice has a major economic drawback because of the high value associated with some of these gases. The separations of these gases are economically prohibitive because of the high energy requirement associated with cryogenic distillation. Zeolites, nanoporous materials suitable for gas separation processes, have exhibited high selectivity for such separations. We have used nonequilibrium molecular dynamics (MD) to investigate the separation performance of DD3R framework zeolitic membrane. The effects of pressure, temperature, and pure vs. mixture gas feed conditions are studied in this work to understand and explain, at the molecular level, the mechanisms of these (Kr/Xe) separations. Our studies have shown that the DD3R membrane shows promise for high selectivity ratios of Kr over Xe. MD runs show agreement with experimental trends of the permeation of Kr/Xe pure and mixed gases using DD3R zeolite with high separation factor. Despite the absence of Xe complete permeation through the membrane because of MD timescale limitations, our results are sufficient to describe the mechanisms of these separations.