Computational Studies On Gas Transport In Metal Organic Frameworks For Membrane Separations

Author : Changlong Zou
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (139 download)

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Download or read book Computational Studies of Membranes for Ethanol/water Separation and Carbon Capture written by Changlong Zou and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Developments of green energy alternatives (e.g., ethanol) and advanced CO2 capture technologies play a crucial role in solving the energy and climate crisis. Specifically, membrane-based separation processes provide opportunities as potentially energy-efficient means to extract alcohols or capture CO2. For alcohol extraction, ultrathin-film nanoporous membranes such as zeolite nanosheets may offer large separation factors and high fluxes because of their selective ethanol-to-water adsorption and short diffusion pathway. However, systematic investigations of potential nanosheet candidates are still missing to date, while atomistic understandings of their separation mechanism and structure-property relationship remain limited. For CO2 capture, facilitated transport membranes (FTMs) that utilize reversible chemical reactions between amino groups and CO2 have been demonstrated to offer notably enhanced selectivity and permeance. However, molecular understandings of the reactive diffusion mechanism of CO2 in the FTMs remain limited. This dissertation conducts computational studies to study membrane materials for ethanol separation and CO2 capture. Specifically, in Chapter 2, a screening study of zeolite nanosheets as pervaporation membranes for ethanol separation is discussed to show their separation performance and shed light on the relationship between separation factors, adsorption selectivities, and structural features. In Chapter 3, understandings achieved in the previous chapter are applied to study the alcohol/water pervaporation separation using zeolite membranes with various Si/Al ratios. Key factors identified in Chapter 2, such as surface silanol density and adsorption selectivity, are again shown to play an important role, which rationalizes the separation performance observed experimentally. Aside from zeolite materials, metal-organic frameworks (MOFs) have emerged as a promising class of nanoporous materials as membrane candidates. In order to facilitate the future large-scale screening study of MOFs, in Chapter 4, a multi-layer connectivity-based atom contribution (m-CBAC) approach has been developed to offer fast and accurate charge assignments for MOFs. Computational studies are also performed to investigate the polymer membranes, particularly facilitated transport membranes (FTMs), for CO2 capture. In Chapter 5, computational techniques have been employed to study the role of mobile carriers at a molecular level from the amine–CO2 reaction chemistry, reactive diffusivities of carriers, and CO2. Moreover, in order to investigate the reactive diffusion mechanism of CO2, reactive force fields (ReaxFFs) have been employed in the MD simulations. A new ReaxFF has been developed to reproduce the energy of inter/intra-molecular interactions and the reaction energy computed by density functional theory (DFT) along the reaction pathways for promising mobile carriers. Overall, this dissertation demonstrates the capability of computational methods to facilitate the development of novel membrane materials for liquid and gas separations.