Download Free Investigating Adsorption And Diffusion Of Gas Mixtures In Zeolite Like Nanoporous Materials Using Computational Techniques Book in PDF and EPUB Free Download. You can read online Investigating Adsorption And Diffusion Of Gas Mixtures In Zeolite Like Nanoporous Materials Using Computational Techniques and write the review.

In this thesis, I investigate nanoporous materials such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) for various gas adsorption applications using a wide array of computational methods. These types of materials are ideal for gas adsorption and separation applications due to their large internal surface areas and tunable chemistry. They are also ideally suited to study using traditional computational methods due to their well-defined structures. In the first chapter, I introduce nanoporous materials and the various molecular mechanics methods which can be used to study them. I also introduce the topic of in silico materials design. Then, in the next chapter, I discuss the development of a DFT-derived force field to accurately study the gas adsorption behavior in materials which contain coordinatively unsaturated metal sites. In such materials, the most commonly used methods fail to accurately model adsorption behavior, and the introduction of the DFT-derived force field has allowed the study of flue-gas mixtures in these frameworks. Following this work, in the third chapter we discuss the use of the DFT-derived force field to study the dynamical behavior of greenhouse gases in the same MOF series. Much of this work was done in collaboration with experimentalists who used NMR as their primary tool to probe the dynamics of these gases in the materials. Our molecular dynamics simulations complemented their NMR experiments. In the fourth chapter, I switch gears and discuss the use of computational methods for the design of new materials, first to characterize experimentally synthesized materials, and then to construct a database of thousands of new COF structures. Finally, I conclude by sharing a summary of my findings from the various investigations discussed in this thesis and my future outlook for the field.
Offering a materials science point of view, the author covers the theory and practice of adsorption and diffusion applied to gases in microporous crystalline, mesoporous ordered, and micro/mesoporous amorphous materials. Examples used include microporous and mesoporous molecular sieves, amorphous silica, and alumina and active carbons, akaganeites, prussian blue analogues, metal organic frameworks and covalent organic frameworks. The use of single component adsorption, diffusion in the characterization of the adsorbent surface, pore volume, pore size distribution, and the study of the parameters characterizing single component transport processes in porous materials are detailed.
This text discusses the synthesis, characterization, and application of metal-organic frameworks (MOFs) for the purpose of adsorbing gases. It provides details on the fundamentals of thermodynamics, mass transfer, and diffusion that are commonly required when evaluating MOF materials for gas separation and storage applications and includes a discussion of molecular simulation tools needed to examine gas adsorption in MOFs. Additionally, the work presents techniques that can be used to characterize MOFs after gas adsorption has occurred and provides guidance on the water stability of these materials. Lastly, applications of MOFs are considered with a discussion of how to measure the gas storage capacity of MOFs, a discussion of how to screen MOFs to for filtration applications, and a discussion of the use of MOFs to perform industrial separations, such as olefin/paraffin separations. Throughout the work, fundamental information, such as a discussion on the calculation of MOF surface area and description of adsorption phenomena in packed-beds, is balanced with a discussion of the results from research literature.
"Molecular Sieves - Science and Technology" covers, in a comprehensive manner, the science and technology of zeolites and all related microporous and mesoporous materials. The contributions are grouped together topically in such a way that each volume deals with a specific sub-field. Volume 7 treats fundamentals and analyses of adsorption and diffusion in zeolites including single-file diffusion. Various methods of measuring adsorption and diffusion are described and discussed.
Molecular simulations are used to assess the ability of metal-organic framework (MOF) materials to store and separate noble gases. Specifically, grand canonical Monte Carlo simulation techniques are used to predict noble gas adsorption isotherms at room temperature. Experimental trends of noble gas inflation curves of a Zn-based material (IRMOF-1) are matched by the simulation results. The simulations also predict that IRMOF-1 selectively adsorbs Xe atoms in Xe/Kr and Xe/Ar mixtures at total feed gas pressures of 1 bar (14.7 psia) and 10 bar (147 psia). Finally, simulations of a copper-based MOF (Cu-BTC) predict this material's ability to selectively adsorb Xe and Kr atoms when present in trace amounts in atmospheric air samples. These preliminary results suggest that Cu-BTC may be an ideal candidate for the pre-concentration of noble gases from air samples. Additional simulations and experiments are needed to determine the saturation limit of Cu-BTC for xenon, and whether any krypton atoms would remain in the Cu-BTC pores upon saturation.
In this work, a systematic computational study directed toward developing a molecular-level understanding of gas adsorption and diffusion characteristics in nano-porous materials is presented. Two different types of porous adsorbents were studied, one crystalline and the other amorphous. Physisorption and diffusion of hydrogen in ten iso-reticular metal-organic frameworks (IRMOFs) were investigated. A set of nine adsorbents taken from a class of novel, amorphous nano-porous materials composed of spherosilicate building blocks and isolated metal sites was also studied, with attention paid to the adsorptive and diffusive behavior of hydrogen, methane, carbon dioxide and their binary mixtures. Both classes of materials were modeled to correspond to experimentally synthesized materials. While much research has targeted adsorption in IRMOFs, very little has appeared for these amorphous silicates, which contain cubic silicate building blocks: Si8O20 [spherosilicate units], cross-linked by SiCl2O2 [silicon chloride] bridges and decorated with either -OTiCl3 [titanium chloride] or -OSiMe3 [trimethylsilyl] groups. Based only on physisorption, the amorphous silicates show competitive adsorptive capacities and selectivities with other commercial gas adsorbents. The tools employed in this dissertation were computational in nature. Adsorptive properties, such as adsorption isotherms, binding energies and selectivities, were generated from Grand Canonical Monte Carlo molecular (GCMC) simulations. Self-diffusivities and activation energies for diffusion were generated using Molecular Dynamics simulations. Adsorption isotherms are reported at temperatures of 77 K [Kelvin] and 300 K for pressures ranging up to 100 bar. The most favorable adsorption sites for all gases studied in the amorphous silicates are located in front of the faces of the spherosilicate cubes. Regardless of material, the hydrogen adsorption process is governed by entropic considerations at 300 K. At 77 K energetic considerations control hydrogen adsorption at low pressures and entropic effects dominate at high pressure. For methane and carbon dioxide at 300 K, the adsorption process is governed by energetic considerations at low pressure and by entropic (packing) constraints at high pressure. The amorphous silicates showed very high selectivity for carbon dioxide over hydrogen. The presence of titanium sitesdid not enhance physisorptive capacity or selectivity.
Nanoporous materials such as zeolites, zeolitic imidazolate frameworks (ZIFs), and metal-organic frameworks (MOFs) are used as sorbents or membranes for gas separations such as carbon dioxide capture, methane capture, paraffin/olefin separations, etc. The total number of nanoporous materials is large; by changing the chemical composition and/or the structural topologies we can envision an infinite number of possible materials. In practice one can synthesize and fully characterize only a small subset of these materials. Hence, computational study can play an important role by utilizing various techniques in molecular simulations as well as quantum chemical calculations to accelerate the search for optimal materials for various energy-related separations. Accordingly, several large-scale computational screenings of over one hundred thousand materials have been performed to find the best materials for carbon capture, methane capture, and ethane/ethene separation. These large-scale screenings identified a number of promising materials for different applications. Moreover, the analysis of these screening studies yielded insights into those molecular characteristics of a material that contribute to an optimal performance for a given application. These insights provided useful guidelines for future structural design and synthesis. For instance, one of the screening studies indicated that some zeolite structures can potentially reduce the energy penalty imposed on a coal-fired power plant by as much as 35% compared to the near-term MEA technology for carbon capture application. These optimal structures have topologies with a maximized density of pockets and they capture and release CO2 molecules with an optimal energy. These screening studies also pointed to some systems, for which conventional force fields were unable to make sufficiently reliable predictions of the adsorption isotherms of different gasses, e.g., CO2 in MOFs with open-metal sites. For these systems, we developed a systematic, transferable, and efficient methodology to generate force fields by using high-level quantum chemical calculations for accurate predictions of properties. The method was first applied to study the adsorption of CO2 and N2 in Mg-MOF-74, an open-metal site MOF. Two different approaches were developed: one approach based on MP2 calculations on a representative cluster and a second approach based on DFT calculations on a fully periodic MOF. Both approaches gave significantly better predictions of the experimental adsorption isotherms compared to conventional force fields. In addition, we extended the DFT approach to study water adsorption in these materials. Moreover, instead of deriving detailed force fields, we have also proposed an alternative method to efficiently correct initial trial force fields with little information obtained from quantum chemical calculations. Finally, we studied the dynamics of CO2 in Mg-MOF-74 using molecular simulations. This study addressed the dynamic behaviors of CO2 adsorbed in Mg-MOF-74, and provided an alternative explanation to the experimentally measured chemical shifts of 13C labeled CO2 adsorbed in a powder Mg-MOF-74 sample. Our results further illustrated that subtle changes in the topology of frameworks greatly influence CO2 dynamics.
This volume compiles and discusses the fundamental and multidisciplinary knowledge on adsorption and separation processes using zeolites as adsorbents. Over the last decade, a large amount of research has been carried out for the development of zeolites as adsorbents. However, there is still a growing interest to increase the understanding of such selective adsorbents. Therefore, synthesis strategies and new approaches for developing new selective zeolite adsorbents for gas separation are presented in the first chapter. In addition, a chapter focused on adsorption characterization techniques of microporous materials is included. This will be helpful for advanced readers, since the new IUPAC recommendations for microporous characterization are not still widely employed by the zeolite community. Experimental and theoretical aspects of economically and environmentally relevant separations, which have been successfully carried out with zeolites, are discussed in detail in subsequent chapters. Finally, industrial zeolite based adsorption and separation processes as well as current perspectives for new zeolite based separations, and improvements of current technologies are presented.