On the Study of Diffusion in Zeolites Using Molecular Dynamics Techniques PDF Download
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Author: Martin J. S. Sanborn
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Molecular dynamics (MD) simulation is a powerful tool for studying diffusion in zeolites. In MD, the equations of motion are integrated forward in time to track the motions of atoms in order to obtain dynamic information. Here we use this information to calculate equilibrium self diffusivities and nonequilibrium transport diffusivities. Better understanding of diffusion leads to improved application of zeolites in catalysis, separations, and novel membranes.
Author: Martin J. S. Sanborn
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Molecular dynamics (MD) simulation is a powerful tool for studying diffusion in zeolites. In MD, the equations of motion are integrated forward in time to track the motions of atoms in order to obtain dynamic information. Here we use this information to calculate equilibrium self diffusivities and nonequilibrium transport diffusivities. Better understanding of diffusion leads to improved application of zeolites in catalysis, separations, and novel membranes.
Author: Hellmut G. Karge
Publisher: Springer Science & Business Media
ISBN: 3540739661
Category : Science
Languages : en
Pages : 411
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Book Description
"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.
Author: Vishwas Gupta
Publisher:
ISBN:
Category :
Languages : en
Pages : 486
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Book Description
Author: D.J. Fisher
Publisher: Trans Tech Publications Ltd
ISBN: 303826461X
Category : Technology & Engineering
Languages : en
Pages : 210
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Book Description
The microporous aluminosilicate minerals known as Zeolites are invaluable as adsorbents, molecular sieves and catalysts because they possess a porous structure that can let pass or accommodate cations such as, Ca2+, K+, Mg2+, Na+, etc. These are nevertheless loosely held and can be easily exchanged for those in an adjacent solution. Movement of other materials through Zeolites is naturally an important factor. The present compilation consists of diffusion data. These represent, as far as possible, pure diffusion, shorn of other transfer mechanisms such as permeation. Most of the results involve well-known artificially produced Zeolites, but also include information on naturally occurring Zeolites such as analcime and clinoptilolite. The 290 entries, 22 figures and 67 tables cover the period from 1961 to 2014.
Author: C.Richard A. Catlow
Publisher: Elsevier
ISBN: 0128050586
Category : Technology & Engineering
Languages : en
Pages : 372
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Book Description
Modelling and Simulation in the Science of Micro- and Meso-Porous Materials addresses significant developments in the field of micro- and meso-porous science. The book includes sections on Structure Modeling and Prediction, Synthesis, Nucleation and Growth, Sorption and Separation processes, Reactivity and Catalysis, and Fundamental Developments in Methodology to give a complete overview of the techniques currently utilized in this rapidly advancing field. It thoroughly addresses the major challenges in the field of microporous materials, including the crystallization mechanism of porous materials and rational synthesis of porous materials with controllable porous structures and compositions. New applications in emerging areas are also covered, including biomass conversion, C1 chemistry, and CO2 capture. Authored and edited by experts in the field of micro- and meso-porous materials Includes introductory material and background both on the science of microporous materials and on the techniques employed in contemporary modeling studies Rigorous enough for scientists conducting related research, but also accessible to graduate students in chemistry, chemical engineering, and materials science
Author: Mahmoud Kamal Forrest Abouelnasr
Publisher:
ISBN:
Category :
Languages : en
Pages : 172
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Book Description
The goal of this work is to develop molecular simulation techniques to characterize the diffusion properties of crystalline microporous materials for separation applications. The conventional simulation type used to study the diffusion behavior of adsorbates in a microporous material is Molecular Dynamics. However, for slowly diffusing systems, these simulations become intractably long. In such situations, the diffusion process can be considered as a series of rare cage-to-cage hops, with the majority of the time (and computational effort) spent on unimportant movements within a cage. Recent work in the field has focused on the application of transition state theory (TST) to this process, allowing an estimation of the diffusion properties with a Monte Carlo simulation. In some cases, for example the diffusion of methane in zeolite LTA at low loading, TST gives a good approximation of the true (MD) diffusion. For the general case, the TST result requires a correction factor, which is calculated with a Bennett-Chandler simulation. The correction factor is the conditional probability the system will undergo a transition given that it is at the transition state; this correction factor is influenced by the number of particles in each cage. For the system of methane in zeolite LTA, there are between zero and fifteen particles in either cage at any time, meaning that 120 different correction factors must be calculated. We developed a mixing rule that relates the correction factor between two cages of unequal loading (a and b) to the correction factors between two cages of equal loading (a and a; b and b). This reduced by an order of magnitude the number of Bennett-Chandler simulations required, from 120 to 16. Next, we investigated a fundamental change in the packing of methane adsorbed in zeolite LTA that occurs at high loadings, where a sub-lattice develops within each supercage leading to increased blocking a divergence between the self- and collective-diffusion coefficients. This qualitative change was replicated in a model kMC system that accounted for this topological shift. As particles move within a cage, their speed fluctuates until at one moment, they happen to be travelling quickly enough to hop out of their potential energy well and through the window. As they fall into the potential energy well of the next cage, they speed up for some time until they re-equilibrate. During this time, they are more likely to hop again. Hopping is no longer a Markovian process, without memory of past events. This has a tremendous impact the diffusion behavior. This behavior was observed for methane adsorbed in zeolites ASV, LTA, and CGS, where various different departures from an expected random walk of Poisson-distributed hops were investigated. Because of the immense number of frameworks available for study, we developed a high-throughput computational screening method, applying TST to a vast database of>80,000 hypothetical zeolite structures in order to asses their suitability for carbon capture. From this large set of structures, several materials were identified with higher predicted performance for carbon capture by a factor of four or more. These high-performing structures were observed to exhibit certain structural similarities. The materials in this large database did not exhibit a Robseon upper bound.
Author: David M. Markus
Publisher:
ISBN:
Category : Amorphous substances
Languages : en
Pages : 234
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Book Description
Author: Susana Valencia
Publisher: Springer Nature
ISBN: 3030638537
Category : Science
Languages : en
Pages : 233
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Book Description
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.
Author: Jörg Kärger
Publisher: John Wiley & Sons
ISBN: 3527651292
Category : Science
Languages : en
Pages : 932
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Book Description
Atoms and molecules in all states of matter are subject to continuous irregular movement. This process, referred to as diffusion, is among the most general and basic phenomena in nature and determines the performance of many technological processes. This book provides an introduction to the fascinating world of diffusion in microporous solids. Jointly written by three well-known researchers in this field, it presents a coherent treatise, rather than a compilation of separate review articles, covering the theoretical fundamentals, molecular modeling, experimental observation and technical applications. Based on the book Diffusion in Zeolites and other Microporous Solids, originally published in 1992, it illustrates the remarkable speed with which this field has developed since that time. Specific topics include: new families of nanoporous materials, micro-imaging and single-particle tracking, direct monitoring of transient profiles by interference microscopy, single-file diffusion and new approaches to molecular modeling.
Author: Shaji Chempath
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Adsorption and diffusion of guest molecules in zeolite channels was studied with molecular simulations. Using improved algorithms we have calculated adsorption equilibria and diffusion coefficients at conditions that could not be studied previously.
