Challenges in Macroscopic Measurement of Diffusion in Zeolites
نویسنده
چکیده
The paper presents a brief historical overview of the field of the measurement of diffusion in zeolites. The focus will be on macroscopic measurements, i.e. when diffusion through entire crystals is studied. While this may appear to be a simple task, we will see that there are difficulties in obtaining reliable results. Two case studies, the volumetric/piezometric experiment and the Transient Analysis of Products (TAP) apparatus are discussed and ways to improve either the experiments or the way in which the results are analyzed are presented. The author’s perspective into what are the current challenges in the field concludes the paper.
منابع مشابه
The Generalized Maxwell-Stefan Model Coupled with Vacancy Solution Theory of Adsorption for Diffusion in Zeolites
It seems using the Maxwell-Stefan (M-S) diffusion model in combination with the vacancy solution theory (VST) and the single-component adsorption data provides a superior, qualitative, and quantitative prediction of diffusion in zeolites. In the M-S formulation, thermodynamic factor (Г) is an essential parameter which must be estimated by an adsorption isotherm. Researchers usually utilize the ...
متن کاملThe working range of static field gradient NMR illustrated by measurements of the intracrystalline diffusion of water in NaA- zeolites
1. Introduction Measuring diffusion in zeolites is a long-lasting challenge. For more than 70 years many efforts have been made to determine the diffusion coefficient of host molecules in the porous framework of zeolites [1]. Actually the different techniques, which were applied, observed different processes and provided dissenting diffusion coefficients. Precisely, there are methods observing ...
متن کاملCellular Automata Simulation of a Bistable Reaction-Diffusion System: Microscopic and Macroscopic Approaches
The Cellular Automata method has been used to simulate the pattern formation of the Schlögl model as a bistable Reaction-Diffusion System. Both microscopic and macroscopic Cellular Automata approaches have been considered and two different methods for obtaining the probabilities in the microscopic approach have been mentioned. The results show the tendency of the system towards the more sta...
متن کاملMolecular Diffusion under Confinement
With reference to molecular transport in manifold media of porous structure, a survey is given on the ample spectrum of diffusion phenomena under confinement. The presentation is mainly based on the evidence provided by pulsed field gradient NMR and by interference and IR microscopy. These "microscopic" techniques of diffusion measurement are particularly powerful for exploring the diverse feat...
متن کاملDiffusion in Porous Media
Porous media are of considerable interest in a very diverse range of activities. They comprise a wide variety of substances—plastics, ceramics, cements, clays, rocks, porous glasses, carbons, silica gels, zeolites, the recently emerging metal–organic frameworks and coordination polymers, and many more. Even biological tissues may share many features of porous media. Depending on the given natur...
متن کامل