scholarly journals The Effect of Mg, Fe(II), and Al Doping on CH4: Adsorption and Diffusion on the Surface of Na-Kaolinite (001) by Molecular Simulations

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 1001 ◽  
Author(s):  
Kai Wang ◽  
Bin Zhang ◽  
Tianhe Kang
Keyword(s):  
Molecular Simulations ◽  
Distribution Functions ◽  
Key Factors ◽  
Al Doping ◽  
Adsorption Sites ◽  
Strong Adsorption ◽  
Ion Doping ◽  
Ch4 Adsorption ◽  
And Diffusion ◽  
Peak Value

Because kaolinite includes a large range of defect elements, the effects of Mg, Fe(II), and Al doping on the CH4 adsorption and diffusion on the surface of Na-kaolinite (001) were investigated by molecular simulations. The simulation results illustrate that ion doping can significantly reduce the amount of CH4 adsorbed by kaolinite, but the type of doped ions has little effect on the amount of adsorption. The specific surface area of kaolinite and the interaction energy between CH4 and the kaolinite’s surface are two key factors that can determine CH4 adsorption capacity. The first peak value of the radial distribution functions (RDFs) between CH4 and the pure kaolinite is larger than that between Mg-, Fe(II)-, and Al-doped kaolinite, which indicates that ion doping can reduce the strength of the interactions between CH4 and the kaolinite’s surface. Besides hydrogen and oxygen atoms, interlayer sodium ions are also strong adsorption sites for CH4 and lead to a weakened interaction between CH4 and the kaolinite’s surface, as well as a decrease in CH4 adsorption. Contrary to the adsorption results, ion doping facilitates the diffusion of CH4, which is beneficial for actual shale gas extraction.

scholarly journals Synergistically enhance confined diffusion by continuum intersecting channels in zeolites

2021 ◽  
Vol 7 (11) ◽  
pp. eabf0775
Author(s):  
Zhiqiang Liu ◽  
Jiamin Yuan ◽  
Jasper M. van Baten ◽  
Jian Zhou ◽  
Xiaomin Tang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Barriers ◽  
Adsorption Sites ◽  
Unique System ◽  
Strong Adsorption ◽  
Weak Adsorption ◽  
Rapid Diffusion ◽  
And Diffusion ◽  
Dependent Mechanism ◽  
Large Diffusion

In separation and catalysis applications, adsorption and diffusion are normally considered mutually exclusive. That is, rapid diffusion is generally accompanied by weak adsorption and vice versa. In this work, we analyze the anomalous loading-dependent mechanism of p-xylene diffusion in a newly developed zeolite called SCM-15. The obtained results demonstrate that the unique system of “continuum intersecting channels” (i.e., channels made of fused cavities) plays a key role in the diffusion process for the molecule-selective pathways. At low pressure, the presence of strong adsorption sites and intersections that provide space for molecule rotation facilitates the diffusion of p-xylene along the Z direction. Upon increasing the molecular uptake, the adsorbates move faster along the X direction because of the effect of continuum intersections in reducing the diffusion barriers and thus maintaining the large diffusion coefficient of the diffusing compound. This mechanism synergistically improves the diffusion in zeolites with continuum intersecting channels.

Molecular simulations of analyte partitioning and diffusion in liquid crystal sensors

2020 ◽  
Vol 5 (1) ◽  
pp. 304-316 ◽  
Author(s):  
Jonathan K. Sheavly ◽  
Jake I. Gold ◽  
Manos Mavrikakis ◽  
Reid C. Van Lehn
Keyword(s):  
Molecular Dynamics ◽  
Liquid Crystal ◽  
Molecular Dynamics Simulations ◽  
Molecular Simulations ◽  
Activation Time ◽  
Dynamics Simulations ◽  
And Diffusion ◽  
Analyte Transport

Molecular dynamics simulations predict the effect of analyte transport on the activation time of chemoresponsive liquid crystal sensors to improve sensor selectivity.

scholarly journals Adsorption and Diffusion of C1 to C4 Alkanes in Dual-Porosity Zeolites by Molecular Simulations

Langmuir ◽  
2017 ◽  
Vol 33 (42) ◽  
pp. 11126-11137 ◽  
Author(s):  
Eliška Rezlerová ◽  
Arnošt Zukal ◽  
Jiří Čejka ◽  
Flor R. Siperstein ◽  
John K. Brennan ◽  
...  
Keyword(s):  
Molecular Simulations ◽  
Dual Porosity ◽  
And Diffusion

Application of a diffusion–desorption rate equation model in astrochemistry

2014 ◽  
Vol 168 ◽  
pp. 517-532 ◽  
Author(s):  
Jiao He ◽  
Gianfranco Vidali
Keyword(s):  
Rate Equation ◽  
Equation Model ◽  
Experimental Investigations ◽  
Desorption Rate ◽  
Desorption Energy ◽  
Energy Distributions ◽  
Rate Equation Model ◽  
Adsorption Sites ◽  
Adsorption Desorption ◽  
And Diffusion

Desorption and diffusion are two of the most important processes on interstellar grain surfaces; knowledge of them is critical for the understanding of chemical reaction networks in the interstellar medium (ISM). However, a lack of information on desorption and diffusion is preventing further progress in astrochemistry. To obtain desorption energy distributions of molecules from the surfaces of ISM-related materials, one usually carries out adsorption–desorption temperature programmed desorption (TPD) experiments, and uses rate equation models to extract desorption energy distributions. However, the often-used rate equation models fail to adequately take into account diffusion processes and thus are only valid in situations where adsorption is strongly localized. As adsorption–desorption experiments show that adsorbate molecules tend to occupy deep adsorption sites before occupying shallow ones, a diffusion process must be involved. Thus, it is necessary to include a diffusion term in the model that takes into account the morphology of the surface as obtained from analyses of TPD experiments. We take the experimental data of CO desorption from the MgO(100) surface and of D2 desorption from amorphous solid water ice as examples to show how a diffusion–desorption rate equation model explains the redistribution of adsorbate molecules among different adsorption sites. We extract distributions of desorption energies and diffusion energy barriers from TPD profiles. These examples are contrasted with a system where adsorption is strongly localized – HD from an amorphous silicate surface. Suggestions for experimental investigations are provided.

Computer Simulation of Xe adsorption in Zeolite Y

1996 ◽  
Vol 431 ◽  
Author(s):  
Vishwas Gupta ◽  
H. Ted Davis ◽  
Alon V. McCormick
Keyword(s):  
Crystal Structure ◽  
Computer Simulation ◽  
Computer Modeling ◽  
Potential Field ◽  
Molecular Level ◽  
Zeolite Y ◽  
Strong Link ◽  
Adsorption Sites ◽  
Commercially Important ◽  
And Diffusion

AbstractComputer modeling of fluids in zeolites can provide a detailed molecular level understanding of the process of adsorption and diffusion under the influence of the 3-D potential field and the confinement offered by the crystal structure. We have shown that there is a strong link between the location, geometry and energetics of sites and the observed thermodynamics and spectroscopy of the adsorbates. Here we report on the modeling of Xe in zeolite Y, which is of interest both because it is commercially important and because it offers two distinct adsorption sites.

Sign in / Sign up

Export Citation Format

Share Document