Simulation of Adsorption, Desorption, and Exchange Kinetics of Mixtures on Planar Surfaces. 1. Kinetic-Diffusion-Controlled Adsorption and Desorption for One-Component Mixtures

Langmuir ◽  
1998 ◽  
Vol 14 (10) ◽  
pp. 2864-2875 ◽  
Author(s):  
Nadezhda L. Filippova
Keyword(s):  
Adsorption And Desorption ◽  
Planar Surfaces ◽  
Diffusion Controlled ◽  
Exchange Kinetics ◽  
Kinetic Diffusion ◽  
Controlled Adsorption ◽  
Adsorption Desorption ◽  
Kinetics Of

GAS–SOLID EXCHANGE REACTIONS: ZINC VAPOR AND POLYCRYSTALLINE ZINC SULPHIDE

1964 ◽  
Vol 42 (6) ◽  
pp. 1396-1400 ◽  
Author(s):  
E. A. Secco
Keyword(s):  
Zinc Sulphide ◽  
Static System ◽  
Zinc Vapor ◽  
Exchange Reactions ◽  
Polycrystalline Zinc ◽  
Diffusion Controlled ◽  
Fraction Versus ◽  
Exchange Kinetics ◽  
Kinetics Of ◽  
Initial Process

The exchange kinetics of zinc vapor with polycrystalline zinc sulphide, wurtzite structure, have been studied in a static system in the temperature range 720–960 °C.Plots of log10(1−α*), i.e. exchange fraction, versus time reveal two processes. The initial process is a rapid simple exchange, for which the data fit a first-order rate law and which persists to a depth of 15–18 molecular thicknesses. At this depth the second, slower process, which appears to be diffusion-controlled, sets in. Kinetic and structural interpretations of these results along with the existing data on Zn–ZnO exchange are discussed.

Gas–solid exchange reactions: Zinc vapor and polycrystalline zinc selenide

1968 ◽  
Vol 46 (10) ◽  
pp. 1621-1624 ◽  
Author(s):  
E. A. Secco ◽  
Chien-Huo Su
Keyword(s):  
Zinc Selenide ◽  
Static System ◽  
Zinc Vapor ◽  
Exchange Reactions ◽  
Polycrystalline Zinc ◽  
Diffusion Controlled ◽  
Initial Stage ◽  
Exchange Kinetics ◽  
Kinetics Of ◽  
Exchange Data

The exchange kinetics of zinc vapor with polycrystalline zinc selenide have been studied in a static system in the temperature range 720–800 °C.The kinetic data are consistent with a diffusion-controlled process from the initial stage, in contrast with existing exchange data on ZnO and ZnS powders. The diffusion equation is given as:[Formula: see text]

On the kinetics of the Langmuir-type heterogeneous reactions

2011 ◽  
Vol 16 (4) ◽  
pp. 467-476 ◽  
Author(s):  
Vladas Skakauskas ◽  
Pranas Katauskis
Keyword(s):  
Steady State ◽  
Surface Coverage ◽  
Surface Reactions ◽  
Heterogeneous Reactions ◽  
The Other ◽  
Two Dimensional ◽  
Finite Difference Technique ◽  
Planar Surfaces ◽  
Adsorption Desorption ◽  
Kinetics Of

In this paper we investigate three two-dimensional in space mathematical models of the kinetics of unimolecular heterogeneous reactions proceeding onto planar surfaces. All models include the diffusion of the reactant from a bounded vessel towards an adsorbent, adsorption of the molecules of the reactant, their desorption, conversion (reaction) of the adsorbate into a product, instantaneous product desorption, and the diffusion of the product from the adsorbent into the same vessel. One of these models is based on the Langmuir-type kinetics of the surface reactions, the other one is based on the local steady-state value of the surface coverage, and the last one, in addition to the first model, involves the diffusion of the adsorbate along the adsorbent. Diffusivity of all species is assumed to be constant. Models were solved numerically by using the finite difference technique. By changing input parameters the effects of the rate constants of the reactant adsorption, desorption, and reaction and the influence of the surface diffusion of the adsorbate and approximation of the surface coverage by its steady-state value on the kinetics of surface reactions were studied numerically.

In Situ Monitoring of Adsorption and Desorption of n-Heptane on Porous Silica by Positron Annihilation Lifetime Spectroscopy

2012 ◽  
Vol 733 ◽  
pp. 207-211 ◽  
Author(s):  
Radosław Zaleski ◽  
Waldemar Dolecki ◽  
Jacek Goworek
Keyword(s):  
Positron Annihilation ◽  
Porous Silica ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Intensity Change ◽  
Adsorption And Desorption ◽  
Positron Annihilation Lifetime ◽  
Adsorption Desorption ◽  
Kinetics Of ◽  
Insight Into

Positron annihilation lifetime spectroscopy study of n-heptane adsorption and desorption on silica gel Si-60 gives insight into a free volume evolution during those processes. Analysis of the lifetime distribution allows to ascribe particular ortho-positronium components to silica walls, mesopores and n-heptane. Hysteresis loop of the intensities of the mesopore and n-heptane related components similar to classic adsorption/desorption isotherms is observed. Transition from an adsorbate multilayer structure to liquid when pores become completely filled, manifests itself as an intensity change. Kinetics of desorption and adsorption studies allows to determine the time of reaching the equilibrium by the Si 60–n-heptane system at various pressures.

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