THERMAL DESORPTION ACCOMPANIED BY DECOMPOSITION OF ADSORBED MOLECULES

1996 ◽  
Vol 03 (04) ◽  
pp. 1555-1559 ◽  
Author(s):  
V.P. Zhdanov
Keyword(s):  
Thermal Desorption ◽  
Lateral Interactions ◽  
Desorption Process ◽  
Adsorbed Molecules ◽  
Kinetics Of

The effect of adsorbate–adsorbate lateral interactions on TPD spectra is analyzed in the case where the desorption process is accompanied by decomposition of molecules remaining on the surface. General results are used to interpret the kinetics of NO desorption from Rh(111).

Associative desorption from adlayers of interacting particles: nitric oxide on Pt, Ni and Ru

1980 ◽  
Vol 370 (1743) ◽  
pp. 545-560 ◽  
Keyword(s):  
Thermal Desorption ◽  
Product Distribution ◽  
Desorption Kinetics ◽  
Lateral Interactions ◽  
Model Calculations ◽  
Mechanical Methods ◽  
Analytic Expressions ◽  
Statistical Mechanical ◽  
Kinetics Of ◽  
Quantitative Account

The kinetics of associative desorption from mixed adlayers containing two kinds of particles (N and 0) have been examined. Standard statistical mechanical methods have been employed to study the effects of lateral interactions (ω NN , ω NO , ω OO ) between near-neighbour particles on the desorption kinetics while the adlayer stoichiometry varies continuously during a desorption sweep. Although the most general case ω NN ≠ ω NO ≠ ω OO ≠ 0) is found to be mathematically intractable, either one of two useful approximations can lead to analytic expressions for the desorption rate of N 2 , NO and O 2 . Both of these approximations have been used to simulate the thermal desorption spectra from a 1:1 layer of N and O atoms absorbed on Pt, Ni and Ru surfaces. The results show that, although the operation of lateral interactions can profoundly affect the desorption kinetics of these systems they cannot significantly alter the product distribution. N 2 and O 2 are overwhelmingly the major products, with NO desorption being entirely negligible in every case. We therefore conclude that observations of molecular NO in thermal desorption in these systems is evidence of molecularly adsorbed NO on the surface. Such desorption of NO is not due to recombination of surface N and O atoms. Reasonable values of the interaction parameters are used in model calculations which give a fairly good quantitative account of the available experimental data. The comparison with experiment leads to the conclusion that O-O repulsions are significant in every case. The N-N interaction is either zero or slightly attractive on Pt and Ni, but is very definitely repulsive on Ru.

scholarly journals Thermal Desorption of N-Nonane from Different Porous Solids

1988 ◽  
Vol 5 (2) ◽  
pp. 139-144 ◽  
Author(s):  
A. Guerrero-Ruiz ◽  
Y. Grillet
Keyword(s):  
Thermal Analysis ◽  
Adsorption Capacity ◽  
Thermal Desorption ◽  
Adsorption Kinetics ◽  
Porous Solids ◽  
Analysis Method ◽  
Desorption Process ◽  
Thermal Analysis Method ◽  
Constant Rate ◽  
Kinetics Of

The adsorption capacity and adsorption kinetics of n-nonane on two carbons and four zeolites have been determined in order to obtain information about the microporous structures present in these solids. In addition thermal desorption of n-nonane has been studied by the Constant Rate Thermal Analysis method. It is observed that hydrocarbon diffusion through pores is the parameter which controls the desorption process. N-nonane adsorption into the micropores of the solids is not a ready process which sometimes exhibits slow adsorption kinetics because of the inaccessibility of the molecules to narrower micropores.

Simulation of Thermal Desorption from Nanometer Catalyst Particles

1998 ◽  
Vol 05 (02) ◽  
pp. 551-558 ◽  
Author(s):  
V. P. Zhdanov ◽  
B. Kasemo
Keyword(s):  
Binding Energy ◽  
Single Crystals ◽  
Thermal Desorption ◽  
Spillover Effect ◽  
Supported Catalyst ◽  
Numerical Calculations ◽  
Desorption Process ◽  
Adsorbed Molecules

General equations are derived to describe monomolecular desorption from small supported catalyst particles in the cases where (i) the desorption process occurs simultaneously from different facets and (ii) adsorbed molecules are allowed to jump from the catalyst onto the support, diffuse on the support, and then desorb (a so-called spillover effect). Numerical calculations carried out on the basis of obtained equations indicate that the TPD spectra for interconnected facets might be qualitatively different from those for extended single crystals. The support-mediated channel has been shown to be important if the binding energy on the support is not too low.

The Kinetics of Hydrogen Desorption From Zirconium Hydride

2013 ◽  
Author(s):  
Mingwang Ma ◽  
Ruiyun Wan ◽  
Yuan Wang ◽  
Yanlin Cheng ◽  
Li Liang ◽  
...  
Keyword(s):  
Thermal Desorption ◽  
Thermal Desorption Spectroscopy ◽  
Hydrogen Desorption ◽  
Pressure Effects ◽  
Zirconium Hydride ◽  
Desorption Kinetics ◽  
Desorption Process ◽  
Exponential Factor ◽  
Predict Weight Loss ◽  
Kinetics Of

Thermal desorption spectroscopy (TDS) was used to study the thermal desorption kinetics of zirconium hydride films, which were deposited on molybdenum substrates and thermally charged with gas phase hydrogen. The observed desorption peaks were attributed to phase transforming steps. The activation energy and pre-exponential factor for desorption kinetics was estimated as 116 kJ/mol and 8762 s−1 according to Kissinger relation, respectively. A simulation of TDS spectra was made, which showed that the desorption process followed a first order kinetics. The kinetic parameters were then utilized to predict weight loss behavior at a temperature profile. Pressure effects that can potentially reduce the desorption rate were discussed.

Adsorption of organics on thermally treated solids obtained from colloidal silica

1987 ◽  
Vol 52 (3) ◽  
pp. 572-581 ◽  
Author(s):  
Miroslav M. Kopečni ◽  
Slobodan K. Milonjic ◽  
Wladyslaw Rudzinski ◽  
Jacek Jagiello
Keyword(s):  
Gas Chromatography ◽  
Thermodynamic Parameters ◽  
Adsorption Isotherms ◽  
Colloidal Silica ◽  
Adsorption Properties ◽  
Thermal Pretreatment ◽  
Lateral Interactions ◽  
Adsorbed Molecules ◽  
Temperature Range ◽  
Thermally Treated

Adsorption isotherms of three adsorbates on the solid beads obtained from colloidal silica were determined by means of gas chromatography at low surface coverages, when lateral interactions between the adsorbed molecules are negligible. The influence of thermal pretreatment on the adsorption properties of the solids was investigated in the temperature range from 343 to 423 K, while the solids were heated between 523 K and 1 223 K. The thermodynamic parameters of adsorption have been determined and used to discuss the adsorbate-adsorbent interactions.

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