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Adsorption models and heat of adsorption of adsorbed ortho di-methyl benzene species on silica by using Temperature Programmed Adsorption Equilibrium methods

Paper ID Volume ID Publish Year Pages File Format Full-Text
43683 45982 2008 10 PDF Available
Title
Adsorption models and heat of adsorption of adsorbed ortho di-methyl benzene species on silica by using Temperature Programmed Adsorption Equilibrium methods
Abstract

The adsorption of ortho dimethyl benzene (o-DMB) at different adsorption temperatures Ta (Ta > 300 K) on a SiO2 solid pretreated at 723 K is studied by the Temperature Programmed Adsorption Equilibrium methods developed previously. These methods provide the evolutions of the adsorption equilibrium coverage of the adsorbed species θe (θe < 0.7) with the adsorption temperature Ta in quasi isobar conditions. These experimental curves θe = f(Ta) are compared to theoretical curves associated to adsorption models developed with the statistical thermodynamics formalism. These models assume either localized or mobile adsorbed species without and with interactions. It is shown that the Langmuir model (localized species without interaction) provides theoretical isobars overlapped with the experimental data for different adsorption pressures Pa considering a heat of adsorption of 61 kJ/mol consistent with the isosteric heat of adsorption. FTIR data show that the adsorption sites are mainly the free OH groups of SiO2 with a small contribution of superficial oxygen species. In line with the development of the experimental microkinetic approach of heterogeneous catalytic processes, and considering previous works dedicated to the adsorption of diatomic molecules such as CO, H2, NO on metal supported particles and metal oxides, it is concluded that adsorption models assuming localized adsorbed species without (Langmuir model) and with (Temkin model) interactions provide robust mathematical expressions, for (a) the adsorption coefficient and (b) the adsorption equilibrium coverage θe = f(Ta, Pa), consistent with the experimental data for Ta > 300 K.

Graphical abstractThe adsorption of ortho dimethyl benzene (o-DMB) at different adsorption temperatures Ta (Ta > 300 K) on a SiO2 solid pretreated at 723 K is studied by Temperature Programmed Adsorption Equilibrium methods developed previously to provide the evolution of the adsorption equilibrium θe with Ta at constant adsorption pressures Pa. These experimental curves are compared to theoretical curves associated to adsorption models developed with the statistical thermodynamics formalism to validate mathematical expressions for the adsorption coefficient K and the θe = f(Ta, Pa) curves.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Ortho di methyl benzene; Silica; Adsorption equilibrium; Heat of adsorption; Adsorption model; FTIR
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Adsorption models and heat of adsorption of adsorbed ortho di-methyl benzene species on silica by using Temperature Programmed Adsorption Equilibrium methods
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 335, Issue 2, 8 February 2008, Pages 220–229
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
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