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| Identifier |
000319293 |
| Title |
Κινητική και μηχανιστική μελέτη των αντιδράσεων ριζών υδροξυλίου και ατόμων χλωρίου με επιλεγμένη σειρά φθοριωμένων αλδεΰδων στην αέρια φάση |
| Alternative Title |
Kinetic and mechanistic stydy for the reactions of OH radicals and Cl atoms with a series of fluorinated aldehydes in the gas phase |
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Author
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Παπαναστασίου, Δημήτρης Κ.
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Thesis advisor
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Παπαγιαννακόπουλος, Πάνος
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| Abstract |
The main objective of the present thesis was the kinetic and mechanistic
investigation of the reactions of OH radicals and Cl atoms with selected fluorinated aldehydes (FAL), CF3CHO, CΗF2CHO, CF3CF2CHO και CF3CH2CHO in the gas phase, in order to assess the tropospheric degradation and fate of FAL as well as their potential importance to secondary aerosol formation in the atmosphere.
In particular, the rate coefficients of the title reactions were determined at low
pressures (2mTorr) and in the temperature range of 273-363K, by using the Very Low Pressure Reactor (VLPR) coupled with the mass spectrometry (MS) detection
technique. The rates were measured by applying both absolute rate (Cl reactions) and relative rate (OH reactions) techniques. The Arrhenius parameters of the title reactions were also determined in the above temperature range. In addition, the
mechanistic investigation for the title reactions showed that the abstraction of the aldehydic hydrogen is the dominant reaction pathway leading to the formation of HX (X = Cl or OH) and the corresponding radical CxF2x+1CO. In addition, the oxidation
process of FAL was investigated by performing experiments in the presence of Ο2/NOx. It was found that perfluorinated carboxylic acids (PFCA) were not detected among the final oxidation products, indicating that the oxidation of FAL is not of great importance to the secondary aerosol formation in troposphere. It was also found
that CxF2x+1CO radicals may undergo oxidation leading to peroxy radicals as well as
unimolecular decomposition leading to CO and CxF2x+1 radicals.
Finally, the UV/Vis cross sections of FAL were determined in order to assess
the importance of photolysis to the degradation of FAL in the troposphere. The IR cross sections were also determined in order to assess their overall impact of FAL in
the atmosphere and the climate. The Global Warming Potential (GWP) of the title FAL was estimated by using the Pinnock model and the lifetime and IR cross sections values obtained by the present work. It was concluded that the selected FAL have
extremely low GWP values (< 10-4 for 100 years time horizon), and therefore their
burden on the greenhouse effect is negligible. It should be noted that the GWP values obtained for FAL represent an upper limit, since the lifetimes used were based only to the chemical degradation process of FAL (excluding the photolysis process).
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| Language |
Greek |
| Subject |
Absorption cross section |
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Atmospheric chemistry |
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Chemical kinetics |
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Chlorine atoms, Cl |
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Fluorinated Aldehydes |
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Global warming potential |
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Hydroxyl radicals, OH |
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Mechanistic Study |
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Άτομα χλωρίου |
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Ατμοσφαιρική χημεία |
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Δυναμικό παγκόσμιας θέρμανσης |
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Ενεργές διατομές απορρόφησης |
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Μηχανιστική μελέτη |
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Ρίζες υδροξυλίου |
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Φθοριωμένες αλδεΰδες |
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Χημική κινητική |
| Issue date |
2007-12-01 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Chemistry--Doctoral theses
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Type of Work--Doctoral theses
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| Views |
263 |
Κινητική και μηχανιστική μελέτη των αντιδράσεων ριζών υδροξυλίου και ατόμων χλωρίου με επιλεγμένη σειρά φθοριωμένων αλδεΰδων στην αέρια φάση
