Athospheric oxidation processes of partially fluorinated ethers

Información del proyecto

Identificador del acuerdo de subvención: ENV4950041

Proyecto cerrado

Fecha de inicio 1 Abril 1996

Fecha de finalización 30 Septiembre 1998

Financiado con arreglo a

• Specific programme of research and technological development in the field of environment and climate, 1994-1998

Coste total

Sin datos

Aportación de la UE

Sin datos

Coordinado por

UNIVERSITY OF CRETE
Greece

Objetivo

This project is concerned with the study of the reaction kinetics of hydroxyl radicals, chlorine atoms, and nitrate radicals with a series of partially fluorinated ethers, which may be used as potential alternatives of chlorofluorocarbons (CFCs). The gas phase reactions of chlorine atoms, hydroxyl and nitrate radicals with partially fluorinated ethers, such as CF2HOCHF2, CF3OCHF2, CF3CH2OCH3, CF3CH2OCHF2, CF3CH2OCH2CF3, and CHF2CF2OCH2CH=CH2, will be studied. They do not contain chlorine or bromine that could be released and enter the ozone destruction cycle. The degree of fluorination in these molecules is expected to affect the rate constants and the temperature dependence of these reactions. The main objectives concerning the atmospheric processes of partially fluorinated ethers are:
- Measure the reaction rate constants of hydroxyl radicals, chlorine atoms, and nitrate radicals with a series of partially fluorinated ethers in the gas phase and over the temperature range 250-370 K.
- Identify the primary reaction channels and the position of the initial attack on partially fluorinated ethers by OH, Cl, and NO3 radicals. This will provide information about the initial steps in the atmospheric degradation of the partially fluorinated ethers.
- Evaluate the degradation processes of the partially fluorinated ethers under atmospheric conditions.

This project will be carry out by using three experimental methods:
1.The Very Low Pressure Reactor technique will be used to study the reaction of Cl atoms with partially
fluorinated ethers. This is a technique for the study of fast radical-molecule reactions in the gas phase, without
complications from secondary reactions, and provides accurate absolute rate constant measurements over a wide
range of temperatures. Cl atoms are produced in a microwave discharge of a Cl2/He mixture. Reaction takes
place at very low pressures in a cylindrical Knudsen reactor coated with Teflon. Reactants and products are
continuously discharged into a two-stage vacuum system, and form an effusive molecular beam that is modulated
by a tuning fork chopper. Chemical analysis and estimation of the concentrations of both reactants and products
is done by a quadrupole mass spectrometer.
2. The Relative Rate technique will be used to study the reaction of OH radicals with partially fluorinated
ethers. This technique provides accurate relative rate constant measurements for radical-molecule reactions, in
relation to the known rate constant of a reference compound. OH radicals are produced via photolysis of O3 in
the presence of water vapor, and reactant and reference compounds are monitored by gas chromatography and
FTIR spectroscopy. Product distribution studies are carried out in a 7 lt Pyrex cell fitted with a White
multireflection optics system, giving pathlengths up to 40 m. Reactant and product analysis is done by in-situ
FTIR spectroscopy, which is capable of determining concentrations in the ppm range. The cell is temperature
controlled and allows the variation of total pressure from 10 to 760 Torr. Products are also analyzed by capillary
gas chromatography coupled with mass spectrometry.
3. The Molecular Beam Mass Spectrometric (MBMS) technique will be used to study the reaction of NO3 and
Cl with partially fluorinated ethers. This a technique for the study of fast radical-molecule reactions in the gas
phase, and provides accurate absolute rate constant measurements over a wide range of temperatures. It includes
focusing magnetic and electrostatic lenses that enables the detection of paramagnetic species and the mass
spectroscopic identification of free radicals and polar species. Furthermore, electrical focusing determines the
geometrical structure of the product radicals. The reactions take place at two ranges of pressures: the low
pressure regime and the near atmospheric pressure regime. Finally, it provides the possibility to investigate the
pressure dependence of bimolecular reactions, at near atmospheric conditions.

Ámbito científico (EuroSciVoc)

• ciencias naturales › ciencias químicas › electroquímica › electrólisis
• ciencias naturales › ciencias químicas › química inorgánica › halógenos
• ciencias naturales › ciencias de la tierra y ciencias ambientales conexas › ciencias de la atmósfera › meteorología › presión atmosférica
• ciencias naturales › ciencias químicas › química analítica › espectrometría de masas
• ciencias naturales › ciencias físicas › óptica › espectroscopia

Programa(s)

• FP4-ENV 2C - Specific programme of research and technological development in the field of environment and climate, 1994-1998

Tema(s)

• 01020101 - Stratospheric chemistry and depletion of the ozone layer

Convocatoria de propuestas

Datos no disponibles

Régimen de financiación

CSC - Cost-sharing contracts

Coordinador

UNIVERSITY OF CRETE

• Aportación de la UE: Sin datos
• Dirección: Knossos Avenue ; 71409 IRAKLION ; Grecia
• Coste total: Sin datos

Participantes (4)

DUBLIN INSTITUTE OF TECHNOLOGY

Irlanda

• Aportación de la UE: Sin datos
• Dirección: 4 DUBLIN
• Coste total: Sin datos

INSTITUTE OF CHEMICAL PHYSICS - RUSSIAN ACADEMY OF SCIENCES

Rusia

• Aportación de la UE: Sin datos
• Dirección: 4,Kosygin Street 4 ; 117334 MOSCOW
• Coste total: Sin datos

National Observatory of Athens

Grecia

• Aportación de la UE: Sin datos
• Dirección: Lofos Nymphon ; 11810 Athens
• Coste total: Sin datos

UNIVERSITY COLLEGE DUBLIN

Irlanda

• Aportación de la UE: Sin datos
• Dirección: Stillorgan Road Belfield ; 4 Dublin
• Coste total: Sin datos