Obiettivo 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. Campo scientifico natural scienceschemical scienceselectrochemistryelectrolysisnatural scienceschemical sciencesinorganic chemistryhalogensnatural sciencesearth and related environmental sciencesatmospheric sciencesmeteorologyatmospheric pressurenatural scienceschemical sciencesanalytical chemistrymass spectrometrynatural sciencesphysical sciencesopticsspectroscopy Programma(i) FP4-ENV 2C - Specific programme of research and technological development in the field of environment and climate, 1994-1998 Argomento(i) 01020101 - Stratospheric chemistry and depletion of the ozone layer Invito a presentare proposte Data not available Meccanismo di finanziamento CSC - Cost-sharing contracts Coordinatore UNIVERSITY OF CRETE Contributo UE Nessun dato Indirizzo Knossos Avenue 71409 IRAKLION Grecia Mostra sulla mappa Costo totale Nessun dato Partecipanti (4) Classifica in ordine alfabetico Classifica per Contributo UE Espandi tutto Riduci tutto DUBLIN INSTITUTE OF TECHNOLOGY Irlanda Contributo UE Nessun dato Indirizzo 4 DUBLIN Mostra sulla mappa Costo totale Nessun dato INSTITUTE OF CHEMICAL PHYSICS - RUSSIAN ACADEMY OF SCIENCES Russia Contributo UE Nessun dato Indirizzo 4,Kosygin Street 4 117334 MOSCOW Mostra sulla mappa Costo totale Nessun dato National Observatory of Athens Grecia Contributo UE Nessun dato Indirizzo Lofos Nymphon 11810 Athens Mostra sulla mappa Costo totale Nessun dato UNIVERSITY COLLEGE DUBLIN Irlanda Contributo UE Nessun dato Indirizzo Stillorgan Road Belfield 4 Dublin Mostra sulla mappa Costo totale Nessun dato
