Electrochemical Decomposition of CFC12 Using Gas Diffusion Electrodes

Environmental Science and Technology (Impact Factor: 5.48). 02/1998; 32(3):375-378. DOI: 10.1021/es970417d

ABSTRACT Chlorofluorocarbons (CFCs) were known to cause the depletion of the ozone layer at the stratosphere. A large amount of CFCs is still in use as a refrigerant or still present in the plastic forms. These CFCs should be collected and retreated to harmless compounds to the environment. Electrochemical decomposition of dichlorodifluoromethane (CFC-12) was carried out using 12 kinds of metal-supported gas diffusion electrodes (GDEs). Ag-, Cu-, In-, and Pb-supported GDEs showed high electrocatalytic activity of decomposition of CFC-12. Especially Cu-, In-, and Pb-supported GDEs showed almost 100% efficiency without producing the byproduct (H2). Zn-, Ag-, Cu-, and In-supported GDEs caused defluorination of CFC-12 as well as dechlorination and produced methane mainly. Pb-supported GDE induced only dechlorination of CFC-12 and produced difluoromethane (HFC-32) in high selectivity (92.6%). With the increase in the current density, the partial current density of methane formation at Cu-supported GDE was saturated at 370 mA cm-2. The partial current density of HFC-32 formation at Pb-supported GDE was not saturated even at 650 mA cm-2 and kept high selectivity of HFC-32 formation.

  • Holzforschung 01/2002; 56(1):20-24. · 2.34 Impact Factor
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    ABSTRACT: Decomposition of dichlorodifluoromethane (CCl2F2 or CFC-12) in aradiofrequency (RF) plasma system is demonstrated. The CCl2F2decomposition fractions ?CCl2F2 and mole fractionsof detected products in the effluent gas stream of CCl2F2/O2/Ar andCCl2F2/H2/Ar plasma, respectively, have been determined. The experimentalparameters including input power wattage, O2/CCl2F2 or H2/CCl2F2 ratio,operational pressure, and CCl2F2 feeding concentration wereinvestigated. The main carbonaceous product in the CCl2F2/O2/Arplasma system was CO2, while that in the CCl2F2/H2/Ar plasma systemwas CH4 and C2H2. Furthermore, the possible reaction pathways werebuilt-up and elucidated in this study. The results of the experimentsshowed that the highly electronegative chlorine and fluorine wouldeasily separate from the CCl2F2 molecule and combine with the addedreaction gas. This led to the reactions terminated with the CO2,CH4, and C2H2 formation, because of their high bonding strength. Theaddition of hydrogen would form a preferential pathway for the HCland HF formations, which were thermodynamically stable diatomicspecies that would limit the production of CCl3F, CClF3, CF4, andCCl4. In addition, the HCl and HF could be removed by neutral orscrubber method. Hence, a hydrogen-based RF plasma system provideda better alternative to decompose CCl2F2.
    Plasma Chemistry and Plasma Processing 01/2000; 20(4):469-494. · 1.60 Impact Factor
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    ABSTRACT: Electrochemical decomposition of CFC-12 at metal-tetra-phenyl-porphyrin (TPP) supported gas diffusion electrodes (GDEs) was attempted. Cu-TPP and Zn-TPP supported GDEs showed high activity for decomposition of CFC-12. The main product at the Cu-TPP supported GDE was methane (73% in current efficiency at 20 mA cm−2) and the selectivity of methane formation was kept at the higher current density, whereas HFC-32 (CH2F2) was the main product at the Zn-TPP supported GDE (60% at 25 mA cm−2) and HFC-32 formation decreased steeply with an increase in the current density. These differences in the electrocatalytic activity seem to be caused by the degree of adsorption of CFC-12 on the metal center of metal-TPPs.
    Advances in Environmental Research 10/2002; 6(4):541-545.


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