SPECTROSCOPIC STUDIES OF THE ADSORPTION AND REACTIONS OF CHLOROFLUOROCARBONS (CFC-11 AND CFC-12) AND HYDROCHLOROFLUOROCARBON (HCFC-22) ON OXIDE SURFACES

Raman and Fourier transform infrared (FT-IR) spectroscopy have been ap plied to a systematic investigation of the adsorption and decompositio n of dichlorodifluoromethane (CCl2F2, CFC-12), fluorotrichloromethane (CCl3F, CFC-11), chlorodifluoromethane (CHCIF2, HCFC-22) and molecular chlorine on oxide surfaces. Additionally, the effects of heating and ultraviolet photolysis of the CFC and HCFCs adsorbed on the oxide surf aces have been investigated. Spectral features for these species indic ated a small wavenumber shift (1-6 cm(-1)) associated with the adsorbe d phase. Some evidence, specifically the appearance of the Raman band at 507 cm(-1), is presented to show that chlorine decomposition specie s are associated with these oxide surfaces. It was concluded that the new spectral feature (at ca. 507 cm(-1)) related with the decompositio n of the CFC and HCFC molecules was an important indicator of the exte nt to which the reaction between the adsorbed CFC and HCFC and oxide s urface has taken place. The extent of CFC-surface interaction has been quantified in terms of a maximum (Raman) frequency shift parameter (A (M)). Wavenumber shifts suggest both cation-adsorbate and non-specific adsorption interactions are occurring in the internal channels of the zeolites. Slow decomposition of the adsorbed CFCs under ultraviolet-v isible photolysis (at lambda > 300 nm) and/or thermal treatment was ob served spectroscopically. Using FT-IR spectroscopy, the formation of g as-phase products (CO, CO2, HCl) both onyn photolysis and heating was evident. Results of these measurements are compared with the observed atmospheric reactivity of these compounds.