Zeolite, CFCs

Other important applications of adsorption are the control of greenhouse gases (CO, CH4, N20), the utilization of CH4, the flue gas treatment (SOx, N()x, Hg removal), and the recovery of the ozone-depleting CFCs (Dabrowski, 2001). Activated carbons and hydrophobic zeolites are used for the adsorption of HCFCs (Tsai, 2002). 

Several potential control technologies have been proposed for controlling CO2, CH4, N20, CFCs, O3. .. emissions, but only some of those concerning CO2 and N20 are based on zeolites materials. 

For the last two decades, attention has been focused on redressing the ozone depletion in the earth s protective layer. It is believed that chlorine radicals dissociated from chlorofluorocarbons (CFCs), upon irradiation of sun s UV in the stratosphere, promotes the ozone depletion. Hence, in addition to development of CFC alternatives there is an urgent need for the safe disposal of CFCs. Several processes such as pyrolysis, incineration, photocatalysis, oxidative destruction over metal oxide or zeolite catalysts and destruction at very high temperatures ( by plasma technique ) are reported in the literature for the disposal of CFCs[ 1-5]. But all these processes yield harmful products like CO, HF/F2 etc. Catalytic conversion of chlorinated organics in presence of hydrogen seems to be a better technique as it yields either hydrofluorocarbons(HFCs) or hydrochlorofluorocarbons(HCFCs) whose ozone depletion potential is either zero or very low and yet most of these products act as CFC alternatives. 

It should be noted that the photon energy and flux emitted from these discharges are not sufficient to explain the enhancement in destruction by photocatalysis. While Ti02 is found to be effective in more than doubling the CFC-12 destruction efficiency, the NaX zeolite catalyst which has no effect in enhancing the CFC-12 destruction (Fig. 6.2) reduces the NOx formation by more than a factor of two compared with the use of a plasma discharge alone. Ideally in plasma catalysis, we wish to achieve both enhancement in destruction and minimisation of unwanted by-products. 

Adsorption of ozone-depleting chlorofluorocarbons (CFG) over zeolite is of major global environmental concern. To investigate the nature of CFCs including fluoro. 

---