Effects of additives on the selectivity of byproducts and dry removal of fluorine for abating tetrafluoromethane in a discharge reactor

The removal efficiency of tetrafluoromethane (CF4) was significantly enhanced by adding additives (H2, O2, H2 + O2, H2O) in an atmospheric-pressure microwave plasma reactor. However, large amounts of fluorine (F2) were produced in this study. Moreover, the selectivity of F2 was apparently greater than that of HF (in H2-based condition) or COF2 (in O2-based abatement). Notably, in an O2-rich environment, more F2 and a larger amount of CO2 were produced. Subsequently, F2 can be effectively removed by reacting with CaO to form CaF2 at 200 deg. C via an in situ dry, chemical absorption process in the low-temperature afterglow discharge zone within the same plasma reactor