CHLORINE CAPTURE BY CATALYST SORBENTS FOR THE OXIDATION OF AIR-POLLUTANTS

Catalytic oxidation can be an effective and economic alternative to thermal oxidation for the destruction of halogenated hydrocarbons (HHC) which are known to deplete stratospheric ozone. Existing oxidation catalysts, noble metal and metal oxides are expensive and can deactivate when treating pollutants containing halogens. Current operation of thermal and catalytic processes require downstream gas scrubbing to remove acidic by-products HCl and Cl2 as well as corrosion resistant materials of construction. In response to the need for a better treatment process, a catalyst-sorbent that simultaneously destroys the HHCs and captures the halogens is being developed, and our initial results are presented in this paper. In this catalyst-sorbent, copper and manganese oxides are supported on sodium carbonate. The metal oxides are responsible for catalyzing the oxidation reactions and sodium carbonate captures the chlorine by forming NaCl and releasing carbon dioxide. Powder X-ray diffraction results show a significant conversion of the carbonate occurs as chlorine is captured. X-ray photoelectron spectroscopy has verified that the change between fresh and used catalyst also occurs near the surface. Trichloroethylene (TCE), trichlorofluoromethane and toluene are shown to be completely converted at a space velocity of 6700 h-1, temperatures 250-degrees-400-degrees-C, and feed concentrations 30-350 ppm of pollutants in moist air. A chlorine balance shows that more than 98% of the chlorine from converted TCE remains in the catalyst-sorbent. Comparisons of this catalyst with others in the literature show it is a viable catalyst for the treatment of low concentrations of air pollutants.