PHOTOOXIDATION OF EXHAUST POLLUTANTS .3. PHOTOOXIDATION OF THE CHLOROETHENES - DEGRADATION EFFICIENCIES, QUANTUM YIELDS AND PRODUCTS

The photochemical decomposition and oxidation of the chloroethenes C2H 4-xClx (x=1-4) was investigated in the gas phase by irradiation with a low pressure mercury lamp in an oxygen atmosphere. Degradation effici encies directly depend on the number of chlorine atoms both at 185 and 254 nm. The quantum yields for degradation increase from 2-3 for viny l chloride to > 100 for tri- and tetrachloroethene at 185 nm in the 10 (-3) bar concentration range. At 254 nm we measured nearly time indepe ndent quantum yields of around 10 for tri- and 40 for tetrachloroethen e. The photooxidation products and their mechanism of formation are di scussed in detail.