Reductive and oxidative destruction of chlorinated hydrocarbons in gas-phase catalytic reactors: Packed-beds and modified fuel cells

The thermochemical destruction of TCE, a major contaminant of soil and groundwater, was studied using a packed-bed reactor to establish the ranges of temperature and H₂/O₂ ratio at which oxidative destruction and reductive chlorination occur. At H₂/O₂ ratios of 2:1 and 3:1, TCE conversion increased with temperature, reaching 100% at ≥ 150°C. When excess hydrogen was present, the main reaction product was ethane. These results showed that the reduction reaction is more efficient for TCE conversion at lower temperatures (50°-200°C) than the oxidation reaction. There was clear evidence of a change in conversion mechanism as the temperature increased; at low temperatures, TCE was converted primarily to ethane. At higher temperatures, ethane yield decreased while C02 production increased. The effluent flow rate and cell current increased as the potential decreased although the influent flow rate was constant. Performance of the modified fuel cell reactor was also evaluated in the presence of 21% oxygen in the influent gas stream. An inhibition of TCE conversion was expected in the presence of oxygen due to a lower availability of hydrogen caused by reduction of oxygen to water. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).