Role of water and other H-rich additives in the catalytic combustion of 1,2-dichloroethane and trichloroethylene

In several practical applications gas streams containing chlorinated volatile organic compounds with variable chemical nature (namely, 1,2-dichloroethane and trichloroethylene) and a significant moisture content (15 000 ppm) must be addressed. In this paper the control of such emissions by catalytic oxidation over Ce/Zr mixed oxides was analysed. Results in terms of activity and selectivity were compared with those obtained when other H-rich additives (1000 ppm), such as hexane or toluene, were fed. High activity was found from mixed oxides featuring a suitable combination of a large population of acid sites, easily accessible oxygen species, and hydrophobic nature attributable to cerium content. The presence of additional H-rich compounds in the feed stream (water, toluene or hexane) tended to decrease the catalytic activity due to the blockage and/or competition for actives sites. However, the increased presence of hydrogen atoms in the stream notably promoted the selectivity to hydrogen chloride instead of molecular chlorine.