Oxidative destruction of dichloromethane over protonic zeolites

Various protonic zeolites (H-Y, H-ZSM-5, and H-MOR) were tested for the total combustion of dichloromethane (DCM) as a model reaction for the catalytic destruction of chlorinated organic pollutants. The order of catalytic activity decreased in the following order: H-MOR > H-ZSM-5 > H-Y Strong Bronsted acidity played a determining role in controlling the active catalytic behavior as revealed by TPD of ammonia and IR measurements of adsorbed pyridine. DCM oxidative decomposition gave rise to CO and HCl as main products along with small amounts of CO2 and Cl-2. In addition, methyl chloride was detected as a reaction intermediate between 250 and 500degreesC The presence of water in the feed stream led to an inhibition of the zeolite activity and resulted in a noticeable change in the reaction product distribution. Water effectively promoted the selectivity toward environmentally desirable reaction products, that is, HCl and CO2, and completely suppressed the formation of methyl chloride.