On the mechanism of the catalytic destruction of 1,2-dichloroethane over Ce/Zr mixed oxide catalysts

This study has been undertaken to investigate the efficiency of ceria, zirconia, and CexZr1-x,O-2 mixed oxides as catalysts for the 1,2-dichloroethane destruction in dry air. Mixed oxides exhibit promoted redox and acidic properties, which result catalytically relevant for the oxidation of this chlorinated compound. Considering all compositions it was observed that catalytic activity varies as a function of zirconia content, being Ce0.5Zr0.5O2 the sample which showed a better performance. The notable improvement in catalyst activity of CeO2 can be achieved through structural doping with Zr ions. Likewise, the present study has been focused on the elucidation of the pathway involved in the progressive oxidation of the chlorinated hydrocarbon as a function of the temperature by means of FTIR. It is postulated that the destruction of 1,2-dichloroethane at low temperatures proceeds through dehydrochlorination into vinyl chloride in the presence of acid sites. This compound can be protonated in the presence of OH surface species forming carbonium ions that can be attacked by nucleophilic oxygen species from the catalyst to form chlorinated alkoxide species. These intermediates readily decompose to generate acetaldehyde, which can be further oxidised into acetates and finally degraded to COx. (c) 2007 Elsevier B.V. All rights reserved.