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

• Published in: Journal of molecular catalysis. A, Chemical Vol. 278; no. 1; pp. 181 - 188
• Main Authors: de Rivas, Beatriz, López-Fonseca, Rubén, González-Velasco, Juan R., Gutiérrez-Ortiz, José I.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 14.12.2007; Elsevier
• Subjects: 1,2-Dichloroethane; Catalysis; Catalytic combustion; Ceria–zirconia mixed oxides; Chemistry; Exact sciences and technology; General and physical chemistry; IR-spectroscopy; Oxidation mechanism; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Ceria–zirconia mixed oxides; 1,2-Dichloroethane; Catalytic combustion; IR-spectroscopy; Oxidation mechanism; Mixed catalyst; Ternary compound; Catalytic reaction; Destruction; Transition element compounds; Cerium oxide; Mechanism; Lanthanide compound; Infrared spectrometry; Zirconia; Zirconium oxide; Chlorocarbon; Oxidation; Ceria-zirconia mixed oxides
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2007.09.006

The oxidation mechanism of the oxidation of 1,2-dichloroethane on Ce/Zr mixed oxides was investigated by means of a combined flow and infrared spectroscopy study. The decomposition occurs through by dehydrochlorination into vinyl chloride in the presence of acid sites. This intermediate can be attacked by nucleophilic oxygen species from the catalyst to form chlorinated alkoxide species, which readily decompose to gradually generate acetaldehyde, acetates and CO x . ▪ This study has been undertaken to investigate the efficiency of ceria, zirconia, and Ce x Zr 1− 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 Ce 0.5Zr 0.5O 2 the sample which showed a better performance. The notable improvement in catalyst activity of CeO 2 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 CO x .