Effect of the presence of n-hexane on the catalytic combustion of chlororganics over ceria–zirconia mixed oxides

The complete oxidation of volatile organic compounds of different chemical natures, such as 1,2-dichloroethane, trichloroethylene and n-hexane, over Ce–Zr mixed oxide catalysts has been studied in a conventional fixed bed flow reactor. Catalytic conversion was found to depend on Ce/Zr molar content. The combination of surface acidity and accessible lattice oxygen appeared to control the catalytic performance of the mixed oxides. Thus, Ce0.5Zr0.5O2 showed the highest combustion activity for the abatement of chlorohydrocarbons, whereas pure ceria was found to be the most active in the oxidation of the non-chlorinated compound. Destruction efficiency for the three VOCs decreased in the order: n-hexane > 1,2-dichloroethane > trichloroethylene. Significant ‘mixture effects’ were noticed when a given chlorinated feed was decomposed in the presence of n-hexane. On one hand, the destruction of the mixture induced an inhibition of the reactivity of each compound, leading to a marked increase in the ignition temperature. Competitive adsorption played an important role in the inhibition detected with CeO2-based catalysts. On the other hand, HCl selectivity was greatly enhanced through the increased presence of water in the reaction atmosphere generated as a reaction product.