Low-temperature combustion of chlorinated hydrocarbons over CeO2/H-ZSM5 catalysts

The performance of various CeO2/H-ZSM5 catalysts was evaluated for the oxidation of one of the most common chlorinated pollutants found in waste streams, namely 1,2-dichloroethane. The supported samples with varying CeO2 loading (6–50 wt.%) were prepared by impregnation and subsequently calcined at 550 °C. Structural, morphological and physico-chemical changes caused by the CeO2 addition were analysed by X-ray diffraction, transmission electronic microscopy, N2-physisorption, temperature-programmed desorption of ammonia and temperature-programmed reduction with hydrogen. The enhancement of the catalytic behaviour of the resulting samples with respect to plain H-ZSM5 could be accounted for on the basis of the synergetic role played by oxygen mobility and acid sites. Hence, an optimum cerium loading of 11 wt.% was found with a T50 value around 210 °C. At 350 °C, where conversion of the chlorinated feed is about 99%, the major oxidation products were carbon oxides and hydrogen chloride with a reduced presence of chlorinated by-products and molecular chlorine. A relatively good catalytic stability was noticed during 80 h time on line.

.Figure optionsDownload high-quality image (90 K)Download as PowerPoint slideHighlights
► CeO2/H-ZSM5 catalysts resulted highly active in the oxidation of 1,2-dichloroethane.
► Activity was attributed to the synergetic role played by oxygen mobility and acid sites.
► This bifunctional character was optimised for the sample with a 11 wt.% CeO2 content.
► The formation of chlorinated intermediates was substantially reduced.