Water-resistant Fe-Ca-Ox/TiO2 catalysts for low temperature 1,2-dichlorobenzene oxidation

Fe-Ca-O-x/TiO2 composite catalysts were synthesized to develop a low-temperature and water-resistant technology for the catalytic oxidation of 1,2-dichlorobenzene (o-DCB), as a model of chlorinated volatile organic compounds. The composite catalysts were characterized by XRD, TEM, N-2 adsorption/desorption and H-2-TPR. Activity measurements were conducted in the range of 200-500 degrees C, in both the presence and absence of water. It was found that the incorporation of FeOx on TiO2 could significantly improve the catalytic activity, but the activity was remarkably inhibited over a broad temperature range centered at 300 degrees C due to the existence of water. Simultaneous incorporation of Fe and Ca oxide (Fe-Ca-O-x) on TiO2 could not only further improve the catalytic activity but also enhance the performance of water-resistance in the wet reaction. Among the tested catalysts, the catalyst with Fe-Ca-O-x, loading of 7 wt% showed the highest catalytic activity. The total conversion of o-DCB could be obtained at 350 degrees C, in both the dry and wet reaction. The catalytic oxidation of o-DCB over TiFeCa-7 followed first-order kinetics with an apparent activation energy of 32 kJ/mol. The surface acidity of the catalyst and the intermediate species in the reaction were investigated by in situ FTIR spectroscopy. It is proposed that o-DCB molecule should be preferentially adsorbed on the Lewis acid sites, forming partial oxidation products, which could be subsequently oxidized to form final products. (C) 2013 Elsevier B.V. All rights reserved.