Promoted activity of sulphated Ce/Zr mixed oxides for chlorinated VOC oxidative abatement

The catalytic oxidative decomposition of 1,2-dichoroethane was examined over a series of Ce/Zr mixed oxides (CeO2, Ce0.8Zr0.2O2, Ce0.5Zr0.5O2, Ce0.15Zr0.85O2 and ZrO2) treated with a 1 M aqueous solution of H2SO4 or HNO3. After calcination at 550 degrees C, the doped samples were characterised by dynamic thermogravimetry. X-ray diffraction. N-2-physisorption, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption of ammonia, adsorption of pyridine followed by Raman spectroscopy and temperature-programmed reduction with hydrogen. A noticeable promotion of activity was found for all sulphated oxides, which was associated with an increase of the total acidity and more particularly with a higher concentration of sites with a moderate/strong acid strength. Also the generation of new Bronsted acid sites was found. Interestingly, sulphation did not lead to a significant loss of surface area (except for sulphated ceria) and redox properties linked to the Ce4+/Ce3+ cycle were not apparently affected. Sulphated Ce0.5Zr0.5O2 and Ce0.15Zr0.85O2 samples showed the highest catalytic activity. Hence, the temperatures for DCE removal (in terms of T-50 and T-90) were considerably lowered by 80 degrees C (T-50) and 120 degrees C (T-90). This behaviour evidenced that sulphation was an effective tool to improve the performance of Ce/Zr mixed oxides for chlorinated VOC abatement. In contrast, the activity of the samples modified with nitric acid hardly showed any variation. (C) 2012 Elsevier B.V. All rights reserved.