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 °C, the doped samples were characterised by dynamic thermogravimetry, X-ray diffraction, N2-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 Brönsted 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 T50 and T90) were considerably lowered by 80 °C (T50) and 120 °C (T90). 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.

Figure optionsDownload as PowerPoint slideHighlights
► Sulphation of Ce/Zr oxides promoted the decomposition of chlorinated VOCs.
► T50 and T90 were considerably lowered by 80 °C (T50) and 120 °C (T90).
► Sulphated Ce0.5Zr0.5O2 and Ce0.15Zr0.85O2 showed the highest activity.
► Overall acidity and concentration of sites with a moderate strength were increased.
► No marked impact on Ce4+/Ce3+ reduction step was found.