Abstract
The surface structures of ZrO 2, Y 2O 3–ZrO 2 and SiO 2–ZrO 2 catalysts were studied in relation to their basicity and acidity, and the relationship between surface structure and gasification gas clean-up activity was evaluated. The physical properties of the catalysts were characterized by BET, XRD and Raman spectroscopy. The basicity and acidity of the catalysts were measured by CO 2-TPD and NH 3-TPD, respectively. The types of active surface sites were determined by in situ DRIFTS experiments for the adsorption and desorption of CO 2. The order of activity of the catalysts in the decomposition of tar from synthetic gasification gas was ZrO 2 > Y 2O 3–ZrO 2 > SiO 2–ZrO 2. Acidity was observed to be an unfavorable characteristic for ZrO 2-based gas clean-up catalysts, whereas basicity seems to be essential. The redox properties of Y 2O 3–ZrO 2 enhance its overall oxidation activity and the lower performance of Y 2O 3–ZrO 2 in tar decomposition compared to ZrO 2 can be explained by its oxidation activity towards other gas compounds than tar.
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