Ruthenium Dispersion: A Key Parameter for the Stability of Supported Ruthenium Catalysts during Catalytic Supercritical Water Gasification

The catalytic supercritical water gasification of isopropanol (450 degrees C, 30 MPa) over Ru catalysts supported on carbon and metal oxides was performed in a fixed-bed plug flow reactor. The Ru loading was between 1.2 and 2%. The catalyst stability over a period of 50h was in the order: Ru/C > Ru/ZrO2 > Ru/Al2O3. Ru/TiO2. Considerable coke deposits were found on Ru/Al2O3 and Ru/TiO2, which suggests that coke formation was responsible for the loss of activity, whereas the coke content was much lower on Ru/C and Ru/ZrO2, which confirms their better coking resistance. Clearly, Ru/C was the most stable catalyst as a loss of only 3% of its initial activity was measured. The high Ru dispersion of Ru/C and Ru/ZrO2 was beneficial for the improvement of the catalyst stability because of the higher gasification rate versus the coke formation rate.