Stability and Performance of Ruthenium Catalysts Based on Refractory Oxide Supports in Supercritical Water Conditions

• Published in: Energy & fuels Vol. 27; no. 8; pp. 4739 - 4747
• Main Authors: Zöhrer, Hemma, Mayr, Franziska, Vogel, Frédéric
• Format: Journal Article
• Language: English
• Published: American Chemical Society 15.08.2013
• Subjects: Catalysis; Catalysts; Ruthenium; Stability; Surface area; Tetragonal zirconia; Titanium dioxide; Zirconium dioxide
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef400707f

Eleven commercial stabilized and unstabilized zirconia and titania samples have been tested for stability as potential catalyst supports for supercritical water gasification at 400 °C and 28.5 MPa. Samples based on monoclinic zirconia and rutile as well as one sample based on stabilized tetragonal zirconia showed good physical stability. Most samples showed a loss of surface area during the first 20 h of hydrothermal treatment, leveling out at longer exposure times. In a continuous fixed-bed reactor setup, a performance and stability test of the samples loaded with 2 wt % ruthenium gave good results for three samples, of which the sample based on stabilized tetragonal zirconia showed the best performance. For those samples, the surface area decreased only to a minor extent, which we attribute to an aging step that has been performed prior to impregnation with ruthenium. The metal surface area showed a minor decrease for all samples. The reason for this decrease is probably the build-up of a layer of carbon deposit on top of the active sites.