Stability of supported ruthenium catalysts for lignin gasification in Supercritical water

We evaluated the stability of several supported ruthenium catalysts, on titania (Ru/TiO2), on gamma-alumina (Ru/gamma-A(2)O(3)), and on activated carbon (Ru/C), for lignin gasification in supercritical water. The initial activity of the catalysts was in the order of Ru/TiO2 > Ru/gamma-A(2)O(3) > Ru/C. The Ru/TiO2 catalyst maintained high gasification activities for three subseqent uses in supercritical water. The Ru/C catalyst showed the high gasification activity for the first run; however, the activity decreased gradually after repetitive use because of its decreasing surface area during the gasification. The Ru/gamma-A(2)O(3) catalyst also showed a high activity at the initial stage; however, it lost its activity fast because of the change in its structure from gamma- to alpha-phase and dissolution of active ruthenium speacies into supercritical water.