Stability of Supported Ruthenium Catalysts for Lignin Gasification in Supercritical Water

Abstract

We evaluated the stability of several supported ruthenium catalysts, on titania (Ru/TiO2), on γ-alumina (Ru/γ-A2O3), 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/γ-A2O3 > 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/γ-A2O3 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.