Activity and stability of a novel Ru modified Ni catalyst for hydrogen generation by supercritical water gasification of glucose

The activities and stabilities of γ-Al2O3 supported Ni catalysts (Ni10/γ-Al2O3 and Ru0.1Ni10/γ-Al2O3) for hydrogen generation through the supercritical water gasification (SCWG) of glucose were investigated at 700 °C, 24 MPa and a weight hourly space velocity (WHSV) of 6 h−1 in a bench-scale continuous down-flow tubular reactor. The Ru0.1Ni10/γ-Al2O3 catalyst (10 wt.% Ni, the Ru-to-Ni molar ratio of 0.1) exhibited higher activity and stability than Ni10/γ-Al2O3 (10 wt.% Ni). With the Ru0.1Ni10/γ-Al2O3 catalyst, negligible catalyst deactivation was observed over a period of 33 h on stream. The H2 yield was maintained as high as ∼50 mol/kg glucose throughout the entire stability test. In contrast, the activity of Ni10/γ-Al2O3 catalyst (10 wt.% Ni) decreased after approximately 7 h on stream, accompanied by a marked decrease in the H2 yield from ∼50 mol/kg glucose initially to ∼25 mol/kg glucose after 7 h. The temperature-programmed reduction (TPR) and H2 chemisorption analyses on the fresh catalysts demonstrated that the addition of a small amount of Ru as a modifier could improve Ni dispersion, which could account for the enhanced activity and higher stability of the Ru0.1Ni10/γ-Al2O3 catalyst.