Hydrogen production by supercritical water gasification of glucose with Ni/CeO₂/Al₂O₃: Effect of Ce loading

Ni-based SCWG catalysts attract more attention for its high activity and relatively low cost. However, carbon deposition, which is one of the serious problems, reduces the activity of Ni-based catalysts. Ni/CeO₂/Al ₂O₃ catalysts with different Ce loading were prepared by a wet impregnation method. The performance of catalyst in supercritical water was tested in an autoclave reactor at 673 K, 24.5 MPa. The catalysts before and after reaction were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET specific surface area measurements and thermo-gravimetric analyses (TGA). The effects of Ce loading in catalysts on glucose gasification were studied. The results showed that hydrogen yield and hydrogen selectivity increased sharply with addition of Ni/CeO₂/Al₂O ₃ catalysts. When the Ce loading content was 8.46 wt.%, the maximum H₂ yield and H₂ selectivity were obtained. The carbon deposition and coking will lead to the deactivation of the catalysts. Based on the thermo-gravimetric analyses, the oxidant kinetic data of carbon deposited on the used catalysts with air was obtained. CeO₂ in the Ni/CeO ₂/Al₂O₃ catalyst plays an important role in inhibiting carbon deposition by increasing the Ni dispersion and reacting with deposited carbon.