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

Abstract

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/Al2O3 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 673K, 24.5MPa. 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/Al2O3 catalysts. When the Ce loading content was 8.46wt.%, 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/CeO2/Al2O3 catalyst plays an important role in inhibiting carbon deposition by increasing the Ni dispersion and reacting with deposited carbon.