Behavior of nickel catalysts in supercritical water gasification of glucose: Influence of support

The catalytic performance of Ni-based supercritical water gasification (SCWG) catalysts may be influenced strongly by the nature of support. In this paper, Ni catalysts with the different supports (CeO2/Al2O3, La2O3/Al2O3, MgO/Al2O3, ZrO2/Al2O3) were prepared by two-step impregnation method. The fresh and used catalysts were characterized by X-ray diffraction patterns (XRD), scanning electron microscopy with an Energy Dispersive X-ray (SEM-EDX), Brunauer-Emmett-Teller (BET) specific surface area measurements, X-ray photoelectron spectroscopy (XPS) and Thermo-gravimetric analyses (TGA). The catalyst performance testing was conducted by SCWG of glucose at 673 K and 23.5 MPa with an autoclave reactor, to evaluate the influence of support on the hydrogen production. The results showed that H2 yield for different supports decreased in order: CeO2/Al2O3 > La2O3/Al2O3 > MgO/Al2O3 > Al2O3 > ZrO2/Al2O3, and H2 selectivity decreased in order: CeO2/Al2O3 > La2O3/Al2O3 > ZrO2/Al2O3 > Al2O3 > MgO/Al2O3. Ni catalysts were deactivated in SCWG reaction because of sintering and coke deposition. Compared with other supports, CeO2 can be used as the promoter of carbon removal from catalyst surfaces.