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 673K and 23.5MPa 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.