Stability and activity maintenance of sol-gel Ni-MxOy (M = Ti, Zr, Ta) catalysts during continuous gasification of glycerol in supercritical water

The long-term stability of activities and physicochemical properties for nickel nanoparticles supported on TiO2, ZrO(2 )and Ta2O5 prepared by sol-gel methods, was evaluated for continuous supercritical water gasification (SCWG) of 3 wt.% glycerol at 425 degrees C and 25.2 MPa. The Ni/TiO2 catalyst bed gradually deactivated while the Ni/ZrO2 and Ni/Ta2O5 catalyst beds showed persistent and high carbon gasification efficiency for 80 h operation. Characterization results verified that property stabilization of the sol-gel Ni/ZrO(2 )and Ni/Ta2O5 catalysts occurred in the long-term SCWG flow, indicating a catalyst in-situ activation effect that enhanced the activity and coking resistance of the as-prepared sol-gel catalysts for continuous SCWG. Results also indicate that sintering of Ni with the supports to form new phases and metal leaching of the catalyst materials in the SCW flow may be key deactivation factors of the catalyst beds.