posted on 2017-04-11, 00:00authored bySai Chen, Liang Zeng, Hao Tian, Xinyu Li, Jinlong Gong
Partially oxidizing
methane into syngas via a two-step chemical
looping scheme is a promising option for methane transformation. Providing
the optimum lattice oxygen to selectively produce syngas represents
the major challenge for the development of oxygen carrier materials
in chemical looping processes. This paper describes the design of
WO3-based oxygen carriers as the primary source of lattice
oxygen with high melting points and attractive syngas selectivity.
To further enhance the lattice oxygen availability and methane conversion
capacity, NiO nanoclusters are introduced, considering the doping
effect on chemical bonding disruption in both bulk and surface regions.
For Ni0.5WOx/Al2O3, the nickel cations incorporated into the bulk of WO3 can strongly weaken the tungsten–oxygen bond strength
and increase the availability of lattice oxygen. The surface-grafted
nickel species can effectively activate methane molecules and catalyze
the partial oxidation reaction. Total methane conversion and syngas
yield can be substantially increased by about 2.7-fold in comparison
with unmodified WO3/Al2O3. This work
demonstrates that the bulk and surface modifications are feasible
to tailor the active lattice oxygen of oxygen-carrying materials in
chemical looping processes.