Abstract:
La
2O
3 catalysts with different grain sizes were prepared under hydrothermal condition. The structure activity relationship of La
2O
3 catalysts with different grain sizes were investigated by using
in-situ XRD, Raman, FT-IR and H
2-TPR, O
2-TPD. The results showed that the La−O bond of the La
2O
3 catalyst showed a significant elongation with increasing temperature, which affected its adsorption and dynamic storage of O
2. When increasing the grain size up to 57.4 nm, the oxygen storage capacity of the La
2O
3 catalyst started to decrease, accompanied by the enrichment of surface oxygen species, especially superoxide species, on the catalyst surface, which led to the over-oxidation of CH
4 and products and reduced the C
2 + hydrocarbons selectivity. The L-La
2O
3 catalyst with a grain size of 52.3 nm had a suitable content of surface oxygen species and a high oxygen storage capacity at 750 ℃. It exhibited the best C
2 + hydrocarbon selectivity up to a CH
4/O
2 of 3 and a vacancy rate of 1.6 × 10
5 mL/(g·h).