Intrinsic safety chemical looping-oxidative coupling of methane (CL-OCM) is an attractive method for direct conversion of methane to ethylene, but well-qualified oxygen carrier catalyst still remains challenging. Herein, we report a promising Na 2 WO 4 -doped Mn 2 O 3 -TiO 2 catalyst toward high-efficiency CL-OCM process. The standout Na 2 WO 4 /2Mn1Ti (Mn 2 O 3 /TiO 2 weight ratio of 2/1) catalyst, with good cycling performance, achieves a high space time yield of 27.8 (or 22.9) g C2-C3 kg cat −1 h −1 with 19.5 % (or 15.7 %) CH 4 conversion and 80 % (or 82.7 %) C 2 -C 3 selectivity at 740 (or 720) o C and a low catalyst/CH 4 weight ratio of 13.5. The TiO 2 substantially lowers the CL-OCM reaction temperature, due to the establishment of a low-temperature light-off “Mn 2 O 3 + TiO 2 ↔ MnTiO 3 ” redox cycle with CH 4 /O 2 . The enabling role of Na 2 WO 4 in modulating the reaction of Mn 2 O 3 with CH 4 into OCM instead of combustion is theoretically unveiled, which in nature benefits the *CH 3 transfer and spontaneous desorption to form ∙CH 3 radicals.
In this paper, monodispersed bicomponent microspheres were synthesized through a facile hydrothermal method with MnSO 4 ·H 2 O acting as soft templates, the target product takes a porous spherical morphology and hierarchical core-shell configuration assembled by primary TiO 2 and Mn 2 O 3 nanoparticles . In evaluating as anode, the Mn 2 O 3 /TiO 2 electrodes exhibit extraordinarily higher reversible capacity (around 1000 mAh g −1 at a current density of 100 mA/g up to 180 cycles) than bare TiO 2 , also deliver advanced rate performance and impressive cyclability (250 mAh g −1 even at 2000 mA g −1 after 1000 cycles) for promising lithium storage. The enhanced performance can be traceable to the synergistic effect and tightly coupled interfacial jointing of different components. Specifically, the differential capacity (dQ/dV) analysis has been applied to explore the capacity increasing behavior during the repeated deep cycles, indicating it is essentially related to the electrochemical reconstruction.
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