Progress in oxygen carrier development of methane-based chemical-looping reforming: A review

• Partial oxidation of CH4 (POM) possesses advantages over steam reforming of CH4.
• Applying chemical-looping combustion concept can resolve the drawbacks of POM.
• The appropriate selection of oxygen carrier becomes a critical issue for POM.
• The use of steam or CO2 to replace air remains to be a great challenge.
• Perovskites using lattice oxygen for syngas production showed prominent results.

This work comprehensively reviews the recent advances for chemical-looping reforming of CH4 (CLR) technology, which breaks down the traditional CH4 reforming process (including steam and dry reforming) into two separate half-steps, namely CH4 oxidation and replenishment of oxygen carrier (OC) with appropriate oxidizing agents. In order to steer the conversion of CH4 toward partial oxidation (POM) for synthesis gas (H2 + CO) production rather than total oxidation for producing CO2 and H2O, the appropriate selection of OC becomes a critical issue. Moreover, instead of the commonly used air to re-oxidize the oxygen-depleted OC after reaction with CH4, steam and CO2 have been proposed as two alternatives, opening up the opportunities to produce extra H2 and CO. However, owing to much weaker oxidization ability of steam and CO2 than air, the low oxidation degree and slow oxidation rate seem to remain as challenges. Furthermore, the resistance of OC to attrition, agglomeration and carbon deposition is also of great importance. In these regards, the latest major milestones are compiled.

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