A Cu–Fe oxygen carrier (OC) with oxygen uncoupling capability is proposed to be applied in chemical-looping gasification with oxygen uncoupling (CLGOU) technology to increase the gasification rate. Density functional theory analysis shows that a chemical reaction occurs after Cu4O4 cluster adsorption onto α - Fe2O3 (001) surface. Extension of bond length and transfer of charge indicate the composite oxide has been activated. An optimal molar ratio of 2:1 of CuO to Fe2O3 is determined for the preparation the OC and the oxygen transport capacity is determined at 3.65 wt% with a starting oxygen uncoupling temperature is 749.5 °C. The composite OC exhibits good low-temperature oxygen uncoupling characteristics. This OC exhibits stable behaviour and satisfactory oxygen recyclability over 15 consecutive redox cycles at 900 °C / 700 °C oxygen uncoupling and absorbing temperatures. The high stability is corresponding to the calculation result (high adsorption energy of CuO onto Fe2O3). And oxygen uncoupling rates are much higher than the lower limit (0.4 wt%/min) for cracking. The chemical phases and surface micromorphology all retain stable after cycles. Using combined Coats-Redfern and Malek method, the oxygen uncoupling kinetic model of Cu–Fe OC is determined as a shrinking core model (m = 3).
Bibliographical noteFunding Information:
This research was financially supported by National Natural Science Foundation of China ( 51604078 ); Fundamental Research Funds for the Central Universities ( N182504011 ).
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- Chemical-looping gasification
- Composite oxygen carrier
- Oxygen uncoupling