Enhanced performance of pyrite cinder oxygen carrier modified by CuO for chemical looping combustion

Due to the abundance of active components and low cost, pyrite cinder has great potential as an oxygen carrier in the process of chemical looping combustion (CLC). In order to improve the fuel combustion reactivity, we modified pyrite cinder with copper oxide (CuO). The addition of copper oxide could effectively increase the pore volume and oxygen vacancy concentration of pyrite cinder. The modified pyrite cinder with 20 wt% CuO possessed the highest pore volume (0.3 cm³/g) and oxygen vacancy concentration (55.61%). During the long-term redox cycles, the modified pyrite cinder samples showed higher fuel combustion reactivity than the undoped sample. The results of characterization indicated that the crystalline phases of CuO and CuFe₂O₄ were formed in the CuO-modified pyrite cinder samples. The active components (Fe₂O₃, CuFe₂O₄ and CuO) in the modified pyrite cinder samples were reduced to Fe₃O₄, FeO, CuFeO₂ and Cu during the reduction half cycle. The modified pyrite cinder with 20 wt% CuO possessed the highest CH₄ conversion (nearly 100%) and CO₂ selectivity (nearly 100%) in multiple redox testing. The CH₄ conversion of undoped pyrite cinder was only about 60%. When the content of CuO reached 30 wt%, surface sintering occurred for the modified pyrite cinder, resulting in the decrease of CH₄ conversion and surface area. After continuous redox cycles, the CuO-modified pyrite cinder samples could maintain the original crystal structure.