Influence of doping Al on the reactivity performance of Cu–Fe spinel-type oxygen carrier during chemical-looping combustion

The development of oxygen carriers with good reactivity and anti-sulfur ability is imperative in the chemical-looping combustion (CLC). In this work, the reaction characteristics of Al-doped Cu-Fe spinel (Al-CuFe 2 O 4 ) were investigated based on experiments and density functional theory calculations. The results showed that the reduction stage of Al-CuFe 2 O 4 reaches the maximal reaction rate at 452 °C. The corresponding weight loss is about 9.71%, higher than that of CuFe 2 O 4 (8.78%). It demonstrates that Al-CuFe 2 O 4 shows better reaction activity than CuFe 2 O 4 at lower temperature. Doping Al can increase the reactivity of Cu-Fe spinel-type oxygen carrier towards CO adsorption and reduce the O vacancy formation energies. Moreover, the adsorption behaviors indicate that H 2 S can hardly adsorb on the Al-CuFe 2 O 4 surface in molecular form, and the adsorption energies of HS* and S* decrease while the energy barriers of H 2 S dissociation increase. Doping Al weakens the interaction between sulfur species and Cu-Fe spinel-type oxygen carrier, thus Al-CuFe 2 O 4 also exhibits good anti-sulfur ability. • Experimental and theoretical studies on Al-CuFe 2 O 4 reaction mechanism were offered. • Conversion of Al-CuFe 2 O 4 to Cu·Al-Fe 3 O 4 leads to the largest CO consumption peak. • Al-CuFe 2 O 4 shows better reactivity towards CO than CuFe 2 O 4 at lower temperature. • Al dopant can weaken the interaction between CuFe 2 O 4 and sulfur species.