Effect of Composition on the Redox Performance of Strontium Ferrite Nanocomposite

Chemical looping dry reforming of methane is an attractive approach to use carbon dioxide and methane, the two most abundant greenhouse gases. For this scheme, the redox material (or oxygen carrier) plays a key role. It is of great significance to improve the redox performance of strontium ferrite (SrFeO3-δ, SFO), a low-cost and easily tunable perovskite-typed oxygen carrier. Here, we present the effect of composition on the redox performance of SrFeO3-δ confined in the matrix of calcium oxide (CaO). The nanocomposites were prepared by the Pechini method, and the redox performance was evaluated in a fixed bed tubular quartz reactor at 980 °C and atmospheric pressure. In the characteristic reduction time, 10 wt % SrFeO3-δ-CaO nanocomposite exhibits the highest methane conversion (88%) and syngas production rate (1.8 mol kgSFO-1 min-1), but 80 wt % SrFeO3-δ-CaO nanocomposite has the highest syngas productivity (27.3 mol kgSFO-1); coke selectivity over the nanocomposite with a perovskite mass fraction of 0.1 (22%) is much higher than that over the others. Partial replacement of Ca ions by Sr ions in the CaO lattice occurs, but substitution of Sr ions by Ca ions in SrFeO3-δ, if it occurs, is insignificant. The predominant role of CaO is to facilitate SFO reduction by methane and improve its recyclability. Besides that, calcium oxide provides oxygen species that participate in methane partial oxidation, but this contribution is relatively small. In addition, the cracking activity of CaO is significantly suppressed after compositing. These findings could inspire the rational design of effective perovskite nanocomposites for chemical looping reforming.