Methane conversion to syngas by chemical looping on La0.8Sr0.2FexCo1-xO3 (x = 0, 0.25, 0.50, 0.75) perovskites with CO2 co-feeding

Abstract

Partial oxidation of methane (POM) by chemical looping with CO2 co-feeding on La0.8Sr0.2FeO3 (LSF) perovskite catalyst yielded a highly selective operation and enabled to extend the duration of reduction cycle. In this work, the conversion of methane to syngas was studied on La0.8Sr0.2Fe(x)Co(1-x)O3 (x = 0, 0.25, 0.5, 0.75) perovskites in chemical-looping mode, co-feeding CO2 and methane. The reaction was conducted at 850 °C, 15 min reduction (10% methane in N2, 0–3% CO2), and 10 min oxidation (10% O2 in N2) cycles. The perovskites activity decreased with increasing Co content, in the absence of CO2, due to intensified coke deposition on the catalyst. Addition of CO2 during the reduction step (1–3%) reduced coke accumulation. A run conducted on La0.8Sr0.2CoO3 (LSC) with continuous feeding of CO2 and periodical (on–off) methane feeding indicated that CO2 reacts with the accumulated coke in reverse-Boudouard reaction, increasing CO selectivity without affecting the methane conversion. XRD analysis of reduced Co-containing perovskites indicates a decreasing perovskite content. Metallic Co and La2O3 phases increased as the Co content in the fresh perovskite increased, increasing coke deposition. As the Co content increased, the process shifts from POM with oxygen replenishment (LSF) to cracking followed by reverse-Boudouard reaction (LSC).