Reduction behavior and kinetics of Ce7O12 in reducing atmospheres: Insights from the comparison of H2 and CO

Abstract

Enhancing separation of iron and rare earths by staged roasting was proposed, with a pilot-scale experiment conducted. However, the reaction of bastnaesite pyrolysis product (Ce₇O₁₂) in reduction roasting stage is rarely reported. This study explored reduction of Ce₇O₁₂ under H₂ and CO using thermogravimetry, and analyzed the non-isothermal reaction kinetics. The results indicated that the unique Ce/O induced by lattice defects enabled Ce₇O₁₂ to react with reducing gases. The weight loss during H₂ and CO reduction was 2.8 % and 2.5 %, with the detection of H₂O and CO₂. The optimal reaction model for H₂ reduction was shrinking core model (m = 1/2), while that for CO reduction was chemical reaction model (n = 3/2). During the reduction process, the CO reduction started at a lower temperature than the H₂ reduction, and the reaction was more intense. After reduction, the XRD peaks shifted to lower angles, the lattice spacing increased, and the Ce oxidation degree decreased, implying the transition of Ce⁴⁺ to Ce³⁺. The reduction products exhibited a decrease in specific surface area and total pore volume, while the pore diameter increased.