Preparation of single-phase three-component alkaline earth oxide of (BaSrMg)O: a high capacity and thermally stable chemisorbent for oxygen separation

Abstract

This study presents a preparation method for a single-phase three-component alkaline earth oxide of (BaSrMg)O that is a high capacity and thermally stable chemisorbent for oxygen separation based on the redox reaction cycle of BaO + 1/2O₂ ↔ BaO₂. First, single-phase (BaSr)CO₃ is co-precipitated based on the reaction of Ba²⁺ and Sr²⁺ with CO₃²⁻ in a solution, and then transformed to single-phase (BaSrMg)CO₃ with the addition of an Mg²⁺ solution. When varying the reaction conditions, such as the reactant concentrations of Ba²⁺, Sr²⁺, Mg²⁺, and CO₃²⁻ and the reaction temperature, (Ba_0.52Sr_0.06Mg_0.42)CO₃ crystals are identified as the most stable phase. The single-phase (BaSrMg)CO₃ is then converted into single-phase (BaSrMg)O by thermal decomposition under an H₂ atmosphere at 750 °C. According to a TGA analysis, the chemisorption and desorption of oxygen in (BaSrMg)O are very fast at t₈₀ = 3.9 min and t₈₀ = 14 min, respectively. In addition, the chemisorption capacity of (BaSrMg)O is higher at 2.02 mmol g⁻¹ at 700 °C when compared with the chemisorption capacity of BaO/MgO at 1.75 mmol g⁻¹ (Jin et al., Ind. Eng. Chem. Res., 2005, 44, 2942). (BaSrMg)O is also thermally stable due to the inclusion of Mg. Thus, the chemisorption capacity of (BaSrMg)O is unchanged, even over 10 redox reaction cycles. Additionally, the transient oxygen pressure required for the redox reaction of BaO–BaO₂ is shifted from 76 mmHg to 148 mmHg due to the inclusion of Sr in (BaSrMg)O. Consequently, the three component alkaline earth oxide (BaSrMg)O can be a highly effective sorbent for industrial applications to oxygen separation in terms of the process design and operation.