Defect Chemistry and Chemical Looping Performance of La1−xMxMnO3 (M = Sr, Ca, (x = 0–0.5)) Perovskites

Abstract

La1−xMxMnO3 (M = Sr, Ca, (x = 0–0.5)) materials of the perovskite structure are synthesized by a co-precipitation method. They are subsequently investigated for their performance in a chemical looping process (fuel CH4) using thermogravimetric analysis with simultaneous reaction. The goal of this work is to determine the relation between the defect chemistry of the materials and their behavior in chemical looping processes. A defect model is proposed that provides an explanation of the dependency of the Oxygen Transfer Capacity and of the CO2/CO selectivity on composition. It appeared that the fuel may react with various types of oxygen available within the materials, generated by different mechanisms. The relative amounts of each oxygen type determine the CO2/CO selectivity and depend on the material composition as well as on the partial pressure of oxygen used for regenerating the materials.

Activity and Thermal Aging Stability of La1−xSrxMnO3 (x = 0.0, 0.3, 0.5, 0.7) and Ir/La1−xSrxMnO3 Catalysts for CO Oxidation with Excess O2

“…As the Sr content increases, the peak shifts to larger angles ( Figure 1 b), which means that the unit cell is being contracted. This result is in agreement with the literature and provides a strong indication that charge compensation of the large substitutional Sr ions in La positions (i.e., according to the Kröger–Vink notation [ 48 ], noted as ) does not proceed through the creation of oxygen vacancies ( ) that would have resulted in a unit cell expansion, but through the oxidation of trivalent Mn to tetravalent ( ) [ 29 , 44 ].…”

“…In particular, they decrease with increasing Sr content [ 49 ]; more about the defect chemistry of La 1−x Sr x MnO 3 perovskites can also be found in Ref. [ 44 ]. This may provide an explanation for the gradual shift of homologous peaks to higher temperatures with increasing Sr content.…”

“…Perovskites as catalytic supports that possess these characteristics are potential candidate materials that could impart resistance properties to the sintering of noble or other metal nanoparticles dispersed on their surface. Among others, such materials are promising as oxygen carriers in chemical looping processes that have recently been of intense technological interest in natural gas and biogas processing [ 42 , 43 , 44 ].…”

Nanocatalysis for Environmental Protection, Energy, and Green Chemistry

“…In this context, this Special Issue compiled 11 high-quality contributions [6][7][8][9][10][11][12][13][14][15][16] (10 collected from PSC participants and 1 from others), covering recent research progress in the titled theme. These articles are briefly discussed below.…”

“…Zaspalis and co-workers [6] synthesized La 1−x Sr x MnO 3±δ and La 1−x Ca x MnO 3±δ (x = 0-0.5) perovskites and studied their performance in a chemical looping process using CH 4 as fuel. La 1−x Sr x MnO 3±δ and La 1−x Ca x MnO 3±δ perovskites exhibited identical defect chemistry obtaining both an excess and a deficiency of oxygen; the oxygen excess increased as x and temperature decreased, while the oxygen deficiency increased as x and temperature increased.…”