Perovskite-structured materials, owing to their chemical-physical properties and tuneable composition, have extended their range of applications to chemical looping processes, in which lattice oxygen provides the oxygen needed for chemical reactions omitting the use of co-fed gaseous oxidants.To optimise their oxygen donating behaviour to the specific application a fundamental understanding of the reduction/oxidation characteristics of perovskite structured oxides and their manipulation through the introduction of dopants is key. In this study, we investigate the structural and oxygen desorption/ sorption properties of Sr 1Àx Ca x FeO 3Àd and SrFe 1Àx Co x O 3Àd (0 r x r 1) to guide the design of more effective oxygen carriers for chemical looping applications at low temperatures (i.e. 400-600 1C).Ca A-or Co B-site substituted SrFeO 3Àd show an increased reducibility, resulting in a higher oxygen capacity at T r 600 1C when compared to the unsubstituted sample. The quantitative assessment of the thermodynamic properties (partial molar enthalpy and entropy of vacancy formation) confirms a reduced enthalpy of vacancy formation upon substitution in this temperature range (i.e. 400-600 1C). Among the examined samples, Sr 0.8 Ca 0.2 FeO 3Àd exhibited the highest oxygen storage capacity (2.15 wt%) at 500 1C, complemented by excellent redox and structural stability over 100 cycles. The thermodynamic assessment, supported by in situ XRD measurements, revealed that the oxygen release occurs with a phase transition perovskite-brownmillerite below 770 1C, while the perovskite structure remains stable above 770 1C.

The oxidative dehydrogenation of ethane (ODH) to produce ethylene offers advantages compared to the industry standard steam cracking, but its industrial application is hindered by costly air separation units needed to supply oxygen. A chemical‐looping‐based oxidative dehydrogenation (CL‐ODH) scheme is presented, in which oxygen carriers supply gaseous oxygen in situ, which then reacts with ethane in the presence of a catalyst at a comparatively low temperature (500 °C). A common challenge of chemical looping processes beyond combustion is to suppress the overoxidation of hydrocarbons to COx to enable high product yields. It is demonstrated that the overoxidation of ethane can be eliminated completely through structural engineering of the perovskite oxygen carrier involving alkali‐metal‐based carbonate coatings, while maintaining the materials’ ability to generate oxygen. Through CL‐ODH, higher ethylene selectivity (≈91%) and yields (≈39%) are achieved compared to the conventional ODH scheme without oxygen carrier and cofeeding air/ethane. 18O‐labeling experiments demonstrate that the carbonate layer functions like a diffusion barrier for ethane while being permeable for oxygen. Both the CL‐ODH scheme and the material design strategy can be extended to other catalytic oxidation or dehydrogenation reactions requiring oxygen at different temperatures, offering enormous potential to intensify such processes.

The oxidative dehydrogenation of propane (ODP) proceeds catalytically on a gas-solid interface (heterogeneous reaction) and/or in the gas phase (homogeneous reaction) via a radical chain process. ODP may therefore combine interrelated contributions from the heterogeneous dehydrogenation and gasphase reactions, which can be initiated by a catalyst. This study demonstrates that relatively high propene and ethene selectivities (ca. 80 % and 10 %) and propane conversions (viz., 10 % at 500 °C) can be achieved with an empty quartz reactor, which is comparable to the performances of state-of-the-art ODP catalysts (boron-based or supported VO x ). Optimization of the post-catalytic volume of a h-BN catalyst bed tested at 490 °C allows to increase the conversion of propane from 9 % to 15 % at a propene selectivity of 77 %, highlighting this parameter as an important variable for improving catalytic ODP performances.

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Brownmillerite-structured Ca2MnAlO5+δ has demonstrated excellent oxygen storage capacity that can be used for chemical looping air separation (CLAS), a potentially efficient approach to produce high-purity oxygen from air. To effectively utilize this material as an oxygen sorbent in CLAS, it is necessary to comprehensively understand its thermodynamic properties and the structure–performance relationships in the operating range of interest. In this work, the oxygen nonstoichiometry (δ) of Ca2MnAlO5+δ was systematically measured by thermogravimetric analysis (TGA) in the temperature ranging from 440 to 660 °C and under an oxygen partial pressure ranging from 0.01 to 0.8 atm. The partial molar enthalpy and entropy for the oxygen-releasing reaction were calculated using the van’t Hoff equation with an average value of 146.5 ± 4.7 kJ/mol O2 and 162.7 ± 5.1 J/K mol O2, respectively. The experimentally measured nonstoichiometry (δ) was well fitted by a point defect model applied in two regions divided by the predicted equilibrium P–T curve. The equilibrium constants for appropriate defect reactions were also determined. The thermochemical parameters, molar enthalpy and entropy for the main reaction, obtained from the defect model were 136.9 kJ/mol O2 and 225.3 J/K mol O2, respectively, showing reasonable agreement with the aforementioned values. The applicability of the defect model was also verified at a higher oxygen partial-pressure environment of up to 4 atm and exhibited reasonable prediction of the trend. The experimental studies on oxygen nonstoichiometry combined with the defect modeling provide useful insights into oxygen sorbents’ redox performances and helpful information for the design and optimization of oxygen sorbents in CLAS.