Abstract
A Sm-deficient Sm0.96MnO3 perovskite was prepared on a gram scale to investigate the influence of the chemical potential of the gas phase on the defect concentration, the oxidation states of the metals and the nature of the oxygen species at the surface. The oxide was treated at 450°C in nitrogen, synthetic air, oxygen, water vapor or CO and investigated for its properties as a catalyst in the oxidative dehydrogenation of propane both before and after treatment. After treatment in water vapor, but especially after treatment with CO, increased selectivity to propene was observed, but only when water vapor was added to the reaction gas. As shown by XRD, SEM, EDX and XRF, the bulk structure of the oxide remained stable under all conditions. In contrast, the surface underwent strong changes. This was shown by AP-XPS and AP-NEXAFS measurements in the presence of the different gas atmospheres at elevated temperatures. The treatment with CO caused a partial reduction of the metals at the surface, leading to changes in the charge of the cations, which was compensated by an increased concentration of oxygen defects. Based on the present experiments, the influence of defects and concentration of electrophilic oxygen species at the catalyst surface on the selectivity in propane oxidation is discussed.
Highlights
The A or B positions in the crystal lattice of ABO3 compounds with perovskite structure can be occupied by almost all metallic elements of the periodic table according to Goldschmidt’s rule (Goldschmidt, 1926)
The optimized combustion method is suitable to achieve batches in gram scale of phase pure Sm0.96MnO3 powders having low bulk density due to the agglomerated crystallites forming caves, hollow spheres, and large networks (Supplementary Figure S3). The in this way prepared Sm0.96MnO3 can be operated as a catalyst in the oxidative dehydrogenation of propane (Koch et al, 2020)
Neither crystallite growth (Table 1) nor lattice expansion, which were observed for similar LaMnO3 perovskites (Miyoshi et al, 2003; Koch et al, 2020) occurred
Summary
The A or B positions in the crystal lattice of ABO3 compounds with perovskite structure can be occupied by almost all metallic elements of the periodic table according to Goldschmidt’s rule (Goldschmidt, 1926). In this way, a wide variety of compounds is obtained. Partial oxidation of the B element may occur if this is possible (Ciambelli et al, 2000; McFarland and Metiu, 2013; Toniolo and Schmal, 2016). For defect formation, only vacancy formation or migration of smaller B elements to vacant A positions, which offer more space, can be considered (Wołcyrz et al, 2003; Ignatans et al, 2019)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
