Industrially Produced Fe- and Mn-Based Perovskites: Effect of Synthesis on Reactivity in Three-Way Catalysis: Part 1

Abstract

La0.6Ca0.2Fe0.8Cu0.2O3, undoped (LF) and Ca, Cu-doped (LCFC), powders, obtained by different industrial procedures, are compared to evaluate reproducibility and scale-up in different industrial synthetic approaches: flame spray pyrolysis (FSP) and coprecipitation (COP). Also the effects of varying composition (doping) and FSP process variability are considered as comparative studies on morphological, crystallographic, redox and compositional properties, and functional activity. A model reaction (CO + NO) and reactions with an automotive exhaust mixture were carried out. Unexpected results on the effectiveness of doping for catalytic activity emerged. Samples with the same compositions proved to be significantly affected by the synthesis, with variability within the same process. The activity of LCFC COP is comparable to the FSP analogue, at stoichiometric conditions, notwithstanding differences highlighted by characterization. In an oxygen-deficient mixture, LCFC-COP yields higher NO reduction and CO oxidation activity than LCFC-FSP. The absence of Ca in the lattice was unexpectedly beneficial. The doping effectiveness must be carefully checked for large-scale production.

Optimizing Citrate Combustion Synthesis of A-Site-Deficient La,Mn-Based Perovskites: Application for Catalytic CH4 Combustion in Stoichiometric Conditions

“…The average perovskite composition until a depth of ~1 µm was explored by energydispersive X-ray analysis (EDX), and the average surface composition (depth of 5-10 nm) was explored by X-ray photoelectron spectroscopy (XPS). Element percentages are reported in Table S1 and Table 3, with and without considering the oxygen content, respectively, which is always excessive at the surface as well as in bulk, as usually occurs for perovskite oxides [28,29]. For all samples, all the expected elements (O, La, Mn, Ni/Cu, if any) were detected by both EDX and XPS, without evidence of a significant amount of impurities.…”

Cr–Fe–Ni–Cu Quaternary Nanostructure as a Substitute for Precious Metals in Automotive Three-Way Catalysts

“…Particularly, Rh is one of the most scarce metals, with TWC accounting for more than 80% of total demand because this metal plays a crucial role in the catalytic NO reduction to N 2 . Several attempts have been made in the past to replace this critical metal with other metals, − but none have been successful for widespread practical use. The high activity is closely associated with dissociative chemisorption of NO as N s + O s (subscript s is the adsorbed species) on the Rh metal surface. , Theoretical investigations suggested that 3d transition metals (M) including Fe, Co, and Ni also facilitate the cleavage of the N–O bond and the formation of M–N s and M–O s bonds. , However, the as-formed M–N s and M–O s bonds are strong enough to monopolize the surface and hinder catalytic cycles.…”