Synthesis, structure and catalytic activity features of alkali-substituted nanostructured lanthanum manganites

Perovskite nanomaterials based on LaMnO_3+δ doped with alkali metals are effective and inexpensive catalysts for the oxidation of soot, a byproduct of the incomplete combustion of fuels or organic compounds. Present study examines the synthesis characteristics and properties of the La_0.9A_0.1MnO_3+δ (A =Li, Na, K, Rb, Cs) catalysts for soot oxidation with atmospheric oxygen as a function of the crystallographic radii and electronegativity of the alkali dopants in the perovskite A-site. Correlations are established between the combustion temperature of the initial precursors, the intensity of the electrical charges generated in the precursors during combustion, the specific surface area of the resulting complex oxides, and the activation energy of the catalytic oxidation of carbon black. The relationship between the above parameters and the ionic radius and electronegativity of the dopants is also considered. It is shown that in the presence of the LaMnO_3+δ-based catalysts: 1) the concentration of released carbon(II) oxide is reduced by '50 times, 2) soot is more completely oxidized to CO₂, and 3) the degree of soot conversion increases when the catalyst is applied to the nickel foam support.