Controlled preparation and high catalytic performance of three-dimensionally ordered macroporous LaMnO3 with nanovoid skeletons for the combustion of toluene

Three-dimensionally ordered macroporous (3DOM) single-phase rhombohedral perovskite-type oxide LaMnO3 materials with nanovoid skeletons were prepared using the poly(methyl methacrylate)-templating methods with the assistance of surfactant (poly(ethylene glycol) (PEG) or triblock copolymer (Pluronic P123)). The nature of surfactant influenced the pore structure of the LaMnO3 sample. The use of PEG400 alone led to a 3DOM-structured LaMnO3 without nanovoid skeletons; with the addition of PEG400 and P123, however, one could prepare LaMnO3 samples with high-quality 3DOM structures, nanovoid skeletons, and high surface areas (37–39 m2/g). Under the conditions of toluene concentration = 1000 ppm, toluene/O2 molar ratio = 1:400, and space velocity = 20,000 mL/(g h), the porous LaMnO3 samples were superior to the bulk counterpart in catalytic performance, with the nanovoid-containing 3DOM-structured LaMnO3 catalyst performing the best (the temperatures for toluene conversions of 50% and 90% were 222–232 and 243–253 °C, respectively). The apparent activation energies (57–62 kJ/mol) over the 3DOM-structured LaMnO3 catalysts were much lower than that (97 kJ/mol) over the bulk LaMnO3 catalyst. We believe that the excellent performance of the 3D macroporous LaMnO3 materials in catalyzing the combustion of toluene might be due to factors such as large surface area, high oxygen adspecies concentration, good low-temperature reducibility, and unique nanovoid-containing 3DOM structure of the materials.

Through the surfactant-assisted PMMA-templating method, we prepared three-dimensionally ordered macroporous (3DOM) LaMnO3 catalysts with nanovoid skeletons. It is found that the excellent performance of the catalysts in toluene combustion can be related to the high surface area and oxygen adspecies concentration as well as low-temperature reducibility of 3DOM LaMnO3.Figure optionsDownload high-quality image (259 K)Download as PowerPoint slideHighlights
► Rhombohedral 3DOM LaMnO3 is prepared by surfactant-assisted PMMA-templating method.
► Surfactant addition is critical in the formation of 3DOM structure with nanovoid walls.
► 3DOM LaMnO3 is high in surface area and Oads concentration and good in reducibility.
► 3DOM LaMnO3 performs excellently in the combustion of toluene.
► Catalytic activity is governed by surface area, Oads, and reducibility of 3DOM LaMnO3.