Search

La-deficient La1-xCexMnO3 mixed oxides, obtained by selective dissolution in 1 ​M nitric acid, were employed in methane complete oxidation. The majority of the La cations in these perovskites were removed, resulting in increased specific surface areas, better reducibility and greater activity. Incorporation of a small amount of Ce stabilized the structure and a perovskite phase persisted in La-deficient La1-xCexMnO3 mixed oxides after 12 ​h of acid dissolution. La0.95Ce0.05MnO3 after the acid treatment exhibited satisfactory catalytic activity, with T50 and T90 values of 365 and 459 ​°C, respectively, which was even comparable to that previously reported 1% Pd/Al2O3 catalysts. And it showed excellent long-term activity even in the presence of CO2 and H2O.

We develop a host–guest strategy to construct cobalt-doped MnO2 nanofibers with dual reactive sites, which exhibit high activity for propane deep oxidation. After the incorporation of cobalt (the actual molar ratio of Co/Mn up to 0.15), no distinct changes of crystal structure and morphology of MnO2 nanofibers were observed, as evidenced by X-ray diffraction and transmission electron microscopy. The optimized MnCo0.2 nanofibers possessed the advantages of Mn and Co and exhibited the propane conversion of 50% (T50) and 90% (T90) at 205 and 223 °C, respectively. The Co-related species is more responsible for reducing the light-off temperature (T50), whereas the Mn-related species helps more to decrease complete oxidation temperature (T90). Furthermore, the in situ diffuse reflectance infrared Fourier transform spectroscopy results revealed the roles of Co-related species and Mn-related species during propane adsorption and oxidation. The finding demonstrates the win-win effect of two active oxides and provi...

SmMn2O5 nanosheets with high specific surface area and (0 0 1) facet orientation were synthesized by a facile and efficient microwave-assisted hydrothermal strategy. The BET surface area of the leaf-like mullite (SMO-MW) reached 122 m2/g, which was about 4 times to that of counterpart (SMO-HT) prepared by conventional hydrothermal method. The relative intensity ratio of (0 0 1) facet to (2 1 1) in SMO-MW was 0.74 ~ 0.87, which was higher than 0.23 ~ 0.28 in SMO-HT. Compared with SMO-HT, the Mnx+ reduction temperature of SMO-MW declined significantly (ΔT = 63 °C for Mn4+→Mn3+, and ΔT = 76 °C for Mn3+→Mn2+) in the temperature-programmed reduction with H2. Moreover, the weakened Mn-O bonds, higher concentration of Mn4+ ions, and more chemisorbed oxygen were obtained via microwave irradiation. The pre-exponential factors of SMO-MW reached about 9 times comparing with those of SMO-HT, revealing the generation of more active sites. Impressively, the MW-500 calcined at 500 °C exhibited high catalytic performance with a 50% C3H8 conversion at 243 °C, which was competitive with 1 wt% Pd/Al2O3 catalyst. Meanwhile, it kept above 90% propane conversion during 80 h durability test at 285 °C. This study was expected to promote a new strategy on developing efficient mixed oxides catalysts for environmental and energy applications.

Porous ceria nanorods modified with Fe or Co were prepared via a hydrothermal method. The structural properties, catalytic activities for the total oxidation of propane, and catalytic mechanisms of these materials were systematically investigated by X-ray diffraction, Raman spectroscopy, N2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, catalytic activity measurements and in situ Fourier transform infrared spectroscopy. Co-modified ceria exhibited the best catalytic activity during propane oxidation as well as enhanced reducibility due to the synergistic interactions between the Co and the CeO2 support. Variations in the activating ability and reducibility of the catalysts resulted in the formation of distinctive intermediates during the catalytic process, and this explained the observed differences in catalytic performance.