Xiuyun Wang

Insights into the high performance of Mn-Co oxides derived from metal-organic frameworks for total toluene oxidation

Mn-Co mixed metal oxide is considered as efficient catalyst for the total oxidation of volatile organic compounds. In this study, nanocube-like metal-organic frameworks (Mn3[Co(CN)6]2·nH2O) are adopted as the precursor to generate Mn-Co oxides with different Mn/Co molar ratios, which affect little on phase structure and textural properties. The obtained MOF-Mn1Co1 with uniform metal dispersion is rich in high valence of surface Mn4+ and Co3+ species, leading to high low-temperature catalytic activity of total toluene oxidation. The results of toluene-TPD followed by TPO and toluene-TPSR match well with the catalytic performances of MOF-Mn1Co1, MOF-Mn1Co2, and MOF-Mn2Co1, and in situ FITR proves that the benzoate route exists over MOF-Mn1Co1. It is found that a moderate ratio of Mn/Co (1:1) favors good low-temperature reducibility and high Oads/Olatt, resulting in superior oxidation performance. However, the stability in the existence of water for MOF-Mn1Co1 is not satisfied, which should be overcome in the future.

Thermally stable lanthanum-doped mesoporous alumina as a stable support for palladium in catalytic oxidation of C3H8

Abstract High thermally stable mesoporous alumina doped with lanthanum was synthesized using inorganic nitrates as precursors and employing pluronic P123 (P123, (EO20PO70EO20, EO=ethylene oxide, PO=propylene oxide)) as a structure-directing agent. After calcination at 400 °C, the resultant lanthanum doped alumina exhibited a γ-Al2O3 phase, which was the same as pure alumina. After the thermal treatment up to 1200 °C, La-doped Al2O3 generated only one phase of θ-Al2O3 rather than two mixed phase of θ-Al2O3 and α-Al2O3 and the surface area could still maintain 101 m2/g with a keeping pore volume of 0.66 cm3/g. The excellent thermal stability was explained by the titration of strong Lewis acid sites of γ-Al2O3 with the assistance of highly dispersed lanthanum species covering on alumina. Furthermore, the lanthanum modified mesoporous alumina was preliminarily employed as a stable support for Pd in the catalytic oxidation of C3H8.

Synthesis of Co–Mn oxides with double-shelled nanocages for low-temperature toluene combustion

In this paper, we report a template-engaged strategy for the synthesis of Co–Mn oxides with double-shell box-in-box hollow nanocage (BHNC) structures. The inner shell of the box is made of Co3O4, while the outer shell is made of Co–Mn oxides. The composition of the outer shell was tuned by changing the Mn/Co molar ratio. This facile method can be used to construct box-in-box hollow structures of other transition metal oxides such as those of Co–Ni, Co–Cu and Co–Fe. These Co–Mn oxides with BHNCs exhibit toluene conversions over 90% at 250 °C, which is much higher than those of Co3O4 nanocages (NCs) and the traditional Co3O4-CP synthesized by co-precipitation method at the same temperature. Moreover, the former is superior to the latter in terms of resistance towards H2O and CO2. The superior catalytic performance of Co1Mn1 BHNCs is attributed to the high mobility of lattice oxygen, low toluene desorption temperature and active Co3+ sites originated from the oxidation of Co2+ by Mn3+.