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KIT-6 mesoporous silica aged at 40, 100, and 150 °C were used as hard templates to prepare different mesoporous MnO2catalysts, marked as Mn-40, Mn-100, and Mn-150, respectively. The catalytic activities of these catalysts and the effect of pore sizes on ethanol catalytic oxidation were investigated. Mn-40, Mn-100, and Mn-150 have triple, double, and single pore systems, respectively. On decreasing the aging temperature of KIT-6, the pore sizes of KIT-6 decrease and that of mesoporous MnO2catalysts increase. The pore sizes and catalytic activities increase in the order: Mn-40 >Mn-100 > Mn-150. Mn-40 catalyst has a higher TOF (0.11 s−1at 120 °C) and the best catalytic activity for ethanol oxidation because of a bigger pore size with three pore systems with maximum distribution at 1.9, 3.4, and 6.6 nm, decrease in symmetry and degree of order, more surface lattice oxygen species, oxygen vacancies resulting from more Mn3+ions, and better low-temperature reducibility.

Three-dimensional (3D) ordered mesoporous MnO2was prepared using KIT-6 mesoporous molecular sieves as a hard template. The material was used for catalytic oxidation of HCHO. The material has high surface areas and the mesoporous characteristics of the template, with cubic symmetry (ia3d). It consists of a β-MnO2crystalline phase corresponding to pyrolusite, with a rutile structure. Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the 3D-MnO2catalyst has a large number of exposed Mn4+ions on the (110) crystal plane surfaces, with a lattice spacing of 0.311 nm; this enhances oxidation of HCHO. Complete conversion of HCHO to CO2and H2O was achieved at 130 °C on 3D-MnO2; the same conversions on α-MnO2and β-MnO2nanorods were obtained at 140 and 180 °C, respectively, under the same conditions. The specific mesoporous structure, high specific surface area, and large number of surface Mn4+ions are responsible for the catalytic activity of 3D-MnO2in HCHO oxidation.

A series of Ag nanoparticles (NPs) supported on three-dimensionally ordered macroporous (3DOM) La0.6Sr0.4MnO3(yAg/3DOM La0.6Sr0.4MnO3; y= 0, 1.57, 3.63, and 5.71 wt %) were successfully prepared with high surface areas (38.2–42.7 m2/g) by a facile novel reduction method using poly methacrylate colloidal crystal as template in a dimethoxytetraethylene glycol (DMOTEG) solution. Physicochemical properties of these materials were characterized by means of numerous techniques, and their catalytic activities were evaluated for the combustion of methane. It is shown that the yAg/3DOM La0.6Sr0.4MnO3materials possessed unique nanovoid-like 3DOM architectures, and the Ag NPs were well dispersed on the inner walls of macropores. Among the La1–xSrxMnO3(x= 0.2, 0.4, 0.6, 0.8) and yAg/3DOM La0.6Sr0.4MnO3(y= 0, 1.57, 3.63, and 5.71 wt %) samples, 3.63 wt % Ag/3DOM La0.6Sr0.4MnO3performed the best, giving T10%, T50%, and T90%(temperatures corresponding to methane conversion =10, 50, and 90%) of 361, 454, and 524 °C, respectively, and the highest turnover frequency (TOFAg) value of 1.86 × 10–5(mol/molAgs) at 300 °C. The apparent activation energies (39.1–37.5 kJ/mol) of the yAg/3DOM La0.6Sr0.4MnO3samples were much lower than that (91.4 kJ/mol) of the bulk La0.6Sr0.4MnO3sample. The effects of water vapor and sulfur dioxide on the catalytic activity of the 3.63 wt % Ag/3DOM La0.6Sr0.4MnO3sample were also examined. It is concluded that its super catalytic activity was associated with its high oxygen adspecies concentration, good low-temperature reducibility, large surface area, and strong interaction between Ag and La0.6Sr0.4MnO3as well as the unique nanovoid-walled 3DOM structure.