Nanorod-like phosphorus-doped ordered mesoporous γ-alumina (OMA), which has abundant ordered pore channels in the nanorods, was rapidly synthesized through a modified sol–gel strategy without use of any mineral acids. Highly dispersed Pd-based catalysts were synthesized by taking as-obtained phosphorus-doped OMA materials as carriers for methane combustion. The crystallization temperature of γ-Al2O3 was increased by phosphorus doping. The surface acidity properties of γ-Al2O3 were modified upon phosphorus incorporation, which had a significant effect on catalyst activities, and this influence was much more conspicuous for the supports calcined at high temperature. The incorporation of phosphorus adjusted the distribution of palladium active species and the reducibility of catalysts, synergistically affecting the low-temperature catalytic performance. Pd/6P-OMA catalyst demonstrated enhanced low-temperature catalytic properties and stability in the 13-cycle stability and long-term stability tests. During the reaction cycles, the total CH4 conversion temperature for Pd/6P-OMA catalyst was as low as 345 °C, which could be reduced to 321 °C via hydrogen reduction treatment. In comparison with the catalyst without dopant, the Pd/6P-OMA catalyst also exhibited higher hydrothermal stability in the presence of excess water vapor in the feed.

In this paper, we propose a facile and efficient strategy for synthesizing mesoporous BaSnO3 with a surface area as large as 67 m(2)/g using a peroxo-precursor decomposition procedure. As far as we know, this is the largest surface area reported in literature for BaSnO3 materials and may have a potential to greatly promote the technological applications of this kind of functional material in the area of chemical sensors, NOx storage, and dye-sensitized solar cells. The structure evolution of the mesoporous BaSnO3 from the precursor was followed using a series of techniques. Infrared analysis indicates large amount of protons and peroxo ligands are contained in the peroxo-precursor. Although the crystal structure of the precursor appears cubic according to the analysis of X-ray diffraction data, Raman and Mössbauer spectroscopy results show that the Sn atom is offset from the center of [SnO6] octahedron. After calcination at different temperatures, the precursor gradually transforms into BaSnO3 by release of water and oxygen, and the distortion degree of [SnO6] octahedral decreases. However, a number of oxygen vacancies are generated in the calcined samples, which are further confirmed by the physical property measurement system, and they would lower the local symmetry to some content. The concentration of the oxygen vacancies reduces simultaneously as the calcination temperature increases, and their contributions to the total heat capacity of the sample are calculated based on theoretical analysis of heat capacity data in the temperature region below 10 K.

Chemical looping partial oxidation of CH4 is a promising method for producing syngas with a suitable H2/CO ratio and avoiding the risk of explosion and use of an expensive air separation plant. However, regeneration of reduced oxygen carriers (OCs) by O2 usually leads to the enrichment of surface electrophilic O2– or O– species and thus CO2 formation and a decrease in total CO selectivity. In this work, it was found that the CO selectivity of the BaFe3Al9O19 hexaaluminate (BF3A) OC was greatly improved from 58% to 83% by tuning the regeneration period, with a CH4 conversion of 86%, an H2/CO ratio of 2, and a syngas yield of 4.2 mmol/g without significant carbon deposition. This resulted from the decrease in regeneration time (from 15 to 4.2 min), leading to a decrease in Fe3+ in Al(1), Al(2), and Al(3) sites (Fe1, Fe2, and Fe3) active for combustion of CH4 and an increase in reduced Fe2+ to Fe0 responsible for the partial oxidation of CH4. Consequently, the amount of CO2 decreased while that of CO increased significantly. In addition, unoxidized surface Fe0 resulting from shorter regeneration periods (5 and 4.2 min) acted as catalysts for dry reforming of CH4 and CO2 at the beginning of the reaction, which also contributed to the increase in CO formation for these two samples.