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A series of mesoporous alumina (MA) doped with acidic (Ti, W) or alkaline earth (Ba, Mg) elements were prepared. They were used as the supports for Pd catalysts. These catalysts were characterized by N2 sorption, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy of CO adsorption and temperature-programmed reduction. Complete oxidation of toluene on these catalysts was tested in a fixed-bed micro-reactor. The results of in situ IR of CO adsorption indicated that the doping of basic element was beneficial for the dispersion of PdO particles, while the doping of acid element suppressed the dispersion of PdO particles. The binding energy of Pd in Pd/Ba-MA shifted to high energy, indicating that the interaction between PdO and support was enhanced. The results of H2-TPR showed that the reducibility of PdO doped with alkaline element was stronger than those of catalysts doped with acidic element. The doping of basic elements promoted the dispersion of PdO particles, changed the electronic state of Pd and enhanced the reducibility of PdO, which led to its high activity. The catalysts doped with the basic elements had higher activities than those doped with acidic elements, among which the Pd/Ba-MA catalyst had the highest activity among all catalysts. [ABSTRACT FROM AUTHOR]

A novel MnO x -CeO 2 nanosphere catalyst with assembled structure from tiny particles was prepared and tested towards low-temperature NH 3 -SCR. A superior deNO x performance compared to that obtained over the catalyst composed of MnO x supported on CeO 2 was obtained. A good resistance to high space velocity and SO 2 present in the feed and an excellent stability (no deactivation was observed during 100-h of testing at 150 °C) were obtained. The characterization results suggested that the higher specific surface area, better redox behavior and larger concentration of surface active oxygen species were responsible for the above mentioned excellent performance. The results of the present study suggest that control of catalyst morphology can be an effective strategy to upgrade low-temperature NH 3 -SCR performance. [ABSTRACT FROM AUTHOR]

Manganese oxide-based catalysts exhibit excellent low-temperature denitration efficiency, making them potential candidates for application. Herein, the relationship between reaction stability and phase structure for MnO 2 , Mn 2 O 3 and Mn 3 O 4 was disclosed. The NO conversion for Mn 2 O 3 drastically reduced after 120 h reaction, while minor decline was detected for MnO 2 and Mn 3 O 4. Based on dedicate qualitative and quantitative analyses on the deposits over catalyst surface, deactivation trigged by ammonium nitrate (AN) deposition was confirmed. Different from penta-coordinated Mn4+ on MnO 2 (110) and tri-coordinated Mn2+, penta-coordinated Mn4+ on Mn 3 O 4 (101), the unique tetra-coordinated Mn3+ on Mn 2 O 3 (200) could stabilize the nitrates and make it difficult to be removed via decomposition or reaction and accumulate continuously, which resulted in the significant deactivation. This research could not only unveil the poisoning mechanism of MnO x based catalysts, but also provide new insights into the relationship between the catalytic stability and surface Mn-O microstructure. [Display omitted] • The relationship between reaction stability and MnO x phase structure was disclosed. • The texture property and Mn valence had finite effect on reaction stability. • The ammonium nitrates (AN) deposition could induce deactivation of catalysts. • A model was proposed to describe the stability of nitrates in AN. [ABSTRACT FROM AUTHOR]

• Thin-layered titania confined in SBA-15 was successfully synthesized by grafting strategy. • The amorphous thin-layered titania exhibited much enhanced surface acidity and regulated electronic state. • Activity of Fe supported titania catalyst were greatly improved, and H 2 O surprisingly promoted the catalyst activity. • The catalyst revealed promising SO 2 resistance, SO 2 was confirmed to have negligible influence on reactants adsorption. TiO 2 is a famous support for selective catalytic reduction of NO with NH 3 (NH 3 -SCR). Engineering the morphology and structure of TiO 2 is effective to modulate the interaction with surface dispersed component, providing further opportunity to improve catalytic performance. In this study, we rationally construct thin-layered titania confined in mesoporous silica via a surface grafting strategy. It exhibits high specific surface area with amorphous structure along mesopore channel, and much more Brønsted acid sites are generated than bulk TiO 2 due to defect induced oxygen-related species. After iron oxide loading, both the denitration activity and H 2 O/SO 2 tolerance are greatly promoted as compared to conventional Fe/TiO 2. Further characterizations reveal the obtained catalyst displays uniform iron oxide dispersion and intense Fe-Ti interaction, resulting in superior redox behavior and increased acidity. Notably, it is found the introduction of H 2 O exhibits a promotional effect on NO conversion efficiency, which can be ascribed to enhancement of NH 3 adsorption capability. Besides, SO 2 has negligible disturbance on NO/NH 3 adsorption, leading to superior sulfur tolerance. The result of present study demonstrates vital role of surface structure engineering of TiO 2 for sustainable denitration, which opens up a new avenue for designing well-performed and stable NH 3 -SCR catalysts. [ABSTRACT FROM AUTHOR]