Synergistic effects of copper and oxygen vacancies in enhancing the efficacy of partially crystalline CuMnxOy catalyst for ozone decomposition.

To tackle the challenge of ground-level ozone pollution, this study proposed a potential catalytic design approach for ozone decomposition using Cu-Mn bimetallic oxide. This approach is grounded in an understanding of the intrinsic reactivity for catalyst and incorporates a novel potassium-driven low-temperature oxidation process for catalyst synthesis. The research highlights the creation of a highly reactive Cu-Mn oxide phase with extensive defect coverage, leading to significantly increased reaction rates. It also identifies the MnO2(100) facet as a crucial active phase, where oxygen vacancies simultaneously enhance O3 adsorption and decomposition, albeit with a concurrent risk of O2 poisoning due to the stabilization of adsorbed O2. Crucially, the incorporation of Cu offsets the effects of oxygen vacancies, influencing conversion rates and lessening O2 poisoning. The synergistic interplay between Cu and oxygen vacancies elevates the performance of the defect-rich Cu-Mn oxide catalyst. By combining computational and experimental methods, this study not only advances the understanding of the Cu-Mn oxide system for ozone decomposition but also contributes valuable insights into developing more efficient catalysts to mitigate ozone pollution.

Improvement on Sulfur Capacity of Cu-Al-Based Desulfurization Sorbents with Various Transition Metal Additives for Coal Derived Synthetic Gas Cleaning.

This study examined the effects of additives to improve the COS absorption capacity of Cu-Al-based sorbents for the integrated gasification fuel cell (IGFC) process. To absorb a small amount of COS, an Al-based precursor was added to the precursor solution for Cu-Al-based sorbents because a high surface area absorber was required. Various transition metals (Zn, Fe, Mn) were used as additives to improve the stability of the Cu-Al-based absorbent. The changes in surface properties and sulfur absorption capacity of the Cu-Al-based absorbent were investigated according to the composition of transition metals. As a result of the sulfur absorption test, the difference in the sulfur absorption capacity of the Cu-based sorbents was confirmed depending on the type of additive, and changes in their surface area. Moreover, the pore characteristics were observed by the nitrogen adsorption method. Sorbents with high surface areas generally have high sulfur capacity, but the additive component has a strong effect. These results can be explained by the transition metal additive binding to Cu to form a composite metal oxide. Furthermore, manganese was found to be suitable for improving the stability and surface area of the copper-based absorbent.

Synthesis of Macro-Porous De-NOx Catalysts for Poly-Tetra-Fluoro-Ethylene Membrane Bag Filter.

This study examined the effects of the porosity of catalytic bag-filter materials for applications to the SNCR (selective noncatalytic reduction)-SCR (selective catalytic reduction) hybrid process for highly treating nitrogen Oxides (NOx) in the exhaust gas of a combustion process. A V2O5/TiO2 catalyst was dispersed in a PTFE (poly-tetra-fluoro-ethylene) used as the catalytic bag-filter material to remove particulate matter and nitrogen oxides contained in the combustion exhaust gas. Macroporous alumina was added into a V2O5/TiO2-dispersed PTFE to improve the catalytic activity of V2O5/TiO2 dispersed in the PTFE material. In this study, the textural properties and denitrification performances of the V2O5/TiO2-dispersed PTFE materials were examined according to the addition of macro-porous alumina. When the denitrification catalyst was solely dispersed in the PTFE material, the catalyst inside the PTFE backbone had low gas-solid contact efficiency owing to the low porosity of the PTFE materials, resulting in low denitrification efficiency. On the other hand, the catalytic activity of V2O5/TiO2 dispersed inside the macro-porous PTFE material was significantly enhanced by adding macro-porous alumina into the PTFE matrix. The enhanced textural properties of the macro-porous PTFE material where V2O5/TiO2 was uniformly dispersed proved the facilitated diffusion of combustion exhaust gas into the PTFE material.

Improvement of Oxygen Mobility with the Formation of Defects in the Crystal Structure of Red Mud as an Oxygen Carrier for Chemical Looping Combustion.

Fe2O3 is the major component of red mud, which is a by-produced after eluting aluminum from bauxite in the Bayer process, and can be used as an oxygen carrier. On the other hand, red mud is unsuitable for using oxygen in the crystal lattice because of its low surface area. In this study the red-mud sample was sulfidated at high temperatures to improve the lattice oxygen mobility by forming lattice defects in the iron oxide crystals. To form crystal defects on red mud, iron oxide was converted to iron sulfide with hydrogen sulfide, and then re-oxidized by air to remove the sulfur components. In these processes, it was possible to generate defects could be generated in the crystal structure. Crystal defects are formed by the difference in the molar volume of oxygen and sulfur bound to the metal in the oxidation-sulfidation process. The surface area of the defective red mud increased from approximately 25.9 m2/g to 122.1 m2/g, and the pore volume increased from 0.1714cc/g to 0.2803 cc/g. In addition, the formation of crystal defects increased the oxygen transfer capacity of red mud from 1.75% to 2.25% at 15 vol.% hydrogen. This means that the amount of oxygen transported during the reduction process could be enhanced approximately 1.29 fold.