To develop highly efficient NH 3 -SCR catalysts with a wide temperature range, catalysts based on MnAlO x and Cerium elements loading with various mixing ratios were prepared for selective catalytic reduction of NO by NH 3 . The special role of cerium was demonstrated by the surface structure characteristics and unique catalytic performance, involving the surface-active sites and compositions analysis. Interestingly, the strengthening of Mn 1.2 Al 0.8 Ce a O x on both acid sites, especially medium acids and strong acids, were clearly manifested. Meanwhile, the strong interaction between MnAlOx and CeO 2 enabled favorable electron transfers from MnOx to CeO 2 while generating more oxygen vacancies and active oxygen species, consequently accelerating the redox cycle. The results illustrate that the NOx conversion and the selectivity of N 2 can be improved with more medium acids tuned by appropriate Ce adding. However, an opposite effect will appear by excessive addition. In addition, the reaction mechanisms at different acid sites are revealed. Our findings, therefore, provide a strategy for the rational design of moderate-temperature NH 3 -SCR catalysts through adding-induced component engineering of composite materials. Graphic Abstract Mn 1.2 Al 0.8 Ce a O x Catalysts with different surface features were fabricated by an environment-friendly method. The strong interaction between MnAlOx and CeO 2 was systematically illustrated. Meanwhile, the importance of medium acids was convincingly revealed. And the reaction mechanisms at different acid sites were demonstrated. These provide a strategy for the rational design of moderate-temperature NH 3 -SCR catalysts through adding-induced component engineering of composite materials.
An unprecedented type of 3D porous millimetric ozonation catalyst confining Mn-Ce dual-atom sites in terracotta support (MCT) was hereby reported through a feasible interface oxygen-induced ordering strategy. The utilization of cerium tailored the electron/valence state of dual-atom sites through its oxyphilic 4 f orbitals, making MCT present excellent ozone catalysis to remove model recalcitrant fulvic-like acids. The TOC removal kinetics value by MCT is 2.71 and 3.68 times higher than those of catalysts confining single Mn and Ce sites, respectively. The optimized MCT exhibited robust reusability without any regeneration (above 87% of TOC removal for each cycle), and desirable removal for the biochemical effluent organics of landfill leachate, showcasing a potential of deeply purifying saline wastewater. The electron complementary effect of cerium in dual-atom sites accelerated the electron transfer for O 3 catalysis, thus promoting the formation of reactive radicals for pollutant degradation via a thermodynamically feasible surface-adsorbed oxygen pathway. This work highlights the importance of elaborately designing dual-atom metal sites to construct reusable monolithic ozonation catalysts with electron self-cycle function for advanced wastewater purification.
As an essential elastomer used in edge technologies, fluorosilicone rubber (FSR) suffers serious oxidative ageing problem when serving at high temperature. Cerium oxide is generally used as an antioxidant additive but remains unsatisfactory. In order to obtain better antioxidant effect on improving the thermal stability of FSR, a kind of cerium-containing polymethylphenyl silicone (PSI-Ce) was synthesized and the structure was verified by Fourier-transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance ( 1 H-NMR). Due to the homogeneous dispersion on molecular scale, PSI-Ce imposed much better antioxidant effect than the commercial CeO 2 did, no matter from isothermal degradation at 320 °C or thermal-oxidative ageing test at 230 °C. In particular, after ageing for 72 h, FSR/PSI-Ce (2 phr) maintained 82% of tensile strength and 63% of elongation at break, in comparison to the corresponding values of 48% and 42% for FSR/CeO 2 (2 phr). Moreover, 2 phr PSI-Ce was equivalent to 0.046 phr CeO 2 according to cerium element conservation.
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