The incorporation of secondary metal ions into Cuexchanged SSZ-13 zeolites could improve their catalytic properties in selective catalytic reduction of NO x with ammonia (NH 3 -SCR), but their essential roles remain unclear at the molecular level. Herein, a series of Cu-Sm-SSZ-13 zeolites have been prepared by ion-exchanging Sm ions followed by Cu ions, which exhibit superior NH 3 -SCR performance. The NO conversion of Cu-Sm-SSZ-13 is nearly 10% higher than that of conventional Cu-SSZ-13 (175−250 °C) after hydrothermal ageing, showing an enhanced low-temperature activity. The Sm ions are found to occupy the sixmembered rings (6MRs) of SSZ-13 by X-ray diffraction Rietveld refinement and aberration-corrected scanning transmission electron microscopy. The Sm ions at 6MRs can facilitate the formation of more active [ZCu 2+ (OH)] + ions at 8MRs, as revealed by temperature-programmed reduction of hydrogen. X-ray photoelectron spectroscopy and density functional theory (DFT) calculations indicate that there exists electron transfer from Sm 3+ to [ZCu 2+ (OH)] + ions, which promotes the activity of [ZCu 2+ (OH)] + ions by decreasing the activation energy of the formation of intermediates (NH 4 NO 2 and H 2 NNO). Meanwhile, the electrostatic interaction between Sm 3+ and [ZCu 2+ (OH)] + results in a highreaction energy barrier for transforming [ZCu 2+ (OH)] + ions into inactive CuO x species, thus enhancing the stability of [ZCu 2+ (OH)] + ions. The influence of the ion-exchanging sequence of Sm and Cu ions into SSZ-13 is further investigated by combining both experiments and theoretical calculations. This work provides a mechanistic insight of secondary ions in regulating the distribution, activity, and stability of Cu active sites, which is helpful for the design of high-performance Cu-SSZ-13 catalysts for the NH 3 -SCR reaction.
Crystalline aluminosilicate zeolites with high sorption capacity and low production cost have been recognized as a promising adsorbent for volatile organic compound (VOC) capture. However, the ubiquitous water vapor in the VOC streams may compete with VOCs during the practical separation process because of the hydrophilic property of aluminosilicate zeolites. Herein, a selfsupporting core−shell structured MFI-type zeolite monolith was fabricated by 3D-printing aluminosilicate ZSM-5 zeolites as the core, followed by coating silicalite-1 zeolites as a hydrophobic shell via post-hydrothermal crystallization. Natural sepiolite nanofibers (SNFs) were employed as printing ink additives for reinforcing the mechanical stability of 3D-printed ZSM-5 monoliths. Colloidal silica was also introduced into the printing inks, affording continuous growth of silicalite-1 layers (with a thickness of ∼200 nm) over ZSM-5 crystals. Such core−shell structured MFI-type zeolite monoliths exhibited superior dynamic adsorption performance for toluene at 298 K under humid conditions (relative humidity: 50%), with a saturated adsorption capacity of 44.3 mg/g. This work provides a facile strategy for designing self-supporting zeolite monoliths with core−shell architectures for adsorption/ separation and other advanced applications.
The longevity and reusability of N95‐grade filtering facepiece respirators (N95 FFRs) are limited by consecutive donning and disinfection treatments. Herein, we developed stable N97 nanofibrous respirators based on chemically modified surface to enable remarkable filtration characteristics via polarity driven interaction. This was achieved by a thin‐film coated polyacrylonitrile nanofibrous membrane (TFPNM), giving an overall long‐lasting filtration performance with high quality factor at 0.42 Pa−1 (filtration efficiency: over 97 %; pressure drop: around 10 Pa), which is higher than that of the commercial N95 FFRs (0.10–0.41 Pa−1) tested with a flow rate of 5 L min−1 and the 0.26 μm NaCl aerosol. A coxsackie B4 virus filtration test demonstrated that TFPNM also had strong virus capture capacity of 97.67 %. As compared with N95 FFRs, the TFPNM was more resistant to a wider variety of disinfection protocols, and the overall filtration characteristics remained N97 standard.
The SSZ-13 zeolite supported Cu catalyst is highly efficient in eliminating the NOx and introduction of Fe3+ ions can significantly improve the high-temperature activity and the hydrothermal stability of Cu-SSZ-13....
Honeycomb cordierite coated with Cu-SSZ-13 zeolite is widely used in the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) to reduce pollutants from vehicle emission. However, the conventional honeycomb catalysts fabricated via coating technique are limited by low zeolite loadings, easy loss of the deposited zeolites, and complicated preparation process. Herein, a facile 3D printing strategy is developed to one-step construct MnO x /Cu-SSZ-13 monolithic catalysts with excellent catalytic performance for NH 3 -SCR. Iron-containing halloysite nanotubes (Fe-HNTs) are introduced as printing ink additives to ensure the mechanical stability and modulate the NH 3 -SCR performance of the monolithic catalysts at high temperature. In-situ incorporating Mn into the Cu-SSZ-13 zeolite monoliths during 3D printing process boosts the mechanical strength of the monolithic structures from 2.54 MPa to 4.33 MPa as well as broadens the temperature window (165-550 o C) of the catalysts for NH 3 -SCR with NO x conversion of above 80%. Such robust multi-component-integrated 3D-
Superhydrophobic dendritic mesoporous organosilica nanoparticles with magnetic cores were fabricated, realizing the efficient adsorption of oils from oil-in-water emulsions.
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