The addition of Triton X-100 slows down the crystallization rate of TS-1, while the rota-crystallization accelerates the incorporation rate of Ti.

A facile strategy affording high-quality single-crystalline MFI-type nanozeolites (10–55 nm) with hexagonal prism morphology, good monodispersity, high crystallinity, and high product yield (above 97%) has been developed. This is achieved by synergistically using an l-lysine-assisted approach and a two-step crystallization process in a concentrated gel system (H2O/Si = 9). The morphological evolution of nanosized silicalite-1 is monitored by high-resolution transmission electron microscopy (HRTEM). In this process, metastable irregular nanoparticles are initially obtained at 80 °C as the first step. Consequently, a rearrangement in morphology toward equilibrium crystal shape and without excessive growth for the metastable nanoparticles occurs at 170 °C as the second step. Throughout the whole process, l-lysine acts as an inhibitor to effectively limit the crystal growth of zeolites. Thanks to the high-quality nanosized crystals, the as-prepared ZSM-5 catalysts exhibit superior performance in methanol-to-propylene (MTP) reactions, which deliver a prolonged lifetime of 54 h with a total light olefin selectivity of 74% and a high propylene selectivity of 49% at 470 °C at a high methanol weight hourly space velocity (WHSV) of 7.2 h–1. This synthetic route provides a general strategy for preparing other types of zeolites with good monodispersity, nanosize, high yield, and high crystallinity.

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.

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A series of nanosized Cu/SAPO‐34 catalysts with different silicon contents were successfully synthesized by in situ hydrothermal method by using tetraethylammonium hydroxide and copper‐tetraethylenepentamine as co‐templates. The in situ prepared nanosized Cu/SAPO‐34 catalysts possess strong Brønsted acidity and well‐dispersed Cu species, showing enhanced performance for selective catalytic reduction of NOx with NH3 compared with micronsized and nanosized counterparts prepared by post impregnation method. Significantly, Cu/SAPO‐34 nanocatalysts prepared by in situ method maintain the catalytic activity after the hydrothermal aging treatment, suggesting their excellent hydrothermal stability. This work will provide some guidance for the design of highly efficient catalysts for NH3−SCR reactions.

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