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N 2 O is typically present as a trace gas in chemical processes, but its emission causes serious environmental issues. We herein demonstrate that ion-exchanged mordenite zeolites (framework code: MOR) can exhibit high capacities for N 2 O adsorption under ambient conditions. In particular, a natural MOR zeolite gives an adsorption capacity as high as 0.34 mmol-N 2 O per g-zeolite (1 atm, 25 °C), representing the best performing material among all zeolite-based adsorbents reported so far. The results contribute toward a comprehensive understanding of the structure-activity relationship and offer insights to establishing a zeolite-based adsorption system for enriching or removing N 2 O.

Erionite (ERI) zeolite has recently attracted considerable attention for its application prospect in the selective catalytic reduction of NOx with NH3 (NH3‐SCR), provided that the high‐silica (Si/Al > 5.5) analog with improved hydrothermal stability can be facilely synthesized. In this work, ERI zeolites with different Si/Al ratios (4.6, 6.4, and 9.1) are synthesized through an ultrafast route, and in particular, a high‐silica ERI zeolite with a Si/Al ratio of 9.1 is obtained by using faujasite (FAU) as a starting material. The solid‐state 29Si MAS NMR spectroscopic study in combination with a computational simulation allows for figuring out the atomic configurations of the Al species in the three ERI zeolites. It is revealed that the ERI zeolite with the highest Si/Al ratio (ERI‐9.1, where the number indicates the Si/Al ratio) exhibits a biased Al occupancy at T1 site, which is possibly due to the presence of a higher fraction of the residual potassium cations in the can cages. In contrast, the Al siting in ERI‐4.6 and ERI‐6.4 proves to be relatively random. [ABSTRACT FROM AUTHOR]

The fast-synthesized Cu-ERI with a proper copper loading exhibited unprecedented high NH3-SCR activity even after severe hydrothermal aging, which is even comparable to that of Cu-CHA, the commercial catalyst for NH3-SCR. • A fast-synthesized ERI zeolite was proven to be highly active in NH 3 -SCR. • Copper loading was crucial to the hydrothermal stability and the NH 3 -SCR activity. • Different copper locations in the Cu-ERI zeolite were proposed. • The structure-activity relationship of Cu-ERI in NH 3 -SCR reaction was elucidated. ERI zeolite is a small-pore zeolite that has been rarely explored as a catalyst in the selective catalytic reduction of NO x with ammonia (NH 3 -SCR) as the performance has been considered to be limited by its insufficient hydrothermal stability. We herein report that a fast-synthesized ERI zeolite, which can be synthesized in only 2 h at a high temperature (210 °C), shows much enhanced hydrothermal stability than the conventional ERI zeolite due to the presence of less silanol defects. The fast-synthesized ERI zeolite with an optimal copper loading (equaling a Cu/Al ratio of 0.20) is demonstrated to be highly active in the NH 3 -SCR, which even rivals Cu-SSZ-13 – the benchmark NH 3 -SCR catalyst. Various characterization techniques are employed to characterize the copper species in the fast-synthesized ERI zeolite in order to understand its high hydrothermal stability and NH 3 -SCR activity. The results indicate that the copper species sitting at different locations exhibit variant hydrothermal stability and NH 3 -SCR activity, suggesting the importance of the interplay between the copper species and the zeolite host. With a deep understanding into the structure-activity relationship, this work presents that the fast-synthesized ERI zeolite holds potential to emerge as a robust NH 3 -SCR catalyst for emission control. [ABSTRACT FROM AUTHOR]

Encapsulating metal nanoclusters into zeolites combines the superior catalytic activity of the nanoclusters with high stability and unique shape selectivity of the crystalline microporous materials. The preparation of such bifunctional catalysts, however, is often restricted by the mismatching in time scale between the fast formation of nanoclusters and the slow crystallization of zeolites. We herein demonstrate a novel strategy to overcome the mismatching issue, in which the crystallization of zeolites is expedited so as to synchronize it with the rapid formation of nanoclusters. The concept was demonstrated by confining Pt and Sn nanoclusters into a ZSM‐5 (MFI) zeolite in the course of its crystallization, leading to an ultrafast, in situ encapsulation within just 5 min. The Pt/Sn‐ZSM‐5 exhibited exceptional activity and selectivity with stability in the dehydrogenation of propane to propene. This method of ultrafast encapsulation opens up a new avenue for designing and synthesizing composite zeolitic materials with structural and compositional complexity. [ABSTRACT FROM AUTHOR]

The present study focuses on the ultrafast synthesis of *BEA zeolite, which constitutes one of the most industrially important zeolites. A pure *BEA phase was successfully synthesized within 10 min at 210 °C by carefully tuning the composition of the initial reactant mixture. To date, the ultrafast synthesis of several industrially important zeolites is achieved with the aid of aging pretreatment, followed by high temperature hydrothermal treatment. In this study, we first demonstrated the 10-min synthesis of *BEA zeolite employing organic structure-directing agents (OSDAs), without any aging process. The employment of sealed pipe reactor in conjunction with the optimization of chemical composition of starting materials are critical in obtaining pure *BEA phase in a short time. The fast-synthesized *BEA zeolite possesses properties that are similar to those synthesized by conventional hydrothermal synthesis methods in terms of crystallinity and micropore volume. A comprehensive investigation on the effects of various parameters on the seed-assisted crystallization of *BEA zeolite was also studied. [ABSTRACT FROM AUTHOR]

High-silica erionite (ERI) zeolites are conventionally synthesised via a so-called charge density mismatch (CDM) approach, and a typical synthesis takes several days to complete. We herein demonstrate an ultrafast route to synthesise high-silica erionite zeolites in as short as 2 h at 210 °C. The fast-synthesised ERI has been proved to show higher hydrothermal stability compared with the conventionally synthesised product. [ABSTRACT FROM AUTHOR]

We present herein an ultrafast, organic structure-directing agent (OSDA)-free synthesis of mordenite zeolite in a tubular reactor capable of fast heating. Using a typical Na2O/SiO2/Al2O3 system, the synthesis time was shortened to 10 min, which is much shorter than the time required by conventional methods (tens of hours). The addition of milled seeds, which have a smaller crystal size (200 nm), was found to be more effective in enhancing the crystallization than the micrometer-sized raw seeds (2 μm). The fast-synthesized mordenite possesses properties similar to those of mordenite synthesized by conventional methods in terms of crystallinity while having a comparably small crystal size. In addition, the effects of the alkalinity and SiO2/Al2O3 ratio of the initial reactant mixture on the crystallization rate were evaluated, but no significant effects were observed. On the contrary, the yield and SiO2/Al2O3 ratio of the product were dependent on the alkalinity and SiO2/Al2O3 ratio of the initial reactant mixture. Based on these observations, the crystallization behavior of mordenite, obtained from an ultrafast, OSDA-free synthesis method, is discussed. [ABSTRACT FROM AUTHOR]

By combining the synthesis at a higher temperature with the addition of seed, ultrafast synthesis of silicalite-1, a pure-silica zeolite with MFI structure, has been achieved in a tubular reactor that can enable a rapid heating. The synthesis period of silicalite-1 has been shortened to 10 min, while it usually takes several hours or days using the conventional methods. Estimated from crystal size, the apparent crystal growth rate of silicalite-1 was on the order of 10 3 nm/h for the synthesis using TEOS as a silica source, while under another synthesis condition using colloidal silica as a silica source, the apparent crystal growth rate could be as high as 10 4 nm/h. High crystal growth rates demonstrated that the crystallization of silicalite-1 in the tubular reactor could be very fast. [ABSTRACT FROM AUTHOR]

We herein present a top-down methodology to prepare nanosized zeolites with tunable size by combining post-synthesis milling and fast recrystallization of several minutes (10 min for SSZ-13 and 5 min for AlPO4-5). A continuous-flow recrystallization process is demonstrated to further enhance the overall product efficiency. [ABSTRACT FROM AUTHOR]

[Display omitted] Introducing intracrystalline mesoporosity to zeolites is an effective way to reduce their diffusion limitations and enhancing their catalytic performance in reactions where large molecules are involved. The emergence of the so-called surfactant-templating technique has enriched the toolbox of methods to prepare mesoporous zeolites, in which amphiphilic molecules are used to assist in and direct the generation of mesopores in a pre-existing zeolite structure under alkaline conditions. We herein present ultrafast surfactant-templating of *BEA zeolite, which is achieved in just a few minutes with a tubular reactor that features fast heating. Two *BEA zeolites of the same Si/Al ratio, but differing in crystal size, are employed to demonstrate the concept. Tuning the interplay between the surfactant concentration and the alkalinity leads to the ultrafast generation of mesoporosity in the *BEA zeolite with the larger crystal size (BEA (L)) in 5 min; while it fails to generate uniform mesopores to the *BEA zeolite with the smaller crystal size (BEA (S)) under otherwise identical conditions. The ultrafast surfactant-templating of *BEA (S) is achieved only when it is partially dealuminated through a pre-treatment with acid. Our results provide new insights on the synergetic effect between the surfactant and the base that governs the surfactant-templating process and on how to produce intracrystalline mesoporosity with narrow pore size distribution under ultrafast conditions (2 min). The resultant mesoporous *BEA zeolites have been tested in the catalytic cracking of the vapours produced by pyrolyzing low-density polyethylene, a promising reaction for converting waste plastics into fuels. Improved selectivity towards aromatic hydrocarbons and light olefins is observed as a result of enhanced accessibility and availability of active sites, validating the superiority of the surfactant-templated *BEA zeolites. [ABSTRACT FROM AUTHOR]

• Metal-incorporated zeolites showing good potential in the ring-opening acidolysis of epoxides. • Moderate Lewis acidity benefitting both catalytic activity and selectivity. • Enhanced mass transfer playing a key role in the improvement of catalysis performance. • Optimized hierarchical Zr-Beta structure showing good catalysis and recycling performance. Metal-incorporated zeolites as heterogeneous Lewis acid were applied in the ring-opening acidolysis of ethylene oxide with acrylic acid to prepare 2-hydroxyethyl acrylate (HEA). The catalysis characteristics, including Lewis acid strength and internal mass transfer resistance, were systematically investigated to facilitate the rational design of zeolite catalysts. Through modifying the Lewis acid strength of zeolites via different metals (Sn, Zr and Ti) incorporation and the internal mass transfer resistance of zeolites from the particle size, pore diameter or pore structure, it was found that the increased Lewis acidity can accelerate both the main and side reactions, resulting in the high activity but low selectivity of zeolite catalysts; the enhanced internal diffusion was the key to limiting subsequent cascade alcoholysis side reactions as well as the decline of catalytic performance. Based on these findings, Zr-containing zeolites featured with moderate Lewis acidity and uniform intracrystalline mesoporosity were designed and prepared, presenting excellent catalysis and recycling performance. These results demonstrated the great potential of the developed zeolite catalysts for the green synthesis of HEA as well as the similar ring-opening acidolysis of epoxides. [ABSTRACT FROM AUTHOR]

The molecular diffusion with zeolites is somewhat limited, particularly for bulky molecules because zeolites only have micropores, which, in turn, limit their use as catalysts. Generation of hierarchically porous ZSM-5 with micro and mesopores has been a rational solution for overcoming this problem. The conventional method for synthesizing hierarchically porous ZSM-5 generally requires high-temperature heating in the presence of an organic structure-directing agent (OSDA) and a mesopore-generating agent (mesoporogen). Herein, we report a new method for the synthesis of hierarchically porous ZSM-5, which leads to the synthesis at low temperature in the presence of a reduced amount of OSDA and in the absence of any mesoporogen. The OSDA seems to play an additional role as a scaffolding agent for mesopore generation. Our study also showed that the control of the molar composition is essential for the crystallization of hierarchically porous-ZSM-5. [ABSTRACT FROM AUTHOR]

Unlike previous reports stating that costly and bulky organic molecules are essential to form MSE-type zeolites, we report herein a simplified and efficient synthesis route to these multi-dimensional, large-pore zeolites by using tetraethylammonium hydroxide (TEAOH) as an organic structure-directing agent (OSDA). Rather than conventional methods, alternative synthesis pathways in which such OSDAs are replaced with inexpensive and simple molecules/cations are recently demanding. In order to select the OSDAs and determine the synthesis conditions from a huge “zeolite synthesis library,” we applied the “composite building unit hypothesis” which we have proposed for the seed-directed, OSDA-free synthesis methods. By applying this hypothesis, a clear relation was found among MSE, *BEA, and MOR framework types. According to this relation, TEAOH which is basically utilized for the industrial production of *BEA-type zeolite was determined to be used in a modified gel composition as an easily reachable and comparatively inexpensive OSDA. This novel approach allowed us to obtain pure solid products with high yields by consecutively applying aging and hydrothermal synthesis steps. The series of characterizations revealed that the features of obtained products were similar to those of conventional MCM-68 with relatively better microporosity characteristics. Remarkably, the “second-generation” products can be synthesized via this novel route by optimizing the aging time. Considering the overall results, this method is the most simplified and efficient synthesis route for MSE-type zeolites, and we believe that this approach can be further extended to the synthesis of other multi-dimensional, large-pore zeolites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrafast dealumination of zeolite was performed using continuous-flow reactor. • The dealuminated zeolites were characterized by PXRD, SEM, MAS NMR and ICP-AES. • The dealuminated zeolites exhibited the enhanced hydrothermal stability. Dealumination is an efficient post-synthetic treatment to enhance the catalytic activity and thermal/hydrothermal stabilities of zeolites. Development of fast dealumination process is a critical requirement from a practical perspective. Herein, the ultrafast dealumination of zeolite is performed in a continuous-flow system, where a slurry of commercial *BEA zeolite, as the parent (Si/Al = 12.2) material, in sulfuric acid solution is fed into the flow reactor preheated at 200 °C. The *BEA zeolites obtained after dealumination in the flow reactor for residence times of 1–5 min possesses increased Si/Al ratios of ∼70, while retaining the original crystalline structure and particle morphology. The heat treatment with various residence periods indicates that the removal of Al atoms from the parent zeolite is completed within 1 min in the flow system. Hydrothermal stability of the dealuminated zeolite for 1 min in the flow system is compared with that of the parent and dealuminated zeolites in various reactors, confirming that the dealumination of the *BEA zeolite at 200 °C for 1 min in the flow system is sufficient to enhance its hydrothermal stability. This study demonstrates the potential of a continuous-flow system for application in post-synthetic treatments with a timescale of the order of minutes. [ABSTRACT FROM AUTHOR]