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The selective oxidation of aromatic C–H bonds to high value-added oxygenated products with molecular oxygen remains a key challenge in heterogeneous catalysis. Eligible heterogeneous catalysts are pursued and the reaction mechanism is hotly debated. Herein, we report that zeolite-encaged single-site cobalt ions can efficiently catalyze the model reaction of ethylbenzene aerobic oxidation to acetophenone, outperforming the industrial benchmark catalyst cobalt naphthenate under identical conditions. The self-accelerating phenomenon is observed in the progress of ethylbenzene aerobic oxidation, corresponding to the self-adjusted reaction pathway as revealed by kinetic studies and density functional theory calculations. The formation of reactive O* species on Co sites, resembling the well-known α-O on Fe sites, is identified to be responsible for the self-adjusted reaction pathway of aromatic C–H bond oxidation.

Due to the epidemic COVID-19 spread and Intelligent Transportation System (ITS) development, investigators are now to conduct their research over the generated Transportation Big Data (TBD) in many critical areas, such as medical supplies, food supplies, as well as logistics supplies. At present, Vehicular Edge Computing (VEC) is an emerging paradigm to integrate resources from vehicles, road-site units, base stations, and cloud center to promote the performance of TBD tasks scheduling and running. In this paper, we design a three-layered TBD task processing architecture with a federated learning mechanism for credit priority-based task scheduling and running. In our design, we consider the efficiency of task offloading and misbehavior attack problems simultaneously. We propose a vehicular federated learning framework combined with Multi-Layer Perceptron (MLP) credit measurement, which can preserve the privacy of vehicles and obtain the related features for vehicular credit prediction. We also propose a task offloading algorithm to solve the optimization problem for credit priority task offloading between edge computing servers and vehicles. The proposed solution can prioritize tasks and assign sufficient resources for reliable and active task requesters. Experimental results expose that the proposed mechanism outperforms the state-of-the-art solutions when considering efficiency and attack simultaneously for TBD tasks scheduling and running.

Coordinatively unsaturated centers (CUCs) in zeolites are emerging as robust active sites for many chemical processes, in analogy to those in organometallic complexes or metal–organic frameworks.Various strategies have been developed for the construction of CUCs within zeolite matrix, either incorporated into zeolite framework or stabilized as extra-framework cations, endowing the zeolite host characteristic functionalities.The explicit structure and coordination environment of CUCs within zeolite matrix can be revealed via the combination of multiple advanced spectroscopy techniques.CUCs within zeolite matrix show unique interactions with small molecules and create unique properties in chemisorption and catalysis, making CUC-containing zeolites promising candidates for various applications.

Olefin selectivity and catalyst lifetime are two key metrics for industrial methanol-to-olefin catalysts. Currently, it is very difficult to obtain high olefin selectivity and long catalyst lifetime at the same time. Herein, a feasible strategy combining precoking and steaming to directionally construct the active naphthalenic species within the crystal center of the SAPO-34 catalyst has been developed, which can not only promote the lower olefin selectivity to ∼89% (ethylene and propylene) but also prolong the catalyst lifetime by ∼3.7-fold in the methanol-to-olefin conversion. Structured illumination microscopy, in situultraviolet–visible spectroscopy, and online mass spectrometry elucidate the spatiotemporal distribution and evolution of the naphthalenic species during the precoking and steaming processes. This one-stone-two-birds strategy is applicable to a commercial SAPO-34 catalyst containing a binder, demonstrating its bright prospect in the methanol-to-olefin industry.

Cascade adsorptive separation of the ternary mixture of C2 hydrocarbons has been achieved with Na-X zeolites viaa two-stage process.

Direct propylene epoxidation with molecular oxygen is a dream reaction with 100% atom economy, but aerobic epoxidation is challenging because of the undesired over-oxidation and isomerization of epoxide products. Herein, we report the construction of uniform cobalt ions confined in faujasite zeolite, namely, Co@Y, which exhibits unprecedented catalytic performance in the aerobic epoxidation of propylene. Propylene conversion of 24.6% is achieved at propylene oxide selectivity of 57% at 773 K, giving a state-of-the-art propylene oxide production rate of 4.7 mmol/gcat/h. The catalytic performance of Co@Y is very stable, and no activity loss can be observed for over 200 h. Spectroscopic analyses reveal the details of molecular oxygen activation on isolated cobalt ions, followed by interaction with propylene to produce epoxide, in which the Co2+–Coδ+–Co2+(2 < δ < 3) redox cycle is involved. The reaction pathway of propylene oxide and byproduct acrolein formation from propylene epoxidation is investigated by density functional theory calculations, and the unique catalytic performance of Co@Y is interpreted. This work presents an explicit example of constructing specific transition-metal ions within the zeolite matrix toward selective catalytic oxidations.

Zeolites with good acid site accessibility and high diffusion rates are highly desirable catalysts, especially when dealing with bulk molecules. In this work, ZSM-5 zeolites with similar Si/Al ratios but different thicknesses along the b-axis (from ∼30 nm to ∼5 μm), namely, two plate-like ZSM-5 zeolites and two reference zeolites have been prepared and the impacts of b-axis thickness on the surface properties and catalytic cracking performances are explored. Comprehensive physiochemical studies demonstrate that reducing the b-axis thickness of the zeolite crystals endows the samples with better acid site accessibility and more external surface acid sites. Two model compounds with different molecule sizes, namely, 1,3,5-triisopropylbenzene (TIPB) and cumene, are selected to explore the catalytic cracking performances of the as-synthesized samples. The results reveal that decreasing the b-axis thickness of zeolite crystals can effectually promote the catalytic activity and stability in catalytic cracking reactions. For TIPB cracking, the greatly enhanced catalytic activity is ascribed to the enhanced acid site accessibility in plate-like ZSM-5 zeolites, and for cumene cracking, the improved catalytic stability is ascribed to the shortened diffusion length of plate-like zeolites.

Understanding the complete reaction network and mechanism of methanol-to-hydrocarbons remains a key challenge in the field of zeolite catalysis and C1 chemistry. Inspired by the identification of the reactive surface methoxy species on solid acids, several direct mechanisms associated with the formation of the first C-C bond in methanol conversion have been recently disclosed. Identifying the stepwise involvement of the initial intermediates containing the first C-C bond in the whole reaction process of methanol-to-hydrocarbons conversion becomes possible and attractive for the further development of this important reaction. Herein, several initial unsaturated aldehydes/ketones containing the C-C bond are identified viacomplementary spectroscopic techniques. With the combination of kinetic and spectroscopic analyses, a complete roadmap of the zeolite-catalyzed methanol-to-hydrocarbons conversion from the initial C-C bonds to the hydrocarbon pool species viathe oxygen-containing unsaturated intermediates is clearly illustrated. With the participation of both Brønsted and Lewis acid sites in H-ZSM-5 zeolite, an initial aldol-cycle is proposed, which can be closely connected to the well-known dual-cycle mechanism in the methanol-to-hydrocarbons conversion.

Solid-state NMR (ssNMR) spectroscopy is a powerful technique for characterizing the surface sites of solid acids and organic intermediates formed during the acid catalyzed reaction. As a very useful probe molecule, ammonia is often utilized to determine the density of solidacids’ surface sites by ssNMR spectroscopy. The present mini-review summarizes some of the latest research developments on the quantitative characterization of the acid sites and carbenium ions during the zeolite catalytic reaction by ammonia probe-assisted ssNMR spectroscopy.

The hydration of alkyne represents the most straightforward and simplest route toward the synthesis of ketone. Herein, Brønsted acidic zeolites are explored as potential catalysts for the liquid-phase phenylacetylene hydration. The topology structure and Si/Al ratio are disclosed to be key factors controlling the catalytic activity of zeolites. Typically, H-MFI zeolite with a Si/Al molar ratio of 13 exhibits the highest catalytic activity, with turnover frequency of 6.0 h−1at 363 K. Besides, H-MFI zeolite shows good catalytic stability and recyclability in the reaction of phenylacetylene hydration, and the substrate scope can be simply extended to other soluble aromatic alkynes. The reaction mechanism of phenylacetylene hydration is investigated by means of kinetic and spectroscopic analyses. The Markovnikov electrophilic addition of phenylacetylene by hydrated protons is established as the rate-determining step, followed by deprotonation and enol isomerization to derive acetophenone product.

Isolated cationic Pd species encapsulated in MFI zeolite, i.e., Pd@MFI, have been successfully prepared via in situhydrothermal route followed by oxidative treatment. The as-prepared Pd@MFI samples are investigated as promising catalysts in the reaction of methane combustion. Typically, Pd@H-ZSM-5 shows remarkable activity in methane catalytic combustion with a low apparent activation energy value of 70.7 kJ/mol as well as good catalytic stability even in excess water vapor. Detailed characterization results demonstrate the strong interaction between Pd sites and zeolite framework in Pd@ZSM-5 and the efficient stabilization of isolated Pd sites by zeolite thereof. Spectroscopy analyses reveal that the presence of Brønsted acid sites is beneficial to methane adsorption and its subsequent activation on adjacent Pd sites, constructing cooperation between Brønsted acid sites and Pd sites within the confined space of MFI zeolite toward high-efficiency methane catalytic combustion. The reaction mechanism of methane combustion catalyzed by Pd@H-ZSM-5 model catalyst is finally discussed.

In this work, based on the quasi-static tensile test and acoustic emission technology, the tensile properties of two types of three-dimensional flat-knitted inlay fabrics reinforced composites are investigated, and the acoustic emission characteristic parameters of various damage mechanisms are obtained. The transverse tensile process of specimens could be divided into the elastic stage, yield stage, and fracture stage. We found that, compared with the fluctuation of the stress-strain curve in the yield stage, weft insertion yarns in composite with interlock structure broke almost simultaneously, while the composite with plain stitch broke successively. The transverse and longitudinal tensile strength of the composite with interlock structure was 44.70% and 28.63% higher than the composite with plain structure, respectively. The SEM micrographs showed that the damage mechanism of the composites was matrix fracture, fiber-matrix debonding, and fiber breakage. The amplitude ranges of the three damage mechanisms were 50–65 dB, 65–80 dB, and 90–100 dB, respectively, and the frequency ranges were 35–114 kHz, 116–187 kHz, and 252–281 kHz, respectively. Fiber-matrix debonding and matrix fracture had large cumulative AE energy, numerous events, and long duration time, while fiber breakage had the characteristics of large amplitude, high frequency, low cumulative AE energy, few events, and short duration time.

The generation of multifunctional isolated active sites in zeolite supports is an attractive method for integrating multistep sequential reactions into a single-pass tandem catalytic reaction. In this study, bifunctional TiSn-Beta zeolite was prepared by a simple and scalable post-synthesis approach, and it was utilized as an efficient heterogeneous catalyst for the tandem conversion of alkenes to 1,2-diols. The isolated Ti and Sn Lewis acid sites within the TiSn-Beta zeolite can efficiently integrate alkene epoxidation and epoxide hydration in tandem in a zeolite microreactor to achieve one-step conversion of alkenes to 1,2-diols with a high selectivity of >90%. Zeolite confinement effects result in high tandem rates of alkene epoxidation and epoxide hydration as well as high selectivity toward the desired product. Further, the novel method demonstrated herein can be employed to other tandem catalytic reactions for sustainable chemical production.

Zeolite stabilized Pt-Zn catalyst has been developed for propane direct dehydrogenation with propane conversion close to the equilibrium and a very low deactivation rate of 0.0018h−1at 823 K.

The self-aldol condensation of aldehydes was investigated with rare-earth cations stabilized by [Si]Beta zeolites in parallel with bulk rare-earth metal oxides. Good catalytic performance was achieved with all Lewis acidic rare-earth cations stabilized by zeolites and yttrium appeared to be the best metal choice. According to the results of several complementary techniques, i.e., temperature-programmed surface reactions, in situdiffuse reflectance infrared Fourier transform spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, the reaction pathway and mechanism of the aldehyde self-aldol condensation over Y/Beta catalyst were studied in more detail. Density functional theory calculations revealed that aldol dehydration was the rate-limiting step. The hydroxyl group at the open yttrium site played an important role in stabilizing the transition state of the aldol dimer reducing the energy barrier for its hydration. Lewis acidic Y(OSi)(OH)2stabilized by zeolites in open configurations were identified as the preferred active sites for the self-aldol condensation of aldehydes.

Zeolite crystals offering a short diffusion pathway through the pore network are highly desired for a number of catalytic and molecule separation applications. Herein, we develop a simple synthetic strategy toward reducing the thickness along the b-axis of MFI-type crystals, thus providing a short diffusion path along the straight channel. Our approach combines preliminary aging and a fluoride-assisted low-temperature crystallization. The synthesized MFI crystals are in the micrometer-size range along the a- and c-axis, while the thickness along the b-axis is a few tens of nanometers. The synthesis parameters controlling the formation of platelike zeolite are studied, and the factors controlling the zeolite growth are identified. The synthesis strategy works equally well with all-silica MFI (silicalite-1) and its Al- and Ga-containing derivatives. The catalytic activity of platelike ZSM-5 in the methanol-to-hydrocarbons (MTH) reaction is compared with a commercial nanosized ZSM-5 sample, as the platelike ZSM-5 exhibits a substantially extended lifetime. The synthesis of platelike MFI crystals is successfully scaled up to a kilogram scale.

The reaction kinetics and mechanism of CH4-SCR on Ru–In/H-SSZ-13 as a model multifunctional catalyst, together with Ru/H-SSZ-13 and In/H-SSZ-13 for reference, were investigated. In the low-temperature region (<260 °C), quite different apparent activation energy values were obtained for the three catalysts investigated, while similar apparent activation energy values were obtained in the high-temperature region (>260 °C). With increasing reaction temperatures from 250 to 500 °C, the reaction orders of NO in CH4-SCR on Ru–In/H-SSZ-13 gradually decreased from 1.80 to 0.43 while the reaction orders of CH4gradually increased from 0.33 to 0.86 instead. The surface species formed on the catalyst samples and their evolutions at 250 and 400 °C were monitored by in situDRIFT spectroscopy. The organonitrogen compounds, i.e.methyl nitrite and its isomer nitromethane, were identified as the key intermediates in CH4-SCR, and their existence was further confirmed by temperature-programmed surface reaction and pulse-response experiments. According to the above-mentioned results, the temperature-dependent CH4-SCR mechanism on Ru–In/H-SSZ-13 was finally established.

The selective oxidation of olefins by molecular oxygen holds great importance in the chemical industry due to its remarkable adaptability in constructing carbonyl compounds. Classical homogeneous Wacker oxidation with a complex system of PdCl2–CuCl2–H2O is currently employed in the industrial production of acetaldehyde, which suffers from several key drawbacks. The development of alternative heterogeneous catalytic systems for Wacker-type oxidations has been hotly pursued for decades. Herein, we report a novel heterogeneous catalyst, namely Pd@FAU containing exclusive singular Pd sites confined in zeolite, showing remarkable performance in the Wacker-type oxidation of light olefins to the corresponding carbonyl compounds. Typically, stable propylene conversion rates of 2.3–3.5 mol/molPd/min and an acetone selectivity of 75–89% can be achieved simultaneously, surpassing the state-of-the-art homogeneous Wacker oxidation systems. In situspectroscopic investigations disclose the spontaneous redox cycle of Pd+-Pd2+-Pd+in Pd@FAU during the reaction, in significant contrast to the known Pd2+-Pd0-Pd2+redox cycle. Theoretical calculations reveal the unique reaction pathway and mechanism of Wacker-type oxidation over Pd@FAU, without the participation of water as the nucleophile. Overall, a novel heterogeneous catalyst of Pd@FAU has been developed for Wacker-type oxidations with the unique reaction mechanism fully interpreted. This study will contribute to more sustainable Wacker-type oxidations and further improve the current understanding of Pd redox catalysis.

The inherent inertness and striking physicochemical similarities of krypton and xenon pose significant challenges to their separation. Reported herein is the efficient xenon capture and xenon/krypton adsorptive separation by transition metal-free zeolites under ambient conditions. The polarized environment of zeolite, denoted as local polarity, can be tuned by changing the topology, framework composition, and counter-cations, which in turn correlates with the guest–host interaction and separation performance. Chabazite zeolite with a framework Si/Al ratio of 2.5 and Ca2+as the counter-cations, namely, Ca-CHA-2.5, is developed as a state-of-the-art zeolite adsorbent, showing remarkable performance, i.e., high dynamic xenon uptake, high xenon/krypton separation selectivity, and good recyclability, in the adsorptive separation of the xenon/krypton mixture. Grand Canonical Monte Carlo simulation reveals that extraframework Ca2+cations act as the primary binding sites for xenon and can stabilize xenon molecules together with the chabazite framework, whereas krypton molecules are stabilized by weak guest–host interaction with the zeolite framework.

As a prominent contributor to air pollution, nitric oxide (NO) has emerged as a critical agent causing detrimental environmental and health ramifications. To mitigate emissions and facilitate downstream utilization, adsorption-based techniques offer a compelling approach for direct NO capture from both stationary and mobile sources. In this study, a comprehensive exploration of NO capture under oxygen-lean and oxygen-rich conditions was conducted, employing Ni ion-exchanged chabazite (CHA-type) zeolites as the adsorbents. Remarkably, Ni/Na-CHA zeolites, with Ni loadings ranging from 3 to 4 wt%, demonstrate remarkable dynamic uptake capacities and exhibit exceptional NO capture efficiencies (NO-to-Ni ratio) for both oxygen-lean (0.17–0.31 mmol/g, 0.32–0.43 of NO/Ni) and oxygen-rich (1.64–1.18 mmol/g) under ambient conditions. An NH3reduction methodology was designed for the regeneration of absorbents at a relatively low temperature of 673 K. Comprehensive insights into the NOxadsorption mechanism were obtained through temperature-programmed desorption experiments, in situFourier transform infrared spectroscopy, and density functional theory calculations. It is unveiled that NO and NO2exhibit propensity to coordinate with Ni2+viaN-terminal or O-terminal, yielding thermally stable complexes and metastable species, respectively, while the low-temperature desorption substances are generated in close proximity to Na+. This study not only offers micro-level perspectives but imparts crucial insights for the advancement of capture and reduction technologies utilizing precious-metal-free materials.

The selective dehydrogenation of ethanol to acetaldehyde is a promising route for acetaldehyde production. Although Cu-based catalysts exhibit high activity in ethanol dehydrogenation, a rapid deactivation due to Cu sintering always occurs. In this study, highly dispersed Cu species were sta-bilized using the silanol defects in Beta zeolite (denoted as Beta) resulting from dealumination, and applied as robust catalysts for ethanol-to-acetaldehyde conversion. Typically, a long catalyst life-time of 100 h with an acetaldehyde yield of ∼70% could be achieved over 5% Cu/Beta. The pres-ence of Cu+and Cu0species and the agglomeration of Cu particles after a long-term reaction for 180 h were revealed by transmission electron microscopy, thermogravimetric analysis, and CO-diffuse-reflectance infrared Fourier transform spectroscopy, and were responsible for the deac-tivation of the Cu/Beta catalyst in the ethanol-to-acetaldehyde conversion.

The selective hydrogenation of alkynes to alkenes is an important type of organic transformation with large-scale industrial applications. This transformation requires efficient catalysts with precise selectivity control, and palladium-based metallic catalysts are currently employed. Here we show that four-coordinated cationic nickel(II) confined in zeolite can efficiently catalyze the selective hydrogenation of acetylene to ethylene, a key process for trace acetylene removal prior to the polymerization process. Under optimized conditions, 100% acetylene conversion and an ethylene selectivity up to 97% are simultaneously achieved. This catalyst system also exhibits good stability and recyclability for potential applications. Spectroscopy investigations and density functional theory calculations reveal the heterolytic dissociation of hydrogen molecules and the importance of hydride and protons in the selective hydrogenation of acetylene to ethylene. This work provides an efficient strategy toward active and selective zeolite catalysts by utilizing the local electrostatic field within the zeolite confined space for small-molecule activation and by linking heterogeneous and homogeneous catalysis.

Bimetallic Cr-In/H-SSZ-13 zeolites were prepared by wet impregnation and investigated for selective catalytic reduction of nitric oxide by methane (CH4-SCR). Reduction-oxidation treatments led to close contact and interaction between Cr and In species in these zeolites, as revealed by transmission electron microscopy and X-ray photoelectron spectroscopy. Compared to monometallic Cr/H-SSZ-13 and In/H-SSZ-13, the bimetallic catalyst system exhibited dramatically enhanced CH4-SCR performance, i.e., NO conversion greater than 90% and N2selectivity greater than 99% at 550 °C in the presence of 6% H2O under a high gas hourly space velocity of 75 000/h. The bimetallic Cr-In/H-SSZ-13 showed very good stability in CH4-SCR with no significant activity loss for over 160 h. Catalytic data revealed that CH4and NO were activated on the In and Cr sites of Cr-In/H-SSZ-13, respectively, both in the presence of O2during CH4-SCR.

Two stable 3D polyoxometalate-based metal–organic frameworks (PMOFs), [CuI12(trz)8(H2O)2][α-SiW12O40]·2H2O (1) and [CuI12(trz)8Cl][α-PW12O40] (2) (Htrz = 1-H-1,2,4-triazole) based on Keggin-type POMs were successfully obtained and fully characterized. The basic building units of the two PMOFs are [CuI12(trz)8], but polyoxoanion (POA) template effect leads to different structures and properties: 1represents an interesting example that [α-SiW12O40]4–locate in the nine-membered Cu-trz rings through Cu···O weak interactions to form a 3D framework, whereas 2shows a 3D structure constructed from 2D bilayer cationic network [CuI12(trz)8Cl]3+and [α-PW12O40]3–lying in the adjacent layers via Cu···O weak interactions. PMOF 1as unusual visible-light photocatalyst exhibit significantly enhanced photocatalytic activity under visible-light and excellent stability during the photocatalysis process for recovering and recycling, as well as photocatalytic hydrogen evolution activity.

The selective catalytic hydrogenation of carboxylic acids is an important process for alcohol production, while efficient heterogeneous catalyst systems are still being explored. Here, we report the selective hydrogenation of carboxylic acids using earth-abundant cobalt oxides through a reaction-controlled catalysis process. The further reaction of the alcohols is completely hindered by the presence of carboxylic acids in the reaction system. The partial reduction of cobalt oxides by hydrogen at designated temperatures can dramatically enhance the catalytic activity of pristine samples. A wide range of carboxylic acids with a variety of functional groups can be converted to the corresponding alcohols at a yield level applicable to large-scale production. Cobalt monoxide was established as the preferred active phase for the selective hydrogenation of carboxylic acids.

Bimetallic Pt–Sn catalysts supported on dealuminated Si-beta zeolite were prepared viawet impregnation and the nanoscale close contact between Pt and Sn species in Pt–Sn/Si-beta was confirmed by electron microscopy analyses. Characterization results from temperature-programmed reduction by hydrogen (H2-TPR) and X-ray photoelectron spectroscopy (XPS) indicated the interaction between Pt and Sn species, and the electron transfer from SnO2to Pt species was clearly demonstrated by the XPS and FTIR spectra of CO adsorption. The as-prepared bimetallic Pt–Sn/Si-beta catalyst exhibited remarkable performance in the oxidative dehydrogenation of propane (ODHP), in great contrast to monometallic Pt/Si-beta and Sn/Si-beta. Typically, a stable propane conversion of 37% and a propylene selectivity of 75% could be simultaneously achieved on 0.5Pt–5Sn/Si-beta at a reaction temperature of 773 K. Temperature-programmed desorption experiments revealed that the propane adsorption significantly strengthened while the propylene adsorption weakened on the bimetallic Pt–Sn/Si-beta catalyst, which accordingly resulted in its remarkable performance in ODHP reaction. The spatial separation of Pt and Sn species was observed on the used Pt–Sn/Si-beta catalyst and it was responsible for the catalytic deactivation.

A direct hydrothermal synthesis approach to Fe/ZSM-5 zeolites was developed by using a ferric complex, i.e.ethylenediaminetetraacetic acid ferric sodium (EDTA-FeNa), as both an iron source and a structure-directing agent. During the hydrothermal synthesis, EDTA-FeNa complexes were encapsulated within zeolite channels of ZSM-5 and they underwent transformation to highly dispersed extraframework iron species, i.e.isolated ferric ions and oligomeric FexOyclusters, upon calcination removal of organic species. The as-prepared Fe/ZSM-5 zeolites could be established as bi-functional catalysts containing both acid sites and iron sites. As expected, the as-prepared Fe/ZSM-5 zeolites exhibited remarkable catalytic activity in the selective reduction of nitrogen oxides by ammonia (NH3-SCR), with a nitrogen oxide conversion of >99% in a wide temperature range of 573–693 K under simulated industrial conditions. Meanwhile, good stability and tolerance to water vapor and sulfur dioxide could be achieved, making these Fe/ZSM-5 zeolites promising candidates for practical application. In contrast to conventional post-synthesis modification approaches to Fe/ZSM-5, the one-pot hydrothermal synthesis approach appeared to be very simple and easily reproducible, and the formation of inactive iron oxide nanoparticles can be completely avoided, which accordingly leads to high NH3-SCR activity.

Low-silica AlPO-34 materials with similar crystal sizes but different Brønsted acid site densities were prepared and investigated as catalysts in methanol-to-olefin (MTO) conversion. The effect of Brønsted acid site density on catalyst activity and the dominant reaction mechanism during the MTO conversion was investigated viaTGA, GC-MS, solid-state NMR spectroscopy, and in situUV/vis spectroscopy together with the catalytic performance. For the catalysts with lower Brønsted acid site densities, the olefin-based cycle mechanism is the dominant mechanism during the MTO conversion. Long-chain alkenes, e.g., C5–C6alkenes, act as intermediates that are cracked to lower olefins, or are converted to dienes viahydride transfer reactions, and can also diffuse out of the cages of low-silica AlPO-34 catalysts as the products. With decreasing Brønsted acid site density or reaction temperature, the methylation route of the olefin-based cycle was found to be much more favored than the cracking route. Therefore, a higher selectivity to C5–C6alkenes (∼50%) is achieved. Simultaneously, dienes are the predominant deposits occluded in the used catalysts. For catalysts with slightly higher Brønsted acid site densities, the long-chain alkenes are rapidly transformed to aromatics and, subsequently, an aromatic-based cycle mechanism contributes to the MTO conversion. Interestingly, the catalyst with the most suitable Brønsted acid site density can well balance the above-mentioned two reaction cycles accompanied by a low deactivation rate, leading to a long catalyst lifetime of up to 15 h.

Al-free Fe-beta was prepared from commercial H-beta viaa post-synthesis solid-state metallation route and applied as a promising catalyst for selective catalytic reduction of nitric oxide by ammonia. NH3-TPD and FTIR spectroscopy of pyridine adsorption analysis results clearly verify the absence of Brønsted acid sites and the formation of strong Lewis acid sites in the as-prepared Fe-beta zeolite. Isolated ferric ions within a zeolite framework are determined to be the dominating iron species in Fe-beta according to the characterization results from TEM, H2-TPR and UV-vis spectroscopy, and these Fe species are exposed and available for reaction as indicated by FTIR spectroscopy of NO adsorption. Fe-beta exhibited good catalytic activity in NH3-SCR reaction at >573 K, comparable with reference Fe–H-beta prepared viaa solid-state ion exchange route, in the presence of SO2and excess H2O. More importantly, Fe-beta exhibited distinctly better durability in NH3-SCR than reference Fe–H-beta, and a nitrogen oxide conversion of >90% at a reaction temperature of 673 K could be maintained for over 400 h. The remarkable durability of Fe-beta is due to the absence of framework aluminum species and the stabilization of active iron species by the zeolite framework. The reaction mechanism of NH3-SCR over an Fe-beta model catalyst with well-defined active iron sites was finally investigated by means of in situDRIFT spectroscopy.

Ce(IV)-containing zeolite Beta was successfully prepared by a reproducible and scalable two-step post-synthesis strategy. This consists of creating vacant T sites that are associated with silanol groups by the dealumination of the H-Beta zeolite and a subsequent dry impregnation of the resultant Si-Beta zeolite with cerium (IV) isopropoxide. XRD, FT-IR, UV-Vis and 1H MAS NMR confirmed that Ce(IV) was successfully incorporated into the Beta zeolite framework by the post-synthesis procedures and that they exist as isolated atoms with tetrahedral coordination. The mechanism of Ce incorporation into the framework of Beta zeolite was confirmed by DRIFT spectroscopy. The ring-opening hydration of epoxides to their corresponding 1,2-diols was selected as a model reaction for an evaluation of the catalytic performance of the as-synthesized Ce-Beta zeolite.

Tantalum pentoxide (Ta2O5) nanorods were hydrothermally synthesized using polyethylene glycol (PEG) as a guiding agent. The nanorods were characterized by X-ray diffraction, scanning and transmission electron microscopies, and diffuse reflectance ultraviolet-visible and photoluminescence spectroscopies. The effects of crystallization duration and Ta2O5/Sr(OH)2ratio on the product morphology were investigated, and a growth mechanism was proposed. Phase-pure Ta2O5nanorods with controlled morphology were formed in the presence of PEG and Sr(OH)2, which was necessary to form the nanorods. Sr(OH)2induced the surface dissolution and re-growth of Ta2O5. PEG induced the anisotropic growth of Ta2O5by acting as a capping agent. The products were used to photocatalytically degrade rhodamine B under ultraviolet irradiation. The catalytic activity directly correlated with the length-diameter ratio of the Ta2O5nanorods. A maximum apparent reaction rate constant of 0.156 min−1was obtained. The Ta2O5nanorods were stable during photocatalytic reaction and could be recycled several times without loss of activity.

The formation and evolution of initial reaction intermediates as well as the reaction mechanism during the early period of the methanol conversion on the silicoaluminophosphate SAPO-41 with one-dimensional and 10-numbered ring pore system was elucidated. According to in situ UV–vis spectroscopy, the formation and nature of intermediates formed on the catalysts in the methanol conversion process were monitored. The intermediates remaining on the catalysts after quenching the methanol conversion were determined by ex situ UV–vis, 1H MAS NMR, and 13C MAS NMR spectroscopy, and the reactivity of these species was investigated by adsorption of ammonia and subsequent solid-state NMR spectroscopy. The above-mentioned spectroscopic studies gave a detailed mechanistic insight into the induction period of the methanol conversion on SAPO-41. Monoenylic carbenium ions, being the dominating species during the initial period of the methanol conversion, were rapidly formed and gradually transferred to dienylic carbenium ions, benzene-based carbenium ions, and trienylic carbenium ions, in addition to three-ring compounds and dienes with different chain lengths. On the basis of these spectroscopic observations and the catalytic results, the olefin-based reaction cycle is disclosed to be the dominating reaction mechanism in the initial period of the methanol conversion on SAPO-41.

In the present work, the mechanism of the methanol-to-hydrocarbon (MTH) conversion over the silicoaluminophosphate SAPO-41 with one-dimensional 10-ring pores has been investigated. For this purpose, catalytic experiments with co-feeding of reactants, in situFTIR and UV/Vis spectroscopy, and 1H MAS NMR spectroscopy of used catalysts upon loading of ammonia were performed. Using these methods, only a low content of aromatics could be observed on the working SAPO-41 catalyst. These findings and the characteristic changes in the ethene selectivity during the co-feeding experiments indicate that alkylaromatics can be excluded as active hydrocarbon pool compounds on SAPO-41 applied as MTH catalysts. On the other hand, dienes and enylic carbenium ions were detected using FTIR and UV/Vis spectroscopy and the formation of amines by reaction of alkenes with ammonia was detected via1H MAS NMR spectroscopy. These results are experimental evidence that large olefins partially existing in their carbenium state dominate the catalytically active hydrocarbon pool on the working SAPO-41. Due to this dominant alkene-based reaction mechanism and the limited formation of aromatics, SAPO-41 is a suitable catalyst for the C3+C4olefin as well as gasoline production.

Fe–MFI prepared by reductive solution ion-exchange was investigated as catalyst for the oxidative dehydrogenation of propane with nitrous oxide, and a maximal propylene yield of ca.14% could be obtained at the reaction temperature of 673 K. Accumulative acid post-treatments were performed on Fe–MFI and a gradual increase of maximal propylene yield to ca.25% could be observed. The Fe–MFI samples before and after acid post-treatments were characterized by means of ICP, XRD, DRIFT, TEM, UV-Vis, H2-TPR, NH3-TPD and EPR. The results clearly indicated the transformation of iron species during acid post-treatments. The active iron species in Fe–MFI before and after acid post-treatments were characterized by FTIR spectra of NO adsorption. Based on the characterization and catalytic results, the extra-framework Fe–O–Al species and/or isolated iron species in Fe–MFI were proposed to be more active than oligonuclear iron species for propane dehydrogenation with nitrous oxide.

A series of Me/TiO2samples (Me = V, Cr, Mn, Fe, Co, Ni, Cu and Zn) with designed Me : TiO2ratio of 1 : 10 were prepared by a photodeposition method and studied for the oxidation of CO. The Cu/TiO2catalyst exhibited remarkably high activity and an overall CO oxidation could be achieved at <100 °C. The effects of activation temperatures, GHSV and initial CO concentration on CO oxidation over Cu/TiO2were further investigated. XRD, TEM, XPS-AES, H2-TPR and FTIR of CO adsorption were employed to characterize Cu/TiO2samples and the exact composition of Cu/TiO2prepared by photo-deposition was determined to be Cu–Cu2O/TiO2. Based on the catalytic and characterization results, the possible mechanism for CO oxidation over Cu–Cu2O/TiO2was discussed. Finally, the durability and deactivation of Cu–Cu2O/TiO2during CO oxidation was investigated in time-on-stream reaction.

Pool yourself together:SAPO‐46 is studied as a catalyst for the methanol‐to‐olefins (MTO) reaction (see figure), which is generally accepted to occur by a hydrocarbon pool mechanism. The organic impurities, which originate from the incomplete combustion of the organic template, play a key role in the MTO reaction.

Size-controlled and coated magnetite nanoparticles with glucose and gluconic acid have been successfully synthesized via a simple and facile hydrothermal reduction route using a single iron precursor, FeCl3, and a combination of the inherent chemical reduction capability of sucrose decomposition products and their inorganic coordinating ability. The particle size can be easily controlled in the range of 4−16 nm. Results obtained with and without the addition of sucrose indicate that sucrose is required for the formation of nanoscale and coated magnetite instead of the much larger hematite. Mass spectrometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetry analysis were used to investigate the formation mechanism of the coated nanomagnetite from the single Fe(III) precursor in sucrose. Sucrose acts as a bifunctional agent: (i) it decomposes into reducing species, causing partial reduction of the Fe3+ions to Fe2+ions as required for the formation of Fe3O4and (ii) acts as the source of a capping agent to adjust the surface properties and enable the formation of nanoscale particles. The saturation magnetization of the as-obtained magnetite is measured and greatly related to the particle size.

Material based emerging separation techniques are attracting more and more attention as alternatives to the traditional ones such as distillation and extraction, aiming to reduce the energy consumption and pollutant emissions. Due to their structure characteristics, zeolites can act as versatile sieves and adsorbents for molecules and have been successfully applied in some very important separation processes. Herein, two major catalogues of zeolite separations, namely membrane separation and adsorptive separation, are discussed and their underlying mechanisms are focused. In the part of membrane separation, the synthesis strategies toward zeolite membranes are introduced and the uniformly-oriented zeolite membranes are emphasized. In the part of adsorptive separation, the industrial and popular adsorptive separations with the corresponding zeolite adsorbents are summarized. Generally, membrane separation relies on the molecular diffusion behavior within zeolites while adsorptive separation relies on the guest-host interaction in principle. The key challenges and misconceptions in zeolite separations are highlighted throughout the article.

A novel and facile β-cyclodextrin-assisted method has been employed in this study to prepare superparamagnetic Fe 3O 4nanoparticles from a single iron precursor of FeCl 3·6H 2O. Various characterization involving X-ray diffraction (XRD), standard and high-resolution transmission electron microscopy (TEM and HRTEM), electron diffraction (ED), and Raman spectroscopy has integrally testified the formation of pure magnetite nanoparticles with homogeneous morphology. The size of nanoparticles can be adjusted from 4 to 17 nm by varying the concentration of β-cyclodextrins. The success is ascribed to in situ formation of reducing sugar originating from the self-decomposition of β-CD under the reaction conditions, which partly reduces Fe 3+ions into Fe 2+ions for final formation of Fe 3O 4. Another function of β-CD is also discussed: that it acts as a coating agent to prevent particle growth and agglomeration, which allows the formation of nanoscale and superparamagnetic magnetite with different particle sizes. The saturation magnetization ( Ms) of the as-obtained magnetite is measured and is strongly related to the particle size.