Zeolite Channels Research Articles

Converting Spent LiFePO4 Battery into Zeolitic Phosphate for Highly Efficient Heavy Metal Adsorption.

Developing efficient recycling technologies for large-scale spent batteries is the key to build a zero-waste city. Herein, a [Al8.5Fe0.5P12O48]·[C24H72N16]·[Li·4H2O]·[12H2O] (AlFePO-Li) zeolite, crystallizing in space group I4̅3m with a = 16.6778(3) Å, has been constructed via the hydrothermal treatment of spent LiFePO4 battery. Benefiting from the three-dimensional 12-member-ring channels in its structure and chemical adsorption, excellent Pb2+ removal capacity up to 723.8 mg g-1 has been achieved. Detailed adsorption mechanism study revealed that the cation exchange capacity is significantly contributed by ion exchange of the protonated organic amine cations in the zeolite channel and the protons from the framework dangling phosphate group. This work demonstrates a novel method of reutilizing spent LIBs to construct zeolite for heavy metal removal. It is of great importance to achieve sustainable development based on the "resource utilization" and "trash-to-treasure" strategy.

Effects of Different Types of Zeolites on the Degradation Kinetics of Malathion Pesticide in Water

The study examined the effects of selected types of zeolites as an environmentally benign and friendly way to degrade, S-1, 2-bis (ethoxycarbonyl) ethyl O, O-dimethylphosphorodithioate (malathion), used as a model pesticide, from river water. The effect of the size of zeolite channels and dimensionality (such as 1D, 2D, and 3D), Si/Al ratio, and operating pH were studied to find a suitable type of zeolite and conditions to optimize the pesticide degradation. Mordenite (MOR (1D): Si/Al=6.83, and Si/Al=10.72), ferrierite (FER (2D): Si/Al=10.71), ZSM-5 (MFI (3D): Si/Al=6.83 and Si/Al=10.72) and USY (FAU (3D): Si/Al=2.77) zeolites were individually mixed with a water sample collected from Monjolinho River in São Carlos (SP), Brazil and the degradation trend studied. The results showed that all the zeolites accelerated the degradation of malathion. Nevertheless, lower zeolite Si/Al ratio and larger 3D channels or cavities had a positive influence on the degradation rate. The FAU zeolite presented the stronger degradation of the malathion with a half-life of 16.5 followed by ZSM-5 with 24.8, ferrierite with 29.7, and finally mordenite with 30.3 hours.

Direct observation of the active sites in methane dehydroaromatization by NMR

Direct observation of the active sites in methane dehydroaromatization by NMR

Molecular dynamics study on water and ions transport mechanism in nanometer channel of 13X zeolite

Understanding the atomistic transport within nanoporous zeolite is essential in a broad field. Herein, molecular dynamics was systematically utilized to elucidate the migration mechanism of pure water and NaCl solution in the 13X zeolite. At nano-scale level, molecular simulation clearly distinguishes the wetting and saturating stages of water transport in porous zeolite. The interior skeleton of 13X zeolite provides plenty of oxygen sites with strong polarity, which attracts frontier water molecules to infiltrate the hydrophilic zeolite surface rapidly in nearly 2 ns. The ladder-like ingress curve for water molecules highlight the discontinuous remain-jump wetting process that is induced by the competition adsorption with oxygen sites between the subsequent water molecules and the front water molecules. Initial wetting on interior surface reduces significantly the permeability of subsequent water transport. Furthermore, the penetrated water molecules, competing oxygen sites with extra-framework cations, can cause cations to exhibit different hydration behavior. Additionally, the permeability of water flux throughout zeolite channel is reduced by 10% as the Na+ and Cl- are incorporated in solution. Na+ with large hydration shells are sieved by bottlenecks formed by the windows of 12-ring structure with a diameter of 7.38 Å. The accumulated Na+ at the entrance region associate with neighboring water molecules and hydroxyl oxygen atoms to form hydrated clusters and ionic pairs, which plays as a physical barrier in blocking water transport. Decoding of the transport mechanism of water and salt solutions in zeolites at the molecular level facilitates breaking the existing upper limit of energy storage density and water treatment efficiency.

Dual Active Sites on Molybdenum/ZSM-5 Catalyst for Methane Dehydroaromatization: Insights from Solid-State NMR Spectroscopy.

Methane dehydroaromatization (MDA) on Mo/ZSM-5 zeolite catalyst is promising for direct transformation of natural gas. Understanding the nature of active sites on Mo/ZSM-5 is a challenge for applications. Herein, using 1 H{95 Mo} double-resonance solid-state NMR spectroscopy, we identify proximate dual active sites on Mo/ZSM-5 catalyst by direct observation of internuclear spatial interaction between Brønsted acid site and Mo species in zeolite channels. The acidic proton-Mo spatial interaction is correlated with methane conversion and aromatics formation in the MDA process, an important factor in determining the catalyst activity and lifetime. The evolution of olefins and aromatics in Mo/ZSM-5 channels is monitored by detecting their host-guest interactions with both active Mo sites and Brønsted acid sites via 1 H{95 Mo} double-resonance and two-dimensional 1 H-1 H correlation NMR spectroscopy, revealing the intermediate role of olefins in hydrocarbon pool process during the MDA reaction.

Dual Active Sites on Molybdenum/ZSM‐5 Catalyst for Methane Dehydroaromatization: Insights from Solid‐State NMR Spectroscopy

AbstractMethane dehydroaromatization (MDA) on Mo/ZSM‐5 zeolite catalyst is promising for direct transformation of natural gas. Understanding the nature of active sites on Mo/ZSM‐5 is a challenge for applications. Herein, using1H{95Mo} double‐resonance solid‐state NMR spectroscopy, we identify proximate dual active sites on Mo/ZSM‐5 catalyst by direct observation of internuclear spatial interaction between Brønsted acid site and Mo species in zeolite channels. The acidic proton–Mo spatial interaction is correlated with methane conversion and aromatics formation in the MDA process, an important factor in determining the catalyst activity and lifetime. The evolution of olefins and aromatics in Mo/ZSM‐5 channels is monitored by detecting their host–guest interactions with both active Mo sites and Brønsted acid sites via1H{95Mo} double‐resonance and two‐dimensional1H–1H correlation NMR spectroscopy, revealing the intermediate role of olefins in hydrocarbon pool process during the MDA reaction.

Confinement of subnanometric PdCo bimetallic oxide clusters in zeolites for methane complete oxidation

• A strategy of encapsulating PdCo clusters into MFI zeolite channels is developed. • PdCo clusters (0.4–0.6 nm) are encapsulated into sinusoidal channels of MFI zeolite. • Co improves the activity of surface oxygen and modulates electronic state of Pd. • PdCo@MFI exhibits high activity and H 2 O-resistance stability for CH 4 combustion. Supported Pd-based catalysts are widely used for various catalytic transformations, but steam-induced sintering remains a critical issue for industrial application. Here, we report a strategy of encapsulating PdCo bimetallic oxide clusters (0.4–0.6 nm) into sinusoidal channels of MFI zeolite used for methane complete oxidation. The introduction of Co species promotes the activation of surface oxygen species and modulates electronic state of Pd species, effectively enhancing the catalytic performance with the lowest temperature of CH 4 complete conversion obtained at 435 °C in the presence of steam. Meanwhile, the PdCo particle size and catalytic activity are remained on PdCo@MFI after 20 h at 420 °C in the presence of steam, much more stable than that of reference catalysts (PdCo/ZSM-5, drop 19% and PdCo/Al 2 O 3 , drop 22%). The strategy of confining bimetallic clusters into zeolites to enhance the activity and stability broadens the avenue to designing better catalysts for methane complete oxidation.

Coking mechanism of Mo/ZSM-5 catalyst in methane dehydroaromatization

Methane dehydroaromatization is a potential technique in converting natural gas into value-added aromatics and clean hydrogen. However, severe coking hinders industrial application of conventionally prepared Mo/ZSM-5 catalyst for methane dehydroaromatization. Usually, Bronsted acid sites (BAS) were considered the key for coking. To gain deeper insight into the coke, here we present a simple post-impregnation of Na+ to Mo/HZSM-5 to regulate its surface acidity. Influences of BAS on catalytic performance and coking behavior were thus exclusively studied. Na+ modified catalysts exhibit lower naphthalene and higher C2 selectivity, while selectivity for benzene is not obviously changed. These results contradict conventional bi-functional pathway that methane is dehydrogenated on Mo while BAS act as the center for intermediates cyclization. Characterizations and calculations indicate restricted growth of hydrocarbon pools confined in zeolite channels of Na+ modified catalysts. Hence, it is proposed that aromatization is the intrinsic property of Mo, and the Mo-associated carbonaceous species act as precursors for both coke and aromatics production.

Pure‐silica MFI zeolite membrane by cooperative templating approach for ethanol‐water separation

AbstractPure‐silica MFI zeolite membrane composed of intergrown four prism crystals was fabricated by using tetrabutylammonium (TBA+) and tetraethylammonium (TEA+) as cooperating templates and the induced function of MFI seeds under synthesis solution with molar composition of 1TEOS:0.2TBAOH:0.2TEABr:180H2O. The ethanol/water separation factor was 64 with a flux of 1.40 kg m−2 hr−1 for 5 wt% ethanol/water mixture at 60°C. In contrast, single TBAOH and TEAOH template led to formation of uncontinuous MEL and MFI membrane respectively, without ethanol‐selectivity. The behavior of quaternary ammonium (TBA+ and TEA+) varied in different system: (a) In “TBA++ TEA+” system, TBA+ and TEA+ were incorporated into MFI zeolite channel simultaneously; (b) In “TPA++ M+” system (M = TEA or TBA), either TEA+ or TBA+ could not be occluded into channel, however, appropriate amount of TBA+ could accelerate membrane crystallization, meanwhile increase in TEA+ slowed down crystallization rate of MFI membrane. This work extends the alternative preparation approaches of ethanol perm‐selective MFI membrane.

Superior Hg0 capture performance and SO2 resistance of Co-Mn binary metal oxide-modified layered MCM-22 zeolite for SO2-containing flue gas.

A Co-Mn binary metal oxide-modified layered MCM-22 zeolite was designed to capture gaseous elemental mercury (Hg0) from SO2-containing flue gas. The physicochemical properties of the Co-Mn/MCM-22 zeolite were characterized by XRD, FESEM, TEM, and XPS, and the results showed that MnO2 was highly dispersed on the surface and in the channel of MCM-22 zeolite. Co3O4 was loaded onto the surface of the MCM-22 zeolite via the stepwise ion exchange method to prevent SO2 poisoning of the MnO2 active site. The Hg0 removal efficiency increased from 54 to 83% at 300°C with 10% Co loading on the 5% Mn/MCM-22 zeolite when 200ppm of SO2 was introduced to the flue gas. The mechanism of Hg0 removal was mainly associated with catalytic oxidation and chemisorption. Mn4+ was the main active site for catalytic oxidation of Hg0 to Hg2+, and the surface adsorbed oxygen re-oxidized Mn3+ and combined with Hg2+ to form Hg-O-Mn, in which Mn acted as a bridge. Co3+ preferentially reacted with SO2 to form CoSO4, thereby protecting the Mn active sites for Hg0 capture. Therefore, Co-Mn/MCM-22 zeolite is a promising sorbent for the removal of Hg0 and SO2 resistance from SO2-containing flue gas.

Crystal Structures of Rb- and Ag-Substituted Forms of Natural Zeolite Amicite

The crystal structures of ion-exchange products of the zeolite-group mineral amicite from Khibiny Alkaline Massif with silver and rubidium salts have been studied. The investigated samples are monoclinic (sp. gr. P21 and I2/a); their crystallochemical formulas (Z = 1) are Ag8(Al8Si8O32) ⋅ 10.6H2O and K0.4Na0.7Rb6.9(Al8Si8O32) ⋅ 4.5H2O; the unit cell parameters are a = 9.272(2) and 10.043(2) A, b = 9.997(2) and 9.748(2) A, c = 10.380(3) and 10.265(2) A, β = 90.821(8)° and 90.09(3)°, V = 962.0(4) and 1005.0(3) A3, respectively. In the Ag-amicite structure, 22 partially occupied sites of the extra-framework components (Ag and H2O) are localized. In the Rb-amicite structure, most of rubidium atoms are located in two sites with the occupancies of 0.414(6) and 0.389(5). The cross-sectional areas of the zeolite channels are 3.5 × 4.5 and 2.3 × 6.3 A2 for Ag-amicite and 3.0 × 4.3 and 3.0 × 3.9 A2 for Rb-amicite.

A highly hydrated variety of elpidite from the Khibiny alkaline complex, Kola Peninsula, Russia

AbstractAn unusual highly hydrated and Na-depleted variety of elpidite was identified in a hydrothermally altered peralkaline pegmatite at Mt. Yukspor in the Khibiny alkaline complex, Kola Peninsula, Russia. It differs from ‘ordinary’ elpidite, ideally Na2ZrSi6O15⋅3H2O, in its crystal chemical features, infrared spectrum and optical characteristics. The chemical composition (wt.%, electron microprobe, H2O by TGA) is: Na2O 5.45, K2O 0.67, CaO 0.05, SiO2 60.32, TiO2 1.34, ZrO2 18.43, Nb2O5 0.65, H2O 12.80, total 99.71. The empirical formula calculated on the basis of 6 Si and 15 O atoms is [(Na1.05K0.08Ca0.01)Σ1.14(H3O)0.74]Σ1.88(Zr0.89Ti0.10Nb0.03)Σ1.02Si6O15⋅3.47H2O; the H2O:H3O ratio was calculated from the charge balance requirement, taking into account the results of crystal structure refinement. The highly hydrated variety of elpidite is orthorhombic, Pma2, a = 14.5916(6), b = 7.3294(3), c = 7.1387(2) Å, V = 763.47(5) Å3 and Z = 2. The crystal structure was solved from single-crystal X-ray diffraction data, R1 = 3.43%. The structure is based upon an elpidite-type heteropolyhedral Zr–Si–O framework with Na+ and H3O+ cations and H2O molecules in the zeolitic channels. Hydronium cations substitute for water molecules in one of the extra-framework sites. This variety of elpidite could be considered as an intermediate product of natural ion-exchange reaction between ‘ordinary’ elpidite and a low-temperature hydrothermal fluid.

Zika Virus Field Effect Transistor

A unique field-effect transistor with an active channel composed of aptamers designed to bind to the Zika virus was fabricated. To immobilize the aptamers in the device channel, we used gold nanoparticles (AuNPs), a 20-40 nm thin film of sputtered gold (Au film), and a molecular sieve material zeolite. The aptamers were functionalized with a thiol end group that enabled them to bind with gold and most other materials. In the case of aptamer/AuNP, when Zika was added to the channel it reduced the channel conductivity from 4.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> S/cm to 3.7 S/cm. The gate field effect clearly showed that the aptamer/AuNP channel is p-type with a relatively large transconductance of 300 μS (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> = 2V) compared to the Zika/aptamer/AuNP channel (also p-type) but with lower transconductance of 2 μ S (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> = 2V). There was large amount of charge trapping (~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) in Zika/aptamer/AuNP channel. In other cases of aptamer/Au film and zeolite channels, there were large changes in the channel conductance when Zika was added. Aptamer/Au and aptamer/zeolite channels were both n-type and their conductivities increased when Zika was added. Combination of AuNP and zeolite biosensing FETs can be used to design complimentary bioFET sensors. We show that the gate voltage in FET biosensors can be used to increase their sensitivity (24 times in Zika/aptamer/AuNP), selectivity and dynamic range (by 10× or more).

L-Lysine Amino Acid Adsorption on Zeolite L: a Combined Synchrotron, X-Ray and Neutron Diffraction Study.

Invited for this month's cover are the groups of Annalisa Martucci and Luisa Pasti at the University of Ferrara (Italy). The cover picture shows L-lysine amino acid adsorption on zeolite L. The role of zeolite channels in the stabilization of the lysine absorbed and the effect of water on protein structure are elucidated at atomistic level. The stabilization of the L α-helical conformation is related to strong H-bonds between the tail aminogroups of lysine molecules and the Brønsted acid site as well as to complex intermolecular H-bond system between water molecules, zeolite and amino acid. Read the full text of their Full Paper at 10.1002/open.202000183.

L-Lysine Amino Acid Adsorption on Zeolite L: a Combined Synchrotron, X-Ray and Neutron Diffraction Study.

Combined neutron and X‐ray powder diffraction techniques highlighted the sorption capacity of the acidic L zeolite towards the L‐lysine amino acid. The role of zeolite channels in the stabilization of the lysine absorbed and the effect of water on protein structure are elucidated at atomistic level. The stabilization of the L α‐helical conformation is related to strong H‐bonds between the tail aminogroups of lysine molecules and the Brønsted acid site as well as to complex intermolecular H‐bond system between water molecules, zeolite and amino acid. This finding is relevant in the catalytic synthesis of polypeptide, as well as in industrial biotechnology by qualitatively predicting binding behaviour

Inorganic–organic hybrids based on sepiolite as efficient adsorbents of caffeine and glyphosate pollutants

Sepiolite clay mineral was functionalized with (3-chloropropyl)triethoxysilane (ClPTES) or 3-[tri(ethoxy/methoxy)silyl] propylurea (TEMSPU) alkoxides and tested as adsorbent for herbicide glyphosate and also of caffeine, two pollutants with very different chemical composition. The materials obtained were characterized by X-ray diffractometry, infrared spectroscopy, thermal analysis, scanning electron microscopy and nitrogen adsorption at −196 °C, and submitted to toxicity and desorption tests. Silane functional groups blocked sepiolite active positions, and adsorption occurred within the zeolitic channels and on the surface of the functionalized solids. Caffeine and glyphosate effectively interacted with urea groups from grafted alkoxide, which could lower the mobility of the adsorbed contaminants. Glyphosate adsorbed on functionalized sepiolite derivatives showed low toxicity.

Elucidating Zeolite Channel Geometry-Reaction Intermediate Relationships for the Methanol-to-Hydrocarbon Process.

The chemical industry has exploited zeolite shape selectivity for more than 50 years, yet our fundamental understanding remains incomplete. Herein, the zeolite channel geometry–reactive intermediate relationships are studied in detail using anisotropic zeolite ZSM‐5 crystals for the methanol‐to‐hydrocarbon (MTH) process, and advanced magic‐angle spinning solid‐state NMR (ssNMR) spectroscopy. The utilization of anisotropic ZSM‐5 crystals enabled the preferential formation of reaction intermediates in single‐orientation zeolite channels, as revealed by molecular dynamics simulations and in situ UV/Vis diffuse‐reflectance spectroscopy. The ssNMR results show that the slightly more constrained sinusoidal zeolite channels favor the olefin cycle by promoting the homologation of alkanes, whereas the more extended straight zeolite channels facilitate the aromatic cycle with a higher degree of alkylation of aromatics. Dynamic nuclear polarization experiments further indicate the preferential formation of heavy aromatics at the zeolite surface dominated by the sinusoidal channels, providing further insight into catalyst deactivation.

Elucidating Zeolite Channel Geometry–Reaction Intermediate Relationships for the Methanol‐to‐Hydrocarbon Process

AbstractThe chemical industry has exploited zeolite shape selectivity for more than 50 years, yet our fundamental understanding remains incomplete. Herein, the zeolite channel geometry–reactive intermediate relationships are studied in detail using anisotropic zeolite ZSM‐5 crystals for the methanol‐to‐hydrocarbon (MTH) process, and advanced magic‐angle spinning solid‐state NMR (ssNMR) spectroscopy. The utilization of anisotropic ZSM‐5 crystals enabled the preferential formation of reaction intermediates in single‐orientation zeolite channels, as revealed by molecular dynamics simulations and in situ UV/Vis diffuse‐reflectance spectroscopy. The ssNMR results show that the slightly more constrained sinusoidal zeolite channels favor the olefin cycle by promoting the homologation of alkanes, whereas the more extended straight zeolite channels facilitate the aromatic cycle with a higher degree of alkylation of aromatics. Dynamic nuclear polarization experiments further indicate the preferential formation of heavy aromatics at the zeolite surface dominated by the sinusoidal channels, providing further insight into catalyst deactivation.

Incorporation of Zinc Oxide Nanoparticles in RHA-MTW Zeolite and its Application for Degradation of Dye

White rice husk ash (RHA), an agricultural waste, was used as a silica source forMTW zeolite synthesis. The RHA-MTW zeolite derived from RHA was preparedby hydrothermal method at 150 °C in the presence of tetraethylammoniumhydroxide. ZnO nanoparticles (NPs) were grown in zeolite substrates using asolid state reaction. The synthesized nanocomposite (NC) was characterized byXRD, SEM, DRS and TEM and tested as photocatalytic degradation of methyleneblue (MB) dye from aqueous solution under ultraviolet (UV) light. The BET resultsindicated that pore volume and surface area of ZnO/RHA-MTW NC was smallerthan RHA-MTW zeolite. On the basis of the obtained experimental results, it wasfound that zinc oxide NPs were encapsulated into the channels of RHA-MTWzeolite. The SEM and TEM images of ZnO/RHA-MTW NC confirmed the formationof RHA-MTW particles with size diameter of 2.5 μm and locating of zinc oxideNPs in channels of zeolite with an average size of between 35 nm. The resultsshowed MB degradation had reached 85 % under UV light. The MB indicatedmaximum adsorption at pH=9. The photocatalytic activity of ZnO was enhancedin the presence of zeolite due to reduction of recombination rate of the electrohole in ZnO semiconductor.ARTICLE INF O

Manganese bridge of mercury and oxygen for elemental mercury capture from industrial flue gas in layered Mn/MCM-22 zeolite

Mn-based oxides have been confirmed to possess gaseous elemental mercury (Hg0) uptake performances. One strategy for Mn-based oxides designing was taking full advantage of surface oxygen to bond surface oxidized mercury. In this study, Mn modified layered MCM-22 zeolite were prepared to get a high dispersion of Mn active sites. The composites were characterized and the results showed that the highly dispersed MnOx particles could be readily deposited on the surface and in the channel of layered MCM-22 zeolite. The results showed 5% Mn/MCM-22 zeolite had a Hg0 removal efficiency of 92% and adsorption capacity of 0.32 mg/g at 300 °C under 5% O2. The mechanism of Hg0 removal is mainly associated catalytic oxidation and chemisorption. Mn4+ is the main active site for Hg0 catalytic oxidation to Hg2+, and Mn4+ is only reduced to Mn3+, some of which is re-oxidized to Mn4+ by active oxygen. The Hg2+ combines with oxygen and form HgO absorbed in the pores of Mn/MCM-22 zeolite. The distribution of Hg elemental was better coincident with Mn elemental which further verified the role of Hg-O-Mn, in which Mn played the role of bridge. Therefore, Mn/MCM-22 zeolite is a promising sorbent for Hg0 removal from flue gas.