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The effect of amorphous aluminosilicate precursor nanoparticles on the formation of nanosized zeolites with faujasite (FAU) and sodalite (SOD) type frameworks is illustrated using a new synthetic strategy to prepare nanosized zeolites with tailored particle size distribution, morphology, and structure. This two‐step synthesis procedure includes the formation of colloidal suspensions followed by separation of the amorphous precursor nanoparticles, and their subsequent transformation into nanosized crystals by treatment with alkali suspensions (NaOH) solutions only. The selective transformation of the amorphous nanoparticles into FAU and SOD nanosized crystals is studied at atomistic and microscopic levels using 29Si and 23Na nuclear magnetic resonanse (NMR) spectroscopy, X‐ray powder diffraction, and N2 physisorption, respectively. The presence of sodalite cages occluding highly mobile sodium in the amorphous nanoparticles is confirmed by 23Na‐1H D‐HMQC NMR spectroscopy. The subsequent treatment of these amorphous precursor particles with aqueous sodium hydroxide illustrates that the cations are not only charge compensators but also inorganic templates stabilizing sodalite cages during the long‐range ordering in the amorphous particles. [ABSTRACT FROM AUTHOR]

FER-type zeolite was recently recognized as good catalyst for DME synthesis via methanol dehydration or one-pot CO2 hydrogenation, in terms of DME selectivity, stability and coke formation. In this research, we investigated the role of crystal size of both FER- and MFI-type zeolites on catalysis of methanol dehydration to DME reaction. The results show that FER-type zeolites, both micro- and nano-sized, exhibit better performances than micro-sized MFI-type zeolite. On the contrary, the application of nano-sized MFI allows to obtain a DME selectivity similar to FER, but with higher DME production rate and a lower coke deposition.

The isotopic substitution in chemistry is characterized by two main effects, i.e., the kinetic isotope effect (KIE), associated with differences in the reaction rates, and the geometric isotope effect (GIE) related to crystallographic features. In this work, considering the difference in the weight of deuterium (D) compared to the weight of hydrogen (H), we use the isotopic substitution to investigate the crystallisation mechanism of template-free nanosized faujasite (FAU) type zeolite in colloidal precursors. Тhe basic hydrothermal synthesis solvent - water (H 2 O), is substituted with heavy water (D 2 O), aiming to understand the isotopic influence and the effect of H-bond networks on the zeolite crystallisation. The crystallinity, viscosity, conductivity, chemical composition, morphology and local order of the FAU zeolites synthesized in both hydrated (H) and deuterated (D) medium are evaluated with X-ray diffraction, TEM microscopy, EDX and ICP analysis, FT-IR and solid-state NMR spectroscopy. The structural directing agent - Na+, exhibits a lower mobility in the deuterated medium, because of a characteristic higher viscosity compared to hydrated medium. This leads to a slower nucleation and crystallisation in the initial stages of hydrothermal treatment in the colloidal suspensions but also to a significant difference in the Al distribution. [Display omitted] [ABSTRACT FROM AUTHOR]

The dealumination of nanosized zeolites is an important scientific problem, which should be solved to improve the activity of catalysts based on this zeolite in a broad range of heterogeneous catalytic reactions, particularly in commercial processes. However, the smaller the required size of the synthesized crystals, the lower the Si/Al ratio and the lower the degree of dealumination of this material can be achieved. In this study, the dealumination of zeolites Y with a crystal size of 50–1100 nm by treatment with ammonium hexafluorosilicate and steam heat treatment is discussed. It is shown that the dealumination with ammonium hexafluorosilicate is a "gentler" method in terms of structure preservation, whereas the dealumination by steam heat treatment provides a higher Si/Al ratio in the products; however, this method is inapplicable for crystals smaller than 500 nm, because it leads to the complete degradation of the structure. However, nanosized crystals can be dealuminated by treating with ammonium hexafluorosilicate. In this case, the degree of dealumination is close to 40%. A significant disadvantage of this method is the formation of a SiO2 film on the crystal surface; this feature substantially restricts the use of the ammonium hexafluorosilicate treatment in the synthesis of cracking catalysts. [ABSTRACT FROM AUTHOR]

The textural, acidic and catalytic properties of nanosized samples of commercial MFI zeolites with SiO2/Al2O3 molar ratios of 30, 50 and 80 supplied by Zeolyst Co. and some synthesized nanocrystallites of MFI zeolites with a SiO2/Al2O3 molar ratio of 55 and 80 were compared. It was shown that the SiO2/Al2O3 ratio had no impact on catalyst deactivation in the slurry reactor as in the conventional fixed-bed reactor. Irreversible deactivation was observed only for the samples with an extremely high external surface Brønsted acidity indicating that near-surface secondary processes are responsible in catalyst deactivation. It was shown that the reaction temperature influenced the product selectivity due to change in the contribution of both hydrogen transfer reaction and arene/alkene circles and can be considered to be an efficient tool of selectivity control for DME conversion in the slurry reactor. [ABSTRACT FROM AUTHOR]

The preparation of responsive multilayered structures with quarter-wave design based on layer-by-layer deposition of sol-gel derived Nb2O5 films and spin-coated MEL type zeolite is demonstrated. The refractive indices (n) and thicknesses (d) of the layers are determined using non-linear curve fitting of the measured reflectance spectra. Besides, the surface and cross-sectional features of the multilayered structures are characterized by scanning electron microscopy (SEM). The quasi-omnidirectional photonic band for the multilayered structures is predicted theoretically, and confirmed experimentally by reflectance measurements at oblique incidence with polarized light. The sensing properties of the multilayered structures toward acetone are studied by measuring transmittance spectra prior and after vapor exposure. Furthermore, the potential of the one-dimensional photonic crystals based on the multilayered structure consisting of Nb2O5 and MEL type zeolite as a chemical sensor with optical read-out is discussed.

Effects of the particle size of a suspended zeolite catalyst based on the commercial MFI-type (high modulus zeolite, HMZ) zeolite on its physicochemical characteristics and catalytic properties in the conversion of dimethyl ether (DME) in a three-phase system with a slurry reactor are studied. In order to gain insight into the relationships between the physicochemical characteristics of MFI-type zeolites and their catalytic properties, the textural, acidic, and catalytic properties of HMZ zeolites and synthesized nanocrystallites of the zeolite with the MFI structure are compared. It was found that, in the conversion of DME in the slurry reactor, the catalytic properties of the MFI zeolite are strongly affected by the size of particles of the suspended catalyst: on passage to nanosized suspensions, the activity of the catalyst grows by several times. Reduction in the size of catalyst particles leads to an increase in the yield of hydrocarbons C and a decrease in the yield of lower olefins. At the same dispersity of suspensions, the catalytic properties of suspended catalysts are considerably affected by the distribution of acid sites over strength in the studied zeolite sample and the fraction of amphoteric sites in them. [ABSTRACT FROM AUTHOR]

Based on a commercial zeolite of the MFI type, nanoparticles have been produced using mechanical methods (grinding in a ball or planetary mill, classification by 'stirring-up') and ultrasonic treatment (UST) of zeolite in water. It has been found by spectral methods (XRD, DRIRS, Al and Si solid-state NMR) and adsorption analysis that the grinding of the zeolite leads to partial degradation of its structure and appearance of defects in the crystalline framework, whereas the zeolite crystal lattice remains completely intact after sonication in the aqueous medium. The sonication destroys MFI agglomerates to form nanoparticles down to 40-50 nm in size. The dispersion of the zeolite nanoparticles in silicone or hydrocarbon oil-(Syltherm 800 or Dowtherm RP, respectively) as a high-boiling-point liquid leads to the formation of ultrafine suspensions, the stability of which depends on the type of the dispersion medium. The nanosized zeolite suspensions are more stable in Dowtherm RP than in Syltherm 800: without agitation, they are persistent for at least 3 weeks (settling at room temperature). [ABSTRACT FROM AUTHOR]

The preparation of responsive multilayered structures with quarter-wave design based on layer-by-layer deposition of sol-gel derived Nb2O5 films and spin-coated MEL type zeolite is demonstrated. The refractive indices (n) and thicknesses (d) of the layers are determined using non-linear curve fitting of the measured reflectance spectra. Besides, the surface and cross-sectional features of the multilayered structures are characterized by scanning electron microscopy (SEM). The quasi-omnidirectional photonic band for the multilayered structures is predicted theoretically, and confirmed experimentally by reflectance measurements at oblique incidence with polarized light. The sensing properties of the multilayered structures toward acetone are studied by measuring transmittance spectra prior and after vapor exposure. Furthermore, the potential of the one-dimensional photonic crystals based on the multilayered structure consisting of Nb2O5 and MEL type zeolite as a chemical sensor with optical read-out is discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Conventional and alternative methods for zeolite synthesis. [•] Parameters governing zeolite synthesis. [•] Crystallization of zeolites from organic- and inorganic-templated suspensions. [•] Zeolite with tunable size- and shape-dependent properties. [•] Zeolites for photovoltaics, sensors, and medical applications. [ABSTRACT FROM AUTHOR]

Abstract: Nanosized ZSM-2 zeolite crystals (∼100nm) with suitable surface acid properties were prepared. ZSM-2 zeolite forms with improved acidity were obtained through thermal deammoniation and steam treatment. Detailed characterization of acidic ZSM-2 zeolite was carried out by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance infrared Fourier transform (DRIFT), nitrogen sorptometry, dynamic light scattering (DLS), thermogravimetry (TGA), potentiometric acidity measurements, and FTIR analysis of pyridine adsorption. Acid properties of ZSM-2 zeolite were significantly improved by conversion into its protonated (H-ZSM-2) and dealuminated (DEAL-ZSM-2) forms, in which bridged Si(OH)Al groups with Brönsted acidity (H-ZSM-2) and aluminium extraframework species with Lewis acid character (DEAL-ZSM-2) are generated. These acidic ZSM-2 zeolite forms also maintain adequate crystalline order and high surface area values, making this nanosized zeolite attractive for catalytic applications. In the context of catalyst supporting materials for the polymerization of olefins, the DEAL-ZSM-2 zeolite form showed Lewis acid properties similar to those of a traditional MAO-modified silica support. Thus, DEAL-ZSM-2 zeolite appears as a promising material to be evaluated as polymerization catalyst support when a reduction of the amount of high-cost MAO cocatalyst is desired. [Copyright &y& Elsevier]

Abstract: The preparation of dealuminated (DEAL) ZSM-2 zeolite nanocrystals for use as an active metallocene polymerization catalyst support is presented. The DEAL-ZSM-2 zeolite form was prepared by using steam treatment; metallocene catalyst was directly supported on the zeolite; and evaluated in the polymerization of ethylene using either methylaluminoxane (MAO) or an alkylaluminun as cocatalysts. In order to elucidate the activator effect of the acidic zeolite support, a detailed material characterization was performed. Metallocene catalyst supported on DEAL-ZSM-2 zeolite exhibited high activity values. The metallocene activation is attributed to the action of soluble cocatalyst (MAO or alkylaluminun) into the reactor and to the activator effect of extraframework aluminum species with strong Lewis acidity existing in the DEAL-ZSM-2 zeolite structure. High external surface area of the nanosized zeolite also contributes to reduce the diffusion effects commonly observed in microsized zeolite supports. The results of this work demonstrate that DEAL-ZSM-2 zeolite support does not necessitate to be treated with MAO previous fixation of the metallocene catalyst, and that polymerization activity can be also achieved using a trialkyaluminum as cocatalyst. Thus, the use of DEAL-ZSM-2 zeolite as metallocene support could contribute to reduce the amount of MAO required for ethylene polymerization. [Copyright &y& Elsevier]

Preparation of nanocrystalline ZSM-5 has been proven possible with carbon matrix by using confined space synthesis. In combination with the hydrothermal method, by the use of a mesoporous carbon nanotube as the inert support material, ZSM-5 with SiO2/Al2O3 ratios of 100 was successfully synthesized with an average crystal size of 27 nm. Their structures were preliminarily characterized by x-ray power diffraction (XRPD) and infrared spectroscopy (IR), and scanning electron microscopy (SEM), respectively. At the same time, we put forward the mechanism about the confined space synthesis in terms of the results. [ABSTRACT FROM AUTHOR]

Partially crystalline and X-ray amorphous ZSM-5 zeolite-based aluminosilicates have been synthesized and thoroughly characterized by chemical analysis, XRD, FT-IR, solid state MAS NMR, N2 adsorption, TEM, NH3-TPD and isopropanol dehydration as the catalytic test reaction. The X-ray amorphous and low-crystallinity samples were hydrothermally synthesized at temperatures as low as 25°C and consisted of nanosized well-formed particles of almost spherical shape and with dimensions of about 20–30nm. These samples exhibited very low microporosity and remarkably high meso/macropore volume (pore diameters ⩾30nm) and/or high external surface area. The first Bragg peaks were observed in the XRD patterns of the samples synthesized at 90°C and their position on the 2θ-axis was the same as those of a reference highly crystalline ZSM-5 zeolite sample. The particle/crystal size and microporosity of the partially crystalline materials increased with increasing hydrothermal synthesis temperature and % relative XRD crystallinity. Incorporation of aluminum in the ZSM-5 zeolitic framework was significantly enhanced at higher relative crystallinities, i.e. >60%. The X-ray amorphous aluminosilicates possessed tetrahedral aluminum atoms which were more zeolitic in character and induced a higher number of acidic framework hydroxyls (Brønsted acid sites), as compared to those found in a conventional silica–alumina. [Copyright &y& Elsevier]

Thin microporous films with MFI type structure were deposited on silicon wafers via the seed method and spin coating of a stable colloidal mixture containing nanosized zeolites. The seed method includes adsorption of nanosized MFI seed crystals followed by hydrothermal synthesis of the seeds in order to obtain an intergrown film with a thickness of about 250 nm. In addition, thin MFI porous films with similar thicknesses were prepared by spin coating of stable colloidal suspensions and are compared with the seeded and grown layers. The diffractograms of the MFI films at grazing incidence and exit geometry were measured, which reflect the distribution of the crystal orientation along the film thickness. Preferred orientation of porous materials in the films is attributed to the deposition techniques and morphological features of the zeolite nanoparticles. The MFI adsorbed seeds and spin-deposited crystals are preferentially oriented with their a-axis perpendicular to the substrate, while the crystals in the grown film show an orientation change from the a- to the b-axis perpendicular to the substrate as a function of the film thickness. [Copyright &y& Elsevier]

FER-type zeolite was recently recognized as good catalyst for DME synthesis via methanol dehydration or one-pot CO 2 hydrogenation, in terms of DME selectivity, stability and coke formation. In this research, we investigated the role of crystal size of both FER- and MFI-type zeolites on catalysis of methanol dehydration to DME reaction. The results show that FER-type zeolites, both micro- and nano-sized, exhibit better performances than micro-sized MFI-type zeolite. On the contrary, the application of nano-sized MFI allows to obtain a DME selectivity similar to FER, but with higher DME production rate and a lower coke deposition. Unlabelled Image • MFI- and FER-zeolites with different crystal size were synthesised. • The effect of crystal size on methanol-to-DME reaction was studied. • The reduction of crystal size improves DME production rate. • The reduction of crystal size delays coke formation. • Nano-sized MFI shows promising catalytic performances. [ABSTRACT FROM AUTHOR]

Approaches able to counteract, at least temporarily, hypoxia, a well-known factor of resistance to treatment in solid tumors are highly desirable. Herein, we report the use of nanosized zeolite crystals as hyperoxic/hypercapnic gas carriers for glioblastoma. First, the non-toxic profile of nanosized zeolite crystals in living animals (mice, rats and non-human primates) and in various cell types is presented. Second, the ability of the nanosized zeolites to act as a vasoactive agent for a targeted re-oxygenation of the tumor after intravenous injection is shown. As attested by an MRI protocol, the zeolites were able to increase oxygenation and blood volume specifically within the brain tumor whilst no changes in the healthy-non tumoral brain-were observed. The first proof of concept for the use of metal-containing nanosized zeolites as a tool for vectorization of hyperoxic/hypercapnic gases in glioblastoma is revealed. Image 1 • Nanosized zeolites show a great affinity to O 2 and CO 2 for in vivo applications. • Nanozeolites are safe in rodents and non-human primates. • Specific accumulation of nanozeolites in the tumor relative to the healthy brain. • Gas-loaded zeolites induce a targeted increase in blood volume in glioblastoma. [ABSTRACT FROM AUTHOR]