Advances in the Synthesis of Crystalline Metallosilicate Zeolites via Interlayer Expansion

Given the numerous industrial applications of zeolites as adsorbents, catalysts, and ion-exchangers, the development of new zeolite structures is highly desired to expand their practical applications. Currently, a general route to develop new zeolite structures is to use interlayer expansion agents to connect layered silicates. In this review, we briefly summarize the novel zeolite structures constructed from the lamellar precursor zeolites MWW, RUB-36, PREFER, Nu-6(1), COK-5, and PLS-1 via interlayer expansion. The contents of the summary contain detailed experiments, physicochemical characterizations, possible expansion mechanisms, and catalytic properties. In addition, the insertion of metal heteroatoms (such as Ti, Fe, Sn) into the layered zeolite precursor through interlayer expansion, which could be helpful to modify the catalytic function, is discussed.

A Study of the Catalytic Properties of Synthetic Aluminosilicates of Different Morphologies in Cracking Reactions of the Byproducts of Isoprene Synthesis

The catalytic activity of synthetic samples of aluminosilicates of various morphologies and chemical compositions in a cascade of reactions that are byproducts (BPs) in the decomposition process of 4,4‑dimethyl-1,3-dioxane is studied. Aluminosilicates with montmorillonite structures (Na0.2Al1.8Mg0.2Si4O10(OH)2⋅nH2O, Mg3Si4O10(OH)2⋅nH2O), and kaolinite (Al2Si2O5(OH)4) with the spherical and platy morphologies of particles, as well as their porous-textural characteristics and surface properties, are studied. It is shown that the specific surface area of the studied samples, depending on the composition, varies from 11 to 470 m2/g, and the content of aluminum oxide in the samples ranged from 0 to 24 wt %. It is found that layered silicates with a montmorillonite structure contribute to reducing the gasification of organic raw materials and increasing the yield of isoprene. Kaolinite with a spherical morphology of particles increases the yield of formaldehyde, and with a platy morphology of particles, it increases the degree of decomposition of heteroatomic and cyclic compounds.

Rb1.66Cs1.34Tb[Si5.43Ge0.57O15]·H2O, a New Member of the OD-Family of Natural and Synthetic Layered Silicates: Topology-Symmetry Analysis and Structure Prediction

Crystals of new silicate-germanate Rb1.66Cs1.34Tb[Si5.43Ge0.57O15]·H2O have been synthesized hydrothermally in a multi-component system TbCl3:GeO2:SiO2 = 1:1:5 at T = 280 °C and P = 100 atm. K2CO3, Rb2CO3 and Cs2CO3 were added to the solution as mineralizers. The crystal structure was solved using single crystal X-ray data: a = 15.9429(3), b = 14.8407(3), c = 7.2781(1) Å, sp. gr. Pbam. New Rb,Cs,Tb-silicate-germanate consists of a [Si5.43Ge0.57O15]∞∞ corrugated tetrahedral layer combined by isolated TbO6 octahedra into the mixed microporous framework as in synthetic K3Nd[Si6O15]·2H2O, K3Nd[Si6O15] and K3Eu[Si6O15]·2H2O with the cavities occupied by Cs, Rb atoms and water molecules. Luminescence spectrum on new crystals was obtained and analysed. A comparison with the other representatives of related layered natural and synthetic silicates was carried out based on the topology-symmetry analysis by the OD (order-disorder) approach. The wollastonite chain was selected as the initial structural unit. Three symmetrical ways of forming ribbon from such a chain and three ways of further connecting ribbons to each other into the layer were revealed and described with symmetry groupoids. Hypothetical structural variants of the layers and ribbons in this family were predicted.

New Flexible Protective Coating for Printed Smart Textiles

In the field of food packaging, the addition of exfoliated layered silicates in polymers has been established to improve the polymers’ gas barrier properties. Using these polymers as coatings to protect smart textiles from oxidation and corrosion while maintaining their textile properties should significantly extend their lifetime and promote their market penetration. The aim of this study was to print new polymer dispersions containing layered silicates to protect screen-printed conductive structures, and to test the resulting samples. For this, appropriate printing parameters were determined by statistical design of experiments. According to these results, conductive structures were printed and protected with the selected coating. The abrasion resistance and the continuity of the protective layer of the printed samples were then measured. A continuous protective coating of approximately 70–80 µm thickness was applied on a conductive structure. The printed samples showed a very high resistance to abrasion (unchanged by 85,000 abrasion cycles) while remaining flexible and presenting a lower water vapor permeability (<2.5 g/m² d) than the coatings commonly used in the textile field.

Polymer/Clay Nanocomposites Produced by Dispersing Layered Silicates in Thermoplastic Melts

Results of the studies of technology, structural features and properties of polymer/clay nanocomposites (n-PCM) prepared by melt compounding of thermoplastic polymers are systematized. Special attention is given to the analysis of the effect of nanoclays modification with surfactants on properties of nanocomposites and preparation features of nanomaterials based on polar, non-polar thermoplastics and polymer blends. Effect of technological factors and special compounding regimes in the technology of n-PCM with advanced technical characteristics is considered. Results of the original studies of the structure and properties of the hybrid composites, filled by high modulus fibers in addition to nanoclays, are presented.

Photophysical Properties and Fluorescence Lifetime Imaging of Exfoliated Near-Infrared Fluorescent Silicate Nanosheets

The layered silicates Egyptian Blue (CaCuSi4O10, EB), Han Blue (BaCuSi4O10, HB) and Han Purple (BaCuSi2O6, HP) emit as bulk material bright and stable fluorescence in the near-infrared (NIR), which is...