Nanoporous Zeolite Research Articles

English

A laboratory study was undertaken to improve the nitrogen (N) use efficiency of urea using microporous natural zeolite (Z) and nanoporous zeolite (NZ) as substrate. The fertilizer composite was prepared under ambient conditions by impregnation urea in adsorbents. Z and nanoporous-zeolite measuring a dimension of 794, 87 nm were used for this study. The commercial urea fertilizer and adsorbents were blended or fused at varying w/w ratios of 1:1 to 1:10 using simple liquid immersion with hydrothermal technique. The 1:1 ratio of natural zeolite: urea and NZ: urea registered the highest total N content of 18.5 and 28%, respectively. The adsorbents and fabricated fertilizers such as zeourea (ZU) and nano-zeourea (NZU) of 1: 1 ratios were characterized using particle size analyzer, zeta potential, X-ray diffraction, FT-IR, Raman spectroscopy, and SEM with EDS besides release pattern of N. The data revealed that, the N release from the urea blended with NZ (1:1) was up to 48 days while the conventional Z - urea (1:1) mix was up to 34 day and the N release ceased to exist in urea within 4 days under ambient conditions. This suggests that, nanoporous zeolite based on N fertilizer (NZU) can be used as alternate strategy to improve the N use efficiency in crop production systems.   Key words: Nanoporous zeolite, Natural zeolite, Nano-fertilizers, Nitrogen, Slow release N fertilizers.

Aminosilane-functionalization of a nanoporous Y-type zeolite for application in a cellulose acetate based mixed matrix membrane for CO2separation

The micro-sized nanoporous Y-type zeolites were silylated and incorporated into a homogeneous cellulose acetate membrane which resulted in an improvement in the morphology and CO2/N2 separation properties of the corresponding mixed matrix membranes.

Fabrication of ceramic membranes on porous ceramic supports by electrophoretic deposition

Nanoporous alumina membrane and continuous zeolite L membrane were fabricated on the inner surface of microporous alumina tubes. In the former case, an electrophoretic deposition (EPD) technique was used for the deposition of bimodal alumina particles for the subsequent low temperature sintering. In the latter case, the EPD was used for the seeding process of zeolite L particles for the subsequent hydrothermal synthesis. A thin layer of polypyrrole was synthesised on the inside wall of the porous tubes by the chemical polymerisation of pyrrole to give the wall electric conduction for the EPD electrode. The thickness of the coating layers was controlled by altering the applied voltage and deposition time. The interfacial connection of the alumina or zeolite coated layer and the substrate was evaluated by SEM observations before and after the thermal treatment. The nanoporous structure of the alumina membrane was also characterised by a pore size analyser.

One-Pot Synthesis of Hierarchically Nanoporous Zeolite Beta Via Resin Template

Nanoporous zeolite Beta with mesopority has been synthesized by one-pot using ion exchange resin as hierarchical nanoporous template, which is so simple and inexpensive. Hierarchically nanoporous zeolite Beta was characterized with X-ray diffraction, N2 isotherms, scanning electron microscopy, and transmission electron microscopy. These results indicated the hierarchical nanoporous were presented in the sample. Catalytic tests showed that nanoporous zeolite Beta was more active than conventional zeolite Beta, which is synthesized in the absence of resin template in vapor-phase alkylation of benzene with isopropanol to cumene.

Effect of Weight Percentage on PTFE/Nanoporous Zeolite Composite

In this research, Zeolite will be selected as a potential material to combine with Polytetrafluoroethylene (PTFE) to form composite. Zeolite is a porous material with known as molecular sieve and aluminosilicate materials that have open structure of interconnected cavities that can be accessed by molecules, atoms and ions species. Besides, PTFE is a polymer of the type of Teflon and most widely used fluorocarbon polymer for engineering applications with a great combination of desirable chemical and physical properties likes excellent high temperature stability, chemical resistance, electric properties and also extremely low coefficient of friction. Experimental process will be included the conversion of Zeolite to nanoporous Zeolite by wet milling method. Then, this nanoporous Zeolite will mix together with PTFE by weight percentage to form a nanocomposite that gives high impact in properties. This composite will characterize via Field Emission Scanning Electron Microscopy (FESEM) and Thermo Gravimetric Analysis (TGA).

Cyclodextrin‐Modified Zeolites: Host–Guest Surface Chemistry for the Construction of Multifunctional Nanocontainers

The functionalization of nanoporous zeolite L crystals with β-cyclodextrin (CD) has been demonstrated. The zeolite surface was first modified with amino groups by using two different aminoalkoxysilanes. Then, 1,4-phenylene diisothiocyanate was reacted with the amino monolayer and used to bind CD heptamine by using its remaining isothiocyanate groups. The use of the different aminoalkoxysilanes, 3-aminopropyl dimethylethoxysilane (APDMES) and 3-aminopropyl triethoxysilane (APTES), led to drastic differences in uptake and release properties. Thionine was found to be absorbed and released from amino- and CD-functionalized zeolites when APDMES was used, whereas functionalization by APTES led to complete blockage of the zeolite channels. Fluorescence microscopy showed that the CD groups covalently attached to the zeolite crystals could bind adamantyl-modified dyes in a specific and reversible manner. This strategy allowed the specific immobilization of His-tagged proteins by using combined host-guest and His-tag-Ni-nitrilotriacetic acid (NTA) coordination chemistry. Such multifunctional systems have the potential for encapsulation of drug molecules inside the zeolite pores and non-covalent attachment of other (for example, targeting) ligand molecules on its surface.

Epoxidation of cyclooctene by host (nanocavity of zeolite-Y) guest (copper(II) complexes with 16- and 17-membered diaza dioxa macrocyclic Schiff bases) nanocomposite materials

This work reports the synthesis and characterization of macrocyclic copper(II) complexes encapsulated within the nanopores of zeolite-Y. The obtained nanoparticles entrapped in the nanopores of zeolite have been characterized by FT-IR, UV–Vis, Diffuse reflectance spectra, spectroscopic techniques, molar conductance, magnetic moment data, XRD, thermal, and elemental analysis. The complexes (neat and encapsulated) were used for the oxidation of cyclooctene with tert-butyl hydroperoxide as oxidant in different solvents. The supported Cu[L1]2+-Y exhibited a moderate 81.9% selectivity for epoxidation with 84.2% conversion. The catalytic activity and selectivity of the heterogeneous catalysts do not change after recycling five times.

New materials for methane capture from dilute and medium-concentration sources

Methane (CH4) is an important greenhouse gas, second only to CO2, and is emitted into the atmosphere at different concentrations from a variety of sources. However, unlike CO2, which has a quadrupole moment and can be captured both physically and chemically in a variety of solvents and porous solids, methane is completely non-polar and interacts very weakly with most materials. Thus, methane capture poses a challenge that can only be addressed through extensive material screening and ingenious molecular-level designs. Here we report systematic in silico studies on the methane capture effectiveness of two different materials systems, that is, liquid solvents (including ionic liquids) and nanoporous zeolites. Although none of the liquid solvents appears effective as methane sorbents, systematic screening of over 87,000 zeolite structures led to the discovery of a handful of candidates that have sufficient methane sorption capacity as well as appropriate CH4/CO2 and/or CH4/N2 selectivity to be technologically promising.

Physicochemical Properties and Different Sequence of Metal Loading (CuFe) Over Nanoporous of SUZ-4 Zeolite

Different sequence of Cu and Fe loading over nanoporous SUZ-4 zeolite were prepared by incipient wetness impregnation method. K/SUZ-4 zeolite was prepared with SiO2:Al2O3 molar ratio of 21.2 under hydrothermal process at 150 degrees C, 250 rpm for 1 day using tetraethylammonium hydroxide (TEAOH) as a template. Copper(II) and Iron(III) were loaded in K/SUZ-4 with 2.3 and 5.5 wt.% of Copper(II) and 1.0 and 5.0 wt.% of Iron(III). The physico-chemical characterization of CuFe/SUZ-4 were investigated using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), BET-N2 adsorption, Scanning electron microscopy (SEM) and chemical element analysis. The results show the several types of sequential loading of Cu and Fe metals did not change the structure and pore size of nanoporous SUZ-4 zeolite. The obtained CuFe/SUZ-4 zeolites has a narrow pore size distribution with approximately 0.06 microm diameter with 0.66 microm length of needle crystal shape.

Encapsulation of copper(I)-Schiff base complex in NaY nanoporosity: An efficient and reusable catalyst in the synthesis of propargylamines via A3-coupling (aldehyde-amine-alkyne) reactions

Nanodimensional microreactor containing bis[2-(phenylthio)benzylidene]-1,2-ethylenediamine copper(I) complexes, [Cu(N2S2)]X-Y (X=CN, Cl, Br, I) was successfully prepared. This nano composite was used as a catalyst in one-pot multicomponent coupling reaction of aldehydes, amines and alkynes toward synthesis of propargylamines. The copper(I) complex with N2S2 donor Schiff base ligand was readily trapped in the nanocavity of zeolite-Y through a template synthetic (TS) method. Two consecutive processes in the liquid phase were carried out: (i) preparation of a solution of [Cu(MeCN)4]X coordinated with 2-(phenylthio)-benzaldehyde in the presence of zeolite-Y. This process caused the inclusion of [Cu(MeCN)2(S2O2)]X complex into the nanopores of zeolite Y via pre-adsorption method; (ii) template synthesis of the [Cu(MeCN)2(N2S2)]X-Y, through Schiff condensation between [Cu(MeCN)2(S2O2)]X and 1,2-ethylenediamine moiety into the nanopores of NaY. The resulting catalysts were fully characterized by spectroscopic techniques such as AAS, FT-IR, BET isotherm, XRD, UV-Vis and TGA. The results confirmed encapsulation of Y-zeolite with copper(I) complex of N2S2 donor ligand. The catalytic activity of this nanocomposite material was investigated for preparation of propargylamines via three-component reaction of aldehydes, amines and alkynes. Also, the effective factors on this condensation reaction were discussed, such as reaction temperature, solvent, catalyst loading, leaching and reusability of the catalyst.

Proton conducting zeolite films for low-voltage oxide-based electric-double-layer thin-film transistors and logic gates

Three-dimensional nanoporous zeolite films with Linde Type A (LTA) structure prepared by a seeding-free synthesis strategy exhibited high room-temperature proton conductivity and large electric-double-layer (EDL) capacitance. In-plane-gate indium-zinc-oxide thin-film transistors gated by such proton conducting zeolite LTA films were fabricated by a simple self-assembled method. Due to the strong EDL capacitive coupling triggered by mobile protons in zeolite LTA, such transistors showed a low-voltage operation of 1.5 V and a high performance with a large field-effect mobility of 13 cm2 V−1 s−1 and a small subthreshold swing of 95 mV per decade. Furthermore, AND logic operation was also experimentally demonstrated on the dual in-plane-gate EDL transistors. Our results strongly indicate that zeolite LTA films are promising gate dielectric candidates for application in low-voltage and low-cost electronics, which greatly expands the application areas of zeolites.

Zeolite films: a new synthetic approach

Dense, adhesive zeolitic films were made for the first time by combining chemical vapour deposition (CVD) and hydrothermal methods. This new method uses a CVD process to deposit dense amorphous silica or titanium doped silica films which are then converted to a crystalline nanoporous zeolite by a hydrothermal process using an organic structure directing agent. To demonstrate the capability of the method, silicalite-1 (S-1) and titanium silicalite-1 (TS-1) zeolites were prepared. Both X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed the presence of crystalline zeolite films with well-defined morphology. Ti K-edge X-ray absorption spectroscopy (XAS) revealed the presence of the metal ions in the framework of the zeolitic matrix and in isolated, tetrahedral sites both in the amorphous and crystalline zeolite films. Both the pores and the titanium centres in the films were also shown to be accessible for molecules, by reacting with n-hexene and H2O2.

Electrical properties of the zeolite composites prepared by using zeolite and copper powders

We present the electrical characterization of a zeolite plate and its composites prepared by using zeolite and copper powders. The experimentally obtained electronic and ionic conductivities and their interactions are discussed. It is established that electrical properties of the powder of natural zeolite which included 10% of the metallic Cu powder is fundamentally changed. However, the non-steady state decaying current in a pure zeolite powder is replaced with the steady state current, strongly dependent on the gas pressure. It is assumed that there is the gas discharge ignition in the nanopores of zeolite, initiated by electrons emission from Cu metal particles.

Deposition of Zeolite Thin Layers Onto Silicon Wafers for Biomedical Use

The spin-coating of silicon wafers, (including integrated field-effect transistors) with nanoporous synthetic zeolite is herein described. The aim of this research is to investigate the feasibility of fabricating low noise ionoelectronic microsystems to acquire different biosignals, particularly the action potential generated by neurons. The proposed technique is fully compatible with standard integrated circuit technology. Results of scanning electron microscopy, microanalysis, and absorption process are discussed.

ChemInform Abstract: A Novel Class of Nonlinear Optical Materials Based on Host—Guest Composites: Zeolites as Inorganic Crystalline Hosts

AbstractReview: 94 refs.

Fiber ring laser interrogated zeolite-coated singlemode-multimode-singlemode structure for trace chemical detection

Zeolite thin films were synthesized on the claddingless multimode portion of a singlemode-multimode-singlemode (SMS) fiber structure to construct a chemical vapor sensor. The zeolite-coated SMS structure was inserted into a fiber ring amplifier to produce a laser line. Combining the strong molecular adsorption capability of the nanoporous zeolite and the high signal-to-noise ratio of the fiber laser, the device was demonstrated for chemical vapor sensing with a low detection limit.

Adsorption of Methane on Several Zeolites by Monte Carlo Method

Grand Canonical Monte Carlo (GCMC) method is employed to simulate the adsorption of methane in several nanoporous zeolites. Adsorption isotherms over the temperature 177-398K and the pressure 0-12MPa are simulated. And their adsorption capacities of methane in these zeolites at different temperatures and pressures are also compared. The results show that: (1) the methane uptake is in the order of LTA>MOR>MFI at the same condition. The isosteric heat can support this conclusion: the value of isosteric heat in LTA is the largest, intermediate in MOR and the least in MFI. (2) The effects of the pore volume, channel size and the energetic interactions between zeolite and methane on adsorption amounts are considered. A large pore volume and a suitable channel size near to the kinetic diameter of a methane molecule are very important for improving the storage capacity of zeolites. Based on this, we conclude that LTA zeolite with a large pore volume and a suitable channel diameter exhibit a most efficient methane storage capacity than MOR and MFI zeolites.

Recent advances in the synthesis of hierarchically nanoporous zeolites

Hierarchically nanoporous zeolites possessing mesopores as well as the inherent micropores of zeolite structures are garnering attention as a solution to the diffusion limitation problem of solely microporous classical zeolites. The hierarchical structure enables zeolites to have maximum structural functions in a limited space and volume owing to the high diffusion efficiency. Hierarchical zeolites are in high demand for the development of advanced materials for applications in adsorption, separation and catalysis. Herein, recent advances in synthesis routes to hierarchically nanoporous zeolites are reviewed with their catalytic contributions. Particular emphasis is given to the recently developed synthesis method which uses surfactants that are functionalized with a zeolite-structure-directing group. This type of surfactants can direct porous structures in micro- and meso-length scales simultaneously.

Transport in nanoporous zeolites: Relationships between sorbate size, entropy, and diffusivity

Molecular dynamics simulations have been performed on monatomic sorbates confined within zeolite NaY to obtain the dependence of entropy and self-diffusivity on the sorbate diameter. Previously, molecular dynamics simulations by Santikary and Yashonath [J. Phys. Chem. 98, 6368 (1994)], theoretical analysis by Derouane et al. [J. Catal. 110, 58 (1988)] as well as experiments by Kemball [Adv. Catal. 2, 233 (1950)] found that certain sorbates in certain adsorbents exhibit unusually high self-diffusivity. Experiments showed that the loss of entropy for certain sorbates in specific adsorbents was minimum. Kemball suggested that such sorbates will have high self-diffusivity in these adsorbents. Entropy of the adsorbed phase has been evaluated from the trajectory information by two alternative methods: two-phase and multiparticle expansion. The results show that anomalous maximum in entropy is also seen as a function of the sorbate diameter. Further, the experimental observation of Kemball that minimum loss of entropy is associated with maximum in self-diffusivity is found to be true for the system studied here. A suitably scaled dimensionless self-diffusivity shows an exponential dependence on the excess entropy of the adsorbed phase, analogous to excess entropy scaling rules seen in many bulk and confined fluids. The two trajectory-based estimators for the entropy show good semiquantitative agreement and provide some interesting microscopic insights into entropy changes associated with confinement.

Molecular Simulations of Hydrogen Storage on Several Nanoporous Zeolites

Zeolites belong to a most prominent class of nanoporous materials which have been considered as potential sorbents for hydrogen storage. The adsorption of hydrogen molecules on MFI, MOR and LTA zeolites, which encompass a range of different pore structure and chemical composition, has been simulated employing Grand Canonical Monte Carlo (GCMC) method. We compare their capacities of hydrogen storage at different temperatures and pressures. The results show that the adsorbed amounts is in order of LTA>MOR>MFI at the same condition. The effects of pore structure of zeolites, temperature and pressure on the hydrogen adsorption has been examined. The results clearly show that: (1) the temperature effect on the adsorption decreases with decreasing in the number of hydrogen molecules adsorbed. (2) A large volume of micropores and a suitable diameter near to the kinetic diameter of a hydrogen molecule are important for improving the hydrogen-storage capacity of zeolites. Based on this, we can conclude that the LTA zeolite with a large pore volume and a suitable channel diameter exhibits a most efficient hydrogen storage capacity than MOR and MFI zeolites.