Type Zeolite Research Articles

Crystalline Zeolite Layers on the Surface of Titanium Alloys in Biomedical Applications: Current Knowledge and Possible Directions of Development

In this review, the main focus was on the use of zeolites as layers to modify the surface of titanium implants. The article discusses the basic methods for modifying the functional properties of zeolites (e.g., ion exchange) as well as biomedical applications of zeolites (e.g., drug delivery systems and biosensors). The article reviews the surface modifications of titanium alloys prepared so far with the use of various types of zeolites and selected examples are presented. This review shows the significant impact of titanium surface modification with zeolites, as well as their post-synthetic modification on implant properties, for instance, better biocompatibility, faster osseointegration, better cell adhesion, and corrosion resistance properties. The results of the research presented so far in this review show that the modification of titanium with zeolite layers is a very prospective subject, but underdeveloped, as evidenced by a small number of studies on this subject. We have shown that the prepared layers can be continuously improved and used, e.g., as local delivery systems for various active pharmaceutical ingredients (APIs). We hope that the prepared review will help research groups around the world in the preparation of implants modified with zeolites with even better properties and utility applications.

Impacts of Clay Content and Type on Shear Strength and Splash Erosion of Clay–Sand Mixtures

Soil characteristics, especially clay content and clay type, have significant impacts on splash erosion. This investigation was conducted to determine the effects of clay content and clay type (zeolite, phlogopite, bentonite, and kaolinite) on the shear strength and splash erosion of clay–sand mixtures compared with a clay soil under controlled conditions. Clay–sand mixtures were prepared by mixing 15, 30, and 45 kg 100 kg−1 of the selected clays with pure sand and a clay soil; these mixtures were pre-treated with three levels of wetting and drying (W&D) cycles, and then shear strength was measured. The splash erosion rate was measured at three levels of water status: air-dry, plastic limit (PL), and liquid limit (LL). The highest values of splash erosion were observed in the samples without the W&D cycle, and after applying the W&D cycles, splash erosion decreased. Moreover, splash erosion was higher in the air-dry and LL groups. Splash erosion decreased with increased clay content because of the structure development in the mixtures. In general, as clay content increased, splash erosion was reduced and shear strength was significantly increased. From the highest to lowest mean of cohesion, the results showed the following order: bentonite > kaolinite > phlogopite > clay soil > zeolite. However, splash erosion showed the following order for the studied clays: zeolite > clay soil > phlogopite > kaolinite > bentonite. Nonlinear power models, best-fitted relations between splash erosion and shear strength, and the shear strength could explain about 30–33% of the splash erosion variability in this study.

Realizing translucency in aluminosilicate glass at ultralow temperature via cold sintering process

Glass with high visible-light transparency is widely considered as the most important optical material, which typically requires a processing temperature higher than 1000 °C. Here, we report a translucent aluminosilicate glass that can be prepared by cold sintering process (CSP) at merely 300 °C. After eliminating structural pores in hexagonal faujasite (EMT)-type zeolite by heat treatment, the obtained highly active nanoparticles are consolidated to have nearly full density by adding NaOH solution as liquid aids. However, direct densification of EMT powder cannot remove the structural pores of zeolite completely, leading to an opaque compact after the CSP. It is proved that the chemical reaction between the NaOH- and zeolite-derived powders is highly beneficial to dissolution-precipitation process during sintering, leading to the ultra-low activation energy of 27.13 kJ/mol. Although the addition of 5 M NaOH solution greatly promotes the densification via the reaction with aluminosilicate powder, lower or higher concentration of solvent can deteriorate the transmittance of glass. Additionally, the CSP-prepared glass exhibits a Vickers hardness of 4.3 GPa, reaching 60% of the reported value for spark plasma sintering (SPS)-prepared sample.

Amorphous Aluminosilicate Nanosheets as Universal Precursors for the Synthesis of Diverse Zeolite Nanosheets for Polymer-Cracking Reactions.

Zeolites catalyze some reactions in their molecular-sized pores, but large molecules can react only on their external surface. Zeolite-nanosheets (NSs) have been developed as catalysts for large molecules. The previously reported methods to synthesize zeolite-NSs are specialized for each zeolite type. Here we propose a new method to synthesize various zeolite-NSs from the same amorphous aluminosilicate NSs (AAS-NSs) as a universal precursor. We successfully synthesized the unprecedented AAS-NSs in the hydrophilic space of the stable hyperswollen lyotropic lamellar (HL) phase. The four zeolite types could be obtained from the single-species AAS-NSs. These results imply that this method enables us to synthesize almost all types of zeolite-NSs. Moreover, the synthesized CHA-NSs have great potential for various applications because of their thickness and large external surface area.

Amorphous Aluminosilicate Nanosheets as Universal Precursors for the Synthesis of Diverse Zeolite Nanosheets for Polymer‐Cracking Reactions

AbstractZeolites catalyze some reactions in their molecular‐sized pores, but large molecules can react only on their external surface. Zeolite‐nanosheets (NSs) have been developed as catalysts for large molecules. The previously reported methods to synthesize zeolite‐NSs are specialized for each zeolite type. Here we propose a new method to synthesize various zeolite‐NSs from the same amorphous aluminosilicate NSs (AAS‐NSs) as a universal precursor. We successfully synthesized the unprecedented AAS‐NSs in the hydrophilic space of the stable hyperswollen lyotropic lamellar (HL) phase. The four zeolite types could be obtained from the single‐species AAS‐NSs. These results imply that this method enables us to synthesize almost all types of zeolite‐NSs. Moreover, the synthesized CHA‐NSs have great potential for various applications because of their thickness and large external surface area.

Possibilities of Using Zeolites Synthesized from Fly Ash in Adsorption Chillers

Adsorption chillers produce cold energy, using heat instead of electricity, thus reducing electrical energy consumption. A major industrial waste, fly ash, can be converted to zeolite and used in adsorption chillers as an adsorbent. In this research, three different types of zeolites were synthesised from fly ash via a hydrothermal reaction in an alkaline solution (NaOH). The obtained samples (Na-A zeolites) were modified with K2CO3 to increase the water adsorption capacity of these samples. Phase and morphology analyses shows that desired zeolites formed properly but other crystalline phases also exist along with nonporous amorphous phases. The determined specific surface areas for Na-A zeolite (12 h) and Na-A zeolite (24 h) are 45 m2/g and 185 m2/g respectively, while the specific surface area for synthesized 13X zeolite is almost negligible. Water-isotherm for each of these samples was measured. Considering the application of adsorption chillers, average adsorption capacity was very low, 1.73% and 1.27%, respectively, for the two most probable operating conditions for synthesized 13X zeolite, whereas no water was available for the evaporation from Na-A zeolite (12 h) and Na-A zeolite (24 h). This analysis implies that among the synthesized materials only 13X zeolite has a potential as an adsorber in sorption chillers.

Characteristics of cytotoxicity of native zeolite against cattle epithelial cells

Relevance. Special attention of researchers is attracted by zeolites — minerals of the family of aluminosilicates of alkaline and alkaline earth metals. Considering that the composition of zeolites is extremely variable, including the content of trace elements, most zeolite tuffs of Russian Federationare not evaluated in terms of possible cytotoxicity. The aim of this study was to characterize the cytotoxicity of native clinoptilolite against epithelial cells of cattle.Methods. To characterize cytotoxicity, 5 fractions of native clinoptilolite (mining quarry — Drozhzhanovsky district of the Republic of Tatarstan) with particle sizes were selected: No. 1 — 0.2 mm, No. 2 — 0.24 mm, No. 3 — 0.8 mm, No. 4 — 0,8–2,5 mm, No. 5 — 2,5–5,0 mm. Two transferable cell lines were selected as models for determining the toxicity of zeolites: LEK (epithelium of the lung of a cow embryo) and TR (tracheal epithelium of a cow embryo) obtained from a Collection of vertebrate cell cultures (ICiG RAS, Russia). MTTtestwas carried out. Cell viability was assessed by the activity of mitochondrial dehydrogenase according to a standard method. Statistical data processing was performed using “GraphPad Prism 6.0” software (USA). The experiments were carried out in 5 repetitions, p ≤ 0.05 was taken as a statistically reliable level.Results. It was found that concentrations up to 300 micrograms/mlof all fractions of zeolites do not have a cytotoxic effect on the studied cells. The cytopathogenic effect manifests itself in the concentration range of 400-1000 micrograms/ml and is in direct correlation with the size of zeolite particles — the proportion of cells in the state of apoptosis is up to 35.23±2.3%, which is probably due to the mechanical effect of large particles of the rocks in question on cellular structures. Information about the cytotoxic effects of different types of zeolites on the cells of the body of productive animals will later form the basis of their toxicological assessment and will allow us to develop a strategy for their safe use.

Catalytic upgrading of bio-oils derived from terrestrial and marine biomass over various types of zeolites

Effects of biomass type and zeolite catalyst type on bio-oil upgrading were investigated in this study, in which terrestrial (rice husk and cedar) and marine (eelgrass) biomass and various commercial zeolites with different frameworks including H-USY, H-Mordenite, H-Ferrierite, H-ZSM-5, H-Beta zeolites were used. The catalytic performance of each catalyst was evaluated with a Py/GC-MS instrument. Thereafter, in-situ catalytic upgrading of the bio-oil derived from fast pyrolysis over those zeolite catalysts with high activity and selectivity towards aromatic hydrocarbons were further investigated in a fixed bed reactor. A highest aromatic hydrocarbons yield up to 77.28% in the upgraded bio-oil was achieved when using eelgrass as the biomass feedstock and a H-ZSM-5–40 zeolite as the catalyst. In addition, the spent catalysts after used for several times can be well regenerated only via a simple calcination at 550 °C for 2 h in air, which showed similar activity as the fresh one. It is expected that such a zeolite catalyst can be applied for the bio-oil upgrading in an industrial scale.

Investigating the Interaction between Methanol and the Heulandite-type Zeolite using First Principle Molecular Dynamic

The interaction between methanol and the Heulandite-type zeolite has been unveiled to give an atomic scale detail regarding the catalytic activity of this zeolite for methanol conversion. The study was carried out by first principle molecular dynamics to get an insight into the structure and electronic behaviour of methanol inside the zeolite structure at different temperatures. The behaviour of methanol was studied when the location of the proton of Bronsted acid sites was varied to give both possible direct and less interaction with methanol. The results show that methanol interacts with the proton from zeolite to give a cationic species of [CH3OH2]+ both in 300K and 573K conditions. However, when the proton is located at different location far from possible interaction with methanol, the formation of a cationic species is hindered. This study provides an insight into the design of Heulandite type zeolite to give a catalytic activity toward methanol transformation.

Effect of Different Zeolite Supports on the Catalytic Behavior of Platinum Nanoparticles in Cyclohexene Hydrogenation Reaction

In this study, 1 wt% platinum (Pt) nanoparticles were incorporated into five types of zeolites (HY, Beta, mordenite, ZSM-5, and ferrierite) with an impregnation technique. The synthesis strategy included the use of water as a solvent for the applied Pt source. Moreover, the incorporation process was performed at ambient conditions followed by calcination at 450 °C. The five prepared materials were characterized by different physical and chemical characterization techniques and the obtained results confirmed the formation of Pt nanoparticles with an average size of 5–10 nm. The catalytic performance of the prepared materials was evaluated in the hydrogenation of cyclohexene under a solvent-free system at room temperature. Pt nanoparticles supported on ZSM-5 zeolite exhibited the best catalytic performance. Moreover, the optimization of operational conditions such as temperature, pressure, and catalyst amount was investigated and the obtained results showed the possibility to convert 100% of cyclohexene within 35 min over Pt-ZSM-5. Finally, the reusability of the Pt-ZSM-5 catalyst was investigated in four consecutive runs without treatment and the obtained results showed a negligible activity loss.

Carbon Nanostructure/Zeolite Y Composites as Supports for Monometallic and Bimetallic Hydrocracking Catalysts.

In this study, we examine the effect of integrating different carbon nanostructures (carbon nanotubes, CNTs, graphene nanoplatelets, GNPs) into Ni- and Ni-W-based bi-functional catalysts for hydrocracking of heptane performed at 400 °C. The effect of varying the SiO2/Al2O3 ratio of the zeolite Y support (between 5 and 30) on the heptane conversion is also studied. The results show that the activity, in terms of heptane conversion, followed the order CNT/Ni-ZY5 (92%) > GNP/Ni-ZY5 (89%) > CNT/Ni-W-ZY30 (86%) > GNP/Ni-W-ZY30 (85%) > CNT/Ni-ZY30 (84%) > GNP/Ni-ZY30 (83%). Thus, the CNT-based catalysts exhibited slightly higher heptane conversion as compared to the GNP-based ones. Furthermore, bimetallic (Ni-W) catalysts possessed higher BET surface areas (725 m2/g for CNT/Ni-W-ZY30 and 612 m2/g for CNT/Ni-ZY30) and exhibited enhanced hydrocracking activity as compared to the monometallic (Ni) catalyst with the same zeolite support and type of carbon structure. It was also shown that CNT-based catalysts possessed higher regeneration capability than their GNP-based counterparts due to the slightly higher thermal stability of the CVD-grown CNTs.

Quantitating Diffusion Enhancement in Pore Hierarchies.

A microporous continuum traversed by a set of mutually perpendicular channels is considered to be a model for a hierarchically porous system of the mesoporous zeolite type. Transient profiles of molecular uptake as determined by kinetic Monte Carlo (kMC) simulation are found to be in excellent agreement with the result attained by the application of the two-region model (the Kärger model) of molecular diffusion. In particular, it is found that, in the two limiting cases referred to as fast exchange and slow exchange, there exist two simple analytical expressions for the rate of molecular uptake and hence for the quantification of transport enhancement in comparison with the purely microporous adsorbent. In the general case, transport enhancement is simply recognized by the reciprocal addition of the expressions in the two limiting cases.

Adsorption of cerium (III) by zeolites synthesized from kaolinite after rare earth elements (REEs) recovery.

REE recovery tests were performed on a kaolinite and the corresponding metakaolinite using pH static leaching method. Test results show that over 90% of REEs were leached from the metakaolinite sample at pH 0.00 and 25°C, while less than 2% of the major constituents were simultaneously extracted. Therefore, selective leaching of REEs from the metakaolinite was achieved through pH static leaching. The leaching residue was then subjected to alkaline activation for zeolites synthesis. The effects of hydrothermal temperature and incubation period under various alkaline conditions on the synthesis of zeolites were systematically investigated. The phase compositions, textual properties, and morphology of the synthesized products were characterized. Pure zeolite A with 100% relative crystallinity was successfully synthesized at 80°C for 6h when using 3M NaOH as the alkaline activator. While as the synthesis conditions became increasingly harsh, the metastable zeolite A gradually transformed into more stable sodalite, and three types of zeolites, including zeolite A, sodalite, and their mixtures, were obtained. After that, various types of zeolites were applied for Ce3+ adsorption from aqueous solutions. High purity sodalite showed a higher adsorption capacity of 53mg/g at pH 6.0 and 25°C as a result of the superior textual properties compared with zeolite A. The adsorption data were suitably fitted by the Langmuir isotherm and pseudo-second-order models. Findings from this study suggest that the kaolinite is a potential source for REE recovery, and the leaching residue is suitable for the synthesis of zeolites, which can be used as promising adsorbents for Ce3+ recovery.

A green process for zeolite synthesis: low-temperature vapor phase treatment of natural bauxites

In this work, three samples of bauxite were used as inexpensive sources for the zeolite formation by a green process based on vapor-phase crystallization (VPC) method. The synthesis was carried out using a water bath with deionized water heated at 35, 45, 60 or 90 °C. During the process, NaOH pre-fused bauxites were contacted only with vapor from the liquid. The results indicate that sodalite formed in all the samples after VPC at higher temperatures (60 °C and 90 °C). Large amount of zeolite A was instead synthesized in the sample characterized by SiO2/Al2O3 ratio next to 1 and after vapor treatment at 35 °C and 45 °C. These data highlight the determining role of both raw material chemical composition and amount of water molecules in type of zeolite formed by vapor crystallization method. Moreover, the results indicate that VPC process made it possible to synthesize zeolite generating no water waste.

Anti-Reflective Zeolite Coating for Implantable Bioelectronic Devices.

Since sunlight is one of the most easily available and clean energy supplies, solar cell development and the improvement of its conversion efficiency represent a highly interesting topic. Superficial light reflection is one of the limiting factors of the photovoltaic cells (PV) efficiency. To this end, interfacial layer with anti-reflective properties reduces this phenomenon, improving the energy potentially available for transduction. Nanoporous materials, because of the correlation between the refractive index and the porosity, allow low reflection, improving light transmission through the coating. In this work, anti-reflective coatings (ARCs) deposited on commercial PV cells, which were fabricated using two different Linde Type A (LTA) zeolites (type 3A and 4A), have been investigated. The proposed technique allows an easier deposition of a zeolite-based mixture, avoiding the use of chemicals and elevated temperature calcination processes. Results using radiation in the range 470–610 nm evidenced substantial enhancement of the fill factor, with maximum achieved values of over 40%. At 590 and 610 nm, which are the most interesting bands for implantable devices, FF is improved, with a maximum of 22% and 10%, respectively. ARCs differences are mostly related to the morphology of the zeolite powder used, which resulted in thicker and rougher coatings using zeolite 3A. The proposed approach allows a simple and reliable deposition technique, which can be of interest for implantable medical devices.

Synthesis of zeolite X from waste basalt powder and its efficient adsorption of uranyl ions in solution

A new type of zeolite X with high purity and crystallinity was prepared from waste basalt powder by alkaline hydrothermal fusion and its adsorption performance as an adsorbent on uranium-containing wastewater was investigated. The results show that the equilibrium adsorption capacity of zeolite X for uranyl ions is 228.4 mg g−1. The adsorption process is spontaneous and exothermic. Langmuir isotherm model and quasi-second-order model are suitable for describing the adsorption process. Studies on the adsorption mechanism have shown that there is an ion exchange between UO22+ and zeolite during the adsorption process.

Comparison of three different structures of zeolites prepared by template-free hydrothermal method and its CO2 adsorption properties

In this study, zeolite sodalite SOD (50NaO2:Al2O3:5SiO2), zeolite LTA (2NaO2:Al2O3:1.926SiO2) and zeolite FAU (16NaO2:Al2O3:4SiO2) of different structures were synthesized successfully through simple conventional hydrothermal crystallization technique without using any template agent. Morphological analysis of three different types of zeolites revealed that the samples exhibit three different shapes such as the “Raspberry-like”, “Dice” cube like and “Octahedral” shaped morphology respectively. The thermal stability was found to be about 4.8%, 14.6% and 20.5% for the synthesized zeolites SOD, LTA and FAU respectively. From the N2 adsorption-desorption studies, it was observed that adsorption types IV and I correspond to the synthesized samples. CO2 adsorption by the synthesized zeolite SOD, LTA and FAU were examined in the pressure range from 0 to 101.325 kPa at a constant temperature of 297.15 K. The highest adsorption capacity of 3.7 mmol/g was obtained for zeolite FAU. The synthesized zeolite was studied using a nonlinear regression curve fit to determine the adsorption isotherm model using Langmuir and Freundlich isotherm model. It has been found that the synthesized zeolites have a large electric field gradient due to which they can strongly adsorb quadrupole of CO2 molecules.

Methanol-to-olefins catalysis on window-cage type zeolites/zeotypes with syngas co-feeds: Understanding syngas-to-olefins chemistry

Catalyst lifetime and product selectivity of methanol-to-olefins (MTO) catalysis on window-cage type zeolites and zeotypes are examined and interpreted to elucidate the critical role of high-pressure H2 and CO in MTO catalysis at conditions relevant for syngas-to-olefins (STO) conversion (H2/CH3OH >100, CO/CH3OH >100). Propylene co-feed experiments elucidate that acid-catalyzed hydrogenation reactions transpire and enhance olefins-cycle propagation by intercepting formaldehyde-mediated condensation and dehydrocyclization reaction cascades to result in an increase in catalyst lifetime (>7×) and decrease ethylene-to-propylene (∼1.5×) and ethylene-to-butenes ratios (∼1.6×) during MTO with high-pressure H2 co-feeds. CO is mechanistically relevant in increasing ethylene-to-propylene (∼1.5–3.0×) and ethylene-to-butenes ratio (∼1.7×) during MTO catalysis only at high CO (3–8 bar) and syngas pressures (24 bar, H2/CO∼2–16); at these high pressures, CO participates in carbonylation reactions to enhance aromatics-cycle propagation and enable a pathway for ethylene production via methyl acetate formation. These results suggest that high-pressure syngas introduces new catalytic pathways to distinguish MTO catalysis from STO catalysis and MTO catalysis in the presence of high-pressure syngas reagents.

Forming of Block Zeolites Using 3D Printing Technology

Zeolite blocks with 10% binder and without binder were formed using 3D printing technology. A polylactide template with the preset shape and structure of channels was printed on a 3D printer. The zeolite material was formed in the voids of this template. Finally, the template was burned out from the final block. Blocks with a binder were prepared by filling the template with a paste containing microcrystalline zeolite of MFI structural type. Blocks without binder were prepared by steam-assisted crystallization leading to the formation of zeolite nanocrystals in the H-form in the template channels. A relatively strong block consisting of MFI-type zeolite and reproducing the polymer template void volume was obtained.

Effects of Zeolite Type on Integrated Fischer–Tropsch Synthesis and Hydroprocessing

Effects of Zeolite Type on Integrated Fischer–Tropsch Synthesis and Hydroprocessing