Type Zeolite Research Articles

Non-Destructive Examination for Cavitation Resistance of Talc-Based Refractories with Different Zeolite Types Intended for Protective Coatings.

In many industrial processes that include fluid flow, cavitation erosion of different engineering structures (pumps, turbines, water levels, valves, etc.) during their operation is expected. Metallic, ceramic, and composite materials are usual candidates considered for application in such extreme conditions. In this study, the idea is to synthesize refractory ceramic material based on talc with the addition of zeolite for utilization as protective coatings in cavitating conditions. Two talc-based refractories with zeolites from two Serbian deposits were produced. The behaviors of the samples in simulated cavitation conditions were examined by an advanced non-destructive methodology consisting of monitoring mass loss and surface degradation using image analysis compiled with principal component analysis (PCA), interior degradation by ultrasonic measurements, and the microstructure by a scanning electron microscope (SEM). Lower mass loss, surface degradation level, and modeled strength decrease indicated better cavitation resistance of the sample with Igros zeolite, whereby measured strength values validated the model. For the chosen critical strength, the critical cavitation period as well as critical morphological descriptors, Area and Diameter (max and min), were determined. A Young's elasticity modulus decrease indicated that surface damage influence progressed towards interior of the material. It can be concluded that the proposed methodology approach is efficient and reliable in predicting the materials' service life in extreme conditions.

Direct imaging of local atomic structures in zeolite using optimum bright-field scanning transmission electron microscopy.

Zeolites are used in industries as catalysts, ion exchangers, and molecular sieves because of their unique porous atomic structures. However, direct observation of zeolitic local atomic structures via electron microscopy is difficult owing to low electron irradiation resistance. Subsequently, their fundamental structure-property relationships remain unclear. A low-electron-dose imaging technique, optimum bright-field scanning transmission electron microscopy (OBF STEM), has recently been developed. It reconstructs images with a high signal-to-noise ratio and a dose efficiency approximately two orders of magnitude higher than that of conventional methods. Here, we performed low-dose atomic-resolution OBF STEM observations of two types of zeolite, effectively visualizing all atomic sites in their frameworks. In addition, we visualized the complex local atomic structure of the twin boundaries in a faujasite (FAU)-type zeolite and Na+ ions with low occupancy in eight-membered rings in a Na-Linde Type A (LTA) zeolite. The results of this study facilitate the characterization of local atomic structures in many electron beam-sensitive materials.

Advantages and limitations of hydrogen peroxide for direct oxidation of methane to methanol at mono-copper active sites in Cu-exchanged zeolites

The efficiency of direct catalytic oxidation of methane to methanol (DMTM) is significantly influenced by oxidants. However, realizing a one-pot DMTM using dioxygen remains challenging. Hydrogen peroxide is still the most frequently reported green oxidant for DMTM, with high selectivity for methanol. To gain insight into the influence of oxidants on DMTM performance, we computationally investigated the reaction mechanisms involved in DMTM using H2O2 at mono-copper sites in three types of Cu-exchanged zeolites with different micropore sizes. We identified the advantages and limitations of H2O2 as an oxidant. In contrast to the O–O bond in O2, the O–O bond in H2O2 can be easily broken to produce reactive surface oxygen species, which enable the facile C–H bond activation of methane at a low temperature. However, because of the radical-like process of C–H bond activation at mono-copper sites, actualizing the preferential C–H bond activation of methane is kinetically challenging compared to that of methanol. Moreover, the lower O–H bonding energy of H2O2 would result in self-decomposition of H2O2. Despite these bottlenecks, kinetic analysis shows that improving catalysts to boost the DMTM performance using H2O2 is a promising approach.

Hydrogen storage behavior of zeolite/graphene, zeolite/multiwalled carbon nanotube and zeolite/green plum stones-based activated carbon composites

In this study, novel zeolite/carbon composites were synthesized to determine hydrogen storage properties. Activated carbon (AC), graphene (GR) and multi-walled carbon nanotubes (MWCNT) were used as carbon sources in the preparation of the composites with faujasite type zeolite. AC was prepared from green plum stones by using ultrasound assisted chemical activation with the use of potassium hydroxide. In order to compare the textural and hydrogen storage properties of the prepared zeolite/activated carbon, zeolite/graphene and zeolite/multiwalled carbon nanotube composites were prepared from commercial GR and MWCNT, respectively. The structures of the obtained AC and composite samples were characterized using BET, DFT, t-plot and SEM-EDX techniques. AC was synthesized with a relatively high BET surface area (1694 m2/g), total pore volume (1.023 cm3/g) and micropore volume (0.780 cm3/g). Zeolite/activated carbon composite (ZAC) has the highest surface area, total pore volume and micropore volume, and zeolite/multiwalled carbon nanotube composite (ZNT) has the highest average pore width (6.64 nm) among all composite samples. Hydrogen sorption processes have been performed for composite samples at −196 °C and ambient pressure. The relationship between hydrogen sorption capacities, BET surface areas and pore volumes of ZAC, ZGR and ZNT composites have been investigated. The hydrogen storage capacity of the ZAC was found to be 1.3 wt%. This value is 1.47 times the hydrogen storage capacity of AC and 4.16 times the hydrogen storage capacity of zeolite. Results indicated that ZAC is a promising adsorbent for hydrogen storage.

Synthesis of Na-LSX type zeolite from Polish fly ash

Synthesis of Na-LSX type zeolite from Polish fly ash

CO2-Induced Gate-Opening Adsorption on a Chabazite/Phillipsite Composite Zeolite Transformed from a Faujasite Zeolite Using Organic Structure-Directing Agent-Free Steam-Assisted Conversion.

Organic structure-directing agent-free steam-assisted conversion and Cs+ ion exchange were used to transform the faujasite (FAU)-type zeolite to the Cs+-type chabazite/phillipsite (CHA/PHI) composite zeolite. Compared with the pure PHI-type zeolite, the Cs+-type CHA/PHI zeolite showed gate-opening CO2 adsorption behavior and good thermal stability. In situ powder X-ray diffraction (PXRD) of the CO2 adsorption was measured to elucidate the mechanism for the gate-opening adsorption on the CHA/PHI zeolite. The Na+-type CHA/PHI zeolite did not show such adsorption behavior, and the PXRD pattern of the Na+-type CHA/PHI zeolite did not change with increasing CO2 partial pressure, which suggests that this unique adsorption behavior was caused by the PHI framework transition or Cs+ ions moving in both the CHA and PHI frameworks. Furthermore, in situ Fourier-transform infrared spectra of CO2 adsorption and CO2 breakthrough measurement on the Cs+-type CHA/PHI zeolite suggest that the CHA and PHI frameworks in the CHA/PHI zeolite shared eight-membered-ring windows and that CO2 molecules could easily diffuse from a CHA cage to a PHI framework. The ideal adsorbed solution theory was used to calculate the CO2/N2 separation selectivity for the Cs+-type CHA/PHI zeolite. At 298 and 318 K, the Cs+-type CHA/PHI composite zeolite showed a high CO2/N2 separation coefficient of >10,000 compared with other zeolites with high CO2 adsorption capacity. Furthermore, the CO2 working capacity was calculated for the Cs+-type CHA/PHI zeolite in both the pressure- and temperature-swing processes, and the results showed that the CHA/PHI composite zeolite could selectively separate CO2 from the CO2/N2 gas mixtures released from power generation plants operating using these processes.

Pengolahan Air Sadah Menggunakan Zeolit Buatan Dari Batu Apung Lampung Dan Daun Kerai Payung

This research was conducted to determine the composition and crystal structure of the artificial zeolite produced, as well as the ability of artificial zeolite to reduce calcium and magnesium content in hard water. The zeolite was prepared using the hydrothermal method by mixing sodium silicate from Lampung pumice silica, sodium aluminate from aluminum can waste and charcoal from sunshade umbrellas. The artificial zeolite products were characterized using XRF, XRD, UV-Vis spectrophotometric and ICP-EOS. The results showed that the composition of the artificial zeolite was aluminum, silica, phosphorus, potassium, calcium, titanium, vanadium, chromium, manganum and ferum. The crystal structure of the optimum sample from the UV-Vis spectrophotometric characterization obtained the crystal structure of a natural zeolite type, namely Chabazite. And the artificial zeolite which was tested for adsorption on hard water could reduce the calcium content by 36.57% but could not reduce the magnesium content.

Insight into the stability and thermal decomposition behavior of nitrocellulose supplemented with different types of zeolites

AbstractNitrocellulose is commonly used as a main ingredient in propellant formulations, but its thermal instability necessitates the employment of stabilizers as additives. In this study, the potential of four adsorbents, namely, zeolites MOR, BEA, MFI, and FAU as stabilizing agents for nitrocellulose was evaluated. Their performance was compared to that of the traditional stabilizer, DPA. The thermal stability of nitrocellulose (NC) that contains each stabilizer was assessed through VST, B&J test, and TGA analysis. The compatibility of NC with each stabilizer was also scrutinized using FTIR, heat of combustion, and DSC. The computation of the kinetic parameters for NC that contains each stabilizer was carried out using non‐isothermal DSC experiments. The obtained results demonstrated that the different zeolites exhibited promising stabilizing efficiency toward NC. The zeolites revealed good compatibility with NC as well, as confirmed by FTIR and DSC analyses. This work contributes to the ongoing efforts to develop environmentally friendly stabilizers for NC.

The production of debrominated aromatics via the catalytic pyrolysis of flexible printed circuit boards

Pyrolysis is an environmental technology for the proper treatment of electronic waste (e-waste) for the production of fuel. However, the presence of brominated compounds in pyrolysis oil makes its commercialization difficult. In this study, various types of zeolites, HY (30), HZSM-5 (30), HZSM-5 (50), HZSM-5 (280), and basic metal oxides (MgO and CaO) were used for the pyrolysis of flexible printed circuit boards (FPCBs) for the first time to produce bromine-free oil. A higher production efficiency of debrominated aromatic hydrocarbons, primarily benzene, toluene, ethylbenzene, xylenes (BTEXs), and naphthalene with zeolites, was achieved over basic metal oxides. The use of HZSM-5 (HZ) (30) increased the amount of benzene (an area of 31.5 × 107) and toluene (an area of 17.6 × 107), and a high debromination efficiency was observed for basic metal oxides owing to the strong affinity of halides toward the Ca2+ and Mg2+ ions. Among the BTEXs, benzene (an area of 31.5 × 107) and toluene (an area of 17.6 × 107) were obtained as highly selective monoaromatics in the presence of the catalyst HZ (30). CaO and HZ (30) were effective for debromination and aromatic production, respectively. The in-situ CaO/ex-situ HZ (30) combination revealed ∼ 100% debromination efficiency; however, the total aromatic hydrocarbon production was higher on the in-situ HZ (30)/ex-situ CaO with ∼ 77.5% debromination efficiency. Meanwhile, the in-situ HZ (30)/ex-situ CaO configuration could achieve ∼ 100% debromination efficiency by increasing the amount of CaO to 7 times to feed.

Characterization and application of natural Moroccan material for methyl violet 2B dye removal from aqueous solution.

In this paper, a natural Moroccan material from the Nador area in the north east of Morocco was studied as an adsorbent to remove methyl violet 2B dye from aqueous solutions. This material has never been studied before in this region, and it will be used in its raw state. It was collected and characterized by X-ray diffraction, FTIR spectroscopy, scanning electron microscopy, X-ray fluorescence, thermal analysis, N2 gas adsorption-desorption, pHPZC, and Brunauer-Emmett-Teller (BET). The studies are realized with a 500-µm grain size and 182m2/g BET surface area. XRD showed the presence of significant peaks belonging to natural zeolite type clinoptilolite-Ca and minor phases. Several parameters were studied such as contact time, adsorbent mass, initial dye concentration, initial pH solution, the particle size of the material, and temperature. Out of the three isotherm models investigated after 60min of contact time in the experiments, the Langmuir model gave the best fit to the experimental data (R2 = 0.99). The results of kinetic and thermodynamic studies revealed that the adsorption process obeyed pseudo-second-order, spontaneous (ΔG° < 0), endothermic (ΔS° > 0). The adsorption of methyl violet 2B dye is chemisorptions and physisorption. The maximum theoretical adsorption capacity was 30.30mg·g-1 at 23°C for a particle diameter of 500µm. The desorption study shows that the material can be desorbed using solvents. The reuse study indicates that the same amount of natural zeolite can be used several times which makes the process efficient and sustainable. The obtained results indicate that the country of Morocco has natural zeolite among its resources and that it can be used as an efficient adsorbent for the removal of dyes.

SYNTHESIS OF A NEW ADSORBENT BASED ON THE MILD DEALUMINATED BINDER FREE GRANULAR Y ZEOLITE

This study investigates, for the first time, the effects of dealumination of binder-free NaY type zeolite on the adsorption properties and porous structure characteristics. In this study, BF-Y zeolite was hydrothermally synthesized from kaolin and powder NaY. BF-Y was then treated with acid to increase Si/Al ratio. X-ray Diffraction (XRED), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray (EDX) have been performed for the characterization. The modified zeolite granules MBF-Y were used as an adsorbent for the removal of methylene blue MB dye from water. The influence of initial MB concentration, contact time, temperature, and adsorbent dosage on adsorption capacity and dye removal percentage on MBF-Y was investigated. The maximum dye removal was attained at a concentration of (8 * 10-6 M) which was more than 93%, and an equilibrium contact time of 60 minutes. Well-known adsorption isotherms (Langmuir, Fruendlich, and Tempkin) were used to study the adsorption mechanism of MB onto MBF-Y.

Zeolite Encapsulation of Indole as an Antibacterial with Controllable Release Property.

Effective regulation of the release behavior of bactericides to avoid both too fast release and too slow release to maximize their antibacterial ability is still the face of a grand challenge. In this study, indole as a bactericide was encapsulated into three types of zeolites (denoted as indole@zeolite), including the ZSM-22 zeolite, ZSM-12 zeolite, and beta zeolite with different topologies, respectively, to obtain indole@ZSM-22, indole@ZSM-12, and indole@Beta complexes finally. Benefiting from the confinement effect of zeolites, the release rate of indole from these three zeolite encapsulation systems showed a much slower release rate than that of indole impregnated onto a counterpart zeolite (denoted as indole/zeolite), thus avoiding the too-fast and too-slow release very well. As determined by molecular dynamics simulation combined with experimental results, attributed to the unequal diffusion coefficient in these three encapsulation systems caused by different zeolite topologies, the release rate of indole within these three complexes was different from each other, hence providing an effective way to avoid a too-slow release rate through choosing different zeolite topologies. The simulation results showed that the timescale of hopping of indoles in zeolites plays an important role in the dynamics in zeolites. Taking killing Escherichia coli as an instance, compared with indole/zeolite, the corresponding indole@zeolite sample exhibited more efficient and sustainable antibacterial activity for its controlled-release behavior.

The effects of clinoptilolite type of zeolite and synthesised zeolite-enriched fertilizer on yield parameters of Cucumber (Cucumis sativus) plant and some chemical properties in dark chestnut soil

Zeolites have been used in agriculture since the 1960s, due to the effectiveness of these crystalline microporous solids as soil amendments for plant growth, their cation exchange capacity (CEC) and slow-release fertilizer properties. Most work on slow-release fertilizers has focused on natural Clinoptilolite, Phillipsite and Chabazite. The aim of this study was to synthesize clinoptilolite type of zeolite-enriched fertilizer study their effectiveness as soil amendments. Greenhouse experiments were performed to study the effects of clinoptilolite type of zeolite, synthesised zeolite-enriched ammophos fertilizer and ammophos fertilizer (12% N, 52% P2O5) on yield parameters of Cucumber (Cucumis sativus) plant and some chemical properties in dark chestnut soil. According to greenhouse experiment results, there were significant differences among the treatments in relation to yield parameters (weight of one cucumber, shoot length, number of leaves, area of 10 leaves, number of fruits and fruit weight per plant) of cucumber and available nutrient contents of soil. It was determined that the yield parameters of cucumber plant, available nutrient contents (N, P and K) and cation exchange capacity were increased the most by synthesised zeolite-enriched fertilizer application.

Preparation of zeolite type faujasite from glass waste and aluminum scraps for the selective catalytic reduction of NO with NH3

Preparation of zeolite type faujasite from glass waste and aluminum scraps for the selective catalytic reduction of NO with NH3

Hydrothermal Synthesis of Mordenite Type Zeolite

Zeolite is a crystalline alumino-silicate microporous material, which has been widely used as ion-exchangers, adsorbent and catalyst.&#x0D; Recently, several researches highlights the progress of zeolite-based catalysts in the CO2 conversion to valuable products.&#x0D; In the present work, hydrothermal synthesis of mordenite zeolite crystals, with composition of the chemical products Al2O3, 12.5 SiO2,2.4 NaOH, 110 H2O at 160°C for 96 hours (4 days) at Ph 11 is described. &#x0D; Results of characterization of the mordenite zeolite by XRD, FTIR, EDAX, SEM, TGA, are presented and discussed.&#x0D; In the present work, hydrothermal synthesis and characterization of mordenite zeolite crystals is described.

Zeolite associated with silicification in a volcano-sedimentary context, southern Brazil

In the Paraná Basin context, a volcano-sedimentary interaction is noticeable and some remarkable zeolite aggregates appear in the sediments deposited inside volcanic cavities (mega vesicles). Silicification is likewise associated with sediments. Consequently, analysis such as petrography, X-ray diffraction, Scanning Electron Microscopy, and mainly electronic microprobe confirmed the clinoptilolite. This type of zeolite, under the given conditions, is attributed to low temperatures and appears in a feature known as geodes with sediments. Clinoptilolite is formed from the alteration of the volcanic host rock. This alteration develops by dissolution, remobilization, and precipitation and can form silicification and zeolitization. The study of this association contributes to the understanding of post-magmatic processes, sedimentary processes, dissolution of the volcanic host rock, remobilization of silica, and then precipitation of silica and zeolite as cementation in the sediments. Since this feature is in the context of volcanic alteration rocks and intense fracturing, the framework suggests a permeable and porous system that contributed to processes like infiltration, transportation, silicification, and zeolitization as cementation. Furthermore, a formation and deposition model for the geodes with sediments feature is also suggested for this context.

Lead, zinc, nickel and chromium ions removal from polluted waters using zeolite formed from bauxite, obsidian and their combination with red mud: Behaviour and mechanisms

Synthetic zeolites obtained combining natural sources (bauxite and obsidian), pure alumina/silica reagents, and waste material (red mud) were tested for heavy metals (i.e., Pb2+, Zn2+, Ni2+, Cr3+) removal. The adsorption capabilities of the formed sodalite, zeolite A and zeolite X (LTA and FAU topology, respectively), were compared through thermodynamic and kinetic experiments. Although all the newly-formed zeolites were able to remove the pollutant elements within 24 h, Zeolite X and sodalite synthesized combining obsidian (natural material as silica source) and red mud (waste material as alumina source) proved to be a better sorbent phase (qmax 20–25 mg g−1) compared to Zeolite A formed from treated bauxite (qmax 4–18 mg g−1). Their removal efficiency was also evaluated in polluted waters (wastewater treatment plant [WWTP] effluent, heavy metals mixture, native pH). Depending on synthesized zeolite type, the adsorption mechanism was accredited to ion exchange and precipitation mechanisms. The location of metal-ions inside the zeolite channels was defined by X-ray Powder Diffraction (XRPD) Rietveld analysis. Host–guest interactions among the framework oxygen atoms, co-adsorbed water molecules, and metal-ions were highlighted by the refined bond distances. Finally, magnetic characterization allowed the recognize of different magnetic properties as a function of raw materials used for zeolite synthesis.

CO2 hydrogenation to light olefins using In2O3 and SSZ-13 catalyst − Understanding the role of zeolite acidity in olefin production

With the aim to explore the effect of acidic properties of zeolites in tandem catalysts on their performance for CO2 hydrogenation, two types of SSZ-13 zeolites with similar bulk composition, but different arrangements of framework Al, were prepared. Their morphology, pore structure, distribution of framework Al, surface acid strength and density, were explored. The results showed that SSZ-13 zeolites with isolated aluminum distribution could be successfully synthesized, however, they contained structural defects. During calcination, the framework underwent dealumination, resulting in weaker Brønsted acidity and lower crystallinity. The morphologies were, however, well preserved. Compared with the SSZ-13 zeolites, synthesized conventionally, these low acidity SSZ-13 zeolites with isolated aluminum were good zeolite components in bifunctional catalysts for CO2 hydrogenation to light olefins. By combining with In2O3, they exhibited better catalytic performance for light olefin production during CO2 hydrogenation at low temperatures. Na+ cation exchange was used to adjust the Brønsted acid site (BAS) density with only minor changes to the cavity structure. Comparative experiments established that the BAS density of the zeolite, rather than the framework Al distribution (BAS distribution), overwhelmingly affected catalyst stability and product selectivity. A higher acid density reduced the selectivity for light olefins, while lower acid density tended to form inert coke species leading to rapid deactivation. The ideal amount of BAS density in the bifunctional catalyst was approximately 0.25 mmol/g, which exhibited 70% selectivity for light olefins among hydrocarbons, and 74% selectivity for CO without deactivation, after 12 h reaction at 325 ℃ and 10 bar.

Comparision of NH3−SCR Activity over Cu‐Ce‐La/MCM‐49 and Cu‐Ce‐La/MCM‐22 Zeolites

AbstractThe addition of La onto Cu‐Ce modified MWW type zeolite (MCM‐49 and MCM‐22) catalysts were synthesized by ion exchange process and the effect of different support (MCM‐49 and MCM‐22) on the activity was also discussed for ammonia selective catalytic reduction of NOx (NH3−SCR). The addition of La can significantly improve the catalytic performance of Cu‐Ce/MCM‐49. Furthermore, the addition of La can also facilitate electron transfer by the cycle of oxidation of Cu2++Ce3+→Cu++Ce4+ for Cu‐Ce‐La/MCM‐49. The electron transfer is beneficial to “FAST SCR” in that it can promote the conversion of NO to NO2, thus improving denitrification performance. Moreover, La can also provide the excellent surface acidity, which is favorable for the generation of oxygen vacancies. Compared with Cu‐Ce‐La/MCM‐22, Cu‐Ce‐La/MCM‐49 catalyst exhibited better SCR activity within 200–450 °C on account of the good redox performance and the more Ce3+ content. In addition, Ce3+ can generate oxygen vacancies, thereby enhancing the catalytic performance. More than anything, Cu‐Ce‐La/MCM‐49 has excellent sulfur tolerance.

Machine learning-assisted crystal engineering of a zeolite

It is shown that Machine Learning (ML) algorithms can usefully capture the effect of crystallization composition and conditions (inputs) on key microstructural characteristics (outputs) of faujasite type zeolites (structure types FAU, EMT, and their intergrowths), which are widely used zeolite catalysts and adsorbents. The utility of ML (in particular, Geometric Harmonics) toward learning input-output relationships of interest is demonstrated, and a comparison with Neural Networks and Gaussian Process Regression, as alternative approaches, is provided. Through ML, synthesis conditions were identified to enhance the Si/Al ratio of high purity FAU zeolite to the hitherto highest level (i.e., Si/Al = 3.5) achieved via direct (not seeded), and organic structure-directing-agent-free synthesis from sodium aluminosilicate sols. The analysis of the ML algorithms’ results offers the insight that reduced Na2O content is key to formulating FAU materials with high Si/Al ratio. An acid catalyst prepared by partial ion exchange of the high-Si/Al-ratio FAU (Si/Al = 3.5) exhibits improved proton reactivity (as well as specific activity, per unit mass of catalyst) in propane cracking and dehydrogenation compared to the catalyst prepared from the previously reported highest Si/Al ratio (Si/Al = 2.8).