Search Results (423)

In our previous work, we fabricated Ni single-atoms within Beta zeolite (Ni₁@Beta-NO₃⁻) using NiNO₃·6H₂O as a metal precursor without any chelating agents, which exhibited exceptional performance in the selective hydrogenation of furfural. Owing to the confinement effect, the as-encapsulated nickel species appears in the form of Ni⁰ and Ni^δ+, which implies its feasibility in metal catalysis and coordination catalysis. In the study reported herein, we further explored the hydrogen production and olefin oligomerization performance of Ni₁@Beta-NO₃⁻. It was found that Ni₁@Beta-NO₃⁻ demonstrated a high H₂ generation turnover frequency (TOF) and low activation energy (E_a) in a sodium borohydride (NaBH₄) hydrolysis reaction, with values of 331 min⁻¹ and 30.1 kJ/mol, respectively. In ethylene dimerization, it exhibited a high butylene selectivity of 99.4% and a TOF as high as 5804 h⁻¹. In propylene oligomerization, Ni₁@Beta-NO₃⁻ demonstrated high selectivity (75.21%) of long-chain olefins (≥C₆⁺), overcoming the problem of cracking reactions that occur during oligomerization using H-Beta. Additionally, as a comparison, the influence of the metal precursor (NiCl₂) on the performance of the encapsulated Ni catalyst was also examined. This research expands the application scenarios of non-noble metal single-atom catalysts and provides significant assistance and potential for the production of H₂ from hydrogen storage materials and the production of valuable chemicals. Full article

Understanding the adsorption mechanism is essential for developing efficient technologies to capture carbon dioxide from industrial flue gases. In this work, laboratory measurements, density functional theory calculations, and molecular dynamics simulations were employed to study CO₂ adsorption and diffusion behavior in LTA-type zeolites. The CO₂ adsorption isotherms measured in zeolite 5A are best described by the Toth model. Thermodynamic analysis indicates that the adsorption process is spontaneous and exothermic, with an enthalpy change of −44.04 kJ/mol, an entropy change of −115.23 J/(mol·K), and Gibbs free energy values ranging from −9.68 to −1.03 kJ/mol over the temperature range of 298–373 K. The isosteric heat of CO₂ adsorption decreases from 40.35 to 21.75 kJ/mol with increasing coverage, reflecting heterogeneous interactions at Ca²⁺ and Na⁺ sites. The adsorption kinetics follow a pseudo-first-order model, with an activation energy of 2.24 kJ/mol, confirming a physisorption mechanism. The intraparticle diffusion model indicates that internal diffusion is the rate-limiting step, supported by a significant reduction in the diffusion rate. The DFT calculations demonstrated that CO₂ exhibited a −35 kJ/mol more negative adsorption energy in zeolite 5A than in zeolite ITQ-29, attributable to strong interactions with Ca²⁺/Na⁺ cations in 5A that were absent in the pure silica ITQ-29 framework. The molecular dynamics simulations based on molecular force fields indicate that CO₂ diffuses more rapidly in ITQ-29, with a diffusion coefficient measuring 2.54 × 10⁻⁹ m²/s at 298 K, whereas it was 1.02 × 10⁻⁹ m²/s in zeolite 5A under identical conditions. The activation energy for molecular diffusion reaches 5.54 kJ/mol in zeolite 5A, exceeding the 4.12 kJ/mol value in ITQ-29 by 33%, which accounts for the slower diffusion kinetics in zeolite 5A. There is good agreement between experimental measurements and molecular simulation results for zeolite 5A across the studied temperature and pressure ranges. This confirms the accuracy and reliability of the selected simulation parameters and allows for the study of zeolite ITQ under similar simulation conditions. This research provides insights into CO₂ adsorption energetics and diffusion within LTA-type zeolite frameworks, supporting the rational design of high-performance adsorbents for industrial gas separation. Full article

In this work, methyl viologen (MV) was adsorbed into the nanopores of Si/Al H-β-zeolite via cation exchange. The resulting MV@β-zeolite possessed absorption/fluorescence dual-mode and photo/chemical synergistic stimuli-responsive chromism. Owing to the acidic surrounding provided by β-zeolite, the chromism of MV required the synergistic stimuli of UV irradiation and a chemical reductant (such as Na₂SO₃). UV irradiation induced single electron transfer from the chemical reductant to MV@β-zeolite, leading to enhanced absorption at 610 nm together with a daylight color change from pale yellow to blue. Meanwhile, the nanopores of β-zeolite inhibited aggregation-caused quenching of MV, enabling MV to emit cyan fluorescence at 500 nm. After the single electron transfer of the chemical reductant under UV irradiation, the cyan fluorescence of MV@β-zeolite was quenched. Additionally, MV@β-zeolite exhibited a short stimulus response time (250 s) and good color change reversibility. These findings in this work provide valuable insights into the design of multi-mode and synergistic stimuli-responsive viologen-based chromic materials, particularly for applications in secure high-throughput information storage, high-level anti-counterfeiting and multi-target multi-mode sensing. Full article

Zeolite adsorption followed by NaCl-NaClO regeneration is an effective method for the on-site treatment of ammonia in initial stormwater. However, the formation and toxicity of chlorine species during the zeolite regeneration process need to be investigated. In this study, under intermittent and continuous operations, zeolites adsorbed NH₄Cl + HA (humic acid) and actual stormwater, then regenerated with NaCl-NaClO (0.5 g/L NaCl, ClO⁻:N molar ratio of 1.8, pH = 10). This technology was assessed from the following three aspects: adsorption and regeneration, chlorine species formation, and toxicity. The results showed that zeolites exhibited a greater adsorption capacity for HA in stormwater compared to that in an NH4Cl + HA solution, and the presence of ammonia had a minimal impact on this process. During zeolite regeneration, ammonia had a competitive advantage over HA for ClO⁻. ClO₃⁻ was inevitably formed in regeneration. The formation of chlorinated organic compounds (COPs) increased over time. The order of chlorine species toxicity in zeolite regeneration solution was free chlorine > COPs > ClO₃⁻. Controlled regeneration time was required to minimize the formation and toxicity of chlorine species. During the 10 cycles of regeneration, chlorine species continued to form and caused high toxicity hazards. Full article

Recognizing the growing importance of natural gas as a transition fuel in Poland’s energy mix and the necessity of reducing CO₂ emissions, this article aims to assess the use of carbon capture and storage (CCS) technology to effectively reduce CO₂ emissions from combined cycle gas turbine (CCGT). The research employs the pressure–temperature swing adsorption (PTSA) to capture CO₂ from flue gases. Computer simulations, using IPSEpro (SimTech), are used to calculate the heat and mass balances for CCGT and PTSA units and assess their performance. In the first part of the research, the effect of sorbent type (Na-A and 5A) and flue gas share directed to the PTSA unit on the performance of the CCGT was investigated. Secondly, the parametric analysis regarding the adsorption and desorption pressures in the PTSA was carried out. The results showed that CO₂ emissions from CCGT can be reduced by 1.1 Mt (megatons) per year, but the use of PTSA was associated with a reduction in net electrical power and efficiency of the CCGT by up to 14.7% for Na-A and 11.1% for 5A sorbent. It was also found that the heat and electricity demand of the PTSA depends on the adsorption and desorption pressures. Full article

ZSM-5 zeolites are primarily used in acid-catalyzed hydrocracking reactions in the petrochemical industry, and it is very important to ensure an adequate number of acidic sites for more efficient catalytic activity. This study investigated the possibility of exchanging sodium ions with hydrogen ions on ZSM-5 zeolite with a molar ratio of (SiO₂/Al₂O₃ = 1000) using an ion-exchange process with acetic acid. By employing the XRD and FT-IR methods, along with chemical analysis of ZSM-5 zeolite samples, the influence of hydrogen ion concentration on the chemical composition and structural characteristics of ZSM-5 zeolite was monitored at different acid concentrations and exchange times. It was shown that ion exchange with acetic acid leads to a significant reduction in sodium content even with less concentrated solutions while maintaining the stability of the crystal structure of ZSM-5 (SiO₂/Al₂O₃ = 1000) and a high degree of crystallinity. Full article

Despite significant advancements in designing tandem catalysts for CO₂ hydrogenation to aromatics, the role of zeolite acid property in regulating the selectivity of light aromatics (benzene, toluene, and xylene, abbreviated as BTX) remains unclear. Herein, we report H-ZSM-5 zeolite (denoted as HZ-X, where X represents the Si/Al ratio) integrated with a Na-promoted FeCo-based catalyst (NaFeCo) for CO₂ hydrogenation into aromatics via a modified Fischer–Tropsch synthesis pathway. This study systematically modulates the Si/Al ratio of acidic zeolite and examines its critical role in influencing the light aromatics selectivity. The optimized NaFeCo/HZ-50 catalyst achieves a CO₂ conversion of 43% with an aromatics selectivity of 41%, including a BTX fraction of 57% in total aromatics. Multiple characterization techniques (NH₃-TPD, Py/DTBPy-IR, ²⁷Al NMR, etc.) clarify that acidic zeolite HZ-50 exhibits appropriate acid density and lower external surface acid sites, which synergistically boost the efficient aromatics and BTX synthesis while suppressing the undesirable alkylation and isomerization reactions on the external acid sites. This work develops a highly efficient multifunctional catalyst for CO₂ hydrogenation to light aromatics, especially offering guidance for the rational design of acidic zeolite with unique shape-selective functions. Full article

Silver nanoclusters that are confined inside zeolites can give off intensive tunable emission across the visible region under UV excitation. In this research, a series of silver nanoclusters loaded with R-FAU/Ag (R = Li, Na, K) zeolites were synthesized and then applied as phosphors for LEDs. The XRD and SEM measurements showed the R-FAU/Ag (R = Li, Na, K) zeolites have high crystallinity and a size distribution of 0.7–1.25 μm. Under excitations of 310–330 nm ultraviolet radiation, Li-FAU/Ag, Na-FAU/Ag, and K-FAU/Ag exhibit monotonically declining emission intensities and red-shifted emissions with peak wavelengths of 520, 527, and 535 nm, respectively. By using silicone-based epoxy resin as the packaging material, a series of LEDs were fabricated by mixing R-FAU/Ag (R = Li, Na, K) phosphors. It is indicated that the Li-FAU/Ag-LED shows the strongest intensity of 94.9 mcd, much higher than that of the LEDs made from Na-FAU/Ag (63.7 mcd) and K-FAU/Ag (74.2 mcd) phosphors. Additionally, the chromaticity coordinate of the Li-FAU/Ag-LED is located at (0.2651, 0.4073) and has a high color temperature of 7873 K. Thermal test data showed that upon heating to 440 K, the intensities of R-FAU/Ag (R = Li, Na, K) LEDs decreased to 81%, 79%, and 75% of their initial intensities measured at 280 K, respectively. This research proposes a method for regulating the luminescent properties of silver nanoclusters in FAU zeolite by modifying the extra-framework cations and demonstrates excellent performance in LED products. Full article

The development of highly effective natural-based adsorbents to face the increasing rates of CO₂ production and their delivery to the atmosphere are a big concern nowadays. For such purposes, synthetic and natural zeolites were modified via an ion exchange procedure to enhance the CO₂ uptake. Samples were characterized by SEM, EDS, TGA and nitrogen adsorption at 77 K, showing the correct incorporation of the new metals; in addition, the CO₂ adsorption isotherms were determined using a gas analyser. During the first stage, the role of the compensation cations for CO₂ adsorption was assessed by modifying a pure ZSM-5 synthetic zeolite with different metal precursors present in salt solutions via an ion exchange procedure. Then, five samples were studied; the samples modified with bivalent cation precursors (Zn²⁺ and Cu²⁺) presented a higher adsorption uptake than those modified with a monovalent cation (Na⁺ and K⁺). Specifically, the substitution of the compensation cations for Cu²⁺ increased the CO₂ capture uptake without affecting the surface properties of the zeolite. The results depict the prevalence of π-cation interactions enhanced by the field gradient induced by divalent cations and their lower ionic radii, if compared to monovalent ones. Subsequently, a natural zeolite was modified considering the best results of the previous phase. This Surface Response Methodology was implemented considering 11 samples by varying the concentration of the copper precursor and the time of the ion exchange procedure. A quantitative quadratic model to predict the adsorption uptake with an R² of 0.92 was obtained. The results depicted the optimal conditions to modify the used natural zeolite for CO₂ capture. The modification procedure implemented increased the CO₂ adsorption capacity of the natural zeolite more than 20%, reaching an adsorption capacity of 75.8 mg CO₂/g zeolite. Full article

As a rarefied metallic element, strontium (Sr) is susceptible to significant environmental radioactive contamination risks during industrial mining and refining processes. In this study, NaA molecular sieves were prepared by alkali excitation using synthetic powders, which were homogeneously blended with the polyacrylonitrile (PAN) matrix, and nanoscale TiO₂ reinforcing phases were introduced. Finally, composite separation membranes (TiO₂-NaA@PANMs) with stable adsorption properties were constructed by electrostatic spinning technology. The micro-morphology and interfacial properties were characterized by SEM, XRD, and FT-IR systems. The adsorption experiments demonstrated that the equilibrium adsorption capacity of the system for Sr²⁺ reached 55.00 mg/g at the optimized pH = 6.0, and the theoretical saturated adsorption capacity at 298 K was 80.89 mg/g. The isothermal process conformed to the Langmuir’s model of monomolecular layer adsorption, and the kinetic behavior followed the quasi-secondary kinetic equation. Following three cycles of regeneration by elution with a 0.3 mol/L sodium citrate solution, the membrane material exhibited 81.60% Sr²⁺ removal efficacy. The composite membrane passages exhibited remarkable potential for utilization in engineering applications involving the treatment of complex nuclear wastewater. Full article

Zeolite Battery Research Africa (ZEBRA) batteries (Na-NiCl₂ solid electrolyte batteries, SEBs) have commercial applications in energy storage due to their low costs and recyclability, long lifetime, and high safety. In commercial ZEBRA batteries, Ni electrode and beta’’-alumina solid electrolyte (BASE) have a more than 70% share of the overall cell material costs. Na-ZnCl₂ all-liquid batteries (ALBs), which replace Ni with abundant and low-cost Zn and BASE electrolyte with molten salt electrolyte, could reduce costs and provide a longer lifetime and higher safety, making their application in grid storage promising. However, compared to SEBs, ALBs are in an early development stage, particularly for their molten salt electrolytes, which have a significant effect on the battery performance. Physical and chemical properties of the salt electrolyte like melting temperatures and solubilities of electrode materials (i.e., Na and Zn metal) are vital for the molten salt electrolyte selection and battery cell design and optimization. In this work, the binary and ternary phase diagrams of salt mixtures containing NaCl, CaCl₂, BaCl₂, SrCl₂, and KCl, obtained via FactSage simulation and DSC measurements, as well as the solubilities of electrode materials (Na and Zn metals), are presented and used for the selection of the molten salt electrolyte. Moreover, various criteria, considered for the selection of the molten salt electrolyte, include high electromotive force (EMF) for suitable electrochemical properties, low melting temperature for large charge/discharge range, low solubilities of electrode materials for low self-discharge, low material costs, and high material abundance for easy scale-up. Based on these criteria, the NaCl-CaCl₂-BaCl₂ and NaCl-SrCl₂-KCl salt mixtures are selected as the two most promising ALB molten salt electrolytes and suggested to be tested in the ALB demonstrators currently under development. Full article

This paper deals with synthesizing Zn, Cu, and AgNPs supported on the surface of zeolite Y for catalytic and antimicrobial applications. Firstly, the zeolite Na-Y was exchanged with solutions containing metal precursors and then a chemical treatment was used to transform the metal cations into metal nanoparticles. The different samples were characterized by different characterization methods. The reduction of methylene blue (MB) and orange (OG) dyes in the presence of NaBH₄ and nanocatalysts in a simple and binary system showed good results. It was shown in this study that the concentration of the reagents, the nature of metal species, and the nature of the dye can influence the conversion of the dye. The calculated kapp obtained by the best catalyst (Ag/Y) in a simple system was 1.882 min⁻¹ and 1.115 min⁻¹ for MB and OG dyes, respectively. It was found that the Ag/Y catalyst was more selective via MB in the binary system containing OG+MB dyes. The reuse of the Ag/Y catalyst in five cycles showed good results via the conversion of the MB dye without losing its performance. For antimicrobial activities, encouraging results have been recorded on different strains having inhibition zones between 14 and 25 mm. Full article

The oxidative coupling of methyl chloride (CH₃Cl) to vinyl chloride (C₂H₃Cl) (MCTV) represents a promising yet challenging direct conversion route for C₂H₃Cl production. In this study, a novel catalyst, cristobalite silica, supported Na₂WO₄ nanoclusters, was fabricated by calcining an intermediate composite composed by β-zeolite and sodium tungstate (Na₂WO₄). The pore structure of this β-zeolite possesses a regular shape and suitable size distribution, providing an accurate geometric matching effect for Na₂WO₄ to homogeneously distribute in the entire β-zeolite matrix with high loading. Accordingly, the excellent dispersity of Na₂WO₄ nanocluster active sites is well maintained even after calcining at 750 °C, and the microporous β-zeolite matrix is completely converted to dense cristobalite phase silica after the calcination. The high-loading and well-dispersed Na₂WO₄ nanocluster leads to a superior performance in MCTV with a CH₃Cl conversion of 81.5%, a C₂H₃Cl selectivity of 42.4%, and a C₂H₃Cl yield of 34.6%. Notably, the catalyst exhibits remarkable stability during the catalytic process. Full article

Marine biofouling causes significant economic losses, and conventional antifouling methods are often associated with environmental pollution. Hydrogen peroxide (H₂O₂), as a clean energy source, has gained increasing attention in recent years. Meanwhile, electrocatalytic 2e⁻ oxygen reduction reaction (ORR) for H₂O₂ production has received growing interest. However, the majority of current studies are conducted on acidic or alkaline electrolytes, and research on 2e⁻ ORR in neutral NaCl solutions remains rare. Here, a bimetallic Zn-Cd zeolitic imidazolate framework (ZnCd-ZIF) is rationally designed to achieve chloride-resistant 2e⁻ ORR catalysis under simulated seawater conditions (pH 7.5, 3.5% Cl⁻). Experimental results demonstrate that the ZnCd-ZIF catalyst exhibits an exceptional H₂O₂ selectivity of 70% at 0.3 V_RHE, surpassing monometallic Zn-ZIF (60%) and Cd-ZIF (50%). Notably, H₂O₂ production reaches 120 mmol g⁻¹ in a Cl⁻-containing neutral electrolyte, exhibiting strong resistance to structural corrosion and Cl⁻ poisoning. This work not only pioneers an effective strategy for designing ORR catalysts adapted to marine environments but also advances the practical implementation of seawater-based electrochemical H₂O₂ synthesis. Full article

This study investigates the adsorption of Acid Black 1 (ABk 1) dye onto natural clinoptilolite (CLIN) and synthetic NaP1 zeolites under various conditions of adsorbent dose (5, 10, 20 g/L), dye concentration (1–1000 mg/L), and contact time (5–1440 min). The adsorption data were analyzed using Freundlich and Langmuir isotherms, as well as pseudo-first-order and pseudo-second-order kinetic models. Both linear and nonlinear regression methods were applied to assess the model fit. The results showed that CLIN exhibited maximum adsorption capacities of 35.32 mg/g, 21.9 mg/g, and 9.39 mg/g at doses of 5 g/L, 10 g/L, and 20 g/L, respectively. For NaP1, the corresponding values were 28.44 mg/g, 12.46 mg/g, and 9.11 mg/g. The pseudo-first-order model described adsorption at low dye concentrations and short contact times, while the pseudo-second-order model successfully explained adsorption across all tested conditions. These findings suggest that both zeolites, particularly CLIN, are effective adsorbents for ABk 1 dye removal, presenting a valuable solution for wastewater treatment applications. Full article