Search Results (333)

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

Microwave-assisted ionothermal strategies offer an effective pathway for rapid zeolite crystallization under mild conditions, while conventional ionothermal approaches are still constrained by prolonged crystallization cycles that limit their industrial applicability. Herein, we report a microwave-activated, ionic liquid-mediated synthesis strategy that enables the precise modulation of crystallization kinetics and composite assembly. By introducing ZSM-5 seeds into the ionic liquid system, the nucleation and growth of AlPO₄-5 were significantly accelerated, reducing crystallization time by up to 75% (optimal condition: 60 min). Among various imidazolium-based ionic liquids, [BMMIm]Br demonstrated an optimal balance of hydrophilic and hydrophobic interactions, yielding composite zeolites with high surface area (350 m²·g⁻¹) and large pore volume (0.28 cm³·g⁻¹). Comprehensive characterization (XRD, SEM-EDX, NH₃-TPD) confirmed the formation of well-defined ZSM-5/AlPO₄-5 core–shell structures and revealed tunable acid site distributions depending on the ionic liquid used. In methanol to olefins (MTO) reactions, the composite catalyst exhibited outstanding selectivity towards light olefins (C₂=–C₄=: 72.84%), markedly outperforming the individual ZSM-5 and AlPO₄-5 components. The superior catalytic behavior is primarily attributed to the synergistic effect of hierarchical acid site tuning and the integrated core–shell architecture, which together optimize reaction selectivity. This strategy provides a promising route for the rational design of high-performance zeolites with significant industrial applicability. Full article

Marine biofouling, the process of marine microorganisms, algae, and invertebrates attaching to and forming biofilms on ship hulls, underwater infrastructure, and marine equipment in ocean environments, severely impacts shipping and underwater operations by increasing fuel consumption, maintenance costs, and corrosion risks, and by threatening marine ecosystem stability via invasive species transport. This study reports the development of a hydrogel-metal-organic framework (MOF)-quorum sensing inhibitor (QSI) antifouling coating on 304 stainless steel (SS) substrates. Inspired by mussel adhesion, a hydrophilic bionic hydrogel was first constructed via metal ion coordination. The traditional metal ion source was replaced with a zeolitic imidazolate framework-8 (ZIF-8) loaded with 2-(5H)-furanone (HF, a QSI) without altering coating formation. Physicochemical characterization using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), the Brunauer–Emmett–Teller (BET) method, and the diffraction of x-rays (XRD) confirmed successful HF loading into ZIF-8 with intact crystal structures. Antifouling tests showed HF@ZIF-8 enhanced antibacterial inhibition against Staphylococcus aureus (97.28%) and Escherichia coli (>97%) and suppressed Chromobacterium violaceum CV026 pigment synthesis at 0.25 mg/mL (sub-growth concentration). The reconstructed PG/PVP/PEI/HF@ZIF-8 coating achieved 72.47% corrosion inhibition via synergistic anodic protection and physical shielding. This work provides a novel green approach for surface antifouling and drag reduction, highlighting MOF-loaded QSIs as promising additives to enhance the antifouling performance of hydrogel coatings, anti-corrosion performance, and QSI performance for sustainable marine engineering applications. Full article

Size restrictions pose increasing challenges to the acoustic performance of microspeakers in portable devices as the size of such devices, and thus the back volume of microspeakers, continues to shrink. Filling the back volume with porous materials, such as zeolites, has been proved to be an effective strategy for improving acoustic performance. In this work, hierarchically structured ZSM-5 zeolites with abundant mesopores were synthesized via the traditional hydrothermal method by adjusting the SiO₂/Al₂O₃ ratios (SAR), and their pore structures and morphologies were systematically investigated. Their acoustic enhancement performance was evaluated using a commercial microspeaker. Based on their acoustic properties, the influence of pore structure on acoustic performance was further studied. The ZSM-5 zeolite sample with an SAR of 614, which exhibited the maximum mesopore volume, demonstrated exceptional acoustic enhancement performance with a resonance offset of 199.53 Hz and an enhanced sound pressure level of 4.74 dB at 500 Hz. The presence of mesopores significantly facilitates diffusion within the zeolite crystals, enabling air molecules to access more micropores for efficient sorption–desorption processes during diaphragm vibration in microspeakers. Furthermore, supermicropores were found to contribute to improved performance by adsorbing air molecules during diaphragm vibration, complementing the role of micropores. Full article

In recent years, climate change has attracted the attention of the scientific community. These changes are attributed to human action, which is responsible for the emission of polluting gases, mainly through the burning of fossil fuels, deforestation, and industrial processes that are responsible for the greenhouse effect. Post-combustion CO₂ capture using solid adsorbents is a technology that is currently gaining prominence as an alternative and viable form of capture to other industrial processes used. Zeolites are adsorbents capable of capturing CO₂ selectively due to their properties such as textural properties, high surface area, and active sites. In this context, this work developed materials with a zeolite structure with an alternative low-cost silica source from beach sand, called MPI silica, to make the process eco-friendly. Crystallization time studies were carried out for materials containing MFI-type zeolites with MPI silica with a time of 15 h (ZM 15 h) and 3 days (SM 3 d), with relative crystallinities of 92.90% and 111.90%, respectively. The synthesized materials were characterized by several techniques such as X-ray diffraction (XRD), X-ray fluorescence (XRF), the textural analysis of N₂ adsorption/desorption isotherms, absorption spectroscopy in the infrared region with Fourier transform (FTIR), scanning electron microscopy (SEM), and thermal analysis. The evaluation of the experimental adsorption isotherms showed that the best results were for the zeolites synthesized in the basic medium, namely ZMP 3 d, ZM 10.5 h, and ZM 15 h, with capacities of 3.72, 3.10, and 3.22 mmol/g of CO₂, respectively, and in the hydrofluoric medium, namely SP 9 d, SM 3 d, and SM 6 d, with capacities of 3.94, 3.78, and 3.60 mmol/g of CO₂, respectively. The evaluation of the mathematical models indicated that the zeolites in the basic medium best fitted the Freündlich model, namely ZMP 3 d, ZM 10.5 h, and ZM 15 h, with capacities of 2.56, 1.68, and 1.87 mmol/g of CO₂, respectively. The zeolites in the hydrofluoric medium are adjusted to the Langmuir model (SP 9 d and SM 3 d) and Temkin model (SM 6 d), with capacities of 3.79, 2.23, and 2.11 mmol/g of CO₂, respectively. Full article

A study systematically investigating the structural modifications and catalytic performance of IM-5 zeolite treated with hexafluorosilicic acid in pseudocumene alkylation with methanol was carried out. Characterization techniques revealed significant alterations in crystal structure, morphology, textural properties, coordination environment, and acidity induced by the modifications. Catalytic evaluations demonstrated altered pseudocumene conversion, durene selectivity, and products distribution for optimized samples, with IM-5-0.01 (treated with 0.01 M modifier) showing superior activity stability. The improved performance was attributed to two key factors: a stable framework with high-density medium-strength Brønsted acid sites facilitating complete alkylation and expanded mesoporous volume promoting efficient product diffusion to mitigate deactivation. Conversely, reduced durene selectivity in modified samples stem from intensified isomerization reactions driven by increased external surface area, resulting in higher C₉ product fractions. In contrast, the parent IM-5 zeolite exhibited rapid deactivation, with durene selectivity peaking at 40 h before declining. Mechanistic insights revealed dynamic processes including dealumination, defect formation, silicon repair, and aluminum redistribution during treatment, providing a theoretical foundation for rational catalyst design in alkylation reactions. Full article

This work is devoted to the study of the effect of acid treatment on the structural and textural properties of natural zeolite and its sorption activity with respect to radioiodide. To carry out the experiments, natural zeolite was treated with nitric acid of various concentrations at 20 and 90 degrees. The following methods were used to study the samples: XRD, SEM, DTA, XRF, FTIR, BET, and CEC analyses. Experiments on the sorption and desorption of radioiodide were carried out. The obtained results indicate that acid treatment results in the gradual leaching of aluminum from the crystal lattice and a significant increase in the specific surface area and microporosity of the zeolite. At the same time, the morphology of clinoptilolite is not significantly changed. Additional studies have shown that acid treatment leads to the hydrophobization of zeolite channels and the formation of an amorphous aluminosilicate phase, which makes a significant contribution to the increase in the specific surface area and microporosity. It was found that, with an increase in the degree of dealumination of the zeolite, there is an increase in the sorption properties with respect to radioiodide. The maximum values of sorption capacity were obtained after treating the zeolite with a 1 M nitric acid solution at 90 °C. With a further increase in the concentration of acid, critical changes in the structure of the zeolite occur, leading to a sharp decrease in the sorption capacity. Iodide sorption is not associated with physical adsorption in the micropores of the zeolite and the newly formed amorphous phase. The main mechanism of the sorption appears to be the interaction with silanol and bridging hydroxyl groups on the surface of the zeolite and the amorphous aluminosilicate phase. Full article

Potassium bitartrate (KHT) crystallization, as the dominant factor compromising wine colloidal stability, necessitates advanced control strategies beyond conventional thermodynamic approaches. The formation of tartrate crystals is influenced by various factors, including temperature, pH, and the concentration of tartrate salts. Traditional methods of tartrate stabilization, such as cold stabilization and ion-exchange resins, while effective, are associated with high energy consumption and significant environmental impact. In recent years, with the growing emphasis on green and sustainable development, researchers have begun exploring more environmentally friendly innovative technologies. This review examines the factors affecting tartrate crystallization and their implications for wine quality, detailing traditional stabilization techniques as well as newer methods involving protective colloids and stabilizers. Special attention is given to recent advancements in green technologies, such as plasma surface modification, the use of zeolites as wine processing aids, and the synergistic application of algal polysaccharides. Finally, the paper outlines future directions for tartrate stabilization technology, underscoring the importance of green and sustainable practices in the wine industry. Full article

Coal mining and washing processes generate substantial amounts of coal gangue, posing significant environmental challenges. Coal gangue as a solid waste is rich in SiO₂ and Al₂O₃, with the SiO₂/Al₂O₃ molar ratio closely aligned with the ideal composition of 4A molecular sieves. In this study, through a synergistic pretreatment process involving low-temperature oxidation and hydrochloric acid leaching, the Fe₂O₃ content in coal gangue was reduced from 7.8 wt% to 1.1 wt%, markedly enhancing raw material purity. The alkali fusion–hydrothermal synthesis parameters were optimized via orthogonal experiments—calcination (750 °C, 2 h), aging (60 °C, 2 h), and crystallization (95 °C, 6 h) to maintain cubic symmetry, yielding highly crystalline 4A zeolite. Characterization via XRD, calcium ion adsorption capacity, SEM, and FTIR elucidated the regulatory mechanism of calcination on kaolinite phase transformation and the critical role of alkali fusion in activating silicon–aluminum component release. The as-synthesized zeolite exhibited a cubic morphology, high crystallinity, and sharp diffraction peaks consistent with the 4A zeolite phase. The pH of the zero point charge (pH_ZPC) of the 4A molecular sieve is 6.13. The 4A molecular sieve has symmetry-driven adsorption sites, and the adsorption of Cu²⁺ follows a monolayer adsorption mechanism (Langmuir model, R² = 0.997) with an average standard enthalpy change of 38.96 ± 4.47 kJ/mol and entropy change of 0.1277 ± 0.0148 kJ/mol, adhering to pseudo-second-order kinetics (R² = 0.999). The adsorption process can be divided into two stages. This study provides theoretical and technical insights into the high-value utilization of coal gangue. Full article

This study examined the hierarchical structuring of *BEA zeolite using two distinct approaches: double aluminum removal with solid ammonium hexafluorosilicate (2x-AHFS) and a solution of 0.2 M sodium hydroxide followed by 0.5 M hydrochloric acid (T-NaOH). Additionally, niobium pentoxide (Nb₂O₅) was impregnated at different loadings (5, 10, 15, and 20 wt.%) onto the hierarchized materials. Both treatments increased the SiO₂/Al₂O₃ ratio and produced crystals with domains of about the same size. The hierarchization methods generated secondary mesopores and reduced the micropores in the treated HB zeolite. The solid-state NMR analysis by ²⁷Al and ²⁹Si indicated that the 2x-AHFS treatment increased the hydrophobic character of the zeolite, while the treatment with NaOH/HCl resulted in a less hydrophobic material. A balanced quantity of Brønsted and Lewis sites was observed for all treated zeolites. Thus, these combined physicochemical characteristics of the new catalysts may explain their superior performance in the dehydration reactions. In the case of ethanol dehydration at 230 °C, the 20 wt.% Nb₂O₅ supported on the T-NaOH catalyst produced an 84% conversion and 86% selectivity for ethylene (EE), with 14% diethyl ether (DEE) as the only products. Conversely, in the 1-propanol dehydration reaction, the 20 wt.% Nb₂O₅ supported on 2x-AHFS achieved 99% conversion, producing 99% propene. Full article

Extracting aluminum from FA is an effective way to improve its utilization rate. Since aluminum oxide is found in high polymerization degree, inert substances such as mullite and sodium aluminosilicate make the reaction process difficult because of their stable chemical properties; within these highly polymerized matrices, the chemical stability of alumina typically persists across a broad temperature range from 1000 °C to over 1600 °C. To address the issue of stable mullite structure that hinders aluminum extraction, a combined acid-base method using sodium carbonate as an activating agent and hydrochloric acid at a temperature of 100 °C as a leaching agent is employed. XRD and SEM were used to analyze the phase characterization and microstructure of fly ash before and after activation and acid leaching, examining the effects of activation parameters and acid leaching parameters on the activation of FA and the aluminum extraction rate. The research results indicate that after calcination activation, mullite is transformed into zeolite, which is easily soluble in acid, and the aluminum within the activated molten material is transferred to the filtrate through acid leaching, achieving the goal of extracting aluminum. Under the activating conditions with sodium carbonate flux, the Al-O bonds in mullite are broken, the crystal structure is transformed, and the aluminum compounds obtained from hydrochloric acid leaching have a stable form of existence, which has a low impact on the error of the experimental results. When the material ratio of fly ash to sodium carbonate is 1:0.7, after reacting at a calcination temperature of 880 °C for 1.5 h, and leaching in 6 mol/L hydrochloric acid at 100 °C with a solid-liquid ratio of 1:6 for 2 h, the extraction rate of aluminum in fly ash is the highest, reaching 97%. Full article

The accumulation of coal gangue (CG), a byproduct of coal mining, poses severe environmental challenges. This study presents a green strategy to convert CG into high-value NaX zeolite via an alkali fusion–hydrothermal method. Through orthogonal experiments, the optimal synthesis conditions (solid–liquid ratio 1:8, crystallization temperature 110 °C, time 12 h) were identified, yielding NaX zeolite with exceptional crystallinity (98%), specific surface area (703.5 m²/g), and pore volume (0.28 cm³/g). Comprehensive characterization (XRD, SEM-EDS, BET, etc.) confirmed its structural integrity and thermal stability. The synthesized zeolite exhibited remarkable adsorption capacities for Cu²⁺ (185.35 mg/g) and CO₂ (5.51 mmol/g), following the Langmuir isotherm model. This work not only addresses gangue disposal challenges but also demonstrates a cost-effective route for producing high-performance adsorbents, aligning with circular economy and carbon neutrality goals. Full article

A simple and low-cost synthesis assisted by seed crystals has been proposed to convert residual colorless glass powder into a Na-X zeolite. For this purpose, the optimal parameters for acid leaching of glass powder were studied to remove impurities that could interfere with the crystallization process. Then, the hydrothermal syntheses were supported by Na-X seed crystals (0% to 5%, wt.) to induce the growth of zeolite X, evaluating the crystallization time (12 h to 48 h) and the variation of the silicon source (acid-treated and untreated residues). The formation of the faujasite as the main phase, with a higher degree of structural order and microporosity, was observed with the previous treatment in the residue, a higher seed loading, and a shorter crystallization time. On the other hand, a phase competition between faujasite, gismondine, Linde type-A, and sodalite structures was observed in the zeolites synthesized from the untreated residue. In this case, the high seed loading and the longer synthesis time allowed the correct targeting of the faujasite structure with low structural order and micro/mesoporous properties. Furthermore, interzeolite transformations occur in all syntheses, where the framework type synthesized was influenced by the presence of a specific ion as a mineralizing agent. Full article

The diagenetic transformation of detrital clay minerals significantly influences sandstone reservoir quality, with fluid chemistry and temperature playing key roles in dictating transformation pathways during burial diagenesis. While these processes are well-documented in basinal settings, the diagenetic alterations of sediments in dynamic environments like estuaries remain underexplored. This study investigates the impact of fluid composition on the transformation of modern estuarine sediments through hydrothermal experiments using sediments from the Gironde estuary, SW France. A range of natural and synthetic solutions including seawater (SW), 0.1 M KCl (SF1), 0.1 M NaCl, KCl, CaCl₂·2H₂O, MgCl₂·6H₂O (SF2), estuarine water (EW), and 0.1 M Na₂CO₃ (SF3) were used under temperatures from 50 °C to 250 °C for 14 days, with a fixed fluid-to-sediment ratio of 10:1. The results revealed distinct mineralogical transformations driven by fluid composition. Dissolution of detrital feldspars and clay materials began at lower temperatures (<100 °C). The authigenic formation of smectite and its subsequent illitization in K-rich fluids (SW, SF1) occurred between 150 °C and 250 °C, replicating potassium-driven illitization processes observed in natural sandstones. Additionally, chlorite formation occurred through the conversion of smectite in SF2 and EW. Geochemical analysis showed that SF2 produced Mg-rich chlorites, while EW yielded Fe-rich chlorites. This aligns with diagenetic trends in coastal environments, where Fe-rich chlorites are typically associated with estuarine systems. The resulting authigenic illite and chlorite exhibited morphological and chemical characteristics similar to those found in natural sandstones, forming through dissolution-crystallization and solid-state transformation mechanisms. In contrast to illite and chlorite, SF3 produced entirely different mineral phases, including halite and analcime (zeolite), attributed to the high alkalinity and Na-rich composition of the solution. These findings provide valuable insights into the role of fluid chemistry in the diagenetic alteration of modern sediments and their implications for the evolution of sandstone reservoirs, which is critical for energy exploration and transition. Full article

The siliceous precursor was hydrolyzed from tetraethylorthosilicate (TEOS) under acidic conditions, followed by the addition of sodium aluminate and sodium hydroxide. Y zeolite was subsequently obtained through hydrothermal crystallization under alkaline conditions. Key synthesis parameters, including reactant molar ratios, crystallization temperature, and time, were systematically varied to optimize the synthesis conditions. The synthesized products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption analysis, and inductively coupled plasma (ICP) elemental analysis. Well-crystallized Y zeolite with a silica-alumina ratio (SAR) of 5.55 was successfully synthesized via TEOS hydrolysis catalyzed by sulfuric acid at a low crystallization temperature of 85 °C. The catalytic performance of benzyl phenyl ether, a lignin model compound, over NiY catalyst was evaluated in a high-pressure reactor. The results indicate that the catalytic efficiency of Y zeolite synthesized using TEOS as the silicon source under acidic hydrolysis conditions is significantly superior to Y zeolite prepared using alkaline silica sol as the silicon source. Full article