Search Results (329)

To reduce environmental pollution caused by volatile organic compounds (VOCs) released during asphalt application, various porous materials have been used to adsorb asphalt VOCs due to their rich pore structures. However, asphalt VOCs are so complex that emission reduction mechanisms still require further study. In this study, Materials Studio was used to simulate the molecular dynamics of asphalt VOC adsorption by ZSM-5 zeolite. The adsorption heat, capacity, and energy of ZSM-5’s adsorption of the main asphalt VOCs was obtained by means of molecular simulation to reveal the adsorption rules and selectivity. Zeolite model simulations with different structures were run to investigate possibilities for the optimization of ZSM-5. In addition, the actual VOC emission reduction effects of ZSM-5 in asphalt were compared with the MS simulation results. The VOC emission reduction mechanism was discussed based on both microscopic simulations and macroscopic verification. The results show that hydrocarbon derivative VOCs are more likely to be adsorbed due to their higher polarity. The smaller molecules of these VOCs are easier to adsorb because they occupy a smaller pore volume. When several molecules are mixed, competitive adsorption occurs. The selective adsorption probabilities of n-hexane, 1-methylcyclopentene, and toluene increase. In relation to the structure of zeolites, the Si/Al ratio and pore size of zeolites can both affect adsorption ability. A low Si/Al ratio can increase the number of surface acid active sites, while a micro–mesoporous structure increases the pore volume. The actual emission reduction data confirm that computational simulation has high accuracy in evaluating VOC emission reduction based on physical adsorption. Low-Si/Al-ratio and micro–mesoporous zeolites show better emission reduction ability for non-benzene VOCs than high-Si/Al-ratio and microporous zeolites. The emission reduction efficiency is up to 44%. However, the aromatization reaction was more easily catalyzed by zeolites, leading to the discrepancy between the simulated adsorption data and the actual situation. In future work, the boundary conditions and parameter settings of the simulations should be changed to achieve greater accuracy. Full article

Fe-ZSM5 zeolite materials were prepared via solid-state ion exchange and comprehensively characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The XRD patterns confirm the successful loading of iron species onto the ZSM-5 support. These materials served as heterogeneous Fenton catalysts for the degradation of methyl orange in simulated wastewater. Key operational parameters—including initial pH, H₂O₂ concentration, catalyst dosage, and reaction temperature—were systematically evaluated to assess their effects on decolorization efficiency. The results indicated that under optimal conditions (initial pH of 3.0, H₂O₂ concentration of 0.3 mol/L, catalyst dosage of 1.6 g/L, reaction temperature of 30 °C), a decolorization efficiency of 92.58% was achieved within 60 min. This study demonstrates that Fe-ZSM5 zeolite is a robust and efficient catalyst for heterogeneous Fenton-based degradation of organic dyes in aqueous systems. Full article

CO₂ methanation with renewable hydrogen is a promising strategy for carbon valorization and synthetic natural gas (SNG) production. However, the molecular mechanisms behind catalyst-dependent adsorption and mass transport in zeolite-confined spaces are still not fully elucidated. Herein, we performed comparative molecular simulations on HZSM-5, Ni/ZSM-5 and Ru/ZSM-5 by combining density functional theory (DFT), grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) methods, aiming to clarify the thermodynamic and mass transport mechanisms of reactant enrichment and product desorption in CO₂ methanation. The electronic structures of the three systems were systematically evaluated via Mulliken charge analysis, differential charge density mapping, and frontier molecular orbital calculations. We further quantified the adsorption thermodynamics and diffusion kinetics of reactants and products, focusing specifically on the effects of temperature and framework Si/Al ratio for Ni/ZSM-5. The results show that Ni doping greatly modulates the local electronic environment of the ZSM-5 framework, enhancing the adsorption of CO₂ (−121.9 kJ·mol⁻¹) and H₂ (−81.6 kJ·mol⁻¹) and weakening the adsorption of CH₄ and H₂O. A higher Si/Al ratio reduces CO₂ adsorption capacity, while elevated temperatures inhibit reactant adsorption and lower the diffusion selectivity of CH₄. This demonstrates that moderately low temperatures and moderate Si/Al ratios can optimize the adsorption and diffusion behaviors of reactants and products. This work provides molecular-level insights into the adsorption and diffusion behaviors of Ni/ZSM-5 and offers theoretical references for the rational development of high-performance CO₂ methanation catalysts. Full article

Zeolites, both natural (e.g., clinoptilolite) and synthetic (e.g., FAU, ZSM-5), provide robust, tunable platforms for the removal of air pollutants and process-stream contaminants via adsorption and catalysis. This author-led article integrates experimental and theoretical insights on the adsorption of odorous compounds and ammonia (NH₃) and the catalytic abatement of nitrogen oxides (NOx) and nitrous oxide (N₂O), highlighting how topology, acidity, and metal speciation jointly control performance. Representative theoretical results show that adsorption on Brønsted acid sites is significantly more favorable (≈−1.1 eV for NH₃ and −0.37 eV for acetaldehyde) than on Na⁺ sites (≈0.02 eV and 1.22 eV, respectively), demonstrating the critical role of acid site distribution in adsorption selectivity. We dissect structure–function relationships encompassing pore size and connectivity, Si/Al ratio, Brønsted/Lewis site distribution, hydrophilicity/hydrophobicity, and the role of water, with emphasis on hierarchical porosity to alleviate transport limitations. Metal exchange and surface functionalization are discussed as levers to tailor adsorption strength and redox activity, supported by density functional theory (DFT) analyses and reaction pathways. We propose practical design descriptors (acid strength metrics, metal nuclearity, and confinement factors) that enable faster iteration of zeolite architecture for targeted separations and reactions. Sustainability considerations include the use of abundant natural zeolites, low-energy regeneration, stability under humid, mixed-stream conditions that minimize pressure drop and waste. The article closes with a forward look at data-guided optimization to accelerate “engineering zeolites” for durable, selective, and energy-efficient clean-air and process-intensification applications. Full article

Plasma electrolytic oxidation (PEO) enables the fabrication of multifunctional oxide coatings with embedded active phases, offering a promising route for durable photocatalytic surfaces in water purification. This study examines how the electrical regime affects particle incorporation and photocatalytic performance. Coatings were produced under a 50% duty cycle in both unipolar mode and during the anodic part of the bipolar mode. A silicate-based electrolyte was modified with zeolites (Y and ZSM5), used in pristine form, Zn-loaded form, and combined with ZnO nanoparticles, to enhance catalytic activity. Photocatalytic performance was evaluated via methyl orange degradation under simulated solar irradiation for 6 h. The highest efficiency (~45%) was achieved with unipolar coatings containing Y zeolite and ZnO. In contrast, bipolar coatings with combined Y and ZnO showed lower efficiency (~35%). Although lower than typical powder photocatalysts, these results are notable since active phases are directly embedded in the coating, and both modes improve the photocatalytic activity by ~10% compared to the standard electrolyte. Microstructural analysis revealed that bipolar coatings were more compact, limiting access to active sites. Unipolar processing enabled better particle incorporation and a morphology more favorable for photocatalytic activity, making it the more effective regime for developing PEO-based photocatalytic coatings. Full article

While the petroleum industry undergoes structural adjustments in supply and demand alongside a green and low-carbon transition, water drilling mud generated during oil extraction poses severe environmental challenges. Consequently, addressing the solid waste pollution and disposal issues associated with drilling mud has become critical. In this study, ZSM-5 zeolite was synthesized using water drilling mud as a silicon and aluminum source, inexpensive n-butylamine as a template agent, and a combined approach of alkali-melting activation pre-treatment and seed-directed hydrothermal synthesis. By adjusting key parameters such as water content, template agent dosage, and seed addition, optimal synthesis conditions were determined. Based on these conditions, a series of ZSM-5 zeolites with varying silicon-to-aluminum ratios were synthesized. Characterization results from XRD, TEM, SEM, and N₂ adsorption–desorption experiments revealed that all prepared samples exhibited high crystallinity, regular morphology, and high specific surface area. ²⁷Al MAS NMR results indicated that almost aluminum species were located at the framework structures with four-coordination. In the 1,3,5-triisopropylbenzene cracking reaction, the conversion rate increased with decreasing silicon-to-aluminum ratio, consistent with variations in acid amount. These findings achieve high-value utilization of waste drilling mud, offering a novel pathway for low-cost synthesis of high-performance ZSM-5 zeolite. This breakthrough injects fresh momentum into the petroleum refining industry’s green sustainable development, fostering a win–win scenario that harmonizes ecological conservation with industrial profitability. Full article

Energy-efficient microwave technologies for the synthesis of zeolites and zeolite-like materials are considered. The use of microwave radiation in the process of material synthesis has a number of advantages, but also some disadvantages in comparison with the traditional hydrothermal synthesis method. The advantages and disadvantages of microwave synthesis of zeolites and zeolite-like materials are presented in the review. The use of microwave synthesis makes it possible to significantly reduce synthesis time, reduce energy costs, and obtain particles with a narrow distribution, usually in the nanoscale range (50–500 nm). The groups of zeolites considered include LTA, BEA, MOR, MFI, MEL, FAU, F, P, T, FER, ANA, MTT, ZSM–22, ZSM-48, SOD, SSZ-11, SSZ-13, SSZ-51, SSZ-54, and others. Among the zeolite-like materials synthesized using microwave radiation, mesoporous silicates MCM-41, SBA-15, alumophosphates, and metallaluminophosphates (AlPO-5, AlPO-11, AlPO-18, SAPO-5, SAPO-11, SAPO-34, SAPO-35) are considered. The proposed methods (microwave processing) significantly expand the range of methods for synthesizing new materials. These methods can reduce the synthesis temperature and affect the structure of the resulting materials. The proposed methods increase the likelihood of obtaining new nanomaterials and hybrid materials, as well as improving the properties of existing ones. Full article

Utilizing the pyrolysis reaction of endothermic hydrocarbon fuels to provide thermal protection for hypersonic vehicles is a feasible approach. The introduction of catalysts or cracking-initiating additives could promote hydrocarbon fuel cracking and increase the reaction heat sink. Catalysts such as ZSM-5 zeolite, Al₂O₃, and precious metals were commonly used for hydrocarbon fuel cracking. By optimizing their pore structure and acidity, their catalytic cracking performance can be effectively improved. These catalysts can function not only as catalytic coatings but also be dispersed in the fuel to act via quasi-homogeneous catalytic cracking. Additionally, small-molecule and macromolecular additives could crack at lower temperatures to generate active free radicals, thereby initiating the cracking of hydrocarbons and increasing the reaction heat sink. Under the conditions of a reaction temperature of 650–750 °C, a pressure of 3–5.5 MPa, and a fuel flow rate of 1 g/s, quasi-homogeneous catalysts can enhance the heat sink of hydrocarbon fuel cracking by 5–21%, while cracking-initiating additives can enhance it by 5.6–8.6%. Therefore, based on the different action modes of catalysts or additives, this review summarizes the recent research on improving the cracking of endothermic hydrocarbons from three aspects: coating catalysts, quasi-homogeneous catalysts, and cracking-initiating additives. Subsequently, the potential challenges of each approach in practical applications are analyzed. Furthermore, based on the current research findings, we outline future research directions with the expectation of facilitating the advancement of efficient cracking technologies for endothermic hydrocarbons. Full article

The purpose of this study is the exploration of the catalytic performance of a ZSM-5 zeolite produced from iron-rich fly ash, without any additional iron loading, in removing paracetamol via a heterogenous Fenton reaction. The structural and textural characterization by powder X-ray diffraction and N₂ adsorption isotherms showed that a pure ZSM-5 phase was synthesized, but lower crystallinity and textural parameters were obtained when compared with commercial ZSM-5. The XPS analysis revealed significant amounts of iron and yttrium, which enhanced the electronic properties of the samples’ surface when compared with iron-impregnated commercial ZSM-5. The catalytic reaction was followed through UV-spectroscopy and kinetic models were applied to the data; the best fit was obtained for a pseudo-first-order model. All fly ash-based zeolites showed increased paracetamol removal when compared with commercial iron-loaded ZSM-5, which may be attributed to the more disordered structure, able to accommodate large paracetamol species (dimers). On the other hand, the effect of yttrium on the electronic properties of iron sites may increase the ^●OH radical formation, thus increasing the paracetamol removal rate, despite the progressive drop on paracetamol removal upon regeneration–reuse cycles due to Fe leaching. Full article

CO₂-assisted catalytic pyrolysis presents a viable and promising approach to addressing plastic waste pollution and mitigating climate change. However, the effects of the metal–catalyst combination mode and the spatial distance between metal–acid sites on catalytic performance remain unclear. In this study, the reaction behaviors of the configurations, Fe₃O₄ and ZSM-5 in tandem catalysis (Fe₃O₄&HZ), their physical mixture (Fe₃O₄-HZ), and Fe-loaded ZSM-5 (Fe/HZ), were compared in polypropylene pyrolysis under a CO₂ atmosphere. The aromatic contents followed this order: Fe/HZ > Fe₃O₄-HZ > Fe₃O₄&HZ > ZSM-5 > Fe₃O₄. Specifically, Fe/HZ with the highest degree of metal–zeolite proximity achieved an aromatic content of 66.1%, significantly higher than the 34.2% obtained with Fe₃O₄&HZ, demonstrating that closer metal–acid proximity promoted aromatic formation. Moreover, Fe/HZ significantly reduced coke deposition. Based on characterization results from XRD, SEM, TEM, XPS, and NH₃-TPD, the enhanced spatial proximity between metal and acid sites strengthened the functional synergy between iron-based redox sites and zeolitic Brønsted acid sites. This synergy facilitated the reverse water–gas shift reaction of CO₂, which consumed hydrogen generated during aromatization and shifted the reaction equilibrium toward enhanced aromatic production. These findings would offer theoretical and strategic insights into the optimization of CO₂-assisted catalytic pyrolysis systems for the sustainable upcycling of plastic waste. Full article

While temperature and acidity dominate the design of zeolite catalysts for olefin cracking, the role of reaction time as an independent variable governing pathway dynamic remains elusive. This study integrates experimental and simulation methods to unravel the dynamic competition among carbenium ion cracking, thermal cracking and Confined Catalytic Radical (CCR) pathways during 1-pentene cracking on H-ZSM-5 zeolite at 650 °C. Analysis of the optimum performance envelope (OPE) curves for cracking products revealed that, in the initial reaction stage, the CCR mechanism significantly enhances ethylene yield. As the reaction time prolongs, C₅+ olefins in the gas phase undergo further cracking on the zeolite surface, markedly increasing the contribution of the carbenium ion pathway. Molecular simulations indicate that C₅+ olefins exhibit stronger adsorption capacity but lower diffusion coefficients on H-ZSM-5, and this adsorption–diffusion disparity is a key factor influencing the evolution of 1-pentene cracking pathways. Concurrently, thermal cracking reactions are also enhanced with increasing residence time, which is unfavorable for ethylene formation. This work elucidates the time-dependent evolution of 1-pentene cracking pathways and the regulatory role of intraparticle mass transfer, providing a theoretical basis for optimizing light olefin selectivity through the adjustment of reaction time and catalyst structure. Full article

The development of Sustainable Aviation Fuel (SAF) is a crucial pathway to achieving carbon neutrality goals in the aviation industry. In the preparation process of SAF, the performance of catalysts is a core factor determining reaction efficiency, product distribution, and selectivity. Among these, zeolite molecular sieves play an irreplaceable key role in catalytic systems. This paper, through an in-depth survey and systematic analysis of over 70 core literature pieces in related fields, primarily elucidates the structural regulation mechanisms of zeolite catalysts in key reaction steps such as deoxygenation, hydrocracking, and isomerization. Research indicates that differences in pore size, pore channel configuration, and acidity distribution of zeolite molecular sieves with different topological structures (one-dimensional channels such as SAPO-11 and ZSM-22; three-dimensional intersecting channel micropores such as ZSM-5; three-dimensional twelve-membered ring micropores such as Y-type and Beta zeolites) directly affect the selectivity of catalytic reactions and product quality. Full article

Gamma-valerolactone (GVL) can be used as a renewable solvent, flavoring agent, and precursor to produce liquid fuels and fine chemicals. GVL is mainly produced by the efficient hydrogenation of levulinic acid and its esters over a wide range of bifunctional catalysts under harsh conditions because high temperature is generally required for GVL formation. So far, the hydrogenation of levulinic acids/esters under mild conditions remains a great challenge. In this study, 2 wt.% Ru was loaded onto ZSM-5 zeolite (MFI) via a deposition–precipitation method and further wrapped by crystallization, forming a core–shell structure. Moreover, the wrapped Ru catalyst was coated with a petal-like layer of Mg₃Si₄O₉(OH)₄ (MgSiO₃) via a hydrothermal reaction in a Mg(NO₃)₂ solution, thereby introducing alkalinity and achieving spatial separation of Mg and Ru. This dual-functional catalyst reduces the inhibitory effect of Mg on the Ru active center and enables efficient preparation of GVL from ethyl levulinate (EL) under mild conditions, achieving 100% EL conversion and 98% GVL selectivity in the aqueous phase at 80 °C in 2 h under 0.5 MPa of H₂. Full article

This study investigates the potential of tomato waste (TW) and hot pepper waste (HPW) biomass from local food industries in Algeria as sustainable feedstocks for fluidized-bed air gasification. Conversion efficiency, syngas composition and energy content were evaluated under different operating conditions, including gasification temperature (750 and 850 °C) and bed material (silica sand, olivine, and a ZSM-5 zeolite catalyst/silica sand mixture). The results demonstrate that gasification of these biomasses in a bubbling fluidized-bed reactor is an effective waste-valorization route, producing a syngas rich in hydrogen and methane, suitable for power generation and biofuel applications. Under all operating conditions, hot pepper waste generated a syngas with higher energy content than tomato pomace. Full article

In order to solve the problems of low calorific value and pipeline corrosion caused by high concentration of CO₂ in oil-associated gas, and promote the resource utilization of associated gas, this study used validated grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulation to investigate the adsorption characteristics of 11 different topological structures (straight-channel MFI/BEA, cage-channel LTA/FAU/CHA) and cation types (Ca²⁺, Na⁺, H⁺) of commercial zeolites for CO₂ and alkanes (CH₄, C₂H₆, C₃H₈) at 0%~90% RH. The results showed that the CO₂ adsorption capacity of all zeolites decreased with increasing humidity, but straight-channel zeolites (ZSM5-300, BETA-25) had excellent moisture resistance, with only a 20.8% and 30.6% decrease in capacity at 90% RH, respectively. The performance of cage-channel zeolite drops sharply under high humidity. Topology structure and cation synergistically regulate separation efficiency, maintaining stable diffusion order in straight channels. Ca²⁺ enhances dry state capacity but is prone to hydrophilic failure. The adsorption heat of CO₂ on straight-channel zeolite is 25–38 kJ/mol, resulting in lower regeneration energy consumption. ZSM5-300 is preferred for PSA (CH₄/CO₂ kinetic separation coefficient of 809.52 at 90% RH), and NaFAU is preferred for TSA (CO₂ adsorption capacity of 3.6 mmol/g and selectivity of 502.6 at 90% RH). This study clarifies the core structure-activity relationship and provides key theoretical support for the decarbonization of oil-associated gas. Full article