The increasing contamination of aquatic systems by synthetic dyes such as methylene blue (MB) underscores the urgent need for sustainable and cost-effective wastewater treatment technologies. In this study, a novel biocomposite photocatalyst composed of chitosan and thermally treated ZSM-5 zeolite, denoted as ZSM-5 (800)/CS, was synthesized and systematically evaluated for its environmental remediation potential. The ZSM-5 (800)/CS composite exhibited superior photocatalytic activity, achieving 63% MB degradation within 210 min-significantly higher than pure chitosan, which achieved only 21% removal under identical conditions. The reduced optical bandgap (2.24 eV) of the biocomposite enhanced visible-light absorption, thereby improving its photocatalytic performance. Moreover, under aerobic conditions, ZSM-5 (800)/CS demonstrated excellent catalytic efficiency for the selective oxidation of organic sulfides to sulfoxides, achieving up to 96% yield and selectivity. These results highlight the dual functionality of the biocomposite for both wastewater detoxification and valuable chemical transformation. The study emphasizes the potential of integrating biopolymeric and zeolitic frameworks to develop sustainable photocatalysts that contribute to cleaner water resources and greener environmental technologies.

Carbenium ions are critical intermediates in zeolite-catalyzed hydrocarbon transformations; yet, their fundamental reactivity and mechanistic pathways remain incompletely understood, particularly under conditions relevant to practical catalysis. Here, we demonstrate that molecular oxygen─often present in catalytic systems but rarely mechanistically considered─profoundly alters carbenium ion chemistry. Through a combination of solid-state 13C NMR, operando UV-vis, and online mass spectrometry, we show that O2 selectively promotes the oxidative transformation of cyclopentenyl cations via cyclopentenone-type intermediates on ZSM-5 zeolite. This oxygen-mediated pathway enhances the formation of methylated aromatics, modulates reaction selectivity, and accelerates the evolution of polyaromatic species, ultimately impacting the catalyst stability. These effects are consistently observed in both methanol-to-hydrocarbon and ethene conversion over zeolites.

ZSM-5 zeolites with varying aluminum content were subjected to steam treatments of different severities by adjusting the temperature, duration, and water vapor pressure. The steamed samples were characterized using a range of analytical techniques. A quantitative assessment of the aluminum species—namely, tetrahedrally coordinated framework Al, dislodged framework Al, non-framework pentacoordinated Al, and non-framework hexacoordinated Al—was achieved through a combination of EDX analysis on Cs-exchanged materials and quantitative 27Al MAS NMR spectroscopy, including spectral simulation. Contrary to previous reports, the catalytic activity per framework Al site in unsteamed ZSM-5 increases with aluminum content at low Si/Al ratios, aligning with recently proposed medium effects. Notably, at the point of maximum activity enhancement due to steaming, equivalent amounts (1:1) of framework and dislodged framework Al—both in tetrahedral coordination—are observed. The maximum enhancement factor per framework Al site, for a given material and reaction, remains independent of the specific steaming conditions (temperature, time, and pressure). However, the degree of activity enhancement varies with the type of reaction: it is more pronounced for n-hexane cracking (α-test) than for m-xylene isomerization. This suggests that both catalyst modification and reaction characteristics contribute to the observed steam-induced activity enhancement. A synergistic interaction between Brønsted and Lewis acid sites appears to underpin these effects. One plausible mechanism involves the strengthening of Brønsted acidity in the presence of adjacent Lewis acid sites. This enhancement is expected to be more significant for n-hexane cracking, which demands higher acid strength compared to m-xylene isomerization. In cases of n-hexane cracking, the increased acid strength and the formation of olefins via reactions on Lewis acid sites may act cooperatively. Importantly, the dislodged framework Al species—tetrahedrally coordinated in the hydrated catalyst at ambient temperature and functioning as Lewis acid sites in the dehydrated zeolite under reaction conditions—are directly responsible for the observed enhancement in acid activity. The transformation of framework Al into dislodged framework Al species is reversible, as demonstrated by hydrothermal treatment of the steamed samples at 150–200 °C. Nonetheless, reinsertion of Al into the framework is not fully quantitative: a portion of the dislodged framework Al is irreversibly converted into non-framework penta- and hexacoordinated species during the hydrothermal process. Among these, non-framework pentacoordinate Al species may serve as counterions to balance the lattice charges associated with framework Al.

Enhanced aromatics production via catalytic pyrolysis of poly(3-hydroxybutyrate) using ZSM-5 catalysts.

Ethylene is a cause of the rotting of fruits and vegetables. Purification of ethylene in high-humidity environments is challenging. In order to improve the purification performance of potassium permanganate impregnated materials in high humidity environments, it is necessary to understand the influence of carrier properties on competitive adsorption behaviour. In this study, ZSM-5 zeolites with different SiO 2 /Al 2 O 3 ratios (25, 50, and 80) were used as carriers for KMnO 4 impregnation. Ethylene adsorption experiments were carried out under different humidity conditions (40% and 80%). It was found that in high-humidity environments, carriers with higher KMnO 4 loading did not necessarily exhibit higher ethylene purification capacity. The competitive adsorption mechanism between ethylene and water vapour in zeolite pores was analysed by GCMC molecular simulation. Under high concentration water vapour, the purification process can be divided into two stages: ethylene first reacts with potassium permanganate on the outer surface, then diffusion into pores is hindered, causing pore-loaded KMnO 4 to fail. This study revealed that specific surface area can dominate water vapour adsorption capacity, while the SiO 2 /Al 2 O 3 ratio controls ethylene adsorption through acid sites. The findings provide fundamental guidance for carrier selection in high-humidity environments and demonstrate that higher loading does not guarantee better performance under competitive adsorption conditions.

Studies on low-temperature degradation for sulfur hexafluoride over sulfidated nanoscale zero-valent iron supported on zeolite ZSM-5: heterostructures, interfacial activation and fluorine migration.

Gas turbines operate at exhaust gas temperatures exceeding 500 °C. Vanadium-based catalysts encounter challenges in NH3-SCR denitrification due to vanadium volatilization and titanium dioxide support phase transition at high temperatures. This restricts the effective denitrification temperature range to 300~400 °C, falling short of gas turbine denitrification requirements. Zeolite-supported catalysts, known for their high specific surface area, abundant acid sites, and stable framework structure, demonstrate superior catalytic activity and hydrothermal stability at high temperatures. This review synthesizes recent advancements in high-temperature catalysts utilizing ZSM-5, Beta, SSZ-13, and SAPO-34 zeolites as supports. It elucidates the interaction mechanisms between active components (e.g., transition metals Fe, Cu, W, rare earth elements) and zeolite supports. Furthermore, it examines variations in denitrification performance through the lens of the high-temperature NH3-SCR reaction mechanism, offering valuable insights for high-temperature denitrification catalyst development.

Regulation of double bond location in skeletal isomerization of light liquid olefins by combining the novel active sites of ZnO and ZSM-22 zeolites: From internal to terminal location

The art of adsorption in Moisture: Improving operational conditions for selective formaldehyde adsorption in ZSM-5 zeolite

Advanced synthesis of ZSM-5 zeolite in tubular reactor: Eliminating seeds and aging for phenol degradation via catalytic ozonation

Theoretical study on selective hydrogenation of acetylene catalyzed by Ni/Cu modified ZSM-12 zeolite

As key intermediate products in petroleum and chemical units, C4 hydrocarbons can be converted to ethene and propylene. While C4 olefins can be cracked into ethene and propylene on acid catalysts, such reactions with C4 paraffins are difficult under these conditions. In this study, a bifunctional metal–acid catalyst, BDHC, was prepared for catalytic dehydrogenation and catalytic cracking, using ZSM-5 zeolite for cracking active groups and Fe2O3 and Cr2O3 for dehydrogenation active groups. In the catalyzed reaction, C4 paraffins are converted to C4 olefins, which are subsequently cracked into ethene and propylene. The BDHC catalyst’s high relative crystallinity and large specific surface area and pore volume promote adsorption of reactant molecules. Moreover, the appropriate acid content suppresses side pathways and produces more ethene and propylene. Under optimized conditions, the ethene yield was 11.20%, the propylene yield was 27.51%, and the sum of the ethene and propylene yields was 38.71%.

Alkali metal-modified M-ZSM-5 zeolites (M: Li+, Na+, K+) were synthesized by cationic exchange and characterized using ICP-MS, XRD, N2 adsorption–desorption, Py-IR and NH3-TPD techniques to evaluate their elemental composition, structure, textural and acidic properties. In addition, XPS and DFT calculations were employed to study the effects of metal ion doping on the electronic structure and catalytic behavior. The latter catalytic performance was assessed in the methanol-to-olefin (MTO) reaction. The results showed that alkali metal doping facilitated the enhancement of the zeolite structural stability, adjustment of acid density, and increase in the adsorption energy of light olefins onto the active sites. During the reaction, olefin products shifted from Brønsted acid sites to alkali metal sites, effectively minimizing hydrogen transfer reactions. This change in the active site nature promoted the olefin cycle, resulting in higher yields in propylene and butylenes, reduced coke deposition, and prolonged catalyst lifetime. Among all zeolites, Li-exchanged ZSM-5 exhibited the best and extending the catalyst lifetime by 5 h.

The appropriate selection of renovation plaster properties is essential for ensuring the durability and effectiveness of conservation works. This study focused on the design and characterization of cement-based renovation mortars modified with synthetic zeolites with different Si/Al ratios. It was assumed that high-silica zeolites would provide more favorable mechanical and hygric performance than low-silica types. Owing to their porous structure and pozzolanic reactivity, zeolites proved to be effective additives, enhancing both the microstructure and functionality of the mortars. The modified mixtures exhibited increased total porosity, higher capillary absorption, and improved moisture transport compared with the reference mortar based on CEM I 52.5R. Dynamic vapor sorption tests confirmed that the zeolite-containing mortars achieved Moisture Buffer Values (MBV) above 2.0 g/m2, which corresponds to the “excellent” moisture buffering class. Electrical resistivity measurements further demonstrated the relationship between denser microstructure and enhanced durability. At the frequency of 10 kHz, the electrical resistivity of the reference mortar reached 43,858 Ω·m, while mortars with 15% ZSM-5 and 15% Na-A achieved 62,110 Ω·m and 21,737 Ω·m. These results show that the addition of high-silica zeolite promotes the formation of a denser and more insulating matrix, highlighting the potential of this method for non-destructive quality assessment. The best overall performance was observed in mortars containing the high-silica zeolite ZSM-5. A 35% replacement of cement with ZSM-5 increased compressive strength by 10.5% compared with the reference mortar R (4.3 MPa). Frost resistance tests showed minimal mass loss (0.03% at 15% and 1.79% at 35% replacement), and ZSM-5 mortars also maintained integrity under salt crystallization. These improvements were attributed to the reaction of reactive SiO2 and Al2O3 from the zeolites with Ca(OH)2, leading to the formation of additional C-S-H. A higher Si/Al ratio promoted a denser, fibrous C-S-H morphology, as confirmed by SEM, which explains the improved strength and durability of mortars modified with ZSM-5.

Improving stability and regenerability of nano-sized ZSM-5 zeolite in MTP reaction: toward a reliable industrial catalyst

ZSM-12 zeolite: The influence of post-synthetic acidic and base treatment on its physicochemical properties and activity in m-Xylene isomerization

Enhanced Aromatization of Light Naphtha Using Ga and Zn-Modified Nano ZSM-11 Zeolites: Structural and Catalytic Insights

Cationic polyelectrolyte stimulated ultrafast synthesis of hierarchical ZSM-11 zeolite with improved methanol to olefin catalytic performances

ZSM-5 zeolite for catalytic pyrolysis of light hydrocarbons to increase light olefins: Research on the loss and stability of Al

Visualization analysis of the mass transfer optimization mechanism of alkali-modified ZSM-5 zeolite