Hierarchical Zeolites Research Articles

Hierarchical zeolite coatings featuring a spatial gradient architecture for sequentially-controlled bisphosphonate release in the modulation of osteogenic–osteoclastic balance

Osteogenic–osteoclastic microenvironment imbalance impairs osseointegration between joint prostheses and the marrow cavity, which is a crucial contributor to the high incidence of complications such as implant loosening and periprosthetic fractures in osteoporosis (OPs). Previously, we employed hydrogel-based bisphosphonate (BPs) coatings on 3D-printed porous titanium alloy implants (pTi) to modulate the OPs microenvironment through controlled release. However, challenges persisted, including the limited duration of BPs release and associated organic material degradation-induced toxicity. To address these issues, we modified pTi surfaces by introducing chemically stable zeolites and BPs. In this study, we applied Ca2+-functionalized hierarchical zeolite coating on pTi for the first time. By combining mesoporous adsorption and Ca2+ chelation, we achieved efficient encapsulation of zoledronate (ZOL), creating a bioactive interface characterized by a spatial gradient structure with a “microporous-mesoporous-macroporous” morphology. The coating achieves the release of ZOL through the mesoporous structure and facilitates the gradual release of chelated ZOL via ion exchange, resulting in hierarchical drug delivery. Moreover, the spatial gradient structure of the coatings significantly influenced cell extension. Simultaneously, we constructed a bioactive coating with a drug concentration gradient, achieving graded drug release within the microenvironment, which facilitated the accurate regulation of osteogenesis and bone resorption. This coating has the potential to substantially enhance the management of postoperative complications in OPs patients undergoing prosthetic replacement surgery by achieving a balanced osteogenic-osteoclastic response.

Hierarchical beta zeolites assisted aromatics production from lignin via catalytic fast pyrolysis

Converting lignin waste into aromatics is a challenging but crucial aspect of lignin valorization. Although ZSM-5 zeolite is extensively used in lignin deoxygenation, its 10-membered ring (MR) channels limit the diffusion of bulky phenols and tend to produce coke. Herein, a series of 12-MR beta zeolites with varying acidity and hierarchical porosity were synthesized for lignin catalytic fast pyrolysis (CFP). An optimal lignin pyrolysis temperature of 600 °C was initially selected. Subsequently, lignin CFP demonstrated that beta zeolite with medium acidity facilitated aromatics production, with Beta(36) even outperforming ZSM-5(36). The introduction of mesopores further enhanced lignin deoxygenation and the hierarchical B36-0.3-24 increased aromatics selectivity to 56.0 area%, which was 1.5 times that of Beta(36). Combined with the CFP of model compounds (vanillin and catechol), it was inferred that the mesopores and weak acidity played a key role in heavy phenols conversion and aromatics production. In addition, B36-0.3-24 exhibited outstanding reusability in pyrolysis regeneration cycles, underscoring its potential for practical application in lignin valorization.

Connectivity assessment in hierarchical zeolites by correlating nuclear magnetic resonance, electron microscopy/tomography and adsorption scanning

Hierarchical zeolites presenting different pore domains have the potential to reduce problems associated with low diffusion in zeolites, thus holding great promise in a wide range of application fields. Nevertheless, efficient transfer between the different porous networks is required for the mesopores (2–50 nm) and macropores (>50 nm) to be effective in promoting the transit of molecules towards the micropores (<2 nm). In this work, the connectivity between the various pore domains in a class of hierarchical zeolites – denominated as nanoparticle aggregates – is investigated through 2D exchange spectroscopy (EXSY) 1H nuclear magnetic resonance (NMR) using paraxylene as a probe molecule. This approach allows to track whether the probe molecule visits distinct pore environments over time, providing unique insight into pore connectivity. The analysis of scanning curves through N2 adsorption/desorption cycles completes the characterization of pore connectivity. Furthermore, electron microscopy and tomography are used as visual techniques to confirm the arrangement of the mesoporous and macroporous networks generated by the nanoparticle aggregates.

Bimetallic PdAg clusters loaded on hierarchical self-pillared pentasil zeolite as efficient catalysts for formic acid dehydrogenation

In the present study, siliceous self-pillared pentasil (SPP) zeolite with regular mesopores was synthesized and used as a support for anchoring bimetallic PdAg clusters through a facile impregnation-reduction method. The as-prepared PdAg/SPP catalysts with different Pd/Ag ratios were demonstrated to catalyze formic acid dehydrogenation for hydrogen production. XRD results confirmed the formation of PdAg alloy on the surface of SPP zeolite. The Pd7Ag3/SPP catalyst showed high activity at 80 °C with an initial turn-over frequency (TOF) of 1263.6 h−1, proving the strategy using hierarchical SPP zeolite as carrier is advantageous over bulky zeolites for making highly active formic acid dehydrogenation catalysts.

Hierarchical carbon with microporous core and mesoporous shell for efficient oxygen reduction application

We synthesize for the first time a novel carbon structure, i.e., “hierarchical core-shell carbon” (HCSC), featuring ordered microporous carbon core and mesoporous carbon shell. The preparation of HCSC is achieved through a two-step approach starting from the formation of hierarchical core-shell zeolite Y (HCSY) in a controllable etching, followed by a chemical vapor deposition using HCSY as the template. The ordered micropores in HCSC provide high specific area and abundant active sites, while the mesoporous shell enhances its efficient mass transfer, making HCSC promising potential as a catalyst support. As a demonstration, HCSC is doped with nitrogen and loaded with Fe single atom (Fe–N/HCSC) and used as an oxygen reduction reaction (ORR) electrocatalyst, exhibiting exceptional catalytic performance in 0.1 M KOH electrolyte, with an onset potential of 1.01 V and a half-wave potential of 0.915 V, significantly higher than those achieved by the commercial 20 wt% Pt/C catalyst. The superior catalytic activity of Fe–N/HCSC is attributed to the mesoporous carbon shell, improving mass transfer efficiency and enhances the accessibility of micropores, enabling the highly dispersed Fe-NX sites to fully utilize their catalytic activity. This study offers an effective solution to address the challenges associated with mass transfer in microporous materials.

Hydrocarbon-Rich Bio-Oil Production from Ex Situ Catalytic Microwave Co-Pyrolysis of Peanut Shells and Low-Density Polyethylene over Zn-Modified Hierarchical Zeolite

Peanut shells, a major economic and oil crop in China, boast an abundant availability and remarkably high lignin content compared to other agricultural residues. Previous work indicated that the modified hierarchical zeolite (Zn-ZSM-5/MCM41) was effective in promoting the conversion of intermediate macromolecules during the lignin pyrolysis reaction and enhancing the yield and selectivity of liquid products. Thereby, this study aims to improve the quality of liquid products in the ex situ catalytic microwave co-pyrolysis of peanut shells and LDPE by utilizing Zn-ZSM-5/MCM41. Employing a compound center experimental design, we optimized reaction conditions through response surface analysis. The impact of microwave pyrolysis temperature and the catalyst-to-feedstock ratio on yield distribution and liquid product selectivity was explored. Results indicated a marginal increase in liquid product yield with rising pyrolysis temperatures. Moreover, an initial increase followed by a subsequent decrease in liquid product yield was observed with an increase in the catalyst-to-feedstock ratio. Optimal conditions of 450 °C and a catalyst-to-peanut hull ratio of 2.34% yielded the highest bio-oil yield at 34.25%. GC/MS analysis of the bio-oil revealed a peak in hydrocarbon content at 68.36% under conditions of 450 °C and a catalyst-to-feedstock ratio of 13.66%. Additionally, the quadratic model effectively predicted bio-oil yield and the selectivity for major chemical components. This study underscores the potential of Zn-ZSM-5/MCM41 in optimizing liquid product quality during catalytic co-pyrolysis, offering insights into bio-oil production and its chemical composition.

Hierarchical Zeolites Prepared Using a Surfactant-Mediated Strategy: ZSM-5 vs. Y as Catalysts for Friedel-Crafts Acylation Reaction.

Hierarchical ZSM5 and Y zeolites were prepared through a surfactant-mediated strategy with NH4OH changing the duration of the treatment and the amount of CTAB surfactant and taking as reference multiples of the critical micellar concentration (CMC). The materials were characterized using powder X-ray diffraction, N2 adsorption isotherms at -196 °C, and SEM and TEM microscopy. The catalytic performance was evaluated in Friedel-Crafts acylation of furan with acetic anhydride at 80 °C. The alkaline surfactant-mediated treatment had different effects on the two zeolites. For ZSM5, the CTAB molecular aggregates can hardly diffuse inside the medium-size pores, leading mainly to intercrystalline mesoporosity and increased external surface area, with no positive catalytic impact. On the other hand, for large-pore Y zeolite, the CTAB molecular aggregates can easily diffuse and promote the rearrangement of crystal units around micelles, causing the enlargement of the pores, i.e., intracrystalline porosity. The optimized Y-based sample, treated for 12 h with a CTAB amount 32 times the CMC, shows an increase in product yield and rate constant that was not observed when a higher amount of surfactant was added. The reuse of spent catalysts upon thermal treatment at 400 °C shows a regeneration efficiency around 90%, showing good potentialities for the modified catalysts.

The Effect of Ga Incorporation in TiO2/SnO2 Nanoparticle‐Decorated Hierarchical ZSM‐5 Composite as Precious‐Metal‐Free Electrocatalysts for Oxygen Electro‐Reduction

AbstractThe slow nature of oxygen electro‐reduction has become a major obstacle in fuel cell commercialization. Researchers have recently focused on developing efficient electrocatalysts to address this issue. In this study, we investigated the catalytic activity of electrocatalysts based on metal‐incorporated zeolites. We prepared the zeolite socony mobil‐5 (ZSM‐5) zeolite samples hydrothermally and modified them to introduce mesopores and metal nanoparticles. The metal nanoparticles were supported on the hierarchical zeolite socony mobil‐5 (HZSM‐5) support materials by ion‐exchange process. Surface morphology analysis revealed that the pristine material had a smooth surface which became rough upon post‐modification of the material. Hierarchical zeolites showed large surface area and pore volume. The TiSn‐loaded‐HZSM‐5 demonstrated higher catalytic efficiency than other prepared electrocatalysts for ORR. The catalytic efficiency of the synthesized electrocatalysts was in the order TiSn‐HZSM‐5&gt;GaSn‐HZSM‐5&gt;TiGaSn‐HZSM‐5&gt;TiGa‐HZSM‐5 with the onset potential of 0.86, 0.81, 0.80 and 0.78 V respectively. Catalysis is affected by the size, dispersion and electronic state of metal nanoparticles as observed by the catalytic efficiency of the trimetallic electrocatalysts which have low catalytic activity compared to bimetallic counterparts. Bimetallic hierarchical zeolites based electrocatalysts have great potential in catalysis, but there is still room for improvement.

The influence of pore-architecture over n-heptane cracking using MFI, *BEA and MSE zeolite catalysts: Multipore versus hierarchical porosity

The catalytic properties of zeolitic materials are governed by the intricate interplay between catalytic and transport processes, which, in turn, depend critically on the topology and morphology features. Here, the catalytic performance of typical three dimensional zeolites, including medium pore MFI, large pore *BEA and multi-pore MSE topologies with comparable Si/Al ratios are employed as n-heptane cracking catalysts to inspect the influence of topology on product slates for naphtha molecules. Furthermore, a bead-milling coupled with porogen assisted recrystallization method is used to fabricate hierarchically porous MSE zeolite for the first time. The catalytic n-heptane cracking properties of hierarchical MSE zeolite are compared with the hierarchical MFI and *BEA analogues, derived from the cracking mechanism ratio and the hydrogen transfer coefficient, respectively, to exam the influence of transport on product distributions. Multi-pore MSE zeolite outperforms MFI and *BEA zeolites in terms of light olefin selectivity and yield, owing to an exaggerated contribution from Haag-Dessau mechanism mediated cracking and a reduced probability for side-reactions, as a consequence of decreased residence time for the primary cracking product olefins. The developed methods to fabricated hierarchical zeolites and the revelation of structure-catalysis relationship may inspire future catalyst design for catalytic naphtha cracking.

Hierarchical ZSM-5 zeolite supported RuOx catalysts via organic mesoporous porogens for catalytic oxidation of vinyl chloride

Hierarchical ZSM-5 zeolites supported RuOx catalysts were prepared via the addition of various organic mesoporous porogens (namely starch, cellulose and sucrose) for catalytic oxidation of vinyl chloride (VC). The usage of mesoporous porogens during catalysts preparation was favorable for boosting the catalytic activity of the resultant catalysts, and 1%RuOx/HZ5-10%sucrose exhibited the optimum catalytic activity, impressive catalytic stability and long-term durability. The structure-activity dependence from catalysts characterizations revealed that the higher specific surface area, more abundant strong acid sites and surface adsorbed oxygen species were regarded as the critical parameters for the noticeable improvement of catalytic activity. Based on in situ infrared spectroscopy analysis, 1%RuOx/HZ5-10%sucrose exhibited higher adsorption capacity and more efficient conversion of VC molecules with fewer formation of organic intermediates because of its superior catalytic activity in comparison with the single 1%RuOx/HZ5. Additionally, enol and carboxylate species were demonstrated to be the key organic intermediates in catalytic VC oxidation.

Eco-friendly synthesis and environmental impact assessment of hierarchical Beta zeolite from kaolinite and recycled mother liquor

The development of sustainable techniques to produce high-performance zeolite is essential to achieve green production in industry. Herein, we report an eco-friendly route to synthesizing hierarchical Beta zeolite from kaolinite and recycled mother liquor. The results reveal that the unutilized species (such as silicon species and Na+) in mother liquor stayed in a stable concentration during eleven recycled experiments. Moreover, the synthesized Beta zeolites still have comparable physicochemical properties and catalytic performance in the esterification of levulinic acid with ethanol over the initial zeolite although eleven recycled experiments. Life cycle assessment exhibits that the synthesis of Beta zeolite with recycled mother liquor can reduce global warming potential by 23% and resource depletion-water use by 36% compared to that without recycled mother liquor. This quantitatively demonstrates that the approach proposed in this work is really a sustainable one, extremely increasing the utilization efficiency of raw materials and decreasing the environmental burden.

Synthesis of hierarchical MFI zeolite by interzeolite conversion of spent FAU zeolite for the methanol-to-olefins reaction

Developing a strategy for the resource utilization of spent zeolite catalysts is essential for addressing the environmental hazards of spent catalysts.

The synergistic interplay of hierarchy, crystal size, and Ga-promotion in the methanol-to-aromatics process over ZSM-5 zeolites.

In the context of advancing social modernization, the projected shortfall in the demand for renewable aromatic hydrocarbons is expected to widen, influenced by industries like high-end materials, pharmaceuticals, and consumer goods. Sustainable methods for aromatic production from alternative sources, particularly the methanol-to-aromatics (MTA) process using zeolite ZSM-5 and associated with the "methanol economy", have garnered widespread attention. To facilitate this transition, our project consolidates conventional strategies that impact aromatics selectivity-such as using hierarchical zeolites, metallic promoters, or altering zeolite physicochemical properties-into a unified study. Our findings demonstrate the beneficial impact of elongated crystal size and heightened zeolite hierarchy on preferential aromatics selectivity, albeit through distinct mechanisms involving the consumption of shorter olefins. While metallic promoters enhance MTA performance, crystal size, and hierarchy remain pivotal in achieving the maximized aromatics selectivity. This study contributes to a deeper understanding of achieving superior aromatics selectivity through physicochemical modifications in zeolite ZSM-5 during MTA catalysis, thereby advancing the field's comprehension of structure-reactivity relationships.

In situ growth-etching synthesis of hierarchical SAPO-34 from recycled mother liquor for ethanol dehydration

Hierarchical SAPO-34 zeolite catalysts were successfully synthesized via a one-step hydrothermal synthesis approach with the assistance of excess triethylamine (TEA).

Novel-ordered hierarchical ZSM-5 zeolite with interconnected macro–meso–microporosity for the enhanced methanol to aromatics reaction

The methanol to aromatics (MTA) process is an attractive non-petroleum route to produce high-value aromatics but suffers from a high rate of carbon deposition and deactivation and relatively low BTX selectivity.

Synthesis of a hierarchical TS-1 zeolite with tunable macropore size and its performance in the catalytic oxidation reactions

Hierarchical TS-1 zeolites with tunable macropore size were synthesized based on a steam-assisted crystallization strategy, which exhibited excellent activity in the catalytic oxidation reactions.

Design of novel hierarchical cage active particles and zeolite for the direct conversion of syngas to gasoline fuel

Physical mixing of SiO2-stabilized novel hierarchical cage particles with zeolites result in hybrid catalysts that provide a C5+ hydrocarbon content of 99.3% in gasoline fuels.

Seed-assisted synthesis of a nanosheet-assembled hierarchical SSZ-13 zeolite by coupling a small amount of TMAdaOH with TPOAC

A nanosheet-assembled SSZ-13-TP0.03 was synthesized with TMAdaOH and TPOAC. Pt/SSZ-13-TP0.03 showed enhanced naphthalene hydrogenation compared to other catalysts.

Sulfonated hierarchical ZSM-5 zeolite monoliths as solid acid catalyst for esterification of oleic acid.

Sulfonated hierarchical H-ZSM-5 monoliths were synthesized via ice-templating as solid acid catalysts for biodiesel production. Characterization confirmed successful -SO3 group grafting, increasing acid density. The catalysts achieved over 90% conversion of oleic acid in esterification, with easy recovery and reuse, and the relationship between porosity and acid density was explored.

Generating zeolite crystals with mesoscopic aperiodic structure to promote catalytic hydroisomerization

Generating hierarchical zeolites provides an effective way to enhance their transport and catalytic properties. Several seminal methods have been reported to fabricate them with mesoscopically periodic order using surfactant-like structure...