Nanoscale Zeolite Research Articles

Zn and N co-doped three-dimensional honeycomb-like carbon featured with interconnected nano-pools for dendrite-free zinc anode

The zinc-ion battery (ZIB) has been extensively researched as one of the promising electrochemical power sources. However, the problem of Zn-dendrite formation during repeated plating and stripping process seriously hinders the development of ZIBs. Herein, three-dimensional (3D) honeycomb-like porous carbon (HPC) with co-doping of zinc and nitrogen is prepared through confining growth of nanoscale zeolite imidazole framework-8 (ZIF-8) on the well-designed nano-pools walls of HPC followed by pyrolysis at 600 ℃ to obtain the final product ZnN/HPC-600, which exhibits large surface area and abundant zincophilic interfaces, ensuring homogeneous distribution of electronic field and low polarization during cycling process. Importantly, ZnN/HPC-600 facilitates the uniform distribution and migration of Zn2+ in this nano-pools structure, avoiding the growth of dendritic Zn crystal during charging stage. The symmetric and asymmetric cells with Zn/ZnN/HPC-600 anodes are assembled, demonstrating excellent cycling reversibility, good rate performance and long-term stability. Besides, a Zn||MnO2 full cell with Zn/ZnN/HPC-600 anode also exhibits robust cycling stability, fast reaction kinetics and almost 100 % coulombic efficiency. This work offers a novel and efficient carbonaceous nano-pools strategy to realize dendrite-free zinc anode in ZIBs.

Production of nanoscale zeolite composite catalysts from liquefied petroleum gases

Cұйытылған мұнай газдарын (СМГ) жоғары талғамдылықпен ароматтыкөмiрсутектерге айналдыру үшiн цеолиттер мөлшерiн және модулiн өзгерту, әртүрлiпромоторларды енгiзу әдiстерiн таңдау жолымен дайындау тәсiлдерiн өзгерте отырып,наноөлшемдi цеолитқұрамды катализаторлар жасалды. Сұйытылған мұнай газдарынароматты көмiрсутектер концентратына бiрсатыда айналдыру технологиясы көмегiменқоспалармен промоторланған, жаңа цеолитқұрамды белсендi және талғампаз нанокатализаторалынды. Ең қолайлысы құрамында 0,5%Zn бар катализатор болып табылды. 650 ◦ Сжәне көлемдiк жылдамдығы 600 сағ −1 болғандағы АрК-тердiң максималды шығымы24,2% құрады. Мақсатты реакция дегидраторлы және қышқылдық қасиеттермен жақсыбiрiгiп жүзеге асады. Көмiрсутектердi өңдеуде әртүрлi элементтермен модификациялауарқылы цеолиттердiң каталитикалық әсерiнiң тиiмдiлiгiн арттыруға болады. Осылайша,төмен молекулалы алкандарды ароматтау процесiнде цеолит катализаторлары шешушi рөлатқарады.

Rapid and low-cost synthesis of ZSM-5 zeolite nanosheet assemblies for conversion of methanol to gasoline

Nanoscale zeolites with short diffusion paths show significantly enhanced mass transportation and easier accessibility for active sites in catalysis compared to microsized zeolites. However, the high cost and complex process involved in existing synthetic methods limit their application, so the development of a rapid and low-cost synthesis technology is of great significance. Herein, ZSM-5 zeolite nanosheet assemblies (Z5-NS-t) are rapidly synthesized by a microwave irradiation (MW) assisted seed-induced method using low-cost polyhexamethylene biguanide hydrochloride (PHMB) as a crystal growth inhibitor of the b-axis. The crystallization kinetics of the resultant materials and the formation mechanism of ZSM-5 zeolite nanosheets, as well as the influence of physico-chemical properties on their catalytic performance for the methanol-to-gasoline (MTG) reaction, are systematically investigated. Compared with the ZSM-5 nanoparticle assemblies (Z5-NP-60), which are synthesized by using the same method except for the addition of PHMB, Z5-NS-180 nanosheets with an approximate density of strong Brønsted acid sites exhibit excellent catalytic performance in the MTG reaction, giving rise to a high gasoline selectivity of 73.2% at a methanol conversion of 99.9% and a large amount of external carbon deposits. This is attributed to the synergy of accessibility of acid sites located in the pore intersections and the shorter diffusion paths for coke precursors out of the zeolite channel. This study provides an effective strategy for the synthesis of ZSM-5 nanosheets as catalysts for the MTG reaction, and it is expected to be applied for the synthesis of other zeolite nanosheets for important catalytic processes.

ZSM-5 nanocrystal promoted low-temperature activity of supported manganese oxides for catalytic oxidation of toluene

• Nano-sized ZSM-5 zeolite was prepared by amino acid assisted method. • Effect of the support size on the formation of MnO x species was studied. • Small-sized ZSM-5 can highly disperse active MnO x species. • Abundant oxygen vacancies are formed on the MnO x supported by small-sized ZSM-5. • MnO x /Z5-L 0.2 shows excellent low-temperature activity in toluene combustion reaction. Nanoscale zeolites are of great practical interest due to their advantages of favorable mass transfer, accessibility to active sites, and large external surface area. Herein, ZSM-5 ( MFI -type) nano-sized zeolites were prepared by conventional hydrothermal and amino acid-assisted approaches to support MnO x species. The morphology, acidity, textural properties, and chemical state of the prepared MnO x /ZSM-5 samples are comprehensively characterized. The size effect of ZSM-5 nanocrystals on the physicochemical properties of supported MnO x species and on their catalytic oxidation behavior for the combustion of toluene is investigated. Beneficially from the larger surface area and smaller crystal size, the smaller-sized ZSM-5 zeolite (Z5-L 0.2 , ∼100 nm) prepared by the amino acid-assisted method can highly disperse more active MnO x species than the larger ZSM-5 counterpart (∼500 nm). Owing to abundant surface oxygen vacancies and surface adsorbed oxygen, as well as superior low-temperature reducibility, the MnO x supported on nanosized Z5-L 0.2 zeolites exhibits remarkably enhanced low-temperature activity for the catalytic oxidation of toluene.

Poly (β-Cyclodextrin-co-citric Acid) Functionalized Natural Nanozeolite: An Eco-Friendly Platform for IB Delivery

Zeolites, due to their porous nature and inherent pH-sensitive properties, are widely studied as drug delivery systems. However, natural zeolite pores are usually larger than drug molecules, which can cause rapid drug release. Consequently, to solve this problem, the zeolite structure must be modified to achieve controlled drug release. On the other hand, the preparation of nanoscale zeolites enables them to enter the living cell. To achieve these objectives, a natural nanozeolite was modified by poly (β-cyclodextrin-co-citric acid) (PCD-zeolite), and used for the loading and release of IB (IB). The PCD-zeolite was synthesized by heating a mixture of citric acid (CA), cyclodextrin (CD), and Na2HPO4; it was characterized by FT-IR, TGA, and TEM analyses. Due to the presence of hydroxyl and carboxyl groups in the PCD-zeolite structure, pH plays a vital role in the adsorbed IB; thus, the maximum adsorbed IB was observed at pH = 7. The in vitro release of IB from PCD-zeolite-IB in a phosphate buffer was examined; the PCD-zeolite containing IB (30 wt%) showed the highest release at pH = 3.6 within the first 3–48 h. As a result, the PCD-zeolite, by trapping IB, can improve its solubility and bioavailability. Moreover, the decrease in the dissolution rate of the polymer matrix in an acidic medium may also lower the toxicity of IB.

Construction of Zeolite-Loaded Fluorescent Supramolecular on-off Probes for Corrosion Detection Based on a Cation Exchange Mechanism.

Metal engineering structures are commonly covered and protected by coatings. However, the early local corrosion under the coatings and at defects is difficult to detect and discover. Visibility to the naked eye means that corrosion has already developed and expanded. Therefore, it is practical significant to detect the early corrosion of coated metal. Based on the formation of iron ions and anodic acidification in the local corrosion process, iron ions and proton responsive fluorescent rhodamine B acylhydrazone on-off probes are prepared by newly improved methods and denoted as RBA. RBA are loaded on the surface and in the lattice cage of zeolite (ZEO) to protect RBA from premature exposure to the corrosive environment and fluorescence quenching. In corrosive environments, the RBA loaded on the surface are released and complex with iron ions in the environment to activate fluorescence characteristics. Simultaneously, due to the cation exchange of ZEO, iron ions enter the lattice cage of ZEO and combine with RBA in the lattice cage to turn on fluorescence. When applied in epoxy coatings, the RBA/ZEO effectively indicate the occurrence of corrosion under the coatings and at defects, and accurately locate the corrosion site. Nano-scale ZEO (or RBA/ZEO) fill the micropores such as pinholes and defects of the coatings, and increase the difficulty of diffusion and penetration of corrosive media into the coatings. The application of RBA/ZEO functional filler not only do not weaken the main anti-corrosion performance of the coatings, but also significantly improve it.

Synthesis of novel chitosan/modified zeolite nanocomposites and their effect on the mechanical properties of cement mortars

In this paper, a novel nanocomposite containing biodegradable chitosan [CS] and modified zeolite [mZeo] was introduced as a cement eco-nano additive and its effects on the mechanical properties of cement mortars were evaluated. The proposed nanocomposite was prepared by using a synergistic sonication-microwave method. The surface morphology and chemical compositions of mZeo and CS/ mZeo nanocomposites were determined using SEM, FTIR, XRF, and BET. Compressive and flexural strength of cement mortars containing mZeo and CS/mZeo in ratios of 0%, 0.2%, 0.5%, 1% and 2% by mass, were investigated. Experimental results showed a significant improvement in the mechanical properties of mortars containing the proposed nanocomposite. The use of nanoscale zeolite in cementitious composites was attempted for the first time within this study and the results so far have been very promising. Therefore, it is concluded that the proposed nanocomposite has great potential to be used as an alternative eco-nano additive, for cementitious composites.

Recyclable synthesis of Cs-ABW zeolite nanocrystals from non-reacted mother liquors with excellent catalytic henry reaction performance

Nanoscale zeolites are very attractive for advanced applications such as in catalysis, adsorption, supports, sensors and carriers. Green synthesis of these materials is highly appreciated aiming to increase product yield while chemical waste and production cost can be reduced. Here we report high-yield, low-cost and green synthesis of nanosized Cs-ABW zeolite by recycling and using the non-reacted mother liquors waste solutions produced from the hydrothermal Cs-ABW zeolite synthesis. The nanocrystalline Cs-ABW solid product of each successive batch was collected and characterized while the non-reacted mother liquors were recovered and re-used for subsequent synthesis of nanozeolites. The synthesized Cs-ABW zeolite nanocrystals from three subsequent cycles possessed fairly similar properties and they exhibited excellent catalytic performance in Henry (nitroaldol) reaction of benzaldehyde and nitroethane thanks to their basic sites, (Si–O–Al)–Cs+, located at the external surface of the zeolite. This approach hence suggests a low-cost and eco-friendly preparation of Cs-ABW zeolite nanocrystals since less chemical waste is disposed while the product yield can be significantly improved which are ideal for industrial scale-up process.

Solvent-free anchoring nano-sized zeolite on layered double hydroxide for highly selective transformation of syngas to gasoline-range hydrocarbons

Nano-sized zeolites (NZs) were anchored on the layered double hydroxide consisting of cobalt and aluminum (Co-Al-LDH) using a solvent-free synthesis method (denoted as Co-Al-LDO-NZs). During the synthesis process, Co-Al-LDH was not only employed as a substrate for the growth of nano-sized zeolites but also acting as Al sources to participate in the formation of acid sites in the zeolite. The well-designed catalyst was used as a bifunctional catalyst for highly selective production of gasoline-range hydrocarbons from syngas through Fischer-Tropsch (FT) synthesis. Benefiting from the unique architecture of Co-Al-LDO-NZs, long-chain hydrocarbons formed on the active FT catalyst could diffuse to the zeolites surface, where hydrocracking and isomerization occurred. Furthermore, different from the traditional zeolite-supported FT catalyst, the nanoscale zeolite in Co-Al-LDO-NZs efficiently suppressed the over-cracking of hydrocarbons, lowering the selectivity of undesirable light hydrocarbons (CH4 and C2–C4 alkanes).

Transformation of Stöber Silica Spheres to Hollow Hierarchical Single-Crystal ZSM-5 Zeolites with Encapsulated Metal Nanocatalysts for Selective Catalysis.

The activity of zeolite-supported nanocatalysts is dependent on both the dispersion, size, and location of metal nanoparticles around the zeolite and the size and pore structure of the zeolite. In this study, a synthetic approach was developed to encapsulate metal catalysts within hollow interiors of single-crystal ZSM-5. Briefly, Stöber silica spheres were synthesized and then transformed to single-crystal nano-ZSM-5 (Si/Al = 60), followed by growth of embedded metal nanoparticles and subsequently creation of a nanosized (30-50 nm shell thickness) hollow hierarchical zeolite structure. Metal nanoparticles such as Co, Cu, Cu-Zn, Fe, and Ni can be supported on the inner wall of the hollow zeolite and the surrounding satellite mesopores, without any particles present on the external zeolite surface. When evaluated as a catalyst for the Fischer-Trøpsch reaction, the Fe@h-ZSM5 catalyst shows high activity, sintering and coking resistance (50% longer stability than Fe@ZSM5), and secondary cracking reactions in the acid sites in the ZSM-5 shell, which reduce C5+ hydrocarbon selectivity and increase smaller-chain hydrocarbon selectivity. In addition, when Pt was further deposited inside the hollow structure, shape-selective alkene hydrogenation was demonstrated. These configured nanoscale zeolite catalysts have potential applications for reactions that involve supported metal nanoparticle catalysis, shape selectivity, or secondary cracking reactions.

Synthesis of Nanoscale Zeolites

The review is devoted to the features of the synthesis of zeolites with nanosized crystals, which are of great interest for the processes of petroleum chemistry, gas chemistry, and organic synthesis. On the basis of analysis of published data, a classification is proposed for methods of directional control of the size of zeolite crystals. Methods for qualitative and quantitative controlling the composition of the reaction mixtures crystallized into nanoscale zeolites are considered in detail, as well as the effect of crystallization conditions on the change in the dispersity of zeolite crystals.

Valorization of coal fly ash into nanozeolite by sonication-assisted hydrothermal method

The study aimed at the recycle and reuse coal fly ash (CFA) via a fast green method. Increasing dependence of coal in power sector results in increased production of CFA, the disposal of which is a major environmental issue. Sonication assisted hydrothermal (UAH) treatment has been employed to convert this CFA into versatile nanozeolite X (NZX) from CFA. The effect of CFA/NaOH, fusion temperature, fusion time and ultrasonication time were investigated. Initial precursor CFA and the synthesized NZX were characterized by XRF, XRD, FESEM, TEM, and FTIR analysis. UAH treatment produced NZX in shorter crystallization time than conventional hydrothermal (CH) method. The particle size of UAH-NZX were obtained from FESEM, BET, TEM analysis as 22–27 nm, 24.36 nm, and 2–5 nm respectively. Average crystal size of UAH-NZX was 21.58 nm as calculated using Scherrer's equation. The optimized condition for the UAH synthesis of NZX was found as CFA/NaOH ratio of 1.25, fusion temperature of 550 °C, fusion time of 1.5 h, and ultrasound time of 20 min. The characteristics of UAH-NZX zeolite was compared with CH-NZX and commercial zeolite X (CZX). The pure NZX was formed by UAH technique with 20 min ultrasound, followed by 6 h hydrothermal treatment at room temperature whereas CH technique took 96 h of hydrothermal digestion at 120 °C. The optimized CEC value of NZX, conventional hydrothermal zeolite X (CH-ZX), and CZX are 428 mmol/100 g, 242 mmol/100 g, and 293 mmol/100 g respectively. The UAH method produced NZX at shorter time with less consumption of energy than CH method with nanozeolite with higher CEC and surface area (797.53 m2/g) than both CH-NZX and CZX. The nanoscale zeolite X can be used efficiently as ion exchanger as well as adsorber.

Сұйытылған мұнай газдарынан наноөлшемдi цеолитқұрамды катализаторлар жасау

Сұйытылған мұнай газдарынан наноөлшемдi цеолитқұрамды катализаторлар жасау

The Aromatization of Propene Via Nano-Size HZSM-5

Zeolite (ZSM) catalysts are known to convert small-size alkenes, e.g., propene, into aromatic hydrocarbons, specifically benzene, toluene and xylenes (BTX), with both high efficiency and specificity. The efficiency of conventional and hierarchical nano-size ZSM-5 for propene aromatization was compared in this study using a Design of Experiments (DOE) approach combined with detailed product analysis. Contrary to our expectations, the former showed a significantly greater BTX yield than the latter. Analysis of the obtained data by DOE and additional experiments with soybean oil cracking using both catalyst types indicated that a reason for the observed reduced activity of nano-scale zeolites may be tenacious water adsorption, which may reduce the catalyst active site availability to the substrate.

Hierarchical Silicoaluminophosphate Catalysts with Enhanced Hydroisomerization Selectivity by Directing the Orientated Assembly of Premanufactured Building Blocks

The ability to generate nanoscale zeolites and direct their assembly into hierarchical structures offers a promising way to maximize their diffusion-dependent catalytic performance. Herein, we report an orientated assembly strategy to construct hierarchical architectures of silicoaluminophosphates (SAPOs) by using prefabricated nanocrystallites as a precursor. Such a synthesis is enabled by interrupting the dry gel conversion process to prepare nanocrystallites, as crystal growth is shown to proceed predominantly by particle attachment. The orientation of assembly can be controlled to form either a three-dimensional, spongelike morphology or a two-dimensional “house-of-cards” structure, by modifying the additives. Structures with a high degree of control over crystal size, shape, architecture, pore network, and acidic properties are achieved. This versatile technique avoids the more tedious and expensive templating routes that have been proposed previously. The catalytic performance for the hydroisomeriza...

Modified nanocrystalline natural zeolite for adsorption of arsenate from wastewater: Isotherm and kinetic studies

This work investigates the efficiency and possibility of modified nanoscale zeolite with baloform for removing of arsenate anions from wastewaters. A combination of scanning electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, Thermogravimetric-differential thermal analysis and Brunauer–Emmett–Teller surface area were used for characterization of zeolitic materials. Effects of different parameters such as pH and dosage of adsorbent, on the arsenate removing yield are studied. The yield of arsenate removing increases by increasing dosage of adsorbent and contact time. The results show that arsenate removal efficiency from wastewaters is higher than 99% at optimum conditions. The adsorption data of the modified zeolite for arsenate removing was consistent with six isotherm equations (Freundlich, Langmuir, Langmuir–Freundlich, Dubinin–Radushkevich, Redlich–Peterson and Toth). The obtained modeling results indicated that, although the three-parameter models, taking into account the surface heterogeneity, provided the closest approach to the measurement data, the parameters estimates could be highly biased. Batch experiments were carried out to study the removal kinetics of arsenate. The kinetic studies proved that the Elovich was the applicable model.

High permeability and salt rejection reverse osmosis by a zeolite nano-membrane

The possibility of employing a zeolite nano-membrane for seawater desalination is studied using comprehensive molecular dynamics simulations. Two types of zeolite with different wetting properties, the hydrophilic FAU and hydrophobic MFI, are used as the reverse osmosis (RO) membrane. Both can reach nearly 100% rejection of salt ions, and when the membrane thickness is smaller than 3.5 nm, the permeability is about 2 × 10(-9) m Pa(-1) s(-1), which is two orders of magnitude higher than that of the commercial state-of-the-art RO membrane. The relation between the permeability and thickness of the zeolite membrane is studied through the pressure drop-flux dependence. The pressure drop is linearly dependent on the thickness of the zeolite membrane. As the thickness approaches nanoscale, the end effect of water molecules entering the zeolite membrane has apparent influence on the pressure drop. For the FAU membrane the hydrophilicity can assist the water molecules entering the nanopore with reduced pressure drop, while for the hydrophobic MFI zeolite additional pressure drop arises from the capillary resistance. In order to sustain the pressure drop during desalination, the nanoscale zeolite membrane should be placed on a porous substrate and the ratio of the thickness of the nano-membrane to the radius of the supporting pore in the substrate should be properly optimized.

Chemical Imaging of Catalyst Deactivation during the Conversion of Renewables at the Single Particle Level: Etherification of Biomass-Based Polyols with Alkenes over H-Beta Zeolites

The etherification of biomass-based alcohols with various linear alpha-olefins under solvent-free conditions was followed in a space- and time-resolved manner on 9 microm large H-Beta zeolite crystals by confocal fluorescence microscopy. This allowed us to visualize the interaction with the substrate and distribution of the coke products into the catalyst at the level of an individual zeolite crystal during the etherification process. The spectroscopic information obtained on the micrometer-scale zeolite was in line with the results obtained with bulk characterization techniques and further confirmed by the catalytic results obtained both for micrometer-scale and nanoscale zeolites. This allowed us to explain the influence of the substrate type (glycerol, glycols, and alkenes) and zeolite properties (Si/Al ratio and particle size) on the etherification activity. The etherification of the biomass-based alcohols takes place mainly on the external surface of the zeolite particles. The gradual blockage of the external surface of the zeolite results in a partial or total loss of etherification activity. The deactivation could be attributed to olefin oligomerization. The high conversions obtained in the etherification of 1,2-propylene glycol with long linear alkenes (up to 80%) and the pronounced deactivation of the zeolite observed in the etherification of glycerol with long linear alkenes (max. 20% conversion) were explained by the spectroscopic measurements and is due to differences in the adsorption, i.e., in the center of the zeolite particle for glycerol and on the external surface in the case of glycols.

Fabrication of ultrathin nanozeolite film modified electrodes and their electrochemical behavior

Ultrathin nanozeolite films were prepared on the surface of Pt and glass carbon electrodes using nanoscale zeolite particles as building block via a layer-by-layer (LbL) technique or by a secondary growth method. Compared to conventional zeolite-modified electrodes, the nanozeolite film modified ones (nanoZMEs) prepared by these methods exhibit good membrane morphologies with controllable thickness in nanometer scale and large zeolite/electrode contact areas due to the nanoscale zeolite film attached directly to the electrode. Ag +, Cd 2+ and Pb 2+ were selected as examples to evaluate the electrochemical performance of nanoZMEs with designed thickness. With the same thickness of zeolite layer, nanoZMEs prepared by the LbL technique possess short preconcentration and response time, while nanoZMEs fabricated through the secondary growth method exhibit high accumulation ability and ion exchange selectivity. It is found that besides the inherent ion exchange selectivity of the zeolite layer, the transport rate of ions in the zeolite layer toward the electrode surface is an important factor that affected the electrochemical selectivity of the ZMEs.

Pure silica BETA colloidal zeolite assembled in thin films.

Pure silica nanoscale zeolite BETA with monomodal particle size distribution was synthesized from a colloidal precursor solution and successfully applied for the preparation of hydrophobic ultrathin films on silicon wafers via spin coating.