Nanosized ZSM-5 Zeolite Research Articles

Constructing immobilized H3PO4 network in nanosized ZSM-5 zeolitic framework achieves high proton conductivity after acceleration acid leaching test

In the midst of demand for the high and stable anhydrous proton conducting membrane for the high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), phosphoric acid (PA)-doped polybenzimidazole (PBI) is positioned as one of the most promising candidates. The key to develop the PA-PBI is to address the issue of phosphoric acid leaching, which causes significant performance deterioration. Here we introduced the nanosized ZSM-5 zeolite which plays the role of the rigid cage for confining H3PO4 to the PBI, and then evaluated by utilizing the acceleration acid leaching test (ALT) to put long-term operation in perspective. The ZSM-5 not only retain the high degree of PA after ALT, but also constructs the efficient proton conducting channel derived by the chemically-immobilized H3PO4 in pore channel. After ALT, PBI electrolyte membrane with 5 wt% of ZSM-5 exhibited 2.8 × 10−5 S cm−1 of proton conductivity at 150 °C anhydrous condition, which is three orders higher magnitude than pure PBI (1.1 × 10−8 S cm−1). Furthermore, H2/O2 HT-PEMFC single-cell constructed with PBI/5%ZSM-5 displayed an excellent maximum power density of 387 mW cm−2 at 150 °C anhydrous conditions, even after the ALT. The results indicate the possible improvement of the long-term stability of the fuel cell by utilizing readily available ZSM-5.

Disinfectant-Assisted Preparation of Hierarchical ZSM-5 Zeolite with Excellent Catalytic Stabilities in Propane Aromatization.

A series of quaternary ammonium or phosphonium salts were applied as zeolite growth modifiers in the synthesis of hierarchical ZSM-5 zeolite. The results showed that the use of methyltriphenylphosphonium bromide (MTBBP) could yield nano-sized hierarchical ZSM-5 zeolite with a "rice crust" morphology feature, which demonstrates a better catalytic performance than other disinfect candidates. It was confirmed that the addition of MTBBP did not cause discernable adverse effects on the microstructures or acidities of ZSM-5, but it led to the creation of abundant meso- to marco- pores as a result of aligned tiny particle aggregations. Moreover, the generation of the special morphology was believed to be a result of the coordination and competition between MTBBP and Na+ cations. The as-synthesized hierarchical zeolite was loaded with Zn and utilized in the propane aromatization reaction, which displayed a prolonged lifetime (1430 min vs. 290 min compared with conventional ZSM-5) and an enhanced total turnover number that is four folds of the traditional one, owing to the attenuated hydride transfer reaction and slow coking rate. This work provides a new method to alter the morphological properties of zeolites with low-cost disinfectants, which is of great potential for industrial applications.

Nonionic polymer and amino acid-assisted synthesis of ZSM-5 nanocrystals and their catalytic application in the alkylation of 2-methylnaphthalene.

The synthesis of nanosized ZSM-5 zeolites with high crystallinity and suitable acidity is very significant for their great potential in various catalytic applications. Herein, a series of zeolite ZSM-5 crystals with different particle sizes and SiO2/Al2O3 ratios (10-30) were synthesized by a temperature-varying two-step crystallization method in a concentrated gel system containing L-lysine and/or polyvinylpyrrolidone (PVP) additives. By optimizing the addition amounts of the two additives, the crystal size of the ZSM-5 zeolite could be reduced to less than 100 nm. Meanwhile, relatively high crystallinity and framework Al incorporation rates could be achieved, resulting in the generation of high-quality ZSM-5 nanocrystals. The nanosized H-form ZSM-5 zeolite with a SiO2/Al2O3 ratio of 20 showed enhanced catalytic efficiency and stability for the alkylation of 2-methylnaphthalene (2-MN) with methanol to produce an important intermediate, 2,6-dimethylnaphthalene (2,6-DMN). A relatively high and steady yield of 2,6-DMN (above 7.2%) could be achieved during 20 h time-on-stream at 400 °C. The smaller crystal size, higher crystallinity and framework Al content could provide more accessible Brønsted acid sites in the 10-membered ring channel of the ZSM-5 nanocrystals, which are the main active sites responsible for the shape-selectivity of the targeted product of 2,6-DMN. As a result, the formation of other side products like 1-MN and poly-MN could be effectively inhibited, thus leading to an improved 2,6-DMN yield and coke resistance over the nanosized ZSM-5 catalyst.

Effects of different phosphorus modification methods on acid and catalytic properties of nano-sized ZSM-5 zeolite in toluene alkylation with methanol

Effects of different phosphorus modification methods on acid and catalytic properties of nano-sized ZSM-5 zeolite in toluene alkylation with methanol

Chemical Shift Anisotropy: A Promising Parameter To Distinguish the 29Si NMR Peaks in Zeolites

Using a combination of (i) symmetry-based recoupling in 29Si NMR, (ii) spin dynamics-based simulations, and (iii) DFT-based theoretical calculations, we show how the 29Si NMR peaks of (≡Si–O–Si≡) (Q4(0Al)), Brønsted acid sites (≡Si–OH–Al≡) (Q4(1Al)), and silanols (≡Si–OH) (Q3) can be characterized in nanosized ZSM-5 zeolites. Significant differences in the chemical shift anisotropy are calculated theoretically and observed experimentally for silicon nuclei close to aluminum (Q4(1Al)) compared to those which are not, i.e., Q4(0Al) and Q3, allowing one to clearly assign the 29Si NMR peaks. The isotropic chemical shift alone cannot resolve such differences.

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.

Preparation of Ga Isomorphic Substituted Ultrafine Nanosized ZSM-5 Zeolite and Its Catalytic Performance for MTG Reaction

Preparation of Ga Isomorphic Substituted Ultrafine Nanosized ZSM-5 Zeolite and Its Catalytic Performance for MTG Reaction

One Step Dimethyl Ether (DME) Synthesis from CO2 Hydrogenation over Hybrid Catalysts Containing Cu/ZnO/Al2O3 and Nano-Sized Hollow ZSM-5 Zeolites

The study has focused on the development of bifunctional catalytic materials for the direct DME synthesis from CO2/H2. The industrial Cu/ZnO/Al2O3 is used as the copper based catalyst for the first step of the methanol synthesis from CO2/H2. It will be combined with hollow nano-ZSM-5 zeolites with mesoporous shell as the acid catalyst of the second step the methanol dehydration to DME. The bifunctional materials will be tested in the direct DME synthesis from CO2/H2 under the following conditions: T = 225 °C, p = 30 bar, H2/CO2 = 3. Under our reaction conditions, CO was not observed, only the DME majority product (77.5%) and CH3OH (22.5%) were obtained.

Hierarchical zeolites obtained by alkaline treatment for enhanced n-pentane catalytic cracking

This study manufactured various hierarchical ZSM-5 zeolites using NaOH, NaAlO2, Na2CO3, K2CO3 and NaHCO3 solutions through post-treatment. Later, X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), X-ray fluorescence (XRF), N2 adsorption and desorption, solid state 29Si and 27Al MAS NMR, ammonia temperature programmed desorption (NH3-TPD) as well as pyridine adsorption infrared spectra (Py-FTIR) were carried out to characterize their structure properties and acidities. Further, this study investigated n-pentane catalytic cracking for producing the light olefins over hierarchical nano-sized ZSM-5 zeolites. Alkaline treatment with milder NaHCO3 was much more controllable and reasonable than treatment with other alkalis, which not only adjusted the acidity to promote n-pentane activation, but also formed hierarchical structures combing micropores and mesopores to reduce diffusion resistance and suppress secondary reaction contributing to an enhanced catalytic ability and anti-coke deposition performance. Among the catalysts, ZNaHCO3 exhibited ∼92% the highest n-pentane conversion and ∼50% light olefins selectivity during n-pentane catalytic cracking under 590 °C for 300 min, simultaneously, and these figures markedly increased relative to those for the parent ZSM-5 zeolite. Most importantly, it was also proved that HTC values are relevant to the degree of effectiveness of NaHCO3 desilication, and that mesopore formation contributes to the desirable selectivity of light olefins and coke amount.

WITHDRAWN: Effects of synthesis parameter on zeolite ZSM-5 properties

Different aspects of ZSM-5 crystallization can be influenced by crystallization time, which can lead to changes in final product properties. Various crystallization times were used to examine the crystallinity of nanosized ZSM-5 zeolite. The samples were examined using XRD, XRF AFM, and BET surface area. The orthorhombic-shaped crystals formed in the as-synthesised ZSM-5 sample after 120 h of crystallization time. The best crystallization time is shown to be 120 h, yielding a substance with 52.2 nm crystal size, 103 percent crystallinity, and 325.14 m2/g surface area.

Synthesis of Nanosized ZSM-5 Zeolites by Different Methods and\t\t\tTheir Catalytic Performance in the Alkylation of Naphthalene

Three nanosized ZSM-5 zeolites were successfully prepared from reactive gels\t\t\t\t\twith the same Si/Al ratios by different synthetic procedures that included the\t\t\t\t\tuse of tetrapropylammonium hydroxide or n-butylamine as a template and a seeding\t\t\t\t\tmethod that did not use an organic additive. The effect of the synthetic method\t\t\t\t\ton the physicochemical properties of the prepared samples was investigated by\t\t\t\t\tXRD, XRF, XPS, N2 physisorption, SEM, TEM,\t\t\t\t\t\t27Al MAS NMR, NH3-TPD, and\t\t\t\t\t\tPy-FTIR. The catalytic performance of the\t\t\t\t\tnanosized ZSM-5 zeolites in the alkylation of naphthalene with methanol was\t\t\t\t\tcompared. The prepared samples were phase-pure, highly crystalline ZSM-5\t\t\t\t\tzeolites, but they had different bulk and surface Si/Al ratios as well as\t\t\t\t\ttextural and acidic properties. The study of the prepared catalysts in\t\t\t\t\tnaphthalene methylation revealed that both the acid characteristics of the ZSM-5\t\t\t\t\tnanosized zeolites and their textural properties were responsible for their\t\t\t\t\tactivity in the reaction. A difference in the composition of\t\t\t\t\tmonomethylnaphthalenes and dimethylnaphthalenes was attributed to the ability of\t\t\t\t\tthe catalyst to isomerize the primary reaction products on acid sites located on\t\t\t\t\tthe external surface of the zeolite crystals. 2,7-DMN was found to be the\t\t\t\t\tpreferred reaction product over 2,6-DMN when formed at pore entrances to ZSM-5\t\t\t\t\tchannels due to the differences in their dimensions. In contrast,\t\t\t\t\t2,6-dimethylnaphthalene could be produced on weaker external Brønsted acid\t\t\t\t\tsites, which are hydroxyls attached to octahedral Al atoms. The presented\t\t\t\t\tresults show that the method used to synthesize nanoscale ZSM-5 zeolites is a\t\t\t\t\tcritical factor that determines the physicochemical properties and catalytic\t\t\t\t\tperformance of the resulting crystals.

Quaternary ammonium cellulose promoted synthesis of hollow nano-sized ZSM-5 zeolite as stable catalyst for benzene alkylation with ethanol

Catalytic alkylation of benzene with ethanol has been considered as a sustainable alternative for producing ethylbenzene/diethylbenzene. This paper reports the promoted synthesis of hollow nano-sized (20–80 nm) ZSM-5 zeolite as excellent yet durable catalyst of benzene alkylation, which is achieved by adding N-methyl-2-pyrrolidone (NMP) and quaternary ammonium cationic hydroxyethyl cellulose (JR-400) in its synthesis gel during the synthesis. It is revealed by the ESI–MS and TEM characterization that the NMP promotes the dissolution–recrystallization of the ZSM-5 and a hollow structure is generated during the process. The JR-400 as special promoter further favors the formation of ordered nano-zeolite grain and suitable microstructure, confirmed by the molecular dynamic modeling and characterization. That action corporately contributed to the hollow nano-sized ZSM-5 zeolite that provided hierarchical porous structure and mild acid centers, as evidenced by the 129Xe and 1H NMR spectra. The obtained hollow zeolite ZSM-5 then exhibits enhanced catalytic activities and selectivity for benzene alkylation. Moreover, it also displays an extremely superior stability (deactivation rate constant, −0.06%/h) in the catalysis of benzene alkylation with ethanol. This behavior is attributed to its hierarchical porous structure (namely less diffusion resistance) and mild acid centers, which is beneficial to moderate the carbon deposition and then the catalyst deactivation. Those research results urge the JR-400-promoted synthesis as a facile strategy for the hollow nano-sized ZSM-5 with enhanced catalytic performance during the benzene alkylation with the ethanol.

Facile synthesis of ultrafine nanosized ZSM-5 zeolite using a hydroxyl radical initiator for enhanced catalytic performance in the MTG reaction

ZSM-5 zeolite is extensively used as a catalyst in the methanol-to-gasoline (MTG) reaction, but many secondary reactions occur because of its large grain size and strong acidity. Thus, it is vital to explore new methods for the preparation of nanosized ZSM-5 zeolite with intercrystalline mesopores to facilitate the diffusion of substances while simultaneously decreasing the acidity. Here, we present a novel procedure for the synthesis of ultrafine nanosized ZSM-5 zeolites (Z5-Sx) at a low temperature (90 °C) that includes the addition of a hydroxyl radical initiator to the initial gel. For comparison, a series of ZSM-5 zeolites (Z5-Ty) were synthesized by crystallization at 170 °C using the traditional hydrothermal method. The influence of hydroxyl radicals on the characteristic properties of the Z5-Sx zeolites was investigated by XRD, SEM, HRTEM, N2 adsorption, and 29Si and 27Al MAS NMR spectroscopy as well as NH3-TPD and Py-IR measurements. The results revealed that the Z5-Sx series samples had smaller crystal sizes and higher mesoporosity than the control samples. In particular, a high content of framework Al atoms was observed at the channel intersections of the Z5-Sx series samples, resulting in a weaker acid strength in comparison with the Z5-Ty samples. This distribution of Al atoms resulted in the excellent catalytic performance of the synthesized Z5-Sx catalysts towards the MTG reaction, and the highest gasoline yield of 65.5% with a methanol conversion of 97.2% was obtained in the reaction with the Z5-S3 catalyst. Markedly, the Z5-S3 sample showed significantly improved catalytic stability and coke tolerance than the control samples.

Novel Strategy for the Synthesis of Ultra-Stable Single-Site Mo-ZSM-5 Zeolite Nanocrystals.

The current energy transition presents many technological challenges, such as the development of highly stable catalysts. Herein, we report a novel "top-down" synthesis approach for preparation of a single-site Mo-containing nanosized ZSM-5 zeolite which has atomically dispersed framework-molybdenum homogenously distributed through the zeolite crystals. The introduction of Mo heals most of the native point defects in the zeolite structure resulting in an extremely stable material. The important features of this single-site Mo-containing ZSM-5 zeolite are provided by an in-depth spectroscopic and microscopic analysis. The material demonstrates superior thermal (up to 1000 °C), hydrothermal (steaming), and catalytic (converting methane to hydrogen and higher hydrocarbons) stability, maintaining the atomically disperse Mo, structural integrity of the zeolite, and preventing the formation of silanols.

Comparison of Morphology and Physicochemical Properties of Embryonic and Nanosized ZSM-5 Zeolites and Their Use in the Dealkylation Reaction of Aromatic Hydrocarbons (a Review)

This review presents the analysis of the characteristic features of the structure, synthesis methods, and physicochemical properties of embryos that form the basis of ZSM-5 zeolites. Various physicochemical characteristics of the embryos and nanocrystals of ZSM-5 (X-ray diffraction, textural characteristics, morphology, infrared and nuclear magnetic resonance spectroscopy) are discussed and compared, and their similarities and differences are analyzed.

Synergistic effect between organic structure-directing agent and crystal seed toward controlled morphology, and bimodal pore structure of aggregated nanosized ZSM-5

Abstract Hierarchical ZSM-5 zeolite has been a growing interest due to their wide applications in petrochemical process. Developing a facile and low cost strategy to synthesize hierarchical ZSM-5 is still a challenge. In this work, aggregated nanosized ZSM-5 with bimodal pore structure was synthesized via the synergistic effect of n-Butylamin (NBA) and ZSM-5 crystal seeds. In the synthesis process, The NBA molecules were transformed into RNH3+ that would adsorbed on the surface of nuclei by electrostatic interaction in aging process. The RNH3+ was subsequently transformed into tetrahedron configuration BuNH+ in crystallization process working as structure directing agent and promoting the aggregation of primary crystals. At low content of NBA, only microscale single crystals tended to aggregate together to form large particles. Crystal seeds were decomposed into small species, which can act as nuclei to direct the formation of primary ZSM-5 crystals and support the surface for the adsorption of RNH3+ assisting the formation of aggregated nanosized ZSM-5. With no addition of seed, the obtained sample had poor structural properties, such as small specific and external surface area. By simply adjusting the content of seed and NBA, aggregated nanosized ZSM-5 zeolite with large surface area, external surface area was obtained.

Facile adjusting the concentration of siliceous seed to obtain ZSM-5 for cycloaddition reaction of styrene oxide and CO2

Cyclic carbonate is an important organic synthesis intermediate in the fine chemistry. The cycloaddition reaction which catalyzed by the nanosized ZSM-5 zeolites can reach a high selectivity of cyclic carbonates. In this study, a facile seed-assisted strategy for synthesis of ZSM-5 zeolites with different sizes was presented. A nano-sized zeolite and another two different sized zeolites with the size range of 4–5 μm were obtained by only changing the seed precursor. The three zeolites all had the MFI structure and a single chemical condition. Moreover, the ZSM-5 zeolites were applied to the cycloaddition of styrene oxide and CO2 in different reaction conditions, and a suitable reaction condition was obtained. In the suitable condition, the catalytic effects of ZSM-5 catalysts were compared, and the final results demonstrated the smallest one had a highest yield, which was 57.6%.

A green route for the synthesis of nano-sized hierarchical ZSM-5 zeolite with excellent DTO catalytic performance

Nano-sized hierarchical ZSM-5 zeolite with high crystallization was prepared by a novel green strategy, that is, the consecutive freezing and vacuum drying route. In comparison with the traditional synthesis process, only 1/5 amount of TPAOH (tetrapropylammonium hydroxide) template was involved. Moreover, hierarchical structured zeolites can be formed even in the absence of mesoporous template (e. g. cetyltrimethylammonium bromide, CTAB). Moreover, the hierarchical ZSM-5 with a wide range of SiO2/Al2O3 ratio (25–200) can be modulated. The effects of the consecutive freezing and vacuum drying methods on the formation process, pore characteristics, crystallinity, morphology and acidity of the ZSM-5 zeolites were explored. It is noted that the abundant intra-crystal mesopores and nanoparticles structure were generated from the porous structure on the surface of the freeze-dried powder. The constructed nano-sized and hierarchical ZSM-5 catalyst exhibits a prolonged lifetime of 110 h in dimethyl ether-to-olefin (DTO) reaction, which is around 3.7-fold lifetime compared to the conventional microporous ZSM-5.

Highly Selective MTO Reaction over a Nanosized ZSM-5 Zeolite Modified by Fe via the Low-Temperature Dielectric Barrier Discharge Plasma Method

Nanosized ZSM-5 zeolites were synthesized by an in situ seed-induced hydrothermal method, and samples modified with an Fe promoter were prepared by the traditional wet impregnation-thermal decomposition and dielectric barrier discharge plasma (DBD) methods, respectively. The physico-chemical properties of the catalysts were studied by XRD, SEM, TEM, BET, XPS, H2-TPR, NH3-TPD and Py-IR techniques. The catalytic performance was eValuated by the methanol-to-olefin (MTO) reaction. The results showed that the acidity of the catalysts, the dispersity of the Fe promoter and the interaction degree with the ZSM-5 zeolite are closely related to product selectivity in the MTO reaction. Compared with the Fe-NZ5 sample prepared by the traditional impregnation-calcination method, the FeD-NZ5 samples prepared by the DBD method exhibited the higher selectivity of C2—C4 light olefins and the lower coke deposition during long-term eValuation (100 h), which can be attributed to the weaker acid strength, more uniform Fe promoter dispersion and strong interaction with the ZSM-5 zeolite. The developed Fe-modified catalysts have high potential for application in the MTO reaction.

Synthesis and Consequence of Aggregated Nanosized ZSM-5 Zeolite Crystals for Methanol to Propylene Reaction

Aggregated nanosized ZSM-5 crystals with a different size from 30–50 nm to 1000–2000 nm were prepared by a hydrothermal synthesis method using a two-step crystallization procedure for methanol to p...