ZSM-5 Particles Research Articles

Self-assembly of hierarchical ZSM-5 particles on rice husk template as hybrid catalysts for boosting methanol aromatization

Herein, natural rice husks with hierarchically porous structures were used as a platform to assemble ZSM-5 particles (denoted as hierarchical ZSM-5) to improve diffusion properties in the methanol-to-aromatics (MTA) reactions. Rice husk could work as the platform to immobilize zeolite grains and provide additional silicon sources for the growth of zeolite particles. Sodium hydroxide amount and SiO2/Al2O3 ratio strongly determined the acid properties, and the rotational crystallization condition favored the zeolite formation. Improved diffusion properties of hierarchical ZSM-5 particles were confirmed by comprehensive pore analysis and benzene diffusion experiments, showing an excellent diffusion property towards aromatic molecules. Compared with commercial microporous zeolite in the catalytic MTA reaction, hierarchical ZSM-5 exhibited superior aromatics selectivity (40.8 vs. 35.8 %), higher liquid hydrocarbon yield (22.3 vs. 14.7 wt%), and longer lifetime (60 vs. 40 h). These results offer new insights into the controllable synthesis of Hier-ZSM-5 with a hierarchically porous structure using biomass as templates.

Improving the Pervaporation Performance of PDMS Membranes for Trichloroethylene by Incorporating Silane-Modified ZSM-5 Zeolite.

The hydrophobic nature of inorganic zeolite particles plays a crucial role in the efficacy of mixed matrix membranes (MMMs) for the separation of trichloroethylene (TCE) through pervaporation. This study presents a novel approach to further augment the hydrophobicity of ZSM-5. The ZSM-5 zeolite molecular sieve was subjected to modification using three different silane coupling agents, namely, n-octyltriethoxysilane (OTES), γ-methacryloxypropyltrimethoxysilane (KH-570), and γ-aminopropyltriethoxysilane (KH-550). The water contact angles of the resulting OTES@ZSM-5, KH-570@ZSM-5, and KH-550@ZSM-5 particles exhibited significant increases from 97.2° to 112.8°, 109.1°, and 102.7°, respectively, thereby indicating a notable enhancement in hydrophobicity. Subsequently, mixed matrix membranes (MMMs) were fabricated by incorporating the aforementioned silane-modified ZSM-5 particles into polydimethylsiloxane (PDMS), leading to a considerable improvement in the adsorption selectivity of these membranes towards trichloroethylene (TCE). The findings indicate that the PDMS membrane with a 20 wt.% OTES@ZSM-5 particle loading exhibits superior pervaporation performance. When subjected to a temperature of 30 °C, flow rate of 100 mL/min, and vacuum of 30 Kpa, the separation factor and total flux of a 3 × 10-7 wt.% TCE solution reach 328 and 155 gm-2·h-1, respectively. In comparison to the unmodified ZSM-5/PDMS membrane, the separation factor demonstrates a 41% increase, while the TCE flux experiences a 6% increase. Consequently, this approach effectively enhances the pervaporation separation capabilities of the PDMS membrane for TCE.

Hydrodeoxygenation of stearic acid over zeolite–MOF composite-supported Pt catalysts

Herein, we report the synthesis of a series of zeolite-porous metal–organic framework (MOF) (ZM) composites with different Pt loadings via a two-step approach, in which –COOH functionalized ZSM-5 particles were added during the formation of MIL-100(Fe) (Materials Institute Lavoisier) by a microwave-assisted solvothermal method. The acidity of the ZM composites was significantly improved compared to that of the parent materials, and the highest acidity was observed for the ZM2-based catalyst. This ZM composite-supported Pt (Pt/ZM) catalyst was investigated as a promising candidate for the selective hydrodeoxygenation (HDO) of stearic acid as a fatty acid model compound. The effect of zeolite/MOF ratio and Pt content on the catalytic behavior was also evaluated. As a result, the 3% Pt/ZM2 catalyst showed a conversion efficiency of 92% for the stearic acid HDO with a hydrocarbon selectivity of 10–11 times higher than that of the original Pt/MIL-100 (Fe). In addition, 3% Pt/ZM2 catalyst exhibited stable catalytic performance for stearic acid HDO during the recycle runs. The optimized Pt/ZM catalyst showed high thermal and catalytic stability, as well as high product yield.

Low-temperature synthesis of three-pore system hierarchical ZSM-5 zeolite for converting palm oil to high octane green gasoline

Microporous zeolite commonly suffers from a slow diffusion rate due to its restricted micropore channel, especially for bulky molecules. In this case, hierarchical zeolite has emerged as an essential functional material because of its excellence in alleviating the diffusion issue and improving the catalytic performances. In this research, hierarchical ZSM-5 zeolite with a three-interconnected-pore system (3 PS, micro-meso-macro) has been synthesized at a low temperature (90 °C) in the presence of CaCO3 nanoparticles. The low-temperature condition leads to the formation of the highly crystalline ZSM-5 particles with intercrystalline mesopores having a pore size distribution ranging from 3 to 6 nm. Moreover, the resulting zeolites also exhibit void spaces in a macroscale (20 nm–80 nm) created from the removal of CaCO3 nanoparticles. Moreover, the catalytic tests on the catalytic cracking of palm oil demonstrate the superior activity of the trimodal porous ZSM-5 in producing high octane gasoline compared to the ZSM-5 with two pore system (2 PS), and one-pore system (1 PS). A three-interconnected-pore system enhances the accessibility of reactant molecules to and the product molecules out of the active sites within the ZSM-5 crystals. As a result, the 3 PS catalyst produces a remarkable gasoline yield (25–26%) with exceptional aromatic content (>90%) and a research octane number (RON) of 114 with a less amount of cokes deposited during the reaction. Ultimately, the 3 PS catalyst also possesses the highest stability as it can maintain the catalytic performance up to the third cycle.

Sub-micron sized hierarchical porous ZSM-5 particles with controllable mesoporous structures by changing the alkalinity in the synthesis using NaOH

This work reports that sub-micron sized hierarchical porous ZSM-5 particles with controllable mesoporous structures can be facilely synthesized in a seed-assisted system without using any secondary templates or organic additives. The results showed that typical samples so-obtained display relative uniform ellipsoidal sub-micron sized particles consisting of loosely packed primary nanocrystals. The mesoporous structures of ZSM-5 zeolite particles can be effectively introduced and adjusted by solely changing the quantity of NaOH in the initial synthesis mixture. The NaOH dosages significantly affect not only hierarchical mesoporosity but also the ratio of Si/Al and thus acidity of the final ZSM-5 product. Moreover, the effect of synthesis hydrothermal procedure was also investigated. The typical sample Z5-0.12 possesses high crystallinity, BET surface area, well-developed mesoporosity and improved catalytic performance in LDPE cracking. This approach constitutes a facile and cost-effective pathway to prepare sub-micron sized hierarchical porous ZSM-5 particles and might promote their application in industry.

Photoluminescence from metal clusters formed in the pores of zeolite by pulsed laser ablation in a liquid phase

Laser ablation (LA) in a liquid was used for loading clusters on various supporting materials. An advantage of LA in a liquid is that the cluster generation conditions are almost independent of the material. Gold, silver, and copper clusters were implanted in the pores of zeolite particles using a laser ablation of an Au, Ag, or a Cu plate in water dispersed with zeolite ZSM-5 particles. We found the evidence for Au and Ag clusters trapped in the pores of the zeolite through LA in water that the samples fluoresced between 400 and 500 nm under 350 nm excitation after calcination at 300 °C. However, the sample with Cu did not exhibit photoluminescence because the Cu particles produced by LA in water were oxidized. The Au and Ag clusters were estimated to be composed of ∼6 atoms based on the relationship between the HOMO–LUMO energy gap and the cluster size predicted using the jellium model.

Carbon molecular sieve/ZSM-5 mixed matrix membranes with enhanced gas separation performance and the performance recovery of the aging membranes

Carbon molecular sieve (CMS)/ZSM-5 mixed matrix membranes (MMMs) were prepared by pyrolysis of PMDA-ODA polyimide/ZSM-5 precursors. The morphology and structure of the CMS/ZSM-5 MMMs were investigated by scanning electron microscope (SEM), X-ray diffractometer (XRD) and transmission electron microscope (TEM). The results indicated that ZSM-5 particles were well dispersed in the carbon matrix and maintained their microstructure during pyrolysis. The gas separation performance of the CMS/ZSM-5 MMMs was evaluated using single gases (H2, CO2, O2, N2, CH4) and mixed gases (21/79 mol.% O2/N2 and 50/50 mol.% CO2/H2). Compared with pure CMS membranes, the CMS/ZSM-5 MMMs exhibited outstanding permeability without significantly sacrificing selectivity. The gas permeabilities of the CMS/ZSM-5 MMMs increased with the increase of ZSM-5 loading and decreased with the increase of pyrolysis temperature. The aging of the CMS/ZSM-5 MMMs in a humid environment was also investigated. After simple thermal treatment, the pure gas permeabilities of the aging membrane were recovered to 39% (CH4), 66% (N2), 74% (H2), 77% (O2) and 83% (CO2) of the non-aging membrane, respectively, and the mixed gas permeabilities of the aging membrane were recovered to 63% (N2), 70% (O2), 82% (CO2) and 90% (H2) of the non-aging membrane, respectively.

Dimethyl ether conversion to hydrocarbons on the closely interconnected FER@ZSM-5 nanostructures

A superior catalyst activity and stability for dimethyl ether (DME) conversion to gasoline-range hydrocarbons (DTG) on a novel hierarchically-structured hybridized FER@ZSM-5 were verified in terms of the strong interactions of ZSM-5 on the plate-like FER nanostructures, which were prepared by alcohol additive with two organic structure-directing agent (OSDA). The highly active nanostructured FER@ZSM-5 with a propanol additive showed the closely interconnected and highly dispersed ZSM-5 aggregates on the larger plate-like FER surfaces, which were mainly responsible for the suppressed heavy coke depositions with the help of the closely interconnected ZSM-5 and FER interfaces with abundant acidic sites on 8-membered ring (8-MR) channels. The well-dispersed ZSM-5 nanoparticles on Brønsted acid sites of FER surfaces showed coke-resistant natures for DTG reaction due to the synergy effects of the strong acidic sites of the smaller ZSM-5 particles and larger Brønsted acid sites on the plate-like FER structures. • Superior activity and stability for DTG on the hybrid FER@ZSM-5 composite were verified. • FER@ZSM-5(Propanol) with closely interconnected nanostructures showed higher stability. • Less coke deposition was observed due to closely interconnected ZSM-5 and FER interfaces.

Unveiling the charge transfer behavior within ZSM-5 and carbon nitride composites for enhanced photocatalytic degradation of methylene blue.

ZSM-5/graphitic carbon nitride (g-C3N4) composites were successfully prepared using a simple solvothermal method. By varying the amount of ZSM-5 and g-C3N4 in the composites, the charge carrier (electrons and holes) transfer within the materials, which contributes to the enhanced photocatalytic performance, was unraveled. The X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and scanning electron microscopy (SEM) analysis revealed that more ZSM-5 component leads to a stronger interaction with g-C3N4. The photocatalytic performance test toward methylene blue (MB) degradation shows that more ZSM-5 in the composites is beneficial in enhancing photocatalytic activity. Meanwhile, the impedance electron spectroscopy (EIS) and photoluminescence (PL) analysis revealed that ZSM-5 facilitates the charge carrier transfer of photogenerated electrons and holes from g-C3N4 to the catalyst surface due to its lower charge transfer resistance. During the charge carrier migration, the interface between g-C3N4 and ZSM-5 particles may induce higher resistance for the charge carrier transfer, however after passing through the interface from g-C3N4 to ZSM-5 particles, the charge carrier can be efficiently transferred to the surface, hence suppressing the charge carrier recombination.

Effect of mesoporous ZSM-5 morphology on the catalytic performance of cobalt catalyst for Fischer-Tropsch synthesis

Mesoporous ZSM-5 with various morphologies loading cobalt were prepared and applied in Fischer-Tropsch synthesis. Smaller ZSM-5 particles showed higher intensity of strong acid sites resulting in higher cobalt-support interaction. The activity and CH4 selectivity were remarkably related with cobalt-support interaction over such acidic supports. Cobalt loaded on spindle mesoporous ZSM-5 exhibited the lowest activity and the highest CH4 selectivity due to the strongest cobalt-support interaction, but the highest activity was obtained over cubic mesoporous ZSM-5 with the lowest cobalt-support interaction originating from weaker acid sites. In addition, adjusting acid intensity and mesopore volumes could successfully tuned hydrocarbon distribution. Spherical ZSM-5 with hierarchical structure containing larger mesopore volumes and moderate acid intensity effectively promoted the production of C12-18 hydrocarbons. The highest C5-11 selectivity was observed over cobalt supported on hexagonal meso-ZSM-5 due to the enhancement in diffusion limitation over lower mesopore volumes and hydrocracking of primary hydrocarbons over higher Brønsted acid sites.

Facile moderate-temperature hydrothermal design of nanocrystalline coffin-shaped ZSM-5 catalyst for transformation of CH3OH to C2H4/C3H6

Different crystallization times were studied during hydrothermally synthesis of ZSM-5 framework at moderate temperature to investigate the physicochemical properties and MTO catalytic behavior. The ZSM-5 samples were synthesized at moderate temperature (250 °C) and different crystallization times (24, 18, 12, 6, and 3 h). The synthesized samples were analyzed by XRD, FESEM, EDX, BET-BJH, FTIR, and TPD-NH3 experimental approaches. The results revealed that the purity of crystalline phase, nucleation rate, crystallinity, morphology, porosity, and acidic properties of catalysts depended on the condition of moderate temperature synthesis with strong dependence on crystallization time. This was indicative of the ZSM-5 zeolite prepared at short crystallization time (3 h) facilitated facile design of coffin-shaped ZSM-5 particles which were capable of producing improved properties could provide some useful indication for MTO reaction. So, the MTO catalytic process was carried out using the specific MTO reaction condition of T = 460 °C, CH3OH: H2O = 1:1 (vol:vol) and the feed gas hourly space velocity (GHSV) = 10500 cm3/gcat.h). The ZSM-5(250-3) catalyst showed an enhanced selectivity toward desired olefins, whereas it presented 65% selectivity to propylene and 9% selectivity to ethylene after 35 h on stream. The possible reaction pathway for facile design synthesis of ZSM-5 catalyst via moderate temperature was proposed.

One-Pot Synthesis and Formation Mechanism of Hollow ZSM-5.

Coffin-shaped hollow ZSM-5 zeolite (HZZ) particles with shell thickness of about 200 nm and hollow diameter of approximately 1.5 μm were synthesized in one pot by using tetrapropylammonium bromide (TPABr), aluminum triisopropoxide Al[OCH(CH3 )2 ]3 and tetraethoxysilane (TEOS) as the structure-directing agent (SDA), aluminum and silica source, respectively. The appropriate molar ratios of TPABr/SiO2 and Si/Al as well as suitable crystallization temperature are the key factors for the formation of HZZ. The formation of the HZZ can be attributed to the existence of intrinsic density variation inside the initial amorphous aggregates and the Al zoning in the outer surface of the ZSM-5 particles. Amorphous silica with low crystallinity formed at early stages and low Al concentration, which has been subsequently dissolved and recrystallized on the ZSM-5 particle surface through Ostwald ripening, leading to the formation of HZZ. This approach, which uses a high concentration of SDA, will provide new possibilities and insight into the prospective fabrication of hollow zeolites.

Characteristic of ZSM-5 catalyst supported by nickel and molybdenum

Ni and Mo doped on the ZSM-5 catalyst has been prepared. In this study the effect of metal concentration on the character of the catalyst was determined by varying the concentration of Ni and Mo by 1 to 5% (wt) against the ZSM-5 using impregnation method. The characterization results show that the catalyst contains Ni by 4%, while Mo was 5%, on the other hand, Mo was more dispersed in ZSM-5 particles compared to Ni. The total acidity for Mo-ZSM-5 catalysts was higher than Ni-ZSM-5. The surface area of ZSM-5 after loading by Ni and Mo decreased significantly, but the pore size increased slightly. Meanwhile the pore volume for the Ni-ZSM-5 was relatively the same as the pore volume of the ZSM-5 but the Mo-ZSM-5 was reduced by about 20%.

Hydrocarbon catalyzed-selective catalytic reduction catalysts using core-shell atomic layer deposited CeO2 and ZrO2

The authors have developed low light-off temperature, hydrothermally stable catalysts for the removal of nitrogen oxide contaminants from lean-diesel emissions using hydrocarbon catalyzed selective catalytic reduction (SCR). This study utilizes the atomic layer deposition (ALD) technique to apply precisely controlled coatings onto metal ion exchanged zeolite particles to prepare drop-in ready catalysts with improved stability and activity. ALD was used to develop a bifunctional, core-shell coating on Cu-exchanged ZSM-5 particles, with ZrO2 deposited within the pore volume acting as a catalytic promoter in conjunction with an outer ZrO2/CeO2 layer for stabilization and to adsorb NOx. The core-shell ALD-catalyst synthesis approach demonstrated here provides a general strategy for a bifunctional zeolite stabilization and promotion. This work offers a pathway to minimize the usage of expensive rare earth metal oxides in the catalyst, providing an NOx removal strategy that mitigates emissions, storage, and corrosion concerns associated with ammonia SCR, the predominant SCR technology.

Highly selective aromatization and isomerization of n-alkanes from bimetallic Pt-Zn nanoparticles supported on a uniform aluminosilicate.

A bimetallic-support interaction through Pt-Zn nanoparticles and uniform compact cylindrical ZSM-5 particles shows selectivity over 90% towards BTX and i-octane at controlled 60% conversion with negligible coke formation when reforming n-octane. This is a significant improvement compared to alternative Pt-Zn on conventional ZSM-5, with a selectivity of less than 40%.

Preparation of Consolidated Body Zeolite from Rice Husk Ash

Rice husks (RHs) are agricultural wastes which include approximately 20 mass% of silica (SiO2). In Thailand, RHs have been applied as fuel for thermal power generation systems and a large amount of ash (Rice husk ash: RHA) was produced. In addition, our research group has reported before that binder-free consolidated zeolite A could be obtained by using SiO2 powder with geopolymer reaction as a humidity conditioning material because zeolite A has been used as desiccant and builder for detergent with low silica content. Moreover, other kind of zeolite with high amount of SiO2 content, such as ZSM-5, was under interest due to its good properties as catalytic activity and a unique pore structure. But, it was not widely utilized because of the difficulty of consolidated body preparation. Therefore, in the present study, the possibility of the usage of RHA as raw materials for consolidated zeolite A and ZSM-5 was investigated for the high-value application of RHA under specific heat treatment condition, molar ratio and preparation technique. After specimens were obtained, XRD analysis and SEM were charactarized for consolidated bodies to confirm cystalline phases and observe microstructure, respectively. Consolidated zeolite A was synthesized with heat treatment above 60°C. The sample heat treated at 60°C for 24 h consisted of homogeneous zeolite A particles with the size smaller than 1 μm. In addition, consolidated ZSM-5 was synthesized with an usual method as TPABr (Tetra propyl ammonium bromide) technique and research method as S.C. (seed crystal) technique. The results showed that although around 10 μm seed crystal was used, around 4~5 μm of ZSM-5 particles were obtained by S.C. technique. This result led to the possibility to use RHA with S.C. technique to synthesize consolidated body and control ZSM-5 particle size.

Fabrication of novel PPSU/ZSM-5 ultrafiltration hollow fiber membranes for separation of proteins and hazardous reactive dyes

Abstract Polyphenylsulfone (PPSU) based asymmetric hollow fiber membranes were prepared by the addition of different percentages of ZSM-5 particles by diffusion induced phase separation method. Polyvinylpyrrolidone (PVP) was used as a pore forming agent. The fabricated membranes were characterized by Field Emission scanning electron microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), contact angle, water permeability, water uptake and by porosity measurements. Membranes filtration study was performed using different proteins namely bovine serum albumin (BSA), egg albumin (EA) and hazardous dyes like Reactive black 5 (RB-5), Reactive orange 16 (RO-16) in aqueous solutions. It was found that, addition of ZSM-5 in membrane matrix showed better dye removal capacity because of its hydrophilic and adsorptive nature. The membrane (PZ-3) with higher loading of additive exhibited rejection percentages of 100% for BSA, 95.23% for EA proteins and with reactive dyes 90.81% for RB-5 and 82.84% for RO-16 as compared to the pristine HF membrane.

Performance of hierarchical ZSM-5 supported cobalt catalyst in the Fischer-Tropsch synthesis

Uniform ZSM-5 nanoparticles (around 180 nm) were synthesized by steam assisted crystallization method (SAC), which have a hierarchically porous structure, composed of abundant open mesopores from the stacking of ZSM-5 particles and micropores in the ZSM-5 crystallites. The hierarchical ZSM-5 supported cobalt catalyst, with a cobalt loading of 15%, was then prepared through incipient impregnation and used in Fischer-Tropsch synthesis (FTS). The hierarchical ZSM-5 support and Co-based catalyst were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 sorption. The results indicate that the hierarchical ZSM-5 supported cobalt catalyst performs excellently in FTS, since the mesoporous structure in the hierarchical ZSM-5 support can enhance the mass transfer of the reaction products and the acid sites on the microporous ZSM-5 framework can promote the hydrocracking of long chain hydrocarbon products. In comparison with the cobalt catalysts supported on bulk ZSM-5 and commercial ZSM-5, the hierarchical ZSM-5 supported cobalt catalyst exhibits much higher activity in FTS, lower selectivity to CH4, and higher selectivity to C5–20 hydrocarbons (68.9%).

Synthesis of ZSM-5 aggregates made of zeolite nanocrystals through a simple solvent-free method

In the traditional hydrothermal synthesis of zeolites, the solvent of water is necessary for crystallization, so large amount of wastewater containing NaOH and organic pollutants could be inevitably produced. The solvent-free route is considered to remarkably enhance the synthesis efficiency and reduce the energy and pollutants in large scale production of zeolites, but the zeolites obtained usually consist of micrometer sized single crystals which only possess micropores and long diffusion pathway for molecules. In this study, a novel solvent-free synthesis system made of solid raw materials of anhydrous silica and aluminum sources, organic template and Na2CO3·10H2O, was demonstrated to synthesize ZSM-5 zeolite particles composed of nanocrystals of about 10–40 nm in size. The obtained ZSM-5 particles possess high crystallinity and surface area, and well-developed mesoporosity (5.2 nm) and excellent catalytic activity in polymer cracking, such as low-density polyethylene (LDPE), which is the main source of white pollution. The ZSM-5 aggregate particles with the micro-/meso- porous structure have the potential used as catalysts and adsorbents in industry.

Pervaporation performance of surface-modified zeolite/PU mixed matrix membranes for separation of phenol from water

Polyurethane (PU) is a kind of promising pervaporation membrane material and silica-rich zeolite is a potential modifier to PU, but the pristine zeolite particles suffer from the bad dispersion in the polymer. This work presents a new route to modify zeolite (ZSM-5) particles via bridging with isocyanate to prepare a membrane for the recovery of phenol from the water. Zeolite ZSM-5 particles were successfully grafted by TDI, β-cyclodextrin, and oleyl alcohol, consecutively. The corresponding zeolites filled PU membranes were prepared and characterized by FTIR, TGA and SEM techniques. The effects of the grafted structures on the pervaporation performances of the zeolites/PU membranes were investigated in the recovery of phenol from the water. The results showed that the modified ZSM-5 particles had a good dispersion in PU, while the pristine ones demonstrated an obvious sedimentation. The modified zeolite/polyurethane membranes achieved better comprehensive separation performance than the neat PU and pristine ZSM-5 modified PU membranes. Depending on the good affinity of the β-cyclodextrin to phenol, ZSM-5 particles grafted by toluene diisocyanate and β-cyclodextrin (ZSM-TC) showed the optimal separation performance with the flux of 46.03 kg μm m−2 h−1 and the separation factor of 15.64 for the 0.3 wt% aqueous phenol solution at 80 °C. With the increase in the zeolite loading from 5 to 25%, ZSM-5/PU membrane showed the decreased separation factor and flux comparing to the neat PU. However, ZSM-TC/PU membrane showed higher flux and better selectivity than the neat PU and pristine ZSM-5 filled PU membranes.