Synthesis Of Hierarchical ZSM-5 Zeolite Research Articles

Upcycling rice husk ash and coal-fired fly ash as si/al sources into hierarchical ZSM-5 for efficient mercury capture from industrial flue gas

Limiting gaseous Hg0 emission is pressing due to the high toxicity in the ecosystem. Zeolites can be regarded as a promising alternative to carbon-based Hg0 adsorbents. However, the mass transfer limitations of conventional singe-sized zeolites constrain the industrial application of zeolites. This study explores the synthesis of hierarchical ZSM-5 zeolites using rice husk ash (RHA) and coal-fired fly ash (FA) as sustainable sources of silicon and aluminum, aimed at enhancing Hg0 removal from industrial flue gases. By adopting a one-step hydrothermal method, we introduced hierarchical porosity into the ZSM-5 framework, enhancing mass transfer and adsorption efficiencies. Iron (III) chloride (FeCl3) was utilized as an active species for modifying the hierarchical ZSM-5, significantly boosting its Hg0 adsorption capabilities. Fe/6RF-hZ demonstrating more than 92% mercury removal efficiency in 60 min under mixed flue gas condition. The structural and chemical attributes of the synthesized ZSM-5 were detailedly characterized, revealing notable differences in surface chemistry and porosity that correlate with varying calcination temperatures of RHA. TEA analysis reveals that hierarchical ZSM-5 zeolites outperform traditional sorbents in demercuration (DeHg) applications, with exceptional DeHg efficiency, energy efficiency (12 kWh), synthesis cost (860 $/ton), and carbon content (non-carbon). This study not only sheds light on the upcycling of solid wastes in synthesizing novel adsorbents but also contributes to the broader application of zeolitic materials in environmental remediation.

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.

One-step synthesis of hierarchical ZSM-5 zeolites with low defect density as long-lived MTH catalysts

The combination of introducing mesopores and minimizing framework defects in zeolite catalysts has been proved to be highly effective in improving their catalytic lifetime in the MTH reaction. However, there is currently a lack of simple method to realize these two purposes at the same time. In this work, we report a simple one-step approach which not only completed the introduction of abundant mesopores into zeolite catalyst but also simultaneously realized the reduction of framework defects. Secondary template, fluoride media and post-treatment technology were not used during the synthetic process. As an example, a hierarchical ZSM-5 zeolite catalyst with low defect density was successfully synthesized. In the MTH reaction, the synergy effect of the hierarchical pore structure and the less framework defects endowed the prepared zeolite catalyst with a very long lifetime, which is 7.1 times that of the reference catalyst.

Dry gel synthesis of hierarchical ZSM-5 zeolite using hydroxyl propyl methyl cellulose (HPMC) as a mesoporogen and its catalytic activity in alkylation reactions

In this work, a “green” and facile method for synthesis of hierarchical ZSM-5 zeolite was presented by combination of a bio-mesoporogen and a dry gel conversion (DGC) process. ZSM-5 zeolite with high hierarchy factors and excellent mesoporosity was synthesized by adding hydroxypropylmethylcellulose (HPMC), which originated from cellulose biomass, to a zeolitic synthetic gel. The obtained zeolite samples were analyzed by X-ray diffraction (XRD), nitrogen adsorption–desorption (BET) and scanning electron microscopy (SEM) to determine their properties. The influence of crystallization time on the crystallinity of ZSM-5 zeolite was investigated. Moreover, the results showed that HPMC as a pore directing agent is an important factor for the formation of hierarchical zeolite with high mesoporosity. The as-prepared ZSM-5 sample with high pore volume, large surface area and abundant accessible acid sites, which seriously improves diffusion efficiency and catalytic activity, exhibited high catalytic performance in the benzylation reaction.

One-Step Synthesis of Hierarchical Zsm-5 Zeolites with Low Defect Density as Long-Lived Mth Catalysts

One-Step Synthesis of Hierarchical Zsm-5 Zeolites with Low Defect Density as Long-Lived Mth Catalysts

Study on using cellulose derivatives as pore directing agent for preparation of hierarchical ZSM-5 zeolite catalyst

Cellulose derivatives such as hydroxyethylmethylcellulose (HEMC), and hydroxypropylmethylcellulose (HPMC), which are originated from biomass, were used as mesoporous directing agent for the synthesis of hierarchical ZSM-5 zeolite. Hierarchical ZSM-5 zeolites with outstanding mesoporosity and high hierarchy factors were achieved by hydrothermal method in the presence of bio-mesoporogen. The as-synthesized hierarchical ZSM-5 zeolites were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption (BET), scanning electron microscope (SEM) to determine the structure of samples. The influences of different mesoporogens with different dosage in the synthetic process on the physicochemical and catalytic properties of hierarchical ZSM-5 zeolite were investigated. Possession of the high mesopores, high surface areas and abundant accessible acid sites, the hierarchical zeolites exhibited excellent catalytic performance in the alkylation reaction of benzene and benzyl alcohol.

Rapid synthesis of hierarchical ZSM-5 zeolites for the reactions involving larger reactant molecules

In this study, the ZSM-5 zeolites with a high hierarchy factor were synthesized rapidly and tested for the furfural hydroxymethylation (FH) to 5-hydroxymethylfurfural (HMF). The effect of seeding techniques (STs) and templates (both soft (Cetrimonium bromide, CTAB) and hard (bio-sourced secondary template, BSST)) on the final zeolite properties were studied. A significant variation in crystallinity and morphology with the ST and type of seed was observed. The CTAB addition increased the hierarchy factor (H factor) by 3 times, and the implicit seeds decreased the hydrothermal time by 2 times. The zeolite yield, crystallinity, and pore geometry were a strong function of [CTA+]/[Na+] ratio. Slit and ink bottle-shaped pore morphologies were observed with only seed or seed + BSST and with seed + CTAB, respectively, and both exhibited the bimodal pore size distribution. The zeolites with ink bottle-shaped pores outperformed those with slit pores in the FH and showed the highest selectivity to HMF of 65%, at 34% furfural conversion. The zeolites with high H factor showed catalytic and structural stability up to 5 successive recycle runs.

Synthesis of hierarchical ZSM-5 zeolite in a rotating packed bed: Mechanism, property and application

Hierarchical (micro/mesopore) ZSM-5 zeolites were hydrothermally synthesized in a rotating packed bed (RPB) which substantially enhances micromixing for the high viscosity reaction system. Herein, the effects of four operating processes with different micromixing intensity on nucleation/crystal growth process as well as physicochemical properties of ZSM-5 zeolites were investigated. Results indicate that enhancing micromixing by RPB in the zeolite synthesis could facilitate the formation of Al sites and shorten the nucleation and crystallization period. ZSM-5 samples prepared by RPB exhibit hierarchical structure, smaller average particle size, more uniform particle size distributions, larger specific surface areas, higher catalytic stability as well as more acid sites than those obtained by (stirring tank reactor) STR. While adopting the ZSM-5 samples prepared by RPB for catalyzing C4-olefin cracking reaction, the conversion of C4-olefin and yield of propylene are higher than those obtained by STR.

Synthesis of hierarchical ZSM-5 zeolites templated by sodium alginate toward enhanced catalytic activity for esterification

Hierarchical zeolites containing secondary mesopores exhibit excellent catalytic performance in the liquid phase reaction due to their low diffusion resistance. In this study, hierarchical ZSM-5 zeolite (ZSM-5-SA) has been successfully prepared via sodium alginate (SA) as macro- and mesoporous template. ZSM-5-SA possessed larger particle size and enhanced crystallinity owing to SA shortening the nucleation period of zeolite crystals. The introduction of SA also promotes Al atoms to enter ZSM-5 zeolite, where the particle size and Al content gradually increase with increasing SA concentration. Compared to conventional ZSM-5 zeolite, ZSM-5-SA possesses higher catalytic activity toward the esterification of acetic acid with n-butyl alcohol due to the synergistic effect of stronger acid sites and hierarchical porosity of ZSM-5-SA. The conversion of acetic acid can reach 47.34% after five cycles.This work paves the way for the development of highly active ZSM-5 zeolite catalysts by simple SA template.

One-step synthesis of hierarchical ZSM-5 zeolites and their catalytic performance on the conversion of methanol to aromatics

Hierarchical ZSM-5 zeolites were successfully prepared with one-step hydrothermal method by adding MTES to the zeolite precursor. The mesoporous structure of zeolite was formed via organosilane interacts with nanoparticles to form a covalent bond of Si–R, and then the alkyl group was removed by calcination. The influence of methyltriethoxysilane on the mesopores, acidity, morphology of the zeolites, and the catalytic performance of the samples was investigated. A mesoporous size about 6.5 nm was formed in the sample, meanwhile, the Bronsted acid density of zeolite was decreased. The yield of the aromatic compound was increased by about 10% after the introduction of the mesoporous structure. The catalyst’s carbon deposition resistance was improved due to a significant decrease of the Bronsted acid density of zeolite, and the catalyst life (methanol conversion rate > 95%) was extended from 41 to 76 h.

Untangling the role of the organosilane functional groups in the synthesis of hierarchical ZSM-5 zeolite by crystallization of silanized protozeolitic units

Abstract Crystallization of hierarchical ZSM-5 zeolite has been performed under hydrothermal conditions from silanized protozeolitic units. The role of amine and phenyl groups present in the organosilanes, as well as the use of dipodal silanization agents, on the creation of mesoporosity in the zeolite samples has been investigated. The presence of amine groups and dipodal moieties in the organosilane increases their interactions with the protozeolitic nanounits in the gel, which results in hierarchical zeolites showing enhanced secondary porosity and a higher degree of modification of the textural properties. Nevertheless, dipodal organosilanes hinder strongly the aggregation of the nanounits, leading to non-completely crystalline materials. In contrast, the combination of phenyl and amine groups into a single organosilane has shown to be effective for the generation of more uniform mesopores. Thus, N-(2-N-Benzylaminoethyl)-3-aminopropyltrimethoxysilane (Ph-2A) has been found as the best silanization agent, affording a hierarchical zeolite with a narrow mesopore size distribution and a high concentration of strong Bronsted acid sites. Moreover, during LDPE catalytic cracking in TGA tests, the latter material allowed the conversion of the polymer to occur in a narrow temperature range as a consequence of its more uniform acid and textural properties. Likewise, this sample exhibited a high activity in LDPE cracking at 340 °C using a laboratory scale reaction system to produce mainly gasoline-range hydrocarbons and light olefins.

Template-Free Synthesis of Hierarchical Zeolite ZSM-5

The influence of the conditions of template-free, seed-assisted synthesis of hierarchical ZSM-5 zeolite on its crystallinity, particle morphology, and texture has been studied. A method for the synthesis of a hierarchical zeolite, which makes it possible to reduce the template consumption three times, has been proposed.

Organosilane Surfactant-Directed Synthesis of Hierarchical ZSM-5 Zeolites with Improved Catalytic Performance in Methanol-to-Propylene Reaction

The hierarchical ZSM-5 zeolites with interconnected meso-/microporosity have been successfully synthesized by using the commercial organosilane surfactant TPOAC as the mesopore structure-directing ...

Synthesis of hierarchical ZSM-5 zeolites with CTAB-containing seed silicalite-1 and its catalytic performance in methanol to propylene

Hierarchical ZSM-5 zeolites were synthesized with cetyltrimethylammonium bromide (CTAB) containing silicalite-1 (S-1) as seed. The characterization results revealed that the CTAB/SiO2 ratio of 0.005–0.1 in S-1 created abundant intercrystal mesopores in ZSM-5 zeolites and resulted in less strong and weaker acid sites. The hierarchical ZSM-5 had a comparable catalytic performance in methanol to propylene (MTP) reaction with the zeolite synthesized by adding S-1 and CTAB directly in the precursor form as reported in the literature. However, in the present proposed method, the use of CTAB was greatly reduced. The very low-cost and facile method developed in this work is expected to be feasible for the synthesis of other zeolites.

A facile and green method for the synthesis of hierarchical ZSM-5 zeolite aggregates from rice husk ash

Hierarchical ZSM-5 zeolite has been successfully synthesized from rice husk ash by a facile and solvent-free method. The obtained samples were characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscopy, magic angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy, ultraviolet raman spectroscopy, thermogravimetric analysis–differential scanning calorimetry, Brunauer–Emmett–Teller (BET) analysis and temperature-programmed desorption of ammonia. The influences of synthesis time on ZSM-5 crystal growth and ZSM-5 zeolite properties were evaluated. The results suggested that the ZSM-5 synthesis process was solid-phase conversion and the crystallization was accomplished within 72 h at 150 °C. The Si, Al and Fe are tetrahedral coordinated and minute quantities of non-framework octahedral coordinated aluminium exist in synthetic ZSM-5, and it has weak and strong acid sites. The resultant ZSM-5 aggregates exhibited well-defined crystallinity and porosity, and possessed micro-/mesoporous structures. The BET surface area of the synthetic ZSM-5 zeolite was 308.41 m2/g, slightly less than that synthesized from a hydrothermal approach (320.69 m2/g). Moreover, this hierarchically porous ZSM-5 zeolite show a high-hierarchy factor up to 0.18. The proposed synthetic route in this work provides novel green alternative for the synthesis of hierarchical ZSM-5 zeolite from rice husk ash.

Anti-cancer activity of hierarchical ZSM-5 zeolites synthesized from rice-based waste materials

We report the organic template-free synthesis of hierarchical ZSM-5 zeolite using waste materials, by a simple hydrothermal method and their excellent anti-cancer activity against A549 human lung epithelial cell lines.

Synthesis of hierarchical ZSM-5 zeolites by solid-state crystallization and their catalytic properties

Hierarchically porous structure is important to promote mass transport and active site utilization of zeolites for many petrochemical reactions involving bulky molecules. Their conventional hydrothermal synthesis with meso-template materials is often complicated and expensive, and produces a large amount of aqueous pollute. We demonstrate here successful synthesis of mesoporous zeolites of MFI structure by solid-state crystallization without meso-template. Aluminosilicate nanogels are produced with only precursors and the dried nanoparticles are then transformed into nanocrystals in solid state using only their intrinsic water storage. After orientating with each other at edges, these nanocrystals join into monolithic zeolites with connecting inter-lattice mesopores. The produced hierarchical ZSM-5 zeolites exhibit superior stability and excellent catalytic performance in reactions such as Friedel-Crafts benzylation, lignin ethanolysis, and naphthalene hydrogenation. Compared with conventional synthesis routes, this new solid crystallization approach simplifies zeolite production, lowers the cost, and avoids toxic liquid waste, which may greatly benefit many energy applications.

Direct synthesis of hierarchical ZSM-5 zeolite using cetyltrimethylammonium as structure directing agent for methanol-to-hydrocarbons conversion

KOH and RbOH are suitable bases to crystallize hierarchical ZSM-5 in one step using cetyltrimethylammonium as the only structure-directing agent.

Direct Synthesis of Hierarchical ZSM-5 Zeolite and Its Performance in Catalyzing Methanol to Gasoline Conversion

A simple method was developed and tested to synthesize hierarchical ZSM-5 zeolites using tetrapropylammonium hydroxide as a sole structure directing agent to generate intercrystalline mesopores. XRD analysis confirmed the formation of ZSM-5 zeolites. SEM and TEM imaging analyses revealed the presence of hierarchical structure, formed by self-assembly of highly crystalline, nanosized primary particles. Solid-state MAS NMR analysis showed the vast majority of Al atoms were tetrahedrally incorporated with Si atoms in the zeolite framework. N2 physisorption studies indicated that the mesopores of an average pore size of 30 nm were created in the hierarchical ZSM-5 zeolites with an abundance of micropores. The performance of these zeolites in catalyzing methanol to gasoline conversion was evaluated using a fixed-bed reactor operating at 350 °C with ca. 16.5% methanol in nitrogen at a total pressure of 1.1 MPa and WHSV of 1.2 h–1. The hierarchical ZSM-5 zeolites exhibited almost 100% methanol conversion and 59% selectivity toward the gasoline range hydrocarbons. The coke formation on the used catalyst was studied using a N2 physisorption technique and a thermogravimetric analyzer. The hierarchical ZSM-5 zeolite showed less than 2% coke formation and deposition over 24 h on stream, much less compared to the conventional ZSM-5 zeolite with nearly 8% carbon deposition under the same reaction conditions.

Synthesis of hierarchical ZSM-5 zeolite using CTAB interacting with carboxyl-ended organosilane as a mesotemplate

A hierarchical ZSM-5 zeolite with uniform mesopores has been synthesized by self-assembly of zeolite seeds capped with carboxyl-ended organosilane. The carboxylate anion enhances the inorganic–surfactant interaction and enables the formation of mesopores.