Synthesis Of ZSM-5 Research Articles

Effect of Seed Amounts on the Synthesis of Zeolite ZSM-5 Using Coal Bottom Ash and Rice Husk as Sources of Silica and Alumina by Using Seeding Method

ZSM-5 has been successfully synthesized by seeding method using coal bottom ash and rice husk as the sources of silica and alumina.Synthesis ZSM-5 were performed by the hydrothermal method in autoclave autogenous at 180 °C for 36 h with molar ratio 10Na : 50SiO : 2Al2O3 : 500H2O with the addition of ZSM-5 commercial as seed. In this experiments, investigated variations seed amounts of 5, 10, 15, and 20% of weight silica. The product was characterized using X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscope (SEM), and Brunauer-Emmet-Teller (BET). Resulted showed that ZSM-5 succeed formed in all variation of seed contain. At variation seed amount 5%, crystallinity obtained still low in which content of quartz phase still be high. Percent crystallinity highest obtained at the variation of seed amount 20% with the result percent crystallinity relative 106%. The experimental results revealed that phase transformation has occurred, in which an amorphous phase of coal bottom ash and rice husk has been transformed to the ZSM-5 crystal with addition seed as substitution organic template.

Deleterious effects of non-framework Al species on the catalytic performance of ZSM-5 crystals synthesized at low temperature

ZSM-5 synthesis at low temperature leads to a large percentage of non-framework octahedral and penta-coordinated aluminum species that negatively impact catalyst performance.

Mechanochemically-assisted solvent-free and template-free synthesis of zeolites ZSM-5 and mordenite.

Aluminosilicate-based zeolite materials, such as ZSM-5 and mordenite, are well-studied as catalysts. Typical approaches to synthesize these zeolites require either templates or seeds to direct ordered crystal growth and both of these are expensive and add to the complexity of zeolite synthesis. In this paper, we describe a solvent-free and template-free method to synthesize crystalline ZSM-5 and mordenite zeolites without any added seed crystals. Key to the success of this approach is a mechanochemical precursor pre-reaction step. High-energy ball-milling is used to initiate a solid-state metathesis (exchange) reaction between Na2SiO3 and Al2(SO4)3 reagents, forming crystalline Na2SO4 and well-mixed aluminosilicate precursor. The solid precursor mixture is thermally converted to crystalline ZSM-5 or mordenite at moderate 180 °C temperatures without solvents or an organic amine structure directing template. Variations in Si/Al ratios in the precursor mixture and additions of solid NaOH to the mechanochemical reaction were found to influence the subsequent growth of either crystalline ZSM-5 or mordenite zeolites. The crystalline zeolites from this solvent-free and template free method have high ∼300 m2 g−1 surface areas directly from the synthesis without requiring high-temperature calcination. These materials are also comparably active to their commercial counterparts in cellulose and glucose biomass catalytic conversion to hydroxymethylfurfural.

Hierarchically Porous ZSM-5/SBA-15 Zeolite: Tuning Pore Structure and Acidity for Enhanced Hydro-Upgrading of FCC Gasoline

The pore structure and acid sites of the catalysts are demonstrated as the main factors for the hydro-upgrading of fluid catalytic cracking (FCC) gasoline. Herein, we report a general synthesis of ZSM-5/SBA-15 composite zeolites with tunable pore structure and acid sites. The effects of the pore structure and acid sites of these catalysts on their hydro-upgrading performance were systematically investigated. The platelet CoMo/AZS-PL (CoMo/ZS-PL-γ-Al2O3) catalyst with the short mesochannels, appropriate Co–Mo–S phase, and suitable acidity exhibited the excellent preservation ability of research octane number (RON) and hydrodesulfurization (HDS) performance, which was better than those of CoMo/AZS-SR (CoMo/ZS-SR-γ-Al2O3), CoMo/AZS-HP (CoMo/ZS-HP-γ-Al2O3), and CoMo/AZS-LR (CoMo/ZS-LR-γ-Al2O3) catalysts. The relationship between the physicochemical properties (acidity, morphology, pore structure, and sulfided active metal) of the catalysts and their isomerization (ISO), aromatization (ARO), as well as HDS abi...

Mechanochemical reaction pathways in solvent-free synthesis of ZSM-5

Abstract Solvent-free methods for the synthesis of ZSM-5 have been previously reported in the literature. These methods typically involve grinding the starting materials together prior to the hydrothermal reaction step. However, very little is known about the reaction intermediates formed during the mechanochemical pre-reaction or about how the pre-reaction impacts the subsequent hydrothermal synthesis conditions (temperature and length of hydrothermal treatment). In this study, the solvent-free synthesis of ZSM-5 was investigated while varying the length and type of grinding (manual, ball-mill) and the components of the reaction mixture. The initial reactions that occurred between the solid-state raw materials during grinding were monitored by powder X-ray diffraction (pXRD). Extended grinding initiates exchange reactions between several reagents to form NaCl and to liberate ammonia and water. The resulting wet paste undergoes facile thermal conversion to crystalline zeolite ZSM-5 framework structures. These results provide valuable insights used to guide the optimization of the synthesis conditions required to prepare stable, crystalline and high surface area ZSM-5 under solvent-free synthesis conditions. The solvent-free approach contributes to the overall goal of a greener, more sustainable ZSM-5 synthesis.

Hierarchical Shell-Like ZSM-5 with Tunable Porosity Synthesized by using a Dissolution-Recrystallization Approach.

Zeolites have been widely used in various fields in industry, such as catalysis, separation, and adsorption, etc. The small pore size of the micropores in the zeolite could lead to severe diffusion resistance in mass transfer. Numerous efforts have been dedicated to imposing hierarchical pore systems into zeolites by using templates or leaching methods. Here, we report the synthesis of single-crystalline hierarchical shell-like ZSM-5 by utilizing a dissolution-recrystallization post-treatment on mesoporous ZSM-5. Tetrapropylammonium hydroxide solution was used in the post-treatment. The hierarchical porosity in the crystalline shell can be controlled by adding sodium cations into the synthesis system. The hierarchical shell-like ZSM-5 reported here shows higher catalytic activity in acetalization reactions containing bulky molecules.

Synthesis and Characterization of ZSM-5 Zeolite from Dealuminated and Fragmentated Bayat-Klaten Natural Zeolite

Synthesis of ZSM-5 zeolite was conducted using natural zeolite of Bayat-Klaten by employing fragmentation method of sub-molten system through breaking zeolite framework into its monomer in alkaline condition at 250°C. Prior to fragmentation, one part of zeolite was treated with dealumination and the other one without dealumination, labeled as ZSM-5_a and ZSM-5_wa, respectively. Characterization with FTIR, XRD, and EDX showed that the fragmentation was successful, in which the structure of zeolite was damaged and the infrared bands due to AlO4 and SiO4 were appeared. The synthesis of ZSM-5 was performed hydrothermally using tetrapropylammonium hydroxide (TPAOH) as a directing agent of pore structure and addition of LUDOX (40% silica suspension in water). The XRD characterization showed the as synthesized materials had the structure of ZSM-5 zeolites with high crystallinity. Imaging with SEM showed the characteristic of hexagonal ZSM-5 crystals. The BET surface area analysis showed a typical surface area of microporous zeolite, 262 m2/g, and pore diameter of 1.496 nm; indicating that the ZSM-5 zeolite obtained was micropore size. The Si/Al ratio of ZSM-5_a and ZSM-5_wa were 18 and 21, respectively. These results indicated that Bayat-Klaten natural zeolite can be used as silica and alumina source for high crystalline ZSM-5 with medium Si/Al ratio and having good thermal stability. Thus, these materials are potential to be tested as fluid hydrocracking catalyst.

Fast synthesis of submicron ZSM-5 zeolite from leached illite clay using a seed-assisted method

Abstract A seed-assisted method enabled the fast synthesis of submicron ZSM-5 from acid-leached illite without the use of any organic templates. In addition, the effects of illite activation temperature, synthesis temperature, synthesis time, Na2O/SiO2 ratio, SiO2/Al2O3, and the amount of commercial seed were investigated. The synthesized zeolite materials were characterized by X-ray diffraction, scanning electron microscopy, and NH3 temperature-programmed desorption. Under these study conditions, submicron-sized ZSM-5 zeolites were synthesized in a relatively short time of 3 h. The relative crystallinity of the ZSM-5 zeolite obtained was up to 115%, and the quartz impurity was kept to a minimum. Aluminium in the framework of zeolite is capable of providing acidic sites. The prepared ZSM-5 zeolite showed a slightly better catalytic performance in toluene disproportionation than ZSM-5 seeds. In addition, different commercial ZSM-5 zeolites could be utilized as seeds, including self-made zeolite crystals.

Hydrothermal synthesis of core-shell ZSM-5/SAPO-34 composite zeolites and catalytic performance in methanol-to-aromatics reaction

A series of core-shell ZSM-5/SAPO-34 composite catalysts with different molar ratios were synthesized using hydrothermal method, and their catalytic performance was tested for the conversion of methanol-to-aromatics. The catalysts were characterized by means of XRD, SEM, NH3-TPD and N2 adsorption-desorption analysis. The results showed that pristine SAPO-34 showed much lower selectivity to aromatics due to its narrow cage structure and lower acid sites. However, with increasing ZSM-5/SAPO-34M ratio, composite zeolite showed higher selectivity to aromatics. As the molar ratio was up to two, the selectivity to aromatics was even higher than that of pristine ZSM-5, indicating that core-shell composite zeolites with hierarchical structure and moderate acid sites were favored for methanol to aromatics. Meanwhile the optimum reaction condition for high yield of aromatics is determined to be 450 °C and 1.5 h−1(WHSV).

Nanocrystalline Hierarchical ZSM-5: An Efficient Catalyst for the Alkylation of Phenol with Cyclohexene.

In this paper, authors report the synthesis of nanocrystalline hierarchical zeolite ZSM-5 and its application as a heterogeneous catalyst in the alkylation of phenol with cyclohexene. The catalyst was synthesized by vacuum-concentration coupled hydrothermal technique in the presence of two templates. This synthetic route could successfully introduce pores of higher hierarchy in the zeolite ZSM-5 structure. Hierarchical ZSM-5 could catalyse effectively the industrially important reaction of cyclohexene with phenol. We ascribe the high efficiency of the catalyst to its conducive structural features such as nanoscale size, high surface area, presence of hierarchy of pores and existence of Lewis sites along with Brønsted acid sites. The effect of various reaction parameters like duration, catalyst amount, reactant mole ratio and temperature were assessed. Under optimum reaction conditions, the catalyst showed up to 65% selectivity towards the major product, cyclohexyl phenyl ether. There was no discernible decline in percent conversion or selectivity even when the catalyst was re-used for up to four runs. Kinetic studies were done through regression analysis and a mechanistic route based on LHHW model was suggested.

Synthesis and physicochemical characterization of hierarchical ZSM-5: Effect of organosilanes on the catalyst properties and performance in the catalytic fast pyrolysis of biomass

Abstract Two series of ZSM-5 catalysts with hierarchical porosity were hydrothermally synthesized by adding two types of organosilane reagents (OSA) into the medial synthesis system. The effects of the types and addition amounts of OSA on the pore characteristics, crystallinity, morphology and acidity of the ZSM-5 zeolites were studied by XRD, SEM, TEM, N2-adsorption, 27Al MAS NMR and NH3-TPD. Mesopores were generated by introducing appropriate amounts of OSA. In addition, the catalytic performance of the hierarchical ZSM-5s were investigated for the catalytic fast pyrolysis (CFP) of cellulose. The increase in the mesoporosity leads to a reduced amount of coke. However, the highest yield of aromatics was obtained for the mesoporous sample with the greatest microporosity. Thus, the right balance between meso- and microporosity is critical for achieving high aromatic yields. In addition, the distribution of aromatic products is directly related to the microporosity.

Optimal Synthesis of Hierarchical Porous Composite ZSM-5/SBA-16 for Ultradeep Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene. Part 2: The Influence of Aging Temperature on the Properties of NiMo Catalysts

ZSM-5/SBA-16 (ZS) supports were prepared using the two-step hydrothermal crystallization method. The effect of the aging temperature on the structural properties of the series ZS supports was studied. The prepared samples were analyzed by X-ray diffraction, scanning electron microscopy, N2 physisorption, 27Al magic angle spinning nuclear magnetic resonance, H2 temperature-programmed reduction, Raman, X-ray photoelectron spectroscopy, pyridine–Fourier transform infrared spectroscopy, and high-resolution transmission electron microscopy. The hydrodesulfurization performances of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) were examined at T = 340 °C and PH2 = 4 MPa. The NiMo/ZS-45 catalyst synthesized at the aging temperature of 45 °C exhibited the best catalytic activities of DBT and 4,6-DMDBT, which were attributed to its regular shape, well-organized pore structure, high sulfidation degree, and a compromise between the acidity and metal–support interaction (MSI, Mo–O–Si). Moreover, the possible DBT and 4,6-DMDBT HDS reaction networks over NiMo/ZS-45 were proposed.

Use of chitin as a template for the preparation of mesostructured ZSM-5

Abstract In this work, mesostructured ZSM-5 zeolite was prepared using chitin as a new template to produce mesoporosity. Different amounts of chitin were used for the synthesis of ZSM-5 in order to verify its influence on the formation of mesopores. All samples were prepared by conventional hydrothermal process. For comparison purposes, ZSM-5 zeolite has also been synthesized without a presence of chitin. The samples were characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption techniques. Experimental results showed that the mesopores volume of the obtained samples increased with increasing amount of chitin in the reaction mixture. Therefore, chitin showed to be a promising template for obtaining the ZSM-5 with mesoporous property.

Sustainable Synthesis of ZSM-5 Zeolite from Rice Husk Ash Without Addition of Solvents

The development of sustainable and environmentally friendly techniques for synthesizing zeolites has attracted much attention, as the use of solvents in the hydrothermal synthesis of zeolites is a major obstacle for realizing green and sustainable synthesis ways. As a solid waste, it still has a challenge for zeolites synthesis from rice husk ash by solvent-free method to increase its recovery rate and economic value. Our approach focused on reutilization of rice husk ash by converting it to ZSM-5 zeolite without employing solvents. The influence of TPABr/SiO2, Na2CO3·10H2O/SiO2 and synthesis time on ZSM-5 crystal growth and ZSM-5 zeolite properties were evaluated by various analytical methods. The results suggested that the optimal conditions of TPABr/SiO2, Na2CO3·10H2O/SiO2 and synthesis time for the ZSM-5 synthesis were 0.125, 0.3 and 72 h, respectively. Base on the optimal synthesis condition, the recovery rate of Si and Al were 98%, which were 70% compared with that of hydrothermal method. The synthesis process was solid phase conversion, Na2CO3·10H2O played key role in promoting hydrolysis and condensation of Si–O–Si and Si–O–Al bonds during synthesis process. The resultant ZSM-5 zeolite exhibited well-defined crystallinity and porosity, ZSM-5 aggregate particles possessed micro-/meso-porous structures. The BET surface area of synthetic ZSM-5 zeolite was 304 m2/g, comparable to hydrothermal synthetic ZSM-5 zeolite (320 m2/g). Overall, proposed synthetic route provides novel green alternative for the recovery of rice husk ash, further mitigating the environmental and health care concerns.

Optimal Synthesis of Hierarchical Porous Composite ZSM-5/SBA-16 for Ultradeep Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene. Part 1: The Influence of Inorganic Salt on the Properties of NiMo Catalysts

Series ZSM-5/SBA-16 (ZS) composites were prepared using various inorganic cations as additives, and the associated catalysts were tested for dibenzothiophene and 4,6-dimethyldibenzothiophene hydrodesulfurization (HDS). The structure–function relationship was investigated through various characterization methods. The NiMo/ZS–Mg catalyst using MgCl2 as an additive displayed higher HDS reaction rate constant and turnover frequency values, which could be attributed to its major acidity, higher metal–support interaction (MSI), higher sulfidation degree, higher dispersion degree, moderate stacking number, and shorter stacking length of sulfide Mo species, of which the higher acidity and higher MSI contributed more to the improvement of its HDS performance. Besides, the possible HDS pathways on the NiMo/ZS–Mg catalyst were provided.

Conversion of South African Coal Fly Ash into High-Purity ZSM-5 Zeolite without Additional Source of Silica or Alumina and Its Application as a Methanol-to-Olefins Catalyst

Characteristics of ZSM-5 synthesized from H2SO4-treated coal fly ash and fused coal fly ash extracts are compared in this study. In the synthesis process, fused coal fly ash extract (without an additional silica source) was used in the synthesis of ZSM-5. The effect of the structure-directing agent (tetrapropylammonium bromide, 1,6-hexanediamine or 1-propylamine) on the properties and methanol-to-olefins (MTO) effectiveness of the fly ash-based ZSM-5 was also investigated. A pure ZSM-5 synthesized from the fused coal fly ash extract led to a methanol conversion higher than 90% after 5 h on stream. The template 1,6-hexanediamine led to the synthesis of the most stable fly ash-based catalyst keeping a 44% methanol conversion after 24 h on stream.

A dual-templating synthesis strategy to hierarchical ZSM-5 zeolites as efficient catalysts for the methanol-to-hydrocarbons reaction

A novel dual-templating synthesis strategy is presented to obtain hierarchical ZSM-5 zeolite using a combination of known structure-directing agents for ZSM-5 synthesis and C16H33-[N+-methylpiperidine] (C16MP) as mesoporogen. C16MP is a cheap surfactant, which can be obtained in a single step by alkylation of N-methylpiperidine. The zeolite materials were extensively characterized for their textural and acidic properties and evaluated on the basis of their ability to convert methanol to hydrocarbons. Bulk and nanosheet (di-quaternary ammonium surfactant) ZSM-5 zeolites served as reference materials. Hierarchical ZSM-5 zeolite can be obtained in this way with diethylamine, n-propylamine, 1,4-diaminobutane, 1,6-diaminohexane. In particular, the combination with diethylamine afforded a material that displayed similar performance in the methanol-to-hydrocarbons reaction as nanosheet ZSM-5. The optimum ZSM-5 zeolite is highly crystalline, contains a large mesopore volume and few silanol groups and external Brønsted acid sites, which contributes to the low rate of deactivation.

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.

High-temperature and short-time hydrothermal fabrication of nanostructured ZSM-5 catalyst with suitable pore geometry and strong intrinsic acidity used in methanol to light olefins conversion

High temperature hydrothermal synthesis method was developed to preparation of nanostructured ZSM-5 molecular sieves at short crystallization time. A series of catalysts were synthesized at various temperatures and crystallization times for achievement of pure ZSM-5 phase with MFI structure. The synthesized catalysts were investigated with XRD, FESEM, EDX, BET-BJH, FTIR and TPD-NH3 techniques. The results revealed that hydrothermal synthesis conditions generally affected the nucleation rate, particle size, textural properties and acidic nature of ZSM-5 catalysts. It was found that pure ZSM-5 materials with high crystallinity could be obtained at specific crystallization conditions of about 300 °C for 1.5 h and also 350 °C for 0.5 h. Increasing the hydrothermal temperature to 350 °C and decreasing the crystallization time to 0.5 h led to the formation of small particles with high specific surface area of 392 m2/g. Furthermore, ammonia TPD spectra showed that ZSM-5(300-1.5) catalyst contained higher amount of acid sites and less acid strength compared to ZSM-5(350-0.5) catalyst. The catalytic performance of samples was studied for conversion of methanol to light olefins under different reaction conditions. Interestingly, the proper pore geometry along with the strong intrinsic acidity resulted in a tendency for excessive production of light olefins for ZSM-5(350-0.5) catalyst. The selectivity of light olefins over this catalyst was increased about 94% in the long time on stream (2100 min). Also, the possible reaction pathway for ZSM-5 synthesis at high temperatures was discussed in details.

Internal structure of a gel leading to NBA-ZSM-5 single crystals

Porous gel structures are formed during the synthesis of the zeolite ZSM-5 due to the reaction between a source of aluminosilicate, sodium hydroxide, water and a structure directing agent, such as e.g. tetrapropylammonium (TPA) or n-butylamine (NBA). In the present work, the formation of the gel in a heterogeneous system leading to the crystallization of NBA-ZSM-5 zeolite from leached metakaolin was studied extensively. The solid and liquid phases obtained after separation were analyzed by inductively coupled plasma sector field mass spectrometry, dynamic light scattering, extreme high resolution-scanning electron microscopy, energy dispersive spectroscopy, high resolution-transmission electron microscopy, X-ray diffraction and nitrogen gas adsorption. The main gel phase formed after hydrothermal treatment exhibited a sponge-like structure resembling those forming in (Na, TPA)-ZSM-5-based systems. For the first time, the walls of the main gel were shown to be inhomogenous and to possess a biphasic internal structure consisting of a mesoporous skeleton of aluminosilicate nanoparticles embedded in a silicate-rich soluble matrix of soft matter. The data presented in this paper is of primary importance to understand the mechanism by which the gel is consumed and contributes to the growth process of the zeolite crystals.