FAU Zeolites Research Articles

A nanoscale investigation of the formation of mesostructured zeolites FAU and LTL

Nanostructured materials can be utilised as potential catalysts for the production of platform chemicals and renewable biofuels from biomass derived molecules. The formation of hierarchical meso-microporous zeolites LTL and FAU via the surfactant assisted tandem acid-base post-synthesis treatment has been investigated by time-resolved in situ synchrotron SAXS and WAXS, providing a new insight into the mechanism of the mesostructuring treatment. Based on the results of TEM and in situ synchrotron measurements, a model for the formation of the core-shell structure of LTL zeolite crystals is proposed. Complementary evaluation using FTIR, NMR and nitrogen adsorption, in conjunction with reaction studies on mesostructured zeolites, demonstrated a potential for enhanced catalytic performance of these materials owing to the increased accessibility of the active sites and reduced transport limitations.

Facile synthesis of SSZ-16 nanoaggregates with excellent performance in NH3-SCR reaction

d6r units were proved to be crucial for the synthesis of SSZ-16 zeolite with AFX topology, and FAU zeolite owning plenty of d6r units was chosen as the essential raw material for constructing AFX frameworks. In this work, SSZ-16 zeolite was directly synthesized using colloidal silica and sodium aluminate as the raw materials in short crystallization time of 5 h. The corresponding crystallization process were carefully investigated by various characterizations, demonstrating that the key to this success was the formation of d6r units built up by a large amount of s4r units which were formed with the assistance of the appropriate organic structure directing agent (OSDA) and seeds in the synthetic media. Interestingly, the products of C-SSZ-16 zeolites presented spherical shapes consisted of relatively small particles with size range from 30 to 50 nm. Moreover, after ion-exchanged with Cu ions, the Cu-C-SSZ-16 products showed excellent performance in the selective catalytic reduction of NOx with NH3 (NH3-SCR) and better hydrothermal stability than conventional Cu-SSZ-16-con samples due to slightly higher Si/Al ratio of the Cu-C-SSZ-16. Therefore, remarkable catalytic performance and the use of low-cost raw materials as well as short period of synthesis time make AFX zeolites as potential applicants in NH3-SCR field, from an industrial viewpoint.

Correction: Effects of organic acids on microwave-assisted leaching for mesopore generation in FAU zeolite

Correction: Effects of organic acids on microwave-assisted leaching for mesopore generation in FAU zeolite

Effects of organic acids on microwave-assisted leaching for mesopore generation in FAU zeolite

Effects of organic acids on microwave-assisted leaching for mesopore generation in FAU zeolite

Competitive Adsorption of Moisture and SO2 for Carbon Dioxide Capture by Zeolites FAU 13X and LTA 5A

Zeolites exhibit significant potential as porous materials for selective carbon dioxide (CO2) capture, leveraging their distinctive adsorption properties. However, the presence of moisture (H2O) and sulfur dioxide (SO2) in flue gas streams can significantly affect the efficiency of CO2 capture. This study investigates the CO2 adsorption characteristics of zeolites FAU 5A and LTA 13X, revealing the competitive adsorption mechanism between H2O(g), SO2, and CO2. The zeolites exhibit CO2 adsorption capacities of 93.19 mg/g and 95.80 mg/g for 5A and 13X, respectively, and demonstrate good regeneration potential. Metal cations correlated positively with CO2 adsorption. H2O(g), SO2, and CO2 exhibit a competitive adsorption relationship, with H2O(g) having the highest adsorption capacity, followed by SO2 and CO2. Additionally, the synergistic effect of SO2 and H2O(g) on CO2 adsorption is elucidated. These findings provide valuable insights into the competitive adsorption behavior of moisture and SO2 for CO2 capture using zeolites LTA 5A and FAU 13X, contributing to the development of more efficient CO2 capture processes and the design of tailored adsorbents for industrial applications.

Preparation of MAZ-Type Zeolite with High Silica.

The Si/Al molar ratio of MAZ aluminosilicate zeolite prepared by the direct hydrothermal method is generally less than five, thus giving rise to poor thermal and hydrothermal stability for this low-silica zeolite. With the purpose of enhancing the Si/Al molar ratio of MAZ zeolite, post-synthesized methods including acetic acid treatment and steaming treatment, as well as interzeolite transformation from FAU zeolite, were employed to prepare MAZ zeolite with high silica. It was found that steaming treatment was more effective in increasing the Si/Al molar ratio in comparison with acetic acid treatment, affording a maximum Si/Al molar ratio of 16.9 along with a preserved crystallinity of approximately 75%. Additionally, high-silica MAZ zeolite with a Si/Al molar ratio of up to 7.3 was also capable of being directly hydrothermally synthesized using interzeolite transformation from FAU zeolite.

In vivo biodistribution and tumor uptake of [64Cu]-FAU nanozeolite via positron emission tomography Imaging.

Nanoparticles have emerged as promising theranostic tools for biomedical applications, notably in the treatment of cancers. However, to fully exploit their potential, a thorough understanding of their biodistribution is imperative. In this context, we prepared radioactive [64Cu]-exchanged faujasite nanosized zeolite ([64Cu]-FAU) to conduct positron emission tomography (PET) imaging tracking in preclinical glioblastoma models. In vivo results revealed a rapid and gradual accumulation over time of intravenously injected [64Cu]-FAU zeolite nanocrystals within the brain tumor, while no uptake in the healthy brain was observed. Although a specific tumor targeting was observed in the brain, the kinetics of uptake into tumor tissue was found to be dependent on the glioblastoma model. Indeed, our results showed a rapid uptake in U87-MG model while in U251-MG glioblastoma model tumor uptake was gradual over the time. Interestingly, a [64Cu] activity, decreasing over time, was also observed in organs of elimination such as kidney and liver without showing a difference in activity between both glioblastoma models. Ex vivo analyses confirmed the presence of zeolite nanocrystals in brain tumor with detection of both Si and Al elements originated from them. This radiolabelling strategy, performed for the first time using nanozeolites, enables precise tracking through PET imaging and confirms their accumulation within the glioblastoma. These findings further bolster the potential use of zeolite nanocrystals as valuable theranostic tools.

Improved Synthesis of Hollow Fiber SSZ-13 Zeolite Membranes for High-Pressure CO2/CH4 Separation.

High-silica CHA zeolite membranes are highly desired for natural gas upgrading because of their separation performance in combination with superior mechanical and chemical stability. However, the narrow synthesis condition range significantly constrains scale-up preparation. Herein, we propose a facile interzeolite conversion approach using the FAU zeolite to prepare SSZ-13 zeolite seeds, featuring a shorter induction and a longer crystallization period of the membrane synthesis on hollow fiber substrates. The membrane thickness was constant at ~3 μm over a wide span of synthesis time (24-96 h), while the selectivity (separation efficiency) was easily improved by extending the synthesis time without compromising permeance (throughput). At 0.2 MPa feed pressure and 303 K, the membranes showed an average CO2 permeance of (5.2±0.5)×10-7 mol m-2 s-1 Pa-1 (1530 GPU), with an average CO2/CH4 mixture selectivity of 143±7. Minimal defects ensure a high selectivity of 126 with a CO2 permeation flux of 0.4 mol m-2 s-1 at 6.1 MPa feed pressure, far surpassing requirements for industrial applications. The feasibility for successful scale-up of our approach was further demonstrated by the batch synthesis of 40 cm-long hollow fiber SSZ-13 zeolite membranes exhibiting CO2/CH4 mixture selectivity up to 400 (0.2 MPa feed pressure and 303 K) without using sweep gas.

Improved Synthesis of Hollow Fiber SSZ‐13 Zeolite Membranes for High‐Pressure CO2/CH4 Separation

AbstractHigh‐silica CHA zeolite membranes are highly desired for natural gas upgrading because of their separation performance in combination with superior mechanical and chemical stability. However, the narrow synthesis condition range significantly constrains scale‐up preparation. Herein, we propose a facile interzeolite conversion approach using the FAU zeolite to prepare SSZ‐13 zeolite seeds, featuring a shorter induction and a longer crystallization period of the membrane synthesis on hollow fiber substrates. The membrane thickness was constant at ~3 μm over a wide span of synthesis time (24‐96 h), while the selectivity (separation efficiency) was easily improved by extending the synthesis time without compromising permeance (throughput). At 0.2 MPa feed pressure and 303 K, the membranes showed an average CO2 permeance of (5.2±0.5)×10−7 mol m−2 s−1 Pa−1 (1530 GPU), with an average CO2/CH4 mixture selectivity of 143±7. Minimal defects ensure a high selectivity of 126 with a CO2 permeation flux of 0.4 mol m−2 s−1 at 6.1 MPa feed pressure, far surpassing requirements for industrial applications. The feasibility for successful scale‐up of our approach was further demonstrated by the batch synthesis of 40 cm‐long hollow fiber SSZ‐13 zeolite membranes exhibiting CO2/CH4 mixture selectivity up to 400 (0.2 MPa feed pressure and 303 K) without using sweep gas.

Highly Active Palladium-Containing FAU Zeolite Catalyst for Suzuki–Miyaura Reaction

Highly Active Palladium-Containing FAU Zeolite Catalyst for Suzuki–Miyaura Reaction

Mechanisms for deNOx and deN2O Processes on FAU Zeolite with a Bimetallic Cu-Fe Dimer in the Presence of a Hydroxyl Group-DFT Theoretical Calculations.

In this paper, a detailed mechanism is discussed for two processes: deNOx and deN2O. An FAU catalyst was used for the reaction with Cu-Fe bimetallic adsorbates represented by a dimer with bridged oxygen. Partial hydration of the metal centres in the dimer was considered. Ab initio calculations based on the density functional theory were used. The electron parameters of the structures obtained were also analysed. Visualisation of the orbitals of selected structures and their interpretations are presented. The presented research allowed a closer look at the mechanisms of processes that are very common in the automotive and chemical industries. Based on theoretical modelling, it was possible to propose the most efficient catalyst that could find potential application in industry-this is the FAU catalyst with a Cu-O-Fe bimetallic dimer with a hydrated copper centre. The essential result of our research is the improvement in the energetics of the reaction mechanism by the presence of an OH group, which will influence the way NO and NH3 molecules react with each other in the deNOx process depending on the industrial conditions of the process. Our theoretical results suggest also how to proceed with the dosage of NO and N2O during the industrial process to increase the desired reaction effect.

Synthesis‐structure‐catalysis relations in CHA zeolites applied for selective catalytic reduction of NOx with ammonia

Microporous aluminosilicate zeolites are useful industrial catalysts. However, their hydrothermal synthesis is a multistep process with complicated and unclear reactions, limiting their rational functional design. Herein, we compare the formation pathway and the structural and catalytic properties of several CHA zeolites to obtain fundamental knowledge for intentionally controlling the catalytic function of zeolites. Three CHA zeolites were synthesized using different starting silica/alumina sources in the presence of tetraethylammonium hydroxide as an inexpensive organic structure‐directing agent. FAU zeolite and an amorphous synthesis gel prepared using two different methods were used as starting materials. The obtained CHA zeolites were applied for exhaust gas purification (selective catalytic reduction of NOx with ammonia, NH3‐SCR), and their structural characteristics and formation pathways were investigated using a combination of analytical methods. Stepwise gel preparation (SGP), which divides the compositional control of the amorphous synthesis gel, promotes the decomposition of the initial additive (zeolite seed), resulting in the formation of CHA zeolites with abundant micropores and paired Al sites. This structural feature obtained using the SGP method improves the catalytic durability of the NH3‐SCR reaction. The present relationship, including different crystallization phenomena, structures, and catalytic abilities, provides useful insights into rational zeolite synthesis and its application.

Catalytic Consequences of Hierarchical Pore Architectures within MFI and FAU Zeolites for Polyethylene Conversion

Catalytic Consequences of Hierarchical Pore Architectures within MFI and FAU Zeolites for Polyethylene Conversion

Hierarchical FAU Zeolites Boosting the Hydrocracking of Polyolefin Waste into Liquid Fuels

Hierarchical FAU Zeolites Boosting the Hydrocracking of Polyolefin Waste into Liquid Fuels

One-pot synthesis of zeolite NaX from agricultural waste for toluene removal application

One-pot conversion of rice-husk ash, which is a huge agriculture solid waste in Vietnam, to a valuable nanoporous material (zeolite FAU type X) is reported. Combined zeolite-TiO2 can be used as Adsorbent-Photocatalyst hybrid (APH) material for treatment of gaseous polluted VOCs. The combination of adsorption and photocatalyst methods in toluene treatment was investigated using TiO2-containing composites on zeolite X support which was successfully generated from one-pot synthesis method with rice husk ash from agricultural waste. The structural properties of the zeolite and the APH were examined by X-ray diffraction analysis, SEM and TGA, while the effect of hydrothermal time and temperature to the one-pot process of zeolite X synthesis was investigated. The ability to handle the toluene of this composite was also studied under humid and dry conditions at a concentration about 1000 ppmv. The results indicate the accomplishment of one-pot synthesis method in creating zeolite X materials with FAU structure and high crystallinity, along with the toluene treatment efficiency of APH materials when combined with TiO2 photocatalyst. This achievement encourages the implementation of one-pot synthesis process to create other VOCs treatment materials.

Hybrid exchange methods regulate Cu+ location on Cu-Y zeolites and improve CO adsorption capacity and selectivity

This work systematically examines the influence of preparation methods on the active Cu+ anchoring sites over FAU zeolites and their CO storage capacity and selectivity. The involved preparation methods here include individual liquid ion exchange method with CuCl2 solution, individual solid ion exchange method with CuCl powder and the hybrid exchange method. For the obtained Cu-Y samples, XRD, Ar adsorption/desorption at 87 K, TEM and NMR were used to characterize their skeleton structure, meanwhile, XPS and H2-TPR were utilized to identify the Cu+, Cu2+ and CuCl distribution. The CO storage capacity was implemented through CO adsorption–desorption isotherms. The correlation between various Cu species and CO storage capacity was analyzed and DFT calculation was employed to further elucidate the optimal Cu+ location induced by preparation methods. Finally, it is found that the isolated Cu+ is the dominating CO adsorption sites and Cu+ on site III present higher bonding energy with CO molecules. The hybrid preparation method seems the optimal choice for Cu-Y synthesis since the initial liquid ion exchange operation could prevent the framework corrosion from the subsequent solid ion exchange process, which benefits the optimal CO storage capacity and CO/N2 selectivity.

Aromatic bio-oil production from corn stover by FAU + MFI dual-catalyst catalytic fast pyrolysis: A study of two catalyst parameters

The dual-catalyst catalytic fast pyrolysis (CFP) is a promising approach for producing hydrocarbon-rich bio-oil from biomass waste. However, the lack of detailed research on the structural parameters of the first- and second-layered catalysts was lacking and hindered the development of this technology. Herein, dual-catalyst CFP of corn stover was conducted, and the effects of the acidity and porosity of the two-layered catalysts were studied in detail to enhance their synergistic effect. The results demonstrated that for the second-layered catalyst (MFI zeolite), the utilization of a strong acidic ZSM-5(25) facilitated the production of aromatic hydrocarbon (38.8 area%). For the first-layered catalyst (FAU zeolite), the employment of medium acidity and microporous HY(2.6) was advantageous for the production of valuable monocyclic aromatic hydrocarbon (MAHs) with a selectivity of 21.5 area%, which was ∼1.6 times higher than that in the less acidic HX(1.5) + ZSM-5(25) trial. These findings confirmed that the synergy between the two-layered catalysts was dramatically enhanced by using the HY(2.6) + ZSM-5(25) catalyst combination. Finally, a proposed reaction pathway for the dual-catalyst CFP of corn stover was provided to guide the optimization of dual-catalyst CFP technology and the design of pyrolysis catalyst.

The isomorphous substitution of Si(4Al) with P in FAU zeolite and its stabilization effect

It's a dream to make zeolites more stable so as to keep the activity and stability of the catalyst. Phosphorus modification is an effective method, however, the known post-modification predominantly presents as non-framework P, and the P-loss is a big trouble in application. We have discovered that in the reaction of PCl3 or SiCl4 + PCl3 with NaY zeolite, a portion of P enters the framework of the zeolite, forming a PO4-AlO4 structure. Further investigations revealed that P cannot be incorporated into the framework through P for Al isomorphous substitution, but rather through isomorphous substitution with Si(4Al). PCl3 exhibits two effects in reaction: at lower quantities, it mainly undergoes isomorphous substitution with Si(4Al); at higher quantities, it leads to zeolite dealumination generating aluminum vacancies, which disrupt the zeolite framework or promotes Si for Al isomorphous substitution. After hydrothermal aging at 800 °C for 4 h, the stable presence of framework PO4-AlO4 implies that the weakest site Si(4Al) becomes the more stable site P(4Al) in the Y zeolite framework. Compared with the JPY (prepared by impregnating (NH4)2HPO4 solution to high silica Y zeolite) sample, after 10 cycles of hydrothermal and water washing treatment, the P2O5 loss rate of DPY (prepared by SiCl4 + PCl3 with NaY) zeolite ranged from 0.4 % to 3.5 %, significantly lower compared to the range of 18.7 % to 25.9 % observed in the JPY sample. This indicates that in DPY zeolite, the interaction between P and the zeolite is stronger and less prone to loss. Moreover, P is more uniformly distributed on the surface and bulk phase of DPY than JPY sample.

Enhancing nucleation to synthesize Al-rich CHA zeolites under ultra-low OSDA contents: Application for heavy-duty NH3-SCR of NOx

The crystallization of Al-rich CHA zeolites with an ultra-low organic structure directing agent (OSDA) content and without using pre-crystallized FAU zeolites as Si and/or Al sources has been accomplished by controlling the nucleation step. Indeed, the use of “gel-type” seeds containing discrete nanosized CHA nanoparticles (i.e. below 100 nm) combined with the understanding of the seed-assisted crystallization mechanism has allowed the efficient preparation of Al-rich CHA materials using ultra-low methyltriethylammonium (MTEA) contents (MTEA/Si molar ratios ∼ 0.03–0.04), making this synthetic route very cost-competitive compared to recent synthesis improvements for CHA using substoichiometric contents of expensive OSDAs (i.e. N,N,N-trimethyladamantammonium, TMAda). The optimized Al-rich CHA materials, after incorporating the catalytically active copper cations, perform as ideal catalysts for the selective catalytic reduction (SCR) of NOx with ammonia relevant for heavy-duty applications.

Desulfurization performance and mechanism for H2S from blast furnace gas over FAU zeolite sorbent

The desulfurization of blast furnace gas is crucial to meet the strict requirements for clean production of steel industry. However, the composition of blast furnace gas is complicated, and the gases of H2O, CO, CO2, and O2 would significantly affect the desulfurization activity. Therefore, the desulfurization performance for H2S in simulated blast furnace gas by Na-type FAU zeolites with different Si/Al was investigated. The physicochemical properties of zeolite sorbents were measured, and their correlation with desulfurization performance was studied. Moreover, the adsorption mechanism of H2S was investigated. The breakthrough sulfur capacity improved with the increase of relative crystallinity, Na+ content, specific surface area, and the decrease of Si/Al ratio. The adsorption mechanism of H2S on Na-type FAU zeolite was proposed. One is the hydrogen bond interaction between the bridging hydroxyl groups and H2S, and the other one is the base-acid interaction between sodium ion and H2S. In blast furnace gas, when interacting with Na+, H2S would be transformed into S, which further oxidized into thiosulfate and sulfate by O2.