Synthesis Of Zeolite Beta Research Articles

Eco-friendly synthesis and environmental impact assessment of hierarchical Beta zeolite from kaolinite and recycled mother liquor

The development of sustainable techniques to produce high-performance zeolite is essential to achieve green production in industry. Herein, we report an eco-friendly route to synthesizing hierarchical Beta zeolite from kaolinite and recycled mother liquor. The results reveal that the unutilized species (such as silicon species and Na+) in mother liquor stayed in a stable concentration during eleven recycled experiments. Moreover, the synthesized Beta zeolites still have comparable physicochemical properties and catalytic performance in the esterification of levulinic acid with ethanol over the initial zeolite although eleven recycled experiments. Life cycle assessment exhibits that the synthesis of Beta zeolite with recycled mother liquor can reduce global warming potential by 23% and resource depletion-water use by 36% compared to that without recycled mother liquor. This quantitatively demonstrates that the approach proposed in this work is really a sustainable one, extremely increasing the utilization efficiency of raw materials and decreasing the environmental burden.

Efficient and controllable synthesis of zeolite Beta nanospheres and hollow-boxes using a temperature-sensitive bifunctional additive

Zeolite Beta nanospheres and hollow-boxes are successfully obtained through a simple one-pot hydrothermal crystallization route, using tetraethylammonium hydroxide (TEAOH) as the structure-directing agent (SDA) assisted with a temperature-sensitive bifunctional additive N-methyl-2-pyrrolidone (NMP). The influences of crystallization temperature, Si/Al ratio, and TEAOH content on the synthesis and physicochemical properties of zeolite Beta as well as the formation of hollow structure are investigated in detail. It reveals that the role of NMP changes from “crystallization promoter” (CP) to “hollow-directing agent” (HDA). And the acceleration effect of NMP decreases upon the crystallization temperature (120–160 °C) due to the decomposition of TEAOH. Meanwhile, high synthesis temperature (≥180 °C), high Si/Al ratio (≥30), and low TEAOH content (TEAOH/SiO2 ≤ 0.2) may lead to the formation of undesired zeolites ZSM-5 and/or ZSM-12. The obtained Beta nanosphere and hollow-box catalysts exhibit excellent catalytic activity in the degradation of low-density polyethylene (LDPE) due to their high external surface area and acid density.

In situ Raman spectroscopy analysis of local structure in dry gel for zeolite beta synthesis

AbstractTo investigate faster crystallization of zeolite beta by the dry‐gel conversion method, the local structure of the dry gel before synthesis was quantitatively evaluated using in situ Raman spectroscopy during the drying process. The dry gel prepared from Si and Al sources, and tetraethylammonium hydroxide solution was crystallized after several hours by the dry‐gel conversion method. The conformational change of TEA+ cations was observed during the drying process by the deconvolution of the spectrum, and the conformational change was larger than that during the synthesis process. The rate of conformational change was increased with the drying temperature, and the apparent activation energy was estimated to be 68.2 kJ/mol. The generation and transformation of double three‐membered silicate rings (D3Rs) and 4‐2 type secondary building units (SBUs), which are essential for the crystallization of zeolite beta, were observed during the drying process. The transformation from D3R to 4‐2 SBU in the dry gel during drying process could be confirmed quantitatively by the difference of the time variation for the amounts of these silicate building units estimated by in situ observation.

OSDA-free synthesis of zeolite beta: Broadening the methodology for a successful use of the product as a seed

The synthesis of zeolite beta without any organic structure directing agents (OSDAs) is achieved by the addition of seed crystals. Applying the obtained OSDA-free synthesized zeolite beta as seed crystals for this purpose was quite tricky and subsequently leads to the formation of mordenite zeolite as a contaminant. Herein, we show a successful post-synthetic powder technology for retrieving the micrometer-sized pure zeolite beta seed particles that were originally blend with mordenite impurity. Taking advantage of the particle size variation, this new technique (involving a specially designed centrifugation unit) allowed us to segregate up to 35% of pure beta microparticles and use them as OSDA-free beta seeds. The recyclability of this technique is successful up to three generations after which the size variation window between the blend beta and mordenite particles become inseparably narrow. It was also clarified that controlling the silicon to aluminum (Si/Al) ratio and dissolution of the segregated microparticles using acid and alkali treatments respectively aid the formation of pure phase of zeolite beta.

Synthesis of Zeolite Beta Using Seawater Instead of Deionized Water

Synthesis of Zeolite Beta Using Seawater Instead of Deionized Water

Synthesis of high hydrothermal stability Beta zeolite with crosslinked starch and catalytic performance in catalytic cracking reaction

Zeolite Beta was directly synthesized by the hydrothermal method with crosslinked starch successfully. When the crosslinked starch was added, the zeolite Beta displayed a larger particle size, fewer external silanol groups, higher ratio of FAl/EFAl (tetrahedral-coordinated framework aluminum/octrahedral-coordinated non-framework aluminum), and higher B/L acid ratio (the ratio of Brönsted acid sites/Lewis acid sites) in comparison with the zeolite Beta-0 synthesized without crosslinked starch. And the zeolite Beta synthesized with crosslinked starch treated by phosphorus modification (P-Beta-S(X%)-SA and CAT-S) presented higher hydrothermal stability after hydrothermal treatment at 820 °C under 100% steam for 17 h. In the catalytic cracking reactions of light diesel oil and heavy oil, P-Beta-S(X%)-SA and CAT-S provided remarkably enhanced activity and higher gasoline and butene yield. The mechanism of synthesis of zeolite Beta synthesized with crosslinked starch was also shown.

Seed-Assisted Synthesis of Zeolite Beta from Solid-State Conversion of Magadiite and an Investigation on the Crystallization Mechanism

Pure zeolite beta was synthesized by conversion of magadiite in solid state with the assistance of seeds for the first time, and the influence of synthesis parameters was discussed in details. To g...

OSDA-free hydrothermal conversion of kenyaite into zeolite beta in the presence of seed crystals

Zeolite beta with high crystallinity has been successfully synthesized by using kenyaite conversion method with seed crystals under hydrothermal treatment at 125 °C for 36 h. The OSDA-free synthesis of zeolite beta could be obtained from the mixture composition of 0.96 NaOH: SiO2: 0.0167 Al2O3: 180 H2O by adding 25 wt % seeds. To study the crystallization behaviours and the medium-range structure changes during the conversion process, the prepared zeolite beta was characterized by powder X-ray diffraction, field-emission scanning electron microscope, Fourier transform infrared spectroscopy, energy dispersive spectroscopy, solid-state 27Al MAS and 29Si MAS NMR spectroscopy. The growth of zeolite beta happened on the surface of kenyaite. The five-membered rings and six-membered rings in kenyaite were partly preserved and the four-membered rings were formed by the connection of five-membered rings during the crystallization process. Meanwhile, the effects of reaction time, the initial mixture composition, the quantity of beta seed crystals and temperature in the synthesis were investigated. The as-synthesized zeolite beta, with relatively high thermal stability, exhibits good catalytic performance in the cyclohexanol dehydration reaction system.

Synthesis of zeolite beta in the presence of alkaline metals Na+ and K+ and its evaluation in hydrocracking of vacuum gas oil

Se sintetizaron zeolitas con fase *BEA y se determino la relacion de las condiciones de sintesis con la composicion final del solido. Los datos de acidez muestran una tendencia lineal con la cantidad de cationes alcalinos intercambiados con amonio. A partir de las zeolitas sintetizadas se prepararon catalizadores para su evaluacion en la reaccion hidrocraqueo de un gasoleo de vacio, donde los catalizadores mas activos son aquellos que presentaron mayor acidez y mayor cantidad de aluminio incorporado en la estructura de la zeolita. Se resalta el hecho de que altos tiempos de cristalizacion le confiere a la zeolita propiedades fisicoquimicas especiales que permiten obtener mayor actividad catalitica comparada con aquellas zeolitas sintetizadas a bajo tiempo de cristalizacion. Por otro lado, el tipo de cation presente en el gel, regula de manera diferente la concentracion de aluminio y por tanto modifica su comportamiento catalitico. Los materiales obtenidos se caracterizaron por diferentes tecnicas analiticas como difraccion de rayos X, analisis termogravimetrico y diferencial, analisis quimico, area BET, desorcion de amoniaco a temperatura programada, resonancia magnetica nuclear 27Al MAS NMR y reduccion a temperatura programada.

A facile method to synthesize hierarchical nano-sized zeolite beta

Abstract A one-pot two-stage synthesis method was developed to synthesize hierarchical nano-sized zeolite beta. The two-stage included the generation of nano-sized zeolite beta precursor and the self-assembly of the zeolite beta precursor around structure directing agent, hexadecyl trimethyl ammonium bromide. The influence of the hydrothermal synthesis time and pH value of the zeolite beta precursors, hydrothermal treatment duration, SDA concentration, and water content during nano-sized zeolite beta precursor self-assembly on the properties of final solid products were studied. The samples were characterized by nitrogen adsorption (BET), NH3-TPD, X-ray powder diffraction, solid state-NMR, and TEM. With the present synthesis method and conditions, compared with the conventional nano-sized zeolite beta synthesis, a longer zeolite precursor crystallization time was required for the successful transformation of the amorphous aluminosilicates precursors into crystalline beta assemblies with hierarchical structure. The further crystallization of zeolite beta precursors during the precursor assembly did not occur under studied pH range, hydrothermal treatment duration, SDA concentration, and water content.

OSDA-free synthesis of zeolite beta by magadiite hydrothermal conversion method and an insight into the changes of medium-range structure during crystallization

Abstract Zeolite beta has been successfully synthesized by magadiite conversion method in the absence of organic structure-directing agents. By using powder X-ray diffraction, fourier transform infrared spectroscopy and Raman spectroscopy, solid-state 27Al and 29Si MAS nuclear magnetic resonance spectroscopy and electron microscope, the crystallization behavior and changes of medium-range structure were investigated in detail. It was found that part of medium-range structure of magadiite remained during the crystallization process and part of seed crystals were dissolved, providing active surface for the formation of zeolite beta. Meanwhile, with the growth of zeolite beta, five-membered rings existing in magadiite were retained and their connection probably resulted in the formation of four-membered rings. An increasing number of Al atoms favourably entered the T1 and T2 positions which were mainly located in four-membered rings, while Si atoms resided in T3-T9 sites. The influence of reaction time, temperature, alkalinity in starting gel and the amount of seed crystals were also examined. With the reactive gel composition: 0.96 NaOH: SiO2: 0.0125 Al2O3: 240 H2O by adding 25 wt % seeds into the synthesis system, pure and highly crystalline zeolite beta could be obtained at 125 °C after 48 h.

Synthesis of Zeolite Beta and Zeolite ZSM-5 from High Silica Raw Kaolinite and Their Catalytic Etherification of Ethylene Glycol

Synthesis of Zeolite Beta and Zeolite ZSM-5 from High Silica Raw Kaolinite and Their Catalytic Etherification of Ethylene Glycol

Organic promoter-driven fast synthesis of zeolite beta and its acceleration mechanism

The crystallization rate of zeolite beta can be accelerated by a factor of as much as nine by the addition of some organic promoters.

Synthesis of beta zeolite with mesopores from a milk containing precursor and its performance in naphthalene isopropylation

The synthesis of micro-/mesoporous beta zeolite by employing a solid precursor was described and its activity in the isopropylation of naphthalene was tested. The precursor was prepared by spray-drying of a homogenous mixture of silica sol, polyaluminum chloride solution and acidophilus milk, the presence of the latter induced formation of mesopores. The volume of mesopores of the synthesized beta zeolites ranged from 0.13 to 0.6 cm3/g and strongly depended on the concentration of tetraethylammonium hydroxide (TEAOH) in the reaction mixtures at the hydrothermal synthesis. Micro-/mesoporous beta zeolites exhibit positive effects of mesopores on the naphtalene conversion in its isopropylation by isopropyl alcohol, by improving the availability of active sites. With an increasing volume of mesopores, the conversion of naphthalene proportionally increases from 12 up to 27% for the volume of mesopores 0.6 cm3/g, while the selectivity to isopropylnaphthalene decreases from 92 to 55–66% for beta zeolites with 0.15–0.45 cm3 of mesopores/g, followed by selectivity increase up to mesopore volume 0.6 cm3/g reaching 81% at conversion 27%. A yield of isopropylnaphthalene is increasing in the whole range, particularly when the volume of mesopores exceeds 0.4 cm3/g. A zeolite with the highest volume of mesopores provides 1.8 times higher yield of isopropylnaphthalene then a microporous beta zeolite without mesopores. The increasing conversion of naphthalene is accompanied by a decrease in the selectivity to isopropylnaphthalene for zeolites with a low volume of mesopores, but an increasing selectivity to isopropylnaphthalene in the case of zeolites with a volume of mesopores above 0.4 cm3/g. This unusual effect can be explained by the mesoporosity of zeolites. Mesopores improve the availability of active centers, so they react faster, but the by-products are also formed faster and later undesired reactions run more easily as active centers are gradually blocked by by-products. Zeolites with the largest pores provide not only better availability of active centers, but the reaction products can also leave the zeolitic phase more easily and undesirable reactions have less chance to occur. This method of micro/mesoporous beta zeolite synthesis is advantageous for its low cost.

Synthesis of zeolite Beta containing ultra-small CoO particles for ethylbenzene oxidation

Zeolite Beta containing ultra-small CoO particles was synthesized from a one-step hydrothermal process. The synthesis route involves the pre-mixture of hydrofluoric acid with tetraethylammonium hydroxide (in a molar ratio of 1.3–1.5:1) before the addition of a silicon and cobalt source. Investigations by scanning electron microscopy, X-ray diffraction, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, H 2 -temperature-programmed reduction and transmission electron microscopy confirm the presence of ultra-small CoO particles in the zeolite Beta structure. The ultra-small CoO particles in zeolite Beta present high stability against both oxidation and reduction atmospheres at high temperatures. The catalytic performance of the CoO-containing zeolite Beta catalysts was compared with other Co-containing zeolites by evaluating ethylbenzene oxidation reactivity. The CoO-containing zeolite Beta exhibits high ethylbenzene conversion and high selectivity to acetophenone and 1-phenylethanol. The high activity of this catalyst system can be attributed to the high dispersion of the ultra-small CoO particles in the Beta structure. Beta zeolite containing ultra-small CoO clusters was synthesized from a one-step hydrothermal process. The CoO-containing Beta zeolite exhibits high activity and selectivity in ethylbenzene oxidation.

Charge density mismatch synthesis of zeolite beta in the presence of tetraethylammonium, tetramethylammonium, and sodium ions: Influence of tetraethylammonium decomposition

The effects of a temperature change on the phase selectivity of crystallization in a tetraethylammonium (TEA+)-tetramethylammonium (TMA+)-Na+ mixed structure-directing agent (SDA) system, which had been previously used in the synthesis of UZM-9 and UZM-5 at 100 and 150 °C, respectively, have been further investigated in order to shed more light on the course of charge density mismatch (CDM) syntheses of aluminosilicate zeolites. Nanocrystalline zeolite beta with a Si/Al ratio of 8.1, essentially the same ratio as that (8.0) of its initial synthesis mixture, was the phase crystallized at 155 °C, whereas heating at higher temperatures ranging from 160 to 200 °C for up to 21 days gave no crystalline products. The course of chemistry at these temperatures is highly influenced by the increasing instability of the TEA+ SDA. The overall results of this study demonstrate that the TMA+, as well as the TEA+ and Na+ ions, plays an important role in the nucleation step of zeolite beta prepared here, providing another example of SDA cooperation in a CDM zeolite synthesis. An idealized charge density disproportionation model is employed to track the evolving chemistry of the aluminosilicate solids and solutions. The discrepancy between the observed solution chemistry and that expected by the model suggests the presence of undesirable reactions in the system, namely TEA+ decomposition.

Methanol conversion to dimethyl ether over beta zeolites derived from bagasse fly ash

ABSTRACTCatalytic performance of beta zeolites derived from bagasse fly ash for methanol dehydration to dimethyl ether, alternative fuel, was investigated. Amorphous silica extracted from bagasse fly ash, a tetraethylammonium hydroxide (TEAOH) were used as a precursor and a template for synthesis of beta-zeolites, respectively. Beta zeolites could be synthesized at a constant hydrothermal temperature of 135°C and a constant initial pressure of 3 bars under the nitrogen atmosphere. The crystallization time and Si/Al ratio were 48 h and 15, respectively. These conditions gave the highest crystallinity for beta zeolites with a crystal size of 0.51 μm as well as a Brunauer–Emmett–Teller surface area of 844 m2 g−1. Beta zeolites with the Si/Al ratios of 15.8 and 24.6 were used as catalysts for methanol conversion to dimethyl ether. Beta zeolites with the Si/Al ratios of 15.8 and 24.6 have the % yields of 84 and 60, respectively. According to the result of NH3-TPD, the beta zeolites with the Si/Al ratio of 15.8 showed higher acidity than beta zeolites with a Si/Al ratio of 24.6. Therefore, the beta zeolites with a Si/Al ratio of 15.8 were more efficiency in methanol conversion reaction than beta zeolites with a Si/Al ratio of 24.6.

Pure-phase zeolite beta synthesized from natural aluminosilicate minerals and its catalytic application for esterification

The use of natural aluminosilicate minerals as the low-cost starting materials for zeolite synthesis is a field of current interest. However, impurities existing in these minerals greatly affect the purity of final products. Herein, we describe a cheap and green route for synthesizing pure-phase zeolite beta from natural aluminosilicate minerals via a modified nanoscale depolymerization-reorganization approach. The physicochemical and catalytic properties of the synthesized zeolite beta were systematically characterized and assessed, respectively. The results indicate that the resulting zeolite beta possesses more moderate Brönsted acid sites compared with the reference one, and thus exhibits higher catalytic activity in the esterification of acetic acid with ethanol. This methodology demonstrates great perspective for the low-cost and environmentally-benign synthesis of zeolite beta that avoids the use of aluminum- and silicon-containing inorganic chemicals, eliminates the interference of impurities, and reduces the usage of the organic template.

CO2 adsorption–desorption properties of zeolite beta prepared from OSDA-free synthesis

Recent research has demonstrated how the economically and environmentally benign organic structure-directing agent (OSDA)-free synthesis of zeolite beta—based on the seed-assisted method—exhibits superior properties in applications as antibacterial agents, catalysts and adsorbents in comparison with conventional zeolite beta. One possible way to take advantage of OSDA-free beta is to apply the material in energy-efficient capture of carbon dioxide (CO2) from a variety of large emission sources. For this reason, we have investigated the CO2 adsorption–desorption properties of OSDA-free beta for the first time. The results of elemental analysis, N2 and CO2 adsorption–desorption, evaluation of the isosteric heat of adsorption and solid-state NMR measurements have shown that OSDA-free beta exhibited higher crystallinity, larger pore volume and higher aluminum (Al) as well as sodium (Na) cation content with enhanced homogeneity in Al distribution within the *BEA framework as compared to the conventional TEA-directed beta synthesized using tetraethylammonium hydroxide (TEAOH). These unique properties of OSDA-free beta resulted in significant improvements of CO2 adsorption–desorption capability over a wide pressure region under moderate temperature in comparison with conventional zeolite beta.

Mechanism of seeding in hydrothermal synthesis of zeolite Beta with organic structure-directing agent-free gel

The organic structure-directing agent-free synthesis of zeolite Beta was carried out using several zeolite Beta seeds that differed in SiO2/Al2O3 ratio and crystal size. The synthesis was studied using X-ray diffraction, X-ray fluorescence, scanning electron microscopy, transmission electron microscopy, ultraviolet-Raman spectroscopy, infrared spectroscopy, and N2 physisorption. Synthesis was successful using different zeolite Beta seeds including pure silica seeds. During the induction period, the seeds underwent dissolution. The SiO2/Al2O3 ratio and crystal size, pretreatment (calcination), and seed addition time had a significant influence on seed dissolution behavior, crystallization process, and product. Morphological studies revealed that the seed residues produced by dissolution (except for pure silica) resulted in the formation of “immobilized” surface nuclei, which allowed for the dense growth of fresh small zeolite Beta crystals. The dissolved small seed fragments yielded dispersed nuclei, which formed relatively scattered small zeolite Beta crystals thought to be the main nuclei source of the pure silica seed. It is suggested that the use of an appropriately high SiO2/Al2O3 ratio, small size, and precalcined zeolite Beta seed is helpful for the synthesis of highly crystalline and pure zeolite Beta from the organic structure-directing agent-free gel.