Preparation of uniform and nano-sized NaA zeolite using silatrane and alumatrane precursors (original) (raw)
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Na-A (LTA) zeolite synthesis directly from alumatrane and silatrane by sol-gel microwave techniques
Journal of the European Ceramic Society, 2003
Na-A (1 mm crystal size) zeolite was successfully synthesized via a sol-gel process and microwave heating technique using alumatrane and silatrane as precursors. After fixing the SiO 2 :Al 2 O 3 ratio at 1:1 and microwave heating temperature at 110 C, increasing the Na 2 O concentration by adding more NaOH exponentially reduces the microwave heating time from 160 min at a Na 2 O:SiO 2 ratio of 3:1 to 5 min at a Na 2 O:SiO 2 ratio of 9:1. The increase of Na 2 O concentration strongly affects the particle size and particle size distribution, but does not affect the product composition. Small crystallite sizes are obtained from a high Na 2 O: SiO 2 ratio (10:1) while a low Na 2 O:SiO 2 ratio (3:1) gives large crystallite sizes ( $4.5 mm). The analyzed Si:Al:Na ratio of synthesized Na-A zeolite is 1:1:1.25. The moisture absorption ability of the synthesized Na-A zeolite is higher than that of the commercial one by approximately 20%. The increase of water ratio also affects the crystal size. As the water ratio increases, larger crystallites with a higher degree of irregularity are formed. #
2003
1 µm crystal-size Na A zeolite (LTA) is successfully synthesized via the sol-gel process and microwave heating technique using alumatrane and silatrane as precursors. The optimal conditions to obtain LTA were 1:1:3:410 SiO 2 :Al 2 O 3 :Na 2 O:H 2 O ratio, microwave heating temperature and a time of 110°C and 160 min, respectively. Under the same conditions, increasing the Na 2 O concentration exponentially reduces the microwave heating time from 160 min at a Na 2 O:SiO 2 ratio of 3:1 to 5 min at a Na 2 O:SiO 2 ratio of 9:1. Increasing the Na 2 O concentration strongly affects the particle size and particle size distribution, but does not affect the product composition. Increasing the amount of water increased the average particle size and also the number of irregular cubic shape crystals. Increasing the aging temperature from 90° to 150°C, everything else being the same (one hour heating time and the loading ratio of SiO 2 :Al 2 O 3 :5Na 2 O:410H 2 O), only amorphous product was produced at 90°C and between 110°-150°C only LTA was produced.
Journal of the European Ceramic Society, 2002
Alumatrane and silatrane were successfully used as precursors to produce aluminosilicate via the sol-gel process. Due to their ability in retarding hydrolysis process, forming meso-porous material was easier. Both NaCl and NaOH can be used as hydrolysis agents, however, NaOH had highly influenced crystalline formation. The higher NaOH concentration, the better crystalline formation was observed. Gel transformation was an endothermic reaction. The maximum transformation occurred at 106 C, as determined by differential scanning calorimetry (DSC). By using NaOH/H 2 O as a hydrolysis agent and treating amorphous metal oxide gel by microwave technique, the crystalline aluminosilicate was formed and narrow particle size distribution was obtained. By fixing the ratio of SiO 2 , Al 2 O 3 , Na 2 O and H 2 O at 1:0.25:3:410, GIS was synthesized at hydrothermal treatment of 3 h at 110 C, while analcium (ANA) was produced at 130 C for 8 h. GIS obtained had 4.55 mm in size while ANA's size was 9.96 mm. #
Synthesis of Zeolite NaA from Low Grade (High Impurities) Indonesian Natural Zeolite
Indonesian Journal of Chemistry, 2014
The zeolite NaA has been successfully synthesized from the low grade natural zeolite with high impurities. The synthesis method was started by mixing natural zeolite powder with NH 4 Cl aqueous solution in the reactor as pretreatment. The use of pretreatment was to reduce the impurities contents in the zeolite. The process was followed by alkaline fusion hydrothermal treatment to modify the framework structure of natural zeolite and reduce the SiO 2 /Al 2 O 3 ratio. Finally, the synthesized zeolite was calcined at 600°C for 2 h. The final zeolite product was characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the morphology of the zeolite NaA was cubic shape as observed by SEM analysis and the synthesized zeolite NaA with pretreatment gave less impurity than without pretreatment.
Journal of Porous Materials, 2013
A number of investigations have demonstrated that zeolite NaA could be synthesized using Si, extracted from rice husk ash; however, experiments on direct extraction of Si from rice husk (RH) are scarce. The main objective of the present study was to explore the possibility to synthesize high-quality zeolite NaA from RH and waste aluminium cans (as a source of Al), applying different procedures for the preparation of initial hydrogel and a unified procedure for crystallization of zeolite NaA. Products were characterized by SEM-EDX and XRD analyses. The investigation demonstrated that Si could be extracted directly from RH, avoiding the process of RH burning. Practically complete dissolution of Si from RH was achieved by alkali treatment (with 10 % NaOH for 7 h) at boiling temperature and atmospheric pressure, i.e. using refluxing system instead of autoclave for the preparation of Si-gel. Zeolite NaA samples synthesized from such Si-gels were pure, highly crystalline and white. Furthermore, it was found that the direct dissolution of Al in Si-gel did not affect the quality of the final product. Although this investigation was not focused on the mechanism of zeolite NaA crystallization, the results obtained indicated clearly that the history of Si-gel preparation played an important role in the nucleation and growth of zeolite NaA crystals and influenced their yield, size, and shape. Therefore, the optimization of Si-gel preparation procedure has to be considered as essential not only for the economy of the synthesis of NaA from RH, but also for the quality of the final product.
Microwave-assisted preparation of zeolite K–H from alumatrane and silatrane
Microporous and Mesoporous Materials, 2004
Using alumatrane and silatrane as sources of silica and alumina, respectively, and potassium hydroxide as the hydrolytic agent, a very high purity K-loaded zeolite was synthesized for the first time, via sol-gel processing and microwave heating techniques. Because of the bulky trialkoxyamine ligands, which shield the silicon and aluminium atoms, both alumatrane and silatrane are inert to hydrolysis, and can therefore be investigated over a wide pH range. By fixing the composition at SiO 2 :0.1Al 2 O 3 :3K 2 O:410H 2 O and the microwave heating temperature at 150°C for 240 min, based on x-ray diffraction analysis, the synthesized product is a K-H zeolite of hitherto unknown structure, designated as PPC-ZM-1. The Si:Al:K ratio of the synthesized product is 1.98:1:0.82, and the polycrystalline morphology resembles flower petals. The Si:Al loading ratio, microwave heating temperature and K 2 O:SiO 2 ratio influence the morphology of the product. In addition, the K 2 O:SiO 2 ratio also influences the microwave heating time to achieve complete crystallinity. Prolonged heating after obtaining crystalline product results in a change of the polycrystalline morphology to longer, more densely packed crystals.
Microporous and Mesoporous Materials, 2011
Influence of the batch molar ratio, y [SiO 2 /Al 2 O 3 ] b , on the size and shape of zeolite A crystals at three different molar ratios [SiO 2 /H 2 O] b and [Na 2 O/H 2 O] b was investigated. Four different morphological entities of zeolite A, namely regular cubic crystals with sharp edges and apexes, cubic crystals with truncated edges, cubic crystals with ''rounded" edges and apexes and pseudo-spherical, face-less particles, were observed in the crystalline end products obtained by hydrothermal treatment (heating at 80°C) of the hydrogels having 1.0 6 [SiO 2 /Al 2 O 3 ] b 6 2.2, 0.006 6 [SiO 2 /H 2 O] b 6 0.0186 and 0.0136 6 [Na 2 O/H 2 O] b 6 0.0424. The chemical conditions with respect to the values of [SiO for obtaining the particular morphological entities of zeolite A are defined, and the possible mechanisms of their formation are discussed. The influence of the mentioned factors on the crystal size and the surface properties of crystallized zeolites is also considered.
Microporous and Mesoporous Materials, 2011
Purely siliceous and Al-containing nano-zeolite Beta (BEA) crystals were synthesized using 4,4 0-trimethylenebis(N-methyl, N-benzyl-piperidinium) cations as structure-directing agent (SDA). The influence of the synthesis parameters (synthesis time and temperature, heating source) as well as the chemical composition of the precursor gel on the nature of the product and its particle size was investigated. Purely siliceous nano-zeolite Beta with a particle size of around 140 nm and single domains of around 30 nm in size was synthesized with a high level of reproducibility and stabilized in colloidal suspension. Aluminium-containing Beta zeolite (Al-BEA) crystals were prepared either under conventional hydrothermal treatment or under microwave irradiation. Stable colloidal suspensions of Al-BEA particles with a size of 200 nm were obtained, consisting of single domains in the range of 5-15 nm, depending on the nature of the heating mode.
Preparation of Free-Template Nanometer-Sized Na–A and –X Zeolites From Rice Husk Ash
Waste and Biomass Valorization
The main objective of the present study was to synthesize nanozeolite Na–A by a hydrothermal method with extracted silica from rice husk ash as source in order to reduce the mean particle size of zeolite Na–A as well as crystallization conditions by keeping the economic interactive in mind. High-grade amorphous silica was extracted from rice husk ash by an appropriate alkali solution. Amorphous extracted silica powder was composed of 88% wt of SiO2. The effects of Na2O/SiO2 ratio in the initial system, the crystallization condition, crystallization time, crystallization temperature and shaking conditions (static, stirring and shaking) on the properties of final products were investigated. Various techniques including X-ray diffraction, scanning electron microscope, energy dispersive X-ray, N2 adsorption/desorption and Fourier transform infrared were then applied for characterization of the synthesized products. The results showed that the crystallization condition and alkalinity have a significant effect on the structural properties of the synthesized nanozeolite Na–A. Without adding any organic additives, nanocrystals of Na–A ranging from 40 to 120 nm in size were synthesized at 40°C and with 18 h aging, whereby crystals with a specific surface area of 36.9 m2 g−1 and an average pore diameter of 10.6 nm (using BJH method) were obtained. Na–X nanocrystals with crystallite size ranging from 70 to 260 nm were obtained from a sodium aluminosilicate solution at 60°C after 2 days in static crystallization condition, whereby crystals with a specific surface area of 89.9 m2 g−1 and an average pore diameter of 9.2 nm (using BJH method) were obtained.
LTA and FAU zeolites were successfully synthesized from a Venezuelan sodium silicate solution, by hydrothermal crystallization under autogenous pressure at 100 °C, with 2 – 24 h crystallization times. The synthesized materials were characterized by XRD, BET specific surface area and SEM. A series of synthesis tests were performed to study the influence of the molar composition of the starting mixture over zeolites crystallization. The effect of crystallization time for a particular synthesis mixture composition was studied for both zeolites types. The reuse as alkaline medium of the mother liquor separated during filtration, and the effect of the aging before crystallization were additionally studied. The experimental results are in agreement with the crystallization mechanism proposed for zeolites synthesis in liquid phase. The use of a 2SiO 2 :Al 2 O 3 :6.Na 2 O:240H 2 O synthesis mixture composition allows obtaining LTA zeolite within 2 h of crystallization. For FAU zeolite, no aging period was needed when starting with a 4SiO 2 :Al 2 O 3 :6.6Na 2 O:264H 2 O composition. It was possible to synthesize both zeolites with high purity and crystallinity and with adequate water adsorption properties.