Synthesis of zeolite Y from diatomite as silica source (original) (raw)
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Journal of Porous Materials, 2016
A new one step approach for the preparation of MFI-type zeolites through direct transformation of premodified diatomite is reported. Two diatomite species modified by calcination and acid treatment were used as silica and alumina sources. The progress of the transformation was investigated by analyzing samples after different crystallization times at 453 K. Tetrapropylammonium hydroxide was utilized for the first time as bi-functional molecule for silica dissolution in diatomite and structure directing agent during zeolite formation. In this way, the use of an additional alkaline source, such as sodium hydroxide, for silica dissolution was not necessary. The applied diatomite samples contained amorphous silica in combination with impurities like feldspar, anatase and quartz. This allowed the systematic investigation of the influence of modification procedure, amorphous silica content and crystalline impurities of the different diatomite samples on the direct transformation in MFI-type zeolites. During the transformation process, the feldspar was totally dissolved. The quartz content was reduced to \10 wt% in the final products as compared with the modified diatomite starting material. X-ray diffraction, nitrogen adsorption, scanning electron microscopy and optical emission spectroscopy were used to characterize these materials.
Influence of Alcalinity on Synthesis of Zeolite a
2011
Two different systems were examined: (1) homogeneous (optically clear solution saturated with Na + , aluminate, silicate and alumosilicate species) and (2) heterogeneous (hydrogel – saturated solution with precipitated gel). Hydrothermal transformation of samples in both systems was made by heating of HDPE reactors (flasks) with samples at 80°C. All systems were prepared adding of the basic sodium silicate solution into the basic sodium aluminate solution. Both solutions were prepared by dissolving of appropriate amounts of sodium silicate (Fluka, > 97% Na2O SiO2 × 5H2O) or sodium aluminate (Riedel de Haën, 54% Al2O3; 41% Na2O) with NaOH (Kemika, 98% NaOH) in deionized water. In order to remove impurities from the sodium aluminate solutions, they were centrifuged and only clear supernatant was used for preparation of starting system. After preparation and ageing for 24 h, starting solution of systems 1 (1a, 1b, 1c) and hydrogel of systems 2 (2a, 2b, 2c) were divided among needed ...
1985
The synthesis, crystallization and structure o f heteroatom containing ZSM-5 type zeolite (M-ZSM-5) (Xu Ruren and Pang Wenqin (Plenary lecture) 27 Synthesis of ZSM-5 type zeolites i n the system (Na, K) 2 0-A1 2 0 3-Si0 2-H 2 0 without and with ΤPA Br (A. Nastro, C. Colella and R. Aiello) 39 Crystallization of ZSM-5 type zeolites from reaction mixtures free o f organic cations (Ü.M. Berak and R. Mostowicz) 47 Nature and structure o f high silica zeolites synthesized i n presence of (poly) alkyl mono-and diamines (Z. Gabelica, M. Cavez-Bierman, P. Bodart, A. Gourgue, and J.B. Nagy) 55 Factors influencing the crystal morphology o f ZSM-5 type zeolites (R. Mostowicz and J.M. Berak) 65 The influence of alkali metal cations on the formation o f silicalite in NH^OH-TBAOH systems (Tu Kungang and Xu Ruren) 73 Template variation i n the synthesis o f zeolite ZSM-5 (F.J. van der Gaag, J.C. Jansen and H.van Bekkum) 81 The synthesis o f high silica zeolites i n the absence of sodium ion
Synthesis and Characterization of Zeolites in the System Na2O-K2O-Al2O3-SiO2-H2O
Clays and Clay Minerals, 1984
Abstraet--Zeolites having the structures of phillipsite, merlinoite, and gobbinsite were synthesized from clear solutions at 80~ in the system Na20-K20-Ai203-SiO2-H20 and their morphologies, cell parameters, and compositions determined. At 3.5 M silica concentration, the formation of merlinoite (synthetic zeolite W) is favored over the formation of phillipsite (synthetic zeolite ZK-19) by solution conditions of high pH (> 13.6) and low Na/(Na + K) ratios (<0.5).
The synthesis of large crystals of zeolite Y re-visited
Microporous and Mesoporous Materials, 2005
The major synthesis routes described in the literature so far for zeolite Y (FAU) with an elevated n Si /n Al -ratio and larger crystallite sizes were systematically re-investigated. Syntheses in the presence of triethanolamine with or without added bis(2-hydroxyethyl)dimethylammonium chloride yielded large crystals (10-100 lm) of faujasite-type zeolites. However, only products with low n Si /n Al -ratios below 1.8 were obtained, and zeolite P was an inevitable side product or even the main product. Furthermore, the outcome of these syntheses was poorly reproducible. Following another known literature procedure, phase-pure zeolite Y could be obtained with the cyclic polyether 15-crown-5 as a structure-directing agent. The influence of ageing, homogenization and seeding of the synthesis gel, the crystallization time and temperature, different Si-and Al-sources and the addition of NaF as a mineralizer or of co-templates such as triethanolamine, ethylene glycol or 1,3,5-trioxane on the resulting product was investigated. A carefully optimized procedure led to large crystals of highly phase-pure zeolite Y with well defined octahedral morphology and a narrow crystal size distribution in the range of 4-5 lm. Such crystals can be reproducibly synthesized in high yields with an n Si /n Al -ratio of 3.4-4.0. Neither crystallization seeds nor an ageing of the synthesis gel before hydrothermal crystallization are required.
The crystal morphology of zeolite A. The effects of the source of the reagents
Microporous Materials, 1997
This study investigates the effects of the variation in reagents on the synthesis of zeolite A. The synthesis was attempted under autogenic conditions and at temperatures of 100 (±1)°C and 70 (±1 )°C, using various aluminium and silicon sources. Preparation of the gels used silica and aluminium to form mixed systems of organic and inorganic reagent sources. Products formed were analysed and characterised instrumentally using X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Systems using aluminium isopropoxide consistently produced uniformly sized crystals, each having deep, chamfered edges. Sodium reagent sources produced sharp edged crystals. The system using tetraethyl-orthosilicate with aluminium powder produced a hexagonal morphology. The change in the hydroxide concentrations, relative to the systems using sodium silicate and sodium aluminate sources was also monitored, and while it had a marked effect on crystallinity and stability, the crystal morphology remained consistent. © 1997 Elsevier Science B.V.
Morphology-Controlled Synthesis of Zeolite and Physicochemical Properties
Engineering Journal, 2012
Zeolite L is a crystalline aluminosilicate compound and a typical chemical composition of K9Al9Si27O72•nH2O (n = 0-36). The structure and chemical properties, as well as their sizes and morphologies of zeolite L has led to various applications in different fields. The aim of this study is to investigate the effects of chemical compositions of the starting gel on the synthesis, size and morphology of zeolite L crystals. Zeolite L had been synthesized hydrothermally at 180 ˚C for 2 days, from gels with the molar compositions of 2.62-3.78 K2O: 0.8-1.4 Al2O3: 8-12 SiO2: 80-200 H2O. The variation of chemical compositions led to the differences in morphologies and crystal sizes. Their morphologies varied from ice hockey to cylindrical shapes and their crystal sizes varying from 1.50-7.53 µm. With an increase in H2O and SiO2, the crystal size was also increased but decreased with an increase in K2O. In varying Al2O3, there was no effect on their shapes which were still cylindrical but with different crystal sizes. Moreover, the adsorption of ethylene on zeolite L samples depended significantly on crystal shapes and sizes.
Synthesis of pure zeolite Y using soluble silicate, a two-level factorial experimental design
Chemical Engineering and Processing: Process Intensification, 2009
Four methods were used for the synthesis of pure zeolite Y using soluble silicate as a silica source: (1) the gelling of soluble silicate to silica-alumina gel, by aluminate (or aluminium sulphate), (2) the precipitation of soluble silicate to precipitated silica-alumina gel, by aluminate (or aluminium sulphate), (3) the gelling of soluble silicate by sulphuric acid plus alumina impregnation, and (4) the precipitation of soluble silicate by sulphuric acid plus alumina impregnation. A 2 4 two-level factorial design was used to study the influence of four different variables on the purity of zeolite Y (expressed in terms of degree of crystallinity). The ageing time turned out to be the most significant variable. Synthesis time, alkalinity and mixing rate were also found to be statistically significant. X-ray diffraction patterns were used to characterize the samples, which ranged from well-crystallized faujasite structures to amorphous materials. The highest purity achieved in method (1) was 38%. The best synthesis condition derived from method (1) was applied to the other three methods. Only method (4) yielded the pure zeolite Y. Therefore, the effect of silica-alumina precursor preparation on producing the pure zeolite Y is extremely important.
SYNTHESIS AND CHARACTERIZATION OF ZEOLITES IN THE SYSTEM Na~OK20-A1203SiO2-H/O
2000
Abstraet--Zeolites having the structures of phillipsite, merlinoite, and gobbinsite were synthesized from clear solutions at 80~ in the system Na20-K20-Ai203-SiO2-H20 and their morphologies, cell parameters, and compositions determined. At 3.5 M silica concentration, the formation of merlinoite (synthetic zeolite W) is favored over the formation of phillipsite (synthetic zeolite ZK-19) by solution conditions of high pH (> 13.6) and low Na/(Na + K) ratios (<0.5).
Incorporation of Brazilian Diatomite in the Synthesis of An MFI Zeolite
Molecules
The need for greener procedures is a fact to reduce residues, to decrease industrial costs, and to accomplish the environmental agreements. In an attempt to address this question, we propose the addition of a natural resource, Brazilian diatomite, to an MFI zeolite traditional synthesis. We have characterized the resulting product with different techniques, such as X-ray diffraction, microscopy, and gas sorption, and, afterwards, we evaluate the greenness of the process by the Green Star method. The results were promising: We obtained the desired topology in the form of small crystallites aggregated and a pore diameter of 0.8 nm. In conclusion, the product has the necessary characteristics for an adsorption or catalytic future tests and escalation to industrial production.