The Use of Combined Thermal Analysis to Study Crystallization, Pore Structure, Catalytic Activity and Deactivation of Synthetic Zeolites (original) (raw)
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A Short Review on Synthesis, Characterization, and Applications of Zeolites
Advances in Materials Science and Engineering
The review emphasizes on synthesis, characterization, and application of zeolite. Zeolite is a hydrated aluminosilicate having a tetrahedral structural framework; it contains channels and cages which are occupied by exchangeable active metal ions and water molecules. Zeolite was synthesized through different synthesis methods, particularly, hydrothermal and green synthesis methods. The review also has tried to address the structure of zeolite such as morphology, functional group, and particle size using different characterization methods as reported via different authors. The characterization results verify that zeolite shows many unique properties such as uniform pore size, acidic properties, thermal stability, mobile extra cation, hydrophilicity, and hydrophobicity. These lead to a number of applications in catalysis, water purification, adsorption, and agriculture.
Hydrothermal Synthesis of Nanocrystalline Zeolite using Clear Solution
Sriwijaya International Seminar on Energy Environmental Science and Technology, 2014
Nano size particles such as nanocrystalline zeolites have unique properties relative to conventional micrometer sized zeolite crystals. The reduction of particle size to the nanometer scale leads to substantial changes in properties of zeolite which make them as promising materials for many applications. Nanocrystalline zeolite A, silicate successfully synthesiszed at temperature of of 1.46, 3.06, 4.59 and 6.79 are effective Si/Al ratio to synthesis LTA zeolite. Further, high Si/Al ratio of 30, 40 and 60 were used for ZSM-5 synthesis. The product could be obtai (aluminum free) could be obtained at 5 time, Si/Al ratio and organic template. Moreover found to influence the particle size. TEOS makes the zeolite particle smaller than Ludox LS. Two stage synthesis conducted on silicate-1 crystallization could decrease time and increase yield. However it is found that t particle size was slightly higher than that in one Key words: Nanocrystalline zeolite, clear solution, organic template, one 1. INTRODUCTION Nanozeolites are crystalline aluminosilicates with molecular dimension in the range of 10 particle size (Mintova, 2003). Nanozeoilites have higher external surface area and reduced diffusion path lengths due to smaller particle size. The red particle size to the nanometer scale leads to substantial changes in properties of zeolite which make them as promising materials for many applications. Zeolite nanocrystals are usually synthesized under hyhrothermal condition using clear alumin solution, usually in the presence of organic compounds as templates such as tetramethylammonium (TMA) and tetrapropylammonium (TPA) (Zhan, et al. 2001). Further, Cundy and Cox (2004) reported aluminosilicate zeolites synthesized under hydrothermal condition from reactive gels in alkaline media at temperature of about 80 0 C and 200 most high Si/Al ratio of zeolites (>10) are synthesized using organic templates, which have to be removed from the zeolites structure by calcinations. Mintova (2003) reported the synthesis of nano size zeolites including nanozeolite A (LTA), nanozeolite Y (FAU), nanozeolite silicate-1 (MFI) and nanozeolite beta (BEA) at temperatures lower than 100 0 C with synthesis time up to 400 hours. The successful synthesis of nanozeolite A was also reported by Rakoczy and Traa
Chemistry
The study on the synthesis of zeolites, including both the development of novel techniques of synthesis and the discovery of new zeolitic frameworks, has a background of several decades. In this context, the application of organic structure-directing agents (SDAs) is one of the key factors having an important role in the formation of porous zeolitic networks as well as the crystallization process of zeolites. There are various elements that are needed to be explored for elucidating the effects of organic SDAs on the final physicochemical properties of zeolites. Although SDAs were firstly used as pore generators in the synthesis of high-silica zeolites, further studies proved their multiple roles during the synthesis of zeolites, such as their influences on the crystallization evolution of zeolite, the size of the crystal and the chemical composition, which is beyond their porogen properties. The aim of this mini review is to present and briefly summarize these features as well as th...
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
Cogent Engineering
Zeolites have been hydrothermally synthesized using alumina and silica based deposits (kaolin, bauxite, silica and feldspar) sampled from three regions in Ghana and the chemical compositions of the zeolites varied by batch formulations. The as-synthesized zeolites were characterized using X-ray Diffraction, Fourier Transform Infra-Red and Porosimetry techniques. The morphology and elemental compositions were examined using Scanning Electron Microscopy and energy dispersive X-ray spectroscopy (EDX). The results indicate that zeolite A was formed with a cubic structure and structural variations depending on the batch formulations. By increasing the silica content (Si/Al ratio) through batch formulations, the crystallite sizes of zeolites increased forming Zeolite A with LTA structure and Zeolite A (K-exchanged dehydrated). Samples with higher alumina content produced Zeolite A (Hydrated), Zeolite-Na and Zeolite A (Na, Dehydrated) with lower crystallite sizes. The zeolite synthesized was then used in the synthesis of zinc exchanged Zeolite A (Zn-zeolite A). EDX analysis confirmed a complete exchange of Na in the Zeolite framework with Zn and the feasibility as an adsorbent for methylene blue tested. The synthesized Zn-exchanged Zeolite A showed strong adsorption for methylene
Powder Technology, 2011
Hydrothermal synthesis of zeolite T in aqueous alkaline solutions without using templates was investigated. Zeolite T crystals were prepared via hydrothermal synthesis using milk-like aluminosilicate gel with a composition of aSiO 2 :bAl 2 O 3 :cNa 2 O:dK 2 O:xH 2 O. The effects of molar compositions including silicon module (n RM = a/b) and relative alkalinity (α = OH/SiO 2), and crystallization conditions including crystallization temperature (T) and time (t) on the yield of T-type crystals were investigated. This research work examines changes in the yield of crystalline zeolite phases by varying the gel composition parameters (n RM =20-25, and α = 0.71-0.82) and crystallization process temperature and time (T = 100°−140°C, t = 120-216 h), while keeping constant the parameters [OH] = 2.77 m, U RM (Na/Na + K) = 0.75, stirring time = 24 h , stirring temperature = 30°C, and drying temperature = 100°C. The crystal species of zeolite T were characterized by XRD (X-ray diffraction) and SEM (Scanning Electron Microscope).
Journal of the American Chemical Society, 2009
All industrially available zeolites are obtained from hydrogel systems. Unfortunately the level of understanding of the events preceding zeolite crystallization is far from satisfactory. In this respect, revealing the nature of the processes taking place in the precursor gel is of paramount importance to understanding zeolite nucleation. The investigation of the gel structure, however, is a difficult task due to the complexity of the object in terms of both composition and topology. Therefore, a combination of hyperpolarized (HP) 129 Xe NMR-N 2 adsorption-high-resolution transmission electron microscopy-energy-dispersive spectrometry methods complemented by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and chemical analyses has been employed to study the changes in composition and structure of sodium hydroxide rich aluminosilicate gel yielding zeolite A. The role of each component in the system and the entire sequence of events during the induction, nucleation, and crystallization stages have been revealed. The high concentration of sodium hydroxide in the studied system has been found to control the size and structure of the gel particles in the beginning stage. During the initial polymerization of aluminosilicate species a significant part of the sodium hydroxide is expelled from the gel into the solution, which restricts extensive polymerization and leads to formation of small aluminosilicate particles with open pore structure. The induction period that follows is marked by incorporation of Na back in the bulk gel. The combined action of the Na ion as a structure-directing agent and the hydroxyl group as a mobilizer results in partial depolymerization of the gel and formation of voids with mesopore sizes. The nucleation maximum coincides temporally with development of pores with sizes in the range of 2-5 nm. The amorphous gel undergoes into crystalline zeolite only after these pores have disappeared and the chemistry of the gel has evolved to reach the stoichiometric zeolite composition. It was established unambiguously by high-resolution transmission electron microscopy and HP 129 Xe NMR that the nucleation of zeolite occurs in the solid part of the system and the succeeding crystallization commences only after the nuclei are released into the liquid, which is consistent with the autocatalytic mechanism. Also this investigation has demonstrated the unrivaled sensitivity of HP 129 Xe NMR that is capable of identifying presence of small amounts of crystalline zeolite material in amorphous medium with detection limit extending below 1 wt %. Figure 6. TEM micrographs of gel treated under hydrothermal conditions at 90°C for (A) 60 and (B) 120 min.
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.
Preparation and characterization of ZSM-5 zeolite
International journal of computational and experimental science and engineering, 2023
The research for new energy sources has promoted hydrocarbon production from biomass and solid wastes over ZSM-5 zeolites. The metal incorporation by different methods has led to a variety of chemical applications. In this way, the combination of the shape selectivity and acidity properties of the pentasil zeolites with the activity of metal oxide under different environments may influence the product distribution in diverse catalytic reactions. In this work, ZSM-5 zeolites were prepared by hydrothermal synthesis employing aluminum nitrate and AIP as aluminium sources and TPAOH as structure director agent at atmospheric pressure and low temperature (90 ºC). In addition, these materials were modified with iron and titanium cations by direct synthesis at 170 °C and autogenous pressure to promote the crystallinity. The characterization of the samples was performed by XRD, XRF, SEM, TPD-NH 3 and nitrogen adsorption. It was observed that the use of AIP and the metal incorporation decreases the crystallinity of the zeolites under synthesis conditions, which leads to increase the specific area value in the BET because of the presence of amorphous material. On the other hand, acidity of the modified zeolites was found to be lower than that of ZSM-5 zeolite.
Study of the crystalline transformation of a ZSM-5 type zeolite by thermal treatments
Journal of Materials Science, 1991
Changes in the framework of an ethanoI-ZSM-5 type zeolite by thermal effects between 673 and 1173 K were investigated using the methods of thermal analysis, infrared, X-ray diffraction and scanning electron microscopy. Crystalline transformation of ZSM-5 into cristobalite at about 973 K was observed in either an air or nitrogen stream and using different heating programmes. The breakdown of the lattice is related to the thermal removal of some species of ethanol from the framework. Total removal of the organic promoter by washing with water prior to thermal treatment leads to a material in which the phase transition temperature is above 1173 K.