Introductory Chapter: Zeolites - From Discovery to New Applications on the Global Market (original) (raw)
Related papers
Potential uses of natural zeolites for the development of new materials: short review
MATEC Web of Conferences, 2016
Zeolites stand apart among the many families of porous materials. Due to their structure, they have a number of important practical properties such as a high adsorption capacity and the ability to cation exchange. However, the main feature distinguishing them from other porous bodies and inherent only for zeolites is the ordering of the pores in their size, orientation, and mutual locations. Pore diameters for the crystalline structures of various zeolites may vary from 0.25 to about 15 nanometers. The crystalline arrangement of these pores in space converts zeolites in the naturally existing nanostructured materials, possessing the unique property to present ordered location of stabilized nanoparticles. 2 Available reserves of zeolites 2.1 Estimates of World reserves Although, there are no certain figures on the total amount of zeolites in the world, it is well known that they are present on all the continents with varying mineral contents and kinds. World production of natural zeolites was estimated in the year 2004 to be between 2.5 and 3 million metric tons (Mt) based on reported production by some countries [5]. Three years later world production of natural zeolites was estimated to be approximately the same [6]. Last year (2015) situation [7] is shown in Figure 1. 2.2 Availability of natural zeolites in Russia Less than ten deposits are exploited at present in Russia, between others the Holinsk deposit (clinoptilolite) and Mukhor-Tala deposit (mordenite) in the Republic of Buryatia, and "Priargunskoe" Mining and Chemical Association [8]. Evaluation of the Mukhor-Tala deposit was reported in Ref. [9]. Such a small amount of produced zeolite
Kinetic and Thermodynamic Studies for Zeolites Synthesis
ZANCO JOURNAL OF PURE AND APPLIED SCIENCES, 2019
Zeolites are compounds which have many applications in chemistry and industry; therefore, studies of synthesis of zeolites are of great importance. In this work, kinetic and thermodynamic study of hydrothermal crystallization for zeolite synthesis process performed at different time intervals (17, 20, 23 and 26 h) and various temperatures (70, 90, 110 and 125 0 C). By time intervals we got out the rate of the zeolite synthesis reaction in this research was first order. The synthesized zeolites were similar in their crystallinity according to the Zeolites synthesis at different of the time intervals. The thermodynamic parameters indicated that the change in Gibbs free energy was negative value. The degrees of crystallinity of the synthesized zeolites decreased with increasing the hydrothermal crystallization temperature. Moreover, the change of hydrothermal crystallization time and temperature caused synthesis of different types of zeolites. The synthesized zeolite samples characterized by Infra-Red (IR), X-ray diffraction (XRD), X-ray Fluorescence (XRF) and scanning electron microscopy (SEM). The variation of chemical compositions led to differences in morphologies and crystallinity of the synthesized zeolites.
Zeolites: A Theoretical and Practical Approach with Uses in (Bio)Chemical Processes
Applied Sciences
This review provides a state-of-the-art summary of distributed zeolite technology, as well as identifying strategies to further promote the absorption of these materials in various areas of study. Zeolites are materials that can be synthesized or found in natural rock deposits a with a basic composition consisting in Al, Si, and O. Zeolite’s consideration as a future material is due to many facile synthesis methods to obtain different structures with variations in pore size, surface area, pore volume and physical properties. These methods are developed using the control of relevant synthesis parameters that influences structure formation, such as crystallization temperature, time of aging and/or crystallization, stoichiometric relationships between components of synthesis gel, pH of the medium, and in some cases the type of structure-directing agent. Each method will lead to geometric changes in the framework formation, making possible the formation of typical chemical bonds that ar...
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
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...
Zeolites upon heating: Factors governing their thermal stability and structural changes
Journal of Physics and Chemistry of Solids, 2006
This paper attempts to review and rationalize the results concerning the zeolite structural changes due to heating treatments. A new parameter, namely the Stability Index, was introduced to quantify the thermal stability of zeolites. Such an index is based on the zeolite breakdown temperatures from X-ray diffraction studies. The correlation between the stability index and the Si/Al ratio confirmed the importance of the latter ratio in controlling thermal stability of zeolites. It was observed that: (i) zeolites with Si/AlX3.80 are very stable; (ii) zeolites with Si/Alp1.28 are quite unstable; and (iii) zeolite stability in the intermediate Si/Al range cannot directly be predicted from the Si/Al ratio. In the present study, the inverse relationship between thermal stability and the ionic potential, (Z/r) wt , was also confirmed: (i) zeolites with (Z/r) wt o0.072 are very stable; (ii) the ones with (Z/r) wt 40.187 are unstable, but (iii) the (Z/r) wt ratio does not allow a discrimination in the intermediate region. The maximum volume contraction of the zeolite unit cell appears to be controlled by the weighted ionic potential. Among different factors related to the framework topology, the expected relationship between the framework density and the Stability Index was not found. r
Effect of H2O Activity on Zeolite Formation
2020
In an effort to understand the effects of H2O activity on zeolite formation, we have synthesized LTA zeolite using a combination of freezing processes and varying drying temperatures. Sodium aluminate and sodium silicate were used to form LTA zeolite, according to the IZA (International Zeolite Association) protocol. The synthesis steps were modified by adding the precursor frozen process by a rapid liquid nitrogen (−196 °C) treatment or slow conventional freezer treatment (−20 °C). The samples were subsequently sonicated and then dried at 80 °C or 40 °C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed on the samples immediately after the drying process as well as after 2 weeks and 1 month of aging the solid products. The results indicated that LTA zeolite does not form. The silica-alumina precursor after both freezing processes and after being dried at 80 °C showed the presence of sodalite displaying stable behavior over time. Both sets of samples drie...
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.
Synthetic zeolites formed from expanded perlite: Type, formation conditions and properties
Mineralogy and Petrology, 1993
The starting material used was expanded perlite with a grain size < 40/~m (74.5 wt.% SiO2; 12.5 wt.% A1203). This material is a waste product obtained during the production of expanded perlite. The experiments were carried out with KOH solutions, mixtures of KOH and NaOH solutions (1 : 1) as well as NaOH solutions in the concentration range 0.5 N to 6.0 N at temperatures of between 100 ° and 140 °C and with reaction periods of 2 hours to 13 days in closed system. In the experiments with KOH containing solutions zeolite ZK-19 (phillipsite), W (merlinoite), G (chabazite) and F (edingtonite) formed. Without addition of aluminium high percentages of zeolite ZK-19 (80-100 wt.%) and zeolite W (90-100 wt.%) were obtained. The addition of aluminium rendered possibly the formation of 90 to 100 wt.% of zeolite G and 85 to 100 wt.% of zeolite F, respectively. In the experiments with NaOH solutions analcime, zeolite Na-Pc (gismondine), zeolite HS (sodalite hydrate) and zeolite A formed. High percentages of zeolite Na-Pc (90-100 wt.%), zeolite HS (up to 100 wt.%) and analcime (up to 100 wt.%) were synthesized without addition of aluminium. The formation of high percentages of zeolite A (95-100 wt.%), however, needs the addition of aluminium, NaC1 and seed crystals. The temperature stability of the zeolites decreases in the following sequence: K-F > K-W >__ KA has a very good temperature stability up to temperatures of ,,~ 550 °C similar to that of zeolite K-W. At higher temperatures, however, its stability is very poor. The NH4+-exchange capacities (meq/g) of the different zeolites amount to the following values: