Morphological Synthesis of Zeolites

Abstract

IntroductionZeolites are crystalline inorganic materials with unique, characteristic micropores. These micropores in molecular scale, which have one to three dimensions, are due to interconnected cavities or channels. The types of assembly of cavities or channels control the size of micropores, orientation of microporous channels, and the morphology of zeolite particles. Undoubtedly, the morphology is originally related to the framework type and also closely related to the micropore size, crystal size, and shape, and directly affects the physicochemical properties of zeolites.Zeolites are extensively used in the fields of heterogeneous catalysis, separations, ion exchange, chemical separation, adsorption, host/guest chemistry, microelectronic devices, optics, and membranes [1][2][3][4]. Such applications of zeolites are strongly affected by the pore size, type of channels, and morphologies [5-9]. Morphological synthesis of zeolites is particularly important in catalytic applications where the particle shape can have a dramatic effect on the product distribution due to differences in rates of transport/diffusion and reaction. Recent research interests have also been directed toward the crystallography of single zeolite crystals by applying nanotechnology. Thus, there has been a great interest in developing synthetic approaches to control crystal size and morphology of zeolites [9][10][11].Fine-tuning of zeolite crystal size and shape is usually accomplished by systematic variation of the composition of the precursor mixture (including the use of additives such as salts) [12]. But through the development of new technology and equipment, synthetic parameters such as temperature, pressure, and stirring rate or even gravity can be controlled.This chapter provides a brief introduction to the morphological synthesis of zeolites and related fabrication methods such as as microwave. Examples in the preparation of well-shaped single crystals, fine control of common particles, and microwave driven fabrication are discussed.

Effect of Crystal Size on Framework Defects and Water Uptake in Fluoride Mediated Silicalite-1

“…Each of the samples exhibited the typical coffin-shaped crystal morphology which has been previously attributed to the use of TPABr as the structure directing agent. 15,16 As shown in the electron micrographs in Figure 2, the five silicalite-1 samples possessed varying a, b, and c dimensions (Figure 2 and Table 2). In particular, the sample I synthesis resulted in the smallest crystals (1.5 μm × 0.4 μm × 9.0 μm), while the sample V synthesis resulted in the largest crystals (35 μm × 30 μm × 120 μm).…”

Biocidal effects of organometallic materials supported on ZSM-5 Zeolite: Influence of the physicochemical and surface properties

“…Zeolites are micro- and mesoporous alkaline earth metal aluminosilicates with tetrahedral [SiO 4 ] 4- and [AlO 4 ] 5- networks interconnected by oxygen atoms. This porous network is sufficiently large to contain extra structural cations within its many molecular scale cavities and channels, allowing the zeolite material to adsorb molecules ranging in size from diatomic hydrogen to organic compounds measuring of several nanometers [ 25 , 26 ]. Similarly, the chemical structure of zeolites and the electronegativity imposed by the aluminates allow the incorporation of compensation cations such as transition metal cations through physical and thermochemical transformations [ 25 , 27 ].…”

High-Performance Microwave Synthesized Mesoporous TS-1 Zeolite for Catalytic Oxidation of Cyclic Olefins

“…31 As a result, it is possible to achieve selective and fast crystallization of the zeolites in high yields. 32 Further, the microwave energy effectively controls the crystal morphology and particle size 33,34 and can lead to enhanced hydrophobicity in the zeolites. 35 There are several reports on the application of microwave irradiation during the synthesis of various zeolites.…”