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Joint Research Center for Harmonized Molecular Materials
Japan Chemical Innovation Institute
Advanced Technology Laboratory, Kubota Corporation
Shinichi Shimizu, Ph.D
National Institute of Materials and Chemical Research
Dept.of Surface Chemistry
Hideaki Hamada, Ph.D
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By the support of New Energy and Industrial Technology Development Organization (NEDO) for an AIST project on "Technology for Novel High Function Materials - Harmonized Molecular Materials - Microporous Materials", Japan Chemical Innovation Institute and Catalyst Design Group of our Institute developed a technique to control zeolite formation, namely bulk-material dissolution (BMD) technique. The world's largest single crystalline zeolites were synthesized successfully by applying this technique. The use of this technique promises the widening of the scope of application of zeolites.
Zeolites are crystalline microporous material having pores with precise and regular diameter and intervals. This porous material which is regarded as a molecular sieve has a pore diameter measuring under 1 nm (10-9m). Due to this pore size which is approximately that of the low molecule compounds, it is considered as an extremely valuable material used widely as an ion exchange materials, an adsorption and separation materials and a catalyst in industrial fields. However, zeolites are generally obtained as rather small crystals ranging from several to some tens of micrometers (10-6m), and therefore, their application has been rather limited. If a technique for synthesizing zeolite crystals of any expected shapes and sizes shall be developed, the zeolites can be used as a material separation device as a molecular sieve membrane, a high performance catalyst membrane reactor and an electronic device with small internal resistance that have not been realized so far. It can also be applied to the fields such as high performance batteries and fuel cells. Furthermore, by a new principle of motion of electronic elements and opto-electronic elements which uses the quantum effect generated by inlaying a functional material in the regular pores of zeolites, the performanc of both electronic and electric products may make rapid progress. The bulk-material dissolution (BMD) technique that we developed recently is to dissolve the raw materials, silicon dioxide and aluminum oxide component, from the surface of the bulk-material, and by controlling the dissolution rate, formation of zeolite crystals is controlled. The (BMD) technique enables us to synthesize various forms of zeolite crystals required for different purposes. Therefore, it is now clear that the synthesis of a giant single crystalline zeolite by applying this technique became possible. The BMD technique is widely adaptable to some other zeolites such as ANA, JBW, CAN, MFI and SOD from which the giant single crystals have already been synthesized successfully. The characteristics of raw materials used for BMD technique are not the conventional powder or colloidal materials, but glassy or sintered (quartz glass, sintered mullite, etc.) bulk materials which contain raw material components. For example, a piece of quartz glass tube was placed in a PTFE sleeve equipped for an autoclave. The sleeve was filled with an aqueous solution containing tetra-n-propylammonium hydroxide (TPAOH) and hydrogen fluoride (HF) and was heated up to 100 to 200 in a thermostat. Eventually, the world's largest giant single crystal MFI zeolite measuring over 3 mm was obtained. The BMD technique may make the application of zeolites which has not been realized hitherto possible. For example, when the synthesis of a zeolite crystals of the sizes usable for electronic elements will be possible, they are expected to be applied to a super high density memory device, a high velocity response semiconductor/optical element, a highly selective sensor and a variable wavelength semiconductor laser, etc. Moreover, even though the satisfactory sizes of zeolite membrane have not been obtained, the problems of the size shall be solved possibly by lining up the large crystals or by further development of the BMD technique, and thus, the application to a molecular sieve membrane, highly selective catalyst membrane reactor, luminous surface zeolite display, etc. is possible. The zeolite crystals formed by BMD technique also have a valuable potential as a solid electrolyte with a small internal resistance that they are expected to be applied to the area of energy such as batteries and fuel cells. The giant zeolite crystals synthesized by this technique are valued as a key material useful in the fields of energy savings, environmental protection and high information technology.
The largest giant MFI zeolite single crystals synthesized by BMD technique
Schematic illustration of the experimental set up for BMD crystallization
The raw materials usable for BMD technique
A: fused quartz glass tube
Microporous material formation control technique)
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Press Release