Zeolite production method
Disclosed is a method for easily and inexpensively producing zeolite without using a natural structure-directing representative (natural SDA). Specifically disclosed is a method where a gel containing a silica source, an alumina source, an alkaline source and water is reacted with zeolite seed crystals, to produce a zeolite with the same kind of skeletal structure since the zeolite. The gel used is a gel of a makeup whereby, when a zeolite is synthesized out of the gel only, the synthesized zeolite contains at least among those sorts of composite building components of the target zeolite.
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Synthetic zeolites are crystalline aluminosilicates, and also have uniform fine pores of a dimension of angstroms which are produced as a result of crystalline structure. Using this feature, artificial zeolites are industrially used as a molecularsieve adsorbent which adsorbs only molecules using a specific dimensions, an adsorption separating agent which adsorbs molecules using a strong predisposition, or a foundation of catalysts.
A number of zeolite production methods have been proposed. When, for instance, beta zeolite, that can be one synthetic zeolite, is thought to be an instance, a normal zeolite manufacturing procedure is a technique in which tetraethylammonium ions areused as a natural structure-directing agent (hereinafter known as an”organic SDA”). Such a technique is explained in, as an instance, the subsequent PTL 1. But while chemicals including tetraethylammonium ions are costly, the chemicals arealmost decomposed after crystallization of beta zeolite is finished, and therefore it’s impossible to collect and reuse the chemicals. Because of this, beta zeolite produced with this procedure is expensive. Furthermore, because tetraethylammonium ions areentrapped from the crystals, it’s necessary to flame and remove tetraethylammonium ions when beta zeolite is used as an adsorbent or even a catalyst. At this time, exhaust gas causes environmental contamination, and also a great deal of chemicals can also be requiredfor a treating treatment of their mom fluid of synthesis. As such, since a method of synthesizing a zeolite in which the organic SDA is used is a manufacturing method that’s not only costly but also causes a large environmental load, there hasbeen a demand for realization of a manufacturing procedure in which the organic SDA isn’t used.
Under such circumstances, in recent years, a way of synthesizing beta zeolite in which the organic SDA is not used was suggested (refer to NPL 1). Within this method, a substance obtained by shooting beta zeolite, which has been synthesizedusing tetraethylammonium ions, in order to get rid of organic elements is used as seed crystals, the substance is added into a sodium aluminosilicate reaction mixture which does not include any substance that is organic, and also a hydrothermal treatment is performed,thus crystallizing beta zeolite. However, in this method, since beta zeolite, which was synthesized using tetraethylammonium ions, is fired and used as seed crystals, tetraethylammonium ions become necessary in all times since the natural SDA whilethe quantity of the natural SDA used decreases. Additionally, according to this method, there’s just 1 type of seed crystal, and there’s just one numerically limited example for the composition of this sodium aluminosilicate reaction mixture.Therefore, whereas the composition of the synthesized beta zeolite is not clearly described, the composition is considered to possess only the determined values.
Meanwhile, PTL two from the authors of NPL 1 discloses the SiO.sub.2/Al.sub.2O.sub.3 ratios of seed crystals, and also clarifies the composition of the sodium aluminosilicate reaction mixture less a point composition however as a narrow range awayfrom a point. But since the contents revealed by PTL two are essentially the same method as the contents of NPL 1, and the composition range of the reaction mixture is narrow, the SiO.sub.2/Al.sub.2O.sub.3 ratio of beta zeolite is restricted only to alimited selection. In order to meet an assortment of requirements, zeolites using a wide SiO.sub.2/Al.sub.2O.sub.3 ratio range are desirable. Additionally, in order to reduce the environmental load as far as you can, there’s a demand for proposing a fresh zeoliteproduction method in which seed crystals that do not have to get fired are utilized, and the organic SDA isn’t utilized.
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