Relationship between Structural Disorder and Activity of Zeolites

沸石的独特特征必然源于其规则的晶体结构。然而，已经报道了许多实例，沸石特性受到其骨架中存在的几种无序的影响。本研究通过四氯化硅、EDTA、氟硅酸盐以及热处理和酸处理制备了不同硅铝比的沸石，分析了沸石结构无序与活性的关系。通过红外光谱、核磁共振、量热、热重和骨架氧交换反应对它们的结构和活性进行了分析。沸石结构保留，除了那些广泛处理。在没有随后的Si插入的脱铝的情况下，所谓的“羟基巢”无序结构形成有四个羟基，这被发现是无活性的。Flurination只发生在外部的非酸性羟基，也形成了脱铝。由于氟原子的高电负性，氟化位点变成酸性。氧交换反应发生在与氟位相邻的羟基上，也发生在必需的酸性羟基上。大量脱铝可在不损失堆积性的情况下形成介孔结构，表明无序结构对沸石的活性和反应性有重要影响。

Peculiar characteristics of zeolites must onginate from their regular crystal structure. However, a number of examples have been reported that zeolitic characteristics are influenced by the presence of several kinds of disorders in their framework. In the present study, correlations between structural disorder and zeolitic acitivity were analyzed.Zeolites with different values of Si/Al ratio were prepared by treatment with silicon tetrachloride, EDTA and fluorosilicate as well as thermal and acid treatments. Their structure and activivies were analyzed by IR,NMR,calorimetry, fluorination and exchange reaction of framework oxygen. The zeolitic structure retained except on those treated extensively. In case of the dealumination without subsequent Si insertion, so called "hydroxy nest" disorder structure was formed with four hydroxyls which was found to be inactive. Flurination occurred only on the extemal non-acidic hydroxyls which were also formed by dealumination. Fluorinated sites became acidic because of high electronegativity of fluorine of fluorine atoms. Oxygen exchange reaction proceeded on the hydroxyls neibouring to fluorinated sites as well as on essential acidic hydroxyls. Extensive dealumination resulted in the formation of meso-pores without any loss of crystallinity.A significant role of disorder struature was clarified in the activities and reactivities of zeolites.