Synthesis of low silica zeolites under the water with alcohols and the surface characterization of gaseous adsorption

Low silica zeolites are synthesized generally by sol-gel method in water. In this study, efforts were made to prepare low silica zeolites from sodium aluminate and sodium silicate, in the presence of alcohols, at 373 K under an atmospheric pressure. It was of our special interest to investigate how the addition of various alcohols into water affects the type of zeolites synthesized during crystallization process for different reaction times (2, 6, 24, 120 hours). Five different types of zeolites were identified during zeolite synthesis process: ZeoliteA, ZeoliteX, Sodalite, Na-Pc, and Analcime. The zeolites synthesized at designated reaction times were characterized by X-ray diffraction (XRD), N2 and H2O vapor adsorption/desorption. The results indicated that zeolite Na-Pc was preferentially synthesized in solely water solvent, whereas in solvent containing alcohols ZeoliteX and ZeoliteA appeared at the early stage of crystallization process, subsequently transforming to Analcime through intermediates of Sodalite and Na-Pc. It was presented that Na-Pc possessed peculiar surface characteristics, which were suggested from a stepwised H2O isotherm and hysteresis loop in N2 isotherm, both of which were not recognized on other types of zeolites synthesized in the present study. INTRODUCTION Zeolites contain crystalline tectoaluminosilicates that are constructed from TO4 tetrahedra (T=Si, Al). Each apical oxygen atom is shared between two adjacent tetrahedral giving a framework ratio of O/T=2 as shown in Figure 1. Figure 1 Unit of TO4 (A center is ether Si or Al) s notation, the frameworks ratios of Si/Al are divided into three kin l nerally low silica zeolites are synthesized in a solvent of water. Table 1 is a list of lit O2O2-