Abstract
The gel of zeolite NaY has potential as a precursor of other zeolites. The particular interest in this work is to convert the gel of NaY to NaP2. We found that the pure phase NaP2 can be produced simply by the conventional hydrothermal (CH) method at 150 °C for 24 h. This NaP2 sample, named CH150, has an average particle size of 10.3 µm and an Si/Al ratio of 1.82. In the case of single crystallization via microwave-assisted hydrothermal (MH) method, various parameters were studied, including the crystallization temperature (90, 150, 175 °C) and time (15, 30, 45, 60 min). The samples were analyzed by X-ray diffraction and scanning electron microscopy. However, mixed phases of P1 and P2 or ANA were obtained from all samples. Another attempt was made by a double crystallization via MH method as followed: at 90 °C for 1 h, quickly cooled down to room temperature in the microwave chamber and aged for 23 h, and finally at 150 °C for 1 h. The sample, named MH90A150, has an average crystal size of 16.45 µm and an Si/Al ratio of 1.85. The high Al content of NaP2 in both samples (CH150 and MH90A150) could lead to interesting applications.
Highlights
Zeolite P has a gismondine (GIS) framework type, composed from secondary building units (SBU)containing four- and eight-membered rings of T atoms (T = Si or Al linked together by sharing oxygen atoms)
The splitting of peaks refers to two rotating types of secondary building units (SBUs) planes or four-membered ring (4MR) in GIS structure [11]
After crystallization at 150 ◦ C, the pattern of MH90A150 exhibits the pure phase of NaP2 zeolite. These results suggest that the synthesis condition of MH90A150 is suitable to transform the gel of zeolite NaY to NaP2
Summary
Zeolite P has a gismondine (GIS) framework type, composed from secondary building units (SBU). Zeolite P is useful for many applications such as the separation of small gases [3,4,5] or heavy metals [6,7] and application in sensing material [8]. Baerlocher et al and Mccusker et al [9,10] have found the differences and flexibility in unit cell structures of zeolite P. The distortion of the SBU planes generates two isotypes, P1 and P2, which have different pore sizes and shapes. Oleksiak et al [11] have reported that the eight-membered pore of P2 is narrower than that of P1. The P2 type has a higher adsorption equilibrium constant for small gases such as H2 [11]
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