An Overview of the Effects of Crystallization Time, Template and Silicon Sources on Hydrothermal Synthesis of SAPO-34 Molecular Sieve with Small Crystals

摘要

Several samples were synthesized under hydrothermal condition by using TEAOH (tetraethyl ammoniumhydroxide), DEA (diethylamine), TEA (triethylamine) and morpholine as structure-directing agents and TEOS and fumed silica as silicon sources. The significance of template, silicon sources and crystallization time on crystal phase, morphology, crystal size and crystallinity were studied and the results were compared with those of obtained from other investigations reported in this field. SAPO-5 and SAPO-34 with different crystal size in the range of 300 nm - 15 μm were formed, using different template and silicon sources. The SAPO crystals were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA) and nitrogen adsorption technique (BET). The results show that TEAOH is the most proper template for SAPO-34 synthesis whereas TEA is an appropriate template for synthesis of SAPO-5. DEA and morpholine, however, can produce SAPO-34 or/and other phases depending on their concentration used. Using TEOS as silica source, results in producing finer particles with narrower size distribution for almost all samples. Crystallization time has a significant effect on crystal size and crystalliniy.