Preparation And Characterization Of Beta/SBA-15 Molecular Sieves

In this research, the impact of silica source's type to Beta zeolite precursor was investigated. Beta/SBA-15 micro/mesoporous aluminosilicates were assembled by theirself using double structure-directing agent through the two-step crystallization method at 100℃. The Beta zeolite structure-directing agent was synthesized by colloidal silica suspension and aluminium isopropylate, and the SBA-15 mesoporous structure-directing agent was synthesized by TEOS. Because of the reaction of double structure-directing agents each other, Beta zeolite's primary and secondary structural units were transferred into SBA-15 mesoporous frame successfully.FTIR, XRD and N2 adsorption-desorption characterization techniques were used to investigate the macroscopic and microscopic view structure of Beta/SBA-15 micro/mesoporous aluminosilicates. Results suggested, the pore structure of Beta/SBA-15 samples synthesized in hydrothermal condition was steady and ordered, even afer being calcined, which contained Beta zeolite particles and SBA-15 mesoporous frame equally.The effects of Si/Al ratio in the process of preparation were studied, and the best craft was determined. When Si/Al ratio was 50, it was helpful to synthesize micro/mesoporous aluminosilicates which had microporous and mesoporous structure equally. In addition, the mechanism of compound molecular sieves also have been discussed, which suggested that liquid phase conversion mechanics could interpret the crystal process logically, and the micro/mesoporous aluminosilicates could be synthesized due to the pore walls're crystallization by liquid phase. The mesoporous frame of Beta/SBA-15 contained some microporousstructure, which could make metal hetero-atom as active center. In this results, the aluminosilicates not only had the dominance of high hydrothermal stability, but also had characteristic of active center. So the promising property of Beta/SBA-15 micro/mesoporous aluminosilicates can be applied in cracking reaction, especially in macromolecule cracking reaction.