SAPO-11/Beta复合分子筛的合成及其异构化性能研究

以Beta分子筛为硅源通过水热合成法合成了SAPO-11/Beta复合分子筛,采用X射线衍射、N2物理吸脱附、扫描电镜、透视电镜-能谱分析、固体核磁及吡啶红外等方法对单分子筛、复合分子筛和机械混合分子筛的物化性质进行了表征.以正十二烷为模型化合物,在固定床反应器上考察了铂负载型分子筛催化剂的异构化性能.结果表明,复合分子筛的物理化学性质明显不同于单分子筛和机械混合分子筛,其呈现核壳结构,SAPO-11和Beta间存在化学作用,使得复合分子筛具有适宜的B酸分布.在正十二烷异构化反应中,复合分子筛催化剂的异构化性能优于单分子筛催化剂和机械混合分子筛催化剂,多支链异构体收率高.

Investigation of synthesis and hydroisomerization performance of SAPO-11/Beta composite molecular sieve

The SAPO-11/Beta composite molecular sieve was synthesized by the hydrothermal method with zeolite Beta as the silicon source. The physicochemical properties of SAPO-11, Beta molecular sieve, the composite molecular sieve, and the mechanical mixture of SAPO-11 and Beta molecular sieve were characterized by X-ray diffraction, N₂ adsorption-desorption, scanning electron microscopy, transmission electron microscopy-energy dispersive spectroscopy, magic-angle spinning nuclear magnetic resonance, and pyridine adsorption infrared spectroscopy. In addition, the catalytic performance of platinum-loaded zeolite samples in the hydroisomerization of n-dodecane was investigated. The results indicate that the properties and catalytic performance of the composite molecular sieve were quite different from those of the pure zeolites and the mechanical mixture. Compared with the mechanical mixture, the combination of SAPO-11 and Beta by chemical bonds was more tightly bound in the composite molecular sieve with a core-shell structure. The acidity and pore structure of the composite were favorable for catalytic performance in the hydroisomerization of n-dodecane. The composite catalyst was superior to the other catalysts, especially in the yield of multibranched isomers.