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本文采用三乙胺为模板剂,用水热法合成不同含硅量的SAPO-5分子筛,并用X射线衍射、扫描电镜、电子探针分析、真空重量吸附等方法对其进行了表征,结果表明硅已进入了骨架,硅同晶非等比取代磷和铝,并且分子筛的孔道是畅通的。 用微型反应器测定了AlPO_4-5及不同量硅取代的SAPO-5分子筛上的异丙苯裂解和邻二甲苯异构化催化反应,结果表明Si引入了催化活性很低的磷酸铝骨架后使其催化活性明显增加,进一步证实了硅是同晶非等比取代磷和铝,因而使分子筛骨架带负电性。 硅进入磷酸铝分子筛骨架的SAPO-5分子筛经红外光谱实验发现不仅具有表面羟基,而且都是酸性羟基。吸附吡啶后的红外光谱结果表明SAPO-5上同时存在B酸和L酸中心,B酸中心数目随着硅含量的增加而增加。
In this paper, triethylamine was used as a template to synthesize SAPO-5 molecular sieves with different silicon content by hydrothermal method and characterized by X-ray diffraction, scanning electron microscopy, electron probe analysis and vacuum gravimetric adsorption. The results show that the silicon Has entered the framework, silicon isomorphous than phosphorus and aluminum substitution, and molecular sieve pore is smooth. Micro-reactor was used to measure the cumene cracking and o-xylene isomerization catalysis on AlPO_4-5 and SAPO-5 zeolites substituted with different amounts of silicon. The results showed that Si introduced the aluminum phosphate skeleton with low catalytic activity Its catalytic activity was significantly increased, further confirmed that silicon is non-isomorphous substitution of phosphorus and aluminum, so that the framework of the molecular sieve negative charge. SAPO-5 zeolite into the framework of aluminum phosphate molecular sieve by infrared spectroscopy found not only having surface hydroxyl groups, but also acidic hydroxyl. The results of infrared spectroscopy after adsorption of pyridine show that there are both B acid and L acid center on SAPO-5, and the number of B acid center increases with the increase of silicon content.