SAPO-31分子筛的微波加热合成、表征及催化性能

Microwave Irradiation Synthesis of SAPO-31 Molecular Sieve and Its Characterization and Catalytic Performance

分别以异丙醇铝和磷酸为铝源和磷源,二正丁胺为模板剂,采用微波加热法成功制得AlPO4-31分子筛,并对其晶化条件进行了优化.在优化的条件下同时合成了不同含硅量的SAPO-31分子筛,采用X射线衍射、N2物理吸附、扫描电镜、固体29Si核磁共振、程序升温脱附以及吡啶吸附的红外光谱等手段对其结构和酸性进行了表征,并考察了Pd/SAPO-31双功能催化剂在正癸烷加氢异构化反应中的催化性能.结果表明,采用微波加热法在170oC晶化2h,即可合成出具有ATO结构的高结晶度的纯相AlPO4-31和SAPO-31分子筛.将Si引入到AlPO4-31骨架中所合成的SAPO-31分子筛的比表面积和微孔体积增大,通过改变初始凝胶中原料组成可调变SAPO-31分子筛骨架中硅物种的分布及酸性质.以酸性适宜的SAPO-31分子筛制备的Pd/SAPO-31双功能催化剂在正癸烷加氢异构化反应中表现出较高的活性和选择性.

AlPO4-31 molecular sieve was synthesized by microwave irradiation using aluminum isopropoxide,orthophosphoric acid,and di-n-butylamine as sources of aluminum,phosphorus,and template,respectively. The crystallization conditions of AlPO4-31 were optimized. SAPO-31 molecular sieve samples with different silicon contents were synthesized at the optimal conditions. The structure and acidity of the samples were characterized by X-ray diffraction,N2 physical adsorption,scanning electron microscopy,29Si MAS NMR,NH3 tempera-ture-programmed desorption,FT-IR of adsorbed pyridine. The catalytic performance of Pd/SAPO-31 bifunctional catalyst for hydroisomeri-zation of n-decane was investigated. The results indicated that the AlPO4-31 and SAPO-31 molecular sieves with pure crystal phase and higher crystallinity assigned to ATO topology structure were obtained at 170 oC for 2 h by microwave irradiation. The BET surface area and micropore volume were increased because of the introduction of Si to the framework of AlPO4-31. The distribution of Si in the framework and the acidity of the SAPO-31 molecular sieve were varied by changing the composition of the reaction mixture. The bifunctional catalyst Pd/SAPO-31 with suitable acidity showed high activity and selectivity for hydroisomerization of n-decane.