硅源量和晶化时间对SAPO-34分子筛结构和性能的影响

Effects of Silicon Source Content and Crystallization Time on the Structure and Catalytic Performance of SAPO-34Molecular Sieve

以吗啡啉为模板剂合成了SAPO-34分子筛,研究了晶化液SiO2/Al2O3比(硅源量)的影响。当SiO2/Al2O3≥0.6时,能合成出纯净的SAPO-34分子筛;SiO2/Al2O3=1.0时,分子筛骨架中出现“硅岛”结构,此时合成的分子筛样品具有最高的(乙烯+丙烯)选择性。继续增大硅铝比对(乙烯+丙烯)选择性是不利的。对SAPO-34分子筛晶化历程的研究结果表明,SAPO-34的晶化存在一个最佳晶化时间,在36h左右;此后继续晶化,将会使更多Si原子进入分子筛骨架,形成更多或者更大的“硅岛”,使(乙烯+丙烯)选择性下降。

SAPO-34 molecular sieve is synthesized using morpholine as the template. The effect of silicon content on structure and catalytic performance of SAPO-34 is investigated. When SiO2/Al2O3 greater than or equal to 0.6 in the initial gel, pure SAPO-34 molecular sieve is obtained; When SiO2/Al2O3 = 1.0, 'silicon island' forms and the sample synthesized has the highest (C-2(=) + C-3(=)) selectivity. However, when SiO2/Al2O3 value is increased to a value greater than 1.2, (C-2(=) + C-3(=)) selectivity decreases. The crystallization process of SAPO-34 is also investigated, and the results show that there is an optimal crystallization time, ca 36h; if the crystallization process continues after 36h, more or bigger 'silicon island' would form and result in low (C-2(=) + C-3(=)) selectivity.