The Synthesis, Characterization And Application Studies In The Super-Microporous Molecular Sieves

The super-microporous molecular sieves is the materials possessing uniform nagoscale porosity in the pore range between the micropore and mesopore (1.0-2.0nm) .Recently, the synthesis and application studies in the tra--iditional zeolites (pores≤1.0nm) and mesoporous molecular sieves (pores≥2.0nm) have acquired great progress, whereas, the special studies in the super-microporous molecular sieves is relatively less. Based on the reason that the super-microporous molecular sieves have the shape catalytic capability and potential industrial importance for the organicmolecules possessing sizes in the 1.0-2.0nm range, in this paper, we employ hexylamine, octylamine and dodecylamine as the template molecules and successfully gain the super-microporous molecular sieves by adjusting the amounts of added Al source. Then, the essential property of the porous materials, such as thermal stability, hydrothermal stability and acidity, are primarily studied.Firstly, we innovatively employ dodecylamine (DDA) as the template molecules and successfully gain the super-microporous aluminosilicate molecular sieves SMS-12 in the absolute ethyl alcohol solution by incorporated Al into product with only one step. The experiment results indicate that the optimum amounts of adding Al source is a Si/Al atomic ratio of 7. The calcined product have the average pore diameter of 1.7nm and its size of sphere is in the 300nm~1@m range. At the same time, the product possess high thermal stability, better hydrothermal stability, weak acid sites and catalytic activity. Thereinto, it can retain its ordered structure even after treatments at 900# for 4h and in boiling water for 4h.Secondly, for the first time, the super-microporous aluminosilicate molecular sieves SMS-8 is synthesized in the absolute ethyl alcohol solution by using octylamine as the template molecules and adjusting the amounts of added Al source. The results indicate that the optimum amounts of adding Al source is a Si/Al atomic ratio of 40. The calcined product have the average pore diameter of 1.6nm and its size of sphere is in the 250nm-1Hm range. Moreover, the product possess high thermal stability, better hydrotherrnal stability and weak acid sites. Thereinto, it can retain its ordered structure after treatments at 900# for 4h and in boiling water for 2h.Thirdly, the formation mechanism of super-microporous aluminosilicate molecular sieves SMS-12 and SMS-8 are discussed. By analyzing experiment phenomenon, XRD and FT-IR data, we postulate that the formation of SMS-12 and SMS-8 occurs through the organization of neutral primary amine surfactant molecules (S0) and neutral Si (OC2H5) 4-x (OH) x precursors with liquid crystal template mechanism (LCT). At the same time, we find that the Al source successfully incorporated into the product is the key factor to reduce pore size and form the super-microporousaluminosilicate molecular sieves at last.Finally, according to the technique that the microporous materials can be achieved by using the short chain template molecules, the super-microporous silica molecular sieves SMS-6 is synthesized in the acidity solution by using hexylamine as the template molecules. The results indicate that the calcined product have the average pore diameter of 1.2nm and its size of sphere is about 25nm. Moreover, the product possess better thermal stability and ordinary hydrothermal stability. Thereinto, it can retain its ordered structure after treatments at 900癈for 2h and in boiling \^ater only for Ih.