无模板变温两段晶化法ZSM-5分子筛的制备与表征

在无模板剂水热体系中,采用高温预晶化、低温晶化的变温两段晶化法,在摩尔组成12Na2O∶80SiO2∶2Al2O3∶2500H2O条件下,成功合成了规整均一的高结晶度HZSM-5分子筛。高温预晶化是为了在短时间内形成大量ZSM-5晶核,而低温晶化是为了控制晶核生长。采用XRD、SEM、DLS和Py-IR对合成的HZSM-5分子筛进行了表征。结果表明,高温预晶化时间的延长可以增加晶核数量,低温短时间晶化可以有效控制晶粒尺寸,合成的类蛹状HZSM-5与商业HZSM-5相比,B、L酸量增加,B/L比值降低。

Template-free synthesis and characterization of ZSM-5 molecular sieves by two-step method with temperature change

The regular and homogeneous HZSM-5 molecular sieves with high crystallinity were hydrothermally synthesized in the template-free system by a two-step method which controls pre-crystallization at high temperature and crystal growth at low temperature under a mole ratio of 12 Na2O∶80 SiO2∶2Al2O3∶2500 H2O. High temperature pre-crystallization is to form a large number of ZSM-5 crystal nucleus in a short time, while low temperature crystallization is to control the growth of crystal nucleus. The prepared molecular sieves were characterized by XRD, SEM, DLS and Py-IR. The results showed that prolonging high-temperature precrystallization time can increase the number of crystal nucleus, while the short-time crystallization at low temperature can effectively control the grain size. Compared with commercial HZSM-5, the synthesized pupal-like crystals of HZSM-5 had higher contents of B and L acids and lower B/L ratio.