MFI型沸石晶体的择优定向生长

Preferentially Oriented Growth of MFI - Type Zeolite Crystals

首次采用'双模板剂'法在SiO2-Na2O-正丙胺-溴化N-乙基-六亚甲基四胺(EtHMTA+)-NaF-H2O体系中合成得到了b轴择优取向的ZSM-5(MFI型)晶体,并用扫描电镜(SEM)和XRD进行表征.择优取向程度与所用的两种模板剂的比例有关,当正丙胺:EtHMTA+比为O.7:0.3时,ZSM-5晶体择优取向最明显.

A novel 'double-template' method has been developed to hydrothermally synthesize high silica MFI-type zeolite crystals with preferentially oriented growth along ac-plane. The reactant system for the synthesis is SiO2-Na2O-n-propylamine (n-PrNH2)-N-ethyl-hexamethylene tetrammium bromide (EtHMTA(+))-NaF-H2O. SEM images show that almost all as-synthesized single crystals of the zeolite are in flat and thin form with (010) plane parallel to the test plate. The XRD patterns show that the intensity of (0k0) (k=2n) peaks is much stronger than that of any other peaks, indicating that the as-synthesized crystals are b-axis preferentially oriented on the test plate. The fraction of b-axis orientation of the crystals is strongly dependent on the ratio of the two templates used in the reactant, n-PrNH2 and EtHMTA(+). The optimal molar ratio of n-PrNH2 to EtHMTA+ is 0.7:0.3 for the preferentially oriented growth of MFI-type zeolite crystals.