Microporous crystalline aluminosilicate zeolites are widely studied for their applications in chemical reaction, separation and purification. X-ray diffraction (XRD) is a standard and reliable method for zeolite characterization, and is arguably the most important technique in zeolite material development. XRD not only qualititavely identifies the zeolite crystaline structure, but also provide a quantitative estimate of the zeolite phase. XRD is also instrumental in determining the positions of the atoms and the bonds that link the atoms in the zeolites. However, XRD has its limitations. Typical instruments are unable to verify zeolite structures that are smaller than 4-5 unit cells in size and samples containing less than 5 wt. % zeolites. There is therefore a need for complementary techniques to bridge the gap left by XRD. This work investigates the possibility of using the Time-of-Flight secondary ion mass spectroscopy for zeolite analysis by detection of the characteristic secondary building units (SBU) and their fragments. The ToF-SIMS data contains rich information on chemical composition, molecular bonds, surface orders and structures that could be deconvoluted and analyzed using multivariate analysis. Principal component analysis show that ToF-SIMS can clearly distinguish between the different forms of ZSM-5 zeolites. The characteristic 5-1 SBU ring structure Si5AlO12(359) and its fragments Si4AlO10 (299) and (SiO2)5�H2O�H3O (337) were detected from the samples. Larger zeolite fragments such as Si6AlO14(419) were also observed. X-ray diffraction can detect zeolites down to 6.25 wt.%, but ToF-SIM can detect the presence of 5-1 SBU ring structure in samples with less than 2 wt.% ZSM-5. In addition, ToF-SIMS is also far more sensitive in detecting different zeolite materials in mixtures that contains MFI, LTA and FAU zeolites.

Detection of zeolite secondary building units by ToF-SIMS

248th National Meeting (2014)

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