Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (03): 720-728.doi: 10.3866/PKU.WHXB201201031

• PHYSICAL CHEMISTRY OF MATERIALS • Previous Articles     Next Articles

Designed Synthesis and Crystallization of Fe-Al-EU-1 Zeolites Containing Framework-Iron

YANG Dong-Hua1, ZHAO Jun-Fu2, ZHANG Jun-Liang3, DOU Tao3,4, WU Zhong-Hua5, CHEN Zhong-Jun5   

  1. 1. College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, P. R. China;
    2. College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, P. R. China;
    3. Key Laboratory of Catalysis, College of Chemical Engineering, China University of Petroleum-Beijing, Beijing 102249, P. R. China;
    4. Research Institute of Special Chemicals, Taiyuan University of Technology, Taiyuan 030024, P. R. China;
    5. Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039, P. R. China
  • Received:2011-09-22 Revised:2011-12-26 Published:2012-02-23
  • Contact: DOU Tao
  • Supported by:

    The project was supported by the National Key Basic Research Program of China (973) (2012CB215002), National Natural Science Foundation of China (20973123), and Open Fund of State Key Laboratory of Coal Conversion, China (11-12-603).

Abstract: Highly crystalline Fe-Al-EU-1 zeolites were hydrothermally synthesized in a HMBr2-Na2OAl2O3- SiO2-Fe2O3-H2O system by using hexamethonium bromide (HMBr2) as a template. The physical and chemical properties, and the bonding state of Fe in the zeolite framework for the prepared Fe-Al-EU-1 samples were characterized by a series of techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric-derivative thermogravimetric (TG-DTG) analysis, N2 adsorption-desorption, solid-state nuclear magnetic resonance (NMR), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), and X-ray absorption fine structure (XAFS). The results show that with increasing the mass fraction of Fe in the original sol-gel, the unit cell volume of Fe-Al-EU-1 zeolite inflates; the zeolite doped with Fe causes an increase in its surface area (BET) from 272 to 365 m2·g-1 and a reduced amount of template removal, as well as a decrease in decomposition temperature. Adding Fe ions into sol-gel also leads to lowered zeta potential, easily gathered colloidal particles, and increased shape of zeolite. The UV-Vis spectrum shows that there is a characteristic peak at about 220-250 nm with a sharply increased intensity due to the p-d transition of the bonding electrons from the 2p-orbital of O atom to the d-orbital of the four-coordinated Fe atom in the framework. Also at around 373 nm, the coordination bonding of fourcoordinated Fe atoms and adjacent Si-O groups leads to a d-d charge transition peak with an energy level splitting and increased peak intensity. The XAFS results show that with the crystallization process going on, the pre-edge absorption peak for 1s→3d and main absorption peak for 1s→4p change significantly. Four-coordinated structural units of iron species formed from the original sol-gel samples are gradually transformed into a tetrahedral coordinated iron-silicon-oxygen skeleton, in which iron-siliconoxygen ionic structural unit is also transformed into skeleton iron species with a tetrahedral covalent bonding structure.

Key words: Fe-Al-EU-1 zeolite, Bonding state, Crystallization, X-ray absorption fine structure, Physical and chemical property, Characterization


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