摘要
研究了Fe在Ferrozeosilite(在非碱性介质中合成的Fe-ZSM-5)分子筛中的存在状态。XPS和Mossbauer谱表明,Fe以Fe(Ⅲ)和Fe(Ⅱ)两种价态共存于Ferrozeosilite分子筛骨架中,同时伴有少量非骨架Fe的存在。用EPR研究了Ferrozeosilite分子筛的生成过程及灼烧后各种状态Fe的变化和迁移行为。Fe对ZSM-5沸石骨架的同晶取代过程在EPR谱中表现为g=4.3处顺磁共振信号的增强。灼烧后样品EPR谱中g=4.3处信号的减弱和g=2.3处宽谱的出现源于骨架Fe在灼烧过程中的部分迁移行为。EPMA对抛光后的分子筛晶体剖面分析表明,Fe原子在Ferrozeosilite晶体中的分布是内层富集。
The location of iron in ferrozeosilite (synthesized in a non-alkaline medium in the presence of fluonde) was studied by means of XPS, Mcssbauer, EPR and EPMA. The results indicated that Fe(III) and Fe(II) coexisted in the ferrozeosilite framework and accompanied with a small quantity of Fe compounds presented in pores and cation sides of the zeolite structure. B.E. = 713.2 and 709.7eV in Fe2p3/2 level of XPS, I.S.=0.35, Q.S. =0.38 and I.S. = 0.95,Q.S. =2.37mm/s in the Mossbauer spectra and a signal of g =4.3 in the EPR spectra were assigned to Fe(III) and Fe(II ) isomorphously substituted in the tetrahedral positions. The results also showed the migration of Fe(III) from framework to non-framework positions after calcination. Electron probe microanalysis indicated that the distribution of the lattice atoms was iron-rich in the inner sphere of the ferrozeosilite crystals.
基金
国家自然科学基金重大项目资助课题
